Journal of Bone and Mineral Research

Journal of Bone and Mineral Research

Calcium‐Sensing Receptors in Chondrocytes and Osteoblasts Are Required for Callus Maturation and Fracture Healing in Mice

18-10-2019 – Zhiqiang Cheng, Alfred Li, Chia‐Ling Tu, Christian Santa Maria, Nicholas Szeto, Amanda Herberger, Tsui‐Hua Chen, Fuqing Song, Jiali Wang, Xiaodong Liu, Dolores M Shoback, Wenhan Chang

Journal Article

ABSTRACTCalcium and its putative receptor (Ca
SR) control skeletal development by pacing chondrocyte differentiation and mediating osteoblast (OB) function during endochondral bone formation—an essential process recapitulated during fracture repair. Here, we delineated the role of the Ca
SR in mediating transition of callus chondrocytes into the OB lineage and subsequent bone formation at fracture sites and explored targeting Ca
SRs pharmacologically to enhance fracture repair. In chondrocytes cultured from soft calluses at a closed, unfixed fracture site, extracellular Ca2+ and the allosteric Ca
SR agonist (NPS‐R568) promoted terminal differentiation of resident cells and the attainment of an osteoblastic phenotype. Knockout (KO) of the Casr gene in chondrocytes lengthened the chondrogenic phase of fracture repair by increasing cell proliferation in soft calluses but retarded subsequent osteogenic activity in hard calluses. Tracing growth plate (GP) and callus chondrocytes that express Rosa26‐td
Tomato showed reduced chondrocyte transition into OBs (by >80%) in the spongiosa of the metaphysis and in hard calluses. In addition, KO of the Casr gene specifically in mature OBs suppressed osteogenic activity and mineralizing function in bony calluses. Importantly, in experiments using PTH (1‐34) to enhance fracture healing, co‐injection of NPS‐R568 not only normalized the hypercalcemic side effects of intermittent PTH (1‐34) treatment in mice but also produced synergistic osteoanabolic effects in calluses. These data indicate a functional role of Ca
SR in mediating chondrogenesis and osteogenesis in the fracture callus and the potential of Ca
SR agonism to facilitate fracture repair. © 2019 American Society for Bone and Mineral Research.

High Plasma Erythropoietin Predicts Incident Fractures in Elderly Men with normal renal function: The MrOS Sweden Cohort

18-10-2019 – Hallgerdur Lind Kristjansdottir, Catharina Lewerin, Ulf H. Lerner, Hans Herlitz, Peter Johansson, Helena Johansson, Magnus Karlson, Mattias Lorentzon, Claes Ohlsson, Östen Ljunggren, Dan Mellström

Abstract
Preclinical studies on the role of erythropoietin (EPO) in bone metabolism are contradictory. Regeneration models indicate an anabolic effect on bone healing while models on physiologic bone remodeling indicate a catabolic effect on bone mass. No human studies on EPO and fracture risk are available. It is known that fibroblast growth factor 23 (FGF23) effects bone mineralization and that serum concentration of FGF23 is higher in men with decreased estimated glomerular filtration rate (e
GFR). Recently, a direct association between EPO and FGF23, has been shown. We have explored the potential association between EPO and bone mineral density (BMD), fracture risk and FGF23 in humans. Plasma levels of EPO were analyzed in 999 men (69‐81 years), participating in the Gothenburg part of the population‐based study Mr
OS Sweden. The mean ± SD EPO was 11.5 ± 9.0 IU/L. Results were stratified by e
GFR 60 ml/min. For men with e
GFR≥60 ml/min (N=728), EPO was associated with age (r=0.13, P<0.001), total hip BMD (r=0.14, P<0.001), intact (i)FGF23 (r=0.11, P=0.004) and osteocalcin (r=‐0.09, P=0.022). The association between total hip BMD and EPO was independent of age, BMI, i
FGF23 and hemoglobin (beta=0.019, P<0.001). During the 10‐year follow up, 164 men had an x‐ray verified fracture, including 117 major osteoporotic fractures (MOF), 39 hip fractures, and 64 vertebral fractures. High EPO was associated with higher risk for incident fractures (HR 1.43 per tertile EPO, 95% CI 1.35‐1.63), MOF (HR 1.40 per tertile EPO, 95% CI 1.08‐1.82) and vertebral fractures (HR 1.42 per tertile EPO, 95% CI 1.00‐2.01) in a fully adjusted Cox regression model. In men with e
GFR<60 ml/min, no association was seen between EPO and BMD or fracture risk. We here demonstrate that high levels of EPO are associated with increased fractures risk and increased BMD in elderly men with normal renal function.
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The associations between seven different types of physical activity and the incidence of fracture at seven sites in healthy postmenopausal UK women

16-10-2019 – Miranda E G Armstrong, Jason Lacombe, Clare J Wotton, Benjamin J Cairns, Jane Green, Sarah Floud, Valerie Beral, Gillian K Reeves, for the Million Women Study Collaborators

Journal Article

Abstract
There is a paucity of information on associations between specific types of physical activity and fracture risk at different sites in otherwise healthy postmenopausal women. Therefore, we examined risk of fracture at 7 different sites associated with 7 different types of physical activity in the population‐based prospective UK Million Women Study. A total of 371,279 postmenopausal women (mean age 59.8 years), rating their health as good or excellent and reporting participation in walking, cycling, gardening, doing housework, yoga, dance and sports club activities, were followed for site‐specific incident fracture through record linkage to national databases on day‐case and overnight hospital admissions. Cox regression yielded adjusted relative risks (RRs) and, because of the large number of statistical tests done, 99% confidence intervals (CIs) for fracture at 7 different sites in relation to 7 different physical activities.
During an average follow‐up of 12 years, numbers with a first site‐specific fracture were: humerus (2341), forearm (1238), wrist (7358), hip (4354), femur (not neck) (617), lower leg (1184), and ankle (3629). For upper limb fractures there was significant heterogeneity across the 7 activity types (test for heterogeneity p=0.004), with gardening more than one hour/week associated with a lower risk (RR=0.91, 99%CI 0.86‐0.96; p<0.0001), whereas cycling more than an hour/week was associated with an increased risk (RR=1.11, 99%CI 1.00‐1.23; p=0.008). For fractures of the lower limb (including hip) there was no significant heterogeneity by type of activity, with significant approximately 5‐15% reductions in risk associated with most activities, except cycling. For hip fractures, there was no significant heterogeneity by type of activity, but with significant 15‐20% reductions in risk associated with walking for 1 hour/day and participating in yoga and sporting activities. Physical activity is a modifiable risk factor for fracture, but the effects differ between different types of activities and different fracture sites.
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Kidney Disease Progression Does Not Decrease Intestinal Phosphorus Absorption in a Rat Model of Chronic Kidney Disease‐Mineral Bone Disorder

16-10-2019 – Colby J. Vorland, Annabel Biruete, Pamela J. Lachcik, Shruthi Srinivasan, Neal X. Chen, Sharon M. Moe, Kathleen M. Hill Gallant

Journal Article

Abstract
The Cy/+ rat has been characterized as a progressive model of chronic kidney disease‐mineral bone disorder (CKD‐MBD). We aimed to determine the effect of kidney disease progression on intestinal phosphorus absorption and whole‐body phosphorus balance in this model. N=48 Cy/+ (CKD) and N=48 normal littermates (NL) rats were studied at two ages: 20‐weeks and 30‐weeks, to model progressive kidney function decline at approximately 50 and 20% of normal kidney function. Sodium‐dependent and sodium‐independent intestinal phosphorus absorption efficiency were measured by the in situ jejunal ligated loop method using 33P radioisotope. Our results show that CKD rats had slightly higher sodium‐dependent phosphorus absorption compared to NL rats, and absorption decreased from 20‐ to 30‐weeks. These results are in contrast to plasma 1,25OH2D, which was lower in CKD rats. Gene expression of the major intestinal phosphorus transporter, Na
Pi‐2b, was not different between CKD and NL rats in the jejunum but was lower in CKD rats versus NL rats in the duodenum. Jejunal ligated loop phosphorus absorption results are consistent with percent net phosphorus absorption results obtained from metabolic balance: higher net percent phosphorus absorption values in CKD rats compared with NL, and lower values in 30‐week‐olds compared with 20‐week‐olds. Phosphorus balance was negative (below zero) in CKD rats, significantly lower in 30‐week‐old rats compared with 20‐week‐old rats, and lower in CKD rats compared with NL rats at both ages. These results demonstrate no reduction in intestinal phosphorus absorption with progression of CKD despite lower 1,25OH2D status when assessed by an in situ ligated loop test, which is in contrast to the majority of in vitro studies, and if confirmed in further studies, could challenge the physiological relevance of in vitro findings.
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Greater Bone Marrow Adiposity Predicts Bone Loss in Older Women

16-10-2019 – Gina N. Woods, Susan K. Ewing, Sigurdur Sigurdsson, Deborah M. Kado, Gudny Eiriksdottir, Vilmundur Gudnason, Trisha F. Hue, Thomas F. Lang, Eric Vittinghoff, Tamara B. Harris, Clifford Rosen, Kaipin Xu, Xiaojuan Li, Ann V. Schwartz

Journal Article

Bone marrow adiposity (BMA) is associated with aging and osteoporosis, but whether BMA can predict bone loss and fractures remains unknown. Using data from the Age Gene/Environment Susceptibility (AGES)‐Reykjavik study, we investigated the associations between 1H‐MRS‐based measures of vertebral bone marrow adipose tissue (BMAT), annualized change in bone density/strength by QCT and DXA, and secondarily, with incident clinical fractures and radiographic vertebral fractures among older adults. The associations between BMAT and annualized change in bone density/strength were evaluated using linear regression models, adjusted for age, body mass index (BMI), diabetes, estradiol and testosterone. Cox proportional hazards models were used to evaluate the associations between baseline BMAT and incident clinical fractures, and logistic regression models for incident vertebral fractures. At baseline, mean age was 80.9 (SD 4.2) and 82.6 (SD 4.2) years in women (n=148) and men (n=150), respectively. Mean baseline BMAT was 55.4% (SD 8.1) in women and 54.1% (SD 8.2) in men. Incident clinical fractures occurred in 7.4% of women over 2.8 years and in 6.0% of men over 2.2 years. Incident vertebral fractures occurred in 12% of women over 3.3 years and in 17% of men over 2.7 years. Each 1 SD increase in baseline BMAT was associated with a 3.9 mg2/cm4/year greater loss of spine compressive strength index (p‐value = 0.003), a 0.9 mg/cm3/year greater loss of spine trabecular BMD (p‐value = 0.02) and a 1.2 mg/cm3/year greater loss of femoral neck trabecular BMD (p‐value = 0.02) in women. Among men, there were no associations between BMAT and changes in bone density/strength. There were no associations between BMAT and incident fractures in women or men. In conclusion, we found greater BMAT is associated with greater loss of trabecular bone at the spine and femoral neck, and greater loss of spine compressive strength, in older women.
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Circulating MicroRNA‐19b Identified from Osteoporotic Vertebral Compression Fracture Patients Increases Bone Formation

15-10-2019 – Mengge Sun, Liqiu Hu, Shang Wang, Tongling Huang, Minyi Zhang, Meng Yang, Wanxin Zhen, Dazhi Yang, William Lu, Min Guan, Songlin Peng

Journal Article

ABSTRACTCirculating micro
RNAs (mi
RNAs) play important roles in regulating gene expression and have been reported to be involved in various metabolic diseases, including osteoporosis. Although the transcriptional regulation of osteoblast differentiation has been well characterized, the role of circulating mi
RNAs in this process is poorly understood. Here we discovered that the level of circulating mi
R‐19b was significantly lower in osteoporotic patients with vertebral compression fractures than that of healthy controls. The expression level of mi
R‐19b was increased during osteoblastic differentiation of human mesenchymal stem cells (h
MSCs) and MC3T3‐E1 cells, and transfection with synthetic mi
R‐19b could promote osteoblastic differentiation of h
MSCs and MC3T3‐E1 cells. PTEN (phosphatase and tensin homolog deleted from chromosome 10) was found to be directly repressed by mi
R‐19b, with a concomitant increase in Runx2 expression and increased phosphorylation of AKT (protein kinase B, PKB). The expression level of circulating mi
R‐19b in aged ovariectomized mice was significantly lower than in young mice. Moreover, the osteoporotic bone phenotype in aged ovariectomized mice was alleviated by the injection of chemically modified mi
R‐19b (agomi
R‐19b). Taken together, our results show that circulating mi
R‐19b plays an important role in enhancing osteoblastogenesis, possibly through regulation of the PTEN/p
AKT/Runx2 pathway, and may be a useful therapeutic target in bone loss disorders, such as osteoporosis.
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Zoledronic acid improves muscle function in healthy mice treated with chemotherapy

15-10-2019 – Brian A. Hain, Baptiste Jude, Haifang Xu, Dallas M. Smuin, Edward J. Fox, John C. Elfar, David L. Waning

Journal Article

ABSTRACTCarboplatin is a chemotherapy drug used to treat solid tumors but also causes bone loss and muscle atrophy and weakness. Bone loss contributes to muscle weakness through bone‐muscle crosstalk which is prevented with the bisphosphonate zoledronic acid (ZA). We treated mice with carboplatin in the presence or absence of ZA to assess the impact of bone resorption on muscle. Carboplatin caused loss of body weight, muscle mass, and bone mass, and also led to muscle weakness as early as 7 days after treatment. Mice treated with carboplatin and ZA lost body weight and muscle mass but did not lose bone mass. In addition, muscle function in mice treated with ZA was similar to control animals. We also used the anti‐TGFβ antibody (1D11) to prevent carboplatin‐induced bone loss and showed similar results to ZA treated mice. We found that atrogin‐1 m
RNA expression was increased in muscle from mice treated with carboplatin, which explained muscle atrophy. In mice treated with carboplatin for 1 or 3 days, we did not observe any bone or muscle loss, or muscle weakness. In addition, reduced caloric intake in the carboplatin treated mice did not cause loss of bone or muscle mass, or muscle weakness. Our results show that blocking carboplatin‐induced bone resorption is sufficient to prevent skeletal muscle weakness and suggests another benefit to bone therapy beyond bone in patients receiving chemotherapy.
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Alveolar bone protection by targeting the SH3BP2‐SYK axis in osteoclasts

15-10-2019 – Mizuho Kittaka, Tetsuya Yoshimoto, Collin Schlosser, Robert Rottapel, Mikihito Kajiya, Hidemi Kurihara, Ernst J Reichenberger, Yasuyoshi Ueki

Journal Article

ABSTRACTPeriodontitis is a bacterially induced chronic inflammatory condition of the oral cavity where tooth‐supporting tissues including alveolar bone are destructed. Previously, we have shown that the adaptor protein SH3‐domain binding protein 2 (SH3BP2) plays a critical role in inflammatory response and osteoclastogenesis of myeloid lineage cells through spleen tyrosine kinase (SYK). In this study, we show that SH3BP2 is a novel regulator for alveolar bone resorption in periodontitis. Micro
CT analysis of SH3BP2‐deficient (Sh3bp2 −/−) mice challenged with ligature‐induced periodontitis revealed that Sh3bp2 −/− mice develop decreased alveolar bone loss (male: 14.9 ± 10.2%, female: 19.0 ± 6.0%) compared to wild‐type control mice (male: 25.3 ± 5.8%, female: 30.8 ± 5.8%). Lack of SH3BP2 did not change the inflammatory cytokine expression and osteoclast induction. Conditional knockout of SH3BP2 and SYK in myeloid lineage cells with Lys
M‐Cre mice recapitulated the reduced bone loss without affecting both inflammatory cytokine expression and osteoclast induction, suggesting that the SH3BP2‐SYK axis plays a key role in regulating alveolar bone loss by mechanisms that regulate the bone‐resorbing function of osteoclasts rather than differentiation. Administration of a new SYK inhibitor GS‐9973 before or after periodontitis induction reduced bone resorption without affecting inflammatory reaction in gingival tissues. In vitro, GS‐9973 treatment of bone marrow‐derived M‐CSF‐dependent macrophages suppressed tartrate‐resistant acid phosphatase (TRAP)‐positive osteoclast formation with decreased mineral resorption capacity even when GS‐9973 was added after RANKL stimulation. Thus, the data suggest that SH3BP2‐SYK is a novel signaling axis for regulating alveolar bone loss in periodontitis and that SYK can be a potential therapeutic target to suppress alveolar bone resorption in periodontal diseases.
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Secular Trends of Hip Fractures in Lebanon, 2006 to 2017: Implications for Clinical Practice and Public Health Policy in the Middle East Region

14-10-2019 – Randa K Saad, Hilda Harb, Ibrahim R Bou‐Orm, Walid Ammar, Ghada El‐Hajj Fuleihan

Journal Article

ABSTRACTCountry‐specific hip fracture incidence rates (IRs) and longevity allow the Fracture Risk Assessment Tool (FRAX) to be adapted to individual countries. Secular trends can affect tool calibration. Data on hip fracture IRs in the Middle East is scarce, and long‐term secular trend studies are nonexistent. Using the Ministry of Public Health hip fracture registry, we calculated age‐ and sex‐specific hip fracture IRs in Lebanon, from 2006 to 2017, among individuals aged ≥50 years. We used Kendalls tau‐b (τb) test to determine the correlation between time and hip fracture IRs, and calculated both the annual % change in IRs and the % change in IR compared to the baseline period (2006 to 2008). The registry recorded 6985 hip fractures, 74% at the femoral neck, 23% intertrochanteric, and 3% subtrochanteric. Men constituted 32% of the population, and were significantly younger than women (76.5 ± 11.0 years versus 77.7 ± 10.3 years; p < 0.001). Annual overall IRs, per 100,000, ranged from 126.6 in 2014 to 213.2 in 2017 in women, and 61.4 in 2015 to 111.7 in 2017 in men. The average women to men IR ratio was 1.8 (range, 1.5 to 2.1). IRs steadily increased with age, and IR ratios increased in parallel in both sexes, with a steeper and earlier rise (by 5 years) in women. Data showed a consistent decline in hip fracture IRs starting in 2006 in women, and in 2009 in men. There was a significant negative correlation between time (2006 to 2014) and hip fracture IRs in women (τb = −0.611, p = 0.022) but not in men (τb = −0.444, p = 0.095). The steady decrease in IRs reversed after 2015 in both sexes. This long‐term data on secular trends in the Middle East is novel and consistent with worldwide changes in hip fracture rates. The impact of such changes on national FRAX‐derived estimates is unclear, should be assessed, and may necessitate an update in the FRAX Lebanon calculator. © 2019 American Society for Bone and Mineral Research.

Extracellular Vesicles from Osteotropic Breast Cancer Cells Affect Bone Resident Cells

14-10-2019 – Alexander Loftus, Alfredo Cappariello, Christopher George, Argia Ucci, Kirsty Shefferd, Alice Green, Riccardo Paone, Marco Ponzetti, Simona Delle Monache, Maurizio Muraca, Anna Teti, Nadia Rucci

Journal Article

ABSTRACTExtracellular vesicles (EVs) are emerging as mediators of a range of pathological processes, including cancer. However, their role in bone metastases has been poorly explored. We investigated EV‐mediated effects of osteotropic breast cancer cells (MDA‐MB‐231) on bone resident cells and endothelial cells. Pretreatment of osteoblasts with conditioned medium (CM) of MDA‐MB‐231 (MDA) cells promoted pro‐osteoclastogenic and ‐angiogenic effects by osteoblast EVs (OB‐EVs), as well as an increase of RANKL‐positive OB‐EVs. Moreover, when treating osteoblasts with MDA‐EVs, we observed a reduction of their number, metabolic activity and Alp activity. MDA‐EVs also reduced transcription of Cyclin D1 and of the osteoblast‐differentiating genes, while enhancing the expression of the pro‐osteoclastogenic factors Rankl, Lcn2, Il1b and Il6. Interestingly, a cytokine array on CM from osteoblasts treated with MDA‐EVs showed an increase of the cytokines CCL3, CXCL2, Reg3G and VEGF, while OPG and WISP1 were downregulated. MDA‐EVs contained m
RNAs of genes involved in bone metabolism, as well as cytokines, including PDGF‐BB, CCL3, CCL27, VEGF and Angiopoietin 2. In line with this profile, MDA‐EVs increased osteoclastogenesis and in vivo angiogenesis. Finally, intraperitoneal injection of MDA‐EVs in mice revealed their ability to reach the bone microenvironment and be integrated by osteoblasts and osteoclasts. In conclusion, we demonstrated a role for osteoblast‐ and tumor cell‐derived‐EVs in the deregulation of bone and endothelial cell physiology, thus fueling the vicious cycle induced by bone tumors via EVs.
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Targeting Bortezomib to Bone Increases its Bone Anabolic Activity and Reduces Systemic Adverse Effects in Mice

14-10-2019 – Hua Wang, Hengwei Zhang, Venkat Srinivasan, Jianguo Tao, Wen Sun, Xi Lin, Tao Wu, Brendan F. Boyce, Frank H. Ebetino, Robert K. Boeckman, Lianping Xing

Journal Article

ABSTRACTBortezomib (Btz) is a proteasome inhibitor approved by the FDA to treat multiple myeloma. It also increases bone volume by promoting osteoblast differentiation and inhibiting osteoclastogenesis in mice. However, Btz has severe systemic adverse effects, which would limit its use as a bone anabolic agent. Here, we designed and synthesized a bone‐targeted form of Btz by conjugating it to a bisphosphonate (BP) with no anti‐resorptive activity. We report that BP‐Btz inhibited osteoclast formation and bone resorption and stimulated osteoblast differentiation in vitro similar Btz. In vivo, BP‐Btz increased bone volume more effectively than Btz in 3 mouse models: untreated wild‐type mice, mice with ovariectomy, and aged mice with tibial factures. Importantly, BP‐Btz had significantly less systemic side effects than Btz, including less thymic cell death, sympathetic nerve damage and thrombocytopenia, and improved survival rates in aged mice. Thus, BP‐Btz represents a novel anabolic agent to treat conditions, such as postmenopausal and age‐related bone loss. Bone‐targeting is an attractive approach to repurpose approved drugs to treat skeletal diseases.
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Zoledronate for the Prevention of Bone Loss in Women Discontinuing Denosumab Treatment. A Prospective 2‐Year Clinical Trial

14-10-2019 – Athanasios D Anastasilakis, Socrates E Papapoulos, Stergios A Polyzos, Natasha M Appelman‐Dijkstra, Polyzois Makras

Journal Article

ABSTRACTCessation of denosumab treatment is associated with increases in bone turnover above baseline values and rapid bone loss. We investigated the efficacy of zoledronate to prevent this bone loss in women with postmenopausal osteoporosis who were treated with denosumab (mean duration 2.2 years) and discontinued treatment after achieving osteopenia. Women were randomized to receive a single 5‐mg infusion of zoledronate (ZOL) (n = 27) or two additional 60‐mg injections of denosumab (Dmab) (n = 30). Both groups were followed for a total period of 24 months. At 24 months lumbar spine–bone mineral density (LS‐BMD) was not different from baseline in the ZOL group, but decreased in the Dmab group by (mean ± SD) 4.82% ± 0.7% (p < 0.001) from the 12‐month value; the difference in BMD changes between the two groups, the primary endpoint of the study, was statistically significant (p = 0.025). Results of femoral neck (FN)‐BMD changes were similar. ZOL infusion was followed by small but significant increases in serum procollagen type 1 N‐terminal propeptide (P1NP) and C‐terminal telopeptide of type 1 collagen (CTX) during the first year and stabilization thereafter. In the Dmab group, bone turnover marker values did not change during the first 12 months but increased significantly at 15 months and in the majority of women these remained elevated at 24 months. Neither baseline nor 12‐month bone turnover marker values were associated with BMD changes in either group of women. In the Dmab group, three patients sustained vertebral fractures (two patients multiple clinical, one patient morphometric) whereas one patient in the ZOL group sustained clinical vertebral fractures 12 months after the infusion. In conclusion, a single intravenous infusion of ZOL given 6 months after the last Dmab injection prevents bone loss for at least 2 years independently of the rate of bone turnover. Follow‐up is recommended, because in a few patients ZOL treatment might not have the expected effect at 2 years. © 2019 American Society for Bone and Mineral Research.

Association of Mineral Bone Disorder with Decline in Residual Kidney Function in Incident Hemodialysis Patients

14-10-2019 – Yu‐Ji Lee, Yusuke Okuda, John Sy, Yoshitsugu Obi, Duk‐Hee Kang, Steven Nguyen, Jui Ting Hsiung, Christina Park, Connie M. Rhee, Csaba P. Kovesdy, Elani Streja, Kamyar Kalantar‐Zadeh

Journal Article

ABSTRACTAbnormalities of mineral bone disorder (MBD) parameters have been suggested to be associated with poor renal outcome in predialysis patients. However, the impact of those parameters on decline in residual kidney function (RKF) is uncertain among incident hemodialysis (HD) patients. We performed a retrospective cohort study in 13,772 patients who initiated conventional HD during 2007–2011 and survived six months of dialysis. We examined the association of baseline serum phosphorus levels with a decline in RKF. We also examined the association of baseline calcium, intact parathyroid hormone (PTH), and alkaline phosphatase (ALP) levels with a decline in RKF. Decline in RKF was assessed by estimated slope of renal urea clearance (KRU) over 6 months from HD initiation. Our cohort had a mean ± SD age of 62 ± 15 years; 64% were men, 57% were Caucasian, 65% had diabetes, and 51% had hypertension. The median (interquartile range, IQR) baseline KRU level was 3.4 (2.0, 5.2) m
L/min/1.73 m2. The median (IQR) estimated 6‐month KRU slope was −1.47 (−2.24, −0.63) m
L/min/1.73 m2 per 6 months. In linear regression models, higher phosphorus categories were associated with a steeper 6‐month KRU slope compared to the reference category (phosphorus 4.0 to <4.5 mg/d
L). Lower calcium and higher intact PTH and ALP categories were also associated with a steeper 6‐month KRU slope compared to their respective reference groups (calcium 9.2 to <9.5 mg/d
L; intact PTH 150 to <250 pg/m
L; ALP <60 U/L). The increased number of parameter abnormalities had an additive effect on decline in RKF. Abnormalities of MBD parameters including higher phosphorus, intact PTH, and ALP and lower calcium levels were independently associated with decline in RKF in incident HD patients.
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“Reply to Clinical Guidelines on Pagets Disease”

14-10-2019 – Bente Langdahl

Letter

YAP and TAZ Mediate Osteocyte Perilacunar/Canalicular Remodeling

14-10-2019 – Christopher D Kegelman, Jennifer C Coulombe, Kelsey M Jordan, Daniel J Horan, Ling Qin, Alexander G Robling, Virginia L Ferguson, Teresita M Bellido, Joel D Boerckel

Journal Article

ABSTRACTBone fragility fractures are caused by low bone mass or impaired bone quality. Osteoblast/osteoclast coordination determines bone mass, but the factors that control bone quality are poorly understood. Osteocytes regulate osteoblast and osteoclast activity on bone surfaces but can also directly reorganize the bone matrix to improve bone quality through perilacunar/canalicular remodeling; however, the molecular mechanisms remain unclear. We previously found that deleting the transcriptional regulators Yes‐associated protein (YAP) and transcriptional co‐activator with PDZ‐motif (TAZ) from osteoblast‐lineage cells caused lethality in mice due to skeletal fragility. Here, we tested the hypothesis that YAP and TAZ regulate osteocyte‐mediated bone remodeling by conditional ablation of both YAP and TAZ from mouse osteocytes using 8 kb‐DMP1‐Cre. Osteocyte‐conditional YAP/TAZ deletion reduced bone mass and dysregulated matrix collagen content and organization, which together decreased bone mechanical properties. Further, YAP/TAZ deletion impaired osteocyte perilacunar/canalicular remodeling by reducing canalicular network density, length, and branching, as well as perilacunar flourochrome‐labeled mineral deposition. Consistent with recent studies identifying TGF‐β as a key inducer of osteocyte expression of matrix‐remodeling enzymes, YAP/TAZ deletion in vivo decreased osteocyte expression of matrix proteases MMP13, MMP14, and CTSK. In vitro, pharmacologic inhibition of YAP/TAZ transcriptional activity in osteocyte‐like cells abrogated TGF‐β‐induced matrix protease gene expression. Together, these data show that YAP and TAZ control bone matrix accrual, organization, and mechanical properties by regulating osteocyte‐mediated bone remodeling. Elucidating the signaling pathways that control perilacunar/canalicular remodeling may enable future therapeutic targeting of bone quality to reverse skeletal fragility. © 2019 American Society for Bone and Mineral Research.

