Hypothermia inhibits Fas-mediated apoptosis of primary mouse hepatocytes in culture

Effect of mild hypothermia preconditioning against low temperature (4°C) induced rat liver cell injury in vitro

Bioartificial liver holds special position in the field of regenerative medicine, and cold environment at 4℃ is widely used for the short storage of both organ and liver cell for later application. However, the disadvantages of such cold storage could influence cell viability and lead to cell apoptosis in different degrees. In this study, we mainly explore the pre-protective effect of mild hypothermia against low temperature (4℃)-induced rat liver cell injury in vitro. Our results indicated that the precondition with mild hypothermia could increase cell viability, such as cell proliferation, LDH regulation and glycogen synthesis ability of liver cell. The precondition also decreased the ROS production and relieved cell apoptosis in liver cells. Compared with the model group, the mitochondrial membrane potential was restored in the mild hypothermia group, as well as the mitochondrial membrane permeability transition pore opening, indicating that the therapeutic mechanism was related to mitochondrial protection. Further analysis showed that PI3K-Akt-GSK3β signal pathway might be associated with the pre-protective effect of mild hypothermia. Thus, our study suggested that the precondition with mild hypothermia hold the protective effect for liver cell in cold environment, and further developed a novel strategy for the storage of liver seed cells, even bioartificial liver.

Experimental models of hepatotoxicity related to acute liver failure

Acute liver failure can be the consequence of various etiologies, with most cases arising from drug-induced hepatotoxicity in Western countries. Despite advances in this field, the management of acute liver failure continues to be one of the most challenging problems in clinical medicine. The availability of adequate experimental models is of crucial importance to provide a better understanding of this condition and to allow identification of novel drug targets, testing the efficacy of new therapeutic interventions and acting as models for assessing mechanisms of toxicity. Experimental models of hepatotoxicity related to acute liver failure rely on surgical procedures, chemical exposure or viral infection. Each of these models has a number of strengths and weaknesses. This paper specifically reviews commonly used chemical in vivo and in vitro models of hepatotoxicity associated with acute liver failure.

Hypothermic storage of human hepatocytes for transplantation

Transplantation of human hepatocytes is gaining recognition as a bridge or an alternative to orthotopic liver transplantation for patients with acute liver failure and genetic defects. Since most patients require multiple cell infusions over an extended period of time, we investigated hepatic functions in cells maintained in University of Wisconsin solution at 4°C up to 72 h. Eleven different assessments of hepatic viability and function were investigated both pre- and posthypothermic storage, including plating efficiency, caspase-3/7 activity, ammonia metabolism, and drug-metabolizing capacity of isolated hepatocytes. Long-term function, basal, and induced cytochrome P450 activities were measured after exposure to prototypical inducing agents. Cells from 47 different human liver specimens were analyzed. Viability significantly decreased in cells cold stored in UW solution, while apoptosis level and plating efficiency were not significantly different from fresh cells. Luminescent and fluorescent methods assessed phases I and II activities both pre- and post-24-72 h of cold preservation. A robust induction (up to 200-fold) of phase I enzymes was observed in cultured cells. Phase II and ammonia metabolism remained stable during hypothermic storage, although the inductive effect of culture on each metabolic activity was eventually lost. Using techniques that characterize 11 measurements of hepatic viability and function from plating efficiency, to ammonia metabolism, to phases I and II drug metabolism, it was determined that while viability decreased, the remaining viable cells in cold-stored suspensions retained critical hepatic functions for up to 48 h at levels not significantly different from those observed in freshly isolated cells.

Establishment and Characterization of an In Vitro Model of Fas-Mediated Hepatocyte Cell Death

Fas-mediated apoptosis underlies a plethora of liver pathologies and toxicities. As a consequence, this process is a major research topic in the field of experimental and clinical hepatology. The present chapter describes the setup of an in vitro model of hepatocellular apoptotic cell death. In essence, this system consists of freshly isolated hepatocytes cultured in a monolayer configuration, which are exposed to a combination of Fas ligand and cycloheximide. This in vitro model has been characterized by using a set of well-acknowledged cell death markers. This experimental system allows the study of the entire course of Fas-mediated hepatocellular cell death, going from early apoptosis to secondary necrosis, and hence can serve a broad range of in vitro pharmaco-toxicological purposes.

