Regulatory T Cell-derived Extracellular Vesicles Modulate Th1/Th17/Treg Imbalance During Experimental Periodontitis

Objectives: The inflammatory nature of periodontitis triggered by polymicrobial dysbiosis sets an exacerbated immune response within periodontal tissue. The local formation of a leucocyte-rich inflammatory infiltrate and accumulation of bone pro-resorptive factors result in destruction of tooth-supporting tissues. This process largely relies on Th1 and Th17 lymphocytes, promoting inflammation and alveolar bone loss. Conversely, CD4+ T regulatory cells (Tregs) dampen damage through immuno-suppressive mechanisms and tissue repairing functions. Recently, secretion of Tregs-derived extracellular vesicles (TEVs) has been identified as an immunosuppressive mechanism from which genetic material, cytoplasmic components, and/or surface molecules transfer and modulate target cells. Novel approaches indicate that immunomodulation may be achieved in a cell-free manner; hence, TEVs could represent an advantageous strategy to facilitate immune tolerance. Therefore, this study aimed to evaluate the immunomodulatory role of TEVs in the regulation of Th1/Th17/Treg imbalance during periodontitis.
Methods: From C57BL/6 mice, TEVs were isolated by serial centrifugation of culture supernatants obtained from induced CD4+CD25+Foxp3+ Tregs. TEVs were characterized by Nanoparticle Tracking Analysis and Scanning Electron Microscope. TEVs immunosuppressive function was evaluated both in vitro, analyzing their ability of diminish proliferation of CD4+ T cells, and in vivo, by assessing T-cell infiltration into periodontal lesions and cervical lymph nodes, as well as the alveolar bone loss, in a ligature-induced murine model of periodontitis.
Results: TEVs display canonical characteristics of EVs, 50-200 nm average size and round morphology. TEVs reduced CD4⁺ T cells proliferation, in vitro. In addition, decreased levels of alveolar bone loss and Th1/Th17 tissue infiltration were detected in TEVs-treated compared with non-treated periodontitis mice.
Conclusions: TEVs reduces CD4⁺ T cells proliferation in cell free manner. Moreover modulates Th1/Th17 phenotype,cell infiltration and alveolar bone loss during experimental periodontitis.