EXPLANT CULTURE OF RABBIT TRACHEOBRONCHIAL EPITHELIUM - STRUCTURE ANDPROSTAGLANDIN METABOLISM

This study examines the potential usefulness of explant culture of rab bit tracheal epithelium as a model for the study of epithelial functio n under normal and potentially pathologic conditions. Accordingly, we assessed the structure and prostaglandin E2 (PGE2) release of tracheal epithelial explants obtained from adult pathogen-free rabbits. Epithe lial cells attached to their native connective tissue substratum were maintained in culture for 5 days in serum-free medium, under bipolar c onditions (air-liquid interface) on a permeable membrane (pore size, 0 .2 mm), and nourished from the basolateral surface. At 5 days in cultu re, scanning and transmission electron microscopy and light microscopy demonstrated a pseudostratified, ciliated columnar epithelium with pr ominent folds and mucus secretion identical in appearance to the mucos a before culture. On the day of dissection (day 0) and after 4 days in culture (day 4), explants released PGE2 into the medium spontaneously . However, day 4 explants produced 3- to 4-fold greater amounts of PGE 2 than day 0 explants. Moreover, day 4 explants demonstrated increased PGE2 release in response to bradykinin, a receptor-dependent agonist, and ionomycin, a calcium ionophore, while day 0 explants did not. Pri mary tracheal epithelial cell cultures grown to confluence (day 9) on a collagen substrate demonstrated PGE2 responses to bradykinin and ion omycin that qualitatively resembled those of day 4 explants. We conclu de that rabbit tracheal explants cultured in vitro under the above con ditions maintain cellular differentiation, in situ three-dimensional o rganization, and PGE2 synthetic pathways over several days in culture. However, the behavior of the PGE, synthetic pathway appears to vary w ith time in culture and does not appear to be regulated by bradykinin or changes in intracellular calcium for the first several hours after dissection.