Life supporting function for over one month of a transgenic porcine heart in a baboon

Background: Inhibition of hyperacute rejection (HAR) and sustained graft survival have been demonstrated in a pig-to-primate model of heterotopic cardiac xenotransplantation using pigs transgenic for human Decay Accelerating Factor (hDAF). Building on this work, an orthotopic model has been developed. This case records 39-day cardiac xenograft function in a life-supporting capacity with clinically applicable immunosuppression. Methods: Using a heart from an hDAF transgenic pig, an orthotopic cardiac transplant was performed on an adult baboon. The immunosuppressive regimen consisted of induction with a short course of cyclophosphamide, followed by maintenance therapy with cyclosporine A, mycophenolate mofetil and a tapering course of corticosteroids. Post-operative monitoring included daily anti-pig hemolytic antibody titer surveillance and endomyocardial biopsy. Results: The animal survived 39 days and was active and energetic throughout its postoperative course, remaining free of signs of cardiopulmonary failure. Endomyocardial biopsy performed on post-operative Day 36 revealed only patches of sub-endocardial fibrosis with no signs of active rejection. The baboon succumbed to an acute cardiopulmonary decompensation immediately following administration of medication via oral gavage. Post-mortem histopathology demonstrated well-preserved myocardial architecture with small foci of mild humoral rejection. Conclusions: This case documents the longest survival recorded to date of a discordant orthotopic cardiac xenograft and illustrates that the hDAF transgene combined with a clinically acceptable maintenance immunosuppressive regimen enables sustained, life-supporting function of porcine cardiac xenografts in non-human primates. The inhibition of hyperacute rejection and the subsequent control of humoral and cellular rejection for over 1 month demonstrated in this experiment represent significant progress in the development of a viable strategy for clinical xenotransplantation.