Inhibition of Vascular Endothelial Growth Factor Reduces Photoreceptor Death in Retinal Neovascular Disease via Neurotrophic Modulation in Müller Glia

VEGF is not only the most potent angiogenic factor, but also an important neurotrophic factor. In this study, vitreous expression of six neurotrophic factors were examined in proliferative diabetic retinopathy (PDR) patients with prior anti-VEGF therapy (n = 48) or without anti-VEGF treatment (n = 41) via ELISA. Potential source, variation and impact of these factors were further investigated in a mouse model of oxygen-induced retinopathy (OIR), as well as primary Müller cells and 661W photoreceptor cell line under hypoxic condition. Results showed that vitreous levels of NGF, NT-3, NT-4, BDNF, GDNF and CNTF were significantly higher in eyes undergoing anti-VEGF therapy compared with PDR controls. Statistical correlation between vitreous VEGF and each trophic factor was found. Hypoxia significantly induced the expressions of these neurotrophic factors, whereas application of anti-VEGF agent in OIR model could further upregulate retinal NGF, NT-3, NT-4, together with downregulation of BDNF, GDNF, CNTF, especially in Müller glia. Inhibition of Müller cell-derived VEGF would result in similar neurotrophic changes under hypoxia. With changes of corresponding neurotrophic receptors in the cocultured photoreceptor cells, their synergic effect could protect hypoxic photoreceptor from apoptosis when VEGF inhibition was present. These findings demonstrated that regulation of Müller cell-derived neurotrophic factors might be one of the possible mechanisms by which anti-VEGF therapy produced neuroprotective effects on PDR. These results provided new evidence for the therapeutic strategy of PDR.