Xenotransplantation utilizing pig donors offers a promising solution to organ shortages, but immune incompatibilities across species remain a major challenge. Current reliance on porcine primary fibroblasts for genome editing is limited by low inefficiency in complex gene editing and difficulties in immunophenotyping edited cells. In this study, we demonstrate that porcine expanded potential stem cells (pEPSCs), derived from preimplantation embryos, provide a robust and versatile platform for generating donor cells for xenotransplantation. These pluripotent cells can differentiate into both embryonic and extraembryonic lineages, maintain genetic stability through multiple edits, and enable precise genome modifications. We performed multiple gene knockouts in pEPSCs targeting key immune rejection genes and precisely inserted a genetic cassette to facilitate streamlined introduction of human cDNAs via cassette exchange. The engineered pEPSCs retained their pluripotency and stability even after multiple rounds of genome editing. When differentiated into endothelial cells, they exhibited high immunogenicity, serving as a rapid and quantitative platform for immune response assessment. Importantly, the edited endothelial cells exhibited substantially reduced immunogenicity, confirming the functional impact of the genetic modifications. Although we have not yet generated live pigs from these gene-edited pEPSCs via somatic cell nuclear transfer (SCNT), our findings establish pEPSCs as a novel and improved platform for generating genetically engineered pig donors and for functionally evaluating genetic modifications, thereby advancing the prospects of xenotransplantation.
In the first half of 2026, xenotransplantation advanced through refinement rather than dramatic new clinical milestones. Clinical studies described graft physiology, immune infiltration, complement activation, coagulation incompatibility, and early function in living recipients, decedent models, and clinical islet xenotransplantation, including the first orthotopic multi-organ decedent xenotransplantation model. Additional preclinical studies in pigs and nonhuman primates on kidney, heart, islets, and blood product models used more advanced engineering of donor organs, including up to ten genetic edits. They identified persistent issues such as thrombotic microangiopathy, renin-angiotensin-aldosterone system dysregulation, and hemolysis-induced ferroptosis. Translational advances in xenotransplantation included the Banff guidelines for xenograft pathology, detection of cell-free DNA derived from the donor, complement, better histocompatibility tests, improved immunosuppressive approaches, and biosafety considerations.
Xenotransplantation has entered a phase of accelerated clinical translation, necessitating renewed international consensus on governance, ethics, safety, and regulatory oversight. In September 2025, the International Xenotransplantation Association (IXA), in partnership with The Transplantation Society (TTS) and with engagement from the World Health Organization (WHO), convened a Global Consultation in Geneva to review, update, and harmonise international guidance for clinical xenotransplantation. This IXA consultation marked the twentieth anniversary of the first WHO Xenotransplantation Advisory Consultation in 2005 and built upon the foundational principles established through the Changsha Communiqué (2008, 2011 and 2018) and subsequent IXA and WHO-led initiatives. Responding to rapid scientific advances, including some defined donor genetic standards, improved immunosuppression, enhanced biosecurity, and strengthened infectious disease surveillance, the IXA undertook an 18‑month, structured, evidence‑based revision process. Seven expert working groups, comprising approximately forty internationally recognised specialists from fourteen countries, reviewed developments across source animal standards and biosecurity, clinical trial design and oversight, immunosuppression and patient management, infectious disease risk and surveillance, ethical and legal frameworks, international governance, and emerging technologies. Draft recommendations were further refined through iterative consultation and plenary deliberation at the in‑person meeting held in Geneva, September 2025. The consultation proposed updated Principles and Recommendations directed to WHO, national regulators, investigators and sponsors, and the IXA/TTS communities. Key elements include proportionate risk benefit assessments, robust donor and recipient surveillance, long‑term biobanking and monitoring, transparency and public engagement, harmonised regulatory oversight consistent with existing allotransplantation frameworks, and equitable access to future clinical applications. The revised guidance aligns with contemporary regulatory expectations of major international jurisdictions regulatory authorities including (AEMPS, ANMAT, CONABIA, CONFEPRIS, EMA, FDA, GTAC, HC, IEC, INCUCAI, Medsafe, MFDS, MHRA, MHLW, NMPA, NZGTAC, MFDS, MHRA, TGA); and consolidates international consensus at a critical juncture for the field. This IXA Global Consultation provides an authoritative, forward‑looking framework to support safe, ethical, and globally coordinated clinical xenotransplantation as it transitions from experimental innovation to regulated clinical practice.
