Improved RANKL production by memory B cells: A way for B cells promote alveolar bone destruction during periodontitis.

Periodontitis is a bacteria-induced disease that always clinically defined as loss of attachment, periodontal pocket and bone loss. Its mechanisms were considered to be complicated, involving an imbalance of the formation and resorption of bone. We sought to determine the function and mechanisms of the effects of B cells on osteoclastogenesis. We purified memory B cells from periodontitis or healthy animals and culture them. Receptor activator of nuclear factor kappa-B ligand (RANKL), expressed by gingival memory B cells, was detected by flow cytometry, enzyme-linked immunosorbent assay and real-time quantitative polymerase chain reaction (RT-qPCR). To discover any direct effects on osteoclastogenesis, gingival memory B cells were co-cultured with bone marrow mononuclear cells, osteoclast number and genes related to osteoclast differentiation were examined. In further investigations, an adoptive transfer experiment of memory B cells was designed, and pathologic indexes and expression of associated cytokines in different tissues were also investigated. We find that memory B cells from inflammatory gingiva produced more RANKL. Notably, such B cells promote osteoclastogenesis. In an adoptive transfer experiment, memory B cells enhanced alveolar bone loss and osteoclast formation. We also find a higher expression of RANKL, TNF-α, IL-1ß and IL-17A in gingival crevicular fluid, gingiva and cervical lymph nodes of adoptive transfer group. Our findings highlighted the considerable importance of B cells in alveolar bone homeostasis independent of antibody production during periodontitis.

CD8+ Foxp3+ T Cells Affect Alveolar Bone Homeostasis via Modulating Tregs/Th17 During Induced Periodontitis: an Adoptive Transfer Experiment.

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-1ß, IL-6, IL-10, IL-17A, RANKL, TGF-ß 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-1ß, IL-6, IL-17A, and RANKL, and less IL-10 and TGF-ß 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.