Blockade of forkhead box protein O1 signaling alleviates primary sclerosing cholangitis-induced sarcopenia in mice model

AIMS

Primary sclerosing cholangitis (PSC) is a cholestatic liver disease that affects the hepatic bile ducts, leading to hepatic inflammation and fibrosis. PSC can also impact skeletal muscle through the muscle-liver axis, resulting in sarcopenia, a complication characterized by a generalized loss of muscle mass and strength. The underlying mechanisms and therapy of PSC-induced sarcopenia are not well understood, but one potential regulator is the transcription factor forkhead box protein O1 (FOXO1), which is involved in the ubiquitin proteasome system. Thus, the aim of this study is to assess the pharmacological potential of FOXO1 inhibition for treating PSC-induced sarcopenia.

MATERIALS AND METHODS

To establish diet-induced PSC model, we provided mice with a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet for 4 weeks. Mice were intramuscularly injected with AS1842856 (AS), a FOXO1 inhibitor, at a dose of 3.5 mg/kg twice a week for last two weeks. C2C12 myotubes with cholic acid (CA) or deoxycholic acid (DCA) were treated with AS.

KEY FINDINGS

We observed a decrease in muscle size and performance in DDC-fed mice with upregulated expression of FOXO1 and E3 ligases such as ATROGIN1 and MuRF1. We found that myotube diameter and MyHC protein level were decreased by CA or DCA in C2C12 myotubes, but treatment of AS reversed these reductions. We observed that intramuscular injection of AS effectively mitigates DDC diet-induced sarcopenia in a rodent PSC model.

SIGNIFICANCE

Our study suggests that a FOXO1 inhibitor could be a potential leading therapeutic drug for relieving PSC-induced sarcopenia.

Gut Pathobiont-Derived Outer Membrane Vesicles Drive Liver Inflammation and Fibrosis in Primary Sclerosing Cholangitis-Associated Inflammatory Bowel Disease

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC), often associated with inflammatory bowel disease (IBD), presents a multifactorial etiology involving genetic, immunologic, and environmental factors. Gut dysbiosis and bacterial translocation have been implicated in PSC-IBD, yet the precise mechanisms underlying their pathogenesis remain elusive. Here, we describe the role of gut pathobionts in promoting liver inflammation and fibrosis due to the release of bacterial outer membrane vesicles (OMVs).

METHODS

Preclinical mouse models in addition to ductal organoids were used to acquire mechanistic data. A proof-of-concept study including serum and liver biopsies of a patient cohort of PSC (n = 22), PSC-IBD (n = 45), and control individuals (n = 27) was performed to detect OMVs in the systemic circulation and liver.

RESULTS

In both preclinical model systems and in patients with PSC-IBD, the translocation of OMVs to the liver correlated with enhanced bacterial sensing and accumulation of the NLRP3 inflammasome. Using ductal organoids, we were able to precisely attribute the pro-inflammatory and pro-fibrogenic properties of OMVs to signaling pathways dependent on Toll-like receptor 4 and NLRP3-gasdermin-D. The immunostimulatory potential of OMVs could be confirmed in macrophages and hepatic stellate cells. Furthermore, when we administered gut pathobiont-derived OMVs to Mdr2-/- mice, we observed a significant enhancement in liver inflammation and fibrosis. In a translational approach, we substantiated the presence of OMVs in the systemic circulation and hepatic regions of severe fibrosis using a PSC-IBD patient cohort.

CONCLUSIONS

This study demonstrates the contribution of gut pathobionts in releasing OMVs that traverse the mucosal barrier and, thus, promote liver inflammation and fibrosis in PSC-IBD. OMVs might represent a critical new environmental factor that interacts with other disease factors to cause inflammation and thus define potential new targets for fibrosis therapy.

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.

Antagonistic effects of the cytotoxic molecules granzyme B and TRAIL in the immunopathogenesis of sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease characterized by biliary inflammation and fibrosis. We showed an elevated interferon γ response in patients with primary sclerosing cholangitis and in multidrug resistance protein 2-deficient ( Mdr2-/- ) mice developing sclerosing cholangitis. Interferon γ induced expression of the cytotoxic molecules granzyme B (GzmB) and TRAIL in hepatic lymphocytes and mediated liver fibrosis in sclerosing cholangitis.

