Alpha-smooth muscle actin expression in cultured lens epithelial cells

PURPOSE. Lens epithelial cells transdifferentiate to myofibroblasts during the formation of anterior subcapsular cataracts and secondary cataracts. On e of the defining characteristics of myofibroblasts is the expression of al pha-smooth muscle actin (alpha-SMA). This study investigated some of the fa ctors that influence alpha-SMA expression in lens epithelial cells. METHODS. Bovine, rabbit, and human lens epithelial explants or cells were c ultured with or without serum. Immunohistochemistry and immunoblotting were used to detect and quantitate alpha-SMA expression. RESULTS. Cells from all species studied expressed alpha-SMA in primary expl ant culture with or without serum. Immunostaining for alpha-SMA first appea red in a diffuse granular pattern, then accumulated at the cell cortex, and eventually was detected along stress fibers. When lens epithelial cells mi grated onto cell-free regions of the capsule or were transferred to a plast ic culture dish, alpha-SMA expression increased significantly. Expression o f alpha-SMA positively correlated with cell size and cell migration. CONCLUSIONS. Expression of alpha-SMA is a common feature of cultured mammal ian lens epithelial cells. Because alpha-SMA expression occurred without th e addition of exogenous factors, the fibrosis seen in anterior subcapsular cataracts or secondary cataracts may reflect the intrinsic properties of le ns epithelial cells. Interaction between lens epithelial cells and their su bstratum appears to be an important regulator of myofibroblast formation. U nderstanding the factors that regulate alpha-SMA expression in lens epithel ial cells could lead to the development of methods for preventing secondary cataracts and anterior subcapsular cataracts.