Effects of extended cold preservation and transplantation on the rat liver microcirculation

Management and outcome of hepatic artery thrombosis with whole-liver transplantation using donors less than one year of age

BACKGROUND/PURPOSE

The incidence of hepatic artery thrombosis (HAT) in recipients is high after pediatric LT using young donors. In this study we investigated the management and outcome of HAT after whole-LT using donors less than one year of age. And evaluate the safety of pediatric donors, and increase the utilization of pediatric donors overall.

METHODS

We retrospectively analyzed the clinical data encompassing children who underwent whole-liver transplantation in our department from January 2014 to December 2019. Recipients receiving a liver from a donor ≥1 month and ≤12 months were included, and a total of 110 patients were included in this study.

RESULTS

The results showed an incidence for HAT of 20% and the median time to HAT diagnosis was 3.0 (2.0, 5.3) days post-operation. Anticoagulant therapy was used for 19 cases and 94.7% of them achieved hepatic artery recanalization or collateral formation. The median time of recanalization was 12 (5, 15) days. Bile leakage and biliary strictures occurring in the HAT group were higher than in the non HAT group (13.6% vs. 1.1% and 31.8% vs. 3.4%). There were no significant differences in the survival rates of recipients or grafts among the two groups (P = 0.474, P = 0.208, respectively).

CONCLUSION

We confirmed that the incidence of HAT in LT recipients use donors less than 1 year is high, but recanalization can be performed using anticoagulant therapy. Although biliary complications increased significantly after HAT, the survival rates of patients and grafts were satisfactory.

LEVEL OF EVIDENCE

Level III.

Nucleotide-binding oligomerization domain 1 (NOD1) modulates liver ischemia reperfusion through the expression adhesion molecules

BACKGROUND & AIMS

In liver transplantation, organ shortage leads to the use of marginal grafts that are more susceptible to ischemia-reperfusion (IR) injury. We identified nucleotide-binding oligomerization domain 1 (NOD1) as an important modulator of polymorphonuclear neutrophil (PMN)-induced liver injury, which occurs in IR. Herein, we aimed to elucidate the role of NOD1 in IR injury, particularly focusing on its effects on the endothelium and hepatocytes.

METHOD

Nod1 WT and KO mice were treated with NOD1 agonists and subjected to liver IR. Expression of adhesion molecules was analyzed in total liver, isolated hepatocytes and endothelial cells. Interactions between PMNs and hepatocytes were studied in an ex vivo co-culture model using electron microscopy and lactate dehydrogenase levels. We generated NOD1 antagonist-loaded nanoparticles (np ALINO).

RESULTS

NOD1 agonist treatment increased liver injury, PMN tissue infiltration and upregulated ICAM-1 and VCAM-1 expression 20 hours after reperfusion. NOD1 agonist treatment without IR increased expression of adhesion molecules (ICAM-1, VCAM-1) in total liver and more particularly in WT hepatocytes, but not in Nod1 KO hepatocytes. This induction is dependent of p38 and ERK signaling pathways. Compared to untreated hepatocytes, a NOD1 agonist markedly increased hepatocyte lysis in co-culture with PMNs as shown by the increase of lactate dehydrogenase in supernatants. Interaction between hepatocytes and PMNs was confirmed by electron microscopy. In a mouse model of liver IR, treatment with np ALINO significantly reduced the area of necrosis, aminotransferase levels and ICAM-1 expression.

CONCLUSION

NOD1 regulates liver IR injury through induction of adhesion molecules and modulation of hepatocyte-PMN interactions. NOD1 antagonist-loaded nanoparticles reduced liver IR injury and provide a potential approach to prevent IR, especially in the context of liver transplantation.

LAY SUMMARY

Nucleotide-binding oligomerization domain 1 (NOD1) is as an important modulator of polymorphonuclear neutrophil (PMN)-induced liver injury, which occurs in ischemia-reperfusion. Here, we show that the NOD1 pathway targets liver adhesion molecule expression on the endothelium and on hepatocytes through p38 and ERK signaling pathways. The early increase of adhesion molecule expression after reperfusion emphasizes the importance of adhesion molecules in liver injury. In this study we generated nanoparticles loaded with NOD1 antagonist. These nanoparticles reduced liver necrosis by reducing PMN liver infiltration and adhesion molecule expression.

Heme Oxygenase 1 Attenuates Hypoxia-Reoxygenation Injury in Mice Liver Sinusoidal Endothelial Cells

BACKGROUND

Heme oxygenase 1 (HO-1), a heat shock protein, can be involved in the resolution of inflammation by modulating cytokine expression and apoptotic cell death. Based on recent evidence that liver sinusoidal endothelial cells (LSECs) is the critical target in early period of liver ischemia-reperfusion injury (IRI), this study aims to clarify whether overexpression of HO-1 gene provides a protective effect on mice LSECs.

METHODS

LSECs were transfected with adenovirus vectors encoding mice HO-1 gene (Ad-HO-1) or green fluorescent protein. Controls were not infected with any vector. LSECs were then treated with hypoxic or normoxic culture. We used low serum culture medium and hypoxia-reoxygenation (H-R) conditions to cause IRI in vitro. The transfection efficiency of HO-1 gene in LSECs, after 48 hours of transfection, and the effect of HO-1 on the model of H-R injury in LSECs were observed.

