Research opportunities and ethical considerations for heart and lung xenotransplantation research: A report from the National Heart, Lung, and Blood Institute workshop.

Xenotransplantation offers the potential to meet the critical need for heart and lung transplantation presently constrained by the current human donor organ supply. Much was learned over the past decades regarding gene editing to prevent the immune activation and inflammation that cause early organ injury, and strategies for maintenance of immunosuppression to promote longer-term xenograft survival. However, many scientific questions remain regarding further requirements for genetic modification of donor organs, appropriate contexts for xenotransplantation research (including nonhuman primates, recently deceased humans, and living human recipients), and risk of xenozoonotic disease transmission. Related ethical questions include the appropriate selection of clinical trial participants, challenges with obtaining informed consent, animal rights and welfare considerations, and cost. Research involving recently deceased humans has also emerged as a potentially novel way to understand how xeno-organs will impact the human body. Clinical xenotransplantation and research involving decedents also raise ethical questions and will require consensus regarding regulatory oversight and protocol review. These considerations and the related opportunities for xenotransplantation research were discussed in a workshop sponsored by the National Heart, Lung, and Blood Institute, and are summarized in this meeting report.

Novel factors potentially initiating acute antibody-mediated rejection in pig kidney xenografts despite an efficient immunosuppressive regimen.

Antibody-mediated rejection (AMR) is a common cause of graft failure after pig-to-nonhuman primate organ transplantation, even when the graft is from a pig with multiple genetic modifications. The specific factors that initiate AMR are often uncertain. We report two cases of pig kidney transplantation into immunosuppressed baboons in which we identify novel factors associated with the initiation of AMR. In the first, membranous nephropathy was the initiating factor that was then associated with the apparent loss of the therapeutic anti-CD154 monoclonal antibody in the urine when severe proteinuria was present. This observation suggests that proteinuria may be associated with the loss of any therapeutic monoclonal antibody, for example, anti-CD154 or eculizumab, in the urine, resulting in xenograft rejection. In the second case, the sequence of events and histopathology tentatively suggested that pyelonephritis may have initiated acute-onset AMR. The association of a urinary infection with graft rejection has been well-documented in ABO-incompatible kidney allotransplantation based on the expression of an antigen on the invading microorganism shared with the kidney graft, generating an immune response to the graft. To our knowledge, these potential initiating factors of AMR in pig xenografts have not been highlighted previously.

Pediatric Cardiac Xenotransplantation: Recommendations for the Ethical Design of Clinical Trials.

For children with complex congenital heart problems, cardiac allotransplantation is sometimes the best therapeutic option. However, availability of hearts for pediatric patients is limited, resulting in a long and growing waitlist, and a high mortality rate while waiting. Cardiac xenotransplantation has been proposed as one therapeutic alternative for neonates and infants, either in lieu of allotransplantation or as a bridge until an allograft becomes available. Scientific and clinical developments in xenotransplantation appear likely to permit cardiac xenotransplantation clinical trials in adults in the coming years. The ethical issues around xenotransplantation of the heart and other organs and tissues have recently been examined, but to date, only limited literature is available on the ethical issues that are attendant with pediatric heart xenotransplantation. Here, we summarize the ethical issues, focusing on (1) whether cardiac xenotransplantation should proceed in adults or children first, (2) pediatric recipient selection for initial xenotransplantation trials, (3) special problems regarding informed consent in this context, and (4) related psychosocial and public perception considerations. We conclude with specific recommendations regarding ethically informed design of pediatric heart xenotransplantation trials.

Novel Imaging Technologies for Accurate Assessment of Cardiac Allograft Performance.

Purpose of the Review: The current lack of objective and quantitative assessment techniques to determine cardiac graft relative viability results in risk-averse decision-making, which negatively impact the utilization of cardiac grafts. The purpose of this review is to highlight the current deficiencies in cardiac allograft assessment before focusing on novel cardiac assessment techniques that exploit conventional and emerging imaging modalities, including ultrasound, magnetic resonance, and spectroscopy. Recent Findings: Extensive work is ongoing by the scientific community to identify improved objective metrics and tools for cardiac graft assessment, with the goal to safely increasing the number and proportion of hearts accepted for transplantation. Summary: This review briefly discusses the in situ and ex vivo tools currently available for clinical organ assessment, before focusing on the individual capabilities of ultrasound, magnetic resonance, and spectroscopy to provide insightful, non-invasive information regarding cardiac graft functional and metabolic status that may be used to predict outcome after transplantation.