Ethical considerations in xenotransplantation: a review

Cardiac transplantation: A review of current status and emerging innovations

Heart transplantation (HTx) is a life-saving procedure for patients with end-stage heart failure and has undergone remarkable advancements since the first successful transplant in 1967. The introduction of cyclosporine in the 1970s significantly improved patient outcomes, leading to a global increase in transplants, including in India, where the practice has grown despite initial challenges. This review provides an extensive overview of HTx, focusing on current practices, technological advancements, and the ongoing challenges the field faces today. It explores the evolution of surgical techniques, such as minimally invasive and robotic-assisted procedures, and the management of posttransplant rejection through tailored immunosuppressive strategies, including new monoclonal antibodies and personalized therapies. The review also highlights emerging innovations such as mechanical circulatory support devices and xenotransplantation as potential solutions to donor shortages while acknowledging the ethical and logistical challenges these approaches entail. Furthermore, the analysis delves into the implications of using extended-criteria donors and the role of multidisciplinary teams in evaluating absolute and relative contraindications. Despite the progress made, the persistent issues of organ scarcity and ethical concerns underscore the need for ongoing research and innovation to further enhance the efficacy, safety, and accessibility of HTx.

Regulation of cyclophosphamide induced hepatotoxicity by REV-ERBα modifiers

INTRODUCTION

Cyclophosphamide (CPA) is a widely used broad-spectrum antitumor drug with severe hepatotoxicity. Finding an effective way to mitigate the hepatotoxicity caused by CPA is a challenge in its clinical application.

METHODS

In Rev-erbα knockout and wild-type mice, hepatotoxicity was evaluated by ALT, AST, and histopathological scores 4-h post dose of CPA (i.p. 300 mg/kg). CYP2B10 expression and pharmacokinetic behavior of CPA were also detected. SR9009 (i.p. 10 mg/kg) and Berberine (BBR, i.p. 50 mg/kg) were pre-administered to mice. Then, the measurements were carried out following the same procedures as previous. The regulation effects of SR9009 and BBR on CYP2B10 were validated using Hepa-1c1c7 cells.

RESULTS

Firstly, REV-ERBα negatively regulated CPA-induced hepatotoxicity by altering the expression of CYP2B10 and CPA pharmacokinetics. Secondly, REV-ERBα agonists, SR9009 and BBR, increased REV-ERBα expression and alleviated hepatic toxicity of CPA. Furthermore, both SR9009 and BBR reduced expression of CYP2B10 and REV-ERBα target gene Bmal1 both in vivo and in vitro.

CONCLUSIONS

REV-ERBα agonists can significantly attenuate the hepatotoxicity of CPA by regulating CYP2B10. The discovery of REV-ERBα as novel regulator for CYP2B10 will help to establish new targets to improve drug efficacy or reduce toxicity.

Considering the Risks and Costs of Solid Organ Xenotransplantation

The standard treatment for end-stage organ failure is transplantation, but demand for organs has always vastly outstripped supply. Discussions are ongoing about the feasibility of addressing the organ shortage through measures like increasing organ donations, improving post-transplant outcomes, and xenotransplantation. This paper examines the rationale, risks, and costs of xenotransplantation, such as xenozoonoses, creating a new form of industrialized animal farming, abandoning animal ethics principles, and the opportunity costs of investing finite research dollars in xenotransplantation instead of investing in more viable strategies. Alternative strategies that can ethically and effectively address the demand for heart, kidney, and other transplants are recommended: Improving disease prevention and management to reduce demand for transplant organs, improving transplantation methods, and systemic changes to donor policies and organ recovery methods to increase overall supply. Upon careful exploration of the full landscape of organ transplantation, it is considered whether these alternative strategies that do not impose the definite harms and significant risks of xenotransplantation are the most ethical and effective means to increase life-saving options and improve clinical outcomes for patients in organ failure.

Research prospects for kidney xenotransplantation: a bibliometric analysis

BACKGROUND

Xenograft kidney transplantation has been receiving increasing attention. The purpose of this study is to use bibliometric analysis to identify papers in this research field and explore their current status and development trends.

