Trabecular Bone Loss Research Articles

Anaerostipes caccae CML199 enhances bone development and counteracts aging-induced bone loss through the butyrate-driven gut–bone axis: the chicken model

BackgroundThe gut microbiota is a key regulator of bone metabolism. Investigating the relationship between the gut microbiota and bone remodeling has revealed new avenues for the treatment of bone-related disorders. Despite significant progress in understanding gut microbiota-bone interactions in mammals, research on avian species remains limited. Birds have unique bone anatomy and physiology to support egg-laying. However, whether and how the gut microbiota affects bone physiology in birds is still unknown. In this study, we utilized laying hens as a research model to analyze bone development patterns, elucidate the relationships between bone and the gut microbiota, and mine probiotics with osteomodulatory effects.ResultsAging led to a continuous increase in bone mineral density in the femur of laying hens. The continuous deposition of medullary bone in the bone marrow cavity of aged laying hens led to significant trabecular bone loss and weakened bone metabolism. The cecal microbial composition significantly shifted before and after sexual maturity, with some genera within the class Clostridia potentially linked to postnatal bone development in laying hens. Four bacterial strains associated with bone development, namely Blautia coccoides CML164, Fournierella sp002159185 CML151, Anaerostipes caccae CML199 (ANA), and Romboutsia lituseburensis CML137, were identified and assessed in chicks with low bacterial loads and chicken primary osteoblasts. Among these, ANA demonstrated the most significant promotion of bone formation both in vivo and in vitro, primarily attributed to butyrate in its fermentation products. A long-term feeding experiment of up to 72 weeks confirmed that ANA enhanced bone development during sexual maturity by improving the immune microenvironment of the bone marrow in laying hens. Dietary supplementation of ANA for 50 weeks prevented excessive medullary bone deposition and mitigated aging-induced trabecular bone loss.ConclusionsThese findings highlight the beneficial effects of ANA on bone physiology, offering new perspectives for microbial-based interventions for bone-related disorders in both poultry and possibly extending to human health.3YvVhM8B6L-RxYm8AZskZyVideo Graphical

Circulating Baseline CXCR3+Th2 and Th17 Cell Proportions Correlate With Trabecular Bone Loss After 48 Weeks of Biological Treatment in Early Rheumatoid Arthritis.

The high prevalence of osteoporosis in rheumatoid arthritis (RA) is due to inflammation that stimulates differentiation of osteoclasts, a process involving circulating monocytes and T cell-derived factors. The aim of this study was to evaluate relations between circulating monocytes, T cell subsets, and changes in bone characteristics before and after treatment with biological disease-modifying antirheumatic drugs (bDMARDs) in RA. Thirty patients with untreated early RA who met the American College of Rheumatology/EULAR 2010 criteria were included. Data were collected before and 48 weeks after treatment with methotrexate (MTX) together with one of three bDMARDs (abatacept, tocilizumab, or certolizumab pegol). Disease activity was measured using the Clinical Disease Activity Index, swollen or tender joint counts, C-reactive protein levels, and erythrocyte sedimentation rates. Proportions of monocyte and CD4+ T cell subsets in blood samples were analyzed by flow cytometry. Bone densitometry was performed using high-resolution peripheral quantitative computed tomography (HR-pQCT). HR-pQCT revealed an overall decrease in cortical (P = 0.009) and trabecular (P = 0.034) bone mineral density, although a subset of patients showed no bone loss after 48 weeks of treatment. The overall bone loss was not associated with age, body mass index, sex, intraarticular glucocorticoid injections, or baseline disease activity. Loss of trabecular bone volume fraction correlated with high proportions of circulating CXCR3+Th2 cells (r = -0.38, P = 0.04) and CXCR3+Th17 cells (r = -0.36, P = 0.05) at baseline. Similarly, no loss of trabecular bone volume fraction correlated with high proportions of regulatory T cells (r = 0.4, P = 0.03) at baseline. However, the associations were not significant when corrected for confounders and multiple testing. MTX together with bDMARDs efficiently reduce disease activity but only prevent bone loss in a subset of patients with RA after 48 weeks of treatment. The correlations of circulating baseline T helper cell and regulatory T cell populations with trabecular bone changes suggest a potential novel role for these cells in systemic bone homeostasis during early RA.

Osteoclastic ATP6AP2 maintains β-catenin levels to prevent hyper-osteoclastic activation and trabecular bone-loss.

