Prolonged Cold-Ischemia Induces Necroptotic Cell Death in Ischemia Reperfusion Injury and Contributes to Primary Graft Dysfunction After Lung Transplantation.

Primary graft dysfunction (PGD), a major cause of morbidity after lung transplantation, is linked to ischemia-reperfusion injury (IRI). Other factors such as preceding brain death (BD), hemorrhagic shock (HS), and pre-engraftment lung management are also important. We hypothesized that a multi-hit isogenic mouse model of lung transplantation is more closely linked to PGD than IRI alone. Left lung transplants were performed between inbred mice. A one-hit model of IRI was established by inducing cold ischemia (CI) to the donor lung at 0°C for 1h, 72h or 96h. Multi-hit models were established by inducing 24h of HS and/or 3h of BD before 24h of CI. The recipients were sacrificed up to 7 days after transplant. In the one-hit model of IRI, up to 72h CI time resulted in mild cellular infiltration after 24h reperfusion, but extension of CI time to 96h resulted in increased airway epithelial necroptotic pathway activation. In contrast, all multi-hit models demonstrated significant PGD, characterized by variable levels of diffuse alveolar damage, increased cellular infiltration, and activation of inflammatory and necroptotic pathways. The degree of epithelial injury was graded mild in "BD+IRI", moderate in "HS+IRI" and severe in "HS+BD+IRI" groups. Thus, activation of necroptosis is a central event in IRI following prolonged CI, however it is insufficient to cause PGD alone. Multi-hit models of donor lung injury after IRI demonstrated evidence of diffuse alveolar damage consistent with PGD. Thus, pre-existing donor lung status may be more important than CI time alone for inflammatory pathway activation in this model.