Journal of Bone and Mineral Research

A Pooled Analysis of Fall Incidence From Placebo‐controlled Trials of Denosumab

30-01-2020 – Pojchong Chotiyarnwong, Eugene McCloskey, Richard Eastell, Michael R. McClung, Evelien Gielen, John Gostage, Michele McDermott, Arkadi Chines, Shuang Huang, Steven R. Cummings

ABSTRACTRecent studies suggest that the RANK/RANKL system impacts muscle function and/or mass. In the pivotal placebo‐controlled fracture trial of the RANKL inhibitor denosumab in women with postmenopausal osteoporosis, treatment was associated with a lower incidence of non‐fracture‐related falls (p = 0.02). This ad hoc exploratory analysis pooled data from five placebo‐controlled trials of denosumab to determine consistency across trials, if any, of the reduction of fall incidence.
The analysis included trials in women with postmenopausal osteoporosis and low bone mass, men with osteoporosis, women receiving adjuvant aromatase inhibitors for breast cancer, and men receiving androgen deprivation therapy for prostate cancer. The analysis was stratified by trial, and only included data from the placebo‐controlled period of each trial. A time‐to‐event analysis of first fall and exposure‐adjusted subject incidence rates of falls were analyzed. Falls were reported and captured as adverse events.
The analysis comprised 10,036 individuals; 5,030 received denosumab 60 mg subcutaneously once every 6 months for 12–36 months and 5,006 received placebo. Kaplan–Meier estimates showed an occurrence of falls in 6.5% of subjects in the placebo group compared with 5.2% of subjects in the denosumab group (hazard ratio 95% CI: 0.79 0.66, 0.93; p = 0.0061). Heterogeneity in study designs did not permit overall assessment of association with fracture outcomes.
In conclusion, denosumab may reduce the risk of falls in addition to its established fracture risk reduction by reducing bone resorption and increasing bone mass. These observations require further exploration and confirmation in studies with muscle function or falls as the primary outcome.
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Long‐term immobilization in elderly females causes a specific pattern of cortical bone and osteocyte deterioration different from postmenopausal osteoporosis

30-01-2020 – Tim Rolvien, Petar Milovanovic, Felix N. Schmidt, Simon Kroge, Eva M. Wölfel, Matthias Krause, Birgit Wulff, Klaus Püschel, Robert O. Ritchie, Michael Amling, Björn Busse

ABSTRACTImmobilization as a result of long‐term bed rest can lead to gradual bone loss. Due to their distribution throughout the bone matrix and remarkable interconnectivity, osteocytes represent the major mechanosensors in bone and translate mechanical into biochemical signals controlling bone remodeling. To test whether immobilization affects the characteristics of the osteocyte network in human cortical bone, femoral diaphyseal bone specimens were analyzed in immobilized female individuals and compared to age‐matched postmenopausal individuals with primary osteoporosis. Premenopausal and postmenopausal healthy individuals served as control groups. Cortical porosity, osteocyte number and lacunar area, the frequency of hypermineralized lacunae as well as cortical bone calcium content (Ca
Mean) were assessed using bone histomorphometry and quantitative backscattered electron imaging (q
BEI). Bone matrix properties were further analyzed by Fourier transform infrared spectroscopy (FTIR). In the immobilization group, cortical porosity was significantly higher, and q
BEI revealed a trend towards higher matrix mineralization compared to osteoporotic individuals. Osteocyte density and canalicular density showed a declining rate from premenopausal towards healthy postmenopausal and osteoporotic individuals with peculiar reductions in the immobilization group, while the number of hypermineralized lacunae accumulated inversely. In conclusion, reduced osteocyte density and impaired connectivity during immobilization are associated with a specific bone loss pattern, reflecting a phenotype clearly distinguishable from postmenopausal osteoporosis. Immobilization periods may lead to a loss of survival signals for osteocytes, provoking bone loss that is even higher than in osteoporosis states, while osteocytic osteolysis remains absent.
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Effects of Supplemental Vitamin D on Bone Health Outcomes in Women and Men in the VITamin D and OmegA‐3 TriaL (VITAL)

30-01-2020 – Meryl S LeBoff, Sharon H Chou, Elle M Murata, Catherine M Donlon, Nancy R Cook, Samia Mora, I‐Min Lee, Gregory Kotler, Vadim Bubes, Julie E Buring, JoAnn E Manson

Journal Article

ABSTRACTAlthough supplemental vitamin D is used to promote bone health in the general population, data from randomized controlled trials (RCTs) have been inconsistent. We determined whether daily, vitamin D3 supplementation improves bone mineral density (BMD) and/or structure. VITamin D and Omeg
A‐3 Tria
L (VITAL) is a double‐blind, placebo‐controlled RCT of supplemental vitamin D3 (2000 IU/d) and/or omega‐3 fatty acids (1 g/d) in 25,871 adults nationwide. This ancillary study included a subcohort of 771 participants (men ≥50 and women ≥55 years; not taking bone active medications) evaluated at baseline and at 2‐year follow‐up (89% retention). Total 25(OH)D levels were measured by liquid chromatography tandem mass spectrometry (Quest Diagnostics, San Juan Capistrano, CA, USA). Free 25(OH)D (FVD) levels were measured using the ELISA assay by Future Diagnostics Solutions BV (Wijchen, Netherlands). Primary endpoints were 2‐year changes in areal (a) BMD at the spine, hip, and whole body determined by dual‐energy X‐ray absorptiometry (DXA). Secondary endpoints were 2‐year changes in volumetric (v) BMD and cortical thickness at the radius and tibia assessed by peripheral quantitative computed tomography. Supplemental vitamin D3 versus placebo had no effect on 2‐year changes in a
BMD at the spine (0.33% versus 0.17%; p = 0.55), femoral neck (−0.27% versus −0.68%; p = 0.16), total hip (−0.76% versus −0.95%; p = 0.23), or whole body (−0.22% versus −0.15%; p = 0.60), or on measures of bone structure. Effects did not vary by sex, race/ethnicity, body mass index, or 25(OH)D levels. Among participants with baseline FVD levels below the median (<14.2 pmol/L), there was a slight increase in spine a
BMD (0.75% versus 0%; p = 0.043) and attenuation in loss of total hip a
BMD (−0.42% versus −0.98%; p = 0.044) with vitamin D3. Whether baseline FVD levels help to identify those more likely to benefit from supplementation warrants further study. Supplemental vitamin D3 versus placebo for 2 years in general healthy adults not selected for vitamin D insufficiency did not improve BMD or structure. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Combining frailty and trabecular bone score did not improve predictive accuracy in risk of major osteoporotic fractures

29-01-2020 – Guowei Li, William D Leslie, Christopher S Kovacs, Jerilynn Prior, Robert G Josse, Tanveer Towheed, K. Shawn Davison, Lehana Thabane, Alexandra Papaioannou, Mitchell AH Levine, David Goltzman, Jie Zeng, Yong Qi, Junzhan Tian, Jonathan D Adachi, for the Canadian Multicentre Osteoporosis Study (CaMos) Research Group

Journal Article

Abstract
It is recognized that the trabecular bone score (TBS) provides skeletal information, and frailty measurement is significantly associated with increased risks of adverse health outcomes. Given the suboptimal predictive power in fracture risk assessment tools, we aimed to evaluate the combination of frailty and TBS regarding predictive accuracy for risk of major osteoporotic fracture (MOF). Data from the prospective longitudinal study of Ca
Mos (Canadian Multicentre Osteoporosis Study) were used for this study. TBS values were estimated using lumbar spine (L1 ‐ L4) DXA images; frailty was evaluated by a frailty index (FI) of deficit accumulation. Outcome was time to first incident MOF during the follow‐up. We used the Harrells C‐index to compare the model predictive accuracy. The Akaike information criterion, likelihood ratio test, and net reclassification improvement (NRI) were used to compare model performances between the model combining frailty and TBS (subsequently called “FI+TBS”), FI‐alone and TBS‐alone models. We included 2730 participants (mean age: 69 years; 70% women) for analyses (mean follow‐up: 7.5 years). There were 243 (8.90%) MOFs observed during follow‐up. Participants with MOF had significantly higher FI (0.24 vs 0.20) and lower TBS (1.231 vs 1.285) than those without MOF. FI and TBS were significantly related with MOF risk in the model adjusted for FRAX with BMD and other covariates: HR = 1.26 (95% CI: 1.11 ‐ 1.43) for per‐SD increase in FI; HR = 1.38 (95% CI, 1.21 ‐ 1.59) for per‐SD decrease in TBS; and these associations showed negligible attenuation (HR = 1.24 for per‐SD increase in FI, and 1.35 for per‐SD decrease in TBS) when combined in the same model. Although the model FI+TBS was a better fit to the data than FI‐alone and TBS‐alone, only minimal and non‐significant enhancement of discrimination and NRI were observed in FI+TBS. To conclude, frailty and TBS are significantly and independently related to MOF risk. Larger studies are warranted to determine whether combining frailty and TBS can yield improved predictive accuracy for MOF risk.
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Both NPY‐ and CART‐expressing neurons increase energy expenditure and trabecular bone mass in response to AP1 antagonism, but have opposite effects on bone resorption

29-01-2020 – Anna Idelevich, Kazusa Sato, Byron Avihai, Kenichi Nagano, Antonin Galien, Glenn Rowe, Francesca Gori, Roland Baron

Journal Article

Energy metabolism and bone homeostasis share several neuronal regulatory pathways. Within the ventral hypothalamus (VHT), the orexigenic neurons co‐express Agouti‐related peptide (Ag
RP) and neuropeptide Y (NPY) and the anorexigenic neurons co‐express, α‐melanocyte stimulating hormone derived from proopiomelanocortin (POMC) and cocaine and amphetamine‐regulated transcript (CART). These neurons regulate both processes, yet their relative contribution is unknown. Previously, using genetically targeted AP1 alterations as a tool, we showed in adult mice that Ag
RP or POMC neurons are capable of inducing whole body energy catabolism and bone accrual, with different effects on bone resorption. Here, we investigated whether co‐residing neurons exert similar regulatory effects. We show that AP1 antagonists targeted to NPY‐ or CART‐producing neurons in adult mice stimulate energy expenditure, reduce body weight gain and adiposity and promote trabecular bone formation and mass, yet again via different effects on bone resorption, as measured by serum level of carboxy‐terminal collagen type I crosslinks (CTX). In addition, AP1 antagonists promote neurite expansion, increasing neurite number, length and surface area in primary hypothalamic neuronal cultures. Overall, our data demonstrate that the orexigenic NPY and anorexigenic CART neurons both have the capacity to stimulate energy burning state and increase bone mass.
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Ovariectomy activates chronic low‐grade inflammation mediated by memory T‐cells which promotes osteoporosis in mice

29-01-2020 – Anna Cline‐Smith, Ariel Axelbaum, Elena Shashkova, Mousumi Chakraborty, Jessie Sanford, Prabhjyot Panesar, Macey Peterson, Linda Cox, Angel Baldan, Deborah Veis, Rajeev Aurora

Journal Article

ABSTRACTThe loss of estrogen (E2) initiates a rapid phase of bone loss leading to osteoporosis in half of postmenopausal women, but the mechanism is not fully understood. Here, we show for the first time how loss of E2 activates low‐grade inflammation to promote the acute phase of bone catabolic activity in ovariectomized (OVX) mice. E2 regulates the abundance of dendritic cells (DC) that express IL‐7 and IL‐15 by inducing Fas
L and apoptosis of the DC. In the absence of E2, DC become long‐lived, leading to increased IL‐7 and IL‐15. We find that IL‐7 and IL‐15 together, but not alone, induced antigen‐independent production of IL‐17A and TNFα in a subset of memory T‐cells (TMEM). OVX of mice with T‐cell—specific ablation of IL15RA showed no IL‐17A and TNFα expression, and no increase in bone resorption or bone loss, confirming the role IL‐15 in activating the TMEM and the need for inflammation. Our results provide a new mechanism by which E2 regulates the immune system, and how menopause leads to osteoporosis. The low‐grade inflammation is likely to cause or contribute to other comorbidities observed postmenopause.
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BMP9 Reduces Bone Loss in Ovariectomized Mice by Dual Regulation of Bone Remodeling

29-01-2020 – Yan‐Man Zhou, Yu‐Ying Yang, Yi‐Xuan Jing, Tian‐Jiao Yuan, Li‐Hao Sun, Bei Tao, Jian‐Min Liu, Hong‐Yan Zhao

Journal Article

ABSTRACTBone remodeling is dynamic and is tightly regulated through bone resorption dominated by osteoclasts and bone formation dominated by osteoblasts. Imbalances in this process can cause various pathological conditions, such as osteoporosis. Bone morphogenetic protein 9 (BMP9), a biomolecule produced and secreted by the liver, has many pharmacological effects, including anti‐liver fibrosis, antitumor, anti‐heart failure, and antidiabetic activities. However, the effects of BMP9 on the regulation of osteoblast and osteoclast functions and the underlying molecular mechanism(s) have not yet been investigated. In this study, BMP9 increased the expression of osteoblastogenic gene markers, such as ALP, Cola1, OCN, RUNX2, and OSX, and ALP activity in MC3T3‐E1 cells by upregulating LGR6 and activating the Wnt/β‐catenin pathway. BMP9 also suppressed receptor activator of nuclear factor‐κB (NF‐κB) ligand (RANKL)‐induced osteoclast differentiation of bone marrow macrophages (BMMs) by inhibiting the Akt‐NF‐κB‐NFATc1 pathway. More importantly, in an ovariectomy (OVX) mouse model, BMP9 attenuated bone loss and improved bone biomechanical properties in vivo by increasing bone‐forming activity and suppressing bone resorption activity. Accordingly, our current work highlights the dual regulatory effects that BMP9 exerts on bone remodeling by promoting bone anabolic activity and inhibiting osteoclast differentiation in OVX mice. © 2020 American Society for Bone and Mineral Research.