Xenotransplantation offers a promising solution to the shortage of human organs for transplantation but requires overcoming numerous immune responses-particularly those mediated by the innate immune system through natural killer (NK) cells and macrophages. This review examines advances demonstrating that the expression of human leukocyte antigen E (HLA-E) on porcine cells contributes to reduce cellular xenograft rejection. HLA-E expression partially inhibits both direct NK cell cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC), while also attenuating macrophage-mediated lysis. Furthermore, perfusion of transgenic porcine organs expressing HLA-E with human blood resulted in significantly less tissue damage compared to wild-type counterparts, thereby confirming the protective effect of HLA-E against innate immunity. Inhibition of NK cell activation can be further enhanced by co-expression of HLA-G and HLA-E. These findings confirm the potential of HLA-E and HLA-G expression as a complementary strategy in the design of immune-compatible porcine organs for clinical xenotransplantation.
PURPOSE:The objective of this review is to map and synthesize the existing literature regarding informed consent for porcine islet xenotransplantation for the treatment of Type 1 Diabetes. METHODS:The search was conducted in May 2025 through the following databases: PubMed, SCOPUS, EMBASE, and CINAHL. Broad search strings were used to combine the text words "islet" AND "xenotransplantation" AND "consent" or similar permutations and combinations. Peer-reviewed articles were included if they were published between January 1990 and May 2025 and written in English. The final search results were manually exported to a reference manager system (Zotero), and the PRISMA-ScR flow diagram was created to depict the data extraction process. RESULTS:From 134 sources, 7 articles met eligibility for this scoping review. Although clinical studies have been sporadically conducted, there is a lack of literature describing informed consent for islet xenotransplantation. CONCLUSION:This review highlighted a scarcity of scholarly discourse and published guidance on informed consent specifically in the context of islet xenotransplantation.
Since January 2022, eleven clinical xenotransplants into living patients involving gene-edited pig hearts (n = 2) or kidneys (n = 9) have provided initial data on patient selection, organ sourcing, and immunosuppression. Lessons from cardiac cases indicate that (i) patient selection must prioritize candidates with a realistic recovery potential from preexisting debility, (ii) immunosuppressive regimens should be initiated 5-7 days pretransplant to ensure therapeutic blood levels, (iii) the administration of products that potentially contain anti-pig antibodies should be avoided, and (iv) highly sensitive assays are essential to ensure the graft is free of pathogenic microorganisms. In renal cases, evidence suggests that (i) pig organs with multiple gene edits may provide superior protection against the human immune response, and (ii) while immunosuppression targeting the CD40/CD154 co-stimulation pathway effectively prevents the adaptive immune response, it currently fails to eliminate the development of thrombotic microangiopathy or proteinuria. It remains to be determined whether the current gene editing and immunosuppressive protocols are sufficient to enable truly long-term survival of patients and grafts.
For the management of type 1 diabetes, islet xenotransplantation has emerged as a potential alternative to lifelong insulin therapy or islet allotransplantation. However, this progress raises significant ethical questions that warrant further exploration. This article will examine the ethical landscape of islet xenotransplantation, highlighting points of convergence and distinction with solid organ xenotransplantation. We focus on four key areas: (i) animal welfare, including the ethical implications of sourcing large numbers of pigs per recipient; (ii) pediatric considerations, given the lifelong impact of early interventions, and the increasing prevalence and burden of pediatric diabetes; (iii) informed consent and obligations for long-term monitoring including sample retention; and (iv) strategies for inclusive public and patient engagement to build trust and transparency.
Inflammatory responses have been shown to contribute significantly to the rejection of grafts in both allo- and xenotransplantation. In particular, they play a pivotal role in promoting endothelial activation, complement deposition, and thrombosis, thereby compromising the graft function. In this study, we investigated the molecular and functional properties of genetically modified porcine aortic endothelial cells (PAECs) that carry a knockout of α1,3-galactosyltransferase and express human CD46 and thrombomodulin (3GM) in xenogeneic and inflammatory environments. Transcriptomic profiling revealed that these genetic modifications effectively reduced the intrinsic inflammatory and procoagulant phenotype of 3GM PAECs. Under xenogeneic activation, 3GM PAECs also exhibited minimal cellular responses distinct from those of wild-type (WT) PAECs, along with robust protection from the activation of the complement and coagulation systems. However, under inflammatory conditions, 3GM and WT PAECs showed more aligned transcriptional and functional profiles characterized by pronounced upregulation of proinflammatory and prothrombotic pathways, increased complement deposition, and a shift toward a more procoagulant state. This loss of protection during inflammatory conditions was associated with the induction of inflammatory and procoagulant mediators, including PAI-1 and uPAR, despite stable transgene expression. Collectively, these insights enhance our understanding of the complex interplay between inflammation, complement, coagulation, and immune regulation in xenotransplantation. Our findings further emphasize the importance of incorporating both genetic and pharmacologic strategies targeting inflammatory pathways to enhance graft compatibility.
