|M.Sc Student||Ordan Alooma|
|Subject||A Potential Rat Model for Proliferative Diabetic Retinopathy|
|Department||Department of Medicine||Supervisor||Professor Emeritus Ido Perlman|
|Full Thesis text|
Studying retinal neovasculariazation due to diabetes is hindered by the lack of
a proper animal model. Attempts to use vascular endothelial growth factor
(VEGF) to induce angiogenesis in animal models did not lead to consistent
results. The aim of this study was to establish an animal model for proliferative
diabetic retinopathy by inducing VEGF release in the retina of
Streptozotocin-induced diabetic rats.
Methods: The right eyes of 54 SPD rats, 36 of which were streptozotocin-induced diabetic and 18 served as control were injected with either AAV-GFP-VEGF or AAV-GFP. Fundus photography and fluorescein angiography were used for in-vivo monitoring of retinal vasculature to track structural and neovascular changes. At 4 different intervals (1, 2, 3, 4 months) after injection, animals were sacrificed for further analysis: FITC-dextran angiography was carried by intravenous injection and the vascular bed was imaged. Real-Time RT-PCR was used for mRNA quantification of VEGF and its receptors. Retinal immunohistochemistry was done on 16?m cryosections for VEGF receptors localization and expression.
Results: Retinae of healthy rats injected with AAV-GFP-VEGF showed iris neovascularization and no changes in retinal blood vessels morphology, compared to healthy rats injected with AAV-GFP. Retinae of diabetic rats injected with AAV-GFP or with AAV-GFP-VEGF showed swollen optic disk, cataract, increased blood vessel permeability, iris neovascularization but no vascular changes. Retinal VEGF/VEGFR system was not upregulated in the diabetic rats.
Conclusions: Inducing over-expression of VEGF by gene transfer in the retina of diabetic rats does not have the potential for creating an animal model of proliferative diabetic retinopathy. VEGF/VEGF receptors system stagnation seems to underlie the absence of rodents' retinal neovascularization.