TGF-β 1–3 are unique multi-functional growth factors that are only expressed in mammals, and mainly secreted and stored as a latent complex in the extracellular matrix(ECM). The biological functions of TGF-β in adu...TGF-β 1–3 are unique multi-functional growth factors that are only expressed in mammals, and mainly secreted and stored as a latent complex in the extracellular matrix(ECM). The biological functions of TGF-β in adults can only be delivered after ligand activation, mostly in response to environmental perturbations. Although involved in multiple biological and pathological processes of the human body, the exact roles of TGF-β in maintaining stem cells and tissue homeostasis have not been well-documented until recent advances, which delineate their functions in a given context. Our recent findings, along with data reported by others, have clearly shown that temporal and spatial activation of TGF-β is involved in the recruitment of stem/progenitor cell participation in tissue regeneration/remodeling process, whereas sustained abnormalities in TGF-β ligand activation, regardless of genetic or environmental origin, will inevitably disrupt the normal physiology and lead to pathobiology of major diseases. Modulation of TGF-β signaling with different approaches has proven effective pre-clinically in the treatment of multiple pathologies such as sclerosis/fibrosis, tumor metastasis, osteoarthritis, and immune disorders. Thus, further elucidation of the mechanisms by which TGF-β is activated in different tissues/organs and how targeted cells respond in a context-dependent way can likely be translated with clinical benefits in the management of a broad range of diseases with the involvement of TGF-β.展开更多
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
Osteoarthritis(OA) causes the destruction of joints. Its pathogenesis is still under investigation, and there is no effective diseasemodifying therapy. Here, we report that elevated cyclooxygenase-2(COX-2) expression ...Osteoarthritis(OA) causes the destruction of joints. Its pathogenesis is still under investigation, and there is no effective diseasemodifying therapy. Here, we report that elevated cyclooxygenase-2(COX-2) expression in the osteocytes of subchondral bone causes both spontaneous OA and rheumatoid arthritis(RA). The knockout of COX-2 in osteocytes or treatment with a COX-2 inhibitor effectively rescues the structure of subchondral bone and attenuates cartilage degeneration in spontaneous OA(STR/Ort)mice and tumor necrosis factor-α transgenic RA mice. Thus, elevated COX-2 expression in subchondral bone induces both OAassociated and RA-associated joint cartilage degeneration. The inhibition of COX-2 expression can potentially modify joint destruction in patients with arthritis.展开更多
Osteoporosis(OP)is a common age-related disease characterized by a deterioration of bone mass and structure that predisposes patients to fragility fractures.Pharmaceutical therapies that promote anabolic bone formatio...Osteoporosis(OP)is a common age-related disease characterized by a deterioration of bone mass and structure that predisposes patients to fragility fractures.Pharmaceutical therapies that promote anabolic bone formation in OP patients and OP-induced fracture are needed.We investigated whether a neutralizing antibody against Siglec-15 can simultaneously inhibit bone resorption and stimulate bone formation.We found that the multinucleation of osteoclasts was inhibited in SIGLEC-15 conditional knockout mice and mice undergoing Siglec-15 neutralizing antibody treatment.The secretion of platelet-derived growth factor-BB(PDGF-BB),the number of tartrate-resistant acid phosphatase-positive(TRAP+)mononuclear cells,and bone formation were significantly increased in the SIGLEC-15 conditional knockout mice and antibody-treated mice.The anabolic effect of the Siglec-15 neutralizing antibody on bone formation was blunted in mice with Pdgfb deleted in TRAP-1"cells.These findings showed that the anabolic effect of the Siglec-15 neutralizing antibody was mediated by elevating PDGF-BB production of TRAP4 mononuclear cells.To test the therapeutic potential of the Siglec-15 neutralizing antibody,we injected the antibody in an ovariectomy-induced osteoporotic mouse model,which mimics postmenopausal osteoporosis in women,and in two fracture healing models because fracture is the most serious health consequence of osteoporosis.The Siglec-15 neutralizing antibody effectively reduced bone resorption and stimulated bone formation in estrogen deficiency-induced osteoporosis.Of note,the Siglec-15 neutralizing antibody promoted intramembranous and endochondral ossification at the damaged area of cortical bone in fracture healing mouse models.Thus,the Siglec-15 neutralizing antibody shows significant translational potential as a novel therapy for OP and bone fracture.展开更多
