Will we ever model PSC? - "it's hard to be a PSC model!"

Overexpression of TNFα in TNF∆ARE+/- mice increases hepatic periportal inflammation and alters bile acid signaling in mice

BACKGROUND

Intestinal inflammation is a common factor in ~70% of patients diagnosed with primary sclerosing cholangitis. The TNF∆ARE+/- mouse overexpresses TNFα and spontaneously develops ileitis after weaning. The aim of this study was to examine the influence of ileitis and TNFα overexpression on hepatic injury, fibrosis, inflammation, and bile acid homeostasis.

METHODS

Using serum, hepatic, and ileal tissue isolated from 24- to 26-week-old C57BL/6 and TNF∆ARE+/- mice, hepatic injury and fibrosis, inflammation, ductal proliferation, and regulation of bile acid synthesis were assessed by immunohistochemical and quantitative PCR methods.

RESULTS

Compared to age-matched C57BL/6 mice, TNF∆ARE+/- mice exhibited increased serum AST, ALT, and serum bile acids, which corresponded to increased hepatic picrosirius red staining, and an increase in hepatic mRNA expression of Tgfb, Timp1, Col1a1, and MMP9 supporting induction of fibrosis. Examining inflammation, immunohistochemical staining revealed a significant periportal increase in MPO+ neutrophils, CD3+ lymphocytes, and a panlobular increase in F4/80+ macrophages. Importantly, periportal inflammation corresponded to significantly increased proinflammatory chemokines as well as hepatic cytokeratin 7 staining supporting increased ductular proliferation. In the liver, increased mRNA expression of bile acid transporters was associated with suppression of classical but not alternative bile acid synthesis. In the ileum, increased inflammation correlated with suppression of Nr1h4 and increased Fgf15 and Nr0b2 mRNA expression.

CONCLUSIONS

Increased TNFα expression is sufficient to promote both intestinal and hepatobiliary inflammation and fibrotic injury and contributes to hepatic dysregulation of FXR signaling and bile acid homeostasis. Overall, these results suggest that the TNF∆ARE+/- mouse may be a useful model for studying chronic hepatic inflammation.

Single-Cell Transcriptomic Profiling of Cholangiocyte Organoids Derived from Bile Ducts of Primary Sclerosing Cholangitis Patients

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a chronic inflammatory liver disorder without effective medical treatment which is characterized by inflammation and fibrotic structures around the bile ducts. Biliary epithelial cells (cholangiocytes) are the target and potential disease drivers in PSC, yet little is known if cholangiocytes from PSC patients differ from non-PSC controls. To characterize cholangiocytes at early rather than end-stage disease, cholangiocyte organoids (COs) were derived from diseased bile ducts of PSC patients and compared to organoids generated from disease controls.

METHODS

Cholangiocytes were obtained during endoscopic retrograde cholangiopancreatography (ERCP) brushing of diseased bile duct areas and expanded as organoids using previously established culture methods. Stable CO lines were analyzed for cell type identity, basic cholangiocyte function, and transcriptomic signature.

RESULTS

We demonstrate that cholangiocytes, derived from the damaged area within the bile ducts of PSC patients, can be expanded in culture without displaying functional or genetic disease-related features. We further show that COs from patients who later were diagnosed with dysplasia exhibit higher expression of the cancer-associated genes PGC, FXYD2, MIR4435-2HG, and HES1.

CONCLUSIONS

Our results demonstrate that PSC organoids are largely similar to control organoids after culture and highlight the significance of COs as a tool for regenerative medicine approaches as well as their potential for discovering new potential biomarkers for diagnosing cholangiocarcinoma.

The autophagic protein p62 is a target of reactive aldehydes in human and murine cholestatic liver disease

Inflammatory cholestatic liver diseases, including Primary Sclerosing Cholangitis (PSC), are characterized by periportal inflammation with progression to cirrhosis. The objective of this study was to examine interactions between oxidative stress and autophagy in cholestasis. Using hepatic tissue from male acute cholestatic (bile duct ligated) as well as chronic cholestatic (Mdr2KO) mice, localization of oxidative stress, the antioxidant response and induction of autophagy were analyzed and compared to human PSC liver. Concurrently, the ability of reactive aldehydes to post-translationally modify the autophagosome marker p62 was assessed in PSC liver tissue and in cell culture. Expression of autophagy markers was upregulated in human and mouse cholestatic liver. Whereas mRNA expression of Atg12, Lamp1, Sqstm1 and Map1lc3 was increased in acute cholestasis in mice, it was either suppressed or not significantly changed in chronic cholestasis. In human and murine cholestasis, periportal hepatocytes showed increased IHC staining of ubiquitin, 4-HNE, p62, and selected antioxidant proteins. Increased p62 staining colocalized with accumulation of 4-HNE-modified proteins in periportal parenchymal cells as well as with periportal macrophages in both human and mouse liver. Mechanistically, p62 was identified as a direct target of lipid aldehyde adduction in PSC hepatic tissue and in vitro cell culture. In vitro LS-MS/MS analysis of 4-HNE treated recombinant p62 identified carbonylation of His123, Cys128, His174, His181, Lys238, Cys290, His340, Lys341 and His385. These data indicate that dysregulation of autophagy and oxidative stress/protein damage are present in the same periportal hepatocyte compartment of both human and murine cholestasis. Thus, our results suggest that both increased expression as well as ineffective autophagic degradation of oxidatively-modified proteins contributes to injury in periportal parenchymal cells and that direct modification of p62 by reactive aldehydes may contribute to autophagic dysfunction.

