Abstract
BACKGROUND: Severe thrombocytopenia and coagulation dysregulation remain major barriers to survival in pig-to-primate liver xenotransplantation models. METHODS: Porcine livers with five genetic modifications (GTKO, CMAHKO, β4GalNT2KO, hCD55, and hTBM) were orthotopically transplanted into four Tibetan macaques under two conventional immunosuppressive protocols. Longitudinal monitoring included graft and multi-organ function, hematology, coagulation, and immune responses. Histopathological and immunohistochemical analyses were performed to characterize graft and recipient pathology. RESULTS: High expression of human thrombomodulin (hTBM) in donor livers effectively prevented early rapid and severe thrombocytopenia, with three of four recipients maintaining platelets >100 × 10(9)/L. Thrombotic microangiopathy (TMA) was absent in grafts and recipient organs despite transient hypercoagulability. No spontaneous bleeding occurred in three of four cases. However, porcine livers failed to synthesize functional coagulation factor II, protein C, and protein S, contributing to progressive coagulopathy. While early graft function and coagulation remained stable for four posttransplant days, late dysfunction ensued, characterized by impaired coagulation factor synthesis and progressive graft failure. Antibody-mediated rejection, accompanied by IgM/IgG/C4b deposition, anti-TKO antibody increase, and pvWF upregulation, triggered injury that was amplified by innate and T cell-mediated responses. CONCLUSIONS: GTKO/CMAHKO/β4GalNT2KO/hCD55/hTBM donor liver transplantation was associated with an absence of early severe thrombocytopenia, transfusion requirement, and TMA, but long-term survival was limited by immune-mediated rejection and cross-species incompatibilities in coagulation factor synthesis. Optimizing (i) donor genetic modifications and (ii) immunosuppressive therapy, with (iii) replacement of targeted coagulation factors will be crucial for achieving durable survival in pig liver xenotransplantation.