Mechanisms of Acute Liver Failure

Acute liver failure (ALF) is characterized by the sudden onset of liver failure in a patient without evidence of chronic liver disease. This definition is important, as it differentiates patients with ALF from patients who suffer from liver failure owing to end-stage chronic liver disease [1].

Primary hepatocytes and their cultures in liver apoptosis research

Apoptosis not only plays a key role in physiological demise of defunct hepatocytes, but is also associated with a plethora of acute and chronic liver diseases as well as with hepatotoxicity. The present paper focuses on the modelling of this mode of programmed cell death in primary hepatocyte cultures. Particular attention is paid to the activation of spontaneous apoptosis during the isolation of hepatocytes from the liver, its progressive manifestation upon the subsequent establishment of cell cultures and simultaneously to strategies to counteract this deleterious process. In addition, currently applied approaches to experimentally induce controlled apoptosis in this in vitro setting for mechanistic research purposes and thereby its detection using relevant biomarkers are reviewed.

Facts and fiction: the impact of hypothermia on molecular mechanisms following major challenge

Numerous multiple trauma and surgical patients suffer from accidental hypothermia. While induced hypothermia is commonly used in elective cardiac surgery due to its protective effects, accidental hypothermia is associated with increased posttraumatic complications and even mortality in severely injured patients. This paper focuses on protective molecular mechanisms of hypothermia on apoptosis and the posttraumatic immune response. Although information regarding severe trauma is limited, there is evidence that induced hypothermia may have beneficial effects on the posttraumatic immune response as well as apoptosis in animal studies and certain clinical situations. However, more profound knowledge of mechanisms is necessary before randomized clinical trials in trauma patients can be initiated.

Hypothermic storage of hepatocytes used for bioartificial liver support system: current status and recent advances

The problem that high-quality hepatocytes are difficult to obtain restricts the use of bioartificial liver support system (BLASS) in clinical practice. Finding an effective way to preserve hepatocytes and constructing a "ready-to-use" hepatocyte bank would efficiently promote the development of the BLASS. Nowadays, the methods for hypothermic storage of hepatocytes could be classified into two types: conventional hypothermic storage at 4 °C or subzero nonfreezing storage, and cryopreservation at -80 °C or -196 °C. Each type of hypothermic storage method has its advantages and disadvantages. Many factors may affect the effect of hypothermic storage (cryopreservation), such as storage solution and cryoprotective agent. Although the precise mechanism underlying the death of hepatocytes during hypothermic storage is not well understood, numerous studies have indicated that apoptosis plays an important role in hypothermic storage injury.

Subzero nonfreezing storage of C3A hepatocytes for use in bioartificial liver support systems

AIM: To investigate whether subzero nonfreezing storage (-0.8 °C) is superior to conventional cold storage in preservation of C3A hepatocytes for use in bioartificial liver support systems.

METHODS: C3A hepatocytes suspended in University of Wisconsin (UW) solution were divided into three groups: subzero nonfreezing group (-0.8 °C), zero nonfreezing group (0 °C) and control group (4 °C). After 24, 48 and 72 hours of hypothermic storage, cell viability and apoptosis were detected by flow cytometry; intracellular adenosine triphosphate (ATP) content, lactate dehydrogenase (LDH) release, lactic acid production, urea synthesis and albumin secretion were determined; and cell morphological changes were observed.