History of Previous Fracture and Imminent Fracture Risk in Swedish Women Aged 55 to 90u2009Years Presenting With a Fragility Fracture

28-01-2020 – Emese Toth, Jonas Banefelt, Kristina Åkesson, Anna Spångeus, Gustaf Ortsäter, Cesar Libanati

Journal Article

ABSTRACTThe term “fracture cascade” refers to the sequence of fragility fractures resulting from the increased fracture risk that occurs with aging and following fractures. Here, we evaluate the sequence of previous fractures in women aged 55 to 90 years presenting with a fragility fracture and subsequent (12 to 24 months) fracture incidence. In this retrospective, observational study, women aged 55 to 90 years with an “index” fragility fracture in 2013 were identified from Swedish national registries. A history of previous fractures (2001 to 2012) and osteoporosis treatment was used to characterize fracture cascade patterns. Cumulative incidence of new fractures within 12 to 24 months following the index fracture, based on index fracture type and age, were used to describe the risk of subsequent fractures. A total of 35,146 women with a mean age of 73.8 years were included (7180 hip, 2786 clinical vertebral, and 25,180 nonhip/nonvertebral NHNV index fractures); 38% of women with hip, 38% with clinical vertebral, and 25% with NHNV index fractures had one or more previous fractures. Across all index fracture types, the proportion of women with any previous fracture increased with age; 34% to 46% of index hip or clinical vertebral fractures in women ≥70 years were not their first fracture. Following any index fracture, cumulative incidence of a new fracture over 24 months was over 11% (index clinical vertebral 18%; index hip 14%). Osteoporosis treatment rates were low both in patients with (27%) and without (18%) a previous fracture. These descriptive data demonstrate that almost one‐third of women aged 55 to 90 years suffering a new fracture have had a previous fragility fracture. Fracture location influences incidence and type of subsequent fracture during the 24 months following a fragility fracture, with clinical vertebral fractures carrying the greatest imminent fracture risk. These data highlight the clinical impact and need for early, effective treatment soon after any fragility fracture. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research

“The loss of Profilin 1 causes early‐onset Pagets disease of bone”

28-01-2020 – Federica Scotto di Carlo, Laura Pazzaglia, Teresa Esposito, Fernando Gianfrancesco

Journal Article

ABSTRACTPagets disease of bone (PDB) is a late‐onset disorder frequently caused by mutations in the SQSTM1 gene, leading to hyperactive osteoclasts and resulting in bone pain, deformities and fractures. However, some more severe forms of PDB – negative for SQSTM1 mutations – have been described, in which the disease degenerates into bone cancers and shows a poor prognosis. Osteosarcoma is the most frequent and aggressive tumor arising in PDB (OS/PDB), with a 5‐year survival rate almost nil, but the underlying molecular mechanism is unknown. Here, we investigated an extended pedigree with 11 individuals affected by early‐onset and polyostotic PDB, mainly interesting the appendicular skeleton. Interestingly, three members also developed secondary osteosarcoma. We performed exome sequencing and identified a 4‐bp‐deletion in the PFN1 gene, resulting in the degradation of the mutant protein. Copy number screening on 218 PDB individuals of our biobank disclosed that four of them (~2%) carry a germline heterozygous deletion of PFN1. The identification of these subjects, who exhibit a particularly severe form of disease, emphasize the diagnostic value of this genetic screening to identify PDB individuals predisposed to develop osteosarcoma. In fact, we detected allelic imbalance at PFN1 locus also in 8 out of 14 (57%) sporadic OS/PDB, further proving its causative role. In vitro experiments also confirmed PFN1 involvement in this form of PDB. Indeed, CRISPR‐Cas9‐mediated Pfn1 knock‐out in pre‐osteoclasts resulted into enhanced osteoclast differentiation and resorption, with the formation of large osteoclasts never described before in PDB. In addition, lacking Pfn1 pre‐osteoblasts lost their differentiation capability and failed to efficiently mineralize bone. Moreover, they acquired features of malignant transformation, including loss of focal adhesions and increased invasion ability. In conclusion, these findings disclose PFN1 haploinsufficiency as the pathological mechanism in OS/PDB.
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Red Cell Distribution Width Is a Risk Factor for Hip Fracture in Elderly Men Without Anemia

28-01-2020 – Kyoung Min Kim, Li‐Yung Lui, Jane A Cauley, Kristine E Ensrud, Eric S Orwoll, John T. Schousboe, Steven R Cummings, the Osteoporotic Fractures in Men (MrOS) Study Research Group

Journal Article

Abstract
Red cell distribution width (RDW), routinely assessed as a component of a complete blood count (CBC), quantifies the variation in the size of red blood cells. It increases with age, and increased RDW predicts many aging‐related diseases and mortality. However, whether it also predicts hip fracture is unknown. We prospectively evaluated the association between RDW and hip fracture using data from the Osteoporotic Fracture in Men (Mr
OS) study. RDW was measured in 3,635 men (aged 71–99 years old) along with bone mineral density (BMD) in Mr
OS. RDW ranged from 11.3%–32.9% (median 14.0%; interquartile range 13.5%–14.8%) and was categorized into 4 groups (≤13.0%, 13.1%–14.0%, 14.1%–15.0%, ≥15.1%). Study participants with a hemoglobin level < 13.0 g/d
L were classified as having anemia. During an average 8.1 years, 164 men suffered hip fractures. The risks of hip fractures increased with increase of RDW category. Furthermore, there was a significant interaction between anemia and RDW: an association between RDW and hip fractures was only observed in participants without anemia. In those without anemia, the relative hazard of hip fractures increased with increases in RDW category: men in the highest RDW category had a 2.8 times higher risk of hip fractures than men in the lowest group (95% confidence interval 1.1‐7.1). The risks of all‐clinical fractures were also increased along with higher RDW values. Additionally, RDW was significantly associated with the risk of having a fall but not with femoral neck or total hip BMD. In conclusion, RDW and anemia defined by hemoglobin are widely available routine laboratory measurements that, together, they could indicate increased risk of hip fracture, reflecting the neuromuscular effects of aging rather than lower hip BMD.

A Single Infusion of Zoledronate in Postmenopausal Women Following Denosumab Discontinuation Results in Partial Conservation of Bone Mass Gains.

28-01-2020 – J. Everts‐Graber, S. Reichenbach, H.R. Ziswiler, U. Studer, T. Lehmann

Journal Article

Abstract
Discontinuation of denosumab is associated with a rapid return of bone mineral density (BMD) to baseline and an increased risk of multiple vertebral fractures. No subsequent treatment regimen has yet been established for preventing either loss of BMD or multiple vertebral fractures after denosumab discontinuation. The aim of this 8‐year observational study was to investigate the effect of a single zoledronate infusion, administered 6 months after the last denosumab injection, on fracture occurrence and loss of BMD. We report on 120 women with postmenopausal osteoporosis who were treated with 60 mg denosumab every 6 months for 2 to 5 years (mean duration 3 years) and then 5 mg zoledronate 6 months after the last denosumab injection. All patients were evaluated clinically, by DXA and vertebral fracture assessment (VFA), before the first and after the last denosumab injection and at 2.5 years (median) after denosumab discontinuation. During this off‐treatment period, 3 vertebral fractures (1.1 per 100 patient years) and 4 non‐vertebral fractures (1.5 per 100 patient years) occurred. No patients developed multiple vertebral fractures. Sixty‐six percent (CI: 57‐75%) of BMD gained with denosumab was retained at the lumbar spine, and 49% (CI: 31‐67%) at the total hip. There was no significant difference in the decrease of BMD between patients with BMD gains of >9% vs. <9% while treated with denosumab. Previous antiresorptive treatment or prevalent fractures had no impact on the decrease of BMD, and all bone loss occurred within the first 18 months after zoledronate infusion. In conclusion, a single infusion of 5 mg zoledronate after a 2 to 5‐year denosumab treatment cycle retained more than half of the gained BMD and was not associated with multiple vertebral fractures, as reported in patients who discontinued denosumab without subsequent bisphosphonate treatment.
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Increased Burden of Common Risk Alleles in Children With a Significant Fracture History

28-01-2020 – Despoina Manousaki, Anders Kämpe, Vincenzo Forgetta, Riikka E Makitie, Ghalib Bardai, Alexandre Belisle, Rui Li, Sture Andersson, Outi Makitie, Frank Rauch, J Brent Richards

Journal Article

ABSTRACTExtreme presentations of common disease in children are often presumed to be of Mendelian etiology, but their polygenic basis has not been fully explored. We tested whether children with significant fracture history and no osteogenesis imperfecta (OI) are at increased polygenic risk for fracture. A childhood significant fracture history was defined as the presence of low‐trauma vertebral fractures or multiple long bone fractures. We generated a polygenic score of heel ultrasound‐derived speed of sound, termed “g
SOS,” which predicts risk of osteoporotic fracture. We tested if individuals from three cohorts with significant childhood fracture history had lower g
SOS. A Canadian cohort included 94 children with suspected Mendelian osteoporosis, of which 68 had negative OI gene panel. Two Finnish cohorts included 59 children with significant fracture history and 22 with suspected Mendelian osteoporosis, among which 18 had no OI. After excluding individuals with OI and ancestral outliers, we generated g
SOS estimates and compared their mean to that of a UK Biobank subset, representing the general population. The average g
SOS across all three cohorts (n = 131) was −0.47 SD lower than that in UK Biobank (n = 80,027, p = 1.1 × 10−5). The g
SOS of 78 individuals with suspected Mendelian osteoporosis was even lower (−0.76 SD, p = 5.3 × 10−10). Among the 131 individuals with a significant fracture history, we observed 8 individuals with g
SOS below minus 2 SD from the mean; their mean lumbar spine DXA‐derived bone mineral density Z‐score was −1.7 (SD 0.8). In summary, children with significant fracture history but no OI have an increased burden of common risk alleles. This suggests that a polygenic contribution to disease should be considered in children with extreme presentations of fracture. © 2020 American Society for Bone and Mineral Research.

Involvement of the Gut Microbiota and Barrier Function in Glucocorticoid‐Induced Osteoporosis

23-01-2020 – Jonathan D Schepper, Fraser Collins, Naiomy Deliz Rios‐Arce, Ho Jun Kang, Laura Schaefer, Joseph D Gardinier, Ruma Raghuvanshi, Robert A Quinn, Robert Britton, Narayanan Parameswaran, Laura R McCabe

Journal Article

ABSTRACTGlucocorticoids (GCs) are potent immune‐modulating drugs with significant side effects, including glucocorticoid‐induced osteoporosis (GIO). GCs directly induce osteoblast and osteocyte apoptosis but also alter intestinal microbiota composition. Although the gut microbiota is known to contribute to the regulation of bone density, its role in GIO has never been examined. To test this, male C57/Bl6J mice were treated for 8 weeks with GC (prednisolone, GC‐Tx) in the presence or absence of broad‐spectrum antibiotic treatment (ABX) to deplete the microbiota. Long‐term ABX prevented GC‐Tx‐induced trabecular bone loss, showing the requirement of gut microbiota for GIO. Treatment of GC‐Tx mice with a probiotic (Lactobacillus reuteri LR) prevented trabecular bone loss. Microbiota analyses indicated that GC‐Tx changed the abundance of Verrucomicobiales and Bacteriodales phyla and random forest analyses indicated significant differences in abundance of Porphyromonadaceae and Clostridiales operational taxonomic units (OTUs) between groups. Furthermore, transplantation of GC‐Tx mouse fecal material into recipient naïve, untreated WT mice caused bone loss, supporting a functional role for microbiota in GIO. We also report that GC caused intestinal barrier breaks, as evidenced by increased serum endotoxin level (2.4‐fold), that were prevented by LR and ABX treatments. Enhancement of barrier function with a mucus supplement prevented both GC‐Tx–induced barrier leakage and trabecular GIO. In bone, treatment with ABX, LR or a mucus supplement reduced GC‐Tx–induced osteoblast and osteocyte apoptosis. GC‐Tx suppression of Wnt10b in bone was restored by the LR and high‐molecular‐weight polymer (MDY) treatments as well as microbiota depletion. Finally, we identified that bone‐specific Wnt10b overexpression prevented GIO. Taken together, our data highlight the previously unappreciated involvement of the gut microbiota and intestinal barrier function in trabecular GIO pathogenesis (including Wnt10b suppression and osteoblast and osteocyte apoptosis) and identify the gut as a novel therapeutic target for preventing GIO. © 2019 American Society for Bone and Mineral Research.

Biomarkers in WNT1 and PLS3 osteoporosis: Altered concentrations of DKK1 and FGF23

22-01-2020 – Riikka E. Mäkitie, Anders Kämpe, Alice Costantini, Jessica J. Alm, Per Magnusson, Outi Mäkitie

Journal Article

Abstract
Recent advancements in genetic research have uncovered new forms of monogenic osteoporosis, expanding our understanding of the molecular pathways regulating bone health. Despite active research, knowledge on the pathomechanisms, disease‐specific biomarkers and optimal treatment in these disorders is still limited. Mutations in WNT1, encoding a WNT/β‐catenin pathway ligand WNT1, and PLS3, encoding X chromosomally inherited plastin 3 (PLS3), both result in early‐onset osteoporosis with prevalent fractures and disrupted bone metabolism. However, despite marked skeletal pathology, conventional bone markers are usually normal in both diseases. Our study aimed to identify novel bone markers in PLS3 and WNT1 osteoporosis that could offer diagnostic potential and shed light on the mechanisms behind these skeletal pathologies. We measured several parameters of bone metabolism, including serum dickkopf‐1 (DKK1), sclerostin, and intact and C‐terminal fibroblast growth factor 23 (FGF23) concentrations in 17 WNT1 and 14 PLS3 mutation‐positive subjects. Findings were compared with 34 healthy mutation‐negative subjects from the same families. Results confirmed normal concentrations of conventional metabolic bone markers in both groups. DKK1 concentrations were significantly elevated in PLS3 mutation‐positive subjects compared with WNT1 mutation‐positive subjects (p<0.001) or the mutation‐negative subjects (p=0.002). Similar differences were not seen in WNT1 subjects. Sclerostin concentrations did not differ between any groups. Both intact and C‐terminal FGF23 were significantly elevated in WNT1 mutation‐positive subjects (p=0.039 and 0.027, respectively) and normal in PLS3 subjects. Our results indicate a link between PLS3 and DKK1 and WNT1 and FGF23 in bone metabolism. The normal sclerostin and DKK1 levels in patients with impaired WNT signaling suggest another parallel regulatory mechanism. These findings provide novel information on the molecular networks in bone. Extended studies are needed to investigate whether these biomarkers offer diagnostic value or potential as treatment targets in osteoporosis.
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Oral bisphosphonate use and all‐cause mortality in patients with moderate‐severe (grade 3B‐5D) chronic kidney disease: a population‐based cohort study

22-01-2020 – Dunia Alarkawi, M Sanni Ali, Dana Bliuc, Natalia Pallares, Cristian Tebe, Leena Elhussein, Fergus J Caskey, Nigel K Arden, Yoav Ben‐Shlomo, Bo Abrahamsen, Adolfo Diez‐Perez, Julio Pascual, María José Pérez‐Sáez, Jacqueline R Center, Andrew Judge, Cyrus Cooper, Muhammad K Javaid, Daniel Prieto‐Alhambra

Journal Article

Abstract
Oral Bisphosphonates (o
BP) have been associated with reduced fractures and mortality. However, their risks and benefits are unclear in patients with moderate‐severe CKD. This study examined the association between o
BP and all‐cause mortality in G3B‐5D CKD. This is a population‐based cohort study including all subjects with an e
GFR<45/ml/min/1.73m2 aged 40+ years from the UK Clinical Practice Research Datalink (CPRD) and the Catalan Information System for Research in Primary Care (SIDIAP). Previous and current users of other anti‐osteoporosis drugs were excluded. o
BP use was modelled as a time‐varying exposure to avoid immortal time bias. Treatment episodes in o
BP users were created by concatenating prescriptions until patients switched or stopped therapy or were censored or died. A washout period of 180 days was added to (date of last prescription +180 days). Propensity scores (PS) were calculated using pre‐specified predictors of mortality including age, gender, baseline e
GFR, socio‐economic status, co‐morbidities, previous fracture, co‐medications and number of hospital admissions in the previous year. Cox models were used for PS adjustment before and after PS trimming (the first and last quintiles). In the CPRD, of 19,351 o
BP users and 210,954 non‐o
BP users, 5,234 (27%) and 85,105 (40%) deaths were recorded over 45,690 and 915,867 person‐years of follow‐up, respectively. o
BP users had 8% lower mortality risk compared to non‐o
BP users (HR 0.92, 95% CI 0.89‐0.95). Following PS trimming, this became non‐significant (HR 0.98, 95% CI 0.94‐1.04). In the SIDIAP, of 4,146 o
BP users 86,127 non‐o
BP users, 1,330 (32%) and 36,513 (42%) died, respectively. o
BP were not associated with mortality in PS adjustment and trimming (HR 1.04, 95% CI 0.99‐1.1 and HR 0.95, 95% CI 0.89‐1.01). In this observational, patient‐based cohort study, o
BP were not associated with increased mortality amongst patients with moderate‐severe CKD. However, further studies are needed on other effects of o
BP in CKD patients.
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Myeloma Cells Down‐Regulate Adiponectin in Bone Marrow Adipocytes Via TNF‐Alpha

16-01-2020 – Emma V Morris, Karla J Suchacki, Joseph Hocking, Rachel Cartwright, Aneka Sowman, Beatriz Gamez, Ryan Lea, Matthew T Drake, William P Cawthorn, Claire M Edwards

Journal Article

ABSTRACTMultiple myeloma is caused by abnormal plasma cells that accumulate in the bone marrow and interact with resident cells of the bone microenvironment to drive disease progression and development of an osteolytic bone disease. Bone marrow adipocytes (BMAds) are emerging as having important endocrine functions that can support myeloma cell growth and survival. However, how BMAds respond to infiltrating tumor cells remains poorly understood. Using the C57BL/Ka
Lw
Rij murine model of myeloma, bone marrow adiposity was found to be increased in early stage myeloma with BMAds localizing along the tumor‐bone interface at later stages of disease. Myeloma cells were found to uptake BMAd‐derived lipids in vitro and in vivo, although lipid uptake was not associated with the ability of BMAds to promote myeloma cell growth and survival. However, BMAd‐derived factors were found to increase myeloma cell migration, viability, and the evasion of apoptosis. BMAds are a major source of adiponectin, which is known to be myeloma‐suppressive. Myeloma cells were found to downregulate adiponectin specifically in a model of BMAds but not in white adipocytes. The ability of myeloma cells to downregulate adiponectin was dependent at least in part on TNF‐α. Collectively our data support the link between increased bone marrow adiposity and myeloma progression. By demonstrating how TNF‐α downregulates BMAd‐derived adiponectin, we reveal a new mechanism by which myeloma cells alter the bone microenvironment to support disease progression. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Disorder of Iron Metabolism Inhibits the Recovery of Unloading‐Induced Bone Loss in Hypomagnetic Field

16-01-2020 – Yanru Xue, Jiancheng Yang, Jie Luo, Li Ren, Ying Shen, Dandan Dong, Yanwen Fang, Lijiang Hu, Mengyu Liu, Zhongcai Liao, Jun Li, Zhicai Fang, Peng Shang

Journal Article

ABSTRACTExposure of humans and animals to microgravity in spaceflight results in various deleterious effects on bone health. In addition to microgravity, the hypomagnetic field (Hy
MF) is also an extreme environment in space, such as on the Moon and Mars; magnetic intensity is far weaker than the geomagnetic field (GMF) on Earth. Recently, we showed that Hy
MF promoted additional bone loss in hindlimb unloading–induced bone loss, and the underlying mechanism probably involved an increase of body iron storage. Numerous studies have indicated that bone loss induced by mechanical unloading can be largely restored after skeletal reloading in GMF conditions. However, it is unknown whether this bone deficit can return to a healthy state under Hy
MF condition. Therefore, the purpose of this study is to examine the effects of Hy
MF on the recovery of microgravity‐induced bone loss, and illustrates the changes of body iron storage in this process. Our results showed that there was lower bone mineral content (BMC) in the Hy
MF reloading group compared to the GMF reloading group. Reloaded mice in the Hy
MF condition had a worse microstructure of femur than in the GMF condition. Femoral mechanical properties, including elastic modulus, stiffness, and ultimate stress, were poorer and toughness was higher in the Hy
MF group compared with the GMF group. Simultaneously, more iron content in serum, the tibia, liver, and spleen was found under Hy
MF reloading than GMF reloading. The iron chelator deferoxamine mesylate (DFO) decreased the iron content in the bone, liver, and spleen, and significantly relieved unloading‐induced bone loss under Hy
MF reloading. These results showed that Hy
MF inhibits the recovery of microgravity‐induced bone loss, probably by suppressing the elevated iron levels’ return to physiological level. © 2019 American Society for Bone and Mineral Research.

