MCP5 as key mediator of TGFbeta signaling in joint maintenance and osteoarthritis

描述（由申请人提供）：项目摘要骨关节炎（OA）是最常见的关节炎。患有OA的患者缺乏有效的医学治疗来再生受损的软骨，并且需要开发新的疗法来治疗关节疾病。保持关节内稳态，保留关节细胞以沿着导致软骨细胞肥大和骨替代的分化途径进行，例如其发生在生长板软骨中。如果OA是祖细胞未能建立正确的微环境的结果，探索关节如何形成可以让我们了解软骨如何退化，并开发能够重新激活形成机制的药物。我们的长期目标是阐明关节祖细胞如何表达生殖和再生关节基因，以操纵它们的表达用于治疗OA。总体目标是确定细胞因子单核细胞趋化蛋白-5（MCP-5）的调节是否是关节维持和创伤后OA中TGF-α（a）II型受体（TaRII）信号传导的关键下游介质。我们的中心假设是，MCP-5的受控表达需要在发育期间在中间区中允许适当的关节形成，并且在成年期对于维持关节完整性和预防OA变性也至关重要。这项研究的基本原理是，细胞因子控制的环境是促进发育和维持体内平衡的共同机制。基于我们的初步数据，我们提出了两个具体目标：1）确定是否需要TaRII信号转导通过下调MCP-5表达来维持关节完整性; 2）确定MCP-5/TaRII轴在创伤后OA中的作用。在第一个目标中，我们将产生Prx 1CreERT 2/Tgfbr 2lox/lox小鼠，以使用他莫昔芬诱导的Cre转基因获得TaRII表达的时间和肢体特异性控制，其中我们将评估在MCP-5信号传导存在或不存在的情况下OA的发展（通过化学和受体操纵）。A）通过在Tgfbr 2-a-Gal-GFP-BAC小鼠中进行内侧半月板的去稳定化来诱导创伤后OA（TaRII表达的成像报告子）并分析在OA发展期间伴随TaRII的MCP-5的表达; B）在分离的表达TaRII的细胞上诱导机械负荷，并评估细胞变形是否导致对TGF-β 1的反应性的进行性丧失，a随之增加MCP-5表达。这一提议是创新的，因为它提供了一个新的视角来评估OA过程：OA不仅被视为细胞因子对被动靶点（关节）的全身性流入所诱导的损伤的结果，而且还被视为活性细胞关节群未能维持受控的细胞因子环境。我们的研究将为关节发育稳态和OA病理生理学提供重要的见解。

DESCRIPTION (provided by applicant): PROJECT ABSTRACT Osteoarthritis (OA) is the most common form of arthritis. Patients with OA lack effective medical treatments to regenerate damaged cartilage and there is a need for developing novel therapies to treat joint disorders. Joint homeostasis is maintained preserving the articular cells to proceed down the differentiation pathway that leads to chondrocyte hypertrophy and bone replacement, such it occurs in the growth plate cartilage. If OA is the result of the failure of progenitor cells to establish a corret microenvironment, exploring how joints form can lead us to understand how cartilage degenerates and develop drugs that are able to reactivate the forming mechanism. Our long-term goal is to elucidate how joint progenitor cells express generative and regenerative joint genes in order to manipulate their expression for therapeutic purpose in OA. The overall objective is to determine whether the regulation of the cytokine monocyte chemoattractant protein-5 (MCP-5) is a key down- stream mediator of TGF-alpha (a) type II receptor (TaRII) signaling in joint maintenance and post-traumatic OA. Our central hypothesis is that a controlled expression of MCP-5 is needed in the interzone to allow proper joint formation during development and is also crucial in adulthood to maintain joint integrity and to prevent OA degeneration. The rationale for the proposed research is that a cytokine controlled environment is a common mechanism in joint to promote development and maintain homeostasis. Based on our preliminary data we are proposing two Specific Aims: 1) To determine whether TaRII signaling is needed to maintain joint integrity through down-regulation of MCP-5 expression; 2) To determine the role of MCP-5/TaRII axis in post-traumatic OA. In the first aim, we will generate the Prx1CreERT2/Tgfbr2lox/lox mouse to obtain temporal and limb-specific control of TaRII expression using a tamoxifen-inducible-Cre transgenic in which we will evaluate OA development in the presence or absence of MCP-5 signaling (by chemical and receptor manipulation). In the second aim, we will: A) induce post-traumatic OA by performing a destabilization of medial meniscus in Tgfbr2-a-Gal-GFP-BAC mice (imaging reporters of TaRII expression) and analyze expression of MCP-5 in concomitance with TaRII during OA development; B) induce mechanical loading on isolated TaRII expressing cells and evaluate whether cell deformation leads to progressive loss of responsiveness to TGF-a with consequent increase in MCP-5 expression. This proposal is innovative because provides a new perspective to evaluate the OA process: OA is not only seen as the result of the damage induced by a systemic influx of cytokines against a passive target (the joint), but rather the failure of an actve cell joint population to maintain a controlled cytokine environment. Our studies will provide critical insights on joint development homeostasis and OA pathophysiology.