In vitro procollagen synthesis and proliferative phenotype of bronchial fibroblasts from normal and asthmatic subjects.

Asthma is characterized histologically by a bronchial subepithelial fibrosis. Cytokines and other mediators released in the asthmatic chronic inflammatory microenvironment can activate the repair process that leads to fibroblast proliferation and collagen synthesis. To our knowledge, there are no data regarding the effect of a chronic inflammatory microenvironment on the phenotype of human bronchial fibroblasts. In the present study, we address this issue by comparing bronchial fibroblasts isolated from normal and asthmatic subjects in terms of: (a) proliferation over cell passage; (b) in vitro lifespan; (c) proliferative response to transforming growth factor-beta 1, platelet-derived growth factor-BB, dexamethasone, and retinoic acid; and (d) base-line synthesis of procollagens I and III. Bronchial fibroblasts from asthmatic subjects demonstrated lower DNA synthesis with cell passage than bronchial fibroblasts from normals. The in vitro lifespan of asthmatic bronchial fibroblasts was lower than in those from normal subjects and was significantly correlated with airway responsiveness. Platelet-derived growth factor-BB and dexamethasone increased 3H-thymidine incorporation in asthmatic bronchial fibroblasts without having any significant effect on normal fibroblast proliferation. Transforming growth factor-beta 1 and retinoic acid had no significant effect on bronchial fibroblast proliferation. Base-line procollagens I and III synthesis measurements showed no differences between normal and asthmatic fibroblasts. Taken together, these results indicate that the chronic inflammatory microenvironment found in asthma can modulate some aspects of bronchial fibroblast phenotype.