Prolonged Administration of Melatonin Ameliorates Liver Phenotypes in Cholestatic Murine Model

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is characterized by biliary senescence and hepatic fibrosis. Melatonin exerts its effects by interacting with Melatonin receptor 1 and 2 (MT1/MT2) melatonin receptors. Short-term (1 wk) melatonin treatment reduces a ductular reaction and liver fibrosis in bile duct-ligated rats by down-regulation of MT1 and clock genes, and in multidrug resistance gene 2 knockout (Mdr2-/-) mice by decreased miR200b-dependent angiogenesis. We aimed to evaluate the long-term effects of melatonin on liver phenotype that may be mediated by changes in MT1/clock genes/miR200b/maspin/glutathione-S transferase (GST) signaling.

METHODS

Male wild-type and Mdr2-/- mice had access to drinking water with/without melatonin for 3 months. Liver damage, biliary proliferation/senescence, liver fibrosis, peribiliary inflammation, and angiogenesis were measured by staining in liver sections, and by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay in liver samples. We confirmed a link between MT1/clock genes/miR200b/maspin/GST/angiogenesis signaling by Ingenuity Pathway Analysis software and measured liver phenotypes and the aforementioned signaling pathway in liver samples from the mouse groups, healthy controls, and PSC patients and immortalized human PSC cholangiocytes.

RESULTS

Chronic administration of melatonin to Mdr2-/- mice ameliorates liver phenotypes, which were associated with decreased MT1 and clock gene expression.

CONCLUSIONS

Melatonin improves liver histology and restores the circadian rhythm by interaction with MT1 through decreased angiogenesis and increased maspin/GST activity.

Recent discoveries in microbiota dysbiosis, cholangiocytic factors, and models for studying the pathogenesis of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a cholangiopathy caused by genetic and microenvironmental changes, such as bile homeostasis disorders and microbiota dysbiosis. Therapeutic options are limited, and proven surveillance strategies are currently lacking. Clinically, PSC presents as alternating strictures and dilatations of biliary ducts, resulting in the typical “beaded” appearance seen on cholangiography. The pathogenesis of PSC is still unclear, but cholangiocytes play an essential role in disease development, wherein a reactive phenotype is caused by the secretion of neuroendocrine factors. The liver–gut axis is implicated in the pathogenesis of PSC owing to the dysbiosis of microbiota, but the underlying mechanism is still poorly understood. Alterations in cholangiocyte responses and related signalling pathways during PSC progression were elucidated by recent research, providing novel therapeutic targets. In this review, we summarise the currently known underlying mechanisms of PSC pathogenesis caused by the dysbiosis of microbiota and newly reported information regarding cholangiocytes in PSC. We also summarise recently reported in vitro and in vivo models for studying the pathogenesis of PSC.

The Gut-Liver Axis in Chronic Liver Disease: A Macrophage Perspective

Chronic liver disease (CLD) is a growing health concern which accounts for two million deaths per year. Obesity, alcohol overconsumption, and progressive cholestasis are commonly characterized by persistent low-grade inflammation and advancing fibrosis, which form the basis for development of end-stage liver disease complications, including hepatocellular carcinoma. CLD pathophysiology extends to the intestinal tract and is characterized by intestinal dysbiosis, bile acid dysregulation, and gut barrier disruption. In addition, macrophages are key players in CLD progression and intestinal barrier breakdown. Emerging studies are unveiling macrophage heterogeneity and driving factors of their plasticity in health and disease. To date, in-depth investigation of how gut-liver axis disruption impacts the hepatic and intestinal macrophage pool in CLD pathogenesis is scarce. In this review, we give an overview of the role of intestinal and hepatic macrophages in homeostasis and gut-liver axis disruption in progressive stages of CLD.

Rodent models of cholestatic liver disease: A practical guide for translational research

Cholestatic liver disease denotes any situation associated with impaired bile flow concomitant with a noxious bile acid accumulation in the liver and/or systemic circulation. Cholestatic liver disease can be subdivided into different types according to its clinical phenotype, such as biliary atresia, drug-induced cholestasis, gallstone liver disease, intrahepatic cholestasis of pregnancy, primary biliary cholangitis and primary sclerosing cholangitis. Considerable effort has been devoted to elucidating underlying mechanisms of cholestatic liver injuries and explore novel therapeutic and diagnostic strategies using animal models. Animal models employed according to their appropriate applicability domain herein play a crucial role. This review provides an overview of currently available in vivo animal models, fit-for-purpose in modelling different types of cholestatic liver diseases. Moreover, a practical guide and workflow is provided which can be used for translational research purposes, including all advantages and disadvantages of currently available in vivo animal models.

Bile acids modulate colonic MAdCAM-1 expression in a murine model of combined cholestasis and colitis

Primary sclerosing cholangitis (PSC) is a progressive fibrosing cholestatic liver disease that is strongly associated with inflammatory bowel disease (IBD). PSC-associated IBD (PSC-IBD) displays a unique phenotype characterized by right-side predominant colon inflammation and increased risk of colorectal cancer compared to non-PSC-IBD. The frequent association and unique phenotype of PSC-IBD suggest distinctive underlying disease mechanisms from other chronic liver diseases or IBD alone. Multidrug resistance protein 2 knockout (Mdr2-/-) mice develop spontaneous cholestatic liver injury and fibrosis mirroring human PSC. As a novel model of PSC-IBD, we treated Mdr2-/- mice with dextran sulfate sodium (DSS) to chemically induce colitis (Mdr2-/-/DSS). Mdr2-/- mice demonstrate alterations in fecal bile acid composition and enhanced colitis susceptibility with increased colonic adhesion molecule expression, particularly mucosal addressin-cell adhesion molecule 1 (MAdCAM-1). In vitro, ursodeoxycholic acid (UDCA) co-treatment resulted in a dose dependent attenuation of TNF-α-induced endothelial MAdCAM-1 expression. In the combined Mdr2-/-/DSS model, UDCA supplementation attenuated colitis severity and downregulated intestinal MAdCAM-1 expression. These findings suggest a potential mechanistic role for alterations in bile acid signaling in modulating MAdCAM-1 expression and colitis susceptibility in cholestasis-associated colitis. Together, our findings provide a novel model and new insight into the pathogenesis and potential treatment of PSC-IBD.

