The role of bile salt toxicity in the pathogenesis of bile duct injury after non-heart-beating porcine liver transplantation. Transplantation. 2008;85:1625-1631. [PMID: 18551070 DOI: 10.1097/tp.0b013e318170f5f7]

Gut microbiota-mediated bile acid metabolism aggravates biliary injury after liver transplantation through mitochondrial apoptosis

Ischemic-type biliary lesions (ITBL) are a major cause of graft loss and even mortality after liver transplantation (LT). The underlying cellular mechanisms for ITBL remain unclear. Gut microbiota has been found to be closely related to complications after LT. Here, using gut microbiome compositions, we found patients with ITBL had a higher abundance of bacteria associated with bile salt metabolism. These bacteria are reported to convert cholic acid (CA) into deoxycholic acid (DCA), consistent with our data that there were higher DCA concentrations and DCA/CA ratio in patients with ITBL than patients without ITBL. Using an in vitro model, human intrahepatic biliary epithelial cells (HIBEC) subjected to DCA showed a higher apoptosis rate, lower viability, and higher levels of cleaved-caspase3 than CA at the same concentration. DCA also changed the morphology of mitochondria and farnesoid X receptor (FXR) expression. Interestingly, DCA-induced apoptosis rate was significantly reduced in HIBEC when the FXR or BAX gene was knocked down, suggesting that DCA-induced apoptosis was dependent on FXR-mitochondrial pathway. Furthermore, increasing DCA/CA ratio in a bile acid-feeding mouse model resulted in cholangiocyte apoptosis and impaired liver function. The patients with ITBL also showed an increased proportion of TUNEL-positive biliary epithelial cells than those without ITBL. These suggest that changes in the gut microbiota following LT may enhance the conversion of CA to DCA, and may contribute to biliary damage via FXR-mitochondrial apoptosis pathway, providing new ideas for the early monitoring and treatment of ITBL.

Primary cilia as a targetable node between biliary injury, senescence and regeneration in liver transplantation

BACKGROUND & AIMS

Biliary complications are a major cause of morbidity and mortality in liver transplantation. Up to 25% of patients that develop biliary complications require additional surgical procedures, re-transplantation or die in the absence of a suitable regraft. Here, we investigate the role of the primary cilium, a highly specialised sensory organelle, in biliary injury leading to post-transplant biliary complications.

METHODS

Human biopsies were used to study the structure and function of primary cilia in liver transplant recipients that develop biliary complications (n = 7) in comparison with recipients without biliary complications (n = 12). To study the biological effects of the primary cilia during transplantation, we generated murine models that recapitulate liver procurement and cold storage, and assessed the elimination of the primary cilia in biliary epithelial cells in the K19CreERTKif3afl/fl mouse model. To explore the molecular mechanisms responsible for the observed phenotypes we used in vitro models of ischemia, cellular senescence and primary cilia ablation. Finally, we used pharmacological and genetic approaches to target cellular senescence and the primary cilia, both in mouse models and discarded human donor livers.

RESULTS

Prolonged ischemic periods before transplantation result in ciliary shortening and cellular senescence, an irreversible cell cycle arrest that blocks regeneration. Our results indicate that primary cilia damage results in biliary injury and a loss of regenerative potential. Senescence negatively impacts primary cilia structure and triggers a negative feedback loop that further impairs regeneration. Finally, we explore how targeted interventions for cellular senescence and/or the stabilisation of the primary cilia improve biliary regeneration following ischemic injury.

CONCLUSIONS

Primary cilia play an essential role in biliary regeneration and we demonstrate that senolytics and cilia-stabilising treatments provide a potential therapeutic opportunity to reduce the rate of biliary complications and improve clinical outcomes in liver transplantation.

IMPACT AND IMPLICATIONS

Up to 25% of liver transplants result in biliary complications, leading to additional surgery, retransplants, or death. We found that the incidence of biliary complications is increased by damage to the primary cilium, an antenna that protrudes from the cell and is key to regeneration. Here, we show that treatments that preserve the primary cilia during the transplant process provide a potential solution to reduce the rates of biliary complications.

In Utero Extrahepatic Bile Duct Damage and Repair: Implications for Biliary Atresia

Biliary atresia (BA) is a cholangiopathy affecting the extrahepatic bile duct (EHBD) of newborns. The etiology and pathophysiology of BA are not fully understood; however, multiple causes of damage and obstruction of the neonatal EHBD have been identified. Initial damage to the EHBD likely occurs before birth. We discuss how different developmental stages in utero and birth itself could influence the susceptibility of the fetal EHBD to damage and a damaging wound-healing response. We propose that a damage-repair response of the fetal and neonatal EHBD involving redox stress and a program of fetal wound healing could-regardless of the cause of the initial damage-lead to either obstruction and BA or repair of the duct and recovery. This overarching concept should guide future research targeted toward identification of factors that contribute to recovery as opposed to progression of injury and fibrosis. Viewing BA through the lens of an in utero damage-repair response could open up new avenues for research and suggests exciting new therapeutic targets.

Comprehensive bile acid pool analysis during ex-vivo liver perfusion in a porcine model of ischemia-reperfusion injury

Bile acids (BA) are key for liver regeneration and injury. This study aims at analyzing the changes in the BA pool induced by ischemia-reperfusion (IRI) and investigates the impact of hypothermic oxygenated perfusion (HOPE) on the BA pool compared to static cold storage (SCS). In a porcine model of IRI, liver grafts underwent 30 min of asystolic warm ischemia followed by 6 h of SCS (n = 6) ± 2 h of HOPE (n = 6) and 2 h of ex-situ warm reperfusion. The BA pool in bile samples was analyzed with liquid chromatography coupled with tandem mass spectrometry. We identified 16 BA and observed significant changes in response to ischemia-reperfusion, which were associated with both protective and injury mechanisms. Second, HOPE-treated liver grafts exhibited a more protective BA phenotype, characterized by a more hydrophilic BA pool compared to SCS. Key BA, such as GlycoCholic Acid, were identified and were associated with a decreased transaminase release and improved lactate clearance during reperfusion. Partial Least Square-Discriminant Analysis revealed a distinct injury profile for the HOPE group. In conclusion, the BA pool changes with liver graft IRI, and preservation with HOPE results in a protective BA phenotype compared to SCS.

