Foley Lesley M, Hitchens T Kevin, Ho Chien, Janesko-Feldman Keri L, Melick John A, Bayir Hulya, Kochanek Patrick M
Pittsburgh NMR Center for Biomedical Research, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA.
J Neurotrauma. 2009 Sep;26(9):1509-19. doi: 10.1089/neu.2008.0747.
Macrophages contribute to secondary damage and repair after central nervous system (CNS) injury. Micron-sized paramagnetic iron oxide (MPIO) particles can label macrophages in situ, facilitating three-dimensional (3D) mapping of macrophage accumulation following traumatic brain injury (TBI), via ex vivo magnetic resonance microscopy (MRM) and in vivo monitoring with magnetic resonance imaging (MRI). MPIO particles were injected intravenously (iv; 4.5 mg Fe/Kg) in male C57BL/6J mice (n = 21). A controlled cortical impact (CCI) was delivered to the left parietal cortex. Five protocols were used in naive and injured mice to assess feasibility, specificity, and optimal labeling time. In vivo imaging was carried out at 4.7 Tesla (T). Brains were then excised for 3D MRM at 11.7 T. Triple-label immunofluorescence (MPIO via Dragon Green, macrophages via F480, and nuclei via 4,6-diamidino-2-phenylindole [DAPI]) of brain sections confirmed MPIO particles within macrophages. MRM of naives showed an even distribution of a small number of MPIO-labeled macrophages in the brain. MRM at 48-72 h after CCI and MPIO injection revealed MPIO-labeled macrophages accumulated in the trauma region. When MPIO particles were injected 6 days before CCI, MRM 48 h after CCI also revealed labeled cells at the injury site. In vivo studies of macrophage accumulation by MRI suggest that this approach is feasible, but requires additional optimization. We conclude that MPIO labeling and ex vivo MRM mapping of macrophage accumulation for assessment of TBI is readily accomplished. This new technique could serve as an adjunct to conventional MR approaches by defining inflammatory mechanisms and therapeutic efficacy of anti-inflammatory agents in experimental TBI.
巨噬细胞在中枢神经系统（CNS）损伤后的继发性损伤和修复过程中发挥作用。微米级顺磁性氧化铁（MPIO）颗粒可原位标记巨噬细胞，通过离体磁共振显微镜（MRM）和磁共振成像（MRI）进行体内监测，有助于对创伤性脑损伤（TBI）后巨噬细胞聚集进行三维（3D）映射。将MPIO颗粒静脉注射（iv；4.5 mg Fe/Kg）到雄性C57BL/6J小鼠（n = 21）体内。对左侧顶叶皮质进行控制性皮质撞击（CCI）。在未受伤和受伤的小鼠中使用了五种方案来评估可行性、特异性和最佳标记时间。在4.7特斯拉（T）下进行体内成像。然后切除大脑，在11.7 T下进行3D MRM。脑切片的三重标记免疫荧光（通过龙绿标记MPIO，通过F480标记巨噬细胞，通过4,6-二脒基-2-苯基吲哚[DAPI]标记细胞核）证实巨噬细胞内存在MPIO颗粒。未受伤小鼠的MRM显示大脑中有少量MPIO标记的巨噬细胞呈均匀分布。CCI和MPIO注射后48 - 72小时的MRM显示MPIO标记的巨噬细胞聚集在创伤区域。当在CCI前6天注射MPIO颗粒时，CCI后48小时的MRM也显示损伤部位有标记细胞。通过MRI对巨噬细胞聚集进行的体内研究表明，这种方法是可行的，但需要进一步优化。我们得出结论，MPIO标记和离体MRM映射巨噬细胞聚集以评估TBI很容易实现。这项新技术可以通过定义实验性TBI中炎症机制和抗炎药物的治疗效果，作为传统MR方法的辅助手段。
