An aged immune system drives senescence and ageing of solid organs.

Ageing of the immune system, or immunosenescence, contributes to the morbidity and mortality of the elderly1,2. To define the contribution of immune system ageing to organism ageing, here we selectively deleted Ercc1, which encodes a crucial DNA repair protein3,4, in mouse haematopoietic cells to increase the burden of endogenous DNA damage and thereby senescence5-7 in the immune system only. We show that Vav-iCre+/-;Ercc1-/fl mice were healthy into adulthood, then displayed premature onset of immunosenescence characterized by attrition and senescence of specific immune cell populations and impaired immune function, similar to changes that occur during ageing in wild-type mice8-10. Notably, non-lymphoid organs also showed increased senescence and damage, which suggests that senescent, aged immune cells can promote systemic ageing. The transplantation of splenocytes from Vav-iCre+/-;Ercc1-/fl or aged wild-type mice into young mice induced senescence in trans, whereas the transplantation of young immune cells attenuated senescence. The treatment of Vav-iCre+/-;Ercc1-/fl mice with rapamycin reduced markers of senescence in immune cells and improved immune function11,12. These data demonstrate that an aged, senescent immune system has a causal role in driving systemic ageing and therefore represents a key therapeutic target to extend healthy ageing.

The Epigenetic Reader, Bromodomain Containing 2, Mediates Cholangiocyte Senescence via Interaction With ETS Proto-Oncogene 1.

BACKGROUND & AIMS: We reported that cholangiocyte senescence, regulated by the transcription factor ETS proto-oncogene 1 (ETS1), is a pathogenic feature of primary sclerosing cholangitis (PSC). Furthermore, histone 3 lysine 27 is acetylated at senescence-associated loci. The epigenetic readers, bromodomain and extra-terminal domain (BET) proteins, bind acetylated histones, recruit transcription factors, and drive gene expression. Thus, we tested the hypothesis that BET proteins interact with ETS1 to drive gene expression and cholangiocyte senescence. METHODS: We performed immunofluorescence for BET proteins (BRD2 and 4) in liver tissue from liver tissue from PSC patients and a mouse PSC model. Using normal human cholangiocytes (NHCs), NHCs experimentally induced to senescence (NHCsen), and PSC patient-derived cholangiocytes (PSCDCs), we assessed senescence, fibroinflammatory secretome, and apoptosis after BET inhibition or RNA interference depletion. We assessed BET interaction with ETS1 in NHCsen and tissues from PSC patient, and the effects of BET inhibitors on liver fibrosis, senescence, and inflammatory gene expression in mouse models. RESULTS: Tissue from patients with PSC and a mouse PSC model exhibited increased cholangiocyte BRD2 and 4 protein (∼5×) compared with controls without disease. NHCsen exhibited increased BRD2 and 4 (∼2×), whereas PSCDCs exhibited increased BRD2 protein (∼2×) relative to NHC. BET inhibition in NHCsen and PSCDCs reduced senescence markers and inhibited the fibroinflammatory secretome. ETS1 interacted with BRD2 in NHCsen, and BRD2 depletion diminished NHCsen p21 expression. BET inhibitors reduced senescence, fibroinflammatory gene expression, and fibrosis in the 3,5-diethoxycarbonyl-1,4-dihydrocollidine-fed and Mdr2-/- mouse models. CONCLUSION: Our data suggest that BRD2 is an essential mediator of the senescent cholangiocyte phenotype and is a potential therapeutic target for patients with PSC.

Immunotherapy-based targeting of MSLN+ activated portal fibroblasts is a strategy for treatment of cholestatic liver fibrosis.

We investigated the role of mesothelin (Msln) and thymocyte differentiation antigen 1 (Thy1) in the activation of fibroblasts across multiple organs and demonstrated that Msln-/- mice are protected from cholestatic fibrosis caused by Mdr2 (multidrug resistance gene 2) deficiency, bleomycin-induced lung fibrosis, and UUO (unilateral urinary obstruction)-induced kidney fibrosis. On the contrary, Thy1-/- mice are more susceptible to fibrosis, suggesting that a Msln-Thy1 signaling complex is critical for tissue fibroblast activation. A similar mechanism was observed in human activated portal fibroblasts (aPFs). Targeting of human MSLN+ aPFs with two anti-MSLN immunotoxins killed fibroblasts engineered to express human mesothelin and reduced collagen deposition in livers of bile duct ligation (BDL)-injured mice. We provide evidence that antimesothelin-based therapy may be a strategy for treatment of parenchymal organ fibrosis.

Autophagy promotes hepatic cystogenesis in polycystic liver disease by depletion of cholangiocyte ciliogenic proteins.

