Roles of SOX8 and SOX9 in Adult Articular Cartilage

项目总结 关节软骨的进行性和不可逆性恶化是骨关节炎(OA)和其他疾病的中心事件 各种形式的退行性关节疾病(DJD)，但尽管这些疼痛和致残的发病率很高 在这种情况下，目前还没有有效保护和恢复健康组织的治疗方法。软骨破裂 这是由于组织分解代谢增加和合成代谢受损所致。战略正在制定中 阻止分解代谢，但主要的知识差距排除了设计恢复正常软骨的策略 合成代谢。该项目旨在填补关键空白。一个空白是关于SOX9转录的确切作用 成人关节软骨中的因子。Sox9在发育中推动软骨细胞的指定和分化 软骨形成，但其在成人软骨内稳态和病理学中的作用尚不清楚。另一个缺口正在打开 SOX8是SOX9的近亲，在软骨中的作用。新数据显示，SOX8与 SOX9存在于关节软骨细胞中，有助于成人关节软骨的完整性。促炎和其他 驱动DJD的通路诱导软骨细胞分解代谢并下调软骨特异性合成代谢。 包括SOX9的表达，体外研究表明软骨细胞对PRO的分解代谢反应。 强迫表达SOX8或SOX9后，炎性细胞因子大大减少。总而言之，这些数据 提出SOX8和SOX9在关节软骨细胞中共同发挥关键作用的创新假设，以及它们的 致病性下调加剧了软骨合成代谢抑制和分解代谢刺激。三 为了检验这一假说，本文提出了具体的目标。目的1是确定SOX8和SOX9在成人中的作用 健康状态下的关节软骨细胞。其中一个基因或两个基因都会在人类初选中被打倒 成年小鼠关节软骨细胞和有条件灭活的关节软骨细胞及其后果 将会被评估。目的2是测试SOX8和SOX9抑制是否会影响骨性关节炎的发展。SOX8和 SOX9的表达和活性将被检测与人类骨性关节炎严重程度的相关性。此外，办公自动化将是 并分析SOX8/SOX9失活对疾病发展的影响。 机械地解剖。目标3是测试强制表达SOX8或SOX9是否有帮助，以及如何有帮助 在骨性关节炎条件下维持关节软骨细胞的正常。SOX蛋白将在原代过表达 评估来自正常和骨关节炎膝关节的人关节软骨细胞及其对细胞行为的影响。老鼠会 有条件地被迫在关节软骨细胞中表达Sox蛋白，并将进行软骨检测 正常情况下和办公自动化条件下的命运。一支由专家调查人员和临床医生组成的团队已被召集起来 确保项目的顺利完成。新发现有望改变目前的状况 理解决定健康和健康关节软骨细胞规格和活动的关键机制 疾病，从而激发新的想法，为数百万人设计急需的有效治疗方法 世界各地患有骨性关节炎和其他关节退行性疾病的患者。

PROJECT SUMMARY Progressive and irreversible deterioration of articular cartilage is a central event in osteoarthritis (OA) and other forms of degenerative joint disease (DJD), but despite the high prevalence of these painful and disabling conditions, no treatment is yet available to effectively protect and restore healthy tissue. Cartilage breakdown occurs as a result of both increased tissue catabolism and impaired anabolism. Strategies are being developed to block catabolism, but major knowledge gaps preclude the design of strategies to restore proper cartilage anabolism. This project is designed to fill key gaps. One gap is on the exact roles of the SOX9 transcription factor in adult articular cartilage. SOX9 drives chondrocyte specification and differentiation in developmental chondrogenesis, but its roles in adult cartilage homeostasis and pathology remain unclear. Another gap is on the role of SOX8, the closest relative of SOX9, in cartilage. New data reveal that SOX8 is co-expressed with SOX9 in articular chondrocytes and contributes to adult articular cartilage integrity. Pro-inflammatory and other pathways driving DJD elicit chondrocyte catabolic actions and downregulate cartilage-specific anabolism, including SOX9 expression, and in vitro studies suggest that the catabolic response of chondrocytes to pro- inflammatory cytokines is greatly reduced upon forced expression of SOX8 or SOX9. Together, these data suggest the innovative hypothesis that SOX8 and SOX9 share key roles in articular chondrocytes and that their pathogenic downregulation exacerbates cartilage anabolism repression and catabolism stimulation. Three specific aims are proposed to test this hypothesis. Aim 1 is to define the roles of SOX8 and SOX9 in adult articular chondrocytes in healthy conditions. Either or both genes will be knocked down in human primary articular chondrocytes and conditionally inactivated in articular chondrocytes in adult mice, and consequences will be assessed. Aim 2 is to test whether SOX8 and SOX9 repression impacts OA development. SOX8 and SOX9 expression and activities will be examined for correlations with OA severity in humans. Also, OA will be induced in adult mice and the effect of SOX8/SOX9 inactivation on disease development will be analyzed and mechanistically dissected. Aim 3 is to test whether and how forced expression of SOX8 or SOX9 helps maintain articular chondrocyte normalcy in OA conditions. The SOX proteins will be overexpressed in primary human articular chondrocytes from normal and OA knees and their impact on cell behavior assessed. Mice will be conditionally forced to express the SOX proteins in articular chondrocytes and will be tested for cartilage fate under normal and OA conditions. A team of expert investigators and clinicians has been assembled to ensure the successful achievement of the project. Novel discoveries are expected to transform current understanding of key mechanisms dictating articular chondrocyte specification and activities in health and disease, and thereby to spark novel ideas for the design of highly needed effective treatments for the millions of patients suffering from OA and other joint degenerative diseases around the world.