Bioactivity and Micro RNA Profile of Mesenchymal Stem Cell Neural Progenitor-Derived Extracellular Vesicles

Mesenchymal stem cell-derived neural progenitors (MSC-NPs) are currently being investigated clinically as a novel cellular therapy aimed at promoting repair and regeneration in patients with progressive multiple sclerosis (MS). Recent results from an open-label phase I clinical trial demonstrated functional neurological improvement in 15 out of 20 progressive MS patients after repeated intrathecal MSC-NP injection. Pre-clinical studies in the EAE mouse model of MS showed that neurological recovery after MSC-NP injection was associated with increased spinal cord myelination, decreased immune infiltration in the CNS, and increased recruitment of endogenous progenitor cells. In addition, in vitro co-culture experiments demonstrated trophic and immunomodulatory effects of MSC-NPs and also conditioned media from MSC-NPs. The specific mechanism by which MSC-NPs exert proximal influence on CNS progenitor populations remains unknown. Extracellular vesicles (EVs) consisting of exosomes and/or microvesicles mediate cell-to-cell communication through transfer of protein and miRNA cargo. We investigated whether MSC-NP-derived EVs could mediate some of the reparative effects of these cells in models of MS. MSC and MSC-NP-derived EVs were purified from 3 day cell-conditioned media by membrane affinity and size exclusion columns. EV concentration and size were quantitated by tunable resistive pulse sensing technology (qNano). Purified EVs were added to cultured rat neural stem cells on day 0 of differentiation by growth factor withdrawal. EVs were found to exert a trophic effect on oligodendroglial differentiation resulting in an increase in the number of mature galactosylceramidase-positive oligodendrocytes. In order to identify candidate micro RNAs (miRNAs) that mediate the trophic effects of MSC-NP EVs, we analyzed EV miRNA expression by qPCR and demonstrated expression of a panel of miRNAs including miR-let7c and let7f. Additional results from miRNA profiling from EVs will be presented. These results suggest that the trophic effects of MSCs and MSC-NPs in MS can be mediated through EV release.

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