The Microglial Transcriptome of Age-Associated Deep Subcortical White Matter Lesions Suggests a Neuroprotective
Taghreed Almansouri1,2, Rachel Waller1, Stephen B Wharton1
1Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield S10 2HQ, UK.
Abstract:
Age-associated deep-subcortical white matter lesions (DSCLs) are an independent risk factor for dementia, displaying high levels of CD68+ microglia. This study aimed to characterize the transcriptomic profile of microglia in DSCLs and surrounding radiologically normal-appearing white matter (NAWM) compared to non-lesional control white matter. CD68+ microglia were isolated from white matter groups (n = 4 cases per group) from the Cognitive Function and Ageing Study neuropathology cohort using immuno-laser capture microdissection. Microarray gene expression profiling, but not RNA-sequencing, was found to be compatible with immuno-LCM-ed post-mortem material in the CFAS cohort and identified significantly differentially expressed genes (DEGs). Functional grouping and pathway analysis were assessed using the Database for Annotation Visualization and Integrated Discovery (DAVID) software, and immunohistochemistry was performed to validate gene expression changes at the protein level. Transcriptomic profiling of microglia in DSCLs compared to non-lesional control white matter identified 181 significant DEGs (93 upregulated and 88 downregulated). Functional clustering analysis in DAVID revealed dysregulation of haptoglobin-haemoglobin binding (Enrichment score 2.5, p = 0.017), confirmed using CD163 immunostaining, suggesting a neuroprotective microglial response to blood-brain barrier dysfunction in DSCLs. In NAWM versus control white matter, microglia exhibited 347 DEGs (209 upregulated, 138 downregulated), with significant dysregulation of protein de-ubiquitination (Enrichment score 5.14, p < 0.001), implying an inability to maintain protein homeostasis in NAWM that may contribute to lesion spread. These findings enhance understanding of microglial transcriptomic changes in ageing white matter pathology, highlighting a neuroprotective adaptation in DSCLs microglia and a potentially lesion-promoting phenotype in NAWM microglia.
Insights
Microglia in deep-subcortical white matter lesions show a neuroprotective response to blood-brain barrier damage. In contrast, microglia in normal-appearing white matter may promote lesion spread due to impaired protein homeostasis.
Area of Science:
- Neuroscience
- Genomics
- Pathology
Background:
- Age-associated deep-subcortical white matter lesions (DSCLs) are linked to dementia and characterized by CD68-positive microglia.
- Understanding microglial behavior in white matter lesions is crucial for dementia research.
Purpose of the Study:
- To characterize the transcriptomic profile of microglia in DSCLs and surrounding normal-appearing white matter (NAWM) compared to control white matter.
- To investigate the functional implications of microglial gene expression changes in aging white matter pathology.
Main Methods:
- Immuno-laser capture microdissection (immuno-LCM) to isolate CD68+ microglia from post-mortem white matter.
- Microarray gene expression profiling to identify differentially expressed genes (DEGs).
- Functional and pathway analysis using DAVID software, validated by immunohistochemistry.
Main Results:
- Microglia in DSCLs exhibited 181 DEGs, with pathways suggesting a neuroprotective response to blood-brain barrier dysfunction (e.g., haptoglobin-haemoglobin binding).
- Microglia in NAWM showed 347 DEGs, with significant dysregulation in protein de-ubiquitination, indicating impaired protein homeostasis.
- Immunohistochemistry confirmed altered protein levels, supporting transcriptomic findings.
Conclusions:
- Microglia in DSCLs display adaptive, potentially neuroprotective responses.
- Microglia in NAWM may have a phenotype that contributes to lesion progression.
- These findings offer insights into microglial roles in aging white matter diseases and dementia risk.
