Wei Meng-Qi, Wen Di-Di, Wang Xiao-Ying, Huan Yi, Yang Yong, Xu Jian, Cheng Kang, Zheng Min-Wen
Department of Radiology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
Department of Ultrasound, The People's Liberation Army No. 323 Hospital, Xi'an, Shaanxi 710054, P.R. China.
Mol Med Rep. 2015 May;11(5):3814-9. doi: 10.3892/mmr.2014.3122. Epub 2014 Dec 22.
Endothelial progenitor cells (EPCs) have an essential role in counteracting risk factor‑induced endothelial injury and protecting against the development of vascular injury, such as myocardial infarction. Magnetic resonance imaging (MRI) was reported to be effective in tracking transplanted stem cells following cell‑labeling with superparamagnetic iron oxide (SPIO) nanoparticles. SPIO has previously been used to label and track EPCs; however, the safest concentration of SPIO for labeling EPCs on a cellular level has remained to be elucidated. In addition, the optimum number of SPIO‑labeled cells required to produce the highest quality magnetic resonance images has not yet been determined. In the present study, EPCs were isolated from the bone marrow of minipigs using density gradient centrifugation. Their biological activity was then studied using flow cytometric analysis. Cells were incubated at different concentrations of SPIO for different durations and then the growth curve, apoptosis, morphology and labeling efficiency of the EPCs were detected using optical and electron microscopy. T2‑weighted fast spin‑echo (T2WITSE) MRI of the different numbers of SPIO‑labeled EPCs (35 µg/ml) were then obtained in axial and sagittal planes. The results of the present study demonstrated that EPCs were efficiently labeled with SPIO, with a labeling efficiency in each group of ~100% following incubation for 24 h. SPIO was found to be localized in the endosomal vesicles of EPCs, which was confirmed by electron microscopy. When the concentration of SPIO was <70 µg/ml, no significant differences were observed in cell viability, proliferative capability (P>0.05) and morphology between labeled and unlabeled EPCs. Furthermore, the T2WITSE signal intensity was significantly decreased in the groups of 5.0x105/ml and 1.0x105/ml compared with that of the control (P<0.05). In conclusion, the results of the present study indicated that 35 µg/ml was the most effective concentration of SPIO to label EPCs in vitro and acquire a high quality MRI. These findings may therefore contribute to the development of a promising novel therapeutic method for the treatment of myocardial infarction following autograft with SPIO‑labeled EPCs in vivo.
内皮祖细胞（EPCs）在对抗危险因素诱导的内皮损伤以及预防血管损伤（如心肌梗死）的发生发展中起着至关重要的作用。据报道，磁共振成像（MRI）在用超顺磁性氧化铁（SPIO）纳米颗粒对细胞进行标记后，可有效追踪移植的干细胞。SPIO此前已被用于标记和追踪EPCs；然而，在细胞水平上用于标记EPCs的最安全的SPIO浓度仍有待阐明。此外，产生最高质量磁共振图像所需的SPIO标记细胞的最佳数量尚未确定。在本研究中，使用密度梯度离心法从小型猪的骨髓中分离出EPCs。然后使用流式细胞术分析研究其生物学活性。将细胞在不同浓度的SPIO中孵育不同时间，然后使用光学显微镜和电子显微镜检测EPCs的生长曲线、凋亡、形态和标记效率。随后在轴向和矢状面获得不同数量（35μg/ml）的SPIO标记EPCs的T2加权快速自旋回波（T2WITSE）MRI。本研究结果表明，EPCs被SPIO有效标记，每组在孵育24小时后标记效率约为100%。电子显微镜证实SPIO定位于EPCs的内体囊泡中。当SPIO浓度<70μg/ml时，标记和未标记的EPCs在细胞活力、增殖能力（P>0.05）和形态方面未观察到显著差异。此外，与对照组相比，5.0x105/ml和1.0x105/ml组的T2WITSE信号强度显著降低（P<0.05）。总之，本研究结果表明，35μg/ml是体外标记EPCs并获得高质量MRI的最有效SPIO浓度。因此，这些发现可能有助于开发一种有前景的新型治疗方法，用于体内自体移植SPIO标记的EPCs后治疗心肌梗死。
