Extended Survival of 9- and 10-Gene-Edited Pig Heart Xenografts with Ischemia Minimization and CD154 Co-stimulation Blockade-Based Immunosuppression

Background: Xenotransplantation has made significant advances recently using pigs genetically engineered to remove carbohydrate antigens, either alone or with addition of various human complement, coagulation, and anti-inflammatory ‘transgenes’. Here we evaluated results associated with gene-edited (GE) pig hearts transplanted in baboons using an established co-stimulation-based immunosuppressive regimen and a cold-perfused graft preservation technique.

Methods: Eight baboons received heterotopic abdominal heart transplants from 3-GE (GalKO.β4GalNT2KO.CD55, n = 3), 9-GE (GalKO.β4GalNT2KO.GHRKO.CD46.CD55.TBM. EPCR.CD47.HO-1, n = 3) or 10-G (9-GE+CMAHKO, n = 2) pigs using Steen’s cold-perfusion approach for ischemia minimization. Immunosuppression (IS) included induction with ATG and aCD20, ongoing aCD154 and MMF, and tapered corticosteroid. IL6 receptor and C1 esterase inhibitors were given perioperatively, along with IV heparin for the first 8-10 days.

Results: All three 3-GE grafts functioned well initially, but failed within 5 days, with graft necrosis and rupture associated with complement deposition, intravascular thrombi, and myocardial infarction. One 9-GE graft was lost intraoperatively due to a technical issue and another was lost at POD 13 associated with antibody mediated rejection (AMR) in a baboon with a strongly positive pre-operative cross-match. One 10-GE heart failed at POD 113 with combined cellular and antibody mediated rejection. One 9-GE and one 10-GE hearts had preserved graft function with normal myocardium on protocol biopsies, but exhibited slowly progressive graft hypertrophy until elective necropsy at POD 393 and 243 respectively. Transient intraventricular clot detected by ultrasound in some 9- and 10-GE grafts peri-transplant resolved with heparin. Elevated levels of IL-6, MCP-1, C-reactive protein, and, with 9- or 10-GE hearts, human thrombomodulin were variably associated with conditioning, the transplant procedure, and clinically significant postoperative events, presumably reflecting inflammation occurring in the context of these pig genetics and the treatment approaches deployed.

Conclusion: Relative to reference genetics without thrombo-regulatory and anti-inflammatory gene expression, 9- or 10-GE pig hearts exhibit promising performance in the context of a clinically applicable regimen including ischemia minimization and aCD154-base IS, justifying further evaluation in an orthotopic model.

Publikationsverlauf

Artikel online veröffentlicht:
13. Februar 2024