Mechanisms Of Liver Regeneration Research Articles

How Glycosylation of Vitronectin Modulates the Tissue Remodeling during Liver Regeneration

Vitronectin (VN) is a multifunctional glycoprotein present in plasma and the extracellular matrix (ECM). VN binds to various biological ligands and it plays a key role in tissue remodeling by regulating cell adhesion and fibrinolysis. The present study attempted to determine the glycan structures and how alternations of glycans modulate the biological activity of VN during liver regeneration. Plasma VN was purified from partially hepatectomized (PH) and sham-operated (SH) rats at 24 hours after operation and non-operated (NO) rats. The liquid chromatography/ multiple-stage mass spectrometry analysis of glycopeptides of each VN determined the site-specific glycosylation. With the major complex-type N-glycans, hybrid-type N-glycans were site-specifically present. The complex-type N-glycans decreased in PH-VN while the fucosylation ratio was increased. Highly sialylated O-glycans were found to be present in the Thr110-Thr124 region, which contained α2,8-linked disialic acid and dramatically decreased after PH. Further study using ultracentrifugation demonstrated that the multimer sizes of PH-VN significantly increased compared with NO-VN. In accordance with this, PH-VN exhibited remarkably enhanced collagen-binding than NO-VN. The results indicate that glycan alterations during tissue remodeling induce increased multimerization state to enhance collagen-binding of VN.Adhesion of rat hepatic stellate cells (HSCs), together with phosphorylation of focal adhesion kinase (FAK), in PH-VN was decreased to half of that in NO- or SH-VN. Adhesion of HSCs in desialylated NO-VN decreased to 1/2 of that of control VN, indicating the importance of sialylation of VN for activation of HSCs. This study proposes that the alteration of glycosylation of VN is very significant in the modulation of the biological activity of VN during many steps of tissue remodeling processes. The elucidation of the molecular mechanisms of liver regeneration from the viewpoint of alterations in glycosylation of VN may contribute to the development of a strategy to regulate matrix deposition in liver cirrhosis.

Compensatory growth mechanisms regulated by BMP and FGF signaling mediate liver regeneration in zebrafish after partial hepatectomy

Here, we describe the zebrafish (Danio rerio) as a vertebrate model system to study liver regeneration with the added benefit of its powerful genetics and screening possibilities to uncover the molecular pathways underlying liver regeneration. We developed a partial hepatectomy (PH) protocol in zebrafish and investigated in detail the cellular and morphological changes during the process of liver regeneration. We show that the type of regenerative response is dependent on the size of the injury sustained by the zebrafish liver. Furthermore, we demonstrate for the first time that the mechanisms of liver regeneration in zebrafish after PH are strikingly similar to those of rodents and humans, with 100% recovery of the liver mass after 6-7 d postsurgery. This occurs via compensatory growth mediated by proliferation of hepatocytes throughout the entire liver remnant. By analyzing transgenic fish expressing dominant-negative forms of either bone morphogenetic protein (BMP) receptor or fibroblast growth factor (FGF) receptor 1, we demonstrate that the BMP and FGF signaling pathways are crucial regulators of the early events during liver regeneration after PH. Our study demonstrates that the mechanisms of liver regeneration in zebrafish are highly similar to the processes ongoing during mammalian liver regeneration and make the adult zebrafish a suitable model system to study the mechanisms of liver regeneration.

Exploring Rat Plasmatic Proteomes: What Triggered the Liver Regeneration? (Supplementary materials)

To further clarify the priming mechanism of liver regeneration, proteins and protein complexes from rat plasma (normal group, partial hepatectomy (PHx) group and sham-operation group) were comparatively studied by two-dimensional gel electrophoresis and two-dimensional blue native gel electrophoresis. Our results suggested that Kupffer cell--NF-kappaB/ROS might trigger the liver regeneration.