RESULTS: Compared to the zero nonfreezing group and the control group, after 72 hours of hypothermic storage, the percentage of viable C3A hepatocytes was significantly higher (86.49% ± 2.80% vs 81.50% ± 2.83% and 77.83% ± 3.40%, respectively; both P < 0.05), and cell apoptosis rate was significantly lower (1.26% ± 0.84% vs 5.34% ± 1.20% and 9.16% ± 1.99%, respectively; both P < 0.05) in the subzero nonfreezing group. Lactic acid and LDH production was more significantly suppressed (lactic acid: 10.38 μg/10⁶ cells ± 1.40 μg/10⁶ cells vs 12.02 μg/10⁶ cells ± 1.64 μg/106 cells and 17.41 μg/10⁶ cells ± 2.40 μg/10⁶ cells; LDH: 80.10 U/L ± 11.10 U/L vs 120.04 U/L ± 14.32 U/L and 148.98 U/L ± 15.37 U/L, respectively; all P < 0.05), and the ability of hepatocytes to synthesize urea and secrete albumin was better maintained in the subzero nonfreezing group (both P < 0.05). Moreover, cells in the subzero nonfreezing storage group had lower death rate and better cellular morphology. A burr-like structure around the cell membrane and an intracellular vacuole-like structure were found in cells in the zero nonfreezing group and the control group, but not in the subzero nonfreezing group.

CONCLUSION: Subzero nonfreezing storage (-0.8 °C) of hepatocytes to construct a "ready-to-use" hepatocyte bank like the "blood bank" will efficiently promote the development of bioartificial liver support systems.

Hypothermia in bleeding trauma: a friend or a foe?

The induction of hypothermia for cellular protection is well established in several clinical settings. Its role in trauma patients, however, is controversial. This review discusses the benefits and complications of induced hypothermia--emphasizing the current state of knowledge and potential applications in bleeding patients. Extensive pre-clinical data suggest that in advanced stages of shock, rapid cooling can protect cells during ischemia and reperfusion, decrease organ damage, and improve survival. Yet hypothermia is a double edged sword; unless carefully managed, its induction can be associated with a number of complications. Appropriate patient selection requires a thorough understanding of the pre-clinical literature. Clinicians must also appreciate the enormous influence that temperature modulation exerts on various cellular mechanisms. This manuscript aims to provide a balanced view of the published literature on this topic. While many of the advantageous molecular and physiological effects of induced hypothermia have been outlined in animal models, rigorous clinical investigations are needed to translate these promising findings into clinical practice.

In vivo study of HCV in mice with chimeric human livers

Estimates of hepatitis C virus infection include 170 million people worldwide, who face increased risk of development of cirrhosis, liver failure, and hepatocellular carcinoma. Standard of care therapy with pegylated interferon and ribavirin is effective in just half of patients, is challenged by substantial treatment-related morbidity, and is prohibitively expensive in most parts of the world. New therapeutics for treatment and prevention are clearly needed. Development of effective therapies has been significantly hampered by difficulties in establishing in vitro and in vivo models of viral replication. This chapter reviews development, validation, and early application of a mouse model with a chimeric human liver.

Biochemical characterisation of an in vitro model of hepatocellular apoptotic cell death

This study was set up to critically evaluate a commonly-used in vitro model of hepatocellular apoptotic cell death, in which freshly isolated hepatocytes, cultured in a monolayer configuration, are exposed to a combination of Fas ligand and cycloheximide for six hours. A set of well-acknowledged cell death markers was addressed: a) cell morphology was studied by light microscopy; b) apoptotic and necrotic cell populations were quantified by in situ staining with Annexin-V, Hoechst 33342 and propidium iodide (PI); c) apoptotic and necrotic activities were monitored by probing caspase 3-like activity and measuring the extracellular leakage of lactate dehydrogenase (LDH), respectively; and d) the expression of apoptosis regulators was investigated by immunoblotting. The initiation of apoptosis was evidenced by the activation of caspase 8 and caspase 9, and increased Annexin-V reactivity. Progression through the apoptotic process was confirmed by the activation of caspase 3 and Bid, the enhanced expression of Bax, and the occurrence of nuclear fragmentation. Late transition to a necrotic appearance was demonstrated by an increased number of PI-positive cells and augmented extracellular release of LDH. Thus, the in vitro model allows the study of the entire course of Fas-mediated hepatocellular apoptotic cell death, which is not possible in vivo. This experimental system can serve a broad range of in vitro pharmaco-toxicological purposes, thereby directly assisting in the reduction of animal experimentation.

Inhibition of oxidative stress and apoptosis enables extended maintenance of integrity and function of isolated hepatocytes in suspension

AIMS

Isolated hepatocytes in suspension may offer an alternative culture system for bioartificial liver devices. However, maintenance of isolated hepatocyte suspensions in conventional media leads to rapid loss of cell integrity. The aim of this study was to develop a modified medium to better maintain hepatocyte integrity.

