TWEAK/FN14 promotes profibrogenic pathway activation in Prominin-1-expressing hepatic progenitor cells in biliary atresia

TWEAK regulates the functions of hair follicle stem cells via the Fn14-Wnt/β-catenin-CXCR4 signalling axis

Hair follicle stem cells (HFSCs) are crucial for maintaining cutaneous functions under various pathological conditions, including wounds. Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) interacts with its receptor, fibroblast growth factor-inducible 14 (Fn14), and plays a role in the development and tissue repair of skin diseases. This study aims to elucidate the effects of TWEAK/Fn14 signalling on HFSCs and the associated mechanisms. The expressions of HFSC markers, including K19, integrin β1 and K15, were analysed via immunohistochemistry in normal and Fn14-deficient mouse skin. Primary HFSCs were cultured in vitro and then treated with TWEAK or a chemokine (CXC motif) (CXCR) 4 inhibitor. The phenotype markers and secreted cytokines of HFSCs were assessed via immunofluorescence analysis, Western blotting and real-time polymerase chain reaction. Our results showed that both Fn14 and CXCR4 were highly expressed in hair follicles. Fn14 deficiency led to a decrease in the expression levels of K19 and CD34. Exogenous TWEAK enhanced the expression of K15, K19, integrin β1, tumour necrosis factor receptor type 2 and CXCR4 in cultured HFSCs. Additionally, TWEAK induced the proliferation, migration and cytokine production in HFSCs. Furthermore, the Wnt/β-catenin signalling pathway was upregulated in HFSCs upon TWEAK stimulation, and inhibitors of β-catenin or CXCR4 suppressed the effects of TWEAK on the differentiation and secretory functions of HFSCs. In conclusion, TWEAK/Fn14 interaction regulates the expression of differentiation markers and secretory functions of HFSCs in vitro. Wnt/β-catenin signalling or CXCR4 activation mediates the effects of TWEAK on HFSCs. Targeting the Fn14-Wnt/β-catenin-CXCR4 signalling axis may offer a potential approach for managing HFSC-related skin diseases, such as wounds.

Evolving Concepts in Etiology of Biliary Atresia: Insights and Perspectives from India

Introduction: Biliary atresia (BA) is a potentially fatal newborn cholestatic disease. It is a rapidly advancing fibro-obliterative cholangiopathy that leads to liver failure and death if not treated early. The well-known multihit hypothesis proposes that viral or chemical disruption to the biliary epithelium triggers an immune-mediated inflammatory response, resulting in fibrosis and blockage of the intra and extrahepatic biliary systems. Methods: In recent years, several papers have noticed an upsurge in many aspects of BA, particularly its etiopathogenesis, which has opened a vista of various probable mechanisms currently being examined. This review brings them together with an emphasis on reflecting current scientific views for those interested in this illness. Conclusions: Among the different etiological factors proposed for BA, viruses and immune-mediated injury are the strongest contenders as contributors to the disease onset and pathogenesis.

Integrative single-cell and spatial transcriptomic analyses identify a pathogenic cholangiocyte niche and TNFRSF12A as therapeutic target for biliary atresia

BACKGROUND AND AIMS

Biliary atresia (BA) is a devastating fibroinflammatory biliary disease that is the leading indication for pediatric liver transplants worldwide. Although cholangiocytes are the primary target cells, the pathogenic mechanisms involving cholangiocytes remain elusive. Here, we aimed to characterize the pathogenic role of cholangiocytes in BA.

APPROACH AND RESULTS

Integration of single-cell RNA sequencing of 12 liver tissues (from 9 BA and 3 controls) and the spatial transcriptome of another four liver sections (from 2 BA and 2 controls) provided a comprehensive spatial liver cell atlas of BA. In particular, we identified a cholangiocyte-enriched spatial niche with infiltration of activated HSCs, activated portal fibroblasts, macrovascular endothelial cells, and TREM2 + macrophages that were elevated in the portal triad of BA. This niche was positively correlated with bile duct profiles, liver fibrosis, and poor survival in 2 independent cohorts of patients with BA. Using integrative bioinformatics analyses to mine the cell-cell communication and regulatory network in BA cholangiocytes, we uncovered the fibroinflammatory phenotype of cholangiocytes with TNFSF12-TNFRSF12A as a significant signal. Genetic ablation or blockade of TNFRSF12A suppresses liver injury, inflammation, and bile duct profiles in a mouse model of disease. Using human biliary organoids, we revealed that BA organoids expressed higher levels of CCL2 in response to TNFSF12 stimulation and promoted monocyte chemotaxis via the CCL2-CCR2 axis.