Comprehensive Approach to Assessment of Liver Viability During Normothermic Machine Perfusion

Liver transplantation is the most effective treatment of advanced liver disease, and the use of extended criteria donor organs has broadened the source of available livers. Although normothermic machine perfusion (NMP) has become a useful tool in liver transplantation, there are no consistent criteria that can be used to evaluate the viability of livers during NMP. This review summarizes the criteria, indicators, and methods used to evaluate liver viability during NMP. The shape, appearance, and hemodynamics of the liver can be analyzed at a macroscopic level, while markers of liver injury, indicators of liver and bile duct function, and other relevant indicators can be evaluated by biochemical analysis. The liver can also be assessed by tissue biopsy at the microscopic level. Novel methods for assessment of liver viability are introduced. The limitations of evaluating liver viability during NMP are discussed and suggestions for future clinical practice are provided.

Protective mechanisms and current clinical evidence of hypothermic oxygenated machine perfusion (HOPE) in preventing post-transplant cholangiopathy

The development of cholangiopathies after liver transplantation impacts on the quality and duration of graft and patient survival, contributing to higher costs as numerous interventions are required to treat strictures and infections at the biliary tree. Prolonged donor warm ischaemia time in combination with additional cold storage are key risk factors for the development of biliary strictures. Based on this, the clinical implementation of dynamic preservation strategies is a current hot topic in the field of donation after circulatory death (DCD) liver transplantation. Despite various retrospective studies reporting promising results, also regarding biliary complications, there are only a few randomised-controlled trials on machine perfusion. Recently, the group from Groningen has published the first randomised-controlled trial on hypothermic oxygenated perfusion (HOPE), demonstrating a significant reduction of symptomatic ischaemic cholangiopathies with the use of a short period of HOPE before DCD liver implantation. The most likely mechanism for this important effect, also shown in several experimental studies, is based on mitochondrial reprogramming under hypothermic aerobic conditions, e.g. exposure to oxygen in the cold, with a controlled and slow metabolism of ischaemically accumulated succinate and simultaneous ATP replenishment. This unique feature prevents mitochondrial oxidative injury and further downstream tissue inflammation. HOPE treatment therefore supports livers by protecting them from ischaemia-reperfusion injury (IRI), and thereby also prevents the development of post-transplant biliary injury. With reduced IRI-associated inflammation, recipients are also protected from activation of the innate immune system, with less acute rejections seen after HOPE.

Bile Composition as a Diagnostic and Prognostic Tool in Liver Transplantation

Bile secretion and composition reflects the functional status of hepatocytes and cholangiocytes. Bile composition can have a role in the assessment of donor grafts before implantation in the recipient. In addition, changes in bile composition after liver transplantation can serve as a diagnostic and prognostic tool to predict posttransplant complications, such as primary nonfunction, acute cellular rejection, or nonanastomotic biliary strictures. With the popularization of liver machine perfusion preservation in the clinical setting, there is a revisited interest in biliary biomarkers to assess graft viability before implantation. This review discusses current literature on biliary biomarkers that could predict or assess liver graft and bile duct viability. Bile composition offers an exciting and novel perspective in the search for reliable hepatocyte and cholangiocyte viability biomarkers.

Pattern Recognition Receptor-reactivity Screening of Liver Transplant Patients: Potential for Personalized and Precise Organ Matching to Reduce Risks of Ischemia-reperfusion Injury

OBJECTIVE AND BACKGROUND

Pattern recognition receptors (PRRs) on immune and parenchymal cells can detect danger-associated molecular patterns (DAMPs) released from cells damaged during ischemia-reperfusion injury (IRI), in heart attack or stroke settings, but also as an unavoidable consequence of solid organ transplantation. Despite IRI being a significant clinical problem across all solid organ transplants, there are limited therapeutics and patient-specific diagnostics currently available.

METHODS

We screened portal blood samples obtained from 67 human liver transplant recipients both pre- [portal vein (PV) sample] and post-(liver flush; LF) reperfusion for their ability to activate a panel of PRRs, and analyzed this reactivity in relation to biopsy-proven IRI.

RESULTS

PV samples from IRI+ orthotopic liver transplantation (OLT) patients (n = 35) decreased activation of hTLR4- and hTLR9-transfected cells, whereas PV from IRI- patients (n = 32) primarily increased hTLR7 and hNOD2 activation. LF samples from OLT-IRI patients significantly increased activation of hTLR4 and hTLR9 over IRI- LF. In addition, the change from baseline reactivity to hTLR4/9/NOD2 was significantly higher in IRI+ than IRI- OLT patients.

CONCLUSIONS

These results demonstrate that TLR4/7/9 and NOD2 are involved in either promoting or attenuating hepatic IRI, and suggest a diagnostic screening of portal blood for reactivity to these PRRs might prove useful for prediction and/or therapeutic intervention in OLT patients before transplantation.

Liver graft preservation methods during cold ischemia phase and normothermic machine perfusion

The growing demand for donor organs requires measures to expand donor pool. Those include extended criteria donors, such as elderly people, steatotic livers, donation after cardiac death, etc. Static cold storage to reduce metabolic requirements developed by Collins in late 1960s is the mainstay and the golden standard for donated organ protection. Hypothermic machine perfusion provides dynamic organ preservation at 4°C with protracted infusion of metabolic substrates to the graft during the ex vivo period. It has been used instead of static cold storage or after it as short perfusion in transplant center. Normothermic machine perfusion (NMP) delivers oxygen, and nutrition at physiological temperature mimicking regular environment in order to support cellular function. This would minimize effects of ischemia/reperfusion injury. Potentially, NMP may help to estimate graft functionality before implantation into a recipient. Clinical studies demonstrated at least its non-inferiority or better outcomes vs static cold storage. Regular grafts donated after brain death could be safely preserved with convenient static cold storage. Except for prolonged ischemia time where hypothermic machine perfusion started in transplant center could be estimated to provide possible positive reconditioning effect. Use of hypothermic machine perfusion in regular donation instead of static cold storage or in extended criteria donors requires further investigation. Multicenter randomized clinical trial supposed to be completed in December 2021. Extended criteria donors need additional measures for graft storage and assessment until its implantation. NMP is actively evaluating promising method for this purpose. Future studies are necessary for precise estimation and confirmation to issue clinical practice recommendations.

Porcine Isolated Liver Perfusion for the Study of Ischemia Reperfusion Injury: A Systematic Review

BACKGROUND

Understanding ischemia reperfusion injury (IRI) is essential to further improve outcomes after liver transplantation (LT). Porcine isolated liver perfusion (ILP) is increasingly used to reproduce LT-associated IRI in a strictly controlled environment. However, whether ILP is a reliable substitute of LT was never validated.

