In our study, exogenous TGF-β1 affected global mucociliary differentiation and subsequently increased the proportion of uncommitted basal cells, both in control and COPD HBEC, suggesting that the defective generation of ciliated cells in the COPD epithelium could at least partly relate to TGF-β1. This evidence concerns the gene TGFB1 and chronic obstructive pulmonary disease.