Cell Proliferation on the Lens Capsule in Low Serum Conditions Is Linked to MMP–Induced Growth Factor Release From the Lens Capsule

Abstract

Abstract: : Purpose: To investigate the role of the lens capsule in the promotion of lens epithelial cell lines growth and survival in low serum culture. Release of known growth factors directly from the capsule was observed and correlated to MMP expression. Methods: Primary bovine (BLEC) and human (H36LE2) lens epithelial cell lines were grown on either plastic or cleaned lens capsules in low serum conditions (0.1% foetal calf serum) and exposed to the protein kinase C inhibitor staurosporine for 48h. Live cell numbers, growth factor levels and gelatinase protein expression were then assessed by MTT assay, ELISA, zymography and immunoblotting, respectively. This experiment was repeated in the presence of either MMP or growth factor inhibitors to assess their effect on cell growth and survival. Also, cell–free bovine lens capsules were exposed to purified MMP–2 and MMP–9 in low serum (0.1% foetal calf serum) cell culture medium, and IGF–1, FGF–2 and TGF–b2 medium levels monitored by ELISA. Results: Cell culture on the bovine lens capsule sustained both lens epithelial cell growth and survival in low–serum conditions and correlated with MMP–2 and MMP–9 expression. Independently, both gelatinases were also shown to release growth factors stored in the cell–free capsule. In turn, inhibition of MMP expression and growth factor signalling reduced both growth and survival of lens epithelial cells on the bovine lens capsule. Conclusions: Growth and survival of lens epithelial cells in low–serum conditions partially depends on their ability to release growth factors directly from the bovine lens capsule via MMP secretion.

Keywords: extracellular matrix • growth factors/growth factor receptors • proliferation