Analysis of the Influence of <i>Porphyromonas gingivalis</i> on the Human Oral Mucosa with a Three-dimensional Construct Model

<p> Purpose: Oral epithelial cells have an important barrier function against bacteria and bacterial toxic substances. Porphyromonas gingivalis (P. g.), a periodontopathic bacteria, is thought to be closely related to the development and aggravation of periodontitis by destruction of the epithelial barrier function. However, the detailed mechanism of how P. g. affects epithelial cells and destroys the barrier function of the epithelium is still unknown. In this experiment we investigated the influence of P. g. on oral epithelial cells.</p><p> Methods: A three-dimensional construct model composed of human oral epithelial cells and rat fibroblasts was established and two groups, with and without ground P. g. ATCC33277, were prepared. The epithelial cell layer was later air-lifted. Samples were collected at 4 to 8 days after incubation, then HE staining and immunohistological staining were performed for morphological observation. DNA microarray analysis and gene expression analysis using qRT-PCR were conducted on the collected epithelium. At air-lift day 6, samples were used for TER and FITC-dextran analyses to evaluate the barrier function.</p><p> Results: A significant increase of the epithelial thickness was found in ground P. g. models at Air-Lift day 6. Microarray pathway analysis revealed that the level of genetic expression related to cell cycle and cell adhesion had changed. As for cell cycle, the expression level of Cdkn1a mRNA was significantly reduced and immunohistological staining showed the number of Ki67 positive cells was significantly increased. As for cell adhesion, a significant reduction of staining intensity and a decreased area of E-cadherin were confirmed. The electrical resistivity of tissue was significantly lowered and the permeability of tissue was significantly increased with dextran permeability assay in the ground P. g. models.</p><p> Conclusion: The three-dimensional construct model revealed that cell proliferation increases, intracellular space increases, and cell adhesion protein reduces when human oral epithelium is exposed to P. g., resulting in lowered barrier functions and aggravated periodontal pathology.</p>