Aims Mesenchymal stromal cells (MSCs) gradually become attractive candidates for cardiac inflammation modulation, yet understanding of the mechanism remains elusive. Strikingly, recent studies indicated that exosomes secreted by MSCs might be a novel mechanism for the beneficial effect of MSCs transplantation after myocardial infarction. We therefore explored the role of MSC-derived exosomes (MSC-Exo) in the immunomodulation of macrophages after myocardial ischaemia/reperfusion (I/R) and its implications in cardiac injury repair. Methods and results Exosomes were isolated from the supernatant of MSCs using gradient centrifugation method. Administration of MSC-Exo to mice through intramyocardial injection after myocardial I/R reduced infarct size and alleviated inflammation level in heart and serum. Systemic depletion of macrophages with clodronate liposomes abolished the curative effects of MSC-Exo. MSC-Exo modified the polarization of M1 macrophages to M2 macrophages both in vivo and in vitro . miRNA sequencing of MSC-Exo and bioinformatics analysis implicated miR-182 as a potent candidate mediator of macrophage polarization and toll-like receptor 4 (TLR4) as a downstream target. Diminishing miR-182 in MSC-Exo partially attenuated its modulation of macrophage polarization. Likewise, knock down of TLR4 also conferred cardioprotective efficacy and reduced inflammation level in a mouse model of myocardial I/R. Conclusion Our data indicate that MSC-Exo attenuates myocardial I/R injury in mice via shuttling miR-182 that modifies the polarization status of macrophages. This study sheds new light on the application of MSC-Exo as a potential therapeutic tool for myocardial I/R injury.

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Dilated cardiomyopathy (DCM) is the major cause of heart failure and has a poor prognosis. The accumulating evidence points to an essential role of the inflammatory component in the process of DCM. Inhibitors of sodium-glucose cotransporter 2 (SGLT2) are widely used to treat heart failure patients due to their cardiac benefits. However, their role in DCM remains unclear. We used the doxorubicin (Dox)-induced DCM model for our study. The SGLT2 inhibitor dapagliflozin (Dapa) improved cardiac function in mice treated with doxorubicin and attenuated the activation of the nucleotide-binding oligomerization domain-like receptor family protein 3 (NLRP3) inflammasome pathway and the expression of inflammatory factors. In addition, dapagliflozin suppresses NLRP3 activation by decreasing p38-dependent toll-like receptor 4 (TLR4) expression. In our study, dagliflozin improves cardiac function in DCM by inhibiting the activity of the NLRP3 inflammasome. Graphical Abstract