RESULTS

Transfection of LSECs with Ad-HO-1 was at an optimal dose (multiplicity of infection = 80) to markedly express HO-1 mRNA and protein. Groups of overexpressed HO-1 showed lower levels of inflammatory factor mediators IL-6 and TNF-α. Survival rate of the cells after H-R injury was higher and attributed to overexpressed HO-1. In contrast, the control adenovirus expressing the enhanced green fluorescent protein failed to induce HO-1 expression and stimulated cell apoptosis. HO-1 expression was downregulated in all H-R groups compared with normoxia groups, which may be related to the disruption of the LSEC structure.

CONCLUSIONS

Upregulation of HO-1 can attenuate H-R injury in LSECs by inhibiting proinflammatory cytokine release and diminishing apoptotic cell death.

Characteristics of fecal microbial communities in patients with non-anastomotic biliary strictures after liver transplantation

AIM

To explore the possible relationship between fecal microbial communities and non-anastomotic stricture (NAS) after liver transplantation (LT).

METHODS

A total of 30 subjects including 10 patients with NAS, 10 patients with no complications after LT, and 10 non-LT healthy individuals were enrolled. Fecal microbial communities were assessed by the 16S rRNA gene sequencing technology.

RESULTS

Different from the uncomplicated and healthy groups, unbalanced fecal bacterium ratio existed in patients with NAS after LT. The results showed that NAS patients were associated with a decrease of Firmicutes and Bacteroidetes and an increase of Proteobacteria at the phylum level, with the proportion-ratio imbalance between potential pathogenic families including Enterococcaceae, Streptococcaceae, Enterobacteriaceae, Pseudomonadaceae and dominant families including Bacteroidaceae.

CONCLUSION

The compositional shifts of the increase of potential pathogenic bacteria as well as the decrease of dominant bacteria might contribute to the incidence of NAS.

Effects of heme oxygenase-1-modified bone marrow mesenchymal stem cells on microcirculation and energy metabolism following liver transplantation

AIM

To investigate the effects of heme oxygenase-1 (HO-1)-modified bone marrow mesenchymal stem cells (BMMSCs) on the microcirculation and energy metabolism of hepatic sinusoids following reduced-size liver transplantation (RLT) in a rat model.

METHODS

BMMSCs were isolated and cultured in vitro using an adherent method, and then transduced with HO-1-bearing recombinant adenovirus to construct HO-1/BMMSCs. A rat acute rejection model following 50% RLT was established using a two-cuff technique. Recipients were divided into three groups based on the treatment received: normal saline (NS), BMMSCs and HO-1/BMMSCs. Liver function was examined at six time points. The levels of endothelin-1 (ET-1), endothelial nitric-oxide synthase (eNOS), inducible nitric-oxide synthase (iNOS), nitric oxide (NO), and hyaluronic acid (HA) were detected using an enzyme-linked immunosorbent assay. The portal vein pressure (PVP) was detected by Power Lab ML880. The expressions of ET-1, iNOS, eNOS, and von Willebrand factor (vWF) protein in the transplanted liver were detected using immunohistochemistry and Western blotting. ATPase in the transplanted liver was detected by chemical colorimetry, and the ultrastructural changes were observed under a transmission electron microscope.

RESULTS

HO-1/BMMSCs could alleviate the pathological changes and rejection activity index of the transplanted liver, and improve the liver function of rats following 50% RLT, with statistically significant differences compared with those of the NS group and BMMSCs group (P < 0.05). In term of the microcirculation of hepatic sinusoids: The PVP on POD7 decreased significantly in the HO-1/BMMSCs and BMMSCs groups compared with that of the NS group (P < 0.01); HO-1/BMMSCs could inhibit the expressions of ET-1 and iNOS, increase the expressions of eNOS and inhibit amounts of NO production, and maintain the equilibrium of ET-1/NO (P < 0.05); and HO-1/BMMSCs increased the expression of vWF in hepatic sinusoidal endothelial cells (SECs), and promoted the degradation of HA, compared with those of the NS group and BMMSCs group (P < 0.05). In term of the energy metabolism of the transplanted liver, HO-1/BMMSCs repaired the damaged mitochondria, and improved the activity of mitochondrial aspartate aminotransferase (ASTm) and ATPase, compared with the other two groups (P <0.05).

CONCLUSION

HO-1/BMMSCs can improve the microcirculation of hepatic sinusoids significantly, and recover the energy metabolism of damaged hepatocytes in rats following RLT, thus protecting the transplanted liver.

Differential bradykinin B1 and B2 receptor regulation in cell death induced by hepatic ischaemia/reperfusion injury

In the present study, we have demonstrated that the kinin B1 receptor may participate in apoptotic cell death signalling, whereas the B2 receptor may be involved in necrotic cell death during IRI.

Biliary complications after liver transplantation: old problems and new challenges

Due to a vulnerable blood supply of the bile ducts, biliary complications are a major source of morbidity after liver transplantation (LT). Manifestation is either seen at the anastomotic region or at multiple locations of the donor biliary system, termed as nonanastomotic biliary strictures. Major risk factors include old donor age, marginal grafts and prolonged ischemia time. Moreover, partial LT or living donor liver transplantation (LDLT) and donation after cardiac death (DCD) bear a markedly higher risk of biliary complications. Especially accumulation of several risk factors is critical and should be avoided. Prophylaxis is still a major issue; however no gold standard is established so far, since many risk factors cannot be influenced directly. The diagnostic workup is mostly started with noninvasive imaging studies namely MRI and MRCP, but direct cholangiography still remains the gold standard. Especially nonanastomotic strictures require a multidisciplinary treatment approach. The primary management of anastomotic strictures is mainly interventional. However, surgical revision is finally indicated in a significant number of cases. Using adequate treatment algorithms, a very high success rate can be achieved in anastomotic complications, but in nonanastomotic strictures a relevant number of graft failures are still inevitable.