METHODS

We systematically reviewed the current experimental setups for ILP and parameters of interest reflecting IRI.

RESULTS

Isolated liver perfusion was never compared with transplantation in animals. Considerable variability exists between setups, and comparative data are unavailable. Experience so far suggests that centrifugal pump(s) with continuous flow are preferred to reduce the risk of embolism. Hepatic outflow can be established by cannulation of the inferior vena cava or freely drained in an open bath. Whole blood at approximately 38°C, hematocrit of 20% or greater, and the presence of leukocytes to trigger inflammation is considered the optimal perfusate. A number of parameters related to the 4 liver compartments (hepatocyte, cholangiocyte, endothelium, immune cells) are available; however, their significance and relation to clinical outcomes is not well described.

CONCLUSIONS

Porcine ILP provides a reproducible model to study early IRI events. As all models, it has its limitations. A standardization of the setup would allow comparison of data and progress in the field.

Impact of Machine Perfusion on Biliary Complications after Liver Transplantation

We describe in this review the different types of injuries caused to the biliary tree after liver transplantation. Furthermore, we explain underlying mechanisms and why oxygenated perfusion concepts could not only protect livers, but also repair high-risk grafts to prevent severe biliary complications and graft loss. Accordingly, we summarize experimental studies and clinical applications of machine liver perfusion with a focus on biliary complications after liver transplantation. Key points: (1) Acute inflammation with subsequent chronic ongoing liver inflammation and injury are the main triggers for cholangiocyte injury and biliary tree transformation, including non-anastomotic strictures; (2) Hypothermic oxygenated perfusion (HOPE) protects livers from initial oxidative injury at normothermic reperfusion after liver transplantation. This is a unique feature of a cold oxygenation approach, which is effective also end-ischemically, e.g., after cold storage, due to mitochondrial repair mechanisms. In contrast, normothermic oxygenated perfusion concepts protect by reducing cold ischemia, and are therefore most beneficial when applied instead of cold storage; (3) Due to less downstream activation of cholangiocytes, hypothermic oxygenated perfusion also significantly reduces the development of biliary strictures after liver transplantation.

Normothermic ex-vivo liver perfusion: where do we stand and where to reach?

Nowadays liver transplantation is considered as the treatment of choice, however, the scarcity of suitable donor organs limits the delivery of care to the end-stage liver disease patients leading to the death while on the waiting list. The advent of ex-situ normothermic machine perfusion (NMP) has emerged as an alternative to the standard organ preservation technique, static cold storage (SCS). The newer technique promises to not only restore the normal metabolic activity but also attempt to recondition the marginal livers back to the pristine state, which are otherwise more susceptible to ischemic injury and foster the poor post-transplant outcomes. Areas covered: An extensive search of all the published literature describing the role of NMP based device in liver transplantation as an alternative to SCS was made on MEDLINE, EMBASE, Cochrane, BIOSIS, Crossref, Scopus databases and clinical trial registry on 10 May 2018. Expert commentary: The main tenet of NMP is the establishment of the physiological milieu, which permits aerobic metabolism to continue through out the period of preservation and limits the effects of ischemia-reperfusion (I/R) injury. In addition, by assessing the various metabolic and synthetic parameters the viability and suitability of donor livers for transplantation can be determined. This important technological advancement has scored satisfactorily on the safety and efficacy parameters in preliminary clinical studies. The present review suggests that NMP can offer the opportunity to assess and safely utilize the marginal donor livers if deemed appropriate for the transplantation. However, ongoing trials will determine its full potential and further adoption.

Effect of heme oxygenase-1 on the protection of ischemia reperfusion injury of bile duct in rats after liver transplantation

OBJECTIVE

To investigate the effect of heme oxygenase-1 (HO-1) on the ischemic reperfusion injury (IRI) of bile duct in rat models after liver transplantation.

METHODS

320 SD rats were equally and randomly divided into 5 groups, which were group A receiving injection of 3×10⁸/pfu/ml adenovirus (adv), group B with donor receiving Adv-HO-1 and recipient receiving Adv-HO-1-siRNA, group C with donor and recipient both receiving Adv-HO-1, group D with donor receiving Adv-HO-1-siRNA and recipient receiving Adv-HO-1, and group E with donor and recipient both receiving Adv-HO-1-siRNA at 24h before liver transplantation. Donor liver was stored in UW liquid at 4°C followed by measuring HO-1 level by western blot before transplantation. On d1, d3, d7 and d14, serum and liver was isolated for analysis of liver function, inflammatory cell infiltration by H&E staining, ultrastructure of liver by transmission electron microscopy as well as the expression of HO-1, Bsep, Mrp2 and Ntcp by western blot.

RESULTS

Compared with group D and E, group B and C displayed improved liver function as demonstrated by lower level of ALT, AST, LDH, TBIL, ALP and GGT, increased secretion of TBA and PL as well as expression of transporter proteins (Bsep, Mrp2 and Ntcp), reduced inflammatory cells infiltration and liver injury.

CONCLUSION

Our study demonstrated that overexpression of HO-1 in donor liver can ameliorate the damage to bile duct and liver, and improved liver function, suggesting HO-1 might be a new therapeutic target in the treatment of IRI after liver transplantation.

The Role of Normothermic Perfusion in Liver Transplantation (TRaNsIT Study): A Systematic Review of Preliminary Studies

INTRODUCTION

The success of liver transplantation has been limited by the unavailability of suitable donor livers. The current organ preservation technique, i.e., static cold storage (SCS), is not suitable for marginal organs. Alternatively, normothermic machine perfusion (NMP) promises to recreate the physiological environment and hence holds promise for the better organ preservation. The objective of this systematic review is to provide an overview of the safety, benefits, and insight into the other potential useful parameters of NMP in the liver preservation.

MATERIAL AND METHODS

We searched the current literature following registration in the International Prospective Register of Systematic Reviews (PROSPERO) with registration number CRD42018086034 for prospective trials comparing the role of NMP device to SCS in liver transplant by searching the PubMed, EMBASE, Cochrane, BIOSIS, Crossref, and Scopus databases and clinical trial registry.

