Pathophysiology of cholangiopathies

Three-dimensional human bile duct formation from chemically induced human liver progenitor cells

Background: The intrahepatic bile ducts (BDs) play an important role in the modification and transport of bile, and the integration between the BD and hepatocytes is the basis of the liver function. However, the lack of a source of cholangiocytes limits in vitro research. The aim of the present study was to establish three-dimensional BDs combined with human mature hepatocytes (hMHs) in vitro using chemically induced human liver progenitor cells (hCLiPs) derived from hMHs. Methods: In this study, we formed functional BDs from hCLiPs using hepatocyte growth factor and extracellular matrix. BDs expressed the typical biliary markers CK-7, GGT1, CFTR and EpCAM and were able to transport the bile-like substance rhodamine 123 into the lumen. The established three-dimensional BDs were cocultured with hMHs. These cells were able to bind to the BDs, and the bile acid analog CLF was transported from the culture medium through the hMHs and accumulated in the lumen of the BDs. The BDs generated from the hCLiPs showed a BD function and a physiological system (e.g., the transport of bile within the liver) when they were connected to the hMHs. Conclusion: We present a novel in vitro three-dimensional BD combined with hMHs for study, drug screening and the therapeutic modulation of the cholangiocyte function.

Primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD): a condition exemplifying the crosstalk of the gut-liver axis

The close relationship between primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) provides a good opportunity to comprehend the gut-liver axis. The gut and the liver have reciprocal interactions, including how gut inflammation influences the liver through immune cells and the microbiota and how the microbiota in the gut modifies bile acids, which are produced and secreted from the liver. PSC-IBD shows distinct clinical findings from classical IBD. In addition, a distinct genetic predisposition and unique microbiota composition suggest that PSC-IBD is an independent disease entity. Understanding the pathogenesis of PSC-IBD helps to develop novel and effective therapeutic agents. Given the high risk of malignancies associated with PSC-IBD, it is critical to identify patients at high risk and implement appropriate surveillance and monitoring strategies. In this review, we provide an overview of PSC-IBD, which exemplifies the gut-liver axis.

Role of bile acids and their receptors in gastrointestinal and hepatic pathophysiology

Bile acids (BAs) can regulate their own metabolism and transport as well as other key aspects of metabolic homeostasis via dedicated (nuclear and G protein-coupled) receptors. Disrupted BA transport and homeostasis results in the development of cholestatic disorders and contributes to a wide range of liver diseases, including nonalcoholic fatty liver disease and hepatocellular and cholangiocellular carcinoma. Furthermore, impaired BA homeostasis can also affect the intestine, contributing to the pathogenesis of irritable bowel syndrome, inflammatory bowel disease, and colorectal and oesophageal cancer. Here, we provide a summary of the role of BAs and their disrupted homeostasis in the development of gastrointestinal and hepatic disorders and present novel insights on how targeting BA pathways might contribute to novel treatment strategies for these disorders.

Maternal obesogenic diet enhances cholestatic liver disease in offspring

Human and animal model data show that maternal obesity promotes nonalcoholic fatty liver disease in offspring and alters bile acid (BA) homeostasis. Here we investigated whether offspring exposed to maternal obesogenic diets exhibited greater cholestatic injury. We fed female C57Bl6 mice conventional chow (CON) or high fat/high sucrose (HF/HS) diet and then bred them with lean males. Offspring were fed 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) for 2 weeks to induce cholestasis, and a subgroup was then fed CON for an additional 10 days. Additionally, to evaluate the role of the gut microbiome, we fed antibiotic-treated mice cecal contents from CON or HF/HS offspring, followed by DDC for 2 weeks. We found that HF/HS offspring fed DDC exhibited increased fine branching of the bile duct (ductular reaction) and fibrosis but did not differ in BA pool size or intrahepatic BA profile compared to offspring of mice fed CON. We also found that after 10 days recovery, HF/HS offspring exhibited sustained ductular reaction and periportal fibrosis, while lesions in CON offspring were resolved. In addition, cecal microbiome transplant from HF/HS offspring donors worsened ductular reaction, inflammation, and fibrosis in mice fed DDC. Finally, transfer of the microbiome from HF/HS offspring replicated the cholestatic liver injury phenotype. Taken together, we conclude that maternal HF/HS diet predisposes offspring to increased cholestatic injury after DDC feeding and delays recovery after returning to CON diets. These findings highlight the impact of maternal obesogenic diet on hepatobiliary injury and repair pathways during experimental cholestasis.

Cystic fibrosis associated liver disease in children

Cystic fibrosis (CF) is an autosomal recessive disorder caused by mutations in the CF transmembrane conductance regulator gene. CF liver disease develops in 5%-10% of patients with CF and is the third leading cause of death among patients with CF after pulmonary disease or lung transplant complications. We review the pathogenesis, clinical presentations, complications, diagnostic evaluation, effect of medical therapies especially CF transmembrane conductance regulator modulators and liver transplantation in CF associated liver disease.

Temporal histopathological changes in biliary atresia: A perspective for rapid fibrosis progression

INTRODUCTION AND OBJECTIVES

Biliary atresia (BA) is characterized by rapid progression of fibrosis with no definite causes. Histopathological findings have been extensively described, but very few studies have assessed temporal changes in BA. Understanding these short-term changes and their relationship with fibrosis progression could have an impact on ameliorating rapid fibrogenesis. We aimed to study the relationship between temporal histopathological changes and fibrosis progression in BA within a short time interval.

PATIENTS AND METHODS

Forty-nine infants with BA who underwent Kasai portoenterostomy, a diagnostic liver biopsy, and an intraoperative liver biopsy were recruited. Histopathological characteristics of the two biopsies were examined. Temporal histopathological changes were assessed by comparing the two types of biopsies. Correlation of temporal changes in fibrosis with age, interval between biopsies, laboratory profiles, and temporal histopathological changes were studied.

RESULTS

In the univariate analysis, bile ductular proliferation (BDP), portal infiltrate, giant cells, hepatocellular swelling, and fibrosis showed significant temporal changes within a short interval (5-31 days). BDP and fibrosis showed the most frequent increase in their grades (32/49 and 31/49 cases, respectively). In the multivariate analysis, BDP was the only independent pathological feature showing a significant temporal increase (p = 0.021, 95% confidence interval: 1.249-16.017). Fibrosis progression was correlated with temporal changes in BDP (r = 0.456, p = 0.001), but not with age (p = 0.283) or the interval between the biopsies (p = 0.309).

CONCLUSIONS

Fibrosis in BA progresses rapidly and is significantly correlated with BDP. Assessment of targeting BDP as an adjuvant medical therapy is recommended.

