Liver fibrosis induced by hepatic overexpression of PDGF-B in transgenic mice

Age-Dependent RGS5 Loss in Pericytes Induces Cardiac Dysfunction and Fibrosis

BACKGROUND

Pericytes are capillary-associated mural cells involved in the maintenance and stability of the vascular network. Although aging is one of the main risk factors for cardiovascular disease, the consequences of aging on cardiac pericytes are unknown.

METHODS

In this study, we have combined single-nucleus RNA sequencing and histological analysis to determine the effects of aging on cardiac pericytes. Furthermore, we have conducted in vivo and in vitro analysis of RGS5 (regulator of G-protein signaling 5) loss of function and finally have performed pericytes-fibroblasts coculture studies to understand the effect of RGS5 deletion in pericytes on the neighboring fibroblasts.

RESULTS

Aging reduced the pericyte area and capillary coverage in the murine heart. Single-nucleus RNA sequencing analysis further revealed that the expression of Rgs5 was reduced in cardiac pericytes from aged mice. In vivo and in vitro studies showed that the deletion of RGS5 impaired cardiac function, induced fibrosis, and morphological changes in pericytes characterized by a profibrotic gene expression signature and the expression of different ECM (extracellular matrix) components and growth factors, for example, TGFB2 and PDGFB. Indeed, culturing fibroblasts with the supernatant of RGS5-deficient pericytes induced their activation as evidenced by the increased expression of αSMA (alpha smooth muscle actin) in a TGFβ (transforming growth factor beta)2-dependent mechanism.

CONCLUSIONS

Our results have identified RGS5 as a crucial regulator of pericyte function during cardiac aging. The deletion of RGS5 causes cardiac dysfunction and induces myocardial fibrosis, one of the hallmarks of cardiac aging.

Inflammatory Protein Signatures as Predictive Disease-Specific Markers for Non-Alcoholic Steatohepatitis (NASH)

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic disease worldwide, consisting of a broad spectrum of diseases such as simple steatosis (NAFL), non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. Hepatic inflammation plays a key role in the pathophysiology of NAFLD. Inflammatory mediators such as cytokines and chemokines are considered as contributing factors to NAFLD development and progression. In the present study, we aimed to investigate the inflammatory protein signatures as predictive disease-specific markers for non-alcoholic fatty liver disease (NAFLD). This cross-sectional study included healthy control (n = 64), NAFL (n = 109), and NASH (n = 60) human subjects. Serum concentrations of various cytokines and chemokines were evaluated using sensitive multiplex assays. We used principal component analysis (PCoA) to reveal distinct differences in the levels of cytokines and chemokines between each of the study groups. Further, a random forest classification model was developed to identify the panel of markers that could predict diseases. The protein-protein network analysis was performed to determine the various signaling pathways associated with the disease-specific panel of markers. Serum concentrations of TNF-α, IL-1β, IL-1ra, G-CSF, PDGF-BB, MCP-1, MIP-1a, MIP-1b, RANTES, eotaxin, IL-8 and IP-10 were significantly increased in NASH group as compared to control group. Furthermore, serum concentrations of IL-9 and IL-13 were significantly lower in the NASH group, whereas IL-2 levels were significantly decreased in the NAFL group when compared to the control group. PCoA results demonstrated statistically significant differences in cytokines and chemokines between each of the study groups (PERMANOVA p = 0.001; R2 = 0.102). RANTES, IL-1ra, MIP-1b, IL-2, and G-CSF could differentiate the NAFL group from the controls; G-CSF, IL-1ra, TNF-α, RANTES, and IL-9 could differentiate the NASH group from the controls; and G-CSF, IL-9, IL-13, eotaxin, and TNF- α could differentiate the NASH group from the NAFL group. Our protein-protein network revealed that these markers are involved in cytokine-cytokine receptor interaction, Th1 and Th2 cell differentiation, TNF, chemokine, JAK/STAT, P13K/Akt, TLR, NOD-like receptor, NF-kB, and adipocytokine signaling pathways which might be responsible for disease pathogenesis. Our study findings revealed a set of distinct cytokine and chemokine markers and they might be considered as biomarkers in distinguishing NASH from NAFL. Future multicentre studies with larger sample size are recommended to determine the potential utility of these panels of markers.

Loss of ZNF451 mediates fibroblast activation and promotes lung fibrosis

BACKGROUND

No effective therapies for pulmonary fibrosis (PF) exist because of the unclear molecular pathogenesis and the lack of effective therapeutic targets. Zinc finger protein 451 (ZNF451), a transcriptional regulator, plays crucial roles in the pathogenesis of several diseases. However, its expression pattern and function in PF remain unknown. This study was designed to investigate the role of ZNF451 in the pathogenesis of lung fibrosis.

