CDC-derived Extracellular Vesicles Reprogram Inflammatory Macrophages to an Arginase 1-dependent Proangiogenic Phenotype

Macrophages play a pivotal role in tissue repair following myocardial infarction (MI). In response to injury, they exist along a spectrum of activation states tightly regulated by their microenvironment. Cardiosphere-derived cells (CDCs) have been shown to mediate cardioprotection via modulation of the macrophage response. Our study was designed to gain mechanistic insight into the role of CDC-derived extracellular vesicles (EVs) in modulating macrophage phenotypes and operant signaling pathways to better understand their potential contribution to immunomodulatory cardioprotection. We found that CDC-derived EVs alter the functional phenotype of macrophages, modifying levels of phagocytosis and efferocytosis without changing viability or proliferation. Interestingly, extracellular vesicles differentially regulate several M1/M2 genes dependent on macrophage activation before EV treatment but consistently upregulate arginase 1 regardless of macrophage origin or polarization state. CDC-derived EVs polarize M1 macrophages to a proangiogenic phenotype dependent on arginase 1 upregulation and independent of VEGF-A. In addition, EV-dependent arginase 1 upregulation downregulates nitric oxide (NO) secretion in activated macrophages. These data suggest a novel urea-cycle-dependent mechanism in macrophages that promotes angiogenesis and provides additional mechanistic insight into the potential contribution of CDC-derived extracellular vesicles in immunomodulatory cardioprotection. We hypothesized that in the window of therapeutic extracellular vesicle (EV) administration, inflammatory M1 macrophages are likely the primary target of cardiosphere-derived cell (CDC)-derived EVs. The effect of CDC-EVs on this population, however, is currently unknown. In this study, we demonstrate that CDC-derived EVs polarize M1 macrophages to a proangiogenic phenotype dependent on arginase 1 upregulation. These results provide insight into an immunomodulatory mechanism of CDC-EVs in a more physiologically relevant model of post-myocardial infarction (post-MI) macrophage polarization.