CD47-SIRPalpha Signaling in Mesenchymal Stem Cell-Mediated Immune Regulation in Liver Transplant Inflammatory Injury

项目总结 肝脏缺血再灌注损伤(IRI)诱导的先天免疫驱动的局部炎症反应 肝移植后的功能障碍和衰竭。间充质干细胞(MSCs)提供了新的 洞察其潜在的临床应用，特别是在治疗各种免疫介导性疾病方面。 先前的研究表明，间充质干细胞和炎症细胞之间的串扰在该机制中起着至关重要的作用。 间充质干细胞介导的免疫调节和组织修复。事实上，基于骨髓间充质干细胞的治疗已经成功 应用于人类的各种疾病。然而，一些MSC免疫疗法的临床III期试验失败了 以满足主要终点，因为植入细胞的低效率。因此，增加 通过探索新的免疫调节机制研究MSC的免疫抑制特性 骨髓间充质干细胞治疗的关键挑战。CD47(整合素相关蛋白，IAP)是一种细胞表面蛋白， 几乎由体内所有细胞表达。CD47在造血干细胞中的表达增加 动员后或引起炎症。CD47的连接可诱导细胞内信号转导 对应激反应的分化和激活。通过与细胞表面糖蛋白结合，信号调节 α是一种存在于髓系细胞上的抑制性跨膜受体，对细胞具有调节作用 在单核/巨噬细胞谱系中发挥作用。事实上，Sirpα在巨噬细胞和 在炎症反应过程中参与调节先天免疫。增强的Sirpα缺陷 巨噬细胞NF-κB的激活和促炎介质的增加，暗示α是一种必不可少的 先天免疫的内源性调节因子。先前的一项研究表明，Notch1信号调节 巨噬细胞功能和TLR4/NF-κB驱动的IR应激小鼠肝脏炎症反应。它还 Notch1信号通路减轻原位肝移植中肝细胞损伤的研究 (Olt)在人类中。因此，CD47/Sirpα和Notch1通路可能在骨髓间充质干细胞介导的 原位肝移植中先天免疫反应的调节。这项提案的总体目标是剖析 细胞内CD47/Sirpα信号在骨髓间充质干细胞介导的免疫调节和促进骨髓间充质干细胞治疗中的作用 CD47/Sirpα基因修饰对小鼠原位肝移植的疗效假设CD47/Sirpα信号转导 通过激活MSC-Hes1-Notch-Hes1轴控制TLR4引起的炎症反应 介导的免疫调节。为了验证这一假设，提出了以下具体目标：1)分析 CD47-Sirpα相互作用在调节骨髓间充质干细胞介导的炎症反应中的作用 2)研究CD47修饰的MSC在体内的免疫调节能力。 这些研究将增加对CD47/Sirpα介导的骨髓间充质干细胞调节网络的理解 免疫疗法。事实上，对骨髓间充质干细胞进行基因改造以提高治疗效果可能是至关重要的。 实体器官移植受者有效靶向IR应激的重要性。

PROJECT SUMMARY Innate immune-driven local inflammation response induced by ischemia-reperfusion injury (IRI) causes hepatic dysfunction and failure following liver transplantation. Mesenchymal stem cells (MSCs) has provided new insights into their potential clinical application, particularly for treating a variety of immune-mediated diseases. Previous studies have shown that crosstalk between MSCs and inflammatory cells is crucial in the mechanism of MSC-mediated immune modulation and tissue repair. Indeed, MSC-based therapy has been successfully applied in various human diseases. However, a number of clinical phase III trials of MSC immunotherapy failed to meet the primary endpoints because of the low efficacy of engrafted cells. Thus, increasing the immunosuppressive property of MSC by exploring novel immunoregulatory mechanisms emerges as one of the key challenges of MSC therapy. CD47 (integrin-associated protein, IAP) is a cell surface protein and expressed by virtually all cells in the body. CD47 expression is increased in hematopoietic stem cells (HSCs) after mobilization or induced inflammation. Ligation of CD47 can induce intracellular signaling resulting in cell differentiation and activation in response to stress. By binding to the cell surface glycoprotein, signal regulatory protein alpha (SIRPα), an inhibitory transmembrane receptor present on myeloid cells, CD47 can regulate cell function in the monocyte/macrophage lineage. Indeed, SIRPα is abundantly expressed in macrophages and has been implicated in regulating innate immunity during inflammatory response. SIRPα deficiency enhanced macrophage NF-κB activation and increased pro-inflammatory mediators, implying that SIRPα is an essential endogenous regulator of the innate immunity. A previous study has shown that Notch1 signaling regulates macrophage function and TLR4/NF-κB-driven inflammatory responses in IR-stressed mouse livers. It has also documented that Notch1 signaling alleviates the hepatocellular damage in orthotopic liver transplantation (OLT) in humans. Thus, CD47/SIRPα and Notch1 pathways are likely essential in the MSC-mediated regulation of innate immune responses in OLT. The overall goal of this proposal is to dissect the function of intracellular CD47/SIRPα signaling in MSC-mediated immune regulation and enhance MSC therapeutic efficacy by genetically modifying CD47/SIRPα in murine OLT. The hypothesis is that CD47/SIRPα signaling controls TLR4-driven inflammation in OLT recipients through activation of the Notch-Hes1 axis in MSC- mediated immune regulation. To test this hypothesis, the following specific aims are proposed: 1) Analyze the role of the CD47-SIRPα interaction in regulating TLR4-driven inflammatory response in MSC-mediated immune regulation in vitro; 2) Investigate the ability of immune regulation by CD47-modified MSC in vivo. These studies will increase understanding of CD47/SIRPα-mediated regulatory networks in MSC-mediated immunotherapy. Indeed, genetic modification of MSC to improve therapeutic efficacy may prove of paramount importance to effectively target IR stress in recipients of solid organ transplants.