Cerebral endothelial derived exosomes abolish cognitive impairment induced by ablation of dicer in adult neural progenitor cells
Zhang RL, Pan W, Zhang X, Liu X, Landschoot-Ward J, Li C, Fan B, Wang X, Chopp M, and Zhang ZG. Cerebral endothelial derived exosomes abolish cognitive impairment induced by ablation of dicer in adult neural progenitor cells. Stroke 2017; 48 (Suppl 1).
Introduction: Dicer processes precursor miRNAs into mature miRNAs. We have demonstrated that conditional knockout of Dicer (Dicer/Cko) in adult neural progenitor cells (NPCs) impairs neurogenesis and cognitive function. The present study tested the hypothesis that cerebral endothelial-derived exosomes carrying mature miRNAs promote neurogenesis and improve cognitive function by communication with NPCs in Dicer/Cko mice. Methods and Results: Exosomes harvested from cultured cerebral endothelial cells (CEC-Ex, 1x109 exosomes) were intranasally administered twice a week for two consecutive weeks into mice (n=10) with conditional ablation of Dicer (Dicer/Cko) in NPCs (Ascl1-CreER:Dicerflox/flox). Dicer/Cko mice treated with saline (n=12) were used as control. Cognitive tests were performed, including Morris Water Maze (MWM) for hippocampal related learning and memory, odor-based novelty recognition for olfactory memory, and social interaction for memory of interactions with novel conspecifics. Compared to wild-type mice,Dicer/Cko mice treated with saline exhibited substantial cognitive impairment. The CEC-Ex treatment diminished cognitive deficits and these mice exhibited an increase of 40% more time spent in the correct quadrant (p<0.05) of the MWM, and increased time exploring new odor objects (71±9% vs 41 ±10% saline, p<0.05) and increased time in contact with a strange mouse during the sociability test. Using a Cre/flox reporter approach, we found that the exosomes carrying Cre mRNA entered NPCs in the subventricular zone (SVZ) and dentate gyrus (DG). The CEC-Ex treatment significantly (p<0.05) increased BrdU NPCs (20 ± 1% vs 14 ± 2%, SVZ, 16±1% vs 12±3%, DG ) and DCX+ neuroblasts (27 ± 2% vs 22 ± 3%, SVZ, 33 ± 2% vs 25 ± 3%, DG), and reduced apoptotic cells by more than 50% in these two areas. RT-PCR analysis showed that Dicer/Cko mice exhibited substantial reduction of mature miRNAs that regulate neurogenesis including miR-124, -146a and -17-92 cluster in NPCs, whereas the CEC-Ex treatment increased these mature miRNAs in Dicer/Cko NPCs. Conclusion: The CEC-Ex can reverse impaired neurogenesis and cognitive function induced by ablation of Dicer, which is likely attributed to the delivery of mature miRNAs into NPCs by CEC-Ex.