These results suggest that CPC-secreted exosomes may be more cardioprotective than BMC-secreted exosomes, and that PAPP-A-mediated IGF-1 release may explain the benefit. They illustrate a general mechanism whereby exosomes may function via an active protease on their surface, which releases a ligand in proximity to the transmembrane receptor bound by the ligand.

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Cell therapy has been evaluated to enhance heart function after injury. Delivered cells mostly act via paracrine mechanisms, including secreted growth factors, cytokines, and vesicles, such as exosomes (Exo). Intramyocardial injection of cardiac-resident progenitor cells (CPC)-derived Exo reduced scarring and improved cardiac function after myocardial infarction in rats. Here, we explore a clinically relevant approach to enhance the homing process to cardiomyocytes (CM), which is crucial for therapeutic efficacy upon systemic delivery of Exo. By overexpressing exosomal CXCR4, we increased the efficacy of plasmatic injection of cardioprotective Exo-CPC by increasing their bioavailability to ischemic hearts. Intravenous injection of ExoCXCR4 significantly reduced infarct size and improved left ventricle ejection fraction at 4 weeks compared to ExoCTRL (p < 0.01). Hemodynamic measurements showed that ExoCXCR4 improved dp/dt min, as compared to ExoCTRL and PBS group. In vitro, ExoCXCR4 was more bioactive than ExoCTRL in preventing CM death. This in vitro effect was independent from SDF-1α, as shown by using AMD3100 as specific CXCR4 antagonist. We showed, for the first time, that systemic administration of Exo derived from CXCR4-overexpressing CPC improves heart function in a rat model of ischemia reperfusion injury These data represent a substantial step toward clinical application of Exo-based therapeutics in cardiovascular disease.

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Heart disease remains an increasing major public health challenge in the United States and worldwide. A common end-organ feature in diseased hearts is myocardial fibrosis, which stiffens the heart and interferes with normal pump function, leading to pump failure. The development of cells for regenerative therapy has been met with many pitfalls on its path to clinical translation. Recognizing that regenerative cells secrete therapeutically bioactive vesicles has paved the way to circumvent many failures of cell therapy. In this review, we provide an overview of extracellular vesicles (EVs), with a focus on their utility as therapeutic agents for cardiac regeneration. We also highlight the engineering potential of EVs to enhance their therapeutic application.

Extracellular vesicles (EVs) are potent signalling mediators. Although interest in EV translation is ever‐increasing, development efforts are hampered by the inability to reliably assess the uptake of EVs and their RNA cargo. Here, we establish a novel qPCR‐based method for the detection of unmodified EVS using an RNA Tracer (DUST). In this proof‐of‐concept study we use a human‐specific Y RNA‐derived small RNA (YsRNA) we dub “NT4” that is enriched in cardiosphere‐derived cell small EVs (CDC‐sEVs). The assay is robust, sensitive, and reproducible. Intravenously administered CDC‐sEVs accumulated primarily in the heart on a per mg basis. Cardiac injury enhanced EV uptake in the heart, liver, and brain. Inhibition of EV docking by heparin suppressed uptake variably, while inhibition of endocytosis attenuated uptake in all organs. In vitro, EVs were uptaken more efficiently by macrophages, endothelial cells, and cardiac fibroblasts compared to cardiomyocytes. These findings demonstrate the utility of DUST to assess uptake of EVs in vivo and in vitro.

Extracellular vesicles (EVs) are secreted lipid bilayer vesicles that mediate cell to cell communication and are effectors of cell therapy. Previous work has shown that canonical Wnt signaling is necessary for cell and EV therapeutic potency. Tryptophan 2,3-dioxygenase (TDO2) is a target gene of canonical Wnt signaling. Augmenting TDO2 in therapeutically inert fibroblasts endows their EVs with immunomodulatory capacity including attenuating inflammatory signaling in macrophages. Transcriptomic analysis showed that macrophages treated with EVs from fibroblasts overexpressing TDO2 had blunted inflammatory response compared to control fibroblast EVs. In vivo, EVs from TDO2-overexpressing fibroblasts preserved cardiac function. Taken together, these results describe the role of a major canonical Wnt-target gene (TDO2) in driving the therapeutic potency of cells and their EVs.

Cardiosphere-derived cell exosomes (CDC exo ) and YF1, a CDC exo -derived non-coding RNA, elicit therapeutic bioactivity in models of myocardial infarction and hypertensive hypertrophy. Here we tested the hypothesis that YF1, a 56-nucleotide Y RNA fragment, could alleviate cardiomyocyte hypertrophy, inflammation, and fibrosis associated with hypertrophic cardiomyopathy (HCM) in transgenic mice harboring a clinically relevant mutation in cardiac troponin I (cTnI Gly146 ). By quantitative PCR, YF1 was detectable in bone marrow, spleen, liver, and heart 30 min after intravenous (i.v.) infusion. For efficacy studies, mice were randomly allocated to receive i.v. YF1 or vehicle, monitored for ambulatory and cardiac function, and sacrificed at 4 weeks. YF1 (but not vehicle) improved ambulation and reduced cardiac hypertrophy and fibrosis. In parallel, peripheral mobilization of neutrophils and proinflammatory monocytes was decreased, and fewer macrophages infiltrated the heart. RNA-sequencing of macrophages revealed that YF1 confers substantive and broad changes in gene expression, modulating pathways associated with immunological disease and inflammatory responses. Together, these data demonstrate that YF1 can reverse hypertrophic and fibrotic signaling pathways associated with HCM, while improving function, raising the prospect that YF1 may be a viable novel therapeutic candidate for HCM.