MiR-142-3p regulates synaptopathy-driven disease progression in multiple sclerosis

Aim: We recently proposed miR-142-3p as a molecular player in inflammatory synaptopathy, a new pathogenic hallmark of multiple sclerosis (MS) and of its mouse model experimental autoimmune encephalomyelitis (EAE), that leads to neuronal loss independently of demyelination. MiR-142-3p seems to be unique among potential biomarker candidates in MS, since it is an inflammatory miRNA playing a dual role in the immune and central nervous systems. Here, we aimed to verify the impact of miR-142-3p circulating in the cerebrospinal fluid (CSF) of MS patients on clinical parameters, neuronal excitability and its potential interaction with disease modifying therapies (DMTs). Methods and Results: In a cohort of 151 MS patients, we found positive correlations between CSF miR-142-3p levels and clinical progression, IL-1β signalling as well as synaptic excitability measured by transcranial magnetic stimulation. Furthermore, therapy response of patients with ‘low miR-142-3p’ to dimethyl fumarate (DMF), an established disease-modifying treatment (DMT), was superior to that of patients with ‘high miR-142-3p’ levels. Accordingly, the EAE clinical course of heterozygous miR-142 mice was ameliorated by peripheral DMF treatment with a greater impact relative to their wild type littermates. In addition, a central protective effect of this drug was observed following intracerebroventricular and ex vivo acute treatments of EAE wild type mice, showing a rescue of miR-142-3p-dependent glutamatergic alterations. By means of electrophysiology, molecular and biochemical analysis, we suggest miR-142-3p as a molecular target of DMF. Conclusion: MiR-142-3p is a novel and potential negative prognostic CSF marker of MS and a promising tool for identifying personalised therapies.