Role of hepatocytes and bile duct cells in preservation-reperfusion injury of liver grafts

Identification of Mulberrofuran as a potent inhibitor of hepatitis A virus 3Cpro and RdRP enzymes through structure-based virtual screening, dynamics simulation, and DFT studies

Hepatitis is a medical condition characterized by inflammation of the liver. It is commonly caused by the hepatitis viruses A, B, C, D, and E. Hepatitis A virus (HAV) is highly contagious and can spread from infected individuals, through contaminated food, blood, or can also be water-borne. As per the statistics of World Health Organization (WHO), HAV infects about 1.4 million individuals each year globally. In this research work, we have focused on identifying natural product-based potential inhibitors for the two major enzymes of HAV namely 3C proteinase (3Cpro) and RNA-directed RNA polymerase (RdRP). The enzyme 3Cpro plays an important role in proteolytic activity that promotes viral maturation and infectivity. RNA-directed RNA polymerase facilitate viral replication and transcription. Structure-based virtual screening was carried out using NPACT database that contains a collection of 1574 curated plant-derived natural compounds that are validated by experiments. The screening procedure identified the phytochemical Mulberrofuran W, which could bind to both the targets 3Cpro and RdRP. The phytochemical Mulberrofuran W also had better binding affinity compared to the control compounds atropine and pyridinyl ester, which are previously identified inhibitors of HAV 3Cpro and RdRP, respectively. The Mulberrofuran W bound 3Cpro and RdRP complexes were subjected to 200 ns molecular dynamics simulations and were found to be stable and interacting with the active site of the enzymes throughout the course of complex MD simulations. In addition to DFT, MMGBSA studies were also performed to validate the identified potential inhibitor further. The identified phytochemical Mulberrofuran W can be considered as a new potential drug candidate and could be taken up for experimental evaluation against HAV infection.

MULTIPLE MACHINE LEARNING METHODS AND COMPARATIVE TRANSCRIPTOMICS IDENTIFY PIVOTAL GENES FOR ISCHEMIA-REPERFUSION INJURY IN HUMAN DONOR TISSUE UNDERGOING ORTHOTOPIC LIVER TRANSPLANTATION

ABSTRACT

Background: Hepatic ischemia-reperfusion injury (HIRI) is a major complication affecting patient prognosis during the period after orthotopic liver transplantation (OLT). Although an increasing number of scientists have investigated the molecular biology of ischemia-reperfusion injury (IRI) during OLT in animal and cellular models in recent years, studies using comprehensive and high-quality sequencing results from human specimens to screen for key molecules are still lacking. Aims: The objective of this study is to explore the molecular biological pathways and key molecules associated with HIRI during OLT through RNA sequencing and related bioinformatics analysis techniques. Methods: The study was done by performing mRNA sequencing on liver tissue samples obtained from 15 cases of in situ liver transplantation patients who experienced ischemia and reperfusion injury within 1 year at Guizhou Medical University, and combined with bioinformatics analysis and machine learning methods, we identified the genes and transcription factors that are closely associated with IRI during in situ liver transplantation surgery. Results: There were 877 differentially expressed genes (DEGs) identified in the included liver samples, of which 817 DEGs were upregulated and 60 were downregulated. Functional enrichment analysis revealed significant enrichment of immune-related terms, such as inflammation, defense responses, responses to cytokines, immune system processes, and cellular activation. In addition, core gene enrichment analysis after cytoHubba screening suggested that liver reperfusion injury might be associated with translation-related elements as a pathway together with protein translation processes. Machine learning with the weighted correlation network analysis screening method identified PTGS2, IRF1, and CDKN1A as key genes in the reperfusion injury process. Conclusions: This study demonstrated that the pathways and genomes whose expression is altered throughout the reperfusion process might be critical for the progression of HIRI during OLT.

SIRT1 regulates hepatocyte programmed cell death via GSDME - IL18 axis in human and mouse liver transplantation

Sirtuin 1 (SIRT1) is a histone/protein deacetylase in the cellular response to inflammatory, metabolic, and oxidative stressors. We previously reported that myeloid SIRT1 regulates the inflamed liver's canonical pyroptosis cell death pathway. However, whether/how hepatocyte SIRT1 is engaged in programmed cell death in the cold-stressed liver remains uncertain. Here, we undertook translational studies in human and mouse orthotopic liver transplantation (OLT) to interrogate the significance of hepatocyte-specific SIRT1 in cold-stored donor livers and liver grafts after reperfusion. In the clinical arm of sixty human OLT patients, hepatic SIRT1 levels in cold-preserved donor livers correlated with the anti-apoptotic Bcl-2 expression. After reperfusion, improved OLT function was accompanied by hepatic SIRT1 levels negatively associated with cleaved caspase-3 expression. In the experimental arm, we compared FLOX-control with hepatocyte-specific SIRT1-KO livers after orthotopic transplantation into WT mouse recipients, parallel with primary murine hepatocyte cultures subjected to cold activation with/without knockdown of SIRT1, GSDME, and IL18Rβ. Indeed, hepatocyte SIRT1 deficiency upregulated apoptosis and GSDME-mediated programmed cell death, deteriorating hepatocellular function and shortening OLT survival. Augmented GSDME processing, accompanied by increased secretion of IL18 by stressed hepatocytes, was prominent in SIRT1-deficient, cold-stored livers. Hepatocyte SIRT1 expression regulated anti-apoptotic Bcl-2/XIAP proteins, suppressed cold stress-triggered apoptosis, and mitigated GSDME licensing to release IL18. Notably, consistent with the ability of IL18 to depress hepatocyte SIRT1 and Bcl-2/XIAP in vitro, IL18 neutralization in vivo prevented hepatocellular damage and restored the anti-apoptotic phenotype in otherwise injury-prone SIRT1-deficient OLTs. In conclusion, this translational study identifies a novel hepatocyte SIRT1-IL18 molecular circuit as a therapeutic target in the mechanism underpinning hepatocyte death pathways in human and mouse liver transplantation.

SIRT1 Regulates Hepatocyte Programmed Cell Death via GSDME - IL18 Axis in Human and Mouse Liver Transplantation

Sirtuin 1 (SIRT1) is a histone/protein deacetylase involved in cellular senescence, inflammation, and stress resistance. We previously reported that myeloid SIRT1 signaling regulates the inflamed liver's canonical pyroptosis cell death pathway. However, whether/how hepatocyte SIRT1 is engaged in programmed cell death in the cold-stressed liver remains uncertain. Here, we undertook translational studies in human and mouse orthotopic liver transplantation (OLT) to interrogate the significance of hepatocyte-specific SIRT1 signaling in cold-stored donor livers and liver grafts after reperfusion. In the clinical arm of sixty human OLT patients, hepatic SIRT1 levels in cold-preserved donor livers correlated with anti-apoptotic Bcl-2 expression. After reperfusion, improved OLT function was accompanied by hepatic SIRT1 levels negatively associated with cleaved caspase-3 expression. In the experimental arm, we compared FLOX-control with hepatocyte-specific SIRT1-KO livers after orthotopic transplantation into WT mouse recipients, parallel with primary murine hepatocyte cultures subjected to cold activation with/without knockdown of SIRT1, GSDME, and IL18Rβ signaling. Hepatocyte SIRT1 deficiency upregulated apoptosis and GSDME-mediated programmed cell death, which in turn deteriorated the hepatocellular function and shortened OLT survival. Augmented GSDME processing, accompanied by increased secretion of IL18 by stressed hepatocytes, was prominent in SIRT1-deficient, cold-stored livers. Hepatocyte SIRT1 signaling regulated anti-apoptotic Bcl-2/XIAP proteins, suppressed cold stress-triggered apoptosis, and mitigated GSDME licensing to release IL18. Notably, while crosslinking IL18R depressed SIRT1 and Bcl-2/XIAP signaling in vitro, IL18 neutralization in vivo prevented hepatocellular damage and restored the anti-apoptotic phenotype in otherwise injury-prone SIRT1-deficient OLTs. In conclusion, this translational study identifies a novel hepatocyte SIRT1-IL18 signaling circuit as a therapeutic target in the mechanism underpinning hepatocyte death in human and mouse liver transplantation.

Donor graft METTL3 gene transfer ameliorates rat liver transplantation ischemia-reperfusion injury by enhancing HO-1 expression in an m6A-dependent manner

Ischemia-reperfusion injury (IRI) is one of the most common complications in liver transplantation. METTL3 regulates inflammation and various cellular stress responses via modulating RNA m6A modification level. Here, the study aimed to investigate the role and mechanism of METTL3 in IRI after rat orthotopic liver transplantation. Firstly, m6A dot blot assay showed that total RNA m6A modification level in grafts was down-regulated, which echoed with the downregulation of METTL3. Furthermore, METTL3 pretreatment in donor significantly reduced liver grafts necrosis formation, apoptosis, improved liver function and depressed the proinflammatory cytokine/chemokine expression. Mechanistically, western blot and immunohistochemical showed that METTL3 inhibited apoptosis via upregulating HO-1. Moreover, MeRIP-qPCR assay revealed that METTL3 promoted HO-1 expression in an m6A-dependent manner. Additionally, METTL3 alleviated primary hepatocytes apoptosis by upregulating HO-1 under hypoxia/reoxygenation condition. Taken together, these results demonstrated that METTL3 exerted a cytoprotective role against IRI via inducing HO-1 in an m6A-dependent manner.

