Mucin expression in peripheral airways of patients with chronic obstructive pulmonary disease G Caramori, C Di Gregorio, 1 I Carlstedt, 2 P Casolari, I Guzzinati, I M Adcock, 3 P J Barnes, 3 A Ciaccia, G Cavallesco, 4 K F Chung 3 & A Papi Centro di Ricerca su Asma e BPCO, University of Ferrara, Ferrara and 1 Dipartimento di Anatomia Patologica, Ospedale di Carpi (MO), Italy, 2 Department of Molecular Biology, Section on Molecular Pathogenesis, University of Lund, Sweden, 3 Imperial College London, National Heart and Lung Institute, Department of Thoracic Medicine, London, UK, and 4 Department of Thoracic Surgery, University of Ferrara, Ferrara, Italy Date of submission 11 November 2003 Accepted for publication 2 March 2004 Caramori G, Di Gregorio C, Carlstedt I, Casolari P, Guzzinati I, Adcock I M, Barnes P J, Ciaccia A, Cavallesco G, Chung K F & Papi A (2004) Histopathology 45, 477–484 Mucin expression in peripheral airways of patients with chronic obstructive pulmonary disease Aims: To study the expression of mucins in peripheral airways in patients with chronic obstructive pulmon- ary disease (COPD). Methods and results: Peripheral lung sections from smokers with COPD (n ¼ 9) and age-matched controls including smokers (n ¼ 11) and lifelong non-smokers with normal lung function (n ¼ 6) were stained with alcian blue, periodic acid–Schiff (PAS) and by immuno- histochemistry of mucins (MUC): MUC2, MUC4, MUC5AC, MUC5B and MUC6. Histochemical staining and immunoreactivity of bronchiolar epithelium were graded and the presence or absence of stained mucus in the bronchiolar lumen was evaluated. There were no differences in alcian blue and PAS epithelial staining between the three groups. Intraluminal PAS staining was significantly more frequent among COPD subjects (P< 0.05). The expression of MUC5AC was signifi- cantly higher in the bronchiolar epithelium of patients with COPD (P< 0.05). Within the bronchiolar lumen, the predominant mucin was MUC5B. Intraluminal MUC5B was significantly more frequent among COPD patients (P< 0.05). Conclusions: COPD is specifically associated with increased expression of MUC5B in the bronchiolar lumen and of the mucin MUC5AC in the bronchiolar epithelium. These changes in mucin production in the peripheral airways may contribute to the pathophys- iology of COPD. Keywords: COPD, MUC5B, MUC5AC, mucins, peripheral airways Abbreviation: COPD, chronic obstructive pulmonary disease Introduction Chronic obstructive pulmonary disease (COPD) is currently defined as ‘a disease state characterized by airflow limitation that is not fully reversible. The airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases’. 1 COPD is a major worldwide respiratory public health problem and one of the leading causes of morbidity and mortality among the adult population in both industrialized and developing countries. 1 Cigarette smoking is the major risk factor for the development of COPD and cigarette smokers constitute over 90% of COPD patients in developed countries. Spirometry is essential for diag- nosis because COPD is characterized by chronic airflow obstruction [forced expiratory volume in 1 s (FEV 1 ) ⁄ forced vital capacity (FVC) ratio < 70%] that does not change significantly, spontaneously or with treatment. 1 The pathological hallmarks of COPD are Address for correspondence: Gaetano Caramori, Centro di Ricerca su Asma e BPCO, Via Savonarola, 9, University of Ferrara, 44100 Ferrara, Italy. e-mail: crm@unife.it Ó 2004 Blackwell Publishing Limited. Histopathology 2004, 45, 477–484