Human EPCR Expression in GalTKO.hCD46 Lungs Extends Survival Time and Lowers PVR in a Xenogenic Lung Perfusion Model

Purpose Analyses of xenogenic GalTKO.hCD46 organ perfusions have revealed that activation of complement cascade and platelets play a substantial role in rejection of the perfused organ. With the aim of better controlling these mechanisms, human endothelial protein C receptor (hEPCR), a receptor facilitating protein C activation by the thrombin-thrombomodulin complex, has been added on the genetic GalTKO.hCD46 background. Here we evaluate effects of this additional genetic modification in a xenogenic lung perfusion model. Methods and Materials 6 GalTKO.hCD46.hEPCR and 37 GalTKO.hCD46 pig lungs were perfused with heparinized fresh human blood until failure (by oxygenation or PA flow and pressure criteria) or elective termination at 4 h. Functional parameters (oxygenation, PVR) were recorded, and blood samples were collected at pre-specified intervals throughout the perfusion for analysis of cell counts and cell activation. Results Median survival time in GalTKO.hCD46 organs was 171’ whereas GalTKO.hCD46.hEPCR lungs all “survived” to an elective termination (MST 240’, p=0.006). Platelet activation was significantly lower in the GalTKO.hCD46.hEPCR group (ΔBTG at 2h: 119±163 vs. 770±377, p=0.008). However, platelet and neutrophil sequestration was not prevented by the additional hEPCR expression. Thrombin generation was lower throughout the perfusion in hEPCR lungs without reaching statistical significance. PVR was lowered in hEPCR organs when compared to the GalTKO.hCD46 controls (PVR at 90’: 76±81 vs. 171±110, p=0.0536). Conclusions Results of this study demonstrate that genetic modifications to the pig, targeting anticoagulant mechanisms, do suppress platelet activation and lower activation of the complement cascade. As a consequence, PVR was lowered and survival was significantly improved. Expression of hEPCR, and perhaps other anticoagulant molecules, may facilitate successful lung xenotransplantation.