Bone

Three-dimensional dual-energy X-ray absorptiometry (3D-DXA) reconstructs proximal femur models from standard scans to estimate cortical and trabecular bone parameters. The aim of this study was to evaluate 3D-DXA against quantitative computed tomography (QCT) across independent international cohorts. The study included 537 subjects from four cohorts: an adult population from Spain, a postmenopausal female population from the United States, an osteoarthrosis population and a young population, both from Japan. Subjects underwent both 3D-DXA and QCT imaging. Accuracy was assessed using linear regression and Bland-Altman analysis to evaluate systematic and random errors. 3D-DXA parameters strongly correlated with QCT across all datasets, with correlation coefficients between 0.82 and 0.97. Random errors were consistent across cohorts and ranged between 16.55 and 19.91 mg/cm3 for integral volumetric bone mineral density (vBMD), between 13.52 and 18.47 mg/cm3 for trabecular vBMD, and between 9.13 and 11.37 mg/cm2 for cortical surface bone mineral density (sBMD). Systematic errors ranged between -14.84 and 4.50 mg/cm3 for integral vBMD, between -8.31 and 14.41 mg/cm3 for trabecular vBMD, and between -5.58 and 3.21 mg/cm2 for cortical sBMD. The variations in systematic errors were likely attributable to differences in QCT acquisition protocols. Overall, these results demonstrate consistent agreement between 3D-DXA and QCT across sex, age, ethnicity, geographic regions, and clinical profiles. Taken together, these findings support the use of 3D-DXA as an accurate, non-invasive, and clinically accessible technology for advanced assessment of the cortical and trabecular compartments of the proximal femur.

PurposeOsteoporosis and associated hip fractures are a major public health concern. Dualenergy X-ray Absorptiometry (DXA) remains the diagnostic gold standard, but its areal (a) bone mineral density (BMD) measurements have limited sensitivity, as many fractures occur at T-scores above -2.5. Three-dimensional (3D) DXA provides compartment-specific volumetric parameters of the hip, potentially improving osteoporosis management. This study aimed to establish reference data for 3D-DXA parameters to improve osteoporosis management and investigate potential compartmental imbalances at the hip. MethodThis multicenter, cross-sectional, population-based observational study (SEIOMM-3D-DXA project), supported by the Spanish Society for Bone and Mineral Metabolism (SEIOMM), analyzed hip DXA scans from 1366 Spanish men and women across six centers. 3D-DXA analyses were conducted using the 3D-Shaper software (3D-Shaper Medical, Barcelona, Spain), producing estimates of trabecular volumetric (v) BMD and cortical surface (s) BMD. Age- and sex-specific reference curves were generated using the LMS method, and thresholds were established based on regression with T-score values. Moreover, trabecular vBMD and cortical sBMD Z-scores were calculated to evaluate potential compartmental imbalances. ResultsThe derived aBMD curves closely aligned with the NHANES III Caucasian reference. Sex-specific thresholds for trabecular vBMD and cortical sBMD were established for patient stratification. Z-score comparisons revealed significant discrepancies between trabecular and cortical compartments in 52.0% of females and 48.7% of males, underlining the importance of compartment-specific bone assessment. ConclusionsThis study establishes reference curves for clinical interpretation of 3D-DXA parameters and demonstrates the potential of 3D-DXA to capture compartmental imbalances at the hip. Mini AbstractIn this study, hip scans from over a thousand men and women in Spain were analyzed to create normative reference values for 3D-DXA parameters. These results can help doctors better stratify people based on the status of each part of the bone and improve the management of osteoporosis.

IntroductionTrabecular bone exhibits brittle behaviour governed by microscale deformation and damage processes, yet quantitative characterisation of crack progression remains challenging because classical fracture mechanics approaches do not apply to architecturally discontinuous porous tissues. This study evaluates whether synchrotron X-ray computed tomography (XCT) combined with digital volume correlation (DVC) can provide a practical experimental approach for quantifying crack opening behaviour in human trabecular bone. MethodSemicylindrical specimens harvested from femoral heads of hip-fracture donors (n = 5) and non-fracture controls (n = 5) underwent stepwise three-point-bending during XCT imaging. Full-field displacement maps enabled direct measurement of crack mouth opening displacement (CMOD), crack length (a), and their ratio, CMOD/a, used here as a geometry-normalised comparative descriptor of brittle response. Automated crack segmentation using phase-congruency crack detection (PCCD) was compared against manual measurements. ResultsXCT-DVC successfully resolved three-dimensional displacement discontinuities during crack initiation and propagation in all specimens. Hip-fracture donors exhibited significantly lower critical crack-opening ratios (CMOD/a)* than Controls (0.31 vs 0.47; p = 0.008) and reached mechanical instability at lower applied loads, consistent with a more brittle structural response under this test configuration. Despite these differences, total crack extension ({Delta}a*) was similar between groups. Automated crack tracking using phase-congruency-based segmentation showed excellent agreement with manual measurements (r{superscript 2} = 0.98), confirming reliable extraction of crack geometry from DVC displacement fields. DiscussionThese results indicate that XCT-DVC can provide a practical approach for quantifying crack-opening behaviour in trabecular bone when classical fracture-mechanics parameters are not applicable in anatomically constrained specimens. The reduced critical crack-opening ratios and earlier instability observed in Hip-fracture donors are consistent with a more brittle comparative mechanical response that is not captured by crack extension alone. The strong agreement between automated and manual crack measurements further supports displacement-based descriptors as reliable comparative indicators of brittle behaviour in porous, architecturally discontinuous tissues. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/714043v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@31c5d7org.highwire.dtl.DTLVardef@1b3d9a4org.highwire.dtl.DTLVardef@95df7borg.highwire.dtl.DTLVardef@1834216_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG

3D-DXA reconstructs DXA hip scans to 3-dimensional images allowing measurement of trabecular and cortical bone parameters. Given the higher image quality of GE Healthcare iDXA than GE Healthcare Prodigy, it could be hypothesized that the reconstruction might differ, thereby affecting 3D-DXA results. The aim of the study was to assess agreement and precision of 3D-DXA cortical and trabecular femur parameters between Prodigy and iDXA densitometers in adult subjects. The study cohort was composed of 391 men and women recruited from 3 clinical centers (USA and Brazil). All subjects were scanned on either Prodigy or iDXA scanners. Short-term precision was assessed on two Prodigy and two iDXA densitometers. 3D-DXA analyses were performed using 3D-Shaper software version 2.14. Agreement between densitometers was assessed by regression and Bland-Altman analyses. Short-term precision was determined following International Society for Clinical Densitometry recommendations. Strong agreements for 3D-DXA parameters were obtained between devices regardless of the center or the DXA device model (all R2 > 0.96). Bland-Altman analyses demonstrated statistically (p < 0.05), but not clinically, significant difference between both aBMD and 3D-DXA measurements obtained using Prodigy and iDXA scanners. Short-term precision of areal BMD and 3D-DXA parameters was similar between densitometers. This study demonstrated excellent 3D-DXA measurement agreement and similar precision between iDXA and Prodigy densitometers. These data provide evidence that no adjustments are required when using 3D-Shaper software on iDXA or Prodigy instruments. Mini AbstractWe assessed agreement and precision of 3D-DXA parameters between GE Healthcare Prodigy and iDXA densitometers in adults. Strong agreement was observed between devices, and short-term precision was comparable. Findings indicate that no adjustment is needed when using 3D-DXA with GE Healthcare densitometers.

Introduction Denosumab increases bone mineral density and reduces fracture risk in patients with osteoporosis. However, whether BMD response to denosumab differs by age, particularly during longer term treatment, remains unclear. This study investigated the association between baseline age and BMD gain during 3 years of denosumab treatment in patients with osteoporosis. Methods This retrospective study included patients with osteoporosis who were treated with denosumab. DXA-based BMD and bone turnover markers were followed for up to 3 years. Percent BMD gain from baseline, defined as %BMD gain, was evaluated. The longitudinal association between baseline age and %BMD gain was assessed using multivariable linear mixed-effects models for the lumbar spine and total hip. Analyses were performed in the treatment naive cohort and the overall cohort according to prior osteoporosis treatment status. Results A total of 255 patients were included in the analysis, of whom 110 had not received prior osteoporosis treatment. In multivariable linear mixed-effects models, older baseline age was associated with smaller lumbar spine %BMD gain in the treatment naive cohort at both 1 and 3 years. Each 1-year increase in age was associated with a 0.187 percentage-point lower lumbar spine %BMD gain at 1 year and a 0.293 percentage-point lower gain at 3 years (1 year: {beta} = -0.187, p = 0.006, 3 years: {beta} = -0.293, p = 0.031). In contrast, baseline age was not significantly associated with total hip %BMD gain in the treatment naive cohort (1 year: {beta} = -0.011, p = 0.826; 3 years: {beta} = 0.028, p = 0.727). In the overall cohort, baseline age was not significantly associated with %BMD gain at either the lumbar spine or total hip at 1 or 3 years (all p > 0.05). Conclusion Older baseline age was associated with a modestly smaller lumbar spine BMD gain in treatment naive patients, whereas no significant age-related association was observed at the total hip. In the overall cohort, age was not significantly associated with BMD gain at either site. These findings suggest that age may have a limited, site specific influence on BMD response to denosumab, particularly in treatment naive patients, and may support more individualized treatment planning in patients with osteoporosis.

