Machine perfusion in liver transplantation: recent advances and coming challenges.

PURPOSE OF REVIEW: Machine perfusion has been adopted into clinical practice in Europe since the mid-2010s and, more recently, in the United States (US) following approval of normothermic machine perfusion (NMP). We aim to review recent advances, provide discussion of potential future directions, and summarize challenges currently facing the field. RECENT FINDINGS: Both NMP and hypothermic-oxygenated perfusion (HOPE) improve overall outcomes after liver transplantation versus traditional static cold storage (SCS) and offer improved logistical flexibility. HOPE offers additional protection to the biliary system stemming from its' protection of mitochondria and lessening of ischemia-reperfusion injury. Normothermic regional perfusion (NRP) is touted to offer similar protective effects on the biliary system, though this has not been studied prospectively.The most critical question remaining is the optimal use cases for each of the three techniques (NMP, HOPE, and NRP), particularly as HOPE and NRP become more available in the US. There are additional questions regarding the most effective criteria for viability assessment and the true economic impact of these techniques. Finally, with each technique purported to allow well tolerated use of riskier grafts, there is an urgent need to define terminology for graft risk, as baseline population differences make comparison of current data challenging. SUMMARY: Machine perfusion is now widely available in all western countries and has become an essential tool in liver transplantation. Identification of the ideal technique for each graft, optimization of viability assessment, cost-effectiveness analyses, and proper definition of graft risk are the next steps to maximizing the utility of these powerful tools.

Viability assessment of the liver during ex-situ machine perfusion prior to transplantation.

PURPOSE OF REVIEW: In an attempt to reduce waiting list mortality in liver transplantation, less-than-ideal quality donor livers from extended criteria donors are increasingly accepted. Predicting the outcome of these organs remains a challenge. Machine perfusion provides the unique possibility to assess donor liver viability pretransplantation and predict postreperfusion organ function. RECENT FINDINGS: Assessing liver viability during hypothermic machine perfusion remains challenging, as the liver is not metabolically active. Nevertheless, the levels of flavin mononucleotide, transaminases, lactate dehydrogenase, glucose and pH in the perfusate have proven to be predictors of liver viability. During normothermic machine perfusion, the liver is metabolically active and in addition to the perfusate levels of pH, transaminases, glucose and lactate, the production of bile is a crucial criterion for hepatocyte viability. Cholangiocyte viability can be determined by analyzing bile composition. The differences between perfusate and bile levels of pH, bicarbonate and glucose are good predictors of freedom from ischemic cholangiopathy. SUMMARY: Although consensus is lacking regarding precise cut-off values during machine perfusion, there is general consensus on the importance of evaluating both hepatocyte and cholangiocyte compartments. The challenge is to reach consensus for increased organ utilization, while at the same time pushing the boundaries by expanding the possibilities for viability testing.

3-O-Methyl-D-Glucose Blunts Cold Ischemia Damage in Kidney via Inhibiting Ferroptosis.

BACKGROUND: The glucose derivative 3-O-methyl-D-glucose (OMG) is used as a cryoprotectant in freezing cells. However, its protective role and the related mechanism in static cold storage (CS) of organs are unknown. The present study aimed to investigate the effect of OMG on cod ischemia damage in cold preservation of donor kidney. METHODS: Pretreatment of OMG on kidney was performed in an isolated renal cold storage model in rats. LDH activity in renal efflux was used to evaluate the cellular damage. Indicators including iron levels, mitochondrial damage, MDA level, and cellular apoptosis were measured. Kidney quality was assessed via a kidney transplantation (KTx) model in rats. The grafted animals were followed up for 7 days. Ischemia reperfusion (I/R) injury and inflammatory response were assessed by biochemical and histological analyses. RESULTS: OMG pretreatment alleviated prolonged CS-induced renal damage as evidenced by reduced LDH activities and tubular apoptosis. Kidney with pCS has significantly increased iron, MDA, and TUNEL+ cells, implying the increased ferroptosis, which has been partly inhibited by OMG. OMG pretreatment has improved the renal function (p <0.05) and prolonged the 7-day survival of the grafting recipients after KTx, as compared to the control group. OMG has significantly decreased inflammation and tubular damage after KTx, as evidenced by CD3-positive cells and TUNEL-positive cells. CONCLUSION: Our study demonstrated that OMG protected kidney against the prolonged cold ischemia-caused injuries through inhibiting ferroptosis. Our results suggested that OMG might have potential clinical application in cold preservation of donor kidney.

