Perfusate Metabolite Profiles in Ex Vivo Lung Perfusion Predict Graft Quality of Lungs Donated after Circulatory Death

Abstract

The use of donation after circulatory death (DCD) lungs may expand the donor pool for lung transplantation. However, due to the variable quality of DCD lungs, many undergo ex vivo lung perfusion (EVLP) for evaluation. DCD lung assessment is challenging but can be greatly aided by biomarker readouts that predict transplant outcome. In this study, we performed a metabolomics analysis of human DCD lungs to identify predictive metabolites that may be clinically useful during EVLP assessment. EVLP perfusate was collected from 20 DCD lungs and evaluated on EVLP. Lungs were divided into 2 groups: 1) Good outcome (n = 11), with no primary graft dysfunction grade 3 (PGD3); 2) Poor outcome (n = 9), including PGD3 (n = 5) and declined lungs due to poor performance on EVLP (n = 4). Metabolomics profiling of perfusate samples taken at 1 h and 4 h of EVLP were processed by liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry. Bioinformatics and pathway analysis were performed with MetaboAnalyst webserver. In total, 275 metabolites were detected. Five metabolites at 1 h and 16 metabolites at 4 h of EVLP were significantly different between good and poor outcome groups (FDR < 0.05, fold change (FC) ≥1.5). Multiple amino acid levels were significantly higher and lipid levels were significantly lower in poor outcome lungs at 1 h and 4 h of EVLP. Metabolomic pathway analysis revealed that aminoacyl-tRNA biosynthesis, and glycine, serine and threonine pathways were affected. While several metabolites achieved statistical significance, it was notable that lysine and ornithine levels separated good vs. bad outcome groups at 1 h and 4 h with minimal overlap (Fig 1). We identified significantly altered metabolites in DCD lungs that distinguish between good and poor recipient outcomes. Future biomarker validation via a larger sample size is necessary prior to their use to optimally select post-EVLP DCD donor lungs for transplantation.