Current Barriers to Clinical Liver Xenotransplantation

The future of liver transplantation

Over the last 50 years, liver transplantation has evolved into a procedure routinely performed in many countries worldwide. Those able to access this therapy frequently experience a miraculous risk-benefit ratio, particularly if they face the imminently life-threatening disease. Over the decades, the success of liver transplantation, with dramatic improvements in early posttransplant survival, has aggressively driven demand. However, despite the emergence of living donors to augment deceased donors as a source of organs, supply has lagged far behind demand. As a result, rationing has been an unfortunate focus in recent decades. Recent shifts in the epidemiology of liver disease combined with transformative innovations in liver preservation suggest that the underlying premise of organ shortage may erode in the foreseeable future. The focus will sharpen on improving equitable access while mitigating constraints related to workforce training, infrastructure for organ recovery and rehabilitation, and their associated costs. Research efforts in liver preservation will undoubtedly blossom with the aim of optimizing both the timing and conditions of transplantation. Coupled with advances in genetic engineering, regenerative biology, and cellular therapies, the portfolio of innovation, both broad and deep, offers the promise that, in the future, liver transplantation will not only be broadly available to those in need but also represent a highly durable life-saving therapy.

Emerging strategies for treating autoimmune disease with genetically modified dendritic cells

Gene editing of living cells has become a crucial tool in medical research, enabling scientists to address fundamental biological questions and develop novel strategies for disease treatment. This technology has particularly revolutionized adoptive transfer cell therapy products, leading to significant advancements in tumor treatment and offering promising outcomes in managing transplant rejection, autoimmune disorders, and inflammatory diseases. While recent clinical trials have demonstrated the safety of tolerogenic dendritic cell (TolDC) immunotherapy, concerns remain regarding its effectiveness. This review aims to discuss the application of gene editing techniques to enhance the tolerance function of dendritic cells (DCs), with a particular focus on preclinical strategies that are currently being investigated to optimize the tolerogenic phenotype and function of DCs. We explore potential approaches for in vitro generation of TolDCs and provide an overview of emerging strategies for modifying DCs. Additionally, we highlight the primary challenges hindering the clinical adoption of TolDC therapeutics and propose future research directions in this field.

Advances in Organ and Tissue Xenotransplantation

End-stage organ failure can result from various preexisting conditions and occurs in patients of all ages, and organ transplantation remains its only treatment. In recent years, extensive research has been done to explore the possibility of transplanting animal organs into humans, a process referred to as xenotransplantation. Due to their matching organ sizes and other anatomical and physiological similarities with humans, pigs are the preferred organ donor species. Organ rejection due to host immune response and possible interspecies infectious pathogen transmission have been the biggest hurdles to xenotransplantation's success. Use of genetically engineered pigs as tissue and organ donors for xenotransplantation has helped to address these hurdles. Although several preclinical trials have been conducted in nonhuman primates, some barriers still exist and demand further efforts. This review focuses on the recent advances and remaining challenges in organ and tissue xenotransplantation.

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.

Survival Benefit Relative to Treatment Modalities Among Patients with Very Early Intrahepatic Cholangiocarcinoma: an Analysis of the National Cancer Database

BACKGROUND

Liver transplantation (LT) has been considered a potential curative treatment for patients with very early intrahepatic cholangiocarcinoma (ICC) and cirrhosis, yet the survival benefit of LT has not been well defined. This study aimed to compare the long-term survival outcomes of patients who underwent LT with that of individuals who received resection and non-curative intent treatment (non-CIT).

METHODS

Patients who underwent LT, hepatectomy, and non-CIT between 2004 and 2018 were included in the National Cancer Database. Survival benefits of LT over resection and non-CIT were analyzed relative to overall survival (OS).

