Zyxin‐involved actin regulation is essential in the maintenance of vinculin focal adhesion and chondrocyte differentiation status

OBJECTIVES: To investigate the role of zyxin‐involved actin regulation in expression level of vinculin focal adhesion and collagen production of chondrocyte and its possible underlying mechanism. MATERIALS AND METHODS: Chondrocytes obtained from rabbit articular cartilage were used in this study. The expression of zyxin, actin and vinculin, as well as the extracellular matrix (ECM) protein collagen type I, II and X (COL I, II and X) of chondrocytes were compared between zyxin‐knockdown group and negative control group, and between transforming growth factor‐β1 (TGF‐β1) treatment group and non‐treatment group, respectively. RESULTS: Knockdown of zyxin increased the ratio of globular actin (G‐actin) to filamentous actin (F‐actin) of chondrocyte, which further inhibited expression of vinculin and chondrogenic marker COL II as well as hypertrophy marker COL X. On the other hand, chondrocytes treated with TGF‐β1 showed an enhanced expression of F‐actin, and a lower expression of zyxin compared to non‐treatment group. In response to TGF‐β1‐induced actin polymerization, expression of vinculin and COL I was increased, while expression of COL II and aggrecan was decreased. CONCLUSIONS: These results demonstrate supporting evidence that in chondrocytes the level of zyxin is closely associated with the state of actin polymerization. In particular, the change of zyxin and F‐actin parallels with the change of COL II and vinculin, respectively, indicating a major role of zyxin‐actin interaction in the synthesis of collagen ECM and the remodelling of cytoskeleton‐ECM adhesion.