APPROACH AND RESULTS

In patient samples and Mdr2-/- mice, we identified lymphocyte clusters with a cytotoxic gene expression profile using single-cell RNA-seq and cellular indexing of transcriptomes and epitopes by sequencing analyses combined with multi-parameter flow cytometry. CD8 + T cells and NK cells showed increased expression of GzmB and TRAIL in sclerosing cholangitis. Depletion of CD8 + T cells ameliorated disease severity in Mdr2-/- mice. By using Mdr2-/- × Gzmb-/- and Mdr2-/- × Tnfsf10-/- mice, we investigated the significance of GzmB and TRAIL for disease progression in sclerosing cholangitis. Interestingly, the lack of GzmB resulted in reduced cholangiocyte apoptosis, liver injury, and fibrosis. In contrast, sclerosing cholangitis was aggravated in the absence of TRAIL. This correlated with elevated GzmB and interferon γ expression by CD8 + T cells and NK cells enhanced T-cell survival, and increased apoptosis and expansion of cholangiocytes.

CONCLUSIONS

GzmB induces apoptosis and fibrosis in sclerosing cholangitis, whereas TRAIL regulates inflammatory and cytotoxic immune responses, subsequently leading to reduced liver injury and fibrosis.

Idiopathic hyalinizing fibrosclerosis: A systemic steroid-resistant condition distinct from IgG4-related disease

Since the concept of IgG4-related disease (IgG4-RD) was proposed, that diagnosis has been considered in idiopathic fibroinflammatory diseases in various organs, particularly in cases with multi-organ involvement. We have recently encountered three cases of fibrosing disease of uncertain etiology with shared microscopic appearances. Case 1 (56-year-old man) had an irregular mass at the base of mesentery. Case 2 (29-year-old woman) presented with obstructive jaundice due to an ill-defined mass at the hepatic hilum and two lung nodules. Case 3 (53-year-old man) had multiple solid nodules in the mediastinum, peritoneum, retroperitoneum, and mesentery; he also had diffuse irregular narrowing of the intra- and extra-hepatic bile ducts in keeping with sclerosing cholangitis. Serum IgG4 concentrations were not elevated. Biopsies from the nodular lesions showed extensive hyalinizing fibrosis with an only focal lymphoplasmacytic infiltrate. Thick collagenous bundles are arranged in an irregular or partly whorl pattern. Typical storiform fibrosis or obliterative phlebitis was not observed. The number of IgG4-positive plasma cells was <10 cells/high-power field; the ratio of IgG4/IgG-positive plasma cells was <30%. After the histological diagnosis of sclerosing mesenteritis, pulmonary hyalinizing granuloma, and mediastinal fibrosis was made, they were treated with a trial of steroids, but none showed a significant response. In conclusion, a hyalinizing fibrotic condition can occur at various anatomical sites. They have shared microscopic findings, and are steroid-resistant. Although the clinical presentation may mimic IgG4-RD, the two conditions are likely distinct. We would propose a diagnostic term of 'idiopathic hyalinizing fibrosclerosis' for this under-recognized, rare, systemic condition.

Increased Active Inflammation in the Colon is Not a Reliable Predictor of an Elevated Risk of Dysplasia in Patients With Primary Sclerosing Cholangitis and Ulcerative Colitis

Although the increased risk of colorectal neoplasia in patients with both primary sclerosing cholangitis (PSC) and ulcerative colitis (UC; termed PSC-UC) is well documented, the mechanism through which concomitant PSC increases the risk of colorectal neoplasia remains unclear. Given that the risk of colorectal neoplasia in UC is positively correlated with increased histologic inflammation, this study sought to investigate whether increased histologic inflammation could be used to stratify the risk of dysplasia development in patients with PSC-UC. Twenty patients with PSC-UC and dysplasia were compared with 30 control patients with PSC-UC who had no history of neoplasia. For each patient, all surveillance biopsies were scored using a 4-point scoring system: (1) no epithelial neutrophils = 0, (2) cryptitis only = 1, (3) cryptitis plus crypt abscess in <50% of crypts = 2, and (4) crypt abscess in ≥50% of crypts, erosion, neutrophilic exudate, and/or ulceration = 3. A score was designated for each biopsy, and both mean and maximum inflammation scores were calculated from all biopsies taken during each colonoscopy. The inflammation burden score was calculated for each surveillance interval by multiplying the average maximum score between each pair of surveillance episodes by the length of the surveillance interval in years. The average scores derived from all colonoscopies for each patient were used to determine the patient's overall mean, maximum, and inflammation burden scores. In both the dysplasia and control groups, the 3 summative inflammation scores were calculated independently for the entire colon, right colon, and left colon. The dysplasia group consisted of 14 (70%) men and 6 (30%) women, with a mean age of 27 years at UC diagnosis and a long history of pancolitis (mean duration: 17 y). A total of 49 dysplastic lesions were detected in the dysplasia group, and 8 (40%) of the 20 patients had multifocal dysplasia. The majority of dysplastic lesions belonged to nonconventional subtypes (n = 28; 57%) and were located in the right colon (n = 37; 76%). Irrespective of the colon segment, there was no significant difference in the 3 summative inflammation scores between the dysplasia and control groups ( P > 0.05). However, in each group, the 3 summative inflammation scores were significantly higher in the right colon than in the left colon ( P < 0.05). In conclusion, patients with PSC-UC exhibit increased histologic inflammation in the right colon compared with the left colon, regardless of the presence of dysplasia. Although this may provide an explanation for the predominance of right-sided colorectal neoplasia in patients with PSC-UC, increased histologic inflammation does not reliably predict an elevated risk of dysplasia in patients with PSC-UC. These findings reinforce the current recommendation for annual endoscopic surveillance for all patients with PSC-UC, irrespective of the extent and severity of inflammation.

