Liver preservation: The past and the future

Optimization of long-term cold storage of rat precision-cut lung slices with a tissue preservation solution

Precision-cut lung slices (PCLS) are used as ex vivo model of the lung to fill the gap between in vitro and in vivo experiments. To allow optimal utilization of PCLS, possibilities to prolong slice viability via cold storage using optimized storage solutions were evaluated. Rat PCLS were cold stored in DMEM/F-12 or two different preservation solutions for up to 28 days at 4°C. After rewarming in DMEM/F-12, metabolic activity, live/dead staining, and mitochondrial membrane potential was assessed to analyze overall tissue viability. Single-cell suspensions were prepared and proportions of CD45⁺, EpCAM⁺, CD31⁺, and CD90⁺ cells were analyzed. As functional parameters, TNF-α expression was analyzed to detect inflammatory activity and bronchoconstriction was evaluated after acetylcholine stimulus. After 14 days of cold storage, viability and mitochondrial membrane potential were significantly better preserved after storage in solution 1 (potassium chloride rich) and solution 2 (potassium- and lactobionate-rich analog) compared with DMEM/F-12. Analysis of cell populations revealed efficient preservation of EpCAM⁺, CD31⁺, and CD90⁺ cells. Proportion of CD45⁺ cells decreased during cold storage but was better preserved by both modified solutions than by DMEM/F-12. PCLS stored in solution 1 responded substantially longer to inflammatory stimulation than those stored in DMEM/F-12 or solution 2. Analysis of bronchoconstriction revealed total loss of function after 14 days of storage in DMEM/F-12 but, in contrast, a good response in PCLS stored in the optimized solutions. An improved base solution with a high potassium chloride concentration optimizes cold storage of PCLS and allows shipment between laboratories and stockpiling of tissue samples.

Preservation of Cell Structure, Metabolism, and Biotransformation Activity of Liver-On-Chip Organ Models by Hypothermic Storage

The liver is a central organ in the metabolization of nutrition, endogenous and exogenous substances, and xenobiotic drugs. The emerging organ-on-chip technology has paved the way to model essential liver functions as well as certain aspects of liver disease in vitro in liver-on-chip models. However, a broader use of this technology in biomedical research is limited by a lack of protocols that enable the short-term preservation of preassembled liver-on-chip models for stocking or delivery to researchers outside the bioengineering community. For the first time, this study tested the ability of hypothermic storage of liver-on-chip models to preserve cell viability, tissue morphology, metabolism and biotransformation activity. In a systematic study with different preservation solutions, liver-on-chip function can be preserved for up to 2 d using a derivative of the tissue preservation solution TiProtec, containing high chloride ion concentrations and the iron chelators LK614 and deferoxamine, supplemented with polyethylene glycol (PEG). Hypothermic storage in this solution represents a promising method to preserve liver-on-chip function for at least 2 d and allows an easier access to liver-on-chip technology and its versatile and flexible use in biomedical research.

Hepatocyte Immobilization on Phema Microcarriers and its Biologically Modified Forms

Polyhydroxyethylmethacrylate (PHEMA) based microcarriers with different bulk structures were prepared by a phase inversion polymerization technique. PHEMA surfaces were further modified chemically by glow-discharge treatment, and biologically by covalent attachment of fibrinogen and collagen. Hepatocytes were isolated from young male Wistar rats using an in situ portal vein collagenase perfusion technique. Freshly isolated hepatocytes were seeded at 6 × 105 cells/mL and microcarrier concentration was 10 g/L. Stationary microcarrier cultures were carried out in standard (nontissue culture) polystyrene petri dishes in a humidified 5% CO2 incubator at 37 ± 0.5°C. Cell attachment was followed by light microscopy by taking samples from the culture medium every 30 min. Urea and protein syntheses by microcarrier-attached hepatocytes were determined by standard techniques. Nonswellable (highly cross-linked) hydrophilic PHEMA microcarriers did not support cell attachment and viability. However, swellable (low cross-linked) PHEMA microcarriers (pretreated in FBS) allowed high attachment and cell spreading. PHEMA microcarriers treated in dimethylaminoethylmethacrylate (DMAEMA) glow-discharge plasma also improved the cell attachment characteristics of the PHEMA microcarriers. The highest attachment efficiencies (immobilization yields) were observed with the biologically modified PHEMA microcarriers, especially modified with fibronectin. Metabolic activity, as estimated by urea and protein syntheses, was also higher in these microcarriers.

Ischemic preconditioning and atenolol on lung injury after intestinal ischemia and reperfusion in rats

The aim of this study was evaluate the beta blocker atenolol (AT) and ischemic preconditioning (IPC) strategies for tissue protection against systemic effects of intestinal ischemia (I) and reperfusion (R) injury. Forty-two rats were pretreated with AT (1.5 mg · kg(-1)), 0.9% saline solution (SS; 0.1 mL), or IPC and then subjected to prolonged occlusion of the superior mesenteric artery for 60 minutes leading to I followed or not by 120 minutes of R, according to the group. For IPC, 5 minutes of I prior to 10 minutes of R were established. After this process of I or I-R, the right lung of each animal was adequately prepared for staining with hematoxylin and eosin and subsequent histologic analysis for quantification of inflammatory infiltrate was done. The left lung was frozen and prepared for assessment of oxidative stress by the quantification of thiobarbituric acid-reactivity substances (TBARS). Histologic analysis showed an important inflammatory infiltrate in the I-R + SS (I-R + SS = 4.5), which was significantly (P < .05) reduced by IPC (I-R + IPC = 3.0) or AT (I-R + AT = 3.0). Likewise, the TBARS levels were decreased by both strategies (I-R + SS = 0.63; I-R + IPC = 0.23; I-R + AT = 0.38; P < .05). Our results showed that AT and IPC attenuate pulmonary lesions caused by intestinal I and R process.

"Resuscitation" of marginal liver allografts for transplantation with machine perfusion technology

As the rate of medically suitable donors remains relatively static worldwide, clinicians have looked to novel methods to meet the ever-growing demand of the liver transplant waiting lists worldwide. Accordingly, the transplant community has explored many strategies to offset this deficit. Advances in technology that target the ex vivo "preservation" period may help increase the donor pool by augmenting the utilization and improving the outcomes of marginal livers. Novel ex vivo techniques such as hypothermic, normothermic, and subnormothermic machine perfusion may be useful to "resuscitate" marginal organs by reducing ischemia/reperfusion injury. Moreover, other preservation techniques such as oxygen persufflation are explored as they may also have a role in improving function of "marginal" liver allografts. Currently, marginal livers are frequently discarded or can relegate the patient to early allograft dysfunction and primary non-function. Bench to bedside advances are rapidly emerging and hold promise for expanding liver transplantation access and improving outcomes.