Heterogeneity and Spatial Distribution of Intravertebral Trabecular Bone Mineral Density in the Lumbar Spine Is Associated With Prevalent Vertebral Fracture

16-01-2020 – Jarred Kaiser, Brett Allaire, Paul M Fein, Darlene Lu, Alexander Adams, Douglas P Kiel, Mohamed Jarraya, Ali Guermazi, Serkalem Demissie, Elizabeth J Samelson, Mary L Bouxsein, Elise F Morgan

Journal Article

ABSTRACTThe spatial heterogeneity in trabecular bone density within the vertebral centrum is associated with vertebral strength and could explain why volumetric bone mineral density (v
BMD) exhibits low sensitivity in identifying fracture risk. This study evaluated whether the heterogeneity and spatial distribution of trabecular v
BMD are associated with prevalent vertebral fracture. We examined the volumetric quantitative computed tomography (QCT) scans of the L3 vertebra in 148 participants in the Framingham Heart Study Multidetector CT study. Of these individuals, 37 were identified as cases of prevalent fracture, and 111 were controls, matched on sex and age with three controls per case. v
BMD was calculated within 5‐mm contiguous cubic regions of the centrum. Two measures of heterogeneity were calculated: (i) interquartile range (IQR); and (ii) quartile coefficient of variation (QCV). Ratios in the spatial distributions of the trabecular v
BMD were also calculated: anterior/posterior, central/outer, superior/mid‐transverse, and inferior/mid‐transverse. Heterogeneity and spatial distributions were compared between cases and controls using Wilcoxon rank sum tests and t tests and tested for association with prevalent fractures with conditional logistic regressions independent of integral v
BMD. Prevalent fracture cases had lower mean ± SD integral v
BMD (134 ± 38 versus165 ± 42 mg/cm3, p < .001), higher QCV (0.22 ± 0.13 versus 0.17 ± 0.09, p = .003), and lower anterior/posterior r
BMD (0.65 ± 0.13 versus 0.78 ± 0.16, p < .001) than controls. QCV was positively associated with increased odds of prevalent fracture (OR 1.61; 95% CI, 1.04 to 2.49; p = .034), but this association was not independent of integral v
BMD (p = .598). Increased anterior/posterior trabecular v
BMD ratio was associated with decreased odds of prevalent fracture independent of integral v
BMD (OR 0.38; 95% CI, 0.20 to 0.71; p = .003). In conclusion, increased trabecular v
BMD in the anterior versus posterior centrum, but not trabecular v
BMD heterogeneity, was associated with decreased risk of prevalent fracture independent of integral v
BMD. Regional measurements of trabecular v
BMD could aid in determining the risk and underlying mechanisms of vertebral fracture. © 2019 American Society for Bone and Mineral Research.

Clinical and Biochemical Phenotypes in a Family With ENPP1 Mutations

16-01-2020 – Anupam Kotwal, Alejandro Ferrer, Rajiv Kumar, Ravinder J Singh, Vishakantha Murthy, Laura Schultz‐Rogers, Michael Zimmermann, Brendan Lanpher, Kristin Zimmerman, Paul R Stabach, Eric Klee, Demetrios T Braddock, Robert A Wermers

Journal Article

ABSTRACTInactivating mutations of the ENPP1 gene are associated with generalized arterial calcification of infancy (GACI) and less often autosomal‐recessive hypophosphatemic rickets type 2 (ARHR2). We aimed to investigate the spectrum of phenotypes in a family with monoallelic and biallelic mutations of ENPP1 after identification through whole exome sequencing of a 54‐year‐old female with biallelic mutation of ENPP1, c.323G > T; p.
Cys108Phe and c.1441C > T; p.
Arg481Trp. Including the proband, 2 subjects had biallelic mutations, 5 had monoallelic mutations, and 2 had no mutation of ENPP1. The maternal mutation, a known pathogenic variant associated with GACI, was found in 3 subjects with monoallelic mutations, while the paternal mutation, which was not previously reported, was present in 2 subjects with monoallelic mutations. Both subjects with biallelic mutations had bowing of bilateral femurs, periarticular mineral deposition, normocalcemic primary hyperparathyroidism with multigland parathyroidectomy, increased carotid intima‐media thickness, and enthesopathy was also noted in one subject. Intact FGF23 was elevated in both subjects with biallelic mutations, while C‐terminal FGF23 was only elevated in one and PPi was reduced in one. Subjects with monoallelic mutations did not have periarticular calcifications or bone deformities. To conclude, patients with biallelic GACI causing mutations can survive well into adulthood, and despite the same biallelic ENPP1 pathogenic variants, clinical and biochemical manifestations can significantly differ, and include enthesopathy and primary hyperparathyroidism, which have not been previously described. Although carriers of monoallelic ENPP1 variants appear unaffected by classic disease manifestations, there may be subtle biochemical and clinical findings that warrant further investigation. © 2019 American Society for Bone and Mineral Research.

Maternal Transmission Ratio Distortion of GNAS Loss‐of‐Function Mutations

13-01-2020 – Sarah Snanoudj, Arnaud Molin, Cindy Colson, Nadia Coudray, Sylvie Paulien, Hervé Mittre, Marion Gérard, Elise Schaefer, Alice Goldenberg, Justine Bacchetta, Sylvie Odent, Sophie Naudion, Bénédicte Demeer, Laurence Faivre, Nicolas Gruchy, Marie‐Laure Kottler, Nicolas Richard

Journal Article

ABSTRACTPseudohypoparathyroidism type 1A (PHP1A) and pseudopseudohypoparathyroidism (PPHP) are two rare autosomal dominant disorders caused by loss‐of‐function mutations in the imprinted Guanine Nucleotide Binding Protein, Alpha Stimulating Activity (GNAS) gene, coding Gsα. PHP1A is caused by mutations in the maternal allele and results in Albrights hereditary osteodystrophy (AHO) and hormonal resistance, mainly to the parathormone (PTH), whereas PPHP, with AHO features and no hormonal resistance, is linked to mutations in the paternal allele. This study sought to investigate parental transmission of GNAS mutations. We conducted a retrospective study in a population of 204 families with 361 patients harboring GNAS mutations. To prevent ascertainment bias toward a higher proportion of affected children due to the way in which data were collected, we excluded from transmission analysis all probands in the ascertained sibships. After bias correction, the distribution ratio of the mutated alleles was calculated from the observed genotypes of the offspring of nuclear families and was compared to the expected ratio of 50% according to Mendelian inheritance (one‐sample Z‐test). Sex ratio, phenotype of the transmitting parent, and transmission depending on the severity of the mutation were also analyzed. Transmission analysis was performed in 114 nuclear families and included 250 descendants. The fertility rates were similar between male and female patients. We showed an excess of transmission from mother to offspring of mutated alleles (59%, p = .022), which was greater when the mutations were severe (61.7%, p = .023). Similarly, an excess of transmission was found when the mother had a PHP1A phenotype (64.7%, p = .036). By contrast, a Mendelian distribution was observed when the mutations were paternally inherited. Higher numbers of females within the carriers, but not in noncarriers, were also observed. The mother‐specific transmission ratio distortion (TRD) and the sex‐ratio imbalance associated to PHP1A point to a role of Gsα in oocyte biology or embryogenesis, with implications for genetic counseling. © 2019 American Society for Bone and Mineral Research.

Propranolol Reverses Impaired Fracture Healing Response Observed With Selective Serotonin Reuptake Inhibitor Treatment

10-01-2020 – Sooyeon Lee, Lindsey H Remark, Daniel B Buchalter, Anne M Josephson, Madeleine Z Wong, Hannah P Litwa, Rivka Ihejirika, Kevin Leclerc, Danielle Markus, Nury L Yim, Ruchi Tejwani, Vivian Bradaschia‐Correa, Philipp Leucht

Journal Article

ABSTRACTSelective serotonin reuptake inhibitors (SSRIs) are one of the most commonly prescribed antidepressants worldwide and recent data show significant impairment of fracture healing after treatment with the SSRI fluoxetine in mice. Here, we provide evidence that the negative effects of SSRIs can be overcome by administration of the beta‐blocker propranolol at the time of fracture. First, in vitro experiments established that propranolol does not affect osteogenic differentiation. We then used a murine model of intramembranous ossification to study the potential rescue effect of propranolol on SSRI‐induced impaired fracture healing. Micro‐CT analysis revealed that fluoxetine treatment resulted in a smaller bony regenerate and that this decrease in bone formation can be overcome by co‐treatment with propranolol. We then tested this in a clinically relevant model of endochondral ossification. Fluoxetine‐treated mice with a femur fracture were treated with propranolol initiated at the time of fracture, and a battery of analyses demonstrated a reversal of the detrimental effect of fluoxetine on fracture healing in response to propranolol treatment. These experiments show for the first time to our knowledge that the negative effects of SSRIs on fracture healing can be overcome by co‐treatment with a beta‐blocker. © 2019 American Society for Bone and Mineral Research.

Rac1 Inhibition Via Srgap2 Restrains Inflammatory Osteoclastogenesis and Limits the Clastokine, SLIT3

09-01-2020 – Bongjin Shin, Justine Kupferman, Ewoud Schmidt, Franck Polleux, Anne M Delany, Sun‐Kyeong Lee

Journal Article

ABSTRACTThe Rac1‐specific guanosine triphosphatase (GTPase)‐activating protein Slit‐Robo GAP2 (Srgap2) is dramatically upregulated during RANKL‐induced osteoclastogenesis. Srgap2 interacts with the cell membrane to locally inhibit activity of Rac1. In this study, we determined the role of Srgap2 in the myeloid lineage on bone homeostasis and the osteoclastic response to TNFα treatment. The bone phenotype of mice specifically lacking Srgap2 in the myeloid lineage (Srgap2 f/f:Lys
M‐Cre; Srgap2 conditional knockout c
KO) was investigated using histomorphometric analysis, in vitro cultures and Western blot analysis. Similar methods were used to determine the impact of TNFα challenge on osteoclast formation in Srgap2 c
KO mice. Bone parameters in male Srgap2 c
KO mice were unaffected. However, female c
KO mice displayed higher trabecular bone volume due to increased osteoblast surface and bone formation rate, whereas osteoclastic parameters were unaltered. In vitro, cells from Srgap2 c
KO had strongly enhanced Rac1 activation, but RANKL‐induced osteoclast formation was unaffected. In contrast, conditioned medium from Srgap2 c
KO osteoclasts promoted osteoblast differentiation and had increased levels of the bone anabolic clastokine SLIT3, providing a possible mechanism for increased bone formation in vivo. Rac1 is rapidly activated by the inflammatory cytokine TNFα. Supracalvarial injection of TNFα caused an augmented osteoclastic response in Srgap2 c
KO mice. In vitro, cells from Srgap2 c
KO mice displayed increased osteoclast formation in response to TNFα. We conclude that Srgap2 plays a prominent role in limiting osteoclastogenesis during inflammation through Rac1, and restricts expression of the paracrine clastokine SLIT3, a positive regulator of bone formation. © 2019 American Society for Bone and Mineral Research.

X‐Linked Hypophosphatemia: Uniquely Mild Disease Associated With PHEX 3′‐UTR Mutation c.*231A>G (A Retrospective Case‐Control Study)

07-01-2020 – Pamela S. Smith, Gary S. Gottesman, Fan Zhang, Fiona Cook, Beatriz Ramirez, Deborah Wenkert, Valerie Wollberg, Margaret Huskey, Steven Mumm, Michael P. Whyte

Journal Article

Abstract
X‐linked hypophosphatemia (XLH), the most prevalent heritable renal phosphate (Pi) wasting disorder, is caused by deactivating mutations of PHEX. Consequently, circulating phosphatonin FGF23 becomes elevated and hypophosphatemia in affected children leads to rickets with skeletal deformity and reduced linear growth while affected adults suffer from osteomalacia and forms of ectopic mineralization. In 2015, we reported uniquely mild XLH in six children and four of their mothers carrying the non‐coding PHEX 3′‐UTR mutation c.*231A>G. Herein, we characterize this mild XLH variant by comparing its features in 30 individuals to 30 age‐ and sex‐matched patients with XLH but without the 3′‐UTR mutation. The “UTR” and “XLH” groups, both comprising 17 children (2‐17 years, 3 girls) and 13 adults (23‐63 years, 10 women), had mean ages of 23 years. Only 43% of the UTR group versus 90% of the XLH group had received medical treatment for their disorder, including 0% versus 85% of the females, respectively (ps< 0.0001). The UTR group was taller: mean (SD) height Z‐score (HZ) ‐1.0 (1.0) versus ‐2.0 (1.4) (p=0.0034), with significantly greater height for females ‐0.9 (0.7) versus ‐2.3 (1.4), (p=0.0050) but not males ‐1.2 (1.1) versus ‐1.9 (1.5) (p=0.1541), respectively. Mean (SD) “arm span Z‐score” (AZ) did not differ between the UTR ‐0.8 (1.3) versus XLH ‐1.3 (1.8) groups (p=0.2269). Consequently, the UTR group was more proportionate with a mean ∆Z (AZ – HZ) of 0.1 (0.6) versus 0.7 (1.0) (p=0.0158), respectively. Compared to the XLH group, the UTR group had significantly higher fasting serum Pi and Tm
P/GFR (ps≤0.0060), serum FGF23 concentrations within the reference range (p=0.0068), and similar serum alkaline phosphatase levels (p = 0.6513). UTR lumbar spine bone mineral density Z‐score was higher (p=0.0343). Thus, the 3′‐UTR variant of XLH is distinctly mild, especially in girls and women, posing challenges for its recognition and management.
This article is protected by copyright. All rights reserved.