Background: A previous meta-analysis by Singh-Ospina et al. (2017) suggested that Gender affirming hormone treatment (GAHT) does not change transgender mens bone mineral density (BMD) at any clinically relevant site; emerging studies and advances in synthesis methods necessitate an updated evaluation. The primary aim was to update the bone measures of Singh-Ospina et al. (2017), with the secondary aim to expand measures to how GAHT affects musculoskeletal health. Methods: A systematic review with meta-analysis was conducted using studies published in English up to 31 July 2024, identified through three electronic databases (PubMed, Embase, SportDiscus), and final cross-referencing in summer 2025. Primary outcomes were longitudinal changes in femoral neck (FN), lumbar spine (LS), and total hip (TH) bone mineral density (BMD). Secondary outcomes included body composition and muscle strength. Standardised effect sizes (Hedges g) were pooled using the inverse heterogeneity (IVhet) model. Results: GAHT (4 years) was not associated with significant longitudinal changes in FN, LS, or TH BMD. In contrast, substantial anabolic effects were observed, including increases in BMI (g = 0.13), body mass (g = 0.18), fat-free mass (g = 0.59), and muscle strength (g = 0.86). Heterogeneity was high for muscle strength, FN and TH BMD, limiting confidence in pooled estimates. Conversely, changes in LS BMD, BMI, body mass and fat-free mass demonstrated low heterogeneity and greater consistency across studies. Conclusion: Masculinising GAHT does not negatively affect clinically relevant BMD sites while reliably increasing lean mass and muscle strength; however, the evidence base remains methodologically weak and highly variable, particularly for FN and TH. The need for continued clinical monitoring of bone health and muscle function, alongside high-quality longitudinal research incorporating advanced imaging modalities such as HR pQCT is emphasised. Strengthening the evidence base will be essential for clarifying long-term skeletal trajectories as transgender men age. PROSPERO registration: CRD42024573102

Social isolation is a known modifiable risk factor for many chronic diseases including cardiovascular, metabolic, and brain disorders. Recent research has demonstrated that social isolation is similarly detrimental to skeletal health, but these effects may be sexually dimorphic. In rodents, isolation negatively affects bone in adult male mice, but not in females. However, these sex differences have not been systematically investigated, and it is unknown if they persist with long-term social isolation. The goal of our study was to investigate if isolation-induced bone loss may occur on different timescales between female and male mice, as well as investigate the potential roles of estrogen and testosterone. We examined bone changes in grouped (4 mice/cage) or isolated (1 mouse/cage) female and male 16-week-old C57BL/6J mice after 2, 4, or 8 weeks of treatment. We found that social isolation through single housing significantly reduced bone parameters across treatment lengths in male mice (20% reduction in Tb.BV/TV; 8% reduction in Ct.Th.) but not in females even with prolonged isolation. Isolation also decreased biomechanical properties in the femur of male but not female mice. While the females overall bone phenotype was unaffected, isolated females did show an increase in bone turnover markers with as little as 2 weeks of isolation. Isolation also altered estrogen-related gene expression in male mice isolated for 4 or 8 weeks. Overall, our results demonstrate that short- and long-term social isolation has sexually dimorphic effects on murine bone. These findings have important clinical implications for individuals at risk for social isolation, as well as for pre-clinical rodent models utilizing single housing.

Background Automated pelvic CT segmentation has advanced to reliable coarse bone extraction. Yet the structured anatomical hierarchy required for morphometry, fixation planning, bone quality mapping, and arthroplasty workflows remains unachieved. This study developed and validated a fully automated anatomy-informed pipeline that converts standard pelvic CT into a comprehensive, surgeon-readable subsegmentation of the pelvis and proximal femur. Methods Pelvic CT datasets were retrospectively collected from anonymized archives of hospitals affiliated with the Directorate of Health Affairs, Sharqia, Egypt. After eligibility screening, 757 normal adult cases were processed using a custom one-click 3D Slicer pipeline integrating TotalSegmentator for coarse extraction, followed by deterministic anatomy-based subsegmentation into 81 segments. One hundred randomly selected cases were validated against expert-corrected reference segmentations using Dice similarity coefficient, volume difference, surface distance metrics, and bilateral symmetry analysis. Results Of 1,316 screened cases, 757 met eligibility criteria. Across 8,100 case-segment observations, the pipeline achieved a mean Dice of 0.9926 +/- 0.0465. Complete agreement was observed for the sacrum, ilium, acetabulum, anterior and posterior columns, sciatic buttress, and all landmarks. Relative decreases were confined to boundary-dependent regions. Bilateral symmetry analysis confirmed a median surface agreement of 99.85% within 5 mm. Conclusion The pipeline demonstrated high accuracy and reproducibility across a large normal adult dataset, establishing a structured anatomical foundation for quantitative pelvic analysis and surgical planning workflows. Clinical feasibility across abnormal anatomy and decision-level applications awaits dedicated validation.

