MUC5AC and MUC5B expression in central airways from non-smokers, smokers with normal lung function and GOLD stage 1 and 2 COPD patients

Mucus expectoration is a common feature of chronic obstructive pulmonary disease (COPD). Sputum is mainly produced in central airways. The two major mucins in sputum are MUC5AC and MUC5B. The major site of mucus production in central airways is represented by the submucosal glands. The expression of MUC5AC and MUC5B in bronchial epithelium and submucosal glands from patients with COPD is not known. We investigated by immunohistochemistry (IHC) the expression of MUC5B and MUC5AC in bronchial rings (obtained at lung resection surgery) from 10 asymptomatic non-smoking subjects, twenty smokers with normal lung function and twenty smokers with COPD. Quantitative analysis of the immunohistochemical staining of bronchial epithelial cells and submucosal glands was performed using dedicated computerised digital software. The total area covered by MUC5AC +ve cells in the bronchial epithelium was increased in smokers (with and without COPD) (66.1 ± 5.7% total epithelial area) compared to non-smoking subjects (21.2 ± 7.1%; p<0.01). The total area covered by MUC5AC+ve cells in the bronchial submucosal glands was significantly higher in patients with COPD (22.2 ± 5.5% total gland area) compared to smokers with normal lung function (10.6 ± 2.1%; p<0.05) and non-smoking subjects (5.9 ± 3.5%; p<0.05). MUC5B expression was not significantly different between groups both in bronchial epithelium and submucosal glands. These results suggest that COPD is associated with increased expression of MUC5AC in the bronchial airways, particularly in bronchial glands. This may be involved in the pathogenesis of the disease.