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Primary sclerosing cholangitis (PSC) is a rare, chronic liver disease with no approved therapies. The ursodeoxycholic acid (UDCA) has been widely used, although there is no evidence that the use of UDCA delays the time to liver transplant or increases survival. Several candidate drugs are currently being developed. The largest group of these new agents is represented by FXR agonists, including obeticholic acid, cilofexor, and tropifexor. Other agents that target bile acid metabolism are ASTB/IBAP inhibitors and fibroblasts growth factor (FGF)19 analogues. Cholangiocytes, the epithelial bile duct cells, play a role in PSC development. Recent studies have revealed that these cells undergo a downregulation of GPBAR1 (TGR5), a bile acid receptor involved in bicarbonate secretion and immune regulation. Additional agents under evaluation are PPARs (elafibranor and seladelpar), anti-itching agents such as MAS-related G-protein–coupled receptors antagonists, and anti-fibrotic and immunosuppressive agents. Drugs targeting gut bacteria and bile acid pathways are also under investigation, given the strong link between PSC and gut microbiota. [ABSTRACT FROM AUTHOR]

Fibrosis resulting from pathological repair secondary to recurrent or persistent tissue damage often leads to organ failure and mortality. Biliary fibrosis is a crucial but easily neglected pathological feature in hepatobiliary disorders, which may promote the development and progression of benign and malignant biliary diseases through pathological healing mechanisms secondary to biliary tract injuries. Elucidating the etiology and pathogenesis of biliary fibrosis is beneficial to the prevention and treatment of biliary diseases. In this review, we emphasized the importance of biliary fibrosis in cholangiopathies and summarized the clinical manifestations, epidemiology, and aberrant cellular composition involving the biliary ductules, cholangiocytes, immune system, fibroblasts, and the microbiome. We also focused on pivotal signaling pathways and offered insights into ongoing clinical trials and proposing a strategic approach for managing biliary fibrosis-related cholangiopathies. This review will offer a comprehensive perspective on biliary fibrosis and provide an important reference for future mechanism research and innovative therapy to prevent or reverse fibrosis.

Biliary fibrosis is seen in cholangiopathies, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). In PBC and PSC, biliary fibrosis is associated with worse outcomes and histologic scores. Within the liver, both hepatic stellate cells (HSCs) and portal fibroblasts (PFs) contribute to biliary fibrosis, but their roles can differ. PFs reside near the bile ducts and may be the first responders to biliary damage, whereas HSCs may be recruited later and initiate bridging fibrosis. Indeed, different models of biliary fibrosis can activate PFs and HSCs to varying degrees. The portal niche can be composed of cholangiocytes, HSCs, PFs, endothelial cells, and various immune cells, and interactions between these cell types drive biliary fibrosis. In this review, we discuss the mechanisms of biliary fibrosis and the roles of PFs and HSCs in this process. We will also evaluate cellular interactions and mechanisms that contribute to biliary fibrosis in different models and highlight future perspectives and potential therapeutics.

The primary cilium is increasingly recognized as a crucial player in the physiology of biliary epithelial cells (BECs). However, the precise role of primary cilia in the development of age‐related biliary fibrosis remains unclear. Herein, using cilium‐deficient mice, we demonstrate that disruption of ciliary homeostasis in BECs in aged mice leads to significant bile duct proliferation, augmented biliary fibrosis, and heightened indicators of liver injury. Our RNA‐sequencing data revealed a dysregulation in genes associated with various biological processes such as bile secretion, fatty acid metabolism, and inflammation. Loss of primary cilia also significantly enhanced signaling pathways driving the development of biliary fibrosis. Our findings collectively suggest that loss of primary cilia in the BECs of aged mice initiates a cascade of signaling events that contribute to biliary fibrosis, highlighting the primary cilium as a potential therapeutic target in the treatment of fibrosing cholangiopathies. [ABSTRACT FROM AUTHOR]