Individuals with chronic kidney disease (CKD) have higher rates of hip fracture and post-fracture mortality. Although they may develop age-related osteoporosis similar to those without CKD, they may also exhibit CKD-related metabolic bone disease (MBD), characterized by low, high, or mixed turnover at similar levels of bone mineral density (BMD). Because BMD does not provide information about turnover status, clinical decision-making is challenging. This study evaluated the associations between circulating bone-turnover biomarkers and static histomorphometry in patients undergoing hip-fracture surgery. In this cross-sectional study, we enrolled adults with and without CKD, defined as estimated glomerular filtration rate (eGFR) [&le;]60 ml/min/1.73m{superscript 2} (CKD-EPI 2021), undergoing hip-fracture surgery. Blood samples, bone specimens from the femoral head or greater trochanter, and demographic and clinical data were collected at the time of surgery. Plasma biomarkers included -Klotho, bone alkaline phosphatase (BAP), dickkopf-related protein 1 (DKK-1), fibroblast growth factor 23 (FGF23), tartrate-resistant acid phosphatase 5b (TRAP5b), parathyroid hormone (PTH), and sclerostin. Logistic regression models, adjusted for age, gender, eGFR, and osteoporosis, assessed associations with CKD status. Tertiles of osteoblast surface (Ob.S/BS) and eroded surface (ES/BS) were defined in participants without CKD and applied to the full cohort. Multinomial and multivariable linear regression evaluated associations of biomarkers with these histomorphometry parameters. Among 97 enrolled participants (mean age 80 {+/-} 11 years; 67% female), 68% had CKD. Of 75 with complete biomarker and histomorphometry data, 96% demonstrated low bone turnover. CKD was associated with lower trabecular thickness (Tb.Th) and higher osteoid thickness (O.Th), osteoid volume (OV/BV), and osteoid surface (OS/BS), suggesting thinner, largely unmineralized trabeculae. Higher BAP (222.2% difference per doubling; 95% CI 77.2-485.8) and TRAP5b (319.3%; 95% CI 128.3-669.5) were directly associated with Ob.S/BS and ES/BS, whereas sclerostin was inversely associated with ES/BS (-28.9%; 95% CI -44.8 to -7.1). PTH was not associated with bone-turnover measures. These findings suggest that BAP, TRAP5b, and sclerostin may provide useful adjunct information alongside PTH for assessing bone turnover and guiding therapy in patients with and without CKD.

Bone is a dynamic tissue that continuously adapts its structure in response to mechanical loading, an essential process for maintaining skeletal health. However, this adaptive capacity declines with aging, contributing to increased fragility and fracture risk. Developing therapeutic strategies that preserve or restore bone mechanoadaptation in patients with increased bone fragility requires identifying key molecular regulators of this process. We applied spatial transcriptomics (GeoMx, NanoString) to characterize gene expression changes induced by mechanical loading in the murine tibia, focusing on periosteal and bone compartments in regions under tension and compression. Spatial data were validated and cross-compared with previously published bulk RNA-seq and laser-capture microdissection datasets, identifying a set of 12 genes consistently regulated by loading across independent platforms and laboratories. As part of a functional analysis, we selected Slc13a5, a citrate transporter implicated in bone mineralization and metabolism. Conditional deletion of Slc13a5 in osteolineage cells using Osteocalcin-Cre significantly increased the loading-induced mineralizing surface in tensile regions compared with Cre- Slc13a5fl/fl littermates. In addition, Slc13a5 cKO mice exhibited lower resorption around the neutral axis after loading compared to controls. Together, these findings identify Slc13a5 as a regulator of bone adaptation in regions experiencing low mechanical stimulation and suggest it as a potential therapeutic target for conditions characterized by impaired mechanoadaptive responses. This study highlights spatial transcriptomics as a powerful gene discovery framework for bone, enabling identification of novel targets to understand mechanisms and develop therapies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=181 SRC="FIGDIR/small/711126v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@5bf180org.highwire.dtl.DTLVardef@4c33b7org.highwire.dtl.DTLVardef@d75668org.highwire.dtl.DTLVardef@169fa97_HPS_FORMAT_FIGEXP M_FIG C_FIG