Exploring the priming mechanism of liver regeneration: proteins and protein complexes

The liver has the ability to restore its functional capacity following injury or resection and the priming of liver regeneration is a complex process that has not been completely elucidated. In the current research, to further reveal the priming mechanism of liver regeneration, hepatocyte total protein and hepatocyte cytosol of the rats at 4 h after 2/3 partial hepatectomy (PHx) were studied, respectively, by 2-DE and 2-D blue native gel electrophoresis. Seventeen unique differential proteins were identified in hepatocyte total protein samples. Nine differential protein complexes containing 41 protein components were identified in hepatocyte cytosol samples. For the first time, at the priming stage of liver regeneration, the variations of serine protease inhibitor 2c, sulfite oxidase and valosin-containing protein (VCP) were presented and validated by Western blotting, and the VCP complex was further validated by antibody super-shift experiments. The current results suggested that at 4 h after PHx, VCP complex was down-regulated in hepatocyte cytosol, apoptosis pathways were inhibited, nuclear factor-kappaB and interleukin 6 pathways worked together and triggered the liver regeneration.

Mechanism of liver regeneration after liver resection and portal vein embolization (ligation) is different?

Whether or not liver regeneration after portal branch embolization (PE) (ligation, PVL) in the non-embolized (ligated) lobe is by the same mechanism as regeneration in the remnant lobe after liver resection has been reviewed. Portal vein branch embolization and heat shock protein are then discussed. Tumor growth accelerated in the remnant liver after hepatectomy. In contrast, PE or PVL resulted in marked contralateral hepatic hypertrophy and significant reduction of tumor growth in the non-embolized (non-ligated) lobes. Follistatin administration significantly increased liver regeneration after hepatectomy in rats. In contrast, regeneration of non-ligated lobes after PVL was not accelerated by exogenous follistatin. Tumor growth also was not accelerated. The liver regeneration rate peaked at 48-72 h in the nonligated lobe after PVL, a delay of 24 h compared with the remnant liver after hepatectomy. In the postoperative early stage, the expression of activin betaA, betaC, and betaE mRNAs was stronger in PVL than in hepatectomy. At 72 h the expression of activin receptor type IIA mRNA reached a peak in hepatectomy, but was significantly lower in PVL. Thus, regulation of activin signaling through receptors is one of the factors determining liver regeneration after hepatectomy and PVL. These serial experimental results imply that the mechanism of liver regeneration after portal branch ligation (embolization) is different from that after hepatectomy. Heat shock protein was induced in the liver experimentally by intermittent ischemic preconditioning and could play some beneficial role in the recovery of liver function after hepatectomy, even in cirrhotic patients. When heat shock protein following right portal vein embolization in both the embolized and non-embolized hepatic lobes was investigated in clinical cases, a two to fourfold increase in HSP70 was induced in the non-embolized lobe compared with the embolized lobe. Oral administration of geranylgeranylacetone (a non-toxic HSP inducer) suppressed inflammatory responses and improved survival after 95% hepatectomy by induction of HSP70 in rats.

Regeneration of Graft Livers and Limited Contribution of Extrahepatic Cells After Partial Liver Transplantation in Humans

Background Liver regeneration is still not fully understood. Partial liver transplantation (LT) can provide the opportunity to investigate the mechanisms of liver regeneration, including the contribution of extrahepatic cells to liver regeneration. Methods Of 61 patients transplanted with partial liver graft between August 1997 and October 2006, 56 patients were studied, including 49 adults and 7 children. Sequential computed tomography volumetric analysis was performed for volume measurement, while proliferating cell nuclear antigen (PCNA) labeling index was investigated for liver cell proliferation in nonprotocol liver biopsy specimens. In addition, 15 male recipients who had female liver grafts were investigated in order to detect Y chromosomes as extrahepatic cells in nonprotocol liver biopsy specimens. Results Graft volume per standard liver volume was markedly increased after adult-to-adult living-donor (LD) LT. In pediatric transplants, there was no volume increase over time. PCNA labeling index was vigorous in adult-to-adult LDLT in the early period after LDLT. No Y chromosome was evident in hepatocytes from female-donor male-recipient grafts during or after liver regeneration. However, in the cases of failing grafts of this type, many Y-chromosome-positive cells were observed in the graft liver. The character of those cells was CD34(−), CK9(−), hepatocyte-specific antigen(−), and CD68(+/−). Conclusion In adult-to-adult LDLT, vigorous liver regeneration occurs in the graft liver, demonstrated by not only volumetric but cell kinetic analysis. Involvement of extrahepatic cells in normal liver regeneration seems limited.

