The liver has long been considered the most difficult organ to transplant across species. Unlike the heart or kidney, whose failures can be bridged by dialysis or mechanical support, the liver performs hundreds of interlocking tasks: synthesising clotting factors and albumin, clearing toxins and ammonia, producing bile, and orchestrating immune surveillance through its unique sinusoidal vasculature. Previous pig-to-human attempts relied on auxiliary transplantation, in which the pig liver was added alongside the recipient’s own liver rather than replacing it, providing partial metabolic support without fully testing the xenograft’s capacity. Earlier work, including a 2024 case in which a gene-edited pig liver supported a patient for ten days, and a 2025 report of gene-modified pig-to-human liver xenotransplantation by the same Chinese group, demonstrated feasibility but left open the question of whether an orthotopic graft, placed where the human liver once sat, could sustain life-sustaining function on its own.

Central to the new study was the donor animal itself. The team used a pig engineered with six genetic modifications, or 6-GE, designed to blunt the three-pronged human immune attack on pig tissue. Three genes were knocked out: GGTA1, CMAH and B4GALNT2, which encode enzymes that decorate pig cell surfaces with carbohydrate antigens, including the galactose-alpha-1,3-galactose epitope, N-glycolylneuraminic acid and the Sd(a)-like antigen, against which humans carry preformed natural antibodies. Three human genes were added: CD46 and CD55, which regulate complement activation at the cell surface, and thrombomodulin (THBD), an anticoagulant protein that helps convert protein C to its activated form and dampens the inflammatory coagulation cascade. Polymerase chain reaction and Sanger sequencing confirmed the edits at the genomic level, and screening found no evidence of porcine endogenous retrovirus transmission or microchimerism in the recipient’s tissues during the observation window.

The recipient was a brain-dead individual, a model that allows researchers to evaluate xenograft function under genuine human physiology while respecting the ethical framework of organ donation. Brain death, however, is a double-edged sword: the dying brain triggers a storm of systemic inflammation and endothelial injury that can itself destabilise haemodynamics and complicate interpretation of graft outcomes. The surgical team performed the orthotopic transplant, removing the native liver and connecting the pig organ to the recipient’s portal vein, hepatic artery, hepatic veins and biliary system. Preoperative ultrasound confirmed that the diameters of the donor and recipient portal veins and hepatic arteries were compatible, a practical prerequisite that is far from trivial given the size and anatomical variability of both human and porcine vasculature.

Over 11 days of continuous monitoring, the xenograft demonstrated that a pig liver can execute core hepatic functions in a human host. The graft produced albumin continuously and generated bile with normal composition, findings that indicate functioning hepatocytes and an intact biliary epithelium, even though the absolute quantities remained below what a healthy human liver would deliver. Metabolomic analyses, deposited in a public database under accession OMIX017282, tracked the biochemical interplay between graft and host. Systemic haemodynamic stability was maintained throughout, meaning the recipient did not require escalating vasopressor support attributable to graft failure, and the pig liver did not provoke the catastrophic collapse that has historically accompanied cross-species organ transplants.

Yet the study is equally notable for what went wrong, and the authors are candid about it. Imaging and functional assessment revealed suboptimal hepatic perfusion arising from microthrombosis, the formation of microscopic clots within the graft’s sinusoidal vessels, which the researchers believe contributed substantially to the late-phase decline in hepatic function. Coagulation abnormalities emerged as progressive thrombocytopenia, a falling platelet count, alongside reduced activity of clotting factors. This pattern echoes the thrombocytopenia and coagulation dysregulation seen in pig-to-baboon liver transplants and in the landmark pig-to-human heart transplants, and it points to a fundamental incompatibility between pig endothelium and the human coagulation system that current genetic engineering has only partially resolved. The liver’s consumption of platelets and clotting factors, combined with impaired thrombomodulin-mediated protein C activation in the face of endothelial stress, appears to drive a vicious cycle of microvascular clotting and bleeding risk.

The immunological portrait drawn from histopathology was in some respects encouraging. Examination of biopsy and autopsy tissue found scant infiltration by T cells and B cells and minimal deposition of immunoglobulin G, suggesting that the adaptive immune response, the arm of immunity responsible for chronic cellular rejection, was largely held in check by the genetic modifications and the targeted immunosuppressive regimen. Instead, the dominant pathology was innate: prominent activation of innate immune cells and evidence of immunoglobulin M-mediated complement activation, the rapid, antibody-triggered cascade that has historically destroyed unmodified pig organs within minutes. That the classical hyperacute rejection was avoided, while a slower innate-driven injury emerged, marks a shift in the nature of the problem rather than its elimination.