The new definition of dominant stricture in primary sclerosing cholangitis: Prevalence and clinical significance

BACKGROUND AND AIMS

A new definition of dominant stricture (NDS) has recently been defined for patients with primary sclerosing cholangitis (PSC). Prevalence and clinical features of this, compared to traditional dominant stricture (TDS), have not been reported.

METHODS

In this single-centre longitudinal prospective cohort study, all PSC patients who underwent endoscopic retrograde cholangiopancreatography (ERCP) between October 2021 and 2022 were recruited. Symptoms of cholestasis, laboratory values (P-alkaline phosphatase, P-Bilirubin), Helsinki PSC-score, brush cytology findings and need for endoscopic therapy (i.e. dilation, stenting) were prospectively collected.

RESULTS

Overall, 228 patients with PSC underwent 248 ERCPs. NDS was detected in 43 (17%; 36 patients) and TDS without NDS (TDS group) was detected in 62 (25%; 58 patients) ERCPs, respectively; in the remaining 143 ERCPs, neither TDS nor NDS was seen (no dominant stricture [NoDS] group). PSC duration (median 8 years) and patient's age did not differ between the three groups; males presented more often with NDS. Patients with NDS were more often symptomatic, had higher cholestatic liver enzymes, advanced bile duct disease and markers of biliary inflammation (p < .001). Patients with NDS needed dilation (81%) and stenting (21%) more often than the TDS group (60% and 5%, respectively). Dysplasia in brush cytology was more common in TDS (5%) and NDS (9%) than in NoDS (3%) groups (p = .04), but did not differ between TDS and NDS groups.

CONCLUSIONS

Dominant stricture according to the new definition developed in 17% of PSC patients in our cohort and identifies patients with more advanced disease, biliary inflammation and need of endo-therapy.

Antimicrobial glycoprotein 2 (GP2) in gallstones, bile fluid and peribiliary glands of patients with primary sclerosing cholangitis

BACKGROUND

Glycoprotein-2 (GP2) IgA is a predictor of disease severity in primary sclerosing cholangitis (PSC). We examined GP2's occurrence in the biliary tract, the site of inflammation.

METHODS

GP2 was analyzed using ELISA, immunoblotting, mass spectrometry, and immunohistochemistry. The samples included: 20 bile and 30 serum samples from PSC patients, 23 bile and 11 serum samples from patients with gallstone disease (GD), 15 bile samples from healthy individuals undergoing liver-donation surgery (HILD), 20 extracts of gallstones (GE) obtained during cholecystectomy, and 101 blood-donor sera.

RESULTS

Biliary GP2 concentrations were significantly higher in patients with PSC and GD than in HILD (p < 0.0001). Serum GP2 levels were similar in PSC and GD patients, and controls, but lower than in bile (p < 0.0001). GP2 was detected in all 20 GEs. Mass spectrometry identified GP2 in the bile of 2 randomly selected GD and 2 PSC patients, and in none of 2 HILD samples. GP2 was found in peribiliary glands in 8 out of 12 PSC patients, showing morphological changes in acinar cells, but not in GD-gallbladders.

CONCLUSIONS

GP2 is present in bile of PSC and GD patients. It is synthesized in the peribiliary glands of PSC patients, supporting a pathogenic role for biliary GP2 in PSC.

Immune-related adverse event-associated sclerosing cholangitis due to immune checkpoint inhibitors: imaging findings and treatments

OBJECTIVES

Immune-related adverse event-sclerosing cholangitis caused by treatment with immune checkpoint inhibitors is rare, and the diagnostic criteria and treatment strategy remain unclear. In this study, we confirmed the clinicopathological features of immune-related adverse event-sclerosing cholangitis and clarified its diagnosis and appropriate management.

METHODS

We retrospectively evaluated 10 patients diagnosed with immune-related adverse event-sclerosing cholangitis and identified by electronic database searches.