Experimental liver models: From cell culture techniques to microfluidic organs-on-chip

The liver is one of the most studied organs of the human body owing to its central role in xenobiotic and drug metabolism. In recent decades, extensive research has aimed at developing in vitro liver models able to mimic liver functions to study pathophysiological clues in high-throughput and reproducible environments. Two-dimensional (2D) models have been widely used in screening potential toxic compounds but have failed to accurately reproduce the three-dimensionality (3D) of the liver milieu. To overcome these limitations, improved 3D culture techniques have been developed to recapitulate the hepatic native microenvironment. These models focus on reproducing the liver architecture, representing both parenchymal and nonparenchymal cells, as well as cell interactions. More recently, Liver-on-Chip (LoC) models have been developed with the aim of providing physiological fluid flow and thus achieving essential hepatic functions. Given their unprecedented ability to recapitulate critical features of the liver cellular environments, LoC have been extensively adopted in pathophysiological modelling and currently represent a promising tool for tissue engineering and drug screening applications. In this review, we discuss the evolution of experimental liver models, from the ancient 2D hepatocyte models, widely used for liver toxicity screening, to 3D and LoC culture strategies adopted for mirroring a more physiological microenvironment for the study of liver diseases.

Drug-induced Bile Duct Injury - A Short Review

The liver represents the major site of drug metabolism, i.e. the key organ in the processes of detoxification and elimination of drugs from the organism. It is therefore often affected by toxic metabolites and suffers sometimes fatal consequences. The spectrum of pathologies differs by the cell type primarily damaged and the group of the cholangiopathies includes those conditions affecting the bile duct epithelium or the cholangiocytes. They can range from transient cholestasis to vanishing bile duct syndrome and sclerosing cholangitis, both leading eventually to the development of biliary fibrosis and cirrhosis. In this review article, we focus on the etiology, predisposing factors, clinical manifestations, and histopathological characteristics of bile duct injury as a consequence of drug treatment and discuss separately the different bile duct pathologies.

SOX9 in biliary atresia: New insight for fibrosis progression

BACKGROUND

Liver fibrosis is a hallmark determinant of morbidity in biliary atresia (BA) even in successfully operated cases. Responsible factors for this rapid progression of fibrosis are not completely defined. Aberrant expression of the transcription factor SOX9 and hepatic progenitor cells (HPCs) proliferation have roles in fibrogenesis in cholestatic disorders. However, they were not investigated sufficiently in BA. We aimed to delineate the relation of SOX9 and HPCs to fibrosis and its progression in BA.

METHODS

Forty-eight patients with BA who underwent an initial diagnostic liver biopsy (LB) and consequent intraoperative LB were recruited and compared to 28 cases with non-BA cholestasis that had an LB in their diagnostic workup. Liver fibrosis, tissue SOX9 and HPC expressions were studied in both BA and non-BA-cholestasis cases. Liver fibrosis, SOX9, and HPCs' dynamic changes in BA cases were assessed. Relation of fibrosis and its progression to SOX9 and HPCs in BA was assessed.

RESULTS

SOX9 and HPCs in ductular reaction (DR) form were expressed in 100% of BA and their grades increased significantly in the second biopsy. The rapidly progressive fibrosis in BA, represented by fibrosis grade of the intraoperative LB, correlated significantly to SOX9-DR and HPC-DR at the diagnostic (r = 0.420, P = 0.003 and r = 0.405, P = 0.004, respectively) and the intraoperative (r = 0.460, P = 0.001 and r = 0.467, P = 0.001, respectively) biopsy. On the other hand, fibrosis, SOX9-DR, and HPC-DR were significantly lower in non-BA cases at a comparable age (P < 0.001, P = 0.006, and P = 0.014, respectively).

CONCLUSIONS

Fibrosis in BA is rapidly progressive within a short time and is significantly correlated to SOX9 and HPCs. Assessment of targeting SOX9 and HPCs on fibrosis progression is warranted.

The Epithelial-to-Mesenchymal Transition as a Possible Therapeutic Target in Fibrotic Disorders

Fibrosis is a chronic and progressive disorder characterized by excessive deposition of extracellular matrix, which leads to scarring and loss of function of the affected organ or tissue. Indeed, the fibrotic process affects a variety of organs and tissues, with specific molecular background. However, two common hallmarks are shared: the crucial role of the transforming growth factor-beta (TGF-β) and the involvement of the inflammation process, that is essential for initiating the fibrotic degeneration. TGF-β in particular but also other cytokines regulate the most common molecular mechanism at the basis of fibrosis, the Epithelial-to-Mesenchymal Transition (EMT). EMT has been extensively studied, but not yet fully explored as a possible therapeutic target for fibrosis. A deeper understanding of the crosstalk between fibrosis and EMT may represent an opportunity for the development of a broadly effective anti-fibrotic therapy. Here we report the evidences of the relationship between EMT and multi-organ fibrosis, and the possible therapeutic approaches that may be developed by exploiting this relationship.

Molecular Physiology of Bile Acid Signaling in Health, Disease, and Aging

Over the past two decades, bile acids (BAs) have become established as important signaling molecules that enable fine-tuned inter-tissue communication from the liver, their site of production, over the intestine, where they are modified by the gut microbiota, to virtually any organ, where they exert their pleiotropic physiological effects. The chemical variety of BAs, to a large extent determined by the gut microbiome, also allows for a complex fine-tuning of adaptive responses in our body. This review provides an overview of the mechanisms by which BA receptors coordinate several aspects of physiology and highlights new therapeutic strategies for diseases underlying pathological BA signaling.

If It Looks Like a Duct and Acts Like a Duct: On the Role of Reprogrammed Hepatocytes in Cholangiopathies

Cholangiopathies are chronic, progressive diseases of the biliary tree, and can be either acquired or genetic. The primary target is the cholangiocyte (CC), the cell type lining the bile duct that is responsible for bile modification and transport. Despite advances in our understanding and diagnosis of these diseases in recent years, there are no proven therapeutic treatments for the majority of the cholangiopathies, and liver transplantation is the only life-extending treatment option for patients with end-stage cholestatic liver disease. One potential therapeutic strategy is to facilitate endogenous repair of the biliary system, which may alleviate intrahepatic cholestasis caused by these diseases. During biliary injury, hepatocytes (HC) are known to alter their phenotype and acquire CC-like features, a process known as cellular reprogramming. This brief review discusses the potential ways in which reprogrammed HC may contribute to biliary repair, thereby restoring bile flow and reducing the severity of cholangiopathies. Some of these include modifying bile to reduce toxicity, serving as a source of de novo CC to repair the biliary epithelium, or creating new channels to facilitate bile flow.

Cystic fibrosis-associated liver disease in children

As improvements in nutritional and pulmonary care increase the life expectancy of cystic fibrosis (CF) patients, CF-associated liver disease (CFLD) is emerging as a cause of mortality. CFLD is the third leading cause of death in CF patients. We performed a search on PubMed and Google Scholar for published articles on CFLD. We reviewed the articles found in the literature search and gave priority to recent publications and studies with larger sample sizes. The prevalence of CFLD in the CF population is around 23% with a range of 2-62% and that prevalence increases linearly with age from 3.7% at age 5 to 32.2% at age 30. CFLD can present clinically in various ways such as hepatomegaly, variceal hemorrhage, persistent elevation of liver enzymes, and micro-gallbladder. Due to the focal nature of fibrosis in majority cases of CFLD, liver biopsies are sparsely performed for diagnosis or the marker of liver fibrosis. Although the mechanism of CFLD development is still unknown, many potential factors are reported. Some mutations of CFTR such as having a homozygous F508del mutation has been reported to increase the risk of developing CFLD and its severity. Having the SERPINA1 Z allele, a history of pancreatic insufficiency, a history meconium ileus, CF-related diabetes, or being male increases the risk of developing CFLD. Environmental factors do not appear to have significant effect on modulating CFLD development. Ursodeoxycholic acid is commonly used to treat or prevent CFLD, but the efficacy of this treatment is questionable.