Determination of Maximum Tolerable Cold Ischemia Time in a Mouse Model of Cervical Heterotopic Uterus Transplantation.

BACKGROUND: Uterus transplantation (UTx) is an emerging treatment for uterine factor infertility. Determining the maximum tolerable cold ischemia time is crucial for successful UTx. However, the limit for cold ischemia in the uterus is unclear. This study aimed to examine cold ischemia's effects on mouse uteri and identify the maximum cold ischemia duration that uteri can endure. METHODS: We systematically assessed the tolerance of mouse uteri to extended cold ischemia, 24 h, 36 h, and 48 h, using the cervical heterotopic UTx model. Multiple indicators were used to evaluate ischemia-reperfusion injury, including reperfusion duration, macroscopic examination, oxidative stress, inflammation, and histopathology. The function of transplants was evaluated through estrous cycle monitoring and embryo transfer. RESULTS: Mouse uteri subjected to 48 h of cold ischemia exhibited significant delays and insufficiencies in reperfusion, substantial tissue necrosis, and loss of the estrous cycle. Conversely, uteri that underwent cold ischemia within 36 h showed long survival, regular estrous cycles, and fertility. CONCLUSIONS: Our study demonstrated that mouse uteri can endure at least 36 h of cold ischemia, extending the known limits for cold ischemia and providing a pivotal reference for research on the prevention and treatment of cold ischemic injury in UTx.

Cold Ischemia Time and Delayed Graft Function in Kidney Transplantation: A Paired Kidney Analysis.

BACKGROUND: We aimed to understand the association between cold ischemia time (CIT) and delayed graft function (DGF) after kidney transplantation and the impact of organ pumping on that association. METHODS: Retrospective cohort study using US registry data. We identified kidney pairs from the same donor where both kidneys were transplanted but had a CIT difference >0 and ≤20 h. We determined the frequency of concordant (both kidneys with/without DGF) or discordant (only 1 kidney DGF) DGF outcomes. Among discordant pairs, we computed unadjusted and adjusted relative risk of DGF associated with longer-CIT status, when then repeated this analysis restricted to pairs where only the longer-CIT kidney was pumped. RESULTS: Among 25 831 kidney pairs included, 71% had concordant DGF outcomes, 16% had only the longer-CIT kidney with DGF, and 13% had only the shorter-CIT kidney with DGF. Among discordant pairs, longer-CIT status was associated with a higher risk of DGF in unadjusted and adjusted models. Among pairs where only the longer-CIT kidney was pumped, longer-CIT kidneys that were pumped had a lower risk of DGF than their contralateral shorter-CIT kidneys that were not pumped regardless of the size of the CIT difference. CONCLUSIONS: Most kidney pairs have concordant DGF outcomes regardless of CIT difference, but even small increases in CIT raise the risk of DGF. Organ pumping may mitigate and even overcome the adverse consequences of prolonged CIT on the risk of DGF, but prospective studies are needed to better understand this relationship.

Recipient-associated risk factors for post-liver transplantation biliary complications: A cohort study.

