SMAD2 and renal fibrosis: In the context of renal interstitial fibrosis, Smad2/3 was reported to be strongly activated in various CKDs.34 In addition, deletion of Smad3 in mice or use of Smad3 inhibitor suppressed the progress of renal fibrosis.35, 36 As expected, excessive expression of Smad 2/3 was observed both in obstructive kidneys and hypoxia‐insulted HK‐2 cells.