Human adipose-derived mesenchymal stem cells reduce inflammatory and T-cell responses and induce regulatory T cells in vitro in rheumatoid arthritis

Objectives: Adult mesenchymal stem cells were recently found to suppress effector T-cell and inflammatory responses and have emerged as attractive therapeutic candidates for immune disorders. In rheumatoid arthritis (RA), a loss in the immunological self-tolerance causes the activation of autorreactive T cells against joint components and subsequent chronic inflammation. The aim of this study is to characterize the immunosuppresive activity of human adipose-derived mesenchymal stem cells (hASCs) on collagen-reactive T cells from RA patients. Methods: We investigated the effects of hASCs on collagen-reactive RA human T-cell proliferation and cytokine production, as well as on the production of inflammatory mediators by monocytes and fibroblast-like synoviocytes from RA patients. Results: hASCs suppressed antigen-specific response of T cells from RA patients. hASCs inhibited the proliferative response and the production of inflammatory cytokines by collagen-activated CD4 and CD8 T cells. In contrast, the number of IL-10-producing T cells and monocytes significantly augmented upon hASC-treatment. The suppressive activity of hASCs was both cell-to-cell contact-dependent and -independent. hASCs also stimulated the generation of FoxP3-expressing CD4+CD25+ regulatory T cells with capacity to suppress collagen-specific T-cell responses. Finally, hASCs donwregulated the inflammatory response and the production of matrix-degrading enzymes by synovial cells isolated from RA patients. Conclusions: Our work identifies to hASCs as key regulators of immune tolerance with capacity to suppress T-cell and inflammatory responses to induce the generation/activation of antigen-specific regulatory T cells.