Comparative study of VEGF inhibitors in Oxygen Induced Retinopathy (OIR) mouse model: Vascular, non-vascular and functional implications

Abstract

Purpose : During the past decade, vascular endothelial growth factor (VEGF) inhibitors have become standard-of-care treatment for neovascular retinopathies. However, clinical management of these diseases is still limited. Recently, it was demonstrated novel anti-angiogenic functions for aflibercept beyond its antagonism against VEGF family members. We hypothesized that aflibercept could be better than anti-VEGF therapy, improving not only vascular but also non-vascular alterations and retinal function.

Methods : The oxygen-induced retinopathy (OIR) mouse model is an excellent platform to test drugs for retinopathy of prematurity or proliferative diabetic retinopathy. Briefly, C57BL/6 mice (OIR, N=27) were exposed to 75% O₂ from postnatal day (P) 7 to P12, after which they were brought to room air for additional five (P17) or nine days (P26). Some OIR mice were intraocular administered at P12 with 1,25 μg of bevacizumab (Anti-VEGF) (N=9), 2 μg of aflibercept (N=9) or vehicle (N=9). At P17 and P26 mice were sacrificed. Some retinas were isolated to analyze Glutamine Synthase (GS), Glial Fibrillary Acidic Protein (GFAP) and total caspase 3 expression by Western blots. Vascular staining at P17 with GSA isolectin B4 conjugated to Alexa 488 was also performed. Finally, retinal function was analyzed by electroretinography (ERG). GraphPad Prism program was employed for statistical analysis according to the experimental data.

Results : Aflibercept therapy reduced the vascular alterations observed in the OIR mice in a similar way to anti-VEGF treatments. The retinas of mice injected with anti-VEGF had lower levels of total caspase 3 than those injected with aflibercept. Furthermore, unlike that observed in mice injected with anti-VEGF, GFAP and GS protein expression alterations observed in control OIR mice were reduced in mice injected with aflibercept. Finally, there were no improvements in ERG response of mice injected with aflibercept compared to those injected with anti-VEGF and OIR control mice

Conclusions : Aflibercept therapy showed vascular improvement in a similar way to anti-VEGF although it also improved non-vascular alterations in the OIR model. However, the functional retinal damage of OIR mice was not able to be reversed with either of these two treatments. These findings highlight the need for novel and combined therapies for neovascular retinopathies.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.