Assessment of liver graft quality during hypothermic oxygenated perfusion: the first international validation study.

BACKGROUND AND AIM: While it is currently assumed that liver assessment is only possible during normothermic machine perfusion (NMP), there is uncertainty regarding a reliable and quick prediction of graft injury during ex situ hypothermic oxygenated perfusion (HOPE). We therefore intended to test, in an international liver transplant cohort, recently described mitochondrial injury biomarkers measured during HOPE before liver transplantation. STUDY DESIGN: Perfusate samples of human livers from 10 centers in 7 countries with HOPE-experience were analyzed for released mitochondrial compounds, i.e. flavin mononucleotide (FMN), NADH, purine derivates and inflammatory markers. Perfusate FMN was correlated with graft loss due to primary non-function or symptomatic non-anastomotic biliary strictures (NAS), and kidney failure, as well as liver injury after transplantation. Livers deemed unsuitable for transplantation served as negative control. RESULTS: We collected 473 perfusate samples of human DCD (n=315) and DBD livers (n=158). Fluorometric assessment of FMN in perfusate was validated by mass spectrometry (R=0.7011,p<0.0001). Graft loss due to primary non-function or cholangiopathy was predicted by perfusate FMN values (c-statistic mass spectrometry 0.8418 (95%CI 0.7466-0.9370,p<0.0001), c-statistic fluorometry 0.7733 (95%CI 0.7006-0.8461,p<0.0001). Perfusate FMN values were also significantly correlated with symptomatic NAS and kidney failure, and superior in prediction of graft loss when compared to conventional scores derived from donor and recipient parameters, such as the donor risk index and the balance of risk score. Mitochondrial FMN values in liver tissues of non-utilized livers were low, and inversely correlated to high perfusate FMN values and purine metabolite release. CONCLUSIONS: This first international study validates the predictive value of the mitochondrial co-factor FMN, released from complex I during HOPE, and may therefore contribute to a better risk stratification of injured livers before implantation. IMPACT AND IMPLICATIONS: Analysis of 473 perfusates, collected from 10 international centers during hypothermic oxygenated perfusion (HOPE), revealed that mitochondria derived flavin mononucleotide (FMN) values in perfusate is predictive for graft loss, cholangiopathy, and kidney failure after liver transplantation. This result is of high clinical relevance, as recognition of graft quality is urgently needed to improve the safe utilization of marginal livers. Ex-situ machine perfusion approaches, such as HOPE, are therefore likely to increase the number of useable liver grafts.

Long-term outcomes after hypothermic oxygenated machine perfusion and transplantation of 1,202 donor livers in a real-world setting (HOPE-REAL study).

BACKGROUND & AIMS: Despite strong evidence for improved preservation of donor livers by machine perfusion, longer post-transplant follow-up data are urgently needed in an unselected patient population. We aimed to assess long-term outcomes after transplantation of hypothermic oxygenated machine perfusion (HOPE)-treated donor livers based on real-world data (i.e., IDEAL-D stage 4). METHODS: In this international, multicentre, observational cohort study, we collected data from adult recipients of HOPE-treated livers transplanted between January 2012 and December 2021. Analyses were stratified by donation after brain death (DBD) and donation after circulatory death (DCD), sub-divided by their respective risk categories. The primary outcome was death-censored graft survival. Secondary outcomes included the incidence of primary non-function (PNF) and ischaemic cholangiopathy (IC). RESULTS: We report on 1,202 liver transplantations (64% DBD) performed at 22 European centres. For DBD, a total number of 99 benchmark (8%), 176 standard (15%), and 493 extended-criteria (41%) cases were included. For DCD, 117 transplants were classified as low risk (10%), 186 as high risk (16%), and 131 as futile (11%), with significant risk profile variations among centres. Actuarial 1-, 3-, and 5-year death-censored graft survival rates for DBD and DCD livers were 95%, 92%, and 91%, vs. 92%, 87%, and 81%, respectively (log-rank p = 0.003). Within DBD and DCD strata, death-censored graft survival was similar among risk groups (log-rank p = 0.26, p = 0.99). Graft loss due to PNF or IC was 2.3% and 0.4% (DBD), and 5% and 4.1% (DCD). CONCLUSIONS: This study shows excellent 5-year survival after transplantation of HOPE-treated DBD and DCD livers with low rates of graft loss due to PNF or IC, irrespective of their individual risk profile. HOPE treatment has now reached IDEAL-D stage 4, which further supports its implementation in routine clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05520320. IMPACT AND IMPLICATIONS: This study demonstrates the excellent long-term performance of hypothermic oxygenated machine perfusion (HOPE) treatment of donation after circulatory and donation after brain death liver grafts irrespective of their individual risk profile in a real-world setting, outside the evaluation of randomised-controlled trials. While previous studies have established safety, feasibility, and efficacy against the current standard, according to the IDEAL-D evaluation framework, HOPE treatment has now reached the final IDEAL-D stage 4, which further supports its implementation in routine clinical practice.