Utility of cryopreserved hepatocytes suspended in serum to predict hepatic clearance in dogs and monkeys

An in vitro-in vivo correlation analysis between observed and predicted metabolic clearance in multiple preclinical species including dogs and monkeys constitutes an integral part of prediction for the pharmacokinetics in humans by using liver-derived in vitro preparations. Empirical values of the scaling factor for the extrapolation of metabolic (intrinsic) clearance in the in vitro preparation to that for whole liver were calculated for each preparation of 8 and 5 cryopreserved dog and monkey hepatocytes, respectively, by optimizing the objective function of average fold error between predicted and observed metabolic (intrinsic) clearance for eight and 11 standard compounds for dogs and monkeys, respectively. Thus obtained values of the scaling factor ranged from 5.46 × 10(9) to 19.9 × 10(9) cells/kg body weight with an average of 10.3 × 10(9) cells/kg body weight in dogs, and the value ranged from 2.36 × 10(9) to 4.21 × 10(9) cells/kg body weight with an average of 3.17 × 10(9) cells/kg body weight in monkeys, which were both consistent with biologically calculated values in corresponding species. These results demonstrated the utility of commercially available cryopreserved preparations of dog and monkey hepatocytes for the in vitro-in vivo correlation analyses with the aid of empirically or biologically obtained scaling factors at the early development stage of new drug candidates.

Preservation solutions for liver transplantation in adults: celsior versus custodiol: a systematic review and meta-analysis with an indirect comparison of randomized trials

BACKGROUND

The University of Wisconsin (UW) solution has been recognized as the gold standard for liver preservation; however, it possesses some limitations, and other solutions exist for organ preservation. The aim of this study was to compare the liver functions of transplanted grafts that had been stored in Celsior and Custodiol solutions.

METHODS

We searched the MEDLINE, EMBASE, LILACS, Cochrane Central Register of Controlled Trials, and SCIELO databases. We included randomized and quasi-randomized, controlled trials that compared the efficacy and safety of Celsior and Custodiol with UW solution for liver preservation in adults. The factors that were considered for analysis were their impacts on primary dysfunction (primary nonfunction and initial poor function), ischemic-type biliary lesions, and patient and graft survival rates. Because of the lack of direct evidence, an indirect comparison of Celsior and Custodiol was calculated.

RESULTS

We identified 3 randomized controlled trials and 1 quasi-randomized, controlled trial to pool in a meta-analysis of Celsior versus UW solutions. The number of episodes of primary dysfunction was lower in the Celsior group (7.4%) than in the UW group (9.8%), but the difference was not significant (relative risk [RR], 0.68; 95% confidence interval [CI], 0.22-1.97). Two randomized controlled trials compared Custodiol and Wisconsin solutions were identified. The number of episodes of primary dysfunction was also lower in the Custodiol group (3.0%) compared with the Wisconsin group (8.4%), but the difference was not significant (RR, 0.36; 95% CI, 0.08-1.70). An indirect comparison using data from the main analysis revealed no difference between the Celsior and Custodiol solutions (RR, 1.88; 95% CI, 0.57-6.16).

CONCLUSION

The Celsior and Custodiol solutions performed similarly to UW solution as preservation solutions in liver transplantation clinical settings.

Altered cellular membrane fluidity levels and lipid peroxidation during experimental pancreas transplantation

Although the pathogenesis of ischemia reperfusion (IR) injury is based on complex mechanisms, free radicals play a central role. We evaluated membrane fluidity and lipid peroxidation during pancreas transplantation (PT) performed in 12 pigs (six donors and six recipients). Fluidity was measured by fluorescence spectroscopy, and malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA) concentrations were used as an index of lipid oxidation. Pancreatic tissues were collected as follows: (A) donor, immediately before vascular clamping; (B) graft, following perfusion lavage with University of Wisconsin preservation fluid; (C) graft, after 16 h of cold ischemia; and (D) recipient, 30 min vascular postreperfusion. Fluidity and MDA and 4-HDA concentrations were similar in cases A, B, and C. However, there was significant membrane rigidity and increased lipid peroxidation after reperfusion (D). These findings suggest that reperfusion exaggerates oxidative damage and may account for the rigidity in the membranes of allografts during PT.

Improvement of the cold storage of isolated human hepatocytes

Increasing amounts of human hepatocytes are needed for clinical applications and different fields of research, such as cell transplantation, bioartificial liver support, and pharmacological testing. This demand calls for adequate storage options for isolated human liver cells. As cryopreservation results in severe cryoinjury, short-term storage is currently performed at 2-8°C in preservation solutions developed for the storage of solid organs. However, besides slowing down cell metabolism, cold also induces cell injury, which is, in many cell types, iron dependent and not counteracted by current storage solutions. In this study, we aimed to characterize storage injury to human hepatocytes and develop a customized solution for cold storage of these cells. Human hepatocytes were isolated from material obtained from partial liver resections, seeded in monolayer cultures, and, after a preculture period, stored in the cold in classical and new solutions followed by rewarming in cell culture medium. Human hepatocytes displayed cold-induced injury, resulting in >80% cell death (LDH release) after 1 week of cold storage in University of Wisconsin solution or cell culture medium and 3 h of rewarming. Cold-induced injury could be significantly reduced by the addition of the iron chelators deferoxamine and LK 614. Experiments with modified solutions based on the new organ preservation solution Custodiol-N showed that ion-rich variants were better than ion-poor variants, chloride-rich solutions better than chloride-poor solutions, potassium as main cation superior to sodium, and pH 7.0 superior to pH 7.4. LDH release after 2 weeks of cold storage in the thus optimized solution was below 20%, greatly improving cold storage of human hepatocytes. The results were confirmed by the assessment of hepatocellular mitochondrial membrane potential and functional parameters (resazurin reduction, glucagon-stimulated glucose liberation) and thus suggest the use of a customized hepatocyte storage solution for the cold storage of these cells.

Evaluation of functional and structural alterations in muscle tissue after short-term cold storage in a new tissue preservation solution

Storage of muscle preparations in vitro is required for the diagnosis of neuromuscular disorders and for electrophysiological tests. The current standard protocols for muscle storage or transport, i.e. placement on 0.9% NaCl-moistened gauze, lead to impaired function and structural alterations. For other tissues, however, improved preservation methods and solutions have recently been described. In this study, functional and structural alterations in the murine diaphragm were compared after storage on 0.9% NaCl-moistened gauze and after storage in different modifications of the new vascular preservation solution TiProtec®. Muscle force generation after nerve stimulation, histological parameters and ATP levels were investigated after 2.5 h of cold storage at 4°C in the different media and 0.5 h of rewarming at 25°C in Tyrode buffer. Murine diaphragms were injured during cold storage and rewarming, with the degree of the alteration being dependent on the type of solution used. There were no histological alterations and no caspase 3 activation in all groups. In contrast, diaphragms stored in the modified TiProtec solution showed markedly better performance concerning force generation after nerve stimulation (7.1 ± 1.1 cN · s) as well as higher ATP content (2.4 ± 0.7 μmol/g) and were superior to storage on 0.9% NaCl-moistened gauze (1.4 ± 0.4 cN · s; 0.3 ± 0.1 μmol/g). In conclusion, the modified TiProtec preservation solution showed promising results for short-term cold storage of murine diaphragms. For further evaluation, the transferability of these positive findings to storage conditions for muscles of other species, especially human muscle tissue, needs to be investigated.