Osteoclast (OC) formation and bone resorption are regulated by several factors, including V-ATPase, Wnt/β-Catenin, and RANKL/RANK signaling. ATP6AP2, also known as the prorenin receptor (PRR), is an accessory subunit of V-ATPase and a regulator of Wnt/β-Catenin signaling. While the V-ATPase subunit ATP6AP1 is essential for osteoclast formation and function, the role of ATP6AP2 in OC-lineage cells is less clear. Here, we provide evidence that ATP6AP2 plays a negative role in osteoclastogenesis and function, contrasting with the positive role of ATP6AP1. Mice with conditional knockout (cKO) of ATP6AP2 in OCs (Atp6ap2LysM) exhibit trabecular bone loss, likely due to the increased osteoclastogenesis and activity, since bone formation rates are comparable to control mice. In vitro assays using bone marrow macrophages (BMMs) show that Atp6ap2LysM cultures have more RANKL-induced TRAP+ OC-like cells and increased bone resorptive activity. Further studies reveal that while RANKL signaling and V-ATPase activity are normal, in ATP6AP2 KO OCs, but not BMMs, have reduced basal levels of Wnt/β-Catenin pathway proteins, such as LRP5/6 and β-Catenin, compared to controls. Wnt3A treatment induces β-Catenin and suppresses osteoclast formation in both control and ATP6AP2 KO OC-lineage cells, indicating that Wnt/β-Catenin signaling negatively regulates OC-formation and operates independently of ATP6AP2. Overall, these results suggest that ATP6AP2 is critical for maintaining basal levels of LRP5/6 receptors and β-Catenin in osteoclasts, thus acting as a negative regulator of osteoclastogenesis and activation.

Long-Term Follow-up After Ovariectomy Reveals Correlations Between Bone Marrow Adiposity and Trabecular Bone Quality in the Proximal Metaphysis of Tibiae in Rats.

This study aimed to evaluate the correlation between BMAT and bone quality, describe the long-term effects of ovariectomy on bone, and investigate BMAT's spatial distribution. Fifteen-months-old female Sprague‒Dawley rats were studied, comparing ovariectomized (OVX, n = 22) and sham-operated (SHAM, n = 11) groups at 6 months. Tibias were analyzed for bone microarchitecture, BMAT (microcomputed tomography), mineral parameters (quantitative backscattered electron imaging), and bone composition (Raman microspectroscopy). The OVX tibias showed severe trabecular bone loss (lower bone volume/total volume, p < 0.001) with increased BMAT (higher adipose volume per marrow volume, p < 0.001), decreased mineral content (lower calcium concentration, p < 0.001), and altered organic components (lower mineral/matrix ratio in new bone, p = 0.03 trabecular surface, p < 0.001 trabecular core). When the data are pooled over both groups (SHAM and OVX), the adipose volume/marrow volume ratio was negatively correlated with bone volume/total volume (r = - 0.79, p < 0.001) and mineral/matrix ratio (r = - 0.37, p = 0.04 trabecular surface; r = - 0.65, p < 0.001 trabecular core) and positively correlated with crystallinity (r = 0.55, p = 0.001 trabecular surface; r = 0.49, p = 0.006 trabecular core). The mineral/matrix ratio of trabecular surface new bone was strongly negatively correlated with the adipose compartment nearest to the bone surface. These findings suggest mechanisms underlying BMAT's role in bone resorption.

7500 Effect Of Orchiectomy On Bone Microarchitecture In Male Mice With Kidney Disease

Abstract Disclosure: D. Wu: None. A. Patwardhan: None. O. Marks: None. Y. Komaru: None. E. Kefalogianni: None. R. Aurora: None. S. Dhindsa: None. A. Herrlich: None. Background: Chronic kidney disease (CKD) leads to decreased bone density and increased fracture risk. In males, an additional factor contributes to the low bone density. Around half of the men with CKD have low serum testosterone concentrations. We hypothesized that CKD and low testosterone would have an additive and detrimental effect on bone. Methods: Forty male C57BL/6 mice were divided into 4 groups: 1) renal injury, induced by ischemia-induced reperfusion (IRI) and sham orchidectomy (IRI-sham, N=8) at 2 months of age; 2) orchidectomy (ORX), performed 4 weeks after IRI (IRI + ORX, N=11); 3) sham-ORX, N=9; and 4) sham-sham surgery, N=12. 12 weeks after IRI, the mice developed renal fibrosis and decreased glomerular filtration rate, indicative of CKD. The mice were sacrificed when they were 7 months old. Femur and tibia were harvested for both histology and μCT analysis. Results: Bone volume to total volume fraction (BV/TV) was lower in the IRI-ORX (0.06±0.02) and sham-ORX (0.08±0.02), as compared to IRI-sham (0.10±0.03, p&amp;lt;0.05) and sham-sham group (0.14±0.03, p&amp;lt;0.05) respectively. Similarly, the volumetric bone mineral density (vBMD) in IRI-ORX (93±27 mgHA/cm3) and sham-ORX (112±39 mgHA/cm3) groups were lower than IRI-sham (150±43 mgHA/cm3, p&amp;lt;0.05) and sham-sham (187±30 mgHA/cm3, p&amp;lt;0.05) mice. Trabecular number (Tb.N) was decreased in the IRI-ORX group (2.7±0.7 #/mm) compared to IRI-sham group (4.1±1.1 #/mm, p&amp;lt;0.05). Tb.N was also lower in sham-ORX (3.2±1.1 #/mm) mice than sham-sham (4.5±0.2 #/mm), but not IRI-sham mice. In contrast, trabecular thickness (Tb.Th) was lower in IRI-ORX (0.035±0.002 mm) and IRI-sham (0.038±0.002 mm) compared to sham-ORX (0.045±0.005 mm) and sham-sham (0.047±0.005 mm, p&amp;lt;0.05). Trabecular spacing (Tb.Sp) was increased by 47% in IRI-ORX group compared to IRI-sham group (0.26±0.09 mm). Decreased trabecular numbers and increased spacing results in reduced connectivity density (Conn.Den), which was decreased by 60% in the IRI-ORX sham-ORX groups as compared to sham-sham group (423±58 #/mm3, p&amp;lt;0.05). 2 way ANOVA analysis showed that ORX significantly contributed to the variance in BV/TV (p&amp;lt;0.001), vBMD (p&amp;lt;0.001), Tb.N (p&amp;lt;0.01), Tb.Sp (p&amp;lt;0.01) and Conn.Den (p&amp;lt;0.001), while IRI contributed to Tb.Th (p&amp;lt;0.0001). There was no significant interaction between IRI and ORX in all endpoints. Conclusions: Taken together, these data indicate that even in the presence of established CKD, ORX has a greater effect on bone mass. ORX decreased trabecular number (Tb.N) and increased trabecular spacing (Tb.Sp) to a greater extent than IRI. IRI decreased trabecular thickness (Tb.Th) while ORX had no effect on that parameter. Trabecular bone loss starts by trabecular thinning. Eventually, the trabeculae will be completely resorbed, resulting in decreased trabecular numbers and increased spacing. Our data indicate that IRI and ORX affect bone at different time points. Presentation: 6/1/2024

