Search Results (21)

Organ failure remains one of the foremost medical and socioeconomic challenges of the twenty-first century, with global transplant waiting lists far exceeding the supply of donor organs. Chronic supportive therapies sustain life but do not restore organ function, underscoring an urgent need for curative alternatives. Bioartificial organs represent a major frontier in organ replacement, driven by converging advances in cell biology, biomaterials science, and bioengineering. By integrating living cells or biologically derived matrices with engineered devices or scaffolds, these systems aim to restore functions that purely mechanical supports cannot reproduce. This review examines the principal technological platforms underpinning the field, including cell encapsulation, decellularization and recellularization, three-dimensional bioprinting, organoids, organ-on-chip systems, and xenotransplantation, and discusses their application to kidney, liver, heart, pancreas, and lung replacement. Across organ systems, progress is advancing from experimental proof-of-concept toward modular and increasingly translational platforms, although whole-organ bioengineering remains largely preclinical for the most structurally complex targets. The major unresolved barriers include vascularization, immune compatibility, scalable cell manufacturing, durable function, and stable integration between biological and engineered components. Overall, bioartificial organ engineering is evolving toward clinically relevant therapeutic strategies capable of complementing, bridging, or eventually reducing dependence on donor-organ transplantation. Full article

End-stage kidney disease (ESKD) is a global health challenge, with kidney transplant demand outstripping supply. Allotransplantation remains the gold standard for treatment but organ scarcity leads to prolonged waiting times and high mortality. Xenotransplantation, using genetically modified porcine kidneys, offers a novel and potentially sustainable solution. Genetic engineering and immunosuppression advances have enabled xenotransplantation to transition from a theoretical possibility to feasible solution. This review explores the evolution of xenotransplantation, the scientific advancements in overcoming immunological barriers, and emerging clinical data. Furthermore, we discuss emerging approaches such as central immune tolerance induction, the ongoing risks of cross-species infection, and the ethical and environmental considerations inherent to scaling up porcine organ donation. With the commencement of the first formal clinical trials, progress in the field could transform kidney transplantation, though questions remain regarding long-term outcomes and societal impact. Full article

Xenotransplantation, particularly the use of genetically modified pigs for kidney transplantation, is gaining attention as a potential solution to the organ shortage. Pigs are ideal donors due to their physiological similarity to humans and rapid reproduction rates. Advances in gene editing technologies like CRISPR have enabled the development of genetically modified pigs that express human-compatible molecules while lacking xenogeneic antigens, such as Galα1-3Gal, which trigger strong immune responses. These modifications significantly reduce the risks of hyperacute and acute rejection, major barriers to successful xenotransplantation. Preclinical studies involving non-human primates and deceased human donors have shown promising short-term results, indicating that pig kidneys can function in human recipients. However, there are no documented cases of long-term survival, and the long-term effects of such transplants remain uncertain. Additionally, concerns about zoonotic disease transmission from pigs to humans necessitate robust pathogen detection systems to ensure safety. More research is also needed to understand immune responses to xenogeneic organs and develop effective immunosuppressive therapies. Ethical considerations surrounding the use of animal organs require ongoing societal dialog. Continued research is essential to establish xenotransplantation as a viable treatment for patients with renal failure. Full article

Porcine cytomegalovirus, more accurately classified as porcine roseolovirus (PCMV/PRV), was shown to be pathogenic in the context of xenotransplantation. Transmission of PCMV/PRV to non-human primates receiving hearts or kidneys from virus-positive pigs significantly reduced the survival time of the recipients. PCMV/PRV was also transmitted to the first human recipient of a pig heart transplant and contributed to the patient’s death. Although PCMV/PRV is highly prevalent in all pig breeds and wild boars, including slaughterhouse pigs, no infections or diseases have been reported in healthy, ill, or immunocompromised humans, suggesting that this virus is not zoonotic and should therefore be classified as xenozoonotic. This indicates that this virus is not zoonotic and must be classified as xenozoonotic. Moreover, it remains unclear whether PCMV/PRV is capable of infecting human cells in vitro. To address this question, human 293T cells resistant to hygromycin were co-cultured with porcine fallopian tube (PFT) cells producing PCMV/PRV. After hygromycin selection, the remaining human cells showed no evidence of infection. Because herpesviruses are generally considered to be species-specific—a notion that has been shown to be not entirely correct—it was also investigated whether PCMV/PRV can infect mouse cells using the same approach. Similarly, no infection was observed. Since the target cells employed in both assays had a reduced capacity to resist viral infection, the findings strongly suggest that PCMV/PRV is unable to infect human or mouse cells, which are equipped with functional antiviral mechanisms. This is supported by findings from the patient who received the first pig heart transplantation. Full article

