Porphyromonas gulae 41-kDa fimbriae induced osteoclast differentiation and cytokine production

Porphyromonas gulae is considered to be associated with canineperiodontitis. We have previously reported that the P. gulae AmericanType Culture Collection (ATCC) 51700 comprised 41-kDa fimbriae. The purpose of the presentstudy was to demonstrate the roles of 41-kDa fimbrial protein in periodontal disease. Inthis study, we examined the involvement of the 41-kDa fimbrial protein in osteoclastdifferentiation and cytokine production in murine macrophages. Furthermore, alveolar boneresorption induced by P. gulae infection in rats was evaluated. Toestimate osteoclast differentiation, bone marrow cells and MC3T3-G2/PA6 cells werecultured with or without the 41-kDa fimbrial protein for 7 days. BALB/c mouse peritonealmacrophages were stimulated with the 41-kDa fimbrial protein, and the levels ofinterleukin (IL)-1β and tumor necrosis factor (TNF)-α production were determined byenzyme-linked immunosorbent assay. Osteoclast differentiation was significantly enhancedby treatment with the 41-kDa fimbrial protein in a dose-dependent manner. The total areaof pits formed on the dentine slices with osteoclasts incubated with the 41-kDa fimbrialprotein was significantly greater than that of the control. The purified 41-kDa fimbrialprotein induced IL-1β and TNF-α production in BALB/c mouse peritoneal macrophages after 6hr of incubation in a dose-dependent manner. The bone loss level in rats infected withP. gulae was significantly higher than that of the sham-infected rats.These results suggest that P. gulae 41-kDa fimbriae play important rolesin the pathogenesis of periodontal disease.