BACKGROUNDS AND AIMS: Polycystic liver disease (PLD) is characterized by defective cholangiocyte cilia that regulate progressive growth of hepatic cysts. Because formation of primary cilia is influenced by autophagy through degradation of proteins involved in ciliogenesis, we hypothesized that ciliary defects in PLD cholangiocytes (PLDCs) originate from autophagy-mediated depletion of ciliogenic proteins ADP-ribosylation factor-like protein 3 (ARL3) and ADP-ribosylation factor-like protein 13B (ARL13B) and ARL-dependent mislocation of a ciliary-localized bile acid receptor, Takeda G-protein-coupled receptor 5 (TGR5), the activation of which enhances hepatic cystogenesis (HCG). The aims here were to determine whether: (1) ciliogenesis is impaired in PLDC, is associated with increased autophagy, and involves autophagy-mediated depletion of ARL3 and ARL13B; (2) depletion of ARL3 and ARL13B in PLDC cilia impacts ciliary localization of TGR5; and (3) pharmacological inhibition of autophagy re-establishes cholangiocyte cilia and ciliary localization of ARL3, ARL3B, and TGR5 and reduces HCG. APPROACH AND RESULTS: By using liver tissue from healthy persons and patients with PLD, in vitro and in vivo models of PLD, and in vitro models of ciliogenesis, we demonstrated that, in PLDCs: ciliogenesis is impaired; autophagy is enhanced; ARL3 and ARL13B are ubiquitinated by HDAC6, depleted in cilia, and present in autophagosomes; depletion of ARL3 and ARL13B impacts ciliary localization of TGR5; and pharmacological inhibition of autophagy with mefloquine and verteporfin re-establishes cholangiocyte cilia and ciliary localization of ARL3, ARL13B, and TGR5 and reduces HCG. CONCLUSIONS: The intersection between autophagy, defective cholangiocyte cilia, and enhanced HCG contributes to PLD progression and can be considered a target for therapeutic interventions.

Long non-coding RNA ACTA2-AS1 promotes ductular reaction by interacting with the p300/ELK1 complex.

BACKGROUND & AIMS: Biliary disease is associated with a proliferative/fibrogenic ductular reaction (DR). p300 is an epigenetic regulator that acetylates lysine 27 on histone 3 (H3K27ac) and is activated during fibrosis. Long non-coding RNAs (lncRNAs) are aberrantly expressed in cholangiopathies, but little is known about how they recruit epigenetic complexes and regulate DR. We investigated epigenetic complexes, including transcription factors (TFs) and lncRNAs, contributing to p300-mediated transcription during fibrosis. METHODS: We evaluated p300 in vivo using tamoxifen-inducible, cholangiocyte-selective, p300 knockout (KO) coupled with bile duct ligation (BDL) and Mdr KO mice treated with SGC-CBP30. Primary cholangiocytes and liver tissue were analyzed for expression of Acta2-as1 lncRNA by qPCR and RNA in situ hybridization. In vitro, we performed RNA-sequencing in human cholangiocytes with a p300 inhibitor. Cholangiocytes were exposed to lipopolysaccharide (LPS) as an injury model. We confirmed formation of a p300/ELK1 complex by immunoprecipitation (IP). RNA IP was used to examine interactions between ACTA2-AS1 and p300. Chromatin IP assays were used to evaluate p300/ELK1 occupancy and p300-mediated H3K27ac. Organoids were generated from ACTA2-AS1-depleted cholangiocytes. RESULTS: BDL-induced DR and fibrosis were reduced in Krt19-CreERT/p300fl/fl mice. Similarly, Mdr KO mice were protected from DR and fibrosis after SGC-CBP30 treatment. In vitro, depletion of ACTA2-AS1 reduced expression of proliferative/fibrogenic markers, reduced LPS-induced cholangiocyte proliferation, and impaired organoid formation. ACTA2-AS1 regulated transcription by facilitating p300/ELK1 binding to the PDGFB promoter after LPS exposure. Correspondingly, LPS-induced H3K27ac was mediated by p300/ELK1 and was reduced in ACTA2-AS1-depleted cholangiocytes. CONCLUSION: Cholangiocyte-selective p300 KO or p300 inhibition attenuate DR/fibrosis in mice. ACTA2-AS1 influences recruitment of p300/ELK1 to specific promoters to drive H3K27ac and epigenetic activation of proliferative/fibrogenic genes. This suggests that cooperation between epigenetic co-activators and lncRNAs facilitates DR/fibrosis in biliary diseases. LAY SUMMARY: We identified a three-part complex containing an RNA molecule, a transcription factor, and an epigenetic enzyme. The complex is active in injured bile duct cells and contributes to activation of genes involved in proliferation and fibrosis.

Bile Acid Profiles in Primary Sclerosing Cholangitis and Their Ability to Predict Hepatic Decompensation.

