Introduction\nThe goal of this study is to analyze the potential immunosuppressive properties of mesenchymal stem cells (MSC) on T cell proliferation and in collagen-induced arthritis (CIA). An additional aim is to investigate the role of interferon-? (IFN-?) in these processes.\n Methods\nMSC were isolated from bone marrow of DBA/1 wild type and IFN-? receptor knock-out (IFN-?R KO) mice and expanded in vitro. Proliferation of anti-CD3-stimulated CD4+ T cells in the presence or absence of MSC was evaluated by thymidine incorporation. CIA was induced in DBA/1 mice and animals were treated with MSC by intravenous or intraperitoneal injections of wild type or IFN-?R KO MSC.\n Results\nPurity of enriched MSC cultures was evaluated by flow cytometry and their ability to differentiate into osteoblasts and adipocytes. In vitro, wild type MSC dose-dependently suppressed anti-CD3-induced T cell proliferation whereas IFN-?R KO MSC had a significantly lower inhibitory potential. A role for inducible nitric oxide (iNOS), programmed death ligand-1 (PD-L1) and prostaglandin E2 (PGE2), but not indoleamine 2,3-dioxigenase (IDO), in the T cell inhibition was demonstrated. In vivo, neither wild type nor IFN-?R KO MSC were able to reduce the severity of CIA or the humoral or cellular immune response toward collagen type II.\n Conclusions\nWhereas MSC inhibit anti-CD3-induced proliferation of T cells in vitro, an effect partially mediated by IFN-?, MSC do not influence in vivo T cell proliferation nor the disease course of CIA. Thus there is a clear discrepancy between the in vitro and in vivo effects of MSC on T cell proliferation and CIA.
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