MicroRNA expression in extracellular vesicles as a novel blood‐based biomarker for Alzheimer's disease

Brain cell-derived small extracellular vesicles (sEVs) in blood offer unique cellular and molecular information related to the onset and progression of Alzheimer's disease (AD). We simultaneously enriched six specific sEV subtypes from the plasma and analyzed a selected panel of microRNAs (miRNAs) in older adults with/without cognitive impairment.Total sEVs were isolated from the plasma of participants with normal cognition (CN; n = 11), mild cognitive impairment (MCI; n = 11), MCI conversion to AD dementia (MCI-AD; n = 6), and AD dementia (n = 11). Various brain cell-derived sEVs (from neurons, astrocytes, microglia, oligodendrocytes, pericytes, and endothelial cells) were enriched and analyzed for specific miRNAs.miRNAs in sEV subtypes differentially expressed in MCI, MCI-AD, and AD dementia compared to the CN group clearly distinguished dementia status, with an area under the curve (AUC) > 0.90 and correlated with the temporal cortical region thickness on magnetic resonance imaging (MRI).miRNA analyses in specific sEVs could serve as a novel blood-based molecular biomarker for AD.Multiple brain cell-derived small extracellular vesicles (sEVs) could be isolated simultaneously from blood. MicroRNA (miRNA) expression in sEVs could detect Alzheimer's disease (AD) with high specificity and sensitivity. miRNA expression in sEVs correlated with cortical region thickness on magnetic resonance imaging (MRI). Altered expression of miRNAs in sEVCD31 and sEVPDGFRβ suggested vascular dysfunction. miRNA expression in sEVs could predict the activation state of specific brain cell types.