INTRODUCTION: Biliary complications (BCs) are a well-documented post-liver transplantation concern with potential implications for patient survival. This study aims at identifying risk factors associated with the development of BCs in recipients after liver transplantation (LT) and exploring strategies for their management. METHODS: We conducted a retrospective analysis of 1595 adult patients (age > 18 years) who underwent LT surgery between 2019 and 2021. The study assessed the incidence of BCs in this cohort. RESULTS: Of 1595 patients, 178 (11.1%) experienced BCs, while 1417 (88.8%) did not exhibit any signs of such complications. Patients who developed BCs were found to have a significantly lower average age (p < 0.001) and longer cold ischemic times (p < 0.001) compared to those without BCs. Variables such as sex, body mass index (BMI), model for end-stage liver disease (MELD) score, primary diagnosis, type of anastomosis, hepatectomy technique, type of transplanted liver and mortality did not demonstrate statistically significant differences between the two groups (p > 0.05). Univariate logistic regression analysis revealed that a cold ischemic time exceeding 12 hours and duct-to-duct anastomosis were positive predictors for BC development (odds ratios of 6.23 [CI 4.29-9.02] and 1.47 [CI 0.94-2.30], respectively). Conversely, increasing age was associated with a protective effect against BC development, with an odds ratio of 0.64 (CI 0.46-0.89). CONCLUSION: Our multi-variate analysis identified cold ischemia time (CIT) as the sole significant predictor of post-liver transplantation biliary complications. Additionally, this study observed that advancing patient age had a protective influence in this context. Notably, no significant disparities were detected between hepatectomy techniques and the etiology of liver disease types in the two study groups.

Liraglutide Protects Pancreatic Islet From Ischemic Injury by Reducing Oxidative Stress and Activating Akt Signaling During Cold Preservation to Improve Islet Transplantation Outcomes.

BACKGROUND: Islet transplantation is a promising therapy for patients with type 1 diabetes. However, ischemic injury to the donor islets during cold preservation leads to reduced islet quality and compromises transplant outcome. Several studies imply that liraglutide, a glucagon-like peptide-1 receptor agonist, has a positive effect on promoting islet survival, but its impact on islet cold-ischemic injury remains unexplored. Therefore, the aim of this study was to investigate whether liraglutide can improve islet transplantation efficacy by inhibiting cold-ischemic injury and to explore the underlying mechanisms. METHODS: Liraglutide was applied in a mouse pancreas preservation model and a human islets cold-preservation model, and islet viability, function, oxidative stress levels were evaluated. Furthermore, islet transplantation was performed in a syngeneic mouse model and a human-to-nude mouse islet xenotransplantation model. RESULTS: The supplementation of liraglutide in preservation solution improved islet viability, function, and reduced cell apoptosis. Liraglutide inhibited the oxidative stress of cold-preserved pancreas or islets through upregulating the antioxidant enzyme glutathione levels, inhibiting reactive oxygen species accumulation, and maintaining the mitochondrial membrane integrity, which is associated with the activation of Akt signaling. Furthermore, the addition of liraglutide during cold preservation of donor pancreas or donor islets significantly improved the subsequent transplant outcomes in both syngeneic mouse islet transplantation model and human-to-nude mouse islet xenotransplantation model. CONCLUSIONS: Liraglutide protects islets from cold ischemia-related oxidative stress during preservation and hence improved islet transplantation outcomes, and this protective effect of liraglutide in islets is associated with the activation of Akt signaling.

Long-term effects of delayed graft function duration on function and survival of deceased donor kidney transplants / Efeitos de longo prazo da duração da função tardia do enxerto sobre a função e sobrevida de transplantes renais com doadores falecidos

Abstract Introduction: Delayed graft function (DGF) is a frequent complication after deceased donor kidney transplantation with an impact on the prognosis of the transplant. Despite this, long-term impact of DGF on graft function after deceased donor kidney transplantation has not been properly evaluated. Objective: The main objective of this study was to evaluate risk factors for DGF and the impact of its occurrence and length on graft survival and function. Methods: A retrospective cohort study was performed in 517 kidney transplant recipients who received a deceased donor organ between January 2008 and December 2013. Results: The incidence of DGF was 69.3% and it was independently associated with donor's final serum creatinine and age, cold ischemia time, use of antibody induction therapy and recipient's diabetes mellitus. The occurrence of DGF was also associated with a higher incidence of Banff ≥ 1A grade acute rejection (P = 0.017), lower graft function up to six years after transplantation and lower death-censored graft survival at 1 and 5 years (P < 0.05). DGF period longer than 14 days was associated with higher incidence of death-censored graft loss (P = 0.038) and poorer graft function (P < 0.001). No differences were found in patient survival. Conclusions: The occurrence of DGF has a long-lasting detrimental impact on graft function and survival and this impact is even more pronounced when DGF lasts longer than two weeks.

