Oxidative stress and oval cell accumulation in mice and humans with alcoholic and nonalcoholic fatty liver disease

Alcohol and gastrointestinal oncology

Results from several large epidemiological studies have firmly established that alcohol is associated with elevated cancer incidence and mortality. Recently the International Agency for Cancer Research stated that acetaldehyde associated with alcoholic beverages is carcinogenic to humans and confirmed the Group 1 classification of alcohol consumption and of ethanol in alcoholic beverages. Alcohol consumption causes cancers of the oral cavity, pharynx, larynx, oesophagus, colorectum, liver, pancreas and female breast. The frequency of most alcohol-induced diseases increases in a linear fashion as intake increases: oral, oesophagus and colon cancer fall into this pattern. Very little is known about safe margins of alcohol consumption. US Department of Health and Human Services suggest a maximum of 28 g of alcohol a day in man and half of this in women.

[Role of environmental factors in the etiology of hepatocellular carcinoma]

Chronic B and C virus hepatitis (HBV and HCV) are the most important risk factors in the development of hepatocellular carcinoma (HCC). About 40-50% of HCC is induced by these two chronic viral infections. Prevalence of HCC is slowly increasing in the United States and in Western-Europe, whereas alcohol consumption is gradually decreasing in the majority of these countries. However, the most important environmental risk factor for HCC is still the heavy long-term alcohol use. The risk of cirrhosis and HCC increases linearly, wherever ethanol intake is greater than 60 g/day for men and women. Aflatoxin, which contaminates grains, mostly in China and Africa, is a well-known mycotoxin. Since geographical distribution of aflatoxin as well as HBV overlaps with each other, they have a synergistic effect on inducing HCC. Cigarette smoking has also hepatocarcinogenic effect, which is significantly enhanced by the concomitant alcohol use or chronic viral hepatitis. Obesity, non-alcoholic fatty liver and steatohepatitis as well as diabetes mellitus together also form a significant risk for HCC, due to the gradually increasing number of patients. Insulin resistance and oxidative stress are the major pathogenetic mechanisms leading to hepatic cell injury in these patients. Oral contraceptive drugs may also play a role in the development of HCC. The long-term exposure to organic solvents is also a risk factor for HCC. Dietary antioxidants, selenium, statins and coffee drinking have protective effect against HCC.

Mass spectrometric profiling of oxidized lipid products in human nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Oxidative stress is a core abnormality responsible for disease progression in nonalcoholic fatty liver disease (NAFLD). However, the pathways that contribute to oxidative damage in vivo are poorly understood. Our aims were to define the circulating profile of lipid oxidation products in NAFLD patients, the source of these products, and assess whether their circulating levels reflect histological changes in the liver. The levels of multiple structurally specific oxidized fatty acids, including individual hydroxy-eicosatetraenoic acids (HETE), hydroxy-octadecadenoic acids (HODE), and oxo-octadecadenoic acids (oxoODE), were measured by mass spectrometry in plasma at time of liver biopsy in an initial cohort of 73 and a validation cohort of 49 consecutive patients. Of the markers monitored, 9- and 13-HODEs and 9- and 13-oxoODEs, products of free radical-mediated oxidation of linoleic acid (LA), were significantly elevated in patients with nonalcoholic steatohepatitis (NASH), compared with patients with steatosis. A strong correlation was revealed between these oxidation products and liver histopathology (inflammation, fibrosis, and steatosis). Further analyses of HODEs showed equivalent R and S chiral distribution. A risk score for NASH (oxNASH) was developed in the initial clinical cohort and shown to have high diagnostic accuracy for NASH versus steatosis in the independent validation cohort. Subjects with elevated oxNASH levels (top tertile) were 9.7-fold (P < 0.0001) more likely to have NASH than those with low levels (bottom tertile). Collectively, these findings support a key role for free radical-mediated linoleic acid oxidation in human NASH and define a risk score, oxNASH, for noninvasive detection of the presence of NASH.

High serum uric acid increases the risk for nonalcoholic Fatty liver disease: a prospective observational study

Nonalcoholic fatty liver disease (NAFLD) is a common form of chronic liver disease, and serum uric acid is observed to be significantly elevated in NAFLD patients. However, whether this elevation is causal, a bystander, or a consequence of NAFLD remains unclear. We performed a population-based prospective study among the employees of Zhenhai Refining & Chemical Company Ltd., Ningbo, China to investigate whether the elevation of serum uric acid has a casual role for NAFLD. A total of 6890 initially NAFLD-free subjects were followed up for 3 years. Overall, 11.80% (813/6890) subjects developed NAFLD over 3 years of follow-up. The cumulative incidence of NAFLD increased with progressively higher baseline serum uric acid levels (the cumulative incidence was 7.2%, 9.5%, 11.5%, 13.8%, and 17.2% in quintile 1, quintile 2, 3, 4 and 5, respectively; P value for trend <0.001). Cox proportional hazards regression analyses showed that serum uric acid levels were independently and positively associated with the risk for incident NAFLD; the age-, gender- and metabolic syndrome adjusted hazard ratio (95% CI) for the subjects in quintile 2, 3, 4 and 5 versus quintile 1 was 1.18 (0.91–1.54), 1.32 (1.03–1.70), 1.39 (1.09–1.78) and 1.50 (1.18–1.92), respectively. Taken together, our prospective observational study showed that elevation of serum uric acid levels independently predicts increase risk for incident NAFLD.

Intermediate hepatobiliary cells predict an increased risk of hepatocarcinogenesis in patients with hepatitis C virus-related cirrhosis

BACKGROUND & AIMS

The expression of biliary lineage markers such as cytokeratin (K) 7 by hepatocytes is thought to reflect an altered regeneration pathway recruiting a stem cell compartment, more prone to carcinogenesis. We aimed to investigate the presence of these so-called intermediate hepatobiliary cells (IHC) in liver biopsies of patients with hepatitis C-related cirrhosis and their potential influence on the subsequent occurrence of hepatocellular carcinoma (HCC).

METHODS

From a cohort of patients with hepatitis C-related cirrhosis, prospectively screened for HCC, we retrospectively selected those with a liver biopsy performed for the initial diagnosis of cirrhosis. Presence of IHC was recorded when foci of K7-positive, intermediate-sized hepatocytes were detected.

RESULTS

A total of 150 patients were included (87 men; mean age, 57 y; range, 19-84 y; body mass index, 25 kg/m(2)). After a median follow-up period of 4.85 years, HCC was diagnosed in 36 patients (24%). Baseline liver biopsy showed intermediate hepatobiliary cell foci in 61 patients (41%). Intermediate cells co-expressed both hepatocytes markers and the progenitor cell markers Ep-CAM and K19. The presence of intermediate hepatobiliary cells was associated independently with HCC occurrence (Fine and Gray model; hazard ratio, 2.48; 95% confidence interval, 1.24-4.96; P = .01). Other predictors of HCC were diabetes and low platelet count. The HCC annual incidence rate was significantly higher in patients with IHC compared with patients without (8.14% vs 3.12%, Gray's test, P = .003).

CONCLUSIONS

The aberrant expression of biliary K by hepatocytes in patients with hepatitis C virus-related cirrhosis is related independently to HCC occurrence.

Recent advances in liver stem cell therapy

PURPOSE OF REVIEW

Patients with liver cirrhosis often require liver transplantation, which remains the only effective treatment of the end-stage cirrhosis. Here we briefly summarize the current concepts in treatment of liver diseases based on the transplantation of intrahepatic liver cells, capable of repopulating the injured liver. These cells include hepatocytes, oval cells (bipotential intrahepatic progenitor cells), bone marrow hematopoietic and mesenchymal stem cells, and induced pluripotent stem (iPS) cells.

RECENT FINDINGS

Although liver transplantation remains the only conventional treatment, liver cell transplantation is an experimental procedure which has been successfully used in clinical trials in patients with acute liver failure, chronic liver disease with end-stage cirrhosis. Extraordinary progress has been made in the field of hepatic progenitors and iPS. Liver precursor cells (oval cells) are recognized as bipotential precursor cells in the damaged liver. They can rapidly proliferate, change their cellular composition, and differentiate into hepatocytes and cholangiocytes to compensate for the cellular loss and maintain liver homeostasis in animal models of liver injury. Similarly, iPS are somatic cells obtained from patients and differentiated into hepatocytes in vitro. Future studies of iPS are designed to develop of specific conditions to expand and in vitro differentiate somatic cells into functionally mature liver cells.

