TGFB1 and renal fibrosis: Smad2/3 are then translocated to the nuclei where they promote expression of TGF-β regulated genes including collagen I. In contrast, bone morphogenetic protein (BMP-7) has been identified as a natural antagonist of TGF-β1signaling and administration of exogenous BMP-7 also protects against renal fibrosis in several experimental models [51-54].