Western blot and immunofluorescent staining for the endothelial marker protein CD31 revealed that its expression in the kidneys at 2 weeks was significantly lower in wild-type CKD mice than in control mice, whereas it was significantly higher in HIF-2α transgenic CKD mice than in wild-type CKD mice (Fig. 3A,B). Here, PECAM1 is linked to chronic kidney disease.