Background: Biliary atresia is a rare congenital bile duct disease that is the leading cause of liver fibrosis in neonates. Granulocyte colony-stimulating factor (GCSF) is a potential therapy for hepatocellular diseases, but data on GCSF for cholestatic conditions remain limited. Materials and methods: The current study examines the role of GCSF in improving bile duct obstruction in mice. Two doses were administered: 10.0 μg/kg/day and 61.5 μg/kg/day, which is the animal equivalent dose of 5.0 μg/kg in humans. Seven days (D7) after bile duct ligation (BDL), Swiss mice were treated with phosphate buffered saline or GCSF for 5 days. The intrahepatic adaptive response of BDL mice was evaluated on postsurgical days D12, D19, and D26. Results: Treatment with 61.5 μg/kg of GCSF resulted in a significant increase in circulating leukocytes and neutrophils on D12. Amelioration of liver injury, as shown by reduced aspartate aminotransferase levels, increased albumin levels and survival rate, as well as reduced intrahepatic inflammation and hepatic myeloperoxidase expression, downregulated ductular proliferation, periportal fibroblast activation, and fibrosis, enhanced expressions of hepatocyte growth factor, peroxisome proliferator-activated receptor-alpha, and ki67, and suppressed expression of cleaved caspase-3 protein, was noted after treatment with 61.5 μg/kg of GCSF. Additionally, GCSF treatment was associated with an increased number of intrahepatic cd3-Sca1+c-Kit+ bone marrow cells. Conclusions: Treatment with 61.5 μg/kg of GCSF resulted in liver regeneration and survival in BDL mice was seen, suggesting its potential use for human liver diseases.

Abstract Background Clonorchiasis caused by Clonorchis sinensis is a zoonotic parasitic disease characterized by cholangitis, biliary proliferation, biliary fibrosis, and even cholangiocarcinoma. Our previous study showed that the expression of interleukin (IL)-33 is increased in both humans and mice infected by C. sinensis, suggesting that IL-33 is potentially involved in the pathogenesis of clonorchiasis. However, the roles and potential mechanism of IL-33 underlying remain unknown. Methods Wild-type (WT) and IL-33 knockout (KO) mice (BALB/c female mice) were orally infected with 45 metacercariae of C. sinensis for 8 weeks. Biliary injuries and fibrosis were extensively evaluated. Hepatic type II cytokines (IL-4, IL-13, and IL-10) were detected by ELISA. Results For wild-type mice, we found that the mice infected with C. sinensis showed severe biliary injuries and fibrosis compared with the normal mice that were free from worm infection. In addition, the levels of type II cytokines such as IL-4, IL-13, and IL-10 in infected wild-type mice were significantly higher than in the control mice without infection (P

Biliary fibrosis is the driving pathological process in cholangiopathies such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). Cholangiopathies are also associated with cholestasis, which is the retention of biliary components, including bile acids, in the liver and blood. Cholestasis may worsen with biliary fibrosis. Furthermore, bile acid levels, composition and homeostasis are dysregulated in PBC and PSC. In fact, mounting data from animal models and human cholangiopathies suggest that bile acids play a crucial role in the pathogenesis and progression of biliary fibrosis. The identification of bile acid receptors has advanced our understanding of various signaling pathways involved in regulating cholangiocyte functions and the potential impact on biliary fibrosis. We will also briefly review recent findings linking these receptors with epigenetic regulatory mechanisms. Further detailed understanding of bile acid signaling in the pathogenesis of biliary fibrosis will uncover additional therapeutic avenues for cholangiopathies. [ABSTRACT FROM AUTHOR]

Background: Biliary atresia (BA) is the most common form of severe neonatal obstructive jaundice. The etiology and pathogenesis of BA are multifactorial, and different factors may interact to produce heterogeneous pathological features and clinical outcomes. Despite different pathological features, all patients received the same treatment strategy. This study performed integrative clustering analysis based on multiple high-throughput datasets to identify the molecular subtypes of BA and provide a new treatment strategy for personalized treatment of the different subtypes of BA. Methods: The RNA sequence dataset GSE122340 in the Gene Expression Omnibus (GEO) database was downloaded; 31 BA and 20 control normal liver tissues were collected at our center for transcriptome sequencing, and clinical and follow-up data of BA patients were available. Molecular subtypes were identified using integrated unsupervised cluster analysis involving gene expression, biliary fibrosis, and immune enrichment scores based on the transcriptome dataset, and the results were validated using independent datasets. Results: Based on the results of the integrated unsupervised clustering analysis, four molecular subtypes were identified: autoimmune, inflammatory, virus infection-related, and oxidative stress. The autoimmune subtype with a moderate prognosis was dominated by autoimmune responses and morphogenesis, such as the Fc-gamma receptor and Wnt signaling pathway. The biological process of the inflammatory subtype was mainly the inflammatory response, with the best prognosis, youngest age at surgery, and lowest liver stiffness. The virus infection-related subtype had the worst prognosis and was enriched for a variety of biological processes such as viral infection, immunity, anatomical morphogenesis, and epithelial mesenchymal transition. The oxidative stress subtype was characterized by the activation of oxidative stress and various metabolic pathways and had a poor prognosis. The above results were verified independently in the validation sets. Conclusions: This study identified four molecular subtypes of BA with distinct prognosis and biological processes. According to the pathological characteristics of the different subtypes, individualized perioperative and preoperative treatment may be a new strategy to improve the prognosis of BA. [ABSTRACT FROM AUTHOR]

