Progenitor cell expansion: an important source of hepatocyte regeneration in chronic hepatitis

Characterisation of forkhead box protein A3 as a key transcription factor for hepatocyte regeneration

Background & Aims

Liver regeneration is vital for the recovery of liver function after injury, yet the underlying mechanism remains to be elucidated. Forkhead box protein A3 (FOXA3), a member of the forkhead box family, plays important roles in endoplasmic reticulum stress sensing, and lipid and glucose homoeostasis, yet its functions in liver regeneration are unknown.

Methods

Here, we explored whether Foxa3 regulates liver regeneration via acute and chronic liver injury mice models. We further characterised the molecular mechanism by chromatin immunoprecipitation sequencing and rescue experiments in vivo and in vitro. Then, we assessed the impact of Foxa3 pharmacological activation on progression and termination of liver regeneration. Finally, we confirmed the Foxa3-Cebpb axis in human liver samples.

Results

Foxa3 is dominantly expressed in hepatocytes and cholangiocytes and is induced upon partial hepatectomy (PH) or carbon tetrachloride (CCl4) administration. Foxa3 deficiency in mice decreased cyclin gene levels and delayed liver regeneration after PH, or acute or chronic i.p. CCl4 injection. Conversely, hepatocyte-specific Foxa3 overexpression accelerated hepatocytes proliferation and attenuated liver damage in an CCl4-induced acute model. Mechanistically, Foxa3 directly regulates Cebpb transcription, which is involved in hepatocyte division and apoptosis both in vivo and in vitro. Of note, Cebpb overexpression in livers of Foxa3-deficient mice rescued their defects in cell proliferation and regeneration upon CCl4 treatment. In addition, pharmacological induction of Foxa3 via cardamonin speeded up hepatocyte proliferation after PH, without interfering with liver regeneration termination. Finally, Cebpb and Ki67 levels had a positive correlation with Foxa3 expression in human chronic disease livers.

Conclusions

These data characterise Foxa3 as a vital regulator of liver regeneration, which may represent an essential factor to maintain liver mass after liver injury by governing Cebpb transcription.

Impact and Implications

Liver regeneration is vital for the recovery of liver function after chemical insults or hepatectomy, yet the underlying mechanism remains to be elucidated. Herein, via in vitro and in vivo models and analysis, we demonstrated that Forkhead box protein A3 (FOXA3), a Forkhead box family member, maintained normal liver regeneration progression by governing Cebpb transcription and proposed cardamonin as a lead compound to induce Foxa3 and accelerate liver repair, which signified that FOXA3 may be a potential therapeutic target for further preclinical study on treating liver injury.

P4HA2 induces hepatic ductular reaction and biliary fibrosis in chronic cholestatic liver diseases

BACKGROUNDS

Prolyl-4-hydroxylases (P4Hs) are key enzymes in collagen synthesis. The P4HA subunit (P4HA1, P4HA2, and P4HA3) contains a substrate binding and catalyzation domain. We postulated that P4HA2 would play a key role in the cholangiocyte pathology of cholestatic liver diseases.

METHODS

We studied humans with primary biliary cholangitis (PBC) and Primary sclerosing cholangitis (PSC), P4HA2 -/- mice injured by DDC, and P4HA2 -/- /MDR2 -/- double knockout mice. A parallel study was performed in patients with PBC, PSC, and controls using immunohistochemistry and immunofluorescence. In the murine model, the level of ductular reaction and biliary fibrosis were monitored by histology, qPCR, immunohistochemistry, and Western blotting. Expression of Yes1 Associated Transcriptional Regulator (YAP) phosphorylation was measured in isolated mouse cholangiocytes. The mechanism of P4HA2 was explored in RBE and 293T cell lines by using qPCR, Western blot, immunofluorescence, and co-immunoprecipitation.

RESULTS

The hepatic expression level of P4HA2 was highly elevated in patients with PBC or PSC. Ductular reactive cholangiocytes predominantly expressed P4HA2. Cholestatic patients with more severe liver injury correlated with levels of P4HA2 in the liver. In P4HA2 -/- mice, there was a significantly reduced level of ductular reaction and fibrosis compared with controls in the DDC-induced chronic cholestasis. Decreased liver fibrosis and ductular reaction were observed in P4HA2 -/- /MDR2 -/- mice compared with MDR2 -/- mice. Cholangiocytes isolated from P4HA2 -/- /MDR2 -/- mice displayed a higher level of YAP phosphorylation, resulting in cholangiocytes proliferation inhibition. In vitro studies showed that P4HA2 promotes RBE cell proliferation by inducing SAV1 degradation, eventually resulting in the activation of YAP.

CONCLUSIONS

P4HA2 promotes hepatic ductular reaction and biliary fibrosis by regulating the SAV1-mediated Hippo signaling pathway. P4HA2 is a potential therapeutic target for PBC and PSC.

Ductular reaction in non-alcoholic fatty liver disease: When Macbeth is perverted

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction)-associated fatty liver disease is the leading cause of chronic liver diseases defined as a disease spectrum comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), liver fibrosis, cirrhosis, and hepatic carcinoma. NASH, characterized by hepatocyte injury, steatosis, inflammation, and fibrosis, is associated with NAFLD prognosis. Ductular reaction (DR) is a common compensatory reaction associated with liver injury, which involves the hepatic progenitor cells (HPCs), hepatic stellate cells, myofibroblasts, inflammatory cells (such as macrophages), and their secreted substances. Recently, several studies have shown that the extent of DR parallels the stage of NASH and fibrosis. This review summarizes previous research on the correlation between DR and NASH, the potential interplay mechanism driving HPC differentiation, and NASH progression.

Clinical, histological and molecular profiling of different stages of alcohol-related liver disease

OBJECTIVE

Alcohol-related liver disease (ALD) ranges from never-decompensated ALD (ndALD) to the life-threatening decompensated phenotype, known as alcohol-related hepatitis (AH). A multidimensional study of the clinical, histological and molecular features of these subtypes is lacking.

DESIGN

Two large cohorts of patients were recruited in an international, observational multicentre study: a retrospective cohort of patients with ndALD (n=110) and a prospective cohort of patients with AH (n=225). Clinical, analytical, immunohistochemistry and hepatic RNA microarray analysis of both disease phenotypes were performed.

RESULTS

Age and mean alcohol intake were similar in both groups. AH patients had greater aspartate amino transferase/alanine amino transferase ratio and lower gamma-glutamyl transferase levels than in ndALD patients. Patients with AH demonstrated profound liver failure and increased mortality. One-year mortality was 10% in ndALD and 50% in AH. Histologically, steatosis grade, ballooning and pericellular fibrosis were similar in both groups, while advanced fibrosis, Mallory-Denk bodies, bilirubinostasis, severe neutrophil infiltration and ductular reaction were more frequent among AH patients. Transcriptome analysis revealed a profound gene dysregulation within both phenotypes when compare to controls. While ndALD was characterised by deregulated expression of genes involved in matrisome and immune response, the development of AH resulted in a marked deregulation of genes involved in hepatocyte reprogramming and bile acid metabolism.

CONCLUSIONS

Despite comparable alcohol intake, AH patients presented with worse liver function compared with ndALD patients. Bilirubinostasis, severe fibrosis and ductular reaction were prominent features of AH. AH patients exhibited a more profound deregulation of gene expression compared with ndALD patients.