BACKGROUND AND AIMS: Altered bile acid (BA) homeostasis is an intrinsic facet of cholestatic liver diseases, but clinical usefulness of plasma BA assessment in primary sclerosing cholangitis (PSC) remains understudied. We performed BA profiling in a large retrospective cohort of patients with PSC and matched healthy controls, hypothesizing that plasma BA profiles vary among patients and have clinical utility. APPROACH AND RESULTS: Plasma BA profiling was performed in the Clinical Biochemical Genetics Laboratory at Mayo Clinic using a mass spectrometry based assay. Cox proportional hazard (univariate) and gradient boosting machines (multivariable) models were used to evaluate whether BA variables predict 5-year risk of hepatic decompensation (HD; defined as ascites, variceal hemorrhage, or encephalopathy). There were 400 patients with PSC and 302 controls in the derivation cohort (Mayo Clinic) and 108 patients with PSC in the validation cohort (Norwegian PSC Research Center). Patients with PSC had increased BA levels, conjugated fraction, and primary-to-secondary BA ratios relative to controls. Ursodeoxycholic acid (UDCA) increased total plasma BA level while lowering cholic acid and chenodeoxycholic acid concentrations. Patients without inflammatory bowel disease (IBD) had primary-to-secondary BA ratios between those of controls and patients with ulcerative colitis. HD risk was associated with increased concentration and conjugated fraction of many BA, whereas higher G:T conjugation ratios were protective. The machine-learning model, PSC-BA profile score (concordance statistic [C-statistic], 0.95), predicted HD better than individual measures, including alkaline phosphatase, and performed well in validation (C-statistic, 0.86). CONCLUSIONS: Patients with PSC demonstrated alterations of plasma BA consistent with known mechanisms of cholestasis, UDCA treatment, and IBD. Notably, BA profiles predicted future HD, establishing the clinical potential of BA profiling, which may be suited for use in clinical trials.

Early Cholangiocarcinoma Detection With Magnetic Resonance Imaging Versus Ultrasound in Primary Sclerosing Cholangitis.

BACKGROUND AND AIMS: Early detection of perihilar cholangiocarcinoma (CCA) among patients with primary sclerosing cholangitis (PSC) is important to identify more people eligible for curative therapy. While many recommend CCA screening, there are divergent opinions and limited data regarding the use of ultrasound or magnetic resonance imaging (MRI) for early CCA detection, and it is unknown whether there is benefit in testing asymptomatic individuals. Our aims were to assess the diagnostic performances and prognostic implications of ultrasound and MRI-based CCA detection. APPROACH AND RESULTS: This is a multicenter review of 266 adults with PSC (CCA, n = 120) who underwent both an ultrasound and MRI within 3 months. Images were re-examined by radiologists who were blinded to the clinical information. Respectively, MRI had a higher area under the curve compared with ultrasound for CCA detection: 0.87 versus 0.70 for the entire cohort; 0.81 versus 0.59 for asymptomatic individuals; and 0.88 versus 0.71 for those listed for CCA transplant protocol. The absence of symptoms at CCA diagnosis was associated with improved 5-year outcomes including overall survival (82% vs. 46%, log-rank P < 0.01) and recurrence-free survival following liver transplant (89% vs. 65%, log-rank P = 0.04). Among those with asymptomatic CCA, MRI detection (compared with ultrasound) was associated with reduction in both mortality (hazard ratio, 0.10; 95% confidence interval, 0.01-0.96) and CCA progression after transplant listing (hazard ratio, 0.10; 95% confidence interval, 0.01-0.90). These benefits continued among patients who had annual monitoring and PSC for more than 1 year before CCA was diagnosed. CONCLUSIONS: MRI is superior to ultrasound for the detection of early-stage CCA in patients with PSC. Identification of CCA before the onset of symptoms with MRI is associated with improved outcomes.

Cellular senescence in the cholangiopathies.

PURPOSE OF REVIEW: Cellular senescence (i.e. permanent withdrawal from the cell cycle) is increasingly recognized as a pathologic feature in a variety of inflammatory liver diseases, including primary sclerosing cholangitis (PSC), primary biliary cholangitis (PBC) and additional cholangiopathies. Herein, we provide an update on the interplay between cholangiocytes, cellular senescence and the cholangiopathies. RECENT FINDINGS: The themes covered by this review include novel models for studying the role of senescent cholangiocytes and the cholangiopathies, identification and modulation of key pathways or molecules regulating cholangiocyte senescence, and discovery of druggable targets to advance therapeutic options for the cholangiopathies. Most recent studies focused on PSC; however, the concepts and findings may be applied to additional cholangiopathies. SUMMARY: Cholangiopathies present unique and divergent clinicopathological features, causes and genetic backgrounds, but share several common disease processes. Cholangiocyte senescence in the cholestatic cholangiopathies, primarily PSC and PBC, is regarded as a key pathogenetic process. Importantly, senescent cholangiocytes exhibit phenotypic features including the senescence-associated secretory phenotype (SASP) and resistance to apoptosis that provide new directions for basic research and new prognostic and therapeutic approaches for clinical practice.

