OBJECTIVE
To compare the thickness of subepithelial reticular basement membrane (BM) in asthmatic patients and healthy subjects and to compare the BM thickness to inflammatory mediators and cytokines.
METHODS
Fiberoptic bronchoscopy with bronchial biopsy was performed on 20 stable asthmatics and 10 normal subjects. The subepithelial reticular BM thickness was measured. Levels of eosinophil cationic protein (ECP), interleukin 5 (IL-5 ), and tumor necrosis factor alpha (TNF alpha ) in sputum were measured by immunoassay. The relationship between ECP, IL-5, TNF alpha and BM thickness was estimated by the spearman rank correlation.
RESULTS
The mean BM thickness was significantly higher in asthmatic patients (10.1 +/- 2.6) microm than in normal subjects (4.4 +/- 1.2) microm (P < 0.005). In asthmatic patients, the ECP (144 +/- 80) microgram/L and the IL-5 (17 +/- 4) microgram/L levels in sputum were positively correlated with BM thickness (r = 0.569, P < 0.005 and r = 0.466 P < 0.005, respectively ). Sputum TNF-alpha (53 +/- 36) microgram/L showed no significant correlation with BM thickness (r = 0.254 P > 0.05).
CONCLUSIONS
Airway remodeling is a distinctive and characteristic pathologic finding of asthma. Airway remodeling is related to levels of sputum ECP and IL-5, but not that of TNF-alpha.