RESULTS

The literature search identified five prospective clinical trials (four being early phase single institutional and single randomized multi-institutional) comparing 187 donor livers on NMP device to 273 donor livers on SCS. The primary outcome of interest was to assess the safety and graft survival at day 30 after transplant following NMP of the donor liver. Secondary outcomes included were early allograft dysfunction (EAD) in the first seven days; serum measures of liver functions as bilirubin, aspartate aminotransferase (AST), alanine amino transferase (ALT), alkaline phosphatase (ALP), and international normalized ratio (INR) on days 1-7; major complications as defined by a Clavien-Dindo score ≥ 3; and patient and graft survival and biliary complications at six months. The peaked median AST level between days 1 and 7 in the five trials was 417-1252 U/L (range 84-15009 U/L) while on NMP and 839-1474 U/L (range 153-8786 U/L) in SCS group. The median bilirubin level on day 7 ranged within 25-79 µmol/L (range 8-344 µmol/l) and 30-47.53 µmol/l (range 9-340 µmol/l) in NMP and SCS groups, respectively. A single case of PNF was reported in NMP group in the randomized trial while none of the other preliminary studies reported any in either group. There was intertrial variability in EAD which ranged within 15-56% in NMP group while being within 23-37% in SCS group. Biliary complications observed in NMP group ranged from 0 to 20%. Single device malfunction was reported in randomized controlled trial leading to renouncement of transplant while none of the other trials reported any machine failure, although two user related device errors inadvertent were reported.

CONCLUSION

This review outlines that NMP not only demonstrated safety and efficacy but also provided the favourable environment of organ preservation, repair, and viability assessment to donor liver prior to the transplantation with low rate of posttransplantation complication as PNF, EAD, and biliary complication; however further studies are needed to broaden our horizon.

Post-transplant cholangiopathy: Classification, pathogenesis, and preventive strategies

Biliary complications are the most frequent cause of morbidity, re-transplantation, and even mortality after liver transplantation. In general, biliary leakage and anastomotic and non-anastomotic biliary strictures (NAS) can be recognized. There is no consensus on the exact definition of NAS and different names and criteria have been used in literature. We propose to use the term post-transplant cholangiopathy for the spectrum of abnormalities of large donor bile ducts, that includes NAS, but also intraductal casts and intrahepatic biloma formation, in the presence of a patent hepatic artery. Combinations of these manifestations of cholangiopathy are not infrequently found in the same liver and ischemia-reperfusion injury is generally considered the common underlying mechanism. Other factors that contribute to post-transplant cholangiopathy are biliary injury due to bile salt toxicity and immune-mediated injury. This review provides an overview of the various types of post-transplant cholangiopathy, the presumed pathogenesis, clinical implications, and preventive strategies.

Liver grafts procured from donors after circulatory death have no increased risk of microthrombi formation

Microthrombi formation provoked by warm ischemia and vascular stasis is thought to increase the risk of nonanastomotic strictures (NAS) in liver grafts obtained by donation after circulatory death (DCD). Therefore, potentially harmful intraoperative thrombolytic therapy has been suggested as a preventive strategy against NAS. Here, we investigated whether there is histological evidence of microthrombi formation during graft preservation or directly after reperfusion in DCD livers and the development of NAS. Liver biopsies collected at different time points during graft preservation and after reperfusion were triple-stained with hematoxylin-eosin (H & E), von Willebrand factor VIII (VWF), and Fibrin Lendrum (FL) to evaluate the presence of microthrombi. In a first series of 282 sections obtained from multiple liver segments of discarded DCD grafts, microthrombi were only present in 1%-3% of the VWF stainings, without evidence of thrombus formation in paired H & E and FL stainings. Additionally, analysis of 132 sections obtained from matched, transplanted donation after brain death and DCD grafts showed no difference in microthrombi formation (11.3% versus 3.3% respectively; P = 0.082), and no relation to the development of NAS (P = 0.73). Furthermore, no microthrombi were present in perioperative biopsies in recipients who developed early hepatic artery thrombosis. Finally, the presence of microthrombi did not differ before or after additional flushing of the graft with preservation solution. In conclusion, the results of our study derogate from the hypothesis that DCD livers have an increased tendency to form microthrombi. It weakens the explanation that microthrombi formation is a main causal factor in the development of NAS in DCD and that recipients could benefit from intraoperative thrombolytic therapy to prevent NAS following liver transplantation. Liver Transplantation 22 1676-1687 2016 AASLD.

Oxygenated Hypothermic Machine Perfusion After Static Cold Storage Improves Hepatobiliary Function of Extended Criteria Donor Livers

BACKGROUND

The mechanism through which oxygenated hypothermic machine perfusion (HMP) improves viability of human extended criteria donor (ECD) livers is not well known. Aim of this study was to examine the benefits of oxygenated HMP after static cold storage (SCS).

METHODS

Eighteen ECD livers that were declined for transplantation underwent ex situ viability testing using normothermic (37 °C) machine perfusion (NMP) after traditional SCS (0 °C-4 °C) for 7 to 9 hours. In the intervention group (n = 6), livers underwent 2 hours of oxygenated HMP (at 12 °C) after SCS and before NMP. Twelve control livers underwent NMP without oxygenated HMP after SCS.

RESULTS

During HMP, hepatic ATP content increased greater than 15-fold, and levels remained significantly higher during the first 4 hours of NMP in the HMP group, compared with controls. Cumulative bile production and biliary secretion of bilirubin and bicarbonate were significantly higher after HMP, compared with controls. In addition, the levels of lactate and glucose were less elevated after HMP compared with SCS preservation alone. In contrast, there were no differences in levels of hepatobiliary injury markers AST, ALT, LDH, and gamma-GT after 6 hours of NMP. Hepatic histology at baseline and after 6 hours of NMP revealed no differences in the amount of ischemic necrosis between both groups.

CONCLUSIONS

Two hours of oxygenated HMP after traditional SCS restores hepatic ATP levels and improves hepatobiliary function but does not reduce (preexisting) hepatobiliary injury in ECD livers.

Key Points in Establishing a Model of Mouse Liver Transplantation

The explosion of interest in research into the mouse genome and immune system has meant that the mouse orthotopic liver transplantation (MOLT) model has become a popular means of studying transplantation immunity, organ preservation, ischemia-reperfusion injury, and surgical techniques, among others. Although numerous modifications and refinements of surgical techniques have simplified the operation, the relatively short duration of postoperative survival after MOLT remains an obstacle to longer-term follow-up studies. Here, we summarize the scientific basis of MOLT and our experience improving and refining the model in six key areas: anesthesia, operative technique, perfusion and preservation of the liver, cuff technique, anhepatic time, and the value of rearterialization for the liver graft. We also compare the characteristics of different surgical techniques, and give recommendations for the best means of tailoring technique to the objectives of a study. In doing so, we aim to assist other investigators in establishing and perfecting the MOLT model in their routine research practice.

