PECAM1 and diabetic retinopathy: Accordingly, cross-sections of the retina revealed the presence of morphological lesions, including thickening of the retinal parenchyma and pathological neovascularization with presence of endothelial cell marker (CD31) within the parenchyma, which are both characteristic of diabetic retinopathy (Black arrows in Fig. 6A and white arrow in Fig. 6B).