Ethanol Exposure Increases miR‐140 in Extracellular Vesicles: Implications for Fetal Neural Stem Cell Proliferation and Maturation

Background Neural stem cells ( NSC s) generate most of the neurons of the adult brain in humans, during the mid‐first through second‐trimester period. This critical neurogenic window is particularly vulnerable to prenatal alcohol exposure, which can result in diminished brain growth. Previous studies showed that ethanol (EtOH) exposure does not kill NSC s, but, rather, results in their depletion by influencing cell cycle kinetics and promoting aberrant maturation, in part, by altering NSC expression of key neurogenic mi RNA s. NSC s reside in a complex microenvironment rich in extracellular vesicles, shown to traffic mi RNA cargo between cells. Methods We profiled the mi RNA content of extracellular vesicles from control and EtOH‐exposed ex vivo neurosphere cultures of fetal NSC s. We subsequently examined the effects of one EtOH‐sensitive mi RNA , miR‐140‐3p, on NSC growth, survival, and maturation. Results EtOH exposure significantly elevates levels of a subset of mi RNA s in secreted extracellular vesicles. Overexpression of one of these elevated mi RNA s, miR‐140‐3p, and its passenger strand relative, miR‐140‐5p, significantly increased the proportion of S‐phase cells while decreasing the proportion of G 0 /G 1 cells compared to controls. In contrast, while miR‐140‐3p knockdown had minimal effects on the proportion of cells in each phase of the cell cycle, knockdown of miR‐140‐5p significantly decreased the proportion of cells in G 2 /M phase. Furthermore, miR‐140‐3p overexpression, during mitogen‐withdrawal–induced NSC differentiation, favors astroglial maturation at the expense of neural and oligodendrocyte differentiation. Conclusions Collectively, the dysregulated mi RNA content of extracellular vesicles following EtOH exposure may result in aberrant neural progenitor cell growth and maturation, explaining brain growth deficits associated with prenatal alcohol exposure.