Ex vivo immunosuppressive effects of mesenchymal stem cells on Crohn’s disease mucosal T cells are largely dependent on indoleamine 2,3-dioxygenase activity and cell-cell contact

Abstract

IntroductionCrohn’s disease (CD) is a disabling chronic enteropathy sustained by a harmful T-cell response toward antigens of the gut microbiota in genetically susceptible subjects. Growing evidence highlights the safety and possible efficacy of mesenchymal stem cells (MSCs) as a new therapeutic tool for this condition. Therefore, we aimed to investigate the effects of bone marrow-derived MSCs on pathogenic T cells with a view to clinical application.MethodsT-cell lines from both inflamed and non-inflamed colonic mucosal specimens of CD patients and from healthy mucosa of control subjects were grown with the antigen muramyl-dipeptide in the absence or presence of donors’ MSCs. The MSC effects were evaluated in terms of T-cell viability, apoptotic rate, proliferative response, immunophenotype, and cytokine profile. The role of the indoleamine 2,3-dioxygenase (IDO) was established by adding a specific inhibitor, the 1-methyl-DL-tryptophan, and by using MSCs transfected with the small interfering RNA (siRNA) targeting IDO. The relevance of cell-cell contact was evaluated by applying transwell membranes.ResultsA significant reduction in both cell viability and proliferative response to muramyl-dipeptide, with simultaneous increase in the apoptotic rate, was found in T cells from both inflamed and non-inflamed CD mucosa when co-cultured with MSCs and was reverted by inhibiting IDO activity and expression. A reduction of the activated CD4+CD25+ subset and increase of the CD3+CD69+ population were also observed when T-cell lines from CD mucosa were co-cultured with MSCs. In parallel, an inhibitory effect was evident on the expression of the pro-inflammatory cytokines tumor necrosis factor-α, interferon-γ, interleukin-17A and -21, whereas that of the transforming growth factor-β and interleukin-6 were increased, and production of the tolerogenic molecule soluble HLA-G was high. These latter effects were almost completely eliminated by blocking the IDO, whose activity was upregulated in MSCs co-cultured with CD T cells. The use of a semipermeable membrane partially inhibited the MSC immunosuppressive effects. Finally, hardly any effects of MSCs were observed when T cells obtained from control subjects were used.ConclusionMSCs exert potent immunomodulant effects on antigen-specific T cells in CD through a complex paracrine and cell-cell contact-mediated action, which may be exploited for widespread therapeutic use.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0122-1) contains supplementary material, which is available to authorized users.

Current and emerging therapeutic targets for IBD

“…Adipose derived allo geneic stem cells have been considered as new treatment approaches for such fistulas 142,143 . Experimental studies revealed that mesenchymal stem cells (MSCs) might exert potent immunomodulatory effects on antigen specific T cells in Crohn's disease through paracrine and cell-cell contact mediated actions 144 . Clinically, local administration of allogeneic, expanded MSCs in initial trials was not associated with severe adverse events in patients with Crohn's disease who had perianal fistulas and seemed to promote healing.…”

Modern management of perianal fistulas in Crohn’s disease: future directions

“…The downregulation of the immune system comes through the inhibition of dendritic cells from monocytes, the suppression of naïve and memory CD4+ cells, prevention of T cell activation by downregulating costimulatory molecules on mature dendritic cells and promotion of regulatory T cells 53–56. Interestingly, in vitro MSCs induce dendritic cells into a regulatory-like profile57 and shift the T cell population to a more tolerogenic pattern 58. Another unique property of MSCs that allows them to be valuable players in the tissue repair process is their ability to migrate to sites of tissue injury and inflammation 59.…”

Mesenchymal stromal cell-based therapy: Regulatory and translational aspects in gastroenterology

“…In contrast, Luetzkendorf and colleagues extensively demonstrated an intact phenotype after MSC thawing under GMP conditions and a similar activity in the leukocyte proliferation assay[43,44]. Higher rate of MSC proliferation can be achieved with hypoxic conditions in culture, so as to reproduce the niche environment, whereas IFNγ/IFNγ + IL1-β pretreatment enhance IDO-mediated T-reg expansion[16,43,44]. …”

“…The latter in turn catabolizes tryptophan producing kynurenins, a potent T-reg lymphocyte inducer[13,14]. MSC-dependent induction of IDO correlates with disease rating in humans[15,16] and, to a lesser extent, in mice where MSC anti-inflammatory action is mostly mediated by iNOS[13,17] (Table 1). Notably, IDO or iNOS-mediated MSC activity was recently shown to correlate with a specific phylogenetic tree (Figure 1)[13].…”

“…In particular, local MSC administration was particularly efficacious in the treatment of perianal fistula, a complication of Crohn’s disease (CD)[39]. In addition, inhibition of pro-inflammatory cytokines and patients activated T-cell apoptosis was described as a cell-to-cell mediated mechanism of MSCs[16]. …”