Endothelial protein C receptor promotes retinal neovascularization through heme catabolism

Pathological retinal neovascularization (RNV) is one of the leading causes of blindness worldwide; however, its underlying mechanism remains unclear. Here, we found that the expression of endothelial protein C receptor (Epcr) was increased during RNV, and its ligand was elevated in the serum or vitreous body of patients with proliferative diabetic retinopathy. Deleting endothelial Epcr or using an EPCR-neutralizing antibody ameliorated pathological retinal angiogenesis. EPCR promoted endothelial heme catabolism and carbon monoxide release through heme oxygenase 1 (HO-1). Inhibition of heme catabolism by deleting endothelial Ho-1 or using an HO-1 inhibitor suppressed pathological angiogenesis in retinopathy. Conversely, supplementation with carbon monoxide rescued the angiogenic defects after endothelial Epcr or Ho-1 deletion. Our results identified EPCR-dependent endothelial heme catabolism as an important contributor to pathological angiogenesis, which may serve as a potential target for treating vasoproliferative retinopathy.