Elevated interleukin-8 in bile of patients with primary sclerosing cholangitis

Microenvironmental control of the ductular reaction: balancing repair and disease progression

The ductular reaction (DR) is a dynamic adaptive cellular response within the liver, triggered by various hepatic insults and characterized by an expansion of dysmorphic biliary epithelial cells and liver progenitors. This complex response presents a dual role, playing a pivotal function in liver regeneration but, paradoxically, contributing to the progression of liver diseases, depending upon specific contextual factors and signaling pathways involved. This comprehensive review aims to offer a holistic perspective on the DR, focusing into its intricate cellular and molecular mechanisms, highlighting its pathological significance, and exploring its potential therapeutic implications. An up-to-date understanding of the DR in the context of different liver injuries is provided, analyzing its contributions to liver regeneration, inflammation, fibrosis, and ultimately carcinogenesis. Moreover, the review highlights the role of multiple microenvironmental factors, including the influence of extracellular matrix, tissue mechanics and the interplay with the intricate hepatic cell ecosystem in shaping the DR's regulation. Finally, in vitro and in vivo experimental models of the DR will be discussed, providing insights into how researchers can study and manipulate this critical cellular response. By comprehensively addressing the multifaceted nature of the DR, this review contributes to a more profound understanding of its pathophysiological role in liver diseases, thus offering potential therapeutic avenues for hepatic disorders and improving patient outcomes.

The liver as a central "hub" of the immune system: pathophysiological implications

The purpose of this review is to describe the immune function of the liver, guiding the reader from the homeostatic tolerogenic status to the aberrant activation demonstrated in chronic liver disease. An extensive description of the pathways behind the inflammatory modulation of the healthy liver will be provided focusing on the complex immune cell network residing within the liver. The limit of tolerance will be presented in the context of organ transplantation, seizing the limits of homeostatic mechanisms that fail in accepting the graft, progressing eventually toward rejection. The triggers and mechanisms behind chronic activation in metabolic liver conditions and viral hepatitis will be discussed. The last part of the review will be dedicated to one of the greatest paradoxes for a tolerogenic organ, developing autoimmunity. Through the description of the three most common autoimmune liver diseases, the autoimmune reaction against hepatocytes and biliary epithelial cells will be dissected.

Immunobiology of bile and cholangiocytes

The biliary tract is now recognized as an immune organ, and within the biliary tract, both bile and cholangiocytes play a key role in maintaining immune defense and homeostasis. First, immunoreactive proteins such as secretory IgA provide local antimicrobial effects. Second, bile acids (BAs) protect the biliary tree from immune-related injury through receptor signaling, mainly via the membrane-bound receptor TGR5 on cholangiocytes. Third, the biliary microbiota, similar to the intestinal microbiota, contributes to sustaining a stable physiobiological microenvironment. Fourth, cholangiocytes actively modulate the expression/release of adhesion molecules and cytokines/chemokines and are involved in antigen presentation; additionally, cholangiocyte senescence and apoptosis also influence immune responses. Conversely, aberrant bile composition, altered BA profiles, imbalances in the biliary microbiota, and cholangiocyte dysfunction are associated with immune-mediated cholangiopathies, including primary biliary cholangitis, primary sclerosing cholangitis, and biliary atresia. While current therapeutic agents that modulate BA homeostasis and receptor signaling have shown promise in preclinical and clinical studies, future research on biliary/intestinal microbiota and cholangiocyte function should focus on developing novel therapeutic strategies for treating cholangiopathies.

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.

Anti-integrin αvβ6 Autoantibodies are Increased in Primary Sclerosing Cholangitis Patients With Concomitant Inflammatory Bowel Disease and Correlate With Liver Disease Severity

BACKGROUND & AIMS

Anti-integrin αvβ6 autoantibodies (anti-αvβ6) are found in more than 50% of individuals with ulcerative colitis (UC). We aimed to determine the prevalence of anti-αvβ6 in patients with primary sclerosing cholangitis (PSC) and their association with liver disease severity.

METHODS

Four cohorts of pre-liver transplant patients with PSC were recruited. Patients with inflammatory bowel disease (IBD) and healthy controls (HCs) served as comparators. Total IgG and anti-αvβ6 levels were measured using enzyme-linked immunosorbent assay. Olink inflammation panel was run on a subset of samples. Multivariable linear regression analysis was performed to assess the association between anti-αvβ6 and indices of liver disease severity.

RESULTS

A total of 137 patients with PSC (including 76 with PSC-UC, 33 with PSC-Crohn's disease (CD), and 28 with PSC alone) and 160 controls (including 91 with IBD and 69 HCs) were enrolled. Anti-αvβ6 levels were significantly higher in PSC-UC and PSC-CD compared with PSC alone (P < .0001 and P < .003) and HCs (P < .0001 and P < .0001). However, anti-αvβ6 levels in PSC alone were not increased compared with HCs. In patients with PSC-IBD, anti-αvβ6 levels correlated with markers of liver disease severity, including alkaline phosphatase level (r = 0.32; P = .004), the revised Mayo PSC risk score (r = 0.25; P = .02), and liver stiffness measurement (r = 0.43; P = .008) after adjusting for age, gender, race/ethnicity, and IBD subtype. Additionally, anti-αvβ6 levels were associated with markers of systemic inflammation and tissue remodeling.

CONCLUSION

Anti-αvβ6 autoantibodies identify a subset of patients with PSC with concomitant IBD.

Cultured Bacteria Isolated from Primary Sclerosing Cholangitis Patient Bile Induce Inflammation and Cell Death

Background

Primary sclerosing cholangitis (PSC) is a chronic liver disease characterized by inflammation and progressive fibrosis of the biliary tree. The pathogenesis of PSC remains poorly understood, and there are no effective therapeutic options. Previous studies have observed associations between changes in the colonic and biliary microbiome and PSC. We aimed to determine whether bacterial isolates cultured from PSC patient bile induced disease-associated phenotypes in cells.

Methods

Bile was collected from PSC patients (n=10) by endoscopic retrograde cholangiography and from non-PSC controls (n=3) undergoing cholecystectomies. Biliary bacteria were cultured anaerobically, and 50 colonies per sample were identified by 16S rRNA sequencing. The effects of supernatants from seven PSC-associated bacterial strains on cellular phenotypes were characterized using human colonic (Caco-2), hepatic (HepG2), and biliary (EGI-1) cells.

