VEGFA and diabetes mellitus: In the development of DR, MCs play a causative role in diabetes-induced upregulation of tumor necrosis factor-α and vascular endothelial growth factor-A (VEGF-A or VEGF) [9,10,11], which leads to retinal hypoxia, oxidative stress, BRB lesions and breakdown, and retinal neurovascularization, major pathological characteristics of DR.