Background and Objective
Periodontitis is a bacteria‐induced disease that often leads to alveolar bone damage. Its mechanisms were considered to be complicated, involving an imbalance of the formation and resorption of bone. We sought to disclose the antibody‐independent function of B cells during periodontitis.
Material and Methods
Production of receptor activator for nuclear factor‐κB ligand (RANKL) by total lymphocytes or sorted B‐cell subsets in gingiva from healthy or experimental periodontitis animals was examined by flow cytometry, real‐time polymerase chain reaction, and enzyme‐linked immunosorbent assay. To define the effects of lymphocytes or B‐cell subsets on osteoclastogenesis induction, bone marrow mononuclear cells were culture in culture medium of lymphocytes or cocultured with B‐cell subsets. Osteoclasts were enumerated by tartrate‐resistant acid phosphatase staining. Constituent ratio of B‐cell subsets in healthy or experimental periodontitis was also detected by flow cytometry.
Result
Gingiva B cells produce more RANKL and support more osteoclastogenesis than T and other lymphocytes, and this potential improved in periodontitis. Memory B cells (CD27+CD38−) decreased their percentage in periodontitis. Memory B cells have the highest propensity for RANKL production. Remarkably, memory B cells from periodontitis animals expressed significantly more RANKL compared to healthy controls. Memory B cells supported osteoclast differentiation in vitro in a RANKL‐dependent manner, and the number of osteoclasts was higher in cultures with memory B cells from periodontitis animals than in those derived from healthy ones. Other B‐cell subsets have limited impact on osteoclast formation.
Conclusion
Findings of this study further disclose the roles of B cells engaged in periodontal immunomodulation and reveal the considerable importance of memory B cells in alveolar bone homeostasis and their likely contribution to alveolar bone destruction in periodontitis.
Periodontitis is a dysbiotic bacteria-mediated disease characterized by periodontal inflammations and alveolar bone damage. Its mechanisms were complicated, involving an inflammation-mediated bone destruction. We sought to determine roles and rules that CD8 regulatory T cells (CD8 Tregs) affect alveolar bone homeostasis during periodontitis. Presence of CD8 Tregs in the gingiva, cervical lymph nodes (CLNs), and spleens of healthy or periodontitis animals was analyzed. CD8 regulatory T cells from periodontitis animals were sorted by magnetic-activated cell sorting and fluorescent-activated cell sorting technique, subsequently injected into recipient animals to set adoptive transfer model. We induced experimental periodontitis on transfer models and equal number healthy animals. Four weeks later, their alveolar bone loss and osteoclast coverage length were measured. We also detected CD8 Tregs, CD4 T cell, CD4 Tregs, Th17 cell, and IL-1β, IL-6, IL-10, IL-17A, RANKL, TGF-β expression in the gingiva, CLNs, and spleen to illustrate possible working mechanism of CD8 regulatory T cells. Periodontitis does not induce significant change on proportion or amount of CD8 Tregs. Adoptive transfer of CD8 Tregs reduces alveolar bone destruction and osteoclast formation. In addition, experimental periodontitis increases percentage of Th17 cells and decreases CD4 Tregs in the gingiva and CLNs. More IL-1β, IL-6, IL-17A, and RANKL, and less IL-10 and TGF-β are also detected in the gingiva and CLNs from animals with periodontitis than the one from healthy animals. Adoptive transfer of CD8 regulatory T cells remedies all above pathological change effectively. We did not find any significant difference in spleen, regardless group and detected items. Outcomes of present study clarify function that CD8 regulatory T cells affect alveolar bone homeostasis, and disclose its possible working mechanisms. CD8 regulatory T cells protect alveolar bone via reducing osteoclastogenesis and modulating local immune response.
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