Results

No bacteria were isolated from non-PSC controls, while bacteria were cultured from most PSC patients. The PSC bile microbiomes exhibited reduced diversity compared to the gut or oral cavity, with one or two bacterial strains predominating. Overall, PSC-associated bacteria produced factors that were cytotoxic to hepatic and biliary cells. Enterococcus faecalis , and to a lesser extent Veillonella parvula , induced epithelial permeability, while Escherichia coli, Fusobacterium necrophorum , and Klebsiella pneumoniae induced inflammatory cytokines in biliary cells.

Conclusions

Our data suggest that bacteria cultured from PSC bile induce cellular changes that may contribute to PSC disease pathogenesis. Enterococcus may promote intestinal permeability, facilitating bacterial migration to the biliary tree. Once there, Escherichia, Fusobacterium and Klebsiella , may cause inflammation and damage in biliary and liver cells.

Immunobiology of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory progressive cholestatic liver disease. Genetic risk factors, the presence of autoantibodies, the strong clinical link with inflammatory bowel disease, and associations with other autoimmune disorders all suggest a pivotal role for the immune system in PSC pathogenesis. In this review, we provide a comprehensive overview of recent immunobiology insights in PSC. A particular emphasis is given to immunological concepts such as tissue residency and knowledge gained from novel technologies, including single-cell RNA sequencing and spatial transcriptomics. This review of the immunobiological landscape of PSC covers major immune cell types known to be enriched in PSC-diseased livers as well as recently described cell types whose biliary localization and contribution to PSC immunopathogenesis remain incompletely described. Finally, we emphasize the importance of time and space in relation to PSC heterogeneity as a key consideration for future studies interrogating the role of the immune system in PSC.

MSC-derived exosomes attenuate hepatic fibrosis in primary sclerosing cholangitis through inhibition of Th17 differentiation

Primary sclerosing cholangitis (PSC) is an autoimmune cholangiopathy characterized by chronic inflammation of the biliary epithelium and periductal fibrosis, with no curative treatment available, and liver transplantation is inevitable for end-stage patients. Human placental mesenchymal stem cell (hpMSC)-derived exosomes have demonstrated the ability to prevent fibrosis, inhibit collagen production and possess immunomodulatory properties in autoimmune liver disease. Here, we prepared hpMSC-derived exosomes (ExoMSC) and further investigated the anti-fibrotic effects and detailed mechanism on PSC based on Mdr2-/- mice and multicellular organoids established from PSC patients. The results showed that ExoMSC ameliorated liver fibrosis in Mdr2-/- mice with significant collagen reduction in the preductal area where Th17 differentiation was inhibited as demonstrated by RNAseq analysis, and the percentage of CD4+IL-17A+T cells was reduced both in ExoMSC-treated Mdr2-/- mice (Mdr2-/--Exo) in vivo and ExoMSC-treated Th17 differentiation progressed in vitro. Furthermore, ExoMSC improved the hypersecretory phenotype and intercellular interactions in the hepatic Th17 microenvironment by regulating PERK/CHOP signaling as supported by multicellular organoids. Thus, our data demonstrate the anti-fibrosis effect of ExoMSC in PSC disease by inhibiting Th17 differentiation, and ameliorating the Th17-induced microenvironment, indicating the promising potential therapeutic role of ExoMSC in liver fibrosis of PSC or Th17-related diseases.

Increased expression of TNFRSF14 and LIGHT in biliary epithelial cells of patients with primary sclerosing cholangitis

BACKGROUND AND AIMS

There is a lack of biliary epithelial molecular markers for primary sclerosing cholangitis (PSC). We analyzed candidates from disease susceptibility genes identified in recent genome-wide association studies (GWAS).

METHODS

Expression levels of GWAS genes were analyzed in archival liver tissues of patients with PSC and controls. Immunohistochemical analysis was performed to evaluate expression levels in the biliary epithelia of PSC (N = 45) and controls (N = 12). Samples from patients with primary biliary cholangitis (PBC) were used as disease controls (N = 20).

RESULTS

Hepatic expression levels of ATXN2, HHEX, PRDX5, MST1, and TNFRSF14 were significantly altered in the PSC group. We focused on the immune-related receptor, TNFRSF14. Immunohistochemistry revealed that high expression of TNFRSF14 in biliary epithelial cells was observed only in the PSC group. In addition, the expression of LIGHT, which encodes a TNFRSF14-activating ligand, was increased in PSC liver. Immunohistochemistry showed that high expression of LIGHT was more common in PSC biliary epithelia (53%) than in the PBC (15%) or control (0%) groups; moreover, it was positively associated with fibrotic progression, although it was not an independent prognostic factor.

CONCLUSIONS

TNFRSF14 and LIGHT are promising candidate markers for PSC.

Cholangiokines: undervalued modulators in the hepatic microenvironment

The biliary epithelial cells, also known as cholangiocytes, line the intra- and extrahepatic bile ducts, forming a barrier between intra- and extra-ductal environments. Cholangiocytes are mostly known to modulate bile composition and transportation. In hepatobiliary diseases, bile duct injury leads to drastic alterations in cholangiocyte phenotypes and their release of soluble mediators, which can vary depending on the original insult and cellular states (quiescence, senescence, or proliferation). The cholangiocyte-secreted cytokines (also termed cholangiokines) drive ductular cell proliferation, portal inflammation and fibrosis, and carcinogenesis. Hence, despite the previous consensus that cholangiocytes are bystanders in liver diseases, their diverse secretome plays critical roles in modulating the intrahepatic microenvironment. This review summarizes recent insights into the cholangiokines under both physiological and pathological conditions, especially as they occur during liver injury-regeneration, inflammation, fibrosis and malignant transformation processes.

Bile Acids and Biliary Fibrosis

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.

Bile proteome analysis by high-precision mass spectrometry to examine novel biomarkers of primary sclerosing cholangitis

BACKGROUND

Primary sclerosing cholangitis (PSC) is a chronic inflammatory disease of unknown etiology that affects the intra- and extrahepatic bile ducts. The present study examined the utility of a bile proteome analysis using a high-sensitivity mass spectrometer to comprehensively screen for novel PSC biomarkers.

