Jalan‐Sakrikar, Nidhi

Abstract Introduction Biliary fibrosis and inflammation are central to the pathogenesis of cholangiopathies such as primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC). Inflammatory and fibrogenic stimuli, such as transforming growth factor-β (TGFβ) and lipopolysaccharide (LPS) signaling, drive these processes, but their underlying transcriptional mechanisms in cholangiocytes remain incompletely defined. We investigated the role of Runt-related transcription factor 1 (RUNX1) as a transcriptional co-regulator of fibroinflammatory signaling in cholangiocytes. Methods Human PSC-derived cholangiocytes (PSC-Cs) and mouse large biliary epithelial cells (MLEs) were subjected to RUNX1 knockdown or pharmacologic inhibition (Ro5-3335 or AI-10-104). Cytokine secretion was profiled by Luminex multiplexing; RUNX1 genomic binding and protein interactome were assessed by ChIP-qPCR, ChIP-seq, and LC-MS/MS. In vivo , Mdr2 −/− mice received Ro5-3335, and cholangiocyte-selective Runx1 knockout mice (Krt19-CreERT) were challenged with a DDC diet, followed by evaluation of fibrosis and inflammation. Results RUNX1 expression was significantly increased in cholangiocytes from PSC and PBC patients, and Mdr2 −/− mice. RUNX1 knockdown or inhibition reduced IL6, TNFα, and other proinflammatory cytokines in PSC-Cs and attenuated TGFβ-, LPS-, and TNFα-induced Il6 and Ccl2 expression in MLEs. ChIP-qPCR and ChIP-seq revealed TGFβ-induced RUNX1 binding to the Il6 promoter and 727 additional genomic sites enriched for fibrosis and inflammatory pathways; predicted upstream regulators included TGFβ, TNF, and NFκB signaling. Proteomic analysis identified TGFβ-induced RUNX1 interactions with SMAD2 and NFκB2. In vivo , Ro5-3335 treatment in Mdr2 −/− mice reduced hepatic collagen, ECM gene expression, immune cell infiltration, and serum liver injury markers and bile acids. Similarly, cholangiocyte-specific Runx1 deletion mitigated fibrosis, inflammation, and liver injury in DDC-fed mice. Conclusion RUNX1 is a central transcriptional hub integrating TGFβ and inflammatory signals in cholangiocytes. Its inhibition attenuates biliary fibrosis and inflammation in cholestatic models, supporting RUNX1 as a potential therapeutic target in fibroinflammatory cholangiopathies.

Cholangiocytes are specialized epithelial cells that line the intrahepatic and extrahepatic biliary tree and play a critical role in bile modification, liver homeostasis, and response to injury. Cholangiocytes exhibit notable heterogeneity and plasticity, and their dysfunction is central to a spectrum of diseases targeting the bile ducts, collectively called cholangiopathies. These disorders include genetic, infectious, immune-mediated, and malignant diseases, with primary sclerosing cholangitis (PSC) representing one of the most complex and enigmatic of these disorders. PSC is a progressive, fibro-inflammatory disease of the bile ducts that is closely linked to inflammatory bowel disease, carries a heightened risk of cancer, and lacks any approved therapies. This review explores the biology of cholangiocytes, including their development, functional plasticity, and roles in secretion, absorption, and cellular signaling. We provide a detailed examination of cholangiopathies, particularly PSC, a complex cholangiopathy characterized by a paradoxical state of cholangiocyte senescence and hyperproliferation. We describe how immune cell dysfunction, the gut microbiome, genetic predispositions, and environmental factors converge to mediate PSC pathogenesis. We revisit the foundational technologies that empowered early discoveries and shaped the field as we know it today. We also explore how newer techniques such as organoid cultures, single-cell transcriptomics, epigenomics, and spatialomics have transformed our modern understanding of biliary pathophysiology. Finally, we provide an overview of existing rodent models of cholangiopathies and discuss their relevance to human disease. PSC remains therapeutically unaddressed, and thus ongoing multidisciplinary efforts are essential to developing targeted interventions. This review serves as a comprehensive resource for researchers and clinicians navigating the rapidly evolving landscape of cholangiocyte-centered liver disease research.