Biliary atresia (BA) is a rare cholangiopathy of infancy in which the bile ducts obliterate, leading to profound cholestasis and liver fibrosis. BA is hypothesized to be caused by a viral insult that leads to over-activation of the immune system. Patients with BA are surgically treated with a Kasai portoenterostomy (KPE), which aims to restore bile flow from the liver to the intestines. After KPE, progressive liver fibrosis is often observed in BA patients, even despite surgical success and clearance of their jaundice. The innate immune response is involved during the initial damage to the cholangiocytes and further differentiation of the adaptive immune response into a T-helper 1 cell (Th1) response. Multiple studies have shown that there is continuing elevation of involved cytokines that can lead to the progressive liver fibrosis. However, the mechanism by which the progressive injury occurs is not fully elucidated. Recently, matrix metalloproteinase-7 (MMP-7) has been investigated to be used as a biomarker to diagnose BA. MMPs are involved in extracellular matrix (ECM) turnover, but also have non-ECM related functions. The role of MMP-7 and other MMPs in liver fibrosis is just starting to be elucidated. Multiple studies have shown that serum MMP-7 measurements are able to accurately diagnose BA in a cohort of cholestatic patients while hepatic MMP-7 expression correlated with BA-related liver fibrosis. While the mechanism by which MMP-7 can be involved in the pathophysiology of BA is unclear, MMP-7 has been investigated in other fibrotic pathologies such as renal and idiopathic pulmonary fibrosis. MMP-7 is involved in Wnt/β-catenin signaling, reducing cell-to-cell contact by shedding of E-cadherin, amplifying inflammation and fibrosis via osteopontin (OPN) and TNF-α while it also appears to play a role in induction of angiogenesis This review aims to describe the current understandings of the pathophysiology of BA. Subsequently, we describe how MMP-7 is involved in other pathologies, such as renal and pulmonary fibrosis. Then, we propose how MMP-7 can potentially be involved in BA. By doing this, we aim to describe the putative role of MMP-7 as a prognostic biomarker in BA and to provide possible new therapeutic and research targets that can be investigated in the future.

The extracellular matrix is a highly reactive scaffold formed by a wide array of multifunctional molecules, encompassing collagens and noncollagenous glycoproteins, proteoglycans, glycosaminoglycans, and polysaccharides. Besides outlining the tissue borders, the extracellular matrix profoundly regulates the behavior of resident cells by transducing mechanical signals, and by integrating multiple cues derived from the microenvironment. Evidence is mounting that changes in the biostructure of the extracellular matrix are instrumental for biliary repair. Following biliary damage and eventually, malignant transformation, the extracellular matrix undergoes several quantitative and qualitative modifications, which direct interactions among hepatic progenitor cells, reactive ductular cells, activated myofibroblasts and macrophages, to generate the ductular reaction. Herein, we will give an overview of the main molecular factors contributing to extracellular matrix remodeling in cholangiopathies. Then, we will discuss the structural alterations in terms of biochemical composition and physical stiffness featuring the "desmoplastic matrix" of cholangiocarcinoma along with their pro-oncogenic effects. [ABSTRACT FROM AUTHOR]

Chronic inflammatory liver disease with an acute deterioration of liver function is named acute-on-chronic inflammation and could be regulated by the metabolic impairments related to the liver dysfunction. In this way, the experimental cholestasis model is excellent for studying metabolism in both types of inflammatory responses. Along the evolution of this model, the rats develop biliary fibrosis and an acute-on-chronic decompensation. The acute decompensation of the liver disease is associated with encephalopathy, ascites, acute renal failure, an acute phase response and a splanchnic increase of pro- and anti-inflammatory cytokines. This multiorgan inflammatory dysfunction is mainly associated with a splanchnic and systemic metabolic switch with dedifferentiation of the epithelial, endothelial and mesothelial splanchnic barriers. Furthermore, a splanchnic infiltration by mast cells occurs, which suggests that these cells could carry out a compensatory metabolic role, especially through the modulation of hepatic and extrahepatic mitochondrial-peroxisome crosstalk. For this reason, we propose the hypothesis that mastocytosis in the acute-on-chronic hepatic insufficiency could represent the development of a survival metabolic mechanisms that mitigates the noxious effect of the hepatic functional deficit. A better understanding the pathophysiological response of the mast cells in liver insufficiency and portal hypertension would help to find new pathways for decreasing the high morbidity and mortality rate of these patients. [ABSTRACT FROM AUTHOR]

