Intravenous administration of cardiac progenitor cell-derived exosomes protects against doxorubicin/trastuzumab-induced cardiac toxicity

BACKGROUND Combined administration of anthracyclines (e.g., doxorubicin; Dox) and trastuzumab (Trz), a humanized anti-human epidermal growth factor receptor 2 (HER2; ErbB2), is an effective treatment for HER2-positive breast cancer. However, both agents are associated with cardiac toxicity. Human cardiac-resident mesenchymal progenitor cells (CPCs) secrete extracellular vesicles including nanosized exosomes which protect against myocardial ischemia. Here, we investigated the effects of these exosomes using a novel model of Dox/Trz-mediated cardiotoxicity. METHODS AND RESULTS CPCs were derived from cardiac atrial appendage specimens from patients who underwent heart surgery for heart valve disease and/or ischemic heart disease, and exosomes were purified from CPC conditioned media. Proteomics analyses revealed that CPC exosomes contained multiple proteins involved in redox processes. Dox/Trz induced a significant increase in reactive oxygen species (ROS) in rat cardiomyocytes, which was prevented by CPC exosomes. In vivo, rats received 6 doses of Dox (days 1-11), followed by 6 doses of Trz (days 19-28). Three doses of either exosomes or exosome suspension vehicle were injected intravenously on days 5, 11 and 19. Dox/Trz induced myocardial fibrosis, CD68+ inflammatory cell infiltrates, inducible nitric oxide synthase (iNOS) expression, and left ventricular (LV) dysfunction. CPC exosomes prevented these effects. These vesicles were highly enriched in miR-146a-5p compared with human dermal fibroblast exosomes. Dox upregulatedTraf6 and Mpo, two known miR-146a-5p target genes (which encode signaling mediators of inflammatory and cell death axes) in myocytes. CPC exosomes suppressed miR-146a-5p target genesTraf6, Smad4, Irak1, Nox4 and Mpo in Dox-treated cells. Specific silencing of miR-146a-5p abrogated exosome-mediated suppression of those genes leading to an increase in Dox-induced cell death. CONCLUSIONS Human CPC exosomes attenuate Dox/Trz-induced oxidative stress in cardiomyocytes. Systemic administration of these vesicles prevents Dox/Trz cardiotoxicity in vivo. miR-146a-5p mediates some of the benefits of exosomes in this setting