Addition of simvastatin to cold storage solution prevents endothelial dysfunction in explanted rat livers

Pathophysiological alterations in the endothelial phenotype result in endothelial dysfunction. Flow cessation, occurring during organ procurement for transplantation, triggers the endothelial dysfunction characteristic of ischemia/reperfusion injury, partly due to a reduction in the expression of the vasoprotective transcription factor Kruppel-like Factor 2 (KLF2). We aimed at (1) characterizing the effects of flow cessation and cold storage on hepatic endothelial phenotype, and (2) ascertaining if the consequences of cold stasis on the hepatic endothelium can be pharmacologically modulated, improving liver graft function. Expression of KLF2 and its vasoprotective programs was determined in (i) hepatic endothelial cells (HEC) incubated under cold storage conditions with or without the KLF2-inducer simvastatin, and (ii) rat livers not cold stored or preserved in cold University of Wisconsin solution (UWS) supplemented with simvastatin or its vehicle. In addition, upon warm reperfusion hepatic vascular resistance, endothelial function, nitric oxide vasodilator pathway, apoptosis, inflammation, and liver injury were evaluated in not cold stored livers or livers preserved in cold UWS supplemented with simvastatin or vehicle. Expression of KLF2 and its vasoprotective programs decrease in HEC incubated under cold storage conditions. Cold-stored rat livers exhibit a time-dependent decrease in KLF2 and its target genes, liver injury, increased hepatic vascular resistance, and endothelial dysfunction. The addition of simvastatin to the storage solution, maintained KLF2-dependent vasoprotective programs, prevented liver damage, inflammation, and oxidative stress and improved endothelial dysfunction.

CONCLUSION

Our results provide a rationale to evaluate the beneficial effects of a vasoprotective preservation solution on human liver procurement for transplantation.

Nicardipine reverses vasoactivity associated with University of Wisconsin solution in the rat peripheral circulation

BACKGROUND

The rapid uniform delivery of University of Wisconsin solution (UW) to the microcirculation may be compromised by its vasoactivity.

METHODS

In 2 different rodent models, we tested whether UW-mediated vasoconstriction could be reversed with nicardipine.

RESULTS

In the perfused, splanchnic circulation, intravascular control solutions (lactated Ringers [LR], Hextend [HEX], histidine-tryptophan-ketoglutarate [HTK]) or UW (± nicardipine) evoked pressure changes in 3 protocols (series 1; n = 35). In the cremaster muscle, topical control solutions or UW (± nicardipine) evoked vascular responses measured by video microscopy in 4 protocols (series 2; n = 47). In series 1A, 37°C UW increased perfusion pressure, but there was no change caused by LR, HEX, or HTK. In series 1B, 4°C UW caused a similar, albeit transient, increase. In series 1C, nicardipine reversed 37°C UW-mediated vasoconstriction in a dose-related manner. In series 2A, UW caused a 30%-59% constriction that varied with arteriolar branching order. In series 2B, the recovery from UW-induced vasoconstriction varied with duration of exposure, but nicardipine fully reversed residual vasoconstriction. In series 2C, cold and warm UW were equipotent, near maximal, vasoconstrictors. In series 2D, UW potentiated no-reflow.

CONCLUSION

UW causes a potent temperature-independent vasoconstriction by a calcium-mediated mechanism and this effect can be mitigated with nicardipine.

Posttransplant biliary complications in the pre- and post-model for end-stage liver disease era

Biliary complications remain a cause of morbidity after liver transplantation. The aim of this study was to determine whether changes in clinical practice in the era of the Model for End-Stage Liver Disease (MELD) has affected biliary complications after liver transplantation. We retrospectively reviewed all deceased donor liver transplants at a single center. Patients were categorized as pre- or post-MELD (transplant before or after February 28, 2002). A total of 1798 recipients underwent deceased donor liver transplants. Biliary stricture was more common in the post-MELD era (15.4% versus 6.4%, P < 0.001). The strongest risk factors for stricture development were donor age (odds ratio [OR] = 1.01), presence of a prior bile leak (OR = 2.24), use of choledochocholedochostomy (OR = 2.22), and the post-MELD era (OR = 2.30). Bile leak was more common in the pre-MELD era (7.5% versus 4.9%, P = 0.02), with use of a T-tube as the strongest risk factor (OR = 3.38). Surgical factors did not influence the biliary complication rate. In conclusion, even when employing multivariate analysis to allow for factors that may influence biliary strictures, transplant in the post-MELD era was an independent predictor for stricture development. Further studies are warranted to determine the etiology of this increase.

Biological modulation of liver ischemia-reperfusion injury

PURPOSE OF REVIEW

This review gives a broad overview of the key factors of ischemic injury to the liver and presents the current modifications of preservation solutions and the few strategies of biological modulation in clinical use today.

RECENT FINDINGS

Protective effects in human-liver transplantation were shown by methylprednisolone treatment in decreased donors, and by inhalation of a nontoxic dose of nitric oxide in recipients. In addition, recent results showed rescue of pig livers, donated after cardiac death by application of a cocktail of substances addressing several previously identified mechanisms of ischemia-reperfusion injury.

SUMMARY

The future of a pharmacological approach attenuating or preventing ischemia-reperfusion injury lies in a combination of drugs acting simultaneously on several steps of the injury cascades. Applying these substances during flush, before, and during implantation appears as an attractive strategy to protect extended criteria liver grafts.