Alagille Syndrome: Diagnostic Challenges and Advances in Management

Alagille syndrome (ALGS) is a multisystem disease characterized by cholestasis and bile duct paucity on liver biopsy in addition to variable involvement of the heart, eyes, skeleton, face, kidneys, and vasculature. The identification of JAG1 and NOTCH2 as disease-causing genes has deepened our understanding of the molecular mechanisms underlying ALGS. However, the variable expressivity of the clinical phenotype and the lack of genotype-phenotype relationships creates significant diagnostic and therapeutic challenges. In this review, we provide a comprehensive overview of the clinical characteristics and management of ALGS, and the molecular basis of ALGS pathobiology. We further describe unique diagnostic considerations that pose challenges to clinicians and outline therapeutic concepts and treatment targets that may be available in the near future.

Tissue engineering of the biliary tract and modelling of cholestatic disorders

Our insight into the pathogenesis of cholestatic liver disease remains limited, partly owing to challenges in capturing the multitude of factors that contribute to disease pathogenesis in vitro. Tissue engineering could address this challenge by combining cells, materials and fabrication strategies into dynamic modelling platforms, recapitulating the multifaceted aetiology of cholangiopathies. Herein, we review the advantages and limitations of platforms for bioengineering the biliary tree, looking at how these can be applied to model biliary disorders, as well as exploring future directions for the field.

Inflammation and Cell Death During Cholestasis: The Evolving Role of Bile Acids

Cholestasis results in blockage of bile flow whether the point of obstruction occurs extrahepatically or intrahepatically. Bile acids are a primary constituent of bile, and thus one of the primary outcomes is acute retention of bile acids in hepatocytes. Bile acids are normally secreted into the biliary tracts and then released into the small bowel before recirculating back to the liver. Retention of bile acids has long been hypothesized to be a primary cause of the associated liver injury that occurs during acute or chronic cholestasis. Despite this, a surge of papers in the last decade have reported a primary role for inflammation in the pathophysiology of cholestatic liver injury. Furthermore, it has increasingly been recognized that both the constituency of individual bile acids that make up the greater pool, as well as their conjugation status, is intimately involved in their toxicity, and this varies between species. Finally, the role of bile acids in drug-induced cholestatic liver injury remains an area of increasing interest. The purpose of this review is to critically evaluate current proposed mechanisms of cholestatic liver injury, with a focus on the evolving role of bile acids in cell death and inflammation.

Cholestatic liver disease results increased production of reactive aldehydes and an atypical periportal hepatic antioxidant response

Cholangiopathies such as primary sclerosing cholangitis (PSC) are chronic liver diseases characterized by increased cholestasis, biliary inflammation and oxidative stress. The objective of this study was to elucidate the impact of cholestatic injury on oxidative stress-related factors. Using hepatic tissue and whole cell liver extracts (LE) isolated from 11-week old C57BL/6J (WT) and Mdr2^KO mice, inflammation and oxidative stress was assessed. Concurrently, specific targets of carbonylation were assessed in LE prepared from murine groups as well as from normal and human patients with end-stage PSC. Identified carbonylated proteins were further evaluated using bioinformatics analyses. Picrosirius red staining revealed extensive fibrosis in Mdr2^KO liver, and fibrosis colocalized with increased periportal inflammatory cells and both acrolein and 4-HNE staining. Western blot analysis revealed elevated periportal expression of antioxidant proteins Cbr3, GSTμ, Prdx5, TrxR1 and HO-1 but not GCLC, GSTπ or catalase in the Mdr2^KO group when compared to WT. From immunohistochemical analysis, increased periportal reactive aldehyde production colocalized with elevated staining of Cbr3, GSTμ and TrxR1 but surprisingly not with Nrf2. Mass spectrometric analysis revealed an increase in carbonylated proteins in the Mdr2^KO and PSC groups compared to respective controls. Gene ontology and KEGG pathway analysis of carbonylated proteins revealed a propensity for increased carbonylation of proteins broadly involved in metabolic processes as well more specifically in Rab-mediated signal transduction, lysosomes and the large ribosomal subunit in human PSC. Western blot analysis of Rab-GTPase expression revealed no significant differences in Mdr2^KO mice when compared to WT livers. In contrast, PSC tissue exhibited decreased levels of Rabs 4, 5 and increased abundance of Rabs 6 and 9a protein. Results herein reveal that cholestasis induces stage-dependent increases in periportal oxidative stress responses and protein carbonylation, potentially contributing to pathogenesis in Mdr2^KO. Furthermore, during early stage cholestasis, there is cell-specific upregulation of some but not all, antioxidant proteins.

Cholestasis induced by bile duct ligation promotes changes in the intestinal microbiome in mice

Increasing evidence point to the relevance of intestinal disfunction and changes in the microbiome composition during chronic liver disease. More specifically, recent studies have highlighted that cholestatic diseases associate with a reduction in the microbiome diversity in patients. Still, the dynamics of the changes in the microbiome composition observed, as well as their implication in contributing to the pathogenesis of this disease remain largely undefined. Hence, experimental mouse models resembling the human pathogenesis are crucial to move forward our understanding on the mechanisms underpinning cholestatic disease and to enable the development of effective therapeutics. Our results show that the bile duct ligation (BDL) experimental model of cholestasis leads to rapid and significant changes in the microbiome diversity, with more than 100 OTUs being significantly different in faecal samples obtained from WT mice at 3 days and 7 days after BDL when compared to control animals. Changes in the microbial composition in mice after BDL included the enrichment of Akkermansia, Prevotella, Bacteroides and unclassified Ruminococcaceae in parallel with a drastic reduction of the presence of Faecalibacterium prausnitzii. In conclusion, our results support that bile duct ligation induces changes in the microbiome that partly resemble the gut microbial changes observed during human cholestatic disease.