Normothermic machine perfusion reduces bile duct injury and improves biliary epithelial function in rat donor livers

Bile duct injury may occur during liver procurement and transplantation, especially in livers from donation after circulatory death (DCD) donors. Normothermic machine perfusion (NMP) has been shown to reduce hepatic injury compared to static cold storage (SCS). However, it is unknown whether NMP provides better preservation of bile ducts. The aim of this study was to determine the impact of NMP on bile duct preservation in both DCD and non-DCD livers. DCD and non-DCD livers obtained from Lewis rats were preserved for 3 hours using either SCS or NMP, followed by 2 hours ex vivo reperfusion. Biomarkers of bile duct injury (gamma-glutamyltransferase and lactate dehydrogenase in bile) were lower in NMP-preserved livers compared to SCS-preserved livers. Biliary bicarbonate concentration, reflecting biliary epithelial function, was 2-fold higher in NMP-preserved livers (P < 0.01). In parallel with this, the pH of the bile was significantly higher in NMP-preserved livers (7.63 ± 0.02 and 7.74 ± 0.05 for non-DCD and DCD livers, respectively) compared with SCS-preserved livers (7.46 ± 0.02 and 7.49 ± 0.04 for non-DCD and DCD livers, respectively). Scanning and transmission electron microscopy of donor extrahepatic bile ducts demonstrated significantly decreased injury of the biliary epithelium of NMP-preserved donor livers (including the loss of lateral interdigitations and mitochondrial injury). Differences between NMP and SCS were most prominent in DCD livers. Compared to conventional SCS, NMP provides superior preservation of bile duct epithelial cell function and morphology, especially in DCD donor livers. By reducing biliary injury, NMP could have an important impact on the utilization of DCD livers and outcome after transplantation. Liver Transplantation 22 994-1005 2016 AASLD.

Using ultrasonography to monitor liver blood flow for liver transplant from donors supported on extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) has been used to support brain-dead donors for liver procurement. This study investigated the potential role of ultrasonographic monitoring of hepatic perfusion as an aid to improve the viability of liver transplants obtained from brain-dead donors who are supported on ECMO. A total of 40 brain-dead patients maintained on ECMO served as the study population. Hepatic blood flow was monitored using ultrasonography, and perioperative optimal perfusion was maintained by calibrating ECMO. Liver function tests were performed to assess the viability of the graft. The hepatic arterial blood flow was well maintained with no significant changes observed before and after ECMO (206 ± 32 versus 241 ± 45 mL/minute; P = 0.06). Similarly, the portal venous blood flow was also maintained throughout (451 ± 65 versus 482 ± 77 mL/minute; P = 0.09). No significant change in levels of total bilirubin, alanine transaminase, and lactic acid were reported during ECMO (P = 0.17, P = 0.08, and P = 0.09, respectively). Before the liver is procured, ultrasonographic monitoring of hepatic blood flow could be a valuable aid to improve the viability of a liver transplant by allowing for real-time calibration of ECMO perfusion in brain-dead liver donors. In our study, ultrasonographic monitoring helped prevent warm ischemic injury to the liver graft by avoiding both overperfusion and underperfusion of the liver.

End-ischemic machine perfusion reduces bile duct injury in donation after circulatory death rat donor livers independent of the machine perfusion temperature

A short period of oxygenated machine perfusion (MP) after static cold storage (SCS) may reduce biliary injury in donation after cardiac death (DCD) donor livers. However, the ideal perfusion temperature for protection of the bile ducts is unknown. In this study, the optimal perfusion temperature for protection of the bile ducts was assessed. DCD rat livers were preserved by SCS for 6 hours. Thereafter, 1 hour of oxygenated MP was performed using either hypothermic machine perfusion, subnormothermic machine perfusion, or with controlled oxygenated rewarming (COR) conditions. Subsequently, graft and bile duct viability were assessed during 2 hours of normothermic ex situ reperfusion. In the MP study groups, lower levels of transaminases, lactate dehydrogenase (LDH), and thiobarbituric acid reactive substances were measured compared to SCS. In parallel, mitochondrial oxygen consumption and adenosine triphosphate (ATP) production were significantly higher in the MP groups. Biomarkers of biliary function, including bile production, biliary bicarbonate concentration, and pH, were significantly higher in the MP groups, whereas biomarkers of biliary epithelial injury (biliary gamma-glutamyltransferase [GGT] and LDH), were significantly lower in MP preserved livers. Histological analysis revealed less injury of large bile duct epithelium in the MP groups compared to SCS. In conclusion, compared to SCS, end-ischemic oxygenated MP of DCD livers provides better preservation of biliary epithelial function and morphology, independent of the temperature at which MP is performed. End-ischemic oxygenated MP could reduce biliary injury after DCD liver transplantation.

High peak alanine aminotransferase determines extra risk for nonanastomotic biliary strictures after liver transplantation with donation after circulatory death

Orthotopic liver transplantation (OLT) with donation after circulatory death (DCD) often leads to a higher first week peak alanine aminotransferase (ALT) and a higher rate of biliary nonanastomotic strictures (NAS) as compared to donation after brain death (DBD). This retrospective study was to evaluate whether an association exists between peak ALT and the development of NAS in OLT with livers from DBD (n = 399) or DCD (n = 97) from two transplantation centers. Optimal cutoff value of peak ALT for risk of development of NAS post-DCD-OLT was 1300 IU/l. The 4-year cumulative incidence of NAS after DCD-OLT was 49.5% in patients with a high ALT peak post-OLT, compared with 11.3% in patients with a low ALT peak. (P < 0.001). No relation between peak ALT and NAS was observed after DBD-OLT. Multivariate analysis revealed peak ALT ≥1300 IU/l [adjusted hazard ratio (aHR) = 3.71, confidence interval (CI) (1.26-10.91)] and donor age [aHR = 1.04, CI 1.00-1.07] to be independently associated with development of NAS post-DCD-OLT. A peak ALT of <1300 IU/l carries a risk for NAS similar to DBD-OLT. Thus, in DCD-OLT, but not in DBD-OLT, peak ALT discriminates patients at high or low risk for NAS.

