Altered compartimentalization of transforming growth factor-β in asthmatic airways

Background Asthma is characterized by alterations of the bronchial epithelium associated with inflammatory cell infiltrates and sub-epithelial fibrosis. Transforming Growth Factor-β (TGF-β) is an anti-inflammatory and fibrosing cytokine normally present in bronchial epithelial cells and also potentially produced by inflammatory cells. Thus, TGF-β could play a role in the asthmatic process, and its expression could be modified in asthmatic airways. Objective To test this latter hypothesis, we studied the bronchial distribution of TGF-β in asthmatic patients. Methods TGF-β1, 2, 3 distribution was studied by immunohistochemistry in bronchial biopsies from 12 asthmatic patients and 10 non-asthmatic subjects. Results Bronchial epithelial cells from asthmatics were negative or faintly positive while a bright staining was detected in these from non-asthmatics (P < 0.0l). In both groups, when inflammatory cells were present beneath the basement membrane, they were stained by the anti-TGF-β antibody. Conclusion This study shows an altered compartimentalization of TGF-β in asthma. (a) TGF-β is scarse in asthmatic bronchial epithelial cells, which could favour the perennization of the bronchial inflammation, and (b) TGF-β is present in inflammatory cells beneath the basement membrane, where it could be involved in the frequent sub-epithelial fibrosis.