【作者】 王东；

【导师】 张苏明；

【作者基本信息】 华中科技大学 ， 神经病学， 2008， 博士

【摘要】 阿尔茨海默病是一种最常见的神经系统变性疾病,其基本的病理学改变是老年斑、神经纤维缠结、突触数目的减少以及神经元的丢失。本研究运用磁共振成像和活体波谱技术,并结合病理学和免疫组织化学技术,对AD转基因小鼠脑组织的微观结构和代谢物的水平进行研究。同时研究了小鼠的基因型对其横向磁豫时间（T₂值）和表观扩散系数（ADC值）的影响。在本文的第一部分中,我们对所获取的APPswe/PS1ΔE9双转基因小鼠进行了传代,繁殖。并通过PCR反应对小鼠的基因型进行了鉴定。应用多层面多回波SE序列和弥散加权成像（DWI）序列对4-8月龄的转基因和野生型小鼠不同脑区的T₂值和ADC值进行了测量。磁共振扫描完成后,进行老年斑和铁的组织学染色。研究发现,与野生型小鼠相比,转基因小鼠皮质和海马区的T₂值明显降低,而丘脑,胼胝体和纹状体的T₂值变化不大。ADC值的改变也与T₂值的改变相类似,转基因小鼠皮质和海马的ADC值较野生型小鼠为低,而纹状体的ADC值变化不大。组织学染色发现,4月龄及8月龄转基因小鼠的皮质及海马可出现老年斑的沉积,并且随着小鼠月龄的增加,老年斑的数目增多,面积也增大。铁染色进一步发现在转基因及野生型小鼠基底神经节处均可见到铁的沉积。铁在转基因小鼠的皮质及海马处呈棕褐色沉积,并且其分布与老年斑的分布相类似,而野生型小鼠的皮质及海马未见铁的沉积.。这些结果说明:小鼠的基因型会影响到磁共振的表型。转基因小鼠皮质和海马区的T₂值的降低可能与老年斑内的铁有关,而ADC值的降低,除了与老年斑形成引起的水分子的弥散能力减低有关之外,还与继发的神经胶质增生有关。在本文的第二部分中,我们主要研究了AD转基因小鼠的磁共振的高分辨成像。通过对PDAPP转基因小鼠的活体扫描和APPswe/PS1ΔE9双转基因小鼠的离体扫描发现:离体扫描组织的对比度和信噪比明显较活体扫描为高,在AD转基因小鼠的活体和离体T2WI上的皮质和海马上可见一些点状的低信号区,部分的低信号区可与老年斑和铁染色相对应。这也说明了老年斑的磁共振显微成像可能有助于AD的早期诊断。在本文的第三部分中,我们对5,8,12,16月龄的APPswe/PS1ΔE9双转基因小鼠的海马进行了活体波谱扫描,结果发现转基因小鼠海马区NAA的含量较同月龄野生型小鼠含量为低,其中16月龄的转基因小鼠海马区内NAA的水平较野生型小鼠下降更为明显。上述结果也提示1H-MRS可作为一种无创性的方法,动态的检测脑内代谢物的水平变化。总之,一系列MRI实验以及组织学染色的结果更加深了对AD转基因小鼠表型的认识,为MRI技术在AD的发病机制和临床药物的筛选等方面提供了实验基础。更多还原

【Abstract】 Alzheimer disease （AD） is one of the most common neurodegenerative diseases , which is characterized by amyloid-βplaques, neurofibrillary tangles, decreased synaptic density and loss of neurons. The main research work described here was focused on the microstructure and the level of the metabolite in the brain of AD transgenic mice by using magnetic resonance imaging （MRI） and in vivo magnetic resonance spectroscopy （1H MRS） in combination with histopathology and immunohistochemistry. At the same time, we investigated the influence of mice genetype on some usual MR parameter（T₂ value and ADC value）.In the first part, APPswe/PS1ΔE9 double transgenic mice that obtained from Jackson lab were transmited and bred, and the genetype of mice were identified by PCR reaction. Using the T₂-weighted multislice multiecho sequence and DWI sequence, the T₂ value and apparent diffusion coefficient were measured in different brain areas. After MR scan, histology staining about senile plaques and iron were performed on the transgenic mice brain aged 4mon and 8mon. The results demonstrated that T₂ value in cortex and hippocampus of double transgenic mice was decreased compared with the wild type mice. There was no difference in the T₂ value in other brain（thalamus,corpus callosum,striatum） areas between double transgenic and wild type mice.The changes of ADC were similar to the T₂ value. The ADC in cortex and hippocampus of double transgenic mice was also decreased compared with the wild type mice. There was no difference in the ADC in the striatum between double transgenic and wild type mice. The result of histology staining shown that senile plaques could be detected in the cortex and hippocampus of double transgenic mice aged 4 mon and 8mon. There was an overall increase in number and area of senile plaques with age. The result of the iron staining shown further that the iron deposition in the basal ganglia of the transgenic mice is similar to the wildtype. But only in the cortex and hippocampus of transgenic mice,we could observe the brown deposition of iron. Iron distribution in the brain of transgenic mice is similar to the senile plaques.There was no iron deposition in the cortex and hippocampus of wild type mice.All these results demostrated that the mice genetype have influences on the MR phenotype,And The decrease of the T₂ value in cortex and hippocampus of double transgenic mice were attributed to iron in senile plaque.However The reduction of ADC parallels the formation of amyloid plaques that causes a decrease of water molecular diffusion ability and might be attributable to the pronounced gliosis associated with the amyloid deposits.In the second part,we investigated the high-resolution magnetic resonance imaging of mouse brain of AD transgenic mice. By using high-resolution magnetic resonance imaging in ex vivo brains of APPswe/PS1ΔE9 double transgenic mice.and in vivo brains of PDAPP mice,we found that the CNR and SNR of ex vivo brain were higher than in vivo brain. The MR images shown that some black spots were visible in the hippocampus and cerebral cortex of the AD transgenic mice and some spots were confirmed by histological sections of the senile plaques and iron in plaques that followed. So, the high-resolution magnetic resonance imaging of senile plaques may be helpful for diagnosis of AD earlier.In the third part, In vivo 1H-MRS was performed on hippocampus of brain of APPswe/PS1ΔE9 double transgenic mice and wild type littermates aged 5,8,12,16 mon using a 4.7T magnet..The levels of N-acetylaspartate（NAA） were lower in transgenic mice as compared to wild type mice at the age of the same months and the level of tg mice at 16 months was significantly reduced. The result described above shown that Proton magnetic resonance spectroscopy （1H MRS） provides a noninvasive way to investigate in vivo neurochemical abnormalities dynamically. The results of the serial MRI and histological staining undoubtedly enriched our understanding of the phenotype of AD transgenic mice, and thus should facilitate the application of MRI techniques to the pathological research and preclinical therapeutic assessments of AD.更多还原