中心聚焦磁场引导下CXCR4基因转染间充质干细胞归巢治疗大鼠心肌梗死的实验研究

Poor cell homing, retention and engraftment are major obstacles for cardiac cellular therapy to achieve an ideal functional benefit. Recently, magnetic targeting has been proved to be a novel method to enhance cell retention and therapeutic outcomes. Supported by the National Natural Science Fundation of China (81000043), we found that conventional magnetic field was not well indicated in stem cell therapy for cardiac diseases, due to the inherent limitation of the attenuation of magnetic flux density. We therefore developed a deep-located magnetic field which can be located at a distance from the magnet surface. We intravenously administered magnetically loaded mesenchymal stem cells (MSCs) into rats with myocardial infarction, meanwhile a deep-located magnetic field is adopted at the area of injured heart. As a result, systemically delivered stem cells were attractted to infarcted heart. The advantage of this method is to avoid the invasive placement of a magnet or magnetized materials on the heart. Our study was highly regarded by the international counterparts. However, the distribution of the deep-located magnetic field was too extensive to focus on the heart, leading to an unsatisfactory cell retention in the heart when applied in animals with myocardial infarction. Recently, we developed a novel centre-focused magnetic field in which the deep-located magnetic flux density can be concentrated in its centre, by means of magnetic shielding, rotating the cantral tube, and adjusting the ratio of the groove to the pole diameter. In the next step, we will try to verify our new centre-focused magnetic field in cellular therapy for rats with myocardial infarction. It is logical to assume that the modified magnetic targeting strategy should be a more effective method to delivery MSCs to the injured heart, and the over-expressed CXCR4 of gene-modified MSCs should further targeted the cells migrating to infarcted myocardium to improve cardiac performance. Our study offers a brand-new, attracting method to effectively overcome the shortcoming of low homing, and subsequently improve the efficacy of cell transplantation for myocardial infarction and heart failure.

细胞归巢效率低下严重制约了细胞移植治疗缺血性心脏病的疗效。磁场引导细胞靶向迁移是促进细胞归巢的一种新兴方法，但目前研究常用的是普通磁场，需要有创性开胸放置磁性材料。在青年科学基金资助下，申请人原创性研发深度（深部）聚焦磁场装置，运用磁力学原理分析细胞在深度磁场中的动力学过程，并证实深度磁场可促进干细胞靶向分布到心脏，从而成功实现了体外无创性磁导向。研究受到国际同行的高度评价。新近申请人提出磁场中心聚焦理论，并通过设置磁屏蔽、旋转中心管、调整槽宽与磁极直径等策略基本完成了中心点聚磁的磁力学论证，可大幅度改进深度磁场的区域聚焦，有望显著提高移植细胞的心脏靶向分布。本项目拟在自主研发中心聚焦磁场的基础上，采用新型磁场引导间充质干细胞更加高效地靶向分布至大鼠梗死心脏，同时CXCR4过表达将促进心脏停留细胞进一步向损伤心肌精确归巢，从而为高效、精确的干细胞心脏靶向归巢提供一种新的调控策略。

细胞归巢效率低下严重制约了细胞移植治疗缺血性心脏病的疗效。磁场引导细胞靶向迁移是促进细胞归巢的一种新兴方法。为克服普通磁场的局限，在自主研发中心聚焦磁场基础上，本课题从改善空间聚焦性能、生物和磁场双靶向、减少磁性细胞栓塞三个方面做了部分工作，丰富了空间磁靶向治疗的理论和实践。.（1）改善空间聚焦性能。发现增大磁极间距有利于磁性微粒的靶向分布，旋转石英管能使磁性微粒更好的深度聚集并促使吸附均匀化，从而大幅度改进深度磁场的区域聚焦。.（2）生物和磁场双重靶向。通过基因工程获得CXCR4过表达MSC细胞（C-MSC），进一步SPIO 磁化标记后获得CXCR4-SPIO双标MSC细胞（C-Mag-MSC），从而成功构建双靶向干细胞。体外Transwell试验发现C-Mag-MSC细胞对SDF-1趋化和磁靶向具有协同作用。SD大鼠I/R模型动物实验进一步证实CXCR4生物靶向能促进磁靶向心脏停留细胞进一步向心肌损伤区靶向迁移。.（3）减少磁性细胞栓塞。发现磁靶向增强细胞停留呈强度依赖性，磁场强度过高时，增加的细胞停留率并未转化为额外的心功能获益。提示“细胞停留和功能获益相分离”的矛盾现象可能与细胞栓塞有关。从磁性微粒团聚过程分析磁靶向治疗导致细胞栓塞的物理学机制。设计并制备出了可植入生物体中、无毒的顺磁性生物贴片膜，在研究该膜吸附磁性微粒的规律的基础上，发现通过打孔技术可改变贴片膜磁场分布，进而改善磁性微粒的吸附分布。.本基金资助下，发表SCI论文15篇，中文论文6篇，申请国家专利2项。