Faculty Bibliography

INTRODUCTION/BACKGROUND:Predicting graft failure risk in pediatric liver transplantation (LT) recipients could identify areas for improving management. Persistent cognitive, motor, academic, and functional deficits are common in recipients and their impact on graft survival following LT helps inform risk prediction. METHODS:Using SRTR data 2008-2023, we evaluated the cognitive, motor, academic, and functional deficits of LT recipients at time of transplant to 14 years post-LT. We compared all cause graft failure (ACGF) among patients with versus without pre-LT and 1-year post-LT deficits using Cox regression, adjusting for recipient characteristics. We calculated an individual risk score for ACGF. RESULTS:In 8062 pediatric LT recipients median age 3 (IQR: 1, 10), 28.0%, 29.5%, 35.0%, and 79.8% of recipients had pre-LT deficits in cognition, motor, academic activity, and functional status respectively. This decreased to 23.0%, 18.1%, 14.2%, and 38.7% 1-year post-LT. Increased hazard of ACGF was noted in recipients with pre-LT decreased functional status (aHR = 1.13 (per 10% decrease), 95% CI: 1.10-1.15, p < 0.001), definite motor delay (aHR = 1.60, 95% CI: 1.21-2.10, p < 0.001), and inability to participate in academics (aHR = 1.49, 95% CI: 1.08-1.89, p = 0.01), but not delays in cognition (aHR = 0.91, 95% CI: 0.69-1.21, p = 0.19). Our risk score predicting ACGF demonstrated improved predictive performance compared to clinical parameters alone (C-statistic = 0.70 (0.67, 0.72) vs. 0.66 (0.64, 0.69), p < 0.001). CONCLUSIONS:Pediatric LT recipients with pre- or post-LT motor, academic, and functional deficits are at higher risk for ACGF. Care should be taken to assess deficits to identify patients who may benefit from functional intervention to potentially reduce ACGF risk.

Organ shortage remains a major challenge in transplantation, and gene-edited pig organs offer a promising solution^1-3. Despite gene-editing, the immune reactions following xenotransplantation can still cause transplant failure⁴. To understand the immunological response of a pig-to-human kidney xenotransplantation, we conducted large-scale multi-omics profiling of the xenograft and the host's blood over a 61-day procedure in a brain-dead human (decedent) recipient. Blood plasmablasts, natural killer (NK) cells, and dendritic cells increased between postoperative day (POD)10 and 28, concordant with expansion of IgG/IgA B-cell clonotypes, and subsequent biopsy-confirmed antibody-mediated rejection (AbMR) at POD33. Human T-cell frequencies increased from POD21 and peaked between POD33-49 in the blood and xenograft, coinciding with T-cell receptor diversification, expansion of a restricted TRBV2/J1 clonotype and histological evidence of a combined AbMR and cell-mediated rejection at POD49. At POD33, the most abundant human immune population in the graft was CXCL9+ macrophages, aligning with IFN-γ-driven inflammation and a Type I immune response. In addition, we see evidence of interactions between activated pig-resident macrophages and infiltrating human immune cells. Xenograft tissue showed pro-fibrotic tubular and interstitial injury, marked by S100A6⁵, SPP1⁶ (Osteopontin), and COLEC11⁷, at POD21-POD33. Proteomics profiling revealed human and pig complement activation, with decreased human component after AbMR therapy with complement inhibition. Collectively, these data delineate the molecular orchestration of human immune responses to a porcine kidney, revealing potential immunomodulatory targets for improving xenograft survival.

Xenotransplantation of genetically-modified pig kidneys offers a solution to the scarcity of organs for end-stage renal disease patients.¹ We performed a 61-day alpha-Gal knock-out pig kidney and thymic autograft transplant into a nephrectomized brain-dead human using clinically approved immunosuppression, without CD40 blockade or additional genetic modification. Hemodynamic and electrolyte stability and dialysis independence were achieved. Post-operative day (POD) 10 biopsies revealed glomerular IgM and IgA deposition, activation of early complement components and mesangiolysis with stable renal function without proteinuria, a phenotype not seen in allotransplantation. On POD 33, an abrupt increase in serum creatinine was associated with antibody-mediated rejection and increased donor-specific IgG. Plasma exchange, C3/C3b inhibition and rabbit anti-thymocyte globulin (rATG), completely reversed xenograft rejection. Pre-existing donor-reactive T cell clones expanded progressively in the circulation post-transplant, acquired an effector transcriptional profile and were detected in the POD 33 rejecting xenograft prior to rATG treatment. This study provides the first long-term physiologic, immunologic, and infectious disease monitoring of a pig-to-human kidney xenotransplant and indicates that pre-existing xenoreactive T cells and induced antibodies to unknown epitope(s) present a major challenge, despite significant immunosuppression. It also demonstrates that a minimally gene-edited pig kidney can support long-term life-sustaining physiologic functions in a human.

BACKGROUND:Intraportal pancreatic islet transplantation could potentially provide a cure for type 1 diabetes, but this procedure usually requires >1 infusion along with loss of function with time posttransplant. We have previously demonstrated in a major histocompatibility complex (MHC) inbred miniature swine large animal model that the construction of an "islet-kidney" (IK) by implantation of autologous donor islets under the kidney capsule several weeks before transplantation reduces the extent of islet loss. The long-term islet function in juvenile recipients, tolerant to allogeneic IKs, is evaluated in this study. METHODS:We transplanted IKs across minor (n = 3) and full MHC (n = 1) mismatches, using a tolerance-inducing regimen consisting of 12-d treatment with either cyclosporine A or FK506. All 4 recipients experienced an increase in their body mass over time and this weight gain coincided significantly (P < 0.01) with the development of hyperglycemia. To test the hypothesis that the hyperglycemia in these recipients might be due to increased body mass rather than islet loss, the grafts were subsequently retransplanted into MHC-matched, diabetic miniature swine, similar in weight to the original recipients, using the same tolerance-inducing regimen. RESULTS:All 4 of the secondary graft recipients regained glycemic control initially, with a similar, significant correlation between body weight and fasting blood glucose (P < 0.001) over time. CONCLUSIONS:These findings indicate that loss of function of a vascularized IK graft with time is likely due to increased insulin demand in a growing animal and not due to islet loss.