Effect of cold ischemia-warm reperfusion on the cirrhotic rat liver

Cirrhosis is known to induce capillarization of the sinusoidal endothelial cells (SECs) and collagenization of the space of Disse, resulting in a reduced access of plasma and plasma-dissolved substances to hepatocytes due to their limited diffusion in the extravascular space. The aim of the present study was to use a well known effect of cold ischemia-warm reperfusion (CI-WR) on liver SECs, that is, their retraction and detachment, progressing to a denudation of the SEC lining. The disappearance of the capillarized SEC lining would improve the access of plasma and plasma-dissolved substances to the hepatocytes and consequently might improve the metabolic function of cirrhotic livers. This study was performed using the isolated perfused rat liver model subjected to 24-hour CI followed by a 60-minute WR in thioacetamide-induced cirrhosis. Liver microcirculation was evaluated using the multiple indicator dilution curve (MIDC) technique. Hepatocyte, SEC, and Kupffer cell functions were evaluated using specific elimination processes. As occurs in normal livers, CI-WR induced extensive SEC necrosis with a marked reduction of the hyaluronic acid elimination. By contrast, the hepatic microcirculation was not modified: vascular, extravascular, and the cellular spaces were similar before and following CI-WR. In addition, the hepatic metabolic functions, as evaluated by propranolol and taurocholate hepatic uptake, were neither improved nor decreased, as were Kupffer cell functions. The present data strongly suggest that capillarization of SECs plays a lesser role than collagenization of the space of Disse in the reduced exchange between sinusoids and hepatocytes in thioacetamide-induced cirrhotic rat livers, which appear to be quite resistant to CI-WR.

Biliary complications after liver transplantation from maastricht category-2 non-heart-beating donors

BACKGROUND

There are unresolved issues regarding the security of liver transplantation with non-heart-beating donors (NHBDs). Recently, an increased incidence of biliary complications, mainly intrahepatic ischemic-type biliary strictures, has been described after controlled NHBDs.

METHODS

We studied the incidence and risk factors for biliary complications among uncontrolled NHBDs recipients compared with a large population of HBD recipients.

RESULTS

Overall, 16.8% of patients in the HBD group and 41.7% of patients in the NHBD group suffered any type of biliary complication (P=0.66). However, the incidence of nonanastomotic biliary strictures was significantly greater in the NHBD group (P<0.001). Multivariate analysis showed that independent risk factors for nonanastomotic strictures were hepatic artery thrombosis (relative risk; 98.7) and receiving a liver from a NHBD (relative risk; 47.1).

CONCLUSIONS

If this type of donors is accepted as a source of liver organs, the high incidence of biliary complications should be considered and efforts should be made to decrease ischemic injury.

Kupffer cells alter organic anion transport through multidrug resistance protein 2 in the post-cold ischemic rat liver

Although Kupffer cells (KCs) may play a crucial role in post-cold ischemic hepatocellular injury, their role in nonnecrotic graft dysfunction remains unknown. This study examined reveal the role of KC in post-cold ischemic liver grafts. Rat livers treated with or without liposome-encapsulated dichloromethylene diphosphonate, a KC-depleting reagent, were stored in University of Wisconsin (UW) solution at 4 degrees C for 8 to 24 hours and reperfused while monitoring biliary output and constituents. The ability of hepatocytes to excrete bile was assessed through laser-confocal microfluorography in situ. Cold ischemia-reperfused grafts decreased their bile output significantly at 8 hours without any notable cell injury. This event coincided with impaired excretion of glutathione and bilirubin-IXalpha (BR-IXalpha), suggesting delayed transport of these organic anions. We examined whether intracellular relocalization of multidrug resistance protein-2 (Mrp2) occurred. Kinetic analyses for biliary excretion of carboxyfluorescein, a fluoroprobe excreted through this transporter, revealed significant delay of dye excretion from hepatocytes into bile canaliculi. The KC-depleting treatment significantly attenuated this decline in biliary anion transport mediated through Mrp2 in the 8-hour cold ischemic grafts via redistribution of Mrp2 from the cytoplasm to the canalicular membrane. Furthermore, thromboxane A(2) (TXA(2)) synthase in KC appeared involved as blocking this enzyme improved 5-carboxyfluorescein excretion while cytoplasmic internalization of Mrp2 disappeared in the KC-depleting grafts. In conclusion, KC activation is an important determinant of nonnecrotic hepatocellular dysfunction, jeopardizing homeostasis of the detoxification capacity and organic anion metabolism of the post-cold ischemic grafts.

Sinusoidal endothelial cell and hepatocyte death following cold ischemia-warm reperfusion of the rat liver

Cold ischemia-warm reperfusion (CI-WR) injury of the liver is characterized by marked alterations of sinusoidal endothelial cells (SECs), whereas hepatocytes appear to be relatively unscathed. However, the time course and mechanism of cell death remain controversial: early versus late phenomenon, necrosis versus apoptosis? We describe the occurrence and nature of cell death after different periods of CI with University of Wisconsin (UW) solution and after different periods of WR in the isolated perfused rat liver model. After 24- and 42-hour CI (viable and nonviable livers, respectively), similar patterns of liver cell death were seen: SEC necrosis appeared early after WR (10 minutes) and remained stable for up to 120 minutes. After 30 minutes of WR, apoptosis increased progressively with WR length. Based on morphological criteria, apoptotic cells were mainly hepatocytes within liver plates or extruded in the sinusoidal lumen. In addition, only after 42-hour CI were large clusters of necrotic hepatocytes found in areas of congested sinusoids. In these same livers, the hepatic microcirculation, evaluated by means of the multiple-indicator dilution technique, revealed extracellular matrix disappearance with no-flow areas. In conclusion, different time courses and mechanisms of cell death occur in rat livers after CI-WR, with early SEC necrosis followed by delayed hepatocyte apoptosis. These processes do not appear to be of major importance in the mechanism of graft failure because they are similar under both nonlethal and lethal conditions; this is not the case for the loss of the extracellular matrix found only under lethal conditions and associated with hepatocyte necrosis.

