The journal retracts the article titled “The Effects of Taurocholic Acid on Biliary Damage and Liver Fibrosis Are Mediated by Calcitonin-Gene-Related Peptide Signaling” [...]

BACKGROUND AND AIMS:NAFLD is characterized by steatosis, hepatic inflammation, and fibrosis, which can develop into NASH. Patients with NAFLD/NASH have increased ductular reaction (DR) and biliary senescence. High fat/high cholesterol diet feeding increases biliary senescence, DR, and biliary insulin-like growth factor-1 (IGF-1) expression in mice. p16/IGF-1 converges with fork-head box transcription factor O1 (FOXO1) through E2F1. We evaluated p16 inhibition on NAFLD phenotypes and biliary E2F1/FOXO1/IGF-1 signaling.APPROACH AND RESULTS:4-week wild-type (C57BL/6J) male mice were fed a control diet (CD) or high fat/high cholesterol diet and received either p16 or control Vivo Morpholino (VM) by tail vein injection 2× during the 16th week of feeding. We confirmed p16 knockdown and examined: (i) NAFLD phenotypes; (ii) DR and biliary senescence; (iii) serum metabolites; and (iv) biliary E2F1/FOXO1/IGF-1 signaling. Human normal, NAFLD, and NASH liver samples and isolated cholangiocytes treated with control or p16 VM were evaluated for p16/E2F1/FOXO1/IGF-1 signaling. p16 VM treatment reduced cholangiocyte and hepatocyte p16. In wild-type high fat/high cholesterol diet mice with control VM, there were increased (i) NAFLD phenotypes; (ii) DR and biliary senescence; (iii) serum metabolites; and (iv) biliary E2F1/FOXO1/IGF-1 signaling; however, p16 VM treatment reduced these parameters. Biliary E2F1/FOX-O1/IGF-1 signaling increased in human NAFLD/NASH but was blocked by p16 VM. In vitro , p16 VM reduced biliary E2f1 and Foxo1 transcription by inhibiting RNA pol II binding and E2F1 binding at the Foxo1 locus, respectively. Inhibition of E2F1 reduced biliary FOXO1 in vitro.CONCLUSION:Attenuating hepatic p16 expression may be a therapeutic approach for improving NAFLD/NASH phenotypes.

The liver has a vital role in many metabolic and regulatory processes in the body. Primary biliary cholangitis (PBC), pre-viously known as primary biliary cirrhosis, is a chronic choles-tatic autoimmune disease of the intrahepatic bile ducts asso-ciated with loss of tolerance to mitochondrial antigens. At this time there is no definitive cure for PBC; however, ursodeoxy-cholic acid (UDCA) has been shown to reduce injury when ad-ministered as the first line of treatment. Additional therapeu-tics can be given concurrently or as an alternative to UDCA to manage the symptoms and further curb disease progression. Currently, a liver transplant is the only potentially curative option when the patient has developed end-stage liver dis-ease or intractable pruritus. This review aims to delineate the pathogenesis of primary biliary cholangitis and shed light on current therapeutic strategies in the treatment of PBC.

Supplementary Figure 4 from Serotonin Metabolism Is Dysregulated in Cholangiocarcinoma, which Has Implications for Tumor Growth

BACKGROUND & AIMS: Nonalcoholic fatty liver disease is highly associated with obesity and progresses to nonalcoholic steatohepatitis when the liver develops overt inflammatory damage. While removing adenosine in the purine salvage pathway, adenosine kinase (ADK) regulates methylation reactions. We aimed to study whether hepatocyte ADK functions as an obesogenic gene/enzyme to promote excessive fat deposition and liver inflammation. METHODS: Liver sections of human subjects were examined for ADK expression using immunohistochemistry. Mice with hepatocyte-specific ADK disruption or overexpression were examined for hepatic fat deposition and inflammation. Liver lipidomics, hepatocyte RNA sequencing (RNA-seq), and single-cell RNA-seq for liver non-parenchymal cells were performed to analyze ADK regulation of hepatocyte metabolic responses and hepatocyte-nonparenchymal cells crosstalk. RESULTS: Whereas patients with nonalcoholic fatty liver disease had increased hepatic ADK levels, mice with hepatocyte-specific ADK disruption displayed decreased hepatic fat deposition on a chow diet and were protected from diet-induced excessive hepatic fat deposition and inflammation. In contrast, mice with hepatocyte-specific ADK overexpression displayed increased body weight and adiposity and elevated degrees of hepatic steatosis and inflammation compared with control mice. RNA-seq and epigenetic analyses indicated that ADK increased hepatic DNA methylation and decreased hepatic Ppara expression and fatty acid oxidation. Lipidomic and single-cell RNA-seq analyses indicated that ADK-driven hepatocyte factors, due to mitochondrial dysfunction, enhanced macrophage proinflammatory activation in manners involving increased expression of stimulator of interferon genes. CONCLUSIONS: Hepatocyte ADK functions to promote excessive fat deposition and liver inflammation through suppressing hepatocyte fatty acid oxidation and producing hepatocyte-derived proinflammatory mediators. Therefore, hepatocyte ADK is a therapeutic target for managing obesity and nonalcoholic fatty liver disease.