Postreperfusion Liver Biopsy as Predictor of Early Graft Dysfunction and Survival After Orthotopic Liver Transplantation

BACKGROUND

Postreperfusion liver biopsy (PRB) can assess the degree of ischemia/reperfusion injury (IRI) after orthotopic liver transplantation (OLT). The influence of IRI on graft outcomes and overall survival is controversial.

AIM

To determine the correlation between the severity of IRI in PRB and overall graft and patient survival and, secondarily, to identify factors on PRB that predict poor graft outcomes.

METHODS

This is a retrospective analysis of all patients who underwent OLT using donation after brain death (DBD) with PRB. The severity of IRI in PRB was graded. Predictors of IRI were assessed using univariate and multivariate analysis and the Kaplan-Meier with log rank test for the graft and overall survival, respectively.

RESULTS

We included 280 OLTs (64.7%). The histopathological assessment of IRI severity was as follows: no IRI (N = 96, 34.3%), mild IRI (N = 65; 23.2%), moderate IRI (N = 101; 36.1%), and severe IRI (N = 18; 6.4%). The incidence rates of initial good graft function (IGGF), primary nonfunction and early allograft dysfunction (EAD) were 32.5%, 3.9%, and 18.6%, respectively. Severe IRI was associated with a lower incidence of IGGF (OR: 0.34, 95% CI 0.12-0.92; P = 0.03). Patients with severe IRI tended to have a higher incidence of EAD (33.2% vs. 18.6, P = 0.23). The cold ischemia time was an independent predictor of severe IRI on the multivariate analysis. Severe IRI was associated with poor 1- and 5-year overall survival rates (67% and 44%, respectively, compared with 84 and 68% in nonsevere IRI). Patients with severe IRI exhibited worse graft and overall survival.

CONCLUSIONS

Cold ischemia time predicts the development of severe IRI. Patients with severe IRI show worse graft and overall survival and a lower incidence of IGGF, suggesting that histopathological findings could be useful for identifying patients at high risk of worse outcomes after OLT.

Inflammasome-Mediated Inflammation in Liver Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is an important cause of liver damage occurring during surgical procedures including hepatic resection and liver transplantation, and represents the main underlying cause of graft dysfunction and liver failure post-transplantation. To date, ischemia-reperfusion injury is an unsolved problem in clinical practice. In this context, inflammasome activation, recently described during ischemia-reperfusion injury, might be a potential therapeutic target to mitigate the clinical problems associated with liver transplantation and hepatic resections. The present review aims to summarize the current knowledge in inflammasome-mediated inflammation, describing the experimental models used to understand the molecular mechanisms of inflammasome in liver ischemia-reperfusion injury. In addition, a clear distinction between steatotic and non-steatotic livers and between warm and cold ischemia-reperfusion injury will be discussed. Finally, the most updated therapeutic strategies, as well as some of the scientific controversies in the field will be described. Such information may be useful to guide the design of better experimental models, as well as the effective therapeutic strategies in liver surgery and transplantation that can succeed in achieving its clinical application.

Recovery of the Cholangiocytes After Ischemia and Reperfusion Injury: Ultra-Structural, Hystological and Molecular Assessment in Rats

INTRODUCTION

Ischemia-reperfusion (I/R) injury of the liver is a common area of interest to transplant and hepatic surgery. Nevertheless, most of the current knowledge of I/R of the liver derives from the hepatocyte and little is known of what happens to the cholangiocytes. Herein, we assess the sequence of early events involved in the I/R injury of the cholangiocytes.

METHODS

Sixty Wistar rats were randomized in a SHAM group and I/R group. Serum biochemistry, histopathology, immunohistochemistry, transmission electron microscopy (TEM) and laser capture microdissection (LCM) were used for group comparison.

RESULTS

There was peak of alkaline phosphatase 24 h after IR injury, and an increase of aspartate aminotransferase and alanine aminotransferase after 6 h of reperfusion, followed by a return to normal levels 24 h after injury. The I/R group presented the liver parenchyma with hepatocellular degeneration up to 6 h, followed by hepatocellular necrosis at 24 h. TEM showed cholangiocyte injury, including a progressive nuclear degeneration and cell membrane rupture, beginning at 6 h and peaking at 24 h after reperfusion. Cytokeratin-18 and caspase-3-positive areas were observed in the I/R group, peaking at 24-h reperfusion. Anti-apoptotic genes Bcl-2 and Bcl-xl activity were expressed from 6 through 24 h after reperfusion. BAX expression showed an increase for 24 h.

CONCLUSIONS

I/R injury to the cholangiocyte occurs from 6 through 24 h after reperfusion and a combination of TEM, immunohistochemistry and LCM allows a better isolation of the cholangiocyte and a proper investigation of the events related to the I/R injury. Apoptosis is certainly involved in the I/R process, particularly mediated by BAX.

Severe Unresolved Cholestasis Due to Unknown Etiology Leading to Early Allograft Failure Within the First 3 Months of Liver Transplantation

BACKGROUND

Causes of severe cholestasis after liver transplantation (LT) are multi-factorial. Although the etiology is predictable in some, others culminate in graft/patient loss without a definitive cause identified. Severe cholestasis is usually associated with overlapped histological findings of rejection and biliary features, and diagnostic interpretation may pose a challenge.

METHODS

This is 10-year retrospective analysis of patients with unexplained severe cholestasis resulting in death/graft loss within 90 days of LT. Of 1 583 LT during the study period, 90-day graft failure occurred in 129 (8%) cases; a total of 45 (3%) patients had unresolving severe cholestasis (bilirubin, >100 μmol/L; alkaline phosphatase, >400 UI/L after 15 days from LT), excluding those due to primary nonfunction/sepsis/vascular causes (n = 84). Demographics, allograft biopsies, radiological investigations, and clinical outcome were analyzed.

RESULTS

All patients had persistent abnormal liver biochemistry. Doppler ultrasound scan was normal in all cases. Thirty-five (78%) recipients had at least 1 allograft biopsy (2 [1-9]). On the first biopsy, 22 (63%) patients had acute rejection, 4 (18%) early-chronic rejection, 12 (34%) antibody-mediated rejection. In subsequent biopsies chronic rejection was evident in 5 (14%) cases. Donor-specific antibodies were detected in all patients tested. Biliary anatomy was studied in detail in 9 (20%) patients, all presenting biliary strictures. The majority (n = 39; 87%) died within 32 (10-91) days, only survivors were from retransplantation (n = 3;6.5%) and biliary intervention (n = 3;6.5%).

CONCLUSIONS

Unresolving severe cholestasis after LT is a key parameter predicting patient/allograft outcome. Histologically, rejection seems to overlap with biliary strictures; hence, allograft biopsy with signs of rejection should not be a reason to overlook biliary problems, in particular when biliary features are present. Only extensive radiological investigation/intervention or retransplantation prevents patient/allograft loss.

Liver Graft Susceptibility during Static Cold Storage and Dynamic Machine Perfusion: DCD versus Fatty Livers

We compared static preservation (cold storage, CS, 4 °C) with dynamic preservation (machine perfusion, MP, 20 °C) followed by reperfusion using marginal livers: a model of donation after cardiac death (DCD) livers and two models of fatty livers, the methionine-choline deficient (MCD) diet model, and obese Zucker (fa/fa) rats. CS injury in DCD livers was reversed by an oxygenated washout (OW): hepatic damage, bile flow, and the ATP/ADP ratio in the OW + CS group was comparable with the ratio obtained with MP. Using fatty livers, CS preservation induced a marked release in hepatic and biliary enzymes in obese Zucker rats when compared with the MCD group. The same trend occurred for bile flow. No difference was found when comparing MP in MCD and obese Zucker rats. Fatty acid analysis demonstrated that the total saturated (SFA)/polyunsaturated fatty acid (PUFA) ratio was, respectively, 1.5 and 0.71 in obese Zucker and MCD rats. While preservation damage in DCD livers is associated with the ATP/ADP recovered with OW, injury in fatty livers is linked to fatty acid constituents: livers from obese. Zucker rats, with greater content in saturated FA, might be more prone to CS injury. On the contrary, MCD livers with elevated PUFA content might be less susceptible to hypothermia.

Incidence and Treatment of Bile Stones After Liver Transplant

OBJECTIVES

Although the incidence of bile stones after liver transplant is rare (2%-6%), various complications can occur, including recurrent cholangitis, biliary strictures, graft loss, and patient mortality.

MATERIALS AND METHODS

We retrospectively evaluated bile stone incidence, pathogenesis, and treatment in 352 liver transplant recipients, comparing demographics, transplant indication, blood lipid profile, bile reconstruction technique, postoperative complications, time of diagnosis, and treatment regimens.

