Cytokeratin patterns of human oral mucosae in histiotypic culture

In a three-dimensional culture model, oral epithelial differentiation was investigated ultrastructurally and biochemically for cytokeratin expression. Epithelia from the hard palate, gingiva and alveolar mucosa grown on freely floating collagen lattices populated with fibroblasts from homotypic origins, and fed with medium containing 10% delipidized fetal calf serum for 21 days before analysis, stratified and differentiated to basal cuboidal cells, polyhydral spinous cells and elongated superficial cells. The epithelium of palatal origin had non-nucleated superficial cells resembling orthokeratinized cells. The upper spinous cells had keratohyalin-like granules. The corresponding cells of gingival and alveolar mucosal origins retained their nuclei and had smaller numbers of keratohyalin-like granules. Basal cell keratins (CK 5 and 14) and those of hyperproliferation (CK 6 and 16) were consistently found in all epithelia. Furthermore, simple epithelial keratins (CK 18 and 19) were variably expressed by cells from different oral origins. In epithelial cells from the alveolar mucosa, CK 13 and 19 formed major bands, which correlates with their expression in vivo. In contrast, these polypeptides were either absent or formed minor bands in extracts of gingival and hard palatal cells. Although in small quantities, keratins of terminal differentiation (CK 1, 2, 10 and 11) were detected in gels prepared from palatal epithelia. This expression correlates with the higher morphological differentiation of these cells in this model. The model is of interest for studies of epithelial differentiation, as the differentiation markers of keratinized epithelia (CK 1 and 10) were expressed by cells from palatal origin, and those of non-keratinized epithelia (CK 4, 13 and 19) were prominent in cells from alveolar mucosal origin.