The Emerging Role of Macrophages in Chronic Cholangiopathies Featuring Biliary Fibrosis: An Attractive Therapeutic Target for Orphan Diseases

Cholangiopathies are a heterogeneous group of chronic liver diseases caused by different types of injury targeting the biliary epithelium, such as genetic defects and immune-mediated attacks. Notably, most cholangiopathies are orphan, thereby representing one of the major gaps in knowledge of the modern hepatology. A typical hallmark of disease progression in cholangiopathies is portal scarring, and thus development of effective therapeutic approaches would aim to hinder cellular and molecular mechanisms underpinning biliary fibrogenesis. Recent lines of evidence indicate that macrophages, rather than more conventional cell effectors of liver fibrosis such as hepatic stellate cells and portal fibroblasts, are actively involved in the earliest stages of biliary fibrogenesis by exchanging a multitude of cues with cholangiocytes, which promote their recruitment from the circulating compartment owing to a senescent or an immature epithelial phenotype. Two cholangiopathies, namely primary sclerosing cholangitis and congenital hepatic fibrosis, are paradigmatic of this mechanism. This review summarizes current understandings of the cytokine and extracellular vesicles-mediated communications between cholangiocytes and macrophages typically occurring in the two cholangiopathies to unveil potential novel targets for the treatment of biliary fibrosis.

Pathobiology of inherited biliary diseases: a roadmap to understand acquired liver diseases

Bile duct epithelial cells, also known as cholangiocytes, regulate the composition of bile and its flow. Acquired, congenital and genetic dysfunctions in these cells give rise to a set of diverse and complex diseases, often of unknown aetiology, called cholangiopathies. New knowledge has been steadily acquired about genetic and congenital cholangiopathies, and this has led to a better understanding of the mechanisms of acquired cholangiopathies. This Review focuses on findings from studies on Alagille syndrome, polycystic liver diseases, fibropolycystic liver diseases (Caroli disease and congenital hepatic fibrosis) and cystic fibrosis-related liver disease. In particular, knowledge on the role of Notch signalling in biliary repair and tubulogenesis has been advanced by work on Alagille syndrome, and investigations in polycystic liver diseases have highlighted the role of primary cilia in biliary pathophysiology and the concept of biliary angiogenic signalling and its role in cyst growth and biliary repair. In fibropolycystic liver disease, research has shown that loss of fibrocystin generates a signalling cascade that increases β-catenin signalling, activates the NOD-, LRR- and pyrin domain-containing 3 inflammasome, and promotes production of IL-1β and other chemokines that attract macrophages and orchestrate the process of pericystic and portal fibrosis, which are the main mechanisms of progression in cholangiopathies. In cystic fibrosis-related liver disease, lack of cystic fibrosis transmembrane conductance regulator increases the sensitivity of epithelial Toll-like receptor 4 that sustains the secretion of nuclear factor-κB-dependent cytokines and peribiliary inflammation in response to gut-derived products, providing a model for primary sclerosing cholangitis. These signalling mechanisms may be targeted therapeutically and they offer a possibility for the development of novel treatments for acquired cholangiopathies.

Pathophysiology of Cystic Fibrosis Liver Disease: A Channelopathy Leading to Alterations in Innate Immunity and in Microbiota

Cystic fibrosis (CF) is a monogenic disease caused by mutation of Cftr. CF-associated liver disease (CFLD) is a common nonpulmonary cause of mortality in CF and accounts for approximately 2.5%-5% of overall CF mortality. The peak of the disease is in the pediatric population, but a second wave of liver disease in CF adults has been reported in the past decade in association with an increase in the life expectancy of these patients. New drugs are available to correct the basic defect in CF but their efficacy in CFLD is not known. The cystic fibrosis transmembrane conductance regulator, expressed in the apical membrane of cholangiocytes, is a major determinant for bile secretion and CFLD classically has been considered a channelopathy. However, the recent findings of the cystic fibrosis transmembrane conductance regulator as a regulator of epithelial innate immunity and the possible influence of the intestinal disease with an altered microbiota on the liver complication have opened new mechanistic insights on the pathogenesis of CFLD. This review provides an overview of the current understanding of the pathophysiology of the disease and discusses a potential target for intervention.

The contributions of mesoderm-derived cells in liver development

The liver is an indispensable organ for metabolism and drug detoxification. The liver consists of endoderm-derived hepatobiliary lineages and various mesoderm-derived cells, and interacts with the surrounding tissues and organs through the ventral mesentery. Liver development, from hepatic specification to liver maturation, requires close interactions with mesoderm-derived cells, such as mesothelial cells, hepatic stellate cells, mesenchymal cells, liver sinusoidal endothelial cells and hematopoietic cells. These cells affect liver development through precise signaling events and even direct physical contact. Through the use of new techniques, emerging studies have recently led to a deeper understanding of liver development and its related mechanisms, especially the roles of mesodermal cells in liver development. Based on these developments, the current protocols for in vitro hepatocyte-like cell induction and liver-like tissue construction have been optimized and are of great importance for the treatment of liver diseases. Here, we review the roles of mesoderm-derived cells in the processes of liver development, hepatocyte-like cell induction and liver-like tissue construction.

Liver diseases in the dish: iPSC and organoids as a new approach to modeling liver diseases

Liver diseases negatively impact the quality of life and survival of patients, and often require liver transplantation in cases that progress to organ failure. Understanding the cellular and molecular mechanisms of liver development and pathogenesis has been a challenging task, in part for the lack of adequate cellular models directly relevant to the human diseases. Recent technological advances in the stem cell field have shown the potentiality of induced pluripotent stem cells (iPSC) and liver organoids as the next generation tool to model in vitro liver diseases. Hepatocyte-like cells and cholangiocyte are currently being generated from skin fibroblasts and mononuclear blood cells reprogrammed into iPSC and have been successfully used for disease modeling, drug testing and gene editing, with the hope to be able to find application also in regenerative medicine. Protocols to generate other liver cell types are still under development, but the field is advancing rapidly. On the other end, liver cells can now be isolated from liver specimens (liver explants or liver biopsies) and cultured in specific conditions to form polarized 3D organoids. The purpose of this review is to summarize all these recent technological advances and their potential applications but also to analyze the current issues to be addressed before the technology can reach its full potential.

