Interaction with collagen IV protects lens epithelial cells from Fas-dependent apoptosis by stimulating the production of soluble survival factors.

PURPOSE To investigate the sensitivity of lens epithelial cells (LECs) to Fas-dependent apoptosis and to determine the role of interaction with the extracellular matrix (ECM) in the regulation of Fas-dependent apoptosis. METHODS Sensitivity to Fas-mediated apoptosis of primary human LECs and HLE-B3 LECs cultured on different substrates was determined by Hoechst staining after incubation with Fas-stimulating or control IgM. Fas expression was determined by Western blot analysis. Effects of varied cell density and conditioned media from HLE-B3 cells cultured on different substrates on the Fas sensitivity of HLE-B3 cells cultured on tissue culture (TC) plastic were determined. RESULTS Primary LECs cultured as free-floating anterior capsulotomy specimens were resistant to Fas-dependent apoptosis. The LE cell line, HLE-B3, was sensitive to Fas-dependent apoptosis when cultured on TC plastic but not on lens capsule. Culture on collagen IV, but not on laminin, rendered HLE-B3 cells resistant to Fas-dependent apoptosis, although Fas was still expressed. Primary LECs cultured on TC plastic after migration from lens capsule explants were resistant to Fas-dependent apoptosis if the lens capsule and attached cells were still present, but not if the lens capsule had been removed. Conditioned medium from LECs cultured on collagen IV, but not TC plastic, protected cells cultured on TC plastic from Fas-dependent apoptosis. The protective effect of culture on collagen IV diminished with decreasing cell density. CONCLUSIONS LECs are protected from Fas-dependent apoptosis by interaction with collagen IV. Soluble factors released by the LECs cultured on collagen IV protect LECs from Fas-dependent apoptosis.