RESULTS

Among 863 patients, 54 (6.3%) underwent LT, while 342 (39.6%) underwent surgical resection, and 467 (54.1%) received non-CIT, respectively. While the rates of non-CIT increased over time, the percentages of LT remained consistent during the study period. LT patients had similar 5-year OS to individuals who underwent resection (referent, resection: LT, HR 0.95, 95%CI 0.84-1.58, p=0.84). In contrast, 5-year OS was better among patients who underwent LT versus individuals who had non-CIT after controlling other variables using propensity score overlapping weighting (5-year OS, LT 57.1% vs. LR 25.8%, p<0.001).

CONCLUSIONS

The outcomes of very early ICC patients who underwent LT were similar to individuals who underwent hepatectomy, but better than patients treated with non-CIT. LT should be may be a consideration as a treatment option for patients with early stage ICC who are unsuitable candidates for resection.

Xenogeneic cross-circulation for physiological support and recovery of ex vivo human livers

BACKGROUND AND AIMS

The scarcity of suitable donor livers highlights a continuing need for innovation to recover organs with reversible injuries in liver transplantation.

APPROACH AND RESULTS

Explanted human donor livers (n = 5) declined for transplantation were supported using xenogeneic cross-circulation of whole blood between livers and xeno-support swine. Livers and swine were assessed over 24 hours of xeno-support. Livers maintained normal global appearance, uniform perfusion, and preservation of histologic and subcellular architecture. Oxygen consumption increased by 75% ( p = 0.16). Lactate clearance increased from -0.4 ± 15.5% to 31.4 ± 19.0% ( p = 0.02). Blinded histopathologic assessment demonstrated improved injury scores at 24 hours compared with 12 hours. Vascular integrity and vasoconstrictive function were preserved. Bile volume and cholangiocellular viability markers improved for all livers. Biliary structural integrity was maintained.

CONCLUSIONS

Xenogeneic cross-circulation provided multisystem physiological regulation of ex vivo human livers that enabled functional rehabilitation, histopathologic recovery, and improvement of viability markers. We envision xenogeneic cross-circulation as a complementary technique to other organ-preservation technologies in the recovery of marginal donor livers or as a research tool in the development of advanced bioengineering and pharmacologic strategies for organ recovery and rehabilitation.

Auxiliary liver xenotransplantation technique in a transgenic pig-to-non-human primate model: A surgical approach to prolong survival

Xenotransplantation using pigs' liver offers a potentially alternative method to overcome worldwide donor shortage, or more importantly as a bridge to allotransplantation. However, it has been challenged by profound thrombocytopenia and fatal coagulopathy in non-human primate models. Here we suggest that a left auxiliary technique can be a useful method to achieve extended survival of the xenograft. Fifteen consecutive liver xenotransplants were carried out in a pig-to-cynomolgus model. Right auxiliary technique was implemented in two cases, orthotopic in eight cases, and left auxiliary in five cases. None of the right auxiliary recipients survived after surgery due to hemorrhage during complex dissection between the primate's right lobe and inferior vena cava. Orthotopic recipients survived less than 7 days secondary to profound thrombocytopenia and coagulopathy. Two out of five left auxiliary xenotransplants survived more than 3 weeks without uncontrolled thrombocytopenia or anemia, with one of them surviving 34 days, the longest graft survival reported to date. Left auxiliary xenotransplant is a feasible approach in non-human primate experiments, and the feared risk of thrombocytopenia and coagulopathy can be minimized. This may allow for longer evaluation of the xenograft and help better understand histopathological and immunological changes that occur following liver xenotransplantation.

Porcine Macrophage Markers and Populations: An Update

Besides its importance as a livestock species, pig is increasingly being used as an animal model for biomedical research. Macrophages play critical roles in immunity to pathogens, tissue development, homeostasis and tissue repair. These cells are also primary targets for replication of viruses such as African swine fever virus, classical swine fever virus, and porcine respiratory and reproductive syndrome virus, which can cause huge economic losses to the pig industry. In this article, we review the current status of knowledge on porcine macrophages, starting by reviewing the markers available for their phenotypical characterization and following with the characteristics of the main macrophage populations described in different organs, as well as the effect of polarization conditions on their phenotype and function. We will also review available cell lines suitable for studies on the biology of porcine macrophages and their interaction with pathogens.

