In this study, however, by PCR array analysis the expression of VEGF and EDN 1 (endothelin 1) was not different between CLU KO and WT kidneys (Additional file 2: Table S1), suggesting that the more severe fibrosis in CLU null kidneys may not be related to the hypoxia/vascular rarefaction, or the hypoxia is not a major factor for the CLU deficiency-related renal fibrosis after IRI. This evidence concerns the gene EDN1 and renal fibrosis.