miRNAs of Astrocyte-Derived Small Extracellular Vesicles Potentially Modulate Adult Neurogenesis Under Stress Conditions

Stressful conditions can alter neurogenesis in the dentate gyrus of the hippocampus, but the mechanisms underlying this phenomenon remain unclear. It is well known that astrocytes form nodal points that connect the systemic signals with the microenvironment of the neurogenic niche; they can interact with adult neural stem and progenitor cells (NSPCs) either through cell-cell contact or by the release of soluble factors for modulating their biology. In this regard the latest evidence suggests that astrocyte-derived small extracellular vesicles (sEVs) may be essential. Different biologically active molecules have been described as integral components of sEVs, including miRNAs, whose deregulation could generate a reduced proliferative/self-renewal potential and defective neurogenesis, as well as aberrant migration of neuroblasts/immature neurons. In this chapter, we review the current knowledge about how stressful conditions alter the hippocampal neurogenesis and how astrocyte-derived sEVs are involved, making special focus on their miRNA cargo.