Exosomes Derived from Human Umbilical Cord Mesenchymal Stem Cells Enhance Angiogenesis Through Upregulation of the VWF and Flk1 Genes in Endothelial Cells

Exosomes derived from mesenchymal stem cells (MSCs) are crucial mediators of the paracrine effects as well as tissue repair and have promising clinical applications. They enhance tissue regeneration by reducing inflammatory responses, enhancing proliferation, inhibiting apoptosis, and stimulating angiogenesis. This study aimed to evaluate the mechanism of angiogenesis supported by exosomes derived from MSCs.Exosomes were isolated via ultracentrifugation of a conditioned medium collected from human umbilical cord MSC (hUCMSC) cultures. These exosomes were characterized using transmission electron microscopy, and the expression of specific markers (CD9, CD81, and CD63) was evaluated. To understand the mechanism of angiogenesis, we evaluated the effects of exosomes in endothelial cells (HUVECs). The obtained exosomes were supplemented at a dose of 20 μg/mL into two kinds of culture media for HUVECs (M200 medium and endothelial cell growth medium), while phosphate-buffered saline was added to these media as a control. The effects of the exosomes were evaluated based on the formation of a tubular structure in the culture and the expression of angiogenic genes (MMP-2, Ephrin B2, Ephrin B4, Flk1, Flt1, VWF, VE-cadherin, CD31, ANG1, ANG2, and HGF) via RT-PCR.The exosomes were obtained from the hUCMSCs at a concentration of 0.7 ± 0.029 μg/mL. They accelerated the formation of new blood vessels by upregulating HGF, VWF, CD31, Flt1, and Flk1 (especially VWF and Flt1).Exosomes derived from hUCMSCs can promote angiogenesis through upregulation of VWF and Flt1 in endothelial cells.