Plasma-Derived Extracellular Vesicle microRNAs in Multiple Sclerosis: An Exploratory Case-Control Study on Phenotypic Discrimination.

Distinguishing relapsing-remitting multiple sclerosis (RRMS) from secondary-progressive disease (SPMS) remains a clinical challenge, as no single laboratory test reliably identifies the transition. We explored whether plasma extracellular-vesicle (EV) microRNAs could separate the two phenotypes. Four candidate EV-miRNAs: miR-30a-5p, miR-223-5p, miR-155-5p, and miR-146a-5p, were quantified by qRT-PCR in plasma-derived EVs from 13 healthy controls (HC), 7 RRMS, and 16 SPMS patients, normalized to miR-16-5p. EVs were characterized by electron microscopy, dynamic light scattering, and zeta potential, confirming vesicles of expected morphology, size, and negative surface charge. Two miRNAs were informative. miR-155-5p was significantly downregulated in both RRMS and SPMS versus controls but did not differentiate the phenotypes (AUC 0.52), behaving as a disease-general marker. In contrast, miR-223-5p was selectively reduced in SPMS, to approximately one-quarter of control abundance, and provided the only signal distinguishing progressive from relapsing disease (AUC 0.73; rank-biserial -0.46). miR-30a-5p and miR-146a-5p were uninformative. These findings, consistent with the circulating/EV literature, suggest EV-miR-223-5p as a candidate marker of the progressive phenotype and EV-miR-155-5p as a disease indicator. Given the small cohort and near-detection-limit measurements, the study is hypothesis-generating and requires validation in larger, longitudinal cohorts.