Intrahepatic cholestasis after liver transplantation

Cholestasis is a common sequela of liver transplantation. Although the majority of cases remain subclinical, severe cholestasis may be associated with irreversible liver damage, requiring retransplantation. Therefore, it is essential that clinicians be able to identify and treat the syndromes associated with cholestasis. In this review, we consider causes of intrahepatic cholestasis. These may be categorized by time of occurrence, namely, within 6 months of liver transplantation (early) and thereafter (late), although there may be an overlap in their causes. The causes of intrahepatic cholestasis include ischemia/reperfusion injury, bacterial infection, acute cellular rejection, cytomegalovirus infection, small-for-size graft, drugs for hepatotoxicity, intrahepatic biliary strictures, chronic rejection, hepatic artery thrombosis, ABO blood group incompatibility, and recurrent disease. The mechanisms of cholestasis in each category and the clinical presentation, diagnosis, treatment, and outcome are discussed in detail.

Protective effect of matrine on sinusoidal endothelial cells of rat liver isograft

AIM

To investigate the protection effect of matrine on cold ischemia and reperfusion injury of sinusoidal endothelial cells (SEC) of liver isograft.

METHODS

Two hundred and twenty-four SD rats were randomly divided into four groups: untreated group, low-dose treated group, high-dose treated group and sham operation group. After 5 hours of cold preservation with Ringer's solution, orthotopic liver transplantation was performed. At 1 h, 2 h and 4 h time-points after reperfusion, 6 rats were killed in each group to collect the serum sample and the middle lobe of liver for detection, and the other 8 rats were raised to study the one week survival rate post-transplantation.

RESULTS

All recipients in control group died within 48 hours, mostly between 10 to 20 hours, and matrine treatment increased one week survival rate to 75% in both treated groups. The level of Hylluronic Acid (HA) and glutamate pyruvate transaminase (ALT) decreased significantly with matrine treatment. And the expression of intercellular adhesion molecule-1 (ICAM-1) decreased significantly in both treated groups, and the pathological changes of SEC ameliorated.

CONCLUSION

Matrine can prevent SEC from cold ischemia and reperfusion injury in rat orthotopic liver transplantation.

Nitric oxide in liver transplantation: pathobiology and clinical implications

The gaseous molecule nitric oxide is involved in a variety of liver transplant-relevant processes, including ischemia-reperfusion injury, acute cellular rejection, and circulatory changes characteristic of advanced liver disease. This review article focuses on new advances relating to the role of nitric oxide in these syndromes with an emphasis on pathobiology and potential clinical implications.

Improvement of rat liver function by energy repletion after the preservation period: implications for hepatic graft management

We very recently showed (using a blood-free perfusion model) that cold preservation sensitized rat hepatocyte functions to rewarming ischemic injury and that the injury can be prevented by repleting high-energy adenylates in the liver by short-term oxygenated warm reperfusion. Here we investigated whether short-term reperfusion after the preservation period can improve hepatic graft function in a blood reperfusion model. Eighteen-hour cold-preserved rat livers either untreated (Group A) or pretreated by 30-min oxygenated warm reperfusion after preservation (Group B) were subjected to 20-min ischemic rewarming and then reperfused with blood. Livers in Group B compared to Group A exhibited approx. three times increased bile production and bromosulfophthalein excretion, nearly 7-fold decreased swelling, and 1.2-fold improved blood flow. These results suggest that repletion of the energy by short-term oxygenated reperfusion after prolonged preservation may improve markedly initial hepatic graft function.

Microcirculatory failure after rat liver transplantation is related to Kupffer cell-derived oxidant stress but not involved in early graft dysfunction

BACKGROUND

Microcirculatory failure, activation of Kupffer cells (KC), and the formation of reactive oxygen species (ROS) are considered pivotal mechanisms of reperfusion injury after orthotopic liver transplantation. However, the sequence of these events and their impact on early graft function remain controversial. We therefore investigated whether KC induce microcirculatory disturbances through ROS release and whether microcirculatory failure contributes to early graft function after liver transplantation.

METHODS

Donor livers of Lewis rats were pretreated either with saline or with gadolinium chloride (GdCl3), an inhibitor of KC function (n=8 each). Syngeneic OLT was performed after 24 hr of hypothermic preservation in University of Wisconsin solution.

RESULTS

Intravital microscopy revealed significantly higher sinusoidal perfusion rates in GdCl3-treated allografts (92+/-1.1% vs. 75.7+/-0.8%; P<0.001) compared with untreated controls; permanent leukocyte sticking in sinusoids (23.5+/-2.1 vs. 62.6+/-3.3 cells/lobule, P<0.001) and in postsinusoidal venules (153.1+/-10.4 vs. 446.6+/-46.4 cells/mm(2), P<0.001) were markedly attenuated in GdCl3-treated allografts. Improvement of microcirculatory parameters in GdCl3-treated livers was correlated with a significant reduction of plasma glutathione disulfide formation by KC-derived ROS (0.96+/-0.1 microM vs. 1.79+/-0.5 microM; P<0.01). Despite these beneficial effects, GdCl3-pretreatment failed to improve postischemic alanine aminotransferase release and bile flow.