METHODS

Bile endoscopically collected from patients with PSC, common bile duct stones, and biliary tract cancer were subjected to high-precision liquid chromatography/mass spectrometry. Some of the proteins specifically up-regulated in the bile of the PSC group were re-examined by an enzyme-linked immunosorbent assay.

RESULTS

A total of 8094 proteins were successfully identified and 332 were specifically up-regulated in the PSC group. The bioinformatics analysis showed that proteins involved in the proliferation and activation of diverse inflammatory cells were up-regulated in the PSC group. A receiver operating characteristic curve analysis showed good area under the curve values for interleukin-8 and annexin A1 (ANXA1) (0.836 and 0.914, respectively). Immunostaining for ANXA1 revealed its strong expression in inflammatory cells infiltrating the peripheral biliary tract in PSC livers.

CONCLUSION

A bile proteome analysis is a useful tool for elucidating the pathogenesis of PSC and developing new diagnostic approaches. Therefore, ANXA1 has potential as a bile biomarker for PSC.

Immunobiology of the biliary tract system

The biliary tract is a complex tubular organ system spanning from the liver to the duodenum. It is the site of numerous acute and chronic disorders, many of unknown origin, that are often associated with cancer development and for which there are limited treatment options. Cholangiocytes with proinflammatory capacities line the lumen and specialised types of immune cells reside in close proximity. Recent technological breakthroughs now permit spatiotemporal assessments of immune cells within distinct niches and have increased our understanding of immune cell tissue residency. In this review, a comprehensive overview of emerging knowledge on the immunobiology of the biliary tract system is provided, with a particular emphasis on the role of distinct immune cells in biliary disorders.

Changes in beta-catenin expression and activation during progression of primary sclerosing cholangitis predict disease recurrence

Primary sclerosing cholangitis (PSC) is a rare, chronic, cholestatic liver disease characterized by progressive inflammation and fibrosis of the bile ducts. We have previously demonstrated the importance of Wnt/β-catenin signaling in mouse models of PSC. In this study, we wished to determine the clinical relevance of β-catenin localization in patient samples. In livers explanted from patients diagnosed with PSC, the majority (12/16; 75%) lacked β-catenin protein expression. Biopsies from patients post-transplant were classified as recurrent or non-recurrent based on pathology reports and then scored for β-catenin activation as a function of immunohistochemical localization. Despite lack of statistical significance, patients with recurrent primary disease (n = 11) had a greater percentage of samples with nuclear, transcriptionally active β-catenin (average 58.8%) than those with no recurrence (n = 10; 40.53%), while non-recurrence is correlated with β-catenin staining at the cell surface (average 52.63% for non-recurrent vs. 27.34% for recurrent), as determined by three different methods of analysis. β-catenin score and years-to-endpoint are both strongly associated with recurrence status (p = 0.017 and p = 0.00063, respectively). Finally, there was significant association between higher β-catenin score and increased alkaline phosphatase, a marker of biliary injury and disease progression. Thus, β-catenin expression and activation changes during the progression of PSC, and its localization may be a useful prognostic tool for predicting recurrence of this disease.

Downregulation of TGR5 (GPBAR1) in biliary epithelial cells contributes to the pathogenesis of sclerosing cholangitis

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is characterized by chronic inflammation and progressive fibrosis of the biliary tree. The bile acid receptor TGR5 (GPBAR1) is found on biliary epithelial cells (BECs), where it promotes secretion, proliferation and tight junction integrity. Thus, we speculated that changes in TGR5-expression in BECs may contribute to PSC pathogenesis.

METHODS

TGR5-expression and -localization were analyzed in PSC livers and liver tissue, isolated bile ducts and BECs from Abcb4^-/-, Abcb4^-/-/Tgr5^Tg and ursodeoxycholic acid (UDCA)- or 24-norursodeoxycholic acid (norUDCA)-fed Abcb4^-/- mice. The effects of IL8/IL8 homologues on TGR5 mRNA and protein levels were studied. BEC gene expression was analyzed by single-cell transcriptomics (scRNA-seq) from distinct mouse models.

RESULTS

TGR5 mRNA expression and immunofluorescence staining intensity were reduced in BECs of PSC and Abcb4^-/- livers, in Abcb4^-/- extrahepatic bile ducts, but not in intrahepatic macrophages. No changes in TGR5 BEC fluorescence intensity were detected in liver tissue of other liver diseases, including primary biliary cholangitis. Incubation of BECs with IL8/IL8 homologues, but not with other cytokines, reduced TGR5 mRNA and protein levels. BECs from Abcb4^-/- mice had lower levels of phosphorylated Erk and higher expression levels of Icam1, Vcam1 and Tgfβ2. Overexpression of Tgr5 abolished the activated inflammatory phenotype characteristic of Abcb4^-/- BECs. NorUDCA-feeding restored TGR5-expression levels in BECs in Abcb4^-/- livers.

CONCLUSIONS

Reduced TGR5 levels in BECs from patients with PSC and Abcb4^-/- mice promote development of a reactive BEC phenotype, aggravate biliary injury and thus contribute to the pathogenesis of sclerosing cholangitis. Restoration of biliary TGR5-expression levels represents a previously unknown mechanism of action of norUDCA.

LAY SUMMARY

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease-associated with progressive inflammation of the bile duct, leading to fibrosis and end-stage liver disease. Bile acid (BA) toxicity may contribute to the development and disease progression of PSC. TGR5 is a membrane-bound receptor for BAs, which is found on bile ducts and protects bile ducts from BA toxicity. In this study, we show that TGR5 levels were reduced in bile ducts from PSC livers and in bile ducts from a genetic mouse model of PSC. Our investigations indicate that lower levels of TGR5 in bile ducts may contribute to PSC development and progression. Furthermore, treatment with norUDCA, a drug currently being tested in a phase III trial for PSC, restored TGR5 levels in biliary epithelial cells.

