EXPRESSION OF BASIC FIBROBLAST GROWTH-FACTOR MESSENGER-RNA IN DEVELOPING CHOROIDAL NEOVASCULARIZATION

Purpose. Basic fibroblast growth factor (bFGF) is an angiogenic peptid e that may be important in the pathogenesis of choroidal neovasculariz ation. We attempted to determine the transcription of the bFGF gene du ring the development of experimentally induced choroidal neovasculariz ation. Methods. Rat bFGF cDNA was inserted in the pBluescript to prepa re antisense and sense riboprobes. Multiple krypton laser burns were a pplied to the posterior poles of the eyes of pigmented rats according to a protocol described for producing subretinal neovascularization in these animals. At intervals of up to 4 weeks after photocoagulation, the eyes were removed and cut into thin sections. The sections were su bjected to histopathological analysis, cell proliferation study, or in situ hybridization with digoxigenin (DIG)-labeled single-strand ribop robes synthesized from rat bFGF cDNA. Results. In normal adult rat ret inas, bFGF mRNA expression was mainly observed in the ganglion cell la yer and the inner nuclear layer. After laser photocoagulation, prolife ration of RPE cells, fibroblast-like cells and cells in the choroid in the lesions were observed. Expression of bFGF mRNA was observed in th e lesions 3 days to 2 weeks after laser treatment. Signals of bFGF mRN A were detected in the proliferating RPE-like cells, choroidal vascula r endothelial cells and fibroblast-like cells, all of which are essent ial for neovascularization. However, bFGF mRNA expression was no longe r detectable in these cells 4 weeks after photocoagulation. Conclusion s. Our findings indicate that bFGF is normally transcribed in ganglion cells and the inner nuclear eel layer. During the neovascularization that followed laser photocoagulation, bFGF mRNA expression was detecte d within the laser lesions. It is thus probable that bFGF acts as a me diator in the neovascularization process.