Methane-Enriched Custodiol Preservation Solution Improves Graft Function in Experimental Model of Heterotopic Heart Transplantation

Purpose The key goal of cold storage is to maintain cell viability for a prolonged time during solid organ transplantation. Methane (CH4) has been recognized as novel therapeutic gas exerting anti-inflammatory effects in ischemia-reperfusion (IR) injuries. We aimed to investigate whether cold storage of donor hearts in CH4-enriched Custodiol preservation solution could protect against IR and preserve myocardial function in a rat model of heterotopic heart transplantation (HTX). Methods The hearts of donor Lewis rats were explanted and stored for 1 h in cold Custodiol (CS group, n=12) or in CH4-saturated (0.054 mg/100 ml) Custodiol (CS-CH4 group, n=12). 60 min after HTX left ventricular (LV) pressure-volume relations and coronary blood flow (CBF) were assessed to evaluate early post-transplant graft function. At the end of haemodynamic measurements, samples were taken for qPCR of endoplasmic reticulum (ER) stress and mitochondria-related apoptosis markers (CHOP, GRP78, GSK3β, VLDR, Caspase 3 and 9, Bcl2, Bax), biochemical parameters and mitochondrial functional analysis with high-resolution respirometry (Oxygraph2K, Austria). Results LV contractility (LV systolic pressure at 120µl of LV volume: 86±6 vs. 57±7mmHg, p=0.01; dP/dtmax: 2326±167 vs. 1583±139mmHg, p=0.007) and active relaxation (dP/dtmin at 120µl of LV volume: -1660±185 vs. -1043±169mmHg, p=0.04) improved significantly after an hour of reperfusion, while alteration of CBF standardized to heart weight (2.11±0.35 vs. 1.13±0.2ml/min/g, p=0.04) was also significantly improved following pretreatment. CS-CH4 storage significantly reduced the transcription of pro-apoptotic proteins and Bcl2/Bax ratios as compared to CS grafts. Increased mitochondrial oxidative phosphorylation, reduced leak respiration and cytochrome c release were demonstrated in response to CS-CH4 preservation. Conclusion These results might provide reliable evidence for the benefit of CH4-enriched preservation solution during HTX, through a mechanism which involves the inhibition of pro-apoptotic signals. Hence CH4-enriched preservation solution could be a potential cardioprotective agent in the inventory of heart transplantation surgery and other cardiac surgical procedures requiring prolonged cardioplegia.