The bile duct in donation after cardiac death donor liver transplant

PURPOSE OF REVIEW

This review considers the biliary complications associated with liver transplantation using donation after cardiac death (DCD) donor grafts.

RECENT FINDINGS

The increasing use of DCD liver grafts with their increased incidence of biliary complications is discussed. The ethics of this greater use is briefly analysed. Recent animal and human study evidence to support the peribiliary vascular plexus' role in ischaemic cholangiopathy is reviewed. Recent advances in in-vivo and ex-vivo perfusion are explored. In particular, the latest theories regarding perfusion's peribiliary plexus preserving effects and the mechanism by which biliary regeneration may be promoted as a consequence are discussed.

SUMMARY

This article explores the need for DCD liver graft use and the associated biliary complications. The current theories regarding the cause of DCD biliary complications are reviewed, as are the current strategies to reduce them.

Criteria for viability assessment of discarded human donor livers during ex vivo normothermic machine perfusion

Although normothermic machine perfusion of donor livers may allow assessment of graft viability prior to transplantation, there are currently no data on what would be a good parameter of graft viability. To determine whether bile production is a suitable biomarker that can be used to discriminate viable from non-viable livers we have studied functional performance as well as biochemical and histological evidence of hepatobiliary injury during ex vivo normothermic machine perfusion of human donor livers. After a median duration of cold storage of 6.5 h, twelve extended criteria human donor livers that were declined for transplantation were ex vivo perfused for 6 h at 37 °C with an oxygenated solution based on red blood cells and plasma, using pressure controlled pulsatile perfusion of the hepatic artery and continuous portal perfusion. During perfusion, two patterns of bile flow were identified: (1) steadily increasing bile production, resulting in a cumulative output of ≥ 30 g after 6 h (high bile output group), and (2) a cumulative bile production <20 g in 6 h (low bile output group). Concentrations of transaminases and potassium in the perfusion fluid were significantly higher in the low bile output group, compared to the high bile output group. Biliary concentrations of bilirubin and bicarbonate were respectively 4 times and 2 times higher in the high bile output group. Livers in the low bile output group displayed more signs of hepatic necrosis and venous congestion, compared to the high bile output group. In conclusion, bile production could be an easily assessable biomarker of hepatic viability during ex vivo machine perfusion of human donor livers. It could potentially be used to identify extended criteria livers that are suitable for transplantation. These ex vivo findings need to be confirmed in a transplant experiment or a clinical trial.

Liver transplantation with grafts obtained after cardiac death-current advances in mastering the challenge

The scarcity of donor livers has increased the interest in donation after cardiac death (DCD) as an additional pool to expand the availability of organs. However, the initial results of liver transplantation with DCD grafts have been suboptimal due to an increased rate of complications, as well as decreased graft survival. These challenges have led to many developments in DCD donation outcome, as well as basic and translational research. In this article we review the unique characteristics of DCD donors, nuances of DCD organ procurement, the effect of prolonged warm and cold ischemia times, and discuss major studies that compared DCD to donation after brain death liver transplantation, in terms of outcomes and complications. We also review the different methods of donor treatment that has been applied to ameliorate DCD organ outcome, and we discuss the role of machine perfusion techniques in organ reconditioning. We discuss the two major perfusion models, namely, hypothermic machine perfusion and normothermic machine perfusion; we compare both methods, and delineate their major differences.

Hypothermic oxygenated machine perfusion prevents arteriolonecrosis of the peribiliary plexus in pig livers donated after circulatory death

Background

Livers derived from donation after circulatory death (DCD) are increasingly accepted for transplantation. However, DCD livers suffer additional donor warm ischemia, leading to biliary injury and more biliary complications after transplantation. It is unknown whether oxygenated machine perfusion results in better preservation of biliary epithelium and the peribiliary vasculature. We compared oxygenated hypothermic machine perfusion (HMP) with static cold storage (SCS) in a porcine DCD model.

Methods

After 30 min of cardiac arrest, livers were perfused in situ with HTK solution (4°C) and preserved for 4 h by either SCS (n = 9) or oxygenated HMP (10°C; n = 9), using pressure-controlled arterial and portal venous perfusion. To simulate transplantation, livers were reperfused ex vivo at 37°C with oxygenated autologous blood. Bile duct injury and function were determined by biochemical and molecular markers, and a systematic histological scoring system.

Results

After reperfusion, arterial flow was higher in the HMP group, compared to SCS (251±28 vs 166±28 mL/min, respectively, after 1 hour of reperfusion; p = 0.003). Release of hepatocellular enzymes was significantly higher in the SCS group. Markers of biliary epithelial injury (biliary LDH, gamma-GT) and function (biliary pH and bicarbonate, and biliary transporter expression) were similar in the two groups. However, histology of bile ducts revealed significantly less arteriolonecrosis of the peribiliary vascular plexus in HMP preserved livers (>50% arteriolonecrosis was observed in 7 bile ducts of the SCS preserved livers versus only 1 bile duct of the HMP preserved livers; p = 0.024).

Conclusions

Oxygenated HMP prevents arteriolonecrosis of the peribiliary vascular plexus of the bile ducts of DCD pig livers and results in higher arterial flow after reperfusion. Together this may contribute to better perfusion of the bile ducts, providing a potential advantage in the post-ischemic recovery of bile ducts.

[Liver transplant with donated graft after controlled cardiac death. Current situation]

An increasing pressure on the liver transplant waiting list, forces us to explore new sources, in order to expand the donor pool. One of the most interesting and with a promising potential, is donation after cardiac death (DCD). Initially, this activity has developed in Spain by means of the Maastricht type II donation in the uncontrolled setting. For different reasons, donation after controlled cardiac death has been reconsidered in our country. The most outstanding circumstance involved in DCD donation is a potential ischemic stress, that could cause severe liver graft cell damage, resulting in an adverse effect on liver transplant results, in terms of complications and outcomes. The complex and particular issues related to DCD Donation will be discussed in this review.

Bile duct damage after cold storage of deceased donor livers predicts biliary complications after liver transplantation

BACKGROUND & AIMS

The aim of this study was to examine the development of biliary epithelial damage between organ retrieval and transplantation and its clinical relevance for patients.

METHODS

Common bile duct samples during donor hepatectomy, after cold storage, and after reperfusion were compared to healthy controls by hematoxylin and eosin (H&E) staining and immunofluorescence for tight junction protein 1 and Claudin-1. A bile duct damage score to quantify biliary epithelial injury was developed and correlated with recipient and donor data and patient outcome.