Gut pathobionts underlie intestinal barrier dysfunction and liver T helper 17 cell immune response in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory liver disease and its frequent complication with ulcerative colitis highlights the pathogenic role of epithelial barrier dysfunction. Intestinal barrier dysfunction has been implicated in the pathogenesis of PSC, yet its underlying mechanism remains unknown. Here, we identify Klebsiella pneumonia in the microbiota of patients with PSC and demonstrate that K. pneumoniae disrupts the epithelial barrier to initiate bacterial translocation and liver inflammatory responses. Gnotobiotic mice inoculated with PSC-derived microbiota exhibited T helper 17 (T_H17) cell responses in the liver and increased susceptibility to hepatobiliary injuries. Bacterial culture of mesenteric lymph nodes in these mice isolated K. pneumoniae, Proteus mirabilis and Enterococcus gallinarum, which were prevalently detected in patients with PSC. A bacterial-organoid co-culture system visualized the epithelial-damaging effect of PSC-derived K. pneumoniae that was associated with bacterial translocation and susceptibility to T_H17-mediated hepatobiliary injuries. We also show that antibiotic treatment ameliorated the T_H17 immune response induced by PSC-derived microbiota. These results highlight the role of pathobionts in intestinal barrier dysfunction and liver inflammation, providing insights into therapeutic strategies for PSC.

Interference with the lower gut-liver axis induces remission of primary sclerosing cholangitis in a patient with ulcerative colitis

The gut-liver axis describes the complex interactions between gut microbiota, the small and large bowel, the immune system and the liver. Current evidence associates abnormalities within the gut-liver axis with liver disease such as primary sclerosing cholangitis (PSC). PSC is believed to be an immune-mediated disease though the exact mechanism of its pathogenesis remains unknown. Here, we report a case of a 66 -year-old woman with treatment-resistant ulcerative colitis and PSC which continued to be active following subtotal colectomy. Interestingly, her PSC achieved full remission after proctectomy for treatment-resistant proctitis in the rectal stump. This case report supports existing hypotheses that PSC is an immune-mediated disease triggered by antigens within the gut. More notably, it suggests the yet unidentified pathogens may be localised to the lower gastrointestinal tract including the rectum.

IL-17 and IL-17-producing cells and liver diseases, with focus on autoimmune liver diseases

The pro-inflammatory cytokine interleukin(IL)-17 and IL-17-producing cells are important players in the pathogenesis of many autoimmune / inflammatory diseases. More recently, they have been associated with liver diseases. This review first describes the general knowledge on IL-17 and IL-17 producing cells. The second part describes the in vitro and in vivo effects of IL-17 on liver cells and the contribution of IL-17 producing cells to liver diseases. IL-17 induces immune cell infiltration and liver damage driving to hepatic inflammation and fibrosis and contributes to autoimmune liver diseases. The circulating levels of IL-17 and the frequency of IL-17-producing cells are elevated in a variety of acute and chronic liver diseases. The last part focuses on the effects of IL-17 deletion or neutralization in various murine models. Some of these observed beneficial effects suggest that targeting the IL-17 axis could be a new therapeutic strategy to prevent chronicity and progression of various liver diseases.

Establishment of a surgical bile duct injection technique giving direct access to the bile ducts for studies of the murine biliary tree

Cholangiopathies are progressive disorders with largely unknown pathoetiology and limited treatment options. We aimed to develop a novel surgical technique with direct access to the bile ducts that would complement existing mouse models of cholestasis, biliary inflammation, and fibrosis and present a new route of administration for testing of potential treatment strategies. We developed a surgical technique to access the murine biliary tree by injection of different solvents through catheterization of the gall bladder with simultaneous clamping of the common bile duct. To demonstrate the applicability of the technique, we injected either phosphate-buffered saline or dimethyl sulfoxide in concentrations of 50 or 65% and compared these groups with sham-operated mice. The surgery was optimized to achieve a mortality rate close to 0. There were no significant changes in pain, activity level, or mortality from the day of the surgery until euthanization for any groups. Injection of phosphate-buffered saline or 50% dimethyl sulfoxide was generally well-tolerated, whereas 65% dimethyl sulfoxide led to higher weight loss, an increase of serum alanine transaminase, and histological portal inflammation. There were no signs of inflammation in the gut. We have developed a bile duct injection technique that is well-tolerated, easily reproducible, and that may complement existing models of cholangiopathies. Direct access to the bile ducts without causing harm to the hepatobiliary or intestinal tissue may be valuable in future studies of normal biliary physiology and different pathophysiological mechanisms of disease and to test novel therapeutic strategies. NEW & NOTEWORTHY To evaluate tolerability of the bile duct to injection of both polar and nonpolar compounds, we established a novel biliary injection technique. This technique is well-tolerated, easily reproducible, and with direct access to the bile ducts for studies of the murine biliary tree. The bile duct injection technique may complement existing animal models and be a valuable tool in future studies of normal biliary physiology or pathophysiology and to test novel therapeutic strategies.

Primary sclerosing cholangitis: A review and update

Primary sclerosing cholangitis (PSC) is a rare, chronic, cholestatic liver disease of uncertain etiology characterized biochemically by cholestasis and histologically and cholangiographically by fibro-obliterative inflammation of the bile ducts. In a clinically significant proportion of patients, PSC progresses to cirrhosis, end-stage liver disease, and/or hepatobiliary cancer, though the disease course can be highly variable. Despite clinical trials of numerous pharmacotherapies over several decades, safe and effective medical therapy remains to be established. Liver transplantation is an option for select patients with severe complications of PSC, and its outcomes are generally favorable. Periodic surveillance testing for pre- as well as post-transplant patients is a cornerstone of preventive care and health maintenance. Here we provide an overview of PSC including its epidemiology, etiopathogenesis, clinical features, associated disorders, surveillance, and emerging potential therapies.