Liver macrophages are central in maintaining hepatic homeostasis and mediating immune responses during liver injury, including fibrosis. Macrophages may have proinflammatory or antiinflammatory properties, but which properties influence fibrosis remains unclear. To explore the role of macrophages in liver fibrosis, we performed single-cell RNA-seq in a mouse model of liver injury and found that macrophage diversity was increased. Marco was among the most significantly upregulated genes, and a population of Marco hi macrophages increased with injury and spatially segregated to nonfibrotic areas. The macrophage receptor with collagenous structure (MARCO) protein is a scavenger receptor expressed by specific subsets of macrophages, and its role in liver fibrosis is unclear. In vitro induction of Marco in bone marrow–derived macrophages decreased proinflammatory gene expression, increased antiinflammatory and antifibrotic gene expression, and enhanced phagocytosis, indicating a restorative phenotype. Adoptive transfer of MARCO + macrophages in a mouse model of liver fibrosis reduced the expression of extracellular matrix–associated (ECM-associated) genes in hepatic stellate cells (HSCs) and reduced collagen deposition, which did not occur with the transfer of MARCO – macrophages. Therefore, MARCO + macrophages have a tissue restorative role in the liver and attenuate fibrogenesis through interaction with HSCs, thereby providing a potential therapeutic pathway for liver fibrosis.

Cholangiocyte pathophysiological activation was examined in a model of murine cholestasis. CX3CR1 + macrophages are recruited to the periportal region, likely mediated by cholangiocyte expression of CX3CL1. Cholangiocyte transcriptomics from cholestatic mice display activation of a “pathogen-induced cytokine storm” pathway, and exhibit activation of the transcription factor NF-Y. In human cholangiocytes, NF-Y promotes expression of the profibrogenic ligand TGFβ1. These observations provide insights into the cholestatic cholangiocyte pathobiology contributing to periductal inflammation and fibrosis.

Background: Cholestatic liver diseases, including primary sclerosing cholangitis, are characterized by biliary fibroinflammation. TGFβ-activated cholangiocytes release signals that recruit immune cells and activate myofibroblasts, promoting inflammation and extracellular matrix (ECM) deposition. TGFβ also regulates stearoyl-CoA desaturase (SCD), an enzyme involved in lipid signaling. Yet, the role of SCD or its inhibitor, Aramchol, in biliary fibroinflammation had not been studied. Methods and Results: Mdr2 -/- with established biliary fibrosis and 3,5-diethoxycarboncyl-1,4-dihydrocollidine (DDC) diet-fed mice were treated with Aramchol meglumine (12.5 mg/kg/day). Hepatic fibrosis was assessed by qPCR, Picrosirius red staining, immunofluorescence, and hydroxyproline content. Human H69 or murine large cholangiocyte cell lines stimulated with TGFβ, as well as PSC-derived cholangiocytes (PSC-C), were treated with Aramchol or SCD siRNA. RNA-seq, fibroinflammatory marker expression, peroxisome proliferator-activated receptor (PPAR) activity, and targeted fatty acid profiling were performed. Aramchol treatment significantly reduced hepatic ECM gene expression, inflammatory cytokines ( Il6 , Tnfa ), collagen content, and myofibroblast activation (aSMA staining) in both mouse models. In TGFβ-stimulated H69 cells, Aramchol suppressed hepatic fibrosis pathways and enhanced PPAR signaling. Aramchol also reduced the expression of fibrotic markers, myofibroblast-activating mediators ( VEGFA and PDGFB ), and IL6, mirroring the effects of SCD knockdown. In PSC-C, Aramchol significantly downregulated SCD, VEGFA and IL6 . Conversely, PPARα and -γ activity and fatty acid agonist, linoleic acid levels were increased in cholangiocyte cell lines. Conclusions: Aramchol attenuates and prevents biliary fibrosis in mouse models of cholestatic liver disease by inhibiting TGFβ-induced fibroinflammatory mediators and activating PPARa/γ in cholangiocytes. These findings, combined with its favorable clinical safety profile, support the potential of Aramchol as a therapeutic candidate for PSC.

