Advancing kidney xenotransplantation with anesthesia and surgery - bridging preclinical and clinical frontiers challenges and prospects.

Xenotransplantation is emerging as a vital solution to the critical shortage of organs available for transplantation, significantly propelled by advancements in genetic engineering and the development of sophisticated immunosuppressive treatments. Specifically, the transplantation of kidneys from genetically engineered pigs into human patients has made significant progress, offering a potential clinical solution to the shortage of human kidney supply. Recent trials involving the transplantation of these modified porcine kidneys into deceased human bodies have underscored the practicality of this approach, advancing the field towards potential clinical applications. However, numerous challenges remain, especially in the domains of identifying suitable donor-recipient matches and formulating effective immunosuppressive protocols crucial for transplant success. Critical to advancing xenotransplantation into clinical settings are the nuanced considerations of anesthesia and surgical practices required for these complex procedures. The precise genetic modification of porcine kidneys marks a significant leap in addressing the biological and immunological hurdles that have traditionally challenged xenotransplantation. Yet, the success of these transplants hinges on the process of meticulously matching these organs with human recipients, which demands thorough understanding of immunological compatibility, the risk of organ rejection, and the prevention of zoonotic disease transmission. In parallel, the development and optimization of immunosuppressive protocols are imperative to mitigate rejection risks while minimizing side effects, necessitating innovative approaches in both pharmacology and clinical practices. Furthermore, the post-operative care of recipients, encompassing vigilant monitoring for signs of organ rejection, infectious disease surveillance, and psychological support, is crucial for ensuring post-transplant life quality. This comprehensive care highlights the importance of a multidisciplinary approach involving transplant surgeons, anesthesiologists, immunologists, infectiologists and psychiatrists. The integration of anesthesia and surgical expertise is particularly vital, ensuring the best possible outcomes of those patients undergoing these novel transplants, through safe procedural practices. As xenotransplantation moving closer to clinical reality, establishing consensus guidelines on various aspects, including donor-recipient selection, immunosuppression, as well as surgical and anesthetic management of these transplants, is essential. Addressing these challenges through rigorous research and collective collaboration will be the key, not only to navigate the ethical, medical, and logistical complexities of introducing kidney xenotransplantation into mainstream clinical practice, but also itself marks a new era in organ transplantation.

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.

Close contacts of xenograft recipients: Ethical considerations due to risk of xenozoonosis.

With decades of pre-clinical studies culminating in the recent clinical application of xenotransplantation, it would appear timely to provide recommendations for operationalizing oversight of xenotransplantation clinical trials. Ethical issues with clinical xenotransplantation have been described for decades, largely centering on animal welfare, the risks posed to the recipient, and public health risks posed by potential spread of xenozoonosis. Much less attention has been given to considerations relating to potentially elevated risks faced by those who may care for or otherwise have close contact with xenograft recipients. This paper examines the ethical and logistical issues raised by the potential exposure to xenozoonotic disease faced by close contacts of xenotransplant recipients-defined herein as including but not limited to caregivers, household contacts, and sexual partners-which warrants special attention given their increased risk of exposure to infection compared to the general public. We discuss implications of assent or consent by these close contacts to potentially undergo, along with the recipient, procedures for infection screening and possible quarantine. We then propose several options and recommendations for operationalizing oversight of xenotransplantation clinical trials that could account for and address close contacts' education on and agency regarding the risk of xenozoonosis.

Monitoring Porcine Cytomegalovirus in Both Donors and Recipients is Crucial for Recipient's Survival in Pig-to-Cynomolgus Xenotransplantation.