Gallbladder Interleukins in Children with Calculous Cholecystitis

Calculous cholecystitis connects to inflammation and various complications. It is a common disease in the paediatric population, yet it is still uncertain how inflammation factors are involved in its morphopathogenesis. Twenty calculous cholecystitis surgery tissue samples were obtained from 20 children. As a control, seven unaffected gallbladders were used. Tissues were immunohistochemically stained for IL-1α, IL-4, IL-6, IL-7, IL-8, IL-10, and IL-17A, and the slides were inspected by light microscopy. To evaluate statistical differences and correlations between interleukins, Mann-Whitney U and Spearman's tests were used. Statistically significant difference between patient and control gallbladder epithelium was for IL-1α and IL-17A, but connective tissue-IL-1α, IL-4, IL-6, IL-7, IL-8, and IL-17A positive structures. A strong positive correlation in patients was detected between epithelial IL-1α and IL-1α in connective tissue, epithelial IL-6 and IL-7, IL-6 and IL-17A, IL-7 and IL-10, IL-7 and IL-17A, as well as between IL-6 and IL-7, IL-7 and IL-10 in connective tissue. The increase of IL-1α, IL-4, IL-6, IL-7, IL-8 and IL-17A positive structures suggests their role in the morphopathogenesis of calculous cholecystitis. The correlations between interleukins in epithelium and in connective tissues prove that the epithelial barrier function and inflammatory response in deeper layers are sustained through intercellular signalling pathways.

A biliary immune landscape map of primary sclerosing cholangitis reveals a dominant network of neutrophils and tissue-resident T cells

The human biliary system, a mucosal barrier tissue connecting the liver and intestine, is an organ often affected by serious inflammatory and malignant diseases. Although these diseases are linked to immunological processes, the biliary system represents an unexplored immunological niche. By combining endoscopy-guided sampling of the biliary tree with a high-dimensional analysis approach, comprehensive mapping of the human biliary immunological landscape in patients with primary sclerosing cholangitis (PSC), a severe biliary inflammatory disease, was conducted. Major differences in immune cell composition in bile ducts compared to blood were revealed. Furthermore, biliary inflammation in patients with PSC was characterized by high presence of neutrophils and T cells as compared to control individuals without PSC. The biliary T cells displayed a CD103⁺CD69⁺ effector memory phenotype, a combined gut and liver homing profile, and produced interleukin-17 (IL-17) and IL-22. Biliary neutrophil infiltration in PSC associated with CXCL8, possibly produced by resident T cells, and CXCL16 was linked to the enrichment of T cells. This study uncovers the immunological niche of human bile ducts, defines a local immune network between neutrophils and biliary-resident T cells in PSC, and provides a resource for future studies of the immune responses in biliary disorders.

Concentration of Gallbladder Phosphatidylcholine in Cholangiopathies: A Phosphorus-31 Magnetic Resonance Spectroscopy Pilot Study

BACKGROUND

Biliary phosphatidylcholine (PtdC) concentration plays a role in the pathogenesis of bile duct diseases. In vivo phosphorus-31 magnetic resonance spectroscopy (³¹ P-MRS) at 7 T offers the possibility to assess this concentration noninvasively with high spectral resolution and signal intensity.

PURPOSE

Comparison of PtdC levels of cholangiopathic patient groups to a control group using a measured T₁ relaxation time of PtdC in healthy subjects.

STUDY TYPE

Case control.

SUBJECTS

Two patient groups with primary sclerosing cholangitis (PSC, 2f/3 m; age: 43 ± 7 years) and primary biliary cholangitis (PBC, 4f/2 m; age: 57 ± 6 years), and a healthy control group (CON, 2f/3 m; age: 38 ± 7 years). Ten healthy subjects for the assessment of the T₁ relaxation time of PtdC.

FIELD STRENGTH/SEQUENCE

A 3D phase-encoded pulse-acquire ³¹ P-MRSI sequence for PtdC quantification and a 1D image-selected in vivo ³¹ P spectroscopy for T₁ estimation at 7 T, and a T2-weighted half-Fourier single-shot turbo spin echo MRI sequence for volumetry at 3 T.

ASSESSMENT

Calculation of gallbladder volumes and PtdC concentration in groups using hepatic gamma-adenosine triphosphate signal as an internal reference and correction for insufficient relaxation of PtdC with a T₁ value assessed in healthy subjects.

STATISTICAL TESTS

Group comparison of PtdC content and gallbladder volumes of the PSC/PBC and CON group using Student's t-tests with a significance level of 5%.

RESULTS

PtdC T₁ value of 357 ± 85 msec in the gallbladder. Significant lower PtdC content for the PSC group, and for the female subgroup of the PBC group compared to the CON group (PSC/CON: 5.74 ± 0.73 mM vs. 9.64 ± 0.97 mM, PBC(f)/CON: 5.77 ± 1.44 mM vs. 9.64 ± 0.97 mM). Significant higher gallbladder volumes of the patient groups compared to the CON group (PSC/CON: 66.3 ± 15.8 mL vs. 20.9 ± 2.2 mL, PBC/CON: 49.8 ± 18.2 mL vs. 20.9 ± 2.2 mL).

DATA CONCLUSION

This study demonstrated the application of a ³¹ P-MRSI protocol for the quantification of PtdC in the human gallbladder at 7 T. Observed differences in PtdC concentration suggest that this metabolite could serve as a biomarker for specific hepatobiliary disorders.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 3.

The Gut-Liver Axis in Cholestatic Liver Diseases

The gut-liver axis describes the physiological interplay between the gut and the liver and has important implications for the maintenance of health. Disruptions of this equilibrium are an important factor in the evolution and progression of many liver diseases. The composition of the gut microbiome, the gut barrier, bacterial translocation, and bile acid metabolism are the key features of this cycle. Chronic cholestatic liver diseases include primary sclerosing cholangitis, the generic term secondary sclerosing cholangitis implying the disease secondary sclerosing cholangitis in critically ill patients and primary biliary cirrhosis. Pathophysiology of these diseases is not fully understood but seems to be multifactorial. Knowledge about the alterations of the gut-liver axis influencing the pathogenesis and the outcome of these diseases has considerably increased. Therefore, this review aims to describe the function of the healthy gut-liver axis and to sum up the pathological changes in these cholestatic liver diseases. The review compromises the actual level of knowledge about the gut microbiome (including the mycobiome and the virome), the gut barrier and the consequences of increased gut permeability, the effects of bacterial translocation, and the influence of bile acid composition and pool size in chronic cholestatic liver diseases. Furthermore, therapeutic implications and future scientific objectives are outlined.