SUMMARY

The current review defines and discusses different populations of hepatic cells which can be potentially used for liver cell transplantation to advance the therapy of hepatic cirrhosis.

Pluripotent plasticity of stem cells and liver repopulation

Different types of stem cells have a role in liver regeneration or fibrous repair during and after several liver diseases. Otherwise, the origin of hepatic and/or extra-hepatic stem cells in reactive liver repopulation is under controversy. The ability of the human body to self-repair and replace the cells and tissues of some organs is often evident. It has been estimated that complete renewal of liver tissue takes place in about a year. Replacement of lost liver tissues is accomplished by proliferation of mature hepatocytes, hepatic oval stem cells differentiation, and sinusoidal cells as support. Hepatic oval cells display a distinct phenotype and have been shown to be a bipotential progenitor of two types of epithelial cells found in the liver, hepatocytes, and bile ductular cells. In gastroenterology and hepatology, the first attempts to translate stem cell basic research into novel therapeutic strategies have been made for the treatment of several disorders, such as inflammatory bowel diseases, diabetes mellitus, celiachy, and acute or chronic hepatopaties. In the future, pluripotent plasticity of stem cells will open a variety of clinical application strategies for the treatment of tissue injuries, degenerated organs. The promise of liver stem cells lie in their potential to provide a continuous and readily available source of liver cells that can be used for gene therapy, cell transplant, bio-artificial liver-assisted devices, drug toxicology testing, and use as an in vitro model to understand the developmental biology of the liver.

Redox control of liver function in health and disease

Reactive oxygen species (ROS), a heterogeneous population of biologically active intermediates, are generated as by-products of the aerobic metabolism and exhibit a dual role in biology. When produced in controlled conditions and in limited quantities, ROS may function as signaling intermediates, contributing to critical cellular functions such as proliferation, differentiation, and cell survival. However, ROS overgeneration and, particularly, the formation of specific reactive species, inflicts cell death and tissue damage by targeting vital cellular components such as DNA, lipids, and proteins, thus arising as key players in disease pathogenesis. Given the predominant role of hepatocytes in biotransformation and metabolism of xenobiotics, ROS production constitutes an important burden in liver physiology and pathophysiology and hence in the progression of liver diseases. Despite the recognized role of ROS in disease pathogenesis, the efficacy of antioxidants as therapeutics has been limited. A better understanding of the mechanisms, nature, and location of ROS generation, as well as the optimization of cellular defense strategies, may pave the way for a brighter future for antioxidants and ROS scavengers in the therapy of liver diseases.

Signals from dying hepatocytes trigger growth of liver progenitors

OBJECTIVE

The death rate of mature hepatocytes is chronically increased in various liver diseases, triggering responses that prevent liver atrophy, but often cause fibrosis. Mice with targeted disruption of inhibitor kappa B kinase (Ikk) in hepatocytes (HEP mice) provide a model to investigate this process because inhibiting Ikk-nuclear factor-kappaB (NF-kappaB) signalling in hepatocytes increases their apoptosis.

METHODS

Cell proliferation, apoptosis, progenitors, fibrosis and production of Hedgehog (Hh) ligands (progenitor and myofibroblast growth factors) were compared in HEP and control mice before and after feeding methionine choline-deficient ethionine-supplemented (MCDE) diets. Ikkbeta was deleted from primary hepatocytes to determine the effects on Hh ligand production; Hh signalling was inhibited directly in progenitors to determine the effects on viability. Liver sections from patients were examined to assess relationships between hepatocyte production of Hh ligands, accumulation of myofibroblastic cells and liver fibrosis.

RESULTS

Disrupting the Ikk-NF-kappaB pathway in hepatocytes inhibited their proliferation but induced their production of Hh ligands. The latter provided viability signals for progenitors and myofibroblasts, enhancing accumulation of these cell types and causing fibrogenesis. Findings in the mouse models were recapitulated in diseased human livers.

CONCLUSION

Dying mature hepatocytes produce Hh ligands which promote the compensatory outgrowth of progenitors and myofibroblasts. These results help to explain why diseases that chronically increase hepatocyte death promote cirrhosis.

Polycystins play a key role in the modulation of cholangiocyte proliferation

BACKGROUND

Polycystin-1 and -2 (PC-1 and PC-2) are critical components of primary cilia, which act as mechanosensors and drive cell response to injury. PC-1 activation involves the cleavage/processing of PC-1 cytoplasmic tail, driven by regulated intramembrane proteolysis or ubiquitine/proteasome, translocation in the nucleus and activation of transcription factors. Mutations of PC-1 or PC-2 occur in polycystic liver where cholangiocyte proliferation is enhanced.

AIM

We evaluated the involvement of PC-1 and PC-2 in modulating cholangiocyte proliferation.

METHODS

We investigated rat cholangiocytes induced to proliferate by 17beta-oestradiol. Proliferation was evaluated by PCNA immunoblotting or [(3)H]-thymidine incorporation into DNA. PC-1 silencing was performed by siRNA, while inhibition of regulated intramembrane proteolysis or proteasome by gamma-secretase inhibitor, leupeptin or MG115.

RESULTS

Cholangiocyte proliferation was associated with decreased PC-1 and PC-2 expression, which was inversely correlated with enhanced PCNA. The selective silencing of PC-1 induced activation of cholangiocyte proliferation in association with decreased PC-1 expression. Two different regulated intramembrane proteolysis inhibitors, gamma-secretase-inhibitor and leupeptin, and the proteasome inhibitor, MG115, abolished the 17beta-oestradiol proliferative effect.

CONCLUSIONS

PC-1 and PC-2 play a major role as modulators of cholangiocyte proliferation suggesting that primary cilia may act as sensors of cell injury driving, when activated, a proliferative cholangiocyte response to trigger the reparative processes.

Emerging use of stem cells in regenerative medicine

Stem cells represent a unique opportunity for regenerative medicine to cure a broad number of diseases for which current treatment only alleviates symptoms or retards further disease progression. However, the number of stem cells available has speedily increased these past 10 years and their diversity presents new challenges to clinicians and basic scientists who intend to use them in clinics or to study their unique properties. In addition, the recent possibility to derive pluripotent stem cells from somatic cells using epigenetic reprogramming has further increased the clinical interest of stem cells since induced pluripotent stem cells could render personalized cell-based therapy possible. The present review will attempt to summarize the advantages and challenges of each type of stem cell for current and future clinical applications using specific examples.

Alcoholic pancreatitis: Lessons from the liver

The association between alcohol consumption and pancreatitis has been recognized for over 100 years. Despite the fact that this association is well recognized, the mechanisms by which alcohol abuse leads to pancreatic tissue damage are not entirely clear. Alcohol abuse is the major factor associated with pancreatitis in the Western world. Interestingly, although most cases of chronic pancreatitis and many cases of acute pancreatitis are associated with alcohol abuse, only a small percentage of individuals who abuse alcohol develop this disease. This situation is reminiscent of the association between alcohol abuse and the incidence of alcoholic liver disease. The liver and the pancreas are developmentally very closely related. Even though these two organs are quite different, they exhibit a number of general structural and functional similarities. Furthermore, the diseases mediated by alcohol abuse in these organs exhibit some striking similarities. The diseases in both organs are characterized by parenchymal cell damage, activation of stellate cells, aberrant wound healing, and fibrosis. Because of the similarities between the liver and the pancreas, and the alcohol-associated diseases of these organs, we may be able to apply much of the knowledge that we have gained regarding the effects of alcohol on the liver to the pancreas.

