Immunosuppression by Adult Stem Cells

描述(申请人提供)：间充质干细胞(MSCs)在体内和体外对动物和人类都有很强的免疫抑制作用。利用从小鼠骨髓克隆的MSCs，我们已经证明MSCs能够有效地抑制TCR激活的新鲜分离的脾细胞的增殖和细胞因子的产生。在体内，MSCs可以预防同种异体皮肤移植的排斥反应，抑制抗原特异性DTH反应，并抑制小鼠的移植物抗宿主病(GvHD)。有趣的是，MSCs不影响IL-2驱动的T细胞母细胞的增殖，除非重新激活，否则T细胞母细胞不会产生炎性细胞因子。MSCs的免疫抑制作用需要IFN3和另一种细胞因子--TNF1、IL-11或IL-12的共同存在。这些细胞因子对刺激MSCs表达诱导型一氧化氮合酶(INOS)，产生NO，并分泌大量T细胞特异性趋化因子，补充NO的活性：在共培养中，这些趋化因子促使T细胞迁移到MSCs附近，在那里高水平的NO可以抑制T细胞。阻断NO产生或趋化因子受体可逆转T细胞的抑制作用。我们最近发现，虽然人类MSCs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MSCs产生趋化因子和NO(在小鼠中)或IDO(在人类中)，它们协同作用而介导免疫抑制。我们提出了两个具体的目标来证明这一假说，使用小鼠和人的MSCs来相互补充。我们将首先研究趋化因子和NO或IDO在体外和体内小鼠GvHD模型中介导MSCs免疫抑制的作用。接下来，我们将确定IDO和NO在小鼠和人骨髓间充质干细胞中调节的分子机制。由于MSC介导的免疫抑制是通过炎性细胞因子上调iNOS/IDO和趋化因子而发生的，因此更好地了解这些作用的机制将有助于制定更好的免疫紊乱、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它们在抑制免疫反应方面具有很高的效力，免疫反应可能与许多疾病有关，如自身免疫性疾病、过敏反应、移植排斥反应以及与骨髓移植相关的移植物抗宿主病。干细胞研究的第一个临床应用很可能是使用间充质干细胞治疗免疫疾病。因此，拟议的研究预计将对人类健康具有巨大的相关性。

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.