RESULTS

Of 352 recipients, 18 had bile stones, with 13 of these patients (72.2%) receiving duct-to-duct bile reconstruction, 17 having biliary complications before bile stone development, 7 (38.9%) having biliary stricture, 6 (33.3%) having biliary leakage, 4 (22.2%) having biliary strictures secondary to biliary leakage, and 7 (38.9%) having hepatic artery complications early posttransplant. Previous biliary complications and recurrent cholangitis significantly increased bile stones. Incidence in patients with triglyceride levels > 250 mg/dL was significantly different from those with levels at < 250 mg/dL. Cold ischemia time was significant in those with and without bile stones (P = .001). Three patients (16%) were treated by endoscopic tools, with others (15/18, 84%) treated via percutaneous procedures.

CONCLUSIONS

Bile stone risk can be greater in those with previous biliary complications, hepatic artery problems, long cold ischemia time, and high cholesterol levels. It can be successfully treated by endoscopic and percutaneous techniques.

Potential benefits of melatonin in organ transplantation: a review

Organ transplantation is a useful therapeutic tool for patients with end-stage organ failure; however, graft rejection is a major obstacle in terms of a successful treatment. Rejection is usually a consequence of a complex immunological and nonimmunological antigen-independent cascade of events, including free radical-mediated ischemia-reperfusion injury (IRI). To reduce the frequency of this outcome, continuing improvements in the efficacy of antirejection drugs are a top priority to enhance the long-term survival of transplant recipients. Melatonin (N-acetyl-5-methoxytryptamine) is a powerful antioxidant and ant-inflammatory agent synthesized from the essential amino acid l-tryptophan; it is produced by the pineal gland as well as by many other organs including ovary, testes, bone marrow, gut, placenta, and liver. Melatonin has proven to be a potentially useful therapeutic tool in the reduction of graft rejection. Its benefits are based on its direct actions as a free radical scavenger as well as its indirect antioxidative actions in the stimulation of the cellular antioxidant defense system. Moreover, it has significant anti-inflammatory activity. Melatonin has been found to improve the beneficial effects of preservation fluids when they are enriched with the indoleamine. This article reviews the experimental evidence that melatonin is useful in reducing graft failure, especially in cardiac, bone, otolaryngology, ovarian, testicular, lung, pancreas, kidney, and liver transplantation.

Correlation of Histopathologic Findings of Non-Graft Threatening Preservation/Reperfusion Injury in Time-Zero Liver Needle Biopsies With Short-Term Post-transplantation Laboratory Alterations

BACKGROUND

Early post-transplantation alterations in liver tests are caused by a variety of etiologies including rejection, biliary or vascular complications, and preservation/reperfusion injury (PRI).

OBJECTIVES

The aim of this study was to show the correlation between histopathologic changes of PRI and the alterations in liver tests in the early post-transplantation period.

MATERIALS AND METHODS

Between April 2013 and August 2014, histopathologic findings of protocol, time-zero, Tru-Cut, liver needle biopsies were evaluated in 94 cases of cadaveric liver transplantation. The histopathologic changes included ballooning degeneration, micro- and macro-vesicular steatosis, bilirubinostasis, apoptotic cells, bile plugs and neutrophilic infiltration. These histopathologic changes were compared with the early (15 days) post-transplantation liver laboratory findings.

RESULTS

Clinico-pathologic evaluation of all 94 cases was done by assessment of PRI findings in time-zero biopsies and possible causes of allograft injury were appraised. In 21 patients, a specific cause for allograft injury was found including rejection and/or surgical complications. In the remaining 73 cases, there was no specific cause for allograft injury and histopathologic findings of time-zero liver needle biopsies supported PRI. We classified liver laboratory tests alterations as: hepatocellular damage (elevation of transaminases and lactate dehydrogenase), cholestatic damage (elevation of alkaline phosphatase and total bilirubin) and mixed. Hepatocellular and cholestatic alterations in liver function tests were associated with the presence of marked apoptotic bodies and neutrophilic aggregates in time zero biopsies, respectively. On the other hand, macrovesicular steatosis was dominantly associated with mixed (hepatocellular and cholestatic) laboratory alterations of liver tests.

CONCLUSIONS

Any discrepancy between histopathologic changes in time-zero biopsies and pattern of early liver laboratory alterations may be considered as a warning for causes other than PRI.

Minimising Warm and Cold Ischaemic Times in Livers Transplanted from Donation after Circulatory Death Donors: Are We Doing Enough?

Warm and cold ischaemic times (WIT and CIT) are two modifiable factors known to have a significant impact on transplant graft survival. The aim of this study was to investigate the changes in WIT and CIT in our unit, and to study whether there was any correlation between them and the outcomes of donation after circulatory death (DCD) liver transplantation. Data was collected by a single-centre retrospective review of all DCD livers transplanted at our unit (n=61) from 2004–2011. The outcome measures were graft survival at one week, three months and one year post-transplant. Each year the CIT and WIT remained relatively constant, with no statistically significant change (p=0.3 and p=0.36 respectively). From 2004–2011, one graft failed within seven days of transplant, two grafts failed within three months and four failed within one year. A statistically significant finding was a correlation between WIT and graft failure at one year post-transplant (p=0.02) with an odds ratio of 0.76 (95% confidence interval 0.59–0.98), which suggested that for each additional minute of WIT, the chance of graft failure at one year increased by 24%. This single-centre study demonstrated a failure to effectively minimise WIT and CIT over eight years in this unit. Our results show that reductions in WIT can have a significant impact on the long-term outcome of DCD liver transplantation. This study has identified modifiable factors which can reduce the overall CIT and WIT affecting livers for DCD transplantation.

Dipeptidylpeptidase-IV activity and expression reveal decreased damage to the intrahepatic biliary tree in fatty livers submitted to subnormothermic machine-perfusion respect to conventional cold storage

Graft steatosis is a risk factor for poor initial function after liver transplantation. Biliary complications are frequent even after normal liver transplantation. A subnormothermic machine perfusion (MP20) preservation procedure was developed by our group with high potential for reducing injury to hepatocytes and sinusoidal cells of lean and fatty livers respect to conventional cold storage (CS). We report the response of the biliary tree to CS or MP20, in lean and obese Zucker rat liver. Dipeptidylpeptidase-IV (DPP-IV), crucial for the inactivation of incretins and neuropeptides, was used as a marker. Liver morphology and canalicular network of lean livers were similar after CS/reperfusion or MP20/reperfusion. CS preservation of fatty livers induced serious damage to the parenchyma and to the canalicular activity/ expression of DPP-IV, whereas with MP20 the morphology and canalicular network were similar to those of untreated lean liver. CS and MP20 had similar effects on DPP-IV activity and expression in the upper segments of the intrahepatic biliary tree of fatty livers. DPP-IV expression was significantly increased after MP20 respect to CS or to the controls, both for lean and obese animals. Our data support the superiority of MP20 over CS for preserving fatty livers. Dipeptidylpeptidase-IV activity and expression reveal decreased damage to the intrahepatic biliary tree in fatty livers submitted to subnormothermic machine-perfusion respect to conventional cold storage.

Hepatic ischemia and reperfusion injury: effects on the liver sinusoidal milieu

Ischemia-reperfusion injury is an important cause of liver damage occurring during surgical procedures including hepatic resection and liver transplantation, and represents the main underlying cause of graft dysfunction post-transplantation. Cellular and biochemical processes occurring during hepatic ischemia-reperfusion are diverse and complex, and include the deregulation of the healthy phenotype of all liver cellular components. Nevertheless, a significant part of these processes are still unknown or unclear. The present review aims at summarizing the current knowledge in liver ischemia-reperfusion, but specifically focusing on liver cell phenotype and paracrine interaction deregulations. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field will be described. Finally, the importance of considering the subclinical situation of liver grafts when translating basic knowledge to the bedside is discussed.

Dipeptidylpeptidase--IV, a key enzyme for the degradation of incretins and neuropeptides: activity and expression in the liver of lean and obese rats

Given the scarcity of donors, moderately fatty livers (FLs) are currently being considered as possible grafts for orthotopic liver transplantation (OLT), notwithstanding their poor tolerance to conventional cold preservation. The behaviour of parenchymal and sinusoidal liver cells during transplantation is being studied worldwide. Much less attention has been paid to the biliary tree, although this is considered the Achille's heel even of normal liver transplantation. To evaluate the response of the biliary compartment of FLs to the various phases of OLT reliable markers are necessary. Previously we demonstrated that Alkaline Phosphatase was scarcely active in bile canaliculi of FLs and thus ruled it out as a marker. As an alternative, dipeptidylpeptidase-IV (DPP-IV), was investigated. This ecto-peptidase plays an important role in glucose metabolism, rapidly inactivating insulin secreting hormones (incretins) that are important regulators of glucose metabolism. DPP-IV inhibitors are indeed used to treat Type II diabetes. Neuropeptides regulating bile transport and composition are further important substrates of DPP-IV in the enterohepatic axis. DPP-IV activity was investigated with an azo-coupling method in the liver of fatty Zucker rats (fa/fa), using as controls lean Zucker (fa/+) and normal Wistar rats. Protein expression was studied by immunofluorescence with the monoclonal antibody (clone 5E8). In Wistar rat liver, DPP-IV activity and expression were high in the whole biliary tree, and moderate in sinusoid endothelial cells, in agreement with the literature. Main substrates of DPP-IV in hepatocytes and cholangiocytes could be incretins GLP-1 and GIP, and neuropeptides such as vasoactive intestinal peptide (VIP) and substance P, suggesting that these substances are inactivated or modified through the biliary route. In lean Zucker rat liver the enzyme reaction and protein expression patterns were similar to those of Wistar rat. In obese rat liver the patterns of DPP-IV activity and expression in hepatocytes reflected the morphological alterations induced by steatosis as lipid-rich hepatocytes had scarce activity, located either in deformed bile canaliculi or in the sinusoidal and lateral domains of the plasma membrane. These findings suggest that bile canaliculi in steatotic cells have an impaired capacity to inactivate incretins and neuropeptides. Incretin and/or neuropeptide deregulation is indeed thought to play important roles in obesity and insulin-resistance. No alteration in enzyme activity and expression was found in the upper segments of the biliary tree of obese respect to lean Zucker and Wistar rats. In conclusion, this research demonstrates that DPP-IV is a promising in situ marker of biliary functionality not only of normal but also of fatty rats. The approach, initially devised to investigate the behaviour of the liver during the various phases of transplantation, appears to have a much higher potentiality as it could be further exploited to investigate any pathological or stressful conditions involving the biliary tract (i.e., metabolic syndrome and cholestasis) and the response of the biliary tract to therapy and/or to surgery.