Pathologic vertebral fractures are a major complication in metastatic spine disease. However, current clinical scores, such as Spinal Instability Neoplastic Score (SINS), show limited predictive capability, particularly within the indeterminate range where most clinical uncertainty lies. This study aimed to develop and evaluate quantitative computed tomography (qCT)-based subject-specific finite element (SSFE) models to predict vertebral strength in presence of different metastatic lesion types. Twelve ex vivo human spine segments, each containing one metastatic (n=12) and one adjacent control vertebra (n=12), were scanned using qCT and calibrated using a calibration phantom. Homogenised nonlinear finite element models were developed with spatially heterogeneous, isotropic, density-dependent material properties and loaded under uniaxial compression corresponding to 1.9% apparent strain. Ultimate failure load, stiffness, and strain distributions were compared between metastatic and control vertebrae. Predicted failure load ranged from 0.2 kN to 6.2 kN (mean. {+/-} standard deviation: 1.8 {+/-} 1.6 kN metastatic; 1.7 {+/-} 1.5 kN control), with no statistically significant difference between groups (p > 0.05). Normalised failure load varied widely, reflecting lesion-specific mechanical heterogeneity. Lytic lesions generally weakened vertebrae, whereas mixed and blastic lesions occasionally enhanced strength, likely due to localised sclerosis or reactive bone formation. High compressive axial strains (greater than 0.019) were frequently concentrated near the endplates, particularly in lytic vertebrae. qCT-derived bone mineral density strongly correlated with failure load (R{superscript 2} = 0.74-0.77). These findings highlight the complexity of metastatic vertebral mechanics and demonstrate that qCT-based SSFE modelling provides a quantitative framework for assessing fracture risk, complementing conventional imaging-based tools.

Osteocytes play a central role in bone remodeling, mineral metabolism, and skeletal homeostasis, but direct molecular analysis of human osteocytes remains technically challenging because they are embedded within the mineralized bone matrix. Surgically obtained human bone specimens provide valuable material for studying human bone biology; however, surface-associated cells, marrow-derived cells, and adherent soft tissues can confound downstream transcript analysis. Here, we describe a bone fragment-based protocol for preparing surgically obtained human bone specimens for molecular analysis of osteocyte-associated transcripts. The protocol consists of mechanical trimming, mincing into small bone fragments, repeated washing, and five sequential rounds of collagenase digestion to reduce non-osteocytic cellular components associated with the bone surface and marrow spaces. The remaining mineralized bone fragments are then frozen in liquid nitrogen, cryogenically pulverized, and lysed in TRIzol reagent for total RNA extraction. Histological validation using residual maxillary bone specimens showed that sequential collagenase digestion markedly reduced adherent soft tissue and extra-matrix nuclei while preserving osteocyte lacunar occupancy. This protocol provides a practical workflow for bone fragment-based RNA analysis focused on osteocyte-associated transcripts in human bone specimens. Specifications table O_TBL View this table: org.highwire.dtl.DTLVardef@1cec618org.highwire.dtl.DTLVardef@2f746forg.highwire.dtl.DTLVardef@1854247org.highwire.dtl.DTLVardef@1c26c1aorg.highwire.dtl.DTLVardef@1473a88_HPS_FORMAT_FIGEXP M_TBL C_TBL

BackgroundLongitudinal bone growth occurs via the process of endochondral ossification, involving a complex interplay of chondrocyte proliferation, differentiation, and matrix remodelling. As with all mammalian cells, chondrocytes require dynamin for mitochondrial fission, to shuttle vesicles from the Golgi apparatus, and for both clathrin- and caveolin-mediated endocytosis. Here, we aimed to test the functions of dynamin on bone growth. To do so, we applied dynasore - a small molecule that is a reversible dynamin inhibitor - to mouse metatarsal bones cultured ex vivo. We assessed gross changes using bone length measurements and histomorphometry, and combined this with EdU detection, immunostaining, super-resolution microscopy and transmission electron microscopy. ResultsDynasore induced a dose-dependent hormetic effect on bone elongation: while high concentrations (220 {micro}M) impaired growth and abolished chondrocyte proliferation, low-dose treatment (40 {micro}M) significantly increased longitudinal bone growth. Histological analysis demonstrated that low dose dynasore augmented epiphyseal cartilage expansion and matrix accumulation, particularly within the resting and proliferative zones, while reducing chondrocyte proliferation. Immunostaining indicated that 40 {micro}M dynasore preserved collagen type X synthesis, activated mTORC1 signalling, and blocked autophagy, based on SQSTM1 accumulation. Low dose dynasore treatment expanded the thickness of the filamentous actin layer at the plasma membrane and deepened collagen fiber-containing endocytic pits, indicating that impaired cartilage remodelling was associated with growth-associated matrix accumulation. ConclusionsThis study reveals that dynasore exerts hormetic effects on growth plate chondrocytes, wherein low doses stimulate bone elongation, and high doses impair chondrocyte function.

