White matter injury and microglia/macrophage polarization are strongly linked with age-related long-term deficits in neurological function after stroke.
White matter injury and microglia/macrophage polarization are strongly linked with age-related long-term deficits in neurological function after stroke.
复制标题
白质损伤和小胶质细胞/巨噬细胞极化与中风后年龄相关的神经功能长期缺陷密切相关
DOI：
10.1016/j.expneurol.2015.03.021
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发表时间：
2015-10
影响因子：
5.3
通讯作者：
Chen J
中科院分区：
文献类型：
--
作者：
Suenaga J;Hu X;Pu H;Shi Y;Hassan SH;Xu M;Leak RK;Stetler RA;Gao Y;Chen J
大多数中风实验模型的成功并没有很好地转化为临床。失败的一个潜在原因是中风主要折磨老年人，而大多数实验性中风研究依赖于从年轻的成年动物身上收集的数据。因此，在本研究中，我们建立了一个可靠的、可重复的、低死亡率的老年（18个月）雄性小鼠中风模型，并将其病理生理变化与幼年（2个月）小鼠进行了对比。为此，对小鼠进行左远端大脑中动脉（dMCAO）和同侧颈总动脉闭塞（CCAO）永久性串联闭塞。反复评估脑血流（CBF）在中风期间和之后。老年小鼠的脑血流减少更为显著和持续。老年小鼠表现出更严重的长期感觉运动缺陷，在中风后35天的Rotarod和悬挂线测试中表现恶化。老年小鼠在中风后也表现出更严重的长期认知缺陷，这是莫里斯水迷宫测试的结果。与这些行为观察相一致的是，dMCAO后老年小鼠的脑梗死面积和神经元组织损失分别在2d和14d显著增大。然而，年轻人和老年人在神经元组织损失方面的差异直到dMCAO后35天才持续存在。与神经元组织损失的短暂差异相反，我们发现老年动物的白质显著且持久的恶化，这是在dMCAO后35d纹状体髓鞘碱性蛋白（MBP）染色丢失所揭示的。我们进一步通过双免疫荧光染色检测了M1 （CD16/CD32）和M2 （CD206）标记物在Iba-1+小胶质细胞中的表达。在幼龄和老年小鼠中，M2标记物的表达在中风后7d左右达到峰值，而M1标记物的表达在中风后14d左右达到峰值，这表明两组小鼠的M2- M1表型发生了进行性转变。然而，与年轻的成年小鼠相比，老年小鼠表现出明显减少的M2极化。值得注意的是，我们发现dMCAO与MBP水平或M2小胶质细胞/巨噬细胞数量之间的良好神经预后呈正相关。总之，我们的研究表明，远端MCAO卒中模型一致导致缺血性脑损伤伴长期行为缺陷，因此适合评估长期卒中结局。此外，老年小鼠在中风后表现出功能结果的恶化，这种恶化与白质损伤和M2小胶质细胞/巨噬细胞极化减少有关。
Most of the successes in experimental models of stroke have not translated well to the clinic. One potential reason for this failure is that stroke mainly afflicts the elderly and the majority of experimental stroke studies rely on data gathered from young adult animals. Therefore, in the present study we established a reliable, reproducible model of stroke with low mortality in aged (18 month) male mice and contrasted their pathophysiological changes with those in young (2 month) animals. To this end, mice were subjected to permanent tandem occlusion of the left distal middle cerebral artery (dMCAO) with ipsilateral common carotid artery occlusion (CCAO). Cerebral blood flow (CBF) was evaluated repeatedly during and after stroke. Reduction of CBF was more dramatic and sustained in aged mice. Aged mice exhibited more severe long-term sensorimotor deficits, as manifested by deterioration of performance in the Rotarod and hanging wire tests up to 35d after stroke. Aged mice also exhibited significantly worse long-term cognitive deficits after stroke, as measured by the Morris water maze test. Consistent with these behavioral observations, brain infarct size and neuronal tissue loss after dMCAO were significantly larger in aged mice at 2d and 14d, respectively. The young versus aged difference in neuronal tissue loss, however, did not persist until 35d after dMCAO. In contrast to the transient difference in neuronal tissue loss, we found significant and long lasting deterioration of white matter in aged animals, as revealed by the loss of myelin basic protein (MBP) staining in the striatum at 35d after dMCAO. We further examined the expression of M1 (CD16/CD32) and M2 (CD206) markers in Iba-1+ microglia by double immunofluorescent staining. In both young and aged mice, the expression of M2 markers peaked around 7d after stroke whereas the expression of M1 markers peaked around 14d after stroke, suggesting a progressive M2-to-M1 phenotype shift in both groups. However, aged mice exhibited significantly reduced M2 polarization compared to young adults. Remarkably, we discovered a strong positive correlation between favorable neurological outcomes after dMCAO and MBP levels or the number of M2 microglia/macrophages. In conclusion, our studies suggest that the distal MCAO stroke model consistently results in ischemic brain injury with long-term behavioral deficits, and is therefore suitable for the evaluation of long-term stroke outcomes. Furthermore, aged mice exhibit deterioration of functional outcomes after stroke and this deterioration is linked to white matter damage and reductions in M2 microglia/macrophage polarization.