Abstract 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. Highlights • Cholestasis is a major determinant of chronic liver disease initiation and progression, in particular of cholangiopathies. • Chemicals, xeno/self-immunization and genetic engineering recapitulate inflammation-driven cholestasis in animal models. • These animal models enable us to unravel the pathogenetic role of innate and adaptive immunity in primary cholangitis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Porphyrias are caused by defects in heme biosynthesis, which can lead to cholestasis, inflammation, and fibrosis. • The Wnt/β-catenin pathway plays a role in pathological processes in the liver, including cholestasis and biliary injury. • Inhibiting β-catenin in a mouse model of porphyria resulted in decreased liver injury. • Several key heme biosynthesis enzymes were downregulated in livers lacking β-catenin signaling. • Mice lacking β-catenin had fewer protein aggregates, resulting in improved proteasomal activity and less autophagy. Background & Aims Porphyrias result from anomalies of heme biosynthetic enzymes and can lead to cirrhosis and hepatocellular cancer. In mice, these diseases can be modeled by administration of a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), which causes accumulation of porphyrin intermediates, resulting in hepatobiliary injury. Wnt/β-catenin signaling has been shown to be a modulatable target in models of biliary injury; thus, we investigated its role in DDC-driven injury. Methods β-Catenin (Ctnnb1) knockout (KO) mice, Wnt co-receptor KO mice, and littermate controls were fed a DDC diet for 2 weeks. β-Catenin was exogenously inhibited in hepatocytes by administering β-catenin dicer-substrate RNA (DsiRNA), conjugated to a lipid nanoparticle, to mice after DDC diet and then weekly for 4 weeks. In all experiments, serum and livers were collected; livers were analyzed by histology, western blotting, and real-time PCR. Porphyrin was measured by fluorescence, quantification of polarized light images, and liquid chromatography-mass spectrometry. Results DDC-fed mice lacking β-catenin or Wnt signaling had decreased liver injury compared to controls. Exogenous mice that underwent β-catenin suppression by DsiRNA during DDC feeding also showed less injury compared to control mice receiving lipid nanoparticles. Control livers contained extensive porphyrin deposits which were largely absent in mice lacking β-catenin signaling. Notably, we identified a network of key heme biosynthesis enzymes that are suppressed in the absence of β-catenin, preventing accumulation of toxic protoporphyrins. Additionally, mice lacking β-catenin exhibited fewer protein aggregates, improved proteasomal activity, and reduced induction of autophagy, all contributing to protection from injury. Conclusions β-Catenin inhibition, through its pleiotropic effects on metabolism, cell stress, and autophagy, represents a novel therapeutic approach for patients with porphyria. Lay summary Porphyrias are disorders resulting from abnormalities in the steps that lead to heme production, which cause build-up of toxic by-products called porphyrins. Liver is commonly either a source or a target of excess porphyrins, and complications can range from minor abnormalities to liver failure. In this report, we inhibited Wnt/β-catenin signaling in an experimental model of porphyria, which resulted in decreased liver injury. Targeting β-catenin affected multiple components of the heme biosynthesis pathway, thus preventing build-up of porphyrin intermediates. Our study suggests that drugs inhibiting β-catenin activity could reduce the amount of porphyrin accumulation and help alleviate symptoms in patients with porphyria. [ABSTRACT FROM AUTHOR]

Fibrosis remains a serious health concern in patients with chronic liver disease. We recently reported that chemically induced chronic murine liver injury triggers increased expression of junctional adhesion molecules (JAMs) JAM-B and JAM-C by endothelial cells and de novo synthesis of JAM-C by hepatic stellate cells (HSCs). Here, we demonstrate that biopsies of patients suffering from primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC) or autoimmune hepatitis (AIH) display elevated levels of JAM-C on portal fibroblasts (PFs), HSCs, endothelial cells and cholangiocytes, whereas smooth muscle cells expressed JAM-C constitutively. Therefore, localization and function of JAM-B and JAM-C were investigated in three mouse models of autoimmune-driven liver inflammation. A PBC-like disease was induced by immunization with 2-octynoic acid-BSA conjugate, which resulted in the upregulation of both JAMs in fibrotic portal triads. Analysis of a murine model of PSC revealed a role of JAM-C in PF cell-cell adhesion and contractility. In mice suffering from AIH, endothelial cells increased JAM-B level and HSCs and capsular fibroblasts became JAM-C-positive. Most importantly, AIH-mediated liver fibrosis was reduced in JAM-B −/− mice or when JAM-C was blocked by soluble recombinant JAM-C. Interestingly, loss of JAM-B/JAM-C function had no effect on leukocyte infiltration, suggesting that the well-documented function of JAMs in leukocyte recruitment to inflamed tissue was not effective in the tested chronic models. This might be different in patients and may even be complicated by the fact that human leukocytes express JAM-C. Our findings delineate JAM-C as a mediator of myofibroblast-operated contraction of the liver capsule, intrahepatic vasoconstriction and bile duct stricture. Due to its potential to interact heterophilically with endothelial JAM-B, JAM-C supports also HSC/PF mural cell function. Together, these properties allow JAM-B and JAM-C to actively participate in vascular remodeling associated with liver/biliary fibrosis and suggest them as valuable targets for anti-fibrosis therapies. [ABSTRACT FROM AUTHOR]

