Different types of liver progenitor cells and their niches

Engineering principles for rationally design therapeutic strategies against hepatocellular carcinoma

The search for new therapeutic strategies against cancer has favored the emergence of rationally designed treatments. These treatments have focused on attacking cell plasticity mechanisms to block the transformation of epithelial cells into cancerous cells. The aim of these approaches was to control particularly lethal cancers such as hepatocellular carcinoma. However, they have not been able to control the progression of cancer for unknown reasons. Facing this scenario, emerging areas such as systems biology propose using engineering principles to design and optimize cancer treatments. Beyond the possibilities that this approach might offer, it is necessary to know whether its implementation at a clinical level is viable or not. Therefore, in this paper, we will review the engineering principles that could be applied to rationally design strategies against hepatocellular carcinoma, and discuss whether the necessary elements exist to implement them. In particular, we will emphasize whether these engineering principles could be applied to fight hepatocellular carcinoma.

Research Progress in Traditional Applications, Phytochemistry, Pharmacology, and Safety Evaluation of Cynomorium songaricum

Cynomorium songaricum Rupr. (CSR) belongs to the family Cynomoriaceae. It is a perennial succulent parasitic herb with a reddish-brown coloration, predominantly submerged in sand and lacking chlorophyll. Traditionally, it has been used in ethnic medicine to treat various diseases, such as gastric ulcers, indigestion, bowel movements, and improving sexual function. To comprehensively collect CSR data, extensive literature searches were conducted using medical, ecological, and scientific databases such as Google Scholar, PubMed, Science Direct, Web of Science, and China National Knowledge Infrastructure (CNKI). This article summarizes and categorizes research on the uses, phytochemical characteristics, pharmacological activities, and toxicity of ethnic medicine, with the aim of establishing a solid foundation and proposing new avenues for exploring and developing potential applications of CSR. So far, a total of 98 compounds have been isolated and identified from CSR, including flavonoids, terpenes, steroids, and other compounds. It is worth noting that flavonoids and polysaccharides have significant antioxidant and anti-inflammatory properties. In addition, these compounds also show good application prospects in anti-tumor, antioxidant, anti-aging, anti-fatigue, anti-diabetes, and other aspects. Although extensive progress has been made in the basic research of CSR, further research is still needed to enhance the understanding of its mechanism of action and explore more unknown compounds. Our review indicates that CSR has broad prospects and deserves further research.

"Small Hepatocytes" in the Liver

Mature hepatocytes (MHs) in an adult rodent liver are categorized into the following three subpopulations based on their proliferative capability: type I cells (MH-I), which are committed progenitor cells that possess a high growth capability and basal hepatocytic functions; type II cells (MH-II), which possess a limited proliferative capability; and type III cells (MH-III), which lose the ability to divide (replicative senescence) and reach the final differentiated state. These subpopulations may explain the liver's development and growth after birth. Generally, small-sized hepatocytes emerge in mammal livers. The cells are characterized by being morphologically identical to hepatocytes except for their size, which is substantially smaller than that of ordinary MHs. We initially discovered small hepatocytes (SHs) in the primary culture of rat hepatocytes. We believe that SHs are derived from MH-I and play a role as hepatocytic progenitors to supply MHs. The population of MH-I (SHs) is distributed in the whole lobules, a part of which possesses a self-renewal capability, and decreases with age. Conversely, injured livers of experimental models and clinical cases showed the emergence of SHs. Studies demonstrate the involvement of SHs in liver regeneration. SHs that appeared in the injured livers are not a pure population but a mixture of two distinct origins, MH-derived and hepatic-stem-cell-derived cells. The predominant cell-derived SHs depend on the proliferative capability of the remaining MHs after the injury. This review will focus on the SHs that appeared in the liver and discuss the significance of SHs in liver regeneration.

Preoperative prediction of cholangiocyte phenotype hepatocellular carcinoma on contrast-enhanced MRI and the prognostic implication after hepatectomy

BACKGROUND

Hepatocellular carcinoma (HCC) expressing cytokeratin (CK) 7 or CK19 has a cholangiocyte phenotype that stimulates HCC proliferation, metastasis, and sorafenib therapy resistance This study aims to noninvasively predict cholangiocyte phenotype-positive HCC and assess its prognosis after hepatectomy.

METHODS

Between January 2010 and May 2022, preoperative contrast-enhanced MRI was performed on consecutive patients who underwent hepatectomy and had pathologically confirmed solitary HCC. Two abdominal radiologists separately assessed the MRI features. A predictive model for cholangiocyte phenotype HCC was created using logistic regression analysis and five-fold cross-validation. A receiver operating characteristic curve was used to calculate the model performance. Kaplan-Meier and log-rank methods were used to evaluate survival outcomes.

RESULTS

In total, 334 patients were included in this retrospective study. Four contrast-enhanced MRI features, including "rim arterial phase hyperenhancement" (OR = 5.9, 95% confidence interval [CI]: 2.9-12.0, 10 points), "nodule in nodule architecture" (OR = 3.5, 95% CI: 2.1-5.9, 7 points), "non-smooth tumor margin" (OR = 1.6, 95% CI: 0.8-2.9, 3 points), and "non-peripheral washout" (OR = 0.6, 95% CI: 0.3-1.0, - 3 points), were assigned to the cholangiocyte phenotype HCC prediction model. The area under the curves for the training and independent validation set were 0.76 and 0.73, respectively. Patients with model-predicted cholangiocyte phenotype HCC demonstrated lower rates of recurrence-free survival (RFS) and overall survival (OS) after hepatectomy, with an estimated median RFS and OS of 926 vs. 1565 days (p < 0.001) and 1504 vs. 2960 days (p < 0.001), respectively.

CONCLUSIONS

Contrast-enhanced MRI features can be used to predict cholangiocyte phenotype-positive HCC. Patients with pathologically confirmed or MRI model-predicted cholangiocyte phenotype HCC have a worse prognosis after hepatectomy.

CRITICAL RELEVANCE STATEMENT

Four contrast-enhanced MRI features were significantly associated with cholangiocyte phenotype HCC and a worse prognosis following hepatectomy; these features may assist in predicting prognosis after surgery and improve personalized treatment decision-making.

KEY POINTS

• Four contrast-enhanced MRI features were significantly associated with cholangiocyte phenotype HCC. • A noninvasive cholangiocyte phenotype HCC predictive model was established based on MRI features. • Patients with cholangiocyte phenotype HCC demonstrated a worse prognosis following hepatic resection.