METHODS

Isolated rat hepatocytes were prepared by collagenase digestion. Hepatocytes were purified in a Percoll gradient, suspended in bicarbonate buffered isotonic saline supplemented with d-alpha-tocopherol succinate and glucose and medium changed at 24 h (modified medium). The properties of cells treated this way were compared with those prepared by collagenase digestion and suspension in bicarbonate buffered isotonic saline (basic medium). Both media were maintained at 30 degrees C for 48 h on an orbital shaker. Markers for oxidative stress, apoptosis and metabolic function were measured enzymatically. Cell morphology was assessed by electron microscopy.

RESULTS

When compared to collagenase-isolated hepatocytes maintained in basic medium, hepatocytes purified by Percoll (Amersham Biosciences, Castle Hill, Australia) and maintained in modified medium demonstrated significantly increased glutathione (GSH) and GSH : glutathione disulphide (GSSH) ratios, decreased lipid peroxidation product formation, decreased caspase-3 protease activity, reduced uptake of trypan blue and loss of lactate dehydrogenase (LDH) and increase preservation of cellular adenosine triphosphate concentration ([ATP]), urea synthesis, ammonia removal and glycogen content. Cell morphology was substantially preserved following 48 h of maintenance in the modified medium.

CONCLUSIONS

The use of Percoll and modified medium reduces cell injury and apoptosis and greatly improves maintenance of cell function and morphology. The modifications reported here and the use of isolated hepatocyte suspensions in bioartificial liver devices are worthy of further investigation.

Evaluation of drug-metabolizing and functional competence of human hepatocytes incubated under hypothermia in different media for clinical infusion

Hepatocyte transplantation has been proposed as a method to support patients with liver insufficiency. Key factors for clinical cell transplantation to progress is to prevent hepatocyte damage, loss of viability and cell functionality, factors that depend on the nature of the tissue used for isolation to a large extent. The main sources of tissue for hepatocyte isolation are marginal livers that are unsuitable for transplantation, and segments from reduced cadaveric grafts. Hepatocellular transplantation requires infusing human hepatocytes in suspension over a period of minutes to hours. The beneficial effect of hypothermic preservation of hepatocytes in infusion medium has been reported, but how critical issues towards the success of cell transplantation, such as the composition of infusion medium and duration of hepatocyte storage will affect hepatocyte quality for clinical cell infusion has not been systematically investigated. Infusion media composition is phosphate-buffered saline containing anticoagulants and human serum albumin. The supplementation of infusion media with glucose or N-acetyl-cystein, or with both components at the same time, has been investigated. After isolation, hepatocytes were suspended in each infusion medium and a sample at the 0 time point was harvested for cell viability and functional assessment. Thereafter, cells were incubated in different infusion media agitated on a rocker platform to simulate the clinical infusion technique. The time course of hepatocyte viability, funtionality (drug-metabolizing enzymes, ureogenic capability, ATP, glycogen, and GSH levels), apoptosis (caspase-3 activation), and attachment and monolayer formation were analyzed. The optimal preservation of cell viability, attaching capacity, and functionality, particularly GSH and glycogen levels, as well as drug-metabolizing cytochrome P450 enzymes, was found in infusion media supplemented with 2 mM N-acetyl-cystein and 15 mM glucose.

Hepatocyte apoptosis

Apoptosis has been documented as a frequent hurdle phenomenon that occurs in human hepatocytes during isolation, storage, infusion and after engraftment within the recipient liver parenchyma. Apoptosis is an active form of cell death that involves programmed cellular machineries leading to a progressive self-destruction of the cell. In contrary to necrosis, it can affect individual cells within a cell population. It is characterized by chronological alteration of intracellular biochemical signaling pathways followed by cellular morphological changes, DNA fragmentation, perturbation of mitochondrial membrane function and changes in the plasma membrane. These cellular alterations can be analyzed using different methodologies on adherent, suspended and in situ engrafted hepatocytes. This chapter presents a brief overview of these techniques and provides methodology for the evaluation of hepatocyte apoptosis at the structural and biochemical levels.