Sex‐Specific Muscular Mediation of the Relationship Between Physical Activity and Cortical Bone in Young Adults

11-10-2019 – Simon Higgins, Chester M Sokolowski, Megha Vishwanathan, Michael D Schmidt, Ellen M Evans, Richard D Lewis

Journal Article

ABSTRACTMuscle mass is a commonly cited mediator of the relationship between physical activity (PA) and bone, representing the mechanical forces generated during PA. However, neuromuscular properties (eg, peak force) also account for unique portions of variance in skeletal outcomes. We used serial multiple mediation to explore the intermediary role of muscle mass and force in the relationships between cortical bone and moderate‐to‐vigorous intensity PA (MVPA). In a cross‐sectional sample of young adults (n = 147, 19.7 ± 0.7 years old, 52.4% female) cortical diaphyseal bone was assessed via peripheral quantitative computed tomography at the mid‐tibia. Peak isokinetic torque in knee extension was assessed via Biodex dynamometer. Thigh fat‐free soft tissue (FFST) mass, assessed via dual‐energy X‐ray absorptiometry, represented the muscular aspect of tibial mechanical forces. Habitual MVPA was assessed objectively over 7 days using Actigraph GT3X+ accelerometers. Participants exceeded MVPA guidelines (89.14 ± 27.29 min/day), with males performing 44.5% more vigorous‐intensity activity relative to females (p < 0.05). Males had greater knee extension torque and thigh FFST mass compared to females (55.3%, and 34.2%, respectively, all p < 0.05). In combined‐sex models, controlling for tibia length and age, MVPA was associated with strength strain index (pSSI) through two indirect pathways: (i) thigh FFST mass (b = 1.11 ± 0.37; 95% CI, 0.47 to 1.93), and (i) thigh FFST mass and knee extensor torque in sequence (b = 0.30 ± 0.16; 95% CI, 0.09 to 0.73). However, in sex‐specific models MVPA was associated with pSSI indirectly through its relationship with knee extensor torque in males (b = 0.78 ± 0.48; 95% CI, 0.04 to 2.02) and thigh FFST mass in females (b = 1.12 ± 0.50; 95% CI, 0.37 to 2.46). Bootstrapped CIs confirmed these mediation pathways. The relationship between MVPA and cortical structure appears to be mediated by muscle in young adults, with potential sex‐differences in the muscular pathway. If confirmed, these findings may highlight novel avenues for the promotion of bone strength in young adults. © 2019 American Society for Bone and Mineral Research.

Effects of Zoledronate on Cancer, Cardiac Events, and Mortality in Osteopenic Older Women

11-10-2019 – Ian R Reid, Anne M Horne, Borislav Mihov, Angela Stewart, Elizabeth Garratt, Sonja Bastin, Gregory D Gamble

Journal Article

ABSTRACTWe recently showed that zoledronate prevented fractures in older women with osteopenia (hip T‐scores between −1.0 and −2.5). In addition to fewer fractures, this study also suggested that women randomized to zoledronate had fewer vascular events, a lower incidence of cancer, and a trend to lower mortality. The present analysis provides a more detailed presentation of the adverse event data from that study, a 6‐year, double‐blind trial of 2000 women aged >65 years recruited using electoral rolls. They were randomly assigned to receive four infusions of either zoledronate 5 mg or normal saline at 18‐month intervals. Supplements of vitamin D, but not calcium, were provided. There were 1017 serious adverse events in 443 participants in the placebo group, and 820 events in 400 participants in those randomized to zoledronate (relative risk = 0.90; 95% CI, 0.81 to 1.00). These events included fractures resulting in hospital admission. Myocardial infarction occurred in 39 women (43 events) in the placebo group and in 24 women (25 events) in the zoledronate group (hazard ratio 0.60 95% CI, 0.36 to 1.00; rate ratio 0.58 95% CI, 0.35 to 0.94). For a prespecified composite cardiovascular endpoint (sudden death, myocardial infarction, coronary artery revascularization, or stroke) 69 women had 98 events in the placebo group, and 53 women had 71 events in the zoledronate group (hazard ratio 0.76 95% CI, 0.53 to 1.08; rate ratio 0.72 95% CI, 0.53 to 0.98). Total cancers were significantly reduced with zoledronate (hazard ratio 0.67 95% CI, 0.51 to 0.89; rate ratio 0.68 95% CI, 0.52 to 0.89), and this was significant for both breast cancers and for non‐breast cancers. Eleven women had recurrent or second breast cancers during the study, all in the placebo group. The hazard ratio for death was 0.65 (95% CI, 0.40 to 1.06; p = 0.08), and 0.51 (95% CI, 0.30 to 0.87) in those without incident fragility fracture. These apparent beneficial effects justify further appropriately powered trials of zoledronate with these nonskeletal conditions as primary endpoints. © 2019 American Society for Bone and Mineral Research.

N‐cadherin Restrains PTH Activation of Lrp6/β‐catenin Signaling and Osteoanabolic Action

11-10-2019 – Leila Revollo, Jacqueline Kading, Sung Yeop Jeong, Jiemin Li, Valerie Salazar, Gabriel Mbalaviele, Roberto Civitelli

Effects of Estrogen Replacement on Bone Geometry and Microarchitecture in Adolescent and Young Adult Oligo‐amenorrheic Athletes‐ a Randomized Trial

11-10-2019 – Kathryn E. Ackerman, Vibha Singhal, Meghan Slattery, Kamryn T. Eddy, Mary L Bouxsein, Hang Lee, Anne Klibanski, Madhusmita Misra

Journal Article

ABSTRACTOligo‐amenorrheic athletes (OA) have lower bone mineral density (BMD) and greater impairment of bone microarchitecture, and therefore higher fracture rates compared to eumenorrheic athletes. While improvements in areal BMD (a
BMD; measured by dual‐energy x‐ray absorptiometry) in OA have been demonstrated with transdermal estrogen treatment, effects of such treatment on bone microarchitecture are unknown. Here we explore effects of transdermal vs. oral estrogen vs. no estrogen on bone microarchitecture in OA. Seventy‐five OA (ages 14‐25 years) were randomized to (i) a 100 mcg 17β‐estradiol transdermal patch (PATCH) administered continuously with 200 mg cyclic oral micronized progesterone, (ii) a combined 30 mcg ethinyl estradiol and 0.15 mg desogestrel pill (PILL), or (iii) no estrogen/progesterone (NONE) and were followed for 12 months. Calcium (≥1200 mg) and vitamin D (800 IU) supplements were provided to all. Bone microarchitecture was assessed using high resolution peripheral quantitative CT at the distal tibia and radius at baseline and one year. At baseline, randomization groups did not differ for age, body mass index, percent body fat, duration of amenorrhea, vitamin D levels, BMD, or bone microarchitecture measurements. After one year of treatment, at the distal tibial there were significantly greater increases in total and trabecular volumetric BMD (v
BMD), cortical area and thickness, and trabecular number in the PATCH vs. PILL groups. Trabecular area decreased significantly in the PATCH group vs. the PILL and NONE groups. Less robust differences between groups were seen at the distal radius, where percent change in cortical area and thickness was significantly greater in the PATCH vs. PILL and NONE groups, and changes in cortical v
BMD were significantly greater in the PATCH vs. PILL groups. In conclusion, in young oligo‐amenorrheic athletes, bone structural parameters show greater improvement after one year of treatment with transdermal 17β‐estradiol vs. ethinyl estradiol containing pills, particularly at the tibia.
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Osteocalcin Regulates Arterial Calcification via Altered Wnt Signalling and Glucose Metabolism

09-10-2019 – Nabil A Rashdan, Alisia M Sim, Lin Cui, Kanchan Phadwal, Fiona L Roberts, Roderick Carter, Derya D Ozdemir, Peter Hohenstein, John Hung, Jakub Kaczynski, David E. Newby, Andrew H. Baker, Gerard Karsenty, Nicholas M Morton, Vicky E. MacRae

Journal Article

ABSTRACTArterial calcification is an important hallmark of cardiovascular disease and shares many similarities with skeletal mineralisation. The bone‐specific protein osteocalcin (OCN) is an established marker of vascular smooth muscle cell (VSMC) osteochondrogenic trans‐differentiation and a known regulator of glucose metabolism. However, the role of OCN in controlling arterial calcification is unclear. We hypothesised that OCN regulates calcification in VSMCs and sought to identify the underpinning signalling pathways. Immunohistochemistry revealed OCN co‐localisation with VSMC calcification in human calcified carotid artery plaques. Additionally, 3 m
M phosphate treatment stimulated OCN m
RNA expression in cultured VSMCs (1.72 fold; p < 0.001). Phosphate‐induced calcification was blunted in VSMCs derived from OCN null mice (Ocn −/−) compared to cells derived from Wild‐Type (WT) mice (0.37 fold, p < 0.001). Ocn −/− VSMCs showed reduced m
RNA expression of the osteogenic marker Runx2 (0.51 fold, p < 0.01) and the sodium‐dependent phosphate transporter, Pi
T1 (0.70 fold, p < 0.001), with an increase in the calcification inhibitor Mgp (1.42 fold, p < 0.05) compared to WT. Ocn −/− VSMCs also showed reduced m
RNA expression of Axin2 (0.13 fold; p < 0.001) and Cyclin D (0.71 fold; p < 0.01), markers of Wnt signalling. CHIR99021 (GSK3β inhibitor) treatment increased calcium deposition in WT and Ocn −/− VSMCs (1 μM; p < 0.001). Ocn −/− VSMCs however calcified less than WT cells (1 μM; 0.27 fold; p < 0.001). Ocn −/− VSMCs showed reduced m
RNA expression of Glut1 (0.78 fold p < 0.001), Hex1 (0.77 fold p < 0.01) and Pdk4 (0.47 fold p < 0.001). This was accompanied by reduced glucose uptake (0.38 fold, p < 0.05). Subsequent mitochondrial function assessment revealed increased ATP‐linked respiration (1.29 fold, p < 0.05), spare respiratory capacity (1.59 fold, p < 0.01) and maximal respiration (1.52 fold, p < 0.001) in Ocn −/− versus WT VSMCs. Together these data suggest that OCN plays a crucial role in arterial calcification mediated by Wnt/β‐catenin signalling through reduced maximal respiration. Mitochondrial dynamics may therefore represent a novel therapeutic target for clinical intervention.
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Increased Fracture Risk in Women Treated with Aromatase Inhibitors versus Tamoxifen: Beneficial Effect of Bisphosphonates

09-10-2019 – Marta Pineda‐Moncusí, Natalia Garcia‐Giralt, Adolfo Diez‐Perez, Sonia Servitja, Ignasi Tusquets, Daniel Prieto‐Alhambra, Xavier Nogués

Journal Article

ABSTRACTAromatase inhibitors have been associated with accelerated bone loss and an increased risk of osteoporotic fractures. Currently, bisphosphonates are recommended to reduce fracture risk in these patients. The aim of this study is to evaluate the fracture risk in breast cancer patients receiving aromatase inhibitors, compared to tamoxifen users, and to assess the effectiveness of oral bisphosphonates in reducing fracture risk. We performed an observational cohort study up to 10 years of follow‐up. Data were extracted from primary care records in a population database. Women diagnosed with breast cancer between 2006 and 2015 and treated with tamoxifen or aromatase inhibitors (n = 36,472) were stratified according to low (without osteoporosis diagnosis nor bisphosphonates exposure) or high (with osteoporosis and/or treated with bisphosphonates) fracture risk. Cox models were used to calculate hazard ratios (HR 95%CI) of fracture from the propensity score matched patients. Sensitivity analyses account for competing risk of death were performed (SHR 95%CI). In postmenopausal women, fracture risk in aromatase inhibitor users showed a HR: 1.40 1.05 to 1.87 and SHR: 1.48 1.11 to 1.98, compared to tamoxifen. Observing aromatase inhibitors patients at high‐risk of fracture, bisphosphonate treated patients had a HR: 0.73 0.51 to 1.04 and SHR: 0.69 0.48 to 0.98 compared to non‐treated.
In conclusion, fracture risk in postmenopausal women during aromatase inhibitor treatment, in real‐life conditions, was >40% compared to tamoxifen, corroborating previous randomized controlled trials results. In high‐risk patients, bisphosphonate users had lower significant fracture incidence during aromatase inhibitor therapy than non‐bisphosphonate‐users. Monitoring fracture risk and related risk factors in aromatase inhibitor patients is advisable.
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Pamidronate Administration During Pregnancy and Lactation Induces Temporal Preservation of Maternal Bone Mass in a Mouse Model of Osteogenesis Imperfecta

09-10-2019 – Diana Olvera, Rachel Stolzenfeld, Emily Fisher, Bonnie Nolan, Michelle S Caird, Kenneth M Kozloff

Journal Article

ABSTRACTDuring pregnancy and lactation, the maternal skeleton undergoes significant bone loss through increased resorption to provide the necessary calcium supply to the developing fetus and suckling neonate. This period of skeletal vulnerability has not been clearly associated with increased maternal fracture risk, but these physiological conditions can exacerbate an underlying metabolic bone condition like osteogenesis imperfecta. Although bisphosphonates (BPs) are commonly used in postmenopausal women, there are cases where premenopausal women taking BPs become pregnant. Given BPs’ long half‐life, there is a need to establish how BPs affect the maternal skeleton during periods of demanding metabolic bone changes that are critical for the skeletal development of their offspring. In the present study, pamidronate‐ (PAM‐) amplified pregnancy‐induced bone mass gains and lactation‐induced bone loss were prevented. This preservation of bone mass was less robust when PAM was administered at late stages of lactation compared with early pregnancy and first day of lactation. Pregnancy‐induced osteocyte osteolysis was also observed and was unaffected with PAM treatment. No negative skeletal effects were observed in offspring from PAM‐treated dams despite lactation‐induced bone loss prevention. These findings provide important insight into (1) a treatment window for when PAM is most effective in preserving maternal bone mass, and (2) the maternal changes in bone metabolism that maintain calcium homeostasis crucial for fetal and neonatal bone development. © 2019 American Society for Bone and Mineral Research

Association Between Abdominal Aortic Calcification, Bone Mineral Density, and Fracture in Older Women

09-10-2019 – Joshua R Lewis, Celeste J Eggermont, John T Schousboe, Wai H Lim, Germaine Wong, Ben Khoo, Marc Sim, MingXiang Yu, Thor Ueland, Jens Bollerslev, Jonathan M Hodgson, Kun Zhu, Kevin E Wilson, Douglas P Kiel, Richard L Prince

Journal Article

ABSTRACTAlthough a relationship between vascular disease and osteoporosis has been recognized, its clinical importance for fracture risk evaluation remains uncertain. Abdominal aortic calcification (AAC), a recognized measure of vascular disease detected on single‐energy images performed for vertebral fracture assessment, may also identify increased osteoporosis risk. In a prospective 10‐year study of 1024 older predominantly white women (mean age 75.0 ± 2.6 years) from the Perth Longitudinal Study of Aging cohort, we evaluated the association between AAC, skeletal structure, and fractures. AAC and spine fracture were assessed at the time of hip densitometry and heel quantitative ultrasound. AAC was scored 0 to 24 (AAC24) and categorized into low AAC (score 0 and 1, n = 459), moderate AAC (score 2 to 5, n = 373), and severe AAC (score >6, n = 192). Prevalent vertebral fractures were calculated using the Genant semiquantitative method. AAC24 scores were inversely related to hip BMD (rs = –0.077, p = 0.013), heel broadband ultrasound attenuation (rs = –0.074, p = 0.020), and the Stiffness Index (rs = –0.073, p = 0.022). In cross‐sectional analyses, women with moderate to severe AAC were more likely to have prevalent fracture and lumbar spine imaging‐detected lumbar spine fractures, but not thoracic spine fractures (Mantel‐Haenszel test of trend p < 0.05). For 10‐year incident clinical fractures and fracture‐related hospitalizations, women with moderate to severe AAC (AAC24 score >1) had increased fracture risk (HR 1.48; 95% CI, 1.15 to 1.91; p = 0.002; HR 1.46; 95% CI, 1.07 to 1.99; p = 0.019, respectively) compared with women with low AAC. This relationship remained significant after adjusting for age and hip BMD for clinical fractures (HR 1.40; 95% CI, 1.08 to 1.81; p = 0.010), but was attenuated for fracture‐related hospitalizations (HR 1.33; 95% CI, 0.98 to 1.83; p = 0.073). In conclusion, older women with more marked AAC are at higher risk of fracture, not completely captured by bone structural predictors. These findings further support the concept that vascular calcification and bone pathology may share similar mechanisms of causation that remain to be fully elucidated © 2019 American Society for Bone and Mineral Research

Regulation of the Bone Vascular Network is Sexually Dimorphic

09-10-2019 – Alice Goring, Aikta Sharma, Behzad Javaheri, Rosanna CG Smith, Janos M Kanczler, Alan Boyde, Eric Hesse, Sumeet Mahajan, Bjorn R Olsen, Andrew A Pitsillides, Philipp Schneider, Richard OC Oreffo, Claire E Clarkin

Journal Article

ABSTRACTOsteoblast (OB) lineage cells are an important source of vascular endothelial growth factor (VEGF), which is critical for bone growth and repair. During bone development, pubertal differences in males and females exist, but little is known about whether VEGF signaling contributes to skeletal sexual dimorphism. We have found that in mice, conditional disruption of VEGF in osteocalcin‐expressing cells (Ocn
VEGFKO) exerts a divergent influence on morphological, cellular, and whole bone properties between sexes. Furthermore, we describe an underlying sexual divergence in VEGF signaling in OB cultures in vitro independent of circulating sex hormones. High‐resolution synchrotron computed tomography and backscattered scanning electron microscopy revealed, in males, extensive unmineralized osteoid encasing enlarged blood vessel canals and osteocyte lacunae in cortical bone after VEGF deletion, which contributed to increased porosity. VEGF was deleted in male and female long bone–derived OBs (OBVEGKO) in vitro and Raman spectroscopic analyses of mineral and matrix repertoires highlighted differences between male and female OBVEGFKO cells, with increased immature phosphate species prevalent in male OBVEGFKO cultures versus wild type (WT). Further sexual dimorphism was observed in bone marrow endothelial cell gene expression in vitro after VEGF deletion and in sclerostin protein expression, which was increased in male Ocn
VEGFKO bones versus WT. The impact of altered OB matrix composition after VEGF deletion on whole bone geometry was assessed between sexes, although significant differences between Ocn
VEGFKO and WT were identified only in females. Our results suggest that bone‐derived VEGF regulates matrix mineralization and vascularization distinctly in males and females, which results in divergent physical bone traits.

Design and Preclinical Development of TransCon PTH, an Investigational Sustained‐Release PTH Replacement Therapy for Hypoparathyroidism

09-10-2019 – Lars Holten‐Andersen, Susanne Pihl, Caroline E Rasmussen, Joachim Zettler, Guillaume Maitro, Julia Baron, Stefan Heinig, Eric Hoffmann, Thomas Wegge, Mathias Krusch, Frank Faltinger, Steffen Killian, Kennett Sprogoe, David B Karpf, Vibeke Miller Breinholt, Felix Cleemann

Journal Article

ABSTRACTHypoparathyroidism (HP) is a condition of parathyroid hormone (PTH) deficiency leading to abnormal calcium and phosphate metabolism. The mainstay of therapy consists of vitamin D and calcium supplements, as well as adjunct Natpara (PTH(1‐84)). However, neither therapy optimally controls urinary calcium (u
Ca) or significantly reduces the incidence of hypercalcemia and hypocalcemia. Trans
Con PTH, a sustained‐release prodrug of PTH(1‐34) in development for the treatment of HP, was designed to overcome these limitations. To determine the pharmacokinetics and pharmacodynamics of Trans
Con PTH, single and repeat s.c. dose studies were performed in rats and monkeys. Trans
Con PTH demonstrated a half‐life of 28 and 34 hours in rats and monkeys, respectively. After repeated dosing, an infusion‐like profile of the released PTH, characterized by low peak‐to‐trough levels, was obtained in both species. In intact rats and monkeys, daily subcutaneous administration of Trans
Con PTH was associated with increases in serum calcium (s
Ca) levels and decreases in serum phosphate levels (s
P). In monkeys, at a single dose of Trans
Con PTH that increased s
Ca levels within the normal range, a concurrent decrease in u
Ca excretion was observed. In 4‐week repeat‐dose studies in intact rats and monkeys, u
Ca excretion was comparable to controls across all dose levels despite increases in s
Ca levels. Further, in a rat model of HP, Trans
Con PTH normalized s
Ca and s
P levels 24 hours per day. This was in contrast to only transient trends toward normalization of s
Ca and s
P levels with an up to 6‐fold higher molar dose of PTH(1‐84). After repeated dosing to HP rats, u
Ca excretion transiently increased, corresponding to increases in s
Ca above normal range, but at the end of the treatment period, u
Ca excretion was generally comparable to sham controls. Trans
Con PTH was well tolerated and the observed pharmacokinetics and pharmacodynamics were in line with the expected action of physiological replacement of PTH. © 2019 American Society for Bone and Mineral Research.

Glycemic Control and Insulin Treatment Alter Fracture Risk in Older Men With Type 2 Diabetes Mellitus

09-10-2019 – Richard H Lee, Richard Sloane, Carl Pieper, Kenneth W Lyles, Robert A Adler, Courtney Houtven, Joanne LaFleur, Cathleen Colón‐Emeric

Journal Article

ABSTRACTDiabetes mellitus among older men has been associated with increased bone mineral density but paradoxically increased fracture risk. Given the interactions among medication treatment, glycemic control, and diabetes‐associated comorbidities, the relative effects of each factor remains unclear. This retrospective study includes 652,901 male veterans aged ≥65 years with diabetes and baseline hemoglobin A1c (Hb
A1c) value. All subjects received primary care in the Veterans Health Administration (VHA) from 2000 to 2010. Administrative data included ICD9 diagnoses and pharmacy records and was linked to Medicare fee‐for‐service data. Hazard ratios (HR) for any clinical fracture and hip fracture were calculated using competing risk hazards models, adjusted for fracture risk factors including age, race/ethnicity, body mass index (BMI), alcohol and tobacco use, rheumatoid arthritis, corticosteroid use, as well as diabetes‐related comorbidities including cardiovascular disease, chronic kidney disease, and peripheral neuropathy. Hb
A1c <6.5% was associated with a higher risk of any clinical fracture (HR = 1.08, 95% confidence interval CI 1.06–1.11) compared with the reference Hb
A1c of 7.5% to 8.5%. Fracture risk was not increased among those with A1c ≥8.5%, nor among those with A1c 6.5% to 7.5%. Use of insulin was independently associated with greater risk of fracture (HR = 1.10, 95% CI 1.07–1.12). There was a significant interaction between insulin use and Hb
A1c level, (p < 0.001), such that those using insulin with Hb
A1c <6.5% had HR = 1.23 and those with Hb
A1c 6.5% to 7.5% had HR = 1.15. Metformin use was associated with decreased fracture risk (HR = 0.88, 95% CI 0.87–0.90). We conclude that among older men with diabetes, those with Hb
A1c lower than 6.5% are at increased risk for any clinical and hip fracture. Insulin use is associated with higher fracture risk, especially among those with tight glycemic control. Our findings demonstrate the importance of the treatment regimen and avoiding hypoglycemia for fracture prevention in older men with diabetes. © 2019 American Society for Bone and Mineral Research.

