中文摘要：

目的探讨超微超顺磁性氧化铁（usPio）对内皮祖细胞（EPCs）生物活性的影响及优化细胞体外磁共振扫描序列。方法常规培养并鉴定EPCs。USPIO（25μg／mL）标记EPCs，普鲁士蓝染色计算细胞标记阳性率，台盼蓝染色、MTT比色法等观察细胞生物活性变化。再用100μL8％明胶将细胞浓度调整为2x106／mL、1×10^6／mL、5×10^5／mL、2．5×10^5／mL．对不同浓度的标记细胞行T2map和T2＊map序列扫描。结果免疫细胞化学染色及Dil标记的乙酰化低密度脂蛋白染色、荧光素标记的荆豆凝集素．1染色均显示培养细胞为EPCs。普鲁士蓝染色显示USP10标记5d后阳性率达（98．45±0．05）％。台盼蓝染色、MTT比色法等证明USP10标记不影响细胞生物活性。T2map和T2＊map体外磁共振扫描显示，弛豫率与细胞浓度呈线性正相关（n=0．990，P1=0．010；r2=0．975，只=0．025），且R2‘效应的直线斜率为R2的3．58倍。结论USPIO可有效标记EPCs，同时对细胞的生物学活性无明显影响。T2＊map和T2map序列均可反映不同浓度USPIO标记细胞的信号变化，其中T2＊map序列更敏感。

英文摘要：

Objective To explore the influence of ultra-small super-paramagnetic iron oxide （USPIO） on the biological activity of endothelial progenitor cells （EPCs） and optimize their MR imaging sequence in vitro. Methods EPCs were cultured and the USPIO particles were inducted as magnetic markers, with the concentration of 25 μg/mL. For different concentrations of cells （2×10^6/mL, 1×10^6/mL, 5×10^5/mL and 2.5×10^5/mL） disposed by 100 μL 8% gelatin, the T2 map and T2＊ map sequences were used to measure the relaxation time and rate. Results Immunocytochemistry, acetylated low density lipoprotein staining marked with Dil and Ulex europaeus agglutinin I staining marked with fluorescein demonstrated that these cells were EPCs. USPIO labeled EPCs efficiently, with （98.45 ±0.05）% positive rate of labeling on the 5th d, and trypan blue staining and MTT assay indicated that it had no significant effect on the stem cell growth and proliferation. The T2 map and T2＊ map sequences showed that the relaxation rates （R2 and R2＊） were linearly related to the cell concentrations in vitro （r1=0.990 ,P1=0.010; r2=0.975 ,P2=0.025）, and the slop of R2＊ was 3.58 times of the R2＇s. Conclusion USPIO can label the EPCs efficiently without changing the biological characteristics of cells. Both T2＊ map and T2 map sequences can test the signal changes with different concentrations of labeled cells, and the former is more sensitively than the later