Hypothermic Machine Perfusion in Liver Transplantation - A Randomized Trial.

BACKGROUND: Transplantation of livers obtained from donors after circulatory death is associated with an increased risk of nonanastomotic biliary strictures. Hypothermic oxygenated machine perfusion of livers may reduce the incidence of biliary complications, but data from prospective, controlled studies are limited. METHODS: In this multicenter, controlled trial, we randomly assigned patients who were undergoing transplantation of a liver obtained from a donor after circulatory death to receive that liver either after hypothermic oxygenated machine perfusion (machine-perfusion group) or after conventional static cold storage alone (control group). The primary end point was the incidence of nonanastomotic biliary strictures within 6 months after transplantation. Secondary end points included other graft-related and general complications. RESULTS: A total of 160 patients were enrolled, of whom 78 received a machine-perfused liver and 78 received a liver after static cold storage only (4 patients did not receive a liver in this trial). Nonanastomotic biliary strictures occurred in 6% of the patients in the machine-perfusion group and in 18% of those in the control group (risk ratio, 0.36; 95% confidence interval [CI], 0.14 to 0.94; P = 0.03). Postreperfusion syndrome occurred in 12% of the recipients of a machine-perfused liver and in 27% of those in the control group (risk ratio, 0.43; 95% CI, 0.20 to 0.91). Early allograft dysfunction occurred in 26% of the machine-perfused livers, as compared with 40% of control livers (risk ratio, 0.61; 95% CI, 0.39 to 0.96). The cumulative number of treatments for nonanastomotic biliary strictures was lower by a factor of almost 4 after machine perfusion, as compared with control. The incidence of adverse events was similar in the two groups. CONCLUSIONS: Hypothermic oxygenated machine perfusion led to a lower risk of nonanastomotic biliary strictures following the transplantation of livers obtained from donors after circulatory death than conventional static cold storage. (Funded by Fonds NutsOhra; DHOPE-DCD ClinicalTrials.gov number, NCT02584283.).

Comparative Analysis of Digestion Methods for Bile Proteomics: The Key to Unlocking Biliary Biomarker Potential.

BACKGROUND: Bile's potential to reflect the health of the biliary system has led to increased attention, with proteomic analysis offering deeper understanding of biliary diseases and potential biomarkers. With the emergence of normothermic machine perfusion (NMP), bile can be easily collected and analyzed. However, the composition of bile can make the application of proteomics challenging. This study systematically evaluated various trypsin digestion methods to optimize proteomics of bile from human NMP livers. METHODS: Bile was collected from 12 human donor livers that were accepted for transplantation after the NMP viability assessment. We performed tryptic digestion using six different methods: in-gel, in-solution, S-Trap, SMART, EasyPep, and filter-aided sample purification, with or without additional precipitation before digestion. Proteins were analyzed using untargeted proteomics. Methods were assessed for total protein IDs, variation, and protein characteristics to determine the most optimal method. RESULTS: Methods involving precipitation surpassed crude methods in protein identifications (4500 vs 3815) except for in-gel digestion. Filtered data (40%) resulted in 3192 versus 2469 for precipitated and crude methods, respectively. We found minimal differences in mass, cellular components, or hydrophobicity of proteins between methods. Intermethod variability was notably diverse, with in-gel, in-solution, and EasyPep outperforming others. Age-related biological comparisons revealed upregulation of metabolic-related processes in younger donors and immune response and cell cycle-related processes in older donors. CONCLUSIONS: Variability between methods emphasizes the importance of cross-validation across multiple analytical approaches to ensure robust analysis. We recommend the in-gel crude method for its simplicity and efficiency, avoiding additional precipitation steps. Sample processing speed, cost, cleanliness, and reproducibility should be considered when a digestion method is selected for bile proteomics.

