The Origin and Fate of Liver Myofibroblasts

Circadian clock regulation of myofibroblast fate

Fibrosis-related disorders represent an increasing medical and economic burden on a worldwide scale, accounting for one-third of all disease-related deaths with limited therapeutic options. As central mediators in fibrosis development, myofibroblasts have been gaining increasing attention in the last 20 years as potential targets for fibrosis attenuation and reversal. While various aspects of myofibroblast physiology have been proposed as treatment targets, many of these approaches have shown limited long-term efficacy so far. However, ongoing research is uncovering new potential strategies for targeting myofibroblast activity, offering hope for more effective treatments in the future. The circadian molecular clock is a feature of almost every cell in the human body that dictates the rhythmic nature of various aspects of human physiology and behavior in response to changes in the surrounding environment. The dysregulation of these rhythms with aging is considered to be one of the underlying reasons behind the development of multiple aging-related chronic disorders, with fibrotic tissue scarring being a common pathological complication among the majority of them. Myofibroblast dysregulation due to skewed circadian clockwork might significantly contribute to fibrotic scar persistence. In the current review, we highlight the role of the circadian clock in the context of myofibroblast activation and deactivation and examine its dysregulation as a driver of fibrogenesis.

Cellular interactions in self-directed immune-mediated liver diseases

The lymphocyte population must traverse a complex path throughout their journey to the liver. The signals which these cells must detect, including cytokines, chemokines and other soluble factors, steer their course towards further crosstalk with other hepatic immune cells, hepatocytes and biliary epithelial cells. A series of specific chemokine receptors and adhesion molecules drive not only the recruitment, migration, and retention of these cells within the liver, but also their localisation. Perturbation of these interactions and failure of self-recognition drive the development of several autoimmune liver diseases. We also describe check point-induced liver injury. Immune cell internalisation into hepatocytes (emperipolesis) in autoimmune hepatitis and into biliary epithelial cells (intra-epithelial lymphocyte) in primary biliary cholangitis are typical features in autoimmune liver diseases. Finally, we describe emerging immune-based therapies, including regulatory T cell, anti-cytokine and anti-chemokine therapies, cytokine supplementation (e.g. interleukin-2), as well as co-inhibitory molecule manipulation, including T-cell engagers, and discuss their potential application in the treatment of autoimmune liver diseases.

The hepatoprotective effects of the polyphenol-enriched n-butanol fraction of Cnicus benedictus against carbon tetrachloride-induced liver fibrosis in rats: In vivo study

Liver fibrosis is a continuous wound-healing response to chronic injury caused by various chemical, virus, and pathological disorders; the lack of approved drugs or methods to reverse or prevent liver fibrosis makes it an interesting area of research. This study investigates the potential hepatoprotective effects of the phenolic extract of Cnicus benedictus in rat's module of liver fibrosis. Liver fibrosis was induced by intraperitoneal injection of carbon tetrachloride (CCl4) for six consecutive weeks; the butanol fraction of Cnicus and silymarin was administered orally concurrently with CCl4. After six weeks, all animals were euthanized. Rat liver tissue levels of malondialdehyde (MDA) and glutathione (GSH) were measured, and serum liver enzymes and protein were measured using the ELISA technique. Histopathological study and immunohistochemistry of liver tissue for transforming growth factor (TGF-β1), alpha-smooth muscle actin (α-SMA), and hydroxyproline were assessed. In HPLC analysis, Cnicus extract showed several components, including quercetin, gallic acid, rutin, kaempferol, silibinin, and apigenin. Treatment with Cnicus butanol extract reduces serum ALT, AST, bilirubin, and albumin levels compared to induction. Additionally, Cnicus extract increases liver GSH levels and decreases liver MDA levels compared to induction. Liver tissue of TGF-β1, α-SMA, and hydroxyproline expression was downregulated in rats receiving Cnicus extract. Liver tissue histopathology showed improvement in its features compared to the induction group. In conclusion, oral administration of the polyphenol-enriched n-butanol fraction of Cnicus benedictus showed a protective effect on liver fibrosis caused by CCl4, possibly through antioxidant and anti-inflammatory mechanisms.

Chronic Inflammation and Immune Dysregulation in Metabolic-Dysfunction-Associated Steatotic Liver Disease Progression: From Steatosis to Hepatocellular Carcinoma

Background/Objectives: Metabolic-dysfunction-associated steatotic liver disease (MASLD) progresses from hepatic steatosis to hepatocellular carcinoma (HCC) as a result of systemic immunometabolic dysfunction. This review summarizes the key roles of the innate and adaptive immune mechanisms driving hepatic injury, fibrogenesis, and carcinogenesis in MASLD. Methods: A comprehensive literature review was performed using PubMed to identify relevant published studies. Eligible articles included original research and clinical studies addressing immunological and metabolic mechanisms in MASLD, as well as emerging therapeutic strategies. Results: We highlight the roles of cytokine networks, the gut-liver axis, and immune cell reprogramming. Emerging therapeutic strategies, including cytokine inhibitors, anti-fibrotic agents, metabolic modulators, and nutraceuticals, offer several indications for attenuating MASLD progression and reducing the prevalence of extrahepatic manifestations. Conclusions: Given the heterogeneity of MASLD, personalized combination-based approaches targeting both inflammation and metabolic stress are essential for effective disease management and the prevention of systemic complications.

