Organ transplants of the future: planning for innovations including xenotransplantation

Xenotransplantation: future frontiers and challenges

PURPOSE OF REVIEW

Recent advancements in genetic engineering have propelled the field of xenotransplantation from preclinical models to early compassionate use cases. As first-in-human clinical trials (FIHCTs) approach, we examine recent developments, ethical and regulatory challenges, immunological considerations, and the clinical infrastructure necessary for successful xenotransplantation trials.

RECENT FINDINGS

Expanded access transplants of pig hearts, kidneys, and livers have identified key challenges. Heart xenotransplants revealed risks of antibody-mediated rejection and zoonotic infections, while kidney xenotransplants suggest that patient selection, rather than immune rejection, may have caused failures. While there has been a report of auxiliary liver transplantation conducted abroad, profound thrombocytopenia poses an obstacle. As FIHCTs draw near, critical clinical challenges include determining the optimal donor genetic constructs and immunosuppressive regimens. Enrollment criteria and patient selection pose additional complexity, alongside ethical concerns such as lifelong zoonosis monitoring. Only a limited number of centers have the expertise needed to conduct these complex trials.

SUMMARY

Xenotransplantation holds great promise as a solution to organ shortages, but success in FIHCTs will require careful design, multidisciplinary collaboration, and strong infrastructure. Addressing immunologic, ethical, and patient selection challenges will be critical. With proper preparation, xenotransplantation could transform organ transplantation.

Prediction model of the T cell-mediated rejection after liver transplantation in children and adults: A case-controlled study

OBJECTIVE

T cell-mediated rejection (TCMR) is a major concern following liver transplantation (LT), and identifying its predictors could help improve post-transplant prognosis. This study aimed to develop a model to predict the risk of TCMR in children and adults after LT.

METHOD

Pre-transplant demographic characteristics, intraoperative parameters, and especially early post-transplant laboratory data for 1221 LT recipients (1096 adults and 125 children) were obtained from the Hospital, University, between 1 January 2015, and 1 January 2022. These data were analyzed to develop the prediction model.

RESULT

The incidence of TCMR was higher in pediatric LT recipients than in adults (17.6% vs. 6.4%, P < 0.001). In adult recipients, seven predictors were identified: donor sex, recipient age, recipient height, and post-transplant levels of serum direct bilirubin, urea, platelets, and neutrophil-to-lymphocyte ratio. In pediatric recipients, four predictors were identified: post-transplant levels of serum monocyte percentage, direct bilirubin, albumin, and gamma-glutamyl transferase. The area under the model's curve incorporating these variables for predicting TCMR after LT was 0.713 (95% confidence interval, CI: 0.655-0.770) in adults and 0.786 (95% CI: 0.675-0.896) in children. Decision curve analyses demonstrated the clinical significance of the model.

CONCLUSION

This study developed a prediction model that may be useful in identifying high-TCMR-risk populations in both adult and pediatric LT recipients.

Expanding Horizons of CRISPR/Cas Technology: Clinical Advancements, Therapeutic Applications, and Challenges in Gene Therapy

CRISPR-Cas technology has transformed the field of gene editing, opening new possibilities for treatment of various genetic disorders. Recent years have seen a surge in clinical trials using CRISPR-Cas-based therapies. This review examines the current landscape of CRISPR-Cas implementation in clinical trials, with data from key registries, including the Australian New Zealand Clinical Trials Registry, the Chinese Clinical Trial Register, and ClinicalTrials.gov. Emphasis is placed on the mechanism of action of tested therapies, the delivery method, and the most recent findings of each clinical trial.

Opinions on the Future of Clinical Pig Kidney Xenotransplantation

Based on promising results obtained in primate models, pioneers in the US have now started to explore the new frontier of genetically-edited pig-to-human transplantation. The recent transition of xenotransplantation into clinical medicine has included transplants in brain-dead subjects and the compassionate use of xenotransplants in living recipients without options for allotransplantation. While the barrier of hyperacute rejection seems to be successfully overcome by gene editing of donor pigs, the occurrence of accelerated rejection could pose significant limitations to the success of the procedure. Ultimately, the establishment of efficient and safe strategies to overcome immunologic barriers will, among other critical factors, such as potential xenozoonotic disease transmission or physiological differences, determine whether and for which indications xenotransplantation will be viable. Considering preliminary outcomes of compassionate use xenotransplantions, which may raise questions about how faithfully data from non-human primate models translate into human outcomes, further research in decedents may be necessary before proceeding with additional clinical transplants. Looking ahead, designing systematic trials in xenotransplantation, including the definition of acceptable eligibility criteria for such high-risk transplants, will be an immense challenge, especially in kidney transplantation, where dialysis provides an effective alternative to transplantation in most cases.

Cognitive and non-cognitive factors affecting decision-making about deceased organ donation in Italy: a systematic review

INTRODUCTION

Decision-making about organ donation (OD) is influenced by interrelated cognitive and non-cognitive factors. The identification of these factors in the general population and among healthcare professionals (HCP) in Italy are key ethical and scientific requirements to inform targeted communication and policy-making interventions, and to promote decision-making processes that are truly informed.

