COL1A1 and chronic obstructive pulmonary disease: Again, the TGF-β1 stimulation of 2.5 ng/ml (p<0.01, Fig 1B) and 7.5 ng/ml was successful as it significantly induced the mRNA expression of FN1, COL1A1, and α-SMA in the primary parenchymal lung fibroblasts of both controls and COPD patients (p<0.01, Fig 1C).