Liver regeneration: prospects for therapy based on new technologies

Clinical implications of advances in liver regeneration

Remarkable advances have been made recently in the area of liver regeneration. Even though liver regeneration after liver resection has been widely researched, new clinical applications have provided a better understanding of the process. Hepatic damage induces a process of regeneration that rarely occurs in normal undamaged liver. Many studies have concentrated on the mechanism of hepatocyte regeneration following liver damage. High mortality is usual in patients with terminal liver failure. Patients die when the regenerative process is unable to balance loss due to liver damage. During disease progression, cellular adaptations take place and the organ microenvironment changes. Portal vein embolization and the associating liver partition and portal vein ligation for staged hepatectomy are relatively recent techniques exploiting the remarkable progress in understanding liver regeneration. Living donor liver transplantation is one of the most significant clinical outcomes of research on liver regeneration. Another major clinical field involving liver regeneration is cell therapy using adult stem cells. The aim of this article is to provide an outline of the clinical approaches being undertaken to examine regeneration in liver diseases.

Sulfation of 25-hydroxycholesterol regulates lipid metabolism, inflammatory responses, and cell proliferation

Intracellular lipid accumulation, inflammatory responses, and subsequent apoptosis are the major pathogenic events of metabolic disorders, including atherosclerosis and nonalcoholic fatty liver diseases. Recently, a novel regulatory oxysterol, 5-cholesten-3b, 25-diol 3-sulfate (25HC3S), has been identified, and hydroxysterol sulfotransferase 2B1b (SULT2B1b) has been elucidated as the key enzyme for its biosynthesis from 25-hydroxycholesterol (25HC) via oxysterol sulfation. The product 25HC3S and the substrate 25HC have been shown to coordinately regulate lipid metabolism, inflammatory responses, and cell proliferation in vitro and in vivo. 25HC3S decreases levels of the nuclear liver oxysterol receptor (LXR) and sterol regulatory element-binding proteins (SREBPs), inhibits SREBP processing, subsequently downregulates key enzymes in lipid biosynthesis, decreases intracellular lipid levels in hepatocytes and THP-1-derived macrophages, prevents apoptosis, and promotes cell proliferation in liver tissues. Furthermore, 25HC3S increases nuclear PPARγ and cytosolic IκBα and decreases nuclear NF-κB levels and proinflammatory cytokine expression and secretion when cells are challenged with LPS and TNFα. In contrast to 25HC3S, 25HC, a known LXR ligand, increases nuclear LXR and decreases nuclear PPARs and cytosol IκBα levels. In this review, we summarize our recent findings, including the discovery of the regulatory oxysterol sulfate, its biosynthetic pathway, and its functional mechanism. We also propose that oxysterol sulfation functions as a regulatory signaling pathway.

Liver bioengineering: Current status and future perspectives

The present review aims to illustrate the strategies that are being implemented to regenerate or bioengineer livers for clinical purposes. There are two general pathways to liver bioengineering and regeneration. The first consists of creating a supporting scaffold, either synthetically or by decellularization of human or animal organs, and seeding cells on the scaffold, where they will mature either in bioreactors or in vivo. This strategy seems to offer the quickest route to clinical translation, as demonstrated by the development of liver organoids from rodent livers which were repopulated with organ specific cells of animal and/or human origin. Liver bioengineering has potential for transplantation and for toxicity testing during preclinical drug development. The second possibility is to induce liver regeneration of dead or resected tissue by manipulating cell pathways. In fact, it is well known that the liver has peculiar regenerative potential which allows hepatocyte hyperplasia after amputation of liver volume. Infusion of autologous bone marrow cells, which aids in liver regeneration, into patients was shown to be safe and to improve their clinical condition, but the specific cells responsible for liver regeneration have not yet been determined and the underlying mechanisms remain largely unknown. A complete understanding of the cell pathways and dynamics and of the functioning of liver stem cell niche is necessary for the clinical translation of regenerative medicine strategies. As well, it will be crucial to elucidate the mechanisms through which cells interact with the extracellular matrix, and how this latter supports and drives cell fate.

