Abstract 4373447: Distinct Mechanisms of Mitochondria-rich extracellular vesicle Therapy in Acute vs. Chronic Ischemic Heart Failure: A Single-Cell Transcriptomic Study

Background: Disruption of mitochondrial energy metabolism plays a critical role in the pathophysiology of ischemic heart failure. We previously demonstrated that intramyocardial injection of mitochondria-rich extracellular vesicles (M-EVs) derived from iPSC-cardiomyocytes (iCMs) promotes mitochondrial transfer and biogenesis in recipient cardiomyocytes, leading to improved cardiac function in both acute myocardial infarction (AMI) and chronic heart failure (CHF) porcine models. In this study, we aimed to characterize single-cell transcriptional responses in the peri-infarct region (PIR) of both AMI and CHF models and to identify the cell-type-specific effects of M-EV therapy. Methods: M-EVs were isolated by differential centrifugation from the conditioned medium of human iCMs. Myocardial infarction was induced in Yorkshire pigs by balloon occlusion of the left anterior descending artery (LAD) for 60 minutes (Week 0). In the AMI model, 1.0 × 10 11 M-EVs or PBS were delivered immediately after MI via transendocardial injection into the PIR using a percutaneous catheter system (Biocardia, Inc.). In the CHF model, the same dose was injected into the PIR four weeks post-MI. Cardiac function and scar size were assessed by gadolinium-enhanced cardiac MRI four weeks after treatment. Myocardial tissue samples were collected from the PIR and remote non-ischemic areas for single-nucleus RNA sequencing to analyze transcriptomic changes. Results: Both AMI and CHF models demonstrated significant improvement in LVEF in the M-EV–treated group compared to PBS controls at four weeks post-treatment. No significant differences in scar size were observed. In the AMI model, cardiomyocytes exhibited suppression of mitochondrial metabolism, which was reversed by M-EV–mediated activation of mitochondrial biogenesis, particularly complex I assembly. In contrast, CHF hearts showed transcriptional signatures indicative of altered substrate utilization, and M-EV therapy was associated with upregulation of PDK4-mediated fatty acid oxidation. Conclusion: M-EV therapy improved cardiac function in both acute and chronic porcine MI models through distinct mechanistic pathways. These findings support M-EVs as a novel therapeutic approach that targets cardiac metabolism by restoring mitochondrial function and cellular bioenergetics in a context-dependent manner.