Transepithelial electrical resistance and tight junctions of human gingival keratinocytes

Human gingival keratinocytes (HGKs) were studied by means of freeze-fractur e technique, conventional electron microscopy and the transepithelial elect rical resistance for the investigation of intercellular contacts. For the p urpose of comparison, MDCK cells and HaCat cells were also included. An une xpected finding was the presence of tight junctions in the HGKs. In. vivo t he tight junctions, which were of low complexity and P-face-associated, wer e co-distributed with desmosomes; in one case, the strands ran directly thr ough desmosomal plaques. Where light junctions and desmosomes occurred toge ther, no gap junctions were seen. In contrast, where no tight junctions wer e present, gap junctions and desmosomes were co-localized. However, the unf avourable fracture planes through the tissue did not allow a clearcut alloc ation of gap junction/tight junction occurrence to certain strata. In vitro , HGKs also expressed tight junctions which formed networks of low complexi ty and high P-face association. Whereas desmosomes were highly expressed, g ap junctions were not observed in cultured keratinocytes. Transepithelial e lectrical resistances (TEER) of cultured HGKs were higher than the values i n low resistance-MDCK cells and HaCat cells but considerably lower than the values in high resistance MDCK cells, supporting the fundamental correlati on between tight junction morphology and TEER. The results with this cell c ulture model of the human gingiva provide some valuable information about i n vitro differentation and concommittent changes in cellular contacts of hu man gingival keratinocytes.