Carbon Monoxide (CO) Inhalation Prolongs Survival of the Fully MHC-Disparate Lung Graft from Brain Death Donors in Miniature Swine

Abstract

Purpose We have previously shown that perioperative CO inhalation prolongs lung graft survival in MHC-inbred CLAWN swine. The physiologic changes at brain death (BD) would affect the organ suitability and outcome of transplantation. Here, we examined whether (1) donor BD affects lung graft survival and (2) CO inhalation to BD donors improves functions and survival of lung grafts using large animal. Methods and Materials 12 CLAWN swine received fully MHC mismatched lungs with 12 days of FK506 (days 0-11; 35-45 ng/ml). Control recipients (n=6) were transplanted from donors without BD. In BD (n=3) and BD+CO (n=3) groups, swine were transplanted from donors that were rendered BD and subsequently ventilated for 6h before procurement. In BD+CO group, donors were additionally treated with 250 ppm CO inhalation for 3h prior to procurement. BD was induced by inflation of a subdural balloon. Graft function was assessed with blood gases from graft PV and serial lung biopsy. The expression of mRNA of proinflammatory cytokines (IL-1β and IL-6) of the grafts were quantified by real-time RT-PCR. Results All control swine rejected the grafts by POD63 (47±7 days). Accelerated graft rejection was observed in BD group and 2 out of 3 swine rejected the grafts at 21days (remaining on-going >14day). CO therapy after BD was effective in prolonging graft survival; all 3 swine accepted the grafts over 21 (82±9) days. PO2 of graft PV in BD+CO group was significantly higher than in BD group (546±57 vs. 349±28 mmHg) associated with fewer inflammatory cell infiltrates on biopsies at day 2. Proinflammatory cytokines up-regulated 6h after BD induction were markedly reduced in BD+CO group at organ procurement, 2h and 2 days after reperfusion. Conclusions These data suggest that CO inhalation after confirmation of brain death exerts cytoprotective effects on inflammatory graft damage, which led to improve not only early function but survival of the lung graft in a clinically relevant large animal model.