Vitamin D metabolism revised: fall of dogmas

07-10-2019 – Roger Bouillon, Dan Bikle

Journal Article

Denosumab Prevents Early Periprosthetic Bone Loss after Uncemented Total Hip Arthroplasty: Results from a Randomized Placebo‐Controlled Clinical Trial

07-10-2019 – Andreas Nyström, Demostenis Kiritopoulos, Gösta Ullmark, Jens Sörensen, Marianne Petrén‐Mallmin, Jan Milbrink, Nils P. Hailer, Hans Mallmin

Journal Article

Abstract
Implant loosening is the most common indication for revision surgery after total hip arthroplasty (THA). Although bone resorption around the implants plays a pivotal role in the pathophysiology of loosening, it is unknown whether potent early inhibition of osteoclasts could mitigate this process and thus reduce the need for revision surgery.
We performed a randomized, double‐blind, placebo‐controlled phase two trial in 64 patients aged 35‐65 years with unilateral osteoarthritis of the hip. They underwent surgery with an uncemented THA and were randomized to either two subcutaneous doses of denosumab (n=32) or placebo (n=32) given 1‐3 days and 6 months after surgery.
Patients were followed for 24 months. Primary outcome was periprosthetic bone mineral density (BMD) of the hip at 12 months as measured by dual‐energy X‐ray absorptiometry. In addition, 18F sodium fluoride positron emission tomography/CT (F‐PET) was performed in half of the patients for analysis of periprosthetic standardized uptake value (SUV). Analyses were made according to intention‐to‐treat principles. Clinical
Trials.gov 2011‐001481‐18, NCT01630941.
Denosumab potently inhibited early periprosthetic bone loss. After 12 months, BMD in the denosumab group was 32% (95% confidence interval CI 22‐44) higher in Gruen zone 7 and 11% (95% CI 8‐15) higher in zones 1‐7. After 24 months, the difference in BMD between groups had decreased to 15% (95% CI 4‐27) in zone 7 and 4% (95% CI 0‐8) in zones 1‐7. In both groups, SUV increased after surgery but the increase was less pronounced in the denosumab group. Biochemical markers of bone metabolism decreased in the denosumab group in the first 12 months but a rebound effect with marker concentrations above baseline was observed after 24 months.
Denosumab potently prevents early periprosthetic bone loss after uncemented THA; however, the effect diminishes after discontinuation of treatment. Further research is needed to determine whether this bone loss will prove to be of clinical importance and, if so, whether the positive effect seen in this study could be preserved by either prolonged treatment with denosumab or additional antiresorptive treatment.
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Fracture Risk in Trans Women and Trans Men Using Long‐Term Gender‐Affirming Hormonal Treatment: A Nationwide Cohort Study

07-10-2019 – Chantal M Wiepjes, Christel JM Blok, Annemieke S Staphorsius, Nienke M Nota, Mariska C Vlot, Renate T Jongh, Martin Heijer

Journal Article

ABSTRACTConcerns about bone health in transgender people using gender‐affirming hormonal treatment (HT) exist, but the fracture risk is not known. In this nationwide cohort study, we aimed to compare the fracture incidence in transgender people using long‐term HT with an age‐matched reference population. All adult transgender people who started HT before 2016 at our gender‐identity clinic were included and were linked to a random population‐based sample of 5 age‐matched reference men and 5 age‐matched reference women per person. Fracture incidence was determined using diagnoses from visits to hospital emergency rooms nationwide between 2013 and 2015. A total of 1089 trans women aged <50 years (mean 38 ± 9 years) and 934 trans women aged ≥50 years (mean 60 ± 8 years) using HT for median 8 (interquartile range IQR 3–16) and 19 (IQR 11–29) years, respectively, were included. A total of 2.4% of the trans women aged <50 years had a fracture, whereas 3.0% of the age‐matched reference men (odds ratio OR = 0.78, 95% confidence interval CI 0.51–1.19) and 1.6% of the age‐matched reference women (OR = 1.49, 95% CI 0.96–2.32) experienced a fracture. In trans women aged ≥50 years, 4.4% experienced a fracture compared with 2.4% of the age‐matched reference men (OR = 1.90, 95% CI 1.32–2.74) and 4.2% of the age‐matched reference women (OR = 1.05, 95% CI 0.75–1.49). A total of 1036 trans men (40 ± 14 years) using HT for median 9 (IQR 2–22) years were included. Fractures occurred in 1.7% of the trans men, 3.0% of the age‐matched reference men (OR = 0.57, 95% CI 0.35–0.94), and 2.2% of the age‐matched reference women (OR = 0.79, 95% CI 0.48–1.30). In conclusion, fracture risk was higher in older trans women compared with age‐matched reference men. In young trans women, fracture risk tended to be increased compared with age‐matched reference women. Fracture risk was not increased in young trans men. © 2019 American Society for Bone and Mineral Research. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

A Personal Tribute to Elizabeth Barrett‐Connor

03-10-2019 – Jane A Cauley

Journal Article

Increased Risk of Bone Fractures in Hemodialysis Patients Treated with Proton Pump Inhibitors in Real World: Results from the Dialysis Outcomes and Practice Patterns Study (DOPPS)

03-10-2019 – “Maria Fusaro, Graziella DArrigo, Annalisa Pitino, Giorgio Iervasi, Francesca Tentori, Bruce Robinson, Andrea Aghi, Brian Bieber, Keith Mccullogh, Fabrizio Fabris, Mario Plebani, Sandro Giannini, Maurizio Gallieni, Giovanni Tripepi”

Journal Article

ABSTRACTLong‐term treatment with proton pump inhibitors (PPIs) is associated with an increased risk of fractures in the general population. PPIs are widely prescribed to dialysis patients but to date no study has specifically tested, by state‐of‐art statistical methods, the relationship between use of PPIs and fractures in this patient population. This study aimed to assess whether use of PPIs is associated with bone fractures (ie, hip fractures and fractures other than hip fractures) in a large international cohort of hemodialysis patients. We considered an observational prospective cohort of 27,097 hemodialysis patients from the Dialysis Outcomes and Practice Patterns Study (DOPPS). Data analysis was performed by the Fine and Gray method, considering the competitive risk of mortality, as well as by a cause‐specific hazards Cox model with death as a censoring event and matching patients according to the prescription time. Of 27,097 hemodialysis patients, 13,283 patients (49%) were on PPI treatment. Across the follow‐up period (median, 19 months), 3.8 bone fractures × 100 person‐years and 1.2 hip fractures × 100 person‐years occurred. In multiple Cox models, considering the competitive risk of mortality, the incidence rate of bone (subdistribution hazard ratio SHR 1.22; 95% CI, 1.10 to 1.36; p < 0.001) and hip fractures (SHR 1.35; 95% CI, 1.13 to 1.62; p = 0.001) was significantly higher in PPI‐treated than in PPI‐untreated patients. These findings also held true in multiple, cause‐specific, hazards Cox models matching patients according to the prescription time (bone fractures: HR 1.47; 95% CI, 1.23 to 1.76; p < 0.001; hip fractures: HR 1.85; 95% CI, 1.37 to 2.50; p < 0.001). The use of PPIs requires caution and a careful evaluation of risks/benefits ratio in hemodialysis patients. © 2019 American Society for Bone and Mineral Research.

Burosumab Improved Histomorphometric Measures of Osteomalacia in Adults with X‐Linked Hypophosphatemia: A Phase 3, Single‐Arm, International Trial

01-10-2019 – Karl L Insogna, Frank Rauch, Peter Kamenický, Nobuaki Ito, Takuo Kubota, Akie Nakamura, Lin Zhang, Matt Mealiffe, Javier San Martin, Anthony A Portale

Journal Article

ABSTRACTIn adults with X‐linked hypophosphatemia (XLH), excess FGF23 impairs renal phosphate reabsorption and suppresses production of 1,25‐dihydroxyvitamin D, resulting in chronic hypophosphatemia and persistent osteomalacia. Osteomalacia is associated with poor bone quality causing atraumatic fractures, pseudofractures, delayed fracture healing, and bone pain. Burosumab is a fully human monoclonal antibody against FGF23. UX023‐CL304 is an ongoing, open‐label, single‐arm, phase 3 study investigating the efficacy of subcutaneous burosumab, 1.0 mg/kg administered every 4 weeks, in improving osteomalacia in adults with XLH who have not been treated for at least 2 years before enrollment. The primary endpoint was improvement in osteoid volume/bone volume assessed by transiliac bone biopsies obtained at baseline and week 48. Additional assessments included serum phosphorus, markers of bone turnover, fracture/pseudofracture healing, and safety. Fourteen subjects enrolled, 13 completed 48 weeks, and 11 completed paired biopsies. All osteomalacia‐related histomorphometric measures improved significantly at week 48 (mean percent change: osteoid volume/bone volume, –54%, osteoid thickness, –32%, osteoid surface/bone surface, –26%, median mineralization lag time, –83%). Mean serum phosphorus concentration averaged across the mid‐point of the dose cycle between weeks 0 and 24 was 3.3 mg/d
L, a 50% increase from 2.2 mg/d
L at baseline. Markers of bone formation and resorption increased at week 48 (least squares LS mean increase: P1NP, +77%; CTx, +36%; both p < 0.0001). All subjects had one or more treatment‐emergent adverse event (AE). Most AEs were mild to moderate in severity. Two subjects experienced serious AEs (migraine; paresthesia) that were unrelated to treatment and resolved. Eleven subjects had 18 biopsy procedure‐related AEs: 14 for pain, two for itch, and one each for headache and bandage irritation. No deaths or incidents of hyperphosphatemia occurred. In conclusion, by normalizing phosphate homeostasis, burosumab significantly improved osteomalacia in adults with XLH, which likely explains the improved fracture healing and amelioration of skeletal complications. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

American Society for Bone and Mineral Research‐Orthopaedic Research Society Joint Task Force Report on Cell‐Based Therapies

23-09-2019 – “Regis J OKeefe, Rocky S Tuan, Nancy E Lane, Frank Barry, Bruce A Bunnell, Céline Colnot, Matthew T Drake, Hicham Drissi, Lisa A Fortier, Robert E Guldberg, David G Little, Mary F Marshall, Jeremy J Mao, Norimasa Nakamura, Pamela G Robey, Vicki Rosen, David W Rowe, Edward M. Schwarz”

Journal Article

ABSTRACTCell‐based therapies, defined here as the delivery of cells in vivo to treat disease, have recently gained increasing public attention as a potentially promising approach to restore structure and function to musculoskeletal tissues. Although cell‐based therapy has the potential to improve the treatment of disorders of the musculoskeletal system, there is also the possibility of misuse and misrepresentation of the efficacy of such treatments. The medical literature contains anecdotal reports and research studies, along with web‐based marketing and patient testimonials supporting cell‐based therapy. Both the American Society for Bone and Mineral Research (ASBMR) and the Orthopaedic Research Society (ORS) are committed to ensuring that the potential of cell‐based therapies is realized through rigorous, reproducible, and clinically meaningful scientific discovery. The two organizations convened a multidisciplinary and international Task Force composed of physicians, surgeons, and scientists who are recognized experts in the development and use of cell‐based therapies. The Task Force was charged with defining the state‐of‐the art in cell‐based therapies and identifying the gaps in knowledge and methodologies that should guide the research agenda. The efforts of this Task Force are designed to provide researchers and clinicians with a better understanding of the current state of the science and research needed to advance the study and use of cell‐based therapies for skeletal tissues. The design and implementation of rigorous, thorough protocols will be critical to leveraging these innovative treatments and optimizing clinical and functional patient outcomes. In addition to providing specific recommendations and ethical considerations for preclinical and clinical investigations, this report concludes with an outline to address knowledge gaps in how to determine the cell autonomous and nonautonomous effects of a donor population used for bone regeneration. © 2019 American Society for Bone and Mineral Research.

Much‐Needed Clarification and Guidance on Cell‐Based Therapies for Musculoskeletal Disorders

23-09-2019 – Matthew P. Murphy, Derrick C. Wan, Michael T. Longaker

Editorial

Secondary Fracture Prevention: Consensus Clinical Recommendations from a Multistakeholder Coalition

20-09-2019 – Robert B. Conley, Gemma Adib, Robert A. Adler, Kristina E. Akesson, Ivy M Alexander, Kelly C. Amenta, Robert D. Blank, William Timothy Brox, Emily E. Carmody, Karen Chapman‐Novakofski, Bart L. Clarke, Kathleen M Cody, Cyrus Cooper, Carolyn J. Crandall, Douglas R. Dirschl, Thomas J Eagen, Ann L. Elderkin, Masaki Fujita, Susan L Greenspan, Philippe Halbout, Marc C. Hochberg, Muhammad Javaid, Kyle J. Jeray, Ann E Kearns, Toby King, Thomas F. Koinis, Jennifer Scott Koontz, Martin Kuzma, Carleen Lindsey, Mattias Lorentzon, George P. Lyritis, Laura Boehnke Michaud, Armando Miciano, Suzanne N Morin, Nadia Mujahid, Nicola Napoli, Thomas P. Olenginski, J. Edward Puzas, Stavroula Rizou, Clifford J Rosen, Kenneth Saag, Elizabeth Thompson, Laura L. Tosi, Howard Tracer, Sundeep Khosla, Doug Kiel

Journal Article

ABSTRACTOsteoporosis‐related fractures are undertreated, due in part to misinformation about recommended approaches to patient care and discrepancies among treatment guidelines. To help bridge this gap and improve patient outcomes, the American Society for Bone and Mineral Research assembled a multistakeholder coalition to develop clinical recommendations for the optimal prevention of secondary fracture among people aged 65 years and older with a hip or vertebral fracture. The coalition developed 13 recommendations (7 primary and 6 secondary) strongly supported by the empirical literature. The coalition recommends increased communication with patients regarding fracture risk, mortality and morbidity outcomes, and fracture risk reduction. Risk assessment (including fall history) should occur at regular intervals with referral to physical and/or occupational therapy as appropriate. Oral, intravenous, and subcutaneous pharmacotherapies are efficacious and can reduce risk of future fracture. Patients need education, however, about the benefits and risks of both treatment and not receiving treatment. Oral bisphosphonates alendronate and risedronate are first‐line options and are generally well tolerated; otherwise, intravenous zoledronic acid and subcutaneous denosumab can be considered. Anabolic agents are expensive but may be beneficial for selected patients at high risk. Optimal duration of pharmacotherapy is unknown but because the risk for second fractures is highest in the early post‐fracture period, prompt treatment is recommended. Adequate dietary or supplemental vitamin D and calcium intake should be assured. Individuals being treated for osteoporosis should be re‐evaluated for fracture risk routinely, including via patient education about osteoporosis and fractures and monitoring for adverse treatment effects. Patients should be strongly encouraged to avoid tobacco, consume alcohol in moderation at most, and engage in regular exercise and fall prevention strategies. Finally, referral to endocrinologists or other osteoporosis specialists may be warranted for individuals who experience repeated fracture or bone loss and those with complicating comorbidities (e.g., hyperparathyroidism, chronic kidney disease).
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A rare mutation in SMAD9 associated with high bone mass identifies the SMAD‐dependent BMP signalling pathway as a potential anabolic target for osteoporosis

16-09-2019 – Celia L Gregson, Dylan Bergen, Paul Leo, Richard B. Sessions, Lawrie Wheeler, April Hartley, Scott Youlten, Peter I Croucher, Aideen M. McInerney‐Leo, William Fraser, Jonathan C.Y. Tang, Lisa Anderson, Mhairi Marshall, Leon Sergot, Lavinia Paternoster, George Davey‐Smith, The AOGC Consortium, Matthew A Brown, Chrissy Hammond, John P Kemp, Jon H Tobias, Emma L Duncan

Journal Article

Abstract
Novel anabolic drug targets are needed to treat osteoporosis. Having established a large national cohort with unexplained high bone mass (HBM), we aimed to identify a novel monogenic cause of HBM and provide insight into a regulatory pathway potentially amenable to therapeutic intervention. We investigated a pedigree with unexplained HBM in whom previous sequencing had excluded known causes of monogenic HBM. Whole exome sequencing identified a rare (minor allele frequency 0.0023), highly evolutionarily conserved, missense mutation in SMAD9 (c.65T>C, p.
Leu22Pro) segregating with HBM in this autosomal dominant family. The same mutation was identified in another two unrelated individuals both with HBM. In‐silico protein modelling predicts the mutation severely disrupts the MH1 DNA‐binding domain of SMAD9. Affected individuals have bone mineral density BMD Z‐Scores +3 to +5, mandible enlargement, a broad frame, torus palatinus/ mandibularis, pes planus, increased shoe size and a tendency to sink when swimming. Peripheral quantitative computer tomography (p
QCT) measurement demonstrates increased trabecular volumetric BMD and increased cortical thickness conferring greater predicted bone strength; bone turnover markers are low/normal. Notably, fractures and nerve compression are not seen. Both genome‐wide, and gene‐based association testing involving estimated‐BMD measured at the heel in 362,924 white British subjects from the UK Biobank Study showed strong associations with SMAD9 (PGWAS = 6 x 10‐16; PGENE = 8 × 10‐17). Furthermore, we found Smad9 to be highly expressed in both murine cortical bone derived osteocytes and skeletal elements of zebrafish larvae. Our findings support SMAD9 as a novel HBM gene, and a potential novel osteoanabolic target for osteoporosis therapeutics. SMAD9 is thought to inhibit bone morphogenetic protein (BMP) dependent target gene transcription to reduce osteoblast activity. Thus, we hypothesise SMAD9 c.65T>C is a loss‐of‐function mutation reducing BMP inhibition. Lowering SMAD9 as a potential novel anabolic mechanism for osteoporosis therapeutics warrants further investigation.

A Lot of Progress, With More to Be Done: A Response to NIH Pathways to Prevention Report “Research Gaps for Long‐Term Drug Therapies for Osteoporotic Fracture Prevention”

13-09-2019 – Benjamin Z Leder, Bart L Clarke, Elizabeth Shane, Sundeep Khosla, Douglas P Kiel

Journal Article

ABSTRACTThe public health implications of osteoporosis are enormous but the disease remains underdiagnosed and undertreated. In October 2018, the National Institutes of Health (NIH) convened a Pathways to Prevention (P2P) Workshop entitled “Appropriate Use of Drug Therapies for Osteoporotic Fracture Prevention” designed to identify research gaps, suggest future research opportunities, and advance the field through an evidence‐based assessment. By design, the P2P report focused on “gaps” in our knowledge base. Unfortunately, however, the report did not sufficiently acknowledge the current evidence that unequivocally demonstrates the therapeutic efficacy of existing pharmacologic therapies for osteoporosis, which has the potential to exacerbate the current crises in osteoporosis diagnosis and treatment. © 2019 American Society for Bone and Mineral Research.

Treatment of Human Immunodeficiency Virus Infection With Tenofovir Disoproxil Fumarate–Containing Antiretrovirals Maintains Low Bone Formation Rate, But Increases Osteoid Volume on Bone Histomorphometry

13-09-2019 – Janaina Ramalho, Carolina Steller Wagner Martins, Juliana Galvão, Luzia N Furukawa, Wagner V Domingues, Ivone B Oliveira, Luciene M dos Reis, Rosa MR Pereira, Thomas L Nickolas, Michael T Yin, Margareth Eira, Vanda Jorgetti, Rosa MA Moyses

Journal Article

ABSTRACTBone mineral density (BMD) loss is a known complication of human immunodeficiency virus (HIV) infection and its treatment, particularly with tenofovir disoproxil fumarate (TDF)‐containing antiretroviral regimens. Although renal proximal tubular dysfunction and phosphaturia is common with TDF, it is unknown whether BMD loss results from inadequate mineralization. We evaluated change in BMD by dual‐energy X‐ray absorptiometry (DXA) and bone histomorphometry by tetracycline double‐labeled transiliac crest biopsies in young men living with HIV before (n = 20) and 12 months after (n = 16) initiating TDF/lamivudine/efavirenz. We examined relationships between calciotropic hormones, urinary phosphate excretion, pro‐inflammatory and pro‐resorptive cytokines, and bone remodeling‐related proteins with changes in BMD and histomorphometry. Mean age was 29.6 ± 5.5 years, with mean CD4 + T cell count of 473 ± 196 cells/mm3. At baseline, decreased bone formation rate and increased mineralization lag time were identified in 16 (80%) and 12 (60%) patients, respectively. After 12 months, we detected a 2% to 3% decrease in lumbar spine and hip BMD by DXA. By histomorphometry, we observed no change in bone volume/total volume (BV/TV) and trabecular parameters, but rather, increases in cortical thickness, osteoid volume, and osteoblast and osteoclast surfaces. We did not observe significant worsening of renal phosphate excretion or mineralization parameters. Increases in PTH correlated with decreased BMD but not histomorphometric parameters. Overall, these data suggest abnormalities in bone formation and mineralization occur with HIV infection and are evident at early stages. With TDF‐containing antiretroviral therapy (ART), there is an increase in bone remodeling, reflected by increased osteoblast and osteoclast surfaces, but a persistence in mineralization defect, resulting in increased osteoid volume. © 2019 American Society for Bone and Mineral Research.

ΔFosB Requires Galanin, but not Leptin, to Increase Bone Mass via the Hypothalamus, but both are needed to increase Energy expenditure

13-09-2019 – Anna Idelevich, Kazusa Sato, Kenichi Nagano, Glenn Rowe, Francesca Gori, Roland Baron

Journal Article

ABSTRACTEnergy metabolism and bone homeostasis share several regulatory pathways. The AP1 transcription factor ΔFos
B and leptin both regulate energy metabolism and bone, yet whether their pathways intersect is not known. Transgenic mice overexpressing ΔFos
B under the control of the Enolase 2 (ENO2) promoter exhibit high bone mass, high energy expenditure, low fat mass, and low circulating leptin levels. Because leptin is a regulator of bone and ΔFos
B acts on leptin‐responsive ventral hypothalamic (VHT) neurons to induce bone anabolism, we hypothesized that regulation of leptin may contribute to the central actions of ΔFos
B in the VHT. To address this question, we used adeno‐associated virus (AAV) expression of ΔFos
B in the VHT of leptin‐deficient ob/ob mice and genetic crossing of ENO2‐ΔFos
B with ob/ob mice. In both models, leptin deficiency prevented ΔFos
B‐triggered reduction in body weight, increase in energy expenditure, increase in glucose utilization, and reduction in pancreatic islet size. In contrast, leptin deficiency failed to prevent ΔFos
B‐triggered increase in bone mass. Unlike leptin deficiency, galanin deficiency blocked both the metabolic and the bone ΔFos
B‐induced effects. Overall, our data demonstrate that, while the catabolic energy metabolism effects of ΔFos
B require intact leptin and galanin signaling, the bone mass–accruing effects of ΔFos
B require galanin but are independent of leptin. © 2019 American Society for Bone and Mineral Research.

Ultrasound‐Based Estimates of Cortical Bone Thickness and Porosity Are Associated With Nontraumatic Fractures in Postmenopausal Women: A Pilot Study

13-09-2019 – J‐G Minonzio, N Bochud, Q Vallet, D Ramiandrisoa, A Etcheto, K Briot, S Kolta, C Roux, P Laugier

Journal Article

ABSTRACTRecent ultrasound (US) axial transmission techniques exploit the multimode waveguide response of long bones to yield estimates of cortical bone structure characteristics. This pilot cross‐sectional study aimed to evaluate the performance at the one‐third distal radius of a bidirectional axial transmission technique (BDAT) to discriminate between fractured and nonfractured postmenopausal women. Cortical thickness (Ct.
Th) and porosity (Ct.
Po) estimates were obtained for 201 postmenopausal women: 109 were nonfractured (62.6 ± 7.8 years), 92 with one or more nontraumatic fractures (68.8 ± 9.2 years), 17 with hip fractures (66.1 ± 10.3 years), 32 with vertebral fractures (72.4 ± 7.9 years), and 17 with wrist fractures (67.8 ± 9.6 years). The areal bone mineral density (a
BMD) was obtained using DXA at the femur and spine. Femoral a
BMD correlated weakly, but significantly with Ct.
Th (R = 0.23, p < 0.001) and Ct.
Po (R = ‐0.15, p < 0.05). Femoral a
BMD and both US parameters were significantly different between the subgroup of all nontraumatic fractures combined and the control group (p < 0.05). The main findings were that (1) Ct.
Po was discriminant for all nontraumatic fractures combined (OR = 1.39; area under the receiver operating characteristic curve AUC equal to 0.71), for vertebral (OR = 1.96; AUC = 0.84) and wrist fractures (OR = 1.80; AUC = 0.71), whereas Ct.
Th was discriminant for hip fractures only (OR = 2.01; AUC = 0.72); there was a significant association (2) between increased Ct.
Po and vertebral and wrist fractures when these fractures were not associated with any measured a
BMD variables; (3) between increased Ct.
Po and all nontraumatic fractures combined independently of a
BMD neck; and (4) between decreased Ct.
Th and hip fractures independently of a
BMD femur. BDAT variables showed comparable performance to that of a
BMD neck with all types of fractures (OR = 1.48; AUC = 0.72) and that of a
BMD femur with hip fractures (OR = 2.21; AUC = 0.70). If these results are confirmed in prospective studies, cortical BDAT measurements may be considered useful for assessing fracture risk in postmenopausal women. © 2019 American Society for Bone and Mineral Research.

Bone‐Forming and Antiresorptive Effects of Romosozumab in Postmenopausal Women With Osteoporosis: Bone Histomorphometry and Microcomputed Tomography Analysis After 2 and 12 Months of Treatment

13-09-2019 – Pascale Chavassieux, Roland Chapurlat, Nathalie Portero‐Muzy, Jean‐Paul Roux, Pedro Garcia, Jacques P Brown, Cesar Libanati, Rogely W Boyce, Andrea Wang, Andreas Grauer

Journal Article

ABSTRACTSclerostin, a protein produced by osteocytes, inhibits bone formation. Administration of sclerostin antibody results in increased bone formation in multiple animal models. Romosozumab, a humanized sclerostin antibody, has a dual effect on bone, transiently increasing serum biochemical markers of bone formation and decreasing serum markers of bone resorption, leading to increased BMD and reduction in fracture risk in humans. We aimed to evaluate the effects of romosozumab on bone tissue. In a subset of 107 postmenopausal women with osteoporosis in the multicenter, international, randomized, double‐blind, placebo‐controlled Fracture Study in Postmenopausal Women with Osteoporosis (FRAME), transiliac bone biopsies were performed either after 2 (n = 34) or 12 (n = 73) months of treatment with 210 mg once monthly of romosozumab or placebo to evaluate histomorphometry and microcomputed tomography‐based microarchitectural endpoints. After 2 months, compared with either baseline values assessed after a quadruple fluorochrome labeling or placebo, significant increases (P < 0.05 to P < 0.001) in dynamic parameters of formation (median MS/BS: romosozumab 1.51% and 5.64%; placebo 1.60% and 2.31% at baseline and month 2, respectively) were associated with a significant decrease compared with placebo in parameters of resorption in cancellous (median ES/BS: placebo 3.4%, romosozumab 1.8%; P = 0.022) and endocortical (median ES/BS: placebo 6.3%, romosozumab 1.6%; P = 0.003) bone. At 12 months, cancellous bone formation was significantly lower (P < 0.05 to P < 0.001) in romosozumab versus placebo and the lower values for resorption endpoints seen at month 2 persisted (P < 0.001), signaling a decrease in bone turnover (P = 0.006). No significant change was observed in periosteal and endocortical bone. This resulted in an increase in bone mass and trabecular thickness with improved trabecular connectivity, without significant modification of cortical porosity at month 12. In conclusion, romosozumab produced an early and transient increase in bone formation, but a persistent decrease in bone resorption. Antiresorptive action eventually resulted in decreased bone turnover. This effect resulted in significant increases in bone mass and improved microarchitecture. © 2019 American Society for Bone and Mineral Research.

Compromised Exercise Capacity and Mitochondrial Dysfunction in the Osteogenesis Imperfecta Murine (oim) Mouse Model

13-09-2019 – Victoria L Gremminger, Youngjae Jeong, Rory P Cunningham, Grace M Meers, R Scott Rector, Charlotte L Phillips

Journal Article

ABSTRACTOsteogenesis imperfecta (OI) is a heritable connective tissue disorder that most often arises from type I collagen—COL1A1 and COL1A2—gene defects leading to skeletal fragility, short stature, blue‐gray sclera, and muscle weakness. Relative to the skeletal fragility, muscle weakness is much less understood. Recent investigations into OI muscle weakness in both patients and mouse models have revealed the presence of an inherent muscle pathology. Understanding the mechanisms responsible for OI muscle weakness is critical, particularly in light of the extensive cross‐talk between muscle and bone via mechanotransduction and biochemical signaling. In the following study we initially subjected WT and oim/oim mice, modeling severe human OI type III, to either weight‐bearing (voluntary wheel‐running) or non‐weight‐bearing (swimming) exercise regimens as a modality to improve muscle strength and ultimately bone strength. The oim/oim mice ran only 35% to 42% of the distance run by age‐ and sex‐matched WT mice and exhibited little improvement with either exercise regimen. Upon further investigation, we determined that oim/oim gastrocnemius muscle exhibited severe mitochondrial dysfunction as characterized by a 52% to 65% decrease in mitochondrial respiration rates, alterations in markers of mitochondrial biogenesis, mitophagy, and the electron transport chain components, as well as decreased mitochondrial citrate synthase activity, relative to age‐ and sex‐matched WT gastrocnemius muscle. Thus, mitochondrial dysfunction in the oim/oim mouse likely contributes to compromised muscle function and reduced physical activity levels. © 2019 American Society for Bone and Mineral Research.

