Growth regulation of retinal pigment epithelial (RPE) cells in vitro.

Studies of growth factor production by chick embryo retinal pigment epithelial (RPE) cells and the effects of cytokines on chick and human RPE cells were performed in vitro. RPE cell growth was evaluated by tritiated thymidine uptake. Chick RPE cells produced growth factors whose molecular weights were 15 and 108 kD. These fractions contained interleukin (IL)-1-like activity which stimulated murine thymocyte proliferation. 100-150 U/ml human IL-1 beta, interferon (IFN)-beta, IFN-gamma and tumor necrosis factor (TNF)-alpha stimulated the growth of both RPE cells. The activity of IFN-beta was the most potent of these cytokines, while IL-2 and IFN-alpha had no effect in chick RPE cells. 100-150 U/ml transforming growth factor (TGF)-beta 1 suppressed cytokine-induced growth of both RPE cells. RPE cells therefore produce growth factors, respond to several growth factors and are regulated by a network of cytokines.