Cellular crosstalk during liver regeneration: unity in diversity

The liver is unique in its ability to regenerate from a wide range of injuries and diseases. Liver regeneration centers around hepatocyte proliferation and requires the coordinated actions of nonparenchymal cells, including biliary epithelial cells, liver sinusoidal endothelial cells, hepatic stellate cells and kupffer cells. Interactions among various hepatocyte and nonparenchymal cells populations constitute a sophisticated regulatory network that restores liver mass and function. In addition, there are two different ways of liver regeneration, self-replication of liver epithelial cells and transdifferentiation between liver epithelial cells. The interactions among cell populations and regenerative microenvironment in the two modes are distinct. Herein, we first review recent advances in the interactions between hepatocytes and surrounding cells and among nonparenchymal cells in the context of liver epithelial cell self-replication. Next, we discuss the crosstalk of several cell types in the context of liver epithelial transdifferentiation, which is also crucial for liver regeneration.

Mechanism of cancer stemness maintenance in human liver cancer

Primary liver cancer mainly includes the following four types: hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), hepatoblastoma (HB), and combined hepatocellular carcinoma and cholangiocarcinoma (cHCC-CCA). Recent studies have indicated that there are differences in cancer stem cell (CSC) properties among different types of liver cancer. Liver cancer stem cells (LCSCs), also called liver tumor-initiating cells, have been viewed as drivers of tumor initiation and metastasis. Many mechanisms and factors, such as mitophagy, mitochondrial dynamics, epigenetic modifications, the tumor microenvironment, and tumor plasticity, are involved in the regulation of cancer stemness in liver cancer. In this review, we analyze cancer stemness in different liver cancer types. Moreover, we further evaluate the mechanism of cancer stemness maintenance of LCSCs and discuss promising treatments for eradicating LCSCs.

Hepatic stellate cells - from past till present: morphology, human markers, human cell lines, behavior in normal and liver pathology

Hepatic stellate cell (HSC), initially analyzed by von Kupffer, in 1876, revealed to be an extraordinary mesenchymal cell, essential for both hepatocellular function and lesions, being the hallmark of hepatic fibrogenesis and carcinogenesis. Apart from their implications in hepatic injury, HSCs play a vital role in liver development and regeneration, xenobiotic response, intermediate metabolism, and regulation of immune response. In this review, we discuss the current state of knowledge regarding HSCs morphology, human HSCs markers and human HSC cell lines. We also summarize the latest findings concerning their roles in normal and liver pathology, focusing on their impact in fibrogenesis, chronic viral hepatitis and liver tumors.

Immuno-comparative screening of adult-derived human liver stem/progenitor cells for immune-inflammatory-associated molecules

OBJECTIVE

One of the main challenges in liver cell therapy is the replacement of damaged cells and the induction of a tolerogenic microenvironment to promote graft acceptance by the recipient. Adult-derived human liver stem/progenitor cells (ADHLSCs) are currently evaluated at the clinical levels as a promising pro-regenerative and immune-modulatory tool. The expression profile of several immunological molecules may influence the local immune-inflammatory response and, therefore, modulate the tissue healing process. To increase the quality and safety of ADHLSCs before transplantation requires an appropriate analysis and characterization of their pattern expression of immune-inflammatory-associated molecules.

METHODS

The expression of 27 molecules belonging to T-cell co-stimulatory pathway, CD47 partners, Ikaros family, CD300 family and TNF family were analyzed using flow cytometry. We compared their expression profiles to PBMCs, hepatocytes and ADHLSCs in both expansion and after hepatogenic differentiation culture conditions.

RESULTS

This original immuno-comparative screening revealed that liver cell populations do not constitutively present significant immunological pattern compared to PBMCs. Moreover, our findings highlight that neither the expansion nor the hepatogenic differentiation induces the expression of immune-inflammatory molecules. The detailed expression characteristics (percentage of positive cells and median fluorescence intensity) of each molecule were analyzed and presented.

CONCLUSION

By analyzing 27 relevant molecules, our immuno-comparative screening demonstrates that ADHLSCs keep a non-immunogenic profile independent of their expansion or hepatogenic differentiation state. Accordingly, the immunological profile of ADHLSCs seems to support their safe and efficient use in liver tissue therapeutic repair strategy.

High-throughput sequencing identifies aetiology-dependent differences in ductular reaction in human chronic liver disease

Ductular reaction (DR) represents the activation of hepatic progenitor cells (HPCs) and has been associated with features of advanced chronic liver disease; yet it is not clear whether these cells contribute to disease progression and how the composition of their micro-environment differs depending on the aetiology. This study aimed to identify HPC-associated signalling pathways relevant in different chronic liver diseases using a high-throughput sequencing approach. DR/HPCs were isolated using laser microdissection from patient samples diagnosed with HCV or primary sclerosing cholangitis (PSC), as models for hepatocellular or biliary regeneration. Key signals were validated at the protein level for a cohort of 56 patients (20 early and 36 advanced stage). In total, 330 genes were significantly differentially expressed between the HPCs in HCV and PSC. Recruitment and homing of inflammatory cells were distinctly different depending on the aetiology. HPCs in PSC were characterised by a response to oxidative stress (e.g. JUN, VNN1) and neutrophil-attractant chemokines (CXCL5, CXCL6, IL-8), whereas HPCs in HCV were identified by T- and B-lymphocyte infiltration. Moreover, we found that communication between HPCs and macrophages was aetiology driven. In PSC, a high frequency of CCL28-positive macrophages was observed in the portal infiltrate, already in early disease in the absence of advanced fibrosis, while in HCV, HPCs showed a strong expression of the macrophage scavenger receptor MARCO. Interestingly, DR/HPCs in PSC showed more deposition of ECM (e.g. FN1, LAMC2, collagens) compared to HCV, where an increase of pro-invasive genes (e.g. PDGFRA, IGF2) was observed. Additionally, endothelial cells in the vicinity of DR/HPCs showed differential immunopositivity (e.g. IGF2 and INHBA expression). In conclusion, our data shine light on the role of DR/HPCs in immune signalling, fibrogenesis and angiogenesis in chronic liver disease. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Heterogeneity of Hepatic Cancer Stem Cells

Hepatocellular carcinoma (HCC) is one of the most common cancers with high mortality rate. It is a heterogeneous cancer with diverse inter- and intra-heterogeneity, also in terms of histology, prognosis, and molecular profiles. A rapidly growing evidence has demonstrated that some HCCs, if not all, were caused by the activation of the cancer stem cells (CSC), a small population within the cancer that is responsible for the initiation and maintenance of cancer growth. Until now, various populations of hepatic CSC with more than ten different phenotypical protein markers, such as CD133, CD90, EpCAM, CD24, and CD13, have been identified and validated in xenotransplantation models. They are associated with risk factors, prognosis, chemo-resistance, and metastasis. This chapter summarizes available data on different hepatic CSC markers for the development of potential future therapy.

