大鼠骨髓间充质干细胞磁标记及MR成像研究

目的应用菲立磁．多聚左旋赖氨酸复合物标记大鼠骨髓间充质干细胞，探讨MR成像显示磁标记干细胞的可行性。方法制备菲立磁-多聚左旋赖氨酸复合物。分离培养Wistar大鼠骨髓间充质干细胞，以菲立磁-多聚左旋赖氨酸复合物标记干细胞。分别于标记后24h及1、2、3周行普鲁士蓝染色观察细胞内铁，台盼蓝排除试验检测细胞活力。应用1．5TMR仪，以SE序列T1WI、T2WI和梯度回波（GRE）序列T2＊WI行磁标记干细胞成像。结果普鲁士蓝染色显示细胞质内大量铁颗粒存在，标记率100％；随细胞分裂增殖，细胞内铁颗粒逐渐减少。干细胞磁标记后24h及1、2、3周的台盼蓝拒染率分别为91．00％、93．00％、91．75％和92．50％，与未标记细胞相比较差异无统计学意义（P〉0．05）。10^3、10^4、10^5个磁标记干细胞T2WI信号降低分别为63．75％、82．31％、91．92％，T2＊WI信号降低分别为68．24％、83．01％、93．94％。10^5个干细胞磁标记后24h及1、2、3周T2＊WI信号降低分别为93．75％、75．92％、41．75％、8．83％。结论应用菲立磁-多聚左旋赖氨酸复合物标记大鼠间充质干细胞安全、有效；T2＊WI对磁标记干细胞的显示最敏感；MR信号改变与干细胞数目及分裂增殖状态相关。

Magnetic labeling and in vitro MR imaging of rat bone marrow mesenchymal stem cells

Objective To label rat bone marrow mesenchymal stem cells with feridex combined with poly-l-lysine (PLL), and to determine the feasibility of detection of magnetically labeled stem cells with MR imaging. Methods Feridex were incubated with PLL for 1 hour to obtain a complex of feridex-PLL. Mesenchymal stem cells isolated from the bone marrows of Wistar rats were cultured and expanded. By the 4 th passage, cells were co-incubated overnight with the feridex-PLL complex. Prussian blue staining for demonstrating intracytoplastic nanoparticles and trypan-blue exclusion test for cell viability were performed respectively at 24 h,1 w,2 w,3 w after labeling. MR imaging of cell suspensions was performed by using T_1WI, T_2WI and T_2*WI sequences at a clinical 1.5 T MR system. Results Numerous intracytoplastic iron particles were stained with Prussian blue. With division of stem cells, the stained particles were seen decreased gradually. Trypan blue exclusion test at 24 h, 1 w, 2 w and 3 w showed that the viability of the labeled cells was 91.00%, 93.00%, 91.75%, and 92.50%,not significantly different with that of nonlabeled cells(P>0.05). For 103 , 104 and 105 cells, T_2 signal intensity decreased by 63.75%, 82.31% and 91.92% respectively, T_2* signal intensity decreased by 68.24%, 83.01%, and 93.94% respectively. For 105 labeled cells, T_2* signal intensity decreased by 93.75%, 75.92%, 41.75% and 8.83% respectively at 24 h, 1 w, 2 w and 3 w after labeling. Conclusion Magnetic labeling of rat bone marrow stem cells with feridex-PLL complex is feasible, efficient and safe. T_2*WI is the most sensitive sequence to detect the labeled cells. The degree of T_2 signal decreasing may be related to the cell count and division phase.