Model Systems for Studying the Role of Canalicular Efflux Transporters in Drug-Induced Cholestatic Liver Disease

Bile formation is a key function of the liver. Disturbance of bile flow may lead to liver disease and is called cholestasis. Cholestasis may be inherited, for example, in progressive familial intrahepatic cholestasis or acquired, for example, by drug-mediated inhibition of bile salt export from hepatocytes into the canaliculi. The key transport system for exporting bile salts into the canaliculi is the bile salt export pump. Inhibition of the bile salt export pump by drugs is a well-established cause of drug-induced cholestasis. Investigation of the role of the multidrug resistance protein 3, essential for biliary phospholipid secretion, is emerging now. This overview summarizes current concepts and methods with an emphasis on in vitro model systems for the investigation of drug-induced cholestasis in the general context of drug-induced liver injury.

Directed differentiation of human induced pluripotent stem cells into functional cholangiocyte-like cells

The difficulty in isolating and propagating functional primary cholangiocytes is a major limitation in the study of biliary disorders and the testing of novel therapeutic agents. To overcome this problem, we have developed a platform for the differentiation of human pluripotent stem cells (hPSCs) into functional cholangiocyte-like cells (CLCs). We have previously reported that our 26-d protocol closely recapitulates key stages of biliary development, starting with the differentiation of hPSCs into endoderm and subsequently into foregut progenitor (FP) cells, followed by the generation of hepatoblasts (HBs), cholangiocyte progenitors (CPs) expressing early biliary markers and mature CLCs displaying cholangiocyte functionality. Compared with alternative protocols for biliary differentiation of hPSCs, our system does not require coculture with other cell types and relies on chemically defined conditions up to and including the generation of CPs. A complex extracellular matrix is used for the maturation of CLCs; therefore, experience in hPSC culture and 3D organoid systems may be necessary for optimal results. Finally, the capacity of our platform for generating large amounts of disease-specific functional cholangiocytes will have broad applications for cholangiopathies, in disease modeling and for screening of therapeutic compounds.

Biliary tract instillation of a SMAC mimetic induces TRAIL-dependent acute sclerosing cholangitis-like injury in mice

Primary sclerosing cholangitis (PSC) is a cholestatic liver disease of unknown etiopathogenesis characterized by fibrous cholangiopathy of large and small bile ducts. Systemic administration of a murine TNF-related apoptosis-inducing ligand (TRAIL) receptor agonist induces a sclerosing cholangitis injury in C57BL/6 mice, suggesting endogenous TRAIL may contribute to sclerosing cholangitis syndromes. Cellular inhibitor of apoptosis proteins (cIAP-1 and cIAP-2) are negative regulators of inflammation and TRAIL receptor signaling. We hypothesized that if endogenous TRAIL promotes sclerosing cholangitis, then cIAP depletion should also induce this biliary tract injury. Herein, we show that cIAP protein levels are reduced in the interlobular bile ducts of human PSC livers. Downregulation of cIAPs in normal human cholangiocytes in vitro by use of a SMAC mimetic (SM) induces moderate, ripoptosome-mediated apoptosis and RIP1-independent upregulation of proinflammatory cytokines and chemokines. Cytokine and chemokine expression was mediated by the non-canonical activation of NF-κB. To investigate whether downregulation of cIAPs is linked to generation of a PSC-like phenotype, an SM was directly instilled into the mouse biliary tree. Twelve hours after biliary instillation, TUNEL-positive cholangiocytes were identified; 5 days later, PSC-like changes were observed in the SM-treated mice, including a fibrous cholangiopathy of the interlobular bile ducts, portal inflammation, significant elevation of serum markers of cholestasis and cholangiographic evidence of intrahepatic biliary tract injury. In contrast, TRAIL and TRAIL-receptor deficient mice showed no sign of cholangiopathy following SM intrabiliary injection. We conclude that in vivo antagonism of cIAPs in mouse biliary epithelial cells is sufficient to trigger cholangiocytes apoptosis and a proinflammatory response resulting in a fibrous cholangiopathy resembling human sclerosing cholangitis. Therefore, downregulation of cIAPs in PSC cholangiocytes may contribute to the development of the disease. Our results also indicate that inhibition of TRAIL signaling pathways may be beneficial in the treatment of PSC.

Application of induced pluripotent stem cells in cholangiopathies

Induced pluripotent stem cells (iPSCs) are similar to embryonic stem cells (ESCs) in morphology, gene expression, cell self-renewal and differentiation potential. They avoid the problem of immune rejection and ethical issues associated with the application of ESCs. The application of iPSCs in a variety of diseases provides favorable experiences to the research of liver diseases. Cholangiopathies, such as primary biliary cirrhosis and primary sclerosing cholangitis, refer to a category of uncommon diseases that possess unclear pathogenesis, lack effective treatment and have a poor prognosis. Hence, investigating cholangiopathies-derived, individualized iPSCs and their differentiation into functional cells can mimic the disease phenotype and pathological process in vitro. The application of these cells has great significance for pathogenesis exploration, drug screening and therapeutic evaluation.

Cholangiocytes derived from human induced pluripotent stem cells for disease modeling and drug validation

The study of biliary disease has been constrained by a lack of primary human cholangiocytes. Here we present an efficient, serum-free protocol for directed differentiation of human induced pluripotent stem cells into cholangiocyte-like cells (CLCs). CLCs show functional characteristics of cholangiocytes, including bile acids transfer, alkaline phosphatase activity, γ-glutamyl-transpeptidase activity and physiological responses to secretin, somatostatin and vascular endothelial growth factor. We use CLCs to model in vitro key features of Alagille syndrome, polycystic liver disease and cystic fibrosis (CF)-associated cholangiopathy. Furthermore, we use CLCs generated from healthy individuals and patients with polycystic liver disease to reproduce the effects of the drugs verapamil and octreotide, and we show that the experimental CF drug VX809 rescues the disease phenotype of CF cholangiopathy in vitro. Our differentiation protocol will facilitate the study of biological mechanisms controlling biliary development, as well as disease modeling and drug screening.