Influence of Progenitor-Derived Regeneration Markers on Hepatitis C Virus-Related Cirrhosis Outcome (ANRS CO12 CirVir Cohort)

Progenitor-derived regeneration gives rise to the aberrant expression of biliary markers such as cytokeratin 7 (K7) and epithelial cell adhesion molecule (EpCAM) in hepatocytes. We aimed to describe the expression of these molecules in patients with compensated hepatitis C virus (HCV)-related cirrhosis and to investigate its potential influence on cirrhosis complications. Among patients with Child-Pugh A uncomplicated HCV-related cirrhosis enrolled in the prospective ANRS CO12 CirVir cohort, we selected individuals with a liver biopsy collected within 2 years before inclusion in the study. K7 and EpCAM immunostaining identified intermediate hepatobiliary cells. The influence of biliary marker expres-sion in hepatocytes on decompensation events and the occurrence of hepatocellular carcinoma (HCC) was studied using a multivariate Cox proportional hazards regression model. Among the 337 patients eligible for the study (men, 67%; median age, 52 years), 198 (58.8%) had biopsies with K7-positive hepatocytes including extensive staining in 40 (11.9%) and 203 had EpCAM-positive hepatocytes (60.6%). During follow-up (median, 54.2 months), 47 patients (14%) experienced a decompensation event, and HCC was diagnosed in 37 patients (11%). Extensive K7 staining was independently associated with the occurrence of a decompensation event (hazard ratio [HR], 3.00; 95% confidence interval [CI], 1.30-6.89; P = 0.010). EpCAM expression was independently associated with HCC occurrence (HR, 2.37; 95% CI, 1.07-5.23; P =0.033) along with age and a low prothrombin ratio.

CONCLUSION

Progenitor-derived regeneration depicted by K7 and EpCAM immunostaining of hepatocytes in liver biopsies of patients with compensated HCV-related cirrhosis marks a cirrhosis stage more prone to develop complications. (HEPATOLOGY 2018; 68:1534-1548).

Role of hepatic stellate cell (HSC)-derived cytokines in hepatic inflammation and immunity

In their quiescent state, Hepatic stellate cells (HSCs), are present in the sub-endothelial space of Disse and have minimal interaction with immune cells. However, upon activation following injury, HSCs directly or indirectly interact with various immune cells that enter the space of Disse and thereby regulate diverse hepatic function and immune physiology. Other than the normal physiological functions of HSCs such as hepatic homeostasis, maturation and differentiation, they also participate in hepatic inflammation by releasing a battery of inflammatory cytokines and chemokines and interacting with other liver cells. Here, we have reviewed the role of HSC in the pathogenesis of liver inflammation and some infectious diseases in order to understand how the interplay between immune cells and HSCs regulates the overall outcome and disease pathology.

Immunohistochemical characterisation of the hepatic stem cell niche in feline hepatic lipidosis: a preliminary morphological study

OBJECTIVES

The aim of this study was to describe the cellular and stromal components of the hepatic progenitor cell niche in feline hepatic lipidosis (FHL).

METHODS

Immunohistochemical staining for the progenitor/bile duct marker (K19), activated Kupffer cells (MAC387), myofibroblasts (alpha-smooth muscle actin [α-SMA]) and the extracellular matrix component laminin were used on seven liver biopsies of cats with FHL and three healthy cats. Double immunofluorescence stainings were performed to investigate co-localisation of different cell types in the hepatic progenitor cell (HPC) niche.

RESULTS

HPCs, Kupffer cells, myofibroblasts and laminin deposition were observed in the liver samples of FHL, although with variability in the expression and positivity of the different immunostainings between different samples. When compared with the unaffected cats where K19 positivity and minimal α-SMA and laminin positivity were seen mainly in the portal area, in the majority of FHL samples K19 and α-SMA-positive cells and laminin positivity were seen also in the periportal and parenchymatous area. MAC387-positive cells were present throughout the parenchyma.

CONCLUSIONS AND RELEVANCE

This is a preliminary morphological study to describe the activation and co-localisation of components of the HPC niche in FHL. Although the HPC niche in FHL resembles that described in hepatopathies in dogs and in feline lymphocytic cholangitis, the expression of K19, α-SMA, MAC387 and lamin is more variable in FHL, and a common pattern of activation could not be established. Nevertheless, when HPCs were activated, a spatial association between HPCs and their niche could be demonstrated.

InForm software: a semi-automated research tool to identify presumptive human hepatic progenitor cells, and other histological features of pathological significance

Hepatic progenitor cells (HPCs) play an important regenerative role in acute and chronic liver pathologies. Liver disease research often necessitates the grading of disease severity, and pathologists’ reports are the current gold-standard for assessment. However, it is often impractical to recruit pathologists in large cohort studies. In this study we utilise PerkinElmer’s “InForm” software package to semi-automate the scoring of patient liver biopsies, and compare outputs to a pathologist’s assessment. We examined a cohort of eleven acute hepatitis samples and three non-alcoholic fatty liver disease (NAFLD) samples, stained with HPC markers (GCTM-5 and Pan Cytokeratin), an inflammatory marker (CD45), Sirius Red to detect collagen and haematoxylin/eosin for general histology. InForm was configured to identify presumptive HPCs, CD45^+ve inflammatory cells, areas of necrosis, fat and collagen deposition (p < 0.0001). Hepatitis samples were then evaluated both by a pathologist using the Ishak-Knodell scoring system, and by InForm through customised algorithms. Necroinflammation as evaluated by a pathologist, correlated with InForm outputs (r² = 0.8192, p < 0.05). This study demonstrates that the InForm software package provides a useful tool for liver disease research, allowing rapid, and objective quantification of the presumptive HPCs and identifies histological features that assist with assessing liver disease severity, and potentially can facilitate diagnosis.

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.

Triple Staining Including FOXA2 Identifies Stem Cell Lineages Undergoing Hepatic and Biliary Differentiation in Cirrhotic Human Liver

Recent investigations have reported many markers associated with human liver stem/progenitor cells, "oval cells," and identified "niches" in diseased livers where stem cells occur. However, there has remained a need to identify entire lineages of stem cells as they differentiate into bile ducts or hepatocytes. We have used combined immunohistochemical staining for a marker of hepatic commitment and specification (FOXA2 [Forkhead box A2]), hepatocyte maturation (Albumin and HepPar1), and features of bile ducts (CK19 [cytokeratin 19]) to identify lineages of stem cells differentiating toward the hepatocytic or bile ductular compartments of end-stage cirrhotic human liver. We identified large clusters of disorganized, FOXA2 expressing, oval cells in localized liver regions surrounded by fibrotic matrix, designated as "micro-niches." Specific FOXA2-positive cells within the micro-niches organize into primitive duct structures that support both hepatocytic and bile ductular differentiation enabling identification of entire lineages of cells forming the two types of structures. We also detected expression of hsa-miR-122 in primitive ductular reactions expected for hepatocytic differentiation and hsa-miR-23b cluster expression that drives liver cell fate decisions in cells undergoing lineage commitment. Our data establish the foundation for a mechanistic hypothesis on how stem cell lineages progress in specialized micro-niches in cirrhotic end-stage liver disease.