BACKGROUND: Xenotransplantation, particularly when involving pig donors, presents challenges related to the transmission of porcine cytomegalovirus (pCMV) and its potential impact on recipient outcomes. This study aimed to investigate the relationship between pCMV positivity in both donors and recipients and the survival time of cynomolgus monkey recipients after xenogeneic kidney transplantation. METHODS: We conducted 20 cynomolgus xenotransplants using 18 transgenic pigs. On the surgery day, donor pig blood was sampled, and DNA was extracted from serum and peripheral blood mononuclear cells. Recipient DNA extraction followed the same protocol from pre-transplantation to post-transplantation. Porcine cytomegalovirus detection used real-time polymerase chain reaction (real-time PCR) with the ViroReal kit, achieving a sensitivity of 50 copies/reaction. A Ct value of 37.0 was the pCMV positivity threshold. RESULTS: Of 20 cynomolgus recipients, when donors tested negative for pCMV, recipients also showed negative results in 9 cases. In 4 cases where donors were negative, recipients tested positive. All 5 cases with pCMV-positive donors resulted in positive assessments for recipients. Detection of donor pCMV correlated with shorter recipient survival. Continuous recipient positivity during observation correlated with shorter survival, whereas transient detection showed no significant change in survival rates. However, donor pig phenotypes and transplantation protocols did not significantly impact survival. CONCLUSION: The detection of pCMV in both donors and recipients plays a crucial role in xenotransplantation outcomes. These findings suggest the importance of monitoring and managing pCMV in xenotransplantation to enhance long-term outcomes.

Heart of the matter-infection and xenotransplantation.

In this clinicopathological conference, invited experts discussed a previously published case of a patient with nonischemic cardiomyopathy who underwent heart transplantation from a genetically modified pig source animal. His complex course included detection of porcine cytomegalovirus by plasma microbial cell-free DNA and eventual xenograft failure. The objectives of the session included discussion of selection of immunosuppressive regimens and prophylactic antimicrobials for human xenograft recipients, description of infectious disease risk assessment and mitigation in potential xenograft donors and understanding of screening and therapeutic strategies for potential xenograft-related infections.

The prevention strategies of swine viruses related to xenotransplantation.

Xenotransplantation is considered a solution for the shortage of organs, and pigs play an indispensable role as donors in xenotransplantation. The biosecurity of pigs, especially the zoonotic viruses carried by pigs, has attracted attention. This review introduces several viruses, including porcine endogenous retroviruses that are integrated into the pig genome in a DNA form, herpesviruses that have been proven to clearly affect recipient survival time in previous xenotransplant surgeries, the zoonotic hepatitis E virus, and the widely distributed porcine circoviruses. The detail virus information, such as structure, caused diseases, transmission pathways, and epidemiology was introduced in the current review. Diagnostic and control measures for these viruses, including detection sites and methods, vaccines, RNA interference, antiviral pigs, farm biosecurity, and drugs, are discussed. The challenges faced, including those posed by other viruses and newly emerged viruses, and the challenges brought by the modes of transmission of the viruses are also summarized.

Porcine endogenous retrovirus: classification, molecular structure, regulation, function, and potential risk in xenotransplantation.

Xenotransplantation with porcine organs has been recognized as a promising solution to alleviate the shortage of organs for human transplantation. Porcine endogenous retrovirus (PERV), whose proviral DNAs are integrated in the genome of all pig breeds, is a main microbiological risk for xenotransplantation. Over the last decades, some advances on PERVs' studies have been achieved. Here, we reviewed the current progress of PERVs including the classification, molecular structure, regulation, function in immune system, and potential risk in xenotransplantation. We also discussed the problem of insufficient study on PERVs as well as the questions need to be answered in the future work.

Microchimerism, PERV and Xenotransplantation.

Microchimerism is the presence of cells in an individual that have originated from a genetically distinct individual. The most common form of microchimerism is fetomaternal microchimerism, i.e., cells from a fetus pass through the placenta and establish cell lineages within the mother. Microchimerism was also described after the transplantation of human organs in human recipients. Consequently, microchimerism may also be expected in xenotransplantation using pig cells or organs. Indeed, microchimerism was described in patients after xenotransplantations as well as in non-human primates after the transplantation of pig organs. Here, for the first time, a comprehensive review of microchimerism in xenotransplantation is given. Since pig cells contain porcine endogenous retroviruses (PERVs) in their genome, the detection of proviral DNA in transplant recipients may be misinterpreted as an infection of the recipient with PERV. To prevent this, methods discriminating between infection and microchimerism are described. This knowledge will be important for the interpretation of screening results in forthcoming human xenotransplantations.