A Fibrosis-Independent Hepatic Transcriptomic Signature Identifies Drivers of Disease Progression in Primary Sclerosing Cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a heterogeneous cholangiopathy characterized by progressive biliary fibrosis. RNA sequencing of liver tissue from patients with PSC (n = 74) enrolled in a 96-week clinical trial was performed to identify associations between biological pathways that were independent of fibrosis and clinical events.

APPROACH AND RESULTS

The effect of fibrosis was subtracted from gene expression using a computational approach. The fibrosis-adjusted gene expression patterns were associated with time to first PSC-related clinical event (e.g., cholangitis, hepatic decompensation), and differential expression based on risk groups and Ingenuity Pathway Analysis were performed. Baseline demographic data were representative of PSC: median age 48 years, 71% male, 49% with inflammatory bowel disease, and 44% with bridging fibrosis or cirrhosis. The first principle component (PC1) of RNA-sequencing data accounted for 18% of variance and correlated with fibrosis stage (ρ = -0.80; P < 0.001). After removing the effect of fibrosis-related genes, the first principle component was not associated with fibrosis (ρ = -0.19; P = 0.11), and a semisupervised clustering approach identified two distinct patient clusters with differential risk of time to first PSC-related event (P < 0.0001). The two groups had similar fibrosis stage, hepatic collagen content, and α-smooth muscle actin expression by morphometry, Enhanced Liver Fibrosis score, and serum liver biochemistry, bile acids, and IL-8 (all P > 0.05). The top pathways identified by Ingenuity Pathway Analysis were eukaryotic translation inhibition factor 2 (eIF2) signaling and regulation of eIF4/p70S6K signaling. Genes involved in the unfolded protein response, activating transcription factor 6 (ATF6) and eIF2, were differentially expressed between the PSC clusters (down-regulated in the high-risk group by log-fold changes of -0.18 [P = 0.02] and -0.16 [P = 0.02], respectively). Clinical events were enriched in the high-risk versus low-risk group (38% [12/32] vs. 2.4% [1/42], P < 0.0001).

CONCLUSIONS

Removing the contribution of fibrosis-related pathways uncovered alterations in the unfolded protein response, which were associated with liver-related complications in PSC.

Fenofibrate Improves Liver Function and Reduces the Toxicity of the Bile Acid Pool in Patients With Primary Biliary Cholangitis and Primary Sclerosing Cholangitis Who Are Partial Responders to Ursodiol

Cholestatic liver diseases result in the hepatic retention of bile acids, causing subsequent liver toxicity. Peroxisome proliferator-activated receptor alpha (PPARα) regulates bile acid metabolism. In this retrospective observational study, we assessed the effects of fenofibrate (a PPARα agonist) therapy on bile acid metabolism when given to patients with primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) who have had an incomplete response to Ursodiol monotherapy. When fenofibrate was added to Ursodiol therapy there was a significant reduction and in some cases normalization of serum alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase abnormalities, as well as pro-inflammatory cytokines. Combination fenofibrate treatment also reduced 7α-hydroxy-4-cholesten-3-one (C4), the bile acid precursor, as well as total, primary, and conjugated bile acids. In addition, principal components analysis and heatmap analysis show that bile acid metabolites trended closer to that of healthy control subjects. These favorable effects of fenofibrate on bile acid metabolism may contribute to its beneficial clinical effects in patients with PBC and PSC experiencing a subtherapeutic response to Ursodiol monotherapy.

Methylation signatures in peripheral blood are associated with marked age acceleration and disease progression in patients with primary sclerosing cholangitis

Background & Aims

A DNA methylation (DNAm) signature derived from 353 CpG sites (the Horvath clock) has been proposed as an epigenetic measure of chronological and biological age. This epigenetic signature is accelerated in diverse tissue types in various disorders, including non-alcoholic steatohepatitis, and is associated with mortality. Here, we assayed whole blood DNAm to explore age acceleration in patients with primary sclerosing cholangitis (PSC).

Methods

Using the MethylationEPIC BeadChip (850K) array, DNAm signatures in whole blood were analyzed in 36 patients with PSC enrolled in a 96-week trial of simtuzumab (Ishak F0-1, n = 13; F5-6, n = 23). Age acceleration was calculated as the difference between DNAm age and chronological age. Comparisons between patients with high and low age acceleration (≥ vs. < the median) were made and Cox regression evaluated the association between age acceleration and PSC-related clinical events (e.g. decompensation, cholangitis, transplantation).

Results

Age acceleration was significantly higher in patients with PSC compared to a healthy reference cohort (median, 11.1 years, p <2.2 × 10^-16). In PSC, demographics, presence of inflammatory bowel disease, and ursodeoxycholic acid use were similar between patients with low and high age acceleration. However, patients with high age acceleration had increased serum alkaline phosphatase, gamma glutamyltransferase, alanine aminotransferase, enhanced liver fibrosis test scores, and greater hepatic collagen and α-smooth muscle actin expression on liver biopsy (all p <0.05). Moreover, patients with high age acceleration had an increased prevalence of cirrhosis (89% vs. 39%; p = 0.006) and greater likelihood of PSC-related events (hazard ratio 4.19; 95% CI 1.15–15.24).

Conclusion

This analysis of blood DNAm profiles suggests that compared with healthy controls, patients with PSC – particularly those with cirrhosis - exhibit significant acceleration of epigenetic age. Future studies are required to evaluate the prognostic implications and effect of therapies on global methylation patterns and age acceleration in PSC.

Lay summary

An epigenetic clock based on DNA methylation has been proposed as a marker of age. In liver diseases such as non-alcoholic steatohepatitis, age acceleration based on this epigenetic clock has been observed. Herein, we show that patients with primary sclerosing cholangitis have marked age acceleration, which is further accentuated by worsening fibrosis. This measure of age acceleration could be a useful marker for prognostication or risk stratification in primary sclerosing cholangitis.

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A peripheral blood DNA methylation (DNAm) score identifies age acceleration in PSC patients vs. healthy controls.

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PSC patients with high age acceleration had significantly more PSC-related events than those with low age acceleration.

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These findings may enable stratification of at-risk PSC patients based on a DNAm score from peripheral blood.