Recent progress has been made toward introducing gene-edited (GE) pig heart and kidney xenotransplantation into clinical practice. In particular, the outcomes of GE pig kidney transplantation have been promising, with three recipients currently surviving between 3 and 9 months after transplantation. These encouraging results highlight the growing feasibility of xenotransplantation as a solution to the shortage of human donor organs. In the United States and many other countries, nearly half of all patients on kidney transplant waiting lists are diabetic. Individuals with diabetic nephropathy often achieve better outcomes when they receive both kidney and islet allotransplants, as this combination restores renal function and improves glucose control. Therefore, such patients would be ideal candidates for combined GE pig kidney and islet xenotransplantation. Because immunosuppressive therapy is essential to maintain a kidney graft, performing a simultaneous islet transplant is clinically justifiable. Studies in nonhuman primates have demonstrated that porcine islet transplantation can achieve long-term glucose regulation, supporting its translational potential. For the foreseeable future, until complications such as post-transplant proteinuria are fully resolved, we propose that patients with diabetic nephropathy receive a human kidney allotransplant in combination with a GE pig islet xenotransplant to optimize outcomes and improve long-term metabolic stability.
BACKGROUND:Xenotransplantation of porcine cells, tissues or organs offers a promising strategy to address the critical shortage of human donor organs. However, cross-species pathogen transmission, instant blood-mediated inflammatory reaction (IBMIR)-related liver injury, chronic over-immunosuppression, and long-term safety remain major challenges in porcine islet xenotransplantation. In this study, we performed a clinical trial aimed to evaluate the biosafety of neonatal porcine islet xenotransplantation in patients with type 1 diabetes. METHODS:Ten recipients were assigned to two groups receiving non-encapsulated neonatal islet cell clusters via the jugular-hepatic-portal vein at mean doses of 6354 ± 835 IEQ/kg and 11 600 ± 1100 IEQ/kg, respectively. Donor pigs originated from a highly inbred, PERV-C-negative colony reared in designated pathogen-free (DPF) conditions, with rigorous pathogen and PERV screening. Immunosuppression included mycophenolate mofetil, tacrolimus, belatacept, and autologous regulatory T-cell therapy, combined with tocilizumab. Continuous low-dose heparin was infused via a portal vein catheter was used for 7 days as anticoagulation therapy. Recipients and spouses were monitored for over 5 years, with 7 followed for more than 10 years. RESULTS:No PERV transmission or transplant-related infections were detected in any recipient or contact during long-term follow-up. The procedure was safe and well-tolerated, with only transient liver function and coagulation changes and mild adverse events. Both groups showed reduced exogenous insulin requirements and markedly lower hypoglycemia incidence, with better glucose control in the higher-dose group. CONCLUSION:This study demonstrates that DPF PERV-C-free neonatal porcine islet xenotransplantation is biologically safe and partially effective, supporting its value as a reliable donor source and foundational platform for advancing clinical islet xenotransplantation. TRIAL REGISTRATION:ClinicalTrials.gov identifier: NCT03162237.
Xenotransplantation has been iteratively improved over the last decade in pre-clinical models, with first-in-human clinical trials underway. The 2025 IXA Congress in Geneva was held in parallel with meetings involving World Health Organization leaders to support the development of new guidance on xenotransplantation in this rapidly evolving field. Key scientific themes of the meeting included the introduction of multiple-gene edited pigs for xenotransplantation research and clinical trials, better characterization of innate and adaptive immune responses and xenograft preservation that optimizes ramifications of ischemia-reperfusion injury during implantation. This comes at a time when gene-edited pig organs are being used for human xenotransplantation, a development that demands safety, reproducibility, durability, and a clear mechanistic understanding of rejection and tolerance.
