MG53 对急性心肌梗死植入干细胞的保护作用及其机制研究

Stem cell-based therapy has recently emerged as a promising approach to repair and improve the regenerative capacity of the dysfunctional myocardium in heart failure patients. A major challenge for cell-based therapy is the poor survival of the implanted stem cells, as these cells are facing a harsh environment that often causes injury and death of the cells. For improvement of the efficacy of cell-based therapy for heart diseases, many researches are focusing on development of methods to improve survival of stem cells after implantation, or conditioning of stem cells to enhance their capacity to secrete paracrine factors for enhancing the innate repair and regenerative capacity of the cardiovascular system. This project builds on our discovery of MG53 as a membrane repair gene that has significant acute tissue injury protective function. We hypothesize that membrane damage could be one of the main mechanisms contributing to death of transplanted stem cells, and MG53 can be used to alleviate this injury process and thus to improve the survival of stem cells and the efficacy of cell based therapy for ischemic heart diseases. .Preliminary studies suggest that the MG53-mediated membrane repair function could be recapitulated in stem cells, and application of the recombinant human MG53 (rhMG53) protein to the extracellular solution could protect injury to stem cells under conditions of mechanical or oxidative stresses. For testing the concept that MG53 in blood circulation can function as a paracrine factor for protection of injury to the implanted stem cells or adult cardiomyocytes, we have generated a cell-based system where controlled secretion of MG53 into the extracellular solution is achieved through the use of the tPA secretory pathway. A transgenic mouse model has been generated that allows secretion of MG53 into the circulation in a doxycycline controllable manner. With this transgenic mouse model, we can begin to explore the concept that stem cell mediated secretion of MG53 can elicit cardioprotection. .This project will focus on testing the hypothesis that “MG53 can protect stems cells from stress-induced injuries for improvement of the regenerative capacity of the dysfunctional myocardium associated with ischemic heart diseases, and delivery of MG53 to the local cardiac injury site can be achieved through transplantation of engineered stem cells that drive secretion of MG53 into circulation”. Specifically, we propose to achieve the following goals: to examine the protective effects of rhMG53 on stem cell implantation for treatment of myocardial infarction, and the mechanisms that underlie the MG53-mediated protection of stem cell survival (Aim 1); and to explore the potential paracrine function for MG53 in cardioprotection through the use of engineered stems that drive controlled secretion of MG53 into blood circulation (Aim 2).

急性心肌梗死是威胁人类健康的重要疾病，干细胞治疗已成为缺血性心脏病治疗的新手段，但植入干细胞的存活率极低，是目前细胞治疗的巨大挑战。研究证实细胞膜损伤是移植干细胞存活率低的重要原因。我们前期研究发现：MG53是细胞膜损伤修复的核心蛋白，对肌营养不良导致动物肌细胞膜损伤有修复作用。预实验的结果也证实MG53对多种外界刺激所致的干细胞膜损伤具有保护作用。因此我们推测MG53可能对急性心肌梗死植入细胞也存在保护作用，可提高细胞存活率。本课题组已经成功获得人重组MG53蛋白和MG53转基因小鼠，本研究将进一步从细胞和动物水平观察MG53蛋白对干细胞的保护作用，及MG53对急性心肌梗死植入干细胞生存率的影响，并确定MG53细胞膜修复作用的锚定分子及锚定分子后的信号通路，为细胞治疗提供新的理论依据。

急性心肌梗死是威胁人类健康的重要疾病，干细胞治疗已成为缺血性心脏病治疗的新手段，但 植入干细胞的存活率极低，是目前细胞治疗的巨大挑战。研究证实细胞膜损伤是移植干细胞存 活率低的重要原因。我们前期研究发现：MG53是细胞膜损伤修复的核心蛋白，对肌营养不良导 致动物肌细胞膜损伤有修复作用。预实验的结果也证实MG53对多种外界刺激所致的干细胞膜损伤具有保护作用。因此我们推测MG53可能对急性心肌梗死植入细胞也存在保护作用，可提高细胞存活率。.在项目资助期间，我们提取了大鼠骨髓干细胞（Bone marrow derived stem cells），建立了干细胞培养方法，研究MG53蛋白在不同生理和病理条件下对于干细胞保护作用； 我们进一步探讨MG53对机体，包括干细胞的保护机制，尤其是建立tPA-MG53 转基因过表达MG53的小鼠系，并对其进行了确定和各种表征检测，包括在LAD 诱导急性心肌梗塞模型中对心脏的保护作用；在细胞分子水平，我们发现干细胞体外培养过程中，外源添加的MG53 蛋白能够快速的被干细胞通过内吞作用进入，我们使用了生物化学，分子和激光捕获显微解剖（LCM）方法的组合，并将VEGFR2鉴定为MG53在干细胞质膜上的潜在受体。上述研究为MG53和干细胞联合应用保护缺血心肌梗死的治疗提供了理论依据。