8711 The Effect of Testosterone Therapy Upon Bone Remodelling in Testosterone Deficient APOE-/- Mice Fed a High Fat Diet

Abstract Disclosure: A. Williamson: None. L. Bateman: None. C. LeMaitre: None. T.H. Jones: None. N. Aberdein: None. D.M. Kelly: None. Introduction: Low testosterone can lead to bone loss in males, but the mechanisms are not fully characterised. This study investigates the effects of testosterone depletion, and subsequent testosterone treatment on parameters of bone remodeling in a murine model of cardiometabolic disease. Methods: At 8 weeks of age, high-fat diet-fed ApoE-/- mice were randomised into three groups: sham surgery + placebo treatment (control, n=9), orchidectomy + placebo treatment (n =8), and orchidectomy + testosterone treatment (n=10). 25 week old mice were sacrificed and tissues collected for analysis. Left tibiae were decalcified, paraffin embedded and sectioned prior to immunostaining of bone turnover markers including receptor activator of nuclear factor κB ligand (RANKL), Osteoprotegerin (OPG), runx2, Alkaline Phosphatase (ALP), adiponectin and marrow lipid content. Right tibiae underwent mechanical 3-point bend testing at 0.05mm/s using a CellScale Univert. Results: µCT demonstrated a significant decrease in trabecular bone volume, number, and bone mineral density (BMD) and increased trabecular thickness in orchidectomised mice compared to controls. These parameters returned to control levels in testosterone treated orchiectomised mice. No significant differences were observed in cortical bone. Lipid deposition within the bone marrow was significantly increased in testosterone deficient mice compared to testosterone replete mice. No significant differences in ALP immunopositivity were detected between groups, and runx2 was significantly decreased in orchiectomised mice treated with testosterone compared to controls. The ratio of RANKL/OPG immunopositivity was significantly increased in testosterone deficient mice compared to testosterone replete mice. 3-point bending demonstrated no significant differences in maximal force between groups despite a downward trend in orchiectomised groups compared to controls. Osteoclast number quantified from TRAP-stained sections was not different between groups. Discussion: Testosterone depletion accelerates trabecular bone loss, mediated by increased osteoclastogenesis via the RANKL/OPG pathway and increased bone marrow adiposity, an effect reversed by testosterone treatment. While this study highlights the benefits of testosterone upon trabecular bone health in male mice these changes may not alter fracture risk as 3-point-bend maximal force was not affected. Presentation: 6/2/2024

Europium-Containing Nanospheres for Treating Ovariectomy-Induced Osteoporosis: Targeted Bone Remodeling and Macrophage Polarization Modulation.