Chondrocyte‐Specific RUNX2 Overexpression Accelerates Post‐traumatic Osteoarthritis Progression in Adult Mice

13-09-2019 – Sarah E Catheline, Donna Hoak, Martin Chang, John P Ketz, Matthew J Hilton, Michael J Zuscik, Jennifer H Jonason

Journal Article

ABSTRACTRUNX2 is a transcription factor critical for chondrocyte maturation and normal endochondral bone formation. It promotes the expression of factors catabolic to the cartilage extracellular matrix and is upregulated in human osteoarthritic cartilage and in murine articular cartilage following joint injury. To date, in vivo studies of RUNX2 overexpression in cartilage have been limited to forced expression in osteochondroprogenitor cells preventing investigation into the effects of chondrocyte‐specific RUNX2 overexpression in postnatal articular cartilage. Here, we used the Rosa26 Runx2 allele in combination with the inducible Col2a1 Cre
ERT2 transgene or the inducible Acan Cre
ERT2 knock‐in allele to achieve chondrocyte‐specific RUNX2 overexpression (OE) during embryonic development or in the articular cartilage of adult mice, respectively. RUNX2 OE was induced at embryonic day 13.5 (E13.5) for all developmental studies. Histology and in situ hybridization analyses suggest an early onset of chondrocyte hypertrophy and accelerated terminal maturation in the limbs of the RUNX2 OE embryos compared to control embryos. For all postnatal studies, RUNX2 OE was induced at 2 months of age. Surprisingly, no histopathological signs of cartilage degeneration were observed even 6 months following induction of RUNX2 OE. Using the meniscal/ligamentous injury (MLI), a surgical model of knee joint destabilization and meniscal injury, however, we found that RUNX2 OE accelerates the progression of cartilage degeneration following joint trauma. One month following MLI, the numbers of MMP13‐positive and TUNEL‐positive chondrocytes were significantly greater in the articular cartilage of the RUNX2 OE joints compared to control joints and 2 months following MLI, histomorphometry and Osteoarthritis Research Society International (OARSI) scoring revealed decreased cartilage area in the RUNX2 OE joints. Collectively, these results suggest that although RUNX2 overexpression alone may not be sufficient to initiate the OA degenerative process, it may predetermine the rate of OA onset and/or progression following traumatic joint injury. © 2019 American Society for Bone and Mineral Research.

18F‐NaF PET/CT IMAGING IN FIBROUS DYSPLASIA OF BONE

13-09-2019 – GeorgiosZ Papadakis, GeorgiosC Manikis, ApostolosH Karantanas, Pablo Florenzano, Ulas Bagci, Kostas Marias, MichaelT Collins, AlisonM Boyce

Journal Article

ABSTRACTFibrous dysplasia (FD) is a mosaic skeletal disorder resulting in fractures, deformity, and functional impairment. Clinical evaluation has been limited by a lack of surrogate endpoints capable of quantitating disease activity. The purpose of this study was to investigate the utility of 18F‐Na
F PET/CT imaging in quantifying disease activity in patients with FD. Fifteen consecutively evaluated subjects underwent whole‐body 18F‐Na
F PET/CT scans, and FD burden was assessed by quantifying FD‐related 18F‐Na
F activity. 18F‐Na
F PET/CT parameters obtained included (i) SUVmax (standardized uptake value SUV of the FD lesion with the highest uptake); (ii) SUVmean (average SUV of all 18F‐Na
F–positive FD lesions); (iii) total volume of all 18F‐Na
F–positive FD lesions (TV); and (iv) total FD lesion activity determined as the product of TV multiplied by SUVmean (TA =  TV ×  SUVmean) (TA). Skeletal outcomes, functional outcomes, and bone turnover markers were correlated with 18F‐Na
F PET/CT parameters. TV and TA of extracranial FD lesions correlated strongly with skeletal outcomes including fractures and surgeries (p values ≤ 0.003). Subjects with impaired ambulation and scoliosis had significantly higher TV and TA values (P < 0.05), obtained from extracranial and spinal lesions, respectively. Craniofacial surgeries correlated with TV and TA of skull FD lesions (P < 0.001). Bone turnover markers, including alkaline phosphatase, N‐telopeptides, and osteocalcin, were strongly correlated with TV and TA (P < 0.05) extracted from FD lesions in the entire skeleton. No associations were identified with SUVmax or SUVmean. Bone pain and age did not correlate with 18F‐Na
F PET/CT parameters. FD burden evaluated by 18F‐Na
F‐PET/CT facilitates accurate assessment of FD activity, and correlates quantitatively with clinically‐relevant skeletal outcomes. © 2019 American Society for Bone and Mineral Research.

Women With Pregnancy and Lactation–Associated Osteoporosis (PLO) Have Low Bone Remodeling Rates at the Tissue Level

13-09-2019 – Adi Cohen, Mafo Kamanda‐Kosseh, David W Dempster, Hua Zhou, Ralph Müller, Elliott Goff, Ivelisse Colon, Mariana Bucovsky, Julie Stubby, Thomas L Nickolas, Emily M Stein, Robert R Recker, Joan M Lappe, Elizabeth Shane

Journal Article

ABSTRACTPregnancy and lactation–associated osteoporosis (PLO) is a rare, severe, early form of osteoporosis in which young women present with fractures, usually multiple vertebral fractures, during late pregnancy or lactation. In studies of idiopathic osteoporosis (IOP) in premenopausal women, we enrolled 78 women with low‐trauma fractures and 40 healthy controls, all with normal menses and no secondary cause of bone loss. In 15 of the affected women, the PLO subgroup, fractures had occurred during late pregnancy or lactation. We hypothesized that clinical, bone structural, and metabolic characteristics would differ between women with PLO and those with (non‐PLO) IOP and controls. All were evaluated > 12 months postpartum, when structural and remodeling characteristics would be expected to reflect baseline premenopausal status rather than transient postpartum changes. As previously reported, affected subjects (PLO and IOP) had BMD and microarchitectural deficiencies compared to controls. Women with PLO did not differ from those with IOP in terms of age, BMI, body fat, menarcheal age, parity, or age at first pregnancy. However, women with PLO had a more severe clinical presentation than those with IOP: more fractures (5.5 ± 3.3 versus 2.6 ± 2.1; p = 0.005); more vertebral fractures (80% versus 17%; p < 0.001); and higher prevalence of multiple fractures. BMD deficits were more profound and cortical width tended to be lower in PLO. PLO subjects also had significantly lower tissue‐level mineral apposition rate and bone formation rates (0.005 ± 0.005 versus 0.011 ± 0.010 mm2/mm/year; p = 0.006), as well as lower serum P1NP (33 ± 12 versus 44 ± 18 µg/L; p = 0.02) and CTX (257 ± 102 versus 355 ± 193 pg/m
L; p = 0.01) than IOP. The finding that women with PLO have a low bone remodeling state assessed more than a year postpartum increases our understanding of the pathogenic mechanism of PLO. We conclude that women with PLO may have underlying osteoblast functional deficits which could affect their therapeutic response to osteoanabolic medications. © 2019 American Society for Bone and Mineral Research.

CTLA4‐Ig Directly Inhibits Osteoclastogenesis by Interfering With Intracellular Calcium Oscillations in Bone Marrow Macrophages

13-09-2019 – Hiroyuki Okada, Hiroshi Kajiya, Yasunori Omata, Takumi Matsumoto, Yuiko Sato, Tami Kobayashi, Satoshi Nakamura, Yosuke Kaneko, Shinya Nakamura, Takuma Koyama, Shunichi Sudo, Masashi Shin, Fujio Okamoto, Hisato Watanabe, Naohiro Tachibana, Jun Hirose, Taku Saito, Toshiyuki Takai, Morio Matsumoto, Masaya Nakamura, Koji Okabe, Takeshi Miyamoto, Sakae Tanaka

Journal Article

ABSTRACTCTLA4‐Ig (cytotoxic T‐lymphocyte antigen 4‐immunoglobulin; Abatacept) is a biologic drug for rheumatoid arthritis. CTLA4 binds to the CD80/86 complex of antigen‐presenting cells and blocks the activation of T cells. Although previous reports showed that CTLA4‐Ig directly inhibited osteoclast differentiation, the whole inhibitory mechanism of CTLA4‐Ig for osteoclast differentiation is unclear. Bone marrow macrophages (BMMs) from WT mice were cultured with M‐CSF and RANKL with or without the recombinant mouse chimera CTLA4‐Ig. Intracellular calcium oscillations of BMMs with RANKL were detected by staining with calcium indicator fura‐2 immediately after administration of CTLA4‐Ig or after one day of treatment. Calcium oscillations were analyzed using Fc receptor gamma‐ (Fc
Rγ‐) deficient BMMs. CTLA4‐Ig inhibited osteoclast differentiation and reduced the expression of the nuclear factor of activated T cells NFATc1 in BMMs in vitro. Calcium oscillations in BMMs were suppressed by CTLA4‐Ig both immediately after administration and after one day of treatment. CTLA4‐Ig did not affect osteoclastogenesis and did not cause remarkable changes in calcium oscillations in Fc
Rγ‐deficient BMMs. Finally, to analyze the effect of CTLA4‐Ig in vivo, we used an LPS‐induced osteolysis model. CTLA4‐Ig suppressed LPS‐induced bone resorption in WT mice, not in Fc
Rγ‐deficient mice. In conclusion, CTLA4‐Ig inhibits intracellular calcium oscillations depending on Fc
Rγ and downregulates NFATc1 expression in BMMs. © 2019 American Society for Bone and Mineral Research.

VEGFA From Early Osteoblast Lineage Cells (Osterix+) Is Required in Mice for Fracture Healing

13-09-2019 – Evan G Buettmann, Jennifer A McKenzie, Nicole Migotsky, David AW Sykes, Pei Hu, Susumu Yoneda, Matthew J Silva

Journal Article

ABSTRACTBone formation via intramembranous and endochondral ossification is necessary for successful healing after a wide range of bone injuries. The pleiotropic cytokine, vascular endothelial growth factor A (VEGFA) has been shown, via nonspecific pharmacologic inhibition, to be indispensable for angiogenesis and ossification following bone fracture and cortical defect repair. However, the importance of VEGFA expression by different cell types during bone healing is not well understood. We sought to determine the role of VEGFA from different osteoblast cell subsets following clinically relevant models of bone fracture and cortical defect. Ubiquitin C (UBC), Osterix (Osx), or Dentin matrix protein 1 (Dmp1) Cre‐ERT2 mice (male and female) containing floxed VEGFA alleles (VEGFAfl/fl) were either given a femur full fracture, ulna stress fracture, or tibia cortical defect at 12 weeks of age. All mice received tamoxifen continuously starting 2 weeks before bone injury and throughout healing. UBC Cre‐ERT2 VEGFAfl/fl (UBC c
KO) mice, which were used to mimic nonspecific inhibition, had minimal bone formation and impaired angiogenesis across all bone injury models. UBC c
KO mice also exhibited impaired periosteal cell proliferation during full fracture, but not stress fracture repair. Osx Cre‐ERT2 VEGFAfl/fl (Osx c
KO) mice, but not Dmp1 Cre‐ERT2 VEGFAfl/fl (Dmp1 c
KO) mice, showed impaired periosteal bone formation and angiogenesis in models of full fracture and stress fracture. Neither Osx c
KO nor Dmp1 c
KO mice demonstrated significant impairments in intramedullary bone formation and angiogenesis following cortical defect. These data suggest that VEGFA from early osteolineage cells (Osx+), but not mature osteoblasts/osteocytes (Dmp1+), is critical at the time of bone injury for rapid periosteal angiogenesis and woven bone formation during fracture repair. Whereas VEGFA from another cell source, not from the osteoblast cell lineage, is necessary at the time of injury for maximum cortical defect intramedullary angiogenesis and osteogenesis. © 2019 American Society for Bone and Mineral Research.

Loss of the Vitamin D Receptor in Human Breast Cancer Cells Promotes Epithelial to Mesenchymal Cell Transition and Skeletal Colonization

13-09-2019 – Konstantin Horas, Yu Zheng, Colette Fong‐Yee, Eugenie Macfarlane, Jeline Manibo, Yunzhao Chen, Jeremy Qiao, Mingxuan Gao, Nancy Haydar, Michelle M McDonald, Peter I Croucher, Hong Zhou, Markus J Seibel

Journal Article

ABSTRACTExpression of the vitamin D receptor (VDR) is thought to be associated with neoplastic progression. However, the role of the VDR in breast cancer metastasis to bone and the molecular mechanisms underlying this process are unknown. Employing a rodent model (female Balb/c nu/nu mice) of systemic metastasis, we here demonstrate that knockdown of the VDR strongly increases the metastatic potential of MDA‐MB‐231 human breast cancer cells to bone, resulting in significantly greater skeletal tumor burden. Ablation of VDR expression promotes cancer cell mobility (migration) and invasiveness, thereby facilitating skeletal colonization. Mechanistically, these changes in tumor cell behavior are attributable to shifts in the expression of proteins involved in cell adhesion, proliferation, and cytoskeletal organization, patterns characteristic for epithelial‐to‐mesenchymal cell transition (EMT). In keeping with these experimental findings, analyses of human breast cancer specimens corroborated the association between VDR expression, EMT‐typical changes in protein expression patterns, and clinical prognosis. Loss of the VDR in human breast cancer cells marks a critical point in oncogenesis by inducing EMT, promoting the dissemination of cancer cells, and facilitating the formation of tumor colonies in bone. © 2019 American Society for Bone and Mineral Research.

Combined Collagen‐Induced Arthritis and Organic Dust‐Induced Airway Inflammation to Model Inflammatory Lung Disease in Rheumatoid Arthritis

13-09-2019 – Jill A Poole, Geoffrey M Thiele, Katherine Janike, Amy J Nelson, Michael J Duryee, Kathryn Rentfro, Bryant R England, Debra J Romberger, Joseph M Carrington, Dong Wang, Benjamin J Swanson, Lynell W Klassen, Ted R Mikuls

Journal Article

ABSTRACTRheumatoid arthritis (RA) is characterized by extra‐articular involvement including lung disease, yet the mechanisms linking the two conditions are poorly understood. The collagen‐induced arthritis (CIA) model was combined with the organic dust extract (ODE) airway inflammatory model to assess bone/joint–lung inflammatory outcomes. DBA/1J mice were intranasally treated with saline or ODE daily for 5 weeks. CIA was induced on days 1 and 21. Treatment groups included sham (saline injection/saline inhalation), CIA (CIA/saline), ODE (saline/ODE), and CIA +  ODE (CIA/ODE). Arthritis inflammatory scores, bones, bronchoalveolar lavage fluid, lung tissues, and serum were assessed. In DBA/1J male mice, arthritis was increased in CIA +  ODE >  CIA >  ODE versus sham. Micro‐computed tomography (µCT) demonstrated that loss of BMD and volume and deterioration of bone microarchitecture was greatest in CIA +  ODE. However, ODE‐induced airway neutrophil influx and inflammatory cytokine/chemokine levels in lavage fluids were increased in ODE >  CIA +  ODE versus sham. Activated lung CD11c+CD11b+ macrophages were increased in ODE >  CIA +  ODE >  CIA pattern, whereas lung hyaluronan, fibronectin, and amphiregulin levels were greatest in CIA +  ODE. Serum autoantibody and inflammatory marker concentrations varied among experimental groups. Compared with male mice, female mice showed less articular and pulmonary disease. The interaction of inhalation‐induced airway inflammation and arthritis induction resulted in compartmentalized responses with the greatest degree of arthritis and bone loss in male mice with combined exposures. Data also support suppression of the lung inflammatory response, but increases in extracellular matrix protein deposition/interstitial disease in the setting of arthritis. This coexposure model could be exploited to better understand and treat RA–lung disease. © 2019 American Society for Bone and Mineral Research.

Treatment of Autosomal Dominant Hypocalcemia Type 1 With the Calcilytic NPSP795 (SHP635)

13-09-2019 – Mary Scott Roberts, Rachel I Gafni, Beth Brillante, Lori C Guthrie, Jamie Streit, David Gash, Jeff Gelb, Eva Krusinska, Sarah C Brennan, Martin Schepelmann, Daniela Riccardi, Mohd Ezuan Bin Khayat, Donald T Ward, Edward F Nemeth, Ralf Rosskamp, Michael T Collins

Journal Article

ABSTRACTAutosomal dominant hypocalcemia type 1 (ADH1) is a rare form of hypoparathyroidism caused by heterozygous, gain‐of‐function mutations of the calcium‐sensing receptor gene (CAR). Individuals are hypocalcemic with inappropriately low parathyroid hormone (PTH) secretion and relative hypercalciuria. Calcilytics are negative allosteric modulators of the extracellular calcium receptor (Ca
R) and therefore may have therapeutic benefits in ADH1. Five adults with ADH1 due to four distinct CAR mutations received escalating doses of the calcilytic compound NPSP795 (SHP635) on 3 consecutive days. Pharmacokinetics, pharmacodynamics, efficacy, and safety were assessed. Parallel in vitro testing with subject Ca
R mutations assessed the effects of NPSP795 on cytoplasmic calcium concentrations (Ca2+i), and ERK and p38MAPK phosphorylation. These effects were correlated with clinical responses to administration of NPSP795. NPSP795 increased plasma PTH levels in a concentration‐dependent manner up to 129% above baseline (p = 0.013) at the highest exposure levels. Fractional excretion of calcium (FECa) trended down but not significantly so. Blood ionized calcium levels remained stable during NPSP795 infusion despite fasting, no calcitriol supplementation, and little calcium supplementation. NPSP795 was generally safe and well‐tolerated. There was significant variability in response clinically across genotypes. In vitro, all mutant Ca
Rs were half‐maximally activated (EC50) at lower concentrations of extracellular calcium (Ca2+o) compared to wild‐type (WT) Ca
R; NPSP795 exposure increased the EC50 for all Ca
R activity readouts. However, the in vitro responses to NPSP795 did not correlate with any clinical parameters. NPSP795 increased plasma PTH levels in subjects with ADH1 in a dose‐dependent manner, and thus, serves as proof‐of‐concept that calcilytics could be an effective treatment for ADH1. Albeit all mutations appear to be activating at the Ca
R, in vitro observations were not predictive of the in vivo phenotype or the response to calcilytics, suggesting that other parameters impact the response to the drug. © 2019 American Society for Bone and Mineral Research.

Multimodal 18FFDG PET/CT Is a Direct Readout for Inflammatory Bone Repair: A Longitudinal Study in TNFα Transgenic Mice

13-09-2019 – Silvia Hayer, Markus Zeilinger, Volker Weiss, Monika Dumanic, Markus Seibt, Birgit Niederreiter, Tetyana Shvets, Florian Pichler, Wolfgang Wadsak, Bruno K Podesser, Thomas H Helbich, Marcus Hacker, Josef S Smolen, Kurt Redlich, Markus Mitterhauser

Journal Article

ABSTRACTIn rheumatoid arthritis (RA), chronic joint inflammation leading to bone and cartilage damage is the major cause of functional impairment. Whereas reduction of synovitis and blockade of joint damage can be successfully achieved by disease modifying antirheumatic therapies, bone repair upon therapeutic interventions has only been rarely reported. The aim of this study was to use fluorodeoxyglucose (18FFDG) and 18Ffluoride µPET/CT imaging to monitor systemic inflammatory and destructive bone remodeling processes as well as potential bone repair in an established mouse model of chronic inflammatory, erosive polyarthritis. Therefore, human tumor necrosis factor transgenic (h
TNFtg) mice were treated with infliximab, an anti‐TNF antibody, for 4 weeks. Before and after treatment period, mice received either 18FFDG, for detecting inflammatory processes, or 18Ffluoride, for monitoring bone remodeling processes, for PET scans followed by CT scans. Standardized uptake values (SUVmean) were analyzed in various joints and histopathological signs of arthritis, joint damage, and repair were assessed. Longitudinal PET/CT scans revealed a significant decrease in 18FFDG SUVs in affected joints demonstrating complete remission of inflammatory processes due to TNF blockade. In contrast, 18Ffluoride SUVs could not discriminate between different severities of bone damage in h
TNFtg mice. Repeated in vivo CT images proved a structural reversal of preexisting bone erosions after anti‐TNF therapy. Accordingly, histological analysis showed complete resolution of synovial inflammation and healing of bone at sites of former bone erosion. We conclude that in vivo multimodal 18FFDG µPET/CT imaging allows to quantify and monitor inflammation‐mediated bone damage and reveals not only reversal of synovitis but also bone repair upon TNF blockade in experimental arthritis. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

Beclin1 Modulates Bone Homeostasis by Regulating Osteoclast and Chondrocyte Differentiation

13-09-2019 – Atsushi Arai, Sol Kim, Vadim Goldshteyn, Terresa Kim, No‐Hee Park, Cun‐Yu Wang, Reuben H. Kim

Journal Article

ABSTRACTAutophagy (ATG), an important cellular recycling process whereby macromolecules or organelles are encapsulated by autophagosome and degraded upon merging with lysosome, has recently been shown to play an essential role in bone biology. However, the involvement of ATG in bone and bone‐related cells remains unclear. Here, we show that Beclin1, an ATG‐related protein involved in ATG initiation, plays a pivotal role in osteoclasts. ATG was activated during osteoclast differentiation in vitro. Beclin1 was enhanced and required for osteoclast differentiation. Mechanistically, we found that TRAF6‐mediated ubiquitination of Beclin1 at K117, but not ULK1‐mediated phosphorylation, is required for RANKL‐stimulated osteoclast differentiation. In vivo, mice lacking Beclin1 in Cst
K‐expressing cells exhibited an increased cortical bone thickness caused by impaired osteoclasts’ function. Interestingly, these mice also exhibited diminished trabecular bone mass, which was associated with a defect in cartilage formation and chondrocyte differentiation. Collectively, our study highlights the functional importance of ATG in osteoclasts and chondrocytes, and identifies ATG as a potential therapeutic target for managing bone‐related diseases. © 2019 American Society for Bone and Mineral Research.

Osteocyte Death and Bone Overgrowth in Mice Lacking Fibroblast Growth Factor Receptors 1 and 2 in Mature Osteoblasts and Osteocytes

13-09-2019 – Jennifer McKenzie, Craig Smith, Kannan Karuppaiah, Joshua Langberg, Matthew J Silva, David M Ornitz

Journal Article

ABSTRACTFibroblast growth factor (FGF) signaling pathways have well‐established roles in skeletal development, with essential functions in both chondrogenesis and osteogenesis. In mice, previous conditional knockout studies suggested distinct roles for FGF receptor 1 (FGFR1) signaling at different stages of osteogenesis and a role for FGFR2 in osteoblast maturation. However, the potential for redundancy among FGFRs and the mechanisms and consequences of stage‐specific osteoblast lineage regulation were not addressed. Here, we conditionally inactivate Fgfr1 and Fgfr2 in mature osteoblasts with an Osteocalcin (OC)‐Cre or Dentin matrix protein 1 (Dmp1)‐Cre
ER driver. We find that young mice lacking both receptors or only FGFR1 are phenotypically normal. However, between 6 and 12 weeks of age, OC‐Cre Fgfr1/Fgfr2 double‐ and Fgfr1 single‐conditional knockout mice develop a high bone mass phenotype with increased periosteal apposition, increased and disorganized endocortical bone with increased porosity, and biomechanical properties that reflect increased bone mass but impaired material properties. Histopathological and gene expression analyses show that this phenotype is preceded by a striking loss of osteocytes and accompanied by activation of the Wnt/β‐catenin signaling pathway. These data identify a role for FGFR1 signaling in mature osteoblasts/osteocytes that is directly or indirectly required for osteocyte survival and regulation of bone mass during postnatal bone growth. © 2019 American Society for Bone and Mineral Research.

Relationship Between Sex Steroids and Deterioration of Bone Microarchitecture in Older Men: The Prospective STRAMBO Study

13-09-2019 – Anne Piot, Roland D Chapurlat, Bruno Claustrat, Pawel Szulc

Journal Article

ABSTRACTIn older men, low estrogen levels are associated with poor bone microarchitecture. Data on androgens are discordant. We studied the link between baseline sex steroid levels (total 17β ‐estradiol 17βE2, total testosterone t
T, calculated bioavailable 17βE2 bio‐17βE2, and apparent free testosterone concentration AFTC) and bone microarchitecture deterioration assessed prospectively in a 820 older men followed for 8 years. Bone microarchitecture was assessed by HR‐p
QCT at baseline, then after 4 and 8 years. At both the skeletal sites, the bone microarchitecture deterioration rate did not correlate with serum levels of t
T and 17βE2. At the distal radius, cortical area (Ct.
Ar) decreased more rapidly in the lowest versus the highest AFTC quartile. At the distal tibia, cortical thickness (Ct.
Th) decreased and trabecular area (Tb.
Ar) increased more rapidly in the highest versus the lowest AFTC quartile. At the tibia, bone mineral content (BMC), total volumetric bone mineral density (Tt.v
BMD), Ct.
Th, and Ct.
Ar decreased, whereas Tb.
Ar increased faster in the lowest versus the highest bio‐17βE2 quartile. In men who had both AFTC and bio‐17βE2 in the lowest quartile (high‐risk group), distal radius cortical v
BMD (Ct.v
BMD) decreased more rapidly compared with men who had both hormones in the three upper quartiles (reference group). At the distal tibia, Tt.v
BMD, Ct.
Th, Ct.
Ar, and Ct.v
BMD decreased, whereas Tb.
Ar increased more rapidly in the high‐risk group versus the reference group. In men receiving androgen deprivation therapy (ADT) for prostate cancer, BMC, Tt.v
BMD, Ct.
Th, Ct.
Ar, and Ct.v
BMD decreased, whereas Tb.
Ar increased more rapidly than in men not receiving ADT at both the skeletal sites. Thus, in older men followed up prospectively, low levels of bio‐17βE2, and to a smaller extent AFTC, are associated with accelerated cortical bone deterioration. Cortical bone deterioration was strongly accelerated in men receiving ADT who had very low levels of all sex steroids. © 2019 American Society for Bone and Mineral Research.

