2017 Volume 42 Issue 1 Pages 1-11
It was demonstrated that periodontopathic bacteria including ‘red complex species’ could invade into the apical gingiva of periodontitis patients. The precise mechanism, however, remains to be elucidated. We assessed here the invasion mechanism of periodontal pathogens across the gingival epithelial barrier through two putative routes (transcellular and paracellular routes). After preculture of a gingival epithelial cell line (Ca9-22) on a filter insert of the double-chamber culture system, the suspensions of the laboratory strains of Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf), Treponema denticola (Td) and Aggregatibacter actinomycetemcomitans (Aa) were added to the upper chamber on the layered cells. At appropriate times of incubation, the translocated bacteria into the lower chamber were quantified by real-time PCR (q-PCR). Then, the disruption of cell-cell junctions in Ca9-22 was examined by the translocation of FITC-dextran. The bacteria which had invaded and persisted within Ca9-22 were also assessed by q-PCR. The results indicated that Pg invaded significantly at 6 hours of incubation through both transcellular and paracellular routes. Tf and Aa could also possess the invasive ability, although they utilized only the transcellular route. Consequently, many periodontal pathogens can invade significantly across the gingival epithelial barrier, whereas the translocation route may differ between the organisms.
