Glioblastoma secretome mediates cardiovascular alterations through distinct EV populations

Introduction: Glioblastoma (GBM) is an aggressive brain tumour with rapid progression, therapy resistance, and a complex microenvironment. GBM-derived extracellular vesicles (EVs) circulate systemically, exert size-dependent effects, and mediate vascular abnormalities. Given the heart's high vascularisation, EVs may also drive cardiovascular dysfunction. While cardio-oncology focuses on therapy-related effects, the role of GBM EVs remains unclear. This study investigates how the GBM secretome contributes to cardiotoxicity, emphasising EV size. Materials & Methods: EVs from the human GBM HROG36 cell line were isolated by centrifugation/ultracentrifugation and characterised by NTA and cryo-EM. Uptake by HUVECs and rat cardiomyocytes was confirmed by immunocytochemistry. Functional effects were assessed in HUVECs (migration, tube formation, TEER, tight junctions), cardiomyocytes (contractility), and both cell types using Seahorse XFp MitoStress analysis. Results: Both EV populations entered HUVECs and cardiomyocytes within 24 h. After 72 h, large EVs impaired HUVEC tube formation but increased motility, while small EVs reduced TEER, altered ZO-1/claudin-5, and shifted metabolism toward glycolysis. Large EVs slowed contraction and relaxation in cardiomyocytes, whereas small EVs enhanced mitochondrial activity and glycolysis. Conclusion: GBM-derived EVs exert size-dependent effects, with large EVs disrupting vascular structure and cardiac contractility, and small EVs impairing endothelial barrier function and metabolism.