The Influence of Hepatic Steatosis and Fibrosis on Postoperative Outcomes After Major Liver Resection of Perihilar Cholangiocarcinoma.

BACKGROUND: Surgical resection for perihilar cholangiocarcinoma (pCCA) is associated with high operative risks. Impaired liver regeneration in patients with pre-existing liver disease may contribute to posthepatectomy liver failure (PHLF) and postoperative mortality. This study aimed to determine the incidence of hepatic steatosis and fibrosis and their association with PHLF and 90-day postoperative mortality in pCCA patients. METHODS: Patients who underwent a major liver resection for pCCA were included in the study between 2000 and 2021 from three tertiary referral hospitals. Histopathologic assessment of hepatic steatosis and fibrosis was performed. The primary outcomes were PHLF and 90-day mortality. RESULTS: Of the 401 included patients, steatosis was absent in 334 patients (83.3%), mild in 58 patients (14.5%) and moderate to severe in 9 patients (2.2%). There was no fibrosis in 92 patients (23.1%), periportal fibrosis in 150 patients (37.6%), septal fibrosis in 123 patients (30.8%), and biliary cirrhosis in 34 patients (8.5%). Steatosis (≥ 5%) was not associated with PHLF (odds ratio [OR] 1.36; 95% confidence interval [CI] 0.69-2.68) or 90-day mortality (OR 1.22; 95% CI 0.62-2.39). Neither was fibrosis (i.e., periportal, septal, or biliary cirrhosis) associated with PHLF (OR 0.76; 95% CI 0.41-1.41) or 90-day mortality (OR 0.60; 95% CI 0.33-1.06). The independent risk factors for PHLF were preoperative cholangitis (OR 2.38; 95% CI 1. 36-4.17) and future liver remnant smaller than 40% (OR 2.40; 95% CI 1.31-4.38). The independent risk factors for 90-day mortality were age of 65 years or older (OR 2.40; 95% CI 1.36-4.23) and preoperative cholangitis (OR 2.25; 95% CI 1.30-3.87). CONCLUSION: In this study, no association could be demonstrated between hepatic steatosis or fibrosis and postoperative outcomes after resection of pCCA.

Clinical Safety and Performance of GATT-Patch for Hemostasis in Minimal to Moderate Bleeding During Open Liver Surgery.

INTRODUCTION: Intraoperative blood loss and postoperative hemorrhage affect outcomes after liver resection. GATT-Patch is a new flexible, pliable hemostatic sealant patch comprising fibrous gelatin carrier impregnated with N-hydroxy-succinimide polyoxazoline. We evaluated safety and performance of the GATT-Patch for hemostasis at the liver resection plane. METHODS: Adult patients undergoing elective open liver surgery were recruited in three centers. GATT-Patch was used for minimal to moderate bleeding at the liver resection plane. The primary endpoint was hemostasis of the first-treated bleeding site at 3 min versus a prespecified performance goal of 65.4%. RESULTS: Two trial stages were performed: I (n = 8) for initial safety and II (n = 39) as the primary outcome cohort. GATT-Patch was applied in 47 patients on 63 bleeding sites. Median age was 60.0 (range 25-80) years and 70% were male. Most (66%) surgeries were for colorectal cancer metastases. The primary endpoint was met in 38 out of 39 patients (97.4%; 95% confidence interval: 84.6%-99.9%) versus 65.4% (P < 0.001). Of all the 63 bleeding sites, hemostasis was 82.7% at 30, 93.7% at 60, and 96.8% at 180 s. No reoperations for rebleeding or device-related issues occurred. CONCLUSIONS: When compared to a performance goal derived from state-of-the-art hemostatic agents, GATT-Patch for the treatment of minimal to moderate bleeding during liver surgery successfully and quickly achieved hemostasis with acceptable safety outcomes. (ClinicalTrials.gov Identifier: NCT04819945).

