Nevertheless, after day-4 and day-5 TGF-β1 exposure, the rate of differentiation into myofibroblasts was significantly reduced in cells obtained from COPD patients (35.3 ± 1.8%, 40.4 ± 6.4% and 20.4 ± 2.4% for C-NS, C-S and COPD respectively at day 4 and 78.7 ± 0.5%, 80.9 ± 3.6% and 69 ± 2.4% at day 5 (Fig 2A), indicating a defective response towards TGF-β1 by COPD fibroblasts. Here, TGFB1 is linked to chronic obstructive pulmonary disease.