Ezh2 ameliorates osteoarthritis by activating TNFSF13B

07-01-2020 – Xiaotian Du, Yishan Chen, Qin Zhang, Junxin Lin, Yeke Yu, Zongyou Pan, Heng Sun, Chunhui Yuan, Dongsheng Yu, Haoyu Wu, Xiaoan Zhang, Jun Dai, Shouan Zhu, Yiting Zhou, Hongwei Ouyang

Journal Article

ABSTRACTEpigenetic regulation is highly correlated with osteoarthritis (OA) development, while the role and detailed mechanisms of it remain elusive. In this study, we explored the expression of EZH2, an H3K27me3 transferase, in human OA cartilages and its roles in regulating OA pathogenesis. Here, we found EZH2 was highly expressed in both mice and human OA cartilage samples by using histological analysis and RNA‐Sequencing. And medial meniscectomy (MMx) OA model results indicated the conditional knockout of Ezh2 deteriorated OA pathological conditions. Furthermore, we demonstrated the positive roles of Ezh2 in cartilage wound healing and inhibition of hypertrophy through activating TNFSF13B, a member of tumor necrosis factor superfamily. Further, we also indicated that the effect of TNFSF13B, increased by Ezh2, might boost the healing of chondrocytes through increasing the phosphorylation of Akt. Taken together, our results argue that An EZH2‐positive subpopulation was existed in OA patients and EZH2‐TNFSF13B signaling was responsible for regulating chondrocyte healing and hypertrophy. Thus, it might act as a new potential target for OA diagnosis and treatment.
This article is protected by copyright. All rights reserved.

Apoptotic osteocytes induce RANKL production in bystanders via purinergic signaling and activation of pannexin channels

07-01-2020 – Sean McCutcheon, Robert J. Majeska, David C. Spray, Mitchell B. Schaffler, Maribel Vazquez

Journal Article

Abstract
Localized apoptosis of osteocytes, the tissue‐resident cells within bone, occurs with fatigue microdamage and activates bone resorption. Osteoclasts appear to target and remove dying osteocytes, resorbing damaged bone matrix as well. Osteocyte apoptosis similarly activates bone resorption with estrogen loss and in disuse. Apoptotic osteocytes trigger viable neighbor (i.e., Bystander) osteocytes to produce RANKL, the cytokine required for osteoclast activation. Signals from apoptotic osteocytes that trigger this bystander RANKL expression remain obscure. Studying signaling among osteocytes has been hampered by lack of in vitro systems that model the limited communication among osteocytes in vivo (i.e., via gap junctions on cell processes and/or paracrine signals through thin pericellular fluid spaces around osteocytes). Here, we used a novel multiscale fluidic device (the Macro‐micro‐nano, or Mμn) that reproduces these key anatomical features. Osteocytes in discrete compartments of the device communicate only via these limited pathways, which allows assessment of their roles in triggering osteocytes RANKL expression. Apoptosis of MLOY‐4 osteocytes in the Mμn device caused increased osteocyte RANKL expression in the neighboring compartment, consistent with in vivo findings. This RANKL upregulation in bystander osteocytes was prevented by blocking Pannexin 1 channels as well as its ATP receptor. ATP alone caused comparable RANKL upregulation in bystander osteocytes. Finally, blocking Connexin 43 gap junctions did not abolish osteocyte RANKL upregulation, but did alter the distribution of RANKL expressing bystander osteocytes. These findings point to extracellular ATP, released from apoptotic osteocytes via Panx1 channels, as a major signal for triggering bystander osteocyte RANKL expression and activating bone remodeling.
This article is protected by copyright. All rights reserved.

The Importance and Possible Clinical Impact of Measuring Trabecular and Cortical Bone Microstructure to Improve Fracture Risk Prediction

07-01-2020 – Mattias Lorentzon

Editorial

Loss‐of‐Function Mutations in the ALPL Gene Presenting with Adult Onset Osteoporosis and Low Serum Concentrations of Total Alkaline Phosphatase

07-01-2020 – Nerea Alonso, Beatriz Larraz‐Prieto, Kathryn Berg, Zoe Lambert, Paul Redmond, Sarah E Harris, Ian J Deary, Carys Pugh, James Prendergast, Stuart H Ralston

Journal Article

ABSTRACTHypophosphatasia (HPP) is a rare inherited disorder characterized by rickets and low circulating concentrations of total alkaline phosphatase (ALP) caused by mutations in ALPL. Severe HPP presents in childhood but milder forms can present in adulthood. The prevalence and clinical features of adult HPP are poorly defined. The aim of this study was to evaluate the prevalence and clinical significance of low serum total alkaline phosphatase (ALP) levels in a clinic‐based population of adult osteoporotic patients. We searched for patients with low ALP in a cohort of 3285 patients referred to an osteoporosis clinic over a 10‐year period and performed mutation screening of ALPL in those with low ALP (≤40 U/L) on two or more occasions. These individuals were matched with four clinic controls with a normal ALP. We also evaluated the prevalence of low ALP and ALPL mutations in 639 individuals from the general population from the same region. We identified 16/3285 (0.49%) clinic patients with low ALP and 14 (87.5%) had potentially pathogenic variants in ALPL. Eight of these individuals were heterozygous for mutations previously described in HPP and 2 were heterozygous for novel mutations (p.
Arg301Trp and p.
Tyr101X). These mutations were not found in clinic controls or in the general population. Eight patients with low ALP, including 4 with ALPL mutations, were treated with bisphosphonates for an average of 6.5 years. In these individuals, the rate of fractures during treatment was comparable to that in normal ALP clinic controls who were treated with bisphosphonates. We conclude that heterozygous loss‐of‐function mutations in ALPL are common in osteoporosis patients with low ALP. Further studies are required to determine how best these individuals should be treated. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

PARP1 Hinders Histone H2B Occupancy at the NFATc1 Promoter to Restrain Osteoclast Differentiation

07-01-2020 – Chun Wang, Jianqiu Xiao, Kathrin Nowak, Kapila Gunasekera, Yael Alippe, Sheree Speckman, Tong Yang, Dustin Kress, Yousef Abu‐Amer, Michael O. Hottiger, Gabriel Mbalaviele

Journal Article

ABSTRACTInduction of nuclear factor of activated T cell cytoplasmic 1 (NFATc1) by macrophage colony‐stimulating factor (M‐CSF) and receptor activator of NF‐κB ligand (RANKL) is essential for macrophage differentiation into osteoclasts (OCs), but the underlying mechanisms remain unclear. The ability of poly(ADP‐ribose) polymerase 1 (PARP1) to poly‐ADP‐ribosylate NFATc1 in T cells prompted us to investigate the PARP1 and NFATc1 interaction during osteoclastogenesis. However, extensive studies failed to directly link PARP1 to NFATc1. A combination of transcriptomics and proteomics studies was then used to identify PARP1 targets under these conditions. These unbiased approaches in conjunction with site‐directed mutagenesis studies revealed that PARP1 inhibited NFATc1 expression and OC formation by ADP‐ribosylating histone H2B at serine 7 and decreasing the occupancy of this histone variant at the NFATc1 promoter. The anti‐osteoclastogenic function of PARP1 was confirmed in vivo in several mouse models of PARP1 loss‐of‐function or gain‐of‐function, including a novel model in which PARP1 was conditionally ablated in myeloid cells. Thus, PARP1 ADP‐ribosylates H2B to negatively regulate NFATc1 expression and OC differentiation. © 2019 American Society for Bone and Mineral Research.

LIGHT/TNFSF14 Promotes Osteolytic Bone Metastases in Non‐small Cell Lung Cancer Patients

07-01-2020 – Giacomina Brunetti, Dimas C Belisario, Sara Bortolotti, Giuseppina Storlino, Graziana Colaianni, Maria F Faienza, Lorenzo Sanesi, Valentina Alliod, Lucio Buffoni, Elisa Centini, Claudia Voena, Roberta Pulito, Silvia Novello, Giuseppe Ingravallo, Rita Rizzi, Giorgio Mori, Janne E Reseland, Carl F Ware, Silvia Colucci, Riccardo Ferracini, Maria Grano, Ilaria Roato

Journal Article

ABSTRACTTumor necrosis factor superfamily member 14 (TNFSF14), LIGHT, is a component of the cytokine network that regulates innate and adaptive immune responses, which promote homeostasis of lymphoid organs, liver, and bone. Metastatic tumors often disrupt the tissue microenvironment, thus altering the homeostasis of the invaded organ; however, the underlying mechanisms required further studies. We investigated the role of LIGHT in osteolytic bone disease induced by metastatic non‐small cell lung cancer (NSCLC). Patients diagnosed with NSCLC bone metastasis show significantly higher levels of LIGHT expressed in monocytes compared with non‐bone metastatic tumors and healthy controls. Serum LIGHT levels were also higher in patients with bone metastases than in controls, suggesting a role for LIGHT in stimulating osteoclast precursors. In bone metastatic patients, we also detected increased RNA expression and serum RANKL levels, thus by adding anti‐LIGHT or RANK–fragment crystallizable region (RANK‐Fc) in PBMC cultures, a significant inhibition of osteoclastogenesis was observed. To model this observation in mice, we used the mouse lung cancer cell line LLC‐1. After intratibial implantation, wild‐type mice showed an increased number of osteoclasts but reduced numbers of osteoblasts and decreased osteoid formation. In contrast, Tnfsf14−/− mice showed no significant bone loss or other changes in bone homeostasis associated with this model. These data indicate LIGHT is a key control mechanism for regulating bone homeostasis during metastatic invasion. Thus, LIGHT may be a novel therapeutic target in osteolytic bone metastases. © 2019 American Society for Bone and Mineral Research.

Genetically Decreased Circulating Vascular Endothelial Growth Factor and Osteoporosis Outcomes: A Mendelian Randomization Study

06-01-2020 – Julyan Keller‐Baruch, Vincenzo Forgetta, Despoina Manousaki, Sirui Zhou, J Brent Richards

Journal Article

ABSTRACTVascular endothelial growth factor (VEGF) is important for bone formation and has been associated with osteoporosis in humans. Therefore, we conducted a two‐sample Mendelian randomization study to test whether genetically decreased circulating VEGF was associated with decreased bone mineral density (BMD) and increased risk of fracture. Summary statistics from a genomewide association study (GWAS) meta‐analysis of circulating VEGF level (n = 16,112) were used to identify 10 genetic variants explaining up to 52% of the variance in circulating VEGF levels. GWAS meta‐analyses on dual‐energy X‐ray absorptiometry (DXA)‐derived BMD of forearm, lumbar spine, and femoral neck (n = up to 32,735) and BMD estimated from heel calcaneus ultrasound (e
BMD) (n = 426,824) were used to assess the effect of genetically lowered circulating VEGF levels on BMD. A GWAS meta‐analysis including a total of 76,549 cases and 470,164 controls was used to assess the effect of genetically lowered circulating VEGF levels on risk of fracture. A natural log‐transformed pg/m
L decrease in circulating VEGF levels was not associated with a decrease in forearm BMD (0.02 standard deviation SD, 95% confidence interval CI −0.024 to 0.064, p = 0.38), lumbar spine BMD (−0.005 SD, 95% CI −0.03 to 0.019, p = 0.67), femoral neck BMD (0.004 SD, 95% CI −0.017 to 0.026, p = 0.68), e
BMD (−0.006 SD, 95% CI −0.012 to −0.001, p = 0.031) or risk of fracture (odds ratio = 0.99, 95% CI 0.98 to 1.0, p = 0.37) in inverse‐variance–weighted Mendelian randomization analyses. Sensitivity analyses did not provide evidence that our results were influenced by pleiotropy. Genetically lowered circulating VEGF was not associated with a decrease in BMD or increased risk of fracture, suggesting that efforts to influence circulating VEGF level are unlikely to have beneficial effects on osteoporosis outcomes and that previous observational associations of circulating VEGF with BMD were influenced by confounding or reverse causation. © 2019 American Society for Bone and Mineral Research.

Irisin Prevents Disuse‐Induced Osteocyte Apoptosis

06-01-2020 – Giuseppina Storlino, Graziana Colaianni, Lorenzo Sanesi, Luciana Lippo, Giacomina Brunetti, Mariella Errede, Silvia Colucci, Giovanni Passeri, Maria Grano

Journal Article

Schematic representation of irisins action on osteocytes to activate ERK phosphorylation, which in turn stimulates the increase of Atf4 m
RNA levels. A recent study showed that irisin increases survival of osteocytes acting through integrin αV/β5 receptors. To elucidate the action of irisin on osteocytes, we investigated the downstream signaling cascades in MLO‐Y4 cells treated with recombinant irisin (rec‐irisin). We found that rec‐irisin activated the MAP kinases Erk1 and Erk2 and increased the expression of the transcription factor Atf4 through an Erk‐dependent pathway in osteocytes.
ABSTRACTPrevious results showed that intermittently administered irisin improves bone mass in normal mice and prevents the development of disuse‐induced osteoporosis and muscular atrophy in hindlimb‐suspended mice, a murine model able to mimic the absence of mechanical loading. A recent study showed that irisin increases survival of osteocytes acting through integrin αV/β5 receptors. To better understand the action of irisin on these cells, we investigated the downstream signaling cascades in osteocyte‐like cells (MLO‐Y4) treated with recombinant irisin (rec‐irisin) in vitro and we analyzed survival of osteocytes and caspase activation in cortical bone of osteoporotic mice treated with rec‐irisin in vivo. Our results revealed that rec‐irisin activated the MAP kinases Erk1 and Erk2 and increased the expression of the transcription factor Atf4 (2.5‐fold, p < .05) through an Erk‐dependent pathway in osteocytes. Some key genes expressed by MLO‐Y4 cells were modulated by long‐term irisin treatment, either continuously administered or given with intermittent short pulses. Interestingly, Sost m
RNA was severely downregulated only upon intermittent irisin administration (10‐fold, p < .001). Furthermore, rec‐irisin upregulated Tfam m
RNA (fourfold, p < .05) and Bcl2/Bax ratio (twofold, p < .05) in MLO‐Y4 cells. By detecting caspase‐9 and caspase‐3, we also found that rec‐irisin inhibited apoptosis induced by hydrogen peroxide and dexamethasone, respectively. In cortical bone of unloading C57BL6 mice treated with vehicle (unload‐veh), irisin prevented disuse‐induced reduction of viable osteocytes (+30% versus unload‐veh, p < .05) and increase of empty lacunae (+110% versus unload‐veh, p < .05), as well as caspase‐9 (threefold, p < .05) and caspase‐3 (twofold, p < .05) activations. Our findings revealed underlying mechanisms of irisin action on osteocytes, which increases their functions and exerts anti‐apoptotic effects, confirming that mechanosensor cells of bone are sensitive to the exercise‐mimetic myokine irisin. © 2019 American Society for Bone and Mineral Research.

Differential Effect of Long‐Term Systemic Exposure of TNFα on Health of the Annulus Fibrosus and Nucleus Pulposus of the Intervertebral Disc

06-01-2020 – Deborah J Gorth, Olivia K Ottone, Irving M Shapiro, Makarand V Risbud

Journal Article

ABSTRACTThe inflammatory cytokine tumor necrosis factor alpha (TNFα) is considered to play a key role in the pathogenesis of intervertebral disc disease. To evaluate the importance of this cytokine we examined the inflammatory environment and spinal phenotype of 9‐month‐old human TNFα overexpressing transgenic (h
TNFα‐TG) mice. The mice evidenced increased circulating levels of interleukin‐1β (IL‐1β), IL‐2, keratinocyte chemoattractant/human growth‐regulated oncogene (KC/GRO), and monocyte chemoattractant protein‐1 (MCP‐1) along with thinning of the cortical and trabecular vertebral bone. Surprisingly, although the nucleus pulposus (NP) of these mice was intact and healthy, the caudal annulus fibrosus (AF) evidenced robust cell death and immune cell infiltration. Despite these differences, there were no obvious alterations in the collagen or aggrecan content in the NP and AF. However, there was a reduction in cartilage oligomeric matrix protein (COMP), suggesting destabilization of the AF matrix. Microarray analysis of the NP from h
TNFα‐TG mice cells revealed minimal changes in global gene expression. These findings lend support to the notion that NP tissue is isolated from systemic inflammation. In contrast, the severe AF phenotype suggests that systemic inflammation interferes with AF health, predisposing discs to herniation as opposed to directly causing NP degeneration. © 2020 American Society for Bone and Mineral Research.

