ESTABLISHMENT OF ORAL-MUCOSA PHENOTYPE IN-VITRO IN CORRELATION TO EPITHELIAL ANCHORAGE

Cell-matrix interactions and the ordered deposition of basement membra ne (BM) components are of major importance for the maintenance of tiss ue homeostasis in complex epithelia. This aspect was studied in vitro in a coculture system designed as an oral mucosa model. As crucial epi thelial features the kinetics of proliferation, expression of site-spe cific keratins as well as integrin patterns in correlation to synthesi s of BM components were assessed by immunohistochemistry and in situ h ybridization. Comparison with non-cornified gingiva as tissue of origi n revealed different stages of epithelial development, eventually lead ing to complete reconstruction within a time frame of 1-3 weeks. First , the initial activated stage up to 1 week was characterized by (a) hi gh keratinocyte proliferation, (b) extended expression of the basal ce ll-specific keratin K5 and (c) a patchy pattern of the differ entiatio n-specific keratins K4 and K13. Second, after 2 weeks the improvement of histoarchitecture correlated to (a) predominant K5 expression in th e basal and (b) extension of K4 and K13 within the suprabasal cell com partment, (c) high expression of integrins alpha 3 beta 1 and alpha 6 beta 4 including their ligand laminin-5 and (d) accumulating depositio n of basement membrane components. Third, virtually complete tissue no rmalization at 3 weeks was indicated by (a) restriction of K5 to the b asal cell area, (b) regular suprabasal localization of K4 and K13, (c) polarization of integrins to basal and parabasal cells and (d) linear codistribution of collagen ni, ''classical'' laminin (-1 or -10) and laminin-5 underneath the basal cells. Thus, these organotypic cocultur es represent relevant equivalents for non-keratinized oral mucosa with typical gingival differentiation features and in addition suitable mo dels for preclinical trials such as prospective dental material testin g.