To investigate the immune response, cardiac functional changes, and tissue remodeling following xenotransplantation of gene-edited pig hearts into rhesus macaques under current immunosuppressive strategies.

A pig-to-rhesus macaque heterotopic heart xenotransplantation model was established using a donor pig with five genes modifications (α-1, 3-galactosyltransferase/β-1, 4-N-acetylgalactosaminyltransferase 2/human CD46 transgene/human CD55 transgene/human thrombomodulin transgene). The immunosuppressive regimen comprised induction and maintenance phases and was based on anti-CD154 antibody and methylprednisolone. During the induction phase, anti-CD20 antibody, antithymocyte globulin, and cobra venom factor were additionally administered. During the maintenance phase, mycophenolate mofetil was added and methylprednisolone was gradually tapered. In the event of acute rejection, intensified methylprednisolone therapy was administered. Postoperative assessments included physiological parameters, cardiac function, immune cell dynamics, and histological features of the recipient monkey.

The recipient monkey survived for 46 days after transplantation. The recipient′s general condition remained relatively stable during the perioperative and early postoperative periods, with no hyperacute or acute rejection observed. Both the donor and recipient hearts maintained effective contractility after transplantation. The left ventricular ejection fraction of the recipient monkey′s native heart remained above 50% throughout the study, whereas that of the donor porcine heart was generally lower. Progressive thickening of the left and right ventricular endocardium was observed in the donor heart, reaching approximately threefold above baseline by the experimental endpoint. Leukocyte counts increased during the early postoperative period, whereas erythrocyte and platelet counts showed no sustained decline. Aminotransferase, total bilirubin, coagulation parameters, and troponin levels fluctuated over different postoperative phases. Immunohistochemistry showed higher CD68 and IgG Fc expression in porcine myocardium than in monkey myocardium. Flow cytometry showed that the proportion of peripheral blood CD3⁺ CD19^- cells increased to 74.9% on postoperative day 5, and thereafter remained between 76.2% and 89.7%. The proportion of CD3^-CD19^- cells decreased from 89.2% on the day of surgery to 81.7% on postoperative day 1, and thereafter remained between 10.2% and 25.0%. The proportion of CD3^-CD19⁺ cells remained below 0.1% throughout the observation period. The proportion of CD3⁺ CD19⁺ cells increased to 3.4% on postoperative day 7, with no marked increase observed at the other time points.

T cell-mediated cellular immune responses are the primary drivers of graft structural changes and functional deterioration under effective humoral immune suppression.