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.

Histidine-tryptophan-ketoglutarate solution vs. University of Wisconsin solution for liver transplantation: a systematic review

University of Wisconsin (UW) solution has been recognized as the gold standard in liver preservation, but its limitations are becoming obvious, such as risk of biliary complications and its high cost. Alternatively, the effects of histidine-tryptophan-ketoglutarate (HTK), such as improved biliary protection and low cost, have been observed. This systematic review is conducted to compare the efficacy and safety of these 2 solutions. Databases from 1966 to June 2006 were searched. Randomized clinical trials (RCTs) and cohort studies comparing HTK and UW solutions for liver transplantation were included. Ten articles including 11 comparisons (1,200 patients) met the inclusion criteria, containing 2 RCTs and 9 cohort studies. No marked differences existed between the 2 groups in patient and graft survival rates, acute rejection, primary nonfunction, primary dysfunction, delayed graft function, and ALT and AST levels after transplantation. The only positive result was observed in the bile production after deceased donor liver transplantation (DDLT), which was statistically significantly higher in HTK group than that of UW group (95% confidence interval, 18.65-57.47; P=0.0001). Although the difference in biliary complications between the 2 groups did not reach statistical significance, HTK was thought to be more effective for biliary tract flush and prevention of biliary complications in some studies. There was no statistically significant difference of effects (except bile production) between HTK and UW. But trends were documented in some studies for the superiority of HTK in biliary tract flush, prevention of biliary complications, and cost saving. Adequately powered RCTs with longer follow-up periods are required to evaluate the long-term effect of these 2 solutions.

New Insights into the Cellular and Molecular Mechanisms of Cold Storage Injury

Solid organ grafts, but also other biologic materials requiring storage for a few hours to a few days, are usually stored under hypothermic conditions. To decrease graft injury during cold storage, organ preservation solutions were developed many years ago. However, since then, modern biochemical and cell biologic methods have allowed further insights into the molecular and cellular mechanisms of cold storage injury, including further insights into alterations of the cellular ion homeostasis, the occurrence of a mitochondrial permeability transition, and the occurrence of free–radical-mediated hypothermic injury and cold-induced apoptosis. These new aspects of cold storage injury, which are not covered by preservation solutions in current clinical use and offer the potential for improvement of organ and tissue preservation, are presented here.

Protective effect of N2-mercaptopropionylglycine on rats and dogs liver during ischemia/reperfusion process

BACKGROUND

N2-mercaptopropionylglycine is a powerful super oxide synthesis inhibitor and has been tested as a preventive agent of metabolic and structural hepatic damage in the ischemia/reperfusion process.

AIM

To analyze some effects of N2-mercaptopropionylglycine administration to animals of two species submitted to normothermic liver ischemia/reperfusion.

MATERIAL AND METHODS

Twenty-two rats and 22 dogs were divided into four groups: group I: rats that received intravenous saline 0.9%; group II: rats that received 100 mg/kg of N2-mercaptopropionylglycine; group III: dogs that received saline intravenous 0.9% and group IV: dogs that received 100 mg/kg N2-mercaptopropionylglycine.

RESULTS

Ten minutes after the saline or drug administration, each group was submitted to left lobe liver ischemia for 25 minutes followed by reperfusion. Biochemical studies 24 hours after reperfusion revealed a significantly lower elevation of transaminases in animals of groups II (AST = 271 +/- 182; ALT = 261 +/- 161 ) and IV (AST = 101 +/- 45; ALT = 123 +/- 89) when compared to the controls group: I (AST = 2144 +/- 966; ALT = 1869 +/- 1040 00) and III (AST = 182 +/- 76.51; ALT = 277 +/- 219), respectively. Histology study demonstrated a significantly minor aggression to animals of groups II and IV when compared to groups I and III, respectively.

CONCLUSION

These results suggest a significant release of free radicals of oxygen in the process and that N2-mercaptopropionylglycine may have a significant protective effect on liver parenchyma when submitted to ischemia/reperfusion.

Mitochondrial calcium uptake regulates cold preservation-induced Bax translocation and early reperfusion apoptosis

Mitochondrial calcium (mCa + 2) overload occurs during cold preservation and is an integral part of mitochondrial-dependent apoptotic pathways. We investigated the role of mCa + 2 overload in cell death following hypothermic storage using HepG2 cells stored in normoxic-hypothermic (4 degrees C) or hypoxic (< 0.1% O2)-hypothermic Belzer storage solution. Cells were stored for 6 h, with or without 10 microM ruthenium red (mCa + 2 uniporter inhibitor) followed by rewarming in oxygenated media at 37 degrees C. Cytoplasmic cytochrome c levels were studied by Western analysis and by fluorescent microscopy after transfection of cytochrome c-GFP expression plasmid. Immunofluorescence determined the intracellular, spatio-temporal distribution of Bax, and TUNEL staining was used to evaluate cell death after 180 min of rewarming. Caspase activation was evaluated using Western analysis and a caspase 3 activity assay. Bax translocation, cytochrome c release, and early rewarming cell death occurred following hypothermic storage and were exacerbated by hypoxia. Caspase 3 activation did not occur following hypothermic storage. Blockade of mCa + 2 uptake prevented Bax translocation, cytochrome c release, and early rewarming cell death. These studies demonstrate that mCa + 2 uptake during hypothermic storage, both hypoxic and normoxic, contributes to early rewarming apoptosis by triggering Bax translocation to mitochondria and cytochrome c release.