EVIDENCE ACQUISITION

A systematic review of articles published between January 1, 1999, and January 31, 2024 was performed by searching four databases using these terms: "organ donation" AND (attitude OR opinion OR knowledge OR awareness OR intention OR beliefs OR norms OR perception) AND (Italy OR Italian). The reference sections of included articles were scrutinized for additional references.

EVIDENCE SYNTHESIS

Most respondents (lay citizens and HCPs) were in favor of OD, but many (mainly but not exclusively lay citizens) would not authorize OD in the event of death of a family member. Lack of knowledge about OD and the gap between demand and supply of organs, fear of body mutilation, doubts about the criteria for brain death diagnosis, doubts about the wishes of the deceased family member, and distrust towards medical doctors and the healthcare system were the most commonly reported reasons, confirming that cognitive and non-cognitive factors are at play.

CONCLUSIONS

The majority of the Italian population supports OD, but cognitive and non-cognitive barriers are present even among HCPs. Communication campaigns, encouraging family discussions about OD, providing better education for HCPs (including medical and nursing students), and making it easier to sign OD cards may promote informed decision-making and possibly increase consent rates.

Comparative Effectiveness of an Autologous Dentin Matrix for Alveolar Ridge Preservation

An urgent issue is the preservation or reconstruction of the volume of bone tissue in planning and surgical treatment in the fields of medicine, such as traumatology, orthopedics, maxillofacial surgery and dentistry. After tooth extraction, resorption of the bone tissue of the alveolar crest of the jaws occurs, which must either be further eliminated by performing additional operations or using osteoplastic material for socket preservation at the extraction stage. Background and Objectives: The aim of the study was a comparative analysis of various osteoplastic materials used to preserve the volume of bone tissue in the preimplantation period. Materials and Methods: As part of the study, 80 patients were treated, who underwent socket preservation using xenografts, plasma enriched with growth factors, an autologous dentin matrix (ADM) and hydroxyapatite. Results: The results of the treatment 16 weeks after removal were comprehensively analyzed using a morphometric analysis of the bone's volume, cone beam tomography and morphological examination of burr biopsy specimens, as well as by determining the stability of the installed implant at different stages of treatment. Conclusions: The lowest level of bone tissue resorption according to the CBCT data was noted in the ADM and xenograft groups. It should be noted that the use of osteoplastic material in jaw surgery when reconstructing alveolar defects is an essential procedure for preventing the atrophy of bone tissue.

Barriers toward xenotransplantation in Arab World

Organ transplant is a crucial therapeutic strategy offering a life-saving and transformative medical intervention. It provides an opportunity to improve their quality of life and increase their lifespan. The shortage of organs remains a critical global challenge, leading to a prolonged waiting times for organ receivers, which contributes to an increase in morbidity and mortality rates. Hence, xenotransplantation offered a promising solution to the global shortage of organs through the use of animal organs, leading to an increase in donor availability, reducing waiting times, minimizing organ trafficking, improving genetic engineering advancements, and driving scientific innovation. Even though xenotransplantation has many benefits in the clinical setting, it has many barriers that are hindering its achievements and constraining its occurrence. Some barriers to xenotransplant are general, such as the immunological barrier, while others are specific to certain regions due to local causes. The Arab region exhibits disparities in clinical settings compared to the global context, marked by the huge economic crisis and a shortage of trained healthcare professionals. Considering the huge resources and advancements needed in the field of xenotransplantation, this review aims to explore the specific barriers toward xenotransplantation in the Arab countries, highlighting the challenges to overcome these barriers.

Evaluation of knowledge, attitude, and awareness of liver transplant patients toward xenotransplantation

BACKGROUND

Xenotransplantation (XTx) is an alternative treatment for organ scarcity. Investigating the acceptance of XTx among patients from diverse cultural and religious backgrounds is essential. This study aimed to evaluate the knowledge, attitudes, and awareness of XTx among patients undergoing liver transplant (LT).

METHODS

This descriptive study was conducted between November 2022 and August 2023. The study population comprised LT patients aged ≥18 years who were admitted to the hepatology clinic of a university hospital in Turkey. Of the 360 patients (n = 360) interviewed, 351 were deemed eligible for inclusion. A questionnaire was used to collect data. The Kolmogorov-Smirnov test, median, standard deviation, minimum-maximum, number, percentage, and Pearson's chi-square test were used for statistical analysis.

RESULTS

Of the patients, 78.3% were religious and adhered to religious requirements, and 87.2% considered their religious beliefs when making important decisions. In all, 41.3% of the participants believed that organ or tissue transplantation from animals to humans is ethical, while 70.1% of the participants believed that organ and tissue transplantation from non-halal animals to humans was impossible. Specifically, 56.7% would not allow organ or tissue transplantation from a non-halal animal to themselves or a relative. Knowledge and attitude towards XTx were not affected by transplantation type (p > .05), but were affected by sex and educational level (p < .05).