Omentum facilitates liver regeneration

To investigate the mechanism of liver regeneration induced by fusing the omentum to a small traumatic injury created in the liver. We studied three groups of rats. In one group the rats were omentectomized; in another group the omentum was left in situ and was not activated, and in the third group the omentum was activated by polydextran particles. We pre-activated the omentum by injecting polydextran particles and then made a small wedge wound in the rat liver to allow the omentum to fuse to the wound. We monitored the regeneration of the liver by determining the ratio of liver weight/body weight, by histological evaluation (including immune staining for cytokeratin-19, an oval cell marker), and by testing for developmental gene activation using reverse transcription polymerase chain reaction (RT-PCR). There was no liver regeneration in the omentectomized rats, nor was there significant regeneration when the omentum was not activated, even though in this instance the omentum had fused with the liver. In contrast, the liver in the rats with the activated omentum expanded to a size 50% greater than the original, and there was histologically an interlying tissue between the wounded liver and the activated omentum in which bile ducts, containing cytokeratin-19 positive oval cells, extended from the wound edge. In this interlying tissue, oval cells were abundant and appeared to proliferate to form new liver tissue. In rats pre-treated with drugs that inhibited hepatocyte growth, liver proliferation was ongoing, indicating that regeneration of the liver was the result of oval cell expansion. Activated omentum facilitates liver regeneration following injury by a mechanism that depends largely on oval cell proliferation.

Protein Profilings in Mouse Liver Regeneration after Partial Hepatectomy Using iTRAQ Technology

Liver is unique in its capability to regenerate after an injury. Liver regeneration after a 2/3 partial hepatectomy served as a classical model and is adopted frequently to study the mechanism of liver regeneration. In the present study, semiquantitative analysis of protein expression in mouse liver regeneration following partial hepatectomy was performed using an iTRAQ technique. Proteins from pre-PHx control livers and livers regenerating for 24, 48 and 72 h were extracted and inspected using 4-plex isotope labeling, followed by liquid chromatography fractionation, mass spectrometry and statistical differential analysis. A total of 827 proteins were identified in this study. There were 270 proteins for which quantitative information was available at all the time points in both biologically duplicate experiments. Among the 270 proteins, Car3, Mif, Adh1, Lactb2, Fabp5, Es31, Acaa1b and LOC100044783 were consistently down-regulated, and Mat1a, Dnpep, Pabpc1, Apoa4, Oat, Hpx, Hp and Mt1 were up-regulated by a factor of at least 1.5 from that of the controls at one time point or more. The regulation of each differential protein was also demonstrated by monitoring its time-dependent expression changes during the regenerating process. We believe this is the first report to profile the protein changes in liver regeneration utilizing the iTRAQ proteomic technique.

Establishment and Characterization of Hepatic Stem-like Cell lines from Normal Adult Rat Liver

The liver is a unique organ with the potential to regenerate from injury. Hepatic stem cells contribute to liver regeneration when surviving hepatocytes in injured liver are unable to proliferate. To investigate the mechanism of liver regeneration in vitro, we established hepatic stem cell lines named HY1, HY2 and HY3, derived from a healthy liver of adult rat. HY cells showed an expression pattern similar to oval cells, and efficiently induced hepatic differentiation following sequential treatment with type I collagen, transforming growth factor-beta1 (TGF-beta1), and hepatocyte growth factor (HGF) or oncostatin M (OSM). These results suggested that HY cells are liver stem cells representing an excellent tool for in vitro studies on liver regeneration.

Liver regeneration: a spotlight on the novel role of platelets and serotonin.