Graft Steatosis and Donor Diabetes Mellitus Additively Impact on Recipient Outcomes After Liver Transplantation-A European Registry Study.

BACKGROUND AND AIMS: Biopsy-proven severe graft steatosis is associated with adverse outcomes after liver transplantation. The concomitant presence of metabolic risk factors might further increase this risk. We studied the association between graft steatosis and metabolic risk factors in the donor, with recipient outcomes after liver transplantation. METHODS: We analyzed data from all consecutive first adult full-graft donation after brain death (DBD) liver transplantations performed in the Eurotransplant region between 2010 and 2020. The presence of graft steatosis and metabolic risk factors was assessed through a review of donor (imaging) reports, and associations with recipient retransplantation-free survival were studied through survival analyses. RESULTS: Of 12 174 transplantations, graft steatosis was detected in 2689 (22.1%), and donor diabetes mellitus (DM), hypertension, and dyslipidemia were present in 1245 (10.2%), 5056 (41.5%), and 524 (4.3%). In multivariable Cox regression analysis, graft steatosis (adjusted HR [aHR] 1.197, p < 0.001) and donor DM (aHR 1.157, p = 0.004) were independently associated with impaired retransplantation-free survival. Graft steatosis and donor DM conferred an additive risk of retransplantation or death (DM alone, aHR: 1.156 [p = 0.0185]; steatosis alone, aHR: 1.200 [p < 0.001]; both steatosis and DM, aHR: 1.381 [p < 0.001]). Findings were consistent in sensitivity analyses focusing on retransplantation-free survival within 7 days. CONCLUSIONS: Graft steatosis and donor diabetes mellitus additively increase the risk of retransplantation or death in adult DBD liver transplantation. Future studies should focus on methods to assess and improve the quality of these high-risk grafts. Until such time, caution should be exercised when considering these grafts for transplantation.

Oxygenated versus non-oxygenated flush out during deceased donor liver procurement: The first proof-of-concept study in humans.

BACKGROUND: Liver transplantation is used for treating end-stage liver disease, fulminant hepatitis, and oncological malignancies and organ shortage is a major limiting factor worldwide. The use of grafts based on extended donor criteria have become internationally accepted. Oxygenated machine perfusion technologies are the most recent advances in organ transplantation; however, it is only applied after a period of cold ischemia. Due to its high cost, we aimed to use a novel device, OxyFlush®, based on oxygenation of the preservation solution, applied during liver procurement targeting the maintenance of ATP during static cold storage (SCS). METHODS: Twenty patients were randomly assigned to the OxyFlush or control group based on a 1:1 ratio. In the OxyFlush group, the perfusion solution was oxygenated with OxyFlush® device while the control group received a non-oxygenated solution. Liver and the common bile duct (CBD) biopsies were obtained at three different time points. The first was at the beginning of the procedure, the second during organ preparation, and the third after total liver reperfusion. Biopsies were analyzed, and adenosine triphosphate (ATP) levels and histological scores of the liver parenchyma and CBD were assessed. Postoperative laboratory tests were performed. RESULTS: OxyFlush® was able to maintain ATP levels during SCS and improved the damage caused by the lack of oxygen in the CBD. However, OxyFlush® did not affect laboratory test results and histological findings of the parenchyma. CONCLUSION: We present a novel low-cost device that is feasible and could represent a valuable tool in organ preservation during SCS.

Graft repair during machine perfusion: a current overview of strategies.

