Abstract

Introduction: Exosomes mediate intercellular communication. We tested the hypothesis that exosomes derived from different area cerebral endothelial cells (CECs) have distinct effects on adult neurogenesis. Methods and Results: Exosomes were isolated from CECs of cortical (Cor-CEC-exo) and subventricular zone (SVZ-CEC-exo) vessels of non-stroke and stroke rats (n=4/group). Neural stem cells (NSCs) from the non-stroke SVZ were treated with CEC-exo. Proliferation and differentiation of NSCs were measured by BrdU + cells and Tuj1 + neuroblasts. There were no significant differences of size distribution and marker proteins among studied exosomes. Treatment of NSCs with non-stroke Cor-CEC-exo did not significantly change NSC proliferation (35%± 2% vs 31%±2% in control) and neuronal differentiation (5%±2% vs 5%± 0.1% in control). However, treatment of NSCs with non-stoke SVZ-CEC-exo significantly (p<0.05) increased BrdU + (42%± 2%) and Tuj1 + cells (10%± 2%). These data suggest that non-stroke Cor-CEC-exo, but not SVZ-CEC-exo, do not affect neurogenesis. RT-PCR analysis showed that Cor-CEC-exo were enriched in selective miRNAs including miR-203 that is known to negatively regulate NSC proliferation. To study whether miRNAs are involved in the effect of CEC-exo on neurogenesis, we isolated NSCs in which miRNA biogenesis gene, Dicer, was ablated. Compared to wild-type (WT) NSCs, ablation of Dicer led to significant reduction of proliferation (16%±1%) and neuronal differentiation (1%±0.1%). Treatment of Dicer knockout NSCs with Cor- or SVZ-CEC-exo significantly increased BrdU+ (25%±2% or 34%±2%) and TuJ1+ cells (3%±0.1% or 5%±0.1%), suggesting that both Cor- and SVZ-CEC-exo can rescue Dicer knockout impaired neurogenesis. Moreover, both stroke Cor- and SVZ-CEC-exo significantly augmented non-stroke WT NSC proliferation (41%±3% and 51%±4%) and differentiation (9%±0.2% and 16%±0.3). Conclusion: Our data demonstrate that under non-stroke condition, Cor-CEC-exo do not promote neurogenesis, while SVZ-CEC-exo enhance neurogenesis. After stroke, both Cor-and SVZ-CEC-exo augment neurogenesis. The effect of CEC-exo on neurogenesis is mediated by miRNAs. This study provides new insight into CEC-exo in mediating neurogenesis.