Scopolamine treatment and muscarinic receptor subtype-3 gene ablation augment azoxymethane-induced murine liver injury

Previous work suggests that vagus nerve disruption reduces hepatocyte and oval cell expansion after liver injury. The role of postneuronal receptor activation in response to liver injury has not been ascertained. We investigated the actions of scopolamine, a nonselective muscarinic receptor antagonist, and specific genetic ablation of a key cholinergic receptor, muscarinic subtype-3 (Chrm3), on azoxymethane (AOM)-induced liver injury in mice. Animal weights and survival were measured as was liver injury using both gross and microscopic examination. To assess hepatocyte proliferation and apoptosis, ductular hyperplasia, and oval cell expansion, we used morphometric analysis of 5-bromo-2'-deoxyuridine-, activated caspase-3-, hematoxylin and eosin-, cytokeratin-19-, and epithelial cell adhesion molecule-stained liver sections. Sirius red staining was used as a measure of collagen deposition and its association with oval cell reaction. In AOM-treated mice, both muscarinic receptor blockade with scopolamine and Chrm3 ablation attenuated hepatocyte proliferation and augmented gross liver nodularity, apoptosis, and fibrosis. Compared with control, scopolamine-treated and Chrm3(-/-) AOM-treated mice had augmented oval cell reaction with increased ductular hyperplasia and oval cell expansion. Oval cell reaction correlated robustly with liver fibrosis. No liver injury was observed in scopolamine-treated and Chrm3(-/-) mice that were not treated with AOM. Only AOM-treated Chrm3(-/-) mice developed ascites and had reduced survival compared with AOM-treated wild-type controls. In AOM-induced liver injury, inhibiting postneuronal cholinergic muscarinic receptor activation with either scopolamine treatment or Chrm3 gene ablation results in prominent oval cell reaction. We conclude that Chrm3 plays a critical role in the liver injury response by modulating hepatocyte proliferation and apoptosis.

Cryptogenic cirrhosis: what are we missing?

Cryptogenic cirrhosis remains a common clinical condition although recent advances have allowed for a better understanding of underlying conditions and associations. The evolving terminology applied to this condition has resulted in some confusion and persistent variation among pathologists and clinicians. Typical patients are middle aged with only minor liver enzyme abnormalities. Presentations range from incidentally discovered cirrhosis to complications of advanced portal hypertension and hepatocellular cancer. Clinicopathologic analysis of these patients indicates that the leading causes include previously unrecognized nonalcoholic steatohepatitis, silent autoimmune hepatitis, non-B, non-C viral hepatitis, and occult past ethanol exposure. In this article, we review these associations as well as a proposed classification system for cryptogenic cirrhosis and other lesser known genetic and syndromic associations that warrant consideration when evaluating these individuals.

Bile ductular cells undergoing cellular senescence increase in chronic liver diseases along with fibrous progression

We investigated the pathologic significance of ductular reactions in chronic liver diseases with respect to cellular senescence. The expression of senescence-associated markers (p16(INK4a) and p21(WAF1/Cip1)), cell proliferation, cell cycle markers (cyclin D and cyclin A), and neural cell adhesion molecule (NCAM) was examined immunohistochemically in primary biliary cirrhosis (PBC, n = 37), chronic viral hepatitis (n = 39), nonalcoholic steatohepatitis (n = 25), and control normal livers (n = 12). The expression of p16(INK4a) and p21(WAF1/Cip1) was frequently found in ductular cells in the advanced stage of chronic liver diseases, especially in PBC (P < .05). Double immunostaining disclosed that most senescent cells expressed cyclin D (G(1)-phase marker). NCAM was frequently coexpressed in ductular cells showing senescence-associated markers. Some ductular cells in ductular reactions in chronic liver diseases were at G(1) arrest and undergoing cellular senescence. Such senescent cells may be involved in the progression of fibrosis of these diseases, particularly in PBC.

The quest for liver progenitor cells: a practical point of view

Many chronic liver diseases can lead to hepatic dysfunction with organ failure. At present, orthotopic liver transplantation represents the benchmark therapy of terminal liver disease. However this practice is limited by shortage of donor grafts, the need for lifelong immunosuppression and very demanding state-of-the-art surgery. For this reason, new therapies have been developed to restore liver function, primarily in the form of hepatocyte transplantation and artificial liver support devices. While already offered in very specialized centers, both of these modalities still remain experimental. Recently, liver progenitor cells have shown great promise for cell therapy, and consequently they have attracted a lot of attention as an alternative or supportive tool for liver transplantation. These liver progenitor cells are quiescent in the healthy liver and become activated in certain liver diseases in which the regenerative capacity of mature hepatocytes and/or cholangiocytes is impaired. Although reports describing liver progenitor cells are numerous, they have not led to a consensus on the identity of the liver progenitor cell. In this review, we will discuss some of the characteristics of these cells and the different ways that have been used to obtain these from rodents. We will also highlight the challenges that researchers are facing in their quest to identify and use liver progenitor cells.

Expansion of hepatic progenitor cell in fatty liver graft after living donor liver transplantation

Although it is known that steatotic livers have a reduced ability to regenerate, most individuals with steatosis show generally benign prognosis. We hypothesized that a proliferative blockade in steatotic hepatocytes results in the compensatory expansion of hepatic progenitor cells (HPC) during fatty liver regeneration. Fifty-four cases of living donor liver transplantation (LDLT) with a liver biopsy performed at the postoperative 10th day were examined. HPC were counted by immunofluorescence histochemical dual-staining technique using cytokeratin 7 and Ki-67, and the replicative arrest of hepatocytes was assessed by p21 immunohistochemistry. The degree of ductular proliferation during regeneration 10 days after LDLT correlated both with the degree of steatosis and the number of HPC (P < 0.001). There was no difference in the average number of HPC and the replicative arrest index between donors with or without steatosis before LDLT (P = 0.111 and P = 0.062). However, degree of steatosis correlated with both the expansion of HPC and the replicative arrest index during liver regeneration 10 days after LDLT (P < 0.001 and P < 0.001, respectively). Moreover, increased replicative arrest was strongly associated with HPC expansion (P < 0.001). In conclusion, the compensatory expansion of HPC as a result of impaired hepatocyte replication occurred during steatotic liver regeneration after LDLT.

The role of stem cells in liver repair and fibrosis

In response to liver injury or loss of liver mass, proliferation of mature liver cells is the first-line defense to restore liver homeostasis. In the setting of chronic liver disease, however, the ability of hepatocytes and cholangiocytes to proliferate is blocked and small bipotential progenitor cells are activated. Recent studies have established the role of these facultative progenitor cells in injury repair and fibrosis in patients with chronic liver disease and in experimental models. Several signaling pathways linking progenitor cell activation and fibrosis have been identified, and there is increasing evidence that cross-talk (both physical and via soluble factors) between progenitor cells and myofibroblasts is essential for both fibrosis and parenchymal regeneration. Even more exciting are new data examining the cellular components of the progenitor cell niche, demonstrating that both resident liver cells and circulating cells from the bone marrow can function as stem cells, suggesting that there is a surprising degree of phenotypic plasticity such that progenitor cells can contribute to the myofibroblast population and vice versa. We highlight here recent findings from the literature demonstrating the cellular and functional complexity of the progenitor cell niche, and emphasize some of the important questions that remain to drive future research.

Hedgehog-mediated epithelial-to-mesenchymal transition and fibrogenic repair in nonalcoholic fatty liver disease

BACKGROUND & AIMS

Repair responses define the ultimate outcomes of liver disease. This study evaluated the hypothesis that fibrogenic repair in nonalcoholic fatty liver disease (NAFLD) is mediated by Hedgehog (Hh) pathway activation and consequent induction of epithelial-to-mesenchymal transitions (EMT) in ductular-type progenitors.

METHODS

Immature ductular cells were exposed to Sonic hedgehog (Shh) in the presence or absence of the Hh inhibitor cyclopamine to determine whether Hh-pathway activation directly modulates EMT in liver progenitors. Potential biologic correlates of progenitor cell EMT were assessed using mice fed methionine-choline-deficient + ethionine (MCDE) diets with or without cyclopamine. The effects of increased Hh signaling on EMT and fibrogenic repair during diet-induced NAFLD were also compared in wild-type (WT) and Patched haplo-insufficient (Ptc(+/-)) mice. Finally, evidence of Hh-pathway activation and EMT was examined in liver sections from patients with NAFLD.

RESULTS

In cultured progenitors, Shh repressed expression of epithelial genes and EMT inhibitors but induced genes that are expressed by myofibroblasts. Cyclopamine reversed these effects. In mouse NAFLD models, Hh-pathway activation, EMT, expansion of myofibroblastic populations, and liver fibrosis occurred. Cyclopamine inhibited Hh-pathway activation and induction of EMT. Ptc(+/-) mice, which have an overactive Hh pathway, exhibited sustained overinduction of Hh target genes and more EMT, myofibroblast accumulation, and fibrosis than WT mice. Numbers of Shh-producing cells and Hh-responsive ductular cells that expressed EMT markers increased in parallel with liver fibrosis in patients with NAFLD.

