Cartilage Extracellular Matrix Fragments and Trauma-Induced Chondrocytes

钝伤对软骨的严重损伤被认为会引发退行性级联反应， 导致创伤后骨关节炎（PTOA）。PTOA的软骨变性始于损伤 在几年内，它会扩散到吞噬以前健康的软骨。很可能 这种缓慢进行的局部软骨溶解过程始于损伤时产生的分解代谢因子 但尚不清楚软骨溶解活性是如何持续的，以及病变是如何在如此长的时间内扩散的。 时间框架。虽然这显然是一个多因素的过程， 创伤机械条件（项目2），假设软骨的蛋白水解片段 细胞外基质（ECM）发挥的作用得到了体外和体内研究的充分支持。这些表明 具有强烈分解代谢作用的ECM片段在关节炎软骨和关节液中富集， 并且它们从关节中去除抑制了关节炎的进展。ECM片段能够 通过正常软骨的有限扩散，并可诱导基质蛋白酶表达， 组织深处的软骨细胞可能会产生新的退化和ECM区域 碎片化表明了一个恶性循环，可能导致周围持续的软骨溶解活性， 受伤部位。在这里，我们建议评估ECM片段在这一过程中的作用，重点是 纤连蛋白片段作为分解代谢刺激的可能来源。体外软骨 损伤模型被开发来研究这些局部分解代谢过程。我们预计 在这种体外系统中，创伤后软骨溶解的机制将反映发生在 然而，在体内，该假设将在动物软骨创伤模型中进行测试。这些系统 将被用来检验以下假设：（1）纤维连接蛋白片段（Fn-fs）产生的影响 损伤部位，刺激健康软骨中的软骨溶解;（2）创伤后软骨溶解是自我- （3）Fn-f诱导的信号传导抑制剂将阻碍后 创伤性软骨溶解;（4）创伤后软骨溶解是由软骨固有的因素驱动的。在 本项目的结论是，我们希望已经确定了一种或多种抑制剂， 软骨保护活性，为进一步测试以确定其治疗作用提供了良好的基础。 值

Severe damage to cartilage from blunt trauma is thought to trigger a degenerative cascade that leads to post-traumatic osteoarthritis (PTOA). Cartilage degeneration in PTOA initiates at injury sites and, over a period of years, spreads to engulf previously healthy cartilage. It seems likely that this slowly advancing process of local chondrolysis starts with catabolic factors produced at injury sites, but it is not clear how chondrolytic activity is sustained and how lesions spread over such long time frames. Although this is obviously a multifactorial process influenced substantially by post- trauma mechanical conditions (Project 2), the hypothesis that proteolytic fragments of the cartilage extracellular matrix (ECM) play a role is well-supported by in vitro and in vivo studies. These show that ECM fragments with strong catabolic effects are enriched in arthritic cartilage and joint fluids and that their removal from joints inhibits the progression of arthritis. ECM fragments are capable of limited diffusion through normal cartilage and can induce matrix protease expression by chondrocytes deep in the tissue. The potential to create new zones of degeneration and ECM fragmentation suggests a vicious cycle that could lead to sustained chondrolytic activity around injury sites. Here we propose to evaluate the role of ECM fragments in this process, focusing on fibronectin fragments as a likely source of catabolic stimulation in this context. An in vitro cartilage injury model was developed to study these local catabolic processes. We expect that the mechanisms of post-traumatic chondrolysis in this in vitro system will reflect processes that occur in vivo, however, this assumption will be tested in an animal cartilage trauma model. These systems will be used to test the following hypotheses: (1) Fibronectin fragments (Fn-fs) generated at impact injury sites, stimulate chondrolysis in healthy cartilage; (2) Post-traumatic chondrolysis is self- sustaining and propagates over time; (3) Inhibitors of Fn-f-induced signaling will impede post- traumatic chondrolysis; (4) Post-traumatic chondrolysis is driven by factors intrinsic to cartilage. At the conclusion of this project we expect to have identified one or more inhibitors that show strong chondroprotective activity, providing a sound basis for further tests to determine their therapeutic value.