Animal models of cholestasis: An update on inflammatory cholangiopathies

Cholestasis is a frequent clinical condition initiating or complicating chronic liver diseases, particularly cholangiopathies, where the biliary epithelium is the primary target of the pathogenetic sequence. Until a few decades ago, understanding of cholestasis relied mostly on the experimental model of bile duct ligation in rodents. However, a simple model of biliary obstruction cannot reproduce the complex mechanisms and networks leading to cholestasis in cholangiopathies. These networks are underpinned by an intricate dysregulation of pro-inflammatory and pro-fibrotic signals involving besides cholangiocytes, multiple cell elements of both innate and adaptive immunity. Therefore, in the last years, a wide range of animal models of biliary injury have been developed, mostly in mice, following three main approaches, chemical induction, immunization and genetic manipulation. In this review, we will give an update of the animal models of the two main cholangiopathies, primary sclerosing cholangitis and primary biliary cholangitis, which have provided us with the most relevant insights into the pathogenesis of these still controversial diseases.

The Pharmacological Targets and Clinical Evidence of Natural Products With Anti-hepatic Inflammatory Properties

Inflammation contributes heavily to the pathogenesis of liver fibrosis, cirrhosis, and even hepatocellular carcinoma. Inflammation is probably a promising target for treatment of liver diseases. The natural products are considered as the potential source of new drug discovery and their pharmacological effects on hepatic inflammation have been widely reported. In this review, the natural products with anti-hepatic inflammatory properties are summarized based on their pharmacological effects and mechanisms, which are related to the suppression on the inflammation mediators including cytokines and chemokines, pattern recognition receptors, the activated transcriptional factors, and the potential regulatory factors. The clinical evidence is also summarized.

β-Catenin and interleukin-1β-dependent chemokine (C-X-C motif) ligand 10 production drives progression of disease in a mouse model of congenital hepatic fibrosis

Congenital hepatic fibrosis (CHF), a genetic disease caused by mutations in the polycystic kidney and hepatic disease 1 (PKHD1) gene, encoding for the protein fibrocystin/polyductin complex, is characterized by biliary dysgenesis, progressive portal fibrosis, and a protein kinase A-mediated activating phosphorylation of β-catenin at Ser675. Biliary structures of Pkhd1^del4/del4 mice, a mouse model of CHF, secrete chemokine (C-X-C motif) ligand 10 (CXCL10), a chemokine able to recruit macrophages. The aim of this study was to clarify whether CXCL10 plays a pathogenetic role in disease progression in CHF/Caroli disease and to understand the mechanisms leading to increased CXCL10 secretion. We demonstrate that treatment of Pkhd1^del4/del4 mice for 3 months with AMG-487, an inhibitor of CXC chemokine receptor family 3, the cognate receptor of CXCL10, reduces the peribiliary recruitment of alternative activated macrophages (cluster of differentiation 45⁺ F4/80⁺ cells), spleen size, liver fibrosis (sirius red), and cyst growth (cytokeratin 19-positive area), consistent with a pathogenetic role of CXCL10. Furthermore, we show that in fibrocystin/polyductin complex-defective cholangiocytes, isolated from Pkhd1^del4/del4 mice, CXCL10 production is mediated by Janus kinase/signal transducer and activator of transcription 3 in response to interleukin 1beta (IL-1β) and β-catenin. Specifically, IL-1β promotes signal transducer and activator of transcription 3 phosphorylation, whereas β-catenin promotes its nuclear translocation. Increased pro-IL-1β was regulated by nuclear factor kappa-light-chain-enhancer of activated B cells, and increased secretion of active IL-1β was mediated by the activation of Nod-like receptors, pyrin domain containing 3 inflammasome (increased expression of caspase 1 and Nod-like receptors, pyrin domain containing 3).

CONCLUSION

In fibrocystin/polyductin complex-defective cholangiocytes, β-catenin and IL-1β are responsible for signal transducer and activator of transcription 3-dependent secretion of CXCL10; in vivo experiments show that the CXCL10/CXC chemokine receptor family 3 axis prevents the recruitment of macrophages, reduces inflammation, and halts the progression of the disease; the increased production of IL-1β highlights the autoinflammatory nature of CHF and may open novel therapeutic avenues. (Hepatology 2018;67:1903-1919).

Src kinase inhibition reduces inflammatory and cytoskeletal changes in ΔF508 human cholangiocytes and improves cystic fibrosis transmembrane conductance regulator correctors efficacy

Cystic fibrosis transmembrane conductance regulator (CFTR), the channel mutated in cystic fibrosis (CF), is expressed by the biliary epithelium (i.e., cholangiocytes) of the liver. Progressive clinical liver disease (CF-associated liver disease; CFLD) occurs in around 10% of CF patients and represents the third leading cause of death. Impaired secretion and inflammation contribute to CFLD; however, the lack of human-derived experimental models has hampered the understanding of CFLD pathophysiology and the search for a cure. We have investigated the cellular mechanisms altered in human CF cholangiocytes using induced pluripotent stem cells (iPSCs) derived from healthy controls and a ΔF508 CFTR patient. We have devised a novel protocol for the differentiation of human iPSC into polarized monolayers of cholangiocytes. Our results show that iPSC-cholangiocytes reproduced the polarity and the secretory function of the biliary epithelium. Protein kinase A/cAMP-mediated fluid secretion was impaired in ΔF508 cholangiocytes and negligibly improved by VX-770 and VX-809, two small molecule drugs used to correct and potentiate ΔF508 CFTR. Moreover, ΔF508 cholangiocytes showed increased phosphorylation of Src kinase and Toll-like receptor 4 and proinflammatory changes, including increased nuclear factor kappa-light-chain-enhancer of activated B cells activation, secretion of proinflammatory chemokines (i.e., monocyte chemotactic protein 1 and interleukin-8), as well as alterations of the F-actin cytoskeleton. Treatment with Src inhibitor (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyramidine) decreased the inflammatory changes and improved cytoskeletal defects. Inhibition of Src, along with administration of VX-770 and VX-809, successfully restored fluid secretion to normal levels.

CONCLUSION

Our findings have strong translational potential and indicate that targeting Src kinase and decreasing inflammation may increase the efficacy of pharmacological therapies aimed at correcting the basic ΔF508 defect in CF liver patients. These studies also demonstrate the promise of applying iPSC technology in modeling human cholangiopathies. (Hepatology 2018;67:972-988).

Emerging concepts in biliary repair and fibrosis

Chronic diseases of the biliary tree (cholangiopathies) represent one of the major unmet needs in clinical hepatology and a significant knowledge gap in liver pathophysiology. The common theme in cholangiopathies is that the target of the disease is the biliary tree. After damage to the biliary epithelium, inflammatory changes stimulate a reparative response with proliferation of cholangiocytes and restoration of the biliary architecture, owing to the reactivation of a variety of morphogenetic signals. Chronic damage and inflammation will ultimately result in pathological repair with generation of biliary fibrosis and clinical progression of the disease. The hallmark of pathological biliary repair is the appearance of reactive ductular cells, a population of cholangiocyte-like epithelial cells of unclear and likely mixed origin that are able to orchestrate a complex process that involves a number of different cell types, under joint control of inflammatory and morphogenetic signals. Several questions remain open concerning the histogenesis of reactive ductular cells, their role in liver repair, their mechanism of activation, and the signals exchanged with the other cellular elements cooperating in the reparative process. This review contributes to the current debate by highlighting a number of new concepts derived from the study of the pathophysiology of chronic cholangiopathies, such as congenital hepatic fibrosis, biliary atresia, and Alagille syndrome.