Osteoporosis, characterized by reduced bone mass and structural deterioration, poses a significant healthcare challenge. Traditional treatments, while effective in reducing fracture risks, are often limited by side effects. This study introduces a novel nanocomplex, europium (Eu) ions-doped superparamagnetic iron oxide (SPIO) nanocrystals encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanospheres, abbreviated as SPIO:Eu@PLGA nanospheres, as a potential therapeutic agent for osteoporosis by modulating macrophage polarization, enhancing osteoblast differentiation and inhibiting osteoclastogenesis. SPIO and SPIO:Eu nanocrystals were synthesized through pyrolysis and encapsulated in PLGA using an emulsification method. To evaluate the impact of SPIO:Eu@PLGA nanospheres on macrophage reprogramming and reactive oxygen species (ROS) production, flow cytometry analysis was conducted. Furthermore, an ovariectomized (OVX) rat model was employed to assess the therapeutic efficacy of SPIO:Eu@PLGA nanospheres in preventing the deterioration of osteoporosis. In vitro, SPIO:Eu@PLGA nanospheres significantly attenuated M1 macrophage activation induced by lipopolysaccharides, promoting a shift towards the M2 phenotype. This action is linked to the modulation of ROS and the NF-κB pathway. Unlike free Eu ions, which do not achieve similar results when not incorporated into the SPIO nanocrystals. SPIO:Eu@PLGA nanospheres enhanced osteoblast differentiation and matrix mineralization while inhibiting RANKL-induced osteoclastogenesis. In vivo studies demonstrated that SPIO:Eu@PLGA nanospheres effectively targeted trabecular bone surfaces in OVX rats under magnetic guidance, preserving their structure and repairing trabecular bone loss by modulating macrophage polarization, thus restoring bone remodeling homeostasis. The study underscores the critical role of Eu doping in boosting the anti-osteoporotic effects of SPIO:Eu@PLGA nanospheres, evident at both cellular and tissue levels in vitro and in vivo. The inclusion of Eu into SPIO matrix suggests a novel approach for developing more effective osteoporosis treatments, particularly for conditions induced by OVX. This research provides essential insights into SPIO:Eu@PLGA nanospheres as an innovative osteoporosis treatment, addressing the limitations of conventional therapies through targeted delivery and macrophage polarization modulation.

Hydroxychloroquine and a low antiresorptive activity bisphosphonate conjugate prevent and reverse ovariectomy-induced bone loss in mice through dual antiresorptive and anabolic effects

Osteoporosis remains incurable. The most widely used antiresorptive agents, bisphosphonates (BPs), also inhibit bone formation, while the anabolic agent, teriparatide, does not inhibit bone resorption, and thus they have limited efficacy in preventing osteoporotic fractures and cause some side effects. Thus, there is an unmet need to develop dual antiresorptive and anabolic agents to prevent and treat osteoporosis. Hydroxychloroquine (HCQ), which is used to treat rheumatoid arthritis, prevents the lysosomal degradation of TNF receptor-associated factor 3 (TRAF3), an NF-κB adaptor protein that limits bone resorption and maintains bone formation. We attempted to covalently link HCQ to a hydroxyalklyl BP (HABP) with anticipated low antiresorptive activity, to target delivery of HCQ to bone to test if this targeting increases its efficacy to prevent TRAF3 degradation in the bone microenvironment and thus reduce bone resorption and increase bone formation, while reducing its systemic side effects. Unexpectedly, HABP-HCQ was found to exist as a salt in aqueous solution, composed of a protonated HCQ cation and a deprotonated HABP anion. Nevertheless, it inhibited osteoclastogenesis, stimulated osteoblast differentiation, and increased TRAF3 protein levels in vitro. HABP-HCQ significantly inhibited both osteoclast formation and bone marrow fibrosis in mice given multiple daily PTH injections. In contrast, HCQ inhibited marrow fibrosis, but not osteoclast formation, while the HABP alone inhibited osteoclast formation, but not fibrosis, in the mice. HABP-HCQ, but not HCQ, prevented trabecular bone loss following ovariectomy in mice and, importantly, increased bone volume in ovariectomized mice with established bone loss because HABP-HCQ increased bone formation and decreased bone resorption parameters simultaneously. In contrast, HCQ increased bone formation, but did not decrease bone resorption parameters, while HABP also restored the bone lost in ovariectomized mice, but it inhibited parameters of both bone resorption and formation. Our findings suggest that the combination of HABP and HCQ could have dual antiresorptive and anabolic effects to prevent and treat osteoporosis.

Passive bicycle training stimulates epiphyseal bone formation and restores bone integrity independent of locomotor recovery in a rat spinal cord injury model.