Urogenital transplantation has emerged as a ground-breaking field with the potential to revolutionize the treatment of end-stage organ failure and congenital or acquired defects of the kidney and urinary bladder. This review provides a comprehensive analysis of the current state, clinical experiences, and experimental progress in kidney and bladder transplantation, with a particular focus on immunological, surgical, and ethical challenges. While kidney transplantation is now a well-established procedure offering improved survival and quality of life for patients with chronic renal failure, bladder transplantation remains in the experimental phase, facing hurdles in vascularization, tissue integration, and functional restoration. Recent advancements in tissue engineering, regenerative medicine, and immunosuppressive strategies are critically discussed, highlighting their role in shaping the future of urogenital grafts. This review also explores xenotransplantation and bio-artificial organ development as promising frontiers. Continued interdisciplinary research is essential to overcome the current limitations and enable routine clinical application of bladder transplantation while optimizing outcomes in kidney grafts. Full article

Solid organ transplantation remains a life-saving treatment for patients worldwide. Unfortunately, the supply of donor organs cannot meet the current need, making the search for alternative sources even more essential. Xenotransplantation using sophisticated genetic engineering techniques to delete and overexpress specific genes in the donor animal has been investigated as a possible option. However, the use of exogenous tissue presents another host of obstacles, particularly regarding organ rejection. Given these limitations, interspecies blastocyst complementation in combination with precise gene knockouts presents a unique, promising pathway for the transplant organ shortage. In recent years, great advancements have been made in the field, with encouraging results in producing a donor-derived organ in a chimeric host. That said, one of the major barriers to successful interspecies chimerism is the mismatch in the developmental stages of the donor and the host cells in the chimeric embryo. Another major barrier to successful chimerism is the mismatch in the developmental speeds between the donor and host cells in the chimeric embryos. This review outlines 19 studies in which blastocyst complementation was used to generate solid organs. In particular, the genesis of the liver, lung, kidney, pancreas, heart, thyroid, thymus and parathyroids was investigated. Of the 19 studies, 7 included an interspecies model. Of the 7, one was completed using human donor cells in a pig host, and all others were rat–mouse chimeras. While very promising results have been demonstrated, with great advancements in the field, several challenges continue to persist. In particular, successful chimerism, organ generation and donor contribution, synchronized donor–host development, as well as ethical concerns regarding human–animal chimeras remain important aspects that will need to be addressed in future research. Full article

Porcine endogenous retrovirus C (PERV-C) is a gammaretrovirus present in the genome of many, but not all, pigs. It is an ecotropic virus, able to infect only pig cells. In contrast, PERV-A and PERV-B, which are present in all pigs, can infect cells of multiple host species, including humans, thereby posing a risk for xenotransplantation when pigs are used as donor animals. Notably, PERV-C can recombine with PERV-A to produce PERV-A/C recombinants that can infect human cells and replicate to higher titers compared to the paternal PERV-A. The objective of this study is to evaluate the reliability of both existing and newly developed polymerase chain reactions (PCR) methods for detecting PERV-C, with the aim of selecting PERV-C-free pigs to be used for xenotransplantation. To detect PERV-C by PCR, specific primers targeting the region of the envelope protein gene, which differs from that of PERV-A and PERV-B due to its unique receptor binding site, must be employed. In this study, new PCR assays were developed to detect PERV-C and a total of ten PCR assays and one real-time PCR assay were evaluated for their reliability in detecting PERV-C. These assays were used to screen indigenous Greek black pigs, Auckland Island pigs, and German slaughterhouse pigs. Two of the PCR assays consistently yielded reliable results, whereas the other PCRs and the real-time PCR gave false positive results. Using the reliable assays, it was shown that one out of four indigenous Greek black pigs (using the same method in a previous publication 11 of 21 pigs were found PERV-C-negative), one out of ten German slaughterhouse pigs, the pig kidney cell line PK15, and all the Auckland Island pigs were PERV-C-negative. The reliable PCR assays will enable the screening of PERV-C-negative donor pigs to be used in xenotransplantation. Most importantly, all the Auckland Island pigs that were genetically modified in Germany for use in clinical trials were PERV-C-negative. Full article

