Suppression of Proteoglycan-Induced Autoimmune Arthritis by Myeloid-Derived Suppressor Cells Generated In Vitro from Murine Bone Marrow

Abstract

BackgroundMyeloid-derived suppressor cells (MDSCs) are innate immune cells capable of suppressing T-cell responses. We previously reported the presence of MDSCs with a granulocytic phenotype in the synovial fluid (SF) of mice with proteoglycan (PG)-induced arthritis (PGIA), a T cell-dependent autoimmune model of rheumatoid arthritis (RA). However, the limited amount of SF-MDSCs precluded investigations into their therapeutic potential. The goals of this study were to develop an in vitro method for generating MDSCs similar to those found in SF and to reveal the therapeutic effect of such cells in PGIA.MethodsMurine bone marrow (BM) cells were cultured for 3 days in the presence of granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin-6 (IL-6), and granulocyte colony-stimulating factor (G-CSF). The phenotype of cultured cells was analyzed using flow cytometry, microscopy, and biochemical methods. The suppressor activity of BM-MDSCs was tested upon co-culture with activated T cells. To investigate the therapeutic potential of BM-MDSCs, the cells were injected into SCID mice at the early stage of adoptively transferred PGIA, and their effects on the clinical course of arthritis and PG-specific immune responses were determined.ResultsBM cells cultured in the presence of GM-CSF, IL-6, and G-CSF became enriched in MDSC-like cells that showed greater phenotypic heterogeneity than MDSCs present in SF. BM-MDSCs profoundly inhibited both antigen-specific and polyclonal T-cell proliferation primarily via production of nitric oxide. Injection of BM-MDSCs into mice with PGIA ameliorated arthritis and reduced PG-specific T-cell responses and serum antibody levels.ConclusionsOur in vitro enrichment strategy provides a SF-like, but controlled microenvironment for converting BM myeloid precursors into MDSCs that potently suppress both T-cell responses and the progression of arthritis in a mouse model of RA. Our results also suggest that enrichment of BM in MDSCs could improve the therapeutic efficacy of BM transplantation in RA.

An epitope-specific DerG-PG70 LEAPS vaccine modulates T cell responses and suppresses arthritis progression in two related murine models of rheumatoid arthritis

“…The percentages of Th (CD4 + ) spleen cells containing intracellular cytokines or Foxp3 in cultures of antigen-stimulated spleen cells were determined by flow cytometry [28] on a BD FACS Canto II flow cytometer and analyzed using FACS Diva software (BD Flow Cytometry Systems, San Jose, CA). 3 …”

GM-CSF: An immune modulatory cytokine that can suppress autoimmunity

“…In another study, heterogeneous populations of MDSCs generated from bone marrow precursors with GM-CSF, G-CSF and IL-6 suppressed autoimmunity in a proteoglycan induced model of arthritis. These cells suppressed T-cell proliferation through the production of nitric oxide (186). …”

Interleukin-10 produced by myeloid-derived suppressor cells is critical for the induction of tregs and attenuation of rheumatoid inflammation in mice

“…Given the potent immuoregulatory activity of MDSCs, it could be expected that MDSCs could have therapeutic impact on RA. There have been discordant results regarding the effect of MDSCs on RA [12][13][14][15][16][17][18][19] . However, all the previous papers performed adoptive transfer of MDSCs in animal model of RA to verify whether the MDSCs had therapeutic effects on RA.…”

“…have therapeutic effects in animal model of RA [12][13][14][15][16] . However, a few recent papers have shown that MDSCs can aggravate inflammatory arthritis in mice [17][18][19] .…”