Under fibrosis conditions, Smad7 is reduced while Smad3 is highly activated as seen in diabetic nephropathy, hypertensive nephropathy, and aristolochic acid-induced nephropathy (Chen et al., 2011; Liu et al., 2012; Chung et al., 2013a; Tian et al., 2015). This evidence concerns the gene SMAD7 and diabetic kidney disease.