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The localization of molecularly distinct microglia populations to Alzheimer's disease pathologies using QUIVER
Ryan K Shahidehpour1,2, Abraham S Nelson1, Lydia G Sanders1
1Spinal Cord and Brain Injury Research Center, University of Kentucky, 741 S. Limestone St., Lexington, KY, 40536, USA.
Insights
A new method called QUIVER enables detailed protein analysis in aging human brain tissue, revealing how microglia respond to Alzheimer's disease pathology. This technique helps understand brain aging and disease.
Area of Science:
- Neuroscience
- Pathology
- Biotechnology
Background:
- Spatial proteomics advances tumor microenvironment studies but is underutilized in aging human brain research.
- Post-mortem brain tissue presents challenges like autofluorescence, limiting traditional fluorescence microscopy.
- Developing novel histological techniques is crucial for understanding protein distribution and disease pathology in human tissues.
Purpose of the Study:
- To develop a multiplex immunohistochemistry approach for analyzing protein distribution in aging human brain tissue.
- To address technical challenges in post-mortem brain tissue analysis, including fixation and autofluorescence.
- To investigate the impact of Alzheimer's disease hallmarks (amyloid plaques, neurofibrillary tangles) on microglia phenotypes.
Main Methods:
- Developed Quantitative multiplex Immunohistochemistry with Visual colorimetric staining to Enhance Regional protein localization (QUIVER).
- Generated ten-channel pseudo-fluorescent images using chromogen removal and digital microscopy.
- Utilized digital pathology tools to visualize and analyze five molecular microglia/macrophage phenotypes in relation to neuropathology.
Main Results:
- QUIVER successfully identified unique molecular microglia phenotypes in human brain tissue.
- Demonstrated spatial polarization of reactive microglia towards amyloid plaques and homeostatic microglia away from them.
- Observed a discrepancy between microglia morphology and molecular phenotype in the context of Alzheimer's disease pathology.
Conclusions:
- QUIVER is a novel tool for examining pathological alterations in the aging human brain.
- Provides insights into microglia biology and their dynamic response to Alzheimer's disease-associated pathologies.
- Highlights the importance of molecular phenotyping over morphology for understanding microglia in disease states.
Abstract:
New histological techniques are needed to examine protein distribution in human tissues, which can reveal cell shape and disease pathology connections. Spatial proteomics has changed the study of tumor microenvironments by identifying spatial relationships of immunomodulatory cells and proteins and contributing to the discovery of new cancer immunotherapy biomarkers. However, the fast-expanding toolkit of spatial proteomic approaches has yet to be systematically applied to investigate pathological alterations in the aging human brain in health and disease states. Moreover, post-mortem human brain tissue presents distinct technical problems due to fixation procedures and autofluorescence, which limit fluorescence methodologies. This study sought to develop a multiplex immunohistochemistry approach (visualizing the immunostain with brightfield microscopy). Quantitative multiplex Immunohistochemistry with Visual colorimetric staining to Enhance Regional protein localization (QUIVER) was developed to address these technical challenges. Using QUIVER, a ten-channel pseudo-fluorescent image was generated using chromogen removal and digital microscopy to identify unique molecular microglia phenotypes. Next, the study asked if the tissue environment, specifically the amyloid plaques and neurofibrillary tangles characteristic of Alzheimer's disease, has any bearing on microglia's cellular and molecular phenotypes. QUIVER allowed the visualization of five molecular microglia/macrophage phenotypes using digital pathology tools. The recognizable reactive and homeostatic microglia/macrophage phenotypes demonstrated spatial polarization towards and away from amyloid plaques, respectively. Yet, microglia morphology appearance did not always correspond to molecular phenotype. This research not only sheds light on the biology of microglia but also offers QUIVER, a new tool for examining pathological alterations in the brains of the elderly.
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