Impact of PCSK5, cargoed by apoptotic endothelial exosome-like vesicles, on vascular repair and angiogenesis

Ischemic preconditioning consists of a first ischemic stress that protects vascularized organs from a second and more intense ischemic episode. In this study, we characterize the functional role of extracellular vesicles (EVs) produced by apoptotic endothelial cells as potential mediators of ischemic preconditioning. We performed characterization of proteomic signatures in human umbilical vein endothelial cells (HUVECs) exposed to either apoptotic bodies (ApoBodies) or apoptotic exosome-like vesicles (ApoExos) derived from serum-starved apoptotic endothelial cells. Although both types of EVs modified endothelial proteomes, ApoExos uniquely induced strong responses associated with vascular repair and angiogenesis. Treatment of endothelial cells in vitro with ApoExos increased angiogenesis and wound closure, while intravenous injection of endothelial ApoExos in a murine hind limb ischemia model significantly increased revascularization and capillary density. We then investigated whether PCSK5, the most highly expressed mRNA cargoed by endothelial ApoExos, is playing a role in the induction of this pro-angiogenic activity. Endothelial cells transfected with PCSK5 in vitro exhibited enhanced angiogenesis and wound closure. Localized injection of a PCSK5-expressing plasmid vector increased reperfusion 7 days after induction of hind limb ischemia in mice. Taken together, these results identify PCSK5, cargoed by endothelial ApoExos, as a novel mediator of vascular repair and angiogenesis after ischemic injury.