Bronchial epithelial cells produce chemotactic activity for bronchial epithelial cells. Possible role for fibronectin in airway repair.

Bronchial mucosal injury initiates a complex series of repair mechanisms, one of which is reepithelialization of a denuded lumenal surface. This suggests the hypothesis that bronchial epithelial cells, the cells initially affected by bronchial injury, might be able to initiate repair of an injured area by producing a chemotactic activity for intact bronchial epithelial cells. To evaluate this, bronchial epithelial cells were prepared from bovine lung by protease digestion and cultured in medium 199 (M199) with 10% fetal calf serum (FCS) until confluence, after which the cells were rinsed with Hanks' balanced salt solution, and serum-free fresh M199 was added. This conditioned medium was then collected and used to test the chemotactic response of bronchial epithelial cells using a blindwell chamber technique. Target cells for this assay were isolated from airways by protease digestion, grown to confluence in M199 with 10% FCS, and then harvested with trypsin. Bronchial epithelial cell-conditioned medium harvested after 3 days attracted more cells (197.0 +/- 5.7 cells/10 high power fields) than did M199 without FCS alone (4.3 +/- 0.9) (p less than 0.01). Checkerboard analysis showed that the migration was chemotactic. The chemotactic activity was nondialyzable, pepsin-labile, acid-stable, heat-labile, and lipid-inextractable. The chemotactic activity accumulated in the culture medium with time. The addition of 25 micrograms/ml of cycloheximide inhibited this accumulation. Column chromatography with Sephadex G-150 revealed a single peak of chemotactic activity in the high molecular weight range. The chemotactic activity was bound to gelatin-Sepharose 4B and was eluted with 6 M urea.(ABSTRACT TRUNCATED AT 250 WORDS)