Citations

Abstract Randomized trials have not been performed, and may never be, to determine if osteoporosis treatment prevents hip fracture in men. Addressing that evidence gap, we analyzed data from an observational study of new hip fractures in a large integrated healthcare system to compare the reduction in hip fractures associated with standard-of-care osteoporosis treatment in men versus women. Sampling from 271,389 patients aged ≥ 65 who had a hip-containing CT scan during care between 2005 and 2018, we selected all who subsequently had a first hip fracture (cases) after the CT scan (start of observation) and a sex-matched equal number of randomly selected patients. From those, we analyzed all who tested positive for osteoporosis (DXA-equivalent hip BMD T-score ≤ −2.5, measured from the CT scan using VirtuOst). We defined “treated” as at least six months of any osteoporosis medication by prescription fill data during follow-up; “not-treated” was no prescription fill. Sex-specific odds ratios of hip fracture for treated vs not-treated patients were calculated by logistic regression; adjustments included age, BMD T-score, BMD-treatment interaction, BMD, race/ethnicity, and seven baseline clinical risk factors. At two-year follow-up, 33.9% of the women (750/2,211 patients) and 24.0% of the men (175/728 patients) were treated primarily with alendronate; 51.3% and 66.3%, respectively, were not-treated; and 721 and 269, respectively, had a first hip fracture since the CT scan. Odds ratio of hip fracture for treated vs not-treated was 0.26 (95% confidence interval: 0.21–0.33) for women and 0.21 (0.13–0.34) for men; the ratio of these odds ratios (men:women) was 0.81 (0.47–1.37), indicating no significant sex effect. Various sensitivity and stratified analyses confirmed these trends, including results at five-year follow-up. Given these results and considering the relevant literature, we conclude that osteoporosis treatment prevents hip fracture similarly in both sexes.

Abstract Histone deacetylase 3 (Hdac3) is an epigenetic regulator of gene expression and interacts with skeletal transcription factors such as Runx2. We previously reported that conditional deletion of Hdac3 in Osterix-Cre recombinase-expressing osteoprogenitor cells (Hdac3 CKOOsx) caused osteopenia and increased marrow adiposity, both hallmarks of skeletal aging. We also showed that Runx2+ cells within osteogenic cultures of Hdac3-depleted bone marrow stromal cells (BMSCs) contain lipid droplets (LDs). Cellular senescence, a nonproliferative metabolically active state, is associated with increased marrow adiposity, bone loss, and aging. In this study, we sought to determine if Hdac3 depleted Runx2+ pre-osteoblasts from young mice exhibit chromatin changes associated with early cellular senescence and how these events correlate with the appearance of LDs. We first confirmed that BMSCs from Hdac3 CKOOsx mice have more Runx2 + LD+ cells compared with controls under osteogenic conditions. We then measured senescence-associated distention of satellite (SADS) DNA and telomere-associated foci (TAFs) in Hdac3 CKOOsx and control BMSCs. In situ, Runx2+ cells contained more SADS per nuclei in Hdac3 CKOOsx femora than in controls. Runx2+ BMSCs from Hdac3 CKOOsx mice also contained more SADS and TAFs per nuclei than Runx2+ cells from age-matched control mice in vitro. SADs and TAFs were present at similar levels in Runx2 + LD+ cells and Runx2 + LD− cells from Hdac3 CKOOsx mice. Hdac inhibitors also increased the number of SADS in Runx2 + LD+ and Runx2 + LD− WT BMSCs. Senolytics reduced viable cell numbers in Hdac3 CKOOsx BMSC cultures. These data demonstrate that the depletion of Hdac3 in osteochondral progenitor cells triggers LD formation and early events in cellular senescence in Runx2+ BMSCs through mutually exclusive mechanisms.

Cells expressing features of senescence, including upregulation of p21 and p16, appear transiently following tissue injury, yet the properties of these cells or how they contrast with age-induced senescent cells remains unclear. Here, we used skeletal injury as a model and identified the rapid appearance following fracture of p21 + cells expressing senescence markers, mainly as osteochondroprogenitors (OCHs) and neutrophils. Targeted genetic clearance of p21 + cells suppressed senescence-associated signatures within the fracture callus and accelerated fracture healing. By contrast, p21 + cell clearance did not alter bone loss due to aging; conversely, p16 + cell clearance, known to alleviate skeletal aging, did not affect fracture healing. Following fracture, p21 + neutrophils were enriched in signaling pathways known to induce paracrine stromal senescence, while p21 + OCHs were highly enriched in senescence-associated secretory phenotype factors known to impair bone formation. Further analysis revealed an injury-specific stem cell–like OCH subset that was p21 + and highly inflammatory, with a similar inflammatory mesenchymal population (fibro-adipogenic progenitors) evident following muscle injury. Thus, intercommunicating senescent-like neutrophils and mesenchymal progenitor cells were key regulators of tissue repair in bone and potentially across tissues. Moreover, our findings established contextual roles of p21 + versus p16 + senescent/senescent-like cells that may be leveraged for therapeutic opportunities.