METHODS

Using the data in the Web of Science core database from Clarivate Analytics as the object of study, we used 'TS = Kidney OR Renal AND xenotransplantation' as the search term to find all literature from 1980 to 2 November 2022.

RESULTS

In total, 1005 articles were included. The United States has the highest number of publications and has made significant contributions in this field. Harvard University was at the forefront of this study. Professor Cooper has published 114 articles in this field. Xenotransplantation has the largest number of relevant articles. Transplantation was the most cited journal. High-frequency keywords illustrated the current state of development and future trends in xenotransplantation. The use of transgenic pigs and the development of coordinated co-stimulatory blockers have greatly facilitated progress in xenotransplantation research. We found that 'co-stimulation blockade', 'xenograft survival', 'pluripotent stem cell', 'translational research', and 'genetic engineering' were likely to be the focus of attention in the coming years.

CONCLUSIONS

This study screened global publications related to xenogeneic kidney transplantation; analyzed their literature metrology characteristics; identified the most cited articles in the research field; understood the current situation, hot spots, and trends of global research; and provided future development directions for researchers and practitioners.

Ethical considerations in xenotransplantation of thoracic organs - a call for a debate on value based decisions

Xenotransplant covers a broad ethical territory and there are several ethical questions that have arisen in parallel with the technological advances that have allowed the first porcine transplants to occur. This brief communication highlights ethical considerations regarding heart and lung xenotransplantation, with an emphasis on unresolved value-based concerns in the field. The aim of this text is therefore to encourage the readers to consider the vast potential of this emerging technique to do good, but also the risk of doing harm, and to participate in a discussion. The list of questions presented here is not exhaustive but hopefully represents some of the questions that appear to be most pressing as the field advances. The focus is on the value-based, or ethical questions, not the questions related to the practical medical procedures.

Effect of resuscitation of cryopreserved porcine adrenal glands at 26 °C on their recovery and functioning under xenotransplantation

The study is devoted to the effect of lowered resuscitation temperature (26 °C) on cryopreserved porcine adrenal glands functional activity in vitro and in vivo under xenotransplantation. The adrenals were collected from newborn pigs, cryopreserved with 5 % DMSO at a rate of 1 °C/min, resuscitated at 26 or 37 °C for 48 h (5 % CO2, DMEM), embedded into small intestinal submucosa, and transplanted to bilaterally adrenalectomized rats. It has been shown that the glands resuscitated at 26 °C have suppressed free-radical processes and can produce cortisol and aldosterone in vitro, and may lead to elevated blood levels of these hormones. Moreover, the adrenal grafts maintain blood glucose levels and promote the formation of glycogen stores. Thus, the resuscitation at 26 °C can improve the quality of grafts and favor the introduction and application of the cryopreserved organs and tissues for transplantation in clinical and experimental practice.

Ethics, virtues and xenotransplantation

Early in 2022 the first pig to human cardiac xenotransplant was performed. The graft initially performed well, and rejection was well controlled. However, the graft failed, and the patient died 60 days after the procedure. The ethical issues relating to xenotransplantation include the risk/benefit to the individual, the risk of porcine-derived infectious agents crossing into humans, animal welfare and rights, issues of human and animal identity and concerns relating to fair allocation of organs and appropriate use of resources.These ethical issues are often addressed using emotional arguments, or through consequentialist or deontological lens. An alternative is to use approaches based on virtue ethics to understand the moral purpose (telos) of the research and the virtues (character traits) needed to be a good research clinician. In this review we will consider the virtues of justice, courage, temperance and practical wisdom, as well as the role of clinical curiosity, and their application to xenotransplantation. This provides an alternative approach for the clinical academic and others involved in the research to reflect on their practice.

