Spleen-derived Small Extracellular Vesicles Protect against Myocardial Infarction via Mediating Spleen-heart Crosstalk

Background and Aims: Acute myocardial infarction (AMI) triggers systemic responses that influence cardiac injury and repair, but protective mediators within the cardiosplenic axis remain incompletely understood. This study aimed to investigate whether spleen-derived small extracellular vesicles (sEVs) exert cardioprotection after AMI, identify critical cargo, and evaluate their clinical relevance. Methods: The effects of splenectomy, spleen derived sEVs and pharmacological inhibition of sEVs biogenesis on cardiac injury were evaluated in mice with AMI. Parabiosis, donor splenectomy, and fluorescent labelling traced the origin and myocardial recruitment of circulating sEVs. 4D proteomics profiled sEVs cargo with a focus on pyruvate carrier 1 (MPC1). Results: Splenectomy worsened survival, ventricular function, infarct size, and fibrosis in mice with AMI. AMI upregulated splenic extracellular vesicle pathways, with sEVs release peaking at day 3 (M3D sEVs). Labelled splenic sEVs preferentially accumulated in ischemic myocardium, confirmed by parabiosis experiments. M3D sEVs improved survival and cardiac function and reduced infarct size, fibrosis, apoptosis, inflammation, and hypertrophy. In addition, anti apoptotic effects were reproduced in vitro. Inhibition of sEVs biogenesis decreased circulating sEVs, aggravated injury, and was rescued by M3D sEVs. M3D sEVs were enriched in MPC1, and MPC1 neutralization or pharmacological blockade abrogated sEVs mediated restoration of respiration, ATP generation, and reduction of reactive oxygen species. Plasma sEVs associated MPC1 was highest in patients with AMI, intermediate in coronary heart disease, and lowest in controls. Conclusions: The spleen responds adaptively to AMI by releasing MPC1‑enriched sEVs that travel to injured myocardium, preserve mitochondrial energetics, and reduce damage, supporting cargo‑specific sEVs augmentation and sEVs‑MPC1 as a potential therapeutic target and biomarker in ischemic heart disease.