Activated cholangiocytes release macrophage-polarizing extracellular vesicles bearing the DAMP S100A11

In mouse models of biliary tract diseases, macrophages are recruited to the periductal milieu and promote injury and cholestasis. Although cell necrosis with release of biomolecules termed damage-associated molecular patterns (DAMPs) promotes recruitment and activation of macrophages, necrosis was not observed in these studies. Because extracellular vesicles (EVs) are important in cell-to-cell communication, we postulated that activated cholangiocytes may release EVs containing DAMPs as cargo. Both the human (NHC) and mouse cholangiocyte (603B) cell lines display constitutive activation with mRNA expression of chemokines. Proteomic analysis revealed that EVs from both cell lines contained the DAMP S100A11, a ligand for the receptor for advanced glycation end products (RAGE). Bone marrow-derived macrophages (BMDM) incubated with EVs derived from the mouse 603B cell line increased mRNA expression of proinflammatory cytokines. Genetic or pharmacologic inhibition of RAGE reduced BMDM expression of proinflammatory cytokines treated with EVs. RAGE signaling resulted in activation of the canonical NF-κB pathway, and consistently, proinflammatory cytokine expression was blunted by the IKKα/β inhibitor TPCA-1 in BMDM incubated with EVs. We also demonstrated that primary mouse cholangiocyte-derived organoids express chemokines indicating cholangiocyte activation, release EVs containing S100A11, and stimulate proinflammatory cytokine expression in BMDM by a RAGE-dependent pathway. In conclusion, these observations identify a non-cell death mechanism for cellular release of DAMPs by activated cholangiocytes, namely by releasing DAMPs as EV cargo. These data also suggest RAGE inhibitors may be salutary in macrophage-associated inflammatory diseases of the bile ducts.

Bile-Derived Organoids From Patients With Primary Sclerosing Cholangitis Recapitulate Their Inflammatory Immune Profile

Primary sclerosing cholangitis (PSC) is a heterogeneous and progressive fibroinflammatory cholangiopathy with no known etiology or effective treatment. Studies of PSC are limited due to difficulty in accessing the cholangiocyte, the small percentage of these cells in the liver, instability of in vitro culture systems, and reliance on samples from end-stage disease. Here, we demonstrate that stem cells can be isolated from the bile of PSC patients undergoing endoscopic retrograde cholangiopancreatography earlier in their clinical course and maintained long term in vitro as three-dimensional (3D) organoids that express a biliary genetic phenotype. Additionally, bile-derived organoids (BDOs) can be biobanked and samples obtained longitudinally over the course of the disease. These BDOs express known cholangiocyte markers including gamma glutamyl transferase, cytokeratin 19, epithelial cellular adhesion molecule, cystic fibrosis transmembrane conductance regulator, and anion exchanger 2. RNA sequence analysis identified 39 genes whose expression differed in organoids from PSC patients compared to non-PSC controls, including human leukocyte antigen DM alpha chain and chemokine (C-C motif) ligand 20 (CCL20), immune-related genes previously described in genome-wide association studies of PSC. Incubation of these BDOs with interleukin 17A or tumor necrosis factor alpha led to an immune-reactive phenotype with a significant increase in secretion of proinflammatory mediators, including CCL20, a T-cell chemoattractant. Conclusion: This study demonstrates that bile can be used as a source of biliary-like cells that can be maintained long term in vitro as 3D organoids; these BDOs retain features of cholangiopathies, including the ability to react to inflammatory stimuli by secreting chemokines and propagating an immune-reactive phenotype reflective of the pathogenesis of these diseases; thus, BDOs represent a platform for the study of the pathogenesis and therapy of cholangiopathies, particularly PSC.

Autotaxin activity predicts transplant-free survival in primary sclerosing cholangitis

Autotaxin has been associated with liver disease severity and transplant-free survival. This study aimed to validate autotaxin as a biomarker in two cohorts of Norwegian large-duct PSC patients, one discovery panel (n = 165) and one validation panel (n = 87). Serum activity of autotaxin was measured in diluted sera by a fluorometric enzymatic assay. Patients reaching an end-point, liver transplantation or death, (discovery panel: n = 118 [71.5%]; validation panel: n = 35 [40.2%]), showed higher autotaxin activity compared with the other patients, P < 0.001 and P = 0.004, respectively. Kaplan-Meier survival analyses showed a strong association between increasing autotaxin activity and shorter liver transplant-free survival (discovery panel: P < 0.001, validation panel: P = 0.001). There was no relationship between autotaxin activity and the presence of inflammatory bowel disease or occurrence of hepatobiliary malignancy. In a multivariable analysis, high autotaxin activity was associated with an increased risk of liver transplantation or death (hazard ratio 2.03 (95% confidence interval 1.21–3.40), P < 0.01), independent from Mayo risk score, an in-house enhanced liver fibrosis score and interleukin-8 in serum. In conclusion, increased serum autotaxin activity is associated with reduced liver transplant-free survival independent from Mayo risk score and markers of inflammation and fibrosis.

Cholangiocyte pathobiology

Cholangiocytes, the epithelial cells lining the intrahepatic and extrahepatic bile ducts, are highly specialized cells residing in a complex anatomic niche where they participate in bile production and homeostasis. Cholangiocytes are damaged in a variety of human diseases termed cholangiopathies, often causing advanced liver failure. The regulation of cholangiocyte transport properties is increasingly understood, as is their anatomical and functional heterogeneity along the biliary tract. Furthermore, cholangiocytes are pivotal in liver regeneration, especially when hepatocyte regeneration is compromised. The role of cholangiocytes in innate and adaptive immune responses, a critical subject relevant to immune-mediated cholangiopathies, is also emerging. Finally, reactive ductular cells are present in many cholestatic and other liver diseases. In chronic disease states, this repair response contributes to liver inflammation, fibrosis and carcinogenesis and is a subject of intense investigation. This Review highlights advances in cholangiocyte research, especially their role in development and liver regeneration, their functional and biochemical heterogeneity, their activation and involvement in inflammation and fibrosis and their engagement with the immune system. We aim to focus further attention on cholangiocyte pathobiology and the search for new disease-modifying therapies targeting the cholangiopathies.

