Weber Ralph, Wegener Susanne, Ramos-Cabrer Pedro, Wiedermann Dirk, Hoehn Mathias
In Vivo NMR Laboratory, Max Planck Institute for Neurological Research, Cologne, Germany.
Magn Reson Med. 2005 Jul;54(1):59-66. doi: 10.1002/mrm.20532.
Focal cerebral ischemia was induced in rats and followed with high-resolution MRI methods for a chronic period of 10 weeks. Two weeks after stroke induction and at the end of the observation period, conventional histological analysis was combined with immunohistochemical staining for macrophages and with Prussian blue staining for the detection of ferric iron. In the late chronic phase, a patchy hypointensity was observed in the ischemic caudoputamen exclusively on T2*-weighted (T2W) images, with no change in quantitative T(1) and T(2) relaxation time maps. This characteristic MRI pattern is different from hemorrhagic transformations (HTs) at earlier time points (2 weeks post stroke induction), which became apparent on images of all three imaging sequences. The exclusive T2-sensitive hypointensity colocalized with iron-positive macrophages in the lesion territory at this time. These iron-containing macrophages were found predominantly around blood vessels in the ischemic tissue, and interpreted as the result of a phagocytotic incorporation of red blood cells leaking from slowly degrading vessels. The present investigation demonstrates the sensitivity of heavily T2*W 3D MRI for observing the inflammatory response in the chronic phase after stroke, without prior systemic labeling of the blood-borne macrophages by iron oxide nanoparticles.
在大鼠中诱导局灶性脑缺血，并采用高分辨率MRI方法随访10周的慢性期。在中风诱导后两周和观察期结束时，将传统组织学分析与巨噬细胞免疫组织化学染色以及普鲁士蓝染色相结合，用于检测三价铁。在慢性晚期，仅在T2 *加权（T2 * W）图像上，在缺血性尾状壳核中观察到斑片状低信号，定量T（1）和T（2）弛豫时间图无变化。这种特征性MRI模式与早期时间点（中风诱导后2周）的出血性转化（HTs）不同，后者在所有三个成像序列的图像上均很明显。此时，仅T2 *敏感的低信号与病变区域内铁阳性巨噬细胞共定位。这些含铁巨噬细胞主要在缺血组织的血管周围发现，并被解释为从缓慢降解的血管中漏出的红细胞吞噬摄取的结果。本研究证明了重度T2 * W 3D MRI对观察中风后慢性期炎症反应的敏感性，而无需事先通过氧化铁纳米颗粒对血源性巨噬细胞进行全身标记。
