Epithelial cell kinetics of rat palatal mucosa in organ culture.

The dynamic behaviour of the epithelial cells was evaluated in explants of rat palatal mucosa maintained in a chemically-defined medium in organ culture for periods up to 28 days. Epithelial mitotic activity, comparable with that in vivo, was observed after 5 h in vitro but after 24 h had increased to 4 times the initial value. This increased activity persisted for 4 days and then gradually declined until at 10 days levels comparable with that at the start of the experiment were reached. During the initial period in culture, the thickness of the nucleated cell layer of the epithelium increased slowly, reaching a maximum after 4 days, and then decreased to the initial values by 12 days. The number of nucleated cells per square millimetre of surface also showed a transient increase but such changes did not correspond with changes in thickness. The changes in average cell volume were interpreted as a change in the relative sizes of the different epithelial compartments. It is suggested that the changes are caused by the surgical wounding of the tissues during excision; consequently, rat palatal mucosa maintained in this organ culture system provides a reliable model system for the study of oral mucosa only after a minimum period of 10 days.