The development of novel approaches in liver surgery in the last decade has saved the lives of a large number of patients via resection of liver tumours previously thought to be non-resectable. Concurrently, living donor liver transplantation has emerged as one of the ways of lowering mortality on the waiting lists. These breakthroughs demanded a rigorous understanding of the mechanisms of liver regeneration after partial hepatectomy. Based on our previous studies on blood platelets and cold ischaemic injury, platelets and serotonin have attracted attention due to their theoretical potential contribution to liver regeneration. Both platelets and serotonin have been proven to be crucially involved in liver regeneration after partial hepatectomy. This review article provides an overview on the process of liver regeneration, with emphasis on its molecular basis and the coordinate contribution of several cells to restoring the organ's original volume and function. The role of platelets and serotonin is highlighted as novel contributors in this process.

Liver regeneration: a spotlight on the novel role of platelets and serotonin.

The development of novel approaches in liver surgery in the last decade has saved the lives of a large number of patients via resection of liver tumours previously thought to be non-resectable. Concurrently, living donor liver transplantation has emerged as one of the ways of lowering mortality on the waiting lists. These breakthroughs demanded a rigorous understanding of the mechanisms of liver regeneration after partial hepatectomy. Based on our previous studies on blood platelets and cold ischaemic injury, platelets and serotonin have attracted attention due to their theoretical potential contribution to liver regeneration. Both platelets and serotonin have been proven to be crucially involved in liver regeneration after partial hepatectomy. This review article provides an overview on the process of liver regeneration, with emphasis on its molecular basis and the coordinate contribution of several cells to restoring the organ's original volume and function. The role of platelets and serotonin is highlighted as novel contributors in this process.

QS212. Limited Involvement of Extrahepatic Cells in Regeneration of the Graft Liver After Living Donor Liver Transplantation

Background: The mechanism of liver regeneration is still not fully understood. Especially the involvement of extrahepatic cells in liver regeneration is charming hypothesis proposed in experiments with rodent, however, it has not been documented in human. Therefore, we investigated liver regeneration after adult-to-adult partial liver transplantation in a male recipient (XY), who was transplanted a female liver (XX) in order to investigate the existence of Y chromosome in a biopsied liver. Patients and Methods: Of 76 living donor liver transplantation (LDLT) between 1997 and September 2007, 49 patients were studied including 9 children and 40 adults.

Gene Expression During Liver Regeneration After Partial Hepatectomy in Mice Lacking Type 1 Tumor Necrosis Factor Receptor

To investigate the function of tumor necrosis factor-alpha (TNF-alpha) during hepatocyte proliferation, we studied liver regeneration following partial hepatectomy in mice lacking type 1 TNF receptor (TNFR-1). TNFR-1 knockout (KO) and wild-type mice were subjected to partial (two-thirds) hepatectomy. Liver regeneration was evaluated by assessing liver weights and Ki67 immunohistochemistry. Riken complementary DNA microarray analysis was performed for liver samples from mice undergoing partial hepatectomy to better compare different mouse partial hepatectomy models (TNFR-1 KO mice, KO group; and wild-type mice, W group). Liver weight was regained after 14 days in the KO group, and after 7 days in the W group. Genes including lipopolysaccharide, toll-like receptor 4 precursor, mitogen-activated protein kinase kinase kinase 4, mitogen-activated protein kinase kinase kinase kinase 4, and mitogen-activated protein kinase 8-interacting protein were up-regulated in the KO group. As for the cell-cycle-regulated genes, the levels of cyclin D1, nuclear factor-kappa B light chain, and TNF receptor super family membrane 1a were down-regulated in the KO group. Microarray analysis showed decreased activities of the hexokinase- and phospho-fructokinase-related glycolytic pathways in the KO group. These results contribute to the better understanding of the mechanisms of liver regeneration after partial hepatectomy in TNFR-1 KO mice.