PURPOSE OF REVIEW: With changing donor characteristics (advanced age, obesity), an increase in the use of extended criteria donor (ECD) livers in liver transplantation is seen. Machine perfusion allows graft viability assessment, but still many donor livers are considered nontransplantable. Besides being used as graft viability assessment tool, ex situ machine perfusion offers a platform for therapeutic strategies to ameliorate grafts prior to transplantation. This review describes the current landscape of graft repair during machine perfusion. RECENT FINDINGS: Explored anti-inflammatory therapies, including inflammasome inhibitors, hemoabsorption, and cellular therapies mitigate the inflammatory response and improve hepatic function. Cholangiocyte organoids show promise in repairing the damaged biliary tree. Defatting during normothermic machine perfusion shows a reduction of steatosis and improved hepatobiliary function compared to nontreated livers. Uptake of RNA interference therapies during machine perfusion paves the way for an additional treatment modality. SUMMARY: The possibility to repair injured donor livers during ex situ machine perfusion might increase the utilization of ECD-livers. Application of defatting agents is currently explored in clinical trials, whereas other therapeutics require further research or optimization before entering clinical research.

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.

Machine perfusion of the liver and bioengineering.

With the increasing number of accepted candidates on waiting lists worldwide, there is an urgent need to expand the number and the quality of donor livers. Dynamic preservation approaches have demonstrated various benefits, including improving liver function and graft survival, and reducing liver injury and post-transplant complications. Consequently, organ perfusion techniques are being used in clinical practice in many countries. Despite this success, a proportion of livers do not meet current viability tests required for transplantation, even with the use of modern perfusion techniques. Therefore, devices are needed to further optimise machine liver perfusion - one promising option is to prolong machine liver perfusion for several days, with ex situ treatment of perfused livers. For example, stem cells, senolytics, or molecules targeting mitochondria or downstream signalling can be administered during long-term liver perfusion to modulate repair mechanisms and regeneration. Besides, today's perfusion equipment is also designed to enable the use of various liver bioengineering techniques, to develop scaffolds or for their re-cellularisation. Cells or entire livers can also undergo gene modulation to modify animal livers for xenotransplantation, to directly treat injured organs or to repopulate such scaffolds with "repaired" autologous cells. This review first discusses current strategies to improve the quality of donor livers, and secondly reports on bioengineering techniques to design optimised organs during machine perfusion. Current practice, as well as the benefits and challenges associated with these different perfusion strategies are discussed.

A fetal wound healing program after intrauterine bile duct injury may contribute to biliary atresia.

BACKGROUND & AIMS: Biliary atresia (BA) is an obstructive cholangiopathy that initially affects the extrahepatic bile ducts (EHBDs) of neonates. The etiology is uncertain, but evidence points to a prenatal cause. Fetal tissues have increased levels of hyaluronic acid (HA), which plays an integral role in fetal wound healing. The objective of this study was to determine whether a program of fetal wound healing is part of the response to fetal EHBD injury. METHODS: Mouse, rat, sheep, and human EHBD samples were studied at different developmental time points. Models included a fetal sheep model of prenatal hypoxia, human BA EHBD remnants and liver samples taken at the time of the Kasai procedure, EHBDs isolated from neonatal rats and mice, and spheroids and other models generated from primary neonatal mouse cholangiocytes. RESULTS: A wide layer of high molecular weight HA encircling the lumen was characteristic of the normal perinatal but not adult EHBD. This layer, which was surrounded by collagen, expanded in injured ducts in parallel with extensive peribiliary gland hyperplasia, increased mucus production and elevated serum bilirubin levels. BA EHBD remnants similarly showed increased HA centered around ductular structures compared with age-appropriate controls. High molecular weight HA typical of the fetal/neonatal ducts caused increased cholangiocyte spheroid growth, whereas low molecular weight HA induced abnormal epithelial morphology; low molecular weight HA caused matrix swelling in a bile duct-on-a-chip device. CONCLUSION: The fetal/neonatal EHBD, including in human EHBD remnants from Kasai surgeries, demonstrated an injury response with prolonged high levels of HA typical of fetal wound healing. The expanded peri-luminal HA layer may swell and lead to elevated bilirubin levels and obstruction of the EHBD. IMPACT AND IMPLICATIONS: Biliary atresia is a pediatric cholangiopathy associated with high morbidity and mortality rates; although multiple etiologies have been proposed, the fetal response to bile duct damage is largely unknown. This study explores the fetal pathogenesis after extrahepatic bile duct damage, thereby opening a completely new avenue to study therapeutic targets in the context of biliary atresia.

A multicenter randomized-controlled trial of hypothermic oxygenated perfusion (HOPE) for human liver grafts before transplantation.

