小鼠脑梗死后小胶质细胞内Toll样受体9选择性上调

 目的：观察脑梗死后Toll 样受体9（TLR9）表达量及其在神经元和神经胶质细胞中的表达变化。方法：线栓法制备C57小鼠大脑中动脉闭塞（MCAO）模型，90 min后再灌注。假手术组为对照。再灌注后6 h、3 d、7 d和14 d处死动物 (n=3)，制备脑冠状位冰冻切片。免疫荧光染色观察TLR9表达量及其在神经元和神经胶质细胞中的表达变化。结果：梗死灶边缘区TLR9的表达量随时间增加，始终高于对侧及假手术组。病变全程偶见神经元胞内小点状TLR9，TLR9阳性率无时间、组间差异。激活态小胶质细胞聚集于梗死灶边缘区，胞内TLR9由散在小点状变为团块状粗颗粒样。TLR9阳性率随时间先升后降，始终高于对侧及假手术组。星形细胞和少突胶质细胞未见TLR9阳性染色。结论：脑梗死后，中枢定居细胞中神经元TLR9维持固有表达，仅小胶质细胞TLR9表达选择性上调，星形细胞及少突胶质细胞无TLR9表达。

Selective up-regulation of Toll-like receptor 9 in mouse microglia after cerebral infarction

AIM：To observe the expression of Toll-like receptor 9 (TLR9) and the distribution of TLR9 in the neurons and glial cells after cerebral infarction. METHODS：With the intraluminal filament method, middle cerebral artery occlusion (MCAO) model of C57 mice was established, and the filament was removed to begin reperfusion 90 min later. A sham-operated group was set up as a control. At 6 h, 3 d, 7 d or 14 d after reperfusion, the mice were randomly killed to prepare brain coronal cryosections (n=3). The level of TLR9 expression and the distribution of TLR9 in the neurons and glial cells were detected by immunofluorescent staining. RESULTS：The level of TLR9 increased significantly in transitional peri-infarct tissues over time and was constantly higher than that in the contralateral and sham-operated ones. Only a few scattered TLR9 staining was found inside the neurons during the whole process. The percentage of TLR9-positive neurons showed no significant difference among groups and time points. Activated microglia aggregated in transitional peri-infarct tissues, with intracellular TLR9 staining from scattered tiny dots to clustered coarse particles. Meanwhile, the percentage of TLR9-positive microglia increased at the beginning and later decreased with time, and was significantly higher than that in the contralateral and sham-operated ones. No TLR9 expression was found in astrocytes or oligodendrocytes. CONCLUSION：TLR9 is triggered in microglia after cerebral infarction in the CNS, while the neurons maintain inherent expression of TLR9. Besides, there is no evidence to support the expression of TLR9 in the astrocytes and oligodendrocytes.