α-SMA-positive cells (myofibroblasts) in SA collagen-1 and fibronectin depositionNegative correlation between increased SA wall thickening and decrease in airflow in the COPD groupsCorrelation between collagen-1 deposition in the SA lamina propria and lung function in the COPD-smokers group. This evidence concerns the gene ACTA1 and chronic obstructive pulmonary disease.