Targeting UBC9-mediated protein hyper-SUMOylation in cystic cholangiocytes halts polycystic liver disease in experimental models.

BACKGROUND & AIMS: Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive development of multiple fluid-filled biliary cysts. Most PLD-causative genes participate in protein biogenesis and/or transport. Post-translational modifications (PTMs) are implicated in protein stability, localization and activity, contributing to human pathobiology; however, their role in PLD is unknown. Herein, we aimed to unveil the role of protein SUMOylation in PLD and its potential therapeutic targeting. METHODS: Levels and functional effects of SUMOylation, along with response to S-adenosylmethionine (SAMe, inhibitor of the SUMOylation enzyme UBC9) and/or short-hairpin RNAs (shRNAs) against UBE2I (UBC9), were evaluated in vitro, in vivo and/or in patients with PLD. SUMOylated proteins were determined by immunoprecipitation and proteomic analyses by mass spectrometry. RESULTS: Most SUMOylation-related genes were found overexpressed (mRNA) in polycystic human and rat liver tissue, as well as in cystic cholangiocytes in culture compared to controls. Increased SUMOylated protein levels were also observed in cystic human cholangiocytes in culture, which decreased after SAMe administration. Chronic treatment of polycystic (PCK: Pkdh1-mut) rats with SAMe halted hepatic cystogenesis and fibrosis, and reduced liver/body weight ratio and liver volume. In vitro, both SAMe and shRNA-mediated UBE2I knockdown increased apoptosis and reduced cell proliferation of cystic cholangiocytes. High-throughput proteomic analysis of SUMO1-immunoprecipitated proteins in cystic cholangiocytes identified candidates involved in protein biogenesis, ciliogenesis and proteasome degradation. Accordingly, SAMe hampered proteasome hyperactivity in cystic cholangiocytes, leading to activation of the unfolded protein response and stress-related apoptosis. CONCLUSIONS: Cystic cholangiocytes exhibit increased SUMOylation of proteins involved in cell survival and proliferation, thus promoting hepatic cystogenesis. Inhibition of protein SUMOylation with SAMe halts PLD, representing a novel therapeutic strategy. LAY SUMMARY: Protein SUMOylation is a dynamic post-translational event implicated in numerous cellular processes. This study revealed dysregulated protein SUMOylation in polycystic liver disease, which promotes hepatic cystogenesis. Administration of S-adenosylmethionine (SAMe), a natural UBC9-dependent SUMOylation inhibitor, halted polycystic liver disease in experimental models, thus representing a potential therapeutic agent for patients.

The Spectrum of Reactive Cholangiocytes in Primary Sclerosing Cholangitis.

Cholangiocytes are the target of a group of chronic liver diseases termed the "cholangiopathies," in which cholangiocytes react to exogenous and endogenous insults, leading to disease initiation and progression. In primary sclerosing cholangitis (PSC), the focus of this review, the cholangiocyte response to genetic or environmental insults can lead to a heterogeneous response; that is, a subpopulation acquires a ductular reactive and proliferative phenotype, while another subpopulation undergoes senescence and growth arrest. Both ductular reactive cholangiocytes and senescent cholangiocytes can modify the periductal microenvironment through their ability to secrete various cytokines, chemokines, and growth factors, initiating and perpetuating inflammatory and profibrotic responses. This review discusses the similarities and differences, the interrelationships, and the potential pathogenic roles of these reactive proliferative and senescent cholangiocyte subpopulations in PSC.

Primary Sclerosing Cholangitis Risk Estimate Tool (PREsTo) Predicts Outcomes of the Disease: A Derivation and Validation Study Using Machine Learning.

Improved methods are needed to risk stratify and predict outcomes in patients with primary sclerosing cholangitis (PSC). Therefore, we sought to derive and validate a prediction model and compare its performance to existing surrogate markers. The model was derived using 509 subjects from a multicenter North American cohort and validated in an international multicenter cohort (n = 278). Gradient boosting, a machine-based learning technique, was used to create the model. The endpoint was hepatic decompensation (ascites, variceal hemorrhage, or encephalopathy). Subjects with advanced PSC or cholangiocarcinoma (CCA) at baseline were excluded. The PSC risk estimate tool (PREsTo) consists of nine variables: bilirubin, albumin, serum alkaline phosphatase (SAP) times the upper limit of normal (ULN), platelets, aspartate aminotransferase (AST), hemoglobin, sodium, patient age, and number of years since PSC was diagnosed. Validation in an independent cohort confirms that PREsTo accurately predicts decompensation (C-statistic, 0.90; 95% confidence interval [CI], 0.84-0.95) and performed well compared to Model for End-Stage Liver Disease (MELD) score (C-statistic, 0.72; 95% CI, 0.57-0.84), Mayo PSC risk score (C-statistic, 0.85; 95% CI, 0.77-0.92), and SAP <1.5 × ULN (C-statistic, 0.65; 95% CI, 0.55-0.73). PREsTo continued to be accurate among individuals with a bilirubin <2.0 mg/dL (C-statistic, 0.90; 95% CI, 0.82-0.96) and when the score was reapplied at a later course in the disease (C-statistic, 0.82; 95% CI, 0.64-0.95). Conclusion: PREsTo accurately predicts hepatic decompensation (HD) in PSC and exceeds the performance among other widely available, noninvasive prognostic scoring systems.