CONCLUSIONS

Hh-mediated EMT in ductular cells contributes to the pathogenesis of cirrhosis in NAFLD.

Attenuation of inflammation and cellular stress-related pathways maintains insulin sensitivity in obese type I interleukin-1 receptor knockout mice on a high-fat diet

The development of insulin resistance in the obese is associated with chronic, low-grade inflammation. We aimed to identify novel links between obesity, insulin resistance and the inflammatory response by comparing C57BL/6 with type I interleukin-1 receptor knockout (IL-1RI(-/-)) mice, which are protected against diet-induced insulin resistance. Mice were fed a high-fat diet for 16 wk. Insulin sensitivity was measured and proteomic analysis was performed on adipose, hepatic and skeletal muscle tissues. Despite an equal weight gain, IL-1RI(-/-) mice had lower plasma glucose, insulin and triacylglycerol concentrations, compared with controls, following dietary treatment. The higher insulin sensitivity in IL-1RI(-/-) mice was associated with down-regulation of antioxidant proteins and proteasomes in adipose tissue and hepatic soluble epoxide hydrolase, consistent with a compromised inflammatory response as well as increased glycolysis and decreased fatty acid beta-oxidation in their muscle. Their lower hepatic triacylglycerol concentrations may reflect decreased flux of free fatty acids to the liver, decreased hepatic fatty acid-binding protein expression and decreased lipogenesis. Correlation analysis revealed down-regulation of classical biomarkers of ER stress in their adipose tissue, suggesting that disruption of the IL-1RI-mediated inflammatory response may attenuate cellular stress, which was associated with significant protection from diet-induced insulin resistance, independent of obesity.

Cross-species immunohistochemical investigation of the activation of the liver progenitor cell niche in different types of liver disease

BACKGROUND

When hepatocyte replication during liver disease is insufficient for regeneration, liver progenitor cells (LPCs) are activated. The cells and stroma in the immediate environment of LPCs, together termed the LPC niche, are thought to play an important role in this activation. Among these cells are the hepatic stellate cells (HSCs)/myofibroblasts (MFs).

AIMS/METHODS

We assessed the activation of HSC/MFs and LPCs in relation to the histological location and extent of liver disease in immunohistochemically (double) stained serial sections. Markers of HSC/MFs [alpha-smooth muscle actin, glial fibrillary acidic protein (GFAP), neurotrophin 3 and neural-cell adhesion molecule], markers of LPCs (keratin 7 and keratin 19) and a proliferation marker (Ki67) were used. A very relevant spontaneous model to evaluate LPC niche activation in a translational approach seems to be the dog. Therefore, both human and canine liver diseases with different degree of fibrosis and disease activity were included.

RESULTS

In human and canine liver disease, type and extent of LPC niche activation depended on type and severity of disease (P<0.05) and corresponded to the main location of disease. Activated HSCs surrounded the activated LPCs. In chronic hepatitis and non-alcoholic steatohepatitis lobular-type HSCs were activated, while during biliary disease portal/septal MFs were mainly activated. In canine liver, GFAP further presented as an early marker of HSC activation. Activation of the LPCs correlated with disease location and severity (P<0.01), and was inversely related to hepatocyte proliferation, as was previously shown in man.

CONCLUSION

A shared involvement of HSC/MFs, LPCs and disease severity during hepatic disease processes is shown, which is highly similar in man and dog.

Stem cells and liver regeneration

One of the defining features of the liver is the capacity to maintain a constant size despite injury. Although the precise molecular signals involved in the maintenance of liver size are not completely known, it is clear that the liver delicately balances regeneration with overgrowth. Mammals, for example, can survive surgical removal of up to 75% of the total liver mass. Within 1 week after liver resection, the total number of liver cells is restored. Moreover, liver overgrowth can be induced by a variety of signals, including hepatocyte growth factor or peroxisome proliferators; the liver quickly returns to its normal size when the proliferative signal is removed. The extent to which liver stem cells mediate liver regeneration has been hotly debated. One of the primary reasons for this controversy is the use of multiple definitions for the hepatic stem cell. Definitions for the liver stem cell include the following: (1) cells responsible for normal tissue turnover, (2) cells that give rise to regeneration after partial hepatectomy, (3) cells responsible for progenitor-dependent regeneration, (4) cells that produce hepatocyte and bile duct epithelial phenotypes in vitro, and (5) transplantable liver-repopulating cells. This review will consider liver stem cells in the context of each definition.

Effect of human patient plasma ex vivo treatment on gene expression and progenitor cell activation of primary human liver cells in multi-compartment 3D perfusion bioreactors for extra-corporeal liver support

Cultivation of primary human liver cells in innovative 3D perfusion multi-compartment capillary membrane bioreactors using decentralized mass exchange and integral oxygenation provides in vitro conditions close to the physiologic environment in vivo. While a few scale-up bioreactors were used clinically, inoculated liver progenitors in these bioreactors were not investigated. Therefore, we characterized regenerative processes and expression patterns of auto- and paracrine mediators involved in liver regeneration in bioreactors after patient treatment. Primary human liver cells containing parenchymal and non-parenchymal cells co-cultivated in bioreactors were used for clinical extra-corporeal liver support to bridge to liver transplantation. 3D tissue re-structuring in bioreactors was studied; expression of proteins and genes related to regenerative processes and hepatic progenitors was analyzed. Formation of multiple bile ductular networks and colonies of putative progenitors were observed within parenchymal cell aggregates. HGF was detected in scattered cells located close to vascular-like structures, expression of HGFA and c-Met was assigned to biliary cells and hepatocytes. Increased expression of genes associated to hepatic progenitors was detected following clinical application. The results confirm auto- and paracrine interactions between co-cultured cells in the bioreactor. The 3D bioreactor provides a valuable tool to study mechanisms of progenitor activation and hepatic regeneration ex vivo under patient plasma treatment.

Diets with corn oil and/or low protein increase acute acetaminophen hepatotoxicity compared to diets with beef tallow in a rat model

It has been reported that dietary polyunsaturated fats (PUFA) increase liver injury in response to ethanol feeding. We tested the hypothesis that diets rich in linoleic acid (18:2n-6) would affect acute liver injury after acetaminophen injection and that protein restriction might exacerbate the liver injury. We examined effects of feeding diets with either 15% (wt/wt) corn oil or 14% beef tallow and 1% corn oil for six weeks with either 6 or 20 g/100 g protein on acute hepatotoxicity. After the feeding period, liver injury was induced by injecting either with 600 mg/kg body weight acetaminophen suspended in gum arabic-based vehicle, or with vehicle alone during fasting status. Samples of liver and plasma were taken for analyses of hepatic glutathione (GSH) levels and liver-specific enzymes [(Glutamate-pyruvate transaminase (GPT) and glutamate-oxaloacetate transaminase (GOT)], respectively. Whereas GSH level was significantly lower in only group fed 15% corn oil with 6 g/100 g protein among acetaminophen-treated groups, activities of GPT and GOT were significantly elevated in all groups except the one fed beef tallow with 20 g/100 g protein, suggesting low protein might exacerbate drug-induced hepatotoxicity. The feeding regimens changed the ratio of 18:2n-6 to oleic acid (18:1n-9) in total liver lipids approximately five-fold, and produced modest changes in arachidonic acid (20:4n-6). We conclude that diets with high 18:2n-6 promote acetaminophen-induced liver injury compared to diets with more saturated fatty acids (SFA). In addition, protein restriction appeared to exacerbate the liver injury.

Similarities and differences in the pathogenesis of alcoholic and nonalcoholic steatohepatitis

Subpopulations of individuals with alcohol-induced fatty livers and nonalcoholic steatosis develop steatohepatitis. Steatohepatitis is defined histologically: increased numbers of injured and dying hepatocytes distinguish this condition from simple steatosis. The increased hepatocyte death is generally accompanied by hepatic accumulation of inflammatory cells and sometimes increases in myofibroblastic cells, leading to hepatic fibrosis and eventually, cirrhosis. The purpose of this review is to summarize similarities and differences in the pathogenesis of steatohepatitis in alcoholic fatty liver disease and nonalcoholic fatty liver disease.

