The Immunomodulation Of Human Umbilical Cord-derived Mesenchymal Stem Cells

BACKGROUND:Mesenchymal stem cells(MSCs), the nonhematopoietic progenitor cells found in various adult tissues, are characterized by their ease of isolation and their rapid growth in vitro while maintaining their differentiation potential, allowing for extensive culture expansion to obtain large quantities suitable for therapeutic use. Mesenchymal stem cells isolated from human bone marrow, which are poorly immunogenic and have potent immunosuppressive activities, have emerged as a promising candidate for cellular therapeutics for the treatment of disorders caused by abnormal immune responses. Human umbilical cord derived mesenchymal stem cells (hUC-MSCs) resemble bone marrow MSCs (BM-MSCs) in many respects, but its immunosuppression are still lack in the literature.OBJECTION:This study was designed to investigat the immunosuppressive action by MSCs derived from human umbilical cord, and in the meantime to analyze the potential mechanism(s).METHODS:hUC-MSCs were co-cultured with MHC-mismatched allogeneic hPBMCs which in response to mitogenic or allogeneic stimulus. Both proliferation of human peripheral blood mononuclear cells (hPBMCs) and their IFN-γproduction were used to determine the immunosuppressive action of hUC-MSCs. And the transwell experiments were carried out for analyzing the contact necessary; Blocking experiments were used to identify which soluble factor(s) mediated the immunosuppressive effects; In addition, the data of Annexin-V showed the ability of hUC-MSCs on the apotosis of activated-hPBMCs.RESULTS:In this study, both proliferation of human peripheral blood mononuclear cells (hPBMCs) and their IFN-γproduction in response to mitogenic or allogeneic stimulus were effectively inhibited by hUC-MSCs. Co-culture experiments in transwell systems indicated that the suppression was largely mediated by soluble factor(s). Blocking experiments identified prostaglandin E2 (PGE2) as the major factor, because inhibition of PGE2 synthesis almost completely mitigated the immunosuppressive effects, whereas neutralization of TGF-β, IDO and NO activities had little effects. Moreover, the inflammatory cytokines, IFN-γand IL-1βproduced by hPBMCs upon activation notably up-regulated the expression of cyclooxygenase-2 (COX-2) and the production of PGE2 by hUC-MSCs. In addition, PGE2 was also found able to protect hPBMCs from apoptosis.CONCLUSION:In conclusion, our data have demonstrated for the first time that the PGE2 mediated mechanism by which hUC-MSCs exert their immunomodulatory effects. These mechanisms can render the theory basic to clinical usage of hUC-MSCs. Background:The emerging role of interleukin(IL)-17 as a hallmark proinflammatory cytokine of the adaptive immune system, producted primarily by a new T helper cell subset termed'Th17', has received considerable attention. There has been much progress in the past year, leading to identification of the molecular mechanisms that drive differentiation of Th17 T cells. This has helped to clarify many aspects of their role in host defense as well as in autoimmunity. Recent studies have shown that inflammation instigated by IL-17-producing cells is central to the development and pathogenesis of several human autoimmune diseases and animal models of autoimmunity. And the activated IL-23/IL-17 axis is important for the inflammatory immunity in SLE. Mesenchymal stem cells (MSC) are multipotent stem cells that can differentiate into tissues of mesodermal origin and can be isolated from various tissues. MSC have also been noted to have profound immunomodulatory effects on immune cells, leading to the modulation of several effector functions. Recently, the expansion of IL-17 producing cells from healthy donors is reportedly promoted by mesenchymal stem cells derived from fetal bone marrow.Objective:This article aimed to investigate the immunoregulatory effects of human umbilical cords-derived MSC on human T lymphocytes from healthy donors and Systemic Lupus Erythematosus patients, especially Th17 cells, so as to broaden our understanding of the immunomodulatory properties of MSC and provide insights as to their potential for clinical use as a cell-based therapy for immune-mediated disorders.Methods:In the present study, We cultured hPBMCs(from healthy donor and SLE patients) and CD4+T cells with or without hUC-MSCs, and named the coculture of hPBMCs or CD+4 T cells with hUC-MSCs as coculture cells. hPBMCs were incubated with PHA, while CD4+T cells were incubated with ati-CD3/CD28 Dynabeads in the presence or absence of hUC-MSCs.①We used qRT-PCR, Elisa analyses to compare the expression levels of IL-17 secretion of hPBMCs from healthy donor or SLE patients. The change of IL-17 expression when supplemented with additional IL-6, PGE2 and IL-1βneutralizing reagent. ②The expression of IL-17 secretion from CD4+T cells was tested by Elisa and Th-17 cells was tested by cytometry analyses.③The expression of IFN-γand TGF-βwere tested by Elisa and the percentage of Thl cells and Treg cells were tested by cytometry analyses.④We used Elisa to compare the expression levels ofIL-23 secretion of hPBMCs from healthy donor or SLE patients.Results:Significantly higher levels of IL-17 were produced when CD4+T cells from healthy donors were cocultured with hUC-MSCs than when CD4+T cells from healthy donors were cultured alone. The similar data was obtained on hPBMCs. Blocking experiments identified that this effect might be partially mediated through prostaglandin E2 (PGE2) and IL-1βwithout IL-23 involvement. We then cocultured hUC-MSCs with human PBMCs from Systemic Lupus Erythematosus patients. Ex vivo inductions of IL-17 by hUC-MSCs in stimulated lymphocytes were significantly higher in SLE patients than in controls, but this effect was not seen for IL-23. Also, hUC-MSC decrease the production of Thl cells and increase the production of Treg cells. Conclusion:Taken together, our results represent the first report of promotion of IL-17 production by hUC MSCs in both healthy donor and SLE patients. PGE2 and IL-1βmight also be partially involved in the promotive effect of hUC-MSCs. This finding may provide a new insight into the potential pathological roles of hUC-MSCs in SLE. Given that serum abundance of IL-17 has been correlated with SLE disease activity, clinical treatments using hUC-MSCs in SLE may require more careful research.