Peritumoral histopathologic findings in patients with chronic viral hepatitis-associated hepatocellular carcinoma

Data on peritumoral histopathologic findings in patients with hepatocellular carcinoma (HCC) is limited. In this retrospective study, we evaluated the peritumoral histopathologic changes in patients with chronic viral hepatitis (CVH)-associated HCC (CVH-HCC) and their prognostic value. 61 consecutive cirrhotic patients who underwent liver transplantation due to CVH-HCC were included. Histopathologic features within 1 cm distance of the tumor, and their association with clinicopathological characteristics and prognosis were evaluated. A random representative slide of cirrhotic parenchyma unrelated to invasive and/or dysplastic foci was also evaluated for the same histopathologic criteria. The majority (85%, n = 52) were male with a median age of 55 ± 6.38 (range, 39-67). The etiologic agent was only HBV in 90% (n = 55). The most common peritumoral findings were portal inflammation (100%; n = 61), ductular reaction (100%; n = 61) and sinusoidal dilatation (95%; n = 58). Macrovascular invasion was observed only in four cases (7%) with mild peritumoral portal inflammation. Neutrophilic infiltration of the peritumoral portal tracts (n = 18; 30%) was significantly associated with pT4 tumor stage, tumor grade, macrovascular invasion, and pretransplant therapy. Patients with moderate or severe peritumoral sinusoidal dilatation tended to have worse prognosis, albeit not significantly. Peritumoral ballooning degeneration was associated with multifocality, recurrence and recurrence-free survival in both uni- and multivariate analysis. Peritumoral histopathologic changes in CVH-HCC can be classified as: changes related to pathogenesis, changes indirectly affecting prognosis, and changes directly affecting prognosis. Peritumoral prominent ballooning degeneration may be a predictor of recurrence while portal neutrophilic infiltration and sinusoidal dilatation seem to indicate poor prognosis.

A review of hepatic fibrosis-associated histopathology in aged cadavers

This article reviews hepatic fibrosis-associated histopathology of aged cadavers (mean age 82 years). A study of 68 livers identified steatosis in 35.5%, central vein fibrosis in 49.2%, perisinusoidal fibrosis in 63.2%, portal tract fibrosis in 47.7%, septa formation in 44.1%, bridging fibrosis in 30.8%, and cirrhosis in 4.4% of the samples as well as one hepatocellular carcinoma and six metastatic tumors. Other studies have revealed that collagens I, III, IV, V, and VI and fibronectin constitute the matrices of fibrous central veins, perisinusoidal space, portal tracts, and septa. Elastin is rich in portal tracts and fibrous septa but absent from the perisinusoidal space. Hepatic stellate cells are ubiquitous in the liver parenchyma while myofibroblasts localize in fibrotic foci. Factor VIII-related antigen expression signals sinusoidal to systemic vascular endothelium transformation while collagen IV and laminin codistribution indicates formation of perisinusoidal membranes. Their coincidence reflects focalized capillarization of sinusoids in the aged liver. In response to fibrogenesis, hepatic progenitor cells residing in the canal of Hering in the periportal parenchyma undergo expansion and migration deep into the lobule. Concomitantly, intermediate hepatocyte-like cells increase in advanced fibrosis stages, which is possibly related to hepatic regeneration. Metabolic zonation of glutamine synthetase expands from the perivenous to non-perivenous parenchyma in fibrosis progression but its expression is lost in cirrhosis, while cytochrome P-4502E1 expression is maintained in centrilobular and midlobular zones in fibrosis progression and expressed in cirrhosis. Hence, cadaveric livers provide a platform for further investigation of hepatic histopathologies associated with the aging liver.

GITR/GITRL reverse signalling modulates the proliferation of hepatic progenitor cells by recruiting ANXA2 to phosphorylate ERK1/2 and Akt

Hepatic stem/progenitor cells are the major cell compartment for tissue repair when hepatocyte proliferation is compromised in chronic liver diseases, but the expansion of these cells increases the risk of carcinogenesis. Therefore, it is essential to explore the pathways restricting their expansion and abnormal transformation. The ligand of glucocorticoid-induced tumour necrosis factor receptor (GITRL) showed the most highly increased expression in hepatic progenitor cells treated with transforming growth factor (TGF)-β1. If overexpressed by hepatic progenitor cells, GITRL stimulated cell proliferation by activating the epithelial–mesenchymal transition pathway and enhancing ERK1/2 and Akt phosphorylation via GITRL binding to ANXA2. However, GITR, the specific GITRL receptor, suppressed the epithelial–mesenchymal transition pathway of GITRL-expressing cells and decreased their growth by dissociating ANXA2 from GITRL and reducing downstream ERK1/2 and Akt phosphorylation. This study identifies GITR/GITRL reverse signalling as a cross-interaction pathway between immune cells and hepatic stem/progenitor cells that restricts the expansion of hepatic stem/progenitor cells and reduces the possibility of carcinogenesis.

Keratin 7 expression in hepatic cholestatic diseases

We evaluated keratin 7 (K7) hepatocellular expression in 92 patients with common types of acute and chronic cholestatic diseases caused by bile duct obstruction/destruction or parenchymal lesions [acute hepatitis (n=20), mixed/pure cholestasis (n=16), primary biliary cholangitis-PBC (n=35), primary sclerosing cholangitis-PSC (n=10), vanishing bile duct syndrome (n=3), complete large bile duct obstruction due to space-occupying lesions (n=8)]. K7 immunohistochemical hepatocellular expression and ductular reaction (DR) were semi-quantitatively assessed. Results were correlated with liver enzyme serum levels, cholestasis type, histological features, hepatocellular Ki67 labelling index (LI) and HepPar1 expression. Hepatocellular K7 expression was detected in 87% (81/92) cases and in all cholestatic disease types with lowest incidence in pure/mixed cholestasis and highest in incomplete bile duct obstruction (iBDO), reaching 100% in PSC. K7-positive hepatocytes had low Ki67 LI (0-5%) retaining HepPar1 expression, irrespective of disease type. PSC cases had high K7 hepatocellular expression even with intact bile ducts, a feature that may aid differential diagnosis of cholestatic syndromes. K7 hepatocellular expression significantly correlated with cholestasis type, bile duct loss and fibrosis stage. It was higher in milder acute cholestatic hepatitis showing inverse correlation with hepatocyte proliferation and serum transaminase levels. In iBDO, younger age independently correlated with high K7 expression, while serum GGT levels showed a nearly significant correlation. Correlation with DR findings implied that K7-positive hepatocytes may result through metaplasia. In conclusion, K7 hepatocellular expression is a sensitive though non-specific marker of cholestasis. It may represent a cytoprotective reaction of resting hepatocytes in cholestasis of longer duration especially in younger patients.

Liver regeneration and liver metastasis

Surgical resection for primary and secondary hepatic neoplasms provides the best chance of cure. Advanced surgical techniques such as portal vein embolisation, two-staged hepatectomy and associated liver partition and portal vein ligation for staged-hepatectomy (ALPPS) have facilitated hepatic resection in patients with previously unresectable, bi-lobar disease. These techniques are frequently employed to ensure favourable clinical outcomes and avoid potentially fatal post-operative complications such as small for size syndrome and post-hepatectomy liver failure. However, they rely on the innate ability of the liver to regenerate. As our knowledge of liver organogenesis, liver regeneration and hepatocarcinogenesis has expanded in recent decades it has come to light that liver regeneration may also drive tumour recurrence. Clinical studies in patients undergoing portal vein embolisation indicate that tumours may progress following the procedure in concordance with liver regeneration and hypertrophy, however overall survival in these patients has not been shown to be worse. In this article, we delve into the mechanisms underlying liver regeneration to better understand the complex ways in which this may affect tumour behaviour and ultimately inform clinical decisions.