Potential of human induced pluripotent stem cells in studies of liver disease

Liver disease is a leading cause of death in the Western world. However, our insight into the underlying disease mechanisms and the development of novel therapeutic agents has been hindered by limited availability of primary tissue, intraspecies variability associated with the use of animal models, and reduced long-term viability of isolated and diseased liver cells. The emergence of human induced pluripotent stem cells and differentiation protocols to generate hepatocyte-like cells has opened the possibility of addressing these issues. Here, we discuss the recent progress and potential in the production of various cell types constituting the liver and their applications to model liver diseases and test drug toxicity in vitro.

Therapeutic Potential of IL-17-Mediated Signaling Pathway in Autoimmune Liver Diseases

Emerging evidence reveals that various cytokines and tissue microenvironments contribute to liver inflammation and autoimmunity, and IL-17 family is one of highlights acknowledged. Although the implication of IL-17 family in most common autoimmune diseases (such as psoriasis, inflammatory bowel disease, and rheumatoid arthritis) has been extensively characterized, the role of this critical family in pathophysiology of autoimmune liver diseases (AILD) still needs to be clarified. In the review, we look into the intriguing biology of IL-17 family and further dissect on the intricate role of IL-17-mediated pathway in AILD. Considering encouraging data from preclinical and clinical trials, IL-17 targeted therapy has shown promises in several certain autoimmune conditions. However, blocking IL-17-mediated pathway is just beginning, and more fully investigation and reflection are required. Taking together, targeting IL-17-mediated responses may open up new areas of potential clinical treatment for AILD.

Characterization of cultured cholangiocytes isolated from livers of patients with primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic, idiopathic cholangiopathy. The role of cholangiocytes (biliary epithelial cells) in PSC pathogenesis is unknown and remains an active area of research. Here, through cellular, molecular and next-generation sequencing (NGS) methods, we characterize and identify phenotypic and signaling features of isolated PSC patient-derived cholangiocytes. We isolated cholangiocytes from stage 4 PSC patient liver explants by dissection, differential filtration and immune-magnetic bead separation. We maintained cholangiocytes in culture and assessed for: (i) cholangiocyte, cell adhesion and inflammatory markers; (ii) proliferation rate; (iii) transepithelial electrical resistance (TEER); (iv) cellular senescence; and (v) transcriptomic profiles by NGS. We used two well-established normal human cholangiocyte cell lines (H69 and NHC) as controls. Isolated PSC cells expressed cholangiocyte (eg, cytokeratin 7 and 19) and epithelial cell adhesion markers (EPCAM, ICAM) and were negative for hepatocyte and myofibroblast markers (albumin, α-actin). Proliferation rate was lower for PSC compared with normal cholangiocytes (4 vs 2 days, respectively, P<0.01). Maximum TEER was also lower in PSC compared with normal cholangiocytes (100 vs 145 Ωcm(2), P<0.05). Interleukin-6 (IL-6) and IL-8 (protein and mRNA) were both increased compared with NHCs and H69s (all P<0.01). The proportion of cholangiocytes staining positive for senescence-associated β-galactosidase was higher in PSC cholangiocytes compared with NHCs (48% vs 5%, P<0.01). Finally, NGS confirmed cholangiocyte marker expression in isolated PSC cholangiocytes and extended our findings regarding pro-inflammatory and senescence-associated signaling. In conclusion, we have demonstrated that high-purity cholangiocytes can be isolated from human PSC liver and grown in primary culture. Isolated PSC cholangiocytes exhibit a phenotype that may reflect their in vivo contribution to disease and serve as a vital tool for in vitro investigation of biliary pathobiology and identification of new therapeutic targets in PSC.

Primary sclerosing cholangitis and the microbiota: current knowledge and perspectives on etiopathogenesis and emerging therapies

Primary sclerosing cholangitis (PSC) is a chronic, fibroinflammatory, cholestatic liver disease of unknown etiopathogenesis. PSC generally progresses to liver cirrhosis, is a major risk factor for hepatobiliary and colonic neoplasia, and confers a median survival to death or liver transplantation of only 12 years. Although it is well recognized that approximately 75% of patients with PSC also have inflammatory bowel disease (IBD), the significance of this association remains elusive. Accumulating evidence now suggests a potentially important role for the intestinal microbiota, and enterohepatic circulation of molecules derived therefrom, as a putative mechanistic link between PSC and IBD and a central pathobiological driver of PSC. In this concise review, we provide a summary of and perspectives regarding the relevant basic, translational, and clinical data, which, taken together, encourage further investigation of the role of the microbiota and microbial metabolites in the etiopathogenesis of PSC and as a potential target for novel pharmacotherapies.

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.

Roux-en-Y choledochojejunostomy versus duct-to-duct biliary anastomosis in liver transplantation for primary sclerosing cholangitis: a meta-analysis

BACKGROUND

Roux-en-Y choledochojejunostomy and duct-to-duct anastomosis are potential methods for biliary reconstruction in liver transplantation (LT) for recipients with primary sclerosing cholangitis (PSC). However, there is controversy over which method yields superior outcomes. The purpose of this study was to evaluate the outcomes of duct-to-duct versus Roux-en-Y biliary anastomosis in patients undergoing LT for PSC.

METHODS

Studies comparing Roux-en-Y versus duct-to-duct anastomosis during LT for PSC were identified based on systematic searches of 9 electronic databases and multiple sources of gray literature.

