The induction of cell differentiation and polarity of tracheal epithelium cultured on the amniotic membrane.

We have developed a culture system of guinea pig tracheal epithelial cells using the epithelium-denuded human amnion as a source of basement membrane. Culture medium fluid over the epithelial cells was replaced by air after 7-day immersion culture and thereafter maintained for 2 weeks. Electron microscopical observations revealed that the height of epithelial cells and the ratio of ciliated epithelial cells looked like that of normal guinea pigs epithelium growth in 2 weeks after the air interface, but that no goblet cells could be found. In order to study cell polarity, we measured endothelin-1 levels in the media of apical and basal sides of the epithelial cell monolayer by means of the enzyme-linked immunosorbent assay. The endothelin-1 content of the submucosal side was over 30 times higher than that of the apical side. These findings suggest that ET-1 would be mainly released from airway epithelial cells toward the submucosal side.