Transforming growth factor-beta expression in mucosal biopsies in asthma and chronic bronchitis.

We assessed whether transforming growth factorb (TGFb), a fibrogenic growth factor, may be involved in remodeling of asthma and chronic bronchitis; its expression was compared with that of epidermal growth factor (EGF) and granulocyte macrophage colony-stimulating factor (GM-CSF) in bronchial mucosal biopsies from 13 normal subjects, 24 asthmatics, and 19 patients with chronic bronchitis. TGFb immunoreactivity was highly increased in epithelium and submucosa of those with bronchitis and to a lesser extent in asthmatics. By comparison, with normal subjects, EGF immunoreactivity was significantly increased in the epithelium of bronchitic subjects and submucosa of asthmatics, and, GM-CSF immunoreactivity was increased in both epithelial and submucosal cells of asthmatics and to a lesser extent in submucosa of bronchitics. A significant correlation was found between the number of epithelial or submucosal cells expressing TGFb in both asthma and chronic bronchitis and basement membrane thickness and fibroblast number. No such correlation was found for EGF or GM-CSF. In situ hybridization for TGFb1 mRNA confirmed the results obtained by immunohistochemistry. By combining in situ hybridization and immunohistochemistry, it was found that eosinophils and fibroblasts were synthetizing TGFb in asthma and bronchitis. These data suggest that TGFb, but not EGF or GM-CSF, is involved in airways remodeling in asthma and chronic bronchitis.