Cardiac xenotransplantation: from concept to clinic.

For many patients with terminal/advanced cardiac failure, heart transplantation is the most effective, durable treatment option, and offers the best prospects for a high quality of life. The number of potentially life-saving donated human organs is far fewer than the population who could benefit from a new heart, resulting in increasing numbers of patients awaiting replacement of their failing heart, high waitlist mortality, and frequent reliance on interim mechanical support for many of those deemed among the best candidates but who are deteriorating as they wait. Currently, mechanical assist devices supporting left ventricular or biventricular heart function are the only alternative to heart transplant that is in clinical use. Unfortunately, the complication rate with mechanical assistance remains high despite advances in device design and patient selection and management, and the quality of life of the patients even with good outcomes is only moderately improved. Cardiac xenotransplantation from genetically multi-modified (GM) organ-source pigs is an emerging new option as demonstrated by the consistent long-term success of heterotopic (non-life-supporting) abdominal and life-supporting orthotopic porcine heart transplantation in baboons, and by a recent 'compassionate use' transplant of the heart from a GM pig with 10 modifications into a terminally ill patient who survived for 2 months. In this review, we discuss pig heart xenotransplantation as a concept, including pathobiological aspects related to immune rejection, coagulation dysregulation, and detrimental overgrowth of the heart, as well as GM strategies in pigs to prevent or minimize these problems. Additional topics discussed include relevant results of heterotopic and orthotopic heart transplantation experiments in the pig-to-baboon model, microbiological and virologic safety concepts, and efficacy requirements for initiating formal clinical trials. An adequate regulatory and ethical framework as well as stringent criteria for the selection of patients will be critical for the safe clinical development of cardiac xenotransplantation, which we expect will be clinically tested during the next few years.

Xenotransplantation and Risks: The Opinion of Veterinary Students at Spanish Universities.

BACKGROUND: Understanding the perception of the risks associated with xenotransplant, especially among professionals who will contribute to the care of the animals, is important for xenotransplant to become a clinical reality. The objective of this study was to analyze opinions regarding the risks of organ xenotransplant among veterinary university students in Spain. METHODS: The study population was 2683 veterinary students from different courses and universities in Spain. Instrument valuation: Validated self-administered questionnaire completed anonymously (PCID-XENOTx-Ríos). Consent to collaborate in the study was requested. Variables for the study: attitude toward xenotransplant and risks (infectious, immunologic, ethical/moral, philosophical, religious, other unspecified risks). STATISTICS: descriptive analysis, Student t test, χ2 test, and Fisher exact test. RESULTS: Of the total number of respondents, 2646 students answered this question, with a completion rate of 98.6%. They considered immunologic risk 78.4% (n = 2074), infectious risk 48.6% (n = 1286), ethical/moral risk 10.7% (n = 284), philosophical risk 5.2% (n = 137), religious risk 1.5% (n = 40), and other risks 3.9% (n = 104). Significant relationships were observed between immunologic risks (P < .001), ethical/moral risks (P < .001), and other risks (P = .002). CONCLUSIONS: Despite the consideration of different types of risks, the favorable attitude toward xenotransplant among veterinary students at Spanish universities is highly prevalent, and evidence-based information campaigns on the different risks associated with xenotransplant are important.

What is the clinical relevance of deviant serum calcium and phosphate levels after pig-to-primate kidney xenotransplantation?

