Oude Engberink Raoul D, van der Pol Susanne M A, Döpp Ed A, de Vries Helga E, Blezer Erwin L A
Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
Radiology. 2007 May;243(2):467-74. doi: 10.1148/radiol.2432060120.
To label human monocytes with superparamagnetic iron oxide (SPIO) and compare labeling efficiency with that of ultrasmall SPIO (USPIO) and evaluate the effect of iron incorporation on cell viability, migratory capacity, and proinflammatory cytokine production.
The study was approved by the institutional ethics committee; informed consent was obtained from donors. Freshly isolated human monocytes were labeled with iron particles of two sizes, USPIOs of 30 nm and SPIOs of 150 nm, for 1.5 hours in culture medium containing 0.1, 0.5, 1.0, and 3.7 mg of iron per milliliter. Labeling efficiency was determined with relaxation time magnetic resonance (MR) imaging (4.7 T) and Prussian blue staining for presence of intracellular iron. Cell viability was monitored; migratory capacity of monocytes after labeling was evaluated by using an in vitro assay with monolayers of brain endothelial cells. Levels of proinflammatory cytokines, interleukin (IL) 1 and IL-6, were measured with enzyme-linked immunosorbent assay 24 hours after labeling. Data were analyzed with Student t test or two-way analysis of variance followed by a multiple-comparison procedure.
R2 relaxation rates increased for cell samples incubated with SPIOs, whereas rates were not affected for samples incubated with highest concentration of USPIOs. Labeling monocytes with SPIOs (1.0 mg Fe/mL) resulted in an R2 of 13.1 sec(-1) +/- 0.8 (standard error of the mean) (7 sec(-1) +/- 0.2 for vehicle-treated cells, P < .05) and had no effect on cell viability. On the basis of T2 relaxation times, the in vitro MR detection limit of 58 labeled monocytes per 0.05 microL was calculated. Migration of labeled monocytes was not different from that of vehicle-treated cells. Intracellular iron had no effect on production of IL-1 and IL-6 24 hours after labeling.
In vitro labeling of human monocytes is effective by using SPIOs, not USPIOs. Incubation with SPIOs (1.0 mg Fe/mL) results in efficient labeling detectable on MR images and does not affect cellular viability and activation markers such as cell migration and cytokine production.
用超顺磁性氧化铁（SPIO）标记人单核细胞，将标记效率与超小超顺磁性氧化铁（USPIO）的标记效率进行比较，并评估铁掺入对细胞活力、迁移能力和促炎细胞因子产生的影响。
本研究经机构伦理委员会批准；获得了捐赠者的知情同意。将新鲜分离的人单核细胞用两种尺寸的铁颗粒进行标记，即30 nm的USPIO和150 nm的SPIO，在每毫升含0.1、0.5、1.0和3.7 mg铁的培养基中培养1.5小时。用弛豫时间磁共振（MR）成像（4.7 T）和普鲁士蓝染色确定细胞内铁的存在情况，以此来测定标记效率。监测细胞活力；通过使用脑内皮细胞单层的体外试验评估标记后单核细胞的迁移能力。标记24小时后，用酶联免疫吸附测定法测量促炎细胞因子白细胞介素（IL）-1和IL-6的水平。数据采用Student t检验或双向方差分析，随后进行多重比较程序分析。
与SPIO孵育的细胞样本的R2弛豫率增加，而与最高浓度USPIO孵育的样本的弛豫率未受影响。用SPIO（1.0 mg Fe/mL）标记单核细胞导致R2为13.1秒-1±0.8（平均标准误差）（载体处理细胞为7秒-1±0.2，P <.05），且对细胞活力无影响。根据T2弛豫时间，计算出每0.05 μL 58个标记单核细胞的体外MR检测限。标记单核细胞的迁移与载体处理细胞的迁移无差异。细胞内铁在标记24小时后对IL-1和IL-6的产生无影响。
使用SPIO而非USPIO对人单核细胞进行体外标记是有效的。用SPIO（1.0 mg Fe/mL）孵育可在MR图像上检测到有效标记，且不影响细胞活力和诸如细胞迁移及细胞因子产生等激活标志物。
