Periodontitis promotes gingival accumulation of cells with MDSC phenotype

BackgroundPeriodontitis is one of the most common inflammatory diseases in humans, mostly caused by bacterial infection and with diverse populations of immune cells involved. Myeloid-derived suppressor cells (MDSCs), a heterogeneous group of immature myeloid cells derived from hematopoietic precursor cells, have exhibited immunomodulatory functions by production of different molecules such as inducible NO synthase (iNOS) and it is thought to be involved in periodontitis. However, reports of characterization of cells with MDSC phenotypes in gingival tissues are very scarce. This study aimed to characterize gingival cells with MDSC phenotypes in healthy gingiva and periodontitis tissues.Methods and ResultsHuman healthy gingival tissues and those with periodontitis were included to analyze cells with MDSC phenotypes by flow cytometry. Additionally, a mouse model of experimental periodontitis was used to identify cells with MDSC phenotypes and production of iNOS. Results showed an increased accumulation of CD45⁺HLA-DR^neg/lowCD11b⁺CD33⁺ cells in human gingival tissues with periodontitis. Experimental periodontitis promotes accumulation of CD45⁺CD11b⁺Gr-1⁺ and CD45⁺CD11b⁺Ly6G⁺ cells in gingival tissues. Experimental periodontitis did not promote accumulation of these subpopulations in other tissues as spleen. Additionally, gingival CD45⁺Gr-1⁺ iNOS⁺ cells were identified.Conclusionscells with MDSC phenotypes are resident in healthy gingival tissues and their accumulation is locally triggered by periodontitis. Cells with capacity of iNOS production could be implicated in generation of reactive nitrogen species, suggesting immunomodulatory properties.