APP/PS1小鼠不同时期灰质体积变化与Aβ沉积和学习记忆功能的相关性分析

Correlation of the Changes of Gray Matter Volume with AβDeposition and Learning and Memory Abilities in APP/PS1 Mice at Different Periods

目的:分析阿尔兹海默病(AD)双转基因APP/PS1模型小鼠大脑灰质体积变化与其学习记忆能力和相关脑区β-淀粉样蛋白(Aβ)沉积的相关性,以期为探明AD动物模型的病理特征提供可靠的行为学和影像学依据。方法:共纳入野生组(WT)和APP/PS1组2组小鼠,每组36只。WT组小鼠选用C57-BL/6小鼠,APP/PS1组选用APP/PS1双转基因小鼠,2组均分别由2、6、12不同月龄小鼠组成,每组每个月龄小鼠12只。通过Morris水迷宫测试(定位航行实验和空间探索实验)检测2组小鼠空间记忆学习能力和空间记忆提取能力;采用磁共振T2加权成像(MRI T2WI)扫描检测小鼠大脑双侧内嗅皮质和海马的灰质体积变化情况;分离和制备2组不同月龄小鼠大脑石蜡切片,采用Thioflavine-s(Th-s)荧光染色检测2组小鼠大脑双侧内嗅皮质和海马的Aβ沉积情况;采用Pearson相关分析法分析2组小鼠不同时期的灰质体积变化与其学习记忆能力和对应脑区Aβ沉积的相关性。结果:①Morris水迷宫测试结果:与WT组比较,APP/PS1组2月龄小鼠行为学结果无明显区别,差异无统计学意义(P>0.05);APP/PS1组6、12月龄小鼠逃避潜伏期明显增加、穿越平台次数明显减少,差异具有统计学意义(P<0.05)。②MRI T2WI扫描结果:与WT组比较,APP/PS1组2月龄小鼠灰质体积无明显变化,差异无统计学意义(P>0.05);APP/PS1组6月龄小鼠内嗅皮质体积明显缩小,APP/PS1组12月龄小鼠内嗅皮质和海马体积均明显缩小,差异具有统计学意义(P<0.05)。③Th-s荧光染色检测结果:WT组、APP/PS1组2月龄小鼠均未检测出Aβ沉积;与WT组比较,APP/PS1组小鼠6月龄内嗅皮质和海马可检测到少量Aβ沉积,而12月龄时内嗅皮质和海马则可检测出大量致密Aβ斑块,差异具有统计学意义(P<0.05)。④相关性分析结果:APP/PS1组小鼠内嗅皮质和海马体积变化与逃避潜伏期呈明显负相关关系(r=-0.729,P<0.001;r=-0.643,P<0.001);APP/PS1组小鼠内嗅皮质和海马体积变化与穿越平台次数呈明显正相关关系(r=0.705,P<0.001;r=0.719,P<0.001);APP/PS1组小鼠内嗅皮质和海马体积变化与Aβ沉积呈明显负相关关系(r=-0.865,P<0.001;r=-0.885,P<0.001)。结论:APP/PS1转基因小鼠可能于6月龄时就发生学习记忆功能障碍,且随时间渐进性加重;这种学习记忆功能障碍可能与大脑内嗅皮质和海马体积萎缩有关;而Aβ过度沉积可能是导致大脑灰质体积萎缩的因素之一。

Objective:To analyze the correlation in the changes of cerebral gray matter volume and the ability of memory learning,and the deposition ofβ-amyloid protein(Aβ)in related brain regions of Alzheimer's disease(AD)double-transgenic APP/PS1 model mice,which is expected to provide reliable behavioral and imaging basis for probing the pathological features of AD animal models.Methods:A total of two groups mice were included in this study,including the wild type(WT)group and the APP/PS1 group,with 36 mice in each group.The C57-BL/6 mice were selected in the WT group,and APP/PS1 double transgenic mice were selected in the APP/PS1 group.The two groups were composed of mice of different ages of 2,6,and 12 months respectively,with 12 mice of each month in each group.The Morris water maze test(including location navigation test and spatial exploration test)was used to detect the spatial memory learning ability and spatial memory extraction ability of the two groups of mice,and the magnetic resonance T2-weighted imaging(MRI T2WI)scan was used to detect the changes of gray matter volume in the bilateral entorhinal cortex and hippocampus of mice.The brain paraffin sections of two groups of mice of different months were separated and prepared,and the Aβdeposition in bilateral entorhinal cortex and hippocampus of the two groups was detected by Thioflavine-s fluorescence staining,and the correlation between the changes of gray matter volume and memory learning ability and Aβdeposition in the corresponding brain area of the two groups was analyzed by Pearson correlation analysis.Results:①The results of Morris water maze test:compared with the WT group,there was no significant difference in the behavioral results of the 2-month-old mice in the APP/PS1 group,and the difference was not statistically significant(P>0.05);the escape latency of mice of the APP/PS1 group at the 6 and 12 month-old increased significantly,the number of crossing platforms of the APP/PS1 group at the 6 and 12 month-old decreased significantly,and the difference was statistically significant(P<0.05).②The results of MRI T2WI scan:compared with the WT group,there was no significant change in the gray matter volume of the APP/PS1 group at 2-month-old,and the difference was not statistically significant(P>0.05);the volume of the entorhinal cortex of the APP/PS1 group at 6-month-old decreased significantly,and the volume of the entorhinal cortex and hippocampus of the APP/PS1 group at 12-month-old mice decreased significantly,the difference was statistically significant(P<0.05).③The results of Th-s fluorescence staining test:Aβdeposition was not detected in WT group and APP/PS1 group at 2-month-old;compared with the WT group,a small amount of Aβdeposition could be detected in the entorhinal cortex and hippocampus of the APP/PS1 group at 6-month-old,while a large number of dense Aβplaques can be detected in the entorhinal cortex and hippocampus of the APP/PS1 group at 12-month-old.④Correlation analysis results:APP/PS1 group mice's entorhinal cortex and hippocampus volume changes were significantly negatively correlated with escape latency(r=-0.729,P<0.001;r=-0.643,P<0.001);the volume changes of the entorhinal cortex and hippocampus in the APP/PS1 group showed a positive correlation with the number of crossing platforms(r=0.705,P<0.001;r=0.719,P<0.001);the volume changes of the entorhinal cortex and hippocampus in the APP/PS1 group were significantly negatively correlated with Aβdeposition(r=-0.865,P<0.001;r=-0.885,P<0.001).Conclusion:APP/PS1 transgenic mice may have learning and memory dysfunction at 6-month-old,and it gradually worsen with time;the learning and memory dysfunction may be related to the atrophy of the entorhinal cortex and hippocampus in the brain of mice,and excessive Aβdeposition may be the one of the factors that cause the brain gray matter volume to shrink.