Liver Stiffness Measured by Either Magnetic Resonance or Transient Elastography Is Associated With Liver Fibrosis and Is an Independent Predictor of Outcomes Among Patients With Primary Biliary Cholangitis.

GOALS: We aimed to describe the diagnostic and prognostic performance of transient elastography (TE) and magnetic resonance elastography (MRE) in patients with primary biliary cholangitis (PBC). BACKGROUND: The diagnostic performance of TE and MRE in detecting advanced fibrosis in PBC and in predicting outcomes independent of existing serologic prognostic markers is incompletely understood. MATERIALS AND METHODS: Five hundred thirty-eight consecutive patients with PBC at 3 centers with liver stiffness (LS) measurements by TE (n=286) or MRE (n=332) were reviewed. LS cutoffs for predicting fibrosis stages were determined by receiver operating characteristic curves among those with a liver biopsy (TE, n=63; MRE, n=98). Cox proportional hazard regression modeling was used to identify associations between covariates and hepatic decompensation. RESULTS: The optimal LS thresholds for predicting histologic stage F4 were 14.40 kPa (area under the curve=0.94) for TE and 4.60 kPa (area under the curve=0.82) for MRE. Both TE and MRE outperformed biochemical markers for the prediction of histologic advanced fibrosis. Optimal LS thresholds to predict hepatic decompensation were 10.20 kPa on TE and 4.30 kPa on MRE. LS by TE and MRE (respectively) remained predictors of hepatic decompensation after adjusting for ursodeoxycholic acid responsiveness [hazard ratio (HR), 1.14; 95% confidence interval (CI), 1.05-1.24 and HR, 1.68; 95% CI, 1.28-2.19] and the GLOBE score (HR, 1.13; 95% CI, 1.07-1.19 and HR, 2.09; 95% CI, 1.57-2.78). CONCLUSION: LS measurement with either TE or MRE can accurately detect advanced fibrosis and offers additional prognostic value beyond existing serologic predictive tools.

The transcription factor ETS1 promotes apoptosis resistance of senescent cholangiocytes by epigenetically up-regulating the apoptosis suppressor BCL2L1.

Primary sclerosing cholangitis (PSC) is an idiopathic, progressive cholangiopathy. Cholangiocyte senescence is important in PSC pathogenesis, and we have previously reported that senescence is regulated by the transcription factor ETS proto-oncogene 1 (ETS1) and associated with overexpression of BCL2 like 1 (BCL2L1 or BCL-xL), an anti-apoptotic BCL2-family member. Here, we further explored the mechanisms regulating BCL-xL-mediated, apoptosis resistance in senescent cholangiocytes and uncovered that ETS1 and the histone acetyltransferase E1A-binding protein P300 (EP300 or p300) both promote BCL-xL transcription. Using immunofluorescence, we found that BCL-xL protein expression is increased both in cholangiocytes of livers from individuals with PSC and a mouse model of PSC. Using an in vitro model of lipopolysaccharide-induced senescence in normal human cholangiocytes (NHCs), we found increased BCL-xL mRNA and protein levels, and ChIP-PCRs indicated increased occupancy of ETS1, p300, and histone 3 Lys-27 acetylation (H3K27Ac) at the BCL-xL promoter. Using co-immunoprecipitation and proximity ligation assays, we further demonstrate that ETS1 and p300 physically interact in senescent but not control NHCs. Additionally, mutagenesis of predicted ETS1-binding sites within the BCL-xL promoter blocked luciferase reporter activity, and CRISPR/Cas9-mediated genetic deletion of ETS1 reduced senescence-associated BCL-xL expression. In senescent NHCs, TRAIL-mediated apoptosis was reduced ∼70%, and ETS1 deletion or RNAi-mediated BCL-xL suppression increased apoptosis. Overall, our results suggest that ETS1 and p300 promote senescent cholangiocyte resistance to apoptosis by modifying chromatin and inducing BCL-xL expression. These findings reveal ETS1 as a central regulator of both cholangiocyte senescence and the associated apoptosis-resistant phenotype.

