Abstract
Acute inflammatory storm is a major cause of myocardial ischemia/reperfusion (I/R) injury, with no effective treatment currently available. The excessive aggregation of neutrophils is correlated with an unfavorable prognosis in acute myocardial infarction (AMI) patients. Exosomes derived from mesenchymal stromal cells (MSC-Exo) have certain immunomodulatory potential and might be a therapeutic application. Therefore, we investigated the protective role of MSC-Exo in modulating neutrophil infiltration and formation of neutrophil extracellular traps (NETs) following myocardial I/R injury. Exosomes were isolated from the supernatant of MSCs using a gradient centrifugation method. We used flow cytometry, histochemistry, and immunofluorescence to detect the changes of neutrophils post-intravenous MSC-Exo injection. Additionally, cardiac magnetic resonance (CMR) and thioflavin S experiments were applied to detect microvascular obstruction (MVO). The NLR family pyrin domain containing 3 (NLRP3) inflammasome was examined for mechanism exploration. Primary neutrophils were extracted for in vitro experiment. Antibody of Ly6G was given to depleting the neutrophils in mice for verification the effect of MSC-Exo. Finally, we analyzed the MiRNA sequence of MSC-Exo and verified it in vitro. MSC-Exo administration reduced neutrophil infiltration and NETs formation after myocardial I/R. MSC-Exo treatment also could attenuate the activation of NLRP3 inflammasome both in vivo and in vitro. At the same time, the infarction size and MVO following I/R injury were reduced by MSC-Exo. Moreover, systemic depletion of neutrophils partly negated the therapeutic effects of MSC-Exo. Up-regulation of miR-199 in neutrophils has been shown to decrease the expression of NETs formation after stimulation. Our results demonstrated that MSC-Exo mitigated myocardial I/R injury in mice by modulating neutrophil infiltration and NETs formation. This study provides novel insights into the potential therapeutic application of MSC-Exo for myocardial ischemia/reperfusion injury.
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