Enhanced Mitochondrial DNA Repair Resuscitates Transplantable Lungs Donated After Circulatory Death

Transplantation of lungs procured after donation after circulatory death (DCD) is challenging because postmortem metabolic degradation may engender susceptibility to ischemia-reperfusion (IR) injury. Because oxidative mitochondrial DNA (mtDNA) damage has been linked to endothelial barrier disruption in other models of IR injury, here we used a fusion protein construct targeting the DNA repair 8-oxoguanine DNA glycosylase-1 (OGG1) to mitochondria (mtOGG1) to determine if enhanced repair of mtDNA damage attenuates endothelial barrier dysfunction after IR injury in a rat model of lung procurement after DCD.

Lungs excised from donor rats 1 h after cardiac death were cold stored for 2 h after which they were perfused ex vivo in the absence and presence of mt-OGG1 or an inactive mt-OGG1 mutant. Lung endothelial barrier function and mtDNA integrity were determined during and at the end of perfusion, respectively.

Mitochondria-targeted OGG1 attenuated indices of lung endothelial dysfunction incurred after a 1h post-mortem period. Oxidative lung tissue mtDNA damage as well as accumulation of proinflammatory mtDNA fragments in lung perfusate, but not nuclear DNA fragments, also were reduced by mitochondria-targeted OGG1. A repair-deficient mt-OGG1 mutant failed to protect lungs from the adverse effects of DCD procurement.

These findings suggest that endothelial barrier dysfunction in lungs procured after DCD is driven by mtDNA damage and point to strategies to enhance mtDNA repair in concert with EVLP as a means of alleviating DCD-related lung IR injury.