Role of temperature on protein and mRNA cytochrome P450 3A (CYP3A) isozymes expression and midazolam oxidation by cultured rat precision-cut liver slices

The cytochrome P450 3A (CYP3A)-mediated midazolam oxidation was studied in rat precision-cut liver slices (PCLS) maintained for 20hr at 4, 20 and 37 degrees, and further incubated for 8hr at 37 degrees. Either at 4 or 20 degrees, midazolam was oxidised by PCLS at similar rates to that observed in freshly cut slices. Moreover, PCLS kept a regioselectivity since 4-hydroxylation was more important than 1'-hydroxylation. Conversely, PCLS totally lost their capacity to oxidise midazolam after 20hr at 37 degrees, and both CYP3A2 protein and mRNA were not detected. CYP3A1 protein was unaffected by a temperature of 37 degrees but its mRNA was totally lost. By blocking transcription with actinomycin D, the decay of both CYP3A mRNAs followed the same profile at either 20 or 37 degrees, indicating that temperature affected the CYP3A2 protein stability. Cell functionality was not involved in such an impairment since the low values of ATP, GSH and protein synthesis rates observed at 4 and 20 degrees were rapidly restored, when PCLS were further incubated at 37 degrees. The use of rat supersomes expressing either CYP3A1 or CYP3A2, strongly supported the hypothesis that 4-hydroxymidazolam was mainly formed by CYP3A2. These results suggest that: (1) CYP3A1 protein is constitutive and largely expressed in rat liver slices; (2) regioselective midazolam oxidation appears to be mainly CYP3A2 dependent; and (3) since CYP3A isoforms have similar half-lives (about 10-14hr), the loss of CYP3A2 protein at 37 degrees might be due to a selective targeting (phosphorylation ?) leading to proteolytic disposal by the proteasome.

Effects of University of Wisconsin and lactated Ringer's solutions to ischemia-reperfusion injury in isolated cremaster flap

Ischemia-reperfusion (I/R) injury is a topic that has been much-discussed by various researchers during the last decade in plastic surgery. Though much progress has occurred, the problem is not totally solved yet. In particular, the pathophysiology of reperfusion injury in skeletal muscle has not been clearly elucidated. The aims of this study are to assess the effects of a variety of perfusants on the microcirculation after reperfusion injury and to better understand the pathophysiology of reperfusion injury. Isolated cremaster flaps were performed in 44 rats, preserving the femoral artery and vein in order to cannulate with microtubes. There were 2 control and 2 experiment groups. In one of the control groups and in both experimental groups, 2 h of ischemia were applied by clamping the iliac vessels. Immediately after this, the muscle was locally perfused and washed with lactated Ringer's (LR) and University of Wisconsin (UW) solutions, given from the femoral artery and drained by the femoral vein in the two respective experimental groups. The effects of these solutions to I/R injury were shown at the microcirculatory level via measuring and determining preischemic and postischemic diameters of arterioles and venules, tissue perfusion, capillary density, velocity of red blood cells, and leukocyte sticking. Both tested perfusion solutions were found to be harmful in all parameters. This study demonstrates that both LR and UW solutions aggravate I/R injury.

Role of cyclic nucleotides in ischemia and reperfusion injury of canine livers

BACKGROUND

In a series of canine liver ischemia experiments, we have shown that amelioration of hepatic injury is achievable by the inhibition of vasoconstriction, cytokine production, platelet aggregation, and neutrophil infiltration. Cyclic adenosine diphosphate (cAMP) was considered to be involved in most of these events. In our study, we tested our hypothesis that augmentation of endogenous cAMP by phosphodiesterase (PDE) 3 inhibitor, amrinone (AM), or adenylate cyclase stimulator, NKH477 (NKH), could attenuate ischemia and reperfusion injury of the liver.

METHODS

Thirty-six beagle dogs were used. They were divided into group CT (untreated control), group AM, group NKH, and group CB (treated by both agents). AM or NKH were administered i.v. 1 hr before ischemia (group preAM and group preNKH) or 15 min before reperfusion (pos-AM and postNKH). Combination group animals were treated only before ischemia. Animal survival, hepatic tissue blood flow, liver enzymes, platelet counts, energy metabolism, hepatic cAMP and cyclic guanosine 3',5'-cyclic monophosphate levels, and histopathology were analyzed.

RESULTS

Two-week animal survival was significantly improved by pre- or posttreatment with either agent. After reperfusion, hepatic tissue blood flow, liver enzyme release, platelet counts, energy metabolism, tissue cAMP levels, and histological architecture were also ameliorated markedly. Combination of both agents induced severe liver damage and lethal hypotension. AM treatment exhibited more protective effects than NKH, particularly when it was given before ischemia. Interestingly, not only cyclic guanosine 3',5'-cyclic monophosphate, were also restored at higher levels after reperfusion by preischemia treatment.

CONCLUSIONS

Administration of amrinone or NKH477 maintained hepatic tissue concentrations of cyclic nucleotides, and attenuated ischemia and reperfusion injury of the liver. Thus, regulation of hepatic tissue cyclic nucleotides is an important alternative for prevention of hepatic damage in liver preservation and surgery.

Cold-induced apoptosis of rat liver cells in University of Wisconsin solution: the central role of chelatable iron

Although University of Wisconsin (UW) solution aims at the prevention of cold-induced cell injury, it failed to protect against cold-induced apoptosis of hepatocytes and liver endothelial cells: when incubated in UW solution at 4 degrees C for 24 hours and subsequently rewarmed at 37 degrees C, 72% +/- 8% of rat hepatocytes and 81% +/- 5% of liver endothelial cells lost viability. In both cell types, the observed cell damage occurred under an apoptotic morphology; it appeared to be mediated by a rapid increase in the cellular chelatable iron pool by a factor > or =2 (as determined in hepatocytes) and subsequent formation of reactive oxygen species (ROS). Consequently, this cell injury was decreased by iron chelators to 6 to 25% (hepatocytes) and 4% +/- 2% (liver endothelial cells). Deferoxamine nearly completely inhibited the occurrence of apoptotic morphology in both cell types. In liver endothelial cells, cold-induced apoptosis occurring during rewarming after 24 hours of cold incubation in UW solution was far more pronounced than in cell culture medium (loss of viability: 81% +/- 5% vs. 28% +/- 13%), but viability could even be maintained for 2 weeks of cold incubation by use of deferoxamine. In conclusion, this pathological mechanism might be an explanation for the strong endothelial cell injury known to occur after cold preservation. With regard to the extent of this iron-mediated injury, addition of a suitable iron chelator to UW solution might markedly improve the outcome of liver preservation.

Mammalian cell injury induced by hypothermia- the emerging role for reactive oxygen species

Hypothermia is a well-known strategem to protect biological material against injurious or degradative processes and is widely used in experimental and especially in clinical applications. However, hypothermia has also proved to be strongly injurious to a variety of cell types. Hypothermic injury to mammalian cells has long been attributed predominantly to disturbances of cellular ion homeostasis, especially of sodium homeostasis. For many years, reactive oxygen species have hardly been considered in the pathogenesis of hypothermic injury to mammalian cells. In recent years, however, increasing evidence for a role of reactive oxygen species in hypothermic injury to these cells has accumulated. Today there seems to be little doubt that reactive oxygen species decisively contribute to hypothermic injury in diverse mammalian cells. In some cell types, such as liver and kidney cells, they even appear to play the central role in hypothermic injury, outruling by far a contribution of the cellular ion homeostasis. In these cells, the cellular chelatable, redox-active iron pool appears to be decisively involved in the pathogenesis of hypothermic injury and of cold-induced apoptosis that occurs upon rewarming of the cells after a (sublethal) period of cold incubation.