Aim Assessing disease progression in patients with primary biliary cholangitis (PBC) is necessary in order to evaluate therapeutic effectiveness. Therefore, the aims of this study were to evaluate both the diagnostic accuracy of both real-time tissue elastography (RTE) and vibration-controlled transient elastography (VCTE), and the usefulness of hepatic and splenic elasticity as predictive markers for the progression of symptomatic PBC. Methods The study participants were 44 patients with PBC. We assessed hepatic and splenic elasticity using RTE and VCTE and measured serum markers related to fibrosis and hepatic and splenic blood flow using Doppler ultrasonography. We then compared RTE and VCTE for diagnostic accuracy. Patients with asymptomatic PBC were followed every 1-3 months. Results Both RTE and VCTE performed well and had superior diagnostic accuracy compared with biochemical markers. The areas under the receiver operating characteristic curve for RTE and VCTE were 0.92 and 0.92, 0.95 and 0.91, and 0.97 and 0.91 for F ≥ 2, F ≥ 3, and F = 4, respectively. During follow-up, nine patients (25.0%) developed liver-related symptoms. Multivariate analysis revealed that splenic elasticity assessed using RTE was a significant independent factor for the development of liver-related symptoms (odds ratio, 2.19; P = 0.024). Conclusions Real-time tissue elastography offered better diagnostic accuracy for severe fibrosis and cholangitis than VCTE. Splenic elasticity determined using RTE is a useful parameter for evaluating liver-related symptoms and an effective predictive marker of disease progression in patients with asymptomatic PBC. [ABSTRACT FROM AUTHOR]

Background & Aims Primary sclerosing cholangitis (PSC) is characterised by fibro-stenosing strictures involving extrahepatic and/or large intrahepatic bile ducts. Mechanisms leading to bile duct injury are poorly understood. We aimed to study the biliary tree stem cell compartment located in peribiliary glands of extrahepatic and large intrahepatic bile ducts and its role in the pathogenesis of biliary fibrosis in PSC. Methods Specimens containing extrahepatic or large intrahepatic bile ducts were obtained from normal liver (n = 6), liver explants from patients with PSC (n = 11), and primary biliary cirrhosis (n = 6). Specimens were processed for histology, immunohistochemistry and immunofluorescence. Results In PSC samples, progressive hyperplasia and mucinous metaplasia of peribiliary glands were observed in large ducts with fibrosis, but not in inflamed ducts without fibrosis. Peribiliary gland hyperplasia was associated with progressive biliary fibrosis and the occurrence of dysplastic lesions. Hyperplasia of peribiliary glands was determined by the expansion of biliary tree stem cells, which sprouted towards the surface epithelium. In PSC, peribiliary glands and myofibroblasts displayed enhanced expression of Hedgehog pathway components. Peribiliary glands in ducts with onion skin-like fibrosis expressed epithelial-to-mesenchymal transition traits associated with components of Hedgehog pathway, markers of senescence and autophagy. Conclusions The biliary tree stem cell compartment is activated in PSC, its activation contributes to biliary fibrosis, and is sustained by the Hedgehog pathway. Our findings suggest a key role for peribiliary glands in the progression of bile duct lesions in PSC and could explain the associated high risk of cholangiocarcinoma. [ABSTRACT FROM AUTHOR]

Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are immune-mediated cholangiopathies with enigmatic etiology and pathogenesis. They have distinct clinical, laboratory, immunological, and histomorphological characteristics. Well-characterized animal models for PBC and PSC are utterly needed to develop novel pathogenetic concepts and to study innovative treatment strategies. The aim of the current paper is to outline the characteristics of ideal PBC and PSC animal models and to contrast this with a real-life up-to-date overview of currently available mouse models. Although some of this models show several individual characteristics of PBC and PSC, it is obvious that all of them have substantial and important limitations. Nevertheless, some may be beneficial to study certain pathophysiological aspects. Potential cholangiopathy animal models should be systematically investigated in regard to elevated serum alkaline phosphatase, bilirubin, and bile acid levels; immunological abnormalities; and longitudinal studies in regard to their liver phenotype. We herein propose a common systematic workup for potential models based on the fact that there are some intriguing disease combinations in specific genetically modified mice and recommend a stepwise process in regard to model characterization with methodical harvesting and screening of numerous organs for potential concomitant diseases. Due to the complex nature of both cholangiopathies, it seems to be very likely that no single perfect PBC or PSC model will ever be generated. The models outlined herein will certainly help to clarify specific pathogenetic aspects and even more important may turn out to be suitable to test potential drugs for treatment. [ABSTRACT FROM AUTHOR]

Summary: 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. [ABSTRACT FROM AUTHOR]

Background & Aims: Retinoid X Receptor α (RXRα) is the principal heterodimerization partner of class II Nuclear Receptors (NRs), and a major regulator of gene expression of numerous hepatic processes, including bile acid (BA) homeostasis through multiple partners. Specific contributions of hepatic RXRα domains in heterodimer function in response to either BA load or ductular cholestasis are not fully characterized. Methods: Wild-type (WT) mice and mice expressing a hepatocyte-specific RXRα lacking the DNA-Binding-Domain (hs-RxrαΔex4 −/− ), which retains partial ability to heterodimerize with its partners, were fed a 1% cholic acid (CA) diet for 5days, a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet for 3weeks, or control diet. Results: Serum ALT (6.5-fold; p <0.05), AST (9.3-fold; p =0.06) and BA (2.8-fold; p <0.05) were increased in CA-fed hs-RxαΔex4 −/− mice compared to CA-fed WT mice, but were equally induced between genotypes by DDC-feeding. CA-feeding elevated total (4.4-fold; p =0.06) and unconjugated (2.2-fold; p <0.02) bilirubin levels in hs-RxrαΔex4 −/− mice compared to WT mice, but not in DDC-fed hs-RxrαΔex4 −/− mice. Increased necrosis and inflammation was observed in CA-fed, but not in DDC-fed hs-RxrαΔex4 −/− mice. Apoptotic markers DR5, CK8, CK18 RNA were increased in CA- and DDC-fed hs-RxrαΔex4 −/− mice. Cleaved caspase 3, CK18 and p-JNK protein were elevated in CA-fed but not in DDC-fed hs-RxrαΔex4 −/− mice. Induction of Ostβ and Cyp2b10 RNA was impaired in CA-fed and DDC-fed hs-RxrαΔex4 −/− mice. Surprisingly, DDC-fed hs-RxrαΔex4 −/− mice showed attenuated fibrosis compared to DDC-fed WT mice. Conclusions: These two models of cholestasis identify common and injury-specific roles for RXRα heterodimers and the functional relevance of an intact RXRα-DBD in the hepatocytic adaptive cholestatic response. [Copyright &y& Elsevier]

Paracrine signaling between cholangiocytes and stromal cells regulates biliary remodeling. Cholangiocytes have neuroepithelial characteristics and serotonin receptor agonists inhibit their growth, but whether they are capable of serotonin biosynthesis is unknown. We hypothesized that cholangiocytes synthesize serotonin and that cross talk between liver myofibroblasts (MF) and cholangiocytes regulates this process to influence biliary remodeling. Transwell cultures of cholangiocytes ± MF, and tryptophan hydroxylase-2 knockin (TPH2KI) mice with an inactivating mutation of the neuronal tryptophan hydroxylase (TPH) isoform, TPH2, were evaluated. Results in the cell culture models confirm that cholangiocytes have serotonin receptors and demonstrate for the first time that these cells express TPH2 and produce serotonin, which autoinhibits their growth but stimulates MF production of TGF-β1. Increased TGF-β1, in turn, counteracts autocrine inhibition of cholangiocyte growth by repressing cholangiocyte TPH2 expression. Studies of TPH2KI mice confirm that TPH2-mediated production of serotonin plays an important role in remodeling damaged bile ducts because mice with decreased TPH2 function have reduced biliary serotonin levels and exhibit excessive cholangiocyte proliferation, accumulation of aberrant ductules and liver progenitors, and increased liver fibrosis after bile duct ligation. This new evidence that cholangiocytes express the so-called neuronal isoform of TPH, synthesize serotonin de novo, and deploy serotonin as an autocrine/paracrine signal to regulate regeneration of the biliary tree complements earlier work that revealed that passive release of serotonin from platelets stimulates hepatocyte proliferation. Given the prevalent use of serotonin-modulating drugs, these findings have potentially important implications for recovery from various types of liver damage. [ABSTRACT FROM AUTHOR]