Transcriptomic and lipidomic analysis of aging-associated inflammatory signature in mouse liver

BACKGROUND

Aging-associated dysbiosis leads to chronic inflammation and the development of a range of aging-related diseases. The gut microbiota crosstalks with the host by providing lipid metabolites and modulating metabolic functions. However, the precise mechanism by which the gut microbiota regulates aging is unknown. The objective of this study was to examine the impact of the gut microbiota on the transcriptome and lipidome associated with aging in mouse liver.

METHODS

RNA-sequencing was conducted on the livers of young and aged male and female-specific pathogen-free (SPF) and germ-free (GF) mice to comprehensively analyze transcriptomic alterations with aging. We also reanalyzed our previously reported results on aging-associated changes in the hepatic lipidome to investigate the gut microbiota-dependent hepatic lipidome signatures associated with aging.

RESULTS

In contrast to the findings in male mice, the changes in hepatic transcriptome associated with aging were attenuated in female GF mice compared with those in SPF mice. In particular, the gene sets associated with inflammatory signatures (i.e., inflammation and tissue remodeling) were found to be suppressed in female GF mice. The ChIP-Atlas database predicted that transcription factors associated with sex differences may be involved in the gene signature of aged female GF mice. Significant differences in the lipid profile were observed between aged SPF and GF female mice, including in bile acids, sterol sulfates, lysophospholipids, oxidized triacylglycerols, vitamin D, and phytoceramides. Moreover, notable alterations were identified in the quality of phospholipids and sphingolipids. Integrated transcriptomic and lipidomic analysis identified candidate enzymes responsible for the change of lipid profiles in aged female mice.

CONCLUSIONS

The findings of this study offer new insights into the molecular mechanisms through which the gut microbiota regulates aging-related phenotypes such as inflammation in the liver, possibly through modulating lipid metabolism in a sex-dependent manner.

Multi-modal analysis of human hepatic stellate cells identifies novel therapeutic targets for metabolic dysfunction-associated steatotic liver disease

BACKGROUND & AIMS

Metabolic dysfunction-associated steatotic liver disease ranges from metabolic dysfunction-associated steatotic liver (MASL) to metabolic dysfunction-associated steatohepatitis (MASH) with fibrosis. Transdifferentiation of hepatic stellate cells (HSCs) into fibrogenic myofibroblasts plays a critical role in the pathogenesis of MASH liver fibrosis. We compared transcriptome and chromatin accessibility of human HSCs from NORMAL, MASL, and MASH livers at single-cell resolution. We aimed to identify genes that are upregulated in activated HSCs and to determine which of these genes are key in the pathogenesis of MASH fibrosis.

METHODS

Eighteen human livers were profiled using single-nucleus (sn)RNA-seq and snATAC-seq. High priority targets were identified, then tested in 2D human HSC cultures, 3D human liver spheroids, and HSC-specific gene knockout mice.

RESULTS

MASH-enriched activated HSC subclusters are the major source of extracellular matrix proteins. We identified a set of concurrently upregulated and more accessible core genes (GAS7, SPON1, SERPINE1, LTBP2, KLF9, EFEMP1) that drive activation of HSCs. Expression of these genes was regulated via crosstalk between lineage-specific (JUNB/AP1), cluster-specific (RUNX1/2) and signal-specific (FOXA1/2) transcription factors. The pathological relevance of the selected targets, such as SERPINE1 (PAI-1), was demonstrated using dsiRNA-based HSC-specific gene knockdown or pharmacological inhibition of PAI-1 in 3D human MASH liver spheroids, and HSC-specific Serpine1 knockout mice.

CONCLUSION

This study identified novel gene targets and regulatory mechanisms underlying activation of fibrogenic HSCs in MASH, and demonstrated that genetic or pharmacological inhibition of select genes suppressed liver fibrosis.

IMPACT AND IMPLICATIONS

Herein, we present the results of a multi-modal sequencing analysis of human hepatic stellate cells (HSCs) from NORMAL, MASL (metabolic dysfunction-associated steatotic liver), and metabolic dysfunction-associated steatohepatitis (MASH) livers. We identified additional subclusters that were not detected by previous studies and characterized the mechanism by which HSCs are activated in MASH livers, including the transcriptional machinery that induces the transdifferentiation of HSCs into myofibroblasts. For the first time, we described the pathogenic role of activated HSC-derived PAI-1 (a product of the SERPINE1 gene) in the development of MASH liver fibrosis. Targeting the RUNX1/2-SERPINE1 axis could be a novel strategy for the treatment of liver fibrosis in patients.