Co-expression of HLA-E and HLA-G on genetically modified porcine endothelial cells attenuates human NK cell-mediated degranulation

Natural killer (NK) cells play an important role in immune rejection in solid organ transplantation. To mitigate human NK cell activation in xenotransplantation, introducing inhibitory ligands on xenografts via genetic engineering of pigs may protect the graft from human NK cell-mediated cytotoxicity and ultimately improve xenograft survival. In this study, non-classical HLA class I molecules HLA-E and HLA-G were introduced in an immortalized porcine liver endothelial cell line with disruption of five genes (GGTA1, CMAH, β4galNT2, SLA-I α chain, and β-2 microglobulin) encoding three major carbohydrate xenoantigens (αGal, Neu5Gc, and Sda) and swine leukocyte antigen class I (SLA-I) molecules. Expression of HLA-E and/or HLA-G on pig cells were confirmed by flow cytometry. Endogenous HLA-G molecules as well as exogenous HLA-G VL9 peptide could dramatically enhance HLA-E expression on transfected pig cells. We found that co-expression of HLA-E and HLA-G on porcine cells led to a significant reduction in human NK cell activation compared to the cells expressing HLA-E or HLA-G alone and the parental cell line. NK cell activation was assessed by analysis of CD107a expression in CD3-CD56+ population gated from human peripheral blood mononuclear cells. CD107a is a sensitive marker of NK cell activation and correlates with NK cell degranulation and cytotoxicity. HLA-E and/or HLA-G on pig cells did not show reactivity to human sera IgG and IgM antibodies. This in vitro study demonstrated that co-expression of HLA-E and HLA-G on genetically modified porcine endothelial cells provided a superior inhibition in human xenoreactive NK cells, which may guide further genetic engineering of pigs to prevent human NK cell mediated rejection.

Liver Transplantation 2023: Status Report, Current and Future Challenges

Liver transplantation offers live-saving therapy for patients with complications of cirrhosis and stage T2 hepatocellular carcinoma. The demand for organs far outstrips the supply, and innovations aimed at increasing the number of usable deceased donors as well as alternative donor sources are a major focus. The etiologies of cirrhosis are shifting over time, with more need for transplantation among patients with alcohol-associated liver disease and nonalcoholic/metabolic fatty liver disease and less for viral hepatitis, although hepatitis B remains an important indication for transplant in countries with high endemicity. The rise in transplantation for alcohol-associated liver disease and nonalcoholic/metabolic fatty liver disease has brought attention to how patients are selected for transplantation and the strategies needed to prevent recurrent disease. In this review, we present a status report on the most pressing topics in liver transplantation and future challenges.

Opinions of nursing and theology faculty students on Xenotransplantation

BACKGROUND

It is mentioned that students' opinions about xenotransplantation (XTx) have been explored in a limited manner. In particular, there is no literature in Turkey on Nursing and Theology students' perspectives on XTx. This research aimed to find out what Nursing and Theology students thought about XTx.

METHODS

This descriptive and cross-sectional study was conducted on students studying at the Theology and Nursing faculties. The study population consisted of 2.581 students educated in these faculties. Without using any sampling method, it was aimed to reach all students, and 1.780 (70%) students were reached. Data were collected using a participant identification form and questionnaire form, which the researchers developed.

RESULTS

The difference between the answers given by the Nursing and Theology students to the information statements about XTx was statistically significant (p < .001). Nursing and Theology students' attitudes to organ or tissue Tx from halal animals in case of necessity were positive (p < .001). While the nursing students' attitude toward organ or tissue Tx from non-helal animals in case of necessity was negative, Theology students had no idea (p < .001). In other attitude statements, while nursing students responded positively, Theology students responded as "I have no idea" (p ≤ .001).

CONCLUSION

Theology students tended to have the question about XTx and only positive attitude towards XTx from halal animals. Nursing students mostly had positive attitude, but negative when XTx is practiced out of necessity.