Fetal organs and organoids are important tools for studying organ development. Recently, porcine organs have garnered attention as potential organs for xenotransplantation because of their high degree of similarity to human organs. However, to meet the prompt demand for porcine fetal organs by patients and researchers, effective methods for producing, retrieving, and cryopreserving pig fetuses are indispensable. Therefore, in this study, to collect fetuses for kidney extraction, we employed cesarean sections to preserve the survival and fertility of the mother pig and a method for storing fetal kidneys by long-term cryopreservation. Subsequently, we evaluated the utility of these two methods. We confirmed that the kidneys of pig fetuses retrieved by cesarean section that were cryopreserved for an extended period could resume renal growth when grafted into mice and were capable of forming renal organoids. These results demonstrate the usefulness of long-term cryopreserved fetal pig organs and strongly suggest the effectiveness of our comprehensive system of pig fetus retrieval and fetal organ preservation, thereby highlighting its potential as an accelerator of xenotransplantation research and clinical innovation. Full article

Human pluripotent stem cells have been employed in generating organoids, yet their immaturity compared to fetal organs and the limited induction of all constituent cell types remain challenges. Porcine fetal progenitor cells have emerged as promising candidates for co-culturing with human progenitor cells in regeneration and xenotransplantation research. This study focused on identifying proper preservation methods for porcine fetal kidneys, hearts, and livers, aiming to optimize their potential as cell sources. Extracted from fetal microminiature pigs, these organs were dissociated before and after cryopreservation–thawing, with subsequent cell quality evaluations. Kidney cells, dissociated and aggregated after vitrification in a whole-organ form, were successfully differentiated into glomeruli and tubules in vivo. In contrast, freezing hearts and livers before dissociation yielded suboptimal results. Heart cells, frozen after dissociation, exhibited pulsating heart muscle cells similar to non-frozen hearts. As for liver cells, we developed a direct tissue perfusion technique and successfully obtained highly viable liver parenchymal cells. Freezing dissociated liver cells, although inferior to their non-frozen counterparts, maintained the ability for colony formation. The findings of this study provide valuable insights into suitable preservation methods for porcine fetal cells from kidneys, hearts, and livers, contributing to the advancement of regeneration and xenotransplantation research. Full article

The scarcity of donor kidneys greatly impacts the survival of patients with end-stage renal failure. Pigs are increasingly becoming potential organ donors but are limited by immunological rejection. Based on the human kidney organoid already established with the CHIR99021 and FGF9 induction strategy, we generated porcine kidney organoids from porcine naïve-like ESCs (nESCs). The derived porcine organoids had a tubule-like constructure and matrix components. The porcine organoids expressed renal markers including AQP1 (proximal tubule), WT1 and PODO (podocyte), and CD31 (vascular endothelial cells). These results imply that the organoids had developed the majority of the renal cell types and structures, including glomeruli and proximal tubules. The porcine organoids were also identified to have a dextran absorptive function. Importantly, porcine organoids have a certain abundance of vascular endothelial cells, which are the basis for investigating immune rejection. The derived porcine organoids might serve as materials for immunosuppressor screening for xenotransplantation. Full article

Auckland Island pigs represent an inbred population of feral pigs isolated on the sub-Antarctic island for over 100 years. The animals have been maintained under pathogen-free conditions in New Zealand; they are well characterized virologically and have been used as donor sources in first clinical trials of porcine neonatal islet cell transplantation for the treatment of human diabetes patients. The animals do not carry any of the xenotransplantation-relevant viruses, and in the first clinical trials, no porcine viruses, including porcine endogenous retroviruses (PERVs) were transmitted to the human recipients. PERVs pose a special risk in xenotransplantation, since they are part of the pig genome. When the copy number of PERVs in these animals was analyzed using droplet digital PCR and primers binding to a conserved region of the polymerase gene (PERVpol), a copy number typical for Western pigs was found. This confirms previous phylogenetic analyses of microsatellites as well as mitochondrial analyses showing a closer relationship to European pigs than to Chinese pigs. When kidney cells from very young piglets were analyzed, only around 20 PERVpol copies were detected. Using these cells as donors in somatic cell nuclear transfer (SCNT), animals were born showing PERVpol copy numbers between 35 and 56. These data indicate that Auckland Island pigs have a similar copy number in comparison with other Western pig breeds and that the copy number is higher in adult animals compared with cells from young piglets. Most importantly, PERV-C-free animals were selected and the absence of an additional eight porcine viruses was demonstrated. Full article

