TRANSFORMING GROWTH-FACTOR-BETA EXPRESSION IN MUCOSAL BIOPSIES IN ASTHMA AND CHRONIC-BRONCHITIS

We assessed whether transforming growth factor-beta (TGF-beta), a fibr ogenic growth factor, may be involved in remodeling of asthma and chro nic bronchitis; its expression was compared with that of epidermal gro wth factor (EGF) and granulocyte macrophage colony-stimulating factor (GM-CSF) in bronchial mucosal biopsies from 13 normal subjects, 24 ast hmatics, and 19 patients with chronic bronchitis. TGF-beta immunoreact ivity was highly increased in epithelium and submucosa of those with b ronchitis and to a lesser extent in asthmatics. By comparison, with no rmal subjects, EGF immunoreactivity was significantly increased in the epithelium of bronchitic subjects and submucosa of asthmatics, and, G M-CSF immunoreactivity was increased in both epithelial and submucosal cells of asthmatics and to a lesser extent in submucosa of bronchitic s. A significant correlation was found between the number of epithelia l or submucosal cells expressing TGF-beta in both asthma and chronic b ronchitis and basement membrane thickness and fibroblast number. No su ch correlation was found for EGF or GM-CSF. In situ hybridization for TGF-beta 1 mRNA confirmed the results obtained by immunohistochemistry . By combining in situ hybridization and immunohistochemistry, it was found that eosinophils and fibroblasts were synthetizing TGF-beta in a sthma and bronchitis. These data suggest that TGF-beta, but not EGF or GM-CSF, is involved in airways remodeling in asthma and chronic bronc hitis.