INFLUENCE OF RETINOIC ACID ON THE EXPRESSION OF CYTOKERATINS, VIMENTIN AND ICAM-1 IN HUMAN GINGIVAL EPITHELIA IN-VITRO

Phenotypic differences exist in vivo between junctional (JE) and oral gingival (OGE) epithelia and an in vitro system has been developed tha t maintains phenotypic differences. This system, which permits in vitr o studies of factors that may influence the epithelial phenotype, was used to investigate the effects of retinoic acid (RA) on epithelial ex pression of various markers known to distinguish JE from OGE. Primary cultures of JE and OGE were initiated from defined gingival regions an d were subcultured and grown for 48 h in 96-well plates or on multiple -well slides. Control cultures were grown in medium supplemented with delipidized serum and all-trans RA was added to experimental groups. O ther cultures were grown in a defined RA-free medium. Cultures were ex amined using monoclonal antibodies against cytokeratins, vimentin, and ICAM-1 and binding displayed by indirect immunocytochemical staining. Staining reactions were assessed by direct microscopic observation an d assayed by spectrophotometric quantitation. The results showed that RA had minor effects on the marker expression of JE but markedly enhan ced expression of cytokeratins 8, 18, 19, vimentin and ICAM-1 in OGE. These markers, which normally distinguish JE from OGE, were expressed at levels approaching or exceeding those of control JE cultures. These observations indicate that RA responsive mechanisms affect the phenot ypes expressed by epithelia in vitro and suggest that such mechanisms may be related to the different phenotypic patterns expressed by gingi val epithelia in vivo.