Early activated hepatic stellate cell-derived molecules reverse acute hepatic injury

AIM: To test whether hepatic stellate cells (HSCs) at different activation stages play different roles in acetaminophen (APAP)-induced acute liver injury (ALI).

METHODS: HSCs were isolated from mouse liver and cultured in vitro. Morphological changes of initiation HSCs [HSCs (5d)] and perpetuation HSCs [HSCs (p3)] were observed by immunofluorescence and transmission electron microscopy. The protective effects of HSC-derived molecules, cell lysates and HSC-conditioned medium (HSC-CM) were tested in vivo by survival and histopathological analyses. Liver injury was determined by measuring aminotransferase levels in the serum and by histologic examination of tissue sections under a light microscope. Additionally, to determine the molecular mediators of the observed protective effects of initiation HSCs, we examined HSC-CM using a high-density protein array.

RESULTS: HSCs (5d) and HSCs (p3) had different morphological and phenotypic traits. HSCs (5d) presented a star-shaped appearance with expressing α-SMA at non-uniform levels between cells. However, HSCs (p3) evolved into myofibroblast-like cells without lipid droplets and expressed a uniform and higher level of α-SMA. HSC-CM (5d), but not HSC-CM (p3), provided a significant survival benefit and showed a dramatic reduction of hepatocellular necrosis and panlobular leukocyte infiltrates in mice exposed to APAP. However, this protective effect was abrogated at higher cell masses, indicating a therapeutic window of effectiveness. Furthermore, the protein array screen revealed that HSC-CM (5d) was composed of many chemokines and growth factors that correlated with inflammatory inhibition and therapeutic activity. When compared with HSC-CM (p3), higher levels of monocyte chemoattractant protein-1, macrophage inflammatory protein-1γ, hepatocyte growth factor, interleukin-10, and matrix metalloproteinase-2, but lower levels of stem cell factor and Fas-Ligand were observed in HSC-CM (5d).

CONCLUSION: These data indicated that initiation HSCs and perpetuation HSCs were different in morphology and protein expression, and provided the first experimental evidence of the potential medical value of initiation HSC-derived molecules in the treatment of ALI.

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.

Impact of microenvironment and stem-like plasticity in cholangiocarcinoma: molecular networks and biological concepts

Clinical complexity, anatomic diversity and molecular heterogeneity of cholangiocarcinoma (CCA) represent a major challenge in the assessment of effective targeted therapies. Molecular and cellular mechanisms underlying the diversity of CCA growth patterns remain a key issue of clinical concern. Crucial questions comprise the nature of the CCA-origin, the initial target for cellular transformation as well as the relationship with the cancer stem cells (CSC) concept. Additionally, since CCA often develops in the context of an inflammatory milieu (cirrhosis and cholangitis), the stromal compartment or tumour microenvironment (TME) likely promotes initiation and progression of this malignancy, contributing to its heterogeneity. This review will emphasize the dynamic interplay between stem-like intrinsic and TME-extrinsic pathways, which may represent novel options for multi-targeted therapies in CCA.

Enhanced Wnt/β-catenin and Notch signalling in the activated canine hepatic progenitor cell niche

Background

The liver has a large regenerative capacity. Hepatocytes can replicate and regenerate a diseased liver. However, as is the case in severe liver diseases, this replication may become insufficient or exhausted and hepatic progenitor cells (HPCs) can be activated in an attempt to restore liver function. Due to their bi-potent differentiation capacity, these HPCs have great potential for regenerative approaches yet over-activation does pose potential health risks. Therefore the mechanisms leading to activation must be elucidated prior to safe implementation in the veterinary clinic. Wnt/β-catenin and Notch signalling have been implicated in the activation of HPCs in mouse models and in humans. Here we assessed the involvement in canine HPC activation. Gene-expression profiles were derived from laser microdissected HPC niches from lobular dissecting hepatitis (LDH) and normal liver tissue, with a focus on Wnt/β-catenin and Notch signalling. Immunohistochemical and immunofluorescent studies were combined to assess the role of the pathways in HPCs during LDH.

Results

Gene-expression confirmed higher expression of Wnt/β-catenin and Notch pathway components and target genes in activated HPC niches in diseased liver compared to quiescent HPC niches from normal liver. Immunofluorescence confirmed the activation of these pathways in the HPCs during disease. Immunohistochemistry showed proliferating HPCs during LDH, and double immunofluorescence showed downregulation of Wnt/β-catenin and Notch in differentiating HPCs. Vimentin, a mesenchymal marker, was expressed on a subset of undifferentiated HPCs.

Conclusions

Together these studies clearly revealed that both Wnt/β-catenin and Notch signalling pathways are enhanced in undifferentiated, proliferating and potentially migrating HPCs during severe progressive canine liver disease (LDH).

Hepatic stellate cells and liver fibrosis

Hepatic stellate cells are resident perisinusoidal cells distributed throughout the liver, with a remarkable range of functions in normal and injured liver. Derived embryologically from septum transversum mesenchyme, their precursors include submesothelial cells that invade the liver parenchyma from the hepatic capsule. In normal adult liver, their most characteristic feature is the presence of cytoplasmic perinuclear droplets that are laden with retinyl (vitamin A) esters. Normal stellate cells display several patterns of intermediate filaments expression (e.g., desmin, vimentin, and/or glial fibrillary acidic protein) suggesting that there are subpopulations within this parental cell type. In the normal liver, stellate cells participate in retinoid storage, vasoregulation through endothelial cell interactions, extracellular matrix homeostasis, drug detoxification, immunotolerance, and possibly the preservation of hepatocyte mass through secretion of mitogens including hepatocyte growth factor. During liver injury, stellate cells activate into alpha smooth muscle actin-expressing contractile myofibroblasts, which contribute to vascular distortion and increased vascular resistance, thereby promoting portal hypertension. Other features of stellate cell activation include mitogen-mediated proliferation, increased fibrogenesis driven by connective tissue growth factor, and transforming growth factor beta 1, amplified inflammation and immunoregulation, and altered matrix degradation. Evolving areas of interest in stellate cell biology seek to understand mechanisms of their clearance during fibrosis resolution by either apoptosis, senescence, or reversion, and their contribution to hepatic stem cell amplification, regeneration, and hepatocellular cancer.

Huge clusters of embryonic stem cells in human embryos: a morphologic study

BACKGROUND

Nothing is known about huge clusters (HC) of embryonic stem cells (ESC) in human fetal organs (HFO).

AIM

To know the status of HC-ESC in HFO.

METHODS

Morphology and immunohistochemistry (IHC) in 32 HFO of 7-40 gestational weeks (GW).