Regeneration and bioengineering of transplantable abdominal organs: current status and future challenges

INTRODUCTION

The most critical issue to organ transplantation is the identification of new sources of organs. The present manuscript illustrates the state-of-the-art regenerative medicine (RM) investigations aiming to manufacturing abdominal organs for transplant purposes.

AREAS COVERED

This manuscript focuses on research in the bioengineering and regeneration of kidneys, insulin-producing cells, livers and small bowel. The main technology currently under development exploits the seeding of cells on supporting scaffolding material. Despite favorable preliminary results obtained with relatively simple, hollow organs, when more complex organs are considered, the scenario changes dramatically. Investigations are still in early stages, and clinical translation is not yet foreseeable based on current knowledge and information. Obstacles are numerous but we believe the critical factor hampering success is lack of in-depth understanding of the extracellular matrix (ECM) and cell-ECM interactions, as well as the mechanisms with which organs develop in utero.

EXPERT OPINION

The success of RM to generate transplantable abdominal organs relies heavily on progress in (stem) cell therapies, developmental and ECM biology, and in the thorough understanding of the intricate relationship and interplay between cells and the ECM. This will require enormous investments in financial and medical resources, which ideally should be embarked upon by governments, the private sector and academia.

A critical appraisal of the hemodynamic signal driving liver regeneration

BACKGROUND

Many aspects of the signaling mechanisms involved in the initiation of hepatic regeneration are under current investigation. Nevertheless, the actual mechanisms switching liver regeneration on and off are still unknown. Hemodynamic changes in the liver following partial hepatectomy have been suggested to be a primary stimulus in triggering liver regeneration. Most of the new knowledge about the impact of hemodynamic changes on liver regeneration is both conceptually important and directly relevant to clinical problems.

PURPOSE

The purpose of this review is therefore to exclusively address the hemodynamic signal driving the liver regeneration process.

Antiangiogenic response after 70% hepatectomy and its relationship with hepatic regeneration and angiogenesis in rats

BACKGROUND

The aim of this study was to evaluate the antiangiogenic response and its relation to regeneration and angiogenesis after 70% hepatectomy in a rat model.

METHODS

Sixty-four Wistar albino rats were included in the study. Animals were allocated into 8 groups (n = 8). After a 70% hepatectomy, liver regeneration, angiogenesis, and antiangiogenic response were evaluated in the remnant liver on days 0, 1, 2, 3, 5, 7, 10, and 14. Regeneration and angiogenesis were determined with immunoreactivity to proliferating cell nuclear antigen and vascular endothelial growth factor. Antiangiogenic response was evaluated by detecting collagen 18 m RNA with reverse transcriptase polymerase chain reaction.

RESULTS

We showed that liver regeneration peaked at day 1, whereas angiogenesis in the periportal and perisinusoidal areas reached their peak values on days 3 and 7, respectively. Both regeneration and angiogenic activity around perisinusoidal hepatocytes returned to basal activity on the day 10. Antiangiogenic response first appeared on day 5, reached a peak on day 10, and returned to basal values on day 14.

CONCLUSION

Collagen18 mRNA expression is present in the normal liver during the regenerative process. We suggest that the stimulus that causes the cessation of regeneration process may come from hepatocytes, and collagen 18 produced by hepatocytes may modulate this event by inhibiting the angiogenesis.

