TGFB1 and renal fibrosis: The paramount importance of the TGF-β1/Smad signaling has been underscored in various DN pathogenesis, includes podocyte injury, mesangial cell proliferation, and especially renal fibrosis (Isacsson et al., 1988; Tang et al., 2018a,b, 2020; Zhang et al., 2019; Qi et al., 2020).