Front. Neurosci.︱High-precision panorama of whole-brain Aβ plaques and surrounding structures in Alzheimer's disease model mice

Simultaneous acquisition of high-resolution maps of various structures in the whole brain is of great significance for in-depth understanding of brain function and the pathogenesis of neurological diseases such as Alzheimer's disease (AD)
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Existing imaging techniques and methods face great challenges in achieving large-scale, high-resolution simultaneous imaging of multiple brain structural elements
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On April 19, 2022, the MOST and Image Fusion Technology Service Department of Shanghai Institute of Materia Medica, Chinese Academy of Sciences published a research paper entitled "High-Resolution Digital Panorama of Multiple Structures in Whole Brain of Alzheimer's Disease Mice" in Frontiers in Neuroscience
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In this study, an information extraction and reconstruction strategy for various structural elements in adjacent grayscale intervals was designed based on the whole-brain Nissl staining data set obtained by the Micro-Optical Sectioning Tomography (MOST) system.
Realized the visualization of Aβ plaque distribution in the whole mouse brain based on Nissl staining, and constructed a high-precision panorama of Aβ plaques and their surrounding cell bodies, nerve dendrites, nerve bundles and blood vessels in the same mouse whole brain (Figure 1).

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The research results provide new ideas for in-depth understanding of the anatomical features of the brain in AD-related pathological conditions
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Emerging whole-brain imaging techniques (such as light-sheet illumination microscopy, STP, etc.
) combined with rapidly developing fluorescent labeling techniques enable the simultaneous imaging of a single structure or even two or three structures fluorescently labeled throughout the brain
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However, simultaneous imaging of samples with three or more fluorescent labels has not been possible due to spectral overlap of fluorophores and crossover of fluorescence emission
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Aβ plaque deposition is one of the main pathological features of AD
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There are various brain structures such as neurons, glia, nerve fibers and blood vessels around Aβ plaques.
These brain structure-related amyloid angiopathy, white matter lesions, ventriculomegaly and brain atrophy are common in AD patients.
in clinical images
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Aβ plaque-associated axonal dystrophy, loss of dendritic spines and synaptic alterations, detachment of astrocyte footplates from the vascular endothelial wall, glial cell recruitment and activation, and neuronal death were also confirmed
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Therefore, in-depth investigation of the interaction of Aβ plaques with various surrounding brain structures is of great significance for understanding the pathological mechanism and progression of AD
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At present, various imaging methods have revealed the structure and distribution characteristics of Aβ plaques, and the effects of Aβ plaques on brain structure have also been observed by methods such as multi-channel fluorescent labeling.
High-precision, cross-scale study of 3D construction of the surrounding environment
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　　The research team found that based on the differences in grayscale and morphology of different structures, MOST combined with whole-brain Nissl staining method can simultaneously provide multiple signals of multiple structural elements in the whole brain
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However, the high-throughput bright-field image data generated by the MOST system is rich in high-content information, and the structures such as cell bodies and blood vessels are complex and widely distributed; compared with fluorescent images, bright-field images have more complex backgrounds and poorer contrast; TB level Difficulties in data storage, reading, and processing caused by the amount of data limit the wide application and expansion of MOST technology in brightfield imaging to a certain extent
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To this end, the research team developed a visualization method for multi-structure extraction and reconstruction based on gray value differences and morphological features, and based on this, a high-precision cross-scale whole-brain construction study of various structures was carried out
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　　The results of the study showed that the areas with the highest density of Aβ plaques and the areas with the most dense distribution of large-sized plaques in the whole brain were both in the entorhinal cortex and the adjacent hippocampal ventral substellar region, suggesting that Aβ pathology may first appear in these densest areas (Fig.
2)
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In the whole brain, regions with denser Aβ plaques usually have relatively more cell bodies and are located distal to blood vessels, while nerve fiber bundles are denser in regions with relatively sparse Aβ plaques
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In regional brain regions, both visualization and quantitative analysis of cortical regions showed that Aβ plaques were densely located near the deep regions where soma was abundant, while Aβ plaques in the hippocampus were distributed in layers near the pyramidal cell layer and the granulosa cell layer
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At the sub-micron resolution level, the dendrites around the Aβ plaques in the radiatum of the hippocampus show obvious bending or truncation, and the capillaries in the subhippocampus pass through or near the plaques, and also show a certain degree of truncation or deformation, and The surface roughness is high (Fig.
3)
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The study's interpretation of Aβ plaques and various fine structures around them at the whole-brain scale will help to systematically investigate the pathological damage of neurological diseases such as AD
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Accurate extraction and accurate reconstruction of various structural information of the same sample, and obtaining the global landscape of multi-structural signals are helpful for comprehensive and precise interpretation of brain tissue structure and function, and inject new impetus into the exploration of brain disease-related pathological mechanisms
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　　The synchronous visualization method developed in this study is not only suitable for synchronous analysis of multiple structures of the whole brain under normal and pathological conditions in mice, but also for other tissues and organs of mice and other larger spatial scales of rats, monkeys and humans.
Research analysis of the MOST dataset of tissue samples
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　　Academician Jiang Hualiang, Researcher Gao Zhaobing, Researcher Zhang Haiyan and Researcher Yin Xianzhen of Lingang Laboratory are the co-corresponding authors, and Researcher Yin Xianzhen and Dr.
Zhang Xiaochuan and Dr.
Zhang Jingjing of Shanghai Institute of Materia Medica are the co-first authors of the paper
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Shanghai Institute of Materia Medica is the first completed unit
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The research was supported by the National Science Fund for Distinguished Young Scholars, the Lingang Laboratory Project, the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the Shanghai Municipal Science and Technology Major Project, the Shanghai Super Postdoctoral Fellow, and the China Postdoctoral Science Foundation
.

Figure 1 Whole-brain Aβ plaques and their simultaneous visualization with multiple brain structures

(AF) Whole-brain visualization of signals from multiple brain structures in 6-month-old 5×FAD mice
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(A) Cell body, blood vessel, nerve bundle and plaque; (B) Cell body, nerve bundle and plaque; (C) Cell body, blood vessel, and plaque; (D) Cell body and plaque; (E) Nerve bundle and plaque block; (F) Vessel and plaque
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Figure 2 Whole brain 3D visualization showing the anatomical distribution of Aβ plaques

(A) Three-dimensional lateral view of Aβ plaque distribution in the whole brain of a 6-month-old 5×FAD mouse
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(B) 3D heat map of patch density distribution
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Patch density is coded on a color scale, with dark blue being the lowest density
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(C) Statistical analysis of the number of plaques with different diameters
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Colors on the x-axis are coded by patch diameter, displayed according to different diameter ranges
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Figure 3 Abnormal dendritic structure and vascular injury around Aβ plaques

(AC) Representative high-resolution images of the hippocampal radiata showing typical Aβ plaques and their surrounding neural dendrites
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(DF) Locally demonstrate the interaction of plaque and blood vessels
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Full text link: https:// Department: MOST and Image Fusion Analysis Technical Service Department; Contributed by: Zhang Xiaochuan)