With U.S. Food and Drug Administration (FDA) clearance of clinical trials of kidney xenotransplantation (XTx) in living humans, understanding the recipient experience is critical. Semi-structured interviews with the three living XTx recipients identified core domains of the recipient experience, including quality of life (QoL), fears about XTx, and healthcare team communication and support. Transcribed interviews were analyzed by two qualitative researchers using an inductive thematic approach and were mapped onto the Warwick Patient Experience Model, a validated framework to assess key aspects of patient satisfaction with the healthcare experience. All three recipients (53-year-old female; 66-year-old male; 54-year old male) described a restoration of hope, contrasted with their poor quality of life on dialysis. They emphasized that access to XTx and graft survival requires mutual confidence and commitment between recipients and healthcare teams. XTx recipients use dialysis as a point of reference when describing changes in their post-transplant QoL and seemed well-situated to handle the possibility of graft failure. These insights may aid in the creation of decision aids and educational materials tailored to the specific needs of XTx recipients.

BACKGROUND:Porcine genome editing has revolutionized xenotransplantation, recently enabling the first pig-to-human heart xenotransplants. However, the xeno-immune response in heart xenografts remains largely unexplored. This study aimed to precisely characterize the xeno-immune response and injury in two heart xenografts, transplanted from 10-gene-edited pigs into brain-dead human recipients. METHODS:We analyzed xenograft biopsies at 66-hour post-reperfusion using a multimodal phenotyping approach combining: morphological evaluation, immunophenotyping, ultrastructural assessment, automated quantification of multiplex immunofluorescence staining and gene expression profiling. Xenografts before implantation and wild-type pig hearts with and without ischemia reperfusion injury and brain death were used as controls. RESULTS:Both xenografts showed evidence of endothelial activation and mild microvascular inflammation without capillary C4d deposition. Immune infiltrates were mainly composed of CD15+ and CD68+ innate immune cells. Ultrastructural assessment showed endothelial swelling with occasional intravascular leucocytes. Deep-learning based automated multiplex immunofluorescence analysis confirmed that microvascular inflammation was primarily associated with CD15+ and CD68+ innate immune cells. Both xenografts showed increased expression of genes and pathways associated with monocyte/macrophage activation, neutrophil activation, interferon-gamma response, natural killer cell burden, endothelial activation, apoptosis and injury repair. This phenotype was absent in all control pig hearts, independently from ischemia reperfusion injury and brain death. CONCLUSIONS:Multimodal phenotyping of pig-to-human heart xenografts revealed early signs of xeno-immune response, characterized by mild innate microvascular inflammation, endothelial activation, and molecular signature characteristic of antibody-mediated rejection. Developing such precision diagnostic system could improve graft monitoring in future clinical settings.

With the increasing incidence of hepatocellular carcinoma (HCC) in both the United States and globally, the role of liver transplantation in management continues to be an area of active conversation as it is often considered the gold standard in the treatment of HCC. The use of living donor liver transplantation (LDLT) and the indications in the setting of malignancy, both generally and in HCC specifically, are frequently debated. In terms of both overall survival and recurrence-free survival, LDLT is at least equivalent to DDLT, especially when performed for disease within Milan criteria. Emerging and compelling evidence suggests that LDLT is superior to DDLT in treating HCC as there is a significant decrease in waitlist mortality. As the oncologic indications for liver transplantation continue to expand and the gap between organ demand and organ availability continues to worsen, high volumes centers should consider using LDLT to shrink the ever-expanding waitlist.

The large deficit in donated organs required to provide transplantation to patients with end-stage organ disease is a global health crisis, exacerbated by regional differences in clinical practice and available resources. This deficit highlights the need for better tools to determine organ suitability for transplantation and to enhance the recovery of potential donor organs which are currently not transplanted due to concerns about organ quality. Novel organ assessment approaches, including epidemiological predictive models, advanced functional biometrics, and refined histological analysis, show potential to better identify donated organs suitable for transplantation. In addition, novel machine perfusion platforms have shown remarkable capacities to preserve and potentially modify injured organs, and a series of xenotransplantation experiments suggest a viable pathway to create a new organ supply. Collectively, these technologies will gradually alleviate the organ shortage and expand access to life-saving transplants.

The increasing demand for donor hearts presents both a critical challenge and a significant opportunity for innovation in cardiac transplantation. Advancements in immunosuppressive regimens and genetic engineering have reignited recent interest in xenotransplantation. Notably, 2 human patients have received genetically modified pig hearts under expanded-access authorization. They survived for 40 and 60 days, with xenograft failure preceding death in both cases. Concurrently, decedent studies have focused on monitoring the short-term physiological function of genetically modified cardiac xenografts in legally brain-dead recipients, representing a novel experimental paradigm for preclinical testing to help bridge the gap between nonhuman primate studies and clinical trials. These contemporary achievements build on a large body of exploratory efforts in cardiac xenotransplantation in nonhuman primates. Despite significant progress in overcoming hyperacute rejection, adaptive cellular and humoral immunological barriers remain. This review aims to critically evaluate the current advancements in xenotransplantation, to explore ongoing challenges, and to discuss the future potential of this innovative approach in addressing the growing demand for donor organs in cardiac transplantation.