Resilience of lung grafts to warm ischemia: assessment by ex vivo perfusion using functional and molecular analysis

To address the shortage of donor lungs, donation after circulatory death with extended warm ischemia (WI) is increasingly used. Normothermic ex vivo lung perfusion (EVLP) allows assessment and rehabilitation of WI lungs. However, the safety limits of WI duration remain unclear due to conflicting preclinical data and variations in clinical protocols across countries. Using a clinically-relevant pig model, we compared paired right (control) and left (WI) lungs from five donors. WI lungs experienced 2-h WI followed by 1-h cold preservation and 6-h EVLP, while control lungs underwent the same protocol without WI. Initial 2-h WI impaired compliance by 32% and increased vascular resistance by 25%, but both parameters normalized during EVLP. Oxidative and mitochondrial stress markers, cytokine release, histological injury, and edema showed no significant difference between control and WI lungs. During EVLP, both control and WI lungs exhibited similar transcriptomic responses in terms of the number of regulated genes (69/96) and their expression levels. Overall, EVLP reversed initial WI-associated functional impairments and led to convergent molecular profiles in WI and control lungs. These findings support the possibility of extending acceptable WI duration thresholds in lung transplantation.