Relation between liver progenitor cell expansion and extracellular matrix deposition in a CDE-induced murine model of chronic liver injury

In chronic liver injury, liver progenitor cells (LPCs) proliferate in the periportal area, migrate inside the lobule, and undergo further differentiation. This process is associated with extracellular matrix (ECM) remodeling. We analyzed LPC expansion and matrix accumulation in a choline-deficient, ethionine-supplemented (CDE) model of LPC proliferation. After day 3, CDE induced collagen deposits in the periportal area. Expansion of LPCs as assessed by increased number of cytokeratin 19 (CK19)-positive cells was first observed at day 7, while ECM accumulated 10 times more than in controls. Thereafter, LPCs and ECM increased in parallel. Furthermore, ECM not only accumulates prior to the increase in number of LPCs, but is also found in front of LPCs along the porto-venous gradient of lobular invasion. Double immunostaining revealed that LPCs are embedded in ECM at all times. Moreover, LPCs infiltrating the liver parenchyma are chaperoned by alpha-smooth muscle actin (alpha-SMA)-positive cells. Gene expression analyses confirmed these observations. The expression of CK19, alpha-fetoprotein, E-cadherin, and CD49f messenger RNA (mRNA), largely overexpressed by LPCs, significantly increased between day 7 and day 10. By contrast, at day 3 there was a rapid burst in the expression of components of the ECM, collagen I and laminin, as well as in alpha-SMA and connective tissue growth factor expression.

CONCLUSION

Our data demonstrate that, in a CDE model, ECM deposition and activation of matrix-producing cells occurred as an initial phase, prior to LPC expansion, and in front of LPCs along the porto-venous gradient of lobular invasion. Those observations may reveal a fundamental role for the established hepatic microenvironment or niche during the process of activation and differentiation of liver progenitor cells.

The clinical utility of biomarkers and the nonalcoholic steatohepatitis CRN liver biopsy scoring system in patients with nonalcoholic fatty liver disease

BACKGROUND AND AIMS

We identified patients with nonalcoholic fatty liver disease (NAFLD) to determine the predictive value of serum markers to diagnose histological steatohepatitis (NASH).

METHODS

Demographic, serological, radiological and histological variables on 95 consecutive patients with NAFLD were recorded. The serum markers studied were CK18, Hyaluronic acid, TIMP 1 and YKL 40. The NAS score and the metavir score were the histological scoring systems used.

RESULTS

CK18 levels were higher in the NASH group compared to the simple steatosis group (394 +/- 53 micro/L vs 194 +/- 26 micro/L; P < 0.05). In assessing clinical effectiveness, CK18 yielded an AUC of 0.8 for NASH (cut-off value 300 micro/L gives PPV 81% and NPV 85%).The fibrosis markers showed no differences between groups. We stratified the same cohort according to liver fibrosis (F0 vs F1-F4). Fibrosis was associated with advanced age, high body mass index and type 2 diabetes. The biomarkers performed relatively poorly at identifying liver fibrosis (F1-F4), with HA performing the best (AUC 0.73); performance improved for advanced fibrosis (F3/F4) - (HA: AUC 0.77). The NAS score performed the best overall at identifying liver fibrosis (AUC 0.79).

DISCUSSION

CK18 is the only biomarker studied that can identify NASH. Additionally, liver biopsy should be performed in all high risk patients to determine the standardised NAS score to identify patients at high risk of disease progression.

The progenitor cell compartment in the feline liver: an (immuno)histochemical investigation

The hepatic progenitor compartment is of vital importance in liver regeneration when hepatocellular replication is impaired, as it occurs in acute fulminant hepatitis or severe liver fibrosis. It consists of resident progenitor cells in the normal liver, and ductular reaction and intermediate hepatobiliary cells in diseased livers. An histologic and immunohistochemical study was conducted to demonstrate putative hepatic progenitor cells in the normal liver (n = 5) and in a range of hepatic diseases (n = 13) in the cat. Formalin-fixed, paraffin-embedded specimens were stained with HE, the van Gieson stain, and the reticulin stain according to Gordon and Sweet, and immunohistochemically stained for cytokeratin-7 (CK7), human hepatocyte marker 1 (Hepar1), and multidrug resistance-binding protein-2/ATP binding cassette C2 (MRP2). The normal feline liver contains a liver progenitor cell morphologically similar to humans and dogs, which resides in the canal of Hering. In acute and chronic feline liver diseases a ductular reaction is present, whether in the parenchyma or in a portal or septal location. The putative progenitor cells could easily be demonstrated by staining for CK7, whereas they were generally negative for Hepar1 and MRP2. In a parenchymal ductular reaction mitotic figures and cells with an intermediate hepatobiliary phenotype could be demonstrated. This is the first account of hepatic progenitor cells in feline liver.

The epidemiology of hepatocellular cancer: from the perspectives of public health problem to tumor biology

The epidemiology of hepatocellular cancer (HCC) can be viewed from several important perspectives. The conventional perspective includes the overall public health impact of HCC, which is increasing in incidence in many regions of the world. The epidemiology of HCC can also be viewed from the perspective of variation in underlying disease associations such as viral hepatitis or the recently recognized link to nonalcoholic fatty liver disease (NAFLD). Of perhaps increasing importance with recent advances in therapy of HCC, the epidemiology of HCC can also be viewed from the perspective of variation in HCC biology. This lesser known perspective may depend in part on the underlying liver disease and the cell origin of the cancer, whether of hepatocyte or stem cell origin. This aspect is likely to become central to diagnosis and management of HCC with the further development of targeted therapeutics. The relative efficacy of these agents will likely depend on the biochemical pathways active in a given hepatocellular malignancy. This, in turn, is likely to be related to the epidemiological associations of HCC.

Hepatocellular carcinomas in patients with metabolic syndrome often develop without significant liver fibrosis: a pathological analysis

Metabolic syndrome (MS) is a newly identified risk factor in chronic liver disease (CLD) and hepatocellular carcinoma (HCC). The aim of this study was to analyze the pathological characteristics of HCC and nontumoral liver in patients with MS as the only risk factor for liver disease in comparison with those that developed in the course of other CLDs in order to provide further insight into the physiopathology of HCC associated with MS. HCC patients with features of MS as the only risk factor for liver diseases (MS group, n = 31) were compared to HCC patients with overt causes of CLD (CLD group, n = 81) or without causes of CLD (cryptogenic group, n = 16) who underwent surgical resection during the same period of time. Among the patients of the MS group, there were 30 males and 1 female. In comparison with the patients with HCC of the CLD group, the patients with MS were older (mean age: 67+/- 7 versus 59 +/- 14 years, P < 0.01), and the background liver was significantly more often free of significant fibrosis (F0-F2: 65% in the MS group versus 26% in the CLD group, P < 0.001). In addition, HCCs associated with MS were more often well differentiated (65% versus 28%, P < 0.001). Five HCCs, all from the MS group, developed on a preexisting liver cell adenoma, with three of them showing typical histological features of telangiectatic adenoma.

CONCLUSION

This study shows that HCCs in patients with features of MS as the only risk factor for liver disease have distinct morphological characteristics and mainly occur in the absence of significant fibrosis in the background liver. In addition, some of them arise through malignant transformation of a preexisting liver cell adenoma.

Mitochondrial H2O2 emission and cellular redox state link excess fat intake to insulin resistance in both rodents and humans

High dietary fat intake leads to insulin resistance in skeletal muscle, and this represents a major risk factor for type 2 diabetes and cardiovascular disease. Mitochondrial dysfunction and oxidative stress have been implicated in the disease process, but the underlying mechanisms are still unknown. Here we show that in skeletal muscle of both rodents and humans, a diet high in fat increases the H(2)O(2)-emitting potential of mitochondria, shifts the cellular redox environment to a more oxidized state, and decreases the redox-buffering capacity in the absence of any change in mitochondrial respiratory function. Furthermore, we show that attenuating mitochondrial H(2)O(2) emission, either by treating rats with a mitochondrial-targeted antioxidant or by genetically engineering the overexpression of catalase in mitochondria of muscle in mice, completely preserves insulin sensitivity despite a high-fat diet. These findings place the etiology of insulin resistance in the context of mitochondrial bioenergetics by demonstrating that mitochondrial H(2)O(2) emission serves as both a gauge of energy balance and a regulator of cellular redox environment, linking intracellular metabolic balance to the control of insulin sensitivity.