CONCLUSIONS

Microcirculatory failure after liver transplantation is related to KC-derived oxidant stress but not involved in early graft dysfunction.

The influence of organ temperature on hepatic ischemia-reperfusion injury: a systematic analysis

BACKGROUND

Although hepatic ischemia-reperfusion (I/R) injury can be reduced by cooling of the ischemic organ, a systematic in vivo analysis of the influence of organ temperature in I/R injury is missing. The aim of this study was to systematically investigate the impact of defined temperatures of the ischemic liver tissue on microvascular I/R injury.

METHODS

Ischemia of the left liver lobe was induced in C57BL/6 mice for 90 min. The ischemic lobe was placed in a polyethylene well and the temperature was adjusted to 37 degrees C, 26 degrees C, 15 degrees C, and 4 degrees C by superfusion with cooled/warmed saline solution. The ischemia groups (n=7 each) were compared with a sham-operated group (n=7). The sinusoidal perfusion index and the number of leukocytes firmly adherent to the endothelium of postsinusoidal venules were assessed using intravital fluorescence microscopy at 30 min, 120 min, and 240 min of reperfusion, respectively. At the end of the experiment, serum activities of the liver enzymes aspartate aminotransferase/alanine aminotransferase were determined, and tissue specimens were examined by electron microscopy.

RESULTS

Core body temperature did not differ significantly between the groups. In the 37 degrees C group, the sinusoidal perfusion index was significantly reduced and the number of adherent leukocytes was significantly increased compared with the sham group. In all hypothermia groups, however, the microcirculatory parameters did not differ from the sham group. Serum activities of aspartate aminotransferase/alanine aminotransferase were significantly increased and hepatocellular integrity was severely affected in the 37 degrees C group as compared with all other groups.

CONCLUSIONS

These findings demonstrate that in the mouse liver the known protective effect of hypothermia is already encountered at 26 degrees C. Further reduction of temperature did not generate additional protection from I/R injury.

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

In liver transplantation, it is currently hypothesized that nonparenchymal cell damage and/or activation is the major cause of preservation-related graft injury. Because parenchymal cells (hepatocytes) appear morphologically well preserved even after extended cold preservation, their injury after warm reperfusion is ascribed to the consequences of nonparenchymal cell damage and/or activation. However, accumulating evidence over the past decade indicated that the current hypothesis cannot fully explain preservation-related liver graft injury. We review data obtained in animal and human liver transplantation and isolated perfused animal livers, as well as isolated cell models to highlight growing evidence of the importance of hepatocyte disturbances in the pathogenesis of normal and fatty graft injury. Particular attention is given to preservation time-dependent decreases in high-energy adenine nucleotide levels in liver cells, a circumstance that (1) sensitizes hepatocytes to various stimuli and insults, (2) correlates well with graft function after liver transplantation, and (3) may also underlie the preservation time-dependent increase in endothelial cell damage. We also review damage to bile duct cells, which is increasingly being recognized as important in the long-lasting phase of reperfusion injury. The role of hydrophobic bile salts in that context is particularly assessed. Finally, a number of avenues aimed at preserving hepatocyte and bile duct cell integrity are discussed in the context of liver transplantation therapy as a complement to reducing nonparenchymal cell damage and/or activation.

Role of Kupffer cells in the survival after rat liver transplantation with long portal vein clamping times

Applying the orthotopic rat liver transplantation (ORLT) model, postoperative survival has been shown to be mainly dependent on the portal vein clamping time (PVCT). It was hypothesized that prolonged intestinal congestion was responsible for the activation of Kupffer cells (KC) with overproduction of TNF, secondary to splanchnic endotoxin accumulation and release on reperfusion. The role of KCs was directly investigated in the context of long PVCTs by eliminating them (using liposome-encapsulated dichloromethylene diphosphonate), by preventing their activation (using a calcium channel blocker, nisoldipine) and by inhibiting TNF production (using thalidomide). Livers from different groups of rats were transplanted following 24-h cold preservation in the UW solution with long PVCTs (from 18-21 min). KCs depletion, preservation with nisoldipine and pretreatment with thalidomide significantly improved survival in conditions using long PVCTs. KC depletion and nisoldipine preservation had no effect on liver enzymes or pathological findings while lung injury was significantly improved. The present data confirm that, in the context of ORLT with long PVCTs, KCs are directly responsible for the systemic endotoxin-like shock syndrome and their effect is mediated through overproduction of TNF.

