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Objective Gingival fibroblasts (GFs) can participate in the immune response and play an immune-regulatory role. This study was to evaluate whether GFs can be differently activated and polarized into distinct functional subtypes in response to T helper type 1 (Th1), or Th2 stimuli. Design Human GFs were stimulated by the Th1 cytokine, IFN-γ, and lipopolysaccharide (LPS), separately or in combination (Th1 stimuli), or by Th2 cytokines, IL-4 and IL-13, separately or in combination (Th2 stimuli). mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6, IL-12), anti-inflammatory cytokines (IL-4, IL-10, IL-13), chemokines ((C-X-C motif chemokine (CXCL)10, CXCL11, C-C motif ligand 20), molecules involved in antigen presentation ((human leukocyte antigen (HLA)-ABC, HLA-DP, CD74, CD40)), LPS-recognizing components (Toll-like receptor 4, CD14), collagen type 1 (COL1), matrix metalloproteinase (MMP)-1, and inducible nitric oxide synthase (iNOS) and the protein levels of IL-6, CXCL11, CD14, and COL1 accumulated in supernatants were analyzed using real-time PCR and ELISA, respectively. The cell surface levels of the molecules involved in antigen presentation were detected by flow cytometry. Results Th1 stimuli strongly upregulated the expression of diverse cytokines, chemokines, molecules involved in antigen presentation, LPS-recognizing components, MMP-1, and iNOS, whereas Th1 stimuli inhibited the expression of COLI. In contrast, Th2 stimuli strongly upregulated the levels of COL1 and IL-4, while the expression levels of the other factors were minimally affected or even inhibited. Conclusion These results show that GFs can be polarized into functionally distinct subtypes, immune-activating but tissue-destructive GF1 or tissue-reparative GF2, in response to Th1 and Th2 stimuli, respectively.

Objective Bacterial invasion into host cells is a common strategy to escape the host immune system. Gingival fibroblasts (GFs) are the most predominant non-phagocytic cell type in gingival connective tissue. Therefore, invasion into GFs was thought to be the first strategy for the survival of Porphyromonas gingivalis . The present study compared the invasive ability of P. gingivalis into GFs with those of other red-complex and relatively less pathogenic bacterial strains, especially Fusobacterium nucleatum . Materials and methods Invasive ability of bacterial strains into GFs was measured using a flow cytometric invasion assay at a multiplicity of infection of 1000. The effect of dual infection with F. nucleatum CCUG 37843T on P. gingivalis ATCC 49417 invasion was investigated. The invasive ability of F. nucleatum and P. gingivalis was confirmed using confocal microscopy. Results The invasive ability of red-complex bacteria was markedly lower than that of F. nucleatum or Campylobacter gracilis . The invasive ability of 4 types and 10 clinical strains of P. gingivalis was less than 6%, and that of F. nucleatum strains was greater than 45%. Confocal analysis revealed that the percentage of bacteria invading GFs in the cell-treated P. gingivalis and F. nucleatum were 0.0068% and 1.22%, respectively. Dual infection with F. nucleatum increased the invasive ability of P. gingivalis . Conclusion The invasive capacities of P. gingivalis into GFs were comparatively lower than those of relatively less pathogenic bacteria. Invasion into GFs cannot be the first strategy for survival of P. gingivalis in gingival connective tissue.