Lung preservation threshold in a compromised septic lung injury model

[Assessment of ischemia-reperfusion injury and early acute rejection in experimental lung transplantation after prolonged ischemia]

OBJECTIVE

To assess ischemia-reperfusion injury and early acute rejection of the lung subjected to ischemia for 10 hours.

MATERIAL AND METHODS

Fifteen of 30 Sprague-Dawley rats underwent transplantation of a left lung that had been subjected to ischemic times of 4 (n=5), 6 (n=5), or 10 hours (n=5). The cardiopulmonary block was removed from the donor, the left lung was dissected, and the transplant was carried out using the cuff technique. The cardiopulmonary block was extracted after 48 hours. We assessed postoperative progress, ischemia-reperfusion injury and acute rejection of the transplanted and contralateral lungs. Statistical probabilities were analyzed using the chi2 and Fisher exact tests.

RESULTS

Clinical course was not worse after an ischemic time of 10 hours (P=.711). No significant differences were observed in histological markers of ischemia-reperfusion injury and acute rejection or in clinical course in relation to the different ischemic times; nor was clinical course related to the presence or severity of lesions or rejection. Similarly, acute rejection was unrelated to ischemia-reperfusion injury (P>.05).

CONCLUSIONS

In this study, a prolonged ischemic time of 10 hours was not associated with ischemia-reperfusion injuries, with more severe acute rejection, or with a worse clinical course. Acute rejection was also unrelated to the presence or severity of ischemia-reperfusion injury.

Sivelestat reduces reperfusion injury of lungs harvested from endotoxin-primed rats by inhibition of neutrophil-mediated inflammation

BACKGROUND

Although liberalization of donor criteria may be one of the solutions to the current serious lung donor shortage, the use of non-standard donor lungs would increase the risk of post-operative complications. In the present study, we investigated the effect of sivelestat, a neutrophil elastase inhibitor, on reperfusion injury of a donor lung that was harvested from endotoxin-primed animals in a rat lung transplantation model.

METHODS

Donor rats received an intraperitoneal injection of Escherichia coli endotoxin (5 mg/kg) 2 hours before lung harvesting. The donor lungs were flushed with an organ preservation solution with or without sivelestat (300 microg/ml), and the left lung was immediately transplanted to the recipient by the cuff technique.

RESULTS

Endotoxin priming did not cause significant lung injury before harvesting. Although these lungs looked normal macroscopically, they were found to contain numerous neutrophils in the alveolar capillaries, even after lung flushing. There was no significant difference in the neutrophil count between the lungs flushed with and without sivelestat. The endotoxin-primed donor lung without sivelestat treatment became edematous immediately after reperfusion. In addition, the recipient's native right lungs were also pathologic. Treatment with sivelestat significantly reduced injury in both the donor and the recipient's native lungs. Treatment with sivelestat also inhibited the increase in tumor necrosis factor-alpha and cytokine-induced neutrophil chemoattractant-1 levels in the recipient circulation after reperfusion.

CONCLUSIONS

We conclude that sivelestat could reduce lung injury after transplantation by inhibiting the deleterious burst of inflammatory reactions that are initiated by reperfusion of the lungs from endotoxin-primed rats.

Lung preservation: the importance of endothelial and alveolar type II cell integrity

The practice of lung transplantation is constrained by a shortage of suitable donor organs. Furthermore, even "optimal" donor lung grafts are at risk of significant dysfunction perioperatively. Significant insights into the cellular and molecular mechanisms of pulmonary ischemia-reperfusion injury have occurred since the publication of previous reviews on lung preservation 3 to 4 years ago. Recent evidence indicates that the endothelium plays an essential role in regulating the dynamic interaction between pulmonary vasodilatation and vasoconstriction and is a major target during lung injury. In addition, the composition, function, and metabolism of pulmonary surfactant produced by alveolar type II cells are increasingly being recognized as important factors in pulmonary ischemia-reperfusion injury. We hypothesize that reperfusion after a period of pulmonary ischemia results in significant endothelial and alveolar type II cell dysfunction and that an important strategy in lung preservation is to preserve the integrity of these cells in the face of this injury. Given the persistent shortage of lungs available for transplantation, laboratory studies need to focus also on the "rescue" of compromised donor lungs that would have been previously regarded as unsuitable. Importantly, innovative work from the laboratory needs to be translated into clinical practice via prospective, randomized trials to ensure that the prevalence of postoperative lung graft dysfunction is reduced and the shortage of lung grafts for transplantation is alleviated.