Early-onset versus late-onset nonanastomotic biliary strictures post liver transplantation: risk factors reflect different pathogenesis

Nonanastomotic biliary strictures (NAS) cause significant morbidity post liver transplantation. Timing of stricture development varies considerably, but the relationship between timing of stricture onset and aetiology has not been fully elucidated. Database analysis was performed on all adult patients undergoing liver transplantation between 1st January 1990 and 31st May 2008. Diagnosis of NAS required demonstration on at least two radiological studies. Early NAS were defined as developing <1 year post transplant (minimum 1-year follow-up) and late NAS developing >1 year post transplant (minimum 10-year follow-up). Ninety-six of 397 patients developed NAS (24%); 54 were early-onset NAS (56%) and 42 late-onset NAS (44%). Primary sclerosing cholangitis (PSC) was the only risk factor for NAS overall (P = 0.001). However, when patients with PSC were excluded, older donor age was a significant risk for NAS (P = 0.003). Early-onset NAS were associated with advanced donor age (P = 0.02), high MELD score (P = 0.001) and ABO-identical grafts (P = 0.02), whereas late-onset NAS were associated with PSC (P = 0.0008), bilio-enteric anastomosis (P = 0.006) and tacrolimus (P = 0.0001). Advanced donor age is a significant risk for NAS in patients without PSC. Importantly, aetiology of NAS varies depending on time to stricture development, suggesting early-onset and late-onset NAS may have different pathogenesis.

Biliary complications after liver transplantation using grafts from donors after cardiac death: results from a matched control study in a single large volume center

OBJECTIVE

To assess the incidence and impact of biliary complications in recipients transplanted from donors after cardiac death (DCD) at one single large institution.

BACKGROUND

Shortage of available cadaveric organs is a significant limiting factor in liver transplantation (LT). The use of DCD offers the potential to increase the organ pool. However, early results with DCD liver grafts were associated with a greater incidence of ischemic cholangiopathy (IC), leading to several programs to abandoning this source of organs.

METHODS

A retrospective analysis of a prospective database from April 2001 to 2010 focused on 167 consecutive DCD-LT. Each DCD transplant was matched with 2 brain death donors (DBD) grafts (n = 333) according to the period of transplantation. Primary outcome measures were biliary complications including the severity of complications, graft survival and patient survival. Minimum follow-up was 3 months.

RESULTS

Anastomotic stricture was the most common biliary complication (DCD = 30, 19% vs. DBD = 41, 13%). Most were treated endocoscopically (grade IIIa = 72%), whereas hepatico-jejunostomy (grade IIIb) was performed in 22%. Primary IC occurred in 4 (2.5%) recipients from the DCD group and was absent in the DBD group (P = 0.005). However, none of these patients required retransplantation. Patient and graft survival at 1, 3, and 5 years were similar between DCD and DBD groups (P = 0.106, P = 0.138, P = 0.113, respectively).

CONCLUSIONS

The encouraging results with DCD-LT are probably due to the selection of DCD grafts and clear definition of warm ischemia.

Is it time to extend liver acceptance criteria for controlled donors after cardiac death?

BACKGROUND

Donation after cardiac death (DCD) has reemerged as potential way to increase donor liver availability. Earlier, programs with DCD liver transplantation used conservative donor criteria to allow safe results. Successful initial outcomes allowed extended DCD criteria to address transplant demand.

METHODS

A total of 63 DCD liver grafts were used during the study period in carefully selected recipients. These were divided into two groups: "Standard" DCD within conservative criteria (n=33; age ≤60 years, body mass index <30 kg/m(2), donor warm ischemia time ≤30 min, and cold ischemia time ≤8 hr) and "Extended" DCD beyond these criteria (n=30). We compared donor and recipient characteristics and postoperative outcomes, including patient and graft survival.

RESULTS

Both groups had satisfactory initial function; liver graft function at 1, 7, and 30 days after liver transplantation were similar. Median follow-up period was 25 and 18.5 months for Standard and Extended criteria DCD grafts, respectively, with 1-year patient and graft survival of 88% and 82% for the Standard group vs. 90% and 90% for the Extended. Overall, 8 of 63 (13%) patients developed biliary complications; however, the incidence was not different between the Standard and Extended groups. Seven early deaths occurred, four and three in the Standard and Extended groups, respectively.

CONCLUSIONS

Recipients of DCDs beyond conventional acceptance criteria have equivalent early outcomes to standard DCD grafts. With careful selection of donors and recipients, these grafts can be safely used to expand the donor pool.

Decreased apoptosis in fatty livers submitted to subnormothermic machine-perfusion respect to cold storage

Machine perfusion at subnormothermic temperature (20°C), MP20, was developed by Vairetti et al. and showed to afford a better preservation of fatty livers respect to traditional cold storage (CS) in terms of enzyme release into the perfusate and bile, glycogen stores, energy charge and oxidative stress. Here we investigated whether it also caused decreased cell death by apoptosis. Fatty and lean Zucker rats were submitted to MP20 or CS for 6 h and reperfused normothermically for 2 h. Apoptotic cells were revealed by immunohistochemistry of activated caspase-3 and M30 (new epitope on CK18 degraded by caspase-3) and by the TUNEL assay. Portal pressure was also determined. A statistically significant reduction of hepatocyte apoptosis, but especially of sinusoidal cells was determined for fatty livers submitted to MP20 respect to CS. Portal pressure was significantly lower after MP20 respect to CS. The reduction of sinusoidal cell death by apoptosis without need for anti-apoptotic therapies appears particularly positive since apoptotic sinusoidal cells hinder microcirculation in the sinusoids and are thrombogenic. These results further confirm the potential of MP20 for preserving fatty livers that would be otherwise discarded as grafts, and thus for increasing the donor pool for liver transplantation.

Biliary complications after orthotopic liver transplantation from donors after cardiac death: broad spectrum of disease

BACKGROUND

Donation-after-death liver transplantation (DCD-LT) carries higher complication rates compared with donation-after-brain death liver transplantation (DBD-LT). In this report we describe our experience with biliary complications in DCD-LT with emphasis on anatomical patterns and outcomes.

MATERIALS AND METHODS

We performed retrospective review of patients' medical records from August 2004 to December 2008, during which time total of 26 DCD-LTs were performed. Mean follow-up was 29 months (range 3 to 51 months).

RESULTS

Biliary complications occurred in 12 patients (46%), of whom 9 were related to DCD (35%). Four patients had more than 1 biliary complication, and 4 had concomitant arterial problems (stricture/thrombosis). Treatment of complications included: ERCP (n = 5, 3 resolved), conversion to roux (n = 5, 2 resolved), revision of roux (n = 1), percutaneous transhepatic cholangiography (n = 1), artery revision (n = 3). Three patients with casts had operative extraction of casts depicting a mummified biliary tree; histology showed casts and fibrosis and anastomotic suture material. Six patients underwent retransplantation (23%). Among retransplanted patients, 2 deaths occurred (7.7%).

CONCLUSION

Our experience with DCD-LT reveals a high prevalence of biliary complications with a new and wide spectrum of clinicopathologic findings. Better strategies for prevention of these unique biliary complications are needed to better justify the added risks and costs for performance of DCD-LT.