Biology of Cholangiocytes: From Bench to Bedside

Cholangiocytes, the lining epithelial cells in bile ducts, are an important subset of liver cells. They are activated by endogenous and exogenous stimuli and are involved in the modification of bile volume and composition. They are also involved in damaging and repairing the liver. Cholangiocytes have many functions including bile production. They are also involved in transport processes that regulate the volume and composition of bile. Cholangiocytes undergo proliferation and cell death under a variety of conditions. Cholangiocytes have functional and morphological heterogenecity. The immunobiology of cholangiocytes is important, particularly for understanding biliary disease. Secretion of different proinflammatory mediators, cytokines, and chemokines suggests the major role that cholangiocytes play in inflammatory reactions. Furthermore, paracrine secretion of growth factors and peptides mediates extensive cross-talk with other liver cells, including hepatocytes, stellate cells, stem cells, subepithelial myofibroblasts, endothelial cells, and inflammatory cells. Cholangiopathy refers to a category of chronic liver diseases whose primary disease target is the cholangiocyte. Cholangiopathy usually results in end-stage liver disease requiring liver transplant. We summarize the biology of cholangiocytes and redefine the concept of cholangiopathy. We also discuss the recent progress that has been made in understanding the pathogenesis of cholangiopathy and how such progress has influenced therapy.

Pathophysiologic implications of innate immunity and autoinflammation in the biliary epithelium

The most studied physiological function of biliary epithelial cells (cholangiocytes) is to regulate bile flow and composition, in particular the hydration and alkalinity of the primary bile secreted by hepatocytes. After almost three decades of studies it is now become clear that cholangiocytes are also involved in epithelial innate immunity, in inflammation, and in the reparative processes in response to liver damage. An increasing number of evidence highlights the ability of cholangiocyte to undergo changes in phenotype and function in response to liver damage. By participating actively to the immune and inflammatory responses, cholangiocytes represent a first defense line against liver injury from different causes. Indeed, cholangiocytes express a number of receptors able to recognize pathogen- or damage-associated molecular patterns (PAMPs/DAMPs), such as Toll-like receptors (TLR), which modulate their pro-inflammatory behavior. Cholangiocytes can be both the targets and the initiators of the inflammatory process. Derangements of the signals controlling these mechanisms are at the basis of the pathogenesis of different cholangiopathies, both hereditary and acquired, such as cystic fibrosis-related liver disease and sclerosing cholangitis. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Animal models of biliary injury and altered bile acid metabolism

In the last 25years, a number of animal models, mainly rodents, have been generated with the goal to mimic cholestatic liver injuries and, thus, to provide in vivo tools to investigate the mechanisms of biliary repair and, eventually, to test the efficacy of innovative treatments. Despite fundamental limitations applying to these models, such as the distinct immune system and the different metabolism regulating liver homeostasis in rodents when compared to humans, multiple approaches, such as surgery (bile duct ligation), chemical-induced (3,5-diethoxycarbonyl-1,4-dihydrocollidine, DDC, α-naphthylisothiocyanate, ANIT), viral infections (Rhesus rotavirustype A, RRV-A), and genetic manipulation (Mdr2, Cftr, Pkd1, Pkd2, Prkcsh, Sec63, Pkhd1) have been developed. Overall, they have led to a range of liver phenotypes recapitulating the main features of biliary injury and altered bile acid metabolisms, such as ductular reaction, peribiliary inflammation and fibrosis, obstructive cholestasis and biliary dysgenesis. Although with a limited translability to the human setting, these mouse models have provided us with the ability to probe over time the fundamental mechanisms promoting cholestatic disease progression. Moreover, recent studies from genetically engineered mice have unveiled 'core' pathways that make the cholangiocyte a pivotal player in liver repair. In this review, we will highlight the main phenotypic features, the more interesting peculiarities and the different drawbacks of these mouse models. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Adenylyl cyclase 5 links changes in calcium homeostasis to cAMP-dependent cyst growth in polycystic liver disease

BACKGROUND & AIMS

Genetic defects in polycystin-1 or -2 (PC1 or PC2) cause polycystic liver disease associated with autosomal dominant polycystic kidney disease (PLD-ADPKD). Progressive cyst growth is sustained by a cAMP-dependent Ras/ERK/HIFα pathway, leading to increased vascular endothelial growth factor A (VEGF-A) signaling. In PC2-defective cholangiocytes, cAMP production in response to [Ca²⁺]_ER depletion is increased, while store-operated Ca²⁺ entry (SOCE), intracellular and endoplasmic reticulum [Ca²⁺]_ER levels are reduced. We investigated whether the adenylyl cyclases, AC5 and AC6, which can be inhibited by Ca²⁺, are activated by the ER chaperone STIM1. This would result in cAMP/PKA-dependent Ras/ERK/HIFα pathway activation in PC2-defective cells, in response to [Ca²⁺]_ER depletion.

METHODS

PC2/AC6 double conditional knockout (KO) mice were generated (Pkd2/AC6 KO) and compared to Pkd2 KO mice. The AC5 inhibitor SQ22,536 or AC5 siRNA were used in isolated cholangiocytes while the inhibitor was used in biliary organoid and animals; liver tissues were harvested for histochemical analysis.

RESULTS

When comparing Pkd2/AC6 KO to Pkd2 KO mice, no decrease in liver cyst size was found, and cellular cAMP after [Ca²⁺]_ER depletion only decreased by 12%. Conversely, in PC2-defective cells, inhibition of AC5 significantly reduced cAMP production, pERK1/2 expression and VEGF-A secretion. AC5 inhibitors significantly reduced growth of biliary organoids derived from Pkd2 KO and Pkd2/AC6 KO mice. In vivo treatment with SQ22,536 significantly reduced liver cystic area and cell proliferation in PC2-defective mice. After [Ca²⁺]_ER depletion in PC2-defective cells, STIM1 interacts with AC5 but not with Orai1, the Ca²⁺ channel that mediates SOCE.

CONCLUSION

[Ca²⁺]_ER depletion in PC2-defective cells activates AC5 and results in stimulation of cAMP/ERK1-2 signaling, VEGF production and cyst growth. This mechanism may represent a novel therapeutic target.

LAY SUMMARY

Polycystic liver diseases are characterized by progressive cyst growth until their complications mandate surgery or liver transplantation. In this manuscript, we demonstrate that inhibiting cell proliferation, which is induced by increased levels of cAMP, may represent a novel therapeutic target to slow the progression of the disease.