RESULTS

HC-ESC were seen in many HFO including central nervous system, spinal cords, spine, soft tissue, bone, skin, thyroid, lung, liver, pancreas, gall bladder, extrahepatic bile duct, adrenal, kidney, bladder, foregut, midgut, hindgut, female and male genital organs, and neurons. HC-ESC's were composed of two populations depending on constituting cells. One were large cells with ample acidophilic cytoplasms with vesicular nuclei and nucleoli. The other were small cells with scant cytoplasm with hyperchromatic nuclei without nucleoli, resembling lymphocytes. The HC-ESC were frequently showed neuronal differentiation. HC-ESC were positive for NCAM, synaptophysin, NSE, chromogranin, PDGFRA, AFP, ErbB2, bcl-2, KIT, MET. They were negative for CD45, CD3, CD20, EMA, CEA, CA19-9, cytokeratin (CK) 7, CK8, CK18, CK19, MUC1, MUC2, MUC5AC, and MUC6. The mean Ki-67 labeling index (LI) was 13% ± 7%. HC-ESC showed a little glycogen but lacked mucins. These HC-ESC were seen in 7-25 GW, and they were rarely seen in 26-40 GW.

CONCLUSIONS

The morphology, IHC, and ontogeny of HC-ESC were described.

Classification of primary hepatic tumours in the cat

Hepatic tumours in dogs have recently been re-classified to follow a revised human classification system that takes account of identified hepatic progenitor cells. This study investigated the presence and relative frequency of morphological types of feline primary hepatic neoplasms and aimed to determine whether a similar new classification scheme could be applied in cats. Feline primary liver tumours (n = 61) were examined histologically and with a series of immunohistochemical markers. Six cases of nodular hyperplasia and 21 tumours of hepatocellular origin were diagnosed. The latter were subdivided into hepatocellular tumours that were well differentiated and had no evidence of metastases (n = 18) and tumours that showed poorly differentiated areas with marked cellular and nuclear pleomorphism and had intrahepatic and, or, distant metastases (n = 3). These malignant feline hepatocellular tumours maintained their hepatocellular characteristics (HepPar-1, MRP2, pCEA positive) and were negative, or only <5% positive, for K19. Twenty-five cholangiocellular tumours were diagnosed and all had intrahepatic and, or, distant metastases. Eight NSE positive small cell carcinomas (carcinoids) were diagnosed and subdivided into small cell carcinomas with HPC characteristics (K19 positive) and neuroendocrine carcinomas (K19 negative). In addition, one squamous cell carcinoma originating from the distal part of the choledochal duct was recognised. Feline primary hepatic neoplasms can be sub-divided into benign and malignant hepatocellular tumours, cholangiocellular carcinomas, small cell carcinomas with HPC characteristics, neuroendocrine carcinomas and squamous cell carcinomas. The marked species difference justifies a specific classification for feline primary hepatic neoplasms.

Hepatic progenitor cells in canine and feline medicine: potential for regenerative strategies

New curative therapies for severe liver disease are urgently needed in both the human and veterinary clinic. It is important to find new treatment modalities which aim to compensate for the loss of parenchymal tissue and to repopulate the liver with healthy hepatocytes. A prime focus in regenerative medicine of the liver is the use of adult liver stem cells, or hepatic progenitor cells (HPCs), for functional recovery of liver disease. This review describes recent developments in HPC research in dog and cat and compares these findings to experimental rodent studies and human pathology. Specifically, the role of HPCs in liver regeneration, key components of the HPC niche, and HPC activation in specific types of canine and feline liver disease will be reviewed. Finally, the potential applications of HPCs in regenerative medicine of the liver are discussed and a potential role is suggested for dogs as first target species for HPC-based trials.

The canine hepatic progenitor cell niche: molecular characterisation in health and disease

Hepatic progenitor cells (HPCs) are an adult stem cell compartment in the liver that contributes to liver regeneration when replication of mature hepatocytes is insufficient. In this study, laser microdissection was used to isolate HPC niches from the livers of healthy dogs and dogs with lobular dissecting hepatitis (LDH), in which HPCs are massively activated. Gene expression of HPC, hepatocyte and biliary markers was determined by quantitative reverse transcriptase PCR. Expression and localisation of selected markers were further studied at the protein level by immunohistochemistry and immunofluorescent double staining in samples of normal liver and liver from dogs with LDH, acute and chronic hepatitis, and extrahepatic cholestasis. Activated HPC niches had higher gene expression of the hepatic progenitor markers OPN, FN14, CD29, CD44, CD133, LIF, LIFR and BMI1 compared to HPCs from normal liver. There was lower expression of albumin, but activated HPC niches were positive for the biliary markers SOX9, HNF1β and keratin 19 by immunohistochemistry and immunofluorescence. Laminin, activated stellate cells and macrophages are abundant extracellular matrix and cellular components of the canine HPC niche. This study demonstrates that the molecular and cellular characteristics of canine HPCs are similar to rodent and human HPCs, and that canine HPCs are distinctively activated in different types of liver disease.

Pituitary stem cells: where do we stand?

Some 5 years ago, the stem cells of the adult pituitary gland were discovered. Subsequent in-depth characterization revealed expression of several stemness markers and embryo-typical factors. Now, the quest is open to decipher their role in the gland. When and how pituitary stem cells differentiate to contribute to the mature hormone-producing cell populations is not known. New research models support their involvement in cell regeneration after injury in the gland, and suggest a possible role in pituitary tumor formation. From their expression phenotype, pituitary stem cells seem to re-use embryonic developmental programs during the creation of new hormonal cells. Here, we will review the latest progression in the domain of pituitary stem cells, including the uncovering of some new molecular flavors and of the first potential functions. Eventually, we will speculate on their differentiation programs towards hormonal cells, with a particular focus on gonadotropes.

Two-tier regenerative response in liver failure in humans

Acute and chronic liver failure is associated with high mortality. The enormous regenerative potential of the liver has generated a lot of attention. We undertook this work to assess the two-tier regenerative response in liver failure by immunohistochemistry and to correlate such response with liver histology in acute liver failure (ALF), acute-on-chronic liver failure (ACLF), and decompensated cirrhosis (CHD). Histological examination and immunohistochemical analysis of proliferating hepatocytes and activated hepatic progenitor cells (HPCs) were performed on the liver tissue of patients with ALF (25), ACLF (70), and CHD (70). Comparative analysis of regenerative markers and correlation with histological parameters were done in ALF, ACLF, and CHD. Hepatocytes proliferated significantly more in ALF in comparison to ACLF (p < 0.001) and CHD (p < 0.001). HPC proliferation was significantly higher in ACLF (p < 0.001) and CHD (p < 0.001) than in ALF. ACLF patients showed the highest HPC proliferation and differentiation. Significantly more intermediate hepatocytes were found in ACLF than in ALF and CHD (p < 0.001). Marked parenchymal replacement by fibrosis and/or necrosis correlated significantly with activation of HPC in ACLF (p = 0.01, odds ratio (OR) 4.95) and in CHD (p = 0.05, OR 4.19). The study of liver regeneration in human acute and chronic liver failure suggests that hepatocyte proliferation, providing the first line of regeneration response, is most active in ALF whereas HPC activation, the second line of defense, is more prominent in ACLF. More HPC differentiate to hepatocytes in ACLF than in CHD, reflecting better regenerative potential in ACLF.

