Mohamed-Ali H
Institut für Anatomie, Freien Universität Berlin.
Wien Med Wochenschr. 1991;141(4):77-85.
The extracellular matrix (ECM) of articular cartilage is subject to a steady remodelling process. The collagenous components of the ECM are characterized by a very low rate of metabolism, whereas the proteoglycans exhibit an active turnover. The main proteolytic enzymes degrading the ECM components are collagenase, gelatinase and stromelysin. These enzymes undergo under pathological circumstances a remarkable enhancement of synthesis and activity. Although each of these enzymes appears to degrade one ECM component specifically, there is evidence for synergistic effects of most of them. Gelatinase acts synergistically with collagenase in degrading insoluble interstitial collagens and stromelysin activates collagenase. Thus a cascade mechanism may exist in which the cartilage-ECM is completely degraded. Yet, it is not crucial which part of the ECM (collagens or proteoglycans) is primarily degraded. The integrity of the ECM rather depends on the balance between anabolic and catabolic processes, the upset of which results in damage of the articular cartilage. Cartilage destruction in rheumatoid arthritis and osteoarthritis is considered to be a result of this imbalance in favour of the catabolic processes. This would lead to a decrease in proteoglycans which causes fibronectin deposition in the cartilage ECM. Due to chemotaxic effects of fibronectin on fibroblasts, the enrichment of this glycoprotein in the ECM gives rise to cartilage fibrosis and early degeneration.
关节软骨的细胞外基质（ECM）处于持续的重塑过程中。ECM的胶原成分代谢率极低，而蛋白聚糖则呈现活跃的周转。降解ECM成分的主要蛋白水解酶是胶原酶、明胶酶和基质溶素。在病理情况下，这些酶的合成和活性会显著增强。尽管这些酶中的每一种似乎都特异性地降解一种ECM成分，但有证据表明它们中的大多数存在协同作用。明胶酶在降解不溶性间质胶原时与胶原酶协同作用，基质溶素激活胶原酶。因此，可能存在一种级联机制，其中软骨ECM被完全降解。然而，ECM的哪一部分（胶原或蛋白聚糖）首先被降解并不关键。ECM的完整性更取决于合成代谢和分解代谢过程之间的平衡，这种平衡的破坏会导致关节软骨受损。类风湿性关节炎和骨关节炎中的软骨破坏被认为是这种有利于分解代谢过程的失衡的结果。这将导致蛋白聚糖减少，从而导致纤连蛋白在软骨ECM中沉积。由于纤连蛋白对成纤维细胞的趋化作用，这种糖蛋白在ECM中的富集导致软骨纤维化和早期退变。