Objectives/Goals: Primary sclerosing cholangitis (PSC) manifests with an inflammatory milieu that leads to fibrotic scarring of the liver. Human PSC liver bile ducts are enriched with neutrophils; however, their infiltration and functional role is unexplored. Our goal is to investigate the mechanism and impact of peribiliary neutrophil infiltration observed in PSC. Methods/Study Population: Primary cholangiocytes (bile duct cells) isolated from WT and mouse models of PSC (3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed mice and Mdr2-/- mice) were analyzed by RNA-sequencing. Immunofluorescence (IF) was performed on liver tissues from PSC patients and mouse models of PSC for markers of bile ducts and neutrophils (KRT19 and MPO). Intrahepatic leukocytes (IHL) isolated from mice livers were evaluated for neutrophil abundance and activation state. Anti-Ly6G antibody-mediated neutrophil depletion in Mdr2-/- mice was analyzed by IF, histology, and cytometry by time-of-flight (CyTOF). Cholangiocytes stimulated with TNFα (to induce an inflammatory phenotype) were analyzed for neutrophil chemoattractants with genetic and pharmacological interventions. Results/Anticipated Results: RNA-seq analysis of primary cholangiocytes from PSC mouse models revealed enrichment in inflammatory and neutrophil degranulation pathways. Flow cytometry and RT-PCR analysis revealed an increase in the neutrophil population in PSC mice with activated phenotype. Peripheral depletion of neutrophils in Mdr2-/- mice alleviated liver injury and inflammation, along with a reduction in peribiliary neutrophil infiltration and attenuated bridging fibrosis. CyTOF analysis showed a significant reduction in CD8+ T cells upon neutrophil depletion, implying neutrophils sustain CD8+ T cells in PSC liver. Mechanistically in cholangiocytes, TNFα mediates expression of neutrophil chemoattractants, CXCL1 and CXCL8, through the cyclic GMP-AMP synthase stimulator of interferon genes (cGAS-STING) pathway. Discussion/Significance of Impact: Our findings suggest that activation of the STING pathway in cholangiocytes in cholestatic liver disease triggers an immune response resulting in peri-portal neutrophil infiltration via CXC chemokines. The sustained presence of these activated neutrophils engages the adaptive immune system to perpetuate the inflammation and fibrosis seen in PSC.

The field of ribonucleic acid (RNA) biology has revealed an array of noncoding RNA species, particularly long noncoding RNAs (lncRNAs), which play crucial roles in liver disease pathogenesis. This review explores the diverse functions of lncRNAs in liver pathology, including metabolic-associated steatotic liver disease, hepatocellular carcinoma, alcohol-related liver disease, and cholangiopathies such as primary sclerosing cholangitis and cholangiocarcinoma. We highlight key lncRNAs that regulate lipid metabolism, inflammation, fibrosis, and oncogenesis in the liver, demonstrating their diagnostic and therapeutic potential. Emerging RNA-based therapies, such as mRNA therapy, RNA interference, and antisense oligonucleotides, offer approaches to modulate lncRNA activity and address liver disease at a molecular level. Advances in sequencing technologies and bioinformatics pipelines are simultaneously enabling the identification and functional characterization of novel lncRNAs, driving innovation in personalized medicine. In conclusion, this review highlights the potential of lncRNAs as biomarkers and therapeutic targets in liver disease and emphasizes the need for further research into their regulatory mechanisms and clinical applications.