Superiority of mild hypothermic (20 degrees C) preservation for pancreatic microvasculature using the two-layer storage method

Hypothermia causes vascular endothelial damage that leads to graft microcirculation disorder and eventually thrombosis after reperfusion. The two-layer cold storage method (TL) was previously demonstrated to supply oxygen to the pancreas graft and maintain high adenosine triphosphate tissue concentration. In this study, we evaluated whether mild hypothermic (20 degrees C) preservation using the TL method could reduce endothelial damage while maintaining parenchymal viability. Graft survival by 20 degrees C preservation was investigated using a dog segmental pancreas autotransplantation model (simple storage in University of Wisconsin solution (UW) for 5 and 8 hours or TL for 5, 8, 12, and 24 hrs. respectively). Subsequently, the grafts were preserved in four different conditions (4 and 20 degrees C UW. 4 and 20 degrees C TL) for 8 hours to evaluate microvascular endothelial damage. Trypan blue uptake of vascular endothelium and pancreatic tissue perfusion were evaluated. No graft preserved by 20 degrees C UW for 5 and 8 hours survived (0/7 and 0/4). In contrast, the graft survival rates by 20 degrees C TL for 5, 8, 12, and 24 hours were 100% (5/5), 80% (4/5), 20% (1/5), and 0% (0/4), respectively. In trypan blue uptake analysis, there were significant differences between 4 and 20 degrees C in both UW and TL (4 degrees C UW, 37% [n = 5) vs. 20 degrees C UW, 13% [n = 4] [p < 0.01]; 4 degrees C TL, 29% [n = 5] vs. 20 degrees C TL, 10% [n = 5] [p < 0.011). The perfusion values in 20 degrees C TL were significantly higher than those in other groups at least for up to 120 minutes after reperfusion (p < 0.01 ). In short-term pancreas preservation, mild hypothermic TL reduced vascular endothelial cell damage and ameliorated graft microcirculation while maintaining parenchymal viability. Mild hypothermic TL may lessen vascular complications in clinical pancreas transplantation when used for several-hour preservation.

Prevention of proteolysis in cold-stored rat liver by addition of amino acids to the preservation solution

BACKGROUND

One process identified as detrimental in liver preservation is proteolysis.

METHODS

We tested the effects of adding antiproteolytic amino acids (L-alanine, L-glutamine, L-histidine, L-leucine, L-methionine, L-phenylalanine, L-proline, L-tryptophan) to the preservation medium, in a model of reperfusion of 24 h cold-stored rat livers.

RESULTS

During the preservation period, antiproteolytic amino acids inhibited the proteolysis observed in stored livers as shown by branched-chain amino acid fluxes, which switched from release to uptake. During reperfusion, cold storage of lives without the addition of antiproteolytic amino acids resulted in a decrease in the total amino acid and branched-chain amino acid uptake and a lower perfusion flow rate. The addition of antiproteolytic amino acids during liver storage resulted in the maintenance of total amino acid and branched-chain amino acid uptake and a significant improvement in the perfusion flow rate during reperfusion.

CONCLUSIONS

The presence of antiproteolytic amino acids in the preservation medium might be of interest in improving hepatic graft viability in transplantation.

Cold-preservation-induced sensitivity of rat hepatocyte function to rewarming injury and its prevention by short-term reperfusion

With increasing time of cold preservation, levels of high-energy nucleotides in the liver are reducing. The authors hypothesized that cold preservation sensitizes hepatocyte function to ischemic injury occurring during graft rewarming and that the injury can be prevented by short-term reperfusion. Rat livers were cold-preserved in University of Wisconsin solution for 0 to 18 hours and ischemically rewarmed for 0 to 45 minutes to simulate the implantation stage of transplantation. Hepatobiliary function was assessed using a blood-free perfusion model. In comparison with controls, neither 18-hour preservation nor 45-minute ischemic rewarming significantly influenced hepatocyte function. Compared with livers subjected to 45-minute ischemic rewarming, livers subjected to 9-hour preservation and 45-minute rewarming, and livers subjected to 18-hour preservation and 45-minute rewarming exhibited, respectively: 3.8 and 24 times reduced bile production, 4.3- and 116-fold decreased taurocholate excretion, and 3.1 and 42 times depressed bromosulfophthalein excretion. Thirty-minute oxygenated warm reperfusion after 9- and 18-hour preservation nearly completely blunted sensitization of hepatocyte function to rewarming ischemia. The authors found that short-term oxygenated reperfusion restored adenine nucleotides in liver tissue to the values found before organ preservation and that reperfusion with energy substrate containing solutions increased tissue adenosine triphosphate concentration to a higher level than that found before preservation. In conclusion, sensitization of hepatocyte function to rewarming ischemia increases disproportionally with storage time, suggesting that this phenomenon may play a role in graft dysfunctions with increasing liver preservation time. Short-term oxygenated reperfusion of the liver may protect hepatocyte functions against warm ischemic insult, even after extended preservation.

Effect of perfusate albumin on organ viability and vascular responses in the in vitro dual-perfused rat liver

Inclusion of albumin in the perfusate has been previously shown to be detrimental to liver function, but its effect on hepatic vascular reactivity remains unknown. The aim of this study was to determine the effects of albumin on hepatic arterial vascular reactivity and liver viability in the isolated dual-perfused rat liver. A total of 12 rat livers were perfused with Krebs-Bülbring buffer without (Group 1) and with (Group 2) addition of 1% bovine serum albumin (BSA) through the hepatic artery and portal vein for up to 5 h. Hepatic arterial responses to acetylcholine and sodium nitroprusside were studied at 30-min intervals. Liver viability was assessed by bile volume production, release of aspartate serine aminotransferase (AST) and lactic acid dehydrogenase (LDH), and histological examination. Hepatic arterial responses to acetylcholine were significantly attenuated in Group 2. No significant differences in sodium nitroprusside responses were noted. However, bile volume production in Group 2 was significantly decreased compared to Group 1. Effluent AST and LDH release increased significantly in Group 1 but not in Group 2. Histological results showed that sinusoidal endothelial cells and hepatocytes were well preserved without significant deterioration in either group, although there was a marked decrease in vasodilatation to acetylcholine in Group 2. This data suggested that the presence of albumin in the perfusate did not improve retention of smooth muscle reactivity and reduced endothelium-dependent vasodilatation and bile volume production during perfusion. However, improved liver parenchymal cell function was observed.

