At variance with the bronchial epithelium, the percentage of TGF-β1+ (Fig 2A, e-Fig 1), TGF-β3+ (Fig 2E, e-Fig 2), and CCN2+ (Fig 2G, e-Fig 3) bronchiolar epithelial cells in the peripheral airways was significantly decreased in patients with COPD compared with control smokers with normal lung function (Table 4). This evidence concerns the gene TGFB3 and chronic obstructive pulmonary disease.