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Updated: Aug 12, 2025
Enrichment of Astrocyte-Derived Extracellular Vesicles from Human Plasma
Published on: August 3, 2022
Plasma derived extracellular vesicle biomarkers of microglia activation in an experimental stroke model
A D Roseborough1, S J Myers1, R Khazaee2,3
1Vulnerable Brain Laboratory, Department of Anatomy and Cell Biology, The Schulich School of Medicine and Dentistry, The University of Western Ontario, 458 Medical Sciences Building, ON, N6A 3K, London, Canada.
Abstract:
Chronic microglia activation post-stroke is associated with worse neurological and cognitive outcomes. However, measurement of microglia activation in vivo is currently limited. Plasma derived extracellular vesicles (EVs) are cell-specific indicators that may allow for non-invasive measurement of microglia phenotype. The aim of this study was to identify activation-state specific microglia EVs (MEVs) in vitro followed by validation in an experimental stroke model. Following pro-inflammatory activation, MEVs contain the microglia protein TMEM119 alongside increased expression of the Toll-like receptor 4 co-receptor CD14. Immunoprecipitation followed by fluorescent nanoparticle tracking analysis (ONI Nanoimager) was used to confirm the isolation of TMEM119+/CD14+ EVs from rat plasma. Electron microscopy confirmed that TMEM119 and CD14 localize to the MEV membrane. To model ischemia, plasma was collected from 3-month wildtype Fischer344 rats prior to, 7 and 28 days after endothelin-1 or saline injection into the dorsal right striatum. Fluorescently labelled MEVs were directly measured in the plasma using nanoflow cytometry (Apogee A60 Microplus). We report a significant increase in circulating TMEM119+/CD14+ EVs 28-days post-stroke in comparison to baseline levels and saline-injected rats, which correlated weakly with stroke volume. TMEM119+/MHC-II+ EVs were also increased post-stroke in comparison to baseline and saline-injected animals. This study is the first to describe an EV biomarker of activated microglia detected directly in plasma following stroke and represents a future tool for the measurement of microglia activity in vivo.
Insights
Researchers identified specific microglial extracellular vesicles (MEVs) in plasma that indicate brain inflammation after stroke. This discovery offers a potential non-invasive method to track microglia activation in vivo.
Area of Science:
- Neuroscience
- Immunology
- Biomarker Discovery
Background:
- Chronic microglia activation following stroke is linked to poor neurological and cognitive outcomes.
- Current methods for measuring microglia activation in vivo are limited.
- Plasma-derived extracellular vesicles (EVs) show potential as non-invasive biomarkers for cell phenotypes.
Purpose of the Study:
- To identify activation-state specific microglia EVs (MEVs) in vitro.
- To validate these MEVs as biomarkers in an experimental stroke model.
- To establish a method for in vivo measurement of microglia activity.
Main Methods:
- Pro-inflammatory activation of microglia to identify specific EV markers (TMEM119, CD14).
- Isolation and characterization of MEVs using immunoprecipitation and electron microscopy.
- Induction of experimental stroke in rats and collection of plasma at multiple time points.
- Quantification of MEVs in plasma using nanoflow cytometry.
Main Results:
- Activated MEVs were characterized by TMEM119 and increased CD14 expression.
- A significant increase in circulating TMEM119+/CD14+ EVs was observed 28 days post-stroke.
- Elevated TMEM119+/MHC-II+ EVs were also detected post-stroke.
- Increased MEV levels correlated weakly with stroke volume.
Conclusions:
- This study describes the first EV biomarker for activated microglia detectable directly in plasma after stroke.
- TMEM119+/CD14+ and TMEM119+/MHC-II+ EVs serve as potential indicators of post-stroke microglia activation.
- These findings represent a promising future tool for non-invasive in vivo monitoring of microglia activity.
