B10 cells regulate macrophage polarization to alleviate inflammation and bone loss in periodontitis

Background: The polarization of macrophages into an anti-inflammatory phenotype is crucial for resolving periodontal inflammation. It has been reported that B10 cells can regulate the immune response of macrophages during inflammation and are also able to regulate inflammation in periodontitis. However, whether B10 cells’ regulation function in periodontitis is related to macrophage polarization remains unclear. This study aims to investigate whether B10 cells can regulate macrophage polarization in periodontitis. Methods: Macrophages were cocultured with B10 cells in vitro for 5 days. After coculture, macrophages were obtained for analysis directly or followed by stimulation with Pg-LPS/IFN-γ or IL-4/IL-13. Flow cytometry and/or reverse transcriptase-polymerase chain reaction (RT-PCR) were employed to detect the expression of IL-1β, iNOS, TNF-α, CD206, and ARG-1 in macrophages. B10 cells were transferred on the 5th day after ligation in wild or macrophage-depletion mice. Toluidine blue and TRAP staining were used to evaluate alveolar bone resorption and osteoclast activation. Immunohistochemistry was employed to detect the expression of CD68, IL-1β, TNF-α, iNOS, ARG-1, and IL-10. Immunofluorescence was used to detect the expression of CD68⁺CD86⁺M1 macrophages and CD68⁺CD206⁺M2 macrophages. Results: In vitro, B10 cells inhibit the expression of IL-1β, iNOS, and TNF-α in macrophages while increasing the expression of CD206 and ARG-1. In experimental periodontitis, B10 cells inhibit the polarization of CD68⁺CD86⁺M1 macrophages and iNOS expression but enhance the polarization of CD68⁺CD206⁺M2 macrophages and ARG-1 expression. Importantly, the depletion of macrophages partially weakened the regulation function of B10 cells in periodontitis. Conclusions: B10 cells promote M2 macrophage polarization, inhibit M1 macrophage polarization in periodontitis, and alleviate periodontitis partially by regulating macrophage polarization.