Hepatic progenitor cells express SerpinB3

Background

In the setting of liver injury hepatic progenitor cells are activated, counterbalancing the inhibited regenerative capacity of mature hepatocytes. Chronic activation of this compartment may give rise to a subset of liver tumours with poor prognosis. SerpinB3, a serpin over-expressed in injured liver and in primary liver cancer, has been shown to induce apoptosis resistance, epithelial to mesenchymal transition and to increase TGF-beta and Myc expression. Aim of the present study was to explore the presence of SerpinB3 in hepatic progenitor cells in human livers and in a mouse model of liver stem/progenitor cell activation.

Hepatic progenitor cells were analysed in foetal and adult livers at protein and transcriptional levels. To induce experimental activation of the liver stem/progenitor compartment, C57BL/6J mice were injected with lipopolysaccharide plus D-galactosamine and were sacrificed at different time points. Liver cDNA was amplified using specific primers for mouse-homologous SerpinB3 isoforms and automatically sequenced.

Results

The presence of SerpinB3 in the progenitor cell compartment was detected in sorted human foetal and adult epithelial cell adhesion molecule (EpCAM) positive liver cells. By immunohistochemistry SerpinB3 was found in human cirrhotic livers in portal areas with progenitor cell activation showing ductular proliferation. CK-7, CK-19, EpCAM and CD-90 positive cell were also positive for SerpinB3. In the animal model, time course analysis in liver specimens revealed a progressive increase of SerpinB3 and a parallel decrease of activated caspase 3, which was barely detectable at 20 hours. Transcription analysis confirmed the presence of SerpinB3-homologous only in the liver of injured mice and sequence analysis proved its belonging to mouse Serpinb3b.

Conclusion

SerpinB3 is highly expressed in hepatic stem/progenitor cell compartment of both foetal and adult livers.

The biological implication of cancer stem cells in hepatocellular carcinoma: a possible target for future therapy

Recent studies indicated the importance of stem cells in cancer, including in hepatocellular carcinoma. The presence of the stem cells and cancer stem cells in liver diseases is associated with the initiation, maintenance, metastasis and chemoresistance. Since hepatocellular carcinoma is a heterogeneous disease with a wide variety of prognostic types, which may limit the efficiency of standardized therapy, the understanding of the source of the cancer, alteration in important molecular signaling pathways and interaction between cancer cells and other cells types will be important in defining future, tailored treatment strategies.

Evidence for a common progenitor of epithelial and mesenchymal components of the liver

Tissues of the adult organism maintain the homeostasis and respond to injury by means of progenitor/stem cell compartments capable to give rise to appropriate progeny. In organs composed by histotypes of different embryological origins (e.g. the liver), the tissue turnover may in theory involve different stem/precursor cells able to respond coordinately to physiological or pathological stimuli. In the liver, a progenitor cell compartment, giving rise to hepatocytes and cholangiocytes, can be activated by chronic injury inhibiting hepatocyte proliferation. The precursor compartment guaranteeing turnover of hepatic stellate cells (HSCs) (perisinusoidal cells implicated with the origin of the liver fibrosis) in adult organ is yet unveiled. We show here that epithelial and mesenchymal liver cells (hepatocytes and HSCs) may arise from a common progenitor. Sca+ murine progenitor cells were found to coexpress markers of epithelial and mesenchymal lineages and to give rise, within few generations, to cells that segregate the lineage-specific markers into two distinct subpopulations. Notably, these progenitor cells, clonally derived, when transplanted in healthy livers, were found to generate epithelial and mesenchymal liver-specific derivatives (i.e. hepatocytes and HSCs) properly integrated in the liver architecture. These evidences suggest the existence of a 'bona fide' organ-specific meso-endodermal precursor cell, thus profoundly modifying current models of adult progenitor commitment believed, so far, to be lineage-restricted. Heterotopic transplantations, which confirm the dual differentiation potentiality of those cells, indicates as tissue local cues are necessary to drive a full hepatic differentiation. These data provide first evidences for an adult stem/precursor cell capable to differentiate in both parenchymal and non-parenchymal organ-specific components and candidate the liver as the instructive site for the reservoir compartment of HSC precursors as yet non-localized in the adult.

Failure of fibrotic liver regeneration in mice is linked to a severe fibrogenic response driven by hepatic progenitor cell activation

Failure of fibrotic liver to regenerate after resection limits therapeutic options and increases demand for liver transplantation, representing a significant clinical problem. The mechanism underlying regenerative failure in fibrosis is poorly understood. Seventy percent partial hepatectomy (PHx) was performed in C57Bl/6 mice with or without carbon tetrachloride (CCl4)-induced liver fibrosis. Liver function and regeneration was monitored at 1 to 14 days thereafter by assessing liver mass, alanine aminotransferase (ALT), mRNA expression, and histology. Progenitor (oval) cell mitogen tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and TWEAK-neutralizing antibody were used to manipulate progenitor cell proliferation in vivo. In fibrotic liver, hepatocytes failed to replicate efficiently after PHx. Fibrotic livers showed late (day 5) peak of serum ALT (3542 ± 355 IU/L compared to 93 ± 65 IU/L in nonfibrotic livers), which coincided with progenitor cell expansion, increase in profibrogenic gene expression and de novo collagen deposition. In fibrotic mice, inhibition of progenitor activation using TWEAK-neutralizing antibody after PHx resulted in strongly down-regulated profibrogenic mRNA, reduced serum ALT levels and improved regeneration. Failure of hepatocyte-mediated regeneration in fibrotic liver triggers activation of the progenitor (oval) cell compartment and a severe fibrogenic response. Inhibition of progenitor cell proliferation using anti-TWEAK antibody prevents fibrogenic response and augments fibrotic liver regeneration. Targeting the fibrogenic progenitor response represents a promising strategy to improve hepatectomy outcomes in patients with liver fibrosis.