It is unknown whether activity-based physical therapy (ABPT) modalities that mobilize the paralyzed limbs improve bone integrity at the highly fracture-prone epiphyseal regions of the distal femur and proximal tibia following severe spinal cord injury (SCI). In this study, 4-mo-old skeletally mature littermate-matched male Sprague-Dawley rats received either SHAM surgery or severe contusion SCI. At 1 wk postsurgery, SCI rats were stratified to undergo no-ABPT, two 20-min bouts/day of quadrupedal bodyweight-supported treadmill training (qBWSTT), or hindlimb passive isokinetic bicycle (cycle) training, 5 days/wk for another 3 wk. We assessed locomotor recovery and plantar flexor muscle mass, tracked cancellous and cortical bone microstructure at the distal femoral and proximal tibial epiphyses using in vivo microcomputed tomography (microCT), and evaluated bone turnover at the tibial epiphysis with histomorphometry. All SCI animals displayed persistent hindlimb paralysis and pervasive muscle atrophy. Over the initial 2 wk, which included 1 wk of no exercise and 1 wk of ABPT acclimation, a similar magnitude of bone loss developed in all SCI groups. Thereafter, cancellous bone loss and cortical bone decrements increased in the SCI no-ABPT group. qBWSTT attenuated this trabecular bone loss but did not prevent the ongoing cortical bone deficits. In comparison, twice-daily cycle training increased the number and activity of osteoblasts versus other SCI groups and restored all bone microstructural parameters to SHAM levels at both epiphyseal sites. These data indicate that a novel passive isokinetic cycle training regimen reversed cancellous and cortical bone deterioration at key epiphyseal sites after experimental SCI via osteoblast-mediated bone anabolic mechanisms, independent of locomotor recovery or increased muscle mass.NEW & NOTEWORTHY This study was the first to assess how quadrupedal bodyweight-supported treadmill training or passive isokinetic bicycle (cycle) training impacts bone recovery at the distal femoral and proximal tibial epiphyses in a rat model of severe contusion spinal cord injury. Our results demonstrate that passive isokinetic cycle training completely restored cancellous and cortical bone microstructural parameters at these sites via osteoblast-mediated bone anabolic actions, independent of locomotor recovery or increased plantar flexor muscle mass.

Bone marrow adipogenic lineage precursors are the major regulator of bone resorption in adult mice.

Bone resorption by osteoclasts is a critical step in bone remodeling, a process important for maintaining bone homeostasis and repairing injured bone. We previously identified a bone marrow mesenchymal subpopulation, marrow adipogenic lineage precursors (MALPs), and showed that its production of RANKL stimulates bone resorption in young mice using Adipoq-Cre. To exclude developmental defects and to investigate the role of MALPs-derived RANKL in adult bone, we generated inducible reporter mice (Adipoq-CreER Tomato) and RANKL deficient mice (Adipoq-CreER RANKLflox/flox, iCKO). Single cell-RNA sequencing data analysis, lineage tracing, and in situ hybridization revealed that Adipoq+ cells contain not only MALPs but also late mesenchymal progenitors capable of osteogenic differentiation. However, RANKLmRNA was only detected in MALPs, but not in osteogenic cells. RANKL deficiency in MALPs induced at 3 months of age rapidly increased trabecular bone mass in long bones as well as vertebrae within 1 month due to diminished bone resorption but had no effect on the cortical bone. Ovariectomy (OVX) induced trabecular bone loss at both sites. RANKL depletion either before OVX or at 6 weeks post OVX protected and restored trabecular bone mass. Furthermore, bone healing after drill-hole injury was delayed in iCKO mice. Together, our findings demonstrate that MALPs play a dominant role in controlling trabecular bone resorption and that RANKL from MALPs is essential for trabecular bone turnover in adult bone homeostasis, postmenopausal bone loss, and injury repair.

Effect of 28 days treatment of baricitinib on mechanical allodynia, osteopenia, and loss of nerve fibers in an experimental model of type-1 diabetes mellitus.

Type-1 diabetes mellitus (T1DM) is associated with numerous health problems, including peripheral neuropathy, osteoporosis, and bone denervation, all of which diminish quality of life. However, there are relatively few therapies to treat these T1DM-related complications. Recent studies have shown that Janus kinase (JAK) inhibitors reverse aging- and rheumatoid arthritis-induced bone loss and reduce pain associated with peripheral nerve injuries, and rheumatoid arthritis. Thus, we assessed whether a JAK1/JAK2 inhibitor, baricitinib, ameliorates mechanical pain sensitivity (a measure of peripheral neuropathy), osteoporosis, and bone denervation in the femur of mice with T1DM. Female ICR mice (13 weeks old) received five daily administrations of streptozotocin (ip, 50mg/kg) to induce T1DM. At thirty-one weeks of age, mice were treated with baricitinib (po; 40mg/kg/bid; for 28 days) or vehicle. Mechanical sensitivity was evaluated at 30, 33, and 35 weeks of age on the plantar surface of the right hind paw. At the end of the treatment, mice were sacrificed, and lower extremities were harvested for microcomputed tomography and immunohistochemistry analyses. Mice with T1DM exhibited greater blood glucose levels, hind paw mechanical hypersensitivity, trabecular bone loss, and decreased density of calcitonin gene-related peptide-positive and tyrosine hydroxylase-positive axons within the marrow of the femoral neck compared to control mice. Baricitinib treatment significantly reduced mechanical hypersensitivity and ameliorated sensory and sympathetic denervation at the femoral neck, but it did not reverse trabecular bone loss. Our findings suggest that baricitinib may represent a new therapeutic alternative to treat T1DM-induced peripheral neuropathy and bone denervation.

