Stem Cell Exosome Therapy Recovers Mitochondrial Respiration in Hypoxic Cardiomyocytes

INTRODUCTION: Hibernating hyocardium (HM) is adaptive response of myocardium to chronic ischemia resulting in reduced myocardial function but preserved viability. Alteration in mitochondrial function is important mechanism of bioenergetic adaptation. Revascularization does not fully recover function. To understand mechanisms of regenerative as adjunctive therapy to restore cardiomyocyte mitochondrial function, we developed in vitro model of ischemia-reperfusion to mimic Hibernating hyocardium treated with mesenchymal stem cell (MSC)–exosomes. Exosomes secrete microvesicles containing microRNA (miRNA) to mediate tissue regeneration. Our data demonstrated improved cardiomyocyte mitochondrial function via an exosomal-related mechanism. miRNA from MSC-exosomes were profiled to identify dominant biological processes and pathways modulated by exosomal miRNA. METHODS: Our in vitro experiments use H9C2 cardiomyocytes exposed to hypoxia to simulate hibernating hyocardium. H9C2 are reoxygenated with/without MSC-exosomes and with GW4869, an exosomal release antagonist. Mitochondrial respiration in hypoxic cardiomyocytes during/after treatment was measured using Seahorse technology. miRNA sequencing was done using Illumina SE50 giving differential expression profiles under different conditions. RESULTS: Our data demonstrated MSC-exosomes applied during reoxygenation improve recovery of hypoxic cardiomyocytes through improved mitochondrial respiration. Pharmacological inhibition of exosomes confirmed by decreased CD63 (exosomal marker) showed depressed ATP production, basal and maximal respiration, indicates inhibition of exosome release prevents recovery of mitochondrial respiration to normal cardiomyocytes. Differential expression of the top 27 miRNAs including high expression of miR-206, miR-152, miR-450a, and miR-196b was identified under hypoxia (Figure). CONCLUSION: MSC-exosomes administered during reoxygenation enhance mitochondrial respiration and bioenergetics in hibernating cardiomyocytes. Future studies focus on elucidating biological processes and pathways targeted by miRNAs in improving mitochondrial bioenergetics.Figure