Stroke Trials Unit, University of Nottingham, Nottingham, UK.
Cytotherapy. 2013 Mar;15(3):384-90. doi: 10.1016/j.jcyt.2012.10.016.
Tracking the fate of cells after infusion would be a valuable asset for many stem cell therapies, but very few (cell) labels are approved for human therapeutic use. Superparamagnetic iron oxide particles (SPIO) can be internalized into stem cells in vitro to allow real-time tracking with gradient echo magnetic resonance imaging, but SPIO are approved for (diagnostic) imaging and not for (therapeutic) cell labeling in vivo. In this study, we investigated the possibility of labeling stem cells with an SPIO approved for patient use, albeit in a novel manner by enhancing uptake with the use of a transfection agent, also approved for patient use. Although there are many reports of hematopoietic stem cells being labeled with SPIO, there is some controversy regarding the efficiency of this and whether undifferentiated CD34+ progenitor (stem) cells are able to take up iron in the absence of a transfection agent to enhance the process.
Human CD34+ cells were treated in vitro as follows: incubation with (i) medium only (control), (ii) ferumoxide (Endorem) and (iii) ferumoxide (Endorem) plus exposure to a transfection agent (protamine sulfate). Cells were incubated for 2, 4 and 24 hours and assessed for viability, differentiation capacity and visualized in vitro with 3-T magnetic resonance imaging. The cells were also analyzed by means of flow cytometry and morphology examined by electron microscopy.
CD34+ hematopoietic progenitor cells can internalize ferumoxide (Endorem) independently of a transfection agent. However, uptake of ferumoxide is enhanced after exposure to protamine sulfate. Iron labeling of CD34+ cells in this manner does not affect cell viability and does not appear to affect the potential of the cells to grow in culture. Iron-labeled CD34+ cells can be visualized in vitro on 3-T magnetic resonance image scanning.
Endorem and protamine sulfate can be combined to promote iron oxide nanoparticle uptake by CD34+ cells, and this methodology can potentially be used to track the fate of cells in a clinical trial setting because both compounds are (separately) approved for clinical use.
追踪细胞输注后的命运对于许多干细胞疗法来说将是一项宝贵的资产，但获得批准用于人体治疗的细胞标记物却很少。超顺磁性氧化铁颗粒（SPIO）可在体外被干细胞内化，以便通过梯度回波磁共振成像进行实时跟踪，但 SPIO 仅被批准用于（诊断）成像，而不能在体内用于（治疗）细胞标记。在这项研究中，我们研究了用一种已获患者使用批准的 SPIO 对干细胞进行标记的可能性，尽管这是一种新颖的方法，即通过使用一种也已获患者使用批准的转染剂来增强摄取。尽管有许多关于用 SPIO 标记造血干细胞的报道，但关于其效率以及未分化的 CD34+祖细胞（干细胞）是否能够在没有转染剂增强该过程的情况下摄取铁，仍存在一些争议。
体外对人 CD34+细胞进行如下处理：（i）仅用培养基孵育（对照）；（ii）用 Ferumoxides（Endorem）孵育；（iii）用 Ferumoxides（Endorem）和转染试剂（鱼精蛋白硫酸盐）孵育。孵育 2、4 和 24 小时后，评估细胞活力、分化能力，并在 3-T 磁共振成像中进行体外可视化。还通过流式细胞术对细胞进行分析，并通过电子显微镜检查形态。
CD34+造血祖细胞可在没有转染剂的情况下内吞 Ferumoxides（Endorem）。然而，在用鱼精蛋白硫酸盐孵育后，Ferumoxides 的摄取会增强。以这种方式对 CD34+细胞进行铁标记不会影响细胞活力，也似乎不会影响细胞在培养中生长的潜力。体外在 3-T 磁共振图像扫描中可以观察到铁标记的 CD34+细胞。
Endorem 和鱼精蛋白硫酸盐可以联合使用，促进 CD34+细胞吸收氧化铁纳米颗粒，并且由于这两种化合物都（分别）获准用于临床使用，这种方法可能被用于在临床试验中追踪细胞的命运。
