Aims: Mucus expectoration is a common feature of chronic obstructive pulmonary disease (COPD). MUC5AC and MUC5B, the major mucins, are released predominantly from submucosal glands in the central airways. The aim was to investigate gland size and MUC5AC and MUC5B expression in bronchial rings from smokers with COPD compared with control groups.
Methods and results: Bronchial rings from 10 non-smoking subjects, 20 smokers with normal lung function and 20 smokers with COPD were studied. Periodic acid-Schiff (PAS) and Alcian blue histochemistry and MUC5AC and MUC5B immunohistochemistry followed by quantification of the immunoreactive area was performed. The area occupied by MUC5AC+ cells in bronchial submucosal glands was increased in COPD [20% (5.5-31.7%) gland area] compared with smokers with normal lung function [9.5% (2.5-17.5%); P < 0.05] and non-smoking subjects [2% (0.4-6.2%); P < 0.05]. The area occupied by MUC5AC+ cells in the bronchial surface epithelium was also increased in smokers (with/without COPD) [73.5% (25-92%) epithelial area] compared with non-smoking subjects [15% (2.7-32%); P < 0.01]. Gland size, PAS, Alcian blue staining and MUC5B expression were not significantly different among groups. MUC5AC expression correlated with the degree of airflow obstruction. MUC5AC and MUC5B expression correlated with pack-years.
Conclusions: COPD is associated with increased MUC5AC expression in submucosal glands, indicating that MUC5AC may be involved in the pathophysiology of the disease.