FasL shedding is reduced by hypothermia in experimental stroke

Protection by mild hypothermia has previously been associated with better mitochondrial preservation and suppression of the intrinsic apoptotic pathway. It is also known that the brain may undergo apoptotic death via extrinsic, or receptor-mediated pathways, such as that triggered by Fas/FasL. Male Sprague-Dawley rats subjected to 2 h middle cerebral artery occlusion with 2 h intraischemic mild hypothermia (33 degrees C) were assayed for Fas, FasL and caspase-8 expression. Ischemia increased Fas, but decreased FasL by approximately 50-60% at 6 and 24 h post-insult. Mild hypothermia significantly reduced expression of Fas and processed caspase-8 both by approximately 50%, but prevented ischemia-induced FasL decreases. Fractionation revealed that soluble/shed FasL (sFasL) was decreased by hypothermia, while membrane-bound FasL (mFasL) increased. To more directly assess the significance of the Fas/FasL pathway in ischemic stroke, primary neuron cultures were exposed to oxygen glucose deprivation. Since FasL is cleaved by matrix metalloproteinases (MMPs), and mild hypothermia decreases MMP expression, treatment with a pan-MMP inhibitor also decreased sFasL. Thus, mild hypothermia is associated with reduced Fas expression and caspase-8 activation. Hypothermia prevented total FasL decreases, and most of it remained membrane-bound. These findings reveal new observations regarding the effect of mild hypothermia on the Fas/FasL and MMP systems.

The extrinsic and intrinsic apoptotic pathways are differentially affected by temperature upstream of mitochondrial damage

It is well known that mild hypothermia prevents neuronal cell death following cerebral ischemia, although it can also cause apoptosis in other cell types. Thus, incubation at room temperature (RT) has been shown to induce apoptosis in hematopoietic cells, including Jurkat T leukemia cells. To further understand the apoptotic events that can be activated at RT, we compared the induction of apoptosis by several apoptotic insults in Jurkat cells stimulated at 37 degrees C or RT. Retinoid-related molecules, which induce apoptosis via the intrinsic pathway, failed to induce apoptosis when cells were treated at RT, as determined by various apoptotic parameters including cytochrome c release and activation of caspase 3. In contrast, most apoptotic events were enhanced by lower temperatures when cells were stimulated with anti-Fas antibody via the extrinsic pathway. Ultraviolet radiation produced partial effects at RT, correlating with its capacity to activate both pathways. Our results indicate that the core caspase machinery is operational under mild hypothermia conditions. Experiments using purified recombinant caspases and cell-free assays confirmed that caspases are fully functional at RT. Other hallmark events of apoptosis, such as phosphatidylserine externalization and formation of apoptotic bodies were variably affected by RT in a stimulus-dependent manner, suggesting the existence of critical steps that are sensitive to temperature. Thus, analysis of apoptosis at RT might be useful to (i) discriminate between the extrinsic and intrinsic pathways in Jurkat cells treated with prospective stimuli, and (ii) to unravel temperature-sensitive steps of apoptotic signaling cascades.

Mechanisms of Acute Liver Failure

Acute liver failure is characterized by the sudden onset of liver failure in a patient without evidence of chronic liver disease. This definition is important, as it differentiates patients with acute liver failure from patients who suffer from liver failure owing to end-stage chronic liver disease.

Mild hypothermia attenuates liver injury and improves survival in mice with acetaminophen toxicity

BACKGROUND & AIMS

Body temperature may critically affect mechanisms of liver injury in acetaminophen (APAP) hepatotoxicity. In addition, mild hypothermia is used to treat intracranial hypertension in human liver failure without detailed information on its effects on the injured liver itself. Therefore, we investigated the effects of body temperature on the progression of APAP-induced liver injury in mice.

METHODS

Male C57BL6 mice treated with saline or APAP (300 mg/kg intraperitoneally) were maintained at normothermia (35.5-37.5 degrees C) by external warming or were allowed to develop mild hypothermia (32.0-35.0 degrees C) after 2 hours from APAP administration.

