Conflicting results have previously been reported for CCN2 mRNA expression in patients with COPD.31, 46 TGF-β1 induces CCN2 expression in fibroblasts in vitro,47 suggesting that the decreased expression of both TGF-β1 and CCN2 observed in the bronchiolar epithelium of the patients in our study with stable COPD may be related. This evidence concerns the gene TGFB1 and chronic obstructive pulmonary disease.