The effects of insulin and basic fibroblast growth factor on fibre differentiation in rat lens epithelial explants

We have shown that fibroblast growth factors (FGFs) induce epithelial cells throughout lens explants to progressively divide, migrate and differentiate into fibres as the concentration of FGF is increased. We now report the effects of insulin and insulin-like growth factor-1 on rat lens epithelial explants, alone or in combination with the basic form of FGF. Fibre cell-specific beta- and gamma-crystallins were localised in explants by immunofluorescence or determined by ELISAs. For insulin, high doses induced limited beta-crystallin accumulation, much less than for FGF and mostly restricted to the explant periphery. When insulin was included with a low concentration of FGF, fibre differentiation was substantially enhanced. Both beta- and gamma-crystallin accumulation were affected synergistically, the effect being greater for gamma- than for beta-crystallin, and epithelial cells in both the central and peripheral region of the explant participated in the synergistic response. Insulin-like growth factor-1 at a concentration of 50 ng/ml mimicked the effects of insulin.