Smad signaling, also known as the canonical TGF-β pathway, is critically involved in renal fibrosis by inducing activation of myofibroblasts, transformation of tubular epithelial cells to myofibroblasts and tubular apoptosis (Sato et al., 2003; Zhang et al., 2015; Guo et al., 2018). Here, TGFB1 is linked to renal fibrosis.