MULTILAYER CULTURE OF PERIODONTAL-LIGAMENT EPITHELIAL-CELLS - A MODELFOR JUNCTIONAL EPITHELIUM

The unique features of junctional epithelium involve lack of keratiniz ation, limited differentiation and a relatively permeable structure. I n order to study the relationship between differentiation and permeabi lity of stratified epithelium a model system was developed. Porcine pe riodontal ligament epithelial cells were cultured on the polycarbonate nucleopore membrane of the Transwell(TM) two-compartment culture syst em. Within 5 days of culture the cells formed a confluent multilayered structure. Subsequently, maturation of the structure and differentiat ion of surface cells took place. Transmission electron microscopy show ed that the cells were arranged into basal and suprabasal layers with sparse desmosomal attachments and wide intercellular spaces resembling the organization of junctional epithelium. The basal cells attached t o a subepithelial basal lamina through numerous hemidesmosomes. The cy tokeratin profile of the cultured epithelium (K5, 6, 14, 16, 19) resem bled that of the cells of junctional epithelium attached to the tooth surface. The older cultures expressed differentiation markers, K4, K13 and involucrin, theraby resembling sulcular epithelium. The epithelia l permeability, measured by diffusion of phenol red, radioactive dextr an or methionine tracers, and as transepithelial electrical resistance , decreased with the increased cell number and maturation of the cultu res. The new model provides an organotypic culture system which allows to control differentiation Of a multilayered periodontal epithelium. It thus may serve as a valuable new tool for studies on the permeabili ty and behaviour of periodontal epithelium under the influence of exog enous and endogenous factors.