RESULTS

Control (N=16) and donor hepatectomy bile ducts (N=10) showed regular epithelial morphology and tight junction architecture. After cold storage (N=37; p=0.0119), and even more after reperfusion (N=62; p=0.0002), epithelial damage, as quantified by the bile duct damage score, was markedly increased, and both tight junction proteins were detected with inappropriate morphology. Patients with major bile duct damage after cold storage had a significantly increased risk of biliary complications (relative risk 18.75; p<0.0001) and graft loss (p=0.0004).

CONCLUSIONS

In many cases, the common bile duct epithelium shows considerable damage after cold ischemia with further damage occurring after reperfusion. The extent of epithelial damage can be quantified by our newly developed bile duct damage score and is a prognostic parameter for biliary complications and graft loss. Possibly, in an intraoperative histological examination, this bile duct damage score may influence decision-making in transplantation surgery.

Establishment of a rat liver transplantation model with prolonged biliary warm ischemia time

AIM: To investigate the impact of different time points of secondary warm ischemia on bile duct in a rat autologous liver transplantation model with external bile drainage.

METHODS: One hundred and thirty-six male inbred SD rats were randomly assigned to one of four groups (I-IV) according to the secondary warm ischemia time of 0, 10, 20 and 40 min. A rat model of autologous liver transplantation with continuous external biliary drainage under ether anesthesia was established. Ten rats in each group were used to evaluate the one-week survival rate. At 6 h, 24 h, 3 d and 7 d after reperfusion of the hepatic artery, 6 rats were killed in each group to collect the blood sample via the infrahepatic vena cava and the median lobe of liver for assay. Warm ischemia time of liver, cold perfusion time, anhepatic phase, operative duration for biliary external drainage and survival rates in the four groups were analyzed for the establishment of models.

RESULTS: No significant difference was shown in warm ischemia time, anhepatic phase and operative duration for biliary external drainage among the four groups. Five of the 40 rats in this study evaluated for the one-week survival rate died, including three deaths of severe pulmonary infection in group IV. A significant decrease of one-week survival rate in group IV was noted compared with the other three groups. With the prolongation of the biliary warm ischemia time, the indexes of the liver function assessment were significantly elevated, and biliary epithelial cell apoptosis index also increased. Pathological examinations showed significantly aggravated inflammation in the portal area and bile duct epithelial cell injury with the prolonged secondary warm ischemia time. Microthrombi were found in the micrangium around the biliary tract in some sections from groups III and IV.

CONCLUSION: The relationship between secondary warm ischemia time and the bile duct injury degree is time-dependent, and 20 min of secondary warm ischemia time is feasible for the study of bile duct injury.

Ischemia-Reperfusion Injury and Ischemic-Type Biliary Lesions following Liver Transplantation

Ischemia-reperfusion (I-R) injury after liver transplantation (LT) induces intra- and/or extrahepatic nonanastomotic ischemic-type biliary lesions (ITBLs). Subsequent bile duct stricture is a significant cause of morbidity and even mortality in patients who underwent LT. Although the pathogenesis of ITBLs is multifactorial, there are three main interconnected mechanisms responsible for their formation: cold and warm I-R injury, injury induced by cytotoxic bile salts, and immunological-mediated injury. Cold and warm ischemic insult can induce direct injury to the cholangiocytes and/or damage to the arterioles of the peribiliary vascular plexus, which in turn leads to apoptosis and necrosis of the cholangiocytes. Liver grafts from suboptimal or extended-criteria donors are more susceptible to cold and warm I-R injury and develop more easily ITBLs than normal livers. This paper, focusing on liver I-R injury, reviews the risk factors and mechanisms leading to ITBLs following LT.

Liver transplantation using Donation after Cardiac Death donors

The success of solid organ transplantation has brought about burgeoning waiting lists with insufficient donation rates and substantial waiting list mortality. All countries have strived to expand donor numbers beyond the standard Donation after Brain Death (DBD). This has lead to the utilization of Donation after Cardiac Death (DCD) donors, also frequently referred to as Non-Heart Beating Donors (NHBD). Organs from these donors inevitably sustain warm ischaemic damage which varies in its extent and affects early graft function as well as graft survival. As a consequence, 'non-vital' organs such as renal transplants have increased rapidly from DCD donors but more 'vital' organ transplants such as the liver have lagged behind. However, an increasing proportion of liver transplants are now derived from DCD donors. This article covers this expansion, current results, pitfalls, and steps taken to minimize complications and to improve outcome, and future developments that are likely to occur.

Current status and recent advances of liver transplantation from donation after cardiac death

The last decade saw increased organ donation activity from donors after cardiac death (DCD). This contributed to a significant proportion of transplant activity. Despite certain drawbacks, liver transplantation from DCD donors continues to supplement the donor pool on the backdrop of a severe organ shortage. Understanding the pathophysiology has provided the basis for modulation of DCD organs that has been proven to be effective outside liver transplantation but remains experimental in liver transplantation models. Research continues on how best to further increase the utility of DCD grafts. Most of the work has been carried out exploring the use of organ preservation using machine assisted perfusion. Both ex-situ and in-situ organ perfusion systems are tested in the liver transplantation setting with promising results. Additional techniques involved pharmacological manipulation of the donor, graft and the recipient. Ethical barriers and end-of-life care pathways are obstacles to widespread clinical application of some of the recent advances to practice. It is likely that some of the DCD offers are in fact probably “prematurely” offered without ideal donor management or even prior to brain death being established. The absolute benefits of DCD exist only if this form of donation supplements the existing deceased donor pool; hence, it is worthwhile revisiting organ donation process enabling us to identify counter remedial measures.

Characterization of the withdrawal phase in a porcine donation after the cardiac death model

Transplantation of donation after cardiac death (DCD) livers has higher rates of organ failure and complications, specifically ischemic biliary injuries. Reported large animal DCD models all employ active means to halt circulation, contrary to human DCD protocol. We report a DCD porcine model in which the animal passively progresses to cardiac death, thereby more closely mimicking human DCD scenario. Sixteen Yorkshire pigs (10 females, 6 males, 30-45 kg) had a mean time of 26:19 min ± 14:14 from withdrawal of ventilatory support (WVS) to circulatory arrest and 44:38 min ± 16:37 from WVS to electrical standstill. Cessation of hepatic flow (HF) occurred well before electrical standstill (22:15 min ± 10:09), previously not described in human or animal DCD. Histologically comparing livers from our DCD model demonstrated a dramatic increase in hepatocyte vacuolization, disorganization of endoplasmic reticulum, formation of mitochondrial inclusions and apoptosis compared with control specimens. Subtle changes were also evident in biliary epithelial cells (BEC). This results in severe cellular changes before reperfusion. Early histologic evidence suggests that there is severe hepatocyte and biliary cell disruption in our DCD model. Further research using this model may provide a deeper understanding of the pathophysiology of the DCD liver.

