Endothelial progenitor cell (EPC) based therapy promotes neovascularization in ischemic myocardium. Studies suggest that therapeutic effect of stem cells is largely due to paracrine mechanisms including stem cell-derived exosomes that are emerging as key paracrine mediators of stem cell functions. However, the autologous transplantation of EPCs in patients with systemic inflammation, which is a common symptom in patients with ischemic heart diseases, yield modest results suggesting the compromised cell function and altered exosome performance. We hypothesized that EPCs under inflammatory stress secrete dysfunctional exosomes with altered contents including packaged microRNAs, which eventually compromises exosomes repair ability in ischemic myocardium. Whether modulation of identified targets like specific microRNAs in the cargo of exosomes can rescue and/or enhance their reparative properties of dysfunctional exosomes is not known. We have previously shown in Interleukin-10 (IL-10) KO mice (model mimicking systemic inflammation) that loss of IL-10 impairs EPCs functions via miR-375. After cell expansion, we isolated exosomes from these two groups and compared their functions in terms of cell survival, proliferation, migration and angiogenic capacity
in vitro
and
in vivo
. We report that WT-EPC-exosomes (Exo) transplantation in the ischemic myocardium after MI significantly improved post-infarct repair, neovascularization and left ventricle functions. Our
in vitro
studies revealed that WT-EPC-Exo treatment enhanced endothelial cells proliferation and tube formation and inhibited apoptosis; whereas IL-10 KO-EPC-Exo exhibited opposite effects, suggesting that reparative capacity of WT-EPC-Exo is lost in exosomes derived from IL-10 KO-EPCs. Exosome miRNA profiling revealed a drastically different expression patterns with enrichment of inflammation induced microRNAs including significantly higher expression of miR-375. Interestingly, Knockdown of miR-375 in IL-10-EPCs decreased the expression level of miR-375 in their exosomes and partly rescued their angiogenic dysfunctions. Taken together, our studies suggest that modulation of miR-375 in IL-10 KO-EPC-Exo can rescue its phenotype and promote cardiac repair.
Phosphoinositide 3-Kinase γ Gene Knockout Impairs Postischemic Neovascularization and Endothelial Progenitor Cell Functions