The use of stem cells in liver disease

PURPOSE OF REVIEW

Cell transplantation to restore liver function as an alternative to whole liver transplantation has thus far not been successful in humans.

RECENT FINDINGS

Adult mature hepatocytes and various populations of liver progenitors and stem cells are being studied for their regenerative capabilities. Hepatocyte transplantation to treat metabolic deficiencies has shown promising early improvement in liver function; however, long-term success has not been achieved. Liver progenitor cells can now be identified and were shown to be capable to differentiate into a hepatocyte-like phenotype. Despite evidence of mesenchymal stem cell fusion in animal models of liver regeneration, encouraging results were seen in a small group of patients receiving autologous transplantation of CD133 mesenchymal stem cells to repopulate the liver after extensive hepatectomy for liver masses. Ethical issues, availability, potential rejection and limited understanding of the totipotent capabilities of embryonic stem cells are the limitations that prevent their use for restoration of liver function. The effectiveness of embryonic stem cells to support liver function has been proven with their application in the bioartificial liver model in rodents.

SUMMARY

There is ongoing research to restore liver function in cell biology, animal models and clinical trials using mature hepatocytes, liver progenitor cells, mesenchymal stem cells and embryonic stem cells.

Liver stem cells and hepatocellular carcinoma

Although the existence of cancer stem cells (CSCs) was first proposed over 40 years ago, only in the past decade have these cells been identified in hematological malignancies, and more recently in solid tumors that include liver, breast, prostate, brain, and colon. Constant proliferation of stem cells is a vital component in liver tissues. In these renewing tissues, mutations will most likely result in expansion of the altered stem cells, perpetuating and increasing the chances of additional mutations and tumor progression. However, many details about hepatocellular cancer stem cells that are important for early detection remain poorly understood, including the precise cell(s) of origin, molecular genetics, and the mechanisms responsible for the highly aggressive clinical picture of hepatocellular carcinoma (HCC). Exploration of the difference between CSCs from normal stem cells is crucial not only for the understanding of tumor biology but also for the development of specific therapies that effectively target these cells in patients. These ideas have drawn attention to control of stem cell proliferation by the transforming growth factor beta (TGF-beta), Notch, Wnt, and Hedgehog pathways. Recent evidence also suggests a key role for the TGF-beta signaling pathway in both hepatocellular cancer suppression and endoderm formation, suggesting a dual role for this pathway in tumor suppression as well as progression of differentiation from a stem or progenitor stage. This review provides a rationale for detecting and analyzing tumor stem cells as one of the most effective ways to treat cancers such as HCC.

Diagnostic use of cytokeratins, CD34, and neuronal cell adhesion molecule staining in focal nodular hyperplasia and hepatic adenoma

Cytokeratins 7 and 19 and neuronal cell adhesion molecule (CD56) are differentially expressed in the hepatocytes and biliary epithelium. CD34 is an endothelial marker that is expressed in hepatic sinusoids in conditions associated with altered vascular flow and neoplasms. Distinct staining patterns using these markers have been shown in resected specimens of focal nodular hyperplasia, telangiectatic focal nodular hyperplasia, and hepatic adenoma. The purpose of this study was to examine the diagnostic use of these markers in needle biopsies. Needle biopsies from focal nodular hyperplasia (n = 21), telangiectatic focal nodular hyperplasia (n = 2), and hepatic adenoma (n = 14) were included in the study. These cases represent typical examples of each entity that have been diagnosed on the basis of clinical, imaging, and histologic features. Corresponding resection specimens available in 9 cases were also included in the study for comparison. Immunohistochemical analysis was performed on 4-mum-thick formalin-fixed and paraffin-embedded sections using antibodies against cytokeratin 7, cytokeratin 19, neuronal cell adhesion molecule, and CD34. The staining patterns and intensity for each marker were analyzed in a blinded fashion, and the patterns were recorded as focal nodular hyperplasia-like, hepatic adenoma-like, or indeterminate for each case. Presence of normal tissue was also recorded in each case. The hepatic adenoma-like pattern is characterized by strong cytokeratin 7 positivity in hepatocytes in patches with a gradual decrease in the staining intensity as the cells differentiate toward mature hepatocytes. Hepatic adenomas lack bile ducts and ductules as highlighted by cytokeratin 7, cytokeratin 19, and neuronal cell adhesion molecule stains. The focal nodular hyperplasia-like pattern is characterized by milder and focal cytokeratin 7 staining of hepatocytes. Cytokeratin 7, cytokeratin 19, and neuronal cell adhesion molecule show a strong staining of bile ductules in the fibrous septa. Normal liver shows cytokeratin 7, cytokeratin 19, and neuronal cell adhesion molecule staining of bile ducts, whereas the hepatocytes are generally negative. Of the 21 focal nodular hyperplasia cases, 20 cases (95.2%) showed a focal nodular hyperplasia-like pattern, whereas 13 (92.2%) of 14 hepatic adenoma cases showed a hepatic adenoma-like pattern. Both cases of telangiectatic focal nodular hyperplasia showed a hepatic adenoma-like pattern. CD34 stain showed areas of diffuse endothelial staining in 2 cases of hepatic adenoma, 3 cases of focal nodular hyperplasia, and both cases of telangiectatic focal nodular hyperplasia, whereas the remaining cases showed staining of endothelial cells only in the inflow areas of the sinusoids. A mixed (diffuse and inflow) pattern of CD34 staining was seen in 1 focal nodular hyperplasia, 1 hepatic adenoma, and 2 telangiectatic focal nodular hyperplasia cases. For statistical analysis, the telangiectatic focal nodular hyperplasia were considered as variants of hepatic adenoma. The findings were found to be highly statistically significant (P < .05) for cytokeratin 7, cytokeratin 19, and neuronal cell adhesion molecule stains. An inflow staining pattern favors a diagnosis of focal nodular hyperplasia; however, overall, CD34 stain was not helpful in differentiating focal nodular hyperplasia and hepatic adenoma. Corresponding resection specimens (hepatic adenoma = 5, focal nodular hyperplasia = 2) showed staining patterns that were identical to the biopsy, whereas resections of the telangiectatic focal nodular hyperplasia cases showed both focal nodular hyperplasia and hepatic adenoma-like areas. Considering that telangiectatic focal nodular hyperplasia is now thought to be a variant of hepatic adenoma, the staining patterns correctly identified all cases, except one case each of focal nodular hyperplasia and hepatic adenoma. In summary, a combination of cytokeratin 7, cytokeratin 19, and neuronal cell adhesion molecule immunostains performed on needle biopsies of liver shows distinctive patterns similar to that of resection specimen. The stains, especially cytokeratins 7 and 19, are very helpful in distinguishing normal from lesional tissue, as well as hepatic adenoma from focal nodular hyperplasia, and could be diagnostically helpful in challenging cases. Prospective studies to evaluate use of these stains in challenging cases are needed to validate these findings.

NASH and cryptogenic cirrhosis: a histological analysis

INTRODUCTION

Epidemiological studies indicate that nonalcoholic steatohepatitis (NASH) is a common cause of cirrhosis described as 'cryptogenic'. To address this from a histological perspective and to examine the significance of residual histological findings as an indication of prior NASH, we looked back at biopsies in patients who presented with cirrhosis without sufficient histological features to diagnose NASH but who had prior histologically confirmed non-cirrhotic NASH.

METHODS

Seven patients were identified with biopsy pairs showing non-specific (cryptogenic) cirrhosis in the latest specimen and a prior biopsy showing non-cirrhotic NASH. Using an expanded NASH-CRN system scored blindly by light microscopy, we compared the early and late biopsies to each other and to a cohort of 13 patients with cirrhosis due to hepatitis C without co-existing metabolic syndrome.

RESULTS

Macrosteatosis, although uniformly present in the non-cirrhotic NASH specimens, declined in the late stage cirrhotic NASH specimens and was not useful in the distinction of late cirrhotic NASH from cirrhotic viral hepatitis. However, the presence of ballooned cells, Mallory-Denk bodies, and megamitochondria and the absence of apoptotic bodies were significantly different in late stage cirrhotic NASH compared to cirrhosis due to hepatitis C.

