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Porphyromonas gingivalis fimbriae stimulate bone resorption in vitro
Y Kawata1, S Hanazawa, S Amano
1Department of Oral Microbiology, Meikai University School of Dentistry, Saitama, Japan.
Abstract:
Our previous study demonstrated that Porphyromonas gingivalis fimbriae induce the expression of interleukin-1, a potent bone-resorbing cytokine, in macrophages. This demonstration suggested to use the possibility that the fimbriae may stimulate bone resorption via the generation of an inflammatory cytokine(s). The present study was performed to test this suggestion. The bone-resorbing activity was evaluated by measuring the area of resorption lacunae on bone slices incubated with calvarial bone cells taken from 14-day-old mouse embryos. Fimbriae at 0.5 micrograms of protein per ml stimulated the bone-resorbing activity significantly, and the effect was dose and treatment time dependent. Since it is well known that interleukin-1 and granulocyte macrophage colony-stimulating factor induce differentiation of osteoclast lineage cells, we examined the involvement of these cytokines in fimbria-stimulated bone resorption. Fimbria-stimulated bone resorption was abolished significantly by antisera against both cytokines. We observed by Northern (RNA) blot assay that both cytokine genes were markedly expressed in the fimbria-treated calvarial bone cells. Our present data demonstrate that P. gingivalis fimbriae stimulate bone resorption in vitro.
Insights
Porphyromonas gingivalis fimbriae stimulate bone resorption by inducing inflammatory cytokines. This study confirms that these bacterial components activate pathways leading to bone loss in vitro.
Area of Science:
- Microbiology
- Immunology
- Bone Biology
Background:
- Porphyromonas gingivalis fimbriae previously shown to induce interleukin-1 in macrophages.
- This suggests fimbriae may stimulate bone resorption through inflammatory cytokines.
Purpose of the Study:
- To investigate if P. gingivalis fimbriae stimulate bone resorption.
- To determine the role of interleukin-1 and granulocyte macrophage-colony stimulating factor in fimbriae-induced bone resorption.
Main Methods:
- Assessing bone-resorbing activity using resorption lacunae area on mouse calvarial bone cells.
- Evaluating the effect of P. gingivalis fimbriae on cytokine gene expression via Northern blot assay.
- Testing the involvement of cytokines using antisera against interleukin-1 and granulocyte macrophage-colony stimulating factor.
Main Results:
- P. gingivalis fimbriae significantly stimulated bone resorption in a dose- and time-dependent manner.
- Fimbriae-induced bone resorption was abolished by antisera against interleukin-1 and granulocyte macrophage-colony stimulating factor.
- Northern blot analysis revealed marked expression of both cytokine genes in fimbria-treated cells.
Conclusions:
- P. gingivalis fimbriae directly stimulate bone resorption in vitro.
- The mechanism involves the induction of interleukin-1 and granulocyte macrophage-colony stimulating factor.
- These findings highlight a potential pathway for periodontal disease-associated bone loss.