RESULTS

The search identified 496 citations, including 7 retrospective series, and 692 patients met eligibility criteria. The use of duct-to-duct anastomosis was not associated with a significant difference in clinical outcomes, including 1-year recipient survival rates (odds ratio [OR], 1.02; 95% confidence interval [CI], 0.65-1.60; P = .95), 1-year graft survival rates (OR, 1.11; 95% CI, 0.72-1.71; P = .64), risk of biliary leaks (OR, 1.23; 95% CI, 0.59-2.59; P = .33), risk of biliary strictures (OR, 1.99; 95% CI, 0.98-4.06; P = .06), or rate of recurrence of PSC (OR, 0.94; 95% CI, 0.19-4.78; P = .94).

CONCLUSIONS

There were no significant differences in 1-year recipient survival, 1-year graft survival, risk of biliary complications, and PSC recurrence between Roux-en-Y and duct-to-duct biliary anastomosis in LT for PSC.

Bile acids trigger cholemic nephropathy in common bile-duct-ligated mice

Tubular epithelial injury represents an underestimated but important cause of renal dysfunction in patients with cholestasis and advanced liver disease, but the underlying mechanisms are unclear. To address the hypothesis that accumulation and excessive alternative urinary elimination of potentially toxic bile acids (BAs) may contribute to kidney injury in cholestasis, we established a mouse model for detailed in vivo time course as well as treatment studies. Three-day common bile duct ligation (CBDL) induced renal tubular epithelial injury predominantly at the level of aquaporin 2-positive collecting ducts with tubular epithelial and basement membrane defects. This was followed by progressive interstitial nephritis and tubulointerstitial renal fibrosis in 3-, 6-, and 8-week CBDL mice. Farnesoid X receptor knockout mice (with a hydrophilic BA pool) were completely protected from CBDL-induced renal fibrosis. Prefeeding of hydrophilic norursodeoxycholic acid inhibited renal tubular epithelial injury in CBDL mice. In addition, we provide evidence for renal tubular injury in cholestatic patients with cholemic nephropathy.

CONCLUSION

We characterized a novel in vivo model for cholemic nephropathy, which offers new perspectives to study the complex pathophysiology of this condition. Our findings suggest that urinary-excreted toxic BAs represent a pivotal trigger for renal tubular epithelial injury leading to cholemic nephropathy in CBDL mice.

Role of the microbiota and antibiotics in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an idiopathic, progressive, cholestatic liver disease with considerable morbidity and mortality and no established pharmacotherapy. In addition to the long-recognized association between PSC and inflammatory bowel disease, several lines of preclinical and clinical evidence implicate the microbiota in the etiopathogenesis of PSC. Here we provide a concise review of these data which, taken together, support further investigation of the role of the microbiota and antibiotics in PSC as potential avenues toward elucidating safe and effective pharmacotherapy for patients afflicted by this illness.

Chronic cholestatic liver diseases: clues from histopathology for pathogenesis

Chronic cholestatic liver diseases include fibrosing cholangiopathies such as primary biliary cirrhosis or primary sclerosing cholangitis. These and related cholangiopathies clearly display pathologies associated with (auto)immunologic processes. As the cholangiocyte's apical membrane is exposed to the toxic actions of the bile fluid, the interaction of bile with cholangiocytes and the biliary tree in general must be considered to completely understand the pathogenesis of cholangiopathies. While the molecular processes involved in the hepatocellular formation of bile are well understood in both normal and pathophysiologic conditions, those in the bile ducts of normal liver and in livers with cholangiopathies lag behind. This survey highlights key mechanisms known to date that are important for the formation of bile by hepatocytes and its modification by the biliary tree. It also delineates the clinical pathophysiologic findings for cholangiopathies and puts them in perspective with current experimental models to reveal the pathogenesis of cholangiopathies and develop novel therapeutic approaches.

Pathogenesis of primary sclerosing cholangitis and advances in diagnosis and management

Primary sclerosing cholangitis (PSC), first described in the mid-1850s, is a complex liver disease that is heterogeneous in its presentation. PSC is characterized by chronic cholestasis associated with chronic inflammation of the biliary epithelium, resulting in multifocal bile duct strictures that can affect the entire biliary tree. Chronic inflammation leads to fibrosis involving the hepatic parenchyma and biliary tree, which can lead to cirrhosis and malignancy. The etiology of PSC is not fully understood, which in part explains the lack of effective medical therapy for this condition. However, we have begun to better understand the molecular pathogenesis of PSC. The recognition of specific clinical subtypes and their pattern of progression could improve phenotypic and genotypic classification of the disease. We review our current understanding of this enigmatic disorder and discuss important topics for future studies.

Micro-computed tomography and nuclear magnetic resonance imaging for noninvasive, live-mouse cholangiography

The cholangiopathies are a diverse group of biliary tract disorders, many of which lack effective treatment. Murine models are an important tool for studying their pathogenesis, but existing noninvasive methods for assessing biliary disease in vivo are not optimal. Here we report our experience with using micro-computed tomography (microCT) and nuclear magnetic resonance (MR) imaging to develop a technique for live-mouse cholangiography. Using mdr2 knockout (mdr2KO, a model for primary sclerosing cholangitis (PSC)), bile duct-ligated (BDL), and normal mice, we performed in vivo: (1) microCT on a Siemens Inveon PET/CT scanner and (2) MR on a Bruker Avance 16.4 T spectrometer, using Turbo Rapid Acquisition with Relaxation Enhancement, IntraGate Fast Low Angle Shot, and Half-Fourier Acquisition Single-shot Turbo Spin Echo methods. Anesthesia was with 1.5-2.5% isoflurane. Scans were performed with and without contrast agents (iodipamide meglumine (microCT), gadoxetate disodium (MR)). Dissection and liver histology were performed for validation. With microCT, only the gallbladder and extrahepatic bile ducts were visualized despite attempts to optimize timing, route, and dose of contrast. With MR, the gallbladder, extra-, and intrahepatic bile ducts were well-visualized in mdr2KO mice; the cholangiographic appearance was similar to that of PSC (eg, multifocal strictures) and could be improved with contrast administration. In BDL mice, MR revealed cholangiographically distinct progressive dilation of the biliary tree without ductal irregularity. In normal mice, MR allowed visualization of the gallbladder and extrahepatic ducts, but only marginal visualization of the diminutive intrahepatic ducts. One mouse died during microCT and MR imaging, respectively. Both microCT and MR scans could be obtained in ≤20 min. We, therefore, demonstrate that MR cholangiography can be a useful tool for longitudinal studies of the biliary tree in live mice, whereas microCT yields suboptimal duct visualization despite requiring contrast administration. These findings support further development and application of MR cholangiography to the study of mouse models of PSC and other cholangiopathies.