Resumo Introdução: A função tardia do enxerto (FTE) é uma complicação frequente após transplantes renais com doadores falecidos com repercussões sobre o prognóstico do transplante. Contudo, o impacto a longo prazo da FTE sobre a função do enxerto após transplante renal com doador falecido não foi avaliado adequadamente. Objetivo: O principal objetivo do presente estudo foi avaliar os fatores de risco para FTE e o impacto de sua ocorrência e duração na sobrevida e função do enxerto. Métodos: O presente estudo observacional retrospectivo incluiu 517 receptores de transplante renal que receberam órgãos de doadores falecidos entre janeiro de 2008 e dezembro de 2013. Resultados: A incidência de FTE foi de 69,3%. Foi identificada associação independente entre FTE e creatinina sérica final e idade do doador, tempo de isquemia fria, uso de terapia de indução com anticorpos e diabetes mellitus do receptor. A ocorrência de FTE também foi associada a incidência mais elevada de rejeição aguda com classificação de Banff ≥ 1 A (P = 0,017), função reduzida do enxerto até seis anos após o transplante e menor sobrevida do enxerto censurada para óbito em 1 e 5 anos (P <0,05). Períodos de FTE superiores a 14 dias foram associados a maior incidência de perda do enxerto censurada para óbito (P = 0,038) e pior função do enxerto (P <0,001). Não foram identificadas diferenças de sobrevida nos pacientes. Conclusões: A ocorrência de FTE traz prejuízos de longa duração à função e sobrevida do enxerto. Tal impacto é ainda mais pronunciado quando a FTE persiste por mais de duas semanas.

Effect of "the Awakening Protocol" in the outcome of liver transplantation / Efeito do "Protocolo Despertar" no resultado do transplante de fígado

PURPOSE: To analyze mortality (7 days) or graft loss in liver transplantation (Tx) performed within the Awakening Protocol (AP) compared to sequential Tx. METHODS: Analysis of 243 liver tx (230 patients), divided into sequential tx or PD (early morning) to compare graft loss or death (7 days). Significant differences at p <0.05 RESULTS: The PD was adopted in 32.5% of tx. The cold ischemia time (p <0.01) and the interval until transplantation (p <0.01) were significantly different. Age of the donor and recipient, Donor Risk Index, MELD score, and donor base excess, sodium, creatinine and glucose were not different between groups. Previous abdominal surgery was a risk factor for early mortality, but was equally distributed between the groups. There was no difference in mortality or graft loss within 7 days (p = 0.521) CONCLUSION: The adoption of PD, to start tx the morning when harvesting occurs after 10p.m. did not result in worse patient and graft survival. Transplant patients with fulminant hepatic failure and high-risk grafts do not apply to this surgical tactics.

OBJETIVO: Analisar a mortalidade (7 dias) ou perda do enxerto em tx de fígado realizado dentro do Protocolo Despertar (PD), em comparação ao tx realizado de maneira sequencial. MÉTODOS: Análise retrospectiva de 243 tx de fígado (230 pacientes), divididos em tx sequencial ou PD (inicio pela manhã). Foram comparados mortalidade ou perda do enxerto (7 dias). Diferenças significantes para p<0,05. RESULTADOS: O PD foi adotado em 32,5% dos tx. O TIF (p<0,01) e o intervalo até o início do transplante (p<0,01) foram significativamente diferentes. Idade do doador e do receptor, Donor Risk Index, escore MELD, Base excess do doador, sódio, creatinina e glicemia do doador não foram diferentes entre os grupos. Antecedentes cirúrgicos abdominais foram fatores de risco para mortalidade precoce, mas estavam distribuídos igualmente entre os grupos. Não houve diferença na mortalidade ou na perda do enxerto em até 7 dias (p=0,521) CONCLUSÃO: A adoção do PD, para inicio do tx pela manhã, quando a captação ocorre após 22:00 h não acarretou piora na sobrevida dos pacientes. Transplante de pacientes com hepatite fulminante e enxertos de alto risco não se aplicam a esta tática cirúrgica.