Altered alkaline phosphatase activity in obese Zucker rats liver respect to lean Zucker and Wistar rats discussed in terms of all putative roles ascribed to the enzyme

Biliary complications often lead to acute and chronic liver injury after orthotopic liver transplantation (OLT). Bile composition and secretion depend on the integrated action of all the components of the biliary tree, starting from hepatocytes. Fatty livers are often discarded as grafts for OLT, since they are extremely vulnerable to conventional cold storage (CS). However, the insufficiency of donors has stimulated research to improve the usage of such marginal organs as well as grafts. Our group has recently developed a machine perfusion system at subnormothermic temperature (20°C; MP20) that allows a marked improvement in preservation of fatty and even of normal rat livers as compared with CS. We sought to evaluate the response of the biliary tree of fatty liver to MP20, and a suitable marker was essential to this purpose. Alkaline phosphatase (AlkP, EC 3.1.3.1), frequently used as marker of membrane transport in hepatocytes and bile ducts, was our first choice. Since no histochemical data were available on AlkP distribution and activity in fatty liver, we have first settled to investigate AlkP activity in the steatotic liver of fatty Zucker rats (fa/fa), using as controls lean Zucker (fa/+) and normal Wistar rats. The AlkP reaction in Wistar rats was in accordance with the existing data and, in particular, was present in bile canaliculi of hepatocytes in the periportal region and midzone, in the canals of Hering and in small bile ducts but not in large bile ducts. In lean ZR liver the AlkP reaction in Hering canals and small bile ducts was similar to Wistar rat liver but hepatocytes had lower canalicular activity and besides presented moderate basolateral reaction. The difference between lean Zucker and Wistar rats, both phenotypically normal animals, could be related to the fact that lean Zucker rats are genotypically heterozygous for a recessive mutated allele. In fatty liver, the activity in ductules and small bile ducts was unchanged, but most hepatocytes were devoid of AlkP activity with the exception of clusters of macrosteatotic hepatocytes in the mid-zone, where the reaction was intense in basolateral domains and in distorted canaliculi, a typical pattern of cholestasis. The interpretation of these data was hindered by the fact that the physiological role of AlkP is still under debate. In the present study, the various functions proposed for the role of the enzyme in bile canaliculi and in cholangiocytes are reviewed. Independently of the AlkP role, our data suggest that AlkP does not seem to be a reliable marker to study the initial step of bile production during OLT of fatty livers, but may still be used to investigate the behaviour of bile ductules and small bile ducts.

IL-6/STAT3/TFF3 signaling regulates human biliary epithelial cell migration and wound healing in vitro

Interleukin-6 (IL-6), through activation of the signal transducer and activator of transcription 3 (STAT3) and trefoil factor family 3 (TFF3), has been implicated in the promotion of mouse biliary epithelial cell (BEC) proliferation and migration. However, it is still unclear whether the IL-6/STAT3/TFF3 signaling had similar effects on human BECs. Here, we showed that exposure of human BECs to recombinant IL-6 resulted in STAT3 phosphorylation and increased the expression of TFF3 at both mRNA and protein levels. Moreover, inhibition of STAT3 using RNA interference significantly abrogated IL-6-induced TFF3 expression. In an in-vitro wound healing model, IL-6 facilitated human BEC migration. This promotion of cell migration by IL-6 was blocked when STAT3 was knocked down. Interestingly, the addition of exogenous TFF3 could rescue the cell migration defects caused by STAT3 silencing. In conclusion, our data indicate that STAT3 plays a critical role in IL-6-induced TFF3 expression in human BECs and the IL-6/STAT3/TFF3 signaling is involved in human BEC migration and wound healing.

Pharmacological strategies against cold ischemia reperfusion injury

IMPORTANCE OF THE FIELD

Good organ preservation is a determinant of graft outcome after revascularization. The necessity of increasing the quality of organ preservation, as well as of extending cold storage time, has made it necessary to consider the use of pharmacological additives.

AREAS COVERED IN THIS REVIEW

The complex physiopathology of cold-ischemia-reperfusion (I/R) injury--and in particular cell death, mitochondrial injury and endoplasmic reticulum stress--are reviewed. Basic principles of the formulation of the different preservation solutions are discussed.

WHAT THE READER WILL GAIN

Current strategies and new trends in static organ preservation using additives such as trimetazidine, polyethylene glycols, melatonin, trophic factors and endothelin antagonists in solution are presented and discussed. The benefits and mechanisms responsible for enhancing organ protection against I/R injury are also discussed. Graft preservation was substantially improved when additives were added to the preservation solutions.

TAKE HOME MESSAGE

Enrichment of preservation solutions by additives is clinically useful only for short periods. For longer periods of cold ischemia, the use of such additives becomes insufficient because graft function deteriorates as a result of ischemia. In such conditions, the preservation strategy should be changed by the use of machine perfusion in normothermic conditions.

Rapamycin inhibits cholangiocyte regeneration by blocking interleukin-6-induced activation of signal transducer and activator of transcription 3 after liver transplantation

Cholangiocyte proliferation is necessary for biliary recovery from cold ischemia and reperfusion injury (CIRI), but there are few studies on its intracellular mechanism. In this process, the role of rapamycin, a new immunosuppressant used in liver transplantation, is still unknown. In order to determine whether rapamycin can depress cholangiocyte regeneration by inhibiting signal transducer and activator of transcription 3 (STAT3) activation, rapamycin (0.05 mg/kg) was administered to rats for 3 days before orthotopic liver transplantation. The results indicated that cholangiocytes responded to extended cold preservation (12 hours) with severe bile duct injures, marked activation of the interleukin-6 (IL-6)/STAT3 signal pathway, and increased expression of cyclin D1 until 7 days after transplantation, and this was followed by compensatory cholangiocyte regeneration. However, rapamycin treatment inhibited STAT3 activation and resulted in decreased cholangiocyte proliferation and delayed biliary recovery after liver transplantation. On the other hand, rapamycin showed no effect on the expression of IL-6. We conclude that the IL-6/STAT3 signal pathway is involved in initiating cholangiocytes to regenerate and repair CIRI. Rapamycin represses cholangiocyte regeneration by inhibiting STAT3 activation, which might have a negative effect on the healing and recovery of bile ducts in grafts with extended cold preservation. Insights gained from this study will be helpful in designing therapy using rapamycin in clinical patients after liver transplantation.

Addition of carvedilol to University Wisconsin solution improves rat steatotic and nonsteatotic liver preservation

Here we examine the effect of adding carvedilol (CVD) to University of Wisconsin (UW) solution on the preservation of steatotic and nonsteatotic livers during cold ischemia and after normothermic reperfusion. We used an isolated perfused rat liver model. The following protocols were evaluated. Protocol 1 concerned the effect of CVD after cold ischemia. Steatotic and nonsteatotic livers were preserved for 24 hours in UW solution alone or with CVD. Livers without cold ischemia were used as controls. Transaminases were evaluated in the flushing effluent. Protocol 2 involved the effect of CVD after reperfusion. Both liver types were preserved for 24 hours in UW solution alone or with CVD and then perfused ex vivo for 2 hours at 37 degrees C. Livers flushed and perfused without ischemia were used as controls. Hepatic injury and functionality [transaminases, bile production, and hepatic clearance of sulfobromophthalein (BSP)] were evaluated after reperfusion. In addition, factors potentially involved in hepatic ischemia-reperfusion injury, including oxidative stress (malondialdehyde and superoxide anion levels), mitochondrial damage (glutamate dehydrogenase activity), microcirculatory disorders (flow rate and vascular resistance), and adenosine triphosphate (ATP) depletion, were evaluated after reperfusion. After cold ischemia, steatotic livers preserved in UW solution showed higher transaminase levels than nonsteatotic livers. After reperfusion, steatotic livers preserved in UW solution showed higher transaminase levels and lower bile production and BSP clearance than nonsteatotic livers. Alterations in the perfusion flow rate and vascular resistance, mitochondrial damage, and reduced ATP content were more evident in steatotic livers preserved in UW solution. The addition of CVD to UW solution reduced hepatic injury, obstructed its mechanisms, and improved hepatic functionality in both liver types. We conclude that CVD is a useful additive for UW solution that improves the preservation of steatotic and nonsteatotic livers subjected to prolonged cold ischemia.

Liver transplantation following donation after cardiac death: an analysis using matched pairs

Grafts from donation after cardiac death (DCD) donors are used to increase the number of organs available for liver transplantation. There is concern that warm ischemia may impair graft function. We compared our DCD recipients with a case-matched group of donation after brain death (DBD) recipients. Between January 2002 and April 2008, 39 DCD grafts were transplanted. These were matched with 39 DBD recipients on the basis of identified variables that had a significant impact on mortality. These were used to individually match DCD and DBD patients with similar predictive mortality. We compared patient/graft survival, primary non-function (PNF), and rates of complications. Of all liver transplants, 6.1% were DCD grafts. PNF occurred twice in the DCD group. The incidence of nonanastomotic biliary strictures (NABS; 20.5% versus 0%, P = 0.005) and hepatic artery stenosis (HAS; 12.8% versus 0%, P = 0.027) in the DCD group was higher. One-year (79.5% versus 97.4%, P = 0.029) and 3-year (63.6% versus 97.4%, P = 0.001) graft survival was lower in the DCD group. Three-year patient survival was also lower (68.2% versus 100%, P < 0.0001). Our study is the first to use case-matched patients and compare groups with similar predictive mortality. There was a higher incidence of NABS and HAS in the DCD group. NABS were likely a result of warm ischemia. HAS may have been due to ischemia or arterial injury during retrieval. The DCD group had significantly poorer outcomes, but DCD grafts remain a valuable resource. With careful donor/recipient selection, minimization of ischemia, and good postoperative care, acceptable results can be achieved.

Subnormothermic machine perfusion protects steatotic livers against preservation injury: a potential for donor pool increase?