BACKGROUND & AIMS: Machine perfusion is a novel method intended to optimize livers before transplantation. However, its effect on morbidity within a 1-year period after transplantation has remained unclear. METHODS: In this multicenter controlled trial, we randomly assigned livers donated after brain death (DBD) for liver transplantation (LT). Livers were either conventionally cold stored (control group), or cold stored and subsequently treated by 1-2 h hypothermic oxygenated perfusion (HOPE) before implantation (HOPE group). The primary endpoint was the occurrence of at least one post-transplant complication per patient, graded by the Clavien score of ≥III, within 1-year after LT. The comprehensive complication index (CCI), laboratory parameters, as well as duration of hospital and intensive care unit stay, graft survival, patient survival, and biliary complications served as secondary endpoints. RESULTS: Between April 2015 and August 2019, we randomized 177 livers, resulting in 170 liver transplantations (85 in the HOPE group and 85 in the control group). The number of patients with at least one Clavien ≥III complication was 46/85 (54.1%) in the control group and 44/85 (51.8%) in the HOPE group (odds ratio 0.91; 95% CI 0.50-1.66; p = 0.76). Secondary endpoints were also not significantly different between groups. A post hoc analysis revealed that liver-related Clavien ≥IIIb complications occurred less frequently in the HOPE group compared to the control group (risk ratio 0.26; 95% CI 0.07-0.77; p = 0.027). Likewise, graft failure due to liver-related complications did not occur in the HOPE group, but occurred in 7% (6 of 85) of the control group (log-rank test, p = 0.004, Gray test, p = 0.015). CONCLUSIONS: HOPE after cold storage of DBD livers resulted in similar proportions of patients with at least one Clavien ≥III complication compared to controls. Exploratory findings suggest that HOPE decreases the risk of severe liver graft-related events. IMPACT AND IMPLICATIONS: This randomized controlled phase III trial is the first to investigate the impact of hypothermic oxygenated perfusion (HOPE) on cumulative complications within a 12-month period after liver transplantation. Compared to conventional cold storage, HOPE did not have a significant effect on the number of patients with at least one Clavien ≥III complication. However, we believe that HOPE may have a beneficial effect on the quantity of complications per patient, based on its application leading to fewer severe liver graft-related complications, and to a lower risk of liver-related graft loss. The HOPE approach can be applied easily after organ transport during recipient hepatectomy. This appears fundamental for wide acceptance since concurring perfusion technologies need either perfusion at donor sites or continuous perfusion during organ transport, which are much costlier and more laborious. We conclude therefore that the post hoc findings of this trial should be further validated in future studies.

Waitlist mortality of young patients with biliary atresia: Impact of allocation policy and living donor liver transplantation.

Patients with biliary atresia (BA) below 2 years of age in need of a transplantation largely rely on partial grafts from deceased donors (deceased donor liver transplantation [DDLT]) or living donors (living donor liver transplantation [LDLT]). Because of high waitlist mortality in especially young patients with BA, the Eurotransplant Liver Intestine Advisory Committee (ELIAC) has further prioritized patients with BA listed before their second birthday for allocation of a deceased donor liver since 2014. We evaluated whether this Eurotransplant (ET) allocation prioritization changed the waitlist mortality of young patients with BA. We used a pre-post cohort study design with the implementation of the new allocation rule between the two periods. Participants were patients with BA younger than 2 years who were listed for liver transplantation in the ET database between 2001 and 2018. Competing risk analyses were performed to assess waitlist mortality in the first 2 years after listing. We analyzed a total of 1055 patients with BA, of which 882 had been listed in the preimplementation phase (PRE) and 173 in the postimplementation phase (POST). Waitlist mortality decreased from 6.7% in PRE to 2.3% in POST ( p = 0.03). Interestingly, the proportion of young patients with BA undergoing DDLT decreased from 32% to 18% after ET allocation prioritization ( p = 0.001), whereas LDLT increased from 55% to 74% ( p = 0.001). The proportional increase in LDLT decreased the median waitlist duration of transplanted patients from 1.5 months in PRE to 0.85 months in POST ( p = 0.003). Since 2014, waitlist mortality in young patients with BA has strongly decreased in the ET region. Rather than associated with prioritized allocation of deceased donor organs, the decreased waitlist mortality was related to a higher proportion of patients undergoing LDLT.