Human PD-L1 overexpression decreases xenogeneic human T-cell immune responses towards porcine kidneys

Xenotransplantation offers a promising alternative to circumvent the lack of donated human organs available for transplantation. Different attempts to improve the survival of xenografts led to the generation of transgenic pigs expressing various combinations of human protective genes or knocked out for specific antigens. Currently, testing the efficiency of porcine organs carrying different genetic modifications in preventing xenogeneic immune responses completely relies on in vitro assays, humanized mouse models, or non-human primate transplantation models. However, these tests are often associated with major concerns due to reproducibility and generation of insufficient data as well as they raise ethical, logistical, and economic issues. In this study, we investigated the feasibility of specifically assessing the strength of human T-cell responses towards the kidneys of wild-type (WT) or transgenic pigs overexpressing human programmed death-1 ligand 1 (hPD-L1) during ex vivo kidney perfusion (EVKP). Human T cells were shown to adhere to the endothelium and transmigrate into WT and hPD-L1 kidneys. However, transcript levels of TNF-a and IFN-y as well as cytotoxic molecules such as granzyme B and perforin secreted by human T cells were significantly decreased in the tissue of hPD-L1 kidneys in comparison to WT kidneys. These results were confirmed via in vitro assays using renal endothelial cells (ECs) isolated from WT and hPD-L1 transgenic pigs. Both CD4+ and CD8+ T cells showed significantly lower proliferation rates after exposure to hPD-L1 porcine renal ECs in comparison to WT ECs. In addition, the secretion of pro-inflammatory cytokines was significantly reduced in cultures using hPD-L1 ECs in comparison to WT ECs. Remarkably, hPD-L1 EC survival was significantly increased in cytotoxic assays. This study demonstrates the feasibility of evaluating the human response of specific immune subsets such as human T cells towards the whole xenograft during EVKP. This may represent a robust strategy to assess the potency of different genetic modifications to prevent xenogeneic immune responses and thereby predict the risk of immune rejection of new genetically engineered xenografts.

Historical Review and Future of Cardiac Xenotransplantation

Along with the development of immunosuppressive drugs, major advances on xenotransplantation were achieved by understanding the immunobiology of xenograft rejection. Most importantly, three predominant carbohydrate antigens on porcine endothelial cells were key elements provoking hyperacute rejection: α1,3-galactose, SDa blood group antigen, and N-glycolylneuraminic acid. Preformed antibodies binding to the porcine major xenoantigen causes complement activation and endothelial cell activation, leading to xenograft injury and intravascular thrombosis. Recent advances in genetic engineering enabled knock-outs of these major xenoantigens, thus producing xenografts with less hyperacute rejection rates. Another milestone in the history of xenotransplantation was the development of co-stimulation blockaded strategy. Unlike allotransplantation, xenotransplantation requires blockade of CD40-CD40L pathway to prevent T-cell dependent B-cell activation and antibody production. In 2010s, advanced genetic engineering of xenograft by inducing the expression of multiple human transgenes became available. So-called 'multi-gene' xenografts expressing human transgenes such as thrombomodulin and endothelial protein C receptor were introduced, which resulted in the reduction of thrombotic events and improvement of xenograft survival. Still, there are many limitations to clinical translation of cardiac xenotransplantation. Along with technical challenges, zoonotic infection and physiological discordances are major obstacles. Social barriers including healthcare costs also need to be addressed. Although there are several remaining obstacles to overcome, xenotransplantation would surely become the novel option for millions of patients with end-stage heart failure who have limited options to traditional therapeutics.

The Need to Adjust the Informed Consent for Jewish Patients for Treatments Involving Porcine Medical Constituents

In order to obtain full informed consent for medical treatments, it is imperative to provide patients of diverse ethnic backgrounds with all relevant information. Since the pig is considered an impure animal in Judaism, Jewish patients may wish to be informed of porcine-derived substances used in treating. The present study is the first to explore the level of knowledge of Jewish participants as to whether the medical use of pig is permitted by their religion, and the extent to which they believe it should be permitted. 714 Jewish participants completed a study questionnaire that included 15 medical uses of pigs. Findings indicated that the knowledge of Jewish law regarding these uses is a significant mediator in predicting the attitude toward the permissibility of these uses. I conclude with practical recommendations as to how to enhance cultural competence and improve the informed consent process when treating Jewish patients with porcine-derived constituents.

Xenotransplantate vom Schwein – ist das Ende des Organmangels in Sicht?

