A reproducible and quantifiable model of choroidal neovascularization induced by VEGF A(165) after subretinal adenoviral gene transfer in the rabbit

PURPOSE: To determine the effects of the vascular endothelial growth factor (VEGF)-A(165) delivered using a high capacity adenoviral vector (HC Ad.VEGF-A) on vascular growth and pathological changes in the rabbit eye. To combine different detection methods of VEGF-A(165) overexpression-induced neovascularization in the rabbit. METHODS: HC Ad.VEGF-A(165) was constructed and injected at 5x10(6) infectious units (iu) into the subretinal space of rabbit eyes. Two and four weeks postinjection, the development of neovascularization and the expression of HC Ad-transduced VEGF-A(165) protein were followed up in vivo by scanning laser ophthalmoscopy, fluorescein and indocyanine green angiographies and ex vivo by electron microscopy and immunohistochemistry RESULTS: We observed a choroidal neovascularization (CNV) with leakage in 83% of the rabbit eyes. Our findings present clear indications that there is a significant effect on the endothelial cells of the choriocapillaris after subretinal transduction of the retinal pigment epithelium (RPE) with VEGF-A(165) vector. The choroidal endothelial cells were activated, adherent junctions opened, and the fenestration was minimized, while the extracellular matrix localized between the RPE and the endothelium of the choriocapillaris was enlarged toward the lumen of the vessels, inducing a deep invagination of the endothelial cells into the vessel lumen. They also proliferated and formed pathological vessels in the subretinal space. Moreover,there was an increased expression of basic fibroblast growth factor and VEGF-A accompanied by macrophage stimulation, retinal edema, and photoreceptor loss. CONCLUSIONS: This is the first model of VEGF-induced CNV in the rabbit in which the pathological events following overexpression of VEGF by RPE cells have been described in detail. Many of the features of our experimental CNV resemble those observed clinically in patients having wet age-related macular degeneration.