Reoxygenation after cold hypoxic storage of cultured precision-cut rat liver slices: effects on cellular metabolism and drug biotransformation

Cultured rat precision-cut liver slices (PCLS) were used to study the influence of hypothermic preservation and reoxygenation at 37 degrees C on cellular metabolism and drug biotransformation. Cold hypoxic storage caused a depressed metabolism in rat liver slices, but reoxygenation for 8 h at 37 degrees C partially restored the levels of both ATP and GSH and totally restored the capacity to synthesize proteins. Metabolism of midazolam (CYP3A-dependent oxidation) by cold preserved liver slices was decreased by 30% but no further affected by reoxygenation, showing the same profile as freshly cut slices. Such a reoxygenation at 37 degrees C is accompanied by a dramatic loss of CYP3A2 protein while CYP3A1 protein was unaffected. These results suggest that CYP3A2 did not play a major role in midazolam oxidation. Such results are not consistent with a putative reoxygenation injury but rather with cold hypoxic damage. Since cold preserved liver slices did not respond to bacterial endotoxin stimulation (lipopolysaccharides), a minor role of non-parenchymal cells is suggested as mediators for deleterious effects developed during the cold storage.

A role for sodium in hypoxic but not in hypothermic injury to hepatocytes and LLC-PK1 cells

BACKGROUND

Hypothermia is considered to be responsible for sodium influx during cold hypoxic incubation. However, we have previously shown that hypothermia alone leads to a pronounced decrease in cellular sodium content when liver endothelial cells or hepatocytes are incubated under such conditions. In the research described here, we therefore studied the effects of hypothermia and hypoxia, alone or combined, on cellular sodium homeostasis and assessed the role sodium plays in the pathogenesis of hypoxic and hypothermic injury to cultured liver and kidney cells.

METHODS

Isolated hepatocytes and LLC-PK1 cells were incubated in Krebs-Henseleit buffer or a sodium-free modification thereof under normoxic and hypoxic conditions at 4 degrees C as well as at 37 degrees C. Cytosolic sodium concentration was determined in isolated hepatocytes under both warm and cold conditions using digital fluorescence microscopy and the Na+-sensitive dye sodium-binding benzofuran isophthalate.

RESULTS

When hepatocytes were incubated under cold normoxic conditions the cellular sodium concentration decreased. However, it increased strongly under hypoxic conditions at 4 degrees C and at 37 degrees C. When either hepatocytes or LLC-PK1 cells were incubated under hypoxic conditions at 4 degrees C or 37 degrees C, sodium-free medium provided protection. In contrast, sodium-free medium did not alleviate the hypothermic injury observed when cells were incubated under cold normoxia.

CONCLUSIONS

The sodium influx observed during cold hypoxia is triggered by hypoxia and not by hypothermia. Sodium plays a prominent role in hypoxic injury to cultured liver and kidney cells, although hypothermic injury of these cells is independent of sodium homeostasis.

Adenosine A2 receptor stimulation protects the predamaged liver from cold preservation through activation of cyclic adenosine monophosphate-protein kinase A pathway

The shortage of organ donors has led to reconsideration for the use of non-heart-beating donors (NHBDs). However, graft injury caused by warm ischemia in livers from NHBDs strongly affects posttransplantation outcome. The aim of the present study is to investigate the role of adenosine A2 receptor with regard to hepatic viability after cold preservation of NHBD livers. Cardiac arrest was induced in Wistar rats by phrenotomy of the anesthetized nonheparinized animal. After 60 minutes, the livers were excised and flushed with 60 mL of histidine-tryptophan-ketoglutarate (HTK) and stored submerged in HTK at 4 degrees C for 24 hours. Reperfusion was performed in vitro after all livers were incubated at 22 degrees C in saline solution to account for the period of slow rewarming during surgical implantation in vivo. Addition of the selective A2-receptor agonist (CGS 21680; 30microg/100 mL) to the preservation solution resulted in a significant reduction to one quarter of the parenchymal enzyme release of alanine aminotransferase or lactate dehydrogenase on reperfusion and promoted a 2-fold increase in hepatic bile production. This salutory effect was accompanied by a significant increase (40%) in the activity ratio of protein kinase A (PKA) in the liver tissue and could be abrogated in large part by the PKA inhibitor, Rp-cAMPs. Stimulation of the adenosine A2 receptor during harvest and storage of the graft improves maintenance of tissue integrity in liver grafts. A major part of this effect, which may represent a promising approach for the use of NHBD grafts, seems to be mediated through activation of PKA.

Cold preservation of fatty liver grafts: prevention of functional and ultrastructural impairments by venous oxygen persufflation

BACKGROUND/AIMS

The incidence of steatosis in livers retrieved for organ transplantation is up to 30%. Due to the shortage of donor organs, many of these livers are accepted for clinical transplantation, although a high rate of graft dysfunction is associated with ischemic preservation of steatotic livers. The present study was intended to reduce the ischemia/reperfusion injury of steatotic grafts by the use of venous systemic oxygen persufflation during cold storage.

METHODS

A histologically-documented mild to moderate steatosis was induced in livers of Wistar rats by fasting for 2 days and subsequent feeding of a fat-free diet enriched in carbohydrates. Fatty livers were retrieved and flushed via the portal vein with 60 ml of HTK. In group A, livers were then stored ischemically at 4 degrees C for 24 h. Livers of group B were additionally connected to a gaseous oxygen supply and persufflated with O2 via the venous vascular system during the cold storage period. Viability of the livers was then assessed upon isolated perfusion in vitro with oxygenated Krebs-Henseleit buffer.

RESULTS

Venous systemic oxygen sufflation resulted in a relevant and significant reduction of parenchymal (ALT: 132+/-90 vs 434+/-172 U/l; p<0.01) and mitochondrial (GLDH: 116+/-57 vs 633+/-241 U/l; p<0.001) enzyme release during reperfusion. Moreover, Kupffer cell activation, as evaluated from acid phosphatase activity in the perfusate, was reduced to about 1/3 (4.0+/-1.3 vs 11.9+/-5.3 U/l; p<0.01). Electron microscopic analysis revealed that the liver mitochondria and sinusoidal endothelial lining were better preserved after oxygen persufflation, which was in line with the data on enzyme release and the increased portal perfusion pressure in the untreated group, while normal values were found after venous systemic oxygen sufflation.

CONCLUSION

Venous oxygen persufflation may thus represent a useful tool for the safe and improved preservation of ischemia-sensitive steatotic livers.