Role of cholangiocyte bile Acid transporters in large bile duct injury after rat liver transplantation

BACKGROUND

The pathogenesis of nonanastomotic strictures with a patent hepatic artery remains to be investigated. This study focuses on the role of cholangiocyte bile acid transporters in bile duct injury after liver transplantation.

METHODS

Sprague-Dawley rats were divided into three groups (n=20 for each): the sham-operated group (Sham), the transplant group with 1-hr donor liver cold preservation (CP-1h), and the transplant group with 12-hr donor liver cold preservation (CP-12h). Bile was collected for biochemical analysis. The histopathologic evaluation of bile duct injury was performed and the cholangiocyte bile acid transporters apical sodium-dependent bile acid transporter (ASBT), ileal lipid binding protein (ILBP), and Ostalpha/Ostbeta were investigated. RESULTS.: The immunohistochemical assay suggested that ASBT and ILBP were expressed exclusively on large bile duct epithelial cells, whereas Ostalpha and Ostbeta were expressed on both small and large bile ducts. Western blot and quantitative polymerase chain reaction analysis showed that the expression levels of these transporters dramatically decreased after transplantation. It took seven to 14 days for ILBP, Ostalpha, and Ostbeta to recover, whereas ASBT recovered within 3 days and even reached a peak above the normal level seven days after operation. In the CP-12h group, the ratios of the ASBT/ILBP, ASBT/Ostalpha and ASBT/Ostbeta expression levels were correlated with the injury severity scores of large but not small bile ducts.

CONCLUSIONS

The results suggest that the unparallel alteration of cholangiocyte bile acid transporters may play a potential role in large bile duct injury after liver transplantation with prolonged donor liver preservation.

Multifactorial biological modulation of warm ischemia reperfusion injury in liver transplantation from non-heart-beating donors eliminates primary nonfunction and reduces bile salt toxicity

OBJECTIVE

To design a multifactorial biological modulation approach targeting ischemia reperfusion injury to augment viability of porcine liver grafts from non-heart-beating donors (NHBD).

BACKGROUND DATA

Liver Transplantation (LTx) from NHBD is associated with an increased risk of primary nonfunction (PNF) and biliary complications. In porcine NHBD-LTx, we previously reported a 50% risk of PNF and toxic bile formation in grafts exposed to > or =30' warm ischemia (WI).

METHODS

Porcine livers exposed to 45' WI were cold stored, transplanted and either modulated (n = 6) or not (controls, n = 9). In the modulation group, donor livers were flushed with warm Ringers (avoiding cold-induced vasoconstriction), streptokinase (eliminating stagnating thrombi), and epoprostenol (vasodilator, platelet aggregation inhibitor) prior to cold storage. In recipients, glycine (Kupffer cell stabilizer), alpha1-acid-glycoprotein (anti-inflammatory protein), MAPKinase-inhibitor (pro-inflammatory cytokine generation inhibitor), alpha-tocopherol and glutathione (anti-oxidants), and apotransferrin (iron chelator) were administrated intravenously. PNF, survival, lactate, transaminase, TNF-alpha, redox-active iron, and biliary bile salt-to-phospholipid ratio were monitored.

RESULTS

No PNF was observed in modulated versus 55% in control pigs (P = 0.025). Survival was 83% in modulated versus 22% in control pigs (P = 0.02). At 180' postreperfusion, lactate was lower in modulated (5.4 +/- 1.9 mmol/L) versus control pigs (9.4 +/- 2.2 mmol/L; P = 0.011). At 60' postreperfusion, there was a trend for lower AST in modulated versus control pigs at 60' (939 +/- 578 vs. 1683 +/- 873 IU/L; P = 0.089). Postreperfusion, TNF-alpha remained stable in modulated pigs (49 +/- 27 pg/mL at 15' and 85 +/- 26 pg/mL at 180'; P = 0.399) but increased in control pigs (107 +/- 36 pg/mL at 15' and 499 +/- 216 pg/mL at 180'; P = 0.023). At 180' postreperfusion, redox-active iron was higher in control pigs versus modulated pigs (0.21+/-0.18 vs. 0.042+/-0.062 mum; P = 0.038). Biliary bile salt-to-phospholipid ratio post-LTx was lower in modulated versus control pigs (1128 +/- 447 vs. 4836 +/- 4619; P = 0.05).

CONCLUSIONS

A multifactorial biological modulation eliminates PNF, improves liver function and increases survival. Biochemically, TNF-alpha and redox-active iron are suppressed and biliary bile salt toxicity is reduced. Translating this strategy clinically may lead to wider and safer use of NHBD.

Altered bile composition after liver transplantation is associated with the development of nonanastomotic biliary strictures

BACKGROUND/AIMS

Nonanastomotic biliary strictures are troublesome complications after liver transplantation. The pathogenesis of NAS is not completely clear, but experimental studies suggest that bile salt toxicity is involved.

METHODS

In one hundred and eleven adult liver transplants, bile samples were collected daily posttransplantation for determination of bile composition. Expression of bile transporters was studied perioperatively.

RESULTS

Nonanastomotic biliary strictures were detected in 14 patients (13%) within one year after transplantation. Patient and donor characteristics and postoperative serum liver enzymes were similar between patients who developed nonanastomotic biliary strictures and those who did not. Secretions of bile salts, phospholipids and cholesterol were significantly lower in patients who developed strictures. In parallel, biliary phospholipids/bile salt ratio was lower in patients developing strictures, suggestive for increased bile cytotoxicity. There were no differences in bile salt pool composition or in hepatobiliary transporter expression.

CONCLUSIONS

Although patients who develop nonanastomotic biliary strictures are initially clinically indiscernible from patients who do not develop nonanastomotic biliary strictures, the biliary bile salts and phospholipids secretion, as well as biliary phospholipids/bile salt ratio in the first week after transplantation, was significantly lower in the former group. This supports the concept that bile cytotoxicity is involved in the pathogenesis of nonanastomotic biliary strictures.