Experience from human renal allotransplantation informs us that disturbances in serum calcium and phosphate levels are relatively common. Post-transplant hypercalcemia is associated with an increased risk of recipient mortality, but not of graft loss or nephropathy, and post-transplant hyperphosphatemia with an increased risk of both recipient mortality and death-censored graft failure, but neither post-transplant hypocalcemia nor hypophosphatemia is associated with adverse outcome. Studies after pig-to-nonhuman primate kidney xenotransplantation have demonstrated consistent supranormal serum calcium and subnormal serum phosphate levels. If these trends in serum electrolyte levels were to occur following pig-to-human kidney xenotransplantation, the data from allotransplant studies would indicate an increased risk of recipient mortality (associated with hypercalcemia) but not of graft loss or nephropathy, and no adverse outcome from hypophosphatemia. Furthermore, some nonhuman primates are now surviving in a healthy state for longer than a year after life-supporting pig kidney transplantation, suggesting that chronic hypercalcemia and/or hypophosphatemia are not detrimental to long-term survival, and should not prevent clinical trials of pig kidney transplantation from being undertaken.

Virus Safety of Xenotransplantation.

The practice of xenotransplantation using pig islet cells or organs is under development to alleviate the shortage of human donor islet cells or organs for the treatment of diabetes or organ failure. Multiple genetically modified pigs were generated to prevent rejection. Xenotransplantation may be associated with the transmission of potentially zoonotic porcine viruses. In order to prevent this, we developed highly sensitive PCR-based, immunologicals and other methods for the detection of numerous xenotransplantation-relevant viruses. These methods were used for the screening of donor pigs and xenotransplant recipients. Of special interest are the porcine endogenous retroviruses (PERVs) that are integrated in the genome of all pigs, which are able to infect human cells, and that cannot be eliminated by methods that other viruses can. We showed, using droplet digital PCR, that the number of PERV proviruses is different in different pigs (usually around 60). Furthermore, the copy number is different in different organs of a single pig, indicating that PERVs are active in the living animals. We showed that in the first clinical trials treating diabetic patients with pig islet cells, no porcine viruses were transmitted. However, in preclinical trials transplanting pig hearts orthotopically into baboons, porcine cytomegalovirus (PCMV), a porcine roseolovirus (PCMV/PRV), and porcine circovirus 3 (PCV3), but no PERVs, were transmitted. PCMV/PRV transmission resulted in a significant reduction of the survival time of the xenotransplant. PCMV/PRV was also transmitted in the first pig heart transplantation to a human patient and possibly contributed to the death of the patient. Transmission means that the virus was detected in the recipient, however it remains unclear whether it can infect primate cells, including human cells. We showed previously that PCMV/PRV can be eliminated from donor pigs by early weaning. PERVs were also not transmitted by inoculation of human cell-adapted PERV into small animals, rhesus monkey, baboons and cynomolgus monkeys, even when pharmaceutical immunosuppression was applied. Since PERVs were not transmitted in clinical, preclinical, or infection experiments, it remains unclear whether they should be inactivated in the pig genome by CRISPR/Cas. In summary, by using our sensitive methods, the safety of xenotransplantation can be ensured.

Mechanisms and strategies to promote cardiac xenotransplantation.

End stage heart failure is a terminal disease, and the only curative therapy is orthotopic heart transplantation. Due to limited organ availability, alternative strategies have received intense interest for treatment of patients with advanced heart failure. Recent studies using gene-edited porcine organs suggest that cardiac xenotransplantation may provide a future source of organs. In this review, we highlight the historical milestones for cardiac xenotransplantation and the gene editing strategies designed to overcome immunological barriers, which have culminated in a recent cardiac pig-to-human xenotransplant. We also discuss recent results of studies on the engineering of human-porcine chimeric organs that may provide an alternative and complementary strategy to overcome some of the major immunological barriers to producing a new source of transplantable organs.

Moving xenotransplantation from bench to bedside: Managing infectious risk.

