Enhanced Recombinant Adeno-Associated Virus-Mediated Vascular Endothelial Growth Factor Expression in the Adult Mouse Retina

Abstract

Diabetic retinopathy, one of the most serious complications of long-term diabetes, could clinically be divided into two stages: 1) background retinopathy that does not cause visual impairment and 2) proliferative retinopathy, which is a potentially blinding condition. This study aims to investigate the correlation between enhancement of vascular endothelial growth factor (VEGF) expression and neovascular changes. A binary recombinant adeno-associated virus construct producing green fluorescent protein (GFP) and VEGF under the control of the human cytomegalovirus promoter, recombinant adeno-associated virus (rAAV).VEGF.GFP, was produced and injected into the subretinal space of C57BL mice. GFP expression was tracked by fluorescence fundus photography, and VEGF expression was confirmed by immunohistochemistry and enzyme-linked immunoassay. Neovascular changes were monitored by fluorescein angiography and histology and by quantifying the number of inner retinal vessels. GFP expression was found in 100% of injected eyes, and vascular changes were detected in 9 of 10 rAAV.VEGF.GFPinjected eyes. Of these, four demonstrated microaneurysms and five showed moderate to severe leakage. There was a statistically significant increase in blood vessel number in the inner nuclear layer (P < 0.03) and dilatation of retinal veins (P < 0.05). This work has demonstrated that the development of different stages of diabetic retinopathy is closely correlated with an increased VEGF level in the retina. Diabetes 52: 857-863, 2003

Generation of transgenic mice with mild and severe retinal neovascularisation

“…The gradual changes observed in line 029 were similar to our previous mouse model in which VEGF upregulation was mediated by a recombinant adeno associated virus vector. 38 However, it differed from an existing VEGF transgenic mouse model, 13 which demonstrated earlier onset and more severe retinopathy. Likewise, a previously reported inducible VEGF transgenic model 39 had variable pathology even when using the same doxycyclin dosage and neovascularisation was rapid and severe with complete retinal detachment.…”

Long-term global retinal microvascular changes in a transgenic vascular endothelial growth factor mouse model

“…In comparison, moderate VEGF expression in another model induced by AAV.VEGF gene transfer also produced a mild phenotype with features similar to trVEGF029 and with no immune reaction elicited [37]. trVEGF029 thus provides an opportunity for detailed examination of vascular changes without the confounding factors of severe and rapid vascular and retinal damage in other models.…”

Gene Therapies for Neovascular Age-Related Macular Degeneration

“…The four main biological effects of VEGF, as determined by Ferrara and Gerber (2001), are increase in vascular permeability, growth and proliferation of vascular endothelial cells, migration of vascular endothelial cells, and survival of immature endothelial cells by preventing apoptosis. The role of VEGF in inducing retinal neovascularization and vascular leakage has been confirmed in several animal models using ocular gene delivery of VEGF (Yu et al 1999;Rakoczy et al 2003;Lebherz et al 2005;Julien et al 2008). Since the original study in rhesus monkeys (Ryan 1979), laser rupture of Bruch's membrane has become a common technique to induce CNV in different animal species.…”