Treatment of primary sclerosing cholangitis in children

Primary sclerosing cholangitis (PSC) is a rare disease of stricturing and destruction of the biliary tree with a complex genetic and environmental etiology. Most patients have co-occurring inflammatory bowel disease. Children generally present with uncomplicated disease, but undergo a variable progression to end-stage liver disease. Within ten years of diagnosis, 50% of children will develop clinical complications including 30% requiring liver transplantation. Cholangiocarcinoma is a rare but serious complication affecting 1% of children. Ursodeoxycholic acid and oral vancomycin therapy used widely in children as medical therapy, and may be effective in a subset of patients. Gamma glutamyltransferase is a potential surrogate endpoint for disease activity, with improved survival in patients who achieve a normal value. Endoscopic retrograde cholangiopancreatography is a necessary adjunct to medical therapy to evaluate mass lesions or dominant strictures for malignancy, and also to relieve biliary obstruction. Liver transplantation remains the only option for patients who progress to end-stage liver disease. We review special considerations for patients before and after transplant, and in patients with inflammatory bowel disease. There is presently no published treatment algorithm or guideline for the management of children with PSC. We review the evidence for drug efficacy, dosing, duration of therapy, and treatment targets in PSC, and provide a framework for endoscopic and medical management of this complex problem.

Metabolomic Profiling of Portal Blood and Bile Reveals Metabolic Signatures of Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is a pathogenically complex, chronic, fibroinflammatory disorder of the bile ducts without known etiology or effective pharmacotherapy. Emerging in vitro and in vivo evidence support fundamental pathophysiologic mechanisms in PSC centered on enterohepatic circulation. To date, no studies have specifically interrogated the chemical footprint of enterohepatic circulation in PSC. Herein, we evaluated the metabolome and lipidome of portal venous blood and bile obtained at the time of liver transplantation in patients with PSC (n = 7) as compared to individuals with noncholestatic, end-stage liver disease (viral, metabolic, etc. (disease control, DC, n = 19)) and to nondisease controls (NC, living donors, n = 12). Global metabolomic and lipidomic profiling was performed on serum derived from portal venous blood (portal serum) and bile using ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and differential mobility spectroscopy-mass spectroscopy (DMS-MS; complex lipid platform). The Mann⁻Whitney U test was used to identify metabolites that significantly differed between groups. Principal-component analysis (PCA) showed significant separation of both PSC and DC from NC for both portal serum and bile. Metabolite set enrichment analysis of portal serum and bile demonstrated that the liver-disease cohorts (PSC and DC) exhibited similar enrichment in several metabolite categories compared to NC. Interestingly, the bile in PSC was uniquely enriched for dipeptide and polyamine metabolites. Finally, analysis of patient-matched portal serum and biliary metabolome revealed that these biological fluids were more homogeneous in PSC than in DC or NC, suggesting aberrant bile formation and enterohepatic circulation. In summary, PSC and DC patients exhibited alterations in several metabolites in portal serum and bile, while PSC patients exhibited a unique bile metabolome. These specific alterations in PSC are amenable to hypothesis testing and, potentially, therapeutic pharmacologic manipulation.

Primary sclerosing cholangitis - a comprehensive review

Primary sclerosing cholangitis (PSC) is a rare disorder characterised by multi-focal bile duct strictures and progressive liver disease. Inflammatory bowel disease is usually present and there is a high risk of cholangiocarcinoma and colorectal cancer. Most patients ultimately require liver transplantation, after which disease recurrence may occur. With limited therapeutic options and a lack of proven surveillance strategies, patients currently have significant unmet needs. In the present seminar, we provide a comprehensive review of the status of the field. We emphasise developments related to patient stratification and disease behaviour, and provide an overview of management options from a practical, patient-centered perspective. We survey advances made in the understanding of PSC pathogenesis and summarise the ongoing efforts to develop an effective therapy based on these insights.

Pathological features of primary sclerosing cholangitis identified by bile proteomic analysis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown origin. Previous bile proteomic analyses in patients with PSC have revealed changes in disease activity specific to malignant transformation. In this study, we established a reference bile duct-derived bile proteome for PSC that can be used to evaluate biliary pathophysiology. Samples were collected from patients with PSC or with choledocholithiasis (control) (n=6 each). Furthermore, patients with PSC-associated cholangiocarcinoma (CC) and with CC without concomitant PSC were analyzed. None of the patients showed signs of inflammation or infection based on clinical and laboratory examinations. Proteins overexpressed in patients with PSC relative to control patients were detected by two-dimensional difference gel electrophoresis and identified by liquid chromatography-tandem mass spectrometry. Functional proteomic analysis was performed using STRING software. A total of 101 proteins were overexpressed in the bile fluid of patients with PSC but not in those of controls; the majority of these were predicted to be intracellular and related to the ribosomal and proteasomal pathways. On the other hand, 91 proteins were found only in the bile fluid of controls; most were derived from the extracellular space and were linked to cell adhesion, the complement system, and the coagulation cascade. In addition, proteins associated with inflammation and the innate immune response-e.g., cluster of differentiation 14, annexin-2, and components of the complement system-were upregulated in PSC. The most prominent pathways in PSC/CC-patients were inflammation associated cytokine and chemokine pathways, whereas in CC-patients the Wnt signaling pathway was upregulated. In PSC/CC-patients DIGE-analysis revealed biliary CD14 and Annexin-4 expression, among others, as the most prominent protein that discriminates between both cohorts. Thus, the bile-duct bile proteome of patients with PSC shows disease-specific changes associated with inflammation and the innate immune response even in the absence of obvious clinical signs of cholangitis, malignancy, or inflammation. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni and Peter Jansen.

Biliary bile acids in hepatobiliary injury - What is the link?

The main trigger for liver injury in acquired cholestatic liver disease remains unclear. However, the accumulation of bile acids (BAs) undoubtedly plays a role. Recent progress in deciphering the pathomechanisms of inborn cholestatic liver diseases, decoding mechanisms of BA-induced cell death, and generating modern BA-derived drugs has improved the understanding of the regulation of BA synthesis and transport. Now is the appropriate time to reassess current knowledge about the specific role of BAs in hepatobiliary injury.