Neuroendocrine differentiation in embryonal type hepatoblastoma

Hepatoblastoma, a malignant tumor which arises occasionally in older children but very rarely in adults, exhibits divergent differentiation with embryonal cells, fetal hepatocytes and immature elements. This report describes an embryonal type hepatoblastoma with neuroendocrine differentiation in a 16-year-old patient, which was diagnosed postoperatively. Clinical and radiologic work-up failed to reveal a primary gastrointestinal malignancy and no primary lesions were detected in any other organ. This feature of hepatoblastoma is considered to be a multidirectional differentiation of the small epithelial or stem cells of the liver. At 2-year follow up, the patient remains symptom-free, with normal laboratory and diagnostic imaging studies, and no recurrent or metastatic disease identified.

Hepatitis C virus and hepatocarcinogenesis

Hepatitis C virus (HCV) is an RNA virus that is unable to integrate into the host genome. However, its proteins interact with various host proteins and induce host responses. The oncogenic process of HCV infection is slow and insidious and probably requires multiple steps of genetic and epigenetic alterations, the activation of cellular oncogenes, the inactivation of tumor suppressor genes, and dysregulation of multiple signal transduction pathways. Stellate cells may transdifferentiate into progenitor cells and possibly be linked to the development of hepatocellular carcinoma (HCC). Viral proteins also have been implicated in several cellular signal transduction pathways that affect cell survival, proliferation, migration and transformation. Current advances in gene expression profile and selective messenger RNA analysis have improved approach to the pathogenesis of HCC. The heterogeneity of genetic events observed in HCV-related HCCs has suggested that complex mechanisms underlie malignant transformation induced by HCV infection. Considering the complexity and heterogeneity of HCCs of both etiological and genetic aspects, further molecular classification is required and an understanding of these molecular complexities may provide the opportunity for effective chemoprevention and personalized therapy for HCV-related HCC patients in the future. In this review, we summarize the current knowledge of the mechanisms of hepatocarcinogenesis induced by HCV infection.

Clinicopathological factors impact the survival outcome following the resection of combined hepatocellular carcinoma and cholangiocarcinoma

Studies have demonstrated poor survival outcomes for patients with resected combined hepatocellular carcinoma-cholangiocarcinoma tumours (CHCC-CC). Our objectives are to report on our institutional experience regarding the clinico-pathological and prognostic features of CHCC-CC and to compare our results with published series. The clinico-pathological features and outcomes of 11 patients with CHCC-CC who had a complete surgical resection for primary liver cancer were reviewed. There were 8 male and 3 female patients. The overall median age was 61 years. Active hepatitis B and hepatitis C infections were present in 6 (54%) and 2 (18%) patients, respectively. Alcoholism was present in one case. Cirrhosis was present in 8 (72%) cases. There were no causative factors identified in 2 patients with non-cirrhotic livers. The median AFP value was 30.56 ng/ml. A single mass located in the right lobe and a single mass located in the left lobe of the liver was noted in 6 (54%) and 4 (36%) patients, respectively. Bilobar involvement was observed in one case. Major and minor resections were performed in 2 (18%) and 9 (81%) cases, respectively. The median tumour size was 3 cm. Tumours measuring >5 cm were identified in only 2 (18%) cases. The majority of the cases were classified as stage I (54%) and stage II (36%). Four patients died 11-50 months after the surgery. Postoperative tumour recurrences were observed in 5 (45.45%) patients within 4 years of surgical resection. The overall 1- and 3-year survival rates in this series were 80% and 69.3%. Our series demonstrated cases of CHCC-CC with more favourable pathological traits and survival outcomes compared with similar studies.

COMMD1-deficient dogs accumulate copper in hepatocytes and provide a good model for chronic hepatitis and fibrosis

New therapeutic concepts developed in rodent models should ideally be evaluated in large animal models prior to human clinical application. COMMD1-deficiency in dogs leads to hepatic copper accumulation and chronic hepatitis representing a Wilson’s disease like phenotype. Detailed understanding of the pathogenesis and time course of this animal model is required to test its feasibility as a large animal model for chronic hepatitis. In addition to mouse models, true longitudinal studies are possible due to the size of these dogs permitting detailed analysis of the sequence of events from initial insult to final cirrhosis. Therefore, liver biopsies were taken each half year from five new born COMMD1-deficient dogs over a period of 42 months. Biopsies were used for H&E, reticulin, and rubeanic acid (copper) staining. Immunohistochemistry was performed on hepatic stellate cell (HSC) activation marker (alpha-smooth muscle actin, α-SMA), proliferation (Ki67), apoptosis (caspase-3), and bile duct and liver progenitor cell (LPC) markers keratin (K) 19 and 7. Quantitative RT-PCR and Western Blots were performed on gene products involved in the regenerative and fibrotic pathways. Maximum copper accumulation was reached at 12 months of age, which coincided with the first signs of hepatitis. HSCs were activated (α-SMA) from 18 months onwards, with increasing reticulin deposition and hepatocytic proliferation in later stages. Hepatitis and caspase-3 activity (first noticed at 18 months) increased over time. Both HGF and TGF-β1 gene expression peaked at 24 months, and thereafter decreased gradually. Both STAT3 and c-MET showed an increased time-dependent activation. Smad2/3 phosphorylation, indicative for fibrogenesis, was present at all time-points. COMMD1-deficient dogs develop chronic liver disease and cirrhosis comparable to human chronic hepatitis, although at much higher pace. Therefore they represent a genetically-defined large animal model to test clinical applicability of new therapeutics developed in rodent models.

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.

Copper-induced hepatitis: the COMMD1 deficient dog as a translational animal model for human chronic hepatitis

Chronic inflammatory liver disease regardless of aetiology leads to failing regeneration and fibrosis, ending in cirrhosis. Both in man and in animals this worldwide health problem has no definitive cure. Chronic liver injury causes hepatic stellate cells to proliferate and differentiate into matrix-producing cells. New therapeutic options will be developed upon detailed understanding of the molecular mechanisms driving liver fibrosis. This may lead to new anti-fibrotic therapies which need to be tested in suitable models before application in the veterinary and human clinic. On the other side, to restore the failing regenerative capacity of the diseased liver cells, adult progenitor cells are of interest, as an alternative to whole organ transplantation. In order to find the most suitable large animal model it is important to recognise that the typical histopathological reaction pattern of the liver can differ between mammalian species. It is therefore imperative that specialists in veterinary internal medicine and pathology, being familiar with the diseases and pathologies of the liver in different animal species, are teaming-up in finding the best models for veterinary and human liver diseases. Several large animal models have been mentioned, like pigs, sheep, and dogs. Based on the observations that man and dog share the same hepatopathies and have identical clinical, pathological and pathogenetic reaction patterns during the development of liver disease, the dog seems to be a properly suited species to test new therapeutic strategies for pets and their best friends.

