Co-localization of Gangliosides with Amyloid Beta Plaques in Alzheimer’s Disease Detected by MALDI-MSI and Histology

Alzheimer’s Disease (AD) is a progressive neurodegenerative disease characterized by cognitive impairment and behavioral changes. Historically, AD research has focused on misfolded proteins, but with advancements in mass spectrometry, lipidomics in AD has garnered increasing attention. Abnormal lipid regulation is believed to play a key role in AD pathogenesis. Gangliosides, a class of glycosphingolipids enriched in the central nervous system, have been implicated in neurodegenerative disease development, particularly the shift from complex GM1 to simpler GM2 and GM3 gangliosides. In aging brains, there is a notable increase in complex gangliosides, especially those with 20-carbon fatty acid chains.

In this study, the research team utilized Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) to investigate the in situ relationships of a-series gangliosides with 18 or 20-carbon fatty acid chains (d18:1 or d20:1) in the brains of deceased AD patients. The results showed a significant decrease in the ratio of GM1 d20:1 to GM1 d18:1 in the dentate gyrus and entorhinal cortex of AD brains. Additionally, GM3 co-localized with histologically confirmed β-amyloid plaques, and there was a significant increase in GM1 and GM3 near these plaques. This suggests that ganglioside characteristics are disrupted in AD and validates the feasibility of combining MALDI-MSI with classical histological staining within the same tissue section, advancing the integration of mass spectrometry imaging into digital pathology frameworks.

Academic Background

Alzheimer’s Disease (AD) is a debilitating neurodegenerative disease clinically characterized by gradual memory loss, cognitive decline, and behavioral changes. Annually, approximately 9.9 million new cases of AD are reported worldwide. Its neuropathological features include the deposition of β-amyloid (Aβ) plaques and the aggregation of hyperphosphorylated tau protein (neurofibrillary tangles, NFTs), accompanied by synaptic degeneration and cell death. For most AD patients, the degenerative process follows a specific pattern, forming the basis for the neuropathological staging of the disease.

With the application of new mass spectrometry imaging technologies, research into lipid metabolism abnormalities in AD has gradually unfolded. Changes in lipid transport, metabolism, and homeostasis, co-existing with AD pathological features, are believed to be significant factors driving AD progression. Based on this background, the research team aimed to further explore the spatial localization of gangliosides in AD using MALDI-MSI and their relationship with known protein markers to better understand the complex interactions between the lipidome and proteome in AD pathogenesis.

Research Source

This original research paper titled “Co-registration of MALDI-MSI and Histology Demonstrates Gangliosides Co-localize with Amyloid Beta Plaques in Alzheimer’s Disease” was authored by Nikita Ollen-Bittle, Shervin Pejhan, Stephen H. Pasternak, C. Dirk Keene, Qi Zhang, and Shawn N. Whitehead. The authors are affiliated with Western University, London Health Sciences Centre, and the University of Washington, among others. The paper was published in 2024 in Acta Neuropathologica.

Research Process

The study involved several key steps:

Sample Collection and Processing

1. Tissue Sample Selection and Ethical Approval: The study samples were derived from formalin-fixed and fresh-frozen tissues of deceased AD patients and healthy controls, approved by the London Health Sciences Centre and the University of Washington repositories and neuropathology laboratories.

2. Tissue Block Cutting and Preparation: Formalin-fixed tissue blocks were mounted on freezing frames for tissue sectioning and MALDI-MSI scanning during both the frozen and fresh tissue stages.

MALDI-MSI Data Acquisition

1. Matrix Application and Scanning: A 1,5-diaminonaphthalene matrix was diluted and sublimated on a hot plate to ensure uniform deposition on the tissue. A SCiEX 5800 TOF/TOF system was used for mass spectrometry imaging scans.

2. Low-Resolution Scanning: Initial low-resolution scans observed the distribution of gangliosides throughout the entire tissue block, revealing a significant decrease in the ratio of GM1 d20:1 to GM1 d18:1 in the hippocampus region of AD brains. Specific regions, such as the dentate gyrus and entorhinal cortex, showed a significant reduction in GM1 d20:1.

High-Resolution Scanning and Histological Staining

1. Combining High-Resolution Scanning with Histological Staining: High-resolution scans provided detailed ganglioside distribution maps in specific regions, followed by Thioflavin S staining for β-amyloid plaques.

2. Data Analysis and Statistics: Mass spectrometry imaging software analyzed the mass spectrometry data of selected regions of interest (ROIs), calculating the area proportion of relevant ganglioside peaks for statistical comparison.

Main Research Results

1. Low-Resolution MALDI-MSI Scan Results: Analysis of the hippocampus region in AD brains revealed a significant decrease in the GM1 d20:1 to GM1 d18:1 ratio in the molecular layer of the dentate gyrus and CA regions. GM1 d20:1 was notably reduced in the molecular layer of the dentate gyrus and the entorhinal cortex.

2. High-Resolution MALDI-MSI Scan Results: High-resolution scans of AD brains with significant plaque load showed that GM3 d20:1 and GM3 d18:1 co-localized with Thioflavin S-stained β-amyloid plaques. GM3 d18:1, GM3 d20:1, GM1 d18:1, and GM1 d20:1 were significantly increased in the plaque regions.

Conclusions and Research Significance

1. Research Validation: This study successfully validated the method of combining MALDI-MSI with classical histological staining, laying the foundation for integrating mass spectrometry imaging into digital pathology.

2. New Pathological Insights: The study revealed the spatial relationship of gangliosides with β-amyloid plaques in AD brains, providing a new perspective on understanding AD lipidomics.

3. Technological Innovation and Application Prospects: Combining high-resolution mass spectrometry imaging with histological staining helps advance the application of molecular changes in tissue pathology and could significantly aid in the discovery of biomarkers and therapeutic targets.

Research Highlights

1. Technological Innovation: The study developed and validated a new workflow combining MALDI-MSI with histological staining, enhancing the practicality of mass spectrometry imaging in pathology.
2. New Insights Provided: The research revealed a significant spatial co-localization of gangliosides with β-amyloid plaques in AD, offering new insights into lipidomic changes in AD.

This study, through innovative experimental techniques and detailed data analysis, demonstrated the significant co-localization of gangliosides with β-amyloid plaques in AD brains, proposing new pathological insights and research directions, and showcasing the vast potential of integrating mass spectrometry imaging with digital pathology.