Background Alcohol-related liver disease (ALD) is characterized by ductular reaction (DR), liver inflammation, steatosis, fibrosis, and cirrhosis. The secretin (Sct)/secretin receptor (SR) axis (expressed only by cholangiocytes) regulates liver phenotypes in cholestasis. We evaluated the role of Sct signaling on ALD phenotypes. Methods We used male wild-type and Sct −/− mice fed a control diet (CD) or ethanol (EtOH) for 8 wk. Changes in liver phenotypes were measured in mice, female/male healthy controls, and patients with alcoholic cirrhosis. Since Cyp4a10 and Cyp4a11/22 regulate EtOH liver metabolism, we measured their expression in mouse/human liver. We evaluated: (i) the immunoreactivity of the lipogenesis enzyme elongation of very-long-chain fatty acids 1 (Elovl, mainly expressed by hepatocytes) in mouse/human liver sections by immunostaining; (ii) the expression of miR-125b (that is downregulated in cholestasis by Sct) in mouse liver by q PCR; and (iii) total bile acid (BA) levels in mouse liver by enzymatic assay, and the mRNA expression of genes regulating BA synthesis (cholesterol 7a-hydroxylase, Cyp27a1, 12a-hydroxylase, Cyp8b1, and oxysterol 7a-hydroxylase, Cyp7b11) and transport (bile salt export pump, Bsep, Na + -taurocholate cotransporting polypeptide, NTCP, and the organic solute transporter alpha (OSTa) in mouse liver by q PCR. Results In EtOH-fed WT mice there was increased biliary and liver damage compared to control mice, but decreased miR-125b expression, phenotypes that were blunted in EtOH-fed Sct −/− mice. The expression of Cyp4a10 increased in cholangiocytes and hepatocytes from EtOH-fed WT compared to control mice but decreased in EtOH-fed Sct −/− mice. There was increased immunoreactivity of Cyp4a11/22 in patients with alcoholic cirrhosis compared to controls. The expression of miR-125b decreased in EtOH-fed WT mice but returned at normal values in EtOH-fed Sct −/− mice. Elovl1 immunoreactivity increased in patients with alcoholic cirrhosis compared to controls. There was no difference in BA levels between WT mice fed CD or EtOH; BA levels decreased in EtOH-fed Sct −/− compared to EtOH-fed WT mice. There was increased expression of Cyp27a1, Cyp8b1, Cyp7b1, Bsep, NTCP and Osta in total liver from EtOH-fed WT compared to control mice, which decreased in EtOH-fed Sct −/− compared to EtOH-fed WT mice. Conclusions Targeting Sct/SR signaling may be important for modulating ALD phenotypes.

Background & Aims: Primary sclerosing cholangitis (PSC) leads to ductular reaction and fibrosis and is complicated by vascular dysfunction. Cholangiocyte and endothelial cell crosstalk modulates their proliferation in cholestatic models. Endothelin (ET)-1 and ET-2 bind to their receptor, ET-A, and cholangiocytes are a key source of ET-1 after bile duct ligation. We aimed to evaluate the therapeutic potential of ET-A inhibition in PSC and biliary-endothelial crosstalk mediated by this pathway. Methods: Wild-type and multidrug resistance 2 knockout (Mdr2-/-) mice at 12 weeks of age were treated with vehicle or Ambrisentan (ET-A antagonist) for 1 week by daily intraperitoneal injections. Human control and PSC samples were used. Results: Mdr2-/- mice at 4, 8, and 12 weeks displayed angiogenesis that peaked at 12 weeks. Mdr2-/- mice at 12 weeks had enhanced biliary ET-1/ET-2/ET-A expression and secretion, whereas human PSC had enhanced ET-1/ET-A expression and secretion. Ambrisentan reduced biliary damage, immune cell infiltration, and fibrosis in Mdr2-/- mice. Mdr2-/- mice had squamous cholangiocytes with blunted microvilli and dilated arterioles lacking cilia; however, Ambrisentan reversed these alterations. Ambrisentan decreased cholangiocyte expression of pro-angiogenic factors, specifically midkine, through the regulation of cFOS. In vitro, ET-1/ET-A caused cholangiocyte senescence, endothelial cell angiogenesis, and macrophage inflammation. In vitro, human PSC cholangiocyte supernatants increased endothelial cell migration, which was blocked with Ambrisentan treatment. Conclusions: ET-A inhibition reduced biliary and liver damage in Mdr2-/- mice. ET-A promotes biliary angiocrine signaling that may, in turn, enhance angiogenesis. Targeting ET-A may prove therapeutic for PSC, specifically patients displaying vascular dysfunction.