Isolation and purification method of mouse fetal hepatoblasts

During development, liver precursors constitute a valuable source of pluripotent stem cells that present the ability to differentiate into both a hepatic and biliary lineage. In the present chapter, we report an experimental procedure developed by our group to isolate mouse fetal hepatoblasts (MFHs) with high purity. The method is based on a selective harvesting of the hepatic parenchymal cells from fetuses (E 14.5), followed by the sorting of E-cadherin(+) progenitors through the use of magnetic beads and specific antibodies. This protocol allows the isolation of bipotent liver stem cells expressing both hepatic and biliary markers. Primary cultures of purified MFHs can be maintained under proliferation until confluence, leading to promotion of the differentiation process in the presence of hepatotrophic factors. By using a quantitative real-time polymerase chain reaction approach, we show the hepatospecific phenotype and the progressive maturation of MFHs, delineating early (α-fetoprotein), mid (albumin), and late (glucose-6-phosphatase) hepatic markers. Consequently, the model appears to be a valuable cell system for the study of molecular and cellular aspects occurring in hepatic differentiation.

Anatomic pathology of hepatocellular carcinoma: impact on prognosis and response to therapy

A better understanding of signaling pathways in HCC pathogenesis has led to targeted therapies against HCC. Identification of liver cancer stem cell markers and their related pathways is one of the most important goals of liver cancer research. New therapies should ideally target cancer stem cells and not normal stem/progenitor cells, because the latter are very important in regeneration and repair. Individualized HCC therapy will require better definition of patient subgroups that benefit most or should be protected from therapy failure and unwanted side effects. Tumor tissue acquisition should be mandatory, reversing the practice that was established years ago when targeted HCC therapy was but a pipe dream.

Pituitary stem/progenitor cells: embryonic players in the adult gland?

The pituitary gland represents the endocrine core of the body, and its hormonal output governs many key physiological processes. Because endocrine demands frequently change, the pituitary has to flexibly remodel its hormone-producing cell compartment. One mechanism of pituitary plasticity may rely on the generation of new hormonal cells from resident stem/progenitor cells. Existence of such 'master' cells in the pituitary has in the past repeatedly been postulated. Only recently, however, very plausible candidates have been identified that express stem cell-associated markers and signalling factors, and display the stem/progenitor cell characteristics of multipotency, efflux capacity (side population phenotype) and niche-like organization. In other adult tissues, stem cells recapitulate the embryonic developmental path on their course towards mature specialized cells. Interestingly, the pituitary stem/progenitor cell compartment shows prominent expression of transcriptional regulators and signalling factors that play a pivotal role during pituitary embryogenesis. This review summarizes the recent progress in pituitary stem/progenitor cell identification, highlights their potential embryonic phenotype, sketches a tentative stem/progenitor cell model, and discusses further research and challenges. Recognizing and scrutinizing the pituitary stem/progenitor cells as embryonic players in the adult gland may profoundly impact on our still poor understanding of the mechanisms underlying pituitary cell turnover and plasticity.

Cholangiocarcinoma: new insights into disease pathogenesis and biology

Cholangiocarcinomas are rare malignant tumors whose incidence is increasing worldwide. Risk factors for this malignancy include both infectious and non-infectious diseases characterized by chronic inflammation of the bile duct epithelia. Diagnosis of these cancers remains difficult because of the lack of sensitive diagnostic tests. The prognosis is poor probably because of the lack of effective treatments for unresectable cancer.

CD133+ stem cell mobilization after partial hepatectomy depends on resection extent and underlying disease

BACKGROUND

Bone marrow stem cells (BMSC) can participate to liver regeneration. However, conflicting results have been reported on this topic in patients undergoing liver resection.

AIMS

To assess the impact of liver resection extent and presence of underlying liver disease in modulating BMSC mobilization.

METHODS

We enrolled 29 patients undergoing liver resection of different extents, 5 surgical controls and 10 blood donors. Circulating CD133+ BMSC were measured by flow cytometry at different time-points after surgery. The hepatic commitment of mobilized BMSC was investigated by polymerase chain reaction. Liver specimens were collected during surgery for histopathological analysis. Hepatocyte growth factor and granulocyte-colony stimulating factor serum levels were measured by enzyme-linked immunosorbent assay.

RESULTS

BMSC mobilization was found in patients undergoing major liver resection, especially in the presence of underlying disease. Ductular reactions were noted in patients with chronic hepatopathy and the hepatic progenitor-like cells expressed CD133, NCAM, cytokeratin-19, and alpha-fetoprotein. Hepatocyte growth factor and granulocyte-colony stimulating factor levels increased following liver resection and the contemporaneous presence of liver disease was associated with their highest raise.

CONCLUSIONS

Liver repair is mainly an endogenous process. BMSC become important in case of extensive resection, especially in the presence of underlying hepatopathy and hepatic progenitor-like cells activation. Hepatocyte growth factor and granulocyte-colony stimulating factor seem to be involved in the dynamics underlying hepatic regeneration and BMSC recruitment.

Hepatic progenitor cells: an update

Liver progenitor cells are activated in most human liver diseases. The dynamics, and therefore subpopulations, of progenitor cells are, however, different in acute versus chronic hepatocytic diseases and in biliary diseases. The role of Wnt and Notch signaling pathways in activation and differentiation of human hepatic progenitor cells holds great promise because they can be manipulated by drugs. Hepatocytic differentiation requires inhibition of Notch (numb switched on), whereas cholangiocytic differentiation requires Notch activation. In this way, the patients' own regenerative response could be supported, which could eventually even avoid the need for transplantation in several patients.

Transcriptional profiling of human embryonic stem cells differentiating to definitive and primitive endoderm and further toward the hepatic lineage

Human embryonic stem cells (hESC) can differentiate into a variety of specialized cell types, and they constitute a useful model system to study embryonic development in vitro. In order to fully utilize the potential of these cells, the mechanisms that regulate the developmental processes of specific lineage differentiation need to be better defined. The aim of this study was to explore the molecular program involved in the differentiation of hESC toward definitive endoderm (DE) and further into the hepatic lineage, and to compare that with primitive endoderm (PrE) differentiation. To that end, we applied two protocols: a specific DE differentiation protocol and an intrinsic differentiation protocol that mainly mediates PrE formation. We collected hESC, hESC-derived DE, DE-derived hepatocyte-progenitors (DE-Prog), DE-derived hepatocyte-like cells (DE-Hep), and the corresponding PrE derivatives. The samples were analyzed using microarrays, and we identified sets of genes that were exclusively up-regulated in DE derivatives (compared to PrE derivatives) at discrete developmental stages. We also investigated known protein interactions among the set of up-regulated genes in DE-Hep. The results demonstrate important differences between DE and PrE differentiation on the transcriptional level. In particular, our results identify a unique molecular program, exclusively activated during development of DE and the subsequent differentiation of DE toward the hepatic lineage. We identified key genes and pathways of potential importance for future efforts to improve hepatic differentiation from hESC. These results reveal new opportunities for rational design of specific interventions with the purpose of generating enriched populations of DE derivatives, including functional hepatocytes.