TGFB1 and idiopathic pulmonary fibrosis: The expression of miR-21 significantly increases in the lungs of both IPF patients and fibrotic mice; its upregulation can be induced by transforming growth factor-β (TGF-β) and promote the epithelial-mesenchymal transition (EMT) process through stimulation of the Smad signal pathway (Liu et al., 2010).