ABSTRACTOrganoids are novelin vitromodels to study intercellular crosstalk between the different types of cells in the pathophysiology of disease. To better understand the underlying mechanisms driving the progression of primary sclerosing cholangitis (PSC), we developed scaffold-free multi-cellular 3D cholangiocyte organoids (3D-CHO) using ‘primary’ liver cell lines derived from normal and PSC patients. Human liver samples from healthy donors and late-stage PSC patients were used to isolate ‘primary’ cholangiocytes (EPCAM+/CK-19+), liver endothelial cells (LECs, CD31+), and hepatic stellate cells (HSCs, CD31−/CD68−/Desmin+/Vitamin A+). 3D-CHOs were formed using cholangiocytes:HSCs:LECs and kept viable for up to 1 month. Isolated primary cell lines and 3D-CHOs were further characterized by immunofluorescence (IF), qRT-PCR, and transmission electron microscopy. Gene expressions for cholangiocytes (SOX9, CFTR, EpCAM, AE, SCT, SCTR), fibrosis (ACTA2, COL1A1, DESMIN, TGFβ1), angiogenesis (PECAM, VEGF, CDH5, vWF), and inflammation (IL-6, TNF-α) confirmed PSC phenotypes of 3D-CHOs. Since cholangiocytes develop a neuroendocrine phenotype and express neuromodulators, confocal-IF demonstrated that neurokinin-1 receptor (NK-1R, expressed by cholangiocytes and upregulated in PSC), was localized within CK-19+cholangiocytes. Moreover, 3D-CHOs from PSC patients confirmed PSC phenotypes with upregulated NK-1R, tachykinin precursor 1, and downregulated membrane metalloendopeptidase. Our viable scaffold-free multiple-cell 3D-CHOs showed superiority as anin vitromodel in mimicking PSCin vivophenotypes compared to 2D cell culture, which can be used in PSC disease-related research.

The biliary tree is an essential component of transplantable human liver tissue. Despite recent advances in liver tissue engineering, attempts at re-creating the intrahepatic biliary tree have not progressed significantly. The finer branches of the biliary tree are structurally and functionally complex and heterogeneous and require harnessing innate developmental processes for their regrowth. Here we demonstrate the ability of decellularized liver extracellular matrix (dECM) hydrogels to induce the in vitro formation of complex biliary networks using encapsulated immortalized mouse small biliary epithelial cells (cholangiocytes). This phenomenon is not observed using immortalized mouse large cholangiocytes, or with purified collagen 1 gels or Matrigel. We also show phenotypic stability via immunostaining for specific cholangiocyte markers. Moreover, tight junction formation and maturation was observed to occur between cholangiocytes, exhibiting polarization and transporter activity. To better define the mechanism of duct formation, we utilized three fluorescently labeled, but otherwise identical populations of cholangiocytes. The cells, in a proximity dependent manner, either branch out clonally, radiating from a single nucleation point, or assemble into multi-colored structures arising from separate populations. These findings present liver dECM as a promising biomaterial for intrahepatic bile duct tissue engineering and as a tool to study duct remodeling in vitro.

Cholestatic liver diseases are named primarily due to the blockage of bile flow and buildup of bile acids in the liver. Cholestasis can occur in cholangiopathies, fatty liver diseases, and during COVID-19 infection. Most literature evaluates damage occurring to the intrahepatic biliary tree during cholestasis; however, there may be associations between liver damage and gallbladder damage. Gallbladder damage can manifest as acute or chronic inflammation, perforation, polyps, cancer, and most commonly gallstones. Considering the gallbladder is an extension of the intrahepatic biliary network, and both tissues are lined by biliary epithelial cells that share common mechanisms and properties, it is worth further evaluation to understand the association between bile duct and gallbladder damage. In this comprehensive article, we discuss background information of the biliary tree and gallbladder, from function, damage, and therapeutic approaches. We then discuss published findings that identify gallbladder disorders in various liver diseases. Lastly, we provide the clinical aspect of gallbladder disorders in liver diseases and ways to enhance diagnostic and therapeutic approaches for congruent diagnosis. © 2023 American Physiological Society. Compr Physiol 13:4909-4943, 2023.