RESULTS

Blood tests revealed liver dysfunction with a predominance of biliary tract enzymes in all patients; however, jaundice was present in only one patient. Contrast-enhanced computed tomography revealed diffuse hypertrophy of the extrahepatic bile duct wall as the most frequent finding; however, endoscopic retrograde cholangiopancreatography showed various imaging features, such as the pruned-tree appearance of intrahepatic bile ducts, in all patients. Transpapillary bile duct biopsy showed inflammatory cell infiltration using immunostaining, with a predominance of cluster of differentiation 8-positive T cells in 63% of the cases. Initial steroid therapy was effective in two cases. Mycophenolate mofetil and tacrolimus were used in steroid-refractory cases. Although six patients showed improvements, all of the remaining patients died owing to immune-related adverse event-sclerosing cholangitis.

CONCLUSIONS

Various bile duct imaging findings of immune-related adverse event-sclerosing cholangitis were revealed; transpapillary bile duct biopsy may be useful in the diagnosis of immune-related adverse event-sclerosing cholangitis. Despite the combination of multiple immunosuppressive agents, prognosis of immune-related adverse event-sclerosing cholangitis remains poor. Longer follow-up and larger clinical studies are necessary to establish its treatment strategy.

COVID-19-associated secondary sclerosing cholangitis with liver transplantation

We report on two cases of orthotopic liver transplantation (OLTX) due to SARS-Cov2-associated secondary sclerosing cholangitis (SSC) following long-term artificial respiration and extra-corporal membrane oxygenation in intensive care. Under these conditions, SSC is a rapidly progredient biliary disease featuring degenerative cholangiopathy, loss of bile ducts, ductular and parenchymal cholestasis, biliary fibrosis, and finally cirrhosis. Reduced perfusion and oxygenation of the peribiliary plexus, severe concurrent infections, and secondary medico-toxic effects appear to play a crucial role in the pathogenesis of the disease. A direct cytopathic effect of SARS-Cov2 on endothelial cells followed by thrombosis and fibrosing obliteration in all parts of the vascular bed of the liver may enhance the virus-associated liver disease and particularly SSC.

Intergenic risk variant rs56258221 skews the fate of naive CD4+ T cells via miR4464-BACH2 interplay in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an immune-mediated liver disease of unknown pathogenesis, with a high risk to develop cirrhosis and malignancies. Functional dysregulation of T cells and association with genetic polymorphisms in T cell-related genes were previously reported for PSC. Here, we genotyped a representative PSC cohort for several disease-associated risk loci and identified rs56258221 (BACH2/MIR4464) to correlate with not only the peripheral blood T cell immunophenotype but also the functional capacities of naive CD4+ T (CD4+ TN) cells in people with PSC. Mechanistically, rs56258221 leads to an increased expression of miR4464, in turn causing attenuated translation of BACH2, a major gatekeeper of T cell quiescence. Thereby, the fate of CD4+ TN is skewed toward polarization into pro-inflammatory subsets. Clinically, people with PSC carrying rs56258221 show signs of accelerated disease progression. The data presented here highlight the importance of assigning functional outcomes to disease-associated genetic polymorphisms as potential drivers of diseases.

What is the appropriate method of pathological specimen collection for cholangiocarcinoma detection in primary sclerosing cholangitis?

BACKGROUND

In primary sclerosing cholangitis (PSC), it is important to understand the cholangiographic findings suggestive of malignancy, but it is difficult to determine whether cholangiocarcinoma is present due to modifications caused by inflammation. This study aimed to clarify the appropriate method of pathological specimen collection during endoscopic retrograde cholangiopancreatography for surveillance of PSC.

METHODS

A retrospective observational study was performed on 59 patients with PSC. The endpoints were diagnostic performance for benign or malignant on bile cytology and transpapillary bile duct biopsy, cholangiographic findings of biopsied bile ducts, diameters of the strictures and upstream bile ducts, and their differences.

RESULTS

The sensitivity (77.8% vs. 14.3%, P = 0.04), specificity (97.8% vs. 83.0%, P = 0.04), and accuracy (94.5% vs. 74.1%, P = 0.007) were all significantly greater for bile duct biopsy than for bile cytology. All patients with cholangiocarcinoma with bile duct stricture presented with dominant stricture (DS). The diameter of the upstream bile ducts (7.1 (4.2-7.2) mm vs. 2.1 (1.2-4.1) mm, P < 0.001) and the diameter differences (6.6 (3.1-7) mm vs. 1.5 (0.2-3.6) mm, P < 0.001) were significantly greater in the cholangiocarcinoma group than in the noncholangiocarcinoma group with DS. For diameter differences, the optimal cutoff value for the diagnosis of benign or malignant was 5.1 mm (area under the curve = 0.972).