The authors argue that these findings define the research agenda for the next phase of clinical translation. Endothelial damage, microthrombosis and coagulopathy now stand out as the critical challenges, and addressing them will likely require additional genetic modifications, such as further human anticoagulant and complement-regulatory transgenes, together with refined immunosuppressive protocols tailored to the liver’s distinctive immunology. The study also underscores the value of the brain-dead recipient model, which generates clinically relevant data without exposing a living patient to an unproven therapy, even as it cautions that the inflammatory milieu of brain death may exaggerate some forms of injury. Metabolomics, serial histology and comprehensive coagulation profiling of the kind reported here give transplant teams a granular, time-resolved picture of how a xenograft fails, information that no animal model can fully replicate.

For the field at large, the experiment represents a careful step forward rather than a breakthrough cure. Global shortages of donor livers leave millions of patients with end-stage liver disease facing limited options, and pig organs, which can be gene-edited, pathogen-screened and produced on demand, remain the most credible long-term solution. The demonstration that a six-gene-edited pig liver can sustain albumin and bile production and haemodynamic stability for 11 days in a human body, while the precise mechanisms of its gradual functional decline are documented at molecular resolution, converts xenogeneic liver transplantation from a speculative concept into an engineering problem with identifiable targets. Whether the next iteration of gene-edited donors and immunosuppressive strategies can extend graft survival from days to months, and ultimately to the years a clinical therapy would demand, will be decided by the coagulation and innate immune pathways this study has now brought into sharp focus.

Subject of Research: Orthotopic xenotransplantation of a six-gene-edited pig liver into a brain-dead human recipient

Article Title: Orthotopic liver xenotransplantation from gene-modified pig to decedent human

Article References: Tao, K., Yang, Z., Zhang, X., Zhang, H., Lin, Z., Yue, S., Yang, Y., Song, W., Wang, D., Liu, Z., Li, H., Chen, Y., Zhou, J., Ding, R., Sun, S., Yu, M., Li, J., Duan, W., Wang, Z., … Dou, K. (2026). Orthotopic liver xenotransplantation from gene-modified pig to decedent human. Nature Biomedical Engineering. https://doi.org/10.1038/s41551-026-01797-2

Image Credits: AI Generated

DOI: 10.1038/s41551-026-01797-2

Keywords: xenotransplantation, pig liver transplant, gene-edited pigs, orthotopic liver transplantation, brain-dead recipient, microthrombosis, coagulopathy, complement activation, thrombocytopenia, albumin production, bile production, organ shortage

The study, published in BMC Genomics, spans five critical developmental stages of the heart, from the neonatal period through adulthood. By combining single-cell RNA sequencing, which captures individual cells, with single-nucleus RNA sequencing, which profiles the genetic activity of nuclei isolated from cells that are difficult to dissociate, the researchers were able to build an integrated picture of the postnatal cardiac landscape. This dual approach is particularly important for heart tissue, where mature cardiomyocytes are large, fragile, and notoriously resistant to standard single-cell preparation techniques.

With this atlas in hand, the team systematically characterized the full cellular panorama of the developing pig heart, documenting how different cell populations emerge, mature, and reorganize as the animal grows. Beyond simply cataloguing cell types, the researchers traced the dynamic changes in gene expression that accompany postnatal cardiac maturation, a period during which the heart transitions from a proliferative, immature state to the hypertrophic, contractile state that defines the adult organ. They also mapped the remodeling of intercellular communication networks—the signaling conversations between cardiomyocytes, fibroblasts, endothelial cells, immune cells, and other residents of the heart—that orchestrate this developmental progression.

The most striking finding emerged from cross-species comparative analysis. When the researchers compared the pig heart atlas with single-cell data from other species, they identified a ventricular cardiomyocyte subpopulation, which they named VCM-LM-SR, characterized by highly active lipid metabolism. This subpopulation is specific to the Wuzhishan miniature pig; it does not appear in the other species examined. The discovery suggests that this breed has evolved, or been selectively bred toward, a distinct metabolic program in its heart muscle cells, one that relies heavily on fatty acid processing as an energy source.