Effects of carvacrol upon the liver of rats undergoing partial hepatectomy

The present study aims to investigate the possible effects of carvacrol obtained from origanum oil upon the regenerative feature of the liver subsequent to partial hepatectomy in rats. Male Wistar Albino rats, weighing 230+/-30g, were divided into three experiment groups. Group I (n=8) were used as sham operation group. Group II (n=8) were applied saline solution and hepatectomy. Carvacrol and hepatectomy (73mg/kg) were applied to Group III (n=8). One dose of test material was injected 1h before 68% partial hepatectomy. At the end of the experiments, blood and organs were removed. The liver regeneration rate of the rats was calculated measuring the weights of their liver before and after the hepatectomy. Hematoxylin and eosin, interleukin-6 (IL-6) and proliferating cell nuclear antigen (PCNA) treatments were applied to liver sections. Aspartate transaminase (AST), alanine transaminase (ALT), tumor necrosis factor-alpha (TNF-alpha) and IL-6 levels were determined in serum samples. The liver regeneration, mitotic index and PCNA index increased significantly in rats of Group III over the Group II at the 72nd hour after partial hepatectomy. Histological evaluations were also similar with these results of PCNA and mitotic indexes. In AST, ALT, TNF-alpha and IL-6 levels, there was no statistically significant difference. According to these results, it is concluded that carvacrol increases the liver regeneration rate.

Platelets Strongly Induce Hepatocyte Proliferation with IGF-1 and HGF In Vitro

BACKGROUND

It is well known that platelets have a thrombotic effect. However, platelets play an important role not only in hemostasis but also in wound healing and tissue regeneration. Platelets have been reported to accumulate in the liver and promote liver regeneration after an extended hepatectomy, but the mechanism is unclear. The present study was designed to clarify the mechanism by which platelets have a direct proliferative effect on hepatocytes in vitro.

MATERIALS AND METHODS

Hepatocytes obtained from male BALB/c mice by collagenase digestion and immortalized hepatocytes (TLR2) were used. To elucidate the mechanism of the proliferative effect of platelets, DNA synthesis of hepatocytes was measured under various conditions and the related cellular signals were analyzed. Chromatographic analysis was also performed to clarify which elements of platelets have mitogenic activity.

RESULTS

DNA synthesis significantly increased in the hepatocytes cultured with platelets (P < 0.001). However, when the platelets and hepatocytes were separated, the platelets did not have a proliferative effect. Whole disrupted platelets, the supernatant fraction, and fresh isolated platelets had a similar proliferative effect, while the membrane fraction did not. After the addition of platelets, both Akt and extracellular signal-regulated kinases ERK1/2 were activated, but extracellular signal-regulated kinase STAT3 was not activated. Some mitogenic fractions were obtained from the platelet extracts by gel exclusion chromatography; the fractions were rich in hepatocyte growth factor and IGF-1.

CONCLUSIONS

Direct contact between platelets and hepatocytes was necessary for the proliferative effect. The direct contact initiated signal transduction involved in growth factor activation. Hepatocyte growth factor, vascular endothelial growth factor, and insulin-like growth factor-1, rather than platelet-derived growth factor, mainly contributed to hepatocyte proliferation.

Mechanisms and outcomes of drug- and toxicant-induced liver toxicity in diabetes

Increase dincidences of hepatotoxicity have been observed in diabetic patients receiving drug therapies. Neither the mechanisms nor the predisposing factors underlying hepatotoxicity in diabetics are clearly understood. Animal studies designed to examine the mechanisms of diabetes-modulated hepatotoxicity have traditionally focused only on bioactivation/detoxification of drugs and toxicants. It is becoming clear that once injury is initiated, additional events determine the final outcome of liver injury. Foremost among them are two leading mechanisms: first, biochemical mechanisms that lead to progression or regression of injury; and second, whether or not timely and adequate liver tissue repair occurs to mitigate injury and restore liver function. The liver has a remarkable ability to repair and restore its structure and function after physical or chemical-induced damage. The dynamic interaction between biotransformation-based liver injury and compensatory tissue repair plays a pivotal role in determining the ultimate outcome of hepatotoxicity initiated by drugs or toxicants. In this review, mechanisms underlying altered hepatotoxicity in diabetes with emphasis on both altered bioactivation and liver tissue repair are discussed. Animal models of both marked sensitivity (diabetic rats) and equally marked protection (diabetic mice) from drug-induced hepatotoxicity are described. These examples represent a remarkable species difference. Availability of the rodent diabetic models offers a unique opportunity to uncover mechanisms of clinical interest in averting human diabetic sensitivity to drug-induced hepatotoxicities. While the rat diabetic models appear to be suitable, the diabetic mouse models might not be suitable in preclinical testing for potential hepatotoxic effects of drugs or toxicants, because regardless of type 1 or type2 diabetes, mice are resistant to acute drug-or toxicant-induced toxicities.