Association of novel markers of liver disease with neonatal liver disease in premature baboons, Papio sp

Parenteral Nutrition (PN) Associated Liver Disease (PNALD) affects up to 60% of neonates; however, techniques for diagnosing and monitoring disease progression remain limited. The neonatal baboon model may provide a unique opportunity to identify serologic markers associated with this disease. The purpose of this study was to investigate if Hyaluronic Acid (HA), TIMP metallopeptidase inhibitor 1 (TIMP1), Amino-terminal Propeptide of Type-III Collagen (PIIINP) and Enhanced Liver Fibrosis (ELF) score associate with histological liver disease in neonatal baboons exposed to PN. Preterm baboons delivered via c-section at 67% gestation received PN for 14 days with or without Intralipid (PRT+IL, PRT-IL, respectively) or were sacrificed after birth (PRTCTR). Term baboons were sacrificed after birth (TERMCTR) or survived 14 days (TERM+14d). Serum HA, TIMP1, and PIIINP concentrations were measured by ELISA. A blinded pathologist assigned liver histological scores following necropsy. HA increased 9.1-fold, TIMP1 increased 2.2-fold, and ELF score increased 1.4-fold in PRT-IL compared to PRTCTR. ALT, AST, and GGT were within normal limits and did not vary between groups. A trend towards increased fibrosis was found in PRT-IL baboons. Microvesicular hepatocyte steatosis and Kupffer cell hypertrophy were elevated in PRT-IL vs PRTCTR. HA and TIMP1 were significantly elevated in preterm baboons with early histological findings of liver disease evidenced by hepatic steatosis, Kupffer cell hypertrophy and a trend towards fibrosis whereas traditional markers of liver disease remained normal. These novel markers could potentially be utilized for monitoring early hepatic injury in neonates.

Cholest-4,6-Dien-3-One Promote Epithelial-To-Mesenchymal Transition (EMT) in Biliary Tree Stem/Progenitor Cell Cultures In Vitro

Human biliary tree stem/progenitor cells (hBTSCs), reside in peribiliary glands, are mainly stimulated by primary sclerosing cholangitis (PSC) and cholangiocarcinoma. In these pathologies, hBTSCs displayed epithelial-to-mesenchymal transition (EMT), senescence characteristics, and impaired differentiation. Here, we investigated the effects of cholest-4,6-dien-3-one, an oxysterol involved in cholangiopathies, on hBTSCs biology. hBTSCs were isolated from donor organs, cultured in self-renewal control conditions, differentiated in mature cholangiocytes by specifically tailored medium, or exposed for 10 days to concentration of cholest-4,6-dien-3-one (0.14 mM). Viability, proliferation, senescence, EMT genes expression, telomerase activity, interleukin 6 (IL6) secretion, differentiation capacity, and HDAC6 gene expression were analyzed. Although the effect of cholest-4,6-dien-3-one was not detected on hBTSCs viability, we found a significant increase in cell proliferation, senescence, and IL6 secretion. Interestingly, cholest-4.6-dien-3-one impaired differentiation in mature cholangiocytes and, simultaneously, induced the EMT markers, significantly reduced the telomerase activity, and induced HDAC6 gene expression. Moreover, cholest-4,6-dien-3-one enhanced bone morphogenic protein 4 (Bmp-4) and sonic hedgehog (Shh) pathways in hBTSCs. The same pathways activated by human recombinant proteins induced the expression of EMT markers in hBTSCs. In conclusion, we demonstrated that chronic exposition of cholest-4,6-dien-3-one induced cell proliferation, EMT markers, and senescence in hBTSC, and also impaired the differentiation in mature cholangiocytes.

A critical role of autophagy in regulating the mesenchymal transition of ductular cells in liver cirrhosis

Our previous studies have shown that autophagy mediates the link between ductular reaction (DR) and liver cirrhosis. Whether the subsequent fibrogenic response is regulated by increased autophagy in DR remains unclear. Here, using both human liver specimens and a rat model of liver cirrhosis induced by 2-acetylaminofluorene (AAF) and carbon tetrachloride (CCL4), we explored the involvement of autophagy in regulating mesenchymal transition of ductular cells. Ductular cells from AAF/CCL4 livers exhibited increased autophagy compared to those of normal livers. These cells showed morphological and functional characteristics of mesenchymal cells. Blocking autophagy using bafilomycin A1 or siRNA targeting ATG7 reduced the expression of mesenchymal markers in these ductular cells from AAF/CCL4 livers, indicating a role for autophagy in regulating the mesenchymal phenotype of ductular cells. Furthermore, we show that the mesenchymal transition in DR requires the activation of transforming growth factor-β (TGF-β) signaling in an autophagy-dependent manner. Importantly, in cirrhotic human livers, ductular cells that are positive for LC3B also showed increased expression of TGF-β and fibroblast-specific protein-1. Our data suggest activation of autophagy in ductular cells, and also demonstrate that it is required for the mesenchymal transition during the DR, processes that are critically involved in the pathogenesis of cirrhosis.

Redox cell signaling and hepatic progenitor cells

Hepatic diseases are widespread in the world and organ transplantation is currently the only treatment for liver failure. New cell-based approaches have been considered, since stem cells may represent a possible source to treat liver diseases. Acute and chronic liver diseases are characterized by high production of reactive oxygen and nitrogen species, with consequent oxidative modifications of cellular macromolecules and alteration of signaling pathways, metabolism and cell cycle. Although considered harmful molecules, reactive species are involved in cell growth and differentiation processes, modulating the activity of transcription factors, which take part in stemness/proliferation. It is conceivable that redox balance may regulate the development of hepatic progenitor cells, function and survival in synchrony with metabolism during chronic liver diseases. This review aims to summarize diverse redox-sensitive signaling pathways involved in stem cell fate, highlighting the important role of hepatic progenitor cells as a possible source to treat end-stage liver disease for organ regeneration.

Ductular reaction correlates with fibrogenesis but does not contribute to liver regeneration in experimental fibrosis models

Background and aims

Ductular reaction is a standard component of fibrotic liver tissue but its function is largely unknown. It is supposed to interact with the matrix producing myofibroblasts and compensate the declining regenerative capacity of hepatocytes. The relationship between the extent of fibrosis—ductular reaction, proliferative activity of hepatocytes and ductular reaction were studied sequentially in experimental hepatic fibrosis models.

Methods

Liver fibrosis/cirrhosis was induced in wild type and TGFβ overproducing transgenic mice by carbon tetrachloride and thioacetamide administration. The effect of thioacetamide was modulated by treatment with imatinib and erlotinib. The extent of ductular reaction and fibrosis was measured by morphometry following cytokeratin 19 immunofluorescent labeling and Picro Sirius staining respectively. The proliferative activity of hepatocytes and ductular reaction was evaluated by BrdU incorporation. The temporal distribution of the parameters was followed and compared within and between different experimental groups.

Results

There was a strong significant correlation between the extent of fibrosis and ductular reaction in each experimental group. Although imatinib and erlotinib temporarily decreased fibrosis this effect later disappeared. We could not observe negative correlation between the proliferation of hepatocytes and ductular reaction in any of the investigated models.

Conclusions

The stringent connection between ductular reaction and fibrosis, which cannot be influenced by any of our treatment regimens, suggests that there is a close mutual interaction between them instead of a unidirectional causal relationship. Our results confirm a close connection between DR and fibrogenesis. However, since the two parameters changed together we could not establish a causal relationship and were unable to reveal which was the primary event. The lack of inverse correlation between the proliferation of hepatocytes and ductular reaction questions that ductular reaction can compensate for the failing regenerative activity of hepatocytes. No evidences support the persistent antifibrotic property of imatinib or erlotinib.

Ketogenic diet attenuates hepatopathy in mouse model of respiratory chain complex III deficiency caused by a Bcs1l mutation

Mitochondrial disorders are among the most prevalent inborn errors of metabolism but largely lack treatments and have poor outcomes. High-fat, low-carbohydrate ketogenic diets (KDs) have shown beneficial effects in mouse models of mitochondrial myopathies, with induction of mitochondrial biogenesis as the suggested main mechanism. We fed KD to mice with respiratory chain complex III (CIII) deficiency and progressive hepatopathy due to mutated BCS1L, a CIII assembly factor. The mutant mice became persistently ketotic and tolerated the KD for up to 11 weeks. Liver disease progression was attenuated by KD as shown by delayed fibrosis, reduced cell death, inhibition of hepatic progenitor cell response and stellate cell activation, and normalization of liver enzyme activities. Despite no clear signs of increased mitochondrial biogenesis in the liver, CIII assembly and activity were improved and mitochondrial morphology in hepatocytes normalized. Induction of hepatic glutathione transferase genes and elevated total glutathione level were normalized by KD. Histological findings and transcriptome changes indicated modulation of liver macrophage populations by the mutation and the diet. These results reveal a striking beneficial hepatic response to KD in mice with mitochondrial hepatopathy and warrant further investigations of dietary modification in the management of these conditions in patients.

