METHANE SUPPLEMENTATION IMPROVES GRAFT FUNCTION IN EXPERIMENTAL HEART TRANSPLANTATION

Abstract Background : Maintenance of cell viability during cold storage is a key issue in organ transplantation. Methane (CH4) bioactivity has recently been recognised in ischaemia/reperfusion conditions; we therefore hypothesised that cold storage in CH4-enriched preservation solution can provide an increased defence against organ dysfunction during experimental heart transplantation (HTX). Methods : The hearts of donor Lewis rats were stored for 60 min in cold histidine-tryptophan-ketoglutarate (CS) or CH4-saturated CS solution (CS-CH4) (n=12 each). Standard heterotopic HTX was performed, and 60 min later the left ventricular (LV) pressure-volume relationship (LVSP), systolic and diastolic pressure changes (dP/dtmax and dP/dtmin) and coronary blood flow (CBF) were measured. Tissue samples were taken to detect pro-inflammatory parameters, structural damage (by light microscopy), endoplasmic reticulum (ER) stress and apoptosis markers (CHOP, GRP78, GSK3β, VLDR, Caspase 3 and 9, Bcl2 and Bax), while mitochondrial functional changes were analysed by high-resolution respirometry. Results : LVSP and dP/dtmax increased significantly at the largest preload volumes in CS-CH4 grafts as compared to the CS group (114.5±16.6 vs 82.8±4.6 mmHg and 3133±430 vs 1739±169 mmHg/s, respectively); the diastolic function and CBF (2.4±0.4 vs 1.3±0.3 ml/min/g) also improved. Mitochondrial oxidative phosphorylation capacity was more preserved (58.5±9.4 vs 27.7±6.6 pmol/s/mL), and cytochrome c release was reduced in CS-CH4 storage. Signs of HTX-caused myocardial damage, level of ER stress and the transcription of pro-apoptotic proteins were significantly lower in CS-CH4 grafts. Conclusion : The addition of CH4 during 1hr cold storage improved early in vitro graft function and reduced mitochondrial dysfunction and activation of inflammation. Evidence shows that CH4 reduced ER-stress-linked proapoptotic signaling.