VASCULAR ENDOTHELIAL GROWTH-FACTOR EXPRESSION IN CHOROIDAL NEOVASCULARIZATION IN RATS

Background: The pathogenesis of choroidal neovascularization is largel y unknown. We investigated vascular endothelial growth factor (VEGF) e xpression in laser-induced choroidal neovascularization (CNV) in rats. Methods: Intense krypton laser photocoagulation was applied to the po sterior poles of the eyes of pigmented rats to induce CNV, which was c onfirmed by fluorescein angiography and histopathology. The eyeballs w ere enucleated 1, 3, 7, 14 and 28 days after laser photocoagulation. C ryostat sections were prepared for immunofluorescence staining using a nti-VEGF and macrophage marker (EDI) antibodies. The posterior segment s of eyeballs pooled from photocoagulated and control rats were submit ted for immunoprecipitation and immunoblotting by the anti-VEGF antibo dy, and reverse transcriptase-polymerase chain reaction (RT-PCR) ampli fication of VEGF mRNA. Results: Very weak immunoreactivity for anti-VE GF antibody was found in the ganglion cell layer, inner nuclear layer, and retinal pigment epithelium (RPE) in the normal retina. In the dev elopment of CNV, strong positive staining for anti-VEGF antibody was f ound in photocoagulated areas in the subretinal space and choroid. Dou ble immunofluorescence staining showed that many cells in lasered lesi ons were positive both for anti-VEGF and macrophage marker ED1 antibod y staining in the early stage of this model. Immunoblots showed a posi tive band for the VEGF molecule in treated but not control animals. RT -PCR results demonstrated upregulation of VEGF transcripts in the CNV model compared with normal animals. Conclusions: Our findings showed t he upregulation of VEGF expression in experimentally induced CNV, wher e it may be involved in promoting choroidal angiogenesis. Macrophages may be one of the main sources of VEGF in the early stage of the disea se.