Growth factors influence contractility and α-smooth muscle actin expression in bovine lens epithelial cells

Purpose. To determine whether basic fibroblast growth factor (bFGF) and transforming growth factor-β2 (TGF-β2) influence the contractile activity and the expression of α-smooth muscle actin (α-SMA) in bovine lens epithelial cells (LECs). To examine whether modulation of contractile activity by these growth factors depends on changes of α-SMA expression. Methods. Bovine LECs were cultured in collagen gel in MED 5 medium (F-12 nutrient mixture supplemented with 5% fatal bovine scrimp) with or without bFGF (1 to 100 ng/ml) or TGF-β2 (0.01 to 10 ng/ml). To evaluate collagen gel contraction, the longest and shortest diameters of the gels were measured daily for 7 days, and the area was determined. Detection of α-SMA in the gels was performed immunohistochemically using a mouse monoclonal antibody against α-SMA. The percentage of α-SMA-positive cells to the total number of cells was determined. Results. Control gels cultured with MED 5 medium alone contracted to 15.8% ± 3.4% of their original area after 7 days. TGF- β2 significantly increased this contraction in a dose-dependent manner, whereas bFGF significantly decreased it. Approximately 30% of cells in the control gels were α-SMA positive. TGF-β2 significantly increased the α- SMA positivity dose dependently, whereas bFGF significantly decreased it. The percent positivity for α-SMA and the gel area showed a significant negative correlation. Conclusions. TGF-β2 increased collagen gel contraction and α- SMA expression in bovine LECs, whereas bFGF decreased these parameters. Because collagen gel contraction was correlated with α-SMA expression, the modulation of LEC contractile activity by growth factors may be related to an effect on α-SMA.