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Administration of human cord blood endothelial colony-forming cells (ECFCs) or their exosomes protects mice against kidney ischemia/reperfusion injury. Here we studied the microRNA (miRNA) content of ECFC exosomes and the role of miRNA transfer in kidney and endothelial cell protection. ECFC exosomes were enriched in miR-486-5p, which targets the phosphatase and tensin homolog (PTEN) and the Akt pathway. In cultured endothelial cells exposed to hypoxia, incubation with ECFC exosomes increased miR-486-5p, decreased PTEN, and stimulated Akt phosphorylation. Exposure of hypoxic endothelial cells to conditioned medium from ECFCs pretreated with anti-miR-486-5p blocked increases in miR-486-5p and phosphorylated Akt, restored expression of PTEN, and enhanced apoptosis. Coculture of endothelial cells with ECFCs enhanced endothelial miR-486-5p levels. Targeting of PTEN by miR-486-5p was observed in endothelial cells, and PTEN knockdown blocked apoptosis. In mice with ischemic kidney injury, infusion of ECFC exosomes induced potent functional and histologic protection, associated with increased kidney miR-486-5p levels, decreased PTEN, and activation of Akt. Infusion of exosomes from ECFCs transfected with anti-miR-486-5p had no protective effect. Thus, delivery of ECFC exosomes reduces ischemic kidney injury via transfer of miR-486-5p targeting PTEN. Exosomes enriched in miR-486-5p could represent a therapeutic tool in acute kidney injury.

Endothelial colony forming cell (ECFC)-derived exosomes protect mice against ischemic kidney injury, via transfer of microRNA-(miR)-486-5p. Mechanisms mediating exosome recruitment to tissues are unclear. We hypothesized that ECFC exosomes target ischemic kidneys, involving interaction between exosomal CXC chemokine receptor type 4 (CXCR4) and stromal cell-derived factor (SDF)-1α. Ischemia-reperfusion was induced in mice by bilateral renal vascular clamp, with intravenous infusion of exosomes at reperfusion. Optical imaging determined exosome biodistribution, and miR-486-5p was measured by real-time PCR. Human umbilical vein endothelial cells (HUVECs) were cultured to study the CXCR4/SDF-1α interaction. Targeting of administered exosomes to ischemic kidneys was detected 30 min and 4 hrs after reperfusion. Exosomes increased miR-486-5p levels only in kidneys, within proximal tubules, glomeruli, and endothelial cells. Uptake of fluorescently-labeled exosomes into HUVECs, and exosomal transfer of miR-486-5p were enhanced by hypoxia, effects blocked by neutralizing antibody to SDF-1α or by the CXCR4 inhibitor plerixafor. Infusion of ECFC exosomes prevented ischemic kidney injury in vivo, an effect that was not observed when exosomes were pre-incubated with plerixafor. These data indicate that ECFC exosomes selectively target the kidneys after ischemic injury, with rapid cellular transfer of miR486-5p. Targeting of exosomes may involve interaction of CXCR4 with endothelial cell SDF-1α.

The administration of certain progenitor cells is protective in experimental acute kidney injury (AKI), and mechanisms may involve the release of paracrine factors. Endothelial colony-forming cells (ECFCs) are endothelial precursor cells with a high proliferative capacity and pro-angiogenic potential. We examined the effects of human umbilical cord blood-derived ECFCs and their extracellular vesicles in a mouse model of ischemic AKI and in cultured human umbilical vein endothelial cells subjected to hypoxia/reoxygenation. In mice with ischemic AKI, administration of ECFCs (i.v.) at the time of reperfusion significantly attenuated increases in plasma creatinine, tubular necrosis, macrophage infiltration, oxidative stress, and apoptosis, without cell persistence in the kidneys. In cultured human umbilical vein endothelial cells, hypoxia/reoxygenation stimulated apoptosis. This effect was inhibited by incubation with conditioned medium or exosomes (40- to 100-nm diameter) derived from ECFCs, but not by microparticles (100- to 1000-nm diameter) or vesicle-depleted conditioned medium. Administration of exosomes (i.v.) directly to mice with ischemic AKI attenuated renal injury, as assessed by plasma creatinine, tubular necrosis, and apoptosis. Taken together, these studies indicate protective effects of human cord blood-derived ECFCs in experimental AKI and suggest that ECFC-derived exosomes may mediate the protective response via inhibition of endothelial cell apoptosis.

The administration of certain progenitor cells is protective in experimental acute kidney injury (AKI), and mechanisms may involve the release of paracrine factors. Endothelial colony-forming cells (ECFCs) are endothelial precursor cells with a high proliferative capacity and pro-angiogenic potential. We examined the effects of human umbilical cord blood-derived ECFCs and their extracellular vesicles in a mouse model of ischemic AKI and in cultured human umbilical vein endothelial cells subjected to hypoxia/reoxygenation. In mice with ischemic AKI, administration of ECFCs (i.v.) at the time of reperfusion significantly attenuated increases in plasma creatinine, tubular necrosis, macrophage infiltration, oxidative stress, and apoptosis, without cell persistence in the kidneys. In cultured human umbilical vein endothelial cells, hypoxia/reoxygenation stimulated apoptosis. This effect was inhibited by incubation with conditioned medium or exosomes (40- to 100-nm diameter) derived from ECFCs, but not by microparticles (100- to 1000-nm diameter) or vesicle-depleted conditioned medium. Administration of exosomes (i.v.) directly to mice with ischemic AKI attenuated renal injury, as assessed by plasma creatinine, tubular necrosis, and apoptosis. Taken together, these studies indicate protective effects of human cord blood-derived ECFCs in experimental AKI and suggest that ECFC-derived exosomes may mediate the protective response via inhibition of endothelial cell apoptosis.