Purpose Apelin is a bioactive peptide growth factor isolated from bovine gastric extract regarding as anendogenous ligand for APJ,able to mediate angiogenesis,and might be involved in the development of DR.Human retinal microvascular endothelial cells(HRMECs)support the integrity of the inner blood-retinal barrier,whereas their dysfunction under pathological conditions may contribute to the formation ofretinal edema especially macular edema.