CONCLUSION

Transpapillary bile duct biopsy should be performed via localized DS with upstream dilation for the detection of cholangiocarcinoma in patients with PSC. Especially when the diameter differences are greater than 5 mm, the development of cholangiocarcinoma should be strongly suspected.

Serologic extracellular matrix remodeling markers are related to fibrosis stage and prognosis in a phase 2b trial of simtuzumab in patients with primary sclerosing cholangitis

BACKGROUND

Novel noninvasive predictors of disease severity and prognosis in primary sclerosing cholangitis (PSC) are needed. This study evaluated the ability of extracellular matrix remodeling markers to diagnose fibrosis stage and predict PSC-related fibrosis progression and clinical events.

METHODS

Liver histology and serum markers of collagen formation (propeptide of type III collagen [Pro-C3], propeptide of type IV collagen, propeptide of type V collagen), collagen degradation (type III collagen matrix metalloproteinase degradation product and type IV collagen matrix metalloproteinase degradation product), and fibrosis (enhanced liver fibrosis [ELF] score and its components [metalloproteinase-1, type III procollagen, hyaluronic acid]) were assessed in samples from baseline to week 96 in patients with PSC enrolled in a study evaluating simtuzumab (NCT01672853). Diagnostic performance for advanced fibrosis (Ishak stages 3-6) and cirrhosis (Ishak stages 5-6) was evaluated by logistic regression and AUROC. Prognostic performance for PSC-related clinical events and fibrosis progression was assessed by AUROC and Wilcoxon rank-sum test.

RESULTS

Among 234 patients, 51% had advanced fibrosis and 11% had cirrhosis at baseline. Baseline Pro-C3 and ELF score and its components provided moderate diagnostic ability for discrimination of advanced fibrosis (AUROC 0.73-0.78) and cirrhosis (AUROC 0.73-0.81). Baseline Pro-C3, ELF score, and type III procollagen provided a moderate prognosis for PSC-related clinical events (AUROC 0.70-0.71). Among patients without cirrhosis at baseline, median changes in Pro-C3 and ELF score to week 96 were higher in those with than without progression to cirrhosis (both p < 0.001).

CONCLUSIONS

Pro-C3 correlated with fibrosis stage, and Pro-C3 and ELF score provided discrimination of advanced fibrosis and cirrhosis and predicted PSC-related events and fibrosis progression. The results support the clinical utility of Pro-C3 and ELF score for staging and as prognostic markers in PSC.

A Gradient of Intestinal Inflammation in Primary Sclerosing Cholangitis

BACKGROUND

Primary sclerosing cholangitis (PSC) is a progressive liver disease associated with inflammatory bowel disease (IBD). The percentage of PSC patients diagnosed with concomitant IBD varies considerably between studies. This raises the question whether all PSC patients would show intestinal inflammation if screened thoroughly, even in the absence of symptoms.

METHODS

To address this question, we collected intestinal biopsies of healthy controls (n = 34), PSC (n = 25), PSC-IBD (n = 41), and IBD (n = 51) patients in a cross-sectional study and carried out cytokine expression profiling, 16S sequencing, in-depth histology, and endoscopy scoring.

RESULTS

We found that the vast majority of PSC patients even without clinically manifest IBD showed infiltration of immune cells and increased expression of IL17A and IFNG in intestinal biopsies. However, expression of IL10 and FOXP3 were likewise increased, which may explain why these PSC patients have intestinal inflammation only on a molecular level. This subclinical inflammation in PSC patients was focused in the distal colon, whereas PSC-IBD patients showed inflammation either at the distal colon or on the right side of the colon and the terminal ileum. Furthermore, we observed that PSC patients without IBD showed signs of dysbiosis and exhibited a distinct microbial profile compared with healthy controls.

CONCLUSIONS

We found a gradient of intestinal inflammation in the vast majority of PSC patients even in the absence of IBD. Thus, further studies evaluating the effect of anti-inflammatory therapies in PSC patients and their impact on the emergence of clinically manifest IBD and colorectal cancer development are needed.

Berberine ameliorates the progression of primary sclerosing cholangitis by activating farnesoid X receptor

Primary sclerosing cholangitis (PSC) is a rare cholestatic disease characterized by biliary infiltration, hepatic fibrosis and bile duct destruction. To date, treatment options for PSC are very limited. Therefore, the current study is aimed to investigate the therapeutic potential of berberine (BBR) against PSC. The disease was induced by feeding the mice with 3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-collidine (DDC) for four weeks. The serum biochemistry and liver histology were analyzed. Furthermore, the expression of farnesoid X receptor (FXR) was also evaluated by real-time PCR. The results indicated that berberine prevents the progression of PSC by modulating the expression of FXR which ultimately regulates other genes (including Cyp7A1 and BSEP) thus maintaining bile acids homeostasis. Furthermore, the docking analysis showed that berberine interacts with the binding pocket of FXR to activate the protein thus acting as an FXR agonist. In conclusion, data indicate that berberine protects the liver from PSC-related injury. This effect might be due to the modulation of FXR activity.