Overestimation of the Limitations of Randomized Controlled Trials

13-09-2019 – Jonathan Bergman, Anna Nordström, Peter Nordström

Letter

Complementarity of Cohort Studies and Randomized Controlled Trials

13-09-2019 – John A Eisman, Piet Geusens, Joop van den Bergh

Letter

Ed Bd, Masthead, Comm List and TOC

13-09-2019 –

Issue Information‐Declaration of Helsinki

13-09-2019 –

Journal of Bone and Mineral Research: Volume 34, Number 9, September 2019

13-09-2019 –

Artificial Intelligence in Musculoskeletal Imaging: A Paradigm Shift

12-09-2019 – Joseph E Burns, Jianhua Yao, Ronald M Summers

Journal Article, Review

ABSTRACTArtificial intelligence is upending many of our assumptions about the ability of computers to detect and diagnose diseases on medical images. Deep learning, a recent innovation in artificial intelligence, has shown the ability to interpret medical images with sensitivities and specificities at or near that of skilled clinicians for some applications. In this review, we summarize the history of artificial intelligence, present some recent research advances, and speculate about the potential revolutionary clinical impact of the latest computer techniques for bone and muscle imaging. © 2019 American Society for Bone and Mineral Research. Published 2019. This article is a U.
S. Government work and is in the public domain in the USA.

Hormone‐Independent Sexual Dimorphism in the Regulation of Bone Resorption by Krox20

12-09-2019 – Elias Sabag, Elinor Halperin, Tamar Liron, Sahar Hiram‐Bab, Baruch Frenkel, Yankel Gabet

Journal Article

ABSTRACTKrox20/EGR2 is a zinc finger transcription factor, implicated in the development of the hindbrain, nerve myelination, and tumor suppression. In skeletal biology, we have demonstrated that Krox20 also regulates adult bone metabolism. We and others have characterized several functions of Krox20 in the osteoclast lineage, namely, preosteoclast proliferation and differentiation, and mature osteoclast apoptosis. We have previously reported that systemically Krox20‐haploinsufficient mice have a low bone mass with increased bone resorption. However, new data have now revealed that this phenotype is restricted to females. In addition, we discovered that conditional knockout of Krox20 (c
KO) restricted to osteoclast progenitors is sufficient to induce the same female‐specific bone loss observed in systemic mutants. To test whether this sexual dimorphism results from an interaction between Krox20 and sex hormones, we examined the sex‐ and hormone‐dependent role of Krox20 deficiency on proliferation and apoptosis in osteoclastic cells. Our results indicate that male and female sex hormones (dihydrotestosterone DHT and estradiol E2, respectively) as well as Krox20 inhibit preosteoclast proliferation and augment osteoclast apoptosis. The observation that Krox20 expression is inhibited by DHT and E2 negates the hypothesis that the effect of sex hormones is mediated by an increase in Krox20 expression. Interestingly, the effect of Krox20 deficiency was observed only with cells derived from female animals, regardless of any sex hormones added in vitro. In addition, we have identified sexual dimorphism in the expression of several Krox20‐related genes, including NAB2. This sex‐specific epigenetic profile was established at puberty, maintained in the absence of sex hormones, and explains the female‐specific skeletal importance of Krox20. The findings described in this study emphasize the medical importance of sex differences, which may be determined at the epigenetic level. © 2019 American Society for Bone and Mineral Research.

Exercise degrades Bone in Caloric Restriction, despite Suppression of Marrow Adipose Tissue (MAT)

11-09-2019 – Cody McGrath, Jeyantt Srinivas Sankaran, Negin Misaghian‐Xanthos, Buer Sen, Zhihui Xie, Martin A. Styner, Xiaopeng Zong, Janet Rubin, Maya Styner

Journal Article

ABSTRACTMarrow adipose tissue (MAT) and its relevance to skeletal health during caloric restriction (CR) is unknown: it remains unclear whether exercise, which is anabolic to bone in a calorie‐replete state, alters bone or MAT in CR. We hypothesized that response of bone and MAT to exercise in CR differs from the calorie‐replete state. Ten‐week‐old female B6 mice fed a regular (RD) or 30% CR‐diet were allocated to sedentary (RD CR, n = 10/group) or running exercise (RD‐E, CR‐E, n = 7/group). After 6 weeks, CR mice weighed 20% less than RD, p < 0.001; exercise did not affect weight. Femoral bone volume (BV) via 3D MRI was 20% lower in CR vs. RD (p < 0.0001). CR was associated with decreased bone by μCT: Tb. Th was 16% less in CR vs. RD, p < 0.003, Ct.
Th was 5% less, p < 0.07. In CR‐E Tb.
Th was 40% less than RD‐E, p < 0.0001. Exercise increased Tb.
Th in RD (+23% RD‐E vs. RD p < 0.003) but failed to do so in CR. Cortical porosity increased after exercise in CR (+28%, p = 0.04), suggesting exercise during CR is deleterious to bone. In terms of bone fat, metaphyseal MAT/ BV rose 159% in CR vs. RD, p = 0.003 via 3D MRI. Exercise decreased MAT/ BV by 52% in RD, p < 0.05 and also suppressed MAT in CR (−121%, p = 0.047). Histomorphometric analysis of adipocyte area correlated with MAT by MRI (R2 = 0.6233, p < 0.0001). With respect to bone, TRAP and Sost m
RNA were reduced in CR. Intriguingly, the repressed Sost in CR rose with exercise and may underlie the failure of CR‐bone quantity to increase in response to exercise. Notably, CD36, a marker of fatty acid uptake, rose 4088% in CR (p < 0.01 vs. RD) suggesting that basal increases in MAT during calorie restriction serve to supply local energy needs, and are depleted during exercise with a negative impact on bone.
This article is protected by copyright. All rights reserved.

In Memoriam: Remembering Elizabeth Barrett‐Connor

11-09-2019 – Robert Marcus, Gail A Greendale

Journal Article

Fracture and Bone Mineral Density Response by Baseline Risk in Patients Treated With Abaloparatide Followed by Alendronate: Results From the Phase 3 ACTIVExtend Trial

11-09-2019 – Benjamin Z Leder, Carol Zapalowski, Ming‐Yi Hu, Gary Hattersley, Nancy E Lane, Andrea J Singer, Robin K Dore

Journal Article

ABSTRACTIn the randomized, placebo‐controlled, double‐blind phase 3 ACTIVE study (NCT01343004), 18 months of abaloparatide 80 μg daily (subcutaneous injection) in postmenopausal women at risk of osteoporotic fracture significantly reduced the risk of vertebral, nonvertebral, clinical, and major osteoporotic fractures and significantly increased bone mineral density (BMD) versus placebo regardless of baseline risk factors. Women from the abaloparatide and placebo groups who completed ACTIVE were eligible for ACTIVExtend (NCT01657162), in which all enrollees received sequential, open‐label monotherapy with alendronate 70 mg once weekly for up to 24 months. This prespecified analysis evaluated whether fracture risk reductions and bone mineral density (BMD) gains associated with abaloparatide during ACTIVE persisted through the full 43‐month ACTIVE–ACTIVExtend study period in nine prespecified baseline risk subgroups. Baseline risk subgroups included BMD T‐score at the lumbar spine, total hip, and femoral neck (≤ − 2.5 versus > − 2.5 and ≤ −3.0 versus > − 3.0), history of nonvertebral fracture (yes/no), prevalent vertebral fracture (yes/no), and age (<65 versus 65 to <75 versus ≥75 years). Forest plots display treatment effect. Treatment‐by‐subgroup interactions were tested using the Breslow‐Day test, Cox proportional hazards model, and ANCOVA model. After the combined ACTIVE–ACTIVExtend study period, reductions in relative risk for new vertebral, nonvertebral, clinical, and major osteoporotic fractures were greater among patients in the abaloparatide/alendronate group than among those in the placebo/alendronate group across all nine baseline risk subgroups. BMD gains at the lumbar spine, total hip, and femoral neck were greater in the abaloparatide/alendronate group versus the placebo/alendronate group. No clinically meaningful interaction between treatment assignment and any baseline risk variable was observed. The sequence of abaloparatide for 18 months followed by alendronate for up to 24 months appears to be an effective treatment option for a wide range of postmenopausal women at risk for osteoporotic fractures. © 2019 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc.

Cytokine‐Induced and Stretch‐Induced Sphingosine 1‐Phosphate Production by Enthesis Cells Could Favor Abnormal Ossification in Spondyloarthritis

10-09-2019 – Alaeddine El Jamal, Anne Briolay, Saida Mebarek, Benoit Le Goff, Frédéric Blanchard, David Magne, Leyre Brizuela, Carole Bougault

Journal Article

ABSTRACTSpondyloarthritis (Sp
A) is a common rheumatic disease characterized by enthesis inflammation (enthesitis) and ectopic ossification (enthesophytes). The current pathogenesis model suggests that inflammation and mechanical stress are both strongly involved in Sp
A pathophysiology. We have previously observed that the levels of sphingosine 1‐phosphate (S1P), a bone anabolic molecule, were particularly high in Sp
A patients serum compared to healthy donors. Therefore, we wondered how this deregulation was related to Sp
A molecular mechanisms. Mouse primary osteoblasts, chondrocytes, and tenocytes were used as cell culture models. The sphingosine kinase 1 (Sphk1) gene expression and S1P secretion were significantly enhanced by cyclic stretch in osteoblasts and chondrocytes. Further, TNF‐α and IL‐17, cytokines implicated in enthesitis, increased Sphk1 m
RNA in chondrocytes in an additive manner when combined to stretch. The immunochemistry on mouse ankles showed that sphingosine kinase 1 (SK1) was localized in some chondrocytes; the addition of a pro‐inflammatory cocktail augmented Sphk1 expression in cultured ankles. Subsequently, fingolimod was used to block S1P metabolism in cell cultures. It inhibited S1P receptors (S1PRs) signaling and SK1 and SK2 activity in both osteoblasts and chondrocytes. Fingolimod also reduced S1PR‐induced activation by Sp
A patients synovial fluid (SF), demonstrating that the stimulation of chondrocytes by SFs from Sp
A patients involves S1P. In addition, when the osteogenic culture medium was supplemented with fingolimod, alkaline phosphatase activity, matrix mineralization, and bone formation markers were significantly reduced in osteoblasts and hypertrophic chondrocytes. Osteogenic differentiation was accompanied by an increase in S1prs m
RNA, especially S1P1/3, but their contribution to S1P‐impact on mineralization seemed limited. Our results suggest that S1P might be overproduced in Sp
A enthesis in response to cytokines and mechanical stress, most likely by chondrocytes. Moreover, S1P could locally favor the abnormal ossification of the enthesis; therefore, blocking the S1P metabolic pathway could be a potential therapeutic approach for the treatment of Sp
A. © 2019 American Society for Bone and Mineral Research.

Vertebral Fracture Assessment Increases Use of Pharmacologic Therapy for Fracture Prevention in Clinical Practice

10-09-2019 – John T Schousboe, Lisa M Lix, Suzanne N Morin, Sheldon Derkatch, Mark Bryanton, Mashael Alhrbi, William D Leslie

Journal Article

ABSTRACTThe impact of vertebral fracture assessment (VFA) on lateral spine images in clinical practice on subsequent patient use of fracture prevention medication is unknown. Our objective was to determine the association of prevalent vertebral fracture identified on bone density lateral spine images (positive VFA) with subsequent use of fracture prevention therapy in usual clinical practice, using the Manitoba Bone Density Program database prospective observational cohort. Since 2010, targeted VFA imaging has been done at the time of bone densitometry in Manitoba for 21% of women and men meeting criteria based on age, bone mineral density (BMD), height loss, and glucocorticoid use. Among 6652 treatment‐naive individuals with at least 90 days follow‐up who had VFA imaging, 923 (13.9%) had one or more definite vertebral fractures identified using a modified algorithm‐based qualitative (ABQ) method. For those with a positive VFA, their bone density reports stated the patient was at high risk of subsequent fracture and qualified for fracture prevention therapy. Subsequent osteoporosis treatment initiated within the next 12 months was identified using population‐based pharmacy data. Logistic regression models were used to estimate the association of positive VFA with subsequent prescription (Rx), compared to negative VFA. Fracture prevention medication was started by 2127 (32%) individuals, 52.3% with positive versus 28.4% with negative VFA (p value <0.001). This association was substantially stronger in those designated (before VFA results were known) to have low or moderate fracture risk compared to high fracture risk (interaction p value <0.001), and in those with osteopenia (OR 4.51; 95% CI, 3.48 to 5.85) compared to those with osteoporosis by BMD criteria (OR 1.72; 95% CI, 1.43 to 2.08, interaction p value <0.001). Targeted VFA imaging at the time of bone densitometry substantially improves identification of those at high fracture risk and fracture prevention medication use among those with prevalent vertebral fracture. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

A CTGF‐RUNX2‐RANKL Axis in Breast and Prostate Cancer cells Promotes Tumor Progression in Bone

10-09-2019 – Bongjun Kim, Haemin Kim, Suhan Jung, Aree Moon, Dong‐Young Noh, Zang Hee Lee, Hyung Joon Kim, Hong‐Hee Kim

Journal Article

Abstract
Metastasis to bone is a frequent occurrence in patients with breast and prostate cancers and inevitably threatens the patients quality of life and survival. Identification of cancer‐derived mediators of bone metastasis and osteolysis may lead to novel therapeutic strategies. In this study, we established highly bone‐metastatic PC3 prostate and MDA‐MB‐231 (MDA) breast cancer cell sublines by in vivo selection in mice. In bone‐metastatic cancer cells, the expression and secretion of connective tissue growth factor (CTGF) were highly upregulated. CTGF knockdown in bone‐metastatic cells decreased invasion activity and MMP expression. RUNX2 overexpression in the CTGF knockdown cells restored the invasion activity and MMP expression. In addition, CTGF increased RUNX2 protein stability by inducing its acetylation via p300 acetyl transferase. The integrin αvβ3 receptor mediated these effects of CTGF. Furthermore, CTGF promoted RUNX2 recruitment to the RANKL promoter, resulting in increased RANKL production from the tumor cells and subsequent stimulation of osteoclastogenesis from precursor cells. In addition, animal model with injection of CTGF knockdowned prostate cancer cells into 6‐week old BALB/c male mice showed reduced osteolytic lesions. More importantly, the expression levels of CTGF and RANKL showed a strong positive correlation in human primary breast tumor tissues and were higher in bone metastases than in other site metastases. These findings indicate that CTGF plays crucial roles for osteolytic bone metastasis both by enhancing invasiveness of tumor cells and by producing RANKL for osteoclastogenesis. Targeting CTGF may lead to the development of effective preventive and therapeutic strategies for osteolytic metastasis.
This article is protected by copyright. All rights reserved.

Absence of Dipeptidyl Peptidase 3 Increases Oxidative Stress and Causes Bone Loss

09-09-2019 – Ciro Menale, Lisa J Robinson, Eleonora Palagano, Rosita Rigoni, Marco Erreni, Alejandro J Almarza, Dario Strina, Stefano Mantero, Michela Lizier, Antonella Forlino, Roberta Besio, Marta Monari, Paolo Vezzoni, Barbara Cassani, Harry C Blair, Anna Villa, Cristina Sobacchi

Journal Article

ABSTRACTControlling oxidative stress through the activation of antioxidant pathways is crucial in bone homeostasis, and impairments of the cellular defense systems involved contribute to the pathogenesis of common skeletal diseases. In this work we focused on the dipeptidyl peptidase 3 (DPP3), a poorly investigated ubiquitous zinc‐dependent exopeptidase activating the Keap1‐Nrf2 antioxidant pathway. We showed Dpp3 expression in bone and, to understand its role in this compartment, we generated a Dpp3 knockout (KO) mouse model and specifically investigated the skeletal phenotype. Adult Dpp3 KO mice showed a mild growth defect, a significant increase in bone marrow cellularity, and bone loss mainly caused by increased osteoclast activity. Overall, in the mouse model, lack of DPP3 resulted in sustained oxidative stress and in alterations of bone microenvironment favoring the osteoclast compared to the osteoblast lineage. Accordingly, in vitro studies revealed that Dpp3 KO osteoclasts had an inherent increased resorptive activity and ROS production, which on the other hand made them prone to apoptosis. Moreover, absence of DPP3 augmented bone loss after estrogen withdrawal in female mice, further supporting its relevance in the framework of bone pathophysiology. Overall, we show a nonredundant role for DPP3 in the maintenance of bone homeostasis and propose that DPP3 might represent a possible new osteoimmunological player and a marker of human bone loss pathology. © 2019 American Society for Bone and Mineral Research.

High impact exercise increased femoral neck bone density with no adverse effects on imaging markers of knee osteoarthritis in postmenopausal women

09-09-2019 – Chris Hartley, Jonathan P Folland, Robert Kerslake, Katherine Brooke‐Wavell

Journal Article

ABSTRACTHigh impact exercise can improve femoral neck bone mass but findings in postmenopausal women have been inconsistent and there may be concern at the effects of high impact exercise on joint health. We investigated the effects of a high impact exercise intervention on bone mineral density (BMD), bone mineral content (BMC) and section modulus (Z) as well as imaging biomarkers of osteoarthritis (OA) in healthy postmenopausal women.
Forty‐two women aged 55–70 who were at least 12 months postmenopausal were recruited. The six‐month intervention consisted of progressive, unilateral, high impact exercise incorporating multidirectional hops on one randomly assigned exercise leg (EL) for comparison with the contralateral control leg (CL). Dual X‐ray absorptiometry (DXA) was used to measure BMD, BMC and Z of the femoral neck. Magnetic resonance imaging (MRI) of the knee joint was used to analyse the biochemical composition of articular cartilage using T2 relaxometry and to analyse joint pathology associated with OA using semi‐quantitative analysis.
Thirty‐five participants (61.7 ± 4.3 yrs) completed the intervention with a mean adherence of 76.8 ± 22.5%. Femoral neck BMD, BMC and Z all increased in the EL (+0.81%, +0.69% and + 3.18% respectively) compared to decreases in the CL (−0.57%, −0.71% and − 0.75%: all interaction effects P < 0.05). There was a significant increase in mean T2 relaxation times (main effect of time P = 0.011) but this did not differ between the EL and CL indicating no global effect. Semi‐quantitative analysis showed high prevalence of bone marrow lesions and cartilage defects, especially in the patellofemoral joint, with no indication that the intervention caused pathology progression.
In conclusion, a high impact exercise intervention that requires little time, cost or specialist equipment improved femoral neck BMD with no negative effects on knee OA imaging biomarkers. Unilateral high impact exercise is a feasible intervention to reduce hip fracture risk in healthy postmenopausal women.
This article is protected by copyright. All rights reserved.

Murine placental‐fetal phosphate dyshomeostasis caused by an Xpr1 deficiency accelerates placental calcification and restricts fetal growth in late gestation

09-09-2019 – Xuan Xu, Xiunan Li, Hao Sun, Zhijian Cao, Ruixi Gao, Tingting Niu, Yanli Wang, Tingbin Ma, Rui Chen, Cheng Wang, Zhengang Yang, Jing Yu Liu

Journal Article

Abstract
Phosphorus is a necessary component of all living organisms. This nutrient is mainly transported from the maternal blood to the fetus via the placenta, and insufficient phosphorus availability via the placenta disturbs the normal development of the fetus, especially fetal bone formation in late gestation. Key proteins (phosphate transporters and exporters) that are responsible for the maintenance of placental‐fetal phosphorus homeostasis have been identified. A deficiency in the phosphate transporter Pit2 has been shown to result in placental calcification and the retardation of fetal development in mice. What roles does XPR1 (the only known phosphate exporter) play in maintaining placental‐fetal phosphorus homeostasis? In this study, we found that Xpr1 expression is strong in the murine placenta and increases with age during gestation. We generated a global Xpr1 knockout mouse and found that heterozygous (Xpr1+/‐) and homozygous (Xpr1‐/‐) fetuses have lower inorganic phosphate (Pi) levels in amniotic fluid and serum and a decreased skeletal mineral content. Xpr1‐deficient placentas show abnormal Pi exchange during gestation. Therefore, Xpr1 deficiency in the placenta disrupts placental‐fetal Pi homeostasis. We also discovered that the placentas of the Xpr1+/‐ and Xpr1‐/‐ embryos are severely calcified. Mendelian inheritance statistics for offspring outcomes indicated that Xpr1‐deficient embryos are significantly reduced in late gestation. In addition, Xpr1‐/‐ mice die perinatally and a small proportion of Xpr1+/‐ mice die neonatally. RNA‐seq analysis of placental m
RNA revealed that many of the transcripts are significantly differentially expressed due to Xpr1 deficiency and are linked to dysfunction of the placenta. This study is the first to reveal that XPR1 plays an important role in maintaining placental‐fetal Pi homeostasis, disruption of which causes severe placental calcification, delays normal placental function and restricts fetal growth.
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Effects of a 12‐month supervised, community‐based, multi‐modal exercise program followed by a 6‐month research‐to‐practice transition on bone mineral density, trabecular micro‐architecture and physical function in older adults: A randomised controlled trial

09-09-2019 – Robin M. Daly, Jenny Gianoudis, Mariana E. Kersh, Christine A. Bailey, Peter R. Ebeling, Roland Krug, Caryl A. Nowson, Keith Hill, Kerrie M. Sanders

Journal Article

Abstract
Multi‐component exercise programs are recommended to reduce fracture risk, however their effectiveness in real world community settings remain uncertain. This 18‐month randomized controlled trial investigated the effects of a 12‐month, community‐based, supervised multi‐component exercise program followed by a 6‐month ‘research‐to‐practice’ transition, on areal BMD, trabecular bone microarchitecture, functional performance and falls in older adults at increased fracture risk. One‐hundred and sixty‐two adults aged ≥60 years with osteopenia or at increased falls risk were randomized to the Osteo‐cise: Strong Bones for Life multi‐component exercise program (n=81) or a control group (n=81). Exercise consisted of progressive resistance, weight‐bearing impact and balance training (3‐days/week) performed at community leisure centres. Overall 148 (91%) participants completed the trial, and mean exercise adherence was 59% after 12‐months, and 45% during the final 6‐months. After 12 months, there were significant net beneficial effects of exercise on lumbar spine and femoral neck BMD (1.0‐1.1%, P<0.05), muscle strength (10‐13%, P<0.05) and physical function (timed stair climb 5%; four‐square step test 6%; sit‐to‐stand 16%, P ranging <0.05 to <0.001), which persisted following the 6‐month transition. There were no significant effects of the 18‐month intervention on distal femur or proximal tibia trabecular bone microarchitecture or falls incidence, but per protocol analysis (≥66% exercise adherence) revealed there was a significant net benefit of exercise mean (95% confidence interval): 2.8% (0.2, 5,4) on proximal tibia trabecular bone volume fraction Osteo‐cise 1.5% (‐1.2, 4.2); controls ‐1.3% (‐2.6, 0.1) after 18‐months, due to changes in trabecular number Osteo‐cise 1.7% (‐0.9, 4.3); controls ‐1.1% (‐2.4, 0.2) and not trabecular thickness Osteo‐cise ‐0.2% (‐0.5, 0.2); controls ‐0.2% (‐0.4, 0.0). In conclusion, this study supports the effectiveness of the Osteo‐cise: Strong Bones for Life program as a real‐world, pragmatic, evidence‐based community exercise program to improve multiple musculoskeletal health outcomes in older adults at increased fracture risk.
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High‐dose TGF‐β1 impairs mesenchymal stem cell‐mediated bone regeneration via Bmp2 inhibition

05-09-2019 – Jiajia Xu, Jinlong Liu, Yaokai Gan, Kerong Dai, Jingyu Zhao, Mingjian Huang, Yan Huang, Yifu Zhuang, Xiaoling Zhang

Journal Article

Abstract
Transforming growth factor‐β1 (TGF‐β1) is a key factor in bone reconstruction. However, its pathophysiological role in non‐union and bone repair remains unclear. Here we demonstrated that TGF‐β1 was highly expressed in both C57BL/6 mice where new bone formation was impaired after autologous bone marrow mesenchymal stem cell (BMMSC) implantation and non‐union patients. High doses of TGF‐β1 inhibited BMMSC osteogenesis and attenuated bone regeneration in vivo. Furthermore, different TGF‐β1 levels exhibited opposite effects on osteogenic differentiation and bone healing. Mechanistically, low TGF‐β1 doses activated smad3, promoted their binding to bone morphogenetic protein 2 (Bmp2) promoter, and upregulated Bmp2 expression in BMMSCs. By contrast, Bmp2 transcription was inhibited by changing smad3 binding sites on its promoter at high TGF‐β1 levels. In addition, high TGF‐β1 doses increased tomoregulin‐1 (Tmeff1) levels, resulting in the repression of Bmp2 and bone formation in mice. Treatment with the TGF‐β1 inhibitor SB431542 significantly rescued BMMSC osteogenesis and accelerated bone regeneration. Our study suggests that high‐dose TGF‐β1 dampens BMMSC‐mediated bone regeneration by activating canonical TGF‐β/smad3 signaling and inhibiting Bmp2 via direct and indirect mechanisms. These data collectively show a previously unrecognized mechanism of TGF‐β1 in bone repair, and TGF‐β1 is an effective therapeutic target for treating bone regeneration disability.
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EZH2 supports osteoclast differentiation and bone resorption via epigenetic and cytoplasmic targets

05-09-2019 – Juraj Adamik, Sree H. Pulugulla, Peng Zhang, Quanhong Sun, Konstantinos Lontos, David A. Macar, Philip E. Auron, Deborah L. Galson

Journal Article

Abstract
Key osteoclast (OCL) regulatory gene promoters in bone marrow derived monocytes harbor bivalent histone modifications that combine activating Histone 3 lysine 4 tri‐methyl (H3K4me3) and repressive H3K27me3 marks, which upon RANKL stimulation resolve into repressive or activating architecture. Enhancer of zeste homologue 2 (EZH2) is the histone methyltransferase component of the polycomb repressive complex 2, which catalyzes H3K27me3 modifications. Immunofluorescence microscopy reveals that EZH2 localization during murine osteoclastogenesis is dynamically regulated. Using EZH2 knockdown and small molecule EZH2 inhibitor GSK126, we show that EZH2 plays a critical epigenetic role in OCL precursors (OCLp) during the first 24 hours of RANKL activation. RANKL triggers EZH2 translocation into the nucleus where it represses OCL negative regulators Maf
B, Irf8 and Arg1. Consistent with its cytoplasmic localization in OCLp, EZH2 methyltransferase activity is required during early RANKL signaling for phosphorylation of AKT, resulting in downstream activation of the m
TOR complex, which is essential for induction of OCL differentiation. Inhibition of RANKL‐induced pm
TOR‐pS6RP signaling by GSK126 altered the translational ratio of the C/EBPβ‐LAP and C/EBPβ‐LIP isoforms and reduced nuclear translocation of the inhibitory C/EBPβ‐LIP, which is necessary for transcriptional repression of the OCL negative‐regulatory transcription factor Maf
B. EZH2 in multinucleated OCL is primarily cytoplasmic and mature OCL cultured on bone segments in the presence of GSK126 exhibit defective cytoskeletal architecture and reduced resorptive activity. Here we present new evidence that EZH2 plays epigenetic and cytoplasmic roles during OCL differentiation by suppressing Maf
B transcription and regulating early phases of PI3K‐AKT‐m
TOR‐mediated RANKL signaling, respectively. Consistent with its cytoplasmic localization, EZH2 is required for cytoskeletal dynamics during resorption by mature OCL. Thus, EZH2 exhibits complex roles in supporting osteoclast differentiation and function.
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CD55 regulates bone mass in mice by modulating RANKL‐mediated Rac signaling and osteoclast function

05-09-2019 – Bongjin Shin, Heeyeon Won, Douglas J. Adams, Sun‐Kyeong Lee

Journal Article

ABSTRACTCD55 is a glycosylphosphatidylinositol (GPI)‐anchored protein, which regulates complement mediated and innate and adaptive immune responses. Although CD55 is expressed in various cell types in the bone marrow, its role in bone has not been investigated. In the current study, trabecular bone volume measured by μCT in the femurs of CD55KO female mice was increased compared to WT. Paradoxically; osteoclast number was increased in CD55KO with no differences in osteoblast parameters. Osteoclasts from CD55KO mice exhibited abnormal actin‐ring formation and reduced bone‐resorbing activity. Moreover, M‐CSF and RANKL treatment failed to activate Rac GTPase in CD55KO BMM cells. In addition, the apoptotic caspases activity was enhanced in CD55KO, which led to the poor survival of mature osteoclasts. Our results imply that CD55KO mice have increased bone mass due to defective osteoclast resorbing activity resulting from reduced Rac activity in osteoclasts. We conclude that CD55 plays an important role in the survival and bone‐resorption activity of osteoclasts through regulation of Rac activity.
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MiR‐146a Deletion Protects From Bone Loss in OVX Mice by Suppressing RANKL/OPG and M‐CSF in Bone Microenvironment

04-09-2019 – Jingyu Zhao, Mingjian Huang, Xudong Zhang, Jiajia Xu, Guoli Hu, Xiaoying Zhao, Penglei Cui, Xiaoling Zhang

Journal Article

ABSTRACTMicro
RNAs play important roles in osteoporosis and show great potential for diagnosis and therapy of osteoporosis. Previous studies have demonstrated that mi
R‐146a affects osteoblast (OB) and osteoclast (OC) formation. However, these findings have yet to be identified in vivo, and it is unclear whether mi
R‐146a is related to postmenopausal osteoporosis. Here, we demonstrated that mi
R‐146a knockout protects bone loss in mouse model of estrogen‐deficient osteoporosis, and mi
R‐146a inhibits OB and OC activities in vitro and in vivo. Mi
R‐146a−/− mice displayed the same bone mass as the wild type (WT) but exhibited a stronger bone turnover than the WT did under normal conditions. Nevertheless, mi
R‐146a−/− mice showed an increase in bone mass after undergoing ovariectomy (OVX) compared with those subjected to sham operation. OC activities were impaired in the mi
R‐146a−/− mice exposed to estrogen deficiency, which was diametrically opposite to the enhanced bone resorption ability of WT. Macrophage colony‐stimulating factor (M‐CSF) and receptor activator of NF‐κB ligand (RANKL)/osteoprotegerin (OPG) from a bone microenvironment affect this extraordinary phenomenon. Therefore, our results implicate that mi
R‐146a plays a key role in estrogen deficiency–induced osteoporosis, and the inhibition of this molecule provides skeleton protection. © 2019 American Society for Bone and Mineral Research.