We tested whether rat liver preservation performed by machine perfusion (MP) at 20 degrees C can enhance the functional integrity of steatotic livers versus simple cold storage. We also compared MP at 20 degrees C with hypothermic MP at 8 degrees C, and 4 degrees C. Obese and lean male Zucker rats were used as liver donors. MP was performed for 6 hours with a glucose and N-acetylcysteine-supplemented Krebs-Henseleit solution. Both MP and cold storage preserved livers were reperfused with Krebs-Henseleit solution (2 hours at 37 degrees C). MP at 4 degrees C and 8 degrees C reduced the fatty liver necrosis compared with cold storage but we further protected the organs using MP at 20 degrees C. Necrosis did not differ in livers from lean animals submitted to the different procedures; the enzymes released in steatotic livers preserved by MP at 20 degrees C were similar to those showed in nonsteatotic organs. The adenosine triphosphate/adenosine diphosphate ratio and bile production were higher and the oxidative stress and biliary enzymes were lower in steatotic livers preserved by MP at 20 degrees C as compared with cold storage. In livers from lean rats, the adenosine triphosphate/adenosine diphosphate ratio appears better conserved by MP at 20 degrees C as compared with cold storage. In steatotic livers preserved by cold storage, a 2-fold increase in tumor necrosis factor-alpha levels and caspase-3 activity was observed as compared with organs preserved by MP at 20 degrees C. These data are substantiated by better morphology, higher glycogen content, and lower reactive oxygen species production by sinusoidal cells in steatotic liver submitted to MP at 20 degrees C versus cold storage. MP at 20 degrees C improves cell survival and leads to a marked improvement in hepatic preservation of steatotic livers as compared with cold storage.

The tolerance time limits of biliary tracts of liver grafts subjected to warm ischemia and cold preservation: an experimental study in swine

OBJECTIVE

The objective of this study was to investigate the tolerance time limits of liver grafts and biliary tracts with warm ischemia to cold preservation providing experimental data to the prevent primary graft nonfunction and biliary necrosis after orthotopic liver transplantation (OLT).

METHODS

OLTs were performed in Bama miniature swine. Morphological and functional changes in the liver graft and biliary tracts were investigated after 10 minutes of warm ischemia and various durations of cold preservation.

RESULTS

When grafts were subjected to 10 minutes of warm ischemia followed by less than 16 hours of cold preservation, all animals survived 1 week; no animal died of biliary necrosis. However, when the cold preservation time exceeded 16 hours, the incidence of biliary necrosis increased significantly (P < .05) with deaths due to bile leaks. As cold preservation persisted, primary graft nonfunction and intraoperative or early postoperative deaths occurred, and all surviving animals developed biliary necrosis. When compared with the group undergoing less than 16 hours of cold preservation, the morphological scores and apoptosis index of epithelial cells of graft bile ducts were significantly increased among the group subjected to more than 16 hours of cold preservation after reperfusion (P < .05), whereas the activity of Na+-K+-ATPase and Ca2+-ATPase of graft bile ducts were reduced significantly (P < .05). Liver function tests showed the concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma glutamyl transpeptidase, and alkaline phosphatase (ALP) decreased more slowly among the group undergoing more than 16 hours of cold preservation after operation.

CONCLUSIONS

We concluded that given 10 minutes of warm ischemia, cold preservation should be less than 16 hours to avoid early biliary necrosis; the corresponding tolerance time limit of the liver to cold preservation was less than 20 hours.

Antioxidant and mitochondrial protective effects of silibinin in cold preservation-warm reperfusion liver injury

AIM OF THE STUDY

Silybum marianum (milk thistle) is a Mediterranean plant that has been used since Greco-Roman times to treat liver ailments. Silibinin, the most active hepatoprotective constituent of the plant's seed, possesses antioxidant and anti-inflammatory properties. We thus assessed its protective potential in liver transplantation injury.

MATERIALS AND METHODS

Rat livers were isolated and preserved during 24h at 4 degrees C in University of Wisconsin (UW) solution alone (control), UW containing 100 microM silibinin or UW containing vehicle (ethanol). Livers were then reperfused at 37 degrees C for 1h with Krebs-Henseleit solution supplemented with 20% erythrocytes.

RESULTS

Compared to control, cold preservation and warm reperfusion promoted lipid peroxidation (+40%) and superoxide anion generation (+147%), while attenuating reduced glutathione (-23%), mitochondrial ATP content (-57%) and respiratory control ratio (RCR; -37%). Preservation done in presence of silibinin improved parameters affected by preservation and reperfusion. In fact, silibinin promoted an increase of ATP and RCR by, respectively, 39 and 16% and decreased oxidative stress to values observed in livers never preserved nor perfused.

CONCLUSIONS

In conclusion, silibinin shows promise in protecting the liver from cold preservation/warm reperfusion damages. Moreover our study suggests that concepts of traditional medicine have the potential to be transposed successfully in the context of modern medical interventions such as liver transplantation surgery.

Biliary complications and outcomes of liver transplantation from donors after cardiac death

Biliary complications after liver transplantation (LT) using organs retrieved from donors after cardiac death are not well characterized. The aim of this study was to evaluate the severity of biliary complications and outcomes after donation after cardiac death liver transplantation (DCD-LT). A retrospective evaluation of 20 DCD-LTs from 1997-2006 was performed. The recipient age was 53+/-8.7, and the donor age was 35+/-11 years. The warm ischemia time, cold ischemia time, peak alanine aminotransferase level, and peak aspartate aminotransferase level were 33+/-12 minutes, 8.7+/-2.7 hours, 1757+/-1477 U/L, and 4020+/-3693 U/L, respectively. The bilirubin and alkaline phosphatase levels at hospital discharge after LT were 3.2+/-5.4 mg/dL and 248+/-200 U/L, respectively. During a median follow-up of 7.5 months (range: 1-73), 5 patients (25%; 1 death after re-LT) died (3 from sepsis, 1 from recurrent hepatocellular carcinoma at 4 months, and 1 from a cardiac event at 46 months), and additionally, 4 patients (20%) required re-LT (1 because of hepatic artery thrombosis, 1 because of primary graft nonfunction, and 2 because of biliary strictures). Twelve (60%) developed biliary complications, and of these, 11 (55%) had serious biliary complications. The biliary complications were as follows: a major bile leak for 2 patients (10%; both eventually underwent retransplantation), anastomotic strictures for 5 patients (25%), hilar strictures for 7 patients (35%), extrahepatic donor duct strictures for 9 patients (45%), intrahepatic strictures for 10 patients (50%), stones for 1 patients (5%), casts for 7 patients (35%), and debris for 2 patients (10%). More than 1 biliary complication was seen in most patients, and these were unpredictable and required multiple diagnostic or therapeutic procedures. Serious biliary complications are common after DCD-LT, and research should focus on identifying donor and recipient factors that predict and prevent serious biliary complications.

Role of perfusion medium, oxygen and rheology for endoplasmic reticulum stress-induced cell death after hypothermic machine preservation of the liver

Recently, the endoplasmic reticulum (ER) has been disclosed as subcellular target reactive to ischaemia/reperfusion and possibly influenced by hypothermic machine preservation. Here, the respective role of perfusate, perfusion itself, and the effect of continuous oxygenation to trigger ER-stress in the graft should be investigated. Livers were retrieved 30 min after cardiac arrest of male Wistar rats and preserved by cold storage (CS) in histidine-tryptophan-ketoglutarate (HTK) for 18 h at 4 degrees C. Other organs were subjected to aerobic conditions either by oxygenated machine perfusion with HTK (MP-HTK) or Belzer solution (MP-Belzer) at 4 degrees C or by venous insufflation of gaseous oxygen during cold storage (VSOP). Viability of livers was evaluated upon reperfusion in vitro according to previously validated techniques for 120 min at 37 degrees C. Oxygenation during preservation (MP-HTK, MP-Belzer or VSOP) concordantly improved functional recovery (bile flow, ammonia clearance), reduced parenchymal enzyme leakage and histological signs of necrosis and significantly attenuated mitochondrial induction of apoptosis (cleavage of caspase 9) compared to CS. However, MP with either medium produced about 500% elevated protein expression of CHOP/GADD153, suggesting pro-apoptotic ER-stress responses, paralleled by a significant elevation of caspase-12 enzyme activity compared to CS or VSOP. Although MP also promoted a slight (20%) induction of the cytoprotective ER-protein Bax inhibitor protein (BI-1), prevailing of proapoptotic reactions was seen by increased cleavage of caspase-3 and poly (ADP-Ribase)-polymerase (PARP) in both MP-groups. Endoplasmic stress activation is conjectured a specific side effect of long-term machine preservation irrespective of the medium, actually promoting cellular apoptosis via activation of caspase-12. The simple insufflation of gaseous O2 may be considered a feasible alternative, apparently indifferent to the endoplasmic reticulum.

Effects of methylprednisolone and its liver-targeted dextran prodrug on ischemia-reperfusion injury in a rat liver transplantation model

PURPOSE

To evaluate the effectiveness of a liver-targeted dextran prodrug (DMP) of methylprednisolone (MP) in cold preservation-warm reperfusion injury associated with liver transplantation.

METHODS

The effects of donor pretreatment with single 5 mg/kg doses of MP or DMP on ischemia-reperfusion damage to the liver were studied after 8 or 24 h of cold preservation in both isolated perfused rat liver (IPRL) and syngeneic orthotopic rat liver transplantation (OLT) models.