RESULTS

Mild hypothermia resulted in improved survival after APAP intoxication. Liver damage was reduced, as assessed histologically and by plasma alanine aminotransferase levels. Early effects of hypothermia included a reduction of hepatic congestion and improved recovery of glycogen stores. At later time points (8-12 hours), APAP-treated mice that were maintained at normothermia manifested increased hepatocyte apoptosis, as assessed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining and cleavage of poly(adenosine diphosphate-ribose) polymerase. Mild hypothermia did not affect the formation of APAP-protein adducts or the depletion of glutathione, nor did it abrogate hepatocyte DNA synthesis.

CONCLUSIONS

Mild hypothermia improved survival and attenuated liver injury and apoptosis in APAP-treated mice by reducing hepatic congestion and improving glycogen recovery without affecting hepatic regeneration. Results of the study underscore the need for a strict control of body temperature in animal models of liver failure and suggest that the benefits of mild hypothermia in liver failure may extend beyond those related to reduced cerebral complications.

Mild hypothermia reduces the inflammatory response and hepatic ischemia/reperfusion injury in rats

BACKGROUND/AIMS

Hypothermia is known to protect against ischemia/reperfusion (I/R) injury. The mechanisms of protection are incompletely understood and a temperature threshold for protection has not been established.

METHODS

In anesthetized Wistar rats, partial (70%) hepatic ischemia was applied for 45 min. Three study groups were used. Group T31 (n = 6) spontaneously cooled to 31.3 +/- 0.8 degrees C, while group T34 (n = 6) spontaneously cooled to 34 degrees C and was then maintained at 34.0 +/- 0.1 degrees C using a heat lamp. The normothermic group (T37, n = 6) was maintained at 37.1 +/- 0.3 degrees C. Hepatic injury, inflammation, lipid peroxidation and metabolic function (using quantitative 1H-NMR) were assessed 24 h after reperfusion.

RESULTS

At 24 h following reperfusion, alanine aminotransferase and aspartate aminotransferase increased to 5101 +/- 2378 and 6409 +/- 4202 U/l in the normothermic T37 group (P < 0.05 vs. T34 and T31), whereas transaminases in hypothermic groups (T31 and T34) were significantly lower. Severe liver necrosis was only noted with T37. Myeloperoxidase activity was increased in the T37 group when compared with hypothermic groups (223 +/- 161 (T37) vs. 16 +/- 10 (T31) and 8 +/- 5 (T34) mU/min/mg of tissue, P<0.05 vs. T31 and T34). 1H-NMR analysis of the blood of normothermic animals revealed metabolic changes consistent with increased ischemic injury, which was almost completely ameliorated in T34 and T31 groups.

CONCLUSIONS

Mild hypothermia of 34 degrees C is sufficient to reduce I/R injury by inhibiting the inflammatory response. Further spontaneous cooling to 31 degrees C did not demonstrate any additional protective effect.

Cirp protects against tumor necrosis factor-alpha-induced apoptosis via activation of extracellular signal-regulated kinase

Mild hypothermia shows protective effects on patients with brain damage and cardiac arrest. To elucidate the molecular mechanisms underlying these effects, we analyzed the effects of low culture temperature (32 degrees C) and cold-inducible RNA-binding protein (Cirp) expression on apoptosis in vitro. In BALB/3T3 cells treated with tumor necrosis factor (TNF)-alpha and cycloheximide, the down-shift in temperature from 37 degrees C to 32 degrees C increased the expression of Cirp and suppressed the apoptosis. Activation of caspase-8 was suppressed, and the level of phosphorylated extracellular signal-regulated kinase (ERK) was increased. Transduction of Cirp into the Cirp-deficient mouse fibroblasts increased the level of phosphorylated ERK and suppressed the TNF-alpha-induced apoptosis both at 37 degrees C and 32 degrees C. The ERK-specific inhibitor PD98059 decreased the cytoprotective effect of Cirp as well as that of low culture temperature. These data suggest that mild hypothermia protects cells from TNF-alpha-induced apoptosis, at least partly, via induction of Cirp, and that Cirp protects cells by activating the ERK pathway.

