Objective To determine the optimal concentration of Resoist labeling for endothelial progenitor cells (EPCs) in vitro,and the tracer method for labeled EPCs with 1.5T magnetic resonance imaging (MRI). Methods EPCs were isolated from human umbilical cord blood by density gradient centrifugation, and then cultured and identified. The EPCs were labeled with different concentrations (0, 10, 25, 50, 75 and 100 μg/ml) of Resovist, and the labeling efficiency, proliferation activity, migration and angiogenesis ability of the EPCs were determined, meanwhile the labeled cells were observed with 1.5T MRI in vitro. Results It was showed by Prussian blue staining that the labeling efficiency of EPCs increased along with the increase of Resovist concentrations, and was nearly 95％ with 50μg/ml Resovist. Aggregation of high-density particles was observed by transmission electron microscopy. MTT test showed that the proliferation activity, migration and angiogenesis ability of EPCs were significantly inhibited by 75 and lOOμg/ml Resovist,and the effect of 100μg/ml Resovist was more obvious than that of 75μg/ml Resoist ( P＜0.05). 1.5T MRI revealed that when the Resovist concentration was lOμg/ml, the labeled EPCs could be detected and showed low signal intensity in T2-weighted images which was significantly lower than that of control group (P＜0.01), and the signal differences were increased along with the Resovist concentrations. Conclusions EPCs may be easily and efficiently labeled by Resovist without any influence on the cellular biological properties. The labeled cells may be tracked by 1.5T MRI, and the optimal labeling concentration was at 25 -50μg/ml.%目的 确定Resovist体外标记内皮祖细胞(EPCs)的最佳条件,并探讨1.5T磁共振体外示踪标记细胞的方法.方法 采用密度梯度离心法从人脐带血中分离、培养、鉴定EPCs,以不同浓度(0、10、25、50、75、100μg/ml)Resovist标记EPCs,分别检测细胞的标记效率、增殖活性、迁移能力及成血管能力,并采用1.5T磁共振对标记的EPCs进行体外成像观察.结果 普鲁士蓝检测表明细胞标记效率随Resovist浓度增加而增高,在50μg/ml浓度时已接近95%.透射电镜观察可见胞质内高密度物质聚集.MTT结果表明75、100μg/ml的Resovist可显著抑制EPCs的增殖活力、迁移能力和成血管能力,且100μg/ml浓度的抑制作用大于75μg/ml浓度(P<0.05).1.5T磁共振成像显示,10μg/ml Resovist标记后EPCs在T2加权像上即呈低信号,与对照组比较差异显著(P<0.01),且浓度越高信号差异越明显.结论 采用Resovist可简单高效标记EPCs,且不影响细胞的生物学特性,并能在1.5T磁共振下进行示踪,其最佳标记浓度为25～50μg/ml.
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