Positive effects of cryopreserved adult or fetal liver cell transplants on hypercholesterolemia and hepatic antioxidant defenses in cholesterol-fed rabbits

The liver plays a central role in lipid metabolism and the pathophysiology of many lipid disorders leads in turn to liver cell injury. Adult hepatocyte transplants provide well-recognized metabolic support, whilst hepatic stem cells may promote liver regeneration and repair, but in both cases, any clinical application would require low temperature banking of the cells. A model of dietary hypercholesterolemia was established in rabbits over 5 months, and transplants of cryopreserved adult hepatocytes (CH) and cryopreserved fetal liver cells (CFLC) were compared to Sham transplants. Cryopreservation was performed by a two-step freezing protocol using 1.5mol/l dimethyl sulfoxide (Me(2)SO). Serum contents of cholesterol lipid classes were measured during the subsequent 4 weeks, in addition to markers of serum and liver oxidative stress. Both CH and CFLC transplantation resulted in a decrease of serum lipids during the 1st week after transplantation. The effect of CH was limited to the 1st week, but CFLC provided a sustained lipid-lowering effect over the 4 weeks. The ultimate outcome of CFLC transplantation by the end of 4 weeks was more pronounced and statistically significant for both serum total cholesterol (0.15+/-0.05 versus 3.65+/-1.4mmol/l) and high-density lipoprotein-cholesterol (0.04+/-0.01 versus 0.56+/-0.06mmol/l) compared to Sham transplants (p<0.05 in both cases). CFLC transplantation also normalized hepatic tissue antioxidant defenses, namely an increase in reduced glutathione content, and enzyme activities for catalase and glutathione reductase (all significantly higher at p<0.05 than in Sham transplants) by 4 weeks.

Proteomic analysis of the transition from quiescent to proliferating stages in rat liver hepatectomy model

The 70% (or 2/3) partial hepatectomy (PHx) rat liver model provides an effective medium for study of the transition and regulation of hepatocytes from quiescent to proliferating phase. Although the gene expression pattern has come under intense scrutiny, a differential proteomic study could help to reveal the mechanism of how the process is initiated and regulated. The proteomic changes were analyzed in two groups, 7 h after 70% PHx test group and sham-operation control group, by two-dimensional gel electrophoresis with 907 +/- 33 and 910 +/- 64 spots on gels, respectively. Twelve down-regulated spots and twenty-six up-regulated spots were recognized using ImageMaster software and were identified by matrix-assisted laser desorption/ionization-mass spectrometry-quadrupole time of flight mass spectrometry and/or tandem mass spectrometry reconfirmation. Some of the differential proteins were associated with stress defense, lipid metabolism, and macromolecular biosynthesis while the others were shown to be involved in regulating transcript factors associated with liver regeneration. A "proteomic model" for liver regeneration was suggested based on our data and related scientific literature to interpret the differential proteome pattern that reflected the transition of cells from quiescent to proliferating state, including but not limited to the rat liver after 70% PHx.

The molecular physiology of liver regeneration following partial hepatectomy

The ability of the liver to regenerate after resection has been known for many years. Two reports from Germany in the late 1800s probably mark the introduction of the phenomenon into the scientific literature, but in the early 1900s the first reviews of this subject had appeared in the English literature. Predating these early scientific reports the legends from the Greek mythology described the fate of Prometheus. As punishment for defying Zeus and revealing the secret of fire to man, Prometheus was chained to a rock and each day had part of his liver ripped out by an eagle which, returning the following day, repeated the torture because his liver regenerated itself overnight. Although the speed of regeneration in the Greek legend is somewhat greater than that observed either clinically or in the laboratory, the myth does serve to emphasise the remarkable ability of the liver to repeatedly regenerate following repeated resections. This review aims to summarise the more recent literature concerning the early molecular events accompanying liver regeneration and to integrate this with the existing knowledge of this subject.