Endotoxin-induced aggravation of preservation-reperfusion injury of rat liver and its modulation

BACKGROUND/AIMS

In clinical transplantation, exposure of donors to gut-derived endotoxin occurs frequently and may adversely affect liver transplantation therapy. The aim of this study was to investigate: 1) whether brief exposure of rats to endotoxin before liver procurement aggravates the early phase of reperfusion injury of hepatic explants; and if so 2) whether Kupffer cell activation is a contributing factor to liver injury; and 3) whether heparin and pentoxifylline could minimize this effect.

METHODS

Male Wistar rats were injected with 0.2-4.0 mg/kg of Escherichia coli lipopolysaccharide 2 h prior to liver harvest. After preservation in University of Wisconsin cold-storage solution, the livers were reperfused using a blood-free perfusion model. To inactivate Kupffer cells, some rats were pretreated with gadolinium chloride or liposome-encapsulated dichloromethylene-diphosphonate before lipopolysaccharide administration. The other rats received lipopolysaccharide with heparin or pentoxifylline.

RESULTS

In a dose-independent fashion, lipopolysaccharide impaired portal flow during graft reperfusion. In a dose-dependent way, lipopolysaccharide increased lactate dehydrogenase release into the perfusate and decreased bile flow and bromosulfophthalein excretion. Gadolinium chloride, liposomal dichloromethylene-diphosphonate, heparin, and pentoxifylline reduced lactate dehydrogenase release by 34%, 43%, 59%, and 64%, respectively, and improved functional parameters of the liver. A 52-fold increased neutrophil infiltration in the liver sinusoids after lipopolysaccharide exposure was not affected significantly by the drugs studied; however, heparin reduced markedly neutrophil activation.

CONCLUSIONS

The results of this investigation provide direct evidence that aggravation of preservation-reperfusion injury of rat liver by endotoxin is mediated by Kupffer cell-dependent mechanism(s) and it can be minimized by heparin and pentoxifylline.

Effects of exogenous superoxide anion and nitric oxide on the scavenging function and electron microscopic appearance of the sinusoidal endothelium in the isolated, perfused rat liver

BACKGROUND/AIMS

Functional and morphological alterations of the hepatic sinusoidal endothelial cell occur in several models of experimental liver injury and in clinical settings. The causes of these alterations are multiple. The aim of this study was to test the hypothesis that the early functional impairment and morphological alterations of the sinusoidal endothelial cell and hepatic sinusoid associated with liver injury are mediated by free radical species, such as superoxide anion and nitric oxide.

METHODS

Isolated rat livers were perfused by recirculation with hemoglobin-free, Krebs-Henseleit bicarbonate buffer and presented with a source of superoxide anion (xanthine oxidase+hypoxanthine) or nitric oxide (S-nitroso-N-acetyl penicillamine). Hyaluronan uptake (an index of sinusoidal endothelial cell scavenging function), thiobarbituric acid-reactive substances content of the tissue (a marker of lipid peroxidation), reduced and oxidized glutathione (a marker of the thiol system oxidation/reduction state), lactate dehydrogenase and alanine aminotransferase activities (markers of cytolysis), as well as scanning and transmission electron microscopic appearance of the sinusoid were evaluated.

RESULTS

At the high concentrations used, both free radical generating systems suppressed hyaluronan uptake, increased malondialdehyde content of the tissue, enhanced the release of both liver enzymes, decreased the total glutathione content of the liver, and altered the ratio of reduced/oxidized glutathione. Both free radical species induced dose-dependent morphological alterations of the sinusoid, consisting of the appearance of large gaps replacing the sieve-plated fenestration.

CONCLUSIONS

The free radical species-induced functional impairment and morphological alterations of the liver sinusoid, presented in this study, closely resemble the early in vivo changes associated with liver injury under a variety of conditions, such as preservation and reperfusion, or administration of hepatotoxicants such as D-galactosamine, Gram-negative bacterial lipopolysaccharides, acetaminophen, alcohol and others. Therefore, we suggest that early liver sinusoid injury, observed under these conditions, can be attributed to the action of free radicals, such as superoxide anion and nitric oxide.

Decreased survival in rat liver transplantation with extended cold preservation: role of portal vein clamping time

Primary liver graft dysfunction is currently related to cold ischemia-reperfusion injury, although a wide survival range has been reported using 24-hour preservation in cold University of Wisconsin (UW) solution. We hypothesized that the portal vein clamping time (PVCT) played a more important role than cold preservation injury in the postoperative outcome. Rat liver transplantation was performed using different clamping times after 24-hour cold ischemia in the UW solution. Survival rates, plasma tumor necrosis factor (TNF), and nitrate/nitrite levels were examined. Subsequently, the effect of clamping time was evaluated on hepatocyte and sinusoidal endothelial cell (SEC) function using isolated perfused livers. Survival rate was directly related to clamping time length. Marked increases in TNF and nitrate/nitrite levels were found after surgery, particularly after long clamping times. In perfusion studies, the SEC function was already markedly altered after preservation alone and was not further modified by transplantation. By contrast, the hepatocyte function was moderately altered after transplantation, irrespective of clamping times, even when rats operated with long clamping times were in terminal conditions. In rats, 24-hour preservation in cold UW solution is not a severely compromising condition leading to primary liver nonfunction. Long PVCTs are associated with an endotoxemia-like syndrome more related to a warm intestinal ischemia than to cold ischemia injury of the liver.