Liver disease is increasingly common in cystic fibrosis (CF). As new therapeutic options emerge, life expectancy increases and common hepatobiliary manifestations impact on quality of life and survival of CF patients. Hepatobiliary abnormalities in CF vary in nature and range from defects attributable to the underlying CFTR gene defect to those related to systemic disease and malnutrition. Today complications of liver disease represent the third most frequent cause of disease-related death in patients with CF. Here we review molecular and clinical genetics of CF, including genetic modifiers of CF-associated liver disease, and provide practical recommendations for genetic testing, diagnosis and treatment of hepatobiliary manifestations in CF. [ABSTRACT FROM AUTHOR]

Aim: Cholestasis triggers fibrogenesis in the liver. Hepatic cyclooxygenase-2 (COX-2) expression increases in various chronic liver diseases caused either by viruses or toxins. We hypothesized that selective COX-2 inhibitor meloxicam could suppress inflammation and fibrogenesis in a rat model of cholestasis induced by bile duct ligation (BDL). Methods: Forty-three Sprague–Dawley rats were assigned to one of four treatment groups (sham-operation, BDL, daily meloxicam injections following BDL, and daily meloxicam injection without BDL). Liver histopathology was analyzed with hematoxylin–eosin and Masson's trichrome staining. The expression of α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), and COX-2 were measured with immunohistochemical staining. The levels of COX-2, TGF-β1, and matrix metalloproteinase-9 (MMP-9) production were measured with the Western blot method and an enzyme immunoassay. Results: Meloxicam treatment attenuated the expression of α-SMA, TGF-β1, and COX-2 in rats that were treated with BDL for 3 weeks. This was associated with a marked reduction in collagen accumulation and histological improvement. In addition, meloxicam treatment was found to downregulate the levels of hepatic COX-2, TGF-β1, and MMP-9 production. Conclusion: Cholestasis in BDL rats induces hepatic COX-2 expression. Selective COX-2 inhibitor meloxicam reduces BDL-induced hepatic fibrosis, and this is associated with reduced hepatic TGF-β1 expression as well as decreased cyclooxygenase activity in the liver. [ABSTRACT FROM AUTHOR]

Keywords: PBC; Cholestasis; Autoimmunity; Biliary fibrosis; Biliary cirrhosis EN PBC Cholestasis Autoimmunity Biliary fibrosis Biliary cirrhosis 255 256 2 11/26/20 20210101 NES 210101 To the Editor: We thank Dr Hydes and Prof. Khakoo for their interest in our snapshot on primary biliary cholangitis (PBC) and for providing the opportunity to comment on the role of natural killer (NK) cells in PBC pathogenesis.[1] SP , sp [2] Indeed, the liver hosts a large number of highly specialized resident NK cells,[3] which are key players in liver immunity. This function is regulated by a large family of inhibitory NK cell receptors, including killer-cell immunoglobulin-like receptors and C-lectin type molecules, which recognize major histocompatibility complex (MHC) class I present on autologous cells. 95, 2018, 159-170 5 S.E. Clark, K.S. Burrack, S.C. Jameson, S.E. Hamilton, L.L. Lenz, NK cell IL-10 production requires IL-15 and IL-10 driven STAT3 activation. [Extracted from the article]

Background and Aim: Bone marrow derived cells are involved in the process of hepatic fibrosis secondary to chronic injury. However, it is not yet known how quickly this event occurs in acute fibrosis models. The purpose of this study was to determine the role of bone marrow cells in rapid fibrosis following bile duct ligation in mice using green fluorescent protein (GFP) expressing bone marrow cells. Method: After whole body irradiation, 1 × 106 donor whole bone marrow cells from green fluorescent protein+/– mice were transplanted into C57BL/6 recipients via the tail vein. Four weeks after bone marrow transplantation, chimeric mice were subjected to common bile duct ligation, and livers of these animals were histologically examined after bile duct ligation using anti-fibroblast specific protein (FSP)-1 antibody and anti-alpha-smooth muscle actin (α-SMA) antibody. Results: Periductal fibrosis consisting of fibroblast specific protein-positive cells was demonstrated histologically as early as day 7. Most of the fibrotic cells were green fluorescent protein-negative, however, a significant number of cells were green fluorescent protein-positive and some were also anti-FSP or α-SMA-positive. Conclusion: Differentiation of bone marrow derived cells into activated fibroblast and myofibroblast-like phenotypes occurs in the very early course of periductal fibrosis following bile duct ligation, suggesting a new strategy for prevention of biliary fibrosis by inhibiting migration of bone marrow cells to liver. [ABSTRACT FROM AUTHOR]