Improved in vivo Experimental Screening Identifies an Anabolic Analog of 1,25 Dihydroxyvitamin D3 With Minimal Bone Resorption Activity

06-01-2020 – Laura M Calvi

Editorial

Inhibition of Osteoclastogenesis by the RNA‐Binding Protein QKI5: a Novel Approach to Protect from Bone Resorption

31-12-2019 – Benjamin Rauwel, Yannick Degboé, Katy Diallo, Souraya Sayegh, Michel Baron, Jean‐Frédéric Boyer, Arnaud Constantin, Alain Cantagrel, Jean‐Luc Davignon

Journal Article

HCMV infection inhibits osteoclastogenesis through a mechanism involving RNA binding protein QKI5. Overexpression of QKI5 protects from bone degradation and could be a new therapeutic target to limit bone erosion during osteoclast‐related diseases.
ABSTRACTIncreased osteoclastogenesis is a common feature of bone erosion, notably in osteoporosis but also in inflammatory diseases such as rheumatoid arthritis (RA) and osteoarticular infections. Human cytomegalovirus (HCMV) infection has been described to impair monocyte differentiation into macrophages and dendritic cells. However, its effect on monocyte‐derived osteoclasts is yet to be determined. We showed here that in vitro HCMV infection is associated with an inhibition of osteoclastogenesis through decreased expression of colony stimulating factor 1 receptor (CSF‐1R) and RANK in monocytes, which was mediated by an upregulation of quaking I‐5 protein (QKI‐5), a cellular RNA‐interacting protein. We found that deliberate QKI5 overexpression in the absence of HCMV infection is able to decrease CSF‐1R and RANK expression, leading to osteoclastogenesis inhibition. Finally, by using lentiviral vectors in a calvarial bone erosion mouse model, we showed that QKI5 inhibits bone degradation. This work identifies QKI5 as a strong inhibitor of bone resorption. Future research will point out whether QKI5 could be a target for bone pathologies. © 2020 American Society for Bone and Mineral Research.

Oral Iron for Prevention and Treatment of Rickets and Osteomalacia in Autosomal Dominant Hypophosphatemia

31-12-2019 – Wolfgang Högler, Klaus Kapelari

Journal Article

ABSTRACTAutosomal dominant hypophosphatemia (ADH) causes rickets, osteomalacia, and taurodontism due to heterozygous mutations in FGF23, which inhibit the inactivation (cleavage) of the encoded protein, the hormone fibroblast growth factor 23 (FGF23). Iron deficiency increases FGF23 m
RNA expression and recent evidence suggests that the recurrent, late‐onset, or waxing‐waning hypophosphatemic phenotype may be linked to synchronous variations in iron status. The fact that most adult symptomatic ADH patients are females during reproductive age supports the notion of a gene‐environmental interaction. Practically all symptomatic hypophosphatemic patients described in the recent literature were also iron deficient (with/without anemia) at presentation, when measured. Given its interaction with FGF23, correcting iron deficiency should therefore also correct FGF23 excess. Following the original report of successful phenotype reversal in an iron‐deficient ADH child using oral iron supplementation in 2015, more evidence has emerged that supports the use of the element iron to restore homoeostasis of the element phosphorus (in addition to its own). We put into perspective the recent evidence and add 14 years observational data on the original case that demonstrates the correlation of serum phosphorus and renal tubular phosphate reabsorption in mass per unit volume of glomerular filtrate (Tm
P/GFR) with serum ferritin. Presentation and relapse of ADH, 12 years apart, occurred during iron deficiency, and the onset of menstrual periods was associated with relapse. Here we propose management guidance for patients affected by ADH throughout the lifespan based on iron stores. Because ferritin correlates best with hypophosphatemia historically, and in long‐term observation of the originally treated case, it should be used as the monitoring tool and kept in the normal range. Women with ADH who are of reproductive age and other risk groups require supplementation with oral iron using WHO guidelines. Treatment of this form of FGF23 excess may not require phosphate and active vitamin D, or burosumab. © 2020 American Society for Bone and Mineral Research

Heterogeneous Spatial and Strength Adaptation of the Proximal Femur to Physical Activity: A Within‐Subject Controlled Cross‐Sectional Study

30-12-2019 – Stuart J Warden, Julio Carballido‐Gamio, Alyssa M Weatherholt, Joyce H Keyak, Chenxi Yan, Mariana E Kersh, Thomas F Lang, Robyn K Fuchs

Journal Article

ABSTRACTPhysical activity (PA) enhances proximal femur bone mass, as assessed using projectional imaging techniques. However, these techniques average data over large volumes, obscuring spatially heterogeneous adaptations. The current study used quantitative computed tomography, statistical parameter mapping, and subject‐specific finite element (FE) modeling to explore spatial adaptation of the proximal femur to PA. In particular, we were interested in adaptation occurring at the superior femoral neck and improving strength under loading from a fall onto the greater trochanter. High/long jump athletes (n = 16) and baseball pitchers (n = 16) were utilized as within‐subject controlled models as they preferentially load their take‐off leg and leg contralateral to their throwing arm, respectively. Controls (n = 15) were included but did not show any dominant‐to‐nondominant (D‐to‐ND) leg differences. Jumping athletes showed some D‐to‐ND leg differences but less than pitchers. Pitchers had 5.8% (95% confidence interval CI 3.9%–7.6%) D‐to‐ND leg differences in total hip volumetric bone mineral density (v
BMD), with increased v
BMD in the cortical compartment of the femoral neck and trochanteric cortical and trabecular compartments. Voxel‐based morphometry analyses and cortical bone mapping showed pitchers had D‐to‐ND leg differences within the regions of the primary compressive trabeculae, inferior femoral neck, and greater trochanter but not the superior femoral neck. FE modeling revealed pitchers had 4.1% (95% CI 1.4%–6.7%) D‐to‐ND leg differences in ultimate strength under single‐leg stance loading but no differences in ultimate strength to a fall onto the greater trochanter. These data indicate the asymmetrical loading associated with baseball pitching induces proximal femur adaptation in regions associated with weight bearing and muscle contractile forces and increases strength under single‐leg stance loading. However, there were no benefits evident at the superior femoral neck and no measurable improvement in ultimate strength to common injurious loading during aging (ie, fall onto the greater trochanter), raising questions as to how to better target these variables with PA. © 2019 American Society for Bone and Mineral Research.

Increased Expression of FGF‐21 Negatively Affects Bone Homeostasis in Dystrophin/Utrophin Double Knockout Mice

30-12-2019 – Hongshuai Li, Hui Sun, Baoli Qian, Wei Feng, Dwayne Carney, Jennifer Miller, MaCalus V Hogan, Ling Wang

Journal Article

ABSTRACTDuchenne muscular dystrophy (DMD) is the most common muscular dystrophy seen in children. In addition to skeletal muscle, DMD also has a significant impact on bone. The pathogenesis of bone abnormalities in DMD is still unknown. Recently, we have identified a novel bone‐regulating cytokine, fibroblast growth factor‐21 (FGF‐21), which is dramatically upregulated in skeletal muscles from DMD animal models. We hypothesize that muscle‐derived FGF‐21 negatively affects bone homeostasis in DMD. Dystrophin/utrophin double‐knockout (d
KO) mice were used in this study. We found that the levels of circulating FGF‐21 were significantly higher in d
KO mice than in age‐matched WT controls. Further tests on FGF‐21 expressing tissues revealed that both FGF‐21 m
RNA and protein expression were dramatically upregulated in dystrophic skeletal muscles, whereas FGF‐21 m
RNA expression was downregulated in liver and white adipose tissue (WAT) compared to WT controls. Neutralization of circulating FGF‐21 by i.p. injection of anti‐FGF‐21 antibody significantly alleviated progressive bone loss in weight‐bearing (vertebra, femur, and tibia) and non–weight bearing bones (parietal bones) in d
KO mice. We also found that FGF‐21 directly promoted RANKL‐induced osteoclastogenesis from bone marrow macrophages (BMMs), as well as promoted adipogenesis while concomitantly inhibiting osteogenesis of bone marrow mesenchymal stem cells (BMMSCs). Furthermore, fibroblast growth factor receptors (FGFRs) and co‐receptor β‐klotho (KLB) were expressed in bone cells (BMM‐derived osteoclasts and BMMSCs) and bone tissues. KLB knockdown by small interfering RNAs (si
RNAs) significantly inhibited the effects of FGF21 on osteoclast formation of BMMs and on adipogenic differentiation of BMMSCs, indicating that FGF‐21 may directly affect dystrophic bone via the FGFRs‐β‐klotho complex. In conclusion, this study shows that dystrophic skeletal muscles express and secrete significant levels of FGF‐21, which negatively regulates bone homeostasis and represents an important pathological factor for the development of bone abnormalities in DMD. The current study highlights the importance of muscle/bone cross‐talk via muscle‐derived factors (myokines) in the pathogenesis of bone abnormalities in DMD. © 2019 American Society for Bone and Mineral Research.

Direct Reprogramming of Mouse Fibroblasts into Functional Osteoblasts

30-12-2019 – Hui Zhu, Srilatha Swami, Pinglin Yang, Frederic Shapiro, Joy Y. Wu

Journal Article

ABSTRACTAlthough induced pluripotent stem cells hold promise as a potential source of osteoblasts for skeletal regeneration, the induction of pluripotency followed by directed differentiation into osteoblasts is time consuming and low yield. In contrast, direct lineage reprogramming without an intervening stem/progenitor cell stage would be a more efficient approach to generate osteoblasts. We screened combinations of osteogenic transcription factors and identified four factors, Runx2, Osx, Dlx5, and ATF4, that rapidly and efficiently reprogram mouse fibroblasts derived from 2.3 kb type I collagen promoter‐driven green fluorescent protein (Col2.3GFP) transgenic mice into induced osteoblast cells (i
OBs). i
OBs exhibit osteoblast morphology, form mineralized nodules, and express Col2.3GFP and gene markers of osteoblast differentiation. The global transcriptome profiles validated that i
OBs resemble primary osteoblasts. Genomewide DNA methylation analysis demonstrates that within differentially methylated loci, the methylation status of i
OBs more closely resembles primary osteoblasts than mouse fibroblasts. We further demonstrate that Col2.3GFP+ i
OBs have transcriptome profiles similar to GFP+ cells harvested from Col2.3GFP mouse bone chips. Functionally, Col2.3GFP+ i
OBs form mineralized bone structures after subcutaneous implantation in immunodeficient mice and contribute to bone healing in a tibia bone fracture model. These findings provide an approach to derive and study osteoblasts for skeletal regeneration. © 2019 American Society for Bone and Mineral Research.

Risk Factors of Severe Hypocalcemia After US‐Guided Percutaneous Microwave Ablation of the Parathyroid Gland in Patients with Secondary Hyperparathyroidism

30-12-2019 – Ying Wei, Li‐li Peng, Zhen‐long Zhao, Yan Li, Ming‐an Yu

Journal Article

ABSTRACTOur aim was to identify potential risk factors associated with severe hypocalcemia (SH) after microwave ablation (MWA) in patients with secondary hyperparathyroidism (SHPT). This retrospective cross‐sectional study enrolled 204 consecutive patients (with 387 parathyroid glands) who underwent MWA between July 2015 and May 2018. Clinical parameters, laboratory indices, and parathyroid gland characteristics were analyzed to assess risk factors associated with SH after MWA. SH was defined as serum calcium level lower than 1.875 mmol/L (7.5 mg/d
L) after MWA. Two models (I and II) for pre‐MWA and post‐MWA prediction were established, respectively. In accordance with the KDIGO guidelines, the target value for intact parathyroid hormone (i
PTH) less than 300 pg/m
L within 7 days after MWA was considered as a successful procedure. The success rate of MWA was 71.6% (146/204). The incidence of hypocalcemia and SH after MWA was 35.8% and 22.06%, respectively. The pre‐MWA prediction models I and II showed that high pre‐MWA i
PTH, a dramatic reduction in i
PTH, low pre‐MWA serum calcium, multiple ablated gland, and lack of pruritus symptoms were risk factors for developing SH. The accuracy (82.23% versus 83.25% in models I and II, respectively), sensitivity (34.88% versus 44.19%), specificity (95.45% versus 94.59%), positive predictive value (PPV) (68.18% versus 70.37%), and negative predictive value (NPV) (84% versus 85.37%) of both models were promising. The logistic regression fitting of the nomograms showed high prediction efficiency (0.845 and 0.863). High pre‐MWA i
PTH, dramatic reductions in i
PTH, low pre‐MWA serum calcium, multiple gland ablation, and no pruritus symptoms were predictors of SH. © 2019 American Society for Bone and Mineral Research.

Effect of Advanced Glycation End‐Products (AGE) Lowering Drug ALT‐711 on Biochemical, Vascular, and Bone Parameters in a Rat Model of CKD‐MBD

30-12-2019 – “Neal X Chen, Shruthi Srinivasan, Kalisha ONeill, Thomas L Nickolas, Joseph M Wallace, Matthew R Allen, Corinne E Metzger, Amy Creecy, Keith G Avin, Sharon M Moe”

Journal Article

ABSTRACTChronic kidney disease–mineral bone disorder (CKD‐MBD) is a systemic disorder that affects blood measures of bone and mineral homeostasis, vascular calcification, and bone. We hypothesized that the accumulation of advanced glycation end‐products (AGEs) in CKD may be responsible for the vascular and bone pathologies via alteration of collagen. We treated a naturally occurring model of CKD‐MBD, the Cy/+ rat, with a normal and high dose of the AGE crosslink breaker alagebrium (ALT‐711), or with calcium in the drinking water to mimic calcium phosphate binders for 10 weeks. These animals were compared to normal (NL) untreated animals. The results showed that CKD animals, compared to normal animals, had elevated blood urea nitrogen (BUN), PTH, FGF23 and phosphorus. Treatment with ALT‐711 had no effect on kidney function or PTH, but 3 mg/kg lowered FGF23 whereas calcium lowered PTH. Vascular calcification of the aorta assessed biochemically was increased in CKD animals compared to NL, and decreased by the normal, but not high dose of ALT‐711, with parallel decreases in left ventricular hypertrophy. ALT‐711 (3 mg/kg) did not alter aorta AGE content, but reduced aorta expression of receptor for advanced glycation end products (RAGE) and NADPH oxidase 2 (NOX2), suggesting effects related to decreased oxidative stress at the cellular level. The elevated total bone AGE was decreased by 3 mg/kg ALT‐711 and both bone AGE and cortical porosity were decreased by calcium treatment, but only calcium improved bone properties. In summary, treatment of CKD‐MBD with an AGE breaker ALT‐711, decreased FGF23, reduced aorta calcification, and reduced total bone AGE without improvement of bone mechanics. These results suggest little effect of ALT‐711 on collagen, but potential cellular effects. The data also highlights the need to better measure specific types of AGE proteins at the tissue level in order to fully elucidate the impact of AGEs on CKD‐MBD. © 2019 American Society for Bone and Mineral Research.

Abaloparatide at the Same Dose Has the Same Effects on Bone as PTH (1‐34) in Mice

27-12-2019 – Carole Le Henaff, Florante Ricarte, Brandon Finnie, Zhiming He, Joshua Johnson, Johanna Warshaw, Victoria Kolupaeva, Nicola C Partridge

Journal Article

ABSTRACTAbaloparatide, a novel analog of parathyroid hormone‐related protein (PTHr
P 1–34), became in 2017 the second osteoanabolic therapy for the treatment of osteoporosis. This study aims to compare the effects of PTH (1‐34), PTHr
P (1‐36), and abaloparatide on bone remodeling in male mice. Intermittent daily subcutaneous injections of 80 μg/kg/d were administered to 4‐month‐old C57Bl/6J male mice for 6 weeks. During treatment, mice were followed by DXA‐Piximus to assess changes in bone mineral density (BMD) in the whole body, femur, and tibia. At either 4 or 18 hours after the final injection, femurs were harvested for μCT analyses and histomorphometry, sera were assayed for bone turnover marker levels, and tibias were separated into cortical, trabecular, and bone marrow fractions for gene expression analyses. Our results showed that, compared with PTH (1‐34), abaloparatide resulted in a similar increase in BMD at all sites, whereas no changes were found with PTHr
P (1‐36). With both PTH (1‐34) and abaloparatide, μCT and histomorphometry analyses revealed similar increases in bone volume associated with an increased trabecular thickness, in bone formation rate as shown by P1NP serum level and in vivo double labeling, and in bone resorption as shown by CTX levels and osteoclast number. Gene expression analyses of trabecular and cortical bone showed that PTH (1‐34) and abaloparatide led to different actions in osteoblast differentiation and activity, with increased Runx2, Col1A1, Alpl, Bsp, Ocn, Sost, Rankl/Opg, and c‐fos at different time points. Abaloparatide seems to generate a faster response on osteoblastic gene expression than PTH (1‐34). Taken together, abaloparatide at the same dose is as effective as PTH (1‐34) as an osteoanabolic, with an increase in bone formation but also an increase in bone resorption in male mice. © 2019 American Society for Bone and Mineral Research.

