SMAD3 and pulmonary fibrosis: On the contrary, Smad7 inhibits pulmonary fibrosis by competitively binding to TGF-β1 and its receptors complex with Smad3 [34].On both day 14 and day 28, it is discovered that the mRNA expression of TGF-β1 and its receptors and Smad3 was significantly downregulated, while the mRNA expression of Smad7 was significantly upregulated.