Life-supporting Function Of Galt ko Pig Lungs In Baboons.
Back to 86th Annual Meeting
Back to Program Outline
Objective: During ex vivo perfusion with human blood, homozygous galactosyl transferase knock-out (GalT KO) pig lungs survived 121 ± 32 minutes (60, 134 and 170 min) compared to 8 ± 1 minutes for wild type lungs (n=7, p=0.007) and 49 ± 16 minutes for hDAF+/+ lungs (n=10, p=0.07). Ex vivo perfused GalT KO lungs ultimately failed in conjunction with thrombin generation (F1+2), platelet activation (CD62P expression), and strong CD41 (platelet) deposition not seen at earlier time points. Their in vivo behavior has not been evaluated.
Methods: 3 GalT KO pig left lungs were transplanted into baboons, and the right PA then occluded. One contemporary allogeneic (baboon) lung and two transgenic MCP (CD46) pig lung xenotransplants provide physiologic and biochemical context.
Results: Whereas 2 MCP lungs exhibited high PVR (>250 mmHg-min/L) and failed to support life beyond 15 minutes, two out of three GalT KO lungs supported life, for 90 and 215 minutes, and displayed low PVR (48 ± 12 mmHg-min/L at 60 min), similar to baboon lung. Complement activation and antibody deposition were minimal in both GalT KO and MCP lungs (delta C3a <250 ng/ml through 60 min). Although circulating platelet activation (as CD62P by flow cytometry) was low (<10%) up to 1 hour in GalT KO lung recipients, 35-50% of neutrophils, monocytes and platelets were sequestered by 5 minutes, unlike allo lung (<20%). Platelet activation (>80% CD62P+) and thrombin formation (delta plasma F1+2: >1.2 nM) confirmed coagulation activation at failure of life-supporting GalT KO lungs. Monocyte chemotactic protein-1, IL6, and intercellular adhesion molecule-1 gene expression (by RT-PCR, standardized to pre-perfusion lung tissue) were up-regulated 5 to 20-fold at 3 hours, suggesting significant activation of macrophages and/or monocytes, while IL-8, cyclooxygenase-2, and protease activated receptor 2 up-regulation reflect endothelial and other innate immune activation pathways.
Conclusions: Confirming observations from an ex vivo perfusion model, transplanted GalT KO pig lungs are significantly protected from the physiologic consequences (increased pulmonary vascular resistance, capillary leak) associated with hyperacute lung rejection (HALR), unlike MCP transgenic lungs. Delayed platelet activation and intravascular thrombosis occur in association with later graft failure, with kinetics and gene expression profile suggesting a threshold pro-coagulant effect mediated by macrophages, monocytes, and endothelium. These observations support the hypothesis that non-physiologic adhesive interactions between primate formed blood elements and pig lung macrophages and endothelium trigger coagulation and associated inflammation. Control of coagulation may be sufficient to overcome HALR in the context of GalT KO, allowing work in this area to progress to the next hurdle.
Back to 86th Annual Meeting
Back to Program Outline
