Neuroprotective Properties of an Anti-VEGF Antibody Delivered by Gene Transfer in the Mouse Retina

Abstract

Purpose:: In the retina, the balance between pro- and anti-angiogenic factors is critical for angiogenesis control but is also involved in cell survival and maintenance. Thus, the anti-angiogenic factor PEDF is neuroprotective for photoreceptors in various models of retinal degeneration. We previously reported that, in the light-induced photoreceptor lesion model, retinal expression of VEGF is upregulated, and systemic delivery of PEDF, as well as of an anti-VEGF antibody (scFv-VEGF), rescues photoreceptors from cell death (Wenzel A. et al., ARVO 2004, program #779). We herein describe the effect of scFv-VEGF local delivery by lentiviral gene transfer.

Methods:: We constructed lentiviral vectors coding scFv-VEGF (LV-antiVEGF) or a control scFv (LV-control). Balb/c mice received subretinal injections of the vectors and were subjected to a light-induced lesion (5'000 lux, 1 hr). We next tested the retinal function by electroretinography (ERG), and estimated the photoreceptor survival rate by rhodopsin dosage and transgene expression by quantitative PCR (Q-PCR).

Results:: In vitro data demonstrated that cells transduced by LV-antiVEGF secrete a high amount of scFv-VEGF. In vivo expression after subretinal injection in mice was also assessed by in situ hybridization. We thus treated a group of mice by a subretinal injection of LV-antiVEGF 3 weeks prior to light damage. Control groups received LV-control, vehicle alone, or no pre-treatment. Assessment of the retinal function by ERG 10 days after the lesion showed an average decrease of the a-wave amplitude of 66.6 ±7.3% in control groups compared to naïve animals. After LV-antiVEGF treatment, the average decrease in a-wave amplitude was only of 37.8 ±6.4%, indicating a better survival rate of the photoreceptors (P=0.033). In line with these results, rhodopsin content of the retina was higher in the LV-antiVEGF group than in controls. Moreover, Q-PCR quantification of transgene expression in the RPE layer demonstrated that the extent of photoreceptor protection correlates with the level of anti-VEGF expression (R²=0.781, P=0.0194).

Conclusions:: This study further involves VEGF in light damage and highlights the prime importance of angiogenic factor balance for photoreceptor survival. This suggests that anti-VEGF gene transfer may help to fight retinal diseases by both its neuroprotective and anti-angiogenic actions.

Keywords: gene transfer/gene therapy • photoreceptors • apoptosis/cell death