Exosomes from Human Umbilical Cord Mesenchymal Stem Cells Facilitate Diabetic Wound Healing through miR-221-3p-mediated Enhancement of Angiogenesis

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Background: Endothelial dysfunction caused by persistent hyperglycemia in diabetes is responsible for impaired angiogenesis in diabetic wounds. Exosomes are considered potential therapeutic tools to promote diabetic wound healing. The aim of this study was to investigate the effects of exosomes secreted by human umbilical cord mesenchymal stem cells (hucMSC-Exos) on angiogenesis under high glucose (HG) conditions in vivo and in vitro and to explore the underlying mechanisms.Methods: HucMSC-Exos were used to treat diabetic wounds and human umbilical vascular endothelial cells (HUVECs) exposed to HG. Wound healing and angiogenesis were assessed in vivo. The biological characteristics of HUVECs were examined in vitro. Expression of pro-angiogenesis genes in HUVECs was also examined by western blotting. The miRNAs contained within hucMSC-Exos were identified using miRNA microarrays and qRT-PCR. The roles of selected miRNAs in angiogenesis were assessed using specific agomirs and inhibitors.Results: In vivo, local application of hucMSC-Exos enhanced wound healing and angiogenesis. In vitro, hucMSC-Exos reduced senescence of HG-treated HUVECs and promoted proliferation, migration, and tube formation by inhibiting phosphatase and tensin homolog (PTEN) expression and activating the AKT/HIF-1α/VEGF pathways. MiR-221-3p was enriched in hucMSC-Exos. In vitro, MiR-221-3p downregulated PTEN and activated the AKT/HIF-1α/VEGF pathway to promote proliferation, migration, and tube formation in HG-treated HUVECs. In vivo, miR-221-3p agomirs mimicked the effects of hucMSC-Exos on wound healing and angiogenesis, whereas miR-221-3p inhibitors reversed their effects.Conclusions: Our findings suggest that hucMSC-Exos have regenerative and protective effects on HG-induced senescence in endothelial cells via transfer of miR-221-3p, thereby accelerating diabetic wound healing. Thus, hucMSC-Exos may be promising therapeutic candidates for improving diabetic wound angiogenesis.