Mitigating aging and doxorubicin induced bone loss in mature mice via mechanobiology based treatments

Aging leads to a reduced anabolic response to mechanical stimuli and a loss of bone mass and structural integrity. Chemotherapy agents such as doxorubicin exacerbate the degeneration of aging skeleton and further subject older cancer patients to a higher fracture risk. To alleviate this clinical problem, we proposed and tested a novel mechanobiology-based therapy. Building upon prior findings that i) Yoda1, the Piezo1 agonist, promoted bone growth in young adult mice and suppressed bone resorption markers in aged mice, and ii) moderate tibial loading protected bone from breast cancer-induced osteolysis, we hypothesized that combined Yoda1 and moderate loading would improve the structural integrity of adult and aged skeletons in vivo and protect bones from deterioration after chemotherapy. We first examined the effects of 4-week Yoda1 (dose 5 mg/kg, 5 times/week) and moderate tibial loading (4.5 N peak load, 4 Hz, 300 cycles for 5 days/week), individually and combined, on mature mice (∼50 weeks of age). Combined Yoda1 and loading was found to mitigate age-associated cortical and trabecular bone loss better than individual interventions. As expected, the non-treated controls experienced an average drop of cortical polar moment of inertia (Ct.pMOI) by −4.3 % over four weeks and the bone deterioration occurred in the majority (64 %) of the samples. Relative to no treatment, loading alone, Yoda1 alone, and combined Yoda1 and loading increased Ct.pMOI by +7.3 %, +9.5 %, +12.0 % and increased the % of samples with positive Ct.pMOI changes by +32 %, +26 %, and +43 %, respectively, suggesting an additive protection of aging-related bone loss for the combined therapy. We further tested if the treatment efficacy was preserved in mature mice following two weeks (six injections) of doxorubicin at the dose of 2.5 or 5 mg/kg. As expected, doxorubicin increased osteocyte apoptosis, altered bone remodeling, and impaired bone structure. However, the effects induced by DOX were too severe to be rescued by Yoda1 and loading, alone or combined, although loading and Yoda1 individually, or combined, increased the number of mice showing positive responsiveness by 0 %, +15 %, and +29 % relative to no intervention after doxorubicin exposure. Overall, this study supported the potentials and challenges of the Yoda1-based strategy in mitigating the detrimental skeletal effects caused by aging and doxorubicin.

Improvement of bone mineral density and new vertebral fractures during 8 years of TNF-α inhibition in patients with axial spondyloarthritis

ObjectiveIn our prospective cohort with standardized bi-annual measurements of bone mineral density (BMD) and spinal radiographs, we evaluated the long-term course of BMD and the development of radiographic vertebral fractures (VFs) during 8 years of TNFi treatment in patients with radiographic axial spondyloarthritis (r-axSpA). MethodsConsecutive axSpA patients from the GLAS cohort receiving TNFi for ≥8 years were included. Patients who received anti-osteoporotic treatment were excluded. Lumbar spine (LS) BMD was assessed at baseline, 1 year and bi-annually using DEXA. Radiographic VFs were evaluated using the Genant classification. Results126 axSpA patients were included; 75 % male, mean age 42 ± 11 years, ASDAS 3.8 ± 0.8, median LS BMD Z-score -0.5 (IQR -1.4–0.7) and 20 % had radiographic VFs at baseline. Disease activity improved rapidly and sustained. LS BMD Z-score improved significantly up to 4 years compared to the previous time point and sustained thereafter. Median percentage of improvement compared to baseline was 8.9 % (2.8–15.8) and 7.2 % (2.2–14.7) after 4 and 8 years, respectively. Of 90 patients with baseline and 8-year radiographs, 14 (16 %) developed new VFs and 5 (6 %) showed an increase in severity of existing VFs. Of all 44 VFs present at 8 years, 30 % were grade 2 (n = 12) or grade 3 (n = 1). ConclusionIn r-axSpA patients treated with TNFi for 8 years, LS BMD Z-score increased significantly, especially during the first 4 year of treatment. Radiographic VFs continued to develop or progressed, irrespective of improvement in BMD. Therefore, clinical attention for trabecular bone loss is important in daily clinical practice.

Sex-Specific Effects of THRβ Signaling on Metabolic Responses to High Fat Diet in Mice.

Thyroid hormone (TH) plays a crucial role in regulating the functions of both bone and adipose tissue. Given that TH exerts its cholesterol-lowering effects in hepatic tissue through the TH receptor-β (TRβ), we hypothesized that TRβ agonist therapy using MGL3196 (MGL) would be effective in treating increased adiposity and bone loss in response to a 12-week high-fat diet (HFD) in adult C57BL/6J mice. Transcriptional and serum profiling revealed that HFD-induced leptin promoted weight gain in both males and females, but MGL only suppressed leptin induction and weight gain in males. In vitro studies suggest that estrogen suppresses MGL activity in adipocytes, indicating that estrogen might interfere with MGL-TRβ function. Compared to systemic adiposity, HFD reduced bone mass in male but not female mice. Paradoxically, MGL treatment reversed macroscopic bone mineral density loss in appendicular bones, but micro-CT revealed that MGL exacerbated HFD-induced trabecular bone loss, and reduced bone strength. In studies on the mechanisms for HFD effects on bone, we found that HFD induced Rankl expression in male femurs that was blocked by MGL. By ex vivo assays, we found that RANKL indirectly represses osteoblast lineage allocation of osteoprogenitors by induction of inflammatory cytokines TNFα, IL-1β, and CCL2. Finally, we found that MGL functions in both systemic adiposity and bone by nongenomic TRβ signaling, as HFD-mediated phenotypes were not rescued in TRβ147F knockout mice with normal genomic but defective nongenomic TRβ signaling. Our findings demonstrate that the negative effects of HFD on body fat and bone phenotypes are impacted by MGL in a gender-specific manner.

