UP-REGULATED EXPRESSION OF VASCULAR ENDOTHELIAL GROWTH-FACTOR IN PROLIFERATIVE DIABETIC-RETINOPATHY

Aims/Background-Vascular endothelial growth factor (VEGF) is a hypoxia induced angiogenic factor. Recent studies have shown that high levels of VEGF accumulate in the vitreous of patients with proliferative dia betic retinopathy (PDR). The purpose of the present study was to ident ify the retinal cells that upregulate VEGF expression in human PDR pat ients representing progressive stages of retina deterioration. Methods Thirteen formalin fixed and paraffin embedded enucleated eyes with PD R were used (eyes were enucleated because of being blind and painful a s a result of neovascular glaucoma). Thin retina sections were hybridi sed in situ with a VEGF specific probe, to identify cells producing VE GF mRNA. Results-All eyes with PDR showed upregulated expression of VE GF mRNA, specifically in the cells of the neurosensory retina. VEGF ex pression was upregulated in all three nuclear layers - namely, the gan glion cell layer, the inner nuclear layer, and the outer nuclear layer . However, in each patient, VEGF producing cells were mostly distribut ed in a different layer, or even confined to a specific region in that layer. For example, expression by the outer nuclear layer was mostly detected in detached (presumably hypoxic) regions of the retina. Concl usions-Progression of PDR is distinguished by a sustained, upregulated expression of VEGF by the neurosensory retina. Cells in all retina la yers can potentially contribute to augmented VEGF production. The rest ricted population of VEGF producing cells in each case is likely to re present cells residing in ischaemic regions of the retina. Thus, VEGF may function as a linking factor between retinal ischaemia and PDR ass ociated neovascularisation.