The alteration of age‐related molecules in the bone marrow microenvironment is one of the driving forces in osteoporosis. These molecules inhibit bone formation and promote bone resorption by regulating osteoblastic and osteoclastic activity, contributing to age‐related bone loss. Here, we observed that the level of microRNA‐31a‐5p (miR‐31a‐5p) was significantly increased in bone marrow stromal cells (BMSCs) from aged rats, and these BMSCs demonstrated increased adipogenesis and aging phenotypes as well as decreased osteogenesis and stemness. We used the gain‐of‐function and knockdown approach to delineate the roles of miR‐31a‐5p in osteogenic differentiation by assessing the decrease of special AT‐rich sequence‐binding protein 2 (SATB2) levels and the aging of BMSCs by regulating the decline of E2F2 and recruiting senescence‐associated heterochromatin foci (SAHF). Notably, expression of miR‐31a‐5p, which promotes osteoclastogenesis and bone resorption, was markedly higher in BMSCs‐derived exosomes from aged rats compared to those from young rats, and suppression of exosomal miR‐31a‐5p inhibited the differentiation and function of osteoclasts, as shown by elevated RhoA activity. Moreover, using antagomiR‐31a‐5p, we observed that, in the bone marrow microenvironment, inhibition of miR‐31a‐5p prevented bone loss and decreased the osteoclastic activity of aged rats. Collectively, our results reveal that miR‐31a‐5p acts as a key modulator in the age‐related bone marrow microenvironment by influencing osteoblastic and osteoclastic differentiation and that it may be a potential therapeutic target for age‐related osteoporosis.

Purpose-Resistance exercise (RE) can improve many cardiovascular disease (CVD) risk factors, but specific data on the effects on CVD events and mortality are lacking. We investigated the associations of RE with CVD and all-cause mortality, and further examined the mediation effect of body mass index between RE and CVD outcomes. Methods-We included 12,591 participants (mean age 47 years) who received at least two clinical examinations 1987-2006. RE was assessed by a self-reported medical history questionnaire.

Bisphosphonate‐related osteonecrosis of the jaw (BRONJ) is a detrimental side effect of the long‐term administration of bisphosphonates. Although macrophages were reported to be an important mediator of BRONJ, the detailed potential mechanism of BRONJ remains unclear. Here, we reported an elevated TLR‐4 expression in macrophages under action of zoledronic acid (ZA), resulting in enhanced M1 macrophage polarization and decreased M2 macrophage polarization both in vitro and in vivo. After inhibiting the TLR‐4 signaling pathway, the activation of the TLR‐4/NF‐κB signaling pathway and the induction of NF‐κB nuclear translocation and production of proinflammatory cytokines by ZA were suppressed in macrophages, thereby inhibiting M1 macrophage polarization. By utilizing the TLR‐4−/− mice, development of BRONJ was markedly ameliorated, and M1 macrophages were significantly attenuated in the extraction socket tissues in the TLR‐4−/− mice. Importantly, the systemic administration of the TLR‐4 inhibitor TAK‐242 improved the wound healing of the extraction socket and decreased the incidence rate of BRONJ. Taken together, our findings suggest that TLR‐4‐mediated macrophage polarization participates in the pathogenesis of BRONJ in mice, and TLR‐4 may be a potential target for the prevention and therapeutic treatment of BRONJ.—Zhu, W., Xu, R., Du, J., Fu, Y., Li, S., Zhang, P., Liu, L., Jiang, H. Zoledronic acid promotes TLR‐4‐mediated M1 macrophage polarization in bisphosphonate‐related osteonecrosis of the jaw. FASEB J. 33, 5208–5219 (2019). http://www.fasebj.org

Non-traumatic osteonecrosis of the femoral head (ONFH) is clinically a devastating and progressive disease without an effective treatment. Mesenchymal stem cells (MSCs) transplantation has been used to treat ONFH in early stage, but the failure rate of this therapy is high due to the reduced osteogenic differentiation and migration of the transplanted MSCs related with pathological bone tissues. However, the mechanism responsible for this decrease is still unclear. Therefore, we assume that the implanted MSCs might be influenced by signals delivered from pathological bone tissue, where the exosomes might play a critical role in this delivery. This study showed that exosomes from ONFH bone tissues (ONFH-exos) were able to induce GC-induced ONFH-like damage, in vivo and impair osteogenic differentiation and migration of MSCs, in vitro. Then, we analyzed the differentially expressed proteins (DEPs) in ONFHexos using proteomic technology and identified 842 differentially expressed proteins (DEPs). On the basis of gene ontology (GO) enrichment analysis of DEPs, fold-changes and previous report, cell adhesion-related CD41 (integrin α2b) was selected for further investigation. Our study showed that the CD41 (integrin α2b) was distinctly decreased in ONFH-exos, compared to NOR-exos, and downregulation of CD41 could impair osteogenic differentiation and migration of the MSCs, where CD41-integrin β3-FAK-Akt-Runx2 pathway was involved. Finally, our study further suggested that CD41-affluent NOR-exos could restore the glucocorticoid-induced decline of osteogenic differentiation and migration in MSCs, and prevent GC-induced ONFH-like damage in rat models. Taken together, our study results revealed that in the progress of ONFH, exosomes from the pathological bone brought about the failure of MSCs repairing the necrotic bone for lack of some critical proteins, like integrin CD41, and prompted the progression of experimentally induced ONFH-like status in the rat. CD41 could be considered as the target of early diagnosis and therapy in ONFH.