Unter „Xenotransplantation“ wird die Übertragung von funktionsfähigen Zellen, Geweben oder Organen zwischen verschiedenen Spezies verstanden, insbesondere von Schweinen auf den Menschen. In den meisten Industrieländern klafft eine große Lücke zwischen der Anzahl geeigneter Spenderorgane und der Anzahl benötigter Transplantate. Weltweit können nur etwa 10% des Organbedarfs durch Spenden gedeckt werden. Eine erfolgreiche Xenotransplantation könnte diesen Mangel mildern oder sogar weitgehend vermeiden. Das Schwein wird aus verschiedenen Erwägungen heraus als am besten geeignete Spenderspezies angesehen. Bei einer Übertragung porziner Organe auf Primaten treten verschiedene immunologisch bedingte Abstoßungsreaktionen auf, die das übertragene Organ innerhalb kurzer Zeit zerstören können, wie die HAR (hyperakute Abstoßung), die AVR (akute vaskuläre Abstoßung) und die spätere zelluläre Abstoßung. Diese Abstoßungsreaktionen müssen durch genetische Modifikationen im Schwein und eine geeignete immunsuppressive Behandlung des Empfängers kontrolliert werden. Dazu müssen Tiere mit mehrfachen genetischen Veränderungen produziert und im Hinblick auf ihre Eignung für eine erfolgreiche Xenotransplantation geprüft werden. Inzwischen können die HAR und auch die AVR durch Knockouts von antigenen Oberflächenepitopen (z. B. αGal [Galaktose-α1,3-Galaktose]) und transgene Expression humaner Gene mit antiinflammatorischer, antiapoptotischer oder antikoagulativer Wirkung zuverlässig kontrolliert werden. Nach orthotopen Transplantationen in nicht humane Primaten konnten inzwischen mit Schweineherzen Überlebensraten von bis zu 264 Tagen und mit porzinen Nieren von 435 Tagen erzielt werden. Eine Übertragung pathogener Erreger auf den Empfänger kann bei Einhaltung einschlägiger Hygienemaßnahmen ausgeschlossen werden. PERV (porzine endogene Retroviren) können durch RNA-(Ribonukleinsäure-)Interferenz oder Gen-Knockout ausgeschaltet werden. Sie stellen damit kein Übertragungsrisiko für den Empfänger mehr dar. Anfang 2022 wurde in Baltimore (USA) ein Schweineherz mit 10 genetischen Modifikationen auf einen Patienten mit schwerem Herzleiden übertragen, mit dem der Empfänger 2 Monate offenbar ohne größere Probleme lebte. Es wird erwartet, dass Xenotransplantate vom Schwein in absehbarer Zeit zur klinischen Anwendungsreife kommen werden. Dazu werden klinische Versuche zur systematischen Erfassung aller Auswirkungen solcher Transplantate auf den Patienten sowie geeignete rechtliche und finanzielle Rahmenbedingungen benötigt.

Classic and Current Opinions in Human Organ and Tissue Transplantation

Graft tolerance is a pathophysiological condition heavily reliant on the dynamic interaction of the innate and adaptive immune systems. Genetic polymorphism determines immune responses to tissue/organ transplantation, and intricate humoral and cell-mediated mechanisms control these responses. In transplantation, the clinician's goal is to achieve a delicate equilibrium between the allogeneic immune response, undesired effects of the immunosuppressive drugs, and the existing morbidities that are potentially life-threatening. Transplant immunopathology involves sensitization, effector, and apoptosis phases which recruit and engages immunological cells like natural killer cells, lymphocytes, neutrophils, and monocytes. Similarly, these cells are involved in the transfer of normal or genetically engineered T cells. Advances in tissue transplantation would involve a profound knowledge of the molecular mechanisms that underpin the respective immunopathology involved and the design of precision medicines that are safe and effective.

Expert consensus on clinical trials of human xenotransplantation in China

The history of xenotransplantation started in the 19th century. After a few decades of investigation, significant breakthroughs and preclinical milestones have been achieved worldwide. With the recent transplantation of genetically modified porcine kidneys and heart into humans, these ground-breaking achievements have attracted great attention worldwide, in the hope that xenotransplantation might alleviate or even solve the problem of organ shortage. On January 20, 2022, the China Organ Transplantation Development Foundation convened a symposium on "The History, Current Situation and Future of Human Xenotransplantation Clinical Trials," where ways to promote the ethical and sustainable development of xenotransplantation in China were discussed among the participating experts. A formal consensus was reached as the product of the symposium, outlining the expert opinions on scientific, regulatory, and ethical issues of clinical trials of xenotransplantation in China.