BackgroundBone formation during development and repair is divergently modulated by osteoblast (OB)-derived vascular endothelial growth factor (VEGF) which drives the skeletal sexual dimorphism of the bone vasculature. While the extracellular matrix (ECM) provides both structural and instructive cues to developing vasculature, the contributions of the bone matrix to this skeletal vascular dimorphism in bone remains undefined at the cellular level. MethodsPrimary OBs were isolated from neonatal female and male C57BL/6 long bones and cultured under basal or osteogenic conditions. ECM composition was quantified by Raman spectroscopy. Primary murine bone marrow endothelial cells (BMECs) were seeded directly onto established OB layers and maintained in heterotypic cocultures to assess contact-mediated effects of OB ECM on BMEC survival and expansion. OB-conditioned media (CM) was used to evaluate soluble-factor contributions, with VEGF-A concentration quantified by ELISA. ResultsRaman spectroscopy, on individual OBs from monotypic cultures, revealed sexually dimorphic ECM signatures that were independent of cellular growth profiles. Female OB matrices were enriched with type I collagen-specific proline and hydroxyproline and octacalcium phosphate with enhanced collagen intra-strand stability consistent with a matrix-dominant signature. Male OB matrices exhibited relatively lower type I collagen content and higher carbonated apatite resulting in an elevated mineral-to-matrix ratio indicative of advanced mineral maturation. After 24-hours of heterotypic culture of BMECs with OBs, BMEC numbers were 1.39-fold higher when in contact with male OBs. CM treatment of BMECs did not recapitulate these effects despite higher VEGF-A release from male OBs. ConclusionsSex differences in OB ECM are linked to divergent, contact-dependent regulation of BMEC behaviour. These findings suggest that differences in matrix maturation stat contribute to the sex-specific regulation of the skeletal vascular niche. Elucidating the mechanisms that regulate sex-specific OB-ECM production may reveal new therapeutic targets for selectively modulating pathological skeletal angiogenesis in men and women. SummaryBone is a sexually dimorphic organ, with men and women differing in bone size, strength and risk of fracture. The skeletal vasculature is essential for bone growth and repair, with bone forming osteoblast (OB) cells influencing blood vessel development through the skeletal extracellular matrix (ECM). Although the interactions between OB and vascular cells are crucial for lifelong skeletal health, it is not yet known whether sex differences in bone structure between men and women arise from differences in OB activity, or whether this divergence is driven by sex differences in blood vessel growth. Here, we show that male and female mouse OBs deposit distinct ECMs that differentially influence vascular endothelial cell behaviour. Female OBs produce a collagen-rich matrix with low mineral content. In contrast, male OB matrices contain less collagen and more mineral while releasing elevated levels of blood vessel promoting VEGF-A than females. When placed directly onto these OBs, vascular cell growth was greater when in contact with male than female OBs. Notably, this sex-dependent effect requires direct contact between both cell types and was not reproduced by exposure to OB-derived substances alone. These findings identify a cellular mechanism by which sex differences in OB matrix composition influences vascular cell behaviour in bone. Understanding how OB-vascular interactions differ by sex may help explain variation in bone health, healing capacity and disease risk between men and women. Further, our approach may support the discovery of new therapeutic targets that support bone growth and repair while targeting abnormal blood vessel growth in a sex-specific manner. HighlightsO_LIPrimary OBs from male and female C57BL/6 mouse long bones synthesise compositionally distinct ECMs. C_LIO_LIFemale OB matrices are type I collagen-rich and enriched with octacalcium phosphate, whereas male OB matrices contain less type I collagen and higher levels of carbonated apatite. C_LIO_LIBone marrow-derived endothelial cell (BMEC) growth is enhanced in heterotypic cocultures with male, but not female, OBs after 24 hours. C_LIO_LIMale OBs release higher levels of the pro-angiogenic factor VEGF-A than female OBs. C_LIO_LIThe sex-specific effects of the OB ECM on BMECs is contact-dependent and are not reproduced by treatment with OB-derived conditioned media. C_LI