Periportal macrophages protect against commensal-driven liver inflammation

The liver is the main gateway from the gut, and the unidirectional sinusoidal flow from portal to central veins constitutes heterogenous zones, including the periportal vein (PV) and the pericentral vein zones1-5. However, functional differences in the immune system in each zone remain poorly understood. Here intravital imaging revealed that inflammatory responses are suppressed in PV zones. Zone-specific single-cell transcriptomics detected a subset of immunosuppressive macrophages enriched in PV zones that express high levels of interleukin-10 and Marco, a scavenger receptor that sequesters pro-inflammatory pathogen-associated molecular patterns and damage-associated molecular patterns, and consequently suppress immune responses. Induction of Marco+ immunosuppressive macrophages depended on gut microbiota. In particular, a specific bacterial family, Odoribacteraceae, was identified to induce this macrophage subset through its postbiotic isoallolithocholic acid. Intestinal barrier leakage resulted in inflammation in PV zones, which was markedly augmented in Marco-deficient conditions. Chronic liver inflammatory diseases such as primary sclerosing cholangitis (PSC) and non-alcoholic steatohepatitis (NASH) showed decreased numbers of Marco+ macrophages. Functional ablation of Marco+ macrophages led to PSC-like inflammatory phenotypes related to colitis and exacerbated steatosis in NASH in animal experimental models. Collectively, commensal bacteria induce Marco+ immunosuppressive macrophages, which consequently limit excessive inflammation at the gateway of the liver. Failure of this self-limiting system promotes hepatic inflammatory disorders such as PSC and NASH.

Challenges and Pitfalls in Pancreatobiliary Cytopathology

INTRODUCTION

The advances of minimally invasive endoscopy-guided procedures that usually yield limited diagnostic material changed pancreaticobiliary cytopathology into one of the most challenging areas of cytopathology given the abundance of differential diagnoses to be considered when dealing with limited specimens.

CASE PRESENTATION

We describe a few challenging examples of potential pitfalls in pancreatobiliary cytopathology evaluation collected from a busy academic hospital (tertiary) center. Case 1 illustrates the challenges in handling paucicellular specimens from pancreatic solid lesions in which differential diagnoses may include acinar cell carcinoma, neuroendocrine tumors, adenocarcinoma, or even benign pancreatic tissue, among others. Case 2 illustrates the pitfalls in evaluating limited specimens from patients with chronic pancreatitis, specially when distinguishing exuberant reactive atypia from dysplastic changes is mandatory. Case 3 illustrates pitfalls in distinguishing malignancy from reactive changes in biliary brushing specimens from patients with primary sclerosing cholangitis. Finally, cases 4 and 5 highlight the importance of including the possibility of pancreatic metastasis in the differential diagnoses of some pancreatic lesions.

CONCLUSION

Over time, there has been an increasing demand for pathologists to render diagnoses on limited specimens obtained through minimally invasive procedures which can be frequently challenging even for the most experienced professionals. In many difficult cases, salvaging additional material for a cell block can turn out to be extremely helpful given the possibility of utilizing additional ancillary tests for diagnostic confirmation.

Cholangiocytes Modulate CD100 Expression in the Liver and Facilitate Pathogenic T-Helper 17 Cell Differentiation

BACKGROUND & AIMS

Chronic inflammation surrounding bile ducts contributes to the disease pathogenesis of most cholangiopathies. Poor efficacy of immunosuppression in these conditions suggests biliary-specific pathologic principles. Here we performed biliary niche specific functional interpretation of a causal mutation (CD100 K849T) of primary sclerosing cholangitis (PSC) to understand related pathogenic mechanisms.

METHODS

Biopsy specimens of explanted livers and endoscopy-guided sampling were used to assess the CD100 expression by spatial transcriptomics, immune imaging, and high-dimensional flow cytometry. To model pathogenic cholangiocyte-immune cell interaction, splenocytes from mutation-specific mice were cocultured with cholangiocytes. Pathogenic pathways were pinpointed by RNA sequencing analysis of cocultured cells and cross-validated in patient materials.