Human liver regeneration in advanced cirrhosis is organized by the portal tree

BACKGROUND & AIMS

In advanced cirrhosis new hepatocytic nodules are generated by budding of ductules in areas of parenchymal extinction. However, the vascular alterations in the areas of parenchymal extinction, the blood supply and the structure of the new hepatocytic nodules have not been analyzed in detail.

METHODS

Explanted human cirrhotic livers of three different etiologies and two experimental rat models of cirrhosis were thoroughly examined. 3D reconstruction of the immunohistochemically stained serial sections and casting of human and experimental cirrhotic livers have been used to reveal the structural organization of the regenerative buds.

RESULTS

In areas of parenchymal extinction the skeleton of the liver, the portal tree is preserved. The developing regenerative nodules are positioned along the portal tree and are directly supplied by terminal portal venules. The expanding nodules grow along the trunks of the portal vein. Casting of human and experimental cirrhotic livers by colored resin confirms that nodules are supplied by portal blood. The two other members of the portal triads become separated from the portal veins.

CONCLUSIONS

As the structure of the hepatocyte nodules (centrally located portal vein branches, bile ducts at the periphery, hepatic veins and arteries in the connective tissue) impedes the restoration of normal liver structure, the basic architecture of hepatic tissue suffers permanent damage. We suggest that "budding" may initiate the second, irreversible stage of cirrhosis.

LAY SUMMARY

Cirrhosis is the final common outcome of long lasting hepatic injury defined as the destruction of the normal liver architecture by scar tissue. In the late phase of cirrhosis stem cells-derived hepatocyte nodules appear along the branches of the portal vein suggesting an important role of this specially composed blood vessels (containing digestive end-products from the stomach and intestines) in liver regeneration. Our results contribute to a better understanding of this serious liver disease.

In hepatic venous outflow obstruction, alcoholic liver disease, and nonalcoholic fatty liver disease, centrilobular scars, CD34+ vessels, and keratin 7+ hepatocytes are in close proximity

For hepatic venous outflow obstruction, alcoholic liver injury, and nonalcoholic fatty liver disease, the term "centrizonal injury disease" (CID) is used, because injury patterns in all three entities are similar. To elucidate CID-related CD34+ vessels (sinusoids and/or microvessels) and keratin 7+ hepatocytes (K7+ Hs), we examined a series of 41 liver tissue specimens obtained at autopsy and surgery, consisting of 32 CID cases and 9 controls. Centrizonal scars were found in 21 CID cases, and these were associated with centrizonal CD34+ vessels (P = 0.009) and centrizonal K7+ Hs (P < 0.001). Centrizonal coexistence of CD34+ vessels and K7+ Hs was observed in 22 CID cases (P = 0.057). These findings suggest close centrizonal proximity of scar, CD34+ vessels, and K7+ Hs in CID. However, centrizonal K7+ Hs without CD34+ vessels were observed in 21 CID cases. CD34+ vessels were detectable in all control samples and may represent the normal vascular bed. In 29 CID cases, centrizonal CD34+ vessel density was higher than that in controls. However, most appeared to be continuous with periportal and/or interlobular CD34+ vessels, and those CD34+ vessels restricted to centrizonal regions were focal and limited in seven CID cases. Centrizonal CD34+ vessels were associated with venoportal adhesions (P = 0.027). Our findings suggest that CID induces both venoportal adhesion-related structural distortion and expansion of normally present CD34+ vessels, which may result in increased centrizonal CD34+ vessel density.

Quantitative morphometric and immunohistochemical analysis and their correlates in cirrhosis--A study on explant livers

BACKGROUND

Reproducible structural analysis was made on cirrhotic human liver samples in order to reveal potential connections between morphological and laboratory parameters.

MATERIAL AND METHODS

Large histological samples were taken from segment VII of 56 cirrhotic livers removed in connection with liver transplantation. Picro Sirius red and immunohistochemically (smooth muscle actin [SMA], cytokeratin 7 [CK7], Ki-67) stained sections were digitalized and morphometric evaluation was performed.

RESULTS

The Picro Sirius-stained fibrotic area correlated with the average thickness of the three broadest septa, extent of SMA positivity, alkaline phosphatase (ALP) values and it was lower in the viral hepatitis related cirrhoses than in samples with non-viral etiology. The extent of SMA staining increased with the CK7-positive ductular reaction. The proliferative activity of the hepatocytes correlated positively with the Ki-67 labeling of the ductular cells and inversely with the septum thickness. These data support the potential functional connection among different structural components, for example, myofibroblasts, ductular reaction and fibrogenesis but challenges the widely proposed role of ductular cells in regeneration.

CONCLUSION

Unbiased morphological characterization of cirrhotic livers can provide valuable, clinically relevant information. Similar evaluation of routine core biopsies may increase the significance of this 'Gold Standard' examination.

Alpha-fetoprotein: A biomarker for the recruitment of progenitor cells in the liver in patients with acute liver injury or failure

AIM

The optimal conditions for hepatocyte proliferation should be clarified in an attempt to improve the impaired liver regeneration observed in patients with acute liver failure (ALF). In order to evaluate the significance of the serum α-fetoprotein (AFP). level and prothrombin time international normalized ratio (PT-INR) as possible biomarkers of the proliferation of liver stem/progenitor cells (LPC) and mature hepatocytes (MH), respectively, we focused on donors of living donor liver transplantation (LDLT) and patients with acute liver injury (ALI), including ALF.

METHODS

Seventy-three patients with ALI/ALF and 11 donors for LDLT were evaluated. LPC induction was histologically evaluated using cytokeratin (CK)-7 staining in 45 ALI/ALF patients.

RESULTS

The AFP level was not apparently elevated during the observation period in any of the LDLT donors, whereas the serum AFP levels were substantially increased in the patients with ALI/ALF and significantly correlated with the number of CK-7 positive LPC in the liver, except for very severe damaged liver. All patients exhibiting an early peak in the AFP level prior to PT-INR elevation died.

CONCLUSION

The serum AFP level may reflect the induction of LPC in ALI/ALF patients. The substantial and persistent induction of LPC until sufficient regeneration of MH may be needed for a recovery from ALF. We herein demonstrate that the serum AFP level may be a serum marker of LPC in patients with ALI/ALF. A comparison of the serial changes in the AFP levels and PT-INR in our study patients showed impaired proliferation of LPC and delayed recovery of MH in the patients who died.

Kupffer cell-monocyte communication is essential for initiating murine liver progenitor cell-mediated liver regeneration

Liver progenitor cells (LPCs) are necessary for repair in chronic liver disease because the remaining hepatocytes cannot replicate. However, LPC numbers also correlate with disease severity and hepatocellular carcinoma risk. Thus, the progenitor cell response in diseased liver may be regulated to optimize liver regeneration and minimize the likelihood of tumorigenesis. How this is achieved is currently unknown. Human and mouse diseased liver contain two subpopulations of macrophages with different ontogenetic origins: prenatal yolk sac-derived Kupffer cells and peripheral blood monocyte-derived macrophages. We examined the individual role(s) of Kupffer cells and monocyte-derived macrophages in the induction of LPC proliferation using clodronate liposome deletion of Kupffer cells and adoptive transfer of monocytes, respectively, in the choline-deficient, ethionine-supplemented diet model of liver injury and regeneration. Clodronate liposome treatment reduced initial liver monocyte numbers together with the induction of injury and LPC proliferation. Adoptive transfer of monocytes increased the induction of liver injury, LPC proliferation, and tumor necrosis factor-α production.

CONCLUSION

Kupffer cells control the initial accumulation of monocyte-derived macrophages. These infiltrating monocytes are in turn responsible for the induction of liver injury, the increase in tumor necrosis factor-α, and the subsequent proliferation of LPCs.