Targeting AMPK as a potential treatment for hepatic fibrosis in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease, and often progresses to hepatic fibrosis, cirrhosis, and liver failure. Despite its increasing prevalence, effective pharmacological treatments for MASLD-related fibrosis remain limited. Recent research has highlighted AMP-activated protein kinase (AMPK) as a key regulator of the processes that promote fibrogenesis, and AMPK activation shows potential in mitigating fibrosis. Advances in AMPK activators and deeper insights into their role in fibrotic pathways have recently revitalized interest in targeting AMPK for fibrosis treatment. This review discusses the molecular mechanisms linking AMPK to hepatic fibrosis and evaluates emerging AMPK-directed therapies. Furthermore, it addresses challenges in clinical translation. Importantly, we combine the latest mechanistic discoveries with recent therapeutic developments to provide a comprehensive perspective on AMPK as a target for hepatic fibrosis treatment.

Regulation of Hepatic Stellate Cell Phenotypes in Metabolic Dysfunction-Associated Steatohepatitis

Hepatic stellate cells (HSCs) play a crucial role in the pathogenesis of liver fibrosis in metabolic dysfunction-associated steatohepatitis (MASH), a condition characterized by excessive fat accumulation in the hepatocytes, unrelated to alcohol consumption. In a healthy liver, HSCs are quiescent, store vitamin A, and function as pericytes. However, in response to liver injury and inflammation, HSCs become activated. In MASH, HSC activation is driven by metabolic stress, lipotoxicity, and chronic inflammation. Injured hepatocytes, recruited macrophage, capillarized sinusoidal endothelial cells, and permeable intestinal epithelium may each contribute to activating HSCS. This leads to a unique inflammatory environment that promotes fibrosis. MASH HSCs change their metabolism to favor glycolysis, glutaminolysis, and lactate generation. Activated HSCs transform into myofibroblast-like cells, producing excessive extracellular matrix components that result in fibrosis. In addition, HSCs in MASH have inflammatory and intermediate activated phenotypes. This fibrotic process is a key feature of MASH, which can lead to cirrhosis and liver cancer. Understanding the mechanisms of HSC activation and their role in MASH progression is essential for developing targeted therapies to treat and prevent liver fibrosis in affected individuals.

Cancer-Associated Fibroblasts in Intrahepatic Cholangiocarcinoma: Insights into Origins, Heterogeneity, Lymphangiogenesis, and Peritoneal Metastasis

Intrahepatic cholangiocarcinoma (iCCA) denotes a rare, highly malignant, and heterogeneous class of primary liver adenocarcinomas exhibiting phenotypic characteristics of cholangiocyte differentiation. Among the distinctive pathological features of iCCA, one that differentiates the most common macroscopic subtype (eg, mass-forming type) of this hepatic tumor from conventional hepatocellular carcinoma is a prominent desmoplastic reaction manifested as a dense fibro-collagenous-enriched tumor stroma. Cancer-associated fibroblasts (CAFs) represent the most abundant mesenchymal cell type in the desmoplastic reaction. Although the protumor effects of CAFs in iCCA have been increasingly recognized, more recent cell lineage tracing studies, advanced single-cell RNA sequencing, and expanded biomarker analyses have provided new awareness into their ontogeny, as well as underscored their biological complexity as reflected by the presence of multiple subtypes. In addition, evidence supports CAFs' potential to display cancer-restrictive roles, including immunosuppression. However, CAFs also play important roles in facilitating metastasis, as exemplified by lymph node metastasis and peritoneal carcinomatosis, which are common in iCCA. Herein, the authors provide a timely appraisal of the origins and phenotypic and functional complexity of CAFs in iCCA, together with providing mechanistic insights into lymphangiogenesis and peritoneal metastasis relevant to this lethal human cancer.

Exosomal miRNA reprogramming in pyroptotic macrophage drives silica-induced fibroblast-to-myofibroblast transition and pulmonary fibrosis

Silicosis is an occupational lung disease characterized by progressive pulmonary fibrosis, threatening millions of occupational workers worldwide due to a lack of effective treatments. To unveil mechanisms underlying silica-induced pulmonary fibrosis, we established in vitro and in vivo silicosis models, then employed scRNA-sequencing to profile the cellular landscape of lung tissues followed by characterization of macrophage pyroptosis and exosome therefrom in driving fibroblast-to-myofibroblast-transdifferentiation. Using hyperspectral imaging and artificial intelligence-powered pathological recognition, we found that silica nanoparticle (SiNP) triggered progressive lung fibrosis in vivo, and scRNA-seq implicated interstitial macrophage as pivotal regulators for fibroblast transdifferentiation. Mechanistically, SiNPs were demonstrated to induce macrophage pyroptosis and liberate exosomes, which upregulated pro-fibrotic markers and promoted myofibroblast transition. Subsequent high-throughput miR-sequencing revealed distinct exosomal miRNA signatures that modulated TGF-β signaling and induced fibroblast transdifferentiation. Lastly, we administered these exosomes into silicotic mice and found exacerbated inflammatory infiltration and pulmonary fibrosis. In conclusion, SiNPs exposure caused the remodeling of exosomal miRNAs by inducing interstitial macrophage pyroptosis, and exosomes derived from pyroptotic macrophage fuel fibroblast transdifferentiation by creating a pro-fibrotic microenvironment and promoting silicotic fibrosis. These findings provide critical insights into the pathogenesis of silicosis and the formulation of emerging therapeutic strategies.

