GROWTH-FACTORS INFLUENCE CONTRACTILITY AND ALPHA-SMOOTH MUSCLE ACTIN EXPRESSION IN BOVINE LENS EPITHELIAL-CELLS

Purpose. To determine whether basic fibroblast growth factor (bFGF) an d transforming growth factor-beta 2 (TGF-beta 2) influence the contrac tile activity and the expression of alpha-smooth muscle actin (alpha-S MA) in bovine lens epithelial cells (LECs). To examine whether modulat ion of contractile activity by these growth factors depends on changes of alpha-SMA expression. Methods. Bovine LECs were cultured in collag en gel in MED 5 medium (F-12 nutrient mixture supplemented with 5% fet al bovine serum) with or without bFGF (1 to 100 ng/ml) or TGF-beta 2 ( 0.01 to 10 ng/ml). To evaluate collagen gel contraction, the longest a nd shortest diameters of the gels were measured daily for 7 days, and the area was determined. Detection of alpha-SMA in the gels was perfor med immunohistochemically using a mouse monoclonal antibody against al pha-SMA. The percentage of alpha-SMA-positive cells to the total numbe r of cells was determined. Results. Control gels cultured with MED 5 m edium alone contracted to 15.8% +/- 3.4% of their original. area after 7 days. TGF-beta 2 significantly increased this contraction in a dose -dependent manner, whereas bFGF significantly decreased it. Approximat ely 30% of cells in the control gels were alpha-SMA positive. TGF-beta 2 significantly increased the alpha-SMA positivity dose dependently, whereas bFGF significantly decreased it. The percent positivity for al pha-SMA and the gel area showed a significant negative correlation. Co nclusions. TGF-beta 2 increased collagen gel contraction and alpha-SMA expression in bovine LECs, whereas bFGF decreased these parameters. B ecause collagen gel contraction was correlated with alpha-SMA expressi on, the modulation of LEC contractile activity by growth factors may b e related to an effect on alpha-SMA.