Persistent biliary hypoxia and lack of regeneration are key mechanisms in the pathogenesis of posttransplant nonanastomotic strictures.

BACKGROUND AND AIMS: Nonanastomotic biliary strictures (NAS) are a major cause of morbidity after orthotopic liver transplantation (OLT). Although ischemic injury of peribiliary glands (PBGs) and peribiliary vascular plexus during OLT has been associated with the later development of NAS, the exact underlying mechanisms remain unclear. We hypothesized that bile ducts of patients with NAS suffer from ongoing biliary hypoxia and lack of regeneration from PBG stem/progenitor cells. APPROACH AND RESULTS: Forty-two patients, requiring retransplantation for either NAS (n = 18), hepatic artery thrombosis (HAT; n = 13), or nonbiliary graft failure (controls; n = 11), were included in this study. Histomorphological analysis of perihilar bile ducts was performed to assess differences in markers of cell proliferation and differentiation in PBGs, microvascular density (MVD), and hypoxia. In addition, isolated human biliary tree stem cells (hBTSCs) were used to examine exo-metabolomics during in vitro differentiation toward mature cholangiocytes. Bile ducts of patients with NAS or HAT had significantly reduced indices of PBG mass, cellular proliferation and differentiation (mucus production, secretin receptor expression, and primary cilia), reduced MVD, and increased PBG apoptosis and hypoxia marker expression, compared to controls. Metabolomics of hBTSCs during in vitro differentiation toward cholangiocytes revealed a switch from a glycolytic to oxidative metabolism, indicating the need for oxygen. CONCLUSIONS: NAS are characterized by a microscopic phenotype of chronic biliary hypoxia attributed to loss of microvasculature, resulting in reduced proliferation and differentiation of PBG stem/progenitor cells into mature cholangiocytes. These findings suggest that persistent biliary hypoxia is a key mechanism underlying the development of NAS after OLT.

Nonmalignant portal vein thrombi in patients with cirrhosis consist of intimal fibrosis with or without a fibrin-rich thrombus.

BACKGROUND AND AIM: Portal vein thrombosis (PVT) is a common complication of cirrhosis. The exact pathophysiology remains largely unknown, and treatment with anticoagulants does not lead to recanalization of the portal vein in all patients. A better insight into the structure and composition of portal vein thrombi may assist in developing strategies for the prevention and treatment of PVT. APPROACH AND RESULTS: Sixteen prospectively and 63 retrospectively collected nonmalignant portal vein thrombi from patients with cirrhosis who underwent liver transplantation were included. Histology, immunohistochemistry, and scanning electron microscopy were used to assess structure and composition of the thrombi. Most recent CT scans were reanalyzed for thrombus characteristics. Clinical characteristics were related to histological and radiological findings. All samples showed a thickened, fibrotic tunica intima. Fibrin-rich thrombi were present on top of the fibrotic intima in 9/16 prospective cases and in 21/63 retrospective cases. A minority of the fibrotic areas stained focally positive for fibrin/fibrinogen (16% of cases), von Willebrand factor (VWF; 10%), and CD61 (platelets, 21%), while most of the fibrin-rich areas stained positive for those markers (fibrin/fibrinogen, 100%; VWF, 77%; CD61, 100%). No associations were found between clinical characteristics including estimated thrombus age and use of anticoagulants and presence of fibrin-rich thrombi. CONCLUSION: We demonstrate that PVT in patients with cirrhosis consists of intimal fibrosis with an additional fibrin-rich thrombus in only one-third of cases. We hypothesize that our observations may explain why not all portal vein thrombi in patients with cirrhosis recanalize by anticoagulant therapy.

Long-term follow-up of a randomized trial of biliary drainage in perihilar cholangiocarcinoma.

