Osmotic Signaling in Chondrocyte Aging and Osteoarthritis

描述(申请人提供)：骨关节炎(OA)是一种使滑膜关节衰弱和疼痛的疾病，在美国估计有2100万人和超过10%的60岁以上人口受到影响。正常的软骨结构是通过软骨细胞介导的细胞外基质(ECM)的合成和降解来维持的。通过关节载荷施加生物力学信号是维持这种组织内稳态的关键。然而，在生理和病理环境中，软骨细胞对软骨的机械负荷的反应机制还不完全清楚。近年来，瞬时受体电位香草酸4(TRPV4)离子通道作为一种钙离子选择性阳离子通道，已成为软骨细胞渗透和机械刺激信号转导的中心焦点。在体外，TRPV4被认为是软骨细胞基因表达和细胞外基质产生的有效调节因子，在体内，自发性关节退行性变被描述为TRPV4基因的全局缺失。这一信号通路中与年龄相关的变化可能解释了软骨老化对进行性退行性变和骨关节炎的易感性。本研究的目的是研究TRPV4在软骨老化过程中的作用。我们推测，衰老过程中关节退变的发生和发展是由于TRPV4介导的钙信号在渗透性和机械性刺激反应中发生改变。在具体目标1中，我们将全面研究软骨细胞在衰老和骨关节炎过程中的TRPV4通道，包括TRPV4基因表达、TRPV4蛋白水平和TRPV4功能，并对相应的形态和物质变化进行定量分析。在特定的目标2中，我们将建立软骨靶向的、可诱导的TRPV4基因敲除小鼠，以进一步研究TRPV4信号在成年软骨和骨关节炎发育中的特定作用，再次观察软骨对TRPV4的宏观和微观依赖性变化。本研究旨在阐明机械因素是如何调节软骨代谢的，以及在衰老和疾病过程中软骨的动态平衡是如何被破坏的。这一奖学金不仅将帮助我掌握知识和工具，开始在矫形外科生物工程和翻译研究方面富有成效的内科科学家职业生涯，而且这里提出的项目将直接将这些人才应用于开发新的诊断、药物和生物物理干预措施，以更好地治疗骨性关节炎。

DESCRIPTION (provided by applicant): Osteoarthritis (OA) is a debilitating and painful disease of synovial joints that affects an estimated 21 million people in the United States and more than 10% of the population over 60 years old. Normal cartilage structure is maintained through chondrocyte-mediated synthesis and degradation of the cartilage extracellular matrix (ECM). The application of biomechanical signals through joint loading is known to be critical in preserving this tissue homeostasis. However, the mechanisms by which chondrocytes respond to mechanical loading of the cartilage, in both physiological and pathological settings, are not fully understood. Recently, the transient receptor potential vanilloid 4 (TRPV4) ion channel, a Ca++ preferred cation channel, has emerged as a central focus in chondrocyte osmotic and mechanical stimuli signal transduction. TRPV4 has been identified as a potent regulator of chondrocyte gene-expression and ECM production in vitro, and spontaneous joint degeneration has been described in vivo with global trpv4 gene deletion. Age-associated changes in this signaling pathway may explain the vulnerability of aging cartilage to progressive degeneration and OA. The goal of this study is to characterize the role of TRPV4 in cartilage maintenance during aging. We hypothesize that the initiation and progression of joint degeneration in aging is due to altered TRPV4-mediated Ca++ signaling in response osmotic and mechanical stimuli. In Specific Aim 1, we will comprehensively characterize the chondrocyte TRPV4 channel during aging and OA, including trpv4 gene expression, TRPV4 protein levels and TRPV4 function, and relate this to quantitative analyses of the corresponding morphological and material changes. In Specific Aim 2, we will generate cartilage-targeted, inducible trpv4 knockout mice to further study the specific role of TRPV4 signaling in adult cartilage and OA development, looking again at both macro and microscopic TRPV4-dependant changes of the cartilage. This study is intended to elucidate how cartilage metabolism is regulated by mechanical factors and how this cartilage homeostasis is disrupted during aging and disease. This fellowship will not only help equip me with the knowledge and tools to begin a productive career as a physician-scientist in orthopedic bioengineering and translational research, but the project proposed here will directly apply these talents towards the development of novel diagnostic, pharmaceutical, and biophysical interventions for better treatment of OA.