Rmrp Mutation Disrupts Chondrogenesis and Bone Ossification in Zebrafish Model of Cartilage‐Hair Hypoplasia via Enhanced Wnt/β‐Catenin Signaling

04-09-2019 – Xianding Sun, Ruobin Zhang, Mi Liu, Hangang Chen, Liang Chen, Fengtao Luo, Dali Zhang, Junlan Huang, Fangfang Li, Zhenhong Ni, Huabing Qi, Nan Su, Min Jin, Jing Yang, Qiaoyan Tan, Xiaolan Du, Bo Chen, Haiyang Huang, Shuai Chen, Liangjun Yin, Xiaoling Xu, Chuxia Deng, Lingfei Luo, Yangli Xie, Lin Chen

Journal Article

ABSTRACTCartilage‐hair hypoplasia (CHH) is an autosomal recessive metaphyseal chondrodysplasia characterized by bone dysplasia and many other highly variable features. The gene responsible for CHH is the RNA component of the mitochondrial RNA‐processing endoribonuclease (RMRP) gene. Currently, the pathogenesis of osteochondrodysplasia and extraskeletal manifestations in CHH patients remains incompletely understood; in addition, there are no viable animal models for CHH. We generated an rmrp KO zebrafish model to study the developmental mechanisms of CHH. We found that rmrp is required for the patterning and shaping of pharyngeal arches. Rmrp mutation inhibits the intramembranous ossification of skull bones and promotes vertebrae ossification. The abnormalities of endochondral bone ossification are variable, depending on the degree of dysregulated chondrogenesis. Moreover, rmrp mutation inhibits cell proliferation and promotes apoptosis through dysregulating the expressions of cell‐cycle‐ and apoptosis‐related genes. We also demonstrate that rmrp mutation upregulates canonical Wnt/β‐catenin signaling; the pharmacological inhibition of Wnt/β‐catenin could partially alleviate the chondrodysplasia and increased vertebrae mineralization in rmrp mutants. Our study, by establishing a novel zebrafish model for CHH, partially reveals the underlying mechanism of CHH, hence deepening our understanding of the role of rmrp in skeleton development.

The Prevalence of Osteoporosis in China, a Nationwide, Multicenter DXA Survey

29-08-2019 – Qiang Zeng, Na Li, Qianqian Wang, Jian Feng, Dongmao Sun, Qiu Zhang, Jiyuan Huang, Qingxiang Wen, Rong Hu, Liang Wang, Yuanzheng Ma, Xiaoxia Fu, Shengyong Dong, Xiaoguang Cheng

Journal Article

ABSTRACTA number of studies investigated the distribution of BMD values and the prevalence of osteoporosis in China, but their findings varied. Until now, a BMD reference database based on uniform measurements in a large‐scale Chinese population has been lacking. A total of 75,321 Chinese adults aged 20 years and older were recruited from seven centers between 2008 and 2018. BMD values at the lumbar spine (L1–L4), femoral neck, and total femur were measured by GE Lunar dual‐energy X‐ray absorptiometry systems. BMD values measured in each center were cross‐calibrated by regression equations that were generated by scanning the same European spine phantom 10 times at every center. Cubic and multivariate linear regression were performed to assess associations between BMD values and demographic variables. Sex‐specific prevalence of osteoporosis was age‐standardized based on the year 2010 national census data for the Chinese population. The sex‐specific BMD values at each site were negatively associated with age, positively associated with body mass index levels, and lower in the participants from southwest China than in those from other geographic regions after multivariate adjustment. Furthermore, BMD values at the femoral neck and total femur decreased with the year of BMD measurement. The peak BMD values at the lumbar spine, femoral neck, and total femur were 1.088 g/cm2, 0.966 g/cm2, and 0.973 g/cm2, respectively, for men, and 1.114 g/cm2, 0.843 g/cm2, and 0.884 g/cm2, respectively, for women. The age‐standardized prevalence of osteoporosis at the spine or hip was 6.46% and 29.13% for men and women aged 50 years and older, respectively. Currently a total of 10.9 million men and 49.3 million women in China are estimated to have osteoporosis. In our national examination of BMD, we found that BMD values differed by demographic characteristics. We estimated the age‐standardize prevalence of osteoporosis in China to be 6.46% and 29.13% respectively, for men and women aged 50 years and older.

A New 1,25 Dihydroxy Vitamin D Analog with Strong Bone Anabolic Activity in OVX Rats with Little or no Bone Resorptive Activity

28-08-2019 – Lori A Plum, Julia Zella, Margaret Clagett‐Dame, Hector F DeLuca

Journal Article

ABSTRACTA new 1α,25‐dihydroxy vitamin D3 analog (2‐methylene‐22(E)‐(24R)‐22‐dehydro‐1α,24,25‐trihydroxy‐19‐norvitamin D3 or WT‐51) has been tested as a possible therapeutic for osteoporosis. It is 1/10th as active as 1,25(OH)2D3 in binding affinity for the vitamin D receptor but is at least 200 times more active than 1,25(OH)2D3 and equal to that of 2MD (2‐methylene‐19‐nor‐(20S)‐1α,25(OH)2D3, an analog previously tested in postmenopausal women), in supporting bone formation by isolated osteoblasts in culture. However, in contrast to 2MD, it is virtually inactive on bone resorption in vivo. WT‐51 markedly increased bone mass (lumbar and femur) in ovariectomized (OVX) female rats. Further, bone strength tested by the three‐point bending system is significantly increased by WT‐51. Thus, WT‐51 is an attractive candidate for the treatment of postmenopausal osteoporosis. © 2019 American Society for Bone and Mineral Research.

Anthony W Norman, PhD, Biochemist, Mentor, Distinguished Professor, and Principal Steward of Vitamin D Science (1938–2019)

28-08-2019 –

Journal Article

Osteogenesis Imperfecta: Skeletal Outcomes After Bisphosphonate Discontinuation at Final Height

26-08-2019 – Marie‐Eve Robinson, Pamela Trejo, Telma Palomo, Francis H Glorieux, Frank Rauch

Journal Article

ABSTRACTIntravenous cyclical bisphosphonates are widely used to treat children with moderate to severe osteogenesis imperfecta (OI). Bisphosphonates are often discontinued when growth is completed, but subsequent skeletal changes have not been studied in detail. We assessed 31 patients (22 females) with OI who had started intravenous bisphosphonates (either pamidronate or zoledronic acid) before 13 years of age, were treated for at least 2 years (range 4.7–15.7 years), and discontinued treatment after completion of growth, when their age ranged from 13.4 to 20.0 years (mean 16.4 years). At 4 years after treatment discontinuation, lumbar spine areal bone mineral density (BMD) had increased by 4% (p < 0.05). Peripheral quantitative computed tomography of the radius showed a decrease in trabecular volumetric BMD at the distal metaphysis of 19% but an increase in cortical volumetric BMD of 4% (p < 0.05 for both). None of the patients sustained a new vertebral compression fracture during follow‐up. The proportion of patients with new long‐bone fractures was higher in the 2 years before treatment discontinuation than in the last 2 years of follow‐up (42% and 16%, respectively; p < 0.05). © 2019 American Society for Bone and Mineral Research.

Glucocorticoids Decrease Longitudinal Bone Growth in Pediatric Kidney Transplant Recipients by Stimulating the FGF23/FGFR3 Signaling Pathway

26-08-2019 – Ángela Delucchi, Luis Toro, Rodrigo Alzamora, Victor Barrientos, Magdalena González, Rodrigo Andaur, Pablo León, Francisco Villanueva, Mario Galindo, Facundo Las Heras, Martín Montecino, Daniel Moena, Andrea Lazcano, Viola Pinto, Paulina Salas, María Loreto Reyes, Verónica Mericq, Luis Michea

Journal Article

ABSTRACTRenal transplantation (RTx) is an effective therapy to improve clinical outcomes in pediatric patients with terminal chronic kidney disease. However, chronic immunosuppression with glucocorticoids (GCs) reduces bone growth and BMD. The mechanisms causing GC‐induced growth impairment have not been fully clarified. Fibroblast growth factor 23 (FGF23) is a peptide hormone that regulates phosphate homeostasis and bone growth. In pathological conditions, FGF23 excess or abnormal FGF receptors (FGFR) activity leads to bone growth impairment. Experimental data indicate that FGF23 expression is induced by chronic GC exposure. Therefore, we hypothesize that GCs impair bone growth by increasing FGF23 expression, which has direct effects on bone growth plate. In a post hoc analysis of a multicentric randomized clinical trial of prepubertal RTx children treated with early GC withdrawal or chronic GC treatment, we observed that GC withdrawal was associated with improvement in longitudinal growth and BMD, and lower plasma FGF23 levels as compared with a chronic GC group. In prepubertal rats, GC‐induced bone growth retardation correlated with increased plasma FGF23 and bone FGF23 expression. Additionally, GC treatment decreased FGFR1 expression whereas it increased FGFR3 expression in mouse tibia explants. The GC‐induced bone growth impairment in tibiae explants was prevented by blockade of FGF23 receptors using either a pan‐FGFR antagonist (PD173074), a C‐terminal FGF23 peptide (FGF23180‐205) which blocks the binding of FGF23 to the FGFR‐Klotho complex or a specific FGFR3 antagonist (P3). Finally, local administration of PD173074 into the tibia growth plate ameliorated cartilage growth impairment in GC‐treated rats. These results show that GC treatment partially reduces longitudinal bone growth via upregulation of FGF23 and FGFR3 expression, thus suggesting that the FGF23/Klotho/FGFR3 axis at the growth plate could be a potential therapeutic target for the management of GC‐induced growth impairment in children.

TGFβ inhibition stimulates collagen maturation to enhance bone repair and fracture resistance in a murine myeloma model

23-08-2019 – Alanna C Green, Darren Lath, Katie Hudson, Brant Walkley, Jennifer M Down, Robert Owen, Holly R Evans, Julia Paton‐Hough, Gwendolen C Reilly, Michelle A Lawson, Andrew D Chantry

Journal Article

ABSTRACTMultiple myeloma is a plasma cell malignancy that causes debilitating bone disease and fractures, in which TGFβ plays a central role. Current treatments do not repair existing damage and fractures remain a common occurrence. We developed a novel low tumour phase murine model mimicking the plateau phase in patients, as we hypothesized this would be an ideal time to treat with a bone anabolic. Using in vivo micro
CT we show substantial and rapid bone lesion repair (and prevention) driven by SD‐208 (TGFβ receptor I kinase inhibitor) and chemotherapy (bortezomib and lenalidomide) in mice with human U266‐GFP‐luc myeloma. We discovered that lesion repair occurred via an intramembranous fracture repair‐like mechanism and that SD‐208 enhanced collagen matrix maturation to significantly improve fracture resistance. Lesion healing was associated with VEGFA expression in woven bone, reduced osteocyte‐derived PTHr
P, increased osteoblasts, decreased osteoclasts and lower serum TRACP‐5b. SD‐208 also completely prevented bone lesion development mice with aggressive JJN3 tumors, and was more effective than an anti‐TGFβ neutralizing antibody (1D11). We also discovered that SD‐208 promoted osteoblastic differentiation (and overcame the TGFβ‐induced block in osteoblastogenesis) in myeloma patient bone marrow stromal cells in vitro, comparable to normal donors. The improved bone quality and fracture‐resistance with SD‐208 provides incentive for clinical translation to improve myeloma patient quality of life by reducing fracture risk and fatality.
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Estradiol and follicle stimulating hormone as predictors of onset of menopause transition‐related bone loss in pre‐ and perimenopausal women

23-08-2019 – Albert Shieh, Gail A. Greendale, Jane A. Cauley, Carrie Karvonen‐Gutierrez, Carolyn J. Crandall, Arun S. Karlamangla

Journal Article

ABSTRACTThe menopause transition (MT) may be an opportunity for early intervention to prevent rapid bone loss. In order to intervene early, we need to be able to prospectively identify pre‐ and perimenopausal women who are beginning to lose bone. This study examined whether estradiol (E2), or follicle stimulating hormone (FSH), measured in pre‐ and perimenopausal women, can predict significant bone loss by the next year. Bone loss was considered significant if BMD decline at the lumbar spine (LS) or femoral neck (FN) from a pre‐ or early perimenopausal baseline to 1 year after the E2 or FSH measurement was greater than the least detectable change. We used data from 1,559 participants in the Study of Womens Health Across the Nation and tested E2 and FSH as separate predictors using repeated measures modified Poisson regression. Adjusted for MT stage, age, race/ethnicity, and body mass index, women with lower E2 (and higher FSH) were more likely to lose BMD: At the LS, each halving of E2 and each doubling of FSH were associated with 10% and 39% greater risk of significant bone loss, respectively (p < 0.0001 for each). At the FN, each halving of E2 and each doubling of FSH were associated with 12% (p = 0.01) and 27% (p < 0.001) greater risk of significant bone loss. FSH was more informative than E2 (assessed by the area under the receiver‐operator curve) at identifying women who were more vs. less likely to begin losing bone, especially at the LS. Prediction was better when hormones were measured in pre‐ or early perimenopause than in late perimenopause. Tracking within‐individual change in either hormone did not predict onset of bone loss better than a single measure. We conclude that measuring FSH in the MT can help prospectively identify woman with imminent or ongoing bone loss at the LS.
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Primary Bone Tumors: Challenges and Opportunities for CAR‐T Therapies

23-08-2019 – Ian W. Folkert, Samir Devalaraja, Gerald P. Linette, Kristy Weber, Malay Haldar

Journal Article

Abstract
Primary malignant bone tumors are rare, occur in all age groups, and include distinct entities such as osteosarcoma, Ewing sarcoma, and Chondrosarcoma. Traditional treatment with some combination of chemotherapy, surgery, and radiation has reached the limit of efficacy, with substantial room for improvement in patient outcome. Furthermore, genomic characterization of these tumors reveals a paucity of actionable molecular targets. Against this backdrop, recent advances in cancer immunotherapy represent a silver lining in the treatment of primary bone cancer. Major strategies in cancer immunotherapy include stimulating naturally occurring anti‐tumor T cells and adoptive transfer of tumor‐specific cytotoxic T cells. Chimeric antigen receptor T cells (CAR‐T cells) belong to the latter strategy and are an impressive application of both insights into T cell biology and advances in genetic engineering. In this review, we briefly describe the CAR‐T approach and discuss its applications in primary bone tumors.
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Sclerostin Antibody‐Induced Changes in Bone Mass are Site Specific in Developing Crania

23-08-2019 – Amanda L. Scheiber, David K. Barton, Basma M. Khoury, Joan C. Marini, Donald L. Swiderski, Michelle S. Caird, Kenneth M. Kozloff

Journal Article

ABSTRACTSclerostin antibody (Scl‐Ab) is an anabolic bone agent that has been shown to increase bone mass in clinical trials of adult diseases of low bone mass, such as osteoporosis and osteogenesis imperfecta (OI). Its use to decrease bone fragility in pediatric OI has shown efficacy in several growing mouse models, suggesting translational potential to pediatric disorders of low bone mass. However, the effects of pharmacologic inhibition of sclerostin during periods of rapid growth and development have not yet been described with respect to the cranium, where lifelong deficiency of functioning sclerostin leads to patterns of excessive bone growth, cranial compression, and facial palsy.
In the present study, we undertook dimensional and volumetric measurements in the skulls of growing Brtl/+ OI mice treated with Scl‐Ab to examine whether therapy induced phenotypic changes similar to those observed clinically in patients with Sclerosteosis or Van Buchem disorder. Mice treated between 3‐14 weeks of age with high doses of Scl‐Ab show significant calvarial thickening capable of rescuing OI‐induced deficiencies in skull thickness. Other changes in cranial morphology, such as lengths and distances between anatomic landmarks, intracranial volume, and suture interdigitation, showed minimal effects of Scl‐Ab when compared to growth‐induced differences over the treatment duration. Treatment‐induced narrowing of foramina was limited to sites of vascular, but not neural passage, suggesting patterns of local regulation. Together, these findings reveal a site‐specificity of Scl‐Ab action in the calvaria with no measurable cranial nerve impingement or brainstem compression. This differentiation from the observed outcomes of lifelong sclerostin deficiency complements reports of Scl‐Ab treatment efficacy at other skeletal sites with the prospect of minimal cranial secondary complications.
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RANKL Inhibition in Fibrous Dysplasia of Bone: A Preclinical Study in a Mouse Model of the Human Disease

21-08-2019 – Biagio Palmisano, Emanuela Spica, Cristina Remoli, Rossella Labella, Annamaria Di Filippo, Samantha Donsante, Fabiano Bini, Domenico Raimondo, Franco Marinozzi, Alan Boyde, Pamela Robey, Alessandro Corsi, Mara Riminucci

Journal Article

ABSTRACTFibrous dysplasia of bone/McCune‐Albright syndrome (Polyostotic FD/MAS; OMIM#174800) is a crippling skeletal disease caused by gain‐of‐function mutations of Gsα. Enhanced bone resorption is a recurrent histological feature of FD and a major cause of fragility of affected bones. Previous work suggests that increased bone resorption in FD is driven by RANKL and some studies have shown that the anti‐RANKL monoclonal antibody, denosumab, reduces bone turnover and bone pain in FD patients. However, the effect of RANKL inhibition on the histopathology of FD and its impact on the natural history of the disease remain to be assessed. In this study, we treated the EF1α‐GsαR201C mice, which develop an FD‐like phenotype, with an anti‐mouse RANKL monoclonal antibody. We found that the treatment induced marked radiographic and microscopic changes at affected skeletal sites in 2‐month‐old mice. The involved skeletal segments became sclerotic due to the deposition of new, highly mineralized bone within developing FD lesions and showed a higher mechanical resistance compared to affected segments from untreated transgenic mice. Similar changes were also detected in older mice with a full‐blown skeletal phenotype. The administration of anti‐mouse RANKL antibody arrested the growth of established lesions and, in young mice, prevented the appearance of new ones. However, after drug withdrawal, the newly formed bone was remodelled into FD tissue and the disease progression resumed in young mice. Taken together, our results show that the anti‐RANKL antibody significantly affected the bone pathology and natural history of FD in the mouse. Pending further work on the prevention and management of relapse after treatment discontinuation, our preclinical study suggests that RANKL inhibition may be an effective therapeutic option for FD patients. © 2019 American Society for Bone and Mineral Research.

Hop2 Interacts with ATF4 to Promote Osteoblast Differentiation

21-08-2019 – Yang Zhang, Tonghui Lin, Na Lian, Huan Tao, Cong Li, Lingzhen Li, Xiangli Yang

Journal Article

Abstract
Activating transcription factor 4 (ATF4) is a member of the basic leucine zipper (b
Zip) transcription factor family required for the terminal differentiation of osteoblasts. Despite its critical importance as one of the three main osteoblast differentiation transcription factors, regulators of osteoblast terminal maturation remain poorly defined. Here we report the identification of homologous pairing protein 2 (Hop2) as a dimerization partner of ATF4 in osteoblasts via the yeast two hybrid system. Deletional mapping revealed that the Zip domain of Hop2 is necessary and sufficient to bind ATF4 and to enhance ATF4‐dependent transcription. Ectopic Hop2 expression in preosteoblasts increased endogenous ATF4 protein content and accelerates osteoblast differentiation. Mice lacking Hop2 (Hop2‐/‐) have a normal stature but exhibit an osteopenic phenotype similar to the one observed in Atf4‐/‐ mice, albeit milder, which is associated with decreased Osteocalcin m
RNA expression and reduced Type I collagen synthesis. Compound heterozygous mice (Atf4+/‐:Hop2+/‐) display identical skeletal defects to those seen in Hop2‐/‐ mice. These results indicate that Hop2 plays a previous unknown role as a determinant of osteoblast maturation via its regulation of ATF4 transcriptional activity. Our work for the first time reveals a function of Hop2 beyond its role in guiding the alignment of homologous chromosomes.
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Reply to: Change in Bone Density and Reduction in Fracture Risk: A Meta‐Regression of Published Trials

21-08-2019 – Mary L Bouxsein, Richard Eastell, Li‐Yung Liu, Lucy A Wu, Anne E Papp, Andreas Grauer, Fernando Marin, Jane A Cauley, Douglas C Bauer, Dennis M Black, for the FNIH Bone Quality Project

Letter

Genetic screening in a large Chinese cohort of childhood onset hypoparathyroidism by next‐generation sequencing combined with TBX1‐MLPA

21-08-2019 – Yabing Wang, Min Nie, Ou Wang, Yuepeng Li, Yan Jiang, Mei Li, Weibo Xia, Xiaoping Xing

Journal Article

ABSTRACTAt least 15 candidate genes have been implicated in hypoparathyroidism (HP). However, comprehensive screening of causative genes for HP is lacking. Here, we investigated the genotype spectrum in a large group of Chinese patients with childhood onset HP. A total of 173 patients with childhood onset HP were analyzed using targeted next‐generation sequencing (NGS), including 15 candidate genes combined with multiplex ligation‐dependent probe amplification (MLPA) of the TBX1 gene. Twenty‐seven pathogenic or likely pathogenic mutations in five genes (TBX1, AIRE, GATA3, FAM111A, and CASR) including 14 novel variants in 23 patients, and 12 variants of uncertain clinical significance in five genes (GATA3, CASR, FAM111A, GCM2, and PTH) in 11 patients, were identified by NGS. And an entire gene deletion of TBX1 in 25 patients was found by TBX1‐MLPA. Combined with clinical data, 26 (15.0%) cases of Di
George syndrome (OMIM #188400), nine (5.2%) autoimmune polyglandular syndrome type 1 (OMIM #240300), eight (4.6%) autosomal dominant hypocalcemia type 1 (OMIM #601198), four (2.3%) hypoparathyroidism‐deafness‐renal dysplasia syndrome (OMIM #146255), and one (0.6%) Kenny‐Caffey syndrome type 2 (OMIM #127000) were verified. Among them, 16/26 (61.5%) of Di
George syndrome cases were undiagnosed due to the lack of obvious clinical clues before genetic testing. The onset age of patients with mutations (2.8 0.1, 9.6 years) was significantly earlier than those without mutations (13.0 8.8, 15.0) (P < 0.001). Family history, early onset age especially prior to 5 years old, and extra‐parathyroid manifestations were clues for hereditary HP. The combined targeted NGS and TBX‐1 MLPA were conveniently and effectively used for comprehensive genetic screening in this large Chinese cohort of childhood onset HP. Genetic defects were identified in 27.7% of early‐onset HP patients, including four kinds of syndromic HP and one isolated HP. A total of 14 novel mutations were detected, which expands the mutation spectrum of hypoparathyroidism.
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Change in Bone Density and Reduction in Fracture Risk: A Meta‐Regression of Published Trials

21-08-2019 – Pierre JM Bergmann

Letter

Pain at Multiple Sites Is Associated With Prevalent and Incident Fractures in Older Adults

19-08-2019 – Feng Pan, Jing Tian, Dawn Aitken, Flavia Cicuttini, Graeme Jones

Journal Article

ABSTRACTMusculoskeletal pain is common and typically occurs at multiple sites. Pain has been shown to be associated with falls risk; however, whether an increased risk for falls associated with multisite pain (MSP) translates into an increased risk of fractures has not been investigated. This study aimed to examine the association of number of painful sites with prevalent and incident fractures. Data from a longitudinal population‐based study of older adults (mean age 63 years) were utilized. Follow‐up was performed at 2.6, 5.1, and 10.7 years later, respectively. Presence/absence of pain at the neck, back, hands, shoulders, hips, knees, and feet was assessed by questionnaire at baseline. Participants were classified into three groups according to the total number of painful sites: zero to two, three to four, and five to seven. Fractures were self‐reported at each time point. BMD was measured by DXA. Falls risk was calculated based on the Short‐Form Physiological Profile Assessment. Log‐binomial regression was used for the analyses. There were 450 fractures at baseline and 154 new fractures reported during a mean follow‐up period of 10.7 years (range 9.2 to 12.5 years). In multivariable analyses, number of painful sites was associated with prevalent fractures at any and nonvertebral site. Furthermore, participants with five to seven painful sites had an increased risk of incident fractures at any site (RR 1.69; 95% CI, 1.13 to 2.53); major site, including the femur, radius, ulnar, vertebral, rib, and humerus (RR 2.17; 95% CI 1.12 to 4.22); and vertebral site (RR 6.44, 95% CI, 1.64 to 25.33) compared with those with pain at zero to two sites. These associations remained statistically significant after further adjustment for falls risk and BMD. Pain at multiple sites was associated with incident fracture risk in a dose‐response manner, suggesting that widespread pain is an independent contributor to fracture risk. The potential for pain management in fracture prevention warrants further exploration. © 2019 American Society for Bone and Mineral Research.