RESULTS

In IPRL studies, donor pretreatment with DMP, and to a lesser degree MP, significantly improved the uptake of hyaluronic acid (HA), a marker of endothelial cell function, following 8 h of cold preservation. However, neither pretreatment was protective after 24 h of preservation. In the OLT model using 24-h-preserved livers, the seven-day survival of untreated grafts was 50%. DMP pretreatment of donors significantly improved graft survival to 100%, whereas MP pretreatment was ineffective. Additionally, only DMP significantly increased the blood glucose concentrations and decreased the plasma concentrations of tumor necrosis factor-alpha after OLT. Other measured markers of liver injury were not affected by either pretreatment.

CONCLUSIONS

Selective delivery of methylprednisolone to the liver as a donor pretreatment strategy improves 24-h preserved graft survival in the OLT model.

A novel way of liver preservation improves rat liver viability upon reperfusion

BACKGROUND/AIM

Currently, the liver is cold-preserved at 0 approximately 4 degrees C for experimental and clinical purposes. Here, we investigated whether milder hypothermia during the initial phase of the preservation period was beneficial for liver viability upon reperfusion.

METHODS

In the first set of experiments, rat livers were preserved either conventionally in clinically used histidine-trypthopan-ketoglutarate (HTK) solution (Group A: 45 min and Group B: 24 h) or by slow cooling HTK solution (from 13 degrees C to 3 degrees C) during the initial 45 min of preservation (Group C: 24 h). In the second set of experiments, additional groups of livers were evaluated: Group BB--preservation according to Group B and Group CC--preservation according to Group C. Further, some livers were preserved at 13 degrees C for 24 h. Livers were then reperfused using a blood-free perfusion model.

RESULTS

Bile production was approximately 2-fold greater in Group C compared to Group B. Alanine transaminase (ALT) and aspartate transaminase (AST) release into perfusate were 2 approximately 3-fold higher in Group B compared to Group C. No significant differences were found in ALT and AST release between Group C and Group A. Livers in Group CC compared to Group BB exhibited significantly lower portal resistance, greater oxygen consumption and bromosulfophthalein excretion into bile and lower lactate dehydrogenase (LDH) release into perfusate. Histological evaluation of tissue sections in Group BB showed parenchymal dystrophy of hepatocytes, while dystrophy of hepatocytes was absent in Group CC. Livers preserved at 13 degrees C for 24 h exhibited severe ischemic injury.

CONCLUSION

These results suggest that the conventional way of liver preservation is not suitable at least for rat livers and that slow cooling of HTK solution during the initial phase of cold storage can improve liver viability during reperfusion.

Biliary-type cytokeratin pattern in a canine isolated perfused liver transplantation model

BACKGROUND

Ischemia-reperfusion (I/R) injury in liver transplantation units and the influence of I/R injury on bile flow dynamics is being intensely investigated in various animal models, but the expression of intracellular intermediate filaments of biliary type as an early sign of cholestasis has not been yet explored.

METHODS

We studied the hepatic elimination kinetics of indocyanine green (ICG), an exclusively biliary excreted cholephilic dye, and the functional and morphological integrity of liver cells in a canine liver transplantation model following I/R. During reperfusion following cold ischemia, we evaluated the ICG excretion curves, biochemical signs of liver damage, the bile canaliculus of the hepatocytes by electron microscopy, and the expression of intermediate filaments of cytokeratin type by immunohistochemistry.

RESULTS

Impairment of the biliary ICG excretion was directly related to ischemia time, but hepatocellular ICG uptake and bile flow rate were not significantly reduced. Liver enzymes increased as early as 6 h of ischemia and hepatocytes showed an increase of the bile canaliculus area. This was correlated to a membranous to cytoplasmatic staining of the cytoskeleton of the hepatocytes.

CONCLUSIONS

To the best of our knowledge, this is the first evidence of cholestatic changes starting early following cold ischemia in a canine isolated perfused liver transplantation model despite prompt recovery of the bile flow.

The response of the hepatocyte to ischemia

BACKGROUND

Ischemia-reperfusion (I/R) injury associated with hepatic resections and liver transplantation remains a serious complication in clinical practice, in spite of several attempts to solve the problem.

AIMS

To evaluate the response of the hepatocyte to ischemia

METHODS

Published data are thus revised.

RESULTS

The response of the hepatocyte to ischemia is based on the sensitivity of hepatocytes to different types of ischemia, the kind of cell death of the hepatocyte when it is subjected to ischemia, and on the response of the hepatocyte to the different times and extents of ischemia. Clinical factors including starvation, graft, age, and hepatic steatosis, all of which contribute to enhancing liver susceptibility to ischemia/reperfusion injury.

CONCLUSION

Ischemic preconditioning, based on the induction of a brief ischemia to the liver prior to a prolonged ischemia, has been applied in tumor hepatic resections for reducing hepatic I/R injury and recent clinical studies suggest that this surgical strategy could be appropriate for liver transplantation.

Interleukin-6 and STAT3 protect the liver from hepatic ischemia and reperfusion injury during ischemic preconditioning

BACKGROUND

Ischemic preconditioning has been shown to protect the liver from ischemia/reperfusion injury. We hypothesized that IL-6 directly modulates the protective effects of ischemic preconditioning.

METHODS

Three weeks after undergoing splenic transposition, wild-type C57BL/6 and IL-6 null mice underwent 75 minutes of total hepatic ischemia with or without prior ischemic preconditioning (10 minutes of ischemia followed by 15 minutes of reperfusion). After reperfusion, serum ALT, serum IL-6, hepatic IL-6 mRNA, hepatic pSTAT3, and liver histology were evaluated.

RESULTS

In wild-type mice, survival at 24 hours was greater in the preconditioned group compared with the non-preconditioned group (75% vs 40%, P<.05). In IL-6 null mice, however, ischemic preconditioning did not improve survival when compared with the non-preconditioned group. Preconditioning significantly reduced hepatocellular injury in wild-type mice (P<.05) when compared with IL-6 null animals. This protection was associated with significant increases in serum IL-6, hepatic IL-6 mRNA, and hepatic pSTAT3 levels (P<.05). The protective effects of ischemic preconditioning that correlated with significant increases in systemic IL-6, hepatic IL-6 mRNA abundance, and pSTAT3 levels, were not observed in IL-6 null mice.

CONCLUSIONS

The protective effects of ischemic preconditioning during total hepatic ischemia/reperfusion injury are dependent on IL-6 signaling and are associated with increased phosphorylation of hepatic STAT3.

Implication of mitochondrial dysfunction and cell death in cold preservation--warm reperfusion-induced hepatocyte injury

Cold ischemia--warm reperfusion (CI/WR) injury of liver transplantation involves hepatocyte cell death, the nature and underlying mechanisms of which remain unclear. Isolated hepatocytes and isolated perfused livers were used to determine the prevalence of necrosis and apoptosis as well as mitochondrial dysfunction. In isolated cells, propidium iodide and Hoechst 33342 staining showed a cold-storage, time-dependent increase in necrosis, whereas apoptosis was minimal even after 48 h of hypothermia. Nonetheless, a progressive loss of mitochondrial membrane potential was observed. Translocation of mitochondrial cytochrome c toward microsomes occurred within 24 h of CI/WR, with cytochrome c reaching the cytosol later. Mitochondria isolated from whole livers subjected to CI/WR also display reduced metabolic parameters and increased susceptibility to swelling. These events are associated with increased activity of major initiator (caspase 9) and effector (caspase 3) caspases. The results demonstrate that CI/WR induces mitochondrial dysfunction in isolated cells and in the whole organ; only in the latter is that sufficient to trigger the classical mitochondrial pathway of apoptosis. Our study also provides evidence for the involvement of endoplasmic reticulum stress in CI/WR hepatocyte injury. Combined protection of mitochondria and endoplasmic reticulum may thus represent an innovative therapeutic avenue to enhance liver graft viability and functional integrity.

Wound healing in the biliary tree of liver allografts

An increasing need for liver transplantation requires evaluation and triage of organs harvested from "extended criteria" donors. Although there is currently no widely accepted definition, most would agree that "extended criteria" includes organs donated by individuals that are old (>65 years), obese, infected with HBV or HCV, non-heart beating (NHBD), or had an unstable blood pressure before harvesting or the organ experienced a long cold ischemic time. These organs carry a statistical risk of dysfunction early after transplantation, but in the majority of recipients, hepatic parenchymal function recovers. Later, however, a small but significant percentage of extended criteria donors develop biliary strictures within several months after transplantation. The strictures occur primarily because of preservation injury that leads to "ischemic cholangitis" or deep wounding of the bile duct wall. Subsequent partial wound healing and wound contraction, but failed restitution of the biliary epithelial cell (BEC) lining, result in biliary tract strictures that cause progressive biliary fibrosis, increased morbidity, and decreased organ half-life. Better understanding of the pathophysiologic mechanisms that lead to biliary strictures in extended criteria donors provides an ideal proving ground for regenerative medicine; it also can provide insights into other diseases, such as extrahepatic biliary atresia and primary sclerosing cholangitis, that likely share certain pathogenic mechanisms. Possible points of therapeutic intervention include limiting cold and warm ischemic times, donor and/or donor organ treatment, ex vivo, to minimize the ischemic/preservation injury, maximize blood flow after transplantation, promote BEC wound healing, and limit myofibroblasts activation and proliferation in the bile duct wall. The pathobiology of biliary wound healing and therapeutic potential of interleukin-6 (IL-6) are highlighted.