C6orf120 Deficiency Inhibits Hepatic Stellate Cell Activation by Upregulating RARβ Signaling

Vitamin A (VA) and its active form, retinoic acid (RA), are crucial for preserving hepatic stellate cells (HSCs) quiescence and reversing fibrosis. While C6orf120 is known to be involved in HSC activation, its role in RA signaling is unclear. This study found that C6orf120 knockdown markedly reduced CCL4-induced liver fibrosis and TGF-β1-induced activation in LX-2 cells, a human HSC line. This inhibition was associated with enhanced RA signaling, particularly affecting the RA receptor beta (RARβ). Inhibition of RARβ significantly reversed the protective effects of C6orf120 knockdown, indicating that RARβ signaling contributes to the inhibitory effect of C6orf120 knockdown on HSC activation. Our results reveal that C6orf120 inhibition could be a therapeutic strategy for liver fibrosis by regulating RARβ signaling.

Bie Jia Jian pill ameliorates BDL-induced cholestatic hepatic fibrosis in rats by regulating intestinal microbial composition and TMAO-mediated PI3K/AKT signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

As a compound of traditional Chinese medicine (TCM), Bie Jia Jian pill (BJJP) is extensively used to treat the clinical chronic liver disease. Nevertheless, the specific mechanism through which BJJP affects hepatic fibrosis (HF) remains unknown.

AIM OF THE STUDY

To explore the role and potential mechanism of BJJP involved in treating HF.

MATERIALS AND METHODS

HF model of Sprague-Dawley (SD) rats was induced by a bile duct ligation (BDL). The function of BJJP involved in the intestinal microbiota (IM) and its metabolites in BDL-induced HF rats were explored through the 16S rRNA sequencing and untargeted metabolomics technologies. Network pharmacology was used to forecast mechanism underlying BJJP's anti-HF effects, which were validated in BDL-induced rats and trimethylamine N-oxide (TMAO)-induced LX-2 and HSC-T6 cells.

RESULTS

BJJP effectively ameliorated pathological liver damage, inflammation, and fibrosis of the BDL-induced HF rats. BJJP regulated IM diversity and composition and interfered with trimethylamine (TMA)-flavin monooxygenase 3 (FMO3)-TMAO process. In vitro, BJJP significantly inhibited the TMAO-induced activation of hepatic stellate cells (HSCs) (rat HSC cell line, HSC-T6; human HSC cell line, LX-2). Network pharmacology results demonstrated that PI3K/AKT signal pathway is crucially involved in BJJP treatment of HF. Further research revealed that BJJP inhibited the PI3K/AKT signal pathway in BDL-induced HF rats. Moreover, TMAO activated the PI3K/AKT pathway, whereas BJJP suppressed TMAO-induced activation. Subsequent intervention with 740Y-P (the PI3K agonist) successfully neutralized the repression effect on PI3K/AKT signal pathway by BJJP.

CONCLUSION

These results clearly show that BJJP attenuates HF by regulating the IM, as well as inhibiting PI3K/AKT pathway mediated by TMAO.

LARP6 regulates the mRNA translation of fibrogenic genes in liver fibrosis

Metabolic syndrome and excessive alcohol consumption result in liver injury and fibrosis, which is characterized by increased collagen production by activated Hepatic Stellate Cells (HSCs). LARP6, an RNA-binding protein, was shown to facilitate collagen production. However, LARP6 expression and functionality as a regulator of fibrosis development in a disease relevant model remains elusive. By using snRNA-sequencing, we show that LARP6 is upregulated mainly in HSCs of liver fibrosis patients. Moreover, LARP6 knockdown in human HSCs suppresses fibrogenic gene expression. By integrating eCLIP analysis and ribosome profiling in HSCs, we show that LARP6 interacts with mature mRNAs comprising over 300 genes, including RNA structural elements within COL1A1 , COL1A2 , and COL3A1 to regulate mRNA expression and translation. Furthermore, LARP6 knockdown in HSC attenuates fibrosis development in human liver spheroids. Altogether, our results suggest that targeting LARP6 in human HSCs may provide new strategies for anti-fibrotic therapy.

Highlights

LARP6 is upregulated in liver fibrosis, mainly in HSCs.LARP6 knockdown in human HSCs reduces liver fibrosis development.Of the hundreds of gene targets, LARP6 interacts most with collagen mRNAs.LARP6 regulates mRNA translation via interaction with 5'UTRs.

