Periodontitis is an inflammatory disease which leads to destruction of alveolar bone. Complex bacteria in subgingival plaque are associated with bone destruction in periodontitis. Osteoclasts are highly specialized multinucleated cells with bone-resorbing activity. Cells of the monocyte-macrophage lineage derived form hematopoietic progenitors are able to differentiate into multinucleated osteoclasts, depending on the extracellular enviroment. RAW 264.7 cells, a mouse macrophage cell line, can differentiate into osteoclasts in the presence of RANKL. To clarify the direct effect of periodontal pathogen on osteoclastogenesis, we estimated the effect of three periodontopathic bacteria such as Porphyromonas gingivalis, Treponema denticola, Treponema socranskii, and Treponema lecithinolyticum on osteoclast formation from RAW 264.7 cells. Sonicates of P. gingivalis, T. denticola and T. socranskii and LPS of T. lecithinolyticum stimulated the osteoclast formation from RAW 264.7 cells in the absense of RANKL. These bacteria and LPS increased the mRNA expression of IL-1ß and IL-6 in RAW 264.7 cells. These findings suggest that periodontal pathogen directly mediates osteoclastogenesis from monocyte macrophage lileage cells without RANKL.
(supported by Korea Science and Engineering Foundation)