The Role of Extracellular Vesicles in Vein Graft Disease.

Coronary artery bypass grafting (CABG) using the autologous saphenous vein (SV) remains widely performed for obstructive atherosclerosis; however, vein graft disease drives recurrent ischaemia through early thrombosis and progressive intimal hyperplasia, and accelerated atherosclerosis developing within the grafts. Extracellular vesicles (EVs) are membrane-bound particles that transfer proteins, lipids, and microRNAs between cells. They modulate endothelial dysfunction, vascular smooth muscle cell phenotypic switching, inflammation, and coagulation, which are core processes in vein graft remodelling. Arterialisation exposes the vein to abrupt rises in shear stress, cyclic stretch, and intraluminal pressure. These forces increase EV release and reshape EV cargo in experimental systems, suggesting a potential mechanism for amplifying early graft injury which warrants direct investigation in vein tissue. This review synthesises current evidence for cell-specific EV contributions from ECs, vascular smooth muscle cells, platelets, and macrophages, and appraises EV-associated microRNAs with biomarker potential relevant to graft failure pathways. We also review therapeutic strategies that may modulate EV signalling including antiplatelet therapy, statins, KCa3.1 inhibition, and pro-reparative mesenchymal stromal cell-derived EVs. No published clinical studies evaluate EV-based biomarkers specifically for saphenous vein graft patency, and none prospectively predict saphenous graft failure. CABG provides a well-defined time zero event that enables longitudinal sampling and risk stratification. Prospective studies linking EV phenotypes and miRNA signatures to imaging-defined graft outcomes are needed to support clinical translation.