Cellular adhesion regulates bFGF gene expression in human retinal pigment epithelial cells

It has previously been shown that cell density has a profound effect on the expression of the basic fibroblast growth factor (bFGF) gene by human retinal pigment epithelial (RPE) cells in vitro. This study was designed to examine cellular mechanisms which may be responsible for the density-dependent expression of bFGF. Examination of RPE labeling index with respect to cell density suggests that cell cycle progression is not responsible for changes in steady-state mRNA levels. Media switch experiments between sparse and dense RPE cell cultures also rule out a soluble mediator. Extracellular matrix deposited within the 3-day plating period could also not account for the observed changes in bFGF gene expression. However, the synchronous loss of cell contact induced by Ca2+ chelation caused a transient elevation in steady-state mRNA levels. These results suggest that changes in cell adhesion may be responsible for the density-dependent regulation of bFGF mRNA levels in RPE cells in vitro.