RESULTS

CD100 is mainly expressed by immune cells in the liver and shows a unique pattern around PSC bile ducts with RNA-level colocalization but poor detection at the protein level. This appears to be due to CD100 cleavage as soluble CD100 is increased. Immunophenotyping suggests biliary-infiltrating T cells as the major source of soluble CD100, which is further supported by reduced surface CD100 on T cells and increased metalloproteinases in cholangiocytes after coculturing. Pathogenic T cells that adhered to cholangiocytes up-regulated genes in the T-helper 17 cell differentiation pathway, and the CD100 mutation boosted this process. Consistently, T-helper 17 cells dominate biliary-resident CD4 T cells in patients.

CONCLUSIONS

CD100 exerts its functional impact through cholangiocyte-immune cell cross talk and underscores an active, proinflammatory role of cholangiocytes that can be relevant to novel treatment approaches.

Bile acid-induced IRF3 phosphorylation mediates cell death, inflammatory responses, and fibrosis in cholestasis-induced liver and kidney injury via regulation of ZBP1

BACKGROUND AND AIMS

Cell death and inflammation play critical roles in chronic tissue damage caused by cholestatic liver injury leading to fibrosis and cirrhosis. Liver cirrhosis is often associated with kidney damage, which is a severe complication with poor prognosis. Interferon regulatory factor 3 (IRF3) is known to regulate apoptosis and inflammation, but its role in cholestasis remains obscure. In this study.

APPROACH AND RESULTS

We discovered increased IRF3 phosphorylation in the liver of patients with primary biliary cholangitis and primary sclerosing cholangitis. In the bile duct ligation model of obstructive cholestasis in mice, we found that tissue damage was associated with increased phosphorylated IRF3 (p-IRF3) in the liver and kidney. IRF3 knockout ( Irf3-/- ) mice showed significantly attenuated liver and kidney damage and fibrosis compared to wide-type mice after bile duct ligation. Cell-death pathways, including apoptosis, necroptosis, and pyroptosis, inflammasome activation, and inflammatory responses were significantly attenuated in Irf3-/- mice. Mechanistically, we show that bile acids induced p-IRF3 in vitro in hepatocytes. In vivo , activated IRF3 positively correlated with increased expression of its target gene, Z-DNA-Binding Protein-1 (ZBP1), in the liver and kidney. Importantly, we also found increased ZBP1 in the liver of patients with primary biliary cholangitis and primary sclerosing cholangitis. We discovered that ZBP1 interacted with receptor interacting protein 1 (RIP1), RIP3, and NLRP3, thereby revealing its potential role in the regulation of cell-death and inflammation pathways. In conclusion.

CONCLUSIONS

Our data indicate that bile acid-induced p-IRF3 and the IRF3-ZBP1 axis play a central role in the pathogenesis of cholestatic liver and kidney injury.

Comparative histologic features among liver biopsies with biliary-pattern injury and confirmed clinical diagnoses

Biliary-pattern injury in the liver (eg, duct injury, ductular reaction, cholestasis) can occur in several conditions, including primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), large duct obstruction (LDO), and drug-induced liver injury (DILI). While the histologic changes in these conditions have been individually well described, distinguishing among them remains often challenging, particularly when biopsy samples are limited in size, robust clinical information is unavailable, and/or the pathologist does not feel confident in evaluating liver disease. This study evaluated histologic features that could aid the diagnosis of biliary-pattern injury on biopsy. We reviewed 121 liver biopsies from clinically confirmed cases of PBC, PSC, chronic LDO, or DILI for multiple clinical and histologic parameters. The rates of these histologic findings were then compared among different entities. Onion-skin fibrosis was seen in 14% of PSC in comparison to 0%, 5%, and 0% of PBC, DILI, and chronic LDO (P = 0.031). Florid duct lesions were identified in 21% of PBC compared to 2% of PSC and 0% of DILI and LDO (P = 0.0065). Similarly, 42% of PBC showed lobular granulomas, compared to 7% of PSC, 11% of DILI, and 33% of chronic LDO (P = 0.0001). Cholestasis was more commonly seen in DILI (42%) and chronic LDO (83%) than in PBC (4%) and PSC (16%) (P < 0.0001). Lobular chronic inflammation was found in a significantly higher percentage of PBC and LDO than of PSC and DILI (P = 0.0009). There were significantly fewer cases of PBC showing neutrophils in ductular reaction than PSC, DILI, and LDO (P = 0.0063). Histologic findings that can help suggest a diagnosis in liver biopsies with biliary-pattern injury include florid duct lesions, lobular granulomas, lack of neutrophils in ductular reaction, and lobular chronic inflammation in PBC; onion-skin fibrosis in PSC; cholestasis and feathery degeneration in DILI; and lobular granulomas, lobular chronic inflammation, cholestasis, and feathery degeneration in chronic LDO. These findings are likely most helpful when complicating factors interfere with biopsy interpretation.

