L1CAM-Enriched Extracellular Vesicle MicroRNAs in Mild Cognitive Impairment and Alzheimer’s Disease: An Exploratory Study

Early diagnosis of Alzheimer’s disease (AD) and the identification of reliable molecular biomarkers remain critical clinical needs. In this context, extracellular vesicles (EVs) enriched by L1CAM immunocapture—L1CAM-enriched EVs—a fraction widely used to obtain material of putative neuronal origin, have been proposed as a minimally invasive source of information on brain molecular changes. We conducted next-generation sequencing (NGS) of microRNAs (miRNAs) from L1CAM-enriched EVs isolated from the plasma of 11 AD patients, 11 mild cognitive impairment (MCI) individuals, and 14 healthy controls (CTRs) to identify a candidate molecular signature. Our analysis identified five differentially expressed miRNAs—miR-423-5p, miR-122-5p, miR-151b, miR-16-5p, and miR-149-3p—in MCI individuals. Three of these—miR-423-5p, miR-122-5p and miR-151b—were higher in MCI and lower in AD, a pattern that differentiated the two clinically defined groups. Furthermore, enrichment analysis of the predicted targets of the differentially expressed miRNAs identified processes relevant to neurodegeneration, including synaptic organisation, cytoskeletal dynamics, and protein degradation. Overall, these preliminary findings identify blood-based L1CAM-enriched EV miRNAs as candidates for further evaluation in cognitive impairment. While validation in larger, biomarker-confirmed and independent cohorts is required, this exploratory study provides data that may guide the design of future biomarker studies.