Reply:

We thank Drs. Feng and Xu for their interest in our recent article published in HEPATOLOGY. The authors bring up a very interesting point regarding the similarities in impairment of liver regeneration between steatosis and concanavalin A–induced hepatitis. Our laboratory has a strong interest both in the mechanisms of liver regeneration but also in the development and progression of fatty liver disease.1, 2 Although we did not directly observe increases in lipid accumulation by routine histopathological examination, we did not perform a systematic evaluation of this possibility in our study as Drs. Feng and Xu have done. In our recent report, we speculated that disruption in key proproliferative cytokine production (particularly interleukin-6) in conjunction with increased expression or activation of inhibitory factors such as p21 and Smad2 likely contribute to the decreased hepatocellular proliferation observed following partial hepatectomy in concanavalin A–pretreated mice, though we stopped short of defining a direct connection. This point should be clarified, because we do not believe that oval cells reduce hepatocellular proliferation but that decreased mature hepatocyte proliferation stimulates or promotes the expansion of oval cells secondarily within the regenerating liver. The inclusion of lipid accumulation as the intermediary between T cell–mediated hepatitis and inhibition of hepatocellular regeneration is novel and most interesting. There is copious evidence in the literature to suggest a connection between lipid accumulation within hepatocytes and their decreased propensity or ability for proliferation.3 Likewise, there is evidence to suggest that key proinflammatory cytokines including tumor necrosis factor α and others may modulate the development and progression of hepatosteatosis.4-6 The ability of T cells to either directly or indirectly modify lipid accumulation within hepatocytes has not been investigated, though very recent preliminary studies by our laboratory would suggest that T cells themselves may indeed contribute to the progression of hepatosteatosis. Together, the findings by Drs. Feng and Xu and our recent preliminary data provide an important and exciting connection between concanavalin A–induced, T cell–mediated liver injury and hepatocellular lipid accumulation. Future investigation into the direct mechanisms by which this occurs will provide the experimental and clinical community with important information regarding the impact of lymphocyte-mediated liver injury on the initiation or enhancement of secondary pathologies including hepatosteatosis. Ian N. Hines Ph.D.*, * Department of Medicine, Division of Gastroenterology and Hepatology, University of North Carolina, Chapel Hill, NC.

Gc-globulin (vitamin D binding protein) is synthesized and secreted by hepatocytes and internalized by hepatic stellate cells through Ca 2+-dependent interaction with the megalin/gp330 receptor

Background Gc-globulin or vitamin D binding protein is a highly expressed, multifunctional and polymorphic serum protein, which also serves as the major transporter for vitamin D metabolites in the circulation. The present study was performed to analyze the interaction between gc-globulin of hepatocytes and hepatic stellate cells, the most important fat-/retinol-storing cell type in the liver, which spontaneously transdifferentiates to myofibroblasts in culture. Methods Hepatic stellate cells and hepatocytes were isolated by the pronase/collagenase reperfusion method, hepatocytes by collagenase reperfusion of the organ. Gc-globulin expression was monitored by immunocytochemistry, immunoblotting, RT-PCR, metabolic labelling with [ 35S]-methionine, and its intracellular binding to α-smooth-muscle actin was investigated by co-immunoprecipitation. Cytoskeletal stainings of gc-globulin and α-smooth-muscle actin in hepatic stellate cells and the identification of the receptors megalin/gp330, HCAM/CD44, cubilin and annexin A2 were performed with confocal immunocytochemistry, immunoblotting and/or FACS-analysis. Results Hepatocytes synthesize and secrete gc-globulin as shown by RT-PCR and [ 35S]-methionine labelling, which could be suppressed by cycloheximide. Also, a strong signal for gc-globulin was detected in the immunoblot of native hepatic stellate cell lysates. However, no mRNA for gc-globulin was found in this cell type, which suggests no active synthesis by hepatic stellate cells. Hepatic stellate cells were tested positively for the presence of known gc-globulin interacting receptors megalin/gp330, HCAM/CD44, cubilin and annexin A2. Inhibition of the megalin/gp330 receptor by a competitive, neutralizing antibody resulted in decreased intracellular availability of gc-globulin in hepatic stellate cells. The latter effect was enhanced by additional incubation of hepatic stellate cells with EDTA for complexing Ca 2+, suggesting a Ca 2+-dependent internalization of gc-globulin into hepatic stellate cells via the megalin/gp300 receptor. This was supported by confocal microscopy which showed a co-localization of gc-globulin with the multifunctional megalin/gp330 receptor on this cell type. Inside hepatic stellate cells, a linkage between gc-globulin and α-smooth muscle actin filaments of hepatic stellate cells was detected by immunocytochemistry. Intracellular binding of gc-globulin to α-smooth-muscle actin filaments was confirmed by co-immunoprecipitation. Conclusion We give evidence to the expression of the megalin/gp330 receptor on hepatic stellate cells and that this receptor is involved in the Ca 2+-dependent internalization of gc-globulin into hepatic stellate cells, a protein synthesized and secreted into the extracellular space and circulation by hepatocytes. Inside hepatic stellate cells, it co-localizes with and binds to α-smooth muscle actin filaments. Under consideration of the available literature, these findings propose a participation of gc-globulin in hepatic vitamin D metabolism as well as in hepatic stellate cell stability and apoptosis as important mechanisms of liver regeneration.