Lebanese medical students' knowledge on and attitude toward xenotransplantation and its ethical issues: A cross-sectional study

INTRODUCTION

Xenotransplantation is the transplantation of animal parts into humans. This study's aim is to assess the Lebanese medical students' attitude toward xenotransplantation and their knowledge of its related ethical issues.

METHODS

A questionnaire was answered by 120 Lebanese medical students. Statistical analysis and ethical reflections were performed on the results.

RESULTS

Out of the 120 participants, 100 already knew about xenotransplantation, and 61.7% of the students believe that it is applied clinically. Only 25% trust that the animals need to be genetically modified for the organs to be eligible for transplantation. About 25.8% and 46.7% of the students, respectively, strongly agree that the patients' and physicians' beliefs play an important role in agreeing to the procedure. Students were likely to accept the animal organ for transplantation if the transplant could completely cure or improve the course of an untreatable disease (86.6% and 75.0%) or if the outcomes and risks were the same as with a human transplant with a shorter waiting period (71.7%). Students who agreed that animal rights and welfare/wellbeing should be respected tended to disagree with the statement that it is acceptable to use animals for human ends (p = .026).

CONCLUSION

Medical students proved to be knowledgeable on the ethical dilemmas related to xenotransplantation and showed a favorable attitude toward this procedure, which is crucial in its establishment as an absolute clinical reality in the near future and in the development and strengthening of research in this field.

Clinical xenotransplantation seems close: Ethical issues persist

Scientific barriers that have prevented successful xenotransplantation are being breached, yet many ethical issues remain. Some are broad issues that accompany the adoption of novel and expensive technologies, and some are unique to xenotransplantation. Major ethical questions include areas such as: viral transmission; zoonoses and lifetime surveillance; interfering with nature; efficacy, access, and expense; treatment of animals; regulation and oversight.

Xenogeneic support for the recovery of human donor organs

VIDEO ABSTRACT.

Synthetic Biology: Old and New Dilemmas—The Case of Artificial Life

This article aims to examine some of the ethical questions emerging from the use of already existing biotechnological tools and the issues which might occur by synthetic biology’s potential future possibilities. In the first part, the essence of synthetic biology and its relation to the contemporary biotechnological research is analyzed. In the second part, the article examines whether the new biotechnological inventions pose new or revive old moral questions about the ethics of science, engineering, and technology in general. After briefly addressing some of the various issues which are raised by experts, philosophers, but also the general public, concerning synthetic biology in general, it focuses on the topic of “artificial life creation” and presents moral reasons which may or may not allow it. The topic is approached by referring to consequentialist, deontological, but also, virtue theory arguments for and against it and the possibility of a partial permission of “artificial life” experiments, asking whether the benefits outweigh the risks and moral implications is explored. Finally, it proposes an argument in favor of the future exploration of biological innovation, underlying the need for a more balanced access to its beneficial results.

CRISPR/Cas Technology in Pig-to-Human Xenotransplantation Research

CRISPR/Cas (clustered regularly interspaced short palindromic repeats linked to Cas nuclease) technology has revolutionized many aspects of genetic engineering research. Thanks to it, it became possible to study the functions and mechanisms of biology with greater precision, as well as to obtain genetically modified organisms, both prokaryotic and eukaryotic. The changes introduced by the CRISPR/Cas system are based on the repair paths of the single or double strand DNA breaks that cause insertions, deletions, or precise integrations of donor DNA. These changes are crucial for many fields of science, one of which is the use of animals (pigs) as a reservoir of tissues and organs for xenotransplantation into humans. Non-genetically modified animals cannot be used to save human life and health due to acute immunological reactions resulting from the phylogenetic distance of these two species. This review is intended to collect and summarize the advantages as well as achievements of the CRISPR/Cas system in pig-to-human xenotransplantation research. In addition, it demonstrates barriers and limitations that require careful evaluation before attempting to experiment with this technology.