Department of Clinical Medicine

Background: Remote ischemic conditioning (RIC) by brief periods of limb ischemia and reperfusion protects against ischemia–reperfusion injury. We studied the cardioprotective role of extracellular vesicles (EV)s released into the circulation after RIC and EV accumulation in injured myocardium. Methods: We used plasma from healthy human volunteers before and after RIC (pre-PLA and post-PLA) to evaluate the transferability of RIC. Pre- and post-RIC plasma samples were separated into an EV enriched fraction (pre-EV + and post-EV +) and an EV poor fraction (pre-EV- and post-EV-) by size exclusion chromatography. Small non-coding RNAs from pre-EV + and post-EV + were purified and profiled by NanoString Technology. Infarct size was compared in Sprague–Dawley rat hearts perfused with isolated plasma and fractions in a Langendorff model. In addition, fluorescently labeled EVs were used to assess homing in an in vivo rat model. (ClinicalTrials.gov, number: NCT03380663) Results: Post-PLA reduced infarct size by 15% points compared with Pre-PLA (55 ± 4% (n = 7) vs 70 ± 6% (n = 8), p = 0.03). Post-EV + reduced infarct size by 16% points compared with pre-EV + (53 ± 15% (n = 13) vs 68 ± 12% (n = 14), p = 0.03). Post-EV- did not affect infarct size compared to pre-EV- (64 ± 3% (n = 15) and 68 ± 10% (n = 16), p > 0.99). Three miRNAs (miR-16-5p, miR-144-3p and miR-451a) that target the mTOR pathway were significantly up-regulated in the post-EV + group. Labelled EVs accumulated more intensely in the infarct area than in sham hearts. Conclusion: Cardioprotection by RIC can be mediated by circulating EVs that accumulate in injured myocardium. The underlying mechanism involves modulation of EV miRNA that may promote cell survival during reperfusion.