Hayato Iwase’s research while affiliated with Johns Hopkins Medicine and other places

Background Xenotransplantation (XTx) is a promising strategy to address the organ shortage. Clinical application will likely require off-site procurement from designated pathogen-free (DPF) facilities, introducing unavoidable cold ischemic time (CIT). The impact of CIT and organ preservation method on graft function in XTx remains unclear. Methods We evaluated eight cases of pig-to-baboon kidney xenotransplantation performed after five hours of CIT, comparing static cold storage (SCS) to hypothermic machine perfusion (HMP) preservation. Outcomes were assessed relative to six additional pig-to-baboon transplants performed with minimal CIT. Results All grafts preserved with SCS experience hyperacute rejection within 90 min of reperfusion, even in recipients with low levels of preformed anti-pig antibodies. In contrast, all HMP-preserved grafts reperfuse without clinical evidence of injury and maintain function for more than 14 days. Grafts transplanted with minimal CIT show similarly favorable outcomes. Conclusions Porcine kidneys are highly sensitive to ischemia-reperfusion injury after cold preservation across xenogeneic barriers. Routine SCS leads to early graft failure, while HMP mitigates ischemic injury and may enable successful clinical XTx despite prolonged CIT.

Xenotransplantation (XTx) is an increasingly realistic solution to the organ shortage. Clinical XTx may require off-site procurement in a designated pathogen free (DPF) facility necessitating a period of cold ischemic time during transportation. This study evaluates the impact of different kidney preservation strategies on early graft function in pig-to-baboon XTx in a series of eight cases of pig-to-baboon xenotransplantation performed after five hours of cold ischemic time and compares these results to six cases of pig-to-baboon xenotransplantation performed with minimal ischemic time. Our data indicates that porcine kidneys appear to be particularly sensitive to IRI after cold preservation, especially across xenogeneic barriers, and routine static cold storage leads to hyperacute graft loss even in recipients with low levels of preformed antibodies. Hypothermic machine perfusion minimizes IRI and may prevent early xenograft loss.

Xenotransplantation represents a possible solution to the organ shortage crisis and is an imminent clinical reality with long-term xenograft survival in pig-to-nonhuman primate (NHP) heart and kidney large animal models, and short-term success in recent human decedent and clinical studies. However, concerns remain about safe clinical translation of these results, given the inconsistency in published survival as well as key differences between preclinical procurement and immunosuppression and clinical standards-of-care. Notably, no studies of solid organ pig-to-NHP transplantation have achieved xenograft survival longer than one month without CD40/CD154 costimulatory blockade, which is not currently an FDA-approved immunosuppression strategy. We now present consistent survival in consecutive cases of pig-to-NHP kidney xenotransplantation, including long-term survival after >3 hours of xenograft cold preservation time as well as long-term survival using FDA-approved immunosuppression. These data provide critical supporting evidence for the safety and feasibility of clinical kidney xenotransplantation. Moreover, long-term survival without CD40/CD154 costimulatory blockade may provide important insights for immunosuppression regimens to be considered for first-in-human clinical trials.

Background Xenotransplantation using pig organs is now a clinical reality. However, the process for xenograft recipient screening lacks clarity and scientific rigor: no established thresholds exist to determine which levels of preformed antipig natural antibodies (Nabs) will be safe for clinical xenograft transplantation, and hyperacute rejection (HAR) or acute humoral xenograft rejection (AHXR), which still impacts pig-to-primate kidney xenograft survivals, may impede broader application of pig-to-human clinical xenograft transplantation. Methods We retrospectively examined 28 cases of pig-to-baboon kidney xenotransplantation using GalTKO±human complement regulatory protein (hCRP)-transgenic (Tg) pig donors, as well as 6 cases of triple-KO multi-Tg (10GE) pig donors, and developed screening algorithms to predict risk of HAR/AHXR based on recipient antipig Nab levels. Preformed Nabs were evaluated using both complement-dependent cytotoxicity and antibody (IgM and IgG) binding flow-cytometry assays. Results High complement-dependent cytotoxicity was associated with HAR/AHXR as expected. However, we also found that high levels of IgG were independently associated with HAR/AHXR, and we developed 2 indices to interpret and predict the risk of IgG-mediated HAR/AHXR. Conclusions Based on the data in this study, we have established a new 2-step screening, which will be used for future clinical kidney xenotransplantation trials.

Combined islet and kidney xenotransplantation for the treatment of diabetic nephropathy represents a compelling and increasingly relevant therapeutic possibility for an ever-growing number of patients who would benefit from both durable renal replacement and cure of the underlying cause of their renal insufficiency: diabetes. Here we briefly review immune barriers to islet transplantation, highlight preclinical progress in the field, and summarize our experience with combined islet and kidney xenotransplantation, including both challenges with islet-kidney composite grafts as well as our recent success with sequential kidney followed by islet xenotransplantation in a pig-to-baboon model.

Background Although improving, survival after pig orthotopic heart transplantation (OHTx) in baboons has been mixed and largely poor. The causes for the high incidence of early failure remain uncertain. Material/Methods We have carried out pig OHTx in 4 baboons. Two died or were euthanized within hours, and 2 survived for 3 and 8 months, respectively. There was evidence of a significant ‘cytokine storm’ in the immediate post-OHTx period with the elevations in IL-6 correlating closely with the final outcome. Results All 4 baboons demonstrated features suggestive of respiratory dysfunction, including increased airway resistance, hypoxia, and tachypnea. Histopathological observations of pulmonary infiltration by neutrophils and, notably, eosinophils within vessels and in the perivascular and peribronchiolar space, with minimal cardiac pathology, suggested a role for early lung acute inflammation. In one, features suggestive of transfusion-related acute lung injury were present. The 2 longer-term survivors died of (i) a cardiac dysrhythmia with cellular infiltration around the conducting tissue (at 3 months), and (ii) mixed cellular and antibody-mediated rejection (at 8 months). Conclusions These initial findings indicate a potential role of acute lung injury early after OHTx. If this response can be prevented, increased survival may result, providing an opportunity to evaluate the factors affecting long-term survival.

Background The aim was to monitor recovery of T/B lymphocytes in baboons after depletion by anti-thymocyte globulin (ATG) and anti-CD20mAb (Rituximab), followed by pig kidney transplantation and maintenance therapy with an anti-CD40mAb-based regimen. Methods In baboons (n = 14), induction was with ATG and anti-CD20mAb, and maintenance with (i) anti-CD40mAb, (ii) rapamycin, and (iii) methylprednisolone. Follow-up was for 6 months, or until rejection or other complication developed. Baboon blood was collected at intervals to measure T/B cells and subsets by flow cytometry. In a separate study in baboons receiving the same immunosuppressive regimen (n = 10), the populations of T/B lymphocytes in PBMCs, lymph nodes, and spleen were examined. Results After induction therapy, the total lymphocyte count and the absolute numbers of CD3⁺, CD4⁺, and CD8⁺T cells fell by >80%, and no CD22⁺B cells remained (all p < 0.001). T cell numbers began to recover early, but no CD22⁺B cells were present in the blood for 2 months. Recovery of both T and B cells remained at <30% of baseline (p < 0.001), even if rejection developed. At 6 months, effector memory CD8⁺T cells had increased more than other T cell subsets, but a greater percentage of B cells were naïve. In contrast to blood and spleen, T and B cells were not depleted in lymph nodes. Conclusions ATG and anti-CD20mAb effectively decreased T and B lymphocytes in the blood and, in the presence of anti-CD40mAb maintenance therapy, recovery of these cells was inhibited. The recovery of effector memory CD8⁺T cells may be detrimental to long-term graft survival.