The Polycomb Protein Bmi1 Plays a Crucial Role in the Prevention of 1,25(OH)2D Deficiency‐Induced Bone Loss

17-12-2019 – Haijian Sun, Wanxin Qiao, Min Cui, Cuicui Yang, Rong Wang, David Goltzman, Jianliang Jin, Dengshun Miao

Journal Article

ABSTRACTWe analyzed the skeletal phenotypes of heterozygous null Cyp27b1 (Cyp27b1+/−) mice and their wild‐type (WT) littermates to determine whether haploinsufficiency of Cyp27b1 accelerated bone loss, and to examine potential mechanisms of such loss. We found that serum 1,25‐dihydroxyvitamin D 1,25(OH)2D levels were significantly decreased in aging Cyp27b1+/− mice, which displayed an osteoporotic phenotype. This was accompanied by a reduction of expression of the B lymphoma Moloney murine leukemia virus (Mo‐MLV) insertion region 1 (Bmi1) at both gene and protein levels. Using chromatin immunoprecipitation (Ch
IP)‐PCR, electrophoretic mobility shift assay (EMSA) and a luciferase reporter assay, we then showed that 1,25(OH)2D3 upregulated Bmi1 expression at a transcriptional level via the vitamin D receptor (VDR). To determine whether Bmi1 overexpression in mesenchymal stem cells (MSCs) could correct bone loss induced by 1,25(OH)2D deficiency, we overexpressed Bmi1 in MSCs using Prx1‐driven Bmi1 transgenic mice (Bmi1Tg) mice. We then compared the bone phenotypes of Bmi1Tg mice on a Cyp27b1+/− background, with those of Cyp27b1+/− mice and with those of WT mice, all at 8 months of age. We found that overexpression of Bmi1 in MSCs corrected the bone phenotype of Cyp27b1+/− mice by increasing osteoblastic bone formation, reducing osteoclastic bone resorption, increasing bone volume, and increasing bone mineral density. Bmi1 overexpression in MSCs also corrected 1,25(OH)2D deficiency‐induced oxidative stress and DNA damage, and cellular senescence of Cyp27b1+/− mice by reducing levels of reactive oxygen species (ROS), elevating serum total superoxide dismutase levels, reducing the percentage of γH2A.
X, p16, IL‐1β, and TNF‐α–positive cells and decreasing γH2A.
X, p16, p19, p53, p21, IL‐1β, and IL‐6 expression levels. Furthermore, 1,25(OH)2D stimulated the osteogenic differentiation of MSCs, both ex vivo and in vitro, from WT mice but not from Bmi1−/− mice and 1,25(OH)2D administration in vivo increased osteoblastic bone formation in WT, but not in Bmi1 −/− mice. Our results indicate that Bmi1, a key downstream target of 1,25(OH)2D, plays a crucial role in preventing bone loss induced by 1,25(OH)2D deficiency. © 2019 American Society for Bone and Mineral Research.

The Accuracy of Prevalent Vertebral Fracture Detection in Children Using Targeted Case‐Finding Approaches

17-12-2019 – Jinhui Ma, Kerry Siminoski, Peiyao Wang, Nathalie Alos, Elizabeth A Cummings, Janusz Feber, Jacqueline Halton, Josephine Ho, Kristin Houghton, Bianca Lang, Paivi M Miettunen, Rosie Scuccimarri, Jacob L Jaremko, Khaldoun Koujok, Brian Lentle, Mary Ann Matzinger, Nazih Shenouda, Frank Rauch, Leanne M Ward, and the Canadian Steroid‐Induced Osteoporosis in the Pediatric Population (STOPP) Consortium

Journal Article

ABSTRACTDue to concerns about cumulative radiation exposure in the pediatric population, it is not standard practice to perform spine radiographs in most conditions that predispose to vertebral fracture (VF). In this study we examined the accuracy of two clinical predictors, back pain and lumbar spine bone mineral density (LS BMD), to derive four case‐finding paradigms for detection of prevalent VF (PVF). Subjects were 400 children at risk for PVF (leukemia 186, rheumatic disorders 135, nephrotic syndrome 79). Back pain was assessed by patient report, LS BMD was measured by dual‐energy X‐ray absorptiometry, and PVF were quantified on spine radiographs using the modified Genant semiquantitative method. Forty‐four patients (11.0%) had PVF. Logistic regression analysis between LS BMD and PVF produced an odds ratio (OR) of 1.9 (95% confidence interval CI, 1.5 to 2.5) per reduction in Z‐score unit, an area under the receiver operating characteristic curve of 0.70 (95% CI, 0.60 to 0.79), and an optimal BMD Z‐score cutoff of −1.6. Case identification using either low BMD alone (Z‐score < −1.6) or back pain alone gave similar results for sensitivity (55%, 52%, respectively), specificity (78%, 81%, respectively), positive predictive value (PPV; 24%, 25%, respectively), and negative predictive value (NPV; 93%, 93%, respectively). The paradigm using low BMD plus back pain produced lower sensitivity (32%), higher specificity (96%), higher PPV (47%), and similar NPV (92%). The approach using low BMD or back pain had the highest sensitivity (75%), lowest specificity (64%), lowest PPV (20%), and highest NPV (95%). All paradigms had increased sensitivities for higher fracture grades. Our results show that BMD and back pain history can be used to identify children with the highest risk of PVF so that radiography can be used judiciously. The specific paradigm to be applied will depend on the expected PVF rate and the clinical approach to the use of radiography. © 2019 American Society for Bone and Mineral Research.

Now That You Can Get What You Want, Can You Keep What You Need?

17-12-2019 – Dennis M. Black, Deborah E. Sellmeyer

Editorial

Acetylcholinesterase Inhibitors Are Associated with Reduced Fracture Risk among Older Veterans with Dementia

12-12-2019 – Abayomi N Ogunwale, Cathleen S Colon‐Emeric, Richard Sloane, Robert A Adler, Kenneth W Lyles, Richard H Lee

Journal Article

ABSTRACTAcetylcholinesterase inhibitors (ACh
EIs) have been noted to increase bone density and quality in mice. Human studies are limited but suggest an association with improved bone healing after hip fracture. We examined the relationship between ACh
EI use and fracture risk in a national cohort of 360,015 male veterans aged 65 to 99 years with dementia but without prior fracture using Veterans Affairs (VA) hospital, Medicare, and pharmacy records from 2000 to 2010. Diagnosis of dementia, any clinical fracture (excluding facial and digital), comorbidities, and medications were identified using ICD‐9 and drug class codes. Cox proportional hazard models considering ACh
EI use as a time‐varying covariate and adjusting for fall and fracture risk factors compared the time‐to‐fracture in ACh
EI users versus non‐ACh
EI users. Potential confounders included demographics (age, race, body mass index), comorbidities associated with fracture or falls (diabetes, lung disease, stroke, Parkinsons, seizures, etc.) and medications associated with fracture or falls (bisphosphonates, glucocorticoids, androgen deprivation therapy ADT, proton pump inhibitors PPIs, selective serotonin receptor inhibitors SSRIs, etc.). Competing mortality risk was considered using the methods of Fine and Gray. To account for persistent effects on bone density or quality that might confer protection after stopping the medication, we completed a secondary analysis using the medication possession ratio (MPR) as a continuous variable in logistic regression models and also compared MPR increments of 10% to minimal/no use (MPR 0 to <0.10). Among older veterans with diagnosis of dementia, 20.1% suffered a fracture over an average of 4.6 years of follow‐up. Overall, 42.3% of the cohort were prescribed ACh
EIs during the study period. The hazard of any fracture among ACh
EI users compared with those on other/no dementia medications was significantly lower in fully adjusted models (hazard ratio HR = 0.81; 95% confidence interval CI 0.75–0.88). After considering competing mortality risk, fracture risk remained 18% lower in veterans using ACh
EIs (HR = 0.82; 95% CI 0.76–0.89). © 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.

Lactate Efflux From Intervertebral Disc Cells Is Required for Maintenance of Spine Health

12-12-2019 – Elizabeth S Silagi, Emanuel J Novais, Sara Bisetto, Aristeidis G Telonis, Joseph Snuggs, Christine L Le Maitre, Yunping Qiu, Irwin J Kurland, Irving M Shapiro, Nancy J Philp, Makarand V Risbud

Journal Article

ABSTRACTMaintenance of glycolytic metabolism is postulated to be required for health of the spinal column. In the hypoxic tissues of the intervertebral disc and glycolytic cells of vertebral bone, glucose is metabolized into pyruvate for ATP generation and reduced to lactate to sustain redox balance. The rise in intracellular H+/lactate concentrations are balanced by plasma‐membrane monocarboxylate transporters (MCTs). Using MCT4 null mice and human tissue samples, complemented with genetic and metabolic approaches, we determine that H+/lactate efflux is critical for maintenance of disc and vertebral bone health. Mechanistically, MCT4 maintains glycolytic and tricarboxylic acid (TCA) cycle flux and intracellular p
H homeostasis in the nucleus pulposus compartment of the disc, where hypoxia‐inducible factor 1α (HIF‐1α) directly activates an intronic enhancer in SLC16A3. Ultimately, our results provide support for research into lactate as a diagnostic biomarker for chronic, painful, disc degeneration. © 2019 American Society for Bone and Mineral Research.

Deterioration of Cortical and Trabecular Microstructure Identifies Women With Osteopenia or Normal Bone Mineral Density at Imminent and Long‐Term Risk for Fragility Fracture: A Prospective Study

10-12-2019 – Roland Chapurlat, Minh Bui, Elisabeth Sornay‐Rendu, Roger Zebaze, Pierre D. Delmas, Danny Liew, Eric Lespessailles, Ego Seeman

Journal Article

ABSTRACTMore than 70% of women sustaining fractures have osteopenia or “normal” bone mineral density (BMD). These women remain undetected using the BMD threshold of −2.5 SD for osteoporosis. As microstructural deterioration increases bone fragility disproportionate to the bone loss producing osteopenia/normal BMD, we hypothesized that the structural fragility score (SFS) of ≥70 units, a measure capturing severe cortical and trabecular deterioration, will identify these women. Distal radial images were acquired using high‐resolution peripheral quantitative tomography in postmenopausal French women, mean age 67 years (range 42–96 years); 1539 women were followed for 4 years (QUALYOR) and 561 women followed for 8 years (OFELY). Women with osteopenia or normal BMD accounted for ~80% of fractures. Women ≥70 years, 29.2% of the cohort, accounted for 39.2% to 61.5% of fractures depending on follow‐up duration. Women having fractures had a higher SFS, lower BMD, and a higher fracture risk assessment score (FRAX) than women remaining fracture‐free. In each BMD category (osteoporosis, osteopenia, normal BMD), fracture incidence was two to three times higher in women with SFS ≥70 than <70. In multivariable analyses, associations with fractures remained for BMD and SFS, not FRAX. BMD was no longer, or weakly, associated with fractures after accounting for SFS, whereas SFS remained associated with fracture after accounting for BMD. SFS detected two‐to threefold more women having fractures than BMD or FRAX. SFS in women with osteopenia/normal BMD conferred an odds ratio for fracture of 2.69 to 5.19 for women of any age and 4.98 to 12.2 for women ≥70 years. Receiver‐operator curve (ROC) analyses showed a significant area under the curve (AUC) for SFS, but not BMD or FRAX for the women ≥70 years of age. Targeting women aged ≥70 years with osteopenia indicated that treating 25% using SFS to allocate treatment conferred a cost‐effectiveness ratio < USD $21,000/QALY saved. Quantifying microstructural deterioration complements BMD by identifying women without osteoporosis at imminent and longer‐term fracture risk. © 2019 American Society for Bone and Mineral Research.

Sclerostin Antibody Treatment Increases Bone Mass and Normalizes Circulating Phosphate Levels in Growing Hyp Mice

10-12-2019 – Kelsey A Carpenter, Ryan D Ross

Journal Article

ABSTRACTX‐linked hypophosphatemia (XLH), caused by a loss‐of‐function mutation in the phosphate regulating gene with homology to endopeptidase located on the X chromosome (PHEX), is the most common form of vitamin D‐resistant rickets. Loss of functional PHEX results in elevated fibroblast growth factor 23 (FGF23) levels, impaired phosphate reabsorption, and inhibited skeletal mineralization. Sclerostin, a protein produced primarily in osteocytes, suppresses bone formation by antagonizing Wnt signaling and is reported to be elevated in XLH patients. This study used the Hyp mouse model to investigate sclerostins role in the pathophysiology of XLH by evaluating the use of a monoclonal antibody to sclerostin in a mouse model of XLH, the Hyp mouse. Male and female wild‐type and Hyp littermates were injected with 25 mg/kg of vehicle or sclerostin antibody (Scl‐Ab) twice weekly, beginning at 4 weeks of age and euthanized at 8 weeks of age. Scl‐Ab treatment increased serum phosphate levels and suppressed circulating levels of intact FGF23 in treated wild‐type and Hyp mice of both sexes. Cortical area, trabecular bone volume fraction (BV/TV), metaphyseal apparent density, and the peak load increased with Scl‐Ab treatment in both sexes. This short‐term treatment study suggests that Scl‐Ab treatment can effectively improve some of the pathologies associated with XLH, including normalization of phosphate, and that sclerostin may play a role in regulating FGF23 and phosphate metabolism in XLH. © 2019 American Society for Bone and Mineral Research.

Temporal Trends and Factors Associated with Bisphosphonate Discontinuation and Restart

10-12-2019 – Giovanni Adami, Ayesha Jaleel, Jeffrey R Curtis, Elizabeth Delzell, Rui Chen, Huifeng Yun, Shanette Daigle, Tarun Arora, Maria I Danila, Nicole C Wright, Suzanne M Cadarette, Amy Mudano, Jeffrey Foster, Kenneth G Saag

Journal Article

ABSTRACTAdverse events related to long‐term use of bisphosphonates have raised interest in temporary drug discontinuation. Trends in bisphosphonate discontinuation and restart, as well factors associated with these decisions, are not fully understood at a population level. We investigated temporal trends of bisphosphonate discontinuation from 2010 to 2015 and identified factors associated with discontinuation and restart of osteoporosis therapy. Our cohort consisted of long‐term bisphosphonate users identified from 2010 to 2015 Medicare data. We defined discontinuation as ≥12 months without bisphosphonate prescription claims. We used conditional logistic regression to compare factors associated with alendronate discontinuation or osteoporosis therapy restart in the 120‐day period preceding discontinuation or restart referent to the 120‐day preceding control periods. Among 73,800 long‐term bisphosphonate users, 59,251 (80.3%) used alendronate, 6806 (9.2%) risedronate, and 7743 (10.5%) zoledronic acid, exclusively. Overall, 26,281 (35.6%) discontinued bisphosphonates for at least 12 months. Discontinuation of bisphosphonates increased from 1.7% in 2010, reaching a peak of 14% in 2012 with levels plateauing through 2015. The factors most strongly associated with discontinuation of alendronate were: benzodiazepine prescription (adjusted odds ratio a
OR = 2.5; 95% confidence interval CI 2.1, 3.0), having a dual‐energy X‐ray absorptiometry (DXA) scan (a
OR = 1.8; 95% CI 1.7, 2.0), and skilled nursing facility care utilization (a
OR = 1.8; 95% CI 1.6, 2.1). The factors most strongly associated with restart of osteoporosis therapy were: having a DXA scan (a
OR = 9.9; 95% CI 7.7, 12.6), sustaining a fragility fracture (a
OR = 2.8; 95% CI 1.8, 4.5), and an osteoporosis or osteopenia diagnosis (a
OR = 2.5; 95% CI 2.0, 3.1). Our national evaluation of bisphosphonate discontinuation showed that an increasing proportion of patients on long‐term bisphosphonate therapy discontinue medications. The factors associated with discontinuation of alendronate were primarily related to worsening of overall health status, whereas traditional factors associated with worsening bone health were associated with restarting osteoporosis medication. © 2019 American Society for Bone and Mineral Research.