Formation of 8-hydroxy-2'-deoxyguanosine and 4-hydroxy-2-nonenal-modified proteins in rat liver after ischemia-reperfusion: distinct localization of the two oxidatively modified products

Ischemia-reperfusion (IR) injury is an intractable process associated not only with therapeutic recanalization of vessels, but also with partial resection or transplantation of solid organs including liver. To develop methods for predicting the degree of hepatic IR injury and further to identify injured cells, we studied the formation of 8-hydroxy-2'-deoxy-guanosine (8-OHdG) and 4-hydroxy-2-nonenal (HNE)-modified proteins in the normothermic hepatic IR model of rats using immunohistochemistry, high-performance liquid chromatography (HPLC) determination and Western blot. The Pringle maneuver for either 15 or 30 min duration produced reversible or lethal damage, respectively. The levels of both products were significantly increased in proportion to ischemia duration 40 min after reperfusion, suggesting the involvement of hydroxyl radicals. Increased immunoreactivity of 8-OHdG was observed not only in the nuclei of hepatocytes but also in those of bile canalicular and endothelial cells. However, immunoreactivity of HNE-modified proteins was detected in the cytoplasm of hepatocytes, which was confirmed by Western blot, and in addition, in the nuclei of hepatocytes after severe injury. Thus, localization of the two oxidatively modified products was not identical. Our data suggest that these two products could be used for the assessment of hepatic IR injury in tissue, but that the biological significance of the two products might be different.

A multi-laboratory evaluation of cryopreserved monkey hepatocyte functions for use in pharmaco-toxicology

Ethical, economic and technical reasons hinder regular supply of freshly isolated hepatocytes from higher mammals such as monkey for preclinical evaluation of drugs. Hence, we aimed at developing optimal and reproducible protocols to cryopreserve and thaw parenchymal liver cells from this major toxicological species. Before the routine use of these protocols, we validated them through a multi-laboratory study. Dissociation of the whole animal liver resulted in obtaining 1-5 billion parenchymal cells with a viability of about 86%. An appropriate fraction (around 20%) of the freshly isolated cells was immediately set in primary culture and various hepato-specific tests were performed to examine their metabolic, biochemical and toxicological functions as well as their ultrastructural characteristics. The major part of the hepatocytes was frozen and their functionality checked using the same parameters after thawing. The characterization of fresh and thawed monkey hepatocytes demonstrated the maintenance of various hepato-specific functions. Indeed, cryopreserved hepatocytes were able to survive and to function in culture as well as their fresh counterparts. The ability for synthesis (proteins, ATP, GSH) and conjugation and secretion of biliary acids was preserved after deep freeze storage. A better stability of drug metabolizing activities than in rodent hepatocytes was observed in monkey. After thawing, Phase I and Phase II activities (cytochrome P450, ethoxycoumarin-O-deethylase, aldrin epoxidase, epoxide hydrolase, glutathione transferase, glutathione reductase and glutathione peroxidase) were well preserved. The metabolic patterns of several drugs were qualitatively and quantitatively similar before and after cryopreservation. Lastly, cytotoxicity tests suggested that the freezing/thawing steps did not change cell sensitivity to toxic compounds.

Genetic modification of liver grafts with an adenoviral vector encoding the Bcl-2 gene improves organ preservation

BACKGROUND

Liver function after transplantation is determined by the quality of the donor organ and the influences of preservation, flush, and reperfusion injury. In this regard, cell death (apoptosis) plays an important role in organ preservation and rejection. Therefore, we examined the possibility of genetic modification of the liver graft with a recombinant adenovirus vector encoding the Bcl-2 gene to reduce apoptosis during the preservation time.

METHODS

Liver grafts from C57B1/6 mice were procured and preserved using standard techniques. A replication defective adenovirus vector (deltaE1) containing the human Bcl-2 gene (AdCMVhBcl-2) was developed in our laboratory. An adenovirus vector encoding an irrelevant gene (Escherichia coli beta-galactosidase) was used as a control. Each mouse received 1 x 10(9) plaque forming units administered i.v. 48 hr before the liver procurement. Analyses of liver enzyme activities were determined in the preservation solution. Apoptosis in liver biopsies was determined by DNA fragmentation with an in situ histochemical assay.

RESULTS

Immunohistochemical analysis and RT-PCR confirmed the expression of hBcl-2 in the grafts. Grafts from livers expressing hBcl-2 showed significant reduction of the aspartame amino transferase (AST) and lactate dehydrogenase (LDH) release compared with grafts from the control groups. After rewarming, significant cytoprotection was also observed in grafts from animals treated with AdCMVhBcl-2. Histological analysis correlated with the hepatocellular injury determined with transaminases and LDH in the preservation solution. Significant reduction in the number of apoptotic cells was observed in grafts expressing hBcl-2.

CONCLUSIONS

We have demonstrated a novel approach to reducing the preservation injury to liver grafts with the human Bcl-2 gene. This approach may allow a longer preservation time, potentially reduce the incidence of primary nonfunction, decrease the immunogenicity of the cold injured organ, and increase the safer use of "marginal" liver grafts.

Hepatoprotective effect of endogenous nitric oxide during ischemia-reperfusion in the rat

The aim of this study was to evaluate the protective or deleterious effects of endogenous nitric oxide (NO) on liver cells during hepatic ischemia-reperfusion (IR) in the rat. Injury to hepatocytes and endothelial cells was evaluated by determining cytolysis-marker activity in plasma (alanine transaminase [ALT]; aspartate transaminase [AST]) and plasma hyaluronic acid (HA) concentration. Clamping the hepatic pedicle for 45 minutes caused a significant increase in plasma AST and ALT activity after 30 minutes of reperfusion, which reached a maximum (+270% and +740%, respectively) after 6 hours of reperfusion. Plasma HA concentration was significantly higher (+130%) only after 6 hours of reperfusion. Administration of a nonselective NO synthase (NOS) inhibitor, Nomega-nitro-L-arginine (L-NNA; 10 mg/kg iv), 30 minutes before IR, caused marked aggravation of postischemic liver injury, as shown by plasma ALT and AST activity and HA concentration. This deleterious effect was partially prevented by the simultaneous injection of L-arginine, the endogenous NO precursor (100 mg/kg iv). Interestingly, L-arginine alone limited postischemic damage (AST, -25%; ALT, -45%; HA, -21% vs. untreated IR rats at 6 hours reperfusion). Pretreatment with the Guanosine 3':5'-cyclic monophosphate-independent vasodilator, prazosin, partially reversed L-NNA effects, but it did not protect untreated IR animals. Pretreatment with aminoguanidine, a selective inhibitor of inducible NOS, did not aggravate hepatic IR injury. Thus, endogenous NO, probably produced by an early and transient activation of a constitutive NOS, protects both hepatocytes and endothelial cells against liver ischemia-reperfusion injury, and this effect is not entirely a result of vasorelaxation.