Keeping cool in acute liver failure: rationale for the use of mild hypothermia

Encephalopathy, brain edema and intracranial hypertension are neurological complications responsible for substantial morbidity/mortality in patients with acute liver failure (ALF), where, aside from liver transplantation, there is currently a paucity of effective therapies. Mirroring its cerebro-protective effects in other clinical conditions, the induction of mild hypothermia may provide a potential therapeutic approach to the management of ALF. A solid mechanistic rationale for the use of mild hypothermia is provided by clinical and experimental studies showing its beneficial effects in relation to many of the key factors that determine the development of brain edema and intracranial hypertension in ALF, namely the delivery of ammonia to the brain, the disturbances of brain organic osmolytes and brain extracellular amino acids, cerebro-vascular haemodynamics, brain glucose metabolism, inflammation, subclinical seizure activity and alterations of gene expression. Initial uncontrolled clinical studies of mild hypothermia in patients with ALF suggest that it is an effective, feasible and safe approach. Randomized controlled clinical trials are now needed to adequately assess its efficacy, safety, clinical impact on global outcomes and to provide the guidelines for its use in ALF.

Mild Hypothermic Preservation for Transport Purposes of the AMC Bioartificial Liver Charged with Porcine Hepatocytes

BACKGROUND

Preservation conditions play a crucial role during transport of a bioartificial liver (BAL) from the laboratory to the hospital. We assessed the possibility to preserve the AMC-BAL loaded with freshly isolated porcine hepatocytes at mild hypothermic temperatures.

METHODS

Two laboratory-scale AMC-bioreactors were loaded with 1 billion freshly isolated porcine hepatocytes per experiment (n=6). Bioreactors in the control group were kept for three days at 37 degrees C. Bioreactors in the transport group were kept at 37 degrees C during day 1, at 15 degrees C during day 2, and again at 37 degrees C during day 3. In addition, long-term mild hypothermic preservation periods of 45 and 110 hr at 15 degrees C and 26 degrees C, respectively, were assessed. The effect of mild hypothermic preservation on hepatocytes inside the bioreactors was tested by determination of cell damage parameters, as well as metabolic and hepatocyte-specific functions.

RESULTS

A 24-hour period of mild hypothermic preservation did not reduce any hepatocyte-specific function. LDH release was significantly higher only at day 2. Albumin production at day 2 and lidocaine elimination at day 3 were significantly higher with glucose consumption and lactate production being significantly lower at both test days. Long-term mild hypothermic preservation had a drastic negative effect on cellular viability and hepatocyte-specific function.

CONCLUSIONS

Mild hypothermic preservation at temperatures as low as 15 degrees C and for a duration of 24 hr is a feasible method to preserve BAL systems loaded with freshly isolated porcine liver cells and will simplify the logistics of BAL transport from the laboratory to the hospital.

Mild hypothermia for acute liver failure: a review of mechanisms of action

Brain edema with intracranial hypertension is a major complication in patients with acute liver failure. Current therapies for this complication include a variety of pharmacologic and interventional measures, some of which are frequently associated with adverse effects or contraindications. Even though these measures usually allow the control of intracranial hypertension for a certain period of time, recurrence is common. New therapies are therefore needed. Increasing clinical and experimental evidence suggests that induction of mild hypothermia (32 degrees C-35 degrees C) may be a therapeutic alternative. Similar to traumatic brain injury or brain stroke, induction of mild hypothermia seems highly effective to reduce intracranial pressure in patients with acute liver failure. Several mechanisms by which mild hypothermia may prevent brain edema and intracranial hypertension in this condition have been disclosed and may include beneficial effects on ammonia metabolism, as well as on the disturbances of brain osmolarity, cerebrovascular hemodynamics, brain glucose metabolism, inflammation, and others. Improvement of systemic hemodynamics and amelioration of liver injury may be other benefits of the systemic induction of mild hypothermia, but the impact of potential adverse events, such as infection, should also be taken into account. At a time when mild hypothermia is increasingly used in several specialized centers, performance of a randomized controlled trial seems critical to confirm the benefits of mild hypothermia in acute liver failure and to provide adequate guidelines for its use.