TGFB1 and renal fibrosis: The silencing of Erbb4-IR blocks TGF-β1–induced collagen I and α–smooth muscle actin expression in vitro [88] and up-regulates Smad7 in the kidneys, thereby attenuating TGF-β1/Smad3-induced renal fibrosis in vivo and in vitro [89,90].