Stem cell factor attenuates liver damage in a murine model of acetaminophen-induced hepatic injury

Acute liver injury is a common cause of intensive care unit visits. In these studies, we used a murine model of acetaminophen poisoning to examine the role of stem cell factor (SCF) on liver damage. In the initial studies, we identified that the liver produces relatively high constitutive levels of SCF. Upon administration of acetaminophen, the levels of SCF fell dramatically, correlating to damage within the liver. When the liver was allowed to regenerate, the levels of SCF again correlated with the liver regeneration. We next treated mice with anti-SCF before sublethal doses of acetaminophen and significantly increased lethality in anti-SCF-treated animals. When exogenous SCF was given to mice, the lethality was significantly reduced compared with the control acetaminophen-treated animals and the damage within the liver tissue was attenuated. The administration of rSCF reduced the level of steady-state mRNA for cytochrome P450 cyp2E1 enzyme both in vitro and in vivo. These data suggest that SCF functions as an important factor that protects livers from acute damage.

Determinants of hepatitis C translational initiation in vitro, in cultured cells and mice

Hepatitis C virus (HCV) is an RNA virus infecting 1 in every 40 people worldwide. Development of new therapeutics for treating HCV has been hampered by the lack of small-animal models. We have adapted existing hydrodynamic transfection methods to optimize the delivery of RNAs to the cytoplasm of mouse liver cells in vivo. Transfected HCV genomic RNA failed to replicate in mouse liver, suggesting a post-entry block to viral replication. Real-time imaging of HCV internal ribosome entry site (IRES) firefly luciferase reporter mRNA translation in living mice demonstrated that the HCV IRES was functional in mouse liver. We then used this system as a model for studying HCV RNA translation in mice. We compared translation by several mutant HCV IRES variants in cell lysates, cultured cells, and mouse liver. We measured the contribution to translation of a cap, HCV 3'-untranslated region (UTR), poly(A) tail, domains II, IIIb, IIIabc, IIIabcd, IIId, and the initiator codon. Efficient translation required a 3'-UTR in mice and HeLa cells, but not in rabbit reticulocyte lysates. Translational regulation of transfected RNAs was stringent in mice. The method we describe could be useful for studies in mice of antisense or ribozyme inhibitors targeting the IRES as well as other RNA biochemical studies in vivo.

Extrachromosomal recombinant adeno-associated virus vector genomes are primarily responsible for stable liver transduction in vivo

Recombinant adeno-associated virus (rAAV) vectors stably transduce hepatocytes in experimental animals. Although the vector genomes are found both as extrachromosomes and as chromosomally integrated forms in hepatocytes, the relative proportion of each has not yet been clearly established. Using an in vivo assay based on the induction of hepatocellular regeneration via a surgical two-thirds partial hepatectomy, we have determined the proportion of integrated and extrachromosomal rAAV genomes in mouse livers and their relative contribution to stable gene expression in vivo. Plasma human coagulation factor IX (hF.IX) levels in mice originating from a chromosomally integrated hF.IX-expressing transposon vector remained unchanged with hepatectomy. This was in sharp contrast to what was observed when a surgical partial hepatectomy was performed in mice 6 weeks to 12 months after portal vein injection of a series of hF.IX-expressing rAAV vectors. At doses of 2.4 x 10(11) to 3.0 x 10(11) vector genomes per mouse (n = 12), hF.IX levels and the average number of stably transduced vector genomes per cell decreased by 92 and 86%, respectively, after hepatectomy. In a separate study, one of three mice injected with a higher dose of rAAV had a higher proportion (67%) of integrated genomes, the significance of which is not known. Nevertheless, in general, these results indicate that, in most cases, no more than approximately 10% of stably transduced genomes integrated into host chromosomes in vivo. Additionally, the results demonstrate that extrachromosomal, not integrated, genomes are the major form of rAAV in the liver and are the primary source of rAAV-mediated gene expression. This small fraction of integrated genomes greatly decreases the potential risk of vector-related insertional mutagenesis associated with all integrating vectors but also raises uncertainties as to whether rAAV-mediated hepatic gene expression can persist lifelong after a single vector administration.