The challenge of cholangiocarcinoma: dissecting the molecular mechanisms of an insidious cancer

Cholangiocarcinoma is a fatal cancer of the biliary epithelium and has an incidence that is increasing worldwide. Survival beyond a year of diagnosis is less than 5%, and therapeutic options are few. Known risk factors include biliary diseases such as primary sclerosing cholangitis and parasitic infestation of the biliary tree, but most cases are not associated with any of these underlying diseases. Numerous in vitro and in vivo models, as well as novel analytical techniques for human samples, are helping to delineate the many pathways implicated in this disease, albeit at a frustratingly slow pace. As yet, however, none of these studies has been translated into improved patient outcome and, overall, the pathophysiology of cholangiocarcinoma is still poorly understood. There remains an urgent need for new approaches and models to improve management of this insidious and devastating disease. In this review, we take a bedside-to-bench approach to discussing cholangiocarcinoma and outline research opportunities for the future in this field.

Primary sclerosing cholangitis: a review and update on therapeutic developments

Primary sclerosing cholangitis (PSC) is a chronic, cholestatic, idiopathic liver disease characterized by fibro-obliterative inflammation of the hepatic bile ducts. In a clinically significant proportion of patients, PSC progresses to cirrhosis, end-stage liver disease, and in some cases, cholangiocarcinoma. Despite clinical trials of nearly 20 different pharmacotherapies over several decades, safe and effective medical therapy, albeit critically needed, remains to be established. PSC is pathogenically complex, with genetic, immune, enteric microbial, environmental and other factors being potentially involved and, thus, not surprisingly, it manifests as a clinically heterogeneous disease with a relatively unpredictable course. It is likely that this complexity and clinical heterogeneity are responsible for the negative results of clinical trials, but novel insights about and approaches to PSC may shift this trend. The authors herein provide a review of previously tested pharmacologic agents, discuss emerging fundamental concepts and present viewpoints regarding how identifying therapies for PSC may evolve over the next several years.

Management of primary sclerosing cholangitis: conventions and controversies

Primary sclerosing cholangitis (PSC) is a chronic inflammatory cholangiopathy that results in fibrotic strictures and dilations of the intra- and extrahepatic bile ducts. PSC is uncommon, occurs predominantly in males and has a strong association with inflammatory bowel disease. While the pathogenesis of PSC has not been fully elucidated, emerging evidence supports roles for the innate and adaptive immune systems, and genome-wide analyses have identified several genetic associations. Using the best available evidence, the present review summarizes the current understanding of the diagnosis, pathogenesis and management of PSC. Despite its rarity, there is an urgent need for collaborative research efforts to advance therapeutic options for PSC beyond liver transplantation.

Pathogenesis of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) represents a chronic cholestatic liver disease with fibroobliterative sclerosis of intra- and/or extrahepatic bile ducts, eventually leading to biliary cirrhosis. The association with human leukocyte antigen (HLA) and non-HLA haplotypes and the presence of autoantibodies in sera of PSC patients support a crucial role for immune-mediated mechanisms in the initiation and progression of PSC. The strong clinical association between PSC and inflammatory bowel diseases led to intriguing pathogenetic concepts, in which the inflamed gut with translocation of bacterial products and homing of gut-primed memory T lymphocytes via aberrantly expressed adhesion molecules plays a fundamental role. Genetically or chemically modified bile composition was shown to induce sclerosing cholangitis and liver fibrosis in a number of animal models ("toxic bile concept"). The potential role of vascular injury with ischemia of bile duct epithelium cells in the development of sclerosing cholangitis is supported by animal models of endothelial cell injury showing close morphological similarities with human PSC.

Genetics in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic and severe inflammatory disease leading to fibrotic bile duct destruction and in most cases liver cirrhosis. As in other complex genetic diseases, the sibling risk of PSC is more than ten times that of the general population. Recent genome-wide association studies have consistently identified several genetic susceptibility loci. The overlap of these loci with susceptibility loci in other chronic inflammatory diseases is considerable, and offers intriguing opportunities for transfer of pathogenetic knowledge and potentially treatment options. In the present article we summarise the present knowledge on PSC genetics with a particular emphasis on the major histocompatibility complex (MHC). We discuss the clinical relevance of the risk loci and elaborate on the insight that may be obtained from associated inflammatory conditions and existing murine knock-out models.

Medical and endoscopic therapy of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease mainly affecting young male patients. PSC is characterised by chronic inflammation and fibrotic strictures of the intra- and extrahepatic biliary system, which eventually lead to cholestasis and biliary cirrhosis. However, the clinical course remains very variable. As the aetiology remains unknown, the development of a causative treatment is challenging and today no specific medical therapy is available. Ursodeoxycholic acid has been widely used for the treatment of PSC, but improved only biochemistry and/or symptoms in low- or medium dosages and is probably harmful in higher dosages. Other drugs such as immunosuppressive, antifibrotic or antibiotic agents have not been proven to be effective in large clinical trials. The endoscopic therapy encompasses balloon-dilatation and/or stenting of strictures, relieves clinical symptoms and improves a cholestatic enzyme profile. However, endoscopic therapy is limited to patients in advanced stages of PSC with biliary obstruction.