Cold-induced apoptosis in cultured hepatocytes and liver endothelial cells: mediation by reactive oxygen species

When cultured hepatocytes were incubated in cell culture medium at 4 degreesC for up to 30 h and then returned to 37 degreesC, blebbing of the plasma membrane, cell detachment, chromatin condensation and margination, enhanced nuclear stainability with Hoechst 33342, ruffling of the nuclear membrane, and DNA fragmentation occurred. Similar to hepatocytes, cultured liver endothelial cells exhibited blebbing, chromatin condensation and margination, marked nuclear condensation, and increased stainability with Hoechst 33342 when exposed to hypothermia/rewarming. In both cell types, the occurrence and extent of these alterations were dependent on the duration of the cold incubation period. This cold-induced apoptosis was inhibited by hypoxia, by an array of free radical scavengers/antioxidants, and by iron chelators. However, the extent of the protection by the different antioxidants was different in the two cell types: iron chelators provided complete protection in liver endothelial cells but only partial protection in hepatocytes, whereas lipophilic antioxidants such as alpha-tocopherol provided complete protection in both cell types. During cold incubation, and especially during rewarming, lipid peroxidation occurred. These results suggest that the formation of reactive oxygen species (ROS) is a key mediator of cold-induced apoptosis, with ROS formation being completely iron-mediated in liver endothelial cells and partially iron-mediated in hepatocytes.

Hypothermic oscillating liver perfusion stimulates ATP synthesis prior to transplantation

BACKGROUND

ATP and glycogen depletion often have been demonstrated during cold storage of the liver prior to transplantation. Suppression of events that lead to metabolic depression and to lipid peroxidation could contribute to improvement of liver preservation. A new method of liver preservation for transplantation is therefore suggested, an oscillating oxygenated hypothermic liver perfusion.

METHODS

Biochemical analysis of liver tissue samples and perfusate after 10 h of perfusion by the presented oscillating perfusion model were compared with results after continuous liver perfusion for 10 h as well as with data derived from cold-stored livers over a period of 10 h. Particular reference was made to nucleotide metabolites, glycogen content, lipid peroxidation, glutathione content, glycolytic metabolites, and enzyme release before and after preservation.

RESULTS

Glycogen depletion occurred to the same degree in hypothermic storage and machine perfusion (oscillating as well as continuous perfusion), but the energy charge was significantly increased after oxygenated perfusion, whereas cold storage resulted in a significant energy charge depletion. In addition, perfusion by an oscillating technique yielded superior energy charge loading compared to the continuous perfusion technique and diminished the other hand lipid peroxidation.

CONCLUSIONS

Hypothermic oscillating oxygenated perfusion could be important for the improvement of the quality of energy-depleted organs prior to transplantation.

Cold-induced release of reactive oxygen species as a decisive mediator of hypothermia injury to cultured liver cells

The mechanisms of hypothermia-induced cell injury are still unclear. The present study provides experimental evidence for the involvement of reactive oxygen species in hypothermia injury: cultured rat hepatocytes incubated in cold (4 degrees C) Krebs-Henseleit buffer or cell culture medium were injured under normoxic conditions and even more so under hyperoxic conditions, whereas the hepatocytes were protected under hypoxic conditions. During warm (37 degrees C) incubation in cell culture medium, on the other hand, cell injury was minimal under normoxic conditions, only slightly increased under hyperoxic conditions, but substantially increased under hypoxic conditions. The injury occurring during cold normoxic incubation was also largely decreased by the addition of the spin-trap 5,5-dimethyl-1-pyrroline N-oxide, the hydroxyl radical scavenger dimethyl sulfoxide, the flavonoid silibinin, or the transition metal chelator 2,2'-dipyridyl to the medium, or by preincubating the cells with the iron chelator deferoxamine or the lipophilic antioxidant alpha-tocopherol before the hypothermic incubation. In addition, marked lipid peroxidation was observed during cold incubations without inhibitors, but not during warm incubations. Similar results were obtained with cultured rat liver endothelial cells. These results suggest that in hepatocytes and in liver endothelial cells, cold-induced release of reactive oxygen species, most likely of hydroxyl radicals, is the main injurious factor under hypothermic conditions.

Rat liver preservation by hypothermic oscillating liver perfusion compared to simple cold storage

Rat livers were preserved hypothermically for 10 or 24 h in vitro as if for transplantation. Two methods of preservation were compared using physiological and biochemical parameters: simple storage and oscillating perfusion. By measuring the nucleotides after preservation the calculated energy charge was significantly higher after 10 and 24 h of oscillating perfusion compared to the simple storage group. In addition, a significant energy charge loading was demonstrated by 10 h oscillating perfusion compared to the initial value prior to perfusion. The oscillating, computer-controlled perfusion permits continuous monitoring of perfusate temperature, O2 consumption, pCO2, portal vein pressure, and pH and also automatic sample collection and pH compensation. In addition, the perfusate can be easily exchanged by using two different pumps or be rewarmed by a heat exchanger. For measuring of short-lived metabolites (interleukins, oxygen radicals, prostaglandins) sampling can be performed directly out of the vena cava outflow. pH and temperature stability was maintained by a data acquisition and controlling system. Because of a special designed liver chamber a combination of storage and perfusion with or without substrates was possible. The demonstrated standardized perfusion technique was achieved by a combination of special equipment and computer-aided monitoring and allows further experiments to improve understanding of ischemic and reperfusion injury.

Organ preservation with EC, HTK, and UW solutions in orthotopic liver transplantation in syngeneic rats. Part I: Functional parameters

Ischemic injury to the liver is known to influence the outcome of liver transplantation. In this study the efficacy of Euro-Collins (EC), histidine-tryptophan-ketoglutarate (HTK), and University of Wisconsin (UW) preservation solution was analyzed in the model of orthotopic liver transplantation in syngeneic rats. The study design was as follows: Group I, Euro-Collins solution (n = 11); Group II, Histidine-Tryptophan-Ketoglutarate solution (n = 11); Group III, University of Wisconsin solution (n = 11). The rat liver transplantation was performed with arterialization of the graft as described by Engemann. The postoperative follow-up was 28 days. The perfusion flow rate of the preservation solution measured during organ perfusion revealed lowest levels in the UW group and comparable levels in Groups I and II. Postoperative graft function was monitored by measuring liver enzymes (aspartate amino-transferase, ASAT, alanine aminotransferase, ALAT), bilirubin and bile production. The survival rate was 10/11 in each group. Liver enzymes and bilirubin increased postoperatively and went back to normal within 2 or 3 weeks. In contrast to bilirubin, the liver enzymes showed a biphasic increase with maxima on the 1st and 5th days (range: ALAT, 220-264 U/L; ASAT, 145-177 U/L). Bile production was observed in all groups, but was significantly higher after UW-preservation (P < .005). Analysis of inflammatory cells revealed high concentrations of intrasinusoidal leukocytes and lymphocytes in the graft with a maximum on the 5th day.