RNF43 and ZNRF3 are transmembrane E3 ubiquitin ligases that negatively regulate Wnt signaling by promoting ubiquitination and degradation of Frizzled receptors. Loss of either gene enhances Wnt/{beta}-catenin signaling and has been linked to tumorigenesis. Wnt signaling is a key regulator of skeletal development and bone homeostasis, and pharmacologic activation of this pathway is an established therapy for osteoporosis. In Xenopus laevis, simultaneous disruption of rnf43 and znrf3 results in supernumerary limb formation; however, their roles in mammalian limb development and skeletal maintenance remain unclear. We demonstrate that mice homozygous for null alleles of both Rnf43 and Znrf3 do not develop supernumerary limbs. Because activation of Wnt/{beta}-catenin signaling in osteoblasts increases bone mass, we hypothesized that osteoblast-specific deletion of Rnf43 and/or Znrf3 would produce a high-bone-mass phenotype. Instead, osteoblast-specific loss of Znrf3 resulted in age-and sex-dependent reductions in trabecular bone mass, characterized by decreased bone mineral density and bone volume fraction, reduced trabecular number, and increased trabecular separation. Cortical bone exhibited increased cross-sectional size with reduced cortical area fraction and altered structural properties, while tissue mineral density was unchanged. In contrast, deletion of Rnf43 had minimal skeletal effects, and combined deletion of both genes did not exacerbate the phenotype observed with loss of Znrf3 alone. These findings identify Znrf3 as the dominant functional paralog regulating bone architecture in mature osteoblasts and underscore the importance of evaluating skeletal geometry when modulating upstream Wnt regulators.

Osteoblasts generate bone by secreting collagen and mineralizing it in response to various signaling cues. We have previously shown that the majority of ATP generated by differentiated osteoblasts in response to glucose is through glycolysis in contrast to undifferentiated cells that are more dependent on oxidative phosphorylation. To confirm our previous findings, metabolomics was performed for unlabeled polar metabolites, revealing elevated glycolytic metabolites at the later stages of differentiation. Krebs cycle (TCA cycle) metabolites were also changed confirming metabolic rerouting with differentiation. We hypothesized that an increase in mitophagy shifts ATP generation towards glycolysis resulting in the observed bioenergetic and metabolic changes. Utilizing calvarial osteoblasts isolated from a mitophagy reporter mouse model (MitoQC), an increase in mitophagy and the mitophagy receptor, Bnip3, was observed with osteoblast differentiation. KD of Bnip3 in osteoblasts inhibited differentiation and mineralization arising from impaired mitochondrial function. In vivo, male Bnip3 null mice exhibited a significant decrease in osteoblast numbers resulting in lower bone mass. Mechanistically we identified decreased fusion and increased fission factors, impaired stress signaling and increased proapoptotic factors in the absence of Bnip3. These data demonstrate for the first time that BNIP3 expression and mitophagy during osteoblast differentiation are necessary for relieving mitochondrial stress to maintain optimal bone mass.

Purpose To determine whether clinically significant weight loss (>5% of body weight) is associated with slower 2-year knee cartilage degeneration in individuals with and without radiographic osteoarthritis. This study used a cartilage structural assessment score derived from the spatial distribution of cartilage thickness, referred to as the Cartilage Thickness Score (CTh-Score). It is based on cartilage thickness patterns and scores the cartilage between 0 and 100, with higher scores indicating greater severity. Methods We conducted a retrospective matched cohort study within the Osteoarthritis Initiative. High-resolution cartilage thickness maps (CTh-Maps), along with their corresponding CTh-Score, were extracted from a public repository. Participants with complete radiographic and MRI data at baseline and 24 months were stratified by baseline Kellgren-Lawrence (KL) grade into non-radiographic OA (non-ROA; KL<2) and radiographic OA (ROA; KL>=2). Within strata, cases (>5% 2-year weight loss) were propensity score-matched 1:2 to weight-stable controls on age, sex, height, weight, KL grade, joint space width (JSW), KOOS Pain, baseline CTh-Score, and mean cartilage thickness in the medial and lateral femoral and tibial compartments. The primary outcome was 2-year change (delta) in CTh-Score, where higher values indicate worsening. Secondary outcomes were delta JSW, delta regional mean cartilage thickness, and delta KOOS Pain. Non-parametric tests were used. Results We included 164 cases and 328 controls in non-ROA, and 266 cases and 532 controls in ROA. Median (interquartile range) weight loss was -6.10 kg (-8.90, -4.70) versus +0.30 kg (-1.30, 2.20) in non-ROA and -6.80 kg (-9.10, -5.02) versus +0.40 kg (-1.40, 2.82) in ROA (both p<0.001). Weight loss was associated with significantly smaller 2-year increases in CTh-Score: in non-ROA, median 1.58 (0.61, 6.53) vs 3.14 (0.44, 7.12) (p=0.005); in ROA, median 1.69 (0.97, 6.71) vs 2.90 (0.19, 7.38) (p=0.004). No between-group differences were detected for delta JSW or delta regional mean cartilage thickness in any of the 4 ROIs. A trend toward greater KOOS Pain improvement with weight loss was observed in ROA: 2.75 (-3.35, 13.40) vs 0.00 (-5.60, 8.40) (p=0.06). Conclusions Achieving >5% weight loss over 2 years is associated with approximately 50% lower progression in median cartilage degeneration, as assessed by CTh-Score, in both non-ROA and ROA. No change was observed with conventional structural metrics. These findings support weight management as a structural disease-modifying strategy and highlight CTh-Score as a sensitive endpoint.