CONCLUSIONS

Pathogenic cholangiocytes-enriched niche identifies TNFRSF12A as a potential therapeutic target for BA.

Diversity and heterogeneity in human pancreaticobiliary maljunction revealed by single-cell RNA sequencing

PURPOSE

The etiology and pathogenesis of pancreaticobiliary maljunction (PBM) remain unclear, thus a comprehensive investigation of cellular diversity and microenvironmental differences is pivotal to elucidate the mechanisms driving PBM.

METHODS

We performed single-cell RNA sequencing on bile duct tissues from six patients, including three with PBM and three without (non-PBM). Pathway enrichment, transcription factor analysis, and cell-cell communication were analyzed to explore cellular interactions and functional states.

RESULTS

A total of 90,996 single cells and 11 distinct cell lineages were identified, revealing significant differences in cellular composition between the two groups. PBM group was characterized by a higher proportion of endothelial cells and fibroblasts, while B and T cells were less abundant. Three subtypes of fibroblasts, antigen-presenting, inflammatory, and myofibroblastic cancer-associated fibroblasts, with the myofibroblast subtype being predominant in PBM. We found heightened activity of the WNT and TWEAK signaling pathways in PBM, as well as increased ligand-receptor interactions between fibroblasts and other cell types, including epithelial and endothelial cells.

CONCLUSION

Fibroblasts play a central role in driving fibrosis and tissue remodeling in PBM through specific signaling pathways. These insights provide a foundation for future therapeutic strategies aimed at modulating fibroblast activity to prevent or mitigate fibrosis in PBM.

The utilisation of biliary organoids for biomedical applications

Biliary duct injury, biliary atresia (BA), biliary tract tumors, primary sclerosing cholangitis (PSC), and other diseases are commonly encountered in clinical practice within the digestive system. To gain a better understanding of the pathogenesis and development of these diseases and explore more effective treatment methods, organoid technology has recently garnered significant attention. Organoids are three-dimensional structures derived from stem/progenitor cells that can faithfully mimic the intricate structure and physiological function of tissues or organs in vitro. They provide a valuable platform for studying the pathogenesis of biliary tract diseases and offer novel possibilities for repairing and regenerating biliary tract injuries. The main seed cells used to construct biliary tract organoids include primary human biliary tract epithelial cells as well as pluripotent stem cells. The construction of these organoids involves various techniques such as traditional embedding technology, rotary culture technology, hanging drop culture technology, along with emerging approaches like organ chip technology, three-dimensional (3D) printing technology, and four-dimensional (4D) printing technology. This article comprehensively reviews the construction methods of biliary tract organoids while discussing their applications in disease modeling research on disease mechanisms drug screening tissue/organ repair; it also highlights current challenges and suggests future research directions regarding biliary tract organoids which will serve as references for treating common refractory digestive system diseases in clinical practice.

TWEAK is an activator of Hippo-YAP signaling protecting against hepatic Ischemia/ reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) represents a formidable complication commonly linked with hemorrhagic shock, liver resection, and transplantation. This study aims to elucidate the role of Tumor Necrosis Factor-like Weak Inducer of Apoptosis (TWEAK) in the pathogenesis of hepatic I/R injury and to delineate the underlying mechanisms involved. Utilizing a hypoxia-reoxygenation model in human liver organoids (HLOs) alongside a murine model of warm ischemia-reperfusion injury, we systematically investigated the interplay between TWEAK, its receptor Fn14, and the HIPPO signaling pathway. Our findings indicate that TWEAK pretreatment significantly mitigates IRI in murine livers as well as hypoxia/reoxygenation injury in HLOs. Notably, administration of adeno-associated virus (AAV) to knock down Fn14 abrogated the protective effects of TWEAK in the murine model. Transcriptome sequencing analysis revealed that the interaction between TWEAK and Fn14 enhances cellular resistance to IRI by activating the HIPPO signaling pathway. Overall, TWEAK emerges as a promising therapeutic target for mitigating hepatic I/R injury, potentially improving outcomes in liver transplantation.

