Exosomes derived from ischemic cerebral endothelial cells promote axonal growth
Zhang Y, Chopp M, Li C, Liu XS, Wang X, Zhang L, and Zhang ZG. Exosomes derived from ischemic cerebral endothelial cells promote axonal growth. Stroke 2019; 50(Suppl 1):A57.
Axonal remodeling is a critical aspect of spontaneous brain repair after stroke. Stroke activates cerebral endothelial cells (CECs) in ischemic blood vessels. Communications between activated CECs and axonal remodeling in ischemic brain have not been fully investigated. Exosomes play vital roles in intercellular communication. We investigated the effect of exosomes derived from CECs harvested from vessels of ischemic rat brains (isCEC-exos) on axonal growth of cortical neurons. Application of isCEC-exos into axons of the neurons cultured in a microfluidic device which separates axons from their somata resulted in significant (p<0.05, n=45 axons) increases of axonal growth (982±24 μm) compared to CEC-exos derived from non-ischemic vessels (nCEC-exos, 793±19 μm). nCEC-exos significantly enhanced axonal growth compared to non-treatment (567±14 μm). Axonal internalization of CEC-exos was confirmed by tracking GFP-exosomes. qRT-PCR and miRNA PCR array analysis revealed that compared to nCEC-exos, >50 mature miRNAs were enriched within isCEC-exos, including miR-19a. Axonal application of isCEC-exos elevated these miRNAs and their pre-miRNAs in axons and somata (from 21 to 85 folds, n=3, p<0.01) compared to non-treated group. Because CEC-exos do not contain the precursor form of miRNAs, these data suggest that CEC-exos transfer their mature miRNAs into distal axons, which triggered increases in precursor and mature miRNAs in distal axons and somata. Moreover, compared to the non-treated group, Western blot analysis (n=3/group) showed that axonal application of isCEC-exos locally reduced axonal growth inhibitory proteins, PTEN (~90%), Sema6A (~75%), and RhoA (~99%), which was inversely associated with increased miRNAs that target these proteins. Furthermore, transient blockage of ribosome translocation with emetine, a protein synthesis inhibitor, in axons abolished the effect of isCEC-exos on distal axonal growth and on alteration of miRNAs and their target proteins. Collectively, our data demonstrate that isCEC-exos internalized by distal axons facilitate axonal growth by altering miRNAs and their target protein profiles in recipient neurons, and these exosomes may potentially provide a therapeutic means to enhance axonal growth.