Background: Traditional bone scintigraphy for detecting malignant bone metastases is limited by suboptimal accuracy and radiation exposure. Whole-body magnetic resonance imaging (WB-MRI), while an alternative, requires lengthy scan times and high patient compliance. Purpose: To develop a novel, rapid whole body bone screening (WB-RBS) MRI protocol and evaluate its diagnostic performance for bone metastasis detection. Materials and Methods: Patients with pathologically confirmed malignancies and healthy controls were prospectively enrolled. All participants underwent WB-RBS (acquisition time: about 10 min); patients additionally underwent WB-MRI (about 70 min). Three radiologists, blinded to clinical data, independently evaluated the images for bone metastases. A consensus expert diagnosis served as the reference standard to calculate the diagnostic performance of WB-RBS. Specificity was further assessed in the healthy control group. Results: Seventy patients and 19 healthy controls were included. WB-RBS demonstrated excellent inter-reader agreement at the patient level. Compared with the reference standard, WB-RBS achieved an accuracy of 77.1%-91.4% at the patient level and a slightly lower accuracy (70.6%-82.5%) at the lesion level. At diagnostic confidence thresholds 1-3, the correlations between WB-RBS ratings and the reference standard were statistically significant for both patient- and lesion-level analyses. Conclusion: WB-RBS showed favorable inter-reader agreement and high accuracy for bone metastasis screening at the patient level, while substantially reducing scan time and cost. Its rapid, radiation-free nature and high accessibility offer distinct clinical advantages, supporting its potential as an alternative screening tool to conventional bone scintigraphy.

BackgroundBone graft biomaterials play a critical role in bone regeneration by influencing osteoblast differentiation and mineralization. However, comparative data regarding the osteogenic potential of commonly used graft materials under standardized conditions remain limited. Method and materialIn this in vitro experimental study, osteoblast-like cells (MG-63) were cultured with four bone graft materials, including Bio-Oss, Cerasorb, Bio-Tiss Cerabone, and Pro Osteon. The relative mRNA expression of osteogenic markers (COL1 and OPN) was evaluated at 1, 7, 14, and 21 days using real-time PCR. Alkaline phosphatase (ALP) activity and mineralization capacity were also assessed using colorimetric assay and Alizarin Red staining. Data were analyzed using one-way ANOVA and Tukey post hoc test (P < 0.05). ResultsSignificant differences were observed among the tested materials across all evaluated parameters. Bio-Oss and Cerasorb demonstrated higher gene expression levels and ALP activity compared to Bio-Tiss Cerabone and Pro Osteon (P < 0.05). Mineralization analysis showed significantly greater calcium deposition in the Bio-Oss and Cerasorb groups, whereas Pro Osteon consistently exhibited the lowest osteogenic performance. ConclusionBone graft biomaterials significantly influence osteogenic activity in osteoblast-like cells. Bio-Oss and Cerasorb showed superior osteogenic potential, while Pro Osteon demonstrated weaker performance. These findings highlight the importance of material properties in optimizing bone regeneration.

BackgroundKidney stones, a prevalent urological disorder, are increasingly associated with potential skeletal health issues, including reduced bone mineral density (BMD) and an elevated risk of osteoporosis. However, the underlying mechanisms and subgroup-specific associations have not yet been adequately explored. MethodsThis study used data from a nationally representative survey with a weighted complex sampling design. A total of 6,464 participants were enrolled in the study. We performed weighted and unweighted comparative analyses, multivariate linear regression, mediation analysis, and subgroup evaluations to examine the association between kidney stones and BMD of the femoral neck and lumbar spine. Potential mediators, including the systemic immune-inflammation index (SII), estimated glomerular filtration rate (eGFR), and calcium-to-phosphorus (CaP) ratio, were investigated. ResultsThe presence of kidney stones was significantly associated with lower femoral neck BMD ({beta} =-0.015, p = 0.046) after adjusting for confounding factors. The CaP ratio was identified as a significant mediator (average causal mediation effect [ACME] = 0.00077, p = 0.028), whereas the SII and eGFR did not show significant mediating effects. Stratified analyses revealed stronger associations in participants aged < 50 years and in those without chronic kidney disease (CKD). No significant interactions according to gender were detected. ConclusionKidney stones are independently associated with reduced BMD, which is partially mediated by altered calcium-phosphorus homeostasis. These findings highlight the importance of monitoring bone health in patients with kidney stones, particularly in younger and non-CKD populations, and suggest that dietary mineral balance may play a critical role in bone-stone interaction.