Xenotransplantation of organs from swine in immunosuppressed human recipients poses many of the same challenges of allotransplantation relative to the risk for infection, malignancy, or graft rejection in proportion to the degree of immunosuppression and epidemiologic exposures. The unique features of xenotransplantation from pigs relative to infectious risk center on the potential for unusual organisms derived from swine causing productive infection, "xenosis" or "xenozoonosis," in the host. Based on experience in allotransplantation, the greatest hazard is due to viruses, due to the relative lack of information regarding the behavior of these potential pathogens in humans, the absence of validated serologic and molecular assays for swine-derived pathogens, and uncertainty regarding the efficacy of therapeutic agents for these organisms. Other known, potential pathogens (i.e., bacteria, fungi, parasites) tend to be comparable to those of humans. Concerns remain for unknown organisms in swine that may replicate in immunosuppressed humans. Clinical trials of genetically modified organs sourced from swine in immunosuppressed humans with organ failure are under development. Such trials require informed consent regarding potential infectious risks to the recipient, determination of breeding characteristics of swine, assessments of potential risks to the public and healthcare providers, consideration of ethical issues posed by this novel therapy, and defined strategies to monitor and address infectious episodes that may be encountered by healthcare teams. Clinical trials in xenotransplantation will allow improved definition of potential infectious risks.

Are we ready for pig-to-human clinical xenotransplantation trials? / Estamos prontos para ensaios clínicos de xenotransplante porco-para-humanos? / ¿Estamos listos para ensayos clínicos de xenotrasplante del cerdo al humano?

Abstract: The invention and widely use of organ allotransplantation provides effective treatment of some originally fetal diseases such as liver/kidney failure and has saved million of lives around the globe. However, the scarcity of human organs has caused many patients, who could have been treated, to die while waiting for suitable organs around the world. Pig-to human xenotransplantation provides a potential solution to solve this tough problem. Pig organs have been considered as major sources of xenotransplantation because of the sufficient number of donors, the sizes of organs, and physiologically structural similarities. However, xenotransplantation also has some problems, such as the possibility of spreading animal diseases to human, the interspecies immunological barrier, organs of animal origin challenging human nature, and potential informed consent issues. This article will discuss these potential issues and to see whether it is the suitable time to conduct clinical xenotransplantation trials in humans.

Resumen: La invención y el amplio uso de trasplantes alógenos proporciona tratamiento efectivo de algunas enfermedades de origen fetal, como la insuficiencia renal y hepática, y ha salvado a millones de pacientes en el mundo. Sin embargo, la escasez de órganos humanos ha causado que muchos pacientes en el mundo, que podrían haber sido tratados, murieran por esperar un órgano adecuado. El xenotrasplante del cerdo al humano proporciona una solución potencial para resolver este difícil problema. Los órganos de cerdo han sido considerados como fuentes mayores para xenotrasplantes debido al suficiente número de donantes, el tamaño de los órganos y estructuras fisiológicas similares. No obstante, el xenotrasplante también tiene algunos problemas, como la posibilidad de expandir enfermedades animales a humanos, la barrera inmunológica entre especies, el desafío para la naturaleza humana de tener órganos de origen animal y problemas potenciales de consentimiento informado. Este artículo discute estos temas potenciales y plantea si estamos en un momento apropiado para realizar ensayos clínicos de xenotrasplantes en humanos.

Resumo: A invenção e amplo uso de alotransplante de órgãos propicia tratamento efetivo para algumas doenças originalmente fetais tais como falência hepática/renal e tem salvo milhões de vidas em todo o globo. Entretanto, a escassez de órgãos humanos tem causado a morte de muitos pacientes que poderiam ter sido tratados - aguardando por órgãos apropriados em todo o globo. Xenotransplante porco-para-humanos propicia uma solução potencial para resolver este difícil problema. Órgãos de porco tem sido considerados como as principais fontes de xenotransplante por causa do número suficiente de doadores, do tamanho dos órgãos e de similaridades estruturais fisiológicas. Entretanto, xenotransplante também tem alguns problemas, tais como a possibilidade de disseminar doenças animais aos humanos, a barreira imunológica entre espécies, órgão de origem animal desafiando a natureza humana e aspectos potenciais de consentimento informado. Esse artigo discutirá esses aspectos potenciais e verificará se é o momento adequado para conduzir ensaios clínicos de xenotransplante em humanos.

Results of Two Cases of Pig-to-Human Kidney Xenotransplantation.

