Metabolites in Human Ex Vivo Lung Perfusates Are Differentially Affected in Brain Death (BDD) vs. Cardiac Death Donors (DCD) and Modified by Duration of Normothermic Perfusion

Abstract

Purpose Normothermic Ex Vivo Lung Perfusion (EVLP) has increased our clinical lung transplantation (LTx) activity by 20% by salvaging marginal lungs, with satisfactory clinical outcomes. Rewarming these lungs on EVLP from 4°C to 37°C normalizes metabolic activity, and studying the dynamic metabolomic profile may help us understand lung injury and predict the ultimate function of the transplanted lung. Metabolic profiling of EVLP perfusate may elucidate the metabolic changes of donor lungs on EVLP. Methods and Materials Donor lungs from 28 BDD and 22 DCD donors were assessed on EVLP for 4 hours prior to LTx. For each lung, EVLP perfusate was sampled at 1 hr and 4 hr perfusion, and global metabolomic profiling was performed with Mass Spectrometry. We examined the results over time and with respect to BDD vs. DCD status. Results Global metabolomics detected 312 metabolites. Statistical analysis with Random Forest (RF) classification showed a dramatic difference in metabolite profiles between EVLP 1hr and 4hr with a 96% accuracy in predicting whether a sample was taken at the start or end of EVLP perfusion. Interestingly, the metabolic profiles grouped by donor status were sufficiently different to be able to predict with RF whether a sample belongs to BDD or DCD donor, with an accuracy of 80% at 1hr and 78% at 4 hr EVLP. Conclusions As we search for opportunities to personalize the diagnosis and treatment of the donor lung, it is evident that EVLP perfusate is easily accessible and is imminently suitable for metabolomics. The changes in metabolites in donor lungs as EVLP progresses confirms that cellular metabolism is active and modified over time in normothermic EVLP. The metabolomic profile demonstrates significant differences between BDD and DCD donor lungs during EVLP as well as dynamic changes over time. Further work is required to determine which of these metabolic changes are important to guide diagnosis, treatment and outcome prediction in EVLP donor lungs used for LTx.