Cartilage Extracellular Matrix Fragments and Trauma-Induced Chondrocytes

钝性创伤对软骨的严重损害被认为会触发退行性级联反应， 导致创伤后骨关节炎(PTOA)。PTOA的软骨退变始于损伤 并在一段时间内扩散到吞噬以前健康的软骨。看起来很有可能 这种缓慢推进的局部软骨溶解过程始于损伤时产生的分解代谢因子。 部位，但尚不清楚软骨溶解活动是如何持续的，病变是如何扩散到如此长的时间的 时间框架。虽然这显然是一个多因素的过程，在很大程度上受到后 创伤机械条件(项目2)，假设软骨的蛋白分解片段 细胞外基质(ECM)的作用得到了体内外研究的支持。这些节目展示了 关节软骨和关节液中富含具有强烈分解代谢作用的细胞外基质碎片 从关节中移除它们可以抑制关节炎的进展。ECM碎片能够 在正常软骨中的有限扩散，并可通过以下方式诱导基质蛋白酶的表达 软骨细胞在组织深处。创造新的退化区和细胞外基质的可能性 碎裂意味着一种恶性循环，可能导致周围持续的软骨溶解活动 受伤地点。在这里，我们建议评估ECM片段在这一过程中的作用，重点是 在这种情况下，纤维连接蛋白片段可能是分解代谢刺激的来源。一种体外软骨 损伤模型被用来研究这些局部分解代谢过程。我们预计， 这个体外系统中创伤后软骨溶解的机制将反映发生在 然而，活体，这一假设将在动物软骨创伤模型中得到验证。这些系统 将用来检验以下假设：(1)撞击时产生的纤维连接蛋白片段(Fn-f) 损伤部位，刺激健康软骨的软骨溶解；(2)创伤后软骨溶解是自发性的 (3)Fn-f诱导的信号转导的抑制剂将阻碍后 创伤性软骨溶解；(4)创伤后软骨溶解是由软骨固有因素驱动的。在… 这个项目的结论，我们希望已经确定了一个或多个抑制剂，显示出很强的 软骨保护活性，为进一步测试以确定其治疗作用提供了可靠的基础 价值。

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.