Emerging concepts in biliary repair and fibrosis

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

Pathophysiologic implications of innate immunity and autoinflammation in the biliary epithelium

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

Mechanisms of bile acid mediated inflammation in the liver

Bile acids are synthesized in the liver and are the major component in bile. Impaired bile flow leads to cholestasis that is characterized by elevated levels of bile acid in the liver and serum, followed by hepatocyte and biliary injury. Although the causes of cholestasis have been extensively studied, the molecular mechanisms as to how bile acids initiate liver injury remain controversial. In this chapter, we summarize recent advances in the pathogenesis of bile acid induced liver injury. These include bile acid signaling pathways in hepatocytes as well as the response of cholangiocytes and innate immune cells in the liver in both patients with cholestasis and cholestatic animal models. We focus on how bile acids trigger the production of molecular mediators of neutrophil recruitment and the role of the inflammatory response in this pathological process. These advances point to a number of novel targets where drugs might be judged to be effective therapies for cholestatic liver injury.

Novel serum and bile protein markers predict primary sclerosing cholangitis disease severity and prognosis

BACKGROUND & AIMS

Prognostic biomarkers are lacking in primary sclerosing cholangitis, hampering patient care and the development of therapy. We aimed to identify novel protein biomarkers of disease severity and prognosis in primary sclerosing cholangitis (PSC).

METHODS

Using a bead-based array targeting 63 proteins, we profiled a derivation panel of Norwegian endoscopic retrograde cholangiography bile samples (55 PSC, 20 disease controls) and a Finnish validation panel (34 PSC, 10 disease controls). Selected identified proteins were measured in serum from two Norwegian PSC cohorts (n=167 [1992-2006] and n=138 [2008-2012]), inflammatory bowel disease (n=96) and healthy controls (n=100).

RESULTS

In the bile derivation panel, the levels of 14 proteins were different between PSC patients and controls (p<0.05); all were confirmed in the validation panel. Twenty-four proteins in the bile derivation panel were significantly (p<0.05) different between PSC patients with mild compared to severe cholangiographic changes (modified Amsterdam criteria); this was replicated for 18 proteins in the validation panel. Interleukin (IL)-8, matrix metallopeptidase (MMP)9/lipocalin (LCN)2-complex, S100A8/9, S100A12 and tryptophan hydroxylase (TPH)2 in the bile were associated with both a PSC diagnosis and grade of cholangiographic changes. Stratifying PSC patients according to tertiles of serum IL-8, but not MMP9/LCN2 and S100A12, provided excellent discrimination for transplant-free survival both in the serum derivation and validation cohort. Furthermore, IL-8 was associated with transplant-free survival in multivariable analyses in both serum panels independently of age and disease duration, indicating an independent influence on PSC progression. However, the Enhanced Liver Fibrosis (ELF®) test and Mayo risk score proved to be stronger predictors of transplant-free survival.

CONCLUSIONS

Based on assaying of biliary proteins, we have identified novel biliary and serum biomarkers as indicators of severity and prognosis in PSC.

LAY SUMMARY

Prognostic biomarkers are lacking in primary sclerosing cholangitis, hampering patient care and the development of therapy. We have identified inflammatory proteins including calprotectin and IL-8 as important indicators of disease severity and prognosis in bile and serum from patients with primary sclerosing cholangitis.

The ascending pathophysiology of cholestatic liver disease

In this review we develop the argument that cholestatic liver diseases, particularly primary biliary cholangitis and primary sclerosing cholangitis (PSC), evolve over time with anatomically an ascending course of the disease process. The first and early lesions are in "downstream" bile ducts. This eventually leads to cholestasis, and this causes bile salt (BS)-mediated toxic injury of the "upstream" liver parenchyma. BS are toxic in high concentration. These concentrations are present in the canalicular network, bile ducts, and gallbladder. Leakage of bile from this network and ducts could be an important driver of toxicity. The liver has a great capacity to adapt to cholestasis, and this may contribute to a variable symptom-poor interval that is often observed. Current trials with drugs that target BS toxicity are effective in only about 50%-60% of primary biliary cholangitis patients, with no effective therapy in PSC. This motivated us to develop and propose a new view on the pathophysiology of primary biliary cholangitis and PSC in the hope that these new drugs can be used more effectively. These views may lead to better stratification of these diseases and to recommendations on a more "tailored" use of the new therapeutic agents that are currently tested in clinical trials. Apical sodium-dependent BS transporter inhibitors that reduce intestinal BS absorption lower the BS load and are best used in cholestatic patients. The effectiveness of BS synthesis-suppressing drugs, such as farnesoid X receptor agonists, is greatest when optimal adaptation is not yet established. By the time cytochrome P450 7A1 expression is reduced these drugs may be less effective. Anti-inflammatory agents are probably most effective in early disease, while drugs that antagonize BS toxicity, such as ursodeoxycholic acid and nor-ursodeoxycholic acid, may be effective at all disease stages. Endoscopic stenting in PSC should be reserved for situations of intercurrent cholestasis and cholangitis, not for cholestasis in end-stage disease. These are arguments to consider a step-wise pathophysiology for these diseases, with therapy adjusted to disease stage. An obstacle in such an approach is that disease stage-defining biomarkers are still lacking. This review is meant to serve as a call to prioritize the development of biomarkers that help to obtain a better stratification of these diseases. (Hepatology 2017;65:722-738).

Impaired Hepatic Adaptation to Chronic Cholestasis induced by Primary Sclerosing Cholangitis

Pathogenesis of primary sclerosing cholangitis (PSC) may involve impaired bile acid (BA) homeostasis. We analyzed expressions of factors mediating enterohepatic circulation of BA using ileal and colonic (ascending and sigmoid) biopsies obtained from patients with PSC with and without ulcerative colitis (UC) and explanted PSC livers. Two-fold increase of BA-activated farnesoid X receptor (FXR) protein levels were seen in ascending and sigmoid colon of PSC patients with correspondingly decreased apical sodium-dependent BA transporter (ASBT) gene expression. This was associated with increased OSTβ protein levels in each part of analyzed gut. An intestinal fibroblast growth factor (FGF19) protein expression was significantly enhanced in ascending colon. Despite increased hepatic nuclear receptors (FXR, CAR, SHP), and FGF19, neither CYP7A1 suppression nor CYP3A4 induction were observed. The lack of negative regulation of BA synthesis may be accountable for lower levels of cholesterol observed in PSC in comparison to primary biliary cholangitis (PBC). In conclusion, chronic cholestasis in PSC induces adaptive changes in expression of BA transporters and FXR in the intestine. However hepatic impairment of expected in chronic cholestasis downregulation of CYP7A1 and upregulation of CYP3A4 may promote BA-induced liver injury in PSC.