Local promotion of B10 function alleviates experimental periodontitis bone loss through antagonizing RANKL-expressing neutrophils

Background: Persistent host immune responses initiated by oral bacteria protect host against infection but may also elicit the process of sustained periodontal inflammation and subsequent alveolar bone loss. Interleukin-10 (IL-10), an anti-inflammatory cytokine, can downregulate pro-inflammatory cytokine and inhibit neutrophil migration in inflammation. IL-10-expressing regulatory B cells (B10) is termed by negatively regulating immune response through IL-10 and are mainly restricted in CD19⁺CD1d^hiCD5⁺B cells in mice. Our current study was aimed to explore the effect of locally transferred CD19⁺CD1d^hiCD5⁺B cells on inflammation and alveolar bone loss in an experimental periodontitis mouse model. Methods: Ligation plus P. gingivalis (Pg) infection was used to induce periodontitis in a mouse model. CD19⁺CD1d^hiCD5⁺ B cells were sorted by flow cytometry and transferred into the gingivae immediately on the fifth day after ligation. All the mice were sacrificed on day 14 after ligation. Results: H&E staining showed that inflammatory cell infiltration was significantly reduced by the CD19⁺CD1d^hiCD5⁺ B cells. Toluidine blue staining showed that the CD19⁺CD1d^hiCD5⁺ B cells alleviated alveolar bone loss in the ligature/Pg-induced periodontitis in mice. Immunohistochemical staining showed Receptor Activator of NF-KappaB Ligand (RANKL), Interleukin-1β(IL-1β) and Interleukin-17 (IL-17) were decreased after the CD19⁺CD1d^hiCD5⁺B cell transfer. Immunofluorescent staining showed that IL-10 was increased while the number of Ly6G⁺ neutrophil and its RANKL production were decreased in gingival tissue. Conclusions: These results indicated that locally transferred CD19⁺CD1d^hiCD5⁺B cells may alleviate alveolar bone loss through inhibiting pro-inflammatory cytokine expression and RANKL-expressing neutrophils in the periodontitis mouse model.