Attenuation of Hyperacute Dysfunction and Coagulopathy in GalT-KO Pulmonary Xenotransplantation

Abstract

Background: The results of both heart and kidney GalT-KO (α-1,3-galactosyltransferase gene knockout) swine-to-primate studies have been more encouraging than for lung xenotransplantation. This may be because research in pulmonary xenotransplantation is limited. Here, we evaluated whether GalT-KO lungs could prevent hyper-acute pulmonary xenograft dysfunction, concomitant with activation of the coagulation cascade and consumptive coagulopathy using ex-vivo lung perfusion or in-vivo orthotopic left lung transplant model. Methods: Porcine heart-lung blocks were procured from wild-type (WT) and Japan domestic GalT-KO swine generated at Meiji University. In Group 1 (n=3), WT lungs were perfused with autologous blood to obtain baseline values of pulmonary physiology using this system. Then, either WT (Group 2: n=2) or GalT-KO (Group 3: n=2) lungs were perfused with human blood for 120 minutes. Changes in pulmonary arterial pressure, pulmonary vascular resistance (PVR), gas exchange, complete blood counts and other key variables were followed serially. Following perfusion, the graft tissue was evaluated histologically. Additionally, one cynomolgus monkey received left lung from GalT-KO swine to determine whether the observations ex-vivo predict in-vivo performance (Group 4). Results: WT lungs perfused with autologous blood displayed nearly normal pulmonary function with only 25% increase of PVR (Group 1). Perfusion of human blood through WT lungs led to 100% increase of PVR within 60 minutes (Group 2). In contrast, GalT-KO lungs with human blood demonstrated nearly stable function for 120 minutes with only 30% increase of PVR regardless of initial rise in PVR (Group 3). After 60 minutes of perfusion, platelet counts within the perfusate markedly decreased to 14% of pre-perfusion levels in group 2, compared with 50% in Group 3. In group 2, interstitial and alveolar hemorrhage as well as intravascular thrombosis was observed. In contrast, minimum cellular infiltration and no hemorrhage and intravascular thrombosis with less neutrophil infiltration, and limited IgM and complement deposition revealed by immunohistochemistry were observed in Group 3. Similar to the ex-vivo model, the recipients of orthotopic pulmonary xenografts in Group 4, platelet counts decreased to 54% (60-min) and 41% (120-min) of pre-transplant levels. Although platelet counts gradually decreased to 18% at 16-hour reperfusion, they promptly recovered to 53% at day 3 without development of consumptive coagulopathy (DIC) or hemodynamic instability. The animal was sacrificed for histological examination at day 3. Grossly, the graft exhibited viable with limited area of edematous and hemorrhagic appearance. Conclusion: GalT-KO lungs exhibited stable pulmonary function compared with WT lungs when perfused with human blood in an ex-vivo perfusion model, which was confirmed by the in-vivo transplant model. Although further studies are required in order to understand better the mechanisms of pulmonary xenograft rejection and dysfunction, GalT-KO lungs could be sufficient to further delay or even prevent DIC and thus facilitate prolonged survival of pulmonary xenografts.