Isquemia fría prolongada, factor para rechazo agudo del injerto en trasplante renal cadavérico / Prolonged cold ischemia: risk factor for acute rejection in renal grafting of cadaveric kidney transplantation

Introducción: Es conocido que la exposición del injerto renal a tiempo prolongado de isquemia fría se asocia con rechazo agudo. Dado que no se encontró evidencia del tema en México, el objetivo de este estudio fue determinar el papel del tiempo de isquemia fría prolongado sobre el injerto en el trasplante renal cadavérico en población mexicana. Material y métodos: Estudio observacional, retrospectivo, transversal y analítico para el que se seleccionaron los expedientes de pacientes con trasplante renal entre julio de 1994 y junio de 2004. Se realizó análisis de diferentes variables para determinar su efecto sobre el rechazo agudo, entre ellas el tiempo prolongado de isquemia fría (≥ 12 horas). Resultados: De los 425 transplantes realizados, 33 fueron de donador cadavérico; 10 pacientes tuvieron rechazo agudo. El tiempo prolongado de isquemia fría (OR = 8.4, IC = 1.5-44.2, p = 0.02) y la combinación azatioprina (AZA)-prednisona (PDN)- ciclosporina (CSA) (OR = 9.1, IC = 1.5-49.4, p = 0.02) fueron factores de riesgo para rechazo agudo. El uso de antiCD25 (OR = 0.6, IC = 0.009-0.37, p = 0.001) y la combinación mofetil micofenolato (MMF)-PDN-CSA (OR = 0.1, IC = 0.02-0.65, p = 0.02) fueron factores protectores de rechazo agudo. Conclusiones: En una población mexicana, el tiempo de isquemia fría prolongado y la combinación AZA-PDN-CSA fueron factores de riesgo para rechazo agudo, mientras que el uso de antiCD25 y la combinación MMF-PDN-CSA fueron protectores para rechazo agudo en trasplantes renales de donadores cadavéricos.

BACKGROUND: Exposure of renal grafting to prolonged cold ischemia time (CIT) and the association with acute rejection (AR) are known. However, there is no evidence in Mexico about this topic. Thus, the objective of this study was to evaluate prolonged CIT as a risk factor for AR in renal grafting of cadaveric kidney transplantation in a Mexican population. METHODS: A cross-sectional study was carried out. Clinical files of patients undergoing renal grafting using cadaveric kidneys were reviewed from July 1994-June 2004. Prolonged CIT (=12 h) as a risk factor for AR was evaluated. Other related variables were also examined. RESULTS: From 425 kidney transplantations, only 33 cases were cadaveric. Ten patients had AR. Prolonged CIT (OR 8.4; CI 1.5-44.2, p = 0.02) and azathioprine (AZA)-prednisone (PDN)-cyclosporine (CSA) combination (OR 9.1; CI 1.5-49.4, p = 0.02) were risk factors for AR. Anti-CD25 use (OR 0.6; CI 0.009-0.37, p = 0.001) and mycofenolate mofetil (MMF)-PDN-CSA combination (OR 0.1; CI 0.02-0.65, p = 0.02) were protective factors for AR. CONCLUSIONS: In a Mexican population, prolonged CIT and AZA-PDN-CSA combination were risk factors for AR. Meanwhile, anti- CD25 use and MMF-PDN-CSA combination were protective factors for AR in cadaveric kidney transplantations.