In that study, not only exposure of PBECs to 2.5% CSE did induce COL1A1 expression, they also showed that in PBECs obtained from small bronchi of smokers with and without COPD, COL1A1 protein expression was shown to be inversely correlated with FEV1 (% of predicted). This evidence concerns the gene COL1A1 and chronic obstructive pulmonary disease.