Suppression of retinal neovascularization in vivo by inhibition of vascular endothelial growth factor (VEGF) using soluble VEGF-receptor chimeric proteins.

Abstract

The majority of severe visual loss in the United States results from complications associated with retinal neovascularization in patients with ischemic ocular diseases such as diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity. Intraocular expression of the angiogenic protein vascular endothelial growth factor (VEGF) is closely correlated with neovascularization in these human disorders and with ischemia-induced retinal neovascularization in mice. In this study, we evaluated whether in vivo inhibition of VEGF action could suppress retinal neovascularization in a murine model of ischemic retinopathy. VEGFneutralizing chimeric proteins were constructed byjoining the extracellular domain of either human (Flt) or mouse (Flk) high-affinity VEGF receptors with IgG. Control chimeric proteins that did not bind VEGF were also used. VEGFreceptor chimeric proteins eliminated in vitro retinal endothelial cell growth stimulation by either VEGF (P < 0.006) or hypoxic conditioned medium (P < 0.005) without affecting growth under nonstimulated conditions. Control proteins had no effect. To assess in vivo response, animals with bilateral retinal ischemia received intravitreal injections of VEGF antagonist in one eye and control protein in the contralateral eye. Retinal neovascularization was quantitated histologically by a masked protocol. Retinal neovascularization in the eye injected with human Flt or murine Flk chimeric protein was reduced in 100% (25/25; P < 0.0001) and 95% (21/22; P < 0.0001) of animals, respectively, compared to the control treated eye. This response was evident after only a single intravitreal injection and was dose dependent with suppression of neovascularization noted after total delivery of 200 ng of protein (P < 0.002). Reduction of histologically evident neovascular nuclei per 6-,um section averaged 47% ± 4% (P < 0.001) and 37% ± 2% (P < 0.001) for Flt and Flk chimeric proteins with maximal inhibitory effects of 77% and 66%,

Vascular endothelial growth factor in eye disease

“…Administration of exogenous VEGF 165 prior to exposure to hyperoxia rescued the vessels from hyperoxia-induced apoptosis and vasoattenuation, thus providing hope for the therapeutic use of VEGF or VEGF analogs in preventing regression of vessels in the early phase of ROP (Alon et al, 1995). Likewise, inhibition of VEGF by injection of VEGF receptor chimeric proteins, anti-VEGF antibodies, or antisense oligonucleotides in the mouse model of retinopathy during the neovascular phase has been shown to decrease abnormal blood vessel growth (Aiello et al, 1995b;Adamis et al, 1996;Robinson et al, 2001). …”

Novel anti-VEGF chimeric molecules delivered by AAV vectors for inhibition of retinal neovascularization

“…[2][3][4] Blocking of VEGF with antibodies, soluble VEGF receptors (sVEGFR) or inhibition of VEGF receptor (VEGFR) tyrosine kinase activity are useful strategies that have shown promising preclinical and clinical results. [4][5][6] Ranibizumab, an anti-VEGF drug given intravitreally to wet-AMD patients results in substantially improved visual acuity. 7 Intraocular gene delivery of VEGF antagonists could have theoretical advantages over the current treatment, which requires monthly intravitreal injections (for years) by a retinal specialist.…”

Diabetic retinopathy is associated with a switch in splicing from anti- to pro-angiogenic isoforms of vascular endothelial growth factor

“…Furthermore, there is mounting functional evidence that inhibition of angiogenesis, both non-specifically with pharmacological anti-angiogenic agents and specifically with anti-VEGF agents, ameliorates neovascularisation in well-characterised animal models of retinopathy [5]. Subtle mutations in the 5′ region of the VEGF gene can predispose to diabetic retinopathy, suggesting that regulation of transcription or splicing of the VEGF gene is important in this condition [6].…”

“…Subtle mutations in the 5′ region of the VEGF gene can predispose to diabetic retinopathy, suggesting that regulation of transcription or splicing of the VEGF gene is important in this condition [6]. Recent clinical trials of agents that inhibit VEGF have been shown to have some effectiveness in choroidal neovascularisation cause by age-related macular degeneration [7] and in animal models of retinal neovascularisation [5].…”