Osmotic Signaling in Chondrocyte Aging and Osteoarthritis

描述（由申请人提供）：骨关节炎（OA）是一种使人衰弱和疼痛的滑膜关节疾病，在美国估计影响2100万人，超过60岁以上人口的10%。正常的软骨结构通过软骨细胞介导的软骨细胞外基质（ECM）的合成和降解来维持。已知通过关节负荷应用生物力学信号对于保持这种组织稳态至关重要。然而，软骨细胞在生理和病理环境中对软骨的机械负荷的反应机制尚未完全了解。近年来，瞬时受体电位香草酸4（TRPV 4）离子通道作为一种Ca++优先的阳离子通道，已成为软骨细胞渗透和机械刺激信号转导的中心焦点。TRPV4已被鉴定为体外软骨细胞基因表达和ECM产生的有效调节剂，并且已经描述了体内自发性关节退行性变与整体trpv4基因缺失。这种信号通路中与软骨相关的变化可以解释老化软骨对进行性退变和OA的脆弱性。本研究的目的是表征TRPV4在老化过程中软骨维护中的作用。我们推测，在老化的关节退行性变的启动和进展是由于改变TRPV4介导的Ca++信号在响应渗透和机械刺激。在具体目标1中，我们将全面表征老化和OA期间软骨细胞TRPV4通道，包括TRPV4基因表达、TRPV4蛋白水平和TRPV4功能，并将其与相应形态学和材料变化的定量分析相关联。在特定目标2中，我们将产生软骨靶向的，可诱导的trpv4敲除小鼠，以进一步研究TRPV4信号在成人软骨和OA发育中的特定作用，再次观察软骨的宏观和微观TRPV4依赖性变化。本研究旨在阐明机械因素如何调节软骨代谢，以及在衰老和疾病过程中软骨稳态如何被破坏。这个奖学金不仅将帮助装备我的知识和工具，开始一个富有成效的职业生涯，作为一个医生，科学家在骨科生物工程和转化研究，但这里提出的项目将直接应用这些人才对新的诊断，制药和生物物理干预的发展，以更好地治疗OA。 公共卫生相关性：衰老是骨关节炎（OA）的主要危险因素之一，尽管与年龄相关的关节退行性变的机制还不清楚。软骨细胞（软骨细胞）对机械负荷的反应对于关节软骨弹性和关节健康至关重要。瞬时受体电位香草酸4（TRPV 4）离子通道是渗透压和机械刺激的转换器，可能是衰老和OA关节退行性变之间的生理联系。我们的目的是表征软骨细胞TRPV4在衰老和OA发病机制中的功能，利用一种新的TRPV4缺陷小鼠模型进一步探索这种关系。

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. PUBLIC HEALTH RELEVANCE: Aging is one of the primary risk factors for osteoarthritis (OA), although the mechanisms responsible for age-related joint degeneration are not well understood. The response of chondrocytes, the cells of cartilage, to mechanical loading is critical for articular cartilage resiliency and joint health. The Transient Receptor Potential Vanilloid 4 (TRPV4) ion channel, a transducer of osmotic and mechanical stimuli, may be the physiological link between aging and OA joint degeneration. We aim to characterize chondrocyte TRPV4 function during aging and OA pathogenesis, utilizing a novel TRPV4-deficient mouse model to further explore this relationship.