CONCLUSION

This study found that LT patients generally oppose XTx. To enhance knowledge and awareness, religious leaders and healthcare professionals should organize comprehensive and effective seminars on this topic.

Decellularized Extracellular Matrix: The Role of This Complex Biomaterial in Regeneration

Organ transplantation is understood as a technique where an organ from a donor patient is transferred to a recipient patient. This practice gained strength in the 20th century and ensured advances in areas of knowledge such as immunology and tissue engineering. The main problems that comprise the practice of transplants involve the demand for viable organs and immunological aspects related to organ rejection. In this review, we address advances in tissue engineering for reversing the current challenges of transplants, focusing on the possible use of decellularized tissues in tissue engineering. We address the interaction of acellular tissues with immune cells, especially macrophages and stem cells, due to their potential use in regenerative medicine. Our goal is to exhibit data that demonstrate the use of decellularized tissues as alternative biomaterials that can be applied clinically as partial or complete organ substitutes.

Current state of clinical trials on xenograft

BACKGROUND

Xenotransplantation is a worth investing branch of science, since it aims to fulfil the demand on human cells, tissues and organs. Despite decades of consistent work in preclinical assessments, clinical trials on xenotransplantation are far from reaching the targeted goal. Our study aims to track the characteristics, assess the content and summarize the plan of each trial on skin, beta-island, bone marrow, aortic valve and kidney xenografts, leading to a clear sorting of efforts made in this field.

METHODS

In December 2022, we searched clinicaltrial.gov for interventional clinical trials related to xenograft of skin, pancreas, bone marrow, aortic valve and kidney. A total of 14 clinical trials are included in this study. Characteristics on each trial were gathered. Linked publications were searched using Medline/PubMed and Embase/Scopus. Content of trials was reviewed and summarized.

RESULTS

Only 14 clinical trials met our study's criteria. The majority were completed, and most of the trials' enrolment was between 11 and 50 participants. Nine trials used a xenograft of porcine origin. Six trials targeted skin xenotransplantation, four targeted β-cells, two targeted bone marrow and one trial targeted each of the kidney and aortic valve. The average length of trials was 3.38 years. Four trials were conducted in the United States and two trials in each of Brazil, Argentina and Sweden. Of all the included trials, none had any results provided and only three had published work. Phases I, III, and IV had only one trial each. A total of 501 participants were enrolled in these trials.

CONCLUSION

This study sheds the light on the current state of clinical trials on xenograft. Characteristically, trials on this field are of low number, low enrolment, short duration, few related publications and no published results. Porcine organs are the most used in these trials, and skin is the most studied organ. An extension of the literature is highly needed due to the variety of conflicts mentioned. Overall, this study sheds the light on the necessity of managing research efforts, leading to the initiation of more trials targeting the field of xenotransplantation.

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.

In defense of xenotransplantation research: Because of, not in spite of, animal welfare concerns

It is envisioned that one day xenotransplantation will bring about a future where transplantable organs can be safely and efficiently grown in transgenic pigs to help meet the global organ shortage. While recent advances have brought this future closer, worries remain about whether it will be beneficial overall. The unique challenges and risks posed to humans that arise from transplanting across the species barrier, in addition to the costs borne by non-human animals, has led some to question the value of xenotransplantation altogether. In response, we defend the value of xenotransplantation research, because it can satisfy stringent welfare conditions on the permissibility of animal research and use. Along the way, we respond to the alleged concerns, and conclude that they do not currently warrant a cessation or a curtailing of xenotransplantation research.

Informed Consent for Potential Recipients of Pig Kidney Xenotransplantation in the United States

Clinical trials of kidney xenotransplantation are being considered in the United States. Before this novel procedure can take place, investigators will have to obtain approval from the institutional review board. The consent form that will be used for such a trial and that will receive approval from the institutional review board will be complex. Informed consent-the process by which a research participant provides his/her permission to participate in a clinical trial-is a staple of the research process and most commonly is in the form of a physical document. In the case of a novel procedure with uncertain benefits and risks and a participant population in acute need of a transplant, the consent process is crucial. These complexities may raise several ethical considerations for the initial pig kidney xenotransplantation recipients in the United States that will require adaptations of the required elements of the informed consent process by the US Department of Human and Health Services. The ethical issues include (1) a subject's ability to withdraw from the trial, (2) restrictions on their reproductive rights, and (3) the possibility of the need for quarantine if there is a perceived risk of xenozoonosis. This article aims to discuss ethical considerations that may challenge the general required elements of the informed consent form stipulated by the 45 Code of Federal Regulations 46 of the US Department of Health and Human Services and to suggest recommendations for deliberation.

Special Issue "New Therapies of Liver Diseases"

Medical and surgical treatments aimed at curing severe liver diseases and prolonging the survival of patients have improved dramatically in recent years [...].