Non-vascular alterations and functional impairment persist after Anti-VEGF therapy in Oxygen Induced Retinopathy (OIR) mouse model.

RIDANO MAGALI E; LORENC VE; SUBIRADA CALDARONE PAULA; PAZ MC; CROCI D; J.D. LUNA PINTO; RABINOVICH G; SANCHEZ MC

Congreso; ARVO Annual Meeting; 2016

Purpose: Neovascular retinopathies are leading causes of irreversible blindness but the successful treatment remains an unmet medical need. Although Vascular Endothelial Growth Factor (VEGF) inhibitors have been established as the mainstay of current treatment, it is unclear why many patients do not improve after therapy. Animal models such as OIR have been developed in order to study these diseases in which hypoxia induces formation of abnormal neovessels (NV) as well as neuronal cell death causing retinal impairment. We hypothesized that although Anti-VEGF therapy reduces the NV do not improve associated non-vascular alterations in these retinopathies.Methods: C57BL/6 mice (OIR, N=33) were exposed to 75% O2 from postnatal day 7 (P7) to P12, after which they were brought to room air for additional five (P17) or nine days (P26). Age-matched mice maintained in room air (RA, N=15) were used as control. Some OIR mice were intraocular administered at P12 with 1,25 µg of Anti-VEGF (N=9) or vehicle (N=9). At P12, P17 and P26 mice were sacrificed and protein expression in their retinas was analyzed by Western blots. TUNEL assay and vascular staining with GSA isolectin B4 conjugated to Alexa 488 were performed. Retinal function was analyzed by electroretinogram (ERG). GraphPad Prism program was used for statistical analysis according to the experimental data. Results: VEGF expression was significantly increased in P17 OIR compared to RA (p<0.05) according to the maximum NV day. Since this animal model produces Müller cell activation and neurodegeneration, Glial Fibrillary Acidic Protein (GFAP) expression was increased in P17 and P26 OIR mice; whereas Glutamine Synthase (GS) showed lower levels respect to RA (p<0.05). OIR mice exhibited more TUNEL positive cells in inner retinal layer and a significant decrease in the amplitude of the B ERG wave compared to RA (p<0.05). Anti-VEGF treatment reduced VEGF levels in P17 OIR at the same level of RA (p<0.05) and improved retinal vascularization. However, this treatment did not restore the changes in GFAP and GS expression (p<0.05), the number of TUNEL positive cells and the ERG alterations.Conclusions: Results in OIR model are consistent with our hypothesis that Anti-VEGF therapy do not prevent or reverse the associated non-vascular alterations. These findings highlight the need for novel and combined therapies for NV retinopathies.