IL-18 Signaling in Mesenchymal Stem Cells: Function and Surgial Protection

描述(申请人提供)：心肌缺血和随后的心力衰竭是住院和死亡的主要原因。干细胞是治疗受损心脏组织的一种很有前途的治疗方法，可能部分通过旁分泌机制来调节其有益的心脏效应。干细胞治疗受损的心脏组织可能通过促进组织修复的因素来减少炎症、细胞凋亡、梗死面积和改善功能。这种旁分泌保护可以通过体外修饰来增强。在动物模型中，基因修饰、血管内皮生长因子转导甚至预适应都能增强干细胞旁分泌的心脏保护作用。有趣的是，我们最近表明，细胞因子的调节可能会增强保护性生长因子的产生。IL-18是IL-1细胞因子超家族中的一个新成员，目前被认为是天然和获得性免疫反应的重要调节因子。最近的研究表明，IL-18可能在干细胞移植后急性移植物抗宿主病中起重要作用。IL-18也被报道在骨髓来源的内皮祖细胞中发挥抗血管生成的作用。然而，IL-18对骨髓间充质干细胞(MSC)产生生长因子的影响尚不清楚。因此，阐明IL-18信号在干细胞激活中的作用，对于进一步了解干细胞在心脏疾病中的作用以及在治疗性心肌保护中最大限度地发挥干细胞保护因子具有重要意义。我们推测：1)IL-18可通过p38Mark、ERK或Akt信号减少MSC产生生长因子；2)IL-18结合蛋白可中和IL-18对MSC释放生长因子的负面影响，增强MSC对缺血再灌注(I/R)时的心肌保护作用。为了解决这些假设，我们提出了以下四个具体目标：1.确定IL-18信号是否影响激活的间充质干细胞产生血管内皮生长因子、肝细胞生长因子、胰岛素样生长因子-1和细胞因子肿瘤坏死因子，如果是，这种影响是否由p38Mark、ERK或Akt信号介导。2.检测IL-18结合蛋白能否中和IL-18对MSC释放血管内皮生长因子(VEGF)、肝细胞生长因子(HGF)、胰岛素样生长因子-1(IGF-1)和细胞因子TNF的影响。3.阐明IL-18信号是否影响骨髓间充质干细胞的增殖和凋亡，如果是，靶向下调血管内皮生长因子或肝细胞生长因子的表达是否可以中和这些影响。4.探讨IL-18结合蛋白是否能增强MSC对心肌的保护作用。公共卫生常识：骨髓干细胞可能有助于修复受伤的心脏。我们的目标是研究一种名为IL-18的蛋白质，以便我们能够利用干细胞的能力来保护心脏。

DESCRIPTION (provided by applicant): Myocardial ischemia and subsequent heart failure are leading causes of hospitalization and death. Stem cells are a promising treatment modality for injured cardiac tissue and may mediate their beneficial cardiac effects in part by paracrine mechanisms. Stem cell treatment of injured cardiac tissue may reduce inflammation, apoptosis, infarct size and improve function via factors that promote tissue repair. This paracrine protection may be enhanced by ex vivo modification. Genetic modification, VEGF transduction, and even preconditioning have been shown to enhance stem cell paracrine cardioprotection in animal models. Interestingly, we have recently shown that modulation of cytokines may enhance protective growth factor production. IL-18, a novel member of the IL-1 cytokine superfamily, is now recognized as an important regulator of innate and acquired immune responses. Recent research indicates that IL-18 may play an important role in acute graft versus host disease after stem cell transplantation. IL-18 has also been reported to play an antiangiogenic role in bone marrow derived endothelial progenitor cells. However, the effect of IL-18 on bone marrow mesenchymal stem cell (MSC) production of growth factors remains unknown. Thus, it is important to delineate the effects of IL-18 signaling in stem cell activation in order to further understand the role of stem cells in cardiac disease and maximize stem cell protective factors during therapeutic myocardial protection. We hypothesize that: 1) IL-18 will decrease MSC production of growth factors through p38 MARK, ERK or Akt signals; 2) IL-18 binding protein may neutralize the negative effects of IL-18 on MSC release of growth factors and enhance MSC cardioprotection during ischemia and reperfusion (I/R). To address these hypotheses we propose the following four specific aims: 1. To determine whether IL-18 signaling affects activated mesenchymal stem cell production of VEGF, HGF, IGF-1 and the cytokine TNF, and if so, whether this effect is mediated by p38 MARK, ERK, or Akt signaling. 2. To determine whether IL-18 binding protein may neutralize the effect of IL-18 on MSC release of VEGF, HGF, IGF-1 and the cytokine TNF. 3. To elucidate whether IL-18 signaling affects mesenchymal stem cell proliferation and apoptosis, and if so, whether targeted knockdown of VEGF or HGF expression by siRNA may neutralize these effects. 4. To determine whether MSC myocardial protection during I/R may be enhanced by IL-18 binding protein. PUBLIC HEALTH IN LAY TERMS: Bone marrow stem cells may be useful to fix injured hearts. We aim to study a protein called IL-18 so that we can utilize the ability of stem cells to protect the heart.