Abstract In a previous study, we observed decreased 1,25-dihydroxyvitamin D levels, secondary hyperparathyroidism, and increased bone turnover markers in living kidney donors (LKDs) at 3 months and 36 months after kidney donation. In our recent survey-based study, we found no increased risk of fractures of all types but observed significantly more vertebral fractures in LKDs compared with matched controls. To elucidate the long-term effects of kidney donation on bone health, we recruited 139 LKDs and 139 age and sex matched controls from the survey-based participants for further mechanistic analyses. Specifically, we assessed whether LKDs had persistent abnormalities in calcium- and phosphorus-regulating hormones and related factors, in bone formation and resorption markers, and in density and microstructure of bone compared with controls. We measured serum markers, bone mineral density (BMD), bone microstructure and strength (via high-resolution peripheral quantitative computed tomography and micro-finite element analysis [HRpQCT]), and advanced glycation end-products in donors and controls. LKDs had decreased 1,25-dihydroxyvitamin D concentrations (donors mean 33.89 pg/mL vs. controls 38.79 pg/mL, percent difference = -12.6%; P < .001), increases in both parathyroid hormone (when corrected for ionized calcium; donors mean 52.98 pg/mL vs. controls 46.89 pg/mL,% difference 13%; P = .03) and ionized calcium levels (donors mean 5.13 mg/dL vs. controls 5.04 mg/dL; P < .001), and increases in several bone resorption and formation markers versus controls. LKDs and controls had similar measures of BMD; however, HRpQCT suggested that LKDs have a statistically insignificant tendency toward thinner cortical bone and lower failure loads as measured by micro-finite element analysis. Our findings suggest that changes in the hormonal mileu after kidney donation and the long-term cumulative effects of these changes on bone health persist for decades after kidney donation and may explain later-life increased rates of vertebral fractures.

Objective To test the hypothesis that the numbers of circulating endothelial progenitor cells (EPC) co-expressing an osteogenic phenotype (EPC-OC) are increased in patients with clinically severe calcific aortic valve stenosis (AoC). Background AoC is one of the most common valvular heart diseases. Recent studies have shifted the old paradigm of AoC being a passive, degenerative process to an active biological process associated with an osteoblast-like phenotype. We have recently identified circulating EPC-OC which are significantly increased in patients with severe coronary artery disease (CAD). Methods and Results Of 38 patients, 14 underwent aortic valve replacement due to AoC with only mild angiographic CAD. Patients with normal aortic valves and coronary arteries (n=12) or severe CAD without aortic valve disease (n=12) served as controls (Table ). Peripheral blood mononuclear cells were analyzed using flow cytometry following staining for EPC markers (CD133, CD34, KDR) and the osteoblastic marker, osteocalcin (OC). Patients with AoC had significantly higher fractions of OC co-expression on EPC of different maturity than normal patients, similar to patients with CAD (Figure ). Conclusions Circulating EPC co-expressing an osteoblastic phenotype are increased and may potentially play a role in the active process of aortic valve calcification. Table. Clinical Data.

Abstract Fracture risk increases with lower areal bone mineral density (aBMD); however, aBMD-related estimate of risk may decrease with age. This may depend on technical limitations of 2-dimensional (2D) dual energy X-ray absorptiometry (DXA) which are reduced with 3D high-resolution peripheral quantitative computed tomography (HR-pQCT). Our aim was to examine whether the predictive utility of HR-pQCT measures with fracture varies with age. We analyzed associations of HR-pQCT measures at the distal radius and distal tibia with two outcomes: incident fractures and major osteoporotic fractures. We censored follow-up time at first fracture, death, last contact or 8 years after baseline. We estimated hazard ratios (HR) and 95%CI for the association between bone traits and fracture incidence across age quintiles. Among 6835 men and women (ages 40–96) with at least one valid baseline HR-pQCT scan who were followed prospectively for a median of 48.3 months, 681 sustained fractures. After adjustment for confounders, bone parameters at both the radius and tibia were associated with higher fracture risk. The estimated HRs for fracture did not vary significantly across age quintiles for any HR-pQCT parameter measured at either the radius or tibia. In this large cohort, the homogeneity of the associations between the HR-pQCT measures and fracture risk across age groups persisted for all fractures and for major osteoporotic fractures. The patterns were similar regardless of the HR-pQCT measure, the type of fracture, or the statistical models. The stability of the associations between HR-pQCT measures and fracture over a broad age range shows that bone deficits or low volumetric density remain major determinants of fracture risk regardless of age group. The lower risk for fractures across measures of aBMD in older adults in other studies may be related to factors which interfere with DXA but not with HR-pQCT measures.