New Insights into AMPK, as a Potential Therapeutic Target in Metabolic Dysfunction-Associated Steatotic Liver Disease and Hepatic Fibrosis

AMP-activated protein kinase (AMPK) activators have garnered significant attention for their potential to prevent the progression of metabolic dysfunction-associated steatotic liver disease (MASLD) into liver fibrosis and to fundamentally improve liver function. The broad spectrum of pathways regulated by AMPK activators makes them promising alternatives to conventional liver replacement therapies and the limited pharmacological treatments currently available. In this study, we aim to illustrate the newly detailed multiple mechanisms of MASLD progression based on the multiple-hit hypothesis. This model posits that impaired lipid metabolism, combined with insulin resistance and metabolic imbalance, initiates inflammatory cascades, gut dysbiosis, and the accumulation of toxic metabolites, ultimately promoting fibrosis and accelerating MASLD progression to irreversible hepatocellular carcinoma (HCC). AMPK plays a multifaceted protective role against these pathological conditions by regulating several key downstream signaling pathways. It regulates biological effectors critical to metabolic and inflammatory responses, such as SIRT1, Nrf2, mTOR, and TGF-β, through complex and interrelated mechanisms. Due to these intricate connections, AMPK's role is pivotal in managing metabolic and inflammatory disorders. In this review, we demonstrate the specific roles of AMPK and its related pathways. Several agents directly activate AMPK by binding as agonists, while some others indirectly activate AMPK by modulating upstream molecules, including adiponectin, LKB1, and the AMP: ATP ratio. As AMPK activators can target each stage of MASLD progression, the development of AMPK activators offers immense potential to expand therapeutic strategies for liver diseases such as MASH, MASLD, and liver fibrosis.

Isoastragaloside I attenuates cholestatic liver diseases by ameliorating liver injury, regulating bile acid metabolism and restoring intestinal barrier

ETHNOPHARMACOLOGICAL RELEVANCE

Cholestatic liver diseases (CLD) are liver disorders resulting from abnormal bile formation, secretion, and excretion from various causes. Due to the lack of suitable and safe medications, liver transplantation is the ultimate treatment for CLD patients. Isoastragaloside I (IAS I) is one of the main saponin found in Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao or Astragalus membranaceus (Fisch.) Bge, which has been demonstrated to obviously alleviate CLD. Nevertheless, the IAS I's specific anti-CLD mechanism remains undecipherable.

AIM OF THE STUDY

This study's purpose was to elucidate the protective consequence of IAS I on 0.1% 3, 5-diethoxycarbonyl-1,4-dihydroxychollidine (DDC) diet-induced CLD mice, and to reveal its potential mechanism.

MATERIALS AND METHODS

In this study, mice with CLD that had been fed a 0.1% DDC diet were distributed two doses of IAS I (20 mg/kg, 50 mg/kg). The effects of IAS I on CLD models were investigated by assessing blood biochemistry, liver histology, and Hyp concentrations. We investigated markers of liver fibrosis and ductular reaction using immunohistochemistry, Western blot, and qRT-PCR. Liver inflammation indicators, arachidonic acid (ARA), and ω-3 fatty acid (FA) metabolites were also analyzed. Quantitative determination of 39 bile acids (BAs) in different organs employing UHPLC-Q-Exactive Orbitrap HRMS technology. Additionally, the H&E and Western blot analysis were used to evaluate differences in intestinal barrier function in DDC-induced mice before and after administering IAS I.

RESULTS

After treatment with IAS I, serum biochemical indicators and liver hydroxyproline (Hyp) increased in a dose-dependent manner in CLD mice. The IAS I group showed significant improvement in indicators of liver fibrosis and ductular response, including as α-smooth muscle actin (α-SMA) and cytokeratin 19 (CK19), and transforming growth factor-β (TGF-β)/Smads signaling pathway. And inflammatory factors: F4/80, tumor necrosis factor-α (TNF-α), Interleukin-1β (IL-1β), ARA and ω-3 FA metabolites showed significant improvement following IAS I treatment. Moreover, IAS I significantly ameliorated liver tau-BAs levels, particularly TCA, THCA, THDCA, TCDCA, and TDCA contents, which were associated with enhanced expression of hepatic farnesoid X receptor (FXR), small heterodimer partner (SHP), cholesterol 7α-hydroxylase (Cyp7a1), and bile-salt export pump (BSEP). Furthermore, IAS I significantly improved pathological changes and protein expression related to intestinal barrier function, including zonula occludens protein 1 (ZO-1), Muc2, and Occludin.

CONCLUSIONS

IAS I alleviated cholestatic liver injury, relieved inflammation, improved the altered tau-BAs metabolism and restored intestinal barrier function to protect against DDC-induced cholestatic liver diseases.

Aryl Hydrocarbon Receptor Alleviates Hepatic Fibrosis by Inducing Hepatic Stellate Cell Ferroptosis

Liver injury-induced activation of hepatic stellate cells (HSCs) is a crucial step in the progression of liver fibrosis. The aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, is highly expressed in the liver. However, the role of AHR in liver fibrosis remains controversial. Our study revealed that the nontoxic ligand YH439 directly activated the AHR and regulated the expression of multidrug-resistant protein 1 (Mrp1) in mouse hepatic stellate cells (mHSCs), thereby diminishing the antioxidant capacity of mHSCs by promoting GSH efflux, and specifically inducing mHSCs ferroptosis without affecting hepatocytes. In a chronic liver fibrosis model, YH439 activated AHR to promote mHSC ferroptosis without causing hepatocyte ferroptosis, thereby alleviating liver fibrosis. Conclusively, this study shows that AHR alleviates liver fibrosis in mice by selectively inducing mHSC ferroptosis without causing hepatocyte ferroptosis and suggests that AHR is a potential target for the treatment of liver fibrosis.

