EPITHELIAL BARRIER FORMATION BY AIRWAY BASAL CELLS

Background - Epithelial shedding processes in airway inflammation and defence may produce damaged areas where basal cells are the main remai ning epithelial cell type. The present study examines the capacity of basal cells to form an epithelial barrier structure after loss of colu mnar epithelial cells. Methods - A technique was developed which allow s selective removal of columnar epithelial cells from isolated airways . A drop of tissue adhesive glue was applied on the mucosal surface sh ortly after excision of guinea pig trachea and human bronchus. Gentle removal of the glue, together with attached columnar cells, left a sin gle layer of cobbled, solitary basal cells. The tissue was kept in cul ture media. Morphological changes of the basal cells were monitored by immunohistochemistry and scanning and transmission electron microscop y at several time points. Results - After 20 minutes the basal cells h ad undergone extensive flattening and established contact with each ot her. The basement membrane thus became covered by a poorly differentia ted epithelium in both guinea pig and human airways. Abundant interdig itating cytoplasmic protrusions were observed at cell borders. Conclus ions - Basal cells promptly flatten out to cover the basement membrane at loss of neighbouring columnar cells. These data may explain why th e epithelial barrier function may be uncompromised in desquamative air way diseases. Furthermore, they suggest the possibility that sacrifici al release of columnar epithelial cells and prompt creation of a barri er structure constitute important roles of basal cells in airway defen ce against severe insults.