A randomized, placebo-controlled, phase II study of obeticholic acid for primary sclerosing cholangitis.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is a rare, cholestatic liver disease with no currently approved therapies. Obeticholic acid (OCA) is a potent farnesoid X receptor (FXR) agonist approved for the treatment of primary biliary cholangitis. We investigated the efficacy and safety of OCA in patients with PSC. METHODS: AESOP was a phase II, randomized, double-blind, placebo-controlled, dose-finding study. Eligible patients were 18 to 75 years of age with a diagnosis of PSC and serum alkaline phosphatase (ALP) ≥2× the upper limit of normal (ULN) and total bilirubin <2.5× ULN. Patients were randomized 1:1:1 to receive placebo, OCA 1.5-3.0 mg, or OCA 5-10 mg once daily for a 24-week, double-blind phase followed by a 2-year, long-term safety extension (LTSE). Primary endpoints were change in ALP from baseline to week 24, and safety. RESULTS: The intent-to-treat population comprised 76 patients randomized to placebo (n = 25), OCA 1.5-3.0 mg (n = 25), and OCA 5-10 mg (n = 26). At week 24, serum ALP was significantly reduced with OCA 5-10 mg vs. placebo (least-square [LS] mean difference = -83.4 [SE = 40.3] U/L; 95% CI -164.28 to -2.57; p = 0.043). Serum ALP was not significantly reduced with OCA 1.5-3.0 mg vs. placebo at week 24 (LS mean [SE] difference = -78.29 [41.81] U/L; 95% CI -162.08 to 5.50; p = 0.067). Total bilirubin remained comparable to baseline in all groups. The most common treatment-emergent adverse event was dose-related pruritus (placebo 46%; OCA 1.5-3.0 mg 60%; OCA 5-10 mg 67%). Reductions in ALP were maintained during the LTSE, and no new safety signals emerged. CONCLUSIONS: Treatment with OCA 5-10 mg reduced serum ALP in patients with PSC. Mild to moderate dose-related pruritus was the most common adverse event. REGISTRATION: ClinicalTrials.gov: NCT02177136; EudraCT: 2014-002205-38. LAY SUMMARY: Primary sclerosing cholangitis (PSC) is a long-term disease that damages the bile ducts in the liver over time. In the AESOP clinical study in patients with PSC, obeticholic acid reduced serum alkaline phosphatase (a potential marker of disease severity) during an initial 24-week treatment period. The result was sustained during the 2-year, long-term extension of the study. The most common side effect of obeticholic acid in the study was itchy skin, which is consistent with earlier clinical studies.

Changes in Liver Stiffness, Measured by Magnetic Resonance Elastography, Associated With Hepatic Decompensation in Patients With Primary Sclerosing Cholangitis.

BACKGROUND & AIMS: Single measurements of liver stiffness (LS) by magnetic resonance elastography (MRE) have been associated with outcomes of patients with primary sclerosing cholangitis (PSC), but the significance of changes in LS over time are unclear. We investigated associations between changes in LS measurement and progression of PSC. METHODS: We performed a retrospective review of 204 patients with patients who underwent 2 MREs at a single center between January 1, 2007 and December 31, 2018. We collected laboratory data and information on revised Mayo PSC risk and model for end-stage liver disease scores, the PSC risk estimate tool, and levels of aspartate transferase at the time of each MRE. The ΔLS/time was determined by the change in LS between the second MRE compared to the first MRE divided by the time between examinations. The primary endpoint was development of hepatic decompensation (ascites, variceal hemorrhage or hepatic encephalopathy). RESULTS: The median LS measurement was 2.72 kPa (interquartile range, 2.32-3.44 kPa) and the overall change in LS was 0.05 kPa/y. However, ΔLS/y was 10-fold higher in patients anticipated to have cirrhosis (0.31 kPa/y) compared to patients with no fibrosis (0.03 kPa/y). The median LS increased over time in patients who ultimately developed hepatic decompensation (0.60 kPa/y; interquartile range, 0.21-1.26 kPa/y) vs but remained static in patients who did not (reduction of 0.04/y; interquartile range, reductions of 0.26 to 0.17 kPa/y) (P < .001). The ΔLS/y value associated with the highest risk of hepatic decompensation was Δ0.34 kPa/y (hazard ratio [HR], 13.29; 95% CI, 0.23-33.78). After we adjusted for baseline LS and other risk factors, including serum level of alkaline phosphatase and the Mayo PSC risk score, ΔLS/y continued to be associated with hepatic decompensation. The optimal single LS cut-off associated with the hepatic decompensation was 4.32 kPa (HR, 60.41; 95% CI, 17.85-204.47). A combination of both cut-off values was associated with risk of hepatic decompensation (concordance score, 0.93; 95% CI, 0.88-0.98) CONCLUSIONS: A single LS measurement and changes in LS over time are independently associated with hepatic decompensation in patients with PSC. However, changes in LS occur slowly in patients without advanced fibrosis or hepatic decompensation.

