Spontaneous release of submucosal gland serous and mucous cell macromolecules from human nasal explants in vitro

Respiratory epithelial and gland cells cultured in vitro demonstrate changes from differentiated serous and mucous cells toward intermediate 'seromucous' cells. This spontaneous process was examined by culturing human nasal mucosal explants in CMRL 1066 medium without growth factors for 6 days and measuring the concentrations of spontaneously released serous cell products [lactoferrin, lysozyme, 7F10-immunoreactive mucoglycoconjugates (7F10-irm)] and Alcian blue-staining mucous cell products. 7F10-irm was progressively and significantly increased on each day of culture. In contrast, lysozyme, lactoferrin, and Alcian blue-staining material decreased significantly. Each had its own pattern of decreasing release. Dexamethasone (1 μM) had no effect on these trends. Phorbol myristate ester (PMA; 100 nM) reduced 7F10-irm release on days 4-6 and delayed the drop in lactoferrin release. Dexamethasone blunted these effects of PMA. These data indicate that respiratory secretory cells alter their phenotypes when cultured in vitro and progressively change the relative amounts of mucoglycoconjugates and proteins spontaneously released. These changes should be anticipated when interpreting experiments involving cultured respiratory cells.