Vanishing bile duct syndrome in Hodgkin’s lymphoma: A case report and literature review

Vanishing bile duct syndrome (VBDS) has been described in different pathologic conditions including infection, ischemia, adverse drug reactions, autoimmune diseases, allograft rejection, and humoral factors associated with malignancy. It is an acquired condition characterized by progressive destruction and loss of the intra-hepatic bile ducts leading to cholestasis. Prognosis is variable and partially dependent upon the etiology of bile duct injury. Irreversible bile duct loss leads to significant ductopenia, biliary cirrhosis, liver failure, and death. If biliary epithelial regeneration occurs, clinical recovery may occur over a period of months to years. VBDS has been described in a number of cases of patients with Hodgkin’s lymphoma (HL) where it is thought to be a paraneoplastic phenomenon. This case describes a 25-year-old man found on liver biopsy to have VBDS. Given poor response to medical treatment, the patient underwent transplant evaluation at that time and was found to have classical stage IIB HL. Early recognition of this underlying cause or association of VBDS, including laboratory screening, and physical exam for lymphadenopathy are paramount to identifying potential underlying VBDS-associated malignancy. Here we review the literature of HL-associated VBDS and report a case of diagnosed HL with biopsy proven VBDS.

Autocrine and Paracrine Mechanisms Promoting Chemoresistance in Cholangiocarcinoma

Resistance to conventional chemotherapeutic agents, a typical feature of cholangiocarcinoma, prevents the efficacy of the therapeutic arsenal usually used to combat malignancy in humans. Mechanisms of chemoresistance by neoplastic cholangiocytes include evasion of drug-induced apoptosis mediated by autocrine and paracrine cues released in the tumor microenvironment. Here, recent evidence regarding molecular mechanisms of chemoresistance is reviewed, as well as associations between well-developed chemoresistance and activation of the cancer stem cell compartment. It is concluded that improved understanding of the complex interplay between apoptosis signaling and the promotion of cell survival represent potentially productive areas for active investigation, with the ultimate aim of encouraging future studies to unveil new, effective strategies able to overcome current limitations on treatment.

Liver - guardian, modifier and target of sepsis

Sepsis and septic shock are characterized by life-threatening organ dysfunction caused by a dysregulated host response to infection. The liver has a central role during sepsis, and is essential to the regulation of immune defence during systemic infections by mechanisms such as bacterial clearance, acute-phase protein or cytokine production and metabolic adaptation to inflammation. However, the liver is also a target for sepsis-related injury, including hypoxic hepatitis due to ischaemia and shock, cholestasis due to altered bile metabolism, hepatocellular injury due to drug toxicity or overwhelming inflammation, as well as distinct pathologies such as secondary sclerosing cholangitis in critically ill patients. Hence, hepatic dysfunction substantially impairs the prognosis of sepsis and serves as a powerful independent predictor of mortality in the intensive care unit. Sepsis is particularly problematic in patients with liver cirrhosis (who experience increased bacterial translocation from the gut and impaired microbial defence) as it can trigger acute-on-chronic liver failure - a syndrome with high short-term mortality. Here, we review the importance of the liver as a guardian, modifier and target of sepsis, the factors that contribute to sepsis in patients with liver cirrhosis and new therapeutic strategies.

The cystic fibrosis transmembrane conductance regulator controls biliary epithelial inflammation and permeability by regulating Src tyrosine kinase activity

In the liver, the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) regulates bile secretion and other functions at the apical membrane of biliary epithelial cells (i.e., cholangiocytes). CF-related liver disease is a major cause of death in patients with CF. CFTR dysfunction affects innate immune pathways, generating a para-inflammatory status in the liver and other epithelia. This study investigates the mechanisms linking CFTR to toll-like receptor 4 activity. We found that CFTR is associated with a multiprotein complex at the apical membrane of normal mouse cholangiocytes, with proteins that negatively control Rous sarcoma oncogene cellular homolog (Src) activity. In CFTR-defective cholangiocytes, Src tyrosine kinase self-activates and phosphorylates toll-like receptor 4, resulting in activation of nuclear factor kappa-light-chain-enhancer of activated B cells and increased proinflammatory cytokine production in response to endotoxins. This Src/nuclear factor kappa-light-chain-enhancer of activated B cells-dependent inflammatory process attracts inflammatory cells but also generates changes in the apical junctional complex and loss of epithelial barrier function. Inhibition of Src decreased the inflammatory response of CF cholangiocytes to lipopolysaccharide, rescued the junctional defect in vitro, and significantly attenuated endotoxin-induced biliary damage and inflammation in vivo (Cftr knockout mice).

CONCLUSION

These findings reveal a novel function of CFTR as a regulator of toll-like receptor 4 responses and cell polarity in biliary epithelial cells; this mechanism is pathogenetic, as shown by the protective effects of Src inhibition in vivo, and may be a novel therapeutic target in CF-related liver disease and other inflammatory cholangiopathies. (Hepatology 2016;64:2118-2134).

[Human pluripotent stem cells and liver disorders]

The liver is associated with many diseases including metabolic and cholestatic diseases, cirrhosis as well as chronic and acute hepatitis. However, knowledge about the mechanisms involved in the pathophysiology of these diseases remains limited due to the restricted access to liver biopsies and the lack of cellular models derived from patients. The liver is the main organ responsible for the elimination of xenobiotics and thus hepatocytes have a key role in toxicology and pharmacokinetics. The induced pluripotent stem cells generated from patients with monogenic metabolic disorders, for which the corresponding gene is identified, are relevant in vitro models for the study of the mechanisms involved in generation of pathologies and also for drug screening. Towards this aim, robust protocols for generating liver cells, such as hepatocytes and cholangiocytes, are essential. Our study focused on familial hypercholesterolemia disease modeling, as well as on establishing a protocol for generation of functional cholangiocytes from pluripotent stem cells.

Statin pretreatment inhibits the lipopolysaccharide-induced epithelial-mesenchymal transition via the downregulation of toll-like receptor 4 and nuclear factor-κB in human biliary epithelial cells

BACKGROUND AND AIM

Epithelial-mesenchymal transition (EMT) of biliary epithelial cells (BECs) plays an important role in biliary fibrosis. This study investigated the effects of simvastatin on the lipopolysaccharide (LPS)-induced EMT and related signal pathways in BECs.

METHODS

Biliary epithelial cells were exposed to LPS (2 µg/mL) or transforming growth factor β1 (TGF-β1) (5 ng/mL) for 5 days. The EMT was assessed by a gain of mesenchymal cell markers (vimentin, N-cadherin, slug, and Twist-1) and a loss of epithelial cell markers (E-cadherin). The effects of simvastatin on the EMT induced by LPS or TGF-β1 were determined by the changes in the levels of EMT markers and TLR4 and in the c-Jun N-terminal kinase (JNK), p38, and nuclear factor-κB (NF-κB) signaling pathways.

