TGFB1 and pulmonary emphysema: Deficiency in various components of the TGF‐β1 signaling pathways led to specific lung abnormalities [52, 61]; TGF‐β2 deficiency leads to collapsed distal airways [54]; TGF‐β3 knockout mice showed alveolar hypoplasia [55]; TGFβRII‐deficient mice demonstrated abnormal alveolarization and emphysema [62]; and TGFβRI deficiency mouse had immature alveoli and reduced club cell population [59].