TGFB1 and renal fibrosis: Previous studies have shown that Smad7 knockout mice exhibit increased susceptibility to renal fibrosis, whereas overexpression of Smad7 through gene transfer ameliorates renal fibrosis.49 In the present study, we demonstrated that exosomal miR-17-5p promotes the expression of genes downstream of TGF-β by targeting the 3′UTR of Smad7.