Ischaemia-reperfusion injury of the liver: treatment in theory and in practice

Cold ischaemia-reperfusion injuries are an unavoidable feature of current liver transplantation procedures. Damage to liver grafts accures mainly from hypothermic storage under hypoxic conditions (cold ischaemia), from sustained ischaemia during implantation into the recipient (rewarming ischaemia) and from restoration of blood and oxygen to the graft (reperfusion injury). These three stages are characterized by progressive deteriorations in hepatic function, with sinusoidal endothelial cells most affected during cold ischaemia. Activation of Kupffer cells (hepatic macrophages) at reperfusion augments damage to both endothelial and parenchymal cells by the release of numerous compounds which initiate and perpetrate injury and impair the hepatic microcirculation. The key events in the expression of ischaemia-reperfusion injury are detailed and therapeutic interventions are described which target these steps. The treatments discussed include University of Wisconsin (UW) preservation solution, calcium channel blockade, inhibitors of Kupffer cell activation, promoters of microvascular vasodilation, hepatoprotectants and the use of anti-oxidants.

Preservation of pig liver allografts after warm ischemia: normothermic perfusion versus cold storage

Warm ischemia is known to induce substantial damage to the liver parenchyma. With respect to clinical liver transplantation, the tolerance of the liver to warm ischemia and the preservation of these organs have not been studied in detail. In isolated reperfused pig livers we proceeded according to the following concept: Livers were subjected to 1 or 3 h of warm ischemia. Subsequently, these organs were preserved by either normothermic perfusion or cold storage (histidine-tryptophan-alpha-ketoglutarate, HTK) for 3 h each. After storage, liver function was assessed in a reperfusion circuit for another 3 h. Parameters under evaluation were bile flow, perfusion flow, oxygen consumption, enzyme release into the perfusate (creatine kinase, glutamic oxaloacetic transaminase (GOT), lactic dehydrogenase, and glutamic pyruvic transaminase), and histomorphology. Damage to the liver was lowest after warm ischemia of 1 h. The results after cold storage were superior to those after normothermic perfusion (GOT: 3.2 +/- 0.3 and 2.6 +/- 0.2 U/g liver; cumulative bile production: 14.7 +/- 2.1 and 9.4 +/- 1 ml, respectively; P < 0.05). In contrast, we found substantial damage at the end of reperfusion in livers undergoing 3 h of warm ischemia under both preservation techniques with severe hepatocellular pyknoses and essentially altered nonparenchymal cells. The results suggest that pig livers undergoing 1 h of warm ischemia and cold storage for 3 h with HTK solution may lead to functioning after transplantation.

Involvement of reactive oxygen species in the preservation injury to cultured liver endothelial cells

We have previously demonstrated an energy-dependent injury to cultured liver endothelial cells during cold incubation in University of Wisconsin (UW) solution. In the present study, we report experimental evidence for the involvement of reactive oxygen species in this injury: LDH release during 48 h of cold incubation in UW solution was decreased from 40-55% under aerobic conditions to less than 20% under hypoxic conditions or by the presence of KCN (1 mM). Similar protection was achieved by the addition of the spin trap 5,5-dimethyl-1-pyrroline N-oxide, the hydroxyl radical scavenger dimethyl sulfoxide, or the flavonoid silibinin to UW solution under aerobic conditions. Preincubating the cells with the iron chelator deferoxamine even decreased the injury to less than 5%. The residual injury (as observed after longer incubation times) under hypoxic conditions or in cells preincubated with deferoxamine was no longer energy dependent. The amount of thiobarbituric acid-reactive substances markedly increased during cold incubation of the cells in UW solution. This increase was not observed in UW solution to which KCN had been added, i.e., under the conditions of energy depletion. These results suggest that an iron-dependent generation of reactive oxygen species with subsequent lipid peroxidation is involved in the pathogenesis of the injury to cultured liver endothelial cells in cold UW solution.

Protective effect of UW solution on postischemic injury in rat liver: suppression of reduction in hepatic antioxidants during reperfusion

Preservation with University of Wisconsin (UW) solution can maintain liver graft function and produces survival rates of recipients higher than that with Euro Collins (EC) solution. To explore the underlying mechanisms, we transplanted rat livers following cold preservation with EC or UW solution for 18 hr, and measured hepatic adenine nucleotide levels, the percentage of water content, lactate levels, and endogenous antioxidant levels (alpha-tocopherol [alpha-Toc], reduced coenzyme Q9 [CoQ9H2], reduced coenzyme Q10, [CoQ1OH2] and reduced glutathione [GSH] during preservation and after transplantation. The adenosine triphosphate levels of the liver grafts preserved with UW solution recovered after reperfusion more rapidly and reached a higher level than those preserved with EC solution. UW solution caused a reduction in hepatic water content during preservation. Conversely, EC solution induced remarkable tissue edema. In addition, UW solution reduced the rate of hepatic lactate production both during preservation and after reperfusion. The concentrations of hepatic GSH, alpha-Toc, CoQ9H2, and CoQ1OH2 immediately after the graftectomy, and after the 18 hr of preservation with both EC and UW solutions, did not differ from those in the normal liver, and decreased only after transplantation. However, UW solution suppressed significantly the reduction in hepatic GSH, alpha-Toc, and CoQ9H2 after reperfusion, compared with EC solution. These results suggest that long-term cold storage induces tissue edema, reflecting a disturbance of the microcirculation during preservation, followed by parenchymal cell damage mediated by free radicals after reperfusion. The protective effects of UW solution could be attributable to the inhibition of free radical production after reperfusion.

Therapeutic modulation of free radical-mediated reperfusion injury of the liver and its surgical implications

It is well known that ischemia causes functional and structural damage to liver cells, and that the status of energy metabolism provides an important means of assessing the functional viability of the ischemic organ. However, the specific sequence leading to ischemic liver cell injury is not yet fully understood; therefore, it is clinically and pathophysiologically important to elucidate the mechanism of cellular injury during hepatic ischemia and subsequent reperfusion. Whereas the conventional view attributes this injury process to the ischemia itself, recent studies have demonstrated that a variable but often substantial proportion of this injury is caused by reactive oxygen metabolites that are generated at the time of reperfusion. This article presents an outline of the mechanism of cellular injury caused during hepatic ischemia and subsequent reperfusion resulting from certain types of surgery, with special reference to the xanthine-xanthine oxidase system and the activation of neutrophils and macrophages.