{
  "abstract": "Background Cardiac surgery can lead to significant muscle loss, prolonging recovery time and increasing mortality. Ischaemia–reperfusion injury and subsequent endothelial damage during aortic valve replacement surgery are established mechanisms that induce skeletal muscle fibre death. Recent evidence highlights the critical contribution of extracellular vesicles (EVs) to vascular endothelial barrier dysfunction during the inflammatory response to injury.EVs are cell membrane-derived phospholipid bilayer nanostructures, 30 nm–1 µm in size, released by cells under both physiological and pathological conditions. They act as shuttles for molecular cargoes such as miRNAs, mRNAs, DNA, and proteins, serving as potential biomarkers for disease diagnosis, prognosis, and treatment. However, it remains unclear how plasma-derived EVs respond to endothelial damage and what role skeletal muscle-derived EVs play in vivo.Methods EVs from healthy donors and aortic surgery patients were isolated from whole plasma by differential centrifugation. Populations were characterised by imaging flow cytometry, nanoparticle tracking analysis (NTA), and Western blotting. The effect of EV stimulation on endothelial barrier function was assessed using a quantitative transwell permeability assay.Results EVs from healthy individuals and patients showed no significant difference in size or protein content. Plasma EV profiling revealed that platelet-, leukocyte-, and endothelial-derived EVs were the main subsets. Healthy donor EVs expressed the anti-inflammatory proteins Annexin A1 (14.1%) and α2-Macroglobulin (13.3%). In vitro, skeletal muscle cells released EVs expressing the skeletal muscle-specific marker creatine kinase MM (CK-MM); over 40% of skeletal muscle-derived EVs expressed CK-MM, while only 4.5% of healthy plasma EVs did.In aortic surgery patients, EV numbers increased from pre-operative to day 1 post-surgery, then gradually declined by day 5–7 (discharge). Platelet-, leukocyte-, and endothelial-derived EV subsets were elevated post-operatively, with neutrophil-, monocyte-, and lymphocyte-EVs particularly increased at day 1. CK-MM and CK-MB expression were significantly higher in patient EVs than in healthy donor EVs, peaking at day 1 and declining by day 3 post-surgery. In permeability assays, 100 ng/mL LPS induced significant endothelial hyperpermeability. Co-stimulation with healthy donor EVs reversed this effect, while patient-derived EVs exacerbated barrier disruption, accompanied by marked reductions in F-actin, VE-cadherin, PECAM, and JAM-C expression.Conclusions We report, for the first time, the identification of skeletal muscle-derived EVs in human plasma, marked by CK-MM expression. Healthy donor EVs exert protective, homeostatic effects on endothelial integrity, whereas EVs from aortic surgery patients compromise endothelial barrier function, implicating them as mediators of post-surgical inflammation.",
  "authors": [
    {
      "affiliations": [
        "William Harvey Research Institute, London, United Kingdom of Great Britain & Northern Ireland, London, United Kingdom"
      ],
      "name": "Nur Mousa"
    }
  ],
  "title": "172 Characterisation of circulating extracellular vesicles in the plasma of aortic surgery patients: a human model of ischaemia reperfusion injury",
  "uid": "5c1d2743-ab37-574f-a2ea-24932c3748b6"
}