Caloric restriction reduces trabecular bone loss during aging and improves bone marrow adipocyte endocrine function in male mice.

Caloric restriction (CR) is a nutritional intervention that increases life expectancy while lowering the risk for cardio-metabolic disease. Its effects on bone health, however, remain controversial. For instance, CR has been linked to increased accumulation of bone marrow adipose tissue (BMAT) in long bones, a process thought to elicit detrimental effects on bone. Qualitative differences have been reported in BMAT in relation to its specific anatomical localization, subdividing it into physiological and potentially pathological BMAT. We here examine the local impact of CR on bone composition, microstructure and its endocrine profile in the context of aging. Young and aged male C57Bl6J mice were subjected to CR for 8 weeks and were compared to age-matched littermates with free food access. We assessed bone microstructure and BMAT by micro-CT, bone fatty acid and transcriptomic profiles, and bone healing. CR increased tibial BMAT accumulation and adipogenic gene expression. CR also resulted in elevated fatty acid desaturation in the proximal and mid-shaft regions of the tibia, thus more closely resembling the biochemical lipid profile of the distally located, physiological BMAT. In aged mice, CR attenuated trabecular bone loss, suggesting that CR may revert some aspects of age-related bone dysfunction. Cortical bone, however, was decreased in young mice on CR and remained reduced in aged mice, irrespective of dietary intervention. No negative effects of CR on bone regeneration were evident in either young or aged mice. Our findings indicate that the timing of CR is critical and may exert detrimental effects on bone biology if administered during a phase of active skeletal growth. Conversely, CR exerts positive effects on trabecular bone structure in the context of aging, which occurs despite substantial accumulation of BMAT. These data suggest that the endocrine profile of BMAT, rather than its fatty acid composition, contributes to healthy bone maintenance in aged mice.

Norisoboldine, a Natural Alkaloid from Lindera aggregata (Sims) Kosterm, Promotes Osteogenic Differentiation via S6K1 Signaling Pathway and Prevents Bone Loss in OVX Mice.

Norisoboldine (NOR) is a major isoquinoline alkaloid component in the traditional Chinese herbal plant Lindera aggregata (Sims) Kosterm, with previously reported anti-osteoclast differentiation and antiarthritis properties. However, the roles of NOR on osteoblasts, bone marrow mesenchymal stem cells (BMSCs), and osteoporosis in vivo have never been well established. This study investigates the ability of NOR to improve bone formation in vitro and in vivo. Osteoblasts and BMSCs are used to study the effect of NOR on osteogenic and adipogenic differentiation. It finds that NOR promotes osteogenic differentiation of osteoblasts and BMSCs, while inhibiting adipogenic differentiation of BMSCs by reducing the relative expression of peroxisome proliferator-activated receptorγ (Ppar-γ) and adiponectin, C1Q and collagen domain containing (Adipoq). Mechanistic studies show that NOR increases osteoblast differentiation through the mechanistic target of rapamycin kinase (mTOR)/ribosomal protein S6 kinase; polypeptide 1 (S6K1) pathway, and treatment with an mTOR inhibitor rapamycin blocked the NOR-induced increase in mineral accumulation. Finally, the study evaluates the therapeutic potential of NOR in a mouse model of ovariectomy (OVX)-induced bone loss. NOR prevents bone loss in both trabecular and cortical bone by increasing osteoblast number and phospho-S6K1 (p-S6K1) expression in osteoblasts. NOR effects in enhancing osteoblast-induced bone formation via S6K1 pathway, suggesting the potential of NOR in osteoporosis treatment by increasing bone formation.

Mitochondria-specific antioxidant MitoTEMPO alleviates senescence of bone marrow mesenchymal stem cells in ovariectomized rats.

Senescence in bone marrow mesenchymal stem cells (BMSCs), triggered by excessive oxidative stress, plays a crucial role in the onset of postmenopausal osteoporosis. Recent studies underscore the importance of mitochondrial rehabilitation and quality control as key determinants in the modulation of oxidative stress and cellular senescence. MitoTEMPO, a mitochondria-targeted antioxidant, has been shown to mitigate the heightened levels of reactive oxygen species (ROS). In our research, we observed that BMSCs from ovariectomized (OVX) rats displayed premature senescence, which was attributed to combined mitochondrial and lysosomal dysfunction, a condition that worsens with extended estrogen deprivation. Treatment with MitoTEMPO effectively reversed these effects, reinstating lysosomal functionality and suppressing the mitochondrial unfolded protein response (UPRmt). Subsequent in vivo experiments corroborated these observations, revealing that MitoTEMPO administration in OVX rats curtailed trabecular bone loss and reduced the expression of p53, HSP60, and CLPP in the trabecular bone region of the proximal tibia. Overall, our findings suggest that MitoTEMPO holds promise as a therapeutic agent to counteract senescence in OVX-BMSCs, offering a potential strategy for treating postmenopausal osteoporosis.