CONCLUSIONS

Histologically advanced NASH presenting as non-specific or cryptogenic cirrhosis has residual changes which are consistent with prior steatohepatitis but which differ from cirrhosis due to hepatitis C. These results provide histological support for the more established epidemiological associations of NASH with cryptogenic cirrhosis and for criteria used in several proposed classifications of cryptogenic cirrhosis.

Liver stem cells and hepatocellular carcinoma

Although the existence of cancer stem cells (CSCs) was first proposed over 40 years ago, only in the past decade have these cells been identified in hematological malignancies, and more recently in solid tumors that include liver, breast, prostate, brain, and colon. Constant proliferation of stem cells is a vital component in liver tissues. In these renewing tissues, mutations will most likely result in expansion of the altered stem cells, perpetuating and increasing the chances of additional mutations and tumor progression. However, many details about hepatocellular cancer stem cells that are important for early detection remain poorly understood, including the precise cell(s) of origin, molecular genetics, and the mechanisms responsible for the highly aggressive clinical picture of hepatocellular carcinoma (HCC). Exploration of the difference between CSCs from normal stem cells is crucial not only for the understanding of tumor biology but also for the development of specific therapies that effectively target these cells in patients. These ideas have drawn attention to control of stem cell proliferation by the transforming growth factor beta (TGF-beta), Notch, Wnt, and Hedgehog pathways. Recent evidence also suggests a key role for the TGF-beta signaling pathway in both hepatocellular cancer suppression and endoderm formation, suggesting a dual role for this pathway in tumor suppression as well as progression of differentiation from a stem or progenitor stage. This review provides a rationale for detecting and analyzing tumor stem cells as one of the most effective ways to treat cancers such as HCC.

Clinical correlates of histopathology in pediatric nonalcoholic steatohepatitis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease in American children. Noninvasive means to discriminate between NAFLD and nonalcoholic steatohepatitis (NASH) might diminish the requirement for liver biopsy or predict those at increased risk for progression.

METHODS

Data obtained prospectively from children (age, 6-17 y) enrolled in the NASH Clinical Research Network were analyzed to identify clinical-pathologic correlates of pediatric NAFLD. All participants underwent liver biopsy within 6 months of clinical data that were reviewed by a central pathology committee.

RESULTS

A total of 176 children (mean age, 12.4 y; 77% male) were eligible for inclusion. By using ordinal logistic regression analysis, increasing aspartate aminotransferase (AST) level (odds ratio [OR], 1.017 per U/L; 95% confidence interval [CI], 1.004-1.031) and gamma-glutamyltransferase level (OR, 1.016 per U/L; 95% CI, 1.000-1.033) were associated independently with increasing severity of NASH. Increasing AST level (OR, 1.015 per U/L; 95% CI, 1.006-1.024), increasing white blood cell count (OR, 1.22 per 1000/mm(3); 95% CI, 1.07-1.38), and decreasing hematocrit (OR, 0.87 per %; 95% CI, 0.79-0.96) were associated independently with increasing severity of fibrosis. Area under the receiver operator characteristic curve for a model with AST and alanine aminotransferase was 0.75 (95% CI, 0.66-0.84) and 0.74 (95% CI, 0.63-0.85) for distinguishing steatosis from more advanced forms of NASH and bridging fibrosis from lesser degrees of fibrosis, respectively.

CONCLUSIONS

Certain components of routine laboratory tests are predictive of NAFLD pattern and fibrosis severity, but do not have adequate discriminate power to replace liver biopsy in evaluating pediatric NAFLD.

Biliary phenotype of hepatocellular carcinoma after preoperative transcatheter arterial chemoembolization

BACKGROUND AND AIM

Transcatheter arterial chemoembolization (TACE) is now the mainstay of treatment for non-curative hepatocellular carcinoma (HCC), and hoped to have chemotherapeutic and ischemic effects; however, the histopathological changes of HCC caused by TACE have not been sufficiently discussed so far. We aimed to assess the morphological and immunohistochemical features of HCC treated with TACE by immunostaining cytokeratin (CK) 7, CK14, CK19 and vimentin, and to correlate these data with observed clinicopathological characteristics.

METHODS

Eighty cases of surgically resected HCC with preoperative TACE and 146 cases of HCC resected without TACE as a control were analyzed.

RESULTS

The incidences of intrahepatic metastasis, poorly differentiated histology, multinucleated giant cells, mitotic figures and cytoplasmic inclusion bodies in the TACE group were significantly higher than those in the non-TACE group. The TACE group showed reactivity for CK7 in 56.3% (45/80) of patients, CK14 in 12.5% (10/80), CK19 in 23.8% (19/80) and vimentin in 6.3% (5/80) of patients. CK19 expression in the TACE group was significantly higher than in the non-TACE group (P = 0.0423). There was no correlation between immunoreactivity and the number of times TACE was carried out, but the expression of CK19 and vimentin in the massive necrotic group was higher than that in the mild necrotic group (P = 0.0197, P = 0.0229, respectively). Only TACE was an independent determinant of CK19 expression in all cases by multivariate analysis.

CONCLUSIONS

These results suggest that preoperative TACE may have an impact on the biliary phenotype of HCC. Some post-therapeutic HCC patients might develop HCC with a biliary phenotype indicating more aggressive malignancies.

Activation of canonical Wnt signaling pathway promotes proliferation and self-renewal of rat hepatic oval cell line WB-F344 in vitro

AIM: To investigate the effect of activation of canonical Wnt signaling pathway on the proliferation and differentiation of hepatic oval cells in vitro.

METHODS: WB-F344 cells were treated with recombinant Wnt3a (20, 40, 80, 160, 200 ng/mL) in serum-free medium for 24 h. Cell proliferation was measured by Brdu incorporation analysis; untreated WB-F344 cells were taken as controls. After treatment with Wnt3a (160 ng/mL) for 24 h, subcellular localization and protein expression of β-catenin in WB-F344 cells treated and untreated with Wnt3a were examined by immunofluorescence staining and Western blot analysis. CyclinD1 mRNA expression was determined by semi-quantitative reverse-transcript polymerase chain reaction (RT-PCR). The mRNA levels of some phenotypic markers (AFP, CK-19, ALB) and two hepatic nuclear factors (HNF-4, HNF-6) were measured by RT-PCR. Expressions of CK-19 and AFP protein were detected by Western blot analysis.

RESULTS: Wnt3a promoted proliferation of WB-F344 cells. Stimulation of WB-F344 cells with recombinant Wnt3a resulted in accumulation of the transcriptional activator β-catenin, together with its translocation into the nuclei, and up-regulated typical Wnt target gene CyclinD1. After 3 d of Wnt3a treatment in the absence of serum, WB-F344 cells retained their bipotential to express several specific phenotypic markers of hepatocytes and cholangiocytes, such as AFP and CK-19, following activation of the canonical Wnt signaling pathway.

CONCLUSION: The canonical Wnt signaling pathway promotes proliferation and self-renewal of rat hepatic oval cells.

Does nonalcoholic fatty liver disease predispose patients to hepatocellular carcinoma in the absence of cirrhosis?

CONTEXT

Hepatocellular carcinoma (HCC) is recognized as a complication of cirrhosis related to nonalcoholic fatty liver disease (NAFLD). Diabetes and the metabolic syndrome are also associated with HCC. However, it is not clear whether NAFLD predisposes patients to HCC in the absence of cirrhosis.

OBJECTIVE

To seek evidence that HCC can develop in NAFLD unaccompanied by cirrhosis.

DESIGN

Retrospective case study was performed on cases from 2004 to 2007 at the University of Illinois at Chicago Medical Center, using the key words hepatocellular carcinoma, liver explant, and liver resection. The diagnosis of HCC was identified and confirmed by hematoxylin-eosin-stained slides in 50 cases. Cause of liver disease was determined by review of liver histology, clinical history, and laboratory data.

RESULTS

Three patients presented with advanced HCC with features of metabolic syndrome, including an elevated body mass index. Each patient had bland steatosis on liver biopsy, without fibrosis or cirrhosis. None of the 3 patients had evidence of any cause for liver disease other than NAFLD.

CONCLUSIONS

The cases presented here suggest that NAFLD may predispose patients to HCC in the absence of cirrhosis. Further studies are needed to confirm this potentially important observation.