RESULTS

Compared with the BECs treated with LPS alone, co-treatment with simvastatin and LPS induced an increase in the expression of E-cadherin and decreases in the expression levels of mesenchymal cell markers. The LPS-induced TLR4 expression level was slightly decreased by co-treatment with simvastatin. LPS-induced BEC growth was markedly inhibited by co-treatment with simvastatin. Furthermore, pretreatment with simvastatin inhibited the LPS-induced EMT in BECs by downregulating NF-κB and JNK phosphorylation. The suppressive effects of simvastatin pretreatment on the induction of the EMT by TGF-β1 were also demonstrated in H69 cells.

CONCLUSIONS

Our results demonstrate that LPS or TGF-β1 promote the EMT in BECs that that pretreatment with simvastatin inhibited the induced EMT by downregulating toll-like receptor 4 and NF-κB phosphorylation. This finding suggests that simvastatin can be considered a new agent for preventing biliary fibrosis associated with the EMT of BECs.

Revisiting Epithelial-to-Mesenchymal Transition in Liver Fibrosis: Clues for a Better Understanding of the "Reactive" Biliary Epithelial Phenotype

Whether liver epithelial cells contribute to the development of hepatic scarring by undergoing epithelial-to-mesenchymal transition (EMT) is a controversial issue. Herein, we revisit the concept of EMT in cholangiopathies, a group of severe hepatic disorders primarily targeting the bile duct epithelial cell (cholangiocyte), leading to progressive portal fibrosis, the main determinant of liver disease progression. Unfortunately, therapies able to halt this process are currently lacking. In cholangiopathies, fibrogenesis is part of ductular reaction, a reparative complex involving epithelial, mesenchymal, and inflammatory cells. Ductular reactive cells (DRC) are cholangiocytes derived from the activation of the hepatic progenitor cell compartment. These cells are arranged into irregular strings and express a “reactive” phenotype, which enables them to extensively crosstalk with the other components of ductular reaction. We will first discuss EMT in liver morphogenesis and then highlight how some of these developmental programs are partly reactivated in DRC. Evidence for “bona fide” EMT changes in cholangiocytes is lacking, but expression of some mesenchymal markers represents a fundamental repair mechanism in response to chronic biliary damage with potential harmful fibrogenetic effects. Understanding microenvironmental cues and signaling perturbations promoting these changes in DRC may help to identify potential targets for new antifibrotic therapies in cholangiopathies.

Stimulation of nuclear receptor peroxisome proliferator-activated receptor-γ limits NF-κB-dependent inflammation in mouse cystic fibrosis biliary epithelium

Cystic fibrosis-associated liver disease is a chronic cholangiopathy that negatively affects the quality of life of cystic fibrosis patients. In addition to reducing biliary chloride and bicarbonate secretion, up-regulation of toll-like receptor 4/nuclear factor kappa light-chain-enhancer of activated B cells (NF-κB)-dependent immune mechanisms plays a major role in the pathogenesis of cystic fibrosis-associated liver disease and may represent a therapeutic target. Nuclear receptors are transcription factors that regulate several intracellular functions. Some nuclear receptors, including peroxisome proliferator-activated receptor-γ (PPAR-γ), may counterregulate inflammation in a tissue-specific manner. In this study, we explored the anti-inflammatory effect of PPAR-γ stimulation in vivo in cystic fibrosis transmembrane conductance regulator (Cftr) knockout mice exposed to dextran sodium sulfate and in vitro in primary cholangiocytes isolated from wild-type and from Cftr-knockout mice exposed to lipopolysaccharide. We found that in CFTR-defective biliary epithelium expression of PPAR-γ is increased but that this does not result in increased receptor activity because the availability of bioactive ligands is reduced. Exogenous administration of synthetic agonists of PPAR-γ (pioglitazone and rosiglitazone) up-regulates PPAR-γ-dependent genes, while inhibiting the activation of NF-κB and the secretion of proinflammatory cytokines (lipopolysaccharide-induced CXC chemokine, monocyte chemotactic protein-1, macrophage inflammatory protein-2, granulocyte colony-stimulating factor, keratinocyte chemoattractant) in response to lipopolysaccharide. PPAR-γ agonists modulate NF-κB-dependent inflammation by up-regulating nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor alpha, a negative regulator of NF-κB. Stimulation of PPAR-γ in vivo (rosiglitazone) significantly attenuates biliary damage and inflammation in Cftr-knockout mice exposed to a dextran sodium sulfate-induced portal endotoxemia.

CONCLUSION

These studies unravel a novel function of PPAR-γ in controlling biliary epithelium inflammation and suggest that impaired activation of PPAR-γ contributes to the chronic inflammatory state of CFTR-defective cholangiocytes.

Update on Sclerosing Cholangitis in Critically Ill Patients

Background

‛Sclerosing cholangitis in critically ill patients' (SC-CIP) is a cholestatic liver disease of unknown etiology and represents the most prevalent form of secondary sclerosing cholangitis.

Methods

This overview is based on a systematic review of the literature searching for ‘secondary sclerosing cholangitis’, ‘SC-CIP’, ‘cast syndrome’, and ‘ischemic cholangitis’ in the database PubMed.

Results

SC-CIP can develop in patients with sepsis and acute respiratory distress syndrome during a long-term intensive care unit (ICU) treatment. It is a rare cholestatic liver disease with a rapid progression to liver cirrhosis and hepatic failure. SC-CIP is initiated by an ischemic injury to the biliary tree with subsequent stenoses of biliary ducts, biliary casts, and infections, often with multi-resistant bacteria. Mechanical ventilation with high positive end-expiratory pressure, prone positioning, and a higher volume of intraperitoneal fat have been proposed as risk factors for developing SC-CIP. Patients with SC-CIP have a poor prognosis, with liver transplantation (LT) being the only curative treatment option.

Conclusion

In patients with sepsis, long-term ICU therapy and ongoing cholestasis SC-CIP must be excluded by endoscopic retrograde cholangiopancreatography. Due to the poor prognosis, the option of LT should be evaluated in all patients with SC-CIP.

Activation of the renin-angiotensin system stimulates biliary hyperplasia during cholestasis induced by extrahepatic bile duct ligation

Cholangiocyte proliferation is regulated in a coordinated fashion by many neuroendocrine factors through autocrine and paracrine mechanisms. The renin-angiotensin system (RAS) is known to play a role in the activation of hepatic stellate cells and blocking the RAS attenuates hepatic fibrosis. We investigated the role of the RAS during extrahepatic cholestasis induced by bile duct ligation (BDL). In this study, we used normal and BDL rats that were treated with control, angiotensin II (ANG II), or losartan for 2 wk. In vitro studies were performed in a primary rat cholangiocyte cell line (NRIC). The expression of renin, angiotensin-converting enzyme, angiotensinogen, and angiotensin receptor type 1 was evaluated by immunohistochemistry (IHC), real-time PCR, and FACs and found to be increased in BDL compared with normal rat. The levels of ANG II were evaluated by ELISA and found to be increased in serum and conditioned media of cholangiocytes from BDL compared with normal rats. Treatment with ANG II increased biliary mass and proliferation in both normal and BDL rats. Losartan attenuated BDL-induced biliary proliferation. In vitro, ANG II stimulated NRIC proliferation via increased intracellular cAMP levels and activation of the PKA/ERK/CREB intracellular signaling pathway. ANG II stimulated a significant increase in Sirius red staining and IHC for fibronectin that was blocked by angiotensin receptor blockade. In vitro, ANG II stimulated the gene expression of collagen 1A1, fibronectin 1, and IL-6. These results indicate that cholangiocytes express a local RAS and that ANG II plays an important role in regulating biliary proliferation and fibrosis during extraheptic cholestasis.