BACKGROUND:Complement activation is critical in xenograft rejection, but the relative efficacy of pharmacological complement inhibitors remains unclear. METHODS:Peripheral blood mononuclear cells (PBMCs) from wild-type (WT) pigs were exposed to human serum in the presence or absence of complement inhibitors. Complement-dependent cytotoxicity (CDC) and complement deposition were measured by flow cytometry. A C1s inhibitor (sutimlimab, 12.5-800 µg/mL), a C1-esterase inhibitor (berinert, 1.25-10U/mL), a C3/C3b inhibitor (pegcetacoplan, 0.25-4.0 mg/mL), and a C5 inhibitor (tesidolumab, 500-800 µg/mL) were applied to dose-response assays. RESULTS:Only pegcetacoplan (C3/C3b inhibitor) achieved complete inhibition of CDC with minimal C3b/iC3b and C5b-9 deposition. Sutimlimab (C1s inhibitor) produced partial inhibition of CDC (hitting a plateau) and complement deposition, while C1-esterase inhibitor had limited CDC effect and did not reduce C3b/iC3b. Tesidolumab (C5 inhibitor) suppressed C5b-9 but failed to prevent CDC or upstream opsonization. CONCLUSIONS:Although these results might reflect experiments conducted at concentrations lower than clinical doses, our data suggest that, of the limited number of agents tested, pegcetacoplan may be the most effective in inhibiting xenoreactive human complement activation in this experimental setting (i.e., CDC of human complement in the pooled-serum against WT pig PBMCs). However, the results we obtained are puzzling because the C5 inhibitor, eculizumab, has been proven to be highly effective in inhibiting human complement activation in the in vitro CDC model. Furthermore, tesidolumab was reported to be effective in an in vivo NHP model. To obtain the additional information required for clinical application, further investigation would be needed. We would need to (i) ensure that the tesidolumab we were using had not deteriorated in any way and lost its efficacy, and (ii) compared pegcetacoplan with other C5 inhibitors (e.g., ravulizumab, eculizumab).
BACKGROUND:Solid organ xenotransplantation using gene-edited porcine organs has emerged as a potential approach to address the global organ shortage. As preclinical animal models have demonstrated prolonged graft survival, research efforts have increasingly shifted toward clinical translation. In this context, the brain-dead recipient model has been explored as a complementary translational platform, while also raising important scientific, ethical, and regulatory questions. METHODS:This scoping review followed the Arksey and O'Malley framework, with literature searches conducted on the Web of Science Core Collection, Scopus, and PubMed. Experimental studies involving the brain-dead recipient model in solid organ xenotransplantation, as well as commentary or perspective articles addressing related technical and ethical issues were included and synthesized. RESULTS:Twenty-six publications were included, comprising 11 experimental studies and 15 commentary articles. The experimental studies reported 13 solid organ xenotransplantation cases in brain-dead recipients from the United States and China, involving kidney, heart, liver, and lung transplantation. Most studies showed good immediate graft function without hyperacute rejection. Commentary articles presented diverse perspectives, noting both translational potential and limitations related to study design, short observation periods, and ethical oversight, including informed consent. CONCLUSIONS:The brain-dead recipient model occupies a limited but distinct position in xenotransplantation research, offering short-term translational insights while posing persistent ethical and regulatory challenges. Clarifying its context-dependent role, together with improved ethical oversight and regulatory guidance, will be essential for its responsible use and for sustaining public trust as the field moves toward clinical application.
Complement activation is a major barrier to xenotransplantation. We report detailed complement monitoring in a 58-year-old man who received a 10 gene-edited porcine heart expressing human complement regulators CD46 and CD55. Despite these transgenes and prophylactic systemic complement inhibition with C1 esterase inhibitor (C1INH), early surveillance biopsy on post-operative day (POD) 13 showed significant histologic evidence of complement deposition with C3d and C4d within capillaries and endothelial activation. In light of these findings, treatment was escalated to terminal complement inhibition using eculizumab. Post-operative complement activity was assessed via immunohistochemistry and dynamic ex vivo serum assays, including a novel bioluminescent modified Ham (bmHam) assay. Following eculizumab initiation, serum sC5b-9 dropped to undetectable levels, and bmHam cytotoxicity decreased significantly, confirming terminal pathway inhibition. Dilutional bmHam assays further demonstrated stronger complement blockade with eculizumab than with C1INH. However, repeat transplant biopsy on POD 30 biopsy showed persistence of anti-C4d+ and anti-C3c+ staining, and increased C5b-9 compared to POD13. This breakthrough was identified by the dilutional bmHam but was not detected by changes in CH50 or sC5b-9. These findings highlight the potential need for early terminal complement inhibition and integrated functional monitoring as critical components of xenotransplant management.
