SMAD2 and idiopathic pulmonary fibrosis: Supporting this notion, the key downstream transcriptional factor Smad2/3 was highly activated in IPF as demonstrated by increased P‐smad2/3 (Figure 2G, I), and there was also a marked increase of Collagen‐I, α‐SMA, and FN levels in IPF lung (Figure 2H, J–L).