Advances in the understanding of the role and mechanism of action of PFKFB3‑mediated glycolysis in liver fibrosis (Review)

Liver fibrosis is a pathophysiologic manifestation of chronic liver disease and a precursor to cirrhosis and hepatocellular carcinoma. Glycolysis provides intermediate metabolites as well as energy support for cell proliferation and phenotypic transformation in liver fibers. 6‑Phosphofructo‑2‑kinase/fructose‑2,6‑bisphosphatase 3 (PFKFB3) is a key activator of glycolysis and plays an important role in the process of glycolysis. The role of PFKFB3‑mediated glycolysis in myocardial fibrosis, renal fibrosis and pulmonary fibrosis has been demonstrated, and the role of PFKFB3 in the activation of hepatic stellate cells by aerobic glycolysis has been proven by relevant experiments. The present study reviews the research progress on the role and mechanism of action of PFKFB3‑mediated glycolysis in the progression of hepatic fibrosis to discuss the role of PFKFB3‑mediated glycolysis in hepatic fibrosis and to provide new ideas for research on PFKFB3 as a target for the treatment of hepatic fibrosis.

Hedgehog Signaling Pathway in Fibrosis and Targeted Therapies

Hedgehog (Hh) signaling is a well-established developmental pathway; it is crucial for early embryogenesis, cell differentiation, and damage-driven regeneration. It is being increasingly recognized that dysregulated Hh signaling is also involved in fibrotic diseases, which are characterized by excessive extracellular matrix deposition that compromises tissue architecture and function. As in-depth insights into the mechanisms of Hh signaling are obtained, its complex involvement in fibrosis is gradually being illuminated. Notably, some Hh-targeted inhibitors are currently under exploration in preclinical and clinical trials as a means to prevent fibrosis progression. In this review, we provide a concise overview of the biological mechanisms involved in Hh signaling. We summarize the latest advances in our understanding of the roles of Hh signaling in fibrogenesis across the liver, kidneys, airways, and lungs, as well as other tissues and organs, with an emphasis on both the shared features and, more critically, the distinct functional variations observed across these tissues and organs. We thus highlight the context dependence of Hh signaling, as well as discuss the current status and the challenges of Hh-targeted therapies for fibrosis.

Modulation of Notch signaling pathway in activated hepatic stellate cells does not ameliorate the outcome of liver fibrosis in carbon tetrachloride and DDC-feeding models

Background

Recent research suggests a possible role of Notch signaling pathway in development of liver fibrosis, but exact cellular and molecular mechanisms are still not well defined. Methods: We modulated Notch signaling in activated hepatic stellate cells/myofibroblasts using the model of inducible activation or inhibition of Notch signaling selective for αSMA positive cells in murine models of toxic fibrosis induced by CCl4 and cholestatic fibrosis induced by DDC supplemented feeding.

Results

Our results confirm that Notch signaling pathway is activated in both CCL4 and DDC model of liver fibrosis and that αSMA positive myofibroblasts are of activated hepatic stellate cells origin. However, neither the inhibition of canonical Notch signaling (in tamoxifen treated αSMACreER/RBP-Jfl/fl mice) nor its overactivation (in tamoxifen treated αSMACreER/NICD1 mice) changed the degree of liver fibrosis in comparison to the control groups in either of the investigated models. Furthermore, after the withdrawal of the fibrogenic treatment the degree of resolution of fibrosis was similar between the animals with Notch overactivation and controls. In addition to genetic manipulation, we investigated the effect of antibodies against NOTCH1 and NOTCH2 on the development of liver fibrosis. Treatment with antibodies had effects on thymus and spleen respectively, but failed to ameliorate liver fibrosis. In conclusion, our data demonstrate that modulation of Notch activity in activated HSC is not sufficient to change the outcome of liver fibrosis. The results obtained with inhibitory antibodies further demonstrate limitations of targeting Notch 1 and 2 receptors as antifibrotic therapy. Notch pathway remains a potential target for the treatment of liver fibrosis, but future studies should be directed to Notch 3 signaling and/or targeting different populations of cells.

Preclinical targeting of liver fibrosis with a 89Zr-labeled Fibrobody® directed against platelet derived growth factor receptor-β

PURPOSE

Hepatic fibrosis develops as a response to chronic liver injury, resulting in the formation of fibrous scars. This process is initiated and driven by collagen-producing activated myofibroblasts which reportedly express high levels of platelet derived growth factor receptor-β (PDGFRβ). We therefore regard PDGFRβ as an anchor for diagnosis and therapy. The Fibrobody® SP02SP26-ABD is a biparatopic VHH-construct targeting PDGFRβ. Here, we explore its potential as a theranostic vector for liver fibrosis.