The critical shortage of donor hearts and the limitations of current mechanical circulatory support devices underscore the need for alternative strategies to address end-stage heart failure. Selective endothelial decellularization has emerged as a promising approach to reduce graft immunogenicity by removing donor endothelial cells while preserving myocardial architecture, thereby enabling subsequent repopulation with recipient-derived cells. However, this technique has never been applied to an intact porcine heart. This pilot study aimed to develop an ex vivo model for partial decellularization of the coronary vasculature in whole porcine hearts. Four hearts were perfused through the aortic root using a controlled circuit, applying variable concentrations of sodium dodecyl sulfate (SDS) or trypsin, followed by washout solutions including saline, distilled water, or hypothermic Buckberg cardioplegia. Histological and immunofluorescence analyses were performed on coronary arteries and ventricular myocardium to assess endothelial removal and tissue preservation. Across all experiments, SDS perfusion achieved effective qualitative and quantitative endothelial decellularization of large-caliber coronary arteries while maintaining the integrity of the internal elastic lamina, extracellular matrix, and myocardial structure. The hypothermic cardioplegic washout protocol demonstrated the highest efficacy, with marked loss of endothelial nuclei and decreased expression of CD31, without evidence of myocardial cell depletion. These findings provide preliminary evidence that selective endothelial decellularization of whole porcine hearts is feasible using SDS under controlled hypothermic conditions. This model may represent an essential step toward generating immunologically compatible xenogeneic hearts through subsequent autologous endothelial repopulation. Further studies are required to standardize the protocol, evaluate microvascular compartments, and explore effective recellularization strategies.
BACKGROUND:Xenotransplantation (XT) has recently been promoted as a potential solution to the organ shortage. While public attitudes toward XT have received increasing attention, little is known about people's XT attitudes when contextualized within the existing human organ supply (deceased, living, and research), and whether XT influences preferences regarding human organ donation. METHODS:This study examines (i) how donation context shapes XT attitudes, (ii) whether framing XT as an alternative acts as a decoy to increase support for human organ donation, and (iii) ethnic differences in XT attitudes in the UK. An online experiment (N = 3142: 1633 White, 600 Asian, 555 Black, 354 Mixed) employed a 3 (donation focus: deceased organ donation, living organ donation, or donating tissue for research) by 2 (XT decoy nudge: present, absent) between-subjects design. RESULTS:Those exposed to the living donation condition and the XT-decoy were more likely to find XT morally justifiable and say that their trust in the NHS would not decline if pig organs were used as transplants. The XT-decoy did not influence support for human organ donation. UK Ethnic minorities strongly oppose XT but showed support for the NHS doing more to encourage human organ donation, particularly the Black community. CONCLUSION:These findings show, for the first time, that presenting XT with living donation increased support for XT and reduced concerns that NHS trust would fall if XT were introduced. This has implications for future XT communications and underscores the need for public consultations tailored to ethnic minorities in the UK.
The aim of this qualitative study is to demonstrate the views of patients who had undergone human-to-human liver transplantation towards xenotransplantation. The study included 20 patients who had experienced the transplant waiting process, transplantation surgery, and posttransplant period. The data were collected through in-depth interviews using a semi-structured interview form. The findings indicated that patients' views on xenotransplantation varied between positive, negative, and ambivalent attitudes. While some of the participants indicated that they could accept such transplantation as the last resort with a utilitarian approach that prioritised the maintenance of life, some of them adopted a cautious or negative attitude due to religious beliefs, ethical concerns, and distrust of the unknown. Lack of information came forth as a determinative factor in indecision and dilemma. The views were categorised under the themes of acceptance for sustaining life, religious beliefs and ethical values, seeking trust in the face of uncertainty, psychosocial domain, and perceived opportunities and challenges. Generally, it was concluded that patients' attitudes towards xenotransplantation were shaped within a conditional acceptance framework and the process should be evaluated multidimensionally.
Objectives This study aimed to investigate the functional recovery of an 8-gene-edited pig heart after orthotopic xenotransplantation, the characteristics of the recipient's immune responses, and the efficacy of postoperative complication management to provide comprehensive experimental evidence for the clinical translation of xenogeneic cardiac transplantation technology.Methods On December 27, 2025, an orthotopic heart was xenotransplanted from an 8-gene-edited pig to a rhesus macaque using the biatrial anastomosis technique. Postoperatively, comprehensive vital sign monitoring, immunosuppressive therapy, and complication interventions were implemented. Donor organ cardiac function, recipient immune indicators, and survival status were evaluated within 30 days after transplantation.Results The recipient macaque survived for more than 30 days postoperatively. The cardiac function of the donor heart gradually stabilized, with the ejection fraction increasing from 58% in the early postoperative phase to 66%. No hyperacute immune rejection occurred. Postoperative complications, including infection, pleural effusion, and blood pressure fluctuations, were effectively controlled with symptomatic treatment.Conclusions An 8-gene-edited pig heart demonstrates good biocompatibility in xenogeneic cardiac transplantation. Standardized surgical procedures, precise immunosuppressive regimens, and comprehensive postoperative care can effectively ensure desirable transplantation outcomes. This study offers an important technical reference for clinical xenogeneic cardiac transplantation.