Induction of hepatocyte proliferation and liver hyperplasia by the targeted expression of cyclin E and skp2

Cells in culture become competent to replicate in the absence of growth factor after progressing beyond the late G1 restriction point, suggesting that a set of genes expressed during G1 phase is sufficient to trigger completion of the cell cycle. However, this has not been demonstrated in an in vivo system. In this study, we examined whether transfection of genes associated with the G1/S transition could trigger hepatocyte replication. Co-transfection of cyclin E and skp2 synergistically promoted cell cycle progression in cultured primary hepatocytes in the absence of mitogen or in the presence of growth inhibitors. Furthermore, transfection of hepatocytes in vivo with cyclin E and skp2 promoted abundant hepatocyte replication and hyperplasia of the liver. These studies confirm that transfection with a small number of genes can trigger proliferation of quiescent hepatocytes in vivo, and suggest that therapies to enhance liver regeneration by targeting cell cycle control genes may be feasible.

Gene therapy for hemophilia

Hemophilia A and B are X-chromosome linked recessive bleeding disorders that result from a deficiency in factor VIII (FVIII) and factor IX (FIX) respectively. Though factor substitution therapy has greatly improved the lives of hemophiliac patients, there are still limitations to the current treatment that have triggered interest in alternative treatments by gene therapy. Significant progress has recently been made in the development of gene therapy for the treatment of hemophilia A and B. These advances parallel the technical improvements of existing vector systems including MoMLV-based retroviral, adenoviral and AAV vectors, and the development of new delivery methods such as lentiviral vectors, helper-dependent adenoviral vectors and improved non-viral gene delivery methods. Therapeutic and physiologic levels of FVIII and FIX could be achieved in FVIII- and FIX-deficient mice and hemophilia dogs by different gene therapy approaches. Long-term correction of the bleeding disorders and in some cases a permanent cure has been realized in these preclinical studies. However, the induction of neutralizing antibodies often precludes stable phenotypic correction. Another complication is that certain promoters are prone to transcriptional inactivation in vivo, precluding long-term FVIII or FIX expression. Several gene therapy phase I clinical trials are currently ongoing in patients suffering from severe hemophilia A or B. No significant adverse side-effects were reported, and semen samples were negative for vector sequences by sensitive PCR assays. Most importantly, some subjects report fewer bleeding episodes and occasionally have very low levels of clotting factor activity detected. The results from the extensive preclinical studies in normal and hemophilic animal models and encouraging preliminary clinical data indicate that the simultaneous development of different strategies is likely to bring a permanent cure for hemophilia one step closer to reality.

Natural intramolecular isotope measurements in physiology: elements of the case for an effort toward high-precision position-specific isotope analysis

Chemical information available in organisms can be categorized into three major domains, macromolecular, small molecules, and isotope ratios. Information about physiological state is commonly obtained by qualitative and quantitative analysis in the macromolecular and small molecule domains. Genomics and proteomics are emerging approaches to analysis of macromolecules, and both areas yield definitive information on present physiological state. There is relatively little record of past physiological states of the individual available in these domains. Natural isotopic variability, particularly on an intramolecular level, is likely to retain more physiological history. Because of ubiquitous isotopic fractionation, every stereochemically unique position in every molecule has an isotope ratio that reflects the processes of synthesis and degradation. This fact highlights a vast amount of organismal chemical information that is essentially unstudied. Isotope measurements can be classified according to the chemical complexity of the analyte into bulk, compound-specific, and position-specific or intramolecular levels. Recent advances in analysis of isotope ratios are transforming natural science, and particularly answering questions about ecosystems using bulk methods; however, they have had relatively little impact on physiology. This may be because the vast complexities of physiological questions demand very selective information available in position-specific isotope analysis (PSIA). The relatively few high-precision PSIA studies, based on isotope ratio mass spectrometry (IRMS), have revealed intramolecular isotope ratio differences in pivotal physiological compounds including amino acids, glucose, glycerol, acetate, fatty acids, and purines. The majority of these analyses have been accomplished by laborious offline methods; however, recent advances in instrumentation presage rapid PSIA that will be necessary to attack real physiological problems. Gas-phase pyrolysis has been shown to be an effective method to determine (13)C/(12)C at high precision for molecular fragments, and technologies to extend C-based PSIA to N and other organic elements are emerging. Two related efforts are warranted, (a) development of rapid, convenient, and sensitive methods for high-precision PSIA, a necessary precursor to (b) a concerted investigation into the relationship of metabolic state to intramolecular isotope ratio. Inherent in this latter goal is the need to identify long-lived molecules in long-lived cells that retain a record of early isotopic conditions, as has been shown for post-mortem human neuronal DNA. Using known metabolic precursor-product relationships between intramolecular positions, future studies of physiological isotope fractionation should reveal the relationship of diet and environment to observed isotope ratio. This science of isotope physiology, or simply isotopics, should add an important tool for elucidation of early factors that effect later health, probably the most difficult class of biomedical issues.