Yin-Chen-Hao-Tang alleviates biliary obstructive cirrhosis in rats by inhibiting biliary epithelial cell proliferation and activation

Background:

Yin-Chen-Hao-Tang (YCHT) consists of three aqueous extracts from Artemisia capillaris, Gardenia sp., and prepared Rheum rhabarbarum (rhubarb) (3:2:1). YCHT is characterized by its anti-inflammatory properties in liver regulation and relief of jaundice. We aimed to study the effects and mechanisms of action of YCHT on biliary obstructive cirrhosis.

Materials and Methods:

Secondary biliary fibrosis was induced in rats by bile duct ligation (BDL) and scission. One week after BDL, rats were randomly divided into a saline-treated BDL or YCHT-treated BDL group for 4 weeks. Liver function and hepatic hydroxyproline (Hyp) content were assessed. Types I and IV collagen (Col-IV), laminin, fibronectin, alpha smooth muscle actin (α-SMA), and proliferating cell nuclear antigen protein and messenger ribonucleic acid (mRNA) expression were assessed with immunohistochemistry and real-time polymerase chain reaction.

Results:

In the YCHT-treated BDL group, serum total bilirubin, total bile acids, aspartate aminotransferase, alanine aminotransferase, and γ-glutamyl transferase were lower than those in the sham-operated BDL group. The proliferation of bile ducts in hepatic tissues and the Hyp content and Col deposition were also significantly lower than those in control rats. In addition, α-SMA and Col-IV staining was less obvious, and mRNA expression of Procol-α1 (IV), platelet derived growth factor subunit B (PDGF)-B, connective tissue growth factor, and transforming growth factor-beta in proliferative biliary epithelial cells (BECs) in the YCHT-treated BDL group was significantly lower than those in controls.

Conclusions:

YCHT effectively reduces the formation of biliary obstructive cirrhosis mainly via inhibition of BEC proliferation by down-regulation of PDGF-B mRNA expression, inhibition of BEC profibrogenic paracrines, and the epithelial-mesenchymal transition pathological process.

Expression of mediators of purinergic signaling in human liver cell lines

Purinergic signaling regulates a diverse and biologically relevant group of processes in the liver. However, progress of research into functions regulated by purinergic signals in the liver has been hampered by the complexity of systems probed. Specifically, there are multiple liver cell subpopulations relevant to hepatic functions, and many of these have been effectively modeled in human cell lines. Furthermore, there are more than 20 genes relevant to purinergic signaling, each of which has distinct functions. Hence, we felt the need to categorize genes relevant to purinergic signaling in the best characterized human cell line models of liver cell subpopulations. Therefore, we investigated the expression of adenosine receptor, P2X receptor, P2Y receptor, and ecto-nucleotidase genes via RT-PCR in the following cell lines: LX-2, hTERT, FH11, HepG2, Huh7, H69, and MzChA-1. We believe that our findings will provide an excellent resource to investigators seeking to define functions of purinergic signals in liver physiology and liver disease pathogenesis.

Generation of functional cholangiocyte-like cells from human pluripotent stem cells and HepaRG cells

Cholangiocytes are biliary epithelial cells, which, like hepatocytes, originate from hepatoblasts during embryonic development. In this study we investigated the potential of human embryonic stem cells (hESCs) to differentiate into cholangiocytes and we report a new approach, which drives differentiation of hESCs toward the cholangiocytic lineage using feeder-free and defined culture conditions. After differentiation into hepatic progenitors, hESCs were differentiated further into cholangiocytes using growth hormone, epidermal growth factor, interleukin-6, and then sodium taurocholate. These conditions also allowed us to generate cholangiocytes from HepaRG-derived hepatoblasts. hESC- and HepaRG-derived cholangiocyte-like cells expressed markers of cholangiocytes including cytokeratin 7 and osteopontin, and the transcription factors SOX9 and hepatocyte nuclear factor 6. The cells also displayed specific proteins important for cholangiocyte functions including cystic fibrosis transmembrane conductance regulator, secretin receptor, and nuclear receptors. They formed primary cilia and also responded to hormonal stimulation by increase of intracellular Ca(2+) . We demonstrated by integrative genomics that the expression of genes, which signed hESC- or HepaRG-cholangiocytes, separates hepatocytic lineage from cholangiocyte lineage. When grown in a 3D matrix, cholangiocytes developed epithelial/apicobasal polarity and formed functional cysts and biliary ducts. In addition, we showed that cholangiocyte-like cells could also be generated from human induced pluripotent stem cells, demonstrating the efficacy of our approach with stem/progenitor cells of diverse origins.

CONCLUSION

We have developed a robust and efficient method for differentiating pluripotent stem cells into cholangiocyte-like cells, which display structural and functional similarities to bile duct cells in normal liver. These cells will be useful for the in vitro study of the molecular mechanisms of bile duct development and have important potential for therapeutic strategies, including bioengineered liver approaches.

Characterization of animal models for primary sclerosing cholangitis (PSC)

Primary sclerosing cholangitis (PSC) is a chronic cholangiopathy characterized by biliary fibrosis, development of cholestasis and end stage liver disease, high risk of malignancy, and frequent need for liver transplantation. The poor understanding of its pathogenesis is also reflected in the lack of effective medical treatment. Well-characterized animal models are utterly needed to develop novel pathogenetic concepts and study new treatment strategies. Currently there is no consensus on how to evaluate and characterize potential PSC models, which makes direct comparison of experimental results and effective exchange of study material between research groups difficult. The International Primary Sclerosing Cholangitis Study Group (IPSCSG) has therefore summarized these key issues in a position paper proposing standard requirements for the study of animal models of PSC.

Notch signaling and new therapeutic options in liver disease

Notch signaling is a crucial determinant of cell fate decision during development and disease in several organs. Notch effects are strictly dependent on the cellular context in which it is activated. In the liver, Notch signaling is involved in biliary tree development and tubulogenesis. Recent advances have shed light on Notch as a critical player in liver regeneration and repair, as well as in liver metabolism and inflammation and cancer. Notch signaling is finely regulated at several levels. The complexity of the pathway provides several possible targets for development of therapeutic agents able to inhibit Notch. Recent reports have shown that persistent activation of Notch signaling is associated with liver malignancies, particularly hepatocellular with stem cell features and cholangiocarcinoma. These novel findings suggest that interfering with the aberrant activation of the Notch pathway may have therapeutic relevance. However, further studies are needed to clarify the mechanisms regulating physiologic and pathologic Notch activation in the adult liver, to better understand the mechanistic role(s) of Notch in liver diseases and to develop safe and specific therapeutic agents.