The Study On The Pathogenicity Of Different FimA Genetypes Of Porphyromonas Gingivalis

Chronic periodontitis is a destructive inflammatory disease of periodontal tissues, which causes the absorption of alveolar bone and the damage of periodontal tissues. Porphyromonas gingivalis is considered to be the most important infectious agent causing chronic periodontitis. P. gingivalis is reportedly detected not only frequently in patients with periodontitis, but also at low frequency in periodontally healthy individuals without marked gingival inflammation. P. gingivalis ,which were collected from different people with different periodontal healthy conditions, caused different degree of inflammation in experiement aninal. These revealed a clonal heterogeneity in virulence among various P. gingivalis strains; the expression of heterogenic virulence properties is dependent on its clonal diversity. Therefore, the search for virulent strains of P.gingivalis and its pathogenesis will be helpful to prevent and cure periodontitis. P. gingivalis fimA gene encoding fimbrillin (the submit of major fimbriae) was present as a single copy on the bacterial chromosome, and no homologous sequences could be found in other black-pigmented porphyromonas species. Gene fimA can be classified into 6 genotypes (I- V and I b) on the basis of its nucleotide sequences. Several epidemiological investigations have reported the distribution of fimA genotype in subjects with different race and different periodontal conditions. A majority of Japanese periodontitis patients were found to carry II and IV fimA organisms, while in healthy Japanese adults, type I was the most prevalent fimA, genotype. The predominant fimA, genotypes in Caucasian and Brazilian periodontitis patients were II, I and II, I b types. These results suggest that the Specific clone variation of P.gingivalis fimA is possibly associated with ethnicity, geographic location and periodontal status of the studied population. There are many differences between different fimA genotypes of P.gingivalis in the ability of adhision and invasion of epithelial cells,induction the host cells to produce cytokines,delay the tissue proliferation and gingival wound healing. These results suggest that the difference of P.gingivalis fimA may result in the different ability of destruct the epithelial barrier. When P.gingivalis destruct the epithelial barrier, the bacteria and its virulent factors will invade gingival tissue, and will change the human gingival fibroblast structure and function. And the degree of tissue dustruction is relevant to P.gingivalis virulence.Now virulence diversities among different fimA genotypes have been one of the hot spots of periodontitis pathogenesis, our investigation have also got some proof about fimA genes and P.gingivalis pathogenicity. Our study aims to investigate the prevalence of 6 genotypes of P.gingivalis in Chinese chronic periodontitis patients compared with periodontally healthy adults, and try to investigate the pathogenesis of P.gingivalis with fimA genotypes closely associated with Chinese chronic periodontitis.In the first part, the occurrence of P.gingivalis in 136 periodontally healthy adults and 115 chronic periodontitis patients was determined by 16S rRNA PCR; the prevalence of P.gingivalis fimA genetypes was assessed in P.gingivalis positive samples by fimA type-specificPCR to investigate the distribution of fimA genetypes of P.gingivalis in periodontally healthy adults and chronic periodontitis patients. Odds ratio and 95% confidence intervals were calculated for finding the specific fimA genotype associated with the development of periodontitis in Chinese.In the second part, chemokine and MMPs of human gingival fibroblasts by different fimA genetypes of P.gingivalis were compared on the two levels of mRNA and protein by TaqMan real-time quantitative RT-PCR and ELISA.And the results are as follows:(1) In patients, 94 of 115 (81.7%) samples were positive for P.gingivalis, P.gingivalis was detected in 30 out of 136 (22.1%) subgingival plaque samples from periodontally healthy adults. the result suggested that: P.gingivalis is a resident oral bacteria, which exist in the subgingival plaque of periodontal healthy adults and periodontitis patients.(2) Type I fimA was detected most frequently(66.7%) among the periodontally healthy subjects. While a majority of the patients were found to carry type II fimA organisms(43.6%), followed by type IV(30.9%). We calculated Odds Ratio and 95% confident interval for a significant association of fimA-type occurrences with periodontal health status. The results demonstrated that the relationship of II fimA genotype with periodontitis was remarkable ,followed by type IV. These findings indicated that there is disease-associated specific-fimA P.gingivalis in Chinese adults.(3) Under the enviroments of our experiment, the regulation effects on MMP-1,MMP-2 expression by type II P.gingivalis were stronger than other fimA types, which happened on the transcription and post- transcription levels. The regulation effects on MMP-1,MMP-2 expression by type III P.gingivalis were less than other fimA types, Which indicated that the difference of fimA genotypes may lead different ability of P.gingivalis to modulate MMPs activity, and then the different ability to destruct the gingival tissue.(4) Under the enviroments of our experiment, the regulation effects on IL-8 and MCP-1 expression by type II P.gingivalis were stronger than other fimA types, which happened on the transcription and post- transcription levels. The regulation effects on MMP-1,MMP-2 expression by type III P.gingivalis were less than other fimA types, Which indicated that the difference of fimA genotypes may lead different ability of P.gingivalis to induce HGFs to express Chemokines , and then the different ability to trigger the inflammation of gingival tissue.Based on these findings, we concluded that P.gingivalis with II fimA and IV fimA were closely associated with the initiation and progression of chronic periodontitis in Chinese adults. The regulation effects of the MMPs and Chemokines production of human gingival fibroblasts by P.gingivalis with II fimA were stronger than any other fimA types, which indicates the virulence and pathogenicity of P.gingivalis was related with its fimA genotypes.