Monitoring Mitochondrial Function With High-Resolution Respirometry During Ex-Situ Heart Perfusion.

BACKGROUND: Due to the high adenosine-triphosphate (ATP) consumption of the myocardial tissue, cardiac function is dependent on efficient mitochondrial respiration. Ischemia and reperfusion injury (I/R) has a severe impact on the function of the mitochondrial respiratory system. Ex-situ heart perfusion (ESHP) can minimize I/R injury. We investigated mitochondrial respiration using high-resolution respirometry (HRR) in a porcine model during ESHP. METHODS: Six German domestic pigs were used as heart and blood donors. Normothermic ESHP was performed over 6 h. Tissue homogenate of porcine myocardium was assessed by HRR at baseline (starting sample), after 60, 180, and 360 min of ESHP. RESULTS: The combined oxidative phosphorylation capacity with NADH, fatty acid and succinate fuel substrates remained stable during ESHP (starting sample: 198 ± 59.7, 60 min: 196.5 ± 66.7, 180 min: 207.5 ± 48.1, 360 min: 200.5 ± 27.9 pmol·s-1·mg wet mass-1; p = 0.707). The flux control ratio of the nicotinamide adenine dinucleotide hydrogen (NADH) pathway (starting sample: 0.43 ± 0.07, 60 min: 0.43 ± 0.05, 180 min: 0.47 ± 0.05, 360 min: 0.44 ± 0.07 pmol·s-1·mg wet mass-1; p = 0.549) and succinate-pathway (starting sample: 0.49 ± 0.06, 60 min: 0.49 ± 0.05, 180 min: 0.48 ± 0.01, 360 min: 0.5 ± 0.05 pmol·s-1·mg wet mass-1; p = 0.814) did not change during perfusion. The mitochondrial outer membrane damage was significantly decreased after 360 min of ESHP (starting sample: 0.39 ± 0.07, 60 min: 0.27 ± 0.06, 180 min: 0.18 ± 0.03, 360 min: 0.17 ± 0.02; p = 0.0124). CONCLUSION: Our findings demonstrate that normothermic ESHP preserves mitochondrial respiratory function in a porcine model over 6 h. These results provide a mechanistic basis for the potential protective role of normothermic ESHP against ischemia-reperfusion injury. HRR represents a promising investigational tool for in-depth mitochondrial assessment during ESHP.