Abstract 167: Exosomes Derived from Mesenchymal Stromal Cells Promote Axonal Outgrowth
Exosomes, small lipid microvesicles, transfer RNAs and proteins thereby mediating cell-cell communication. The present study investigated the effect of exosomes released from mesenchymal stromal cells (MSCs) on axonal outgrowth, that may play an important role in promoting brain repair after stroke.
Embryonic cortical neurons were cultured in a microfluidic culture device which separates somata and axons. Exosomes (3x109 particles/ml) harvested from MSCs were applied into the somal chamber. 24h in culture, exosomes increased axonal growth (396±8 vs 297±9 μm in non-treated axon, p<0.001, n=6). To examine whether miRNAs in exosomes mediate axonal growth, neurons were treated with exosomes with attenuated-Ago2, a key protein regulates miRNA biogenesis, derived from Ago2 knockdown MSCs. These exosomes abolished the axonal growth increased by exosomes from MSCs transfected with control siRNA (298±8 μm vs 396±11 μm in control, p<0.001, n=3), suggesting that miRNAs in exosomes mediate the exosome-enhanced axonal growth. We previously showed that the miR-17-92 cluster enhances axonal growth. Thus, we treated neurons with miR-17-92 cluster elevated-exosomes from MSCs transfected with a miR-17-92 vector. Compared to non-exosome treatment, neurons treated with exosomes from MSCs transfected with a control vector considerably increased axonal growth (406±8 μm, p<0.001, n=6). Moreover, neurons treated with miR-17-92 cluster elevated-exosomes exhibited further increases in axonal growth (595±10 μm, p<0.001, n=6). RT-PCR showed substantial elevation of individual members of the miR-17-92 cluster in axons of the neurons treated with the miR-17-92 cluster elevated-exosomes, which was associated with reduction of their target protein, PTEN, in axons. Western blots also showed that reduction of axonal PTEN by the miR-17-92 cluster elevated-exosomes activated PTEN downstream proteins mTOR and GSK3β, indicating that the miR-17-92 cluster delivered by exosomes targets the PTEN/GSK3β pathway in axons.
Conclusion: The present study demonstrates that miRNAs in the exosomes can be delivered into neurons to promote axonal growth, which provides a novel therapy to enhance axonal growth.
Author Disclosures: Y. Zhang: None. M. Chopp: None. M. Katakowski: None. X. Liu: None. Z. Zhang: None.
- © 2015 by American Heart Association, Inc.