Osteoarthritis (OA), one of the most widespread musculoskeletal joint diseases among the aged, is characterized by the progressive loss of articular cartilage and continuous changes in subchondral bone. The exact pathogenesis of osteoarthritis is not completely clear. In this work, ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF-MS) in combination with multivariate statistical analysis was applied to analyze the metabolic profiling of subchondral bone from 42 primary osteoarthritis patients. This paper described a modified two-step method for extracting the metabolites of subchondral bone from primary osteoarthritis patients. Finally, 68 metabolites were identified to be significantly changed in the sclerotic subchondral bone compared with the non-sclerotic subchondral bone. Taurine and hypotaurine metabolism and beta-alanine metabolism were probably relevant to the sclerosis of subchondral bone. Taurine, L-carnitine, and glycerophospholipids played a vital regulation role in the pathological process of sclerotic subchondral bone. In the sclerotic process, beta-alanine and L-carnitine might be related to the increase of energy consumption. In addition, our findings suggested that the intra-cellular environment of sclerotic subchondral bone might be more acidotic and hypoxic compared with the non-sclerotic subchondral bone. In conclusion, this study provided a new insight into the pathogenesis of subchondral bone sclerosis. Our results indicated that metabolomics could serve as a promising approach for elucidating the pathogenesis of subchondral bone sclerosis in primary osteoarthritis. Graphical Abstract Metabolic analysis of osteoarthritis subchondral bone.

Diabetes induces impairment in cognitive function. There is substantial evidence that hippocampal endoplasmic reticulum (ER) stress is involved in diabetic cognitive impairment. Hydrogen sulfide (H2S) attenuates the learning and memory decline in experimental Alzheimer's disease and inhibits the hippocampal ER stress in homocysteine-exposed rats. Therefore, this aim of the present work was to investigate whether H2S ameliorates the diabetic cognitive dysfunction involving inhibition of hippocampal ER stress. In the present work, we found that stretozotocin (STZ, 40 mg/kg)-induced diabetic rats exhibited impairment in cognitive function, as judged by the novel objective recognition task (NOR) test, the Y-maze test and the Morris water maze (MWM) test. Notably, treatment of diabetic rats with sodium hydrosulfide (NaHS, a donor of H2S, 30 or 100 μmol/kg/d, for 30 d) significantly reversed diabetes-induced impairment in cognitive function. We also found that STZ (40 mg/kg)-induced diabetic rats exhibited hippocampal ER stress, as evidenced by upregulations of glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), and cleaved caspase-12 in the hippocampus. However, treatment with NaHS (30 or 100 μmol/kg/d, for 30 d) markedly suppressed the increases in GRP78, CHOP, and cleaved caspase-12 expressions in the hippocampus of diabetic rats. In addition, we noted that NaHS (30 or 100 μmol/kg/d, for 30 d) significantly enhanced the generation of hippocampal endogenous H2S in STZ-induced diabetic rats. These results suggest that H2S exhibits therapeutic potential for diabetes-associated cognitive dysfunction, which is most likely related to its protective effects against hippocampal ER stress.

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Aged bone marrow mesenchymal stem cells (BMSCs) exhibit aberrant self-renewal and lineage specification, which contribute to imbalanced bone-fat and progressive bone loss. In addition to known master regulators of lineage commitment, it is crucial to identify pivotal switches governing the specific differentiation fate of aged BMSCs. Here, we profiled differences in epigenetic regulation between adipogenesis and osteogenesis and identified super-enhancer associated lncRNA nuclear-enriched abundant transcript 1 (NEAT1) as a key bone-fat switch in aged BMSCs. We validated that NEAT1 with high enhancer activity was transcriptionally activated by ATF2 and directed aged BMSCs to a greater propensity to differentiate toward adipocytes than osteoblasts by mediating mitochondrial function. Furthermore, we confirmed NEAT1 as a protein-binding scaffold in which phosphorylation modification of SOX2 Ser249/250 by CDK2 impaired SOX2/OCT4 complex stability and dysregulated downstream transcription networks of pluripotency maintenance. In addition, by sponging miR-27b-3p, NEAT1 upregulated BNIP3L, BMP2K, and PPARG expression to shape mitochondrial function and osteogenic/adipogenic differentiation commitment, respectively. In extracellular communication, NEAT1 promoted CSF1 secretion from aged BMSCs and then strengthened osteoclastic differentiation by extracellular vesicle delivery. Notably, Neat1 small interfering RNA delivery induced increased bone mass in aged mice and decreased fat accumulation in the bone marrow. These findings suggest that NEAT1 regulates the lineage fates of BMSCs by orchestrating mitochondrial function and pluripotency maintenance, and might be a potential therapeutic target for skeletal aging.