Site-directed Growth Factor Expression and Photocoagulation:A New Mouse Model for Retinal Neovascularization

Abstract

Abstract: : Purpose:There are to date no adequate rodent models of proliferative diabetic retinopathy (PDR). Oxygen-induced retinopathy in neonatal animals mimics retinopathy of prematurity, but differs from adult PDR in two important respects: the anatomical loci of neovascular lesions and regression of these lesions with time. We sought to develop an adult animal model of retinal neovascularization that more closely resembles PDR. Methods:Adult mice were anesthetized and one eye injected with an adeno-associated virus construct expressing human VEGF under control of the CMV promoter. Three weeks later animals underwent venous occlusion by laser photocoagulation to selected sites next to the optic nerve. From three to six weeks after the latter treatment, animals were killed and eyes removed for evaluation. The contralateral (untreated) eye was used as control. Qualitative assessment of retinal neovascularization was accomplished by examining whole retinal flat mounts of animals perfused with fluorescein Dextran. Degree of neovascularization was quantified by counting cell nuclei above the internal limiting membrane (ILM) in multiple stained sections (10 per eye) of treated and control eyes. Results:Eyes receiving either expression vector or occlusion alone failed to develop consistent neovascular lesions. The combination of these treatments resulted in consistent vascular engorgement and tortuosity with central and peripheral neovascular tufts. Treated eyes showed a 4 to 10-fold increase (P<0.01) in cell nuclei above the ILM. These changes persisted throughout the duration of the study. Conclusion:The combination of site-specific VEGF expression followed by venous occlusion results in consistent and reproducible vascular changes similar to PDR. This model may thus prove useful in examining the biochemical and physiological processes leading to adult retinal vascular pathologies.

Keywords: 566 retinal neovascularization • 316 animal model • 506 pathology: experimental