Clinical in Vivo Assessment of Bone Microarchitecture With CT Scanners: An Enduring Challenge

10-12-2019 – Doris My‐Lan Tran, Nicolas Vilayphiou, Bruno Koller

Letter

Human Heterozygous ENPP1 Deficiency Is Associated With Early Onset Osteoporosis, a Phenotype Recapitulated in a Mouse Model of Enpp1 Deficiency

05-12-2019 – Ralf Oheim, Kristin Zimmerman, Nathan D Maulding, Julian Stürznickel, Simon von Kroge, Dillon Kavanagh, Paul R Stabach, Uwe Kornak, Steven M Tommasini, Mark C Horowitz, Michael Amling, David Thompson, Thorsten Schinke, Björn Busse, Thomas O. Carpenter, Demetrios T Braddock

Journal Article

ABSTRACTBiallelic ENPP1 deficiency in humans induces generalized arterial calcification of infancy (GACI) and/or autosomal recessive hypophosphatemic rickets type 2 (ARHR2). The latter is characterized by markedly increased circulating FGF23 levels and renal phosphate wasting, but aberrant skeletal manifestations associated with heterozygous ENPP1 deficiency are unknown. Here, we report three adult men with early onset osteoporosis who presented with fractures in the thoracic spine and/or left radius, mildly elevated circulating FGF23, and hypophosphatemia. Total hip bone mineral density scans demonstrated osteoporosis (Z‐score < −2.5) and HRp
QCT demonstrated microarchitectural defects in trabecular and cortical bone. Next‐generation sequencing revealed heterozygous loss‐of‐function mutations in ENPP1 previously observed as biallelic mutations in infants with GACI. In addition, we present bone mass and structure data as well as plasma pyrophosphate (PPi) data of two siblings suffering from ARHR2 in comparison to their heterozygous and wild‐type family members indicative of an ENPP1 gene dose effect. The skeletal phenotype in murine Enpp1 deficiency yielded nearly identical findings. Ten‐week‐old male Enpp1 asj/asj mice exhibited mild elevations in plasma FGF23 and hypophosphatemia, and micro‐CT analysis revealed microarchitectural defects in trabecular and cortical bone of similar magnitude to HRp
QCT defects observed in humans. Histomorphometry revealed mild osteomalacia and osteopenia at both 10 and 23 weeks. The biomechanical relevance of these findings was demonstrated by increased bone fragility and ductility in Enpp1 asj/asj mice. In summary, ENPP1 exerts a gene dose effect such that humans with heterozygous ENPP1 deficiency exhibit intermediate levels of plasma analytes associated with bone mineralization disturbance resulting in early onset osteoporosis. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Reply Letter to the Editor: Clinical in Vivo Assessment of Bone Microarchitecture With CT Scanners: An Enduring Challenge

05-12-2019 – Karen Mys, Peter Varga, Boyko Gueorguiev, Haniyeh Hemmatian, Filip Stockmans, G Harry Lenthe

Letter

Smoking and Alcohol Intake but Not Muscle Strength in Young Men Increase Fracture Risk at Middle Age: A Cohort Study Linked to the Swedish National Patient Registry

04-12-2019 – Daniel Prieto‐Alhambra, Aleksandra Turkiewicz, Carlen Reyes, Simon Timpka, Björn Rosengren, Martin Englund

Journal Article

ABSTRACTWe aimed to determine the relationship between handgrip strength, smoking, and alcohol consumption in young men and fracture risk at middle age. Thus, we carried out a cohort study including young men undergoing conscription examination in Sweden from September 1969 to May 1970 at a typical age of 18 years. Data on muscle strength, height, weight, and lifestyle factors were linked to the National Patient Register 1987–2010. Handgrip strength was considered the main exposure and smoking and alcohol consumption as secondary exposures. Outcomes were all fractures (except face, skull, digits), major osteoporotic fractures (thoracic/lumbar spine, proximal humerus, distal forearm or hip), and major traumatic fractures (shaft of humerus, forearm, femur, or lower leg) based on ICD‐9 and ‐10 codes. We used Cox regression models to estimate hazard ratios (HR) and 95% confidence intervals (CI) according to handgrip strength as a continuous variable (per 1 SD), after adjustment for weight, height, parental education, smoking, and alcohol consumption. A total of 40,112 men were included, contributing 892,572 person‐years. Overall, 3974 men fractured in middle age with the incidence rate (95% CI) of 44.5 (43.2–45.9) per 1000 person‐years. The corresponding rates were12.2 and 5.6 per 1000 person‐years for major osteoporotic and traumatic fractures, respectively. Handgrip strength‐adjusted HR (95% CI) was 1.01 (0.98–1.05), 0.94 (0.88–1.00), and 0.98 (0.88–1.08) per SD for all, major osteoporotic, and major traumatic fractures, respectively. Adjusted HR (95% CI) for smokers (>21 cigarettes/d) was 1.44 (1.21, 1.71) for all fractures, while the association between alcohol consumption and hazards of fracture was J‐shaped. Therefore, young adult handgrip strength was not associated with fracture risk in middle‐age men, although smoking and high alcohol consumption did confer an increased risk. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

“An Inverse Agonist Ligand of the PTH Receptor Partially Rescues Skeletal Defects in a Mouse Model of Jansens Metaphyseal Chondrodysplasia”

04-12-2019 – Hiroshi Noda, Jun Guo, Ashok Khatri, Thomas Dean, Monica Reyes, Michael Armanini, Daniel J Brooks, Janaina S Martins, Ernestina Schipani, Mary L Bouxsein, Marie B Demay, John T Potts, Harald Jüppner, Thomas J Gardella

Journal Article

ABSTRACTJansens metaphyseal chondrodysplasia (JMC) is a rare disease of bone and mineral ion physiology that is caused by activating mutations in PTHR1. Ligand‐independent signaling by the mutant receptors in cells of bone and kidney results in abnormal skeletal growth, excessive bone turnover, and chronic hypercalcemia and hyperphosphaturia. Clinical features further include short stature, limb deformities, nephrocalcinosis, and progressive losses in kidney function. There is no effective treatment option available for JMC. In previous cell‐based assays, we found that certain N‐terminally truncated PTH and PTHr
P antagonist peptides function as inverse agonists and thus can reduce the high rates of basal cAMP signaling exhibited by the mutant PTHR1s of JMC in vitro. Here we explored whether one such inverse agonist ligand, Leu11,d
Trp12,Trp23,Tyr36‐PTHr
P(7‐36)NH2 (IA), can be effective in vivo and thus ameliorate the skeletal abnormalities that occur in transgenic mice expressing the PTHR1‐H223R allele of JMC in osteoblastic cells via the collagen‐1α1 promoter (C1HR mice). We observed that after 2 weeks of twice‐daily injection and relative to vehicle controls, the IA analog resulted in significant improvements in key skeletal parameters that characterize the C1HR mice, because it reduced the excess trabecular bone mass, bone marrow fibrosis, and levels of bone turnover markers in blood and urine. The overall findings provide proof‐of‐concept support for the notion that inverse agonist ligands targeted to the mutant PTHR1 variants of JMC can have efficacy in vivo. Further studies of such PTHR1 ligand analogs could help open paths toward the first treatment option for this debilitating skeletal disorder. © 2019 American Society for Bone and Mineral Research.

Back Pain‐Inducing Test, a Novel and Sensitive Screening Test for Painful Osteoporotic Vertebral Fractures: A Prospective Clinical Study

04-12-2019 – Huaijian Jin, Xiaoyuan Ma, Yaoyao Liu, Xiang Yin, Jun Zhu, Zhong Wang, Weili Fan, Yufei Jin, Jungang Pu, Jianhua Zhao, Mingyong Liu, Peng Liu

Journal Article

ABSTRACTTo detect painful vertebral fractures (VFs) in back pain populations at risk of osteoporosis, we designed a physical examination test (the Back Pain‐Inducing Test BPIT) that included three movements: lying supine, rolling over, and sitting up. If back pain is induced during any of these movements, the result is defined as positive, thereby establishing a presumptive diagnosis of painful VFs. Pain severity is quantified using a self‐reported numerical rating scale (NRS). The presence or absence of painful VFs is verified by whole‐spine magnetic resonance imaging (MRI), the gold standard for final diagnosis. According to the standards for reporting diagnostic accuracy, a real‐world, prospective, and observational study was performed on 510 back pain patients (enrolled from a single institute) at risk of osteoporosis. The sensitivity, specificity, and accuracy of the BPIT for identifying painful VFs were 99.1% (95% CI, 97.5% to 99.8%), 67.9% (95% CI, 60.4% to 74.5%), and 89.0%, respectively. The positive and negative predictive values were 86.6% (95% CI, 82.9% to 89.6%) and 97.4% (95% CI, 92.6% to 99.3%), respectively. Cutoff NRS scores for lying supine, rolling over, and sitting up were 3, 0, and 2, respectively. The corresponding area under the receiver operating characteristic curves (AUROCs) of each movement was 0.898 (95% CI, 0.868 to 0.922), 0.884 (95% CI, 0.854 to 0.911), and 0.910 (95% CI, 0.882 to 0.933), respectively. Although the high prevalence of VFs in the enrolled cohort partially limits the external validity of the predictive value in the general population, we conclude that the BPIT is potentially effective for detecting painful VFs in back pain populations at risk of osteoporosis. This test may be used as a stratification tool in decision‐making on subsequent imaging procedures: a negative BPIT rules out painful VFs and indicates that an MRI should be spared, whereas a positive BPIT means that an MRI is necessary and is likely to identify painful VFs. © 2019 American Society for Bone and Mineral Research.

Effect of Aerobic or Resistance Exercise, or Both, on Bone Mineral Density and Bone Metabolism in Obese Older Adults While Dieting: A Randomized Controlled Trial

04-12-2019 – Reina Armamento‐Villareal, Lina Aguirre, Debra L Waters, Nicola Napoli, Clifford Qualls, Dennis T Villareal

Journal Article

ABSTRACTWeight loss therapy of older adults with obesity is limited by weight loss–induced decrease in bone mineral density (BMD), which could exacerbate ongoing age‐related bone loss and increase the risk for fractures. Therefore, it is recommended that weight loss therapy of older adults with obesity should include an intervention such as regular exercise to reduce the concomitant bone loss. However, the most appropriate exercise types to combine with weight loss therapy in this older population is unknown. In a randomized controlled trial, we performed a head‐to‐head comparison of aerobic or resistance exercise, or both, during matched ~10% weight loss in 160 older adults with obesity. We measured changes in BMD (total hip, femoral neck, trochanter, intertrochanter, one‐third radius, lumbar spine) and bone markers. Changes between groups were analyzed using mixed‐model repeated measures analyses of variance. After 6 months of intensive lifestyle interventions, BMD decreased less in the resistance group (−0.006 g/cm2 −0.7%) and combination group (−0.012 g/cm2 −1.1%) than in the aerobic group (−0.027 g/cm2 −2.6%) (p = 0.001 for between‐group comparisons). Serum C‐telopeptide, procollagen type 1 N‐propeptide, and osteocalcin concentrations increased more in the aerobic group (33%, 16%, and 16%, respectively) than in the resistance group (7%, 2%, and 0%, respectively) and combination group (11%, 2%, and 5%, respectively) (p = 0.004 to 0.048 for between‐group comparisons). Multiple regression analyses revealed that the decline in whole body mass and serum leptin were the independent predictors of the decline in hip BMD (multiple R = 0.45 p < .001). These findings indicate that compared with aerobic exercise, resistance and combined aerobic and resistance exercise are associated with less weight loss–induced decrease in hip BMD and less weight loss–induced increase in bone turnover. Therefore, both resistance and combined aerobic and resistance exercise can be recommended to protect against bone loss during weight loss therapy of older adults with obesity. (LITOE Clinical
Trials.gov number NCT01065636.) © 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.

Articular Cartilage Degradation and Aberrant Subchondral Bone Remodeling in Patients with Osteoarthritis and Osteoporosis

22-11-2019 – Linyang Chu, Xuqiang Liu, Zihao He, Xuequan Han, Mengning Yan, Xinhua Qu, Xiaofeng Li, Zhifeng Yu

Journal Article

ABSTRACTOsteoarthritis (OA) and osteoporosis (OP) are two skeletal disorders associated with joint structures. Occasionally, OA and OP occur in the same patient. However, the effect of OP changes on OA progression in patients with osteoporotic OA (OP‐OA) has not been reported, especially the potential association between subchondral bone and articular cartilage. Thus we investigated the alterations in the microstructure, biomechanical properties, and remodeling of subchondral bone as well as their association with cartilage damage in the hip joint of patients with OP‐OA. Thirty‐nine femoral head specimens were obtained from patients who underwent total hip arthroplasty (OA group, n = 19; OP‐OA group, n = 20), and healthy specimens from cadaver donors were used (control group, n = 10). The microstructure and biomechanical properties of subchondral bone were evaluated by micro–computed tomography and micro–finite‐element analysis. Histology, histomorphometric measurements, and immunohistochemistry were used to assess subchondral bone remodeling and cartilage damage. Linear regression analysis was performed to elucidate the relationship between subchondral bone and articular cartilage. In the subchondral bone of the OP‐OA group, compared with that of the OA group, aberrant bone remodeling leads to an inferior microstructure and worsening biomechanical properties, potentially affecting transmission of loading stress from the cartilage to the subchondral bone, and then resulting in accelerated OA progression in patients with OP‐OA. The results indicate that changes in subchondral bone could affect OA development and the improvement in subchondral bone with bone‐metabolism agents may help mitigate OA progression when OP and OA coexist in the same patients. © 2019 American Society for Bone and Mineral Research.

Circulating MicroRNA‐19b Identified From Osteoporotic Vertebral Compression Fracture Patients Increases Bone Formation

22-11-2019 – 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. © 2019 American Society for Bone and Mineral Research.

IFT80 Is Required for Fracture Healing Through Controlling the Regulation of TGF‐β Signaling in Chondrocyte Differentiation and Function

22-11-2019 – Min Liu, Mohammed Alharbi, Dana Graves, Shuying Yang

Journal Article

ABSTRACTPrimary cilia are essential cellular organelles that are anchored at the cell surface membrane to sense and transduce signaling. Intraflagellar transport (IFT) proteins are indispensable for cilia formation and function. Although major advances in understanding the roles of these proteins in bone development have been made, the mechanisms by which IFT proteins regulate bone repair have not been identified. We investigated the role of the IFT80 protein in chondrocytes during fracture healing by creating femoral fractures in mice with conditional deletion of IFT80 in chondrocytes utilizing tamoxifen inducible Col2α1‐Cre
ER mice. Col2α1cre
IFT80f/f mice had smaller fracture calluses than IFT80f/f (control) mice. The max‐width and max‐callus area were 31% and 48% smaller than those of the control mice, respectively. Col2α1cre
IFT80f/f mice formed low‐density/porous woven bony tissue with significantly lower ratio of bone volume, Trabecular (Tb) number and Tb thickness, and greater Tb spacing compared to control mice. IFT80 deletion significantly downregulated the expression of angiogenesis markers‐VEGF, PDGF and angiopoietin and inhibited fracture callus vascularization. Mechanistically, loss of IFT80 in chondrocytes resulted in a decrease in cilia formation and chondrocyte proliferation rate in fracture callus compared to the control mice. Meanwhile, IFT80 deletion downregulated the TGF‐β signaling pathway by inhibiting the expression of TGF‐βI, TGF‐βR, and phosphorylation of Smad2/3 in the fracture callus. In primary chondrocyte cultures in vitro, IFT80 deletion dramatically reduced chondrocyte proliferation, cilia assembly, and chondrogenic gene expression and differentiation. Collectively, our findings demonstrate that IFT80 and primary cilia play an essential role in fracture healing, likely through controlling chondrocyte proliferation and differentiation, and the TGF‐β signaling pathway. © 2019 American Society for Bone and Mineral Research.