IRS‐1 Functions as a Molecular Scaffold to Coordinate IGF‐I/IGFBP‐2 Signaling During Osteoblast Differentiation

19-08-2019 – Gang Xi, Xinchun Shen, Clifford J Rosen, David R Clemmons

Gender‐Affirming Hormone Treatment Decreases Bone Turnover in Transwomen and Older Transmen

19-08-2019 – Mariska C Vlot, Chantal M Wiepjes, Renate T Jongh, Guy T’Sjoen, Annemieke C Heijboer, Martin den Heijer

Journal Article

ABSTRACTSex steroids play a key role in bone turnover and preserving BMD; hence, gender‐affirming hormone treatment (HT) in transgender people affects bone metabolism. Most studies have looked into the effect of HT on changes in BMD; however, they do not provide insights into changes in bone metabolism caused by HT. This study investigated changes in bone turnover markers (BTMs) and sclerostin, as well as their correlations with change in BMD in transwomen and transmen during the first year of HT. Transwomen received estradiol and antiandrogens; transmen received testosterone. Sclerostin; P1NP; alkaline phosphatase (ALP); CTx; and BMD of the total hip, the femoral neck, and the lumbar spine were evaluated at baseline and after 1 year of HT. There were 121 transwomen (median age 30 years, interquartile range IQR 24 to 41 years) and 132 transmen (median age 24 years, IQR 21 to 33 years) included in the study. In transwomen, ALP decreased in 19% (95% CI, –21 to–16), CTx in 11% (95% CI, –18 to–4), and sclerostin in 8% (95%CI, –13 to–4) of study participants after 1 year of HT. In contrast, in transmen P1NP, ALP, and sclerostin increased in 33% (95% CI, 24 to 42), 16% (95% CI, 12 to 20), and 15% (95% CI, 10 to 20) of study participants, respectively, after 1 year of HT. No age differences were seen in transwomen, whereas in transmen aged ≥50 years a decrease in all BTMs was found in contrast with the other age groups. These transmen had low estrogen concentration at the start of HT based on their postmenopausal state before the start of HT; their estradiol concentrations increased during testosterone treatment. Changes in BTMs and BMD were weakly correlated (correlation coefficient all <0.30). To conclude, 1 year of HT resulted in decreased bone turnover in transwomen and older transmen, whereas it increased in younger transmen. The decrease in bone resorption in older transmen shows the importance of estrogen as a key regulator of bone turnover. © 2019 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc.

Elevated BMP and Mechanical Signaling Through YAP1/RhoA Poises FOP Mesenchymal Progenitors for Osteogenesis

19-08-2019 – Alexandra Stanley, Su‐jin Heo, Robert L Mauck, Foteini Mourkioti, Eileen M Shore

Journal Article

ABSTRACTFibrodysplasia ossificans progressiva (FOP) is a rare genetic disease characterized by the formation of extraskeletal bone, or heterotopic ossification (HO), in soft connective tissues such as skeletal muscle. All familial and sporadic cases with a classic clinical presentation of FOP carry a gain‐of‐function mutation (R206H; c.617 G > A) in ACVR1, a cell surface receptor that mediates bone morphogenetic protein (BMP) signaling. The BMP signaling pathway is recognized for its chondro/osteogenic‐induction potential, and HO in FOP patients forms ectopic but qualitatively normal endochondral bone tissue through misdirected cell fate decisions by tissue‐resident mesenchymal stem cells. In addition to biochemical ligand‐receptor signaling, mechanical cues from the physical environment are transduced to activate intracellular signaling, a process known as mechanotransduction, and can influence cell fates. Utilizing an established mesenchymal stem cell model of mouse embryonic fibroblasts (MEFs) from the Acvr1 R206H/+ mouse model that mimics the human disease, we demonstrated that activation of the mechanotransductive effectors Rho/ROCK and YAP1 are increased in Acvr1 R206H/+ cells. We show that on softer substrates, a condition associated with low mechanical signaling, the morphology of Acvr1 R206H/+ cells is similar to the morphology of control Acvr1 +/+ cells on stiffer substrates, a condition that activates mechanotransduction. We further determined that Acvr1 R206H/+ cells are poised for osteogenic differentiation, expressing increased levels of chondro/osteogenic markers compared with Acvr1 +/+ cells. We also identified increased YAP1 nuclear localization in Acvr1 R206H/+ cells, which can be rescued by either BMP inhibition or Rho antagonism. Our results establish Rho
A and YAP1 signaling as modulators of mechanotransduction in FOP and suggest that aberrant mechanical signals, combined with and as a result of the increased BMP pathway signaling through mutant ACVR1, lead to misinterpretation of the cellular microenvironment and a heightened sensitivity to mechanical stimuli that promotes commitment of Acvr1 R206H/+ progenitor cells to chondro/osteogenic lineages.

Clinical performance of the updated trabecular bone score (TBS) algorithm which accounts for the soft tissue thickness: The OsteoLaus Study

16-08-2019 – Enisa Shevroja, Bérengère Aubry‐Rozier, Gabriel Hans, Elena Gonzalez Rodriguez, Delphine Stoll, Olivier Lamy, Didier Hans

Journal Article

ABSTRACTRegional soft tissue may have a noise effect on trabecular bone score (TBS) and eventually alter its estimate. The current TBS software (TBS i
Nsight®) is based on an algorithm accounting for body mass index (BMI) (TBSv3.03). We aimed to explore the updated TBS algorithm that accounts for soft tissue thickness (TBSv4.0). This study was embedded in the Osteo
Laus cohort of women in Lausanne, Switzerland. Hip and lumbar spine (LS) dual‐energy X‐ray absorptiometry (DXA) scans were performed using Discovery A System (Hologic, 123, MA, USA). The incident major osteoporotic fractures (MOFs) were assessed from vertebral fracture assessments using the Genant`s method or questionnaires (non‐vertebral MOF). We assessed the correlations of bone mineral density (BMD) or TBS with body composition parameters; MOF prediction ability of both versions of TBS; and the differences between FRAX adjusted for TBSv3.03 or TBSv4.0. In total, 1,362 women with mean age (SD) 64.4 (7.5) years and mean BMI (SD) 25.9 (4.5) kg/m2 were followed up for 4.4 years and 132 experienced a MOF. All the anthropometric measurements of our interest were positively correlated with LS, femoral neck or hip BMD and TBSv4.0; whereas with TBSv3.03 their correlations were negative. In the models adjusted for age, soft tissue thickness, osteoporotic treatment and LS‐BMD, for each SD decline in TBSv3.03, there was a 43% (OR (95% CI): 1.43 (1.12‐1.83)) increase in the odds of having MOF; whereas for each SD decline in TBSv4.0, there was a 54% (OR (95% CI): 1.54 (1.18‐2.00)) increase in the odds of having a MOF. Both FRAXs were very strongly correlated and the mild differences were present in the already highly risked women for MOF. This study demonstrates that TBSv4.0 overcomes the debatable residual negative correlation of the current TBS with body size and composition parameters, postulating itself as free from the previously acknowledged technical limitation of TBS.
This article is protected by copyright. All rights reserved.

Standard vs Cyclic Teriparatide and Denosumab Treatment for Osteoporosis: A Randomized Trial

16-08-2019 – Felicia Cosman, Donald McMahon, David Dempster, Jeri W. Nieves

Journal Article

Abstract
In the absence of an intervening antiresorptive agent, cyclic administration of teriparatide does not increase BMD more than standard daily therapy. Since denosumab is a potent antiresorptive agent with a rapid off‐effect, we hypothesized that it might be the optimal agent to help maximize bone gains with cyclic teriparatide. In this 3 year protocol, 70 postmenopausal women with osteoporosis were randomized to: 18 months teriparatide followed by 18 months denosumab (Standard) or 3 separate 12 month cycles of 6 months teriparatide followed by 6 months denosumab (Cyclic). BMD (DXA) measurements of lumbar spine (LS), total hip (TH), femoral neck (FN), and 1/3 radius (RAD) were performed every 6 months and Total Body Bone Mineral (TBBM) at 18 and 36 months. Baseline descriptive characteristics did not differ between groups except for a minimal difference in LS BMD, but not T‐Score (mean age 65, mean LS T‐Score ‐2.7). In the Standard group, BMD increments at 36 months were: LS 16%, TH 4%, FN 3% and TBBM 4.8% (all p<0.001 vs baseline). In the Cyclic group, 36‐month BMD increments were similar: LS 12%, TH 4%, FN 4%, TBBM 4.1% (all p<0.001 vs baseline). At 36 months, the LS BMD increase with Standard was slightly larger than with Cyclic (p=0.04), but at 18 months, in the Cyclic group, there was no decline in RAD or TBBM (p=0.007 and <0.001, respectively vs Standard). Although the Cyclic regimen did not improve BMD compared with Standard at 36 months, there appeared to be a benefit at 18 months, especially in the highly cortical skeletal sites. This could be clinically relevant in patients at high imminent risk of fracture, particularly at nonvertebral sites.
This article is protected by copyright. All rights reserved.

Post‐fracture Risk Assessment: Target the Centrally Sited Fractures First! A Substudy of NoFRACT

16-08-2019 – Tove T Borgen, åshild Bjørnerem, Lene B Solberg, Camilla Andreasen, Cathrine Brunborg, May‐Britt Stenbro, Lars M Hübschle, Anne Froholdt, Wender Figved, Ellen M Apalset, Jan‐Erik Gjertsen, Trude Basso, Ida Lund, Ann K Hansen, Jens‐Meinhard Stutzer, Tone K Omsland, Lars Nordsletten, Frede Frihagen, Erik F Eriksen

Journal Article

Fractures at central sites are associated with lower BMD at the femoral neck, total hip, and the site with lowest T‐score, lower TBS, and higher prevalence of vertebral fractures. BMD = bone mineral density; TBS = trabecular bone score.
ABSTRACTThe location of osteoporotic fragility fractures adds crucial information to post‐fracture risk estimation. Triaging patients according to fracture site for secondary fracture prevention can therefore be of interest to prioritize patients considering the high imminent fracture risk. The objectives of this cross‐sectional study were therefore to explore potential differences between central (vertebral, hip, proximal humerus, pelvis) and peripheral (forearm, ankle, other) fractures. This substudy of the Norwegian Capture the Fracture Initiative (No
FRACT) included 495 women and 119 men ≥50 years with fragility fractures. They had bone mineral density (BMD) of the femoral neck, total hip, and lumbar spine assessed using dual‐energy X‐ray absorptiometry (DXA), trabecular bone score (TBS) calculated, concomitantly vertebral fracture assessment (VFA) with semiquantitative grading of vertebral fractures (SQ1–SQ3), and a questionnaire concerning risk factors for fractures was answered. Patients with central fractures exhibited lower BMD of the femoral neck (765 versus 827 mg/cm2), total hip (800 versus 876 mg/cm2), and lumbar spine (1024 versus 1062 mg/cm2); lower mean TBS (1.24 versus 1.28); and a higher proportion of SQ1‐SQ3 fractures (52.0% versus 27.7%), SQ2–SQ3 fractures (36.8% versus 13.4%), and SQ3 fractures (21.5% versus 2.2%) than patients with peripheral fractures (all p < 0.05). All analyses were adjusted for sex, age, and body mass index (BMI); and the analyses of TBS and SQ1–SQ3 fracture prevalence was additionally adjusted for BMD). In conclusion, patients with central fragility fractures revealed lower femoral neck BMD, lower TBS, and higher prevalence of vertebral fractures on VFA than the patients with peripheral fractures. This suggests that patients with central fragility fractures exhibit more severe deterioration of bone structure, translating into a higher risk of subsequent fragility fractures and therefore they should get the highest priority in secondary fracture prevention, although attention to peripheral fractures should still not be diminished. © 2019 American Society for Bone and Mineral Research. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Explicit Finite Element Models Accurately Predict Subject‐Specific and Velocity‐Dependent Kinetics of Sideways Fall Impact

14-08-2019 – Ingmar Fleps, Pierre Guy, Stephen J Ferguson, Peter A Cripton, Benedikt Helgason

Journal Article

ABSTRACTThe majority of hip fractures in the elderly are the result of a fall from standing or from a lower height. Current injury models focus mostly on femur strength while neglecting subject‐specific loading. This article presents an injury modeling strategy for hip fractures related to sideways falls that takes subject‐specific impact loading into account. Finite element models (FEMs) of the human body were used to predict the experienced load and the femoral strength in a single model. We validated these models for their predicted peak force, effective pelvic stiffness, and fracture status against matching ex vivo sideways fall impacts (n = 11) with a trochanter velocity of 3.1 m/s. Furthermore, they were compared to sideways impacts of volunteers with lower impact velocities that were previously conducted by other groups. Good agreement was found between the ex vivo experiments and the FEMs with respect to peak force (root mean square error RMSE = 10.7%, R2 = 0.85) and effective pelvic stiffness (R2 = 0.92, RMSE = 12.9%). The FEMs were predictive of the fracture status for 10 out of 11 specimens. Compared to the volunteer experiments from low height, the FEMs overestimated the peak force by 25% for low BMI subjects and 8% for high BMI subjects. The effective pelvic stiffness values that were derived from the FEMs were comparable to those derived from impacts with volunteers. The force attenuation from the impact surface to the femur ranged between 27% and 54% and was highly dependent on soft tissue thickness (R2 = 0.86). The energy balance in the FEMS showed that at the time of peak force 79% to 93% of the total energy is either kinetic or was transformed to soft tissue deformation. The presented FEMs allow for direct discrimination between fracture and nonfracture outcome for sideways falls and bridge the gap between impact testing with volunteers and impact conditions representative of real life falls. © 2019 American Society for Bone and Mineral Research.

Reduced Bone Loss Is Associated With Reduced Mortality Risk in Subjects Exposed to Nitrogen Bisphosphonates: A Mediation Analysis

12-08-2019 – Dana Bliuc, Thach Tran, Tineke Geel, Jonathan D Adachi, Claudie Berger, Joop den Bergh, John A Eisman, Piet Geusens, David Goltzman, David A Hanley, Robert Josse, Stephanie Kaiser, Christopher S Kovacs, Lisa Langsetmo, Jerilynn C Prior, Tuan V Nguyen, Jacqueline R Center, for the CaMOS Research Group

Journal Article

ABSTRACTBisphosphonates, potent antiresorptive agents, have been found to be associated with mortality reduction. Accelerated bone loss is, in itself, an independent predictor of mortality risk, but the relationship between bisphosphonates, bone loss, and mortality is unknown. This study aimed to determine whether the association between bisphosphonates and mortality is mediated by a reduction in the rate of bone loss. Participants from the population‐based Canadian Multicentre Osteoporosis Study were followed prospectively between1996 and 2011. Comorbidities and lifestyle factors were collected at baseline and bone mineral density (BMD) at baseline and at years 3 (for those aged 40 to 60 years), 5, and 10. Rate of bone loss was calculated using linear regression. Information on medication use was obtained yearly. Bisphosphonate users grouped into nitrogen bisphosphonates (n
BP; alendronate or risedronate) and etidronate and non‐users (No
Rx) were matched by propensity score, including all baseline factors as well as time of treatment. Coxs proportional hazards models, unadjusted and adjusted for annual rate of bone loss, were used to determine the association between n
BP and etidronate versus No
Rx. For the treatment groups with significant mortality risk reduction, the percent of mortality reduction mediated by a reduction in the rate of bone loss was estimated using a causal mediation analysis. There were 271 pairs of n
BP and matched No
Rx and 327 pairs of etidronate and matched No
Rx. n
BP but not etidronate use was associated with significant mortality risk reduction (hazard ratios HR = 0.61 95% confidence interval 0.39–0.96 and 1.35 95% CI 0.86–2.11 for n
BP and etidronate, respectively). Rapid bone loss was associated with more than 2‐fold increased mortality risk compared with no loss. Mediation analysis indicated that 39% (95% CI 7%–84%) of the n
BP association with mortality was related to a reduction in the rate of bone loss. This finding provides an insight into the mechanism of the relationship between n
BP and survival benefit in osteoporotic patients. © 2019 American Society for Bone and Mineral Research.

Association of Bone Density Monitoring in Routine Clinical Practice With Anti‐Osteoporosis Medication Use and Incident Fractures: A Matched Cohort Study

07-08-2019 – William D Leslie, Suzanne N Morin, Patrick Martineau, Mark Bryanton, Lisa M Lix

Journal Article

ABSTRACTRoutine bone mineral density (BMD) monitoring of individuals during the initial 5 years of anti‐osteoporosis treatment is controversial. Using a registry‐based cohort from the Province of Manitoba, Canada, we compared anti‐osteoporosis medication use and fracture outcomes in women with versus without BMD monitoring receiving anti‐osteoporosis medication. We identified 4559 women aged 40 years and older receiving anti‐osteoporosis therapy with serial BMD testing (monitoring) within 5 years (mean interval 3.2 years) and 4559 propensity score–matched women without BMD monitoring. We assessed anti‐osteoporosis medication use over 5 years from a population‐based retail pharmacy database. Incident fractures to 10 years from health services data. During median 10 years observation, 1225 (13.4%) women developed major osteoporotic fracture, including 382 (4.2%) with hip fractures. Monitored women had significantly better fracture‐free survival for major osteoporotic fracture (p = 0.040; 10‐year cumulative risk 1.9% lower, 95% confidence interval CI 0.3–3.6%) and hip fracture (p = 0.001; 10‐year cumulative risk 1.8% lower, 95% CI 0.7–2.8%) compared with women who were not monitored. Hazard ratios (HRs) were significantly lower in monitored versus not monitored women for major osteoporotic fracture (HR = 0.89, 95% CI 0.80–0.98) and hip fracture (HR = 0.74, 95% CI 0.63–0.87). Days of medication use, medication persistence ratio, and treatment switching over 5 years were greater in monitored versus not monitored women. At the end of 5 years, more women in the monitored group persisted on treatment and more switched treatment, with switching behavior associated with an observed interval reduction in BMD. In conclusion, our findings suggest a possible role for BMD monitoring after initiating anti‐osteoporosis therapy in the routine clinical practice setting. © 2019 American Society for Bone and Mineral Research.

Changes in Bone Marrow Adipose Tissue One Year After Roux‐en‐Y Gastric Bypass: A Prospective Cohort Study

07-08-2019 – Ingvild Kristine Blom‐Høgestøl, Tom Mala, Jon A Kristinsson, Ellen‐Margrethe Hauge, Cathrine Brunborg, Hanne Løvdal Gulseth, Erik Fink Eriksen

Journal Article

ABSTRACTBone marrow adipose tissue (BMAT) has been postulated to mediate skeletal fragility in type 2 diabetes (T2D) and obesity. Roux‐en‐Y gastric bypass (RYGB) induces a substantial weight loss and resolution of comorbidities. However, the procedure induces increased bone turnover and fracture rates. No previous study has evaluated biopsy‐measured BMAT fraction preoperatively and after RYGB. In this study, we aimed to investigate BMAT fraction of the hip in participants with and without T2D preoperatively and 1 year after RYGB and explore factors associated with BMAT change. Patients with morbid obesity scheduled for RYGB were examined preoperatively and 1 year after RYGB. Forty‐four participants were included and preoperative examinations were possible in 35. Of these, 33 (94%) met for follow‐up, 2 were excluded, and BMAT estimation was not possible in 1. Eighteen (60%) of the participants were females and 11 (37%) had T2D. Preoperative BMAT fraction was positively associated with glycosylated hemoglobin and negatively associated with areal bone mineral density (a
BMD). After RYGB, BMAT fraction decreased from 40.4 ± 1.7% to 35.6 ± 12.8%, p = 0.042, or with mean percent change of 10.7% of preoperative BMAT fraction. Change in BMAT fraction was positively associated with change in body mass index (BMI) and total body fat. In females, we observed a mean percent reduction of 22.4 ± 19.6%, whereas in males BMAT increased with a mean percent of 6.8 ± 37.5%, p = 0.009. For males, changes in estradiol were associated with BMAT change; this was not observed for females. In participants with and without T2D, the mean percent BMAT reduction was 5.8 ± 36.9% and 13.5 ± 28.0%, respectively, p = 0.52. We conclude that a high BMAT seems to be associated with lower a
BMD and poorer glycemic control in obese subjects. After RYGB, we observed a significant decrease in BMAT. The reduction in BMAT did not differ between participants with and without T2D, but appeared sex specific. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

Denosumab Improves Glomerular Filtration Rate in Osteoporotic Patients With Normal Kidney Function by Lowering Serum Phosphorus

07-08-2019 – Daichi Miyaoka, Masaaki Inaba, Yasuo Imanishi, Noriyuki Hayashi, Masaya Ohara, Yuki Nagata, Masafumi Kurajoh, Shinsuke Yamada, Katsuhito Mori, Masanori Emoto

Journal Article

ABSTRACTHigher serum phosphorus (Pi) increases the risk for chronic kidney disease (CKD). It was reported that a single administration of denosumab or zoledronate significantly suppressed serum Pi levels as well as those of bone resorption markers in serum. Also, previous evidences suggest a link between bone anti‐resorptive therapy and vasoprotective/renoprotective effects through mechanisms that remain unexplored. The aim of this study is to assess the renoprotective effect of denosumab and involvement of denosumab‐induced reduction in serum Pi in osteoporotic patients. Osteoporotic patients (n = 73) without overt proteinuria in dipstick test results were treated with denosumab (60 mg) every 6 months during the study period (24 months). Estimated glomerular filtration rate based on serum cystatin C (e
GFRcys) was used as a filtration marker and tartrate‐resistant acid phosphatase‐5b (TRACP‐5b) as a bone resorption marker. For analysis of non‐CKD patients (n = 56), those with e
GFRcys <60 m
L/min/1.73 m2 were excluded. A single injection of denosumab suppressed serum Pi as well as TRACP‐5b during the first 6 months, whereas age‐related decline in e
GFRcys was significantly reversed, with an increase of 2.75 ± 1.2 m
L/min/1.73 m2 after 24 months noted. Multivariate analysis showed that serum Pi reduction following the initial denosumab injection was positively associated with serum TRACP‐5b suppression during that same period (β = 0.241, p = 0.049). In addition, a positive association of serum Pi suppression, but not of corrected calcium or TRACP‐5b, with e
GFRcys increase after 24 months (β = 0.321, p = 0.014) was found after adjustments for gender, age, BMI, antihypertensive drug use, albumin, and e
GFRcys. The same was observed in osteoporotic cases restricted to non‐CKD patients. In conclusion, serum Pi reduction resulting from phosphorus load decrement from bone induced by denosumab is a determinant for e
GFRcys increase. Early introduction of bone antiresorptive therapy can retain glomerular filtration in osteoporosis cases, including non‐CKD patients. © 2019 American Society for Bone and Mineral Research.

The Design and Validation of a New Algorithm to Identify Incident Fractures in Administrative Claims Data

05-08-2019 – Nicole C Wright, Shanette G Daigle, Mary E Melton, Elizabeth S Delzell, Akhila Balasubramanian, Jeffrey R Curtis

Journal Article, Review

ABSTRACTOur study validated a claims‐based algorithm for the identification of incident and recurrent fractures in administrative data. We used Centers for Medicare and Medicaid (CMS) claims from 2005 to 2014 linked to the Reasons for Geographic and Racial Differences in Stroke (REGARDS) database. Case qualifying (CQ) fractures were identified among participants with ≥12 months of fee‐for‐service coverage before first fracture claim and ≥6 months after. Recurrent fractures were defined as the first CQ fracture that occurred following a clean period of at least 90 days from the last claim associated with the preceding incident fracture. We used medical records (discharge summary, imaging, and surgical report) to adjudicate fractures. We calculated positive predictive values (PPVs) for incident and recurrent fractures. Our study was not designed to assess the algorithm sensitivity or negative predictive value. We identified 2049 potential incident fractures from claims among 1650 participants. Record retrieval was attempted for 728 (35.5%) suspected incident fractures (prioritizing more recent CQ fractures associated with osteoporosis, but without explicitly requiring any osteoporosis ICD‐9 diagnosis code). Our final sample included 520 claims‐identified fractures with medical records, of which 502 (96.5%) were confirmed. The PPVs (95% CI) of the hip, wrist, humerus, and clinical vertebra—all exceeded 95%. We identified 117 beneficiaries with 292 ≥2 CQ fracture episodes at the same site, and attempted retrieval on 105 (36.0%) episodes. Our analytic sample included 72 (68.5%) CQ episodes from 33 participants. The PPVs for identifying recurrent clinical vertebral, hip/femur, and nonvertebral fractures with a 90‐day clean period exceeded 95%. Although we could not ascertain sensitivity, our updated fracture identification algorithms had high PPV for the identification of incident and recurrent fractures of the same site. Although medical record review and clinical adjudication remain a gold standard, our claims‐based algorithm provides an alternative approach to fracture ascertainment when high PPV is desired. © 2019 American Society for Bone and Mineral Research.

