Immunosuppression by Adult Stem Cells

描述（由申请人提供）：间充质干细胞（MSC）在动物和人的体内和体外均具有强烈的免疫抑制作用。 使用从小鼠骨髓克隆的MSC，我们已经表明MSC有效地抑制新鲜分离的脾细胞的TCR激活的增殖和细胞因子产生。 在体内，骨髓间充质干细胞可防止同种异体皮肤移植排斥反应，抑制抗原特异性DTH反应，并抑制小鼠移植物抗宿主病（GvHD）。 有趣的是，MSC不影响IL-2驱动的T细胞母细胞增殖，除非重新激活，否则不产生炎性细胞因子。 MSC的免疫抑制作用需要IFN 3和另一种细胞因子-TNF 1、IL-11或IL-12的共同存在。 这种细胞因子对刺激MSC表达诱导型一氧化氮合酶（iNOS），产生NO，并分泌大量的T细胞特异性趋化因子，其补充NO的活性：在共培养物中，这些趋化因子驱使T细胞迁移到MSC附近，其中高水平的NO可以抑制T细胞。 阻断NO产生或趋化因子受体逆转了T细胞的抑制。 我们最近发现，虽然人MSC在抑制T细胞方面同样有效，并且具有相似的趋化因子产生谱，但它们利用IDO来影响免疫抑制。 因此，我们假设促炎细胞因子诱导MSC产生趋化因子和NO（在小鼠中）或IDO（在人中），其协同作用以介导免疫抑制。 我们提出了两个具体的目标来证明这一假设，使用小鼠和人类MSC相互补充。 我们将首先研究趋化因子和NO或IDO在体外小鼠细胞和人细胞中以及在体内小鼠GvHD模型中介导MSC的免疫抑制中的作用。 接下来，我们将确定小鼠和人MSC中IDO和NO调节的分子机制。由于MSC介导的免疫抑制通过iNOS/IDO和趋化因子的炎性丝氨酸上调发生，因此更好地理解这些作用的机制将导致更好的免疫疾病，癌症免疫治疗和疫苗设计的临床方案。 公共卫生相关性：间充质干细胞最重要的特性之一是其在抑制免疫反应方面的高效力，这可涉及许多疾病，诸如与骨髓移植相关的自身免疫性疾病、过敏反应、移植排斥和移植物抗宿主病。 干细胞研究的第一个临床应用可能是使用间充质干细胞治疗免疫疾病。 因此，预计拟议的研究将对人类健康产生巨大的影响。

DESCRIPTION (provided by applicant): Mesenchymal stem cells (MSCs) are strongly immunosuppressive in vivo and in vitro in both animals and humans. Using cloned MSCs from mouse bone marrow, we have shown that MSCs potently inhibit TCR-activated proliferation and cytokine production of freshly-isolated splenocytes. In vivo, MSCs prevented the rejection of allogeneic skin transplants, suppressed antigen-specific DTH responses, and inhibited graft-versus-host disease (GvHD) in mice. Interestingly, MSCs did not affect the IL-2-driven proliferation of T cell blasts, which do not produce inflammatory cytokines unless re-activated. The immunosuppressive effect of MSCs requires the co-presence of IFN3 and another cytokine - either TNF1, IL-11 or IL-12. Such cytokine pairs provoked MSCs to express inducible nitric oxide synthase (iNOS), produce NO, and secrete of large amounts of T cell specific-chemokines, which complement the activity of NO: in co-cultures, these chemokines drove T cells to migrate into proximity with MSCs, where high levels of NO can suppress T cells. Blockade of NO production or chemokine receptors reversed the inhibition of T cells. We recently found that while human MSCs are equally effective in suppressing T cells and have a similar spectrum of chemokine production, they utilize IDO to affect immunosuppression. Thus, we hypothesize that proinflammatory cytokines induce MSCs to produce chemokines and NO (in mouse) or IDO (in human) which act in concert to mediate immunosuppression. We propose two specific aims to prove this hypothesis using mouse and human MSCs to complement each other. We will first investigate the role of chemokines and NO or IDO in mediating immunosuppression of MSCs in both mouse cells and human cells in vitro and in the mouse GvHD model in vivo. Next, we will determine the molecular mechanisms of the regulation of IDO and NO in mouse and human MSC. Since MSC-mediated immunosuppression occurs through inflammatory cytokine-upregulation of iNOS/IDO and chemokines, a better understanding of the mechanisms underlying these effects will lead to better clinical protocols for immune disorders, cancer immunotherapy and vaccine design. PUBLIC HEALTH RELEVANCE: One of the most important properties of mesenchymal stem cells is their high potency in suppressing immune reactions, which can be involved in many diseases such autoimmune disorders, allergic reactions, rejection of transplants and graft-versus-host disease associated with bone marrow transplantation. It is likely that the very first clinical application of stem cell research will be the use of mesenchymal stem cells to treat immune disorders. Therefore, the proposed studies are expected to have enormous relevance to human health.