Hepatic progenitor cells in children with chronic hepatitis C: correlation with histopathology, viremia, and treatment response

OBJECTIVE

Hepatic progenitor cells (HPCs) are bipotential stem cells that can differentiate towards the hepatocytic and cholangiocytic lineages. Many studies have investigated HPCs in adults with hepatitis C virus infection; however, none has been carried out in the pediatric population. Therefore, this work aimed to investigate HPCs expansion in children with chronic hepatitis C (CHC) and its correlation with histopathology, viremia, and treatment response.

PATIENTS AND METHODS

Eighty children with CHC, 73 of whom received interferon-based therapy, were recruited. Sections of their liver biopsies were prepared for immunostaining of HPCs using cytokeratin-7 antibody.

RESULTS

HPCs were expanded in most children (81.3%) with CHC. Expansion occurred in two forms: intraparenchymal isolated hepatic progenitor cell form and periportal ductular reaction form. There was a significant increase in HPCs expansion in higher stages of fibrosis (50, 81.8, and 100% in no, mild, and moderate fibrosis, respectively, with P=0.029). Also, HPCs expansion increased with increased grade of necroinflammatory activity (0, 77.8, 81.8, and 100%, in no, minimal, mild, and moderate activity, respectively), although this was statistically insignificant. Moreover, a significant positive correlation was found between the isolated hepatic progenitor cell number and ductular reaction grade (r=0.755, P<0.0001), and both were significantly correlated with the level of viremia and the grade of necroinflammatory activity. Finally, HPCs expansion was not related to the treatment response.

CONCLUSION

The relationship of HPCs with both the severity of hepatitis and the stage of fibrosis may be because of a role of HPCs in their pathogenesis.

Analysis of glial fibrillary acidic protein (GFAP)-expressing ductular cells in a rat liver cirrhosis model induced by repeated injections of thioacetamide (TAA)

Glial fibrillary acidic protein (GFAP), a type III intermediate filament protein, is expressed in hepatic stellate cells (HSCs), the principal fibrogenic cell type in the liver. Further, GFAP could be a marker for hepatic progenitor cells (HPCs). In this study, the participation of GFAP-expressing cells in HPC expansion/ductular reaction was investigated in a rat model of liver cirrhosis. Six-week-old male F344 rats were injected intraperitoneally with thioacetamide (100mg/kg BW, twice a week) and examined at post-first injection weeks 5, 10, 15, 20 and 25. Fibrosis-related proliferation of ductular cells was observed as demonstrated by CK19 immunostaining. Some of these cells were stained with GFAP. No co-staining was observed between CK19 and α-smooth muscle actin (α-SMA; myofibroblast marker). There were proliferating ductular cells stained with α-fetoprotein or β-catenin; the ductular reaction was related to increased expression of hepatocarcinogenesis-related factors (Wnt2, Wnt4 and glypican-3). These results for the first time show the participation of GFAP-positive HPCs in ductular reaction in a chemically induced rodent model. Though the ductular cells were chaperoned by myofibroblasts, they show no direct evidence for epithelial to mesenchymal transition. These findings shed new light in understanding the roles of GFAP-expressing HPCs in liver cirrhosis and provide further evidence of interaction between newly-formed bile ductules and HSCs, suggesting that both cells could be in the common lineage of HPCs.

The CD133+CD44+ precancerous subpopulation of oval cells is a therapeutic target for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a malignant tumor associated with a generally poor prognosis and a high rate of recurrence. HCC usually develops in the context of chronic liver diseases, and long-lasting premalignant conditions precede cancer development. A promising therapeutic approach is to eliminate precancerous cells, which are considered as the precursors of cancer stem cells, to prevent further malignant transformation. In this study, we identified a subpopulation of precancerous cells in a rat liver carcinogenesis model, which were enriched in CD133(+)CD44(+)CD45(-)HIS49(-) cells that formed part of the hepatic oval cells fraction. Prospective isolation of the precancerous cells using flow cytometry identified stem cell properties such as the ability to expand clonally and differentiate into bi-lineage cell types. Furthermore, an acyclic retinoid, which was recently shown to improve overall survival after HCC resection, directly inhibited the extensive expansion of the isolated precancerous cells in vitro and decreased the emergence of the precancerous cells and their progeny in vivo. Long-term follow-up after the acyclic retinoid treatment confirmed reduction in precancerous changes, ultimately resulting in suppression of HCC development. These findings, together with data from recent clinical trials showing marked reduction in intrahepatic recurrence, suggest that acyclic retinoid directly prevents de novo HCC by inhibiting the development of precancerous cells. Given recent advances in diagnostic techniques and the establishment of surveillance programs, the targeting of precancerous cells may have a huge impact on preventative cancer therapies.

HBx protein promotes oval cell proliferation by up-regulation of cyclin D1 via activation of the MEK/ERK and PI3K/Akt pathways

Growing evidence has shown that hepatic oval cells, also named liver progenitor cells, play an important role in the process of liver regeneration in various liver diseases. Oval cell proliferation has been reported in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) and chronic liver disease. Studies have found expression of HBV surface and core antigens in oval cells in the livers of patients with HCC, suggesting that HBV infection of oval cells could be a mechanism of human hepatocarcinogenesis. In addition, there is evidence of multiplication of HBV in oval cell culture. However, little research has been performed to explore the role of HBV-encoded proteins in the proliferation of hepatic oval cells. Previously, we successfully transfected the HBV x (HBx) gene, one of the four genes in the HBV genome, into a rat LE/6 oval cell line. In this study, we tested whether or not the transfected HBx gene could affect oval cell proliferation in vitro. Our results show that overexpression of HBx promotes the proliferation of oval cells and increases cyclin D1 expression, assessed at both the mRNA and protein levels. We also found that HBx activated the PI-3K/Akt and MEK/ERK1/2 pathways in HBx-transfected oval cells. Furthermore, the HBx-induced increases in cyclin D1 expression and oval cell proliferation were completely abolished by treatment with either MEK inhibitor PD184352 or PI-3K inhibitor LY294002. These results demonstrated that HBx has the ability to promote oval cell proliferation in vitro, and its stimulatory effects on cell proliferation and expression of cyclin D1 depend on the activation of the MEK/ERK and PI3K/Akt signaling pathways in cultured oval cells.

Improved Serum Alpha-Fetoprotein Levels after Iron Reduction Therapy in HCV Patients

Background and Aims. To examine the changes in serum alpha-fetoprotein (AFP) levels after iron reduction by therapeutic phlebotomy in chronic hepatitis C patients. Methods. This retrospective study included 26 chronic hepatitis C patients. The patients were developed iron depletion by repeated therapeutic phlebotomies. Results. Iron reduction therapy significantly reduced the median level of serum AFP from 13 to 7 ng/mL, ALT from 96 to 50 IU/L, gamma-glutamyl transpeptidase (GGT) from 55 to 28 IU/L, and ferritin from 191 to 10 ng/mL (P < 0.001 for each). The rate of decline in the AFP level correlated positively only with that in GGT (r = 0.695, P = 0.001), although a spurious correlation was observed between the rates of decline for AFP and ALT. The AFP level normalized (<10 ng/mL) posttreatment in eight (50%) of 16 patients who had elevated pretreatment AFP levels. Normalized post-treatment ALT and GGT levels were seen in 12% (3 of 26) and 39% (7 of 18) of the patients, respectively. Multivariate analysis identified a post-treatment GGT level of <30 IU/L as an independent factor associated with post-treatment AFP normalization (odds ratio, 21; 95% confidence interval, 1.5-293; P = 0.024). Conclusions. Iron reduction by therapeutic phlebotomy can reduce serum AFP and GGT levels in chronic hepatitis C patients.

