Human bone marrow stromal cells inhibit allogeneic T-cell responses by indoleamine 2,3-dioxygenase–mediated tryptophan degradation

Abstract

IntroductionHuman bone marrow stromal cells (MSCs), more recently referred to as mesenchymal stem cells, are capable of differentiating along multiple mesenchymal lineages in addition to supporting hematopoiesis. 1,2 Due to their potential for differentiation into osteocytes, chondrocytes, myocytes, and adipocytes, MSCs have emerged as a promising tool for clinical applications such as tissue engineering and cell and gene therapy. 3,4 MSCs are of inherently low immunogenicity and, more importantly, are capable of inhibiting allogeneic T-cell responses. 5-8 These intriguing observations have prompted clinical studies to investigate cotransplantation of MSCs in allogeneic hematopoietic stem cell transplantation (HSCT) in order to promote hematopoietic engraftment by preventing host-versusgraft reactivity and to suppress graft-versus-host reactions. 9,10 As of yet, the molecular mechanisms responsible for the immunosuppressive effects of MSCs have not been unequivocally identified. The reports describing a potential role of transforming growth factor-␤1 and hepatocyte growth factor as mediators of T-cell inhibition remain controversial, but most studies agree that soluble factors are involved. [6][7][8]11 In professional antigen-presenting cells (APCs), expression of indoleamine 2,3-dioxygenase (IDO) induced by interferon-␥ (IFN-␥) and other proinflammatory cytokines catalyzes conversion from tryptophan to kynurenine and has recently been identified as a major immunosuppressive effector pathway that inhibits T-cell responses to autoantigens and fetal alloantigens in vivo. [12][13][14][15][16] Based on these findings, we investigated whether MSCs exhibit IFN-␥-inducible IDO activity and whether this mechanism contributes to T-cell inhibition mediated by MSCs. Study design Culture of human bone marrow-derived MSCsBone marrow aspirates were harvested from volunteer donors who had provided informed consent; the study was approved by the institutional review board of the University Clinic, Düsseldorf, Germany. Primary human MSCs were generated as previously described 17 except that culture medium was supplemented with 3 ng/mL basic fibroblast growth factor (R&D Systems, Minneapolis, MN). Mixed lymphocyte reactions (MLRs)Standard 5-day MLR cultures were set up with 5 ϫ 10 4 mitomycin C-treated human peripheral blood mononuclear cells (PBMCs) as stimulators and 2 ϫ 10 5 human T cells purified using sheep red blood cell rosetting as responder cells. 5,11 In MSC/MLR coculture experiments, MLRs were performed on a layer of either 5 ϫ 10 3 or 2 ϫ 10 4 MSCs seeded one day before. IFN-␥ concentration was determined in MSC/MLR coculture supernatants using a commercially available enzyme-linked immunosorbent assay (ELISA; R&D Systems) according to manufacturer's instructions. Detection of IDO expression and activityMSCs were stimulated with IFN-␥ (R&D Systems) and assayed for IDO expression and function. Standard Western blot analysis for IDO protein expression was performed. 18 IDO enzyme activity following IFN-␥ stimulation of ...

How stem cells speak with host immune cells in inflammatory brain diseases

“…MSCs express indoleamine 2,3-dioxygenase (IDO)-an immune regulatory enzyme that catalyses the degradation of tryptophan via the kynurenine pathway-and exhibit functional IDO activity and IDO-dependent apoptotic effects on allogeneic human T cells upon stimulation with IFN-γ (Meisel et al, 2004;Plumas et al, 2005). In vivo in mice with EAE, transplanted syngeneic MSCs prevent relapses and promote myelin repair via an IFN-γ-dependent mechanism that induces IDO in CD11c + DCs and leads to the inhibition of antigen reactivity and disease spread (Matysiak et al, 2008(Matysiak et al, , 2011.…”

“…Data in Table 1 are in part summarized in (Chamberlain et al, 2008;Hall et al, 2006;Martino and Pluchino 2006;Pluchino et al, 2009b;Rojewski et al, 2008;Uccelli et al, 2008;Yuan et al, 2011). (Cusimano et al, 2012;Jaderstad et al, 2010) aracrine IDO-kynurenine MSCs (h) T cells, DCs T cell apoptosis, inhibition of antigen presentation (Lanz et al, 2010;Matysiak et al, 2008Matysiak et al, , 2011Meisel et al, 2004;Plumas et al, 2005 Bonnamain et al, 2012;Chabannes et al, 2007;Moll et al, 2011) Paracrine VEGF NPCs Microglia/macrophages Inhibition of microglial activation, proliferation and phagocytosis (Horie et al, 2011;Kim et al, 2009a;Mosher et al, 2012) Paracrine LIF NPCs Th17 cells Inhibition of Th17 cell differentiation (Cao et al, 2011;Horie et al, 2011;Kim et al, 2009a;Mosher et al, 2012) Paracrine Galectins MSCs/NPCs T cells Inhibition of T cell proliferation (Gieseke et al, 2010;Sioud 2011;Yamane et al, 2010Yamane et al, , 2011 Endocrine/Paracrine TSG-6 MSCs Macrophages Inhibition of macrophage activation, proliferation and phagocytosis (Fisher-Shoval et al, 2012;Lee et al, 2009;Roddy et al, 2011) EVs miR transfer MSCs/NPCs Multiple Post-transcriptional regulation (Bruno et al, 2009;Chen et al, 2010;…”

Immunoregulatory function of mesenchymal stem cells

“…Inhibition of T cell proliferation by MSC appears to be subsequent both to cell-to-cell interaction and to the release of soluble factors, and it is conceivable that discrepant findings reported in the literature reflect differences in the experimental conditions used [13,14,16,48,49]. TGF-b1 and HGF [13], indoleamine 2,3-dioxygenase (IDO) [50] and prostaglandin E2 (PGE-2) [46] represent MSC-derived molecules that have been proposed to exert immunomodulatory activity on T cell responses. However, most of these results need to be confirmed, and it is likely that key molecules will be identified through functional molecular profiling of the MSC transcriptome.…”

Human mesenchymal stem cells respond to native but not oxidized damage associated molecular pattern molecules from necrotic (tumor) material

“…Local decrease of tryptophan and an increase of kynurenine are associated with immunosuppression and a shift from a Th1 to a Th2 response [14]. Expression of IDO in MSCs is induced by interferon-g (IFN-g) [12].We have already demonstrated that eosinophilic granulocytes (Eos) are attracted by necrotic material and respond to DAMPs by releasing reactive oxygen species, which are capable of oxidizing native/active DAMPs [3], including HMGB1 [3]. Oxidized DAMPs lose their capacity to further attract and activate Eos [3].…”