BACKGROUND: Xenografts from genetically modified pigs have become one of the most promising solutions to the dearth of human organs available for transplantation. The challenge in this model has been hyperacute rejection. To avoid this, pigs have been bred with a knockout of the alpha-1,3-galactosyltransferase gene and with subcapsular autologous thymic tissue. METHODS: We transplanted kidneys from these genetically modified pigs into two brain-dead human recipients whose circulatory and respiratory activity was maintained on ventilators for the duration of the study. We performed serial biopsies and monitored the urine output and kinetic estimated glomerular filtration rate (eGFR) to assess renal function and xenograft rejection. RESULTS: The xenograft in both recipients began to make urine within moments after reperfusion. Over the 54-hour study, the kinetic eGFR increased from 23 ml per minute per 1.73 m2 of body-surface area before transplantation to 62 ml per minute per 1.73 m2 after transplantation in Recipient 1 and from 55 to 109 ml per minute per 1.73 m2 in Recipient 2. In both recipients, the creatinine level, which had been at a steady state, decreased after implantation of the xenograft, from 1.97 to 0.82 mg per deciliter in Recipient 1 and from 1.10 to 0.57 mg per deciliter in Recipient 2. The transplanted kidneys remained pink and well-perfused, continuing to make urine throughout the study. Biopsies that were performed at 6, 24, 48, and 54 hours revealed no signs of hyperacute or antibody-mediated rejection. Hourly urine output with the xenograft was more than double the output with the native kidneys. CONCLUSIONS: Genetically modified kidney xenografts from pigs remained viable and functioning in brain-dead human recipients for 54 hours, without signs of hyperacute rejection. (Funded by Lung Biotechnology.).

The Influence of Microenvironment on Survival of Intraportal Transplanted Islets.

Clinical islet transplantation has the potential to cure type 1 diabetes. Despite recent therapeutic success, it is still uncommon because transplanted islets are damaged by multiple challenges, including instant blood mediated inflammatory reaction (IBMIR), inflammatory cytokines, hypoxia/reperfusion injury, and immune rejection. The transplantation microenvironment plays a vital role especially in intraportal islet transplantation. The identification and targeting of pathways that function as "master regulators" during deleterious inflammatory events after transplantation, and the induction of immune tolerance, are necessary to improve the survival of transplanted islets. In this article, we attempt to provide an overview of the influence of microenvironment on the survival of transplanted islets, as well as possible therapeutic targets.

Measuring success in pig to non-human-primate renal xenotransplantation: Systematic review and comparative outcomes analysis of 1051 life-sustaining NHP renal allo- and xeno-transplants.

Facile gene editing has accelerated progress in pig to non-human-primate (NHP) renal xenotransplantation, however, outcomes are considered inferior to NHP-allotransplantation. This systematic review and outcomes analysis of life-sustaining NHP-renal transplantation aimed to benchmark "preclinical success" and aggregated 1051 NHP-to-NHP or pig-to-NHP transplants across 88 articles. Although protocols varied, NHP-allotransplantation survival (1, 3, 12months, 67.5%, 37.1%, 13.2%) was significantly greater than NHP-xenotransplantation (1, 3, 12 months, 38.8%, 14.0%, 4.4%; p < .001); a difference partially mitigated by gene-edited donors containing at least knockout of alpha-1,3-galactosyltransferase (1, 3, 12 months, 47.1%, 24.2%, 7.6%; p < .001). Pathological analysis demonstrated more cellular rejection in allotransplantation (62.8% vs. 3.1%, p < .001) and more antibody-mediated rejection in xenotransplantation (6.8% vs. 45.5%, p < .001). Nonrejection causes of graft loss between allotransplants and xenotransplants differed; infection and animal welfare (1.7% vs. 11.2% and 3.9% vs. 17.0%, respectively, p < .001 for both). Importantly, even among a subgroup of unsensitized rhesus macaques under long-term immunosuppression, NHP-allotransplant survival was significantly inferior to clinical allotransplantation (6 months, 36.1% vs. 94.0%; p < .001), which suggests clinical outcomes with renal xenografts may be better than predicted by current preclinical data.