On bioartificial liver assist system: theoretical exploration and strategies for further development

The major difficulty in establishing a clinical effective bioartificial liver assist device for treatment of fulminate hepatic failure is limitation of our knowledge and technologies about fresh cell behaviors in culture and a lack of knowledge about the etiology and pathogenesis of hepatic coma. Increasing data from clinical and laboratory investigation have accrued indicating that toxins from necrotic liver tissue, mainly as oxygen reactive substances, have a role in the pathogenesis of hepatic encephalopathy and even multiple system organs failure. This paper presents the data available and suggests a new pathway for artificial and bioartificial liver assist system.

Somatic integration and long-term transgene expression in normal and haemophilic mice using a DNA transposon system

The development of non-viral gene-transfer technologies that can support stable chromosomal integration and persistent gene expression in vivo is desirable. Here we describe the successful use of transposon technology for the nonhomologous insertion of foreign genes into the genomes of adult mammals using naked DNA. We show that the Sleeping Beauty transposase can efficiently insert transposon DNA into the mouse genome in approximately 5-6% of transfected mouse liver cells. Chromosomal transposition resulted in long-term expression (>5 months) of human blood coagulation factor IX at levels that were therapeutic in a mouse model of haemophilia B. Our results establish DNA-mediated transposition as a new genetic tool for mammals, and provide new strategies to improve existing non-viral and viral vectors for human gene therapy applications.

Novel CXCR2-dependent liver regenerative qualities of ELR-containing CXC chemokines

Severe acute liver injury due to accidental or intentional acetaminophen overdose presents a major clinical dilemma often requiring liver transplantation. In the present study, liver regeneration after profound liver injury in mice challenged with acetaminophen was facilitated by the exogenous addition of ELR-containing CXC chemokines such as macrophage inflammatory protein-2 (MIP-2), epithelial neutrophil-activating protein-78 (ENA-78), or interleukin 8. Intravenous administration of ELR-CXC chemokines or N-acetyl-cysteine (NAC) immediately after acetaminophen challenge in mice significantly reduced histological and biochemical markers of hepatic injury. However, when the intervention was delayed until 10 h after acetaminophen challenge, only ELR-CXC chemokines significantly reduced liver injury and mouse mortality. The delayed addition of ELR-CXC chemokines to cultured hepatocytes maintained the proliferation of these cells in a CXCR2-dependent fashion after acetaminophen challenge whereas delayed NAC treatment did not. These observations demonstrate that ELR-CXC chemokines represent novel hepatic regenerative factors that exhibit prolonged therapeutic effects after acetaminophen-induced hepatotoxicity.