What makes the VCM-LM-SR subpopulation particularly intriguing is its position within the adult cardiac cellular interactome. The researchers found that these lipid-metabolic cardiomyocytes occupy a hub position, meaning they serve as central nodes in the communication network connecting different cell types in the adult heart. Cells that act as hubs typically exert outsized influence over tissue function, coordinating signals and resources across the cellular community. The fact that a metabolically specialized cardiomyocyte subset holds this role hints at a previously unappreciated layer of metabolic regulation in cardiac homeostasis.

The cross-species comparisons also revealed something unexpected about the transcriptional baseline of the Wuzhishan miniature pig heart. The activity of multiple human cardiac disease-related pathways was found to be significantly lower in the pig’s cardiomyocytes compared with the other species examined. In other words, the genetic programs that, when dysregulated, drive heart failure, hypertrophy, and other cardiovascular conditions in humans appear to be running at a quieter baseline level in this donor animal. This finding has direct implications for how researchers interpret data from pig models of cardiac disease, because a lower baseline could mask or alter disease phenotypes in experimental settings.

For the xenotransplantation field, these results carry particular weight. Pig-to-human heart transplantation has moved from theory to clinical reality in recent years, with genetically engineered pig hearts successfully transplanted into human recipients. Understanding the cellular and molecular differences between pig and human hearts is essential for predicting how xenografts will behave after transplantation. The identification of a species-specific lipid-metabolic cardiomyocyte population, and the demonstration that disease-related pathway activity differs between pigs and other species, provides transplant researchers with new molecular features to consider when selecting and engineering donor animals.

The atlas also serves as a foundational resource for studying human cardiac metabolism using large-animal models. Rodent models, while genetically tractable, differ substantially from humans in cardiac physiology, metabolism, and disease susceptibility. Large animals such as pigs bridge this gap far more effectively, and a detailed reference map of the pig heart at single-cell resolution gives researchers a benchmark against which they can measure how cardiac cell states shift in response to disease, diet, surgical intervention, or genetic modification. The developmental dimension of the atlas adds further value, allowing investigators to pinpoint when specific cell populations or communication networks become established during maturation.

Technically, the study showcases the power of integrating single-cell and single-nucleus sequencing data. The researchers employed computational tools including Uniform Manifold Approximation and Projection for visualizing cell populations, differential expression analysis to identify marker genes, transcription factor regulon analysis to infer gene regulatory networks, and Gene Set Variation Analysis to assess pathway activity across cell types and developmental stages. This combination of methods allowed them to move beyond simple cell-type identification toward a functional understanding of how the heart’s cellular ecosystem changes over time and how it differs between species.

The work was funded by the National Key R&D Program Project and the Academician Workstation of the Hainan Academy of Agricultural Sciences, and all animal procedures were approved by the institute’s Animal Care and Use Committee. As genetically engineered pigs edge closer to routine clinical use as organ donors, and as metabolic heart disease continues to rise worldwide, resources like this atlas will become increasingly indispensable. By revealing that even within a single breed, the heart can harbor specialized metabolic cell states unique to that species, the study opens a new window onto the diversity of cardiac biology—and reminds researchers that the choice of model organism matters more, at the single-cell level, than ever before.

Subject of Research: Construction of a single-cell transcriptomic atlas of the Wuzhishan miniature pig heart across postnatal development and cross-species identification of a species-specific lipid-metabolic cardiomyocyte subpopulation.

Article Title: Single-cell atlas of the Wuzhishan miniature pig heart identifies a species-specific lipid-metabolic cardiomyocyte subpopulation

Article References: Xin, W., Li, C., Wang, Z., Han, J., Duan, D., Yuan, J., Qiao, C., Tan, S., Chao, Z., Wang, M., Zhou, S., & Li, X. (2026). Single-cell atlas of the Wuzhishan miniature pig heart identifies a species-specific lipid-metabolic cardiomyocyte subpopulation. BMC Genomics. https://doi.org/10.1186/s12864-026-13335-0

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13335-0

Keywords: Wuzhishan miniature pig, single-cell atlas, cardiomyocytes, lipid metabolism, heart development, xenotransplantation, single-nucleus RNA sequencing, cross-species comparison, cardiac metabolism, BMC Genomics, translational model, cell communication