TGFB1 and pulmonary fibrosis: The mucociliary dysfunction combined with the weakened epithelial progenitor cells differentiation may worsen the damage of respiratory epithelium (Kotton and Morrisey, 2014; Benam et al., 2018), resulting in the up-regulation of several profibrotic pathways including TGF-β signaling and Wnt/β-catenin signaling, followed by epithelial-to-mesenchymal transition (EMT) and pulmonary fibrosis (Kage and Borok, 2012; Jones et al., 2019).