The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin(OPG). However, the mechanisms of osteocyte ...The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin(OPG). However, the mechanisms of osteocyte mechanotransduction remain poorly understood. We've previously shown that osteocyte mechanosensitivity is encoded through unique intracellular calcium (Ca^(2+) ) dynamics. Here, by simultaneously monitoring Ca^(2+) and actin dynamics in single cells exposed to fluid shear flow, we detected actin network contractions immediately upon onset of flow-induced Ca^(2+) transients, which were facilitated by smooth muscle myosin and further confirmed in native osteocytes ex vivo. Actomyosin contractions have been linked to the secretion of extracellular vesicles(EVs), and our studies demonstrate that mechanical stimulation upregulates EV production in osteocytes through immunostaining for the secretory vesicle marker Lysosomal-associated membrane protein 1(LAMP1) and quantifying EV release in conditioned medium, both of which are blunted when Ca^(2+) signaling was inhibited by neomycin. Axial tibia compression was used to induce anabolic bone formation responses in mice, revealing upregulated LAMP1 and expected downregulation of sclerostin in vivo. This load-related increase in LAMP1 expression was inhibited in neomycin-injected mice compared to vehicle.Micro-computed tomography revealed significant load-related increases in both trabecular bone volume fraction and cortical thickness after two weeks of loading, which were blunted by neomycin treatment. In summary, we found mechanical stimulation of osteocytes activates Ca^(2+) -dependent contractions and enhances the production and release of EVs containing bone regulatory proteins. Further, blocking Ca^(2+) signaling significantly attenuates adaptation to mechanical loading in vivo, suggesting a critical role for Ca^(2+) -mediated signaling in bone adaptation.展开更多
Introduction Osteocytes are interconnected through numerous intercellular processes,forming extensive cell networks throughout the bone tissue[1]. It has been shown that osteocyte density is an important physiological...Introduction Osteocytes are interconnected through numerous intercellular processes,forming extensive cell networks throughout the bone tissue[1]. It has been shown that osteocyte density is an important physiological parameter,which decreases展开更多
基金supported by NIH R01 AR052461 and NIH R01 AR069148supported by a NSF Graduate Research Fellowship. A. E. M.supported by training grant T32 AR059038
文摘The vast osteocytic network is believed to orchestrate bone metabolic activity in response to mechanical stimuli through production of sclerostin, RANKL, and osteoprotegerin(OPG). However, the mechanisms of osteocyte mechanotransduction remain poorly understood. We've previously shown that osteocyte mechanosensitivity is encoded through unique intracellular calcium (Ca^(2+) ) dynamics. Here, by simultaneously monitoring Ca^(2+) and actin dynamics in single cells exposed to fluid shear flow, we detected actin network contractions immediately upon onset of flow-induced Ca^(2+) transients, which were facilitated by smooth muscle myosin and further confirmed in native osteocytes ex vivo. Actomyosin contractions have been linked to the secretion of extracellular vesicles(EVs), and our studies demonstrate that mechanical stimulation upregulates EV production in osteocytes through immunostaining for the secretory vesicle marker Lysosomal-associated membrane protein 1(LAMP1) and quantifying EV release in conditioned medium, both of which are blunted when Ca^(2+) signaling was inhibited by neomycin. Axial tibia compression was used to induce anabolic bone formation responses in mice, revealing upregulated LAMP1 and expected downregulation of sclerostin in vivo. This load-related increase in LAMP1 expression was inhibited in neomycin-injected mice compared to vehicle.Micro-computed tomography revealed significant load-related increases in both trabecular bone volume fraction and cortical thickness after two weeks of loading, which were blunted by neomycin treatment. In summary, we found mechanical stimulation of osteocytes activates Ca^(2+) -dependent contractions and enhances the production and release of EVs containing bone regulatory proteins. Further, blocking Ca^(2+) signaling significantly attenuates adaptation to mechanical loading in vivo, suggesting a critical role for Ca^(2+) -mediated signaling in bone adaptation.
基金supported by US National Institute of Health grants (National Institute of Arthritis and Musculoskeletal and Skin Diseases) R21 AR052417,R01 AR1R052461,and RC1 AR058453
文摘Introduction Osteocytes are interconnected through numerous intercellular processes,forming extensive cell networks throughout the bone tissue[1]. It has been shown that osteocyte density is an important physiological parameter,which decreases
