EPCs示踪大鼠脑原位胶质瘤的动态MRI研究

目的：探讨超微型超顺磁性氧化铁粒子（USPIO）标记的外源性内皮祖细胞（EPCs）在大鼠脑原位胶质瘤内的动态归巢特点，为利用磁性标记的EPCs作为MRI示踪细胞载体提供可行性的实验依据。材料与方法将SD大鼠分为假肿瘤组、肿瘤组和对照组3组，每组16只，肿瘤组和对照组在脑组织内移植C6胶质瘤细胞，而假肿瘤组仅刺破脑组织不移植胶质瘤细胞。待肿瘤组和假肿瘤组模型建立后第8天从尾静脉内注射2＆#215;106 USPIO-EPCs，分别在EPCs移植前、移植后1、3、5 d和7 d进行MRI扫描，观察病变区域在T2WI、SWI上信号和T2值的变化情况。在相对应时间点获取组织标本进行病理学分析，用普鲁士蓝染色检测有无阳性结果，并观察CD34＋、SDF-1、MMP-9、VEGF等蛋白的表达以及与普鲁士蓝阳性细胞分布的关系。结果假肿瘤组在MRI上各时间点均无变化，T2值无明显变化，对照组肿瘤体积逐渐增大，但其内信号无明显变化，肿瘤组在移植USPIO-EPCs第1天后外周区在SWI上出现低信号，随着瘤龄的增长低信号逐渐增多并向肿瘤内部迁移，兴趣区T2值随时间逐渐下降。假肿瘤组普鲁士蓝染色见零星阳性细胞，肿瘤组移植USPIO-EPCs第1天见蓝染细胞主要分布于肿瘤外周区，之后逐渐向内迁移分布于肿瘤内部。同时，USPIO-EPCs移植后早期发现CD34＋、SDF-1和MMP-9在肿瘤外周区表达较多，在USPIO-EPCs移植后第7天在肿瘤中央区域表达增多，且与肿瘤外周区并无明显差异，VEGF随着瘤龄的增长表达逐渐增多，但各时间点肿瘤中央区及肿瘤外周区表达无明显差异。结论MRI可以动态观察USPIO-EPCs在大鼠原位脑胶质瘤内归巢的变化过程，肿瘤组织不同区域SDF-1和MMP-9表达变化与USPIO标记的EPCs在肿瘤内的分布变化有相似性，这一发现表明SDF-1和MMP-9可能是促使移植的外源性EPCs由肿瘤周边向肿瘤中央区域迁

Dynamic MRI research of EPCs tracing rat glioma

Objective：The aim of this study was to investigate the dynamic homing characteristic of exogenous endothelial progenitor cells （EPCs） in rat glioma in vivo to provide an experimental basis for the feasibility of using magnetically labeled EPCs as MRI target tracing vectors. Materials and Methods：Three models of Sprague-Dawley at glioma （48 rats in total） were established as control group, experimental group and fake experimental group, In the control group and experimental group, orthotopic transplantation of C6 glioma cells was performed, compared to above groups, only the brain was punctured and no C6 glioma cells was performed. 8 days after the models were established, in the control group and experimental group, 2＆#215;106 USPIO-labeled EPCs were transplanted via the tail vein. Magnetic resonance imaging and perfusion-weighted imaging were performed on several days. The conventional MR imaging, including spin echo and gradin-echo sequence, were performed at before and 1, 3, 5, 7 days after transplantation on each group to observe the signal change of the diseased region on T2WI, SWI and T2 value. Tumors were excised from experimental rat of every group at each examined point to make pathological assay. Prussian blue staining represent the distribution of USPIO-EPCs in the tumor. CD34＋, SDF-1, MMP-9 and VEGF staining were used to observe the distribution relationship between the Prussian blue staining positive cells and these antibody. Results：In fake experimental group, the MRI signal was similar all the time. The T2 value-time curve was straight. In control group, tumor size developed gradually but the no signal changed, in the experimental group, hypointense areas were detected at the periphery of the tumor on the ifrst day after transplantation of EPCs, and much more hypointense areas were observed inside the tumor over time. The T2 value-time curve was downtrending. There were a little blue-stained cells in fake experimental group, and several blue-stained cells were observed at the the