自主跑步运动对APP/PS1小鼠内侧前额叶皮质少突胶质细胞的作用

Effect of voluntary running exercise on oligodendrocytes in the medial prefrontal cortex of APP/PS1 mice

目的:研究自主跑步运动对APP/PS1双转基因AD(Alzheimer’s disease,AD)模型小鼠内侧前额叶皮质(medial prefrontal cortex,mPFC)内少突胶质细胞数量,少突胶质细胞分化、成熟以及髓鞘形成的作用。方法:将10月龄雄性转基因AD模型小鼠随机分为AD组和AD跑步(AD+RUN)组,另外将同月龄同窝生野生型小鼠随机分为正常(WT)组和正常跑步(WT+RUN)组。其中跑步组于跑步笼内给予3个月自主跑步锻炼,AD组和WT组不做处理。跑步锻炼结束后4组小鼠同时给予行为学测试,用Morris水迷宫检测小鼠空间学习、记忆能力;用Y迷宫检测小鼠工作记忆能力;用新物体识别实验检测小鼠的认知记忆功能;利用无偏体视学技术和免疫组化技术相结合精确定量小鼠大脑mPFC内成熟少突胶质细胞(CC1^(+))总数量;同时分析小鼠mPFC内边缘皮层、Ⅱ、Ⅲ、Ⅵ、Ⅵ层成熟少突胶质细胞密度;利用免疫荧光和激光共聚焦显微镜分析小鼠mPFC内未成熟少突胶质细胞(PDGFα^(+)/Olig2^(+))密度、髓鞘标志物髓鞘碱性蛋白(myelin basic protein,MBP)荧光强度。结果:AD+RUN组和WT组在Morris水迷宫、Y迷宫以及新物体识别实验中的表现优于AD组,AD组mPFC内MBP荧光强度明显低于WT组(P<0.05),而AD+RUN组mPFC内MBP荧光强度明显大于AD组(P<0.001)。AD+RUN组mPFC内CC1^(+)细胞总数较AD组明显增加(P<0.05)。AD+RUN组mPFC内第Ⅲ层和第Ⅴ层CC1^(+)细胞密度较AD组明显增高(P<0.05),AD组mPFC内第Ⅴ层和第Ⅵ层CC1^(+)细胞密度较WT组明显降低(P<0.05)。AD组mPFC内PDGFα^(+)/Olig2^(+)细胞密度明显大于WT组,而AD+RUN组mPFC内PDGFα^(+)/Olig2^(+)细胞密度明显小于AD组(P<0.05)。结论:自主跑步运动能促进AD小鼠少突胶质细胞分化和髓鞘形成,这可能与运动能改善APP/PS1转基因AD小鼠的学习记忆能力有关。

Objective:To investigate the effect of voluntary running exercise on the number,differentiation,maturation,and myelination of oligodendrocytes in the medial prefrontal cortex(mPFC)of APP/PS1 double transgenic mice with Alzheimer’s disease(AD).Methods:Male transgenic mice with AD,aged 10 months,were randomly divided into AD group and AD+running group(AD+RUN group),and in addition,wild-type littermates with the same age were randomly divided into normal group(WT group)and normal+running group(WT+RUN group).The mice in the two running groups were given voluntary running exercise in running cage for 3 months,while those in the AD group and the WT group were not given any treatment.After running exercise,behavioral tests were performed for the mice of all four groups at the same time;the Morris water maze test was used to observe the spatial learning and memory abilities of mice,and Y maze was used to observe the working memory abilities of mice;the novel object recognition test was used to assess the cognitive and memory functions of mice;the unbiased stereological method and immunohistochemistry were used for accurate quantification of the total number of mature oligodendrocytes(CC1^(+))in mPFC,as well as the density of mature oligodendrocytes in limbic cortex andⅡ,Ⅲ,V,andⅥlayers of mPFC;immunofluorescence assay and a laser scanning confocal microscope were used to observe the density of immature oligodendrocytes(PDGFα^(+)/Olig2^(+))and the fluorescence intensity of myelin basic protein(MBP)as a myelin marker.Results:Compared with the AD group,the AD+RUN group and the WT group had significantly better performance in the Morris water maze,the Y maze test,and the novel object recognition test,and the AD group had a significantly lower fluorescence intensity of MBP in mPFC than the WT group(P<0.05),while the AD+RUN group had a significantly higher fluorescence intensity of MBP in mPFC than the AD group(P<0.001).The AD+RUN group had a significant increase in the total number of CC1^(+)cells in mPFC compared with the AD group(P<0.05).Compared with the AD group,the AD+RUN group had a significant increase in the density of CC1^(+)cells inⅢand V layers of mPFC(P<0.05),and compared with the WT group,the AD group had a significant reduction in the density of CC1^(+)cells in V andⅥlayers of mPFC(P<0.05).Compared with the WT group,the AD group had a significantly higher density of PDGFα^(+)/Olig2^(+)cells in mPFC,and compared with the AD group,the AD+RUN group had a significantly lower density of PDGFα^(+)/Olig2^(+)cells in mPFC(P<0.05).Conclusion:Voluntary running exercise can promote oligodendrocyte differentiation and myelination in AD mice,which might be related to the result that exercise can improve the learning and memory abilities of APP/PS1 transgenic AD mice.