Blockade of Apelin Receptor (APJ) can inhibit developmental retinal vessel outgrowth in pups and promote normal revascularization and reduce pathological neovascularization in OIR model in mice

Abstract

Purpose : During angiogenesis, apelin/apelin receptor (APJ) in combination with VEGF, induces the proliferation and assembly of endothelial cells (H Kidoya, et al. EMBO J, 2008; 27). Much remains to be discovered about the expression of the apelinergic system and precisely how it affects numerous physiological functions. In this study, we evaluate apelin receptor inhibition in normal retinal vascular development and in oxygen retinopathy model (OIR) in mice.

Methods : Study 1: Humanized (Hu) ApelinR mice were systemically (IP) injected with 25 mg/kg and 50 mg/kg Fc (control) and anti-Apelin Receptor (αAR) at P2 and collected at P5;
Study 2: Repeat of Study 1 at the highest dose, analyzed by masked graders.
Study 3: P2 Hu pups were IP injected with 50 mg/kg Fc, αAR or aflibercept and collected at P5;
Study 4: Hu were place in a hyperoxic environment (75% O₂) at P6 and returned to room air at P11. Pups were injected systemically with 50 mg/kg Fc (control), αAR, or aflibercept at P12 and collected at P16;
Study 5: OIR Hu mice were injected intravitreally (IVT) with 5 µg Fc, αAR, or aflibercept at P12 and collected at P16.
All retinas were stained with FITC-labeled Griffornia simplicifolia lectin I (Vector Laboratories).

Results : By injecting αAR at P2, vascular outgrowth was reduced by 23% (n= 6 eyes/groups, p < 0.05) at 25 mg/kg and 35% (n= 6 eyes/group, p < 0.005) at 50 mg/kg at P6. Aflibercept administration produced 43% reduction in blood vessel outgrowth at 50 mg/kg. In the OIR model, αAR and aflibercept were able to promote vessel regrowth. When pups were IP injected at OIR P12, αAR and aflibercept significantly reduced avascular areas by 29% and 27% (n= 6 eyes/group, p < 0.005) and neovascularizations by 69% and 94% (n= 6 eyes/group, p < 0.0001) at P16 respectively. With IVT administration aflibercept reduced vessel regrowth by 30% (n= 4 eyes/group, p < 0.0001) and eliminated all neovascularization, while αAR was able to promote vessel regrowth by 30% (n= 4 eyes/group, p < 0.0001) and reduce neovascularizations by 60% (n= 4 eyes/group, p < 0.0001).

Conclusions : Our data suggest that apelin/APJ is an important mediator of developmental angiogenesis and both pathologic and normal angiogenesis in hypoxia-driven proliferative retinopathy.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.