Unbalanced distribution of materials: the art of giving rise to hepatocytes from liver stem/progenitor cells

Liver stem/progenitor cells (LSPCs) are able to duplicate themselves and differentiate into each type of cells in the liver, including mature hepatocytes and cholangiocytes. Understanding how to accurately control the hepatic differentiation of LSPCs is a challenge in many fields from preclinical to clinical treatments. This review summarizes the recent advances made to control the hepatic differentiation of LSPCs over the last few decades. The hepatic differentiation of LSPCs is a gradual process consisting of three main steps: initiation, progression and accomplishment. The unbalanced distribution of the affecting materials in each step results in the hepatic maturation of LSPCs. As the innovative and creative works for generating hepatocytes with full functions from LSPCs are gradually accumulated, LSPC therapies will soon be a new choice for treating liver diseases.

Isolation of EpCAM(+)/CD133 (-) hepatic progenitor cells

Progenitor cell-derived hepatocytes are critical for hepatocyte replenishment. Therefore, we established a line of human hepatic progenitor (HNK1) cells and determined their biological characteristics for experimental and therapeutic applications. HNK1 cells, isolated from human noncirrhotic liver samples with septal fibrosis, showed high expression of the hepatic progenitor cell (HPC) markers EpCAM, CK7, CK19, alpha-fetoprotein (AFP), CD90 (Thy1), and EFNA1. Expression of CD133 was very low. Ductular reactions at the periphery of cirrhotic nodules were immunohistochemically positive for these HPC markers, including EFNA1. Sodium butyrate, a differentiation inducer, induced hepatocyte-like morphological changes in HNK1 cells. It resulted in down-regulation of the hepatic progenitor cell markers EpCAM, CK7, CK19, AFP, and EFNA1 and up-regulation of mature hepatocyte markers, including albumin, CK8, and CK18. Furthermore, sodium butyrate treatment and a serial passage of HNK1 cells resulted in enhanced albumin secretion, ureagenesis, and CYP enzyme activity, all of which are indicators of differentiation in hepatocytes. However, HNK1 cells at passage 50 did not exhibit anchorage-independent growth capability and caused no tumors in immunodeficient mice, suggesting that they had no spontaneous malignant transformation ability. From this evidence, HNK1 cells were found to be EpCAM(+)/CD133(-) hepatic progenitor cells without spontaneous malignant transformation ability. We therefore conclude that HNK1 cells could be useful for experimental and therapeutic applications.

Clinicopathologic analysis of combined hepatocellular-cholangiocarcinoma according to the latest WHO classification

Combined hepatocellular-cholangiocarcinoma comprises <1% of all liver carcinomas. The histogenesis of combined hepatocellular-cholangiocarcinoma has remained unclear for many years. However, recent advances in hepatic progenitor cell (HPC) investigations have provided new insights. The concept that combined hepatocellular-cholangiocarcinoma originates from HPCs is adopted in the chapter "combined hepatocellular-cholangiocarcinoma" of the latest World Health Organization (WHO) classification. In this study, we conducted clinicopathologic analysis of combined hepatocellular-cholangiocarcinoma according to the latest WHO classification. Fifty-four cases were included in this study. Pathologic diagnosis was made according to the WHO classification. When a tumor contained plural histologic patterns, predominant histologic pattern (≥50%) was defined. Minor histologic patterns were also appended. Immunohistochemical staining with biliary markers (CK7, CK19, and EMA), hepatocyte paraffin (HepPar)-1, HPC markers (CD56, c-kit, CD133, and EpCAM), and vimentin was performed. Forty-five and 50 patients were analyzed for progression-free survival and overall survival, respectively. Ten, 1, 32, and 11 cases were diagnosed as: combined hepatocellular-cholangiocarcinoma, classical type; combined hepatocellular-cholangiocarcinoma, stem cell features, typical subtype; combined hepatocellular-cholangiocarcinoma, stem cell features, intermediate cell subtype; and combined hepatocellular-cholangiocarcinoma, stem cell features, cholangiolocellular type, respectively. Combined hepatocellular-cholangiocarcinomas usually have high expression of biliary markers. CD56, c-kit, and EpCAM were expressed to various degrees in all combined hepatocellular-cholangiocarcinomas apart from the hepatocellular carcinoma component of combined hepatocellular-cholangiocarcinoma, classical type. The expression of CD133 and vimentin was observed only in combined hepatocellular-cholangiocarcinoma, stem cell features of intermediate cell subtype and cholangiolocellular subtype. The expression of CD133, EpCAM, and vimentin was significantly high in combined hepatocellular-cholangiocarcinoma, subtypes with stem cell features, especially cholangiolocellular subtype. Minor histologic patterns were significantly frequent in combined hepatocellular-cholangiocarcinoma, subtypes with stem cell features, compared with combined hepatocellular-cholangiocarcinoma, classical type. There was no significant difference in clinical outcome between each subtype. Combined hepatocellular-cholangiocarcinoma has wide histologic diversity and shows immunophenotypic expression of not only biliary markers but also HPC markers to various degrees, suggesting that the histogenesis of combined hepatocellular-cholangiocarcinoma could be strongly associated with HPCs. Our results pathologically validate the latest WHO classification of combined hepatocellular-cholangiocarcinoma. However, the complex mixture of histologic subtypes has presented a challenge to the classification of combined hepatocellular-cholangiocarcinoma. Further study should be conducted using a large cohort to support this classification.

Background progenitor activation is associated with recurrence after hepatectomy of combined hepatocellular-cholangiocarcinoma

Hepatic progenitor cells (HPC) play important roles in both liver regeneration and carcinogenesis. Combined hepatocellular-cholangiocarcinoma (CHC), a malignant primary liver tumor with poor prognosis, is thought to be of HPC origin. However, the prognostic significance of this etiology is not well defined. Therefore, we retrospectively investigated the relationship of HPC-related pathological features and long-term outcome in patients with CHC in our department. In a cohort of 80 patients identified between 1997 and 2003, including 70 patients who underwent resection with curative intent, overall survival (OS) and disease-free survival (DFS) were correlated with the proliferative activity of nontumor ductular reaction (DR) and the expression levels of HPC and biliary markers including α-fetoprotein (AFP), keratin 7 (K7), keratin 19 (K19), oval cell (OV)-6, epithelial cell adhesion molecule (EpCAM), and c-Kit in both tumor and nontumor liver. We found that nontumor ductular reactions (DRs), specifically the proliferating cell nuclear antigen (PCNA) labeling index of the ductular reaction (PI-DR), a surrogate for transit-amplifying compartments, was an independent prognostic factor for both OS and DFS. By contrast, intratumoral expression of only one marker, absence of AFP, was associated with OS. PI-DR was also independently associated with synchronous "multicentric occurrence" in hepatocellular carcinoma components, a feature of CHC that may predispose to metachronous multifocal tumorigenesis.

CONCLUSION

Proliferative ductular reaction related to HPC activation is associated with recurrence of CHC. Background HPC activation is strongly associated with multifocal occurrence and related tumor recurrence, highlighting the critical role of background liver disease, a "field effect," in the recurrence of CHC.

Sustained liver regeneration after portal vein embolization --a human molecular pilot study

BACKGROUND

Portal vein embolization is a treatment option to achieve a sufficient future remnant liver volume for patients with central liver tumours requiring an extended resection with an extensive parenchymal loss. However, molecular mechanisms of this intervention are up to now poorly understood. The objective of this prospective pilot study was the characterization of molecular events leading to late hypertrophy of the non-embolized liver tissue in the human liver.

METHODS

Liver tissue of ten patients was collected before and intraoperatively more than one month after embolization. Investigation of molecular features was performed by pangenomic chips, polymerase chain reaction, immunostaining of proliferation marker Ki-67 and immunofluorescence measurements.

RESULTS

Significantly elevated genes hint towards angiogenesis and signalling by insulin-like growth factor and associated binding proteins. Increased transcript levels of activator protein 1 complex members like c-jun were reflecting potential molecular events of liver growth after embolization. Immunofluorescence data confirmed a predominant upregulation of β-catenin and c-jun (p<0.1) supported by Ki-67 (p<0.05) in the non-embolized liver. In silico analysis of transcriptomic dysplasia and hepatocellular carcinoma data showed divergent signatures compared to embolization.