METHODS

Specificity, cross-species binding, and cellular uptake of SP02SP26-ABD was assessed using human, mouse and rat PDGFRβ ectodomains and PDGFRβ-expressing cells. Cellular uptake by PDGFRβ-expressing cells was also evaluated by equipping the Fibrobody® with auristatinF and reading out in vitro cytotoxicity. The validity of PDGFRβ as a marker for active fibrosis was confirmed in human liver samples and 3 mouse models of liver fibrosis (DDC, CCl4, CDA-HFD) through immunohistochemistry and RT-PCR. After radiolabeling of DFO*-SP02SP26-ABD with 89Zr, its in vivo targeting ability was assessed in healthy mice and mice with liver fibrosis by PET-CT imaging, ex vivo biodistribution and autoradiography.

RESULTS

SP02SP26-ABD shows similar nanomolar affinity for human, mouse and rat PDGFRβ. Cellular uptake and hence subnanomolar cytotoxic potency of auristatinF-conjugated SP02SP26-ABD was observed in PDGFRβ-expressing cell lines. Immunohistochemistry of mouse and human fibrotic livers confirmed co-localization of PDGFRβ with markers of active fibrosis. In all three liver fibrosis models, PET-CT imaging and biodistribution analysis of [89Zr]Zr-SP02SP26-ABD revealed increased PDGFRβ-specific uptake in fibrotic livers. In the DDC model, liver uptake was 12.15 ± 0.45, 15.07 ± 0.90, 20.23 ± 1.34, and 20.93 ± 4.35%ID/g after 1,2,3 and 4 weeks of fibrogenesis, respectively, compared to 7.56 ± 0.85%ID/g in healthy mice. Autoradiography revealed preferential uptake in the fibrotic (PDGFRβ-expressing) periportal areas.

CONCLUSION

The anti-PDGFRβ Fibrobody® SP02SP26-ABD shows selective and high-degree targeting of activated myofibroblasts in liver fibrosis, and qualifies as a vector for diagnostic and therapeutic purposes.

Iron chelation as a new therapeutic approach to prevent senescence and liver fibrosis progression

Iron overload and cellular senescence have been implicated in liver fibrosis, but their possible mechanistic connection has not been explored. To address this, we have delved into the role of iron and senescence in an experimental model of chronic liver injury, analyzing whether an iron chelator would prevent liver fibrosis by decreasing hepatocyte senescence. The model of carbon tetrachloride (CCl4) in mice was used as an experimental model of liver fibrosis. Results demonstrated that during the progression of liver fibrosis, accumulation of iron occurs, concomitant with the appearance of fibrotic areas and cells undergoing senescence. Isolated parenchymal hepatocytes from CCl4-treated mice present a gene transcriptomic signature compatible with iron accumulation and senescence, which correlates with induction of Reactive Oxygen Species (ROS)-related genes, activation of the Transforming Growth Factor-beta (TGF-β) pathway and inhibition of oxidative metabolism. Analysis of the iron-related gene signature in a published single-cell RNA-seq dataset from CCl4-treated livers showed iron accumulation correlating with senescence in other non-parenchymal liver cells. Treatment with deferiprone, an iron chelator, attenuated iron accumulation, fibrosis and senescence, concomitant with relevant changes in the senescent-associated secretome (SASP), which switched toward a more anti-inflammatory profile of cytokines. In vitro experiments in human hepatocyte HH4 cells demonstrated that iron accumulates in response to a senescence-inducing reagent, doxorubicin, being deferiprone able to prevent senescence and SASP, attenuating growth arrest and cell death. However, deferiprone did not significantly affect senescence induced by two different agents (doxorubicin and deoxycholic acid) or activation markers in human hepatic stellate LX-2 cells. Transcriptomic data from patients with different etiologies demonstrated the relevance of iron accumulation in the progression of liver chronic damage and fibrosis, correlating with a SASP-related gene signature and pivotal hallmarks of fibrotic changes. Altogether, our study establishes iron accumulation as a clinically exploitable driver to attenuate pathological senescence in hepatocytes.

Hepatic Extracellular Matrix and Its Role in the Regulation of Liver Phenotype

The hepatic extracellular matrix (ECM) is most accurately depicted as a dynamic compartment that comprises a diverse range of players that work bidirectionally with hepatic cells to regulate overall homeostasis. Although the classic meaning of the ECM referred to only proteins directly involved in generating the ECM structure, such as collagens, proteoglycans, and glycoproteins, the definition of the ECM is now broader and includes all components associated with this compartment. The ECM is critical in mediating phenotype at the cellular, organ, and even organismal levels. The purpose of this review is to summarize the prevailing mechanisms by which ECM mediates hepatic phenotype and discuss the potential or established role of this compartment in the response to hepatic injury in the context of steatotic liver disease.