Molecular Mechanisms of Fibrosis in Cholestatic Liver Diseases and Regenerative Medicine-Based Therapies

The aim of this review is to explore the potential of new regenerative medicine approaches in the treatment of cholestatic liver fibrosis. Cholestatic liver diseases, such as primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and biliary atresia (BA), due to the accumulation of bile, often progress to liver fibrosis, cirrhosis, and liver failure. When the disease becomes severe enough to require liver transplantation. Deeply understanding the disease's progression and fibrosis formation is crucial for better diagnosis and treatment. Current liver fibrosis treatments mainly target the root causes and no direct treatment method in fibrosis itself. Recent advances in regenerative medicine offer a potential approach that may help find the ways to target fibrosis directly, offering hope for improved outcomes. We also summarize, analyze, and discuss the current state and benefits of regenerative medicine therapies such as mesenchymal stem cell (MSC) therapy, induced pluripotent stem cells (iPSCs), and organoid technology, which may help the treatment of cholestatic liver diseases. Focusing on the latest research may reveal new targets and enhance therapeutic efficacy, potentially leading to more effective management and even curative strategies for cholestatic liver diseases.

Predicting and managing liver fibrosis in biliary atresia

Regardless of the underlying etiology and success of PE, progressive liver fibrosis and eventually cirrhosis represent the dominant pathology and the end-stage of BA. Ascending bile duct injury-induced cholestasis, inflammation and ductular reaction provide profibrogenic cytokine environment leading to myofibroblast activation and rapid progression of fibrosis especially after unsuccessful portoenterostomy. Although liver fibrosis and development of cirrhosis play a crucial role in determining BA outcomes, the exact prognostic significance and dynamics of mild to moderate liver fibrosis remain unclear. Manual scoring systems categorizing the degree of liver fibrosis are prone to intra- and interobserver variability, whereas novel combinations of digital pathology with artificial intelligence quantification can provide accurate information on fibrosis structure and dynamics at the level of individual collagen fibers. Although several studies have analyzed noninvasive assessment of fibrosis at time of PE, including imaging-based elastography and different serum biomarkers, current knowledge on their accuracy during the postoperative follow-up of BA is scarce. While therapeutic management of liver fibrosis in BA remains in its infancy, the resolution potential for liver fibrosis has been demonstrated after successful PE. Achievement of effective antifibrotic treatment may require combination of different therapies with complementary modes of action like anti-inflammatory medication, antioxidants and bile acid lowering agents.

Ductular Reactions in Liver Injury, Regeneration, and Disease Progression-An Overview

Ductular reaction (DR) is a complex cellular response that occurs in the liver during chronic injuries. DR mainly consists of hyper-proliferative or reactive cholangiocytes and, to a lesser extent, de-differentiated hepatocytes and liver progenitors presenting a close spatial interaction with periportal mesenchyme and immune cells. The underlying pathology of DRs leads to extensive tissue remodeling in chronic liver diseases. DR initiates as a tissue-regeneration mechanism in the liver; however, its close association with progressive fibrosis and inflammation in many chronic liver diseases makes it a more complicated pathological response than a simple regenerative process. An in-depth understanding of the cellular physiology of DRs and their contribution to tissue repair, inflammation, and progressive fibrosis can help scientists develop cell-type specific targeted therapies to manage liver fibrosis and chronic liver diseases effectively.

Unraveling the complexities of fibrosis and ductular reaction in liver disease: pathogenesis, mechanisms, and therapeutic insights

Ductular reaction and fibrosis are hallmarks of many liver diseases including primary sclerosing cholangitis, primary biliary cholangitis, biliary atresia, alcoholic liver disease, and metabolic dysfunction-associated steatotic liver disease/metabolic dysfunction-associated steatohepatitis. Liver fibrosis is the accumulation of extracellular matrix often caused by excess collagen deposition by myofibroblasts. Ductular reaction is the proliferation of bile ducts (which are composed of cholangiocytes) during liver injury. Many other cells including hepatic stellate cells, hepatocytes, hepatic progenitor cells, mesenchymal stem cells, and immune cells contribute to ductular reaction and fibrosis by either directly or indirectly interacting with myofibroblasts and cholangiocytes. This review summarizes the recent findings in cellular links between ductular reaction and fibrosis in numerous liver diseases.

Vitreous Olink proteomics reveals inflammatory biomarkers for diagnosis and prognosis of traumatic proliferative vitreoretinopathy

Background

The aim of this study was to identify inflammatory biomarkers in traumatic proliferative vitreoretinopathy (TPVR) patients and further validate the expression curve of particular biomarkers in the rabbit TPVR model.

