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The structural and functional barrier preventing the free advancement of microbial plaque subgingivally along the tooth surface is formed by the junctional epithelial (JE) cells directly attached to the tooth (DAT cells). The mechanism leading to degeneration of the DAT cells is not known. In the present study we examined the possible role of short chain fatty acids (SCFAs) on epithelial cells by making use of 2 epithelial cell cultures (HaCaT and ERM) and an explant culture model of human JE. The SCFAs butyrate and propionate were used in concentrations found in human plaque and gingival crevicular fluid (0.25-16.0 mM). The SCFAs had no effect on primary cell adhesion nor on the epithelial attachment apparatus (EAA). By contrast, even 0.25 mM of butyrate significantly retarded epithelial cell growth. Similar effects with propionate were first observed at concentrations higher than 1.0 mM. The retardation of epithelial cell growth was found to be due to inhibition of cell division. Furthermore, after butyrate treatment dense accumulations of intermediate filaments and cytoplasmic vacuolization were characteristically seen in cells adjacent to cells of normal appearance. This suggests that some cells of the growing epithelial cell population are more sensitive to the SCFAs than others, and agrees with previous reports on the DAT cells of periodontally-involved teeth in vivo. The results suggest that SCFAs are microbial factors that play a role in the initiation and progression of periodontal pocket formation by impairing epithelial cell function rather than having a direct effect on the EAA. [ABSTRACT FROM AUTHOR]

The unique features of junctional epithelium involve lack of keratinization. limited differentiation and a relatively permeable structure. In order to study the relationship between differentiation and permeability of stratified epithelium a model system was developed. Porcine periodontal ligament epithelial cells were cultured on the polycarbonate nucleopore membrane of the Transwell &Trade; two- compartment culture system. Within 5 days of culture the cells formed a confluent multilayered structure. Subsequently, maturation of the structure and differ- entiation of surface cells took place. Transmission electron microscopy showed that the cells were arranged into basal and suprabasa! layers with sparse desmosomal attachments and wide intercellular spaces resembling the organization of junctional epithelium. The basal cells attached to a subepithelial basal lamina through numerous hemidesmosomes. The cytokeratin profile of the cultured epithelium (K5, 6, 14, 16, 19) resembled 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 epithelial permeability, measured by diffusion of phenol red, radioactive dextran or methionine tracers, and as transepithelial electrical resistance, decreased with the increased cell number and maturation of the cultures. 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 permeability and behaviour of periodontal epithelium under the influence of exogenous and endogenous factors. [ABSTRACT FROM AUTHOR]

The rate of cell proliferation, which is associated with the density of transferrin receptors on the cell surface, may have an effect on the homeostasis of epithelial cell populations in the dento-gingival junction. In addition to moderate labeling of basal cells, intensive labeling of transferrin receptors was found on suprabasal cells of sulcular epithelium towards the gingival margin of healthy tissues. In contrast, biopsies from diseased tissue exhibited increased labeling towards the base of the pocket. This distribution of labeling suggests that the distinct suprabasal population of cells expressing the transferrin receptors is associated with the process of pocket formation. The density of transferrin receptors decreased towards the lamina propria of gingiva and towards the apical termination of the junctional epithelium. In samples from periodontal pockets, the number of receptors was high even in the germinative cell layers. Labeled cells were also demonstrated in crevicular washings. The washing method together with the demonstration of transferrin receptors may provide a new approach for the study of epithelial cell homeostasis in the dento-gingival tissues. [ABSTRACT FROM AUTHOR]

Pieces of human masticatory mucosa were maintained in a Trowell-type organ culture. The explants were placed on their side on either microporous filters or decalcified dentin matrix slices. The presence of serum in the culture medium enhanced epithelial outgrowth (epibolus) from the explants. The epibolus grew longer in contact with the substratum than along the free connective tissue surface of the explant. When grown on microporous filters, the flow of migrating cells was directed between the explant and substratum. As a sign of epitheial attachment to the filter, a structure morphologically similar to basal lamina and hemidesmosomes was seen. The decalcified dentin matrix, however, caused the epithelial cells to migrate outwards from the explant. The explants became loosely attached to the matrix. Although some electron-dense material was secreted into the contact area, a typical basal lamina was not seen.

The composition of the extracellular matrix produced by epithelial cells in contact with metabolically inert substrata was studied with antibodies specific for type VIII collagen. Type VIII collagen was present in the cell layer of cultured gingival epithelial cells, and at the epithelium-substratum interface of an explant culture model for junctional epithelium. Samples of the epithelial attachment apparatus (EAA) in vivo were collected by removing the junctional cells directly attached to the tooth (DAT cells) and the associated EAA matrix. The amount of material collected was sufficient for biochemical analysis of both intra- and extracellular components of the junctional cell-EAA complex. Immunological examination of the samples revealed that type VIII collagen was associated with epithelial cells forming the EAA in vivo. We suggest that this collagen type functions in the extracellular space as an attachment-promoting factor for gingival epithelial cells at the tooth surface.

Materials used in guided tissue regeneration were examined in an in vitro model for regenerating human junctional epithelium. The extent of epithelial migration from gingival explants (epibolus) between the explant and an experimental substratum was significantly greater with a Millipore filter (HA) than with a teflon membrane (Biopore; BO) and a teflon periodontal material (Goretex; GT). Epithelial cells attached to HA, formed a morphologically and functionally distinct layer of proliferating cells along the substratum. In contrast, epithelial cells did not attach to either teflon material. The cells adjacent to the teflon substrata were nonproliferative and exhibited signs of degeneration or cell differentiation. Furthermore, epithelial cell migration along BO was significantly greater than along GT. Our results suggest that the low protein-binding capacity of the teflon material and the rough-textured surface of GT inhibit epithelial cell migration. The results may provide a rationale for understanding the differences in epithelial behavior after conventional therapy for periodontitis and during guided tissue regeneration.

The relationship between cell attachment and the phenotype of the attached oral epithelial cells was studied by comparing junctional epithelium (JE) with a culture model for JE in which epithelial cells form an equivalent organization of tissues. Gingival explants were cultured on either a high or a low protein-binding membrane. The cut edge of epithelium and connective tissue was placed on the membrane; epithelial cells migrated to form a sheet of tissue between the explant and the membrane substratum. Cells which grew in contact with the high protein-binding membrane attached to the substratum and assumed a cuboidal shape. With time in culture these cells showed a decrease in reactivity with antibodies to psi-3 antigen (an antigen associated with epithelial migration) and an increase in reactivity with antibodies to cytokeratin 19 (a marker for JE). Cells grown on the low protein-binding membrane did not exhibit changes in shape or antigens. Because similar features were found in the JE in vivo, it was concluded that the junctional cells which are directly attached to the tooth (DAT cells) have a nonmigratory phenotype that develops as a response to the tooth surface. Because the cells are in contact with a metabolically inert material the changes appear to be largely self-induced. The culture method allows studies on putative inducer molecules and on mechanisms which may control the phenotype of epithelial cells at the dentogingival interface.