TGFB1 and idiopathic pulmonary fibrosis: A range of pro-fibrotic mediators acting on fibroblasts derived from AECs have been strongly implicated in IPF, including multiple growth factors (e.g., TGFβ, PDGF, CTGF, TNF-α, osteopontin, angiotensinogen, and endothelin-1) and some developmental pathways (e.g., Wnt/β-catenin and Sonic hedgehog).69