Neural retinas promote cell division and fibre differentiation in lens epithelial explants.

Histological analysis of lens epithelial cells from newborn rats co-cultured with neural retinas over a 12 day period showed stimulation of cell division and fibre differentiation. Cell division increased to a peak of 0.54 +/- 0.13% at 6 days and then decreased to near zero at 12 days. Early signs of differentiation at 3 days included some cell elongation and weak fluorescence for beta-crystallin. Differentiation was progressive and by 12 days there was further elongation and multi-layering of cells with most cells fluorescing strongly for beta-crystallin and some cells fluorescing strongly for gamma-crystallin. Cell free, neural retina conditioned medium ( NRCM ) also stimulated epithelial cell division and fibre differentiation. The peak mitotic index was 0.12% at 2 days. Although there were no signs of differentiation at 3 days, by 12 days the majority of cells fluoresced strongly for beta-crystallin and less than half fluoresced for gamma-crystallin. Our interpretation of these results is that neural retinas release diffusable substances that stimulate division and differentiation of lens epithelial cells. The stronger proliferation and differentiation responses of epithelial cells in explants co-cultured with neural retinas is probably due to continual release of the factors and their build-up in the medium during the 12 day culture period.