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Background: The immunoregulatory cytokine interleukin-10 (IL-10) has been shown to be a promising therapy for donor lung injuries before transplantation. However, the very short half-life of IL-10 in vivo (∼2 hours) has necessitated the use of gene therapy in almost all animal models of lung transplantation. Because isolation of the donor lung on the ex vivo lung perfusion (EVLP) circuit removes it from the influence of renal and hepatic clearance mechanisms, a much-prolonged half-life of IL-10 is anticipated. Thus, we hypothesized that delivery of recombinant IL-10 (rIL-10) to injured donor lungs isolated on EVLP could be a clinically relevant and a logistically simpler method of employing IL-10 therapy in lung transplantation. Methods: Injured human donor lungs clinically rejected for transplantation were split into single lungs and the better of the 2 subjected to 12 hours of EVLP and randomized (n = 5/group) to receive either saline (control), rIL-10 (5 µg in 2-liter perfusate), or rIL-10 (25 µg) aerosolized into the airways. Results: Perfusate and intratracheal delivery of rIL-10 did not provide the therapeutic anti-inflammatory action that has been traditionally achieved with gene therapy. It appears that intratracheally delivered rIL-10 moves into the perfusate where it seems to be biologically inactive. Conclusions: Gene therapy remains superior as it allows for continued production of IL-10 within the alveoli where it has the potential to continuously act on alveolar macrophages and epithelial cells in a paracrine fashion.

An established pig lung transplantation model was used to study the effects of cold ischemia time, normothermic acellular ex vivo lung perfusion (EVLP) and reperfusion after lung transplantation on l-arginine/NO metabolism in lung tissue. Lung tissue homogenates were analyzed for NO metabolite (NOx) concentrations by chemiluminescent NO-analyzer technique, and l-arginine, l-ornithine, l-citrulline and asymmetric dimethylarginine (ADMA) quantified using liquid chromatography-mass spectrometry (LC-MS/MS). The expression of arginase and nitric oxide synthase (NOS) isoforms in lung was measured by real-time polymerase chain reaction. EVLP preservation resulted in a significant decrease in concentrations of NOx and l-citrulline, both products of NOS, at the end of EVLP and after reperfusion following transplantation, compared to control, respectively. The ratio of l-ornithine over l-citrulline, a marker of the balance between l-arginine metabolizing enzymes, was increased in the EVLP group prior to reperfusion. The expression of both arginase isoforms was increased from baseline 1 h post reperfusion in EVLP but not in the no-EVLP group. These data suggest that EVLP results in a shift of the l-arginine balance towards arginase, leading to NO deficiency in the lung. The arginase/NOS balance may, therefore, represent a therapeutic target to improve lung quality during EVLP and, subsequently, transplant outcomes.