Effect of oxytocin receptor antagonist (GSK-221-149-A) on mandibular bone porosity in peri-menopausal rats

The period of peri-menopause (PMP) is characterized by hormonal fluctuations that impact the strength and health of bones. Oxytocin (OX), a small peptide known to be present in bone tissue, is the focus of this study. The objective of this research is to gain a better understanding of how OX precisely functions in the remodeling process of the mandibular bone. This understanding is seen as a crucial step in preventing the loss of both cortical and trabecular bone during the PMP. The current findings indicate that OX plays a role in preserving both compact and trabecular bone tissues, enhancing the mineral-to-matrix ratio, and regulating bone markers. Furthermore, it reduces porosity in both cortical and trabecular bone levels. Interestingly, these effects are reversed when an oxytocin receptor antagonist (GSK-221,149-A) is introduced, suggesting that OX’s bone-preserving action is primarily mediated through the oxytocin receptor, rather than other mechanisms.

Surgical restabilization reduces the progression of post-traumatic osteoarthritis initiated by ACL rupture in mice

ObjectivePeople who sustain joint injuries such as anterior cruciate ligament (ACL) rupture often develop post-traumatic osteoarthritis (PTOA). In human patients, ACL injuries are often treated with ACL reconstruction. However, it is still unclear how effective joint restabilization is for reducing the progression of PTOA. The goal of this study was to determine how surgical restabilization of a mouse knee joint following non-invasive ACL injury affects PTOA progression. DesignIn this study, 187 mice were subjected to non-invasive ACL injury or no injury. After injury, mice underwent restabilization surgery, sham surgery, or no surgery. Mice were then euthanized on day 14 or day 49 after injury/surgery. Functional analyses were performed at multiple time points to assess voluntary movement, gait, and pain. Knees were analyzed ex vivo with micro-computed tomography, RT-PCR, and whole-joint histology to assess articular cartilage degeneration, synovitis, and osteophyte formation. ResultsBoth ACL injury and surgery resulted in loss of epiphyseal trabecular bone (-27-32%) and reduced voluntary movement at early time points. Joint restabilization successfully lowered OA score (-78% relative to injured at day 14, p<0.0001), and synovitis scores (-37% relative to injured at day 14, p=0.042), and diminished the formation of chondrophytes/osteophytes (-97% relative to injured at day 14, p<0.001, -78% at day 49, p<0.001). ConclusionsThis study confirmed that surgical knee restabilization was effective at reducing articular cartilage degeneration and diminishing chondrophyte/osteophyte formation after ACL injury in mice, suggesting that these processes are largely driven by joint instability in this mouse model. However, restabilization was not able to mitigate the early inflammatory response and the loss of epiphyseal trabecular bone, indicating that these processes are independent of joint instability.

Novel Nonthermal Atmospheric Plasma Irradiation of Titanium Implants Promotes Osteogenic Effect in Osteoporotic Conditions.

Osteoporosis is a metabolic disease characterized by bone density and trabecular bone loss. Bone loss may affect dental implant osseointegration in patients with osteoporosis. To promote implant osseointegration in osteoporotic patients, we further used a nonthermal atmospheric plasma (NTAP) treatment device previously developed by our research group. After the titanium implant (Ti) is placed into the device, the working gas flow and the electrode switches are turned on, and the treatment is completed in 30 s. Previous studies showed that this NTAP device can remove carbon contamination from the implant surface, increase the hydroxyl groups, and improve its wettability to promote osseointegration in normal conditions. In this study, we demonstrated the tremendous osteogenic enhancement effect of NTAP-Ti in osteoporotic conditions in rats for the first time. Compared to Ti, the proliferative potential of osteoporotic bone marrow mesenchymal stem cells on NTAP-Ti increased by 180% at 1 day (P = 0.004), while their osteogenic differentiation increased by 149% at 14 days (P < 0.001). In addition, the results indicated that NTAP-Ti significantly improved osseointegration in osteoporotic rats in vivo. Compared to the Ti, the bone volume fraction (BV/TV) and trabecular number (Tb.N) values of NTAP-Ti in osteoporotic rats, respectively, increased by 18% (P < 0.001) and 25% (P = 0.007) at 6 weeks and the trabecular separation (Tb.Sp) value decreased by 26% (P = 0.02) at 6 weeks. In conclusion, this study proved a novel NTAP irradiation titanium implant that can significantly promote osseointegration in osteoporotic conditions.