Macrophage infiltration induced by donor hypovolemia protects against severe primary graft dysfunction in mouse lung transplantation. Macrophage infiltration induced by donor hypovolemia protects against severe primary graft dysfunction in mouse lung transplantation

BACKGROUND: Hypovolemia is common in lung donors before or after brain death. However, its impact on primary graft function (PGD) remains obscure. METHODS: A clinically relevant two-hit model of PGD was established by integrating hypovolemic shock (HS) and cold ischemia-reperfusion in a mouse model of orthotopic lung transplantation (LTx) from C57BL/6 to Balb/c. At -48 hours, HS was induced to donor by withdrawal of blood from femoral artery and keeping the mean arterial pressure at 15±5 mmHg for 4 h. At -24 hours, donor lungs were retrieved from mice with or without HS and stored at 0ºC until transplantation. CD11b-DTR mice were used as donor and treated with Diphtheria Toxin (DT) to deplete graft-infiltrating macrophages. RESULTS: HS mainly caused macrophage-predominant infiltration around pulmonary artery injury systemic inflammatory response, but little impairment of lung function even if in combination with cold ischemia-reperfusion. Transcriptional profiling showed HS pretreatment increased pulmonary damage and alveolar remodeling but ameliorated inflammatory infiltration when compared to one-hit model of 12 hours cold ischemia-reperfusion injury. The allografts with donor DT-treatment one day ahead of HS showed injury and dysfunction at donation and worsened further at 24 hours reperfusion, whereas the allografts with recipient DT-treatment immediately after transplantation showed similar function and histology to the control treated with saline. CONCLUSION: Donor hypovolemia causes pulmonary artery injury and infiltration but has little impact on allograft function, even in combination with 24 h cold ischemia. Graft-infiltrating macrophages are critical in protecting graft from HS-induced injury and cold ischemia-reperfusion injury. Overall design: Transcriptional profiling were performed on three naïve lung samples, three lung allografts that experienced 24 hours of cold ischemia and 2 hours of reperfusion, and three lung allografts that experienced additionally 4 hours of hypovolemic shock and 20 hours recovery before ischemia-reperfusion.