The effect of folic acid on the drug metabolizing liver function in man with viral hepatitis

The investigations were carried out on 31 patients (16 men and 15 women, at the age of 20-50) with viral hepatitis. The all patients were divided at two groups. The first group (12 man) received usual treatment (diet, corsil), the second group (19 man) received in addition to the base treatment folic acid (5 mg per day, 10 days). It was found, that at patients with viral hepatitis was decreased the activity of monooxygenase system of liver. So, period of semielimination (T1/2) of antipyrine (AP) was greater in 1,4 time, area under the pharmacokinetic curve - 1,5 time and clearance was below by 39% than in volunteers (29 man). On day of treatment only by corsil, the rate of elimination of AP and clearance were increased by 34 and 31% (p < 0.05) respectively, T1/2 was decreased by 23% (p < 0.05) and area under the pharmacokinetic curve - 17 %. On 10 day of treatment by corsil with folic acid (5 mg per day), the rate of elimination of AP and clearance was increased by 43% (p < 0.05), area under the pharmacokinetic curve and T 1/2 were decreased by 30 and 33% (p < 0.05) respectively. The positive effect of folic acid in treatment of hepatitis at restoration period may be cause participating its derivatives in de novo nucleotide synthesis.

Macrophage inflammatory protein-2 gene therapy attenuates adenovirus- and acetaminophen-mediated hepatic injury

Profound hepatocellular injury is often a consequence of adenovirus-mediated gene therapy or acetaminophen ingestion. The aim of the present study was to examine the role of a CXC chemokine, macrophage inflammatory protein-2 (MIP-2), in the hepatotoxic response by mice infected with adenovirus and challenged with acetaminophen. CD1 mice that received a replication-defective human type 5 adenovirus vector (Ad70-3) intravenously exhibited hepatic injury that peaked at 24 h after infection. In contrast, mice that received a similar adenovirus vector containing a rodent MIP-2 cDNA insert had no hepatic injury at any time after infection. The combination of Ad70-3 infection and an intraperitoneal challenge with 400 mg/kg of acetaminophen was fatal in 50% of the mice, but only 10% of the AdMIP-2 group receiving acetaminophen were similarly affected. Furthermore, AdMIP-2 mice had significantly lower hepatic injury and serum aminotransaminases compared with the Ad70-3 group. However, AdMIP-2 infection in mice lacking the CXC chemokine receptor that binds MIP-2, CXCR2, did not attenuate any of the markers of liver injury after adenovirus and acetaminophen challenge. AdMIP-2 treatment of CD1 mice was also associated with significantly decreased leukocyte infiltration into the liver and an earlier increase in hepatic 3H-thymidine incorporation compared with the control group. Taken together, these data demonstrate that MIP-2 has a protective role in both adenovirus- and acetaminophen-mediated hepatotoxicity, and suggest that MIP-2 may promote rapid hepatic regeneration following acute hepatic injury.

The effects of serum from patients with acute liver failure on the growth and metabolism of Hep G2 cells

In many bioartificial liver systems currently being designed and evaluated for use in fulminant hepatic failure, direct contact is required between the patient's blood and the liver cells in the device. The efficacy of such devices will be influenced by the interaction of fulminant hepatic failure (FHF) patient serum with the cells. We have found that FHF serum inhibits the growth rate and the synthesis of DNA, RNA, and protein; disturbs glutathione homeostasis; and induces morphological changes in cultured human Hep G2 cells. These interactions should influence the design of bioartificial liver devices based on proliferating cell lines and indicate the requirement to pretreat FHF patient plasma to reduce the toxin load.

The current status of primary hepatocyte culture

Recently, there have been significant advances toward the development of culture conditions that promote proliferation of primary rodent hepatocytes. There are two major methods for the multiplication of hepatocytes in vitro: one is the use of nicotinamide, the other is the use of a nutrient-rich medium. In the medium containing a high concentration of nicotinamide and a growth factor, primary hepatocytes can proliferate well. In this culture condition small mononucleate cells, which are named small hepatocytes, appear and form colonies. Small hepatocytes have a high potential to proliferate while maintaining hepatic characteristics, and can differentiate into mature ones. On the other hand, combining the nutrient-rich medium with 2% DMSO, the proliferated hepatocytes can recover the hepatic differentiated functions and maintain them for a long time. In this review I describe the culture conditions for the proliferation and differentiation of primary hepatocytes and discuss the small hepatocytes, especially their roles in liver growth.