Senescent cholangiocytes release extracellular vesicles that alter target cell phenotype via the epidermal growth factor receptor.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is a chronic liver disease characterized by peribiliary inflammation and fibrosis. Cholangiocyte senescence is a prominent feature of PSC. Here, we hypothesize that extracellular vesicles (EVs) from senescent cholangiocytes influence the phenotype of target cells. METHODS: EVs were isolated from normal human cholangiocytes (NHCs), cholangiocytes from PSC patients and NHCs experimentally induced to senescence. NHCs, malignant human cholangiocytes (MHCs) and monocytes were exposed to 108 EVs from each donor cell population and assessed for proliferation, MAPK activation and migration. Additionally, we isolated EVs from plasma of wild-type and Mdr2-/- mice (a murine model of PSC), and assessed mouse monocyte activation. RESULTS: EVs exhibited the size and protein markers of exosomes. The number of EVs released from senescent human cholangiocytes was increased; similarly, the EVs in plasma from Mdr2-/- mice were increased. Additionally, EVs from senescent cholangiocytes were enriched in multiple growth factors, including EGF. NHCs exposed to EVs from senescent cholangiocytes showed increased NRAS and ERK1/2 activation. Moreover, EVs from senescent cholangiocytes promoted proliferation of NHCs and MHCs, findings that were blocked by erlotinib, an EGF receptor inhibitor. Furthermore, EVs from senescent cholangiocytes induced EGF-dependent Interleukin 1-beta and Tumour necrosis factor expression and migration of human monocytes; similarly, Mdr2-/- mouse plasma EVs induced activation of mouse monocytes. CONCLUSIONS: The data continue to support the importance of cholangiocyte senescence in PSC pathogenesis, directly implicate EVs in cholangiocyte proliferation, malignant progression and immune cell activation and migration, and identify novel therapeutic approaches for PSC.

Proteostasis disturbances and endoplasmic reticulum stress contribute to polycystic liver disease: New therapeutic targets.

BACKGROUND & AIMS: Polycystic liver diseases (PLDs) are genetic disorders characterized by progressive development of multiple biliary cysts. Recently, novel PLD-causative genes, encoding for endoplasmic reticulum (ER)-resident proteins involved in protein biogenesis and transport, were identified. We hypothesized that aberrant proteostasis contributes to PLD pathogenesis, representing a potential therapeutic target. METHODS: ER stress was analysed at transcriptional (qPCR), proteomic (mass spectrometry), morphological (transmission electron microscopy, TEM) and functional (proteasome activity) levels in different PLD models. The effect of ER stress inhibitors [4-phenylbutyric acid (4-PBA)] and/or activators [tunicamycin (TM)] was tested in polycystic (PCK) rats and cystic cholangiocytes in vitro. RESULTS: The expression levels of unfolded protein response (UPR) components were upregulated in liver tissue from PLD patients and PCK rats, as well as in primary cultures of human and rat cystic cholangiocytes, compared to normal controls. Cystic cholangiocytes showed altered proteomic profiles, mainly related to proteostasis (ie synthesis, folding, trafficking and degradation of proteins), marked enlargement of the ER lumen (by TEM) and hyperactivation of the proteasome. Notably, chronic treatment of PCK rats with 4-PBA decreased liver weight, as well as both liver and cystic volumes, of animals under baseline conditions or after TM administration compared to controls. In vitro, 4-PBA downregulated the expression (mRNA) of UPR effectors, normalized proteomic profiles related to protein synthesis, folding, trafficking and degradation and reduced the proteasome hyperactivity in cystic cholangiocytes, reducing their hyperproliferation and apoptosis. CONCLUSIONS: Restoration of proteostasis in cystic cholangiocytes with 4-PBA halts hepatic cystogenesis, emerging as a novel therapeutic strategy.

Combination of a Histone Deacetylase 6 Inhibitor and a Somatostatin Receptor Agonist Synergistically Reduces Hepatorenal Cystogenesis in an Animal Model of Polycystic Liver Disease.

Hepatic cystogenesis in polycystic liver disease (PLD) is associated with abnormalities in multiple cellular processes, including elevated cAMP and overexpression of histone deacetylase 6 (HDAC6). Disease progression in polycystic kidney (PCK) rats (an animal model of PLD) is attenuated by inhibition of either cAMP production or HDAC6. Therefore, we hypothesized that concurrent targeting of HDAC6 and cAMP would synergistically reduce cyst growth. Changes in hepatorenal cystogenesis were examined in PCK rats treated with a pan-HDAC inhibitor, panobinostat; three specific HDAC6 inhibitors, ACY-1215, ACY-738, and ACY-241; and a combination of ACY-1215 and the somatostatin receptor analogue, pasireotide. We also assessed effects of ACY-1215 and pasireotide alone and in combination on cell proliferation, cAMP production, and expression of acetylated α-tubulin in vitro in cultured cholangiocytes and the length of primary cilia and the frequency of ciliated cholangiocytes in vivo in PCK rats. Panobinostat and all three HDAC6 inhibitors decreased hepatorenal cystogenesis in PCK rats. ACY-1215 was more effective than other HDAC inhibitors and was chosen for combinational treatment. ACY-1215 + pasireotide combination synergistically reduced cyst growth and increased length of primary cilia in PCK rats. In cultured cystic cholangiocytes, ACY-1215 + pasireotide combination concurrently decreased cell proliferation and inhibited cAMP levels. These data suggest that the combination of drugs that inhibit HDAC6 and cAMP may be an effective therapy for PLD.

