Inhibition of neovascularization and expression shift of pro-/anti-angiogenic vascular endothelial growth factor isoforms after intravitreal bevacizumab injection in oxygen-induced- retinopathy mouse model

Abstract

Background Retinopathy of prematurity (ROP) has become one of the leading causes of visual loss in children. Vascular endothelial growth factor A (VEGF-A) is the principal stimulator of angiogenesis. VEGF was differentially spliced from exon 8 to exons 8a and 8b to form two families: the pro-angiogenic VEGFxxx family and the anti-angiogenic VEGFxxxb family. Previous research has shown variable effeteness of bevacizumab in inhibiting retinal neovascularization in ROP. This study aimed to investigate whether the effectiveness of this inhibition depends on the relative ratio of the two VEGF isoforms. Methods Intravitreal bevacizumab injection (IVB) was performed in the oxygen-induced-retinopathy (OIR) mice on postnatal day 12 (P12) (intravitreal phosphate buffered saline (PBS) injection as control). The Evans blue perfused retina were used to test the retinal neovascularization-leakage (NVL) area and non-perfusion (NP) area. Results The retinal NVL and NP area in the IVB group were significantly smaller than the intravitreal PBS injection group (IVP group). On P17, the protein level of total VEGF isoforms was significantly inhibited compared to IVP group (P <0.05) while VEGF165b isoform was slight reduced (P >0.05). The switch from pro-angiogenic isoforms to anti-angiogenic isoforms after IVB could be found. The relative protein expression of VEGF165b isoform was significantly higher in IVB group than in IVP group (P <0.05) on P17 which was correlated with the reduced ischemia-induced angiogenesis in OIR mice after IVB. Conclusions The anti-angiogenic effectiveness might depend on the relative high expression of VEGF165b after intravitreal bevacizumab injection. Anti-angiogenic therapy is a more effective therapy for ROP.