| Summary: | 碩士 === 國防醫學院 === 微生物及免疫學研究所 === 102 === Periodontitis can be characterized by the accumulation of a specific gram-negative periodontopathogens (i.e., Porphyromonas gingivalis), but progression of the disease is dependent on the host response to these pathogenic bacteria. As the number of microbial factors, such as lipopolysaccharide (LPS) from P. gingivalis (P.g), increases surface receptors known as Toll-like receptors (TLR) in the oral cavity function to recognize and respond to this change. This interaction leads to the production of inflammatory cytokines by myeloid differentiation primary response protein 88 (MyD88)-dependent and -independent pathways, which may in turn initiate a local immune response, release of inflammatory mediators, and activation of osteoclasts responsible for bone resorption. Moreover, the T helper 17 (Th17)/ regulatory T (Treg) imbalance has recently been suggested to play a role in the development of periodontitis. Although the role of adapter molecule MyD88 in controlling infection and immune system activation has been examined, its function/involvement in the development and progression of periodontal destruction has not been investigated. The aim of current study was to assess the involvement of MyD88 in alveolar bone loss (ABL) induced by P.g in mice, to investigate whether Th17/Treg imbalance plays a role in the development of experimental periodontitis, and to examine the role of MyD88 in osteoclast differentiation and function in vitro. Experimental periodontitis will be induced in C57BL/6 wild-type 1 and MyD88 KO mice by oral infection with P. gingivalis. Animals will be sacrificed at indicated time points (D14-D60) and the maxillae removed for micro-CT analyses. ABL will be assessed by measuring the distance from the cemento-enamel junction (CEJ) to the alveolar bone crest (ABC). CD4+ T cell subsets (Th17 and Treg cells)in the cervical lymph nodes (CLNs) and spleen will be analyzed by flow cytometry. Bone marrow-derived osteoclasts will be isolated, tartrate resistant acid phosphate (TRAP) staining and TRAP activity will be measured in vitro. Our data showed that increased CEJ-ABC distance was observed in WT mice at 42 days post infection, Th17/Treg imbalance in the CLNs, and blunted osteoclast differentiation of hematopoietic bone marrow cells from MyD88 KO mice was also noted when compared with WT mice after P. gingivalis LPS stimulation.
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