Abstract

The neural stem and intermediate progenitors (NSPCs) proliferate and differentiate into neurons in the adult hippocampal neurogenic niche. A key component of the neurogenic niche that links systemic signals with NSPCs are astrocytes, being able to modulate the neurogenesis by means of cell–cell contact and the secretion of soluble factors. Stress conditions and the subsequent elevation of systemic glucocorticoids modify the proliferation and/or differentiation of NSPCs. Astrocytes in the neurogenic niche suffer structural and functional modifications after stress, negatively affecting the neurogenesis process. The secretion of small extracellular vesicles by astrocytes may contribute to it. Astrocyte-derived small extracellular vesicles (sEVs) containing biologically active cargo such as miRNA can modulate the biology of neural stem precursor cells (NSPCs) under stress conditions. The miRNA content of astrocyte-derived sEVs positively regulate neurogenesis, while under stress conditions a negative regulation, mediated by a different miRNA cargo in sEVs, is induced. Here, we review how stressful conditions alter hippocampal neurogenesis and how astrocyte-derived sEVs are involved with special reference to their miRNA content.