Considering the mechanism of TGF-β1 in renal fibrosis, it was found that TGF-β1 causes increased production of ECM like collagen I and fibronectin via Smad3-dependent pathways such as induction of tissue inhibitor of metalloproteinase and trans differentiation of myofibroblast, epithelial cells (Wu et al., 2013). Here, SMAD3 is linked to renal fibrosis.