Effects of Mitochondrial Transplant on Phenylephrine-induced Cardiomyocyte Dysfunction

Abstract

Right ventricular (RV) failure, which carries in-hospital mortality rates of 5–17%, represents a particularly understudied and therapeutically limited disease. Though mitochondrial dysfunction is a key factor in the development of RV hypertrophy/failure, few studies have examined the effects of mitochondrial transplantation on RV hypertrophy/failure. Therefore, this in vitro study aimed to determine whether the non-autologous transplantation of L6 myotube mitochondria mitigates potentially negative outcomes in H9C2 cardiomyocytes that were stimulated to hypertrophy with phenylephrine. Control (CTL), control with mitochondrial transplant (MitoTx), Phenylephrine only (Phe-only), and phenylephrine with mitochondrial transplant (Phe+MitoTx) treatments were evaluated. Pilot experiments indicated mitochondrial transplantation into healthy cardiomyocytes acutely increased Complex I-linked OXPHOS capacity (p=0.005) and maximal respiratory capacity (p=0.022) within 24 hours, and these data alongside microscopic evidence of fluorescently labelled L6 mitochondria in H9C2 cardiomyocytes suggested successful transplantation. Regarding treatment comparisons, Phe-only showed a significant increase in cell area (p<0.05), while Phe+MitoTx blunted the hypertrophic cardiomyocyte response. Consistent with these results, deep proteomic analysis across 4,806 proteins revealed that Phe+MitoTx upregulated pathways involved in oxidative phosphorylation, fatty acid and amino acid metabolism, mitochondrial transport, and mitochondrial protein quality control, while suppressing maladaptive extracellular matrix remodeling and de-differentiation signatures. In conclusion, our in vitro data indicating that transplantation of L6 skeletal muscle mitochondria mitigates negative effects induced by phenylephrine in H9C2 cardiomyocytes adds mechanistic insight regarding the therapeutic utility of mitochondrial transplantation.