Effect of growth factors on proliferation and expression of growth factor receptors in a human lens epithelial cell line

Abstract

To investigate the effect of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin-like growth factor 1 (IGF-1), and transforming growth factor beta 2 (TGFbeta2) on proliferation of a human lens epithelial cell line (HLEC-SRA 01/04); the effect of bFGF and TGFbeta2 on proliferation of human lens epithelial cells (HLECs); and the expression of bFGF, EGF, IGF-1, and TGFbeta2 receptors in an HLEC-SRA 01/04 cell line. Department of Ophthalmology, University of Ulm, Ulm, Germany. Both HLEC and HLEC-SRA 01/04 were treated with 1 to 50 ng/mL bFGF and TGFbeta2) Additionally, HLEC-SRA 01/04 were cultured with EGF and IGF-1 at a concentration of 1 to 50 ng/mL for 48 hours in the presence of [3H]-thymidine. In all experiments, untreated serum-free negative controls were used. (3H)-thymidine incorporation as a direct measure of lens epithelial cell proliferation was assessed by liquid scintillation counting. The expression of bFGF, EGF, IGF-1, and TGFbeta2 receptors in HLEC-SRA 01/04 were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). Statistical analysis was performed using the 2-sample t test for the means. Proliferation of HLECs was dose dependently induced by bFGF and TGFbeta2, showing maximum effects at 10 ng/mL (P = .0003) and at 50 ng/mL (P < .0001), respectively. Proliferation of HLEC-SRA 01/04 was also induced by bFGF, showing slight but significant effects (P < .03). Additionally, HLEC-SRA 01/04 proliferation was dose-dependently induced by EGF with a maximum effect at 5 ng/mL (P < .01), IGF-1 with a maximum effect at 5 ng/mL (P < .0001), and TGFbeta2 with a maximum effect at 10 ng/mL (P < .0001) compared with the control. The RT-PCR analysis revealed bFGF, EGF, IGF-1, and TGFbeta2 receptor expression in the HLEC-SRA 01/04 cell line. The data showed that bFGF and TGFbeta2 are strong mitogens for HLEC. The HLEC-SRA 01/04 cell line derived from HLEC reacted to growth factors, with cell proliferation only to a lesser extent. Such quiescence of these cells, when compared with cells in primary culture, cannot be explained by the lack of respective receptors for growth factors. Further investigation of growth factor-induced responses of both cell types will provide new insight into the proliferative processes involved in postoperative secondary cataract formation.