Osteoclasts Regulate Osteocyte Viability and Function

摘要 与年龄相关的骨丢失使个人面临衰弱骨折的风险，这增加了发病率和 死亡率。骨细胞占骨骼的95%，越来越多地被认为是骨骼的主要调节细胞 骨骼动态平衡。随着年龄的增长，骨细胞密度降低，选择性地删除骨细胞会导致 骨质疏松。这表明，维持骨细胞的活性和功能可能是一种有效的策略 缓解与年龄相关的骨质流失。众所周知，骨细胞可以调节破骨细胞；然而， 破骨细胞对骨细胞的影响尚未得到评估。初步数据表明，受损害的小鼠 破骨细胞转化生长因子-信号转导促进体内骨细胞凋亡，转化生长因子-处理破骨细胞 体外条件培养液对地塞米松诱导的骨细胞凋亡的保护作用。破骨细胞的作用 在促进骨细胞存活和/或功能方面，由我的初步数据支持的关系将具有 对于大多数通过减少破骨细胞数量起作用的骨质疏松症治疗方法具有重要意义。这个 这项为期五年的职业发展申请的总体目标是检验转化生长因子-β信号转导在 破骨细胞诱导产生旁分泌因子，促进维持骨细胞活性所必需的 骨骼动态平衡。具体地说，我将完成对小鼠骨细胞表型的表征 破骨细胞转化生长因子-信号转导受损及其机制探讨 在体外和体内促进骨细胞的活性。其次，我将评估破骨细胞的效果 基因(小鼠)和药物(人)对小鼠和人骨细胞的消融/耗竭 方法：研究方法。这项提议提供了大量的骨细胞表型鉴定技术培训机会，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，以及不需要体外培养的骨细胞基因表达的直接分析。此外，学习 药物耗尽破骨细胞对骨细胞的影响提供了宝贵的经验 临床机制研究。将动物研究的结果与人类相关联是推进基础研究的关键 把结果带到诊所。因此，拟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R01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.