The molecular control of osteoclast formation is still not clearly elucidated. Here, we show that a process of cell recognition mediated by Siglec15-TLR2 binding is indispensable and occurs prior to cell fusion in RAN...The molecular control of osteoclast formation is still not clearly elucidated. Here, we show that a process of cell recognition mediated by Siglec15-TLR2 binding is indispensable and occurs prior to cell fusion in RANKL-mediated osteoclastogenesis. Siglec15 has been shown to regulate osteoclastic bone resorption. However, the receptor for Siglec15 has not been identified, and the signaling mechanism involving Siglec15 in osteoclast function remains unclear. We found that Siglec15 bound sialylated TLR2 as its receptor and that the binding of sialylated TLR2 to Siglec15 in macrophages committed to the osteoclast-lineage initiated cell fusion for osteoclast formation, in which sialic acid was transferred by the sialyltransferase ST3 Gal1. Interestingly, the expression of Siglec15 in macrophages was activated by M-CSF, whereas ST3 Gal1 expression was induced by RANKL. Both Siglec15-specific deletion in macrophages and intrafemoral injection of sialidase abrogated cell recognition and reduced subsequent cell fusion for the formation of osteoclasts, resulting in increased bone formation in mice. Thus, our results reveal that cell recognition mediated by the binding of sialylated TLR2 to Siglec15 initiates cell fusion for osteoclast formation.展开更多
The field of research on pain originating from various bone diseases is expanding rapidly, with new mechanisms and targets asserting both peripheral and central sites of action. The scope of research is broadening fro...The field of research on pain originating from various bone diseases is expanding rapidly, with new mechanisms and targets asserting both peripheral and central sites of action. The scope of research is broadening from bone biology to neuroscience,neuroendocrinology, and immunology. In particular, the roles of primary sensory neurons and non-neuronal cells in the peripheral tissues as important targets for bone pain treatment are under extensive investigation in both pre-clinical and clinical settings. An understanding of the peripheral mechanisms underlying pain conditions associated with various bone diseases will aid in the appropriate application and development of optimal strategies for not only managing bone pain symptoms but also improving bone repairing and remodeling, which potentially cures the underlying etiology for long-term functional recovery. In this review, we focus on advances in important preclinical studies of significant bone pain conditions in the past 5 years that indicated new peripheral neuronal and non-neuronal mechanisms, novel targets for potential clinical interventions, and future directions of research.展开更多
基金supported by U.S. National Institutes of Health grants (AR063943 and DK057501 to X.C. AR064833 to J.L.C.)+3 种基金the National Natural Science Foundation of China (81771099 to X.X.)the Key Project for Frontier Research of Science and Technology Department of Sichuan Province (2016JY0006 to X.Z.)Sichuan Province Science and Technology Innovation Team Program (2017TD0016 to Q.Y.).X.X.supported by the visiting scholar fellowship from West China Hospital of Stomatology, Sichuan University
文摘TGF-β 1–3 are unique multi-functional growth factors that are only expressed in mammals, and mainly secreted and stored as a latent complex in the extracellular matrix(ECM). The biological functions of TGF-β in adults can only be delivered after ligand activation, mostly in response to environmental perturbations. Although involved in multiple biological and pathological processes of the human body, the exact roles of TGF-β in maintaining stem cells and tissue homeostasis have not been well-documented until recent advances, which delineate their functions in a given context. Our recent findings, along with data reported by others, have clearly shown that temporal and spatial activation of TGF-β is involved in the recruitment of stem/progenitor cell participation in tissue regeneration/remodeling process, whereas sustained abnormalities in TGF-β ligand activation, regardless of genetic or environmental origin, will inevitably disrupt the normal physiology and lead to pathobiology of major diseases. Modulation of TGF-β signaling with different approaches has proven effective pre-clinically in the treatment of multiple pathologies such as sclerosis/fibrosis, tumor metastasis, osteoarthritis, and immune disorders. Thus, further elucidation of the mechanisms by which TGF-β is activated in different tissues/organs and how targeted cells respond in a context-dependent way can likely be translated with clinical benefits in the management of a broad range of diseases with the involvement of TGF-β.
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 the NIH/NIAMS grants AR071432 and AR063943 (to X.C.)