Mimickers of immunoglobulin G4-related hepatobiliary disease on biopsy

With the growing recognition of IgG4-related hepatobiliary disease, establishing a definitive diagnosis relies mainly on a combination of clinical findings, serological markers, and imaging modalities. However, the role of histopathological evaluation remains indispensable, particularly in cases necessitating differential diagnosis or malignancy exclusion. While diagnosing IgG4-related hepatobiliary disease through surgical resection specimens is often straightforward, pathologists encounter substantial challenges when evaluating biopsies. The increasing rarity of surgical interventions exacerbates this due to improved disease recognition and suspicion. Numerous confounding factors, including the absence of the characteristic histologic features, limited tissue sample size, biopsy artifacts, and the limited value of IgG4 counts, further complicate the diagnostic process. Additionally, many other disorders exhibit clinical and histological features that overlap with IgG4-related disease, intensifying the complexity of interpreting biopsy specimens. This article explores the clinical and histomorphologic features of IgG4-related hepatobiliary disease and its potential mimickers. It offers valuable insights for pathologists and clinicians when confronted with biopsy specimens from hepatobiliary organs.

Osteopontin characterizes bile duct-associated macrophages and correlates with liver fibrosis severity in primary sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is an immune-mediated cholestatic liver disease for which pharmacological treatment options are currently unavailable. PSC is strongly associated with colitis and a disruption of the gut-liver axis, and macrophages are involved in the pathogenesis of PSC. However, how gut-liver interactions and specific macrophage populations contribute to PSC is incompletely understood.

APPROACH AND RESULTS

We investigated the impact of cholestasis and colitis on the hepatic and colonic microenvironment, and performed an in-depth characterization of hepatic macrophage dynamics and function in models of concomitant cholangitis and colitis. Cholestasis-induced fibrosis was characterized by depletion of resident KCs, and enrichment of monocytes and monocyte-derived macrophages (MoMFs) in the liver. These MoMFs highly express triggering-receptor-expressed-on-myeloid-cells-2 ( Trem2 ) and osteopontin ( Spp1 ), markers assigned to hepatic bile duct-associated macrophages, and were enriched around the portal triad, which was confirmed in human PSC. Colitis induced monocyte/macrophage infiltration in the gut and liver, and enhanced cholestasis-induced MoMF- Trem2 and Spp1 upregulation, yet did not exacerbate liver fibrosis. Bone marrow chimeras showed that knockout of Spp1 in infiltrated MoMFs exacerbates inflammation in vivo and in vitro , while monoclonal antibody-mediated neutralization of SPP1 conferred protection in experimental PSC. In human PSC patients, serum osteopontin levels are elevated compared to control, and significantly increased in advanced stage PSC and might serve as a prognostic biomarker for liver transplant-free survival.

CONCLUSIONS

Our data shed light on gut-liver axis perturbations and macrophage dynamics and function in PSC and highlight SPP1/OPN as a prognostic marker and future therapeutic target in PSC.

Enteroblastic cholangiocarcinoma: An uncommon, underrecognized subtype of bile duct cancer

Enteroblastic carcinoma is clinically characterized by an elevated serum level of alpha-fetoprotein (AFP) and is histologically characterized by cancer cells with a clear cytoplasm and 'blastic' coarse chromatin. It sometimes has an element of hepatoid carcinoma; therefore, these two neoplasms are often regarded as sister entities. Although hepatoid carcinoma in the biliary tree has been reported, enteroblastic cholangiocarcinoma is extremely uncommon. In the present study, four cases of enteroblastic cholangiocarcinoma were examined. Tumors were located inside the liver (n = 2) or common bile duct (n = 2). The two intrahepatic cases had a history of primary sclerosing cholangitis, and serum AFP levels were elevated in both. One unresectable case was diagnosed by needle liver biopsy, while the remaining three underwent surgical resection. Histologically, all cases showed similar microscopic features. Cuboidal or polygonal cancer cells with the characteristic clear cytoplasm and subnuclear vacuoles were arranged in a papillary, micropapillary, tubular, or solid architecture. One case had an element of pancreatobiliary-type adenocarcinoma, while a hepatoid carcinoma element was not observed in any cases. All cases were positive for AFP, glypican 3, and SALL4, with SALL4 being the most widely expressed. Heppar-1 and arginase-1 were negative, except for one case, which was positive for Heppar-1. In conclusion, enteroblastic cholangiocarcinoma is an uncommon subtype of biliary tract malignancy. These cases may have been categorized as 'clear cell' cholangiocarcinoma. Although enteroblastic cholangiocarcinoma seems to occur more commonly in extrahepatic regions, including the gallbladder, it may also develop in the liver, particularly in patients with primary sclerosing cholangitis.