小鼠胚胎干细胞磁标记共振成像的研究

目的 应用超顺磁氧化铁（SPIO）标记小鼠胚胎干细胞（ESC）,并行磁共振成像,为心肌细胞移植体内示踪作初步准备。方法 小鼠ESC及其分化的心肌细胞与SPIO孵育后行电镜分析、细胞内铁含量测定、[Ca^2＋]共聚焦测定和MR成像。结果 铁颗粒分布在胞质吞饮小泡内;使用转染技术的铁摄取高于未使用组;T2WI和T2^＊ WI扫描序列均见标记细胞呈信号下降,程度随标记浓度的增加而增强;T2^＊ WI图像信号强度变化更大。标记心肌细胞在T2^＊ WI序列也呈显著的低信号改变。结论 SPIO可有效标记ESC及其分化的心肌细胞,对细胞活性和分化能力无明显影响。常规1．5TMR仪可进行标记细胞成像。

MR imaging of embryonic stem cells labeled by superparamagnetic iron oxide

OBJECTIVE: To evaluate the labeling efficiency of superparamagnetic iron oxide (SPIO) nanoparticles and its toxicity to mouse embryonic stem cells (ESCs) and (embryoid body (ES)-derived cardiomyocytes. METHODS: Mouse ESCs of the line CGR8 were cultured and induced to differentiate into ES-derived cardiomyocytes. The EB-derived cardiomyocytes were coincubated with SPIO contrast agent at different concentrations (1, 8, 9.3, 14, 28, and 56 mg/L) and transfection agent for 24 and 48 hours for cell labeling. Cells not labeled by SPIO and cells labeled by SPIO without transfection agent were used as controls. Spectrophotometer was used to detect the iron concentration in the cells. Confocal microscopy was used to test the intracellular calcium levels ([Ca(2+)] i). The ultrastructure of the cells was observed by electron microscopy. Ex vivo MRI was used to observe the signals of the cells. RESULTS: Iron-containing intracytoplasmic vesicles could be observed clearly with electron microscopy. The intracellular iron concentration was higher in the cells treated with transfection agent than in the cells not treated with transfection agent. The iron concentration of the cells treated with the SPIO at the concentration of 9.3 microg/ml for 24 hours was the highest. There were no differences in the morphology, contractile areas (chi(2) = 1.32; P = 0.25), and the beating frequency (t = 1.73; P = 0.10) between the EBs from iron-labeled ESCs and from the control ESCs. The rhythmic intracellular free Ca(2+) fluctuation in the labeled cardiomyocytes was similar to that of the controls. The MR images with T(2)WI and T(2)WI sequences, especially those with T(2)WI sequence, of the ESCs showed that the signals of the SPIO labeled cells were lower than those of the SPIO-labeled cells. CONCLUSION: SPIO labeling of ESCs and ES-derived cardiomyocytes does not influence the cell viability and proliferation. The standard 1.5T MR equipment can image the labeled cells, thus offering the possibility of cell tracking and migration monitoring in MRI.