The purpose of the study is to determine the effect of exogenous vascular endothelial
growth factor (VEGF) on the primate retina and its vasculature.
Ten eyes of five animals were studied. Physiologically relevant amounts of the 165
amino acid isoform of human recombinant VEGF were injected into the vitreous of six
healthy cynomolgus monkey eyes. Inactivated human recombinant VEGF or vehicle was
injected into four contralateral control subject eyes. Eyes were assessed by slit-lamp
biomicroscopy, tonometry, fundus color photography, fundus fluorescein angiography,
light microscopy, and immunostaining with antibodies against proliferating cell nuclear
antigen and factor VIII antigen.
All six bioactive VEGF-injected eyes developed dilated, tortuous retinal vessels that
leaked fluorescein. Eyes receiving multiple injections of VEGF developed progressively
dilated and tortuous vessels, venous beading, edema, microaneurysms, intraretinal
hemorrhages and capillary closure with ischemia. The severity of the retinopathy correlated
with the number of VEGF injections. None of the four control eyes exhibited any abnormal
retinal vascular changes. The endothelial cells of retinal blood vessels were proliferating
cell nuclear antigen positive only in the bioactive VEGF-injected eyes.
Vascular endothelial growth factor is sufficient to produce many of the vascular abnormalities
common to diabetic retinopathy and other ischemic retinopathies, such as hemorrhage,
edema, venous beading, capillary occlusion with ischemia, microaneurysm formation,
and intraretinal vascular proliferation.