Exosomal microRNAs from ischemic cerebral endothelial cells and neural stem cells regulate coupling of neurogenesis and angiogenesis

Introduction: Molecular mechanisms underlying coupling of angiogenesis and neurogenesis remain unknown. We tested the hypothesis that exosomes mediate coupling of stroke-induced angiogenesis and neurogenesis by transferring exosomal cargo miRNAs between ischemic cerebral endothelial cells (CECs) and neural stem cells (NSCs). Methods and Results: Cell-type specific exosomes were purified from conditional media of cultured CECs and NSCs harvested from non-ischemic and ischemic rats, respectively. Exosome markers and size distribution were verified with Western blot and transmission electron microscopy, respectively. Using an advanced Cre-Loxp system, we found CEC-exosomes carrying Cre recombinase were taken up by recipient NSCs to induce genome recombination. We then tested if exosomal miRNAs mediated cell-to-cell interplay. First, using miRNA array, we identified that miR-146a and miR-125a were the most upregulated miRNAs in ischemic CECs-exosomes. Incubation of non-ischemic NSCs with ischemic CECs-exosomes substantially increased these two miRNA levels in recipient NSCs, which led to downregulation of their target genes, IRAK1, TRAF6 as well as BAK1 and KLF13, consequently leading to an increase in Tuj1 and NG2 cells (