CONCLUSIONS

Our findings indicate a sustained regeneration after portal vein embolization reflected in hyperplasia and angiogenesis in the human liver and provide novel molecular mechanisms of interlobe crosstalk.

Aberrant cytokeratin 7 expression of centrilobular hepatocytes: a clinicopathological study

AIMS

This study has attempted to elucidate the clinicopathological features of aberrant cytokeratin 7 (CK7) expression by centrilobular hepatocytes.

METHODS AND RESULTS

A total of 113 liver biopsy specimens from patients with common non-neoplastic liver diseases, including hepatitis B or C, non-alcoholic steatohepatitis, alcoholic liver disease and other diseases were examined. In 56 specimens (49.6%), CK7-positive centrilobular hepatocytes (CK7 + CHs) were identified and sometimes showed binuclear features. CK7 + CHs were associated with patients' older age (P = 0.004), higher serum levels of aspartate aminotransferase (P = 0.016) and γ-glutamyltransferase (P = 0.006), centrilobular fibrosis (P < 0.001), prominent thickening of hepatocytic plates (P < 0.001) and higher scores of total and periportal CK7-positive hepatocytes (both P < 0.001), but were not correlated with gender, steatosis, serum levels of total bilirubin or alanine aminotransferase. In 55 cases of hepatitis B and hepatitis C only, CK7 + CHs were related to a higher stage of fibrosis (P = 0.006).

CONCLUSION

CK7 + CHs occur relatively frequently in non-neoplastic liver disease, associated with centrilobular scarring and the presence of CK7-positive periportal hepatocytes, and appear to be a non-specific phenomenon with respect aetiology of underlying disease. CK7 + CHs may represent age-dependent activation of hepatic progenitor cells or a regenerative phenomenon of hepatocytes themselves, both of which might contribute to liver regeneration.

Liver progenitor cell markers correlate with liver damage and predict short-term mortality in patients with alcoholic hepatitis

Alcoholic hepatitis (AH) is a severe condition developed in patients with underlying alcoholic liver disease. Ductular reaction has been associated with chronic alcohol consumption but there is no information regarding the extent of liver progenitor cell (LPC) proliferation in AH. The aim of this study was to investigate LPC markers in AH and its correlation with disease severity. Fifty-nine patients with clinical and histological diagnosis of AH were included in the study. LPC markers were assessed by real-time polymerase chain reaction (PCR) and immunohistochemistry. Standard logistic regression analysis and classification and regression trees (CART) analysis were used for statistical analysis. A microarray analysis showed an up-regulation of LPC markers in patients with AH. Real-time PCR demonstrated that epithelial cell adhesion molecule (EpCAM), Prominin-1, and Keratin7 were significantly increased in patients with AH compared with normal livers (P ≤ 0.01), chronic hepatitis C (P ≤ 0.01), and HCV-induced cirrhosis (P ≤ 0.01). Immunohistochemistry scores generated for Keratin7 and EpCAM demonstrated a good correlation with gene expression. Keratin7 gene expression correlated with liver failure as assessed by model for endstage liver disease score (r = 0.41, P = 0.006) and Maddrey's discriminant function (r = 0.43, P = 0.004). Moreover, Keratin7 (OR1.14, P = 0.004) and Prominin-1 (OR1.14, P = 0.002), but not EpCAM (OR1.16, P = 0.06), were identified as independent predictors of 90-day mortality. CART analysis generated an algorithm based on the combination of Keratin7 and EpCAM gene expression that stratified three groups of patients with high, intermediate, and low short-term mortality (89%, 33%, and 6%, respectively; area under the receiver operating curve 0.73, 95% confidence interval 0.60-0.87). Keratin7 expression provided additional discrimination potential to the age, bilirubin, international normalization ratio, creatinine (ABIC) score.

CONCLUSION

LPC markers correlate positively with severity of liver disease and short-term mortality in AH patients. This study suggests that LPC proliferation may be an important feature of AH pathophysiology.

Cytokeratin expression as an aid to diagnosis in medical liver biopsies

The study of cytokeratin expression has provided a valuable insight into the biliary microanatomy of the liver in health and disease. The canals of Hering are a putative site of origin for progenitor cells, which may repopulate the liver after cellular damage and loss. Normal bile ducts and the bile ductular reaction that occurs in many chronic liver diseases - especially chronic biliary tract disease - express cytokeratin (CK) 7 and CK19. Therefore, both ductopenia and the process of bile ductular reaction can be highlighted with immunohistochemistry for these cytokeratins. Furthermore, CK7 is usually expressed in an increasingly widespread manner by hepatocytes as chronic cholestatic liver disease progresses. For these reasons, CK immunohistochemistry is a very useful adjunct to morphological assessment and histochemical stains for copper retention when a diagnosis of chronic biliary disease is being considered. This review describes the anatomical theory behind the use of CK immunohistochemistry for the assessment of bile duct number and distribution in the liver and provides practical advice for the application of this technique in the diagnostic setting of common medical liver diseases.

Architectural and immunohistochemical characterization of biliary ductules in normal human liver

The canals of Hering or biliary ductules have been described to connect the bile canaliculi with the interlobular bile ducts, and thus forming the distal part of the biliary tree. Studies in the last two decades suggested that the cells constructing these ductules could behave as hepatic progenitor cells. The canals of Hering are confined to the periportal space in the rat, while they have been reported to spread beyond the limiting plate in human liver. The distribution of the distal biliary ductules in normal human hepatic tissue has been investigated in our recent experiments. We could demonstrate the presence of interlobular connective tissue septa in a rudimentary form in healthy livers. The canals of Hering run in these septa in line with the terminal branches of the portal vein and hepatic arteries. This arrangement develops in the postnatal period but regresses after early childhood. The canals of Hering can be identified by the unique epithelial membrane antigen (EMA)-/CD56+/CD133+ immunophenotype. The canals of Hering leave the periportal space and spread into the liver parenchyma along rudimentary interlobular septa outlining the hepatic lobules. Our observations refine the original architectural description of the intraparenchymal portion of the canals of Hering in the human liver. The distinct immunophenotype supports their unique biological function.

Hepatic stem cells and liver development

The liver consists of many cell types with specialized functions. Hepatocytes are one of the main players in the organ and therefore are the most vulnerable cells to damage. Since they are not everlasting cells, they need to be replenished throughout life. Although the capacity of hepatocytes to contribute to their own maintenance has long been recognized, recent studies have indicated the presence of both intrahepatic and extrahepatic stem/progenitor cell populations that serve to maintain the normal organ and to regenerate damaged parenchyma in response to a variety of insults.The intrahepatic compartment most likely derives primarily from the biliary tree, particularly the most proximal branches, i.e. the canals of Hering and smallest ductules. The extrahepatic compartment is at least in part derived from diverse populations of cells from the bone marrow. Embryonic stem cells (ES's) are considered as a part of the extrahepatic compartment. Due to their pluripotent capabilities, ES cell-derived cells form a potential future source of hepatocytes, to replace or restore hepatic tissues that have been damaged by disease or injury. Progressing knowledge about stem cells in the liver would allow a better understanding of the mechanisms of hepatic homeostasis and regeneration. Although a human stem cell-derived cell type equivalent to primary hepatocytes does not yet exist, the promising results obtained with extrahepatic stem cells would open the way to cell-based therapy for liver diseases.

Expression of contactin associated protein-like 2 in a subset of hepatic progenitor cell compartment identified by gene expression profiling in hepatitis B virus-positive cirrhosis

BACKGROUND

Hepatic progenitor cells (HPC), a cell compartment capable of differentiating into hepatocytic and biliary lineages, may give rise to the formation of intermediate hepatobiliary cells (IHBC) or ductular reactions (DR).

