Bronchial brush biopsies for studies of epithelial inflammation in stable asthma and nonobstructive chronic bronchitis

Abstract

Recently, bronchial brush biopsy (BBB) has been introduced as a complimentary method to bronchial forceps biopsy for the study of bronchial epithelial cells. We wanted to determine whether epithelial inflammatory cells in bronchial brush biopsies can reflect mucosal inflammation assessed indirectly by levels of cellular activation markers in bronchial lavage fluid. We studied 15 healthy controls, 11 asthmatics with regular steroid inhalation therapy, 13 asthmatics without steroids, and 10 smokers with nonobstructive chronic bronchitis. Differential counts of epithelial and inflammatory cells were made from the BBB material. Bronchial lavage levels of eosinophil cationic protein (ECP), myeloperoxidase (MPO), tryptase, hyaluronan and interleukin-8 (IL-8) were measured as indirect markers for inflammatory cell activation. We found an increased percentage of eosinophil granulocytes in the BBB from the steroid-untreated asthmatic patients (1.16%) in comparison to the other groups (0.11%, 0.09% and 0.02%, respectively; p<0.01). In the steroid-untreated asthmatic patients, the percentage of eosinophils correlated with ECP in bronchial lavage fluid (r=0.73; p<0.01), indicating that the BBB method can reflect the degree of eosinophilic activation. A negative correlation was found for the percentage of eosinophils in BBB with levels of provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (PC20) for the asthmatic patients in the study (r= -0.67; p<0.003). The bronchial brush biopsy method appears to give information on the changes present in superficial bronchial epithelium in inflammatory airways disease. These changes appear to relate to the degree of inflammatory activity and disease severity in asthma.