Supplementary Figure 3 from Serotonin Metabolism Is Dysregulated in Cholangiocarcinoma, which Has Implications for Tumor Growth

Background & Aims: Primary biliary cholangitis (PBC) is characterised by ductopenia, ductular reaction, impairment of anion exchanger 2 (AE2) and the 'bicarbonate umbrella'. Ductulo-canalicular junction (DCJ) derangement is hypothesised to promote PBC progression. The secretin (Sct)/secretin receptor (SR) axis regulates cystic fibrosis transmembrane receptor (CFTR) and AE2, thus promoting choleresis. We evaluated the role of Sct/SR signalling on biliary secretory processes and subsequent injury in a late-stage PBC mouse model and human samples. Methods: At 32 weeks of age, female and male wild-type and dominant-negative transforming growth factor beta receptor II (late -stage PBC model) mice were treated with Sct for 1 or 8 weeks. Bulk RNA-sequencing was performed in isolated cholangiocytes from mouse models. Results: Biliary Sct/SR/CFTR/AE2 expression and bile bicarbonate levels were reduced in late-stage PBC mouse models and human samples. Sct treatment decreased bile duct loss, ductular reaction, inflammation, and fibrosis in late-stage PBC models. Sct reduced hepatic bile acid levels, modified bile acid composition, and restored the DCJ and 'bicarbonate umbrella'. RNA -sequencing identified that Sct promoted mature epithelial marker expression, specifically anterior grade protein 2 (Agr2). Late -stage PBC models and human samples exhibited reduced biliary mucin 1 levels, which were enhanced by Sct treatment. Conclusion: Loss of Sct/SR signalling in late-stage PBC results in a faulty 'bicarbonate umbrella' and reduced Agr2-mediated mucin production. Sct restores cholangiocyte secretory processes and DCJ formation through enhanced mature chol-angiocyte phenotypes and bile duct growth. Sct treatment may be beneficial for individuals with late-stage PBC. (c) 2022 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Supplementary Figure 1 from Serotonin Metabolism Is Dysregulated in Cholangiocarcinoma, which Has Implications for Tumor Growth

Interleukin-22 (IL-22) has been demonstrated as a critical regulator of epithelial homeostasis and repair; it showed an anti-inflammatory effect against ulcerative colitis. Local microinjection of IL-22 cDNA vector has been shown to be effective in treating ulcerative colitis in mouse models. However, microinjection comes with multiple technical challenges for routine colon-targeted drug delivery. In contrast, oral administration can get around these challenges and provide comparable efficacy. We showed in previous studies that oral administration of new lipid nanoparticles (nLNP)-encapsulated IL-22 mRNA targets the colon region and efficiently ameliorates colitis. This protocol describes the details of preparing and characterizing the nLNP-encapsulated IL-22 mRNA using three major lipids that mimic the natural ginger-derived nanoparticles. It provides an nLNP platform that can be used to orally deliver other types of nucleic acids to the colon.

Supplementary Figure 2 from Serotonin Metabolism Is Dysregulated in Cholangiocarcinoma, which Has Implications for Tumor Growth

BackgroundPrimary biliary cholangitis (PBC) is characterized by increased biliary damage, inflammation and liver fibrosis. Early stage PBC is marked by biliary proliferation, whereas late stage PBC shows ductopenia. We have shown that dominant‐negative transforming growth factor b receptor II (dnTGFβRII) mice at 12 wk of age mimic early stage PBC. We have found that melatonin therapy or prolonged exposure to complete darkness reduces biliary hyperplasia and liver fibrosis in models of cholestasis. However, the impact of melatonin or dark therapy on PBC‐related injury is unknown. The aim of our study was to evaluate the effects of melatonin or dark therapy in a mouse model of early stage PBC.MethodsWe used background‐matched, male wild‐type (WT) and dnTGFβRII at 12 wk of age that were given drinking water containing melatonin (0.03%) or placed in complete darkness for 1 wk along with the related controls. Liver damage was evaluated by H&E. Intrahepatic bile duct mass (IBDM) was measured by CK‐19 staining. Biliary senescence was evaluated by staining for p16 and p21, and SA‐β‐galactosidase activity. Biliary and liver inflammation were determined by IL‐6 and F4/80 (Kupffer cell marker) staining. Liver fibrosis was determined by Sirius Red staining and immunofluorescence for collagen type‐1a. Hepatic stellate cell (HSC) activation was shown by SYP‐9 and α‐SMA staining. Human control and early stage PBC serum samples were obtained, and serum melatonin levels were measured by EIA.ResultsdnTGFβRII at 12 wk of age (early stage PBC mouse model) treated with melatonin or complete darkness had decreased (i) IBDM, (ii) biliary senescence, (iii) liver fibrosis, (iv) biliary and liver inflammation, and (v) HSC activation/liver fibrosis. Human early stage PBC samples had decreased serum melatonin levels.ConclusionInhibition of melatonin signaling perpetuates biliary damage associated with PBC. Restoration of melatonin‐dependent signaling via melatonin treatment or dark therapy may be therapeutic for patients with early stage PBC.Support or Funding InformationNIH NIDDK R01, VA MeritThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.