Lee Jin Seong, Kang Hee Jung, Gong Gyungyub, Jung Heun-Don, Lim Keun Ho, Kim Sang Tae, Lim Tae-Hwan
Departments of Radiology and Pathology, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Pungnapdong, Songpa-gu, Seoul 138-736, South Korea.
Radiology. 2006 Oct;241(1):142-8. doi: 10.1148/radiol.2403051156.
To evaluate the feasibility of magnetic resonance (MR) imaging in depicting in vivo recruitment of iron oxide-labeled macrophages in experimentally induced soft-tissue infection.
The study was performed according to the guidelines of the U.S. National Institutes of Health and recommendations of the committee on animal research. The protocol was approved by the local institutional review committee on animal care. Experimental soft-tissue infection in 12 mice was induced by inoculation with a 5 x 10(7) colony-forming units of Staphylococcus aureus into the left calf. Peritoneal macrophages were harvested from thioglycollate-treated mice, cultured, and labeled with iron oxide in vitro. The iron oxide-labeled macrophage (macrophage group, n = 6) or iron oxide solution (control group, n = 6) was administered through the tail vein. The left calf of the mice was imaged on days 2 and 3 with a 4.7-T MR unit. Changes in relative signal intensity (SI) and pattern of contrast material enhancement (macrophage distribution) were analyzed and compared with histopathologic findings. Statistical analysis was performed with the Wilcoxon matched-pairs signed rank test.
On MR images obtained 24 hours after administration of macrophage labeled with iron oxide, a band-shaped lower SI zone was noted in the abscess wall, which corresponded to the distribution of the iron oxide-labeled macrophages at histopathologic examination. The relative SI of the abscess wall significantly decreased after injection of iron oxide-labeled macrophages (median, 0.42) compared with that before injection (median, 1.23) (P = .031). In the control group, the SI change after administration of iron oxide solution was not significant (P = .688).
Homing of intravenously administered iron oxide-labeled macrophages can be monitored with MR imaging and may provide a tool to investigate interactions between macrophages and the invading pathogens.
评估磁共振（MR）成像在描绘实验性诱导的软组织感染中氧化铁标记巨噬细胞的体内募集情况的可行性。
本研究按照美国国立卫生研究院的指南及动物研究委员会的建议进行。该方案经当地机构动物护理审查委员会批准。通过将5×10⁷个金黄色葡萄球菌菌落形成单位接种到12只小鼠的左小腿来诱导实验性软组织感染。从经巯基乙酸盐处理的小鼠中收获腹腔巨噬细胞，进行培养并在体外用氧化铁标记。通过尾静脉注射氧化铁标记的巨噬细胞（巨噬细胞组，n = 6）或氧化铁溶液（对照组，n = 6）。在第2天和第3天用4.7-T MR设备对小鼠的左小腿进行成像。分析相对信号强度（SI）的变化和对比剂增强模式（巨噬细胞分布），并与组织病理学结果进行比较。采用Wilcoxon配对符号秩检验进行统计学分析。
在注射氧化铁标记的巨噬细胞24小时后获得的MR图像上，脓肿壁出现一条带状低SI区，这与组织病理学检查中氧化铁标记巨噬细胞的分布相对应。与注射前（中位数，1.23）相比，注射氧化铁标记的巨噬细胞后脓肿壁的相对SI显著降低（中位数，0.42）（P = 0.031）。在对照组中，注射氧化铁溶液后SI变化不显著（P = 0.688）。
静脉注射的氧化铁标记巨噬细胞的归巢情况可用MR成像监测，这可能为研究巨噬细胞与入侵病原体之间的相互作用提供一种工具。