Cholangiopathies comprise a spectrum of chronic intrahepatic and extrahepatic biliary tract disorders culminating in progressive cholestatic liver injury, fibrosis, and often cirrhosis and its sequela. Treatment for these diseases is limited, and collectively, they are one of the therapeutic “black boxes” in clinical hepatology. The etiopathogenesis of the cholangiopathies likely includes disease-specific mediators but also common cellular and molecular events driving disease progression (eg, cholestatic fibrogenesis, inflammation, and duct damage). The common pathways involve cholangiocytes, the epithelial cells lining the intrahepatic and extrahepatic bile ducts, which are central to the pathogenesis of these disorders. Current information suggests that cholangiocytes function as a signaling “hub” in biliary tract-associated injury. Herein, we review the pivotal role of cholangiocytes in cholestatic fibrogenesis, focusing on the crosstalk between cholangiocytes and portal fibroblasts and HSCs. The proclivity of these cells to undergo a senescence-associated secretory phenotype, which is proinflammatory and profibrogenic, and the intrinsic intracellular activation pathways resulting in the secretion of cytokines and chemokines are reviewed. The crosstalk between cholangiocytes and cells of the innate (neutrophils and macrophages) and adaptive (T cells and B cells) immune systems is also examined in detail. The information will help consolidate information on this topic and guide further research and potential therapeutic strategies for these diseases.

Liver fibrosis is characterized by the activation of perivascular hepatic stellate cells (HSCs), the release of fibrogenic nanosized extracellular vesicles (EVs), and increased HSC glycolysis. Nevertheless, how glycolysis in HSCs coordinates fibrosis amplification through tissue zone-specific pathways remains elusive. Here, we demonstrate that HSC-specific genetic inhibition of glycolysis reduced liver fibrosis. Moreover, spatial transcriptomics revealed a fibrosis-mediated up-regulation of EV-related pathways in the liver pericentral zone, which was abrogated by glycolysis genetic inhibition. Mechanistically, glycolysis in HSCs up-regulated the expression of EV-related genes such as Ras-related protein Rab-31 ( RAB31 ) by enhancing histone 3 lysine 9 acetylation on the promoter region, which increased EV release. Functionally, these glycolysis-dependent EVs increased fibrotic gene expression in recipient HSC. Furthermore, EVs derived from glycolysis-deficient mice abrogated liver fibrosis amplification in contrast to glycolysis-competent mouse EVs. In summary, glycolysis in HSCs amplifies liver fibrosis by promoting fibrogenic EV release in the hepatic pericentral zone, which represents a potential therapeutic target.

In this study, a mixed porcine–human bioengineered liver (MPH-BEL) was used in a preclinical setup of extracorporeal liver support devices as a treatment for a model of post-resection liver failure (PRLF). The potential for human clinical application is further illustrated by comparing the functional capacity of MPH-BEL grafts as assessed using this porcine PRLF model with fully human (FH-BEL) grafts which were perfused and assessed in vitro. BEL grafts were produced by reseeding liver scaffolds with HUVEC and primary porcine hepatocytes (MPH-BEL) or primary human hepatocytes (FH-BEL). PRLF was induced by performing an 85% liver resection in domestic white pigs and randomized into the following three groups 24 h after resection: standard medical therapy (SMT) alone, SMT + extracorporeal circuit (ECC), and SMT + MPH-BEL. The detoxification and metabolic functions of the MPH-BEL grafts were compared to FH-BEL grafts which were perfused in vitro. During the 24 h treatment interval, INR values normalized within 18 h in the MPH-BEL therapy group and urea synthesis increased as compared to the SMT and SMT + ECC control groups. The MPH-BEL treatment was associated with more rapid decline in hematocrit and platelet count compared to both control groups. Histological analysis demonstrated platelet sequestration in the MPH-BEL grafts, possibly related to immune activation. Significantly higher rates of ammonia clearance and metabolic function were observed in the FH-BEL grafts perfused in vitro than in the MPH-BEL grafts. The MPH-BEL treatment was associated with improved markers of liver function in PRLF. Further improvement in liver function in the BEL grafts was observed by seeding the biomatrix with human hepatocytes. Methods to reduce platelet sequestration within BEL grafts is an area of ongoing research.