TNFRSF11A‐Associated Dysosteosclerosis: A Report of the Second Case and Characterization of the Phenotypic Spectrum

05-08-2019 – Jing‐yi Xue, Zheng Wang, Satoshi Shinagawa, Hirofumi Ohashi, Nao Otomo, Nursel H Elcioglu, Tomoki Nakashima, Gen Nishimura, Shiro Ikegawa, Long Guo

Journal Article

ABSTRACTDysosteosclerosis (DOS) is a distinct form of sclerosing bone disease characterized by irregular osteosclerosis and platyspondyly. DOS is genetically heterogeneous; however, only five cases with SLC29A3 mutations and a single case with a splice‐site mutation of TNFRSF11A have been reported, and TNFRSF11A is also a causal gene for osteopetrosis, autosomal recessive 7 (OP‐AR7). Thus, the causal genes of DOS and their genotype‐phenotype associations remain unclear. In this study, we examined a Japanese patient with DOS and found a novel variant in TNFRSF11A. The homozygous variant was a G to T transversion at the first nucleotide of exon 9 (c.784G>T). Although the variant was predicted to cause a stop codon mutation (p.
E262*), in silico evaluation of the exonic splicing elements followed by RT‐PCR for the patient‐derived cells showed that it caused aberrant splicing due to the change in the exonic splicing element and produced two types of aberrant transcripts: One caused a premature stop codon (p.
E262Vfs*17) leading to nonsense mutation‐mediated m
RNA decay; the other produced a protein with interstitial deletion (p.
E262_Q279del). The effects of the mutation on five splicing isoforms of TNFRSF11A were different from those in OP‐AR7, but comparable with those in the first DOS with the TNFRSF11A mutation. Thus, we identified the second case of DOS caused by the TNFRSF11A splice‐site mutation and confirmed the novel disease entity. © 2019 American Society for Bone and Mineral Research.

Expression of a Degradation‐Resistant β‐Catenin Mutant in Osteocytes Protects the Skeleton From Mechanodeprivation‐Induced Bone Wasting

05-08-2019 – Whitney A Bullock, April M Hoggatt, Daniel J Horan, Karl J Lewis, Hiroki Yokota, Steven Hann, Matthew L Warman, Aimy Sebastian, Gabriela G Loots, Fredrick M Pavalko, Alexander G Robling

Journal Article

ABSTRACTMechanical stimulation is a key regulator of bone mass, maintenance, and turnover. Wnt signaling is a key regulator of mechanotransduction in bone, but the role of β‐catenin—an intracellular signaling node in the canonical Wnt pathway—in disuse mechanotransduction is not defined. Using the β‐catenin exon 3 flox (constitutively active CA) mouse model, in conjunction with a tamoxifen‐inducible, osteocyte‐selective Cre driver, we evaluated the effects of degradation‐resistant β‐catenin on bone properties during disuse. We hypothesized that if β‐catenin plays an important role in Wnt‐mediated osteoprotection, then artificial stabilization of β‐catenin in osteocytes would protect the limbs from disuse‐induced bone wasting. Two disuse models were tested: tail suspension, which models fluid shift, and botulinum‐toxin (botox)‐induced muscle paralysis, which models loss of muscle force. Tail suspension was associated with a significant loss of tibial bone mass and density, reduced architectural properties, and decreased bone formation indices in uninduced (control) mice, as assessed by dual‐energy X‐ray absorptiometry (DXA), micro‐computed tomography (µCT), and histomorphometry. Activation of the βcat
CA allele in tail‐suspended mice resulted in little to no change in those properties; ie, these mice were protected from bone loss. Similar protective effects were observed among botox‐treated mice when the βcat
CA was activated. RNAseq analysis of altered gene regulation in tail‐suspended mice yielded 35 genes, including Wnt11, Gli1, Nell1, Gdf5, and Pgf, which were significantly differentially regulated between tail‐suspended β‐catenin stabilized mice and tail‐suspended nonstabilized mice. Our findings indicate that selectively targeting/blocking of β‐catenin degradation in bone cells could have therapeutic implications in mechanically induced bone disease. © 2019 American Society for Bone and Mineral Research.

Parathyroid Hormone Shifts Cell Fate of a Leptin Receptor‐Marked Stromal Population from Adipogenic to Osteoblastic Lineage

02-08-2019 – Mengyu Yang, Atsushi Arai, Nobuyuki Udagawa, Lijuan Zhao, Daisuke Nishida, Kohei Murakami, Toru Hiraga, Ryoko Takao‐Kawabata, Koichi Matsuo, Toshihisa Komori, Yasuhiro Kobayashi, Naoyuki Takahashi, Yukihiro Isogai, Toshinori Ishizuya, Akira Yamaguchi, Toshihide Mizoguchi

Journal Article

ABSTRACTIntermittent parathyroid hormone (i
PTH) treatment induces bone anabolic effects that result in the recovery of osteoporotic bone loss. Human PTH is usually given to osteoporotic patients because it induces osteoblastogenesis. However, the mechanism by which PTH stimulates the expansion of stromal cell populations and their maturation toward the osteoblastic cell lineage has not be elucidated. Mouse genetic lineage tracing revealed that i
PTH treatment induced osteoblastic differentiation of bone marrow (BM) mesenchymal stem and progenitor cells (MSPCs), which carried the leptin receptor (Lep
R)‐Cre. Although these findings suggested that part of the PTH‐induced bone anabolic action is exerted because of osteoblastic commitment of MSPCs, little is known about the in vivo mechanistic details of these processes. Here, we showed that Lep
R+MSPCs differentiated into type I collagen (Col1)+ mature osteoblasts in response to i
PTH treatment. Along with osteoblastogenesis, the number of Col1+ mature osteoblasts increased around the bone surface, although most of them were characterized as quiescent cells. However, the number of Lep
R‐Cre‐marked lineage cells in a proliferative state also increased in the vicinity of bone tissue after i
PTH treatment. The expression levels of SP7/osterix (Osx) and Col1, which are markers for osteoblasts, were also increased in the Lep
R+MSPCs population in response to i
PTH treatment. In contrast, the expression levels of Cebpb, Pparg, and Zfp467, which are adipocyte markers, decreased in this population. Consistent with these results, i
PTH treatment inhibited 5‐fluorouracil‐ or ovariectomy (OVX)‐induced Lep
R+MSPC‐derived adipogenesis in BM and increased Lep
R+MSPC‐derived osteoblasts, even under the adipocyte‐induced conditions. Treatment of OVX rats with i
PTH significantly affected the osteoporotic bone tissue and expansion of the BM adipose tissue. These results indicated that i
PTH treatment induced transient proliferation of the Lep
R+MSPCs and skewed their lineage differentiation from adipocytes toward osteoblasts, resulting in an expanded, quiescent, and mature osteoblast population. © 2019 American Society for Bone and Mineral Research.

Specific RANK Cytoplasmic Motifs Drive Osteoclastogenesis

02-08-2019 – Yuyu Li, Zhenqi Shi, Joel Jules, Shenyuan Chen, Robert A Kesterson, Dongfeng Zhao, Ping Zhang, Xu Feng

Journal Article

ABSTRACTUpon receptor activator of NF‐κB ligand (RANKL) binding, RANK promotes osteoclast formation through the recruitment of tumor necrosis factor (TNF) receptor‐associated factors (TRAFs). In vitro assays identified two RANK intracellular motifs that bind TRAFs: PVQEET560–565 (Motif 2) and PVQEQG604–609 (Motif 3), which potently mediate osteoclast formation in vitro. To validate the in vitro findings, we have generated knock‐in (KI) mice harboring inactivating mutations in RANK Motifs 2 and 3. Homozygous KI (RANKKI/KI) mice are born at the predicted Mendelian frequency and normal in tooth eruption. However, RANKKI/KI mice exhibit significantly more trabecular bone mass than age‐ and sex‐matched heterozygous KI (RANK+/KI) and wild‐type (RANK+/+) counterparts. Bone marrow macrophages (BMMs) from RANKKI/KI mice do not form osteoclasts when they are stimulated with macrophage colony‐stimulating factor (M‐CSF) and RANKL in vitro. RANKL is able to activate the NF‐κB, ERK, p38, and JNK pathways in RANKKI/KI BMMs, but it cannot stimulate c‐Fos or NFATc1 in the RANKKI/KI cells. Previously, we showed that RANK signaling plays an important role in Porphyromonas gingivalis (Pg)‐mediated osteoclast formation by committing BMMs into the osteoclast lineage. Here, we show that RANKL‐primed RANKKI/KI BMMs are unable to differentiate into osteoclasts in response to Pg stimulation, indicating that the two RANK motifs are required for Pg‐induced osteoclastogenesis. Mechanistically, RANK Motifs 2 and 3 facilitate Pg‐induced osteoclastogenesis by stimulating c‐Fos and NFATc1 expression during the RANKL pretreatment phase as well as rendering c‐Fos and NFATc1 genes responsive to subsequent Pg stimulation. Cell‐penetrating peptides (CPPs) conjugated with RANK segments containing Motif 2 or 3 block RANKL‐ and Pg‐mediated osteoclastogenesis. The CPP conjugates abrogate RANKL‐stimulated c‐Fos and NFATc1 expression but do not affect RANKL‐induced activation of NF‐κB, ERK, p38, JNK, or Akt signaling pathway. Taken together, our current findings demonstrate that RANK Motifs 2 and 3 play pivotal roles in osteoclast formation in vivo and mediate Pg‐induced osteoclastogenesis in vitro.

Lymphatic Endothelial Cells Produce M‐CSF, Causing Massive Bone Loss in Mice

02-08-2019 – Wensheng Wang, Hua Wang, Xichao Zhou, Xing Li, Wen Sun, Michael Dellinger, Brendan F Boyce, Lianping Xing

Mendelian Randomization Analysis Reveals a Causal Influence of Circulating Sclerostin Levels on Bone Mineral Density and Fractures

02-08-2019 – Jie Zheng, Winfried Maerz, Ingrid Gergei, Marcus Kleber, Christiane Drechsler, Christoph Wanner, Vincent Brandenburg, Sjur Reppe, Kaare M Gautvik, Carolina Medina‐Gomez, Enisa Shevroja, Arthur Gilly, Young‐Chan Park, George Dedoussis, Eleftheria Zeggini, Mattias Lorentzon, Petra Henning, Ulf H Lerner, Karin H Nilsson, Sofia Movérare‐Skrtic, Denis Baird, Benjamin Elsworth, Louise Falk, Alix Groom, Terence D Capellini, Elin Grundberg, Maria Nethander, Claes Ohlsson, George Davey Smith, Jonathan H Tobias

Journal Article

ABSTRACTIn bone, sclerostin is mainly osteocyte‐derived and plays an important local role in adaptive responses to mechanical loading. Whether circulating levels of sclerostin also play a functional role is currently unclear, which we aimed to examine by two‐sample Mendelian randomization (MR). A genetic instrument for circulating sclerostin, derived from a genomewide association study (GWAS) meta‐analysis of serum sclerostin in 10,584 European‐descent individuals, was examined in relation to femoral neck bone mineral density (BMD; n = 32,744) in GEFOS and estimated bone mineral density (e
BMD) by heel ultrasound (n = 426,824) and fracture risk (n = 426,795) in UK Biobank. Our GWAS identified two novel serum sclerostin loci, B4GALNT3 (standard deviation SD) change in sclerostin per A allele (β = 0.20, p = 4.6 × 10−49) and GALNT1 (β  = 0.11 per G allele, p = 4.4 × 10−11). B4GALNT3 is an N‐acetyl‐galactosaminyltransferase, adding a terminal Lacdi
NAc disaccharide to target glycocoproteins, found to be predominantly expressed in kidney, whereas GALNT1 is an enzyme causing mucin‐type O‐linked glycosylation. Using these two single‐nucleotide polymorphisms (SNPs) as genetic instruments, MR revealed an inverse causal relationship between serum sclerostin and femoral neck BMD (β = –0.12, 95% confidence interval CI –0.20 to –0.05) and e
BMD (β = –0.12, 95% CI –0.14 to –0.10), and a positive relationship with fracture risk (β = 0.11, 95% CI 0.01 to 0.21). Colocalization analysis demonstrated common genetic signals within the B4GALNT3 locus for higher sclerostin, lower e
BMD, and greater B4GALNT3 expression in arterial tissue (probability >99%). Our findings suggest that higher sclerostin levels are causally related to lower BMD and greater fracture risk. Hence, strategies for reducing circulating sclerostin, for example by targeting glycosylation enzymes as suggested by our GWAS results, may prove valuable in treating osteoporosis. © 2019 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc.

Low Vitamin D Status Is Associated With Impaired Bone Quality and Increased Risk of Fracture‐Related Hospitalization in Older Australian Women

01-08-2019 – Kun Zhu, Joshua R Lewis, Marc Sim, Richard L Prince

Journal Article

ABSTRACTThe vitamin D debate relates in part to ideal public health population levels of circulating 25‐hydroxyvitamin D (25OHD) to maintain bone structure and reduce fracture. In a secondary analysis of 1348 women aged 70 to 85 years at baseline (1998) from the Perth Longitudinal Study of Aging in Women (a 5‐year calcium supplementation trial followed by two 5‐year extensions), we examined the dose‐response relations of baseline plasma 25OHD with hip DXA BMD at year 1, lumbar spine BMD, and trabecular bone score (TBS) at year 5, and fracture‐related hospitalizations over 14.5 years obtained by health record linkage. Mean baseline plasma 25OHD was 66.9 ± 28.2 nmol/L and 28.5%, 36.4%, and 35.1% of women had levels <50, 50 to 74.9, and ≥75 nmol/L, respectively. Generalized additive models showed that total hip and femoral neck BMD and TBS, but not spine BMD, were higher with increasing plasma 25OHD up to 100 nmol/L. Compared with those with 25OHD <50 nmol/L, women with 25OHD ≥75 nmol/L had significantly higher total hip and femoral neck BMD at year 1 (3.3% to 3.9%) and TBS at year 5 (2.0%), all P < 0.05. During the follow‐up, 27.6% of women experienced any fracture‐related hospitalization and 10.6% hip fracture‐related hospitalization. Penalized spline regression models showed a decrease in risk with increased 25OHD levels up to 65 nmol/L and 75 nmol/L for hip fracture and any fracture‐related hospitalization, respectively. Cox regression grouped analyses showed that compared with women with 25OHD <50 nmol/L, those with 25OHD levels 50 to 74.9 and ≥75 nmol/L had significantly lower risk for hip fracture HR 0.60 (95% CI, 0.40 to 0.91) and 0.61 (95% CI, 0.40 to 0.92), respectively, and any fracture‐related hospitalization HR 0.77 (95% CI, 0.59 to 0.99) and 0.70 (95% CI, 0.54 to 0.91), respectively. In older white women, 25OHD levels >50 nmol/L are a minimum public health target and 25OHD levels beyond 75 nmol/L may not have additional benefit to reduce fracture risk. © 2019 American Society for Bone and Mineral Research.

The Effect of a Screening and Treatment Program for the Prevention of Fractures in Older Women: A Randomized Pragmatic Trial

01-08-2019 – Thomas Merlijn, Karin MA Swart, Natasja M Schoor, Martijn W Heymans, Babette C Zwaard, Amber A Heijden, Femke Rutters, Paul Lips, Henriëtte E Horst, Christy Niemeijer, J Coen Netelenbos, Petra JM Elders

Journal Article

ABSTRACTPopulation screening for fracture risk may reduce the fracture incidence. In this randomized pragmatic trial, the SALT Osteoporosis Study (SOS), we studied whether screening for fracture risk and subsequent treatment in primary care can reduce fractures compared with usual care. A total of 11,032 women aged 65 to 90 years with ≥1 clinical risk factor for fractures were individually randomized to screening (n = 5575) or usual care (n = 5457). Participants in the screening group underwent a screening program, including bone densitometry and vertebral fracture assessment. Participants with a high 10‐year fracture probability (FRAX) or a vertebral fracture were offered treatment with anti‐osteoporosis medication by their general practitioner. Incident fractures as reported by questionnaires were verified with medical records. Follow‐up was completed by 94% of the participants (mean follow‐up = 3.7 years). Of the 5575 participants in the screening group, 1417 (25.4%) had an indication for anti‐osteoporosis medication. Screening and subsequent treatment had no statistically significant effect on the primary outcome fracture (hazard ratio HR = 0.97; 95% confidence interval CI 0.87–1.08), nor on the secondary outcomes osteoporotic fractures (HR = 0.91; 95% CI 0.81–1.03), major osteoporotic fractures (HR = 0.91; 95% CI 0.80–1.04), hip fractures (HR = 0.91; 95% CI 0.71–1.15), falls (odds ratio OR = 0.91; 95% CI 0.72–1.15), or mortality (HR = 1.03; 95% CI 0.91–1.17). Post hoc explorative finding suggested that screening might be most effective after a recent fracture (HR = 0.65; 95% CI 0.44–0.96 for major osteoporotic fractures and HR = 0.38; 95% CI 0.18–0.79 for hip fractures). The results of this study might have been compromised by nonparticipation and medication nonadherence in the screening group. Overall, this study does not provide sufficient indications to consider screening for fracture prevention. However, we cannot exclude its clinical relevance to reduce (major) osteoporotic fractures and hip fractures because of the relatively small number of women with a treatment indication in the intervention group. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc.

Conditional Activation of NF‐κB Inducing Kinase (NIK) in the Osteolineage Enhances Both Basal and Loading‐Induced Bone Formation

31-07-2019 – Jennifer L Davis, Linda Cox, Christine Shao, Cheng Lyu, Shaopeng Liu, Rajeev Aurora, Deborah J Veis

Journal Article

ABSTRACTStudies from global loss‐of‐function mutants suggest that alternative NF‐κB downstream of NF‐κB inducing kinase (NIK) is a cell‐intrinsic negative regulator of osteogenesis. However, the interpretation of the osteoblast and/or osteocyte contribution to the bone phenotype is complicated by simultaneous osteoclast defects in these models. Therefore, we turned to a transgenic mouse model to investigate the direct role of NIK in the osteolineage. Osx‐Cre;NT3 animals (NT3‐Cre +), which bear a constitutively active NIK allele (NT3) driven by Osx‐Cre, were compared with their Cre‐negative, Control (Ctrl) littermates. NT3‐Cre + mice had elevated serum P1NP and CTX levels. Despite this high turnover state, µCT showed that constitutive activation of NIK resulted in a net increase in basal bone mass in both cortical and cancellous compartments. Furthermore, NT3‐Cre + mice exhibited a greater anabolic response following mechanical loading compared with controls. We next performed RNA‐Seq on nonloaded and loaded tibias to elucidate possible mechanisms underlying the increased bone anabolism seen in NT3‐Cre + mice. Hierarchical clustering revealed two main transcriptional programs: one loading‐responsive and the other NT3 transgene‐driven. Gene ontology (GO) analysis indicated a distinct upregulation of receptor, kinase, and growth factor activities including Wnts, as well as a calcium‐response signature in NT3‐Cre + limbs. The promoters of these GO‐term associated genes, including many known to be bone‐anabolic, were highly enriched for multiple κB recognition elements (κB‐RE) relative to the background frequency in the genome. The loading response in NT3‐Cre + mice substantially overlapped (>90%) with Ctrl. Surprisingly, control animals had 10‐fold more DEGs in response to loading. However, most top DEGs shared between genotypes had a high incidence of multiple κB‐RE in their promoters. Therefore, both transcriptional programs (loading‐responsive and NT3 transgene‐driven) are modulated by NF‐κB. Our studies uncover a previously unrecognized role for NF‐κB in the promotion of both basal and mechanically stimulated bone formation. © 2019 American Society for Bone and Mineral Research.

Prolonged effect of zoledronic acid on bone mineral density and turnover in HIV‐infected adults on tenofovir: a randomized, open‐label study

30-07-2019 – A Carr, SJ Kerr, R Richardson, P Ebeling, N Pocock, J Rojas, E Martinez, J Hoy, ZEST study investigators

Journal Article

ABSTRACTZoledronic acid (ZOL) 5 mg annually was more effective than tenofovir disoproxil fumarate (TDF) switching at increasing bone mineral density (BMD) over 24 months in HIV‐infected, osteopenic adults. To determine whether the effects of ZOL would persist without further infusions, we compared changes in left hip and spine BMD over 36 months in participants randomised to ZOL 5 mg at baseline and Month 12 (and to continue TDF) or to switch TDF (without receiving ZOL). We also compared changes in the plasma bone turnover markers (BTMs) C‐terminal telopeptide of type 1 collagen (CTX; bone resorption) and procollagen type 1 N propeptide (P1NP; bone formation) and determined whether CTX and P1NP changes at Month 3 predicted BMD changes at Month 36. Changes were compared in the per‐protocol populations, which included 32 (74%) of 43 participants randomised to ZOL and 37 (88%) of 42 participants who switched TDF. Despite not receiving ZOL after Month 12, mean hip and spine BMD change from baseline were stable and remained greater with ZOL at Month 36 than with TDF switching (spine: 7.5% vs 2.7%, mean difference 4.7%, p < 0.001; hip: 5.5% vs 1.5%, mean difference 4.0%, p < 0.001). CTX and P1NP levels declined in both groups, but significantly more with ZOL. Only percent changes in P1NP at Month 3 correlated inversely with BMD changes at Month 36 (spine, rho = −0.442, p < 0.001; hip, rho = −0.373, p = 0.002). Two infusions of ZOL (in the presence of ongoing TDF) yielded sustained BMD increases through Month 36 that remained greater than with TDF switching.
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Age‐Related Changes in the Mechanical Regulation of Bone Healing Are Explained by Altered Cellular Mechanoresponse

29-07-2019 – Edoardo Borgiani, Christine Figge, Bettina Kruck, Bettina M Willie, Georg N Duda, Sara Checa

Journal Article

ABSTRACTIncreasing age is associated with a reduced bone regeneration potential and increased risk of morbidities and mortality. A reduced bone formation response to mechanical loading has been shown with aging, and it remains unknown if the interplay between aging and mechanical stimuli during regeneration is similar to adaptation. We used a combined in vivo/in silico approach to investigate age‐related alterations in the mechanical regulation of bone healing and identified the relative impact of altered cellular function on tissue patterns during the regenerative cascade. To modulate the mechanical environment, femoral osteotomies in adult and elderly mice were stabilized using either a rigid or a semirigid external fixator, and the course of healing was evaluated using histomorphometric and micro‐CT analyses at 7, 14, and 21 days post‐surgery. Computer models were developed to investigate the influence of the local mechanical environment within the callus on tissue formation patterns. The models aimed to identify the key processes at the cellular level that alter the mechanical regulation of healing with aging. Fifteen age‐related biological alterations were investigated on two levels (adult and elderly) with a design of experiments setup. We show a reduced response to changes in fixation stability with age, which could be explained by reduced cellular mechanoresponse, simulated as alteration of the ranges of mechanical stimuli driving mesenchymal stem cell differentiation. Cellular mechanoresponse has been so far widely ignored as a therapeutic target in aged patients. Our data hint to mechanotherapeutics as a potential treatment to enhance bone healing in the elderly. © 2019 American Society for Bone and Mineral Research.

Novel Role for Claudin‐11 in the Regulation of Osteoblasts via Modulation of ADAM10‐Mediated Notch Signaling

26-07-2019 – Richard C Lindsey, Weirong Xing, Sheila Pourteymoor, Catrina Godwin, Alexander Gow, Subburaman Mohan

Journal Article

ABSTRACTThe claudin (Cldn) family comprises 27 members of 20 to 34 k
Da transmembrane tight junction proteins. In addition to Cldns’ established canonical role as barriers controlling paracellular flow of molecules, a distinct noncanonical role for them as mediators of cell signaling is now emerging. In our studies evaluating Cldn family expression levels during osteoblast differentiation, Cldn‐11 showed the largest increase (60‐fold). Immunohistochemistry studies revealed high Cldn‐11 expression in trabecular (Tb) bone lining cells. Micro‐CT analysis of femurs and vertebrae of Cldn‐11 knock‐out (KO) mice at 12 weeks of age exhibited a 40% (p < 0.01) reduction in Tb bone volume adjusted for tissue volume compared with control mice, a change caused by significant reductions in Tb number and thickness and increase in Tb separation. Histomorphometry and serum biomarker studies revealed that reduced bone formation, not increased resorption, is the cause for reduced Tb bone volume in the Cldn‐11 KO mice. Cldn‐11 KO osteoblasts expressed reduced ALP and BSP, whereas Cldn‐11 overexpression in MC3T3‐E1 cells increased expression of ALP and BSP. Mechanistically, Cldn‐11 interacted with tetraspanin (Tspan)3 in osteoblasts, and Tspan3 knockdown reduced osteoblast differentiation. Because members of the Tspan family regulate cell functions via Notch signaling, we evaluated whether Cldn‐11/Tspan3 regulates Notch signaling in osteoblasts. Accordingly, Notch targets Hey1 and Hey2 were significantly upregulated in Cldn‐11 overexpressing cultures but downregulated in both Cldn‐11 KO and Tspan3 knockdown osteoblasts. Because ADAM10 has been shown to interact with Tspan family members to regulate Notch signaling, we evaluated whether Cldn‐11 regulates ADAM10 expression. Cldn‐11 overexpressing cells express more mature ADAM10, and an ADAM10 inhibitor blocked the Cldn‐11 effect on osteoblast differentiation. Based on these data, we propose Cldn‐11 as a novel component of an osteoblast cell surface protein complex, comprising Tspan3 and ADAM10, which regulates Notch signaling and cell differentiation. © 2019 American Society for Bone and Mineral Research.

Attenuation of NF‐κB in Intestinal Epithelial Cells Is Sufficient to Mitigate the Bone Loss Comorbidity of Experimental Mouse Colitis

25-07-2019 – Ke Ke, Tim (Hung‐Po) Chen, Manoj Arra, Gabriel Mbalaviele, Gaurav Swarnkar, Yousef Abu‐Amer

Journal Article

ABSTRACTSkeletal abnormalities are common comorbidities of inflammatory bowel disease (IBD). Patients suffering from IBD, including ulcerative colitis and Crohns disease, present with skeletal complications. However, the mechanism underpinning IBD‐associated bone loss remains vague. Intestinal inflammation generates an inflammatory milieu at the intestinal epithelium that leads to dysregulation of mucosal immunity through gut‐residing innate lymphoid cells (ILCs) and other cell types. ILCs are recently identified mucosal cells considered as the gatekeeper of gut immunity and their function is regulated by intestinal epithelial cell (IEC)‐secreted cytokines in response to the inflammatory microenvironment. We first demonstrate that serum as well as IECs collected from the intestine of dextran sulfate sodium (DSS)‐induced colitis mice contain high levels of inflammatory and osteoclastogenic cytokines. Mechanistically, heightened inflammatory response of IECs was associated with significant intrinsic activation of NF‐κB (nuclear factor kappa‐light‐chain‐enhancer of activated B cells) in IECs and increased frequency of ILC1, ILC3, and myeloid osteoclast progenitors. Validating the central role of IEC‐specific NF‐κB activation in this phenomenon, conditional expression of constitutively active inhibitor kappa B kinase 2 (IKK2) in IECs in mice recapitulates the majority of the cellular, inflammatory, and osteolytic phenotypes observed in the chemically induced colitis. Furthermore, conditional deletion of IKK2 from IECs significantly attenuated inflammation and bone loss in DSS‐induced colitis. Finally, using the DSS‐induced colitis model, pharmacologic inhibition of IKK2 was effective in reducing frequency of ILC1 and ILC3 cells, attenuated circulating levels of inflammatory cytokines, and halted colitis‐associated bone loss. Our findings identify IKK2 in IECs as viable therapeutic target for colitis‐associated osteopenia.