Bone Marrow and Muscle Fat Infiltration Are Correlated among Postmenopausal Women With Osteoporosis: The AMBERS Cohort Study

20-11-2019 – Andy K Wong, Abinaa Chandrakumar, Rachel Whyte, Shannon Reitsma, Hana Gillick, Anthony Pokhoy, Alexandra Papaioannou, Jonathan D Adachi

Journal Article

ABSTRACTBone and muscle have shown to interact, but little is known about fat within bone and muscle. Clinical studies have isolated fat within bone and muscle using MRI. In this cross‐sectional study, we hypothesized that bone marrow adiposity and muscle adiposity are related and that this relationship is associated with osteoporosis. Postmenopausal women aged 60 to 85 years were recruited as part of the Appendicular Muscle and Bone Extension Research Study (AMBERS). Participants completed dual‐energy X‐ray absorptiometry (DXA) of the hip and spine to diagnose osteoporosis. Muscle adiposity was measured with MRI at the 66% site of the leg. Fat segmentation was achieved using a semi‐automated iterative threshold‐optimizing algorithm (error < 5%). Peripheral quantitative computed tomography measured marrow density of the 4% distal tibia (surrogate for marrow fat) by threshold‐based, edge‐detection segmentations and by examining residuals from trabecular bone density regressed on trabecular tissue mineral density. Muscle adiposity from MRI was regressed on marrow density using linear regression. Models were further examined with an interaction with osteoporosis status. Among 312 women (aged 75.4 ± 5.9 years, body mass index BMI 29.5 ± 5.7 kg/m2), a larger amount of muscle fat was associated with lower marrow density at the 66% mid‐tibia (B = 84.08 27.56, p = 0.002) and at the 4% distal tibia (B = 129.17 55.96, p = 0.022) after accounting for age, height, weight, average daily energy expenditure, hypertension, and diabetes. Interactions of this relationship with osteoporosis status were also significant. Upon probing these interactions, the relationships were significant only in women with osteoporosis but not in those without osteoporosis. Fat from bone marrow and muscle may be related to one another through the same phenomenon, which is likely also responsible for osteoporosis, but independent of hypertension and diabetes. More research should focus on the potential abnormalities in muscle and bone fat metabolism and mesenchymal cell commitment to fat within patients with osteoporosis. © 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

20-11-2019 – Hallgerdur Lind Kristjansdottir, Catharina Lewerin, Ulf H. Lerner, Hans Herlitz, Peter Johansson, Helena Johansson, Magnus Karlsson, Mattias Lorentzon, Claes Ohlsson, Östen Ljunggren, Dan Mellström

Journal Article

ABSTRACTPreclinical studies on the role of erythropoietin (EPO) in bone metabolism are contradictory. Regeneration models indicate an anabolic effect on bone healing, whereas 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) affects 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 (aged 69 to 81 years), participating in the Gothenburg part of the population‐based Osteoporotic Fractures in Men (Mr
OS) study, Mr
OS Sweden. The mean ± SD EPO was 11.5 ± 9.0 IU/L. Results were stratified by e
GFR 60 m
L/min. For men with e
GFR ≥60 m
L/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, body mass index (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 (hazard ratio HR = 1.43 per tertile EPO, 95% confidence interval 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 m
L/min, no association was found between EPO and BMD or fracture risk. We here demonstrate that high levels of EPO are associated with increased fracture risk and increased BMD in elderly men with normal renal function. © 2019 American Society for Bone and Mineral Research.

HR‐pQCT Measures of Bone Microarchitecture Predict Fracture: Systematic Review and Meta‐Analysis

19-11-2019 – Nicholas Mikolajewicz, Nick Bishop, Andrew J Burghardt, Lars Folkestad, Anthony Hall, Kenneth M Kozloff, Pauline T Lukey, Michael Molloy‐Bland, Suzanne N Morin, Amaka C Offiah, Jay Shapiro, Bert Rietbergen, Kim Wager, Bettina M Willie, Svetlana V Komarova, Francis H Glorieux

Journal Article

ABSTRACTHigh‐resolution peripheral quantitative computed tomography (HR‐p
QCT) is a noninvasive imaging modality for assessing volumetric bone mineral density (v
BMD) and microarchitecture of cancellous and cortical bone. The objective was to (1) assess fracture‐associated differences in HR‐p
QCT bone parameters; and (2) to determine if HR‐p
QCT is sufficiently precise to reliably detect these differences in individuals. We systematically identified 40 studies that used HR‐p
QCT (39/40 used Xtreme
CT scanners) to assess 1291 to 3253 and 3389 to 10,687 individuals with and without fractures, respectively, ranging in age from 10.9 to 84.7 years with no comorbid conditions. Parameters describing radial and tibial bone density, microarchitecture, and strength were extracted and percentage differences between fracture and control subjects were estimated using a random effects meta‐analysis. An additional meta‐analysis of short‐term in vivo reproducibility of bone parameters assessed by Xtreme
CT was conducted to determine whether fracture‐associated differences exceeded the least significant change (LSC) required to discern measured differences from precision error. Radial and tibial HR‐p
QCT parameters, including failure load, were significantly altered in fracture subjects, with differences ranging from −2.6% (95% confidence interval CI −3.4 to −1.9) in radial cortical v
BMD to −12.6% (95% CI −15.0 to −10.3) in radial trabecular v
BMD. Fracture‐associated differences reported by prospective studies were consistent with those from retrospective studies, indicating that HR‐p
QCT can predict incident fracture. Assessment of study quality, heterogeneity, and publication biases verified the validity of these findings. Finally, we demonstrated that fracture‐associated deficits in total and trabecular v
BMD and certain tibial cortical parameters can be reliably discerned from HR‐p
QCT‐related precision error and can be used to detect fracture‐associated differences in individual patients. Although differences in other HR‐p
QCT measures, including failure load, were significantly associated with fracture, improved reproducibility is needed to ensure reliable individual cross‐sectional screening and longitudinal monitoring. In conclusion, our study supports the use of HR‐p
QCT in clinical fracture prediction. © 2019 American Society for Bone and Mineral Research.

Targeting Bortezomib to Bone Increases Its Bone Anabolic Activity and Reduces Systemic Adverse Effects in Mice

19-11-2019 – 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 antiresorptive activity. We report that BP‐Btz inhibited osteoclast formation and bone resorption and stimulated osteoblast differentiation in vitro similar to Btz. In vivo, BP‐Btz increased bone volume more effectively than Btz in three 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 it 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. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

Nonremission and Recurrent Tumor‐Induced Osteomalacia: A Retrospective Study

15-11-2019 – Xiang Li, Yan Jiang, Li Huo, Huanwen Wu, Yong Liu, Jin Jin, Wei Yu, Wei Lv, Lian Zhou, Yu Xia, Ou Wang, Mei Li, Xiaoping Xing, Yue Chi, Ruizhi Jiajue, Lijia Cui, Xunwu Meng, Weibo Xia

Journal Article

ABSTRACTTumor‐induced osteomalacia (TIO) is a rare paraneoplastic syndrome. It is curable by excision of the causative tumor. However, a few cases may persist or relapse after tumor resection. We aimed to investigate the rate of these events and related factors. We retrospectively studied TIO patients treated with surgery in a tertiary hospital. TIO was established based on a pathologic examination or the reversion of hypophosphatemia. Refractory TIO patients consisted of those with nonremission or recurrent hypophosphatemia after surgery. A total of 230 patients were confirmed as having TIO. After primary surgery, 26 (11.3%) cases persisted, and 16 (7.0%) cases recurred. The overall refractory rate was 18.3%. The median time of recurrence was 33 months. Compared with patients in the recovery group, patients in the refractory group were more likely to be female (59.5% versus 41.0%, p = .029) and have a lower serum phosphate level (0.44 ± 0.13 versus 0.50 ± 0.11 mmol/L, p = .002). The refractory rate was lowest in head/neck tumors (7.5%) and highest in spine tumors (77.8%). Regarding the tissue involved of tumor location, the refractory rate was higher in tumors involving bone than tumors involving soft tissue (32.7% versus 7.0%, p < .001). The outcomes of malignant tumors were worse than those of benign tumors (p < .001): nonremission rate, 21.4% versus 9.7%; recurrence rate, 28.6% versus 6.5%. In the multivariate regression analysis, female sex, spine tumors, bone tissue‐involved tumors, malignancy, and low preoperation serum phosphorus levels were identified as risk factors for refractory outcomes. High preoperative fibroblast growth factor 23 (FGF23) levels were also associated with refractory after adjusting for involving tissue and tumor malignancy. In summary, we are the first to report the rate and clinical characteristics of refractory TIO in a large cohort. For patients with multiple risk factors, especially spine tumors, clinical practitioners should be aware of a poor surgical prognosis. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

The Associations Between Seven Different Types of Physical Activity and the Incidence of Fracture at Seven Sites in Healthy Postmenopausal UK Women

15-11-2019 – Miranda EG 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

ABSTRACTThere 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 seven different sites associated with seven 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 seven different sites in relation to seven different physical activities. During an average follow‐up of 12 years, numbers with a first site‐specific fracture were as follows: 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 seven activity types (test for heterogeneity p = 0.004), with gardening more than 1 hour/week associated with a lower risk (RR = 0.91; 99% CI, 0.86 to 0.96; p < 0.0001), whereas cycling more than 1 hour/week was associated with an increased risk (RR = 1.11; 99% CI, 1.00 to 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% to 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% to 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. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Kidney Disease Progression Does Not Decrease Intestinal Phosphorus Absorption in a Rat Model of Chronic Kidney Disease–Mineral Bone Disorder

15-11-2019 – Colby J Vorland, Annabel Biruete, Pamela J Lachcik, Shruthi Srinivasan, Neal X Chen, Sharon M Moe, Kathleen M Hill Gallant

Journal Article

ABSTRACTThe 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. A total of 48 Cy/+ (CKD) and 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. © 2019 American Society for Bone and Mineral Research.

Greater Bone Marrow Adiposity Predicts Bone Loss in Older Women

14-11-2019 – 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

ABSTRACTBone 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 quantitative computed tomography (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 ± SD age was 80.9 ± 4.2 and 82.6 ± 4.2 years in women (n = 148) and men (n = 150), respectively. Mean baseline BMAT was 55.4% ± 8.1% in women and 54.1% ± 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 = .003), a 0.9 mg/cm3/year greater loss of spine trabecular BMD (p value = .02), and a 1.2 mg/cm3/year greater loss of femoral neck trabecular BMD (p value = .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. © 2019 American Society for Bone and Mineral Research.

Effects of Estrogen Replacement on Bone Geometry and Microarchitecture in Adolescent and Young Adult Oligoamenorrheic Athletes: A Randomized Trial

07-11-2019 – Kathryn E Ackerman, Vibha Singhal, Meghan Slattery, Kamryn T Eddy, Mary L Bouxsein, Hang Lee, Anne Klibanski, Madhusmita Misra

Journal Article

ABSTRACTOligoamenorrheic athletes (OAs) have lower bone mineral density (BMD) and greater impairment of bone microarchitecture, and therefore higher fracture rates compared to eumenorrheic athletes. Although improvements in areal BMD (a
BMD; measured by dual‐energy X‐ray absorptiometry) in OAs have been demonstrated with transdermal estrogen treatment, effects of such treatment on bone microarchitecture are unknown. Here we explore effects of transdermal versus oral estrogen versus no estrogen on bone microarchitecture in OA. Seventy‐five OAs (ages 14 to 25 years) were randomized to (i) a 100‐μg 17β‐estradiol transdermal patch (PATCH) administered continuously with 200 mg cyclic oral micronized progesterone; (ii) a combined 30 μg 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 1 year. At baseline, randomization groups did not differ by age, body mass index, percent body fat, duration of amenorrhea, vitamin D levels, BMD, or bone microarchitecture measurements. After 1 year of treatment, at the distal tibia there were significantly greater increases in total and trabecular volumetric BMD (v
BMD), cortical area and thickness, and trabecular number in the PATCH versus PILL groups. Trabecular area decreased significantly in the PATCH group versus 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 versus PILL and NONE groups, and changes in cortical v
BMD were significantly greater in the PATCH versus PILL groups. In conclusion, in young OAs, bone structural parameters show greater improvement after 1 year of treatment with transdermal 17β‐estradiol versus ethinyl estradiol–containing pills, particularly at the tibia. © 2019 American Society for Bone and Mineral Research.

“Short Sleep Is Associated With Low Bone Mineral Density and Osteoporosis in the Womens Health Initiative”

06-11-2019 – Heather M Ochs‐Balcom, Kathleen M Hovey, Christopher Andrews, Jane A Cauley, Lauren Hale, Wenjun Li, Jennifer W Bea, Gloria E Sarto, Marcia L Stefanick, Katie L Stone, Nelson B Watts, Oleg Zaslavsky, Jean Wactawski‐Wende

Journal Article

ABSTRACTShort sleep duration, recognized as a public health epidemic, is associated with adverse health conditions, yet little is known about the association between sleep and bone health. We tested the associations of usual sleep behavior and bone mineral density (BMD) and osteoporosis. In a sample of 11,084 postmenopausal women from the Womens Health Initiative (WHI; mean age 63.3 years, SD = 7.4), we performed a cross‐sectional study of the association of self‐reported usual hours of sleep and sleep quality (WHI Insomnia Rating Score) with whole body, total hip, femoral neck, and spine BMD using linear regression models. We also studied the association of sleep duration and quality with dual‐energy X‐ray absorptiometry (DXA)‐defined low bone mass (T‐score < −2.5 to <−1) and osteoporosis (T‐score ≤ −2.5) using multinomial regression models. We adjusted for age, DXA machine, race, menopausal symptoms, education, smoking, physical activity, body mass index, alcohol use, physical function, and sleep medication use. In adjusted linear regression models, women who reported sleeping 5 hours or less per night had on average 0.012 to 0.018 g/cm2 significantly lower BMD at all four sites compared with women who reported sleeping 7 hours per night (reference). In adjusted multinomial models, women reporting 5 hours or less per night had higher odds of low bone mass and osteoporosis of the hip (odds ratio OR = 1.22; 95% confidence interval CI 1.03–1.45, and 1.63; 1.15–2.31, respectively). We observed a similar pattern for spine BMD, where women with 5 hours or less per night had higher odds of osteoporosis (adjusted OR = 1.28; 95% CI 1.02–1.60). Associations of sleep quality and DXA BMD failed to reach statistical significance. Short sleep duration was associated with lower BMD and higher risk of osteoporosis. Longitudinal studies are needed to confirm the cross‐sectional effects of sleep duration on bone health and explore associated mechanisms. © 2019 American Society for Bone and Mineral Research.

Extracellular Vesicles From Osteotropic Breast Cancer Cells Affect Bone Resident Cells

05-11-2019 – 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 pro‐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 alkaline phosphatase (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 showed a role for osteoblast‐derived EVs and tumor cell–derived EVs in the deregulation of bone and endothelial cell physiology, thus fueling the vicious cycle induced by bone tumors. © 2019 American Society for Bone and Mineral Research.

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

04-11-2019 – Andreas Nyström, Demostenis Kiritopoulos, Gösta Ullmark, Jens Sörensen, Marianne Petrén‐Mallmin, Jan Milbrink, Nils P Hailer, Hans Mallmin

Journal Article

ABSTRACTImplant 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 2 trial in 64 patients aged 35 to 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 to 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 (DXA). 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. The trial was registered at 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 to 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 to 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 observed in this study could be preserved by either prolonged treatment with denosumab or additional antiresorptive treatment. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

A Geriatric Exercise Program May Yield Multiple Benefits

31-10-2019 – Jodi Dowthwaite

Editorial

Increased Fracture Risk in Women Treated With Aromatase Inhibitors Versus Tamoxifen: Beneficial Effect of Bisphosphonates

31-10-2019 – 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 (subdistribution hazard ratio SHR 95% CI). In postmenopausal women, fracture risk in aromatase inhibitor users showed an HR 1.40 95% CI,1.05 to 1.87 and SHR 1.48 95% CI, 1.11 to 1.98, compared to tamoxifen. Observing aromatase inhibitors patients at high risk of fracture, bisphosphonate‐treated patients had an HR 0.73 95% CI, 0.51 to 1.04 and SHR 0.69 95% CI, 0.48 to 0.98 compared to nontreated. 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 nonbisphosphonate users. Monitoring fracture risk and related risk factors in aromatase inhibitor patients is advisable. © 2019 American Society for Bone and Mineral Research.