Extracellular vesicles derived from the periodontal pathogen Filifactor alocis induce systemic bone loss through Toll‐like receptor 2

Abstract

Periodontitis is an inflammatory disease induced by local infection in toothsupporting tissue. Periodontitis is associated with systemic bone diseases, but little is known about the mechanism of the causal effect of periodontitis on systemic bone resorption. Bacteria-derived extracellular vesicles (EVs) act as natural carriers of virulence factors that are responsible for systemic inflammation. In this study, we investigated the role of EVs derived from Filifactor alocis, a Gram-positive, anaerobic periodontal pathogen, in systemic bone loss and osteoclast differentiation. F. alocis EVs accumulated in the long bones of mice after intraperitoneal administration. These EVs induced proinflammatory cytokines, osteoclastogenesis, and bone resorption via Toll-like receptor 2 (TLR2). The phase separation of F. alocis EVs showed that amphiphilic molecules were responsible for the induced bone resorption and osteoclastogenesis. The osteoclastogenic effects of F. alocis EVs were reduced by lipoprotein lipase. Proteomic analysis of the amphiphilic molecules identified seven lipoproteins. Our results indicate that lipoprotein-like molecules in F. alocis EVs may contribute to systemic bone loss via TLR2.

Effects of extracellular vesicles derived from oral bacteria on osteoclast differentiation and activation

“…TLR2 signalling plays an important role in T. forsythia -mediated alveolar bone loss and activation of osteoclasts 20 . The osteoclastogenic activity of Pg EVs and Tf EVs was reduced by lipoprotein lipase treatment, suggesting that lipoproteins are active molecules, as shown in our previous study 15 . Jain et al reported that P. gingivalis induced inflammation via TLR2 signalling, which was attenuated by lipoprotein lipase treatment 21 .…”

“…Local infection of periodontal pathogens can cause osteoclast differentiation and bone resorption 17 . Recently, we determined that EVs from the Gram-positive periodontal pathogen F. alocis efficiently induce osteoclast differentiation and activation 15 . We used Fa EVs as a positive control to induce osteoclast differentiation in further experiments in this study.…”

“…Bacterial lipoproteins and LPS are known as major TLR2 and TLR4 ligands of bacterial EVs, respectively 11 , 12 . Recently, we identified that lipoproteins of Fa EVs are major inducers of osteoclast differentiation 15 . To identify the role of lipoproteins and LPS in oral bacterial EVs, we incubated the EVs with lipoprotein lipase or polymyxin B and collected the EVs by ultracentrifugation to remove residual treatments.…”

“…Recently, we reported that EVs from Gram-positive periodontal pathogen (Fa EVs) induced osteoclast differentiation and bone resorption through TLR2 15 . In the present study, we observed that EVs derived from the Gram-negative periodontal pathogens P. gingivalis and T. forsythia also preferentially activate TLR2 rather than TLR4 and induce osteoclastogenesis mainly via TLR2.…”

“…Recently, we reported for the first time that EVs derived from the Gram-positive periodontal pathogen F. alocis induced osteoclast differentiation through TLR2 15 . In the present study, we evaluated the effects of EVs from Gram-negative periodontal pathogens P. gingivalis and T. forsythia , oral commensal bacterium Streptococcus oralis , and a gut probiotic strain Lactobacillus reuteri on osteoclast differentiation.…”