Mai Xiao-Li, Ma Zhan-Long, Sun Jun-Hui, Ju Sheng-Hong, Ma Ming, Teng Gao-Jun
Jiangsu Key Laboratory of Molecular Imaging and Functional Imaging, Department of Radiology, Zhongda Hospital, Southeast University, Nanjing, China.
Cell Transplant. 2009;18(2):171-81. doi: 10.3727/096368909788341306.
Magnetic resonance imaging (MRI) has proven to be effective in tracking the distribution of transplanted stem cells to target organs by way of labeling cells with superparamagnetic iron oxide particles (SPIO). However, the effect of SPIO upon labeled cells is still unclear on a cellular level. With this study, the proliferation and viability of New Zealand rabbit peripheral blood endothelial progenitor cells (EPCs) labeled with SPIO were evaluated and in vitro images were obtained using a 1.5 T MR scanner. Mononuclear cells (MNCs) were isolated from peripheral blood of the adult New Zealand rabbit and cultured in fibronectin-coated culture flasks, in which EPCs were identified from cell morphology, outgrowth characteristics, and internalization of DiI-Ac-LDL and binding to FITC-UEA I. EPCs were incubated with the self-synthesized poly-L-lysine-conjugated SPIO (PLL-SPIO) particles in a range of concentrations. The prevalence of iron-containing vesicles or endosomes in the cytoplasm of labeled cells was confirmed with Prussian blue staining and transmission electron microscopy. Tetrazolium salt (MTT) assay, cell apoptosis, and cycle detection were assessed to evaluate proliferation and function of various concentrations, magnetically labeled EPCs. The quantity of iron per cell was determined by atomic absorption spectrometry. The cells underwent MRI with different sequences. The result showed that rabbit EPCs were efficiently labeled with the home synthesized PLL-SPIO. There was found to be no statistically significant difference in the MTT values of light absorption measured on the third and fifth days. Between labeled and unlabeled cells, there were also no aberrations found in the cell cycles, apoptosis, or growth curves. The atomic absorption spectrophotometer showed that the intracellular content of Fe decreased as more time elapsed after labeling. The labeled EPCs demonstrated a loss of MRI signal intensity (SI) when compared with the SI of unlabeled cells. These signal changes (ASI) were visible when cells were labeled with more than 5 x 104/ml of SPIO. The change in SI corresponded to the amount of iron in the EPCs, which reached a maximum at T2*WI. These data demonstrate that EPCs from the peripheral blood of the New Zealand rabbit can be effectively labeled with self-synthesized PLL-SPIO with minimal effects on cell proliferation and activity. Magnetically labeled EPCs can be imaged at 1.5 T MR and can therefore be used as an MR tracker of implanted EPCs.
磁共振成像（MRI）已被证明通过用超顺磁性氧化铁颗粒（SPIO）标记细胞来追踪移植干细胞在靶器官中的分布是有效的。然而，在细胞水平上，SPIO对标记细胞的影响仍不清楚。通过本研究，评估了用SPIO标记的新西兰兔外周血内皮祖细胞（EPC）的增殖和活力，并使用1.5 T MR扫描仪获得了体外图像。从成年新西兰兔外周血中分离单核细胞（MNC），并在纤连蛋白包被的培养瓶中培养，从细胞形态、生长特性、DiI-Ac-LDL内化和与FITC-UEA I结合方面鉴定EPC。将EPC与一系列浓度的自合成聚-L-赖氨酸偶联SPIO（PLL-SPIO）颗粒孵育。用普鲁士蓝染色和透射电子显微镜证实标记细胞胞质中含铁囊泡或内体的存在。采用四氮唑盐（MTT）法、细胞凋亡检测和细胞周期检测来评估不同浓度磁性标记EPC的增殖和功能。通过原子吸收光谱法测定每个细胞的铁含量。细胞用不同序列进行MRI检查。结果表明，兔EPC被自制的PLL-SPIO有效标记。在第三天和第五天测得的光吸收MTT值之间没有发现统计学上的显著差异。在标记和未标记细胞之间，细胞周期、细胞凋亡或生长曲线也没有发现异常。原子吸收分光光度计显示，标记后随着时间的推移，细胞内铁含量降低。与未标记细胞的信号强度（SI）相比，标记的EPC显示出MRI信号强度降低。当细胞用超过5×104/ml的SPIO标记时，这些信号变化（ΔSI）是可见的。SI的变化与EPC中的铁含量相对应，在T2*WI时达到最大值。这些数据表明，新西兰兔外周血中的EPC可以被自制的PLL-SPIO有效标记，对细胞增殖和活性的影响最小。磁性标记的EPC可以在1.5 T MR下成像，因此可以用作植入EPC的MR追踪剂。