Portal fibroblasts (PF) are fibrogenic liver cells distinct from hepatic stellate cells (HSC). Recent evidence suggests that PF may be important mediators of biliary fibrosis and cirrhosis. The cytokine monocyte chemoattractant protein-1 (MCP-1)/CCL2 is upregulated in biliary fibrosis by bile duct epithelia (BDE) and induces functional responses in HSC. Thus we hypothesized that release of MCP-1 may mediate biliary fibrosis. We report that PF express functional receptors for MCP-1 that are distinct from the receptor CCR2. MCP-1 induces proliferation, increase and redistribution of α-smooth muscle (α-SMA) expression, loss of the ectonucleotidase NTPDase2, and upregulation of α1-procollagen production in PF. BDE secretions induce α-SMA levels in PF, and this is inhibited by MCP-1 blocking antibody. Together, these data suggest that BDE regulate PF proliferation and myofibroblastic transdifferentiation in a paracrine fashion via release of MCP-1. [ABSTRACT FROM AUTHOR]

Biliary fibrosis is an important pathological indicator of hepatobiliary damage. Cholangiocyte is the key cell type involved in this process. To reveal the pathogenesis of biliary fibrosis, it is essential to understand the normal development as well as the aberrant generation and proliferation of cholangiocytes. Numerous reports suggest that the Wnt signaling pathway is implicated in the physiological and pathological processes of cholangiocyte development and ductular reaction. In this review, we summarize the effects of Wnt pathway in cholangiocyte development from embryonic stem cells, as well as the underlying mechanisms of cholangiocyte responses to adult ductal damage. Wnt signaling pathway is regulated in a step-wise manner during each of the liver differentiation stages from embryonic stem cells to functional mature cholangiocytes. With the modulation of Wnt pathway, cholangiocytes can also be generated from adult liver progenitor cells and mature hepatocytes to repair liver damage. Non-canonical Wnt signaling is triggered in the active ductal cells during biliary fibrosis. Targeted control of the Wnt signaling may hold the great potential to reduce and/or reverse the biliary fibrogenic process.

Fibrocystic liver diseases (FLDs) comprise a heterogeneous group of rare diseases of the biliary tree, having in common an abnormal development of the embryonic ductal plate caused by genetically-determined dysfunctions of proteins expressed in the primary cilia of cholangiocytes (and therefore grouped among the "ciliopathies"). The ductal dysgenesis may affect the biliary system at multiple levels, from the small intrahepatic bile ducts [congenital hepatic fibrosis (CHF)], to the larger intrahepatic bile ducts [Caroli disease (CD), or Caroli syndrome (CS), when CD coexists with CHF], leading to biliary microhamartomas and segmental bile duct dilations. Biliary changes are accompanied by progressive deposition of abundant peribiliary fibrosis. Peribiliary fibrosis and biliary cysts are the fundamental lesions of FLDs and are responsible for the main clinical manifestations, such as portal hypertension, recurrent cholangitis, cholestasis, sepsis and eventually cholangiocarcinoma. Furthermore, FLDs often associate with a spectrum of disorders affecting primarily the kidney. Among them, the autosomal recessive polycystic kidney disease (ARPKD) is the most frequent, and the renal function impairment is central in disease progression. CHF, CD/CS, and ARPKD are caused by a number of mutations in polycystic kidney hepatic disease 1 ( PKHD1 ), a gene that encodes for fibrocystin/polyductin, a protein of unclear function, but supposedly involved in planar cell polarity and other fundamental cell functions. Targeted medical therapy is not available yet and thus the current treatment aims at controlling the complications. Interventional radiology or surgical treatments, including liver transplantation, are used in selected cases., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/tgh-2020-04). The series “Recent Advances in Rare Liver Diseases” was commissioned by the editorial office without any funding or sponsorship. LF and MS served as the unpaid Guest Editors of the series. LF serves as an unpaid editorial board member of Translational Gastroenterology and Hepatology from Sep 2018 to Aug 2020. MS is a member of the advisory board of Esiai/Merk, Bayer, and Engitix, during the conduct of the study. The authors have no other conflicts of interest to declare., (2021 Translational Gastroenterology and Hepatology. All rights reserved.)