Methods

The Olink Inflammation Panel was used to compare the differentially expressed proteins (DEPs) in the vitreous of TPVR patients 7-14 days after open globe injury (OGI) (N = 19) and macular hole patients (N = 22), followed by correlation analysis between DEPs and clinical signs, protein-protein interaction (PPI) analysis, area under the receiver operating characteristic curve (AUC) analysis, and function enrichment analysis. A TPVR rabbit model was established and expression levels of candidate interleukin family members (IL-6, IL-7, and IL-33) were measured by enzyme-linked immunosorbent assay (ELISA) at 0, 1, 3, 7, 10, 14, and 28 days after OGI.

Results

Forty-eight DEPs were detected between the two groups. Correlation analysis showed that CXCL5, EN-RAGE, IL-7, ADA, CD5, CCL25, CASP8, TWEAK, and IL-33 were significantly correlated with clinical signs including ocular wound characteristics, PVR scoring, PVR recurrence, and final visual acuity (R = 0.467-0.699, p < 0.05), and all with optimal AUC values (0.7344-1). Correlations between DEP analysis and PPI analysis further verified that IL-6, IL-7, IL-8, IL-33, HGF, and CXCL5 were highly interactive (combined score: 0.669-0.983). These DEPs were enriched in novel pathways such as cancer signaling pathway (N = 14, p < 0.000). Vitreous levels of IL-6, IL-7, and IL-33 in the rabbit TPVR model displayed consistency with the trend in Olink data, all exhibiting marked differential expression 1 day following the OGI.

Conclusion

IL-7, IL-33, EN-RAGE, TWEAK, CXCL5, and CD5 may be potential biomarkers for TPVR pathogenesis and prognosis, and early post-injury may be an ideal time for TPVR intervention targeting interleukin family biomarkers.

Cellular and Molecular Mechanisms of Toxic Liver Fibrosis in Rats Depending on the Stages of Its Development

The aim is to study the cellular and molecular features of toxic liver fibrosis in rats and its dependence on development stages of this pathological condition.

Materials and Methods

Liver fibrogenesis in male Wistar rats was induced with the thioacetamide solution by introducing into the stomach with a probe at a dose of 200 mg/kg of animal body weight 2 times per week. The process dynamics was studied at 5 time points (control, week 3, week 5, week 7, and week 9). The mRNA levels of tweak, fn14, ang, vegfa, cxcl12, and mmp-9 genes in liver were detected by real-time polymerase chain reaction. Immunohistochemical study was performed on paraffin sections. The CD31, CD34, CK19, α-SMA, FAP, CD68, CD206, CX3CR1, and CD45 cells were used as markers. Fibrosis degree was determined in histological sections, stained in line with the Mallory technique, according to the Ishak's semi-quantitative scale.

Results

Two simultaneously existing morphologically heterogeneous populations of myofibroblasts expressing different types of markers (FAP, α-SMA) were identified in rat liver. Prior to the onset of transformation of fibrosis into cirrhosis (F1-F4, weeks 3-7), FAP+ and SMA+ cells were localized in different places on histological specimens. All stages of liver fibrosis development were accompanied by an increase in the number (p=0.0000), a change in the phenotypic structure and functional properties of macrophages. The CK19+ cells of the portal areas differentiated into cholangiocytes that formed interlobular bile ducts and ductules, as well as hepatocytes that formed rudiments of new hepatic microlobules. Pathological venous angiogenesis and heterogeneity of endotheliocytes of the intrahepatic vascular bed were detected. Two options for changes in mRNA expression of the selected genes were identified. The level of the fn14 and mmp-9 mRNAs at all stages of fibrosis was higher (p=0.0000) than in control rats. For tweak, ang, vegfa, and cxcl12 mRNAs, the situation was the opposite - the level of genes decreased (p=0.0000). There were strong and moderate correlations between the studied target genes (p<0.05).

Conclusion

It was established that the stages of toxic fibrosis had morphological and molecular genetic features. The FAP+ cells make the main contribution to development of portal and initial stage of bridging fibrosis. The stellate macrophages and infiltrating monocytes/ macrophages can potentially be used for development of new therapeutic strategies for liver pathology treatment. One should take into account the features of the markers' expression by endothelial cells during the study of the intrahepatic vascular bed. Joint study of genes is a necessary ad-hoc parameter in fundamental and preclinical research.