Relationships among stellate cell activation, progenitor cells, and hepatic regeneration

Hepatic stellate cells (HSC) play an important role in liver fibrogenesis. They are also key players in liver regeneration as part of the stem cell niche of hepatocytes and hepatic progenitor cells. They produce growth stimulating and inhibiting factors for these epithelial cell compartments. In addition, recent studies suggest a role for HSCs themselves for being progenitors of epithelial cells through a transitional mesenchymal phase.

Impact of visceral fat on the metabolic syndrome and nonalcoholic fatty liver disease

Visceral fat has been reported to be associated with nonalcoholic fatty liver disease (NAFLD) and the metabolic syndrome (MetS). We assessed the prevalence of both NAFLD and the MetS, measured visceral fat thickness VFT), and estimated the physical activity indexes of 224 relatively healthy hospital workers. We also investigated the associations between both VFT and physical activity index and each of NAFLD and the MetS. The MetS was diagnosed according to the guidelines outlined by the Adult Treatment Panel III, and NAFLD was diagnosed by ultrasonography. Subjects with hepatitis B and C infections and those reporting moderate alcohol consumption were excluded from the study. The prevalence of the MetS was 11.6% and that of NAFLD was 41.5%. Many subjects with the MetS had NAFLD (73.1%), and some subjects with NAFLD (20.4%) also had several components of the MetS (p=0.001). VFT was significantly increased by both the addition of components of the MetS and the severity of NAFLD (p<0.001). In addition, VFT was independently associated with NAFLD (odds ratio [OR], 1.10; 95% confidence interval [CI], 1.02-1.19) in subjects with more than 2 components of the MetS. In contrast, habitual physical activity was reversely associated with NAFLD (OR, 0.29; 95% CI, 0.10-0.87). In conclusion, an increased visceral fat content and reduced physical activity could be not only biological markers but also therapeutic targets in the treatment of NAFLD and the MetS.

Granulocyte-colony stimulating factor induces proliferation of hepatic progenitors in alcoholic steatohepatitis: a randomized trial

Liver failure is the major cause of death in alcoholic steatohepatitis (ASH). In experimental hepatitis, granulocyte-colony stimulating factor (G-CSF) mobilizes hematopoietic stem cells, induces liver regeneration, and improves survival. We studied the short-term effects of G-CSF on CD34+ stem cell mobilization, liver cell proliferation, and liver function in patients with ASH. Twenty-four patients (mean age 54 years) with alcoholic cirrhosis [Child-Turcotte-Pugh score 10 (7-12)] and concomitant biopsy-proven ASH [Maddrey score 36 (21-60)] were randomized to standard care associated with 5 days of G-CSF (10 microg/kg/day, group A, n = 13) or standard care alone (group B, n = 11). Serial measurement of CD34+ cells, liver tests, cytokines [hepatocyte growth factor (HGF); tumor necrosis factor alpha; tumor necrosis factor-R1; interleukin-6; alfa-fetoprotein], and (13)C-aminopyrine breath tests were performed. Proliferating hepatic progenitor cells [HPC; double immunostaining (Ki67/cytokeratin 7)], histology, and neutrophils were assessed on baseline and day 7 biopsies. Abstinent alcoholic patients with cirrhosis served as controls for immunohistochemistry. G-CSF was well tolerated. At day 7, both CD34+ cells (+747% versus -6%, P < 0.003), and HGF (+212% versus -7%, P < 0.03) increased in group A but not in group B. Cytokines and aminopyrine breath test changes were similar between groups. On repeat biopsy, a >50% increase in proliferating HPC was more frequent in group A than in group B (11 versus 2, P < 0.003). Changes in Ki67+/cytokeratin 7+ cells correlated with changes in CD34+ cells (r = 0.65, P < 0.03). Neutrophils and histological changes were similar in both groups.

CONCLUSION

G-CSF mobilizes CD34+ cells, increases HGF, and induces HPC to proliferate within 7 days of administration. Larger trials would be required to determine whether these changes translate into improved liver function.

Dysregulation of adipose glutathione peroxidase 3 in obesity contributes to local and systemic oxidative stress

Glutathione peroxidase 3 (GPx3) accounts for the major antioxidant activity in the plasma. Here, we demonstrate that down-regulation of GPx3 in the plasma of obese subjects is associated with adipose GPx3 dysregulation, resulting from the increase of inflammatory signals and oxidative stress. Although GPx3 was abundantly expressed in kidney, lung, and adipose tissue, we observed that GPx3 expression was reduced selectively in the adipose tissue of several obese animal models as decreasing plasma GPx3 level. Adipose GPx3 expression was greatly suppressed by prooxidative conditions such as high levels of TNFalpha and hypoxia. In contrast, the antioxidant N-acetyl cysteine and the antidiabetic drug rosiglitazone increased adipose GPx3 expression in obese and diabetic db/db mice. Moreover, GPx3 overexpression in adipocytes improved high glucose-induced insulin resistance and attenuated inflammatory gene expression whereas GPx3 neutralization in adipocytes promoted expression of proinflammatory genes. Taken together, these data suggest that suppression of GPx3 expression in the adipose tissue of obese subjects might constitute a vicious cycle to expand local reactive oxygen species accumulation in adipose tissue potentially into systemic oxidative stress and obesity-related metabolic complications.

Fate-mapping evidence that hepatic stellate cells are epithelial progenitors in adult mouse livers

Liver injury activates quiescent hepatic stellate cells (Q-HSC) to proliferative myofibroblasts. Accumulation of myofibroblastic hepatic stellate cells (MF-HSC) sometimes causes cirrhosis and liver failure. However, MF-HSC also promote liver regeneration by producing growth factors for oval cells, bipotent progenitors of hepatocytes and cholangiocytes. Genes that are expressed by primary hepatic stellate cell (HSC) isolates overlap those expressed by oval cells, and hepatocytic and ductular cells emerge when HSC are cultured under certain conditions. We evaluated the hypothesis that HSC are a type of oval cell and, thus, capable of generating hepatocytes to regenerate injured livers. Because Q-HSC express glial fibrillary acidic protein (GFAP), we crossed mice in which GFAP promoter elements regulated Cre-recombinase with ROSA-loxP-stop-loxP-green fluorescent protein (GFP) mice to generate GFAP-Cre/GFP double-transgenic mice. These mice were fed methionine choline-deficient, ethionine-supplemented diets to activate and expand HSC and oval cell populations. GFP(+) progeny of GFAP-expressing precursors were characterized by immunohistochemistry. Basal expression of mesenchymal markers was negligible in GFAP(+)Q-HSC. When activated by liver injury or culture, HSC downregulated expression of GFAP but remained GFP(+); they became highly proliferative and began to coexpress markers of mesenchyme and oval cells. These transitional cells disappeared as GFP-expressing hepatocytes emerged, began to express albumin, and eventually repopulated large areas of the hepatic parenchyma. Ductular cells also expressed GFAP and GFP, but their proliferative activity did not increase in this model. These findings suggest that HSC are a type of oval cell that transitions through a mesenchymal phase before differentiating into hepatocytes during liver regeneration. Disclosure of potential conflicts of interest is found at the end of this article.

Liver stem cells: a scientific and clinical perspective

The promise of liver stem cells lie in their potential to provide a continual and readily available source of liver cells that can be used for gene therapy, cellular transplant, bioartificial liver-assisted devices, drug toxicology testing and use as an in vitro model to understand the developmental biology of the liver. Both the rodent and human embryonic stem cell, bone marrow hematopoietic stem cell, mesenchymal stem cell, umbilical cord blood cell, fetal liver progenitor cell, adult liver progenitor cell as well as the mature hepatocyte have been reported to be capable of self-renewal, giving rise to daughter hepatocytes both in vivo and in vitro. These cells can repopulate livers in animal models of liver injury and seemingly improve liver function. However, significant challenges still exist before these cells can be used in humans. These include lack of consensus in immunophenotype of liver progenitor cells, uncertainty of the physiological role of reported candidate stem/progenitor cell, practicality in obtaining sufficient quantity of cells for clinical use and concerns over ethics, long-term efficacy and safety. Current molecular techniques of stem cell identification are confounded by cell fusion, horizontal gene transfer, incomplete differentiation and fetal microchimerism. Reports of stem cell transplantation and phase 1 trials of bone marrow transplantation in humans for liver diseases are exciting but require more robust verification. We review the evidence for various candidate stem cells, human clinical trials reported to date and highlight the challenges facing clinicians in their quest to use liver stem cells to save lives.