Cholangiocyte autophagy contributes to hepatic cystogenesis in polycystic liver disease and represents a potential therapeutic target.

Polycystic liver disease (PLD) is a group of genetic disorders with limited treatment options and significant morbidity. Hepatic cysts arise from cholangiocytes exhibiting a hyperproliferative phenotype. Considering that hyperproliferation of many cell types is associated with alterations in autophagy, we hypothesized that autophagy is altered in PLD cholangiocytes, contributes to hepatic cystogenesis, and might represent a potential therapeutic target. We employed functional pathway cluster analysis and next-generation sequencing, transmission electron microscopy, immunofluorescence confocal microscopy, and western blotting to assess autophagy in human and rodent PLD cholangiocytes. A three-dimensional culture model was used to study the effects of molecular and pharmacologic inhibition of autophagy on hepatic cystogenesis in vitro, and the polycystic kidney disease-specific rat, an animal model of PLD, to study the effects of hydroxychloroquine, a drug that interferes with the autophagy pathway, on disease progression in vivo. Assessment of the transcriptome of PLD cholangiocytes followed by functional pathway cluster analysis revealed that the autophagy-lysosomal pathway is one of the most altered pathways in PLD. Direct evaluation of autophagy in PLD cholangiocytes both in vitro and in vivo showed increased number and size of autophagosomes, lysosomes, and autolysosomes; overexpression of autophagy-related proteins (Atg5, Beclin1, Atg7, and LC3); and enhanced autophagic flux associated with activation of the cAMP-protein kinase A-cAMP response element-binding protein signaling pathway. Molecular and pharmacologic intervention in autophagy with ATG7 small interfering RNA, bafilomycin A1 , and hydroxychloroquine reduced proliferation of PLD cholangiocytes in vitro and growth of hepatic cysts in three-dimensional cultures. Hydroxychloroquine also efficiently inhibited hepatic cystogenesis in the polycystic kidney disease-specific rat. CONCLUSION: Autophagy is increased in PLD cholangiocytes, contributes to hepatic cystogenesis, and represents a potential therapeutic target for disease treatment. (Hepatology 2018;67:1088-1108).

Targeting senescent cholangiocytes and activated fibroblasts with B-cell lymphoma-extra large inhibitors ameliorates fibrosis in multidrug resistance 2 gene knockout (Mdr2-/- ) mice.

Cholangiocyte senescence has been linked to primary sclerosing cholangitis (PSC). Persistent secretion of growth factors by senescent cholangiocytes leads to the activation of stromal fibroblasts (ASFs), which are drivers of fibrosis. The activated phenotype of ASFs is characterized by an increased sensitivity to apoptotic stimuli. Here, we examined the mechanisms of apoptotic priming in ASFs and explored a combined targeting strategy to deplete senescent cholangiocytes and ASFs from fibrotic tissue to ameliorate liver fibrosis. Using a coculture system, we determined that senescent cholangiocytes promoted quiescent mesenchymal cell activation in a platelet-derived growth factor (PDGF)-dependent manner. We also identified B-cell lymphoma-extra large (Bcl-xL) as a key survival factor in PDGF-activated human and mouse fibroblasts. Bcl-xL was also up-regulated in senescent cholangiocytes. In vitro, inhibition of Bcl-xL by the small molecule Bcl-2 homology domain 3 mimetic, A-1331852, or Bcl-xL-specific small interfering RNA induced apoptosis in PDGF-activated fibroblasts, but not in quiescent fibroblasts. Likewise, inhibition of Bcl-xL reduced the survival and increased apoptosis of senescent cholangiocytes, compared to nonsenescent cells. Treatment of multidrug resistance 2 gene knockout (Mdr2-/- ) mice with A-1331852 resulted in an 80% decrease in senescent cholangiocytes, a reduction of fibrosis-inducing growth factors and cytokines, decrease of α-smooth muscle actin-positive ASFs, and finally in a significant reduction of liver fibrosis. CONCLUSION: Bcl-xL is a key survival factor in ASFs as well as in senescent cholangiocytes. Treatment with the Bcl-xL-specific inhibitor, A-1331852, reduces liver fibrosis, possibly by a dual effect on activated fibroblasts and senescent cholangiocytes. This mechanism represents an attractive therapeutic strategy in biliary fibrosis. (Hepatology 2018;67:247-259).