Importance Living kidney donors may have an increased risk of fractures due to reductions in kidney mass, lower concentrations of serum 1,25-dihydroxyvitamin D, and secondary increases in serum parathyroid hormone. Objective To compare the overall and site-specific risk of fractures among living kidney donors with strictly matched controls from the general population who would have been eligible to donate a kidney but did not do so. Design, Setting, and Participants This survey study was conducted between December 1, 2021, and July 31, 2023. A total of 5065 living kidney donors from 3 large transplant centers in Minnesota were invited to complete a survey about their bone health and history of fractures, and 16 156 population-based nondonor controls without a history of comorbidities that would have precluded kidney donation were identified from the Rochester Epidemiology Project and completed the same survey. A total of 2132 living kidney donors and 2014 nondonor controls responded to the survey. Statistical analyses were performed from May to August 2023. Exposure Living kidney donation. Main Outcomes and Measures The rates of overall and site-specific fractures were compared between living kidney donors and controls using standardized incidence ratios (SIRs). Results At the time of survey, the 2132 living kidney donors had a mean (SD) age of 67.1 (8.9) years and included 1245 women (58.4%), and the 2014 controls had a mean (SD) age of 68.6 (7.9) years and included 1140 women (56.6%). The mean (SD) time between donation or index date and survey date was 24.2 (10.4) years for donors and 27.6 (10.7) years for controls. The overall rate of fractures among living kidney donors was significantly lower than among controls (SIR, 0.89; 95% CI, 0.81-0.97). However, there were significantly more vertebral fractures among living kidney donors than among controls (SIR, 1.42; 95% CI, 1.05-1.83). Conclusions and Relevance This survey study found a reduced rate of overall fractures but an excess of vertebral fractures among living kidney donors compared with controls after a mean follow-up of 25 years. Treatment of excess vertebral fractures with dietary supplements such as vitamin D 3 may reduce the numbers of vertebral fractures and patient morbidity.

AbstractSenescent cells compromise tissue structure and function in older organisms. We recently identified senescent fibroadipogenic progenitors (FAPs) with activated chemokine signaling pathways in the skeletal muscle of old mice, and hypothesized these cells may contribute to the age‐associated accumulation of immune cells in skeletal muscle. In this study, through cell–cell communication analysis of skeletal muscle single‐cell RNA‐sequencing data, we identified unique interactions between senescent FAPs and macrophages, including those mediated by Ccl2 and Spp1. Using mouse primary FAPs in vitro, we verified increased expression of Ccl2 and Spp1 and secretion of their respective proteins in the context of both irradiation‐ and etoposide‐induced senescence. Compared to non‐senescent FAPs, the medium of senescent FAPs markedly increased the recruitment of macrophages in an in vitro migration assay, an effect that was mitigated by preincubation with antibodies to either CCL2 or osteopontin (encoded by Spp1). Further studies demonstrated that the secretome of senescent FAPs promotes polarization of macrophages toward an M2 subtype. These data suggest the unique secretome of senescent FAPs may compromise skeletal muscle homeostasis by recruiting and directing the behavior of macrophages.

Cachexia is a debilitating skeletal muscle wasting condition for which we currently lack effective treatments. In the context of cancer, certain chemotherapeutics cause DNA damage and cellular senescence. Senescent cells exhibit chronic activation of the transcription factor NF-κB, a known mediator of the proinflammatory senescence-associated secretory phenotype (SASP) and skeletal muscle atrophy. Thus, targeting NF-κB represents a logical therapeutic strategy to alleviate unintended consequences of genotoxic drugs. Herein, we show that treatment with the IKK/NF-κB inhibitor SR12343 during a course of chemotherapy reduces markers of cellular senescence and the SASP in liver, skeletal muscle, and circulation and, correspondingly, attenuates features of skeletal muscle pathology. Lastly, we demonstrate that SR12343 mitigates chemotherapy-induced reductions in body weight, lean mass, fat mass, and muscle strength. These findings support senescent cells as a promising druggable target to counteract the SASP and skeletal muscle wasting in the context of chemotherapy.