Stimulation of PAR2 during OIR reduces endothelial cell death and provokes rapid revascularization

Abstract

In the retina, a highly regulated vascular meshwork irrigates neurons and supplies necessary metabolic requirements. Sustained vessel loss, as in Retinopathy of Prematurity (ROP), prompts revascularization despite initial suppression of vaso‐survival cues such as VEGF. Thus, other forces are likely involved. Importantly, we have previously demonstrated the substantial role of Protease‐activated receptor 2 (PAR2), a GPCR, in the developing retina. The exact mechanism by which PAR‐2 modulates angiogenic cues in ROP remains elusive.Expression and localization of PAR2 was determined by Western blot and immunohistochemistry in mouse whole retina. Appraisal of retinal vasculature and expression of pro‐ and anti‐angiogenic cues was assessed following intravitreal administration of PAR2 agonist peptide (SLIGRL) or lentiviral shRNA knockdown of PAR2 (LV shPAR2) in mice exposed to a murine oxygen‐induced retinopathy model (75% O2 from P7‐P12).Our results demonstrate a pronounced expression of PAR2 preferentially in RGC. PAR2 sharply increases during the initial phases of vaso‐obliteration (VO) and during the neovascularization (NV) phase. Activation of PAR2 with SLIGRL in vivo reduced Sema3A while increasing VEGF. Importantly, SLIGRL treatment in vivo prior to and following oxygen exposure significantly decreased VO and NV. Treatment with LV shPAR2 increased VO while augmenting NV.This study underscores the importance of the coupling between neurons and vessels and shows that RGC‐specific PAR2 plays a pivotal role in modulating angiogenesis in a pathological context.