Serial analysis of gene expression (SAGE) in rat liver regeneration

We have applied serial analysis of gene expression for studying the molecular mechanism of the rat liver regeneration in the model of 70% partial hepatectomy. We generated three SAGE libraries from a normal control liver (NL library: 52,343 tags), from a sham control operated liver (Sham library: 51,028 tags), and from a regenerating liver (PH library: 53,061 tags). By SAGE bioinformatics analysis we identified 40 induced genes and 20 repressed genes during the liver regeneration. We verified temporal expression of such genes by real time PCR during the regeneration process and we characterized 13 induced genes and 3 repressed genes. We found connective tissue growth factor transcript and protein induced very early at 4 h after PH operation before hepatocytes proliferation is triggered. Our study suggests CTGF as a growth factor signaling mediator that could be involved directly in the mechanism of liver regeneration induction.

Expression of interleukin 6 and apoptosis-related genes in suckling and weaning rat models of hepatectomy and liver regeneration

Background/Purpose The most commonly used model to study the mechanisms of liver regeneration is the adult rat submitted to 70% to 80% hepatectomy. However, there are no studies using newborn or weaning rat models. The process of liver regeneration includes both the hypertrophy and hyperplasia of cells (processes regulated by growth factors and cytokines, mainly interleukin 6 [IL-6]) as well as apoptosis, or programmed cell death (a process regulated mainly by the Bcl-2 family of proteins). Proapoptotic proteins in this family include Bax and Bak. Conversely, Bcl-2 and Bcl-XL are antiapoptotic regulators. Therefore, to expand our understanding of liver regeneration, our study had 2 goals: first, to standardize 2 animal models of hepatectomy and liver regeneration using the newborn suckling and the weaning rat and second, to quantitate the expression levels of IL-6 and several members of the Bcl-2 gene family during the regeneration process. Methods To create the experimental models, newborn suckling rats (age, 5-7 days; weight, 6-10 g) and weaning rats (age, 21-23 days; weight, 30-50 g) underwent 70% hepatectomy. The animals were subsequently sacrificed at days 1, 2, 3, 4, and 7 after hepatectomy, and the remnant liver lobes were harvested for routine histologic examination. Groups of healthy animals not operated on served as controls. For the experimental study, 6 newborn rats and 6 weaning rats underwent hepatectomy. The animals were killed 1 day after liver resection and the remnant livers were harvested to assess gene expression by quantitative reverse transcription-polymerase chain reaction. The hepatectomized groups were compared with control and sham groups. Results During the creation of the experimental models, 70% of the suckling animals and all the weaning animals survived the hepatectomy. The decreased liver weight was completely restored to control levels by day 7 after hepatectomy. Histologically, the remnant livers of both hepatectomy groups exhibited steatosis, tumefaction of hepatocytes, and mitosis, which ceased at 7 days after the hepatectomy. The weaning rat model showed more robust gene expression responses. Specifically, expression levels of IL-6 gene were significantly increased after both surgical insult (sham group) and hepatectomy. However, this increase was significantly higher in the latter group. Furthermore, hepatectomy promoted a decrease in the expression levels of the proapoptotic genes and an increase in the expression levels of Bcl-2. Conclusions Our data indicate that regulation of both IL-6 and genes involved in apoptosis are strongly implicated in the mechanisms of liver regeneration and that the weaning rat model represents an attractive model system for future investigations in this area.