Xenotransplantation reemerged as a promising alternative to conventional transplantation enlarging the available organ pool. However, success of xenotransplantation depends on the design and selection of specific genetic modifications and on the development of robust assays allowing for a precise assessment of tissue-specific immune responses. Nevertheless, cell-based assays are often compromised by low proliferative capacity of primary cells. Proximal tubular epithelial cells (PTECs) play a crucial role in kidney function. Here, we generated immortalized PTECs (imPTECs) by overexpression of simian virus 40 T large antigen. ImPTECs not only showed typical morphology and phenotype, but, in contrast to primary PTECs, they maintained steady cell cycling rates and functionality. Furthermore, swine leukocyte antigen (SLA) class I and class II transcript levels were reduced by up to 85% after transduction with lentiviral vectors encoding for short hairpin RNAs targeting β2-microglobulin and the class II transactivator. This contributed to reducing xenogeneic T-cell cytotoxicity (p < 0.01) and decreasing secretion of pro-inflammatory cytokines such as IL-6 and IFN-γ. This study showed the feasibility of generating highly proliferative PTECs and the development of tissue-specific immunomonitoring assays. Silencing SLA expression on PTECs was demonstrated to be an effective strategy to prevent xenogeneic cellular immune responses and may strongly support graft survival after xenotransplantation. Full article

Revascularization of the kidney transplant is classically performed by anastomosing the renal vessels to the recipient iliac vessels. This technique is not applicable when the renal vessels are very small, numerous or anomalous and aberrant. In these instances, the donor aorta and the vena cava have to be used for vascular anastomosis. It would be useful to briefly review the development and the use of the donor aorta and cava in renal transplantation during the last century and discuss the potential clinical application of this technique in xenotransplantation of the porcine kidneys in humans at the dawn of the 21st century. Full article

Kidney xenotransplantation has been attracting attention as a treatment option for end-stage renal disease. Fetal porcine kidneys are particularly promising grafts because they can reduce rejection through vascularization from host vessels. We are proposing xenogeneic regenerative medicine using fetal porcine kidneys injected with human nephron progenitor cells. For clinical application, it is desirable to establish reliable methods for the preservation and quality assessment of grafts. We evaluated the differentiation potency of vitrified porcine fetal kidneys compared with nonfrozen kidneys, using an in vivo differentiation model. Fetal porcine kidneys connected to the bladder were frozen via vitrification and stored in liquid nitrogen. Several days later, they were thawed and transplanted under the retroperitoneum of immunocompromised mice. After 14 days, the frozen kidneys grew and differentiated into mature nephrons, and the findings were comparable to those of nonfrozen kidneys. In conclusion, we demonstrated that the differentiation potency of vitrified fetal porcine kidneys could be evaluated using this model, thereby providing a practical protocol to assess the quality of individual lots. Full article

Transplantation is an effective approach for treating end-stage organ failure. There has been a long-standing interest in xenotransplantation as a means of increasing the number of available organs. In the past decade, there has been tremendous progress in xenotransplantation accelerated by the development of rapid gene-editing tools and immunosuppressive therapy. Recently, the heart and kidney from pigs were transplanted into the recipients, which suggests that xenotransplantation has entered a new era. The genetic discrepancy and molecular incompatibility between pigs and primates results in barriers to xenotransplantation. An increasing body of evidence suggests that innate immune responses play an important role in all aspects of the xenogeneic rejection. Simultaneously, the role of important cellular components like macrophages, natural killer (NK) cells, and neutrophils, suggests that the innate immune response in the xenogeneic rejection should not be underestimated. Here, we summarize the current knowledge about the innate immune system in xenotransplantation and highlight the key issues for future investigations. A better understanding of the innate immune responses in xenotransplantation may help to control the xenograft rejection and design optimal combination therapies. Full article