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Three-dimensional analysis of synaptic organization in the hippocampal CA1 field in Alzheimer's disease.

阿尔茨海默病海马CA1区突触组织的三维分析。

  • 影响因子:7.52
  • DOI:10.1093/brain/awaa406
  • 作者列表:"Montero-Crespo M","Domínguez-Álvaro M","Alonso-Nanclares L","DeFelipe J","Blazquez-Llorca L
  • 发表时间:2021-03-03
Abstract

:Alzheimer's disease is the most common form of dementia, characterized by a persistent and progressive impairment of cognitive functions. Alzheimer's disease is typically associated with extracellular deposits of amyloid-β peptide and accumulation of abnormally phosphorylated tau protein inside neurons (amyloid-β and neurofibrillary pathologies). It has been proposed that these pathologies cause neuronal degeneration and synaptic alterations, which are thought to constitute the major neurobiological basis of cognitive dysfunction in Alzheimer's disease. The hippocampal formation is especially vulnerable in the early stages of Alzheimer's disease. However, the vast majority of electron microscopy studies have been performed in animal models. In the present study, we performed an extensive 3D study of the neuropil to investigate the synaptic organization in the stratum pyramidale and radiatum in the CA1 field of Alzheimer's disease cases with different stages of the disease, using focused ion beam/scanning electron microscopy (FIB/SEM). In cases with early stages of Alzheimer's disease, the synapse morphology looks normal and we observed no significant differences between control and Alzheimer's disease cases regarding the synaptic density, the ratio of excitatory and inhibitory synapses, or the spatial distribution of synapses. However, differences in the distribution of postsynaptic targets and synaptic shapes were found. Furthermore, a lower proportion of larger excitatory synapses in both strata were found in Alzheimer's disease cases. Individuals in late stages of the disease suffered the most severe synaptic alterations, including a decrease in synaptic density and morphological alterations of the remaining synapses. Since Alzheimer's disease cases show cortical atrophy, our data indicate a reduction in the total number (but not the density) of synapses at early stages of the disease, with this reduction being much more accentuated in subjects with late stages of Alzheimer's disease. The observed synaptic alterations may represent a structural basis for the progressive learning and memory dysfunctions seen in Alzheimer's disease cases.

摘要

: 阿尔茨海默病是最常见的痴呆形式,其特征在于认知功能的持续和进行性损害。阿尔茨海默病通常与淀粉样蛋白-β 肽的细胞外沉积和异常磷酸化的tau蛋白在神经元内的积累有关 (淀粉样蛋白-β 和神经原纤维病变)。已经提出这些病理学引起神经元变性和突触改变,其被认为构成阿尔茨海默病中认知功能障碍的主要神经生物学基础。在阿尔茨海默病的早期阶段,海马结构特别脆弱。然而,绝大多数电子显微镜研究是在动物模型中进行的。在本研究中,我们对neuropil进行了广泛的3D研究,使用聚焦离子束/扫描电子显微镜 (FIB/SEM) 研究了阿尔茨海默病不同阶段病例CA1区锥体和辐射层的突触组织。在阿尔茨海默病早期的病例中,突触形态看起来正常,我们观察到对照和阿尔茨海默病病例在突触密度、兴奋性和抑制性突触的比例或突触的空间分布方面没有显著差异。然而,发现了突触后靶标和突触形状的分布差异。此外,在阿尔茨海默病病例中发现两个层中较大兴奋性突触的比例较低。处于疾病晚期的个体遭受最严重的突触改变,包括突触密度的降低和剩余突触的形态学改变。由于阿尔茨海默病病例显示皮质萎缩,我们的数据表明疾病早期突触的总数 (但不是密度) 减少,这种减少在阿尔茨海默病晚期的受试者中更加突出。观察到的突触改变可以代表在阿尔茨海默病病例中看到的进行性学习和记忆功能障碍的结构基础。

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