文摘Osteoarthritis(OA) causes the destruction of joints. Its pathogenesis is still under investigation, and there is no effective diseasemodifying therapy. Here, we report that elevated cyclooxygenase-2(COX-2) expression in the osteocytes of subchondral bone causes both spontaneous OA and rheumatoid arthritis(RA). The knockout of COX-2 in osteocytes or treatment with a COX-2 inhibitor effectively rescues the structure of subchondral bone and attenuates cartilage degeneration in spontaneous OA(STR/Ort)mice and tumor necrosis factor-α transgenic RA mice. Thus, elevated COX-2 expression in subchondral bone induces both OAassociated and RA-associated joint cartilage degeneration. The inhibition of COX-2 expression can potentially modify joint destruction in patients with arthritis.
基金This research was partially supported by a grant from NextCure,Inc.and the NIH National Institute on Aging under Award Number P01AG066603.
文摘Osteoporosis(OP)is a common age-related disease characterized by a deterioration of bone mass and structure that predisposes patients to fragility fractures.Pharmaceutical therapies that promote anabolic bone formation in OP patients and OP-induced fracture are needed.We investigated whether a neutralizing antibody against Siglec-15 can simultaneously inhibit bone resorption and stimulate bone formation.We found that the multinucleation of osteoclasts was inhibited in SIGLEC-15 conditional knockout mice and mice undergoing Siglec-15 neutralizing antibody treatment.The secretion of platelet-derived growth factor-BB(PDGF-BB),the number of tartrate-resistant acid phosphatase-positive(TRAP+)mononuclear cells,and bone formation were significantly increased in the SIGLEC-15 conditional knockout mice and antibody-treated mice.The anabolic effect of the Siglec-15 neutralizing antibody on bone formation was blunted in mice with Pdgfb deleted in TRAP-1"cells.These findings showed that the anabolic effect of the Siglec-15 neutralizing antibody was mediated by elevating PDGF-BB production of TRAP4 mononuclear cells.To test the therapeutic potential of the Siglec-15 neutralizing antibody,we injected the antibody in an ovariectomy-induced osteoporotic mouse model,which mimics postmenopausal osteoporosis in women,and in two fracture healing models because fracture is the most serious health consequence of osteoporosis.The Siglec-15 neutralizing antibody effectively reduced bone resorption and stimulated bone formation in estrogen deficiency-induced osteoporosis.Of note,the Siglec-15 neutralizing antibody promoted intramembranous and endochondral ossification at the damaged area of cortical bone in fracture healing mouse models.Thus,the Siglec-15 neutralizing antibody shows significant translational potential as a novel therapy for OP and bone fracture.
基金supported by US National Institutes of Health grants AR 071432 (to X.C.)
文摘The molecular control of osteoclast formation is still not clearly elucidated. Here, we show that a process of cell recognition mediated by Siglec15-TLR2 binding is indispensable and occurs prior to cell fusion in RANKL-mediated osteoclastogenesis. Siglec15 has been shown to regulate osteoclastic bone resorption. However, the receptor for Siglec15 has not been identified, and the signaling mechanism involving Siglec15 in osteoclast function remains unclear. We found that Siglec15 bound sialylated TLR2 as its receptor and that the binding of sialylated TLR2 to Siglec15 in macrophages committed to the osteoclast-lineage initiated cell fusion for osteoclast formation, in which sialic acid was transferred by the sialyltransferase ST3 Gal1. Interestingly, the expression of Siglec15 in macrophages was activated by M-CSF, whereas ST3 Gal1 expression was induced by RANKL. Both Siglec15-specific deletion in macrophages and intrafemoral injection of sialidase abrogated cell recognition and reduced subsequent cell fusion for the formation of osteoclasts, resulting in increased bone formation in mice. Thus, our results reveal that cell recognition mediated by the binding of sialylated TLR2 to Siglec15 initiates cell fusion for osteoclast formation.
文摘The field of research on pain originating from various bone diseases is expanding rapidly, with new mechanisms and targets asserting both peripheral and central sites of action. The scope of research is broadening from bone biology to neuroscience,neuroendocrinology, and immunology. In particular, the roles of primary sensory neurons and non-neuronal cells in the peripheral tissues as important targets for bone pain treatment are under extensive investigation in both pre-clinical and clinical settings. An understanding of the peripheral mechanisms underlying pain conditions associated with various bone diseases will aid in the appropriate application and development of optimal strategies for not only managing bone pain symptoms but also improving bone repairing and remodeling, which potentially cures the underlying etiology for long-term functional recovery. In this review, we focus on advances in important preclinical studies of significant bone pain conditions in the past 5 years that indicated new peripheral neuronal and non-neuronal mechanisms, novel targets for potential clinical interventions, and future directions of research.