Single-cell RNA sequencing reveals reduced intercellular adhesion molecule crosstalk between activated hepatic stellate cells and neutrophils alleviating liver fibrosis in hepatitis B virus transgenic mice post menstrual blood-derived mesenchymal stem cell transplantation

Liver fibrosis can cause hepatitis B virus (HBV)-associated hepatocellular carcinoma. Menstrual blood-derived mesenchymal stem cells (MenSCs) can ameliorate liver fibrosis through paracrine. Single-cell RNA sequencing (scRNA-seq) may be used to explore the roadmap of activated hepatic stellate cell (aHSC) inactivation to target liver fibrosis. This study established HBV transgenic (HBV-Tg) mouse model of carbon tetrachloride (CCl4)-induced liver fibrosis and demonstrated that MenSCs migrated to the injured liver to improve serological indices and reduce fibrotic accumulation. RNA-bulk analysis revealed that MenSCs mediated extracellular matrix accumulation and cell adhesion. Liver parenchymal cells and nonparenchymal cells were identified by scRNA-seq in the control, CCl4, and MenSC groups, revealing the heterogeneity of fibroblasts/HSCs. A CellChat analysis revealed that diminished intercellular adhesion molecule (ICAM) signaling is vital for MenSC therapy. Specifically, Icam1 in aHSCs acted on Itgal/Itgb2 and Itgam/Itgb2 in neutrophils, causing decreased adhesion. The expression of Itgal, Itgam, and Itgb2 was higher in CCl4 group than in the control group and decreased after MenSC therapy in neutrophil clusters. The Lcn2, Pglyrp1, Wfdc21, and Mmp8 had high expression and may be potential targets in neutrophils. This study highlights interacting cells, corresponding molecules, and underlying targets for MenSCs in treating HBV-associated liver fibrosis.

Protocol to generate human liver spheroids to study liver fibrosis induced by metabolic stress

Currently, there is no effective treatment for obesity and alcohol-associated liver diseases, partially due to the lack of translational human models. Here, we present a protocol to generate 3D human liver spheroids that contain all the liver cell types and mimic "livers in a dish." We describe strategies to induce metabolic and alcohol-associated hepatic steatosis, inflammation, and fibrosis. We outline potential applications, including using human liver spheroids for experimental and translational research and drug screening to identify potential anti-fibrotic therapies.

The Renin-Angiotensin System in Liver Disease

The renin-angiotensin system (RAS) is a complex homeostatic entity with multiorgan systemic and local effects. Traditionally, RAS works in conjunction with the kidney to control effective arterial circulation, systemic vascular resistance, and electrolyte balance. However, chronic hepatic injury and resulting splanchnic dilation may disrupt this delicate balance. The role of RAS in liver disease, however, is even more extensive, modulating hepatic fibrosis and portal hypertension. Recognition of an alternative RAS pathway in the past few decades has changed our understanding of RAS in liver disease, and the concept of opposing vs. "rebalanced" forces is an ongoing focus of research. Whether RAS inhibition is beneficial in patients with chronic liver disease appears to be context-dependent, but further study is needed to optimize clinical management and reduce organ-specific morbidity and mortality. This review presents the current understanding of RAS in liver disease, acknowledges areas of uncertainty, and describes potential areas of future investigation.

Two-dimensional vascularized liver organoid on extracellular matrix with defined stiffness for modeling fibrotic and normal tissues

Antifibrotic drug screening requires evaluating the inhibitory effects of drug candidates on fibrotic cells while minimizing any adverse effects on normal cells. It is challenging to create organ-specific vascularized organoids that accurately model fibrotic and normal tissues for drug screening. Our previous studies have established methods for culturing primary microvessels and epithelial cells from adult tissues. In this proof-of-concept study, we used rats as a model organism to create a two-dimensional vascularized liver organoid model that comprised primary microvessels, epithelia, and stellate cells from adult livers. To provide appropriate substrates for cell culture, we engineered ECMs with defined stiffness to mimic the different stages of fibrotic tissues and normal tissues. We examined the effects of two TGFβ signaling inhibitors, A83-01 and pirfenidone, on the vascularized liver organoids on the stiff and soft ECMs. We found that A83-01 inhibited fibrotic markers while promoting epithelial genes of hepatocytes and cholangiocytes. However, it inhibited microvascular genes on soft ECM, indicating a detrimental effect on normal tissues. Furthermore, A83-01 significantly promoted the expression of markers of stem cells and cancers, increasing the potential risk of it being a carcinogen. In contrast, pirfenidone, an FDA-approved compound for antifibrotic treatments, did not significantly affect all the genes examined on soft ECM. Although pirfenidone had minor effects on most genes, it did reduce the expression of collagens, the major components of fibrotic tissues. These results explain why pirfenidone can slow fibrosis progression with minor side effects in clinical trials. In conclusion, our study presents a method for creating vascularized liver organoids that can accurately mimic fibrotic and normal tissues for drug screening. Our findings provide valuable insights into the potential risks and benefits of using A83-01 and pirfenidone as antifibrotic drugs. This method can be applied to other organs to create organ-specific vascularized organoids for drug development.