Role of ischaemic preconditioning in liver regeneration following major liver resection and transplantation

Liver ischaemic preconditioning (IPC) is known to protect the liver from the detrimental effects of ischaemic-reperfusion injury (IRI), which contributes significantly to the morbidity and mortality following major liver surgery. Recent studies have focused on the role of IPC in liver regeneration, the precise mechanism of which are not completely understood. This review discusses the current understanding of the mechanism of liver regeneration and the role of IPC in this setting. Relevant articles were reviewed from the published literature using the Medline database. The search was performed using the keywords "liver", "ischaemic reperfusion", "ischaemic preconditioning", "regeneration", "hepatectomy" and "transplantation". The underlying mechanism of liver regeneration is a complex process involving the interaction of cytokines, growth factors and the metabolic demand of the liver. IPC, through various mediators, promotes liver regeneration by up-regulating growth-promoting factors and suppresses growth-inhibiting factors as well as damaging stresses. The increased understanding of the cellular mechanisms involved in IPC will enable the development of alternative treatment modalities aimed at promoting liver regeneration following major liver resection and transplantation.

β‐Catenin is essential for liver regeneration following acetaminophen‐induced acute liver failure.

Overdose of acetaminophen (APAP) is the leading cause of acute liver failure (ALF). Understanding the mechanisms of liver regeneration following APAP-induced liver injury are of high therapeutic relevance. To investigate the role of Wnt/β-catenin, an important pathway in liver biology, in liver regeneration after APAP-induced ALF, male CD-1 mice were treated with a non-lethal dose of APAP (500 mg/kg), which induced extensive liver injury and subsequent regeneration. Rapid induction in the total and active β-catenin was evident at 1–3 hr after APAP treatment, along with its nuclear translocation at 6 hr. Further studies revealed that both canonical (GSK-3β-dependent) and non-canonical (c-met-dependent) pathways were involved in β-catenin activation. Administration of a lethal dose of APAP (700 mg/kg) known to inhibit liver regeneration completely suppressed β-catenin activation. Further, β-catenin conditional knockout mice, which have low CYP2E1 expression, exhibited increased APAP-mediated injury and decreased cell proliferation following CYP2E1 induction. Furthermore, suppression of β-catenin activation was observed in human APAP-induced ALF liver samples along with suppression of liver regeneration. Taken together, these data indicate that β-catenin activation plays an important role in stimulation of liver regeneration following APAP overdose and might have therapeutic and prognostic implications in APAP ALF.

Gene Expression Profiles in Living Donors Immediately After Partial Hepatectomy—The Initial Response of Liver Regeneration

Gene expression profiles of liver regeneration are well explored in rat models. However, there are limited relative data in humans. This study aimed to show that mRNA expression profiles change immediately after right hepatectomy in living-related donors and correlate with mechanisms of liver regeneration reported in the literature. Prospective study was conducted from March 2003 to August 2004. Living-related donors who donated right lobe of liver were included. Liver biopsies were performed at the beginning and, 5 hours later, at the end of liver resection. RNAs were isolated to synthesize cRNA. Oligo DNA microarray experiments were conducted and paired signal intensity ratios (Cy3/Cy5) were normalized with rank-invariant global Lowess regression analysis by taking base two logarithms. Genes whose average residuals more than 2.5-fold increased or less than -2.5-fold decreased were selected to get the most pronounced expression changes during this period. Five of 34 donors were included with qualified samples. The expression patterns of paired DNA microarray experiments were similar in five donors. A total of 28 upregulated and 14 downregulated genes were collected. Acute-phase proteins (serum amyloid A, complement-reactive protein, heme oxygenase-1) were upregulated. Genes related to growth signal transduction (G-protein coupled receptor-30) were downregulated. Gene expression profiles immediately after partial hepatectomy were reported first in humans with the techniques of oligo DNA microarray, which were compatible with the initial gene expression patterns of liver regeneration in rats.