Stimulatory effects of basic fibroblast growth factor on DNA synthesis in the human embryonic cornea.

First trimester human embryonic eye globes were micro-dissected so that a passage was opened between the outer environment and the anterior chamber, which rendered free access of tissue culture medium to the endothelial cell monolayer. The dissected eye globes were maintained in organ culture for 24h in the continuous presence of tritiated thymidine. Sections were cut through the whole eye globes and were subject to autoradiographic analysis in order to estimate the mitogenic response of human corneal endothelial cells to externally supplied growth factors and hormones. It was found that the corneal endothelial cells could be stimulated to initiate DNA synthesis by exposure to basic fibroblast growth factor (bFGF). The thymidine labelling index nearly doubled after bFGF addition. Northern blot analysis revealed the presence of bFGF transcripts in the embryonic eye. In contrast we were unable to trace any bFGF transcripts in other first trimester human embryonic organs. In an attempt to determine the topographical distribution of bFGF mRNA within the eye, we found that transcript levels were higher in the posterior regions of the eye globe. Immunostaining with the appropriate antibody showed conclusively that bFGF protein was present in both the anterior and posterior human eye. These results suggest that local production of bFGF may stimulate cell proliferation in vivo.