Biliary wound healing, ductular reactions, and IL-6/gp130 signaling in the development of liver disease

Basic and translational wound healing research in the biliary tree lag significantly behind similar studies on the skin and gastrointestinal tract. This is at least partly attributable to lack of easy access to the biliary tract for study. But clinical relevance, more interest in biliary epithelial cell (BEC) pathophysiology, and widespread availability of BEC cultures are factors reversing this trend. In the extra-hepatic biliary tree, ineffectual wound healing, scarring and stricture development are pressing issues. In the smallest intra-hepatic bile ducts either impaired BEC proliferation or an exuberant response can contribute to liver disease. Chronic inflammation and persistent wound healing reactions in large and small bile ducts often lead to liver cancer. General concepts of wound healing as they apply to the biliary tract, importance of cellular processes dependent on IL-6/gp130/STAT3 signaling pathways, unanswered questions, and future directions are discussed.

Liver protection by hypothermic perfusion at different temperatures during total vascular exclusion

INTRODUCTION

In situ hypothermic perfusion (HP) can be applied to attenuate ischemia and reperfusion (I/R) injury during liver resection under total vascular exclusion (TVE). This study examines the protective effect of cooling by HP at 20 and 28 degrees C as compared with no HP during TVE in a porcine liver I/R model.

METHODS

Twenty-one pigs underwent 60 min TVE of the liver followed by 24 h reperfusion. HP was performed via the portal vein using ringerlactate solution of 4 degrees C. Pigs were assigned to three groups: TVE without HP (no-HP, n=9), TVE with HP at 28 degrees C (HP-28, n=6) and TVE with HP at 20 degrees C (HP-20, n=6).

RESULTS

Perfusion volumes during TVE were 5.1+/-0.5 and 17.3+/-1.7 l in HP-28 and HP-20, respectively (P<0.05). Aspartate aminotransferase (AST) after 24 h reperfusion was 1172+/-440 U/l in no-HP as compared with 223+/-69 and 180+/-22 U/l in HP-28 and HP-20, respectively (P<0.05). No differences in liver function or histopathology were found between the HP-28 and HP-20 groups.

CONCLUSIONS

HP at 20 degrees C is equally effective in preserving liver function and preventing hepatocellular injury under TVE as compared with HP at 28 degrees C. HP at 28 degrees C is advised, because of the lesser perfusion volume necessary for cooling of the liver.

Trimetazidine: is it a promising drug for use in steatotic grafts?

AIM

Chronic organ-donor shortage has led to the acceptance of steatotic livers for transplantation, despite the higher risk of graft dysfunction or nonfunction associated with the ischemic preservation period of these organs. The present study evaluates the effects of trimetazidine (TMZ) on an isolated perfused liver model.

METHODS

Steatotic and non-steatotic livers were preserved for 24 h in the University of Wisconsin (UW) solution with or without TMZ. Hepatic injury and function (transaminases, bile production and sulfobromophthalein (BSP) clearance) and factors potentially involved in the susceptibility of steatotic livers to ischemia-reperfusion (I/R) injury, including oxidative stress, mitochondrial damage, microcirculatory diseases, and ATP depletion were evaluated.

RESULTS

Steatotic livers preserved in UW solution showed higher transaminase levels, lower bile production and BSP clearance compared with non-steatotic livers. Alterations in perfusion flow rate and vascular resistance, mitochondrial damage, and reduced ATP content were more evident in steatotic livers. TMZ addition to UW solution reduced hepatic injury and ameliorated hepatic functionality in both types of the liver and protected against the mechanisms potentially responsible for the poor tolerance of steatotic livers to I/R.

CONCLUSION

TMZ may constitute a useful approach in fatty liver surgery, limiting the inherent risk of steatotic liver failure following transplantation.

Recurrent hepatitis C posttransplant: early preservation injury may predict poor outcome

Organ cold/warm ischemia is thought to be a risk factor for increased severity of recurrence of hepatitis C (HCV) post liver transplantation. We had noted some HCV patients with preservation injury (PI) to have particularly poor outcomes. Our goal was to determine if PI on biopsy in HCV patients is associated with earlier, more rapidly progressive recurrence or graft and patient survival. Sixty-nine patients from the University of Nebraska transplant database were included: 23 HCV patients with PI (group = 1), 23 non-HCV patients with PI (group = 2), and 23 HCV patients without PI (group = 3). Patient groups were matched for gender, age, immunosuppression, and time of transplantation for analysis. No difference in time to recurrence was noted between HCV groups (256 vs. 316 days posttransplant). More patients in group 1 had progression to stage 3 or 4 fibrosis, compared to group 3 (43 vs. 9%, P = 0.02). One-year survival for groups 1, 2, and 3 was 78, 82, and 100% respectively, whereas 3-yr survival was 59, 82, and 88% (group 1 vs. group 2 or 3 respectively, P = 0.0055). There was no difference in survival between groups 2 and 3. Patients in group 1 that received antiviral treatment had improved survival, compared to those who did not (P = 0.012). Risk factors for poor survival on univariate analysis included severity of PI (Relative Risk = 2.78, P < 0.001) and donor age of >55 (P = 0.014). Multivariate analysis shows HCV is the most important factor. In conclusion, HCV transplant patients with evidence of early PI on biopsy have poorer survival outcomes than non-HCV transplant patients with PI or HCV transplant patients without PI. Consideration for antiviral therapy early in the posttransplant course may be warranted in this subset of patients.

Effects of duration of ischemia and donor pretreatment with methylprednisolone or its macromolecular prodrug on the disposition of indocyanine green in cold-preserved rat livers

PURPOSE

Cold preservation of the liver before transplantation may change uptake and excretory functions of hepatocytes. We hypothesized that an increase in the duration of preservation would result in a progressive decrease in the hepatic uptake and/or biliary excretion of indocyanine green (ICG), which would be attenuated by pharmacologic interventions.

METHODS

Donor rats (n = 40) were administered saline (control) or single 5 mg/kg doses of methylprednisolone (MP) or its liver-targeted prodrug (DMP) 2 h prior to liver harvest. Following preservation in cold University of Wisconsin solution for 0, 24, 48, or 72 h, livers were reperfused in a single-pass manner for 30 min in the presence of ICG (approximately 4 microg/ml), followed by 60 min of ICG-free perfusion. The inlet, outlet, and bile concentrations of ICG were measured periodically by high performance liquid chromatography (HPLC), and kinetic parameters were estimated.

RESULTS

Effects of duration of preservation: In unpreserved livers, a significant portion of ICG dose (16%) was effluxed from the liver during the washout period. Cold preservation for 24-72 h progressively increased (p < 0.05) the efflux of ICG (>2-fold at 72 h). Similarly, average extraction ratio showed a modest (30-40%) decrease with increasing preservation time (p < 0.05). However, biliary excretion of ICG showed the most sensitivity to the preservation time (14 to >800-fold decline). Effects of pretreatment: DMP caused significant (p < 0.05) increases in biliary ICG levels (>12-fold) and bile flow rates (6-15-fold) of preserved livers. Although MP pretreatment significantly (p < 0.05) increased (6-fold) bile flow rates in 48-h preserved livers, its effects on biliary ICG levels were not significant (p > 0.05).

CONCLUSIONS

Biliary excretion of ICG is the most sensitive kinetic parameter to prolonged cold ischemia-reperfusion injury in a rat liver perfusion model. The injury may be significantly attenuated by pharmacologic pretreatment of the liver donors.

Protection by cyclosporin A of mitochondrial and cellular functions during a cold preservation-warm reperfusion of rat liver

Liver transplantation is an effective therapeutic option for end-stage liver disease, but initial poor graft function still occurs, often related to cold preservation-warm reperfusion (CPWR) conditions. Damages to mitochondria could be implicated in hepatocyte cell death since opening of the permeability transition pore (PTP) can lead to necrosis and apoptosis. The purpose of this study was to test the hypothesis that inhibition of mitochondrial permeability transition by cyclosporin A could improve rat liver mitochondrial and hepatocellular parameters after 24-h cold preservation followed by a warm reperfusion in Krebs-Henseleit Buffer. Mitochondrial functions were assessed by measuring respiratory parameters, swelling, cytochrome c release and caspases activation. Hepatocyte injury was assessed by evaluation of ATP energetic charge, lactate dehydrogenase (LDH) leakage, apoptosis and necrosis. Results show that CPWR induces liver mitochondrial and cellular damages. CPWR induced damages on the mitochondrial respiratory chain, leading to mitochondrial swelling. The consequences are the loss of ATP energetic charge, the initiation of apoptosis through cytochrome c release and the activation of caspases. Cyclosporin A partially protects respiratory chain integrity and totally prevents mitochondrial swelling, allowing better recovery of energetic charge. It also partially limits the activation of the apoptotic machinery and subsequent cell death by apoptosis in both the organ and isolated hepatocytes. Inhibition of permeability transition thus provides only partial protection against CPWR. However, this target can be considered as a promising adjunct therapeutic approach to improve the primary function of the grafted liver after transplantation.