AIMS

The aim of this study was to analyse the gene expression profiles of DR in cirrhosis and further investigate novel proteins expressed by HPC and their intermediate progeny.

METHODS

DR in hepatitis B virus (HBV)-positive cirrhotic liver tissues adjacent to hepatocellular carcinoma and interlobular bile ducts (ILBDs) in normal liver tissues were isolated by laser capture microdissection and then subjected to microarray analysis. Differential gene expression patterns were verified by quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry on serial sections. HPC and their intermediate progeny were recognized by immunostaining with hepatocytic and biliary markers [HepPar1, cytokeratin (CK)7, CK19, neural cell adhesion molecule (NCAM), epithelial cell adhesion molecule (EpCAM)].

RESULTS

A total of 88 genes showed upregulation in DR compared with ILBDs. Gene ontology analyses revealed that these upregulated genes were mostly associated with cell adhesion, immune response and the metabolic process. Contactin associated protein-like 2 (CNTNAP2) was first confirmed to be a novel protein expressed in a subpopulation of DR that was positive for CK7, NCAM or EpCAM. In addition, immunoreactivity for CNTNAP2 was also noted in a subset of isolated CK7-positive HPC as well as some ductular IHBC positive for CK19 and HepPar1 in DR.

CONCLUSION

CNTNAP2 is specifically associated with the emergence of ductular populations and may be identified as a novel protein for defining a subset of HPC and their intermediate progeny in cirrhosis.

Influence of portosystemic shunt on liver regeneration after hepatic resection in pigs

Objective. The minimal amount of liver mass necessary for regeneration is still a matter of debate. The aim of the study was to analyze liver regeneration factors after extended resection with or without portosystemic shunt. Methods. An extended left hemihepatectomy was performed in 25 domestic pigs, in 15 cases after a portosystemic H-shunt. The expression of Ki-67, VEGF, TGF-α, FGF, and CK-7 was analyzed in paraffin-embedded tissue sections. Results. The volume of the remnant liver increased about 2.5-fold at the end of the first week after resection. With 19 cells/10 Glisson fields versus 4/10, Ki-67-expression was significantly higher in the H-shunt group. VEGF- and CK-7-expressions were significantly higher in the control group. No significant change was found in FGF-expression. The expression of TGF-α was higher, but not significantly, in the control group. Conclusions. The expression of Ki-67, and therefore hepatocyte regeneration, was increased in the shunt group. The expression of CK-7 on biliary epithelium and the expression of VEGF, however, were stronger in the control group.

Expression and localization of aquaporin-1 in human cirrhotic liver

We investigated the expression and localization of aquaporin-1 (AQP-1) in hepatitis B virus (HBV)-associated cirrhotic human liver tissues. The expression of AQP-1 at the protein and mRNA levels was analyzed by immunohistochemistry, quantitative real-time polymerase chain reaction (qPCR) and Western blotting in normal and HBV-associated cirrhotic human liver tissues. The correlation with the expression of CK19, CK7 and AQP-1 was also compared. AQP-1 staining was strongly and uniformly positive in mature bile ducts, isolated hepatic progenitor cells (HPCs) and ductular reactions. Scattered intermediate hepatocyte-like cells expressed AQP-1, which are often intimately associated with CK7 positive hepatocytes. However, the number of AQP-1+ intermediate hepatocyte-like cells was lower than that of CK7+ cells, and such positivity was rarely seen on stains for CK19. When compared with normal liver tissues, AQP-1 was overexpressed at both the mRNA and protein levels in the cirrhotic liver tissues. AQP-1 was overexpressed in the cirrhotic liver tissues. AQP-1, similar to CK19, might be a more specific and more sensitive marker than CK7 for the identification of HPCs.

Expression of c-kit protooncogen in hepatitis B virus-induced chronic hepatitis, cirrhosis and hepatocellular carcinoma: has it a diagnostic role?

AIM

There are more than 350 million people worldwide chronically infected with hepatitis B virus (HBV), who are at high risk for the development of hepatitis, cirrhosis and hepatocellular carcinoma (HCC). Because of the conflicting results about c-kit expression in HCC and the key role played by c-kit in gastrointestinal stromal tumours (GIST) and other solid tumours, the aim of this study was to determine c-kit expression in the course of hepatitis B infection.

MATERIALS AND METHODS

Paraffin-embedded tissues in Cukurova University Faculty of Medicine Department of Pathology between January 2002 and February 2006 were searched restrospectively to investigate this issue. We performed immunohistochemistry on biopsies of 125 patients with HBV infection, grouped as: mild, moderate and severe hepatitis, cirrhosis and HCC, 25 patients in each of them, using anti c-kit monoclonal antibody. The severity of parenchymal inflammation and of interface hepatitis was semiquantitatively graded on a haematoxylin and eosin stained paraffin sections. Additionally, 50 more HCC, formed on HBV basis, were studied to determine the prevalence of c-kit overexpression.

RESULTS

In cirrhotic liver, lower intensity of staining and rarely c-kit positivity were present. The greatest number of the c-kit positivity and higher intensity of staining was found in the livers of patients with severe hepatitis and HCC. In chronic hepatitis B infection, the staining intensity was parallel with the grade and stage of the disease. In the areas where fibrosis was seen, c-kit positivity was rare or absent. In the HCC specimens, c-kit positivity appeared both inside and around the cancerous nodes. C-kit expression was observed in 62 of 75 HCC tissue specimens (82%) (p < 0.001).

CONCLUSIONS

C-kit positivity was observed in the mitotic, proliferating and also dysplastic hepatic cells. These results suggest that c-kit expression may be used as an early diagnostic indicator for HBV induced HCC.

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.

Combined hepatocellular cholangiocarcinoma originating from hepatic progenitor cells: immunohistochemical and double-fluorescence immunostaining evidence

AIMS

Combined hepatocellular cholangiocarcinoma (CHC) is a rare form of primary liver cancer, showing a mixture of hepatocellular and biliary features. Data suggest that most CHC arise from hepatic progenitor cells (HPCs). The aim was to investigate the origin of CHC.

METHODS AND RESULTS

Twelve cases of CHC were studied by immunohistochemistry for hepatocytic (hepPar1, alpha-fetoprotein), cholangiocytic cytokeratin [(CK) 7, CK19], hepatic progenitor cell (OV-6), haematopoietic stem cell (c-kit, CD34), as well as CD45 and chromogranin-A markers. The combination of double-fluorescence immunostaining consisted of HepPar1 with CK19, and c-kit with OV-6. All 12 cases demonstrated more or less transitional areas, with strands/trabeculae of small, uniform, oval-shaped cells including scant cytoplasm and hyperchromatic nuclei embedded within a thick, desmoplastic stroma; however, two cases were found to consist entirely of such transitional areas. Simultaneous co-expression of hepPar1 and CK7, or CK19, was demonstrated in 10/12 (83.3%) cases of CHC. c-kit expression was noted in 10/12 (83.3%) cases, of which 7/10 (70%) showed co-expression of OV-6.

CONCLUSIONS

The results suggest that CHC are of HPC origin, supporting the concept that human hepatocarcinogenesis may originate from the transformation of HPCs.

Liver biopsy assessment in chronic hepatitis

Liver biopsy has been a major diagnostic tool in the evaluation of individuals with chronic hepatitis for many decades and remains the most direct way of visualizing hepatic necroinflammation and fibrosis. In chronic viral hepatitis B and C, immune attack on hepatocytes bearing viral antigens results in the entry of lymphocytes and other effector cells through the portal tracts from which other lesions may evolve, including interface and lobular hepatitis as well as fibrosis or cirrhosis. Classification systems have been developed in order to provide semiquantitative grading of necroinflammation and staging of fibrosis and include the Scheuer, Batts and Ludwig, Ishak, and METAVIR systems. This review provides an historical perspective on histopathological methods of analyzing chronic hepatitis, describes the essential criteria of each of the major scoring systems and discusses problems related to sampling error, observer variation, and specimen size.