Osteoclasts Regulate Osteocyte Viability and Function

摘要 骨质疏松相关的骨丢失使个体处于使人衰弱的骨折的风险中，这增加了发病的风险， mortality.骨细胞占骨骼的95%，并且越来越多地被认为是骨形成的主要调节者。 骨稳态随着年龄的增长，骨细胞密度降低，骨细胞的选择性缺失导致 骨质疏松这表明，维持骨细胞的活力和功能可能是一种有效的策略， 减轻与年龄相关的骨质流失。众所周知，骨细胞调节破骨细胞;然而， 破骨细胞对骨细胞的影响尚未评估。初步数据表明， 破骨细胞TGF-β信号转导在体内表现出增加的骨细胞凋亡，并且TGF-β处理的破骨细胞 条件培养基保护骨细胞免受地塞米松诱导的体外凋亡。破骨细胞的作用 在促进骨细胞活力和/或功能方面，我的初步数据支持了这种关系， 对大多数通过减少破骨细胞数量起作用的骨质疏松症治疗具有重要意义。的 这个为期五年的职业发展申请的总体目标是检验TGF-β信号在 破骨细胞诱导旁分泌因子的产生，所述旁分泌因子促进维持骨形成所必需的骨细胞活力。 骨骼稳态具体来说，我将完成小鼠骨细胞表型的表征， 破坏破骨细胞TGF-β信号传导，并评估TGF-β信号传导在破骨细胞中的机制 在体外和体内促进骨细胞的活力。其次，我将评估破骨细胞的作用 通过遗传学（小鼠）和药理学（人类）对小鼠和人类骨细胞的消融/消耗 方法.该提案为骨细胞表型技术提供了重要的培训机会，包括 酸蚀/扫描电子显微镜，分析骨细胞对体内轴向的功能反应 加载，以及直接分析骨细胞基因表达而无需体外培养。此外，学习 药物消耗破骨细胞对人体骨细胞的影响提供了宝贵的经验， 临床机理研究将动物研究结果与人类相关联对于推进基础研究至关重要。 发现诊所。因此，建议的研究将为我的职业生涯提供必要的培训 开发并为开发独立的R 01应用程序奠定基础。

Abstract Age-related bone loss puts individuals at risk for debilitating fractures that increase the risk for morbidity and mortality. Osteocytes make up 95% of the skeleton and are increasingly recognized as master regulators of bone homeostasis. With age there is reduced osteocyte density, and selective deletion of osteocytes results in osteoporosis. This suggests that maintaining osteocyte viability and function may be an effective strategy to mitigate age-related bone loss. Osteocytes are well-known to regulate osteoclasts; however, the potential effects of osteoclasts on osteocytes have not been evaluated. Preliminary data suggest that mice with impaired osteoclast TGF- signaling exhibit increased osteocyte apoptosis in vivo, and TGF- treated osteoclast conditioned media protects osteocytes from dexamethasone-induced apoptosis in vitro. A role for osteoclasts in promoting osteocyte viability and/or function, a relationship supported by my preliminary data, would have important implications for the majority of osteoporosis therapies that act by reducing osteoclast numbers. The overall goal of this five year career development application is to test the hypothesis that TGF-β signaling in osteoclasts induces the production of paracrine factors that promote osteocyte viability necessary to maintain skeletal homeostasis. Specifically, I will complete the characterization of the osteocyte phenotype in mice with impaired osteoclast TGF- signaling and evaluate the mechanism by which TGF- signaling in osteoclasts promotes osteocyte viability in vitro and in vivo. Secondly, I will evaluate the effect of osteoclast ablation/depletion on osteocytes in mice and humans through genetic (mouse) and pharmacologic (humans) methods. This proposal offers significant training opportunities in osteocyte phenotyping techniques, including acid etching/scanning electron microscopy, analysis of the functional response of osteocytes to in vivo axial loading, as well as direct analysis of osteocyte gene expression without in vitro culture. In addition, studying the effects of pharmacological depletion of osteoclasts on osteocytes in humans offers valuable experience in clinical mechanistic research. Correlating the results of animal studies to humans is crucial to advancing basic findings to the clinic. Therefore, the proposed studies will provide me with training essential to my career development and lay the ground work for developing an independent R01 application.