TGFB1 and chronic obstructive pulmonary disease: In contrast to the reduction in TGF-β1, TGF-β3, and CCN2 protein expression in COPD compared with cells from healthy smokers, there was no difference in TGF-β3 mRNA in small airway epithelial cells, but there was an increase in TGF-β1 and CCN2 mRNA expression (e-Table 3).