BACKGROUND AND AIMS: The DRAINAGE trial was a randomized controlled trial comparing preoperative endoscopic (EBD) and percutaneous biliary drainage (PTBD) in patients with potentially resectable, perihilar cholangiocarcinoma (pCCA). The aim of this study was to compare the long-term outcomes. METHODS: Patients were randomized in four tertiary referral centers. Follow-up data were available for all included patients. Primary outcome was overall survival (OS). Secondary outcomes were readmissions, and re-interventions not including in-trial interventions. RESULTS: A total of 54 patients were randomized; 27 in both groups. Median follow-up for both groups was 62 months (95% CI 54-70). The median OS was 13 months (95% CI 7.9-18.1) in the EBD and 7 months (95% CI 0.0-17.2) in the PTBD group (P = 0.28). Twenty (37%, n = 8 EBD vs n = 12 PTBD, P = 0.43) of 54 patients were readmitted at least once, mostly due to drainage-related complications (n = 13, 24%). Of note, 14 out of the 54 patients died within the trial. A total of 76 drainage procedures (32 EBD and 44 PTBD) were performed in 28 patients. The median number of stent or drain placements was 2 (2-4) for the EBD group and 2 (1-3) for the PTBD group (P = 0.77). DISCUSSION: Although this follow-up study represented a small cohort, no long-term differences in survival, readmissions, and drainage procedures for EBD and PTBD were found, even when comparing the resected and unresected group. However, this study demonstrates the complexity of biliary drainage for patients with potentially resectable pCCA, even in tertiary referral centers.

Prolonged preservation by hypothermic machine perfusion facilitates logistics in liver transplantation: A European observational cohort study.

A short period (1-2 h) of hypothermic oxygenated machine perfusion (HOPE) after static cold storage is safe and reduces ischemia-reperfusion injury-related complications after liver transplantation. Machine perfusion time is occasionally prolonged for logistical reasons, but it is unknown if prolonged HOPE is safe and compromises outcomes. We conducted a multicenter, observational cohort study of patients transplanted with a liver preserved by prolonged (≥4 h) HOPE. Postoperative biochemistry, complications, and survival were evaluated. The cohort included 93 recipients from 12 European transplant centers between 2014-2021. The most common reason to prolong HOPE was the lack of an available operating room to start the transplant procedure. Grafts underwent HOPE for a median (range) of 4:42 h (4:00-8:35 h) with a total preservation time of 10:50 h (5:50-20:50 h). Postoperative peak ALT was 675 IU/L (interquartile range 419-1378 IU/L). The incidence of postoperative complications was low, and 1-year graft and patient survival were 94% and 88%, respectively. To conclude, good outcomes are achieved after transplantation of donor livers preserved with prolonged (median 4:42 h) HOPE, leading to a total preservation time of almost 21 h. These results suggest that simple, end-ischemic HOPE may be utilized for safe extension of the preservation time to ease transplantation logistics.

Sequential hypothermic and normothermic machine perfusion enables safe transplantation of high-risk donor livers.

Ex situ normothermic machine perfusion (NMP) is increasingly used for viability assessment of high-risk donor livers, whereas dual hypothermic oxygenated machine perfusion (DHOPE) reduces ischemia-reperfusion injury. We aimed to resuscitate and test the viability of initially-discarded, high-risk donor livers using sequential DHOPE and NMP with two different oxygen carriers: an artificial hemoglobin-based oxygen carrier (HBOC) or red blood cells (RBC). In a prospective observational cohort study of 54 livers that underwent DHOPE-NMP, the first 18 procedures were performed with a HBOC-based perfusion solution and the subsequent 36 procedures were performed with an RBC-based perfusion solution for the NMP phase. All but one livers were derived from extended criteria donation after circulatory death donors, with a median donor risk index of 2.84 (IQR 2.52-3.11). After functional assessment during NMP, 34 livers (63% utilization), met the viability criteria and were transplanted. One-year graft and patient survival were 94% and 100%, respectively. Post-transplant cholangiopathy occurred in 1 patient (3%). There were no significant differences in utilization rate and post-transplant outcomes between the HBOC and RBC group. Ex situ machine perfusion using sequential DHOPE-NMP for resuscitation and viability assessment of high-risk donor livers results in excellent transplant outcomes, irrespective of the oxygen carrier used.