The Case for Cardiac Xenotransplantation in Neonates: Is Now the Time to Reconsider Xenotransplantation for Hypoplastic Left Heart Syndrome?

Neonatal cardiac transplantation for hypoplastic left heart syndrome (HLHS) is associated with excellent long-term survival compared to older recipients. However, heart transplantation for neonates is greatly limited by the critical shortage of donor hearts, and by the associated mortality of the long pre-transplant waiting period. This led to the development of staged surgical palliation as the first-line surgical therapy for HLHS. Recent advances in genetic engineering and xenotransplantation have provided the potential to replicate the excellent results of neonatal cardiac allotransplantation while eliminating wait-list-associated mortality through genetically modified pig-to-human neonatal cardiac xenotransplantation. The elimination of the major pig antigens in addition to the immature B-cell response in neonates allows for the potential to induce B-cell tolerance. Additionally, the relatively mature neonatal T-cell response could be reduced by thymectomy at the time of operation combined with donor-specific pig thymus transplantation to "reprogram" the host's T-cells to recognize the xenograft as host tissue. In light of the recent significantly increased graft survival of genetically-engineered pig-to-baboon cardiac xenotransplantation, we propose that now is the time to consider devoting research to advance the potential clinical application of cardiac xenotransplantation as a treatment option for patients with HLHS. Employing cardiac xenotransplantation could revolutionize therapy for complex congenital heart defects and open a new chapter in the field of pediatric cardiac transplantation.