METHODS

GEO dataset analysis, RT‒PCR, and immunoblot assays were used to examine the expression of ZNF451 in PF; ZNF451 knockout mice and ZNF451-overexpressing lentivirus were used to determine the importance of ZNF451 in PF progression; and migration assays, immunofluorescence staining, and RNA-seq analysis were used for mechanistic studies.

RESULTS

ZNF451 is downregulated and negatively associated with disease severity in PF. Compared with wild-type (WT) mice, ZNF451 knockout mice exhibited much more serious PF changes. However, ZNF451 overexpression protects mice from BLM-induced pulmonary fibrosis. Mechanistically, ZNF451 downregulation triggers fibroblast activation by increasing the expression of PDGFB and subsequently activating PI3K/Akt signaling.

CONCLUSION

These findings uncover a critical role of ZNF451 in PF progression and introduce a novel regulatory mechanism of ZNF451 in fibroblast activation. Our study suggests that ZNF451 serves as a potential therapeutic target for PF and that strategies aimed at increasing ZNF451 expression may be promising therapeutic approaches for PF.

The role of matrix metalloproteinase 9 in fibrosis diseases and its molecular mechanisms

Fibrosis is a process of tissue repair that results in the slow creation of scar tissue to replace healthy tissue and can affect any tissue or organ. Its primary feature is the massive deposition of extracellular matrix (mainly collagen), eventually leading to tissue dysfunction and organ failure. The progression of fibrotic diseases has put a significant strain on global health and the economy, and as a result, there is an urgent need to find some new therapies. Previous studies have identified that inflammation, oxidative stress, some cytokines, and remodeling play a crucial role in fibrotic diseases and are essential avenues for treating fibrotic diseases. Among them, matrix metalloproteinases (MMPs) are considered the main targets for the treatment of fibrotic diseases since they are the primary driver involved in ECM degradation, and tissue inhibitors of metalloproteinases (TIMPs) are natural endogenous inhibitors of MMPs. Through previous studies, we found that MMP-9 is an essential target for treating fibrotic diseases. However, it is worth noting that MMP-9 plays a bidirectional regulatory role in different fibrotic diseases or different stages of the same fibrotic disease. Previously identified MMP-9 inhibitors, such as pirfenidone and nintedanib, suffer from some rather pronounced side effects, and therefore, there is an urgent need to investigate new drugs. In this review, we explore the mechanism of action and signaling pathways of MMP-9 in different tissues and organs, hoping to provide some ideas for developing safer and more effective biologics.

Therapeutic role of FNDC5/irisin in attenuating liver fibrosis via inhibiting release of hepatic stellate cell-derived exosomes

OBJECTIVE

Cleavage of fibronectin type III domain-containing protein 5 (FNDC5), a membrane-bound precursor protein, would cleave into a myokine, irisin, which is also expressed in the liver. FNDC5/Irisin has been reported to play a critical role in maintaining glucose and lipid homeostasis in the liver and in combating liver fibrosis. Recently, several studies have shown that extracellular vesicles (EVs) derived from hepatic stellate cells (HSCs) could modulate liver fibrosis; however, there is a large gap in understanding whether inhibition of fibrogenic EVs derived from HSCs could alleviate the progression of liver fibrosis. Here, we investigated the role of FNDC5/irisin in liver fibrosis and the mechanism of its inhibitory role in the release of HSC-derived fibrogenic EVs.

METHODS

Experiments were performed in wild-type and FNDC5-/- mice, primary mouse HSCs, and human hepatic stellate cell line (LX2). Mice were treated with carbon tetrachloride (CCl4) or bile duct ligation (BDL) to induce liver fibrosis. EVs derived from HSCs were purified and injected intraperitoneally into mice.

RESULTS

Our results showed that FNDC5 deficiency exacerbated CCl4-induced liver fibrosis and activation of HSCs in mice. Moreover, fibrogenic EVs derived from PDGF-BB-treated HSCs promoted HSC migration in vitro and liver fibrosis in vivo. However, administration of irisin, a cleavage of FNDC5, inhibited the release of fibrogenic EVs and activation of HSCs by promoting ubiquitylation degradation of Rab27b. In vivo, the promoting role of HSC-derived fibrogenic EVs in liver fibrosis was also reversed by irisin.

CONCLUSION

All these results demonstrate that FNDC5/irisin is a novel therapeutic agent for chronic liver fibrosis.

Neuroimmunomodulation of adrenoblockers during liver cirrhosis: modulation of hepatic stellate cell activity

The sympathetic nervous system and the immune system are responsible for producing neurotransmitters and cytokines that interact by binding to receptors; due to this, there is communication between these systems. Liver immune cells and nerve fibres are systematically distributed in the liver, and the partial overlap of both patterns may favour interactions between certain elements. Dendritic cells are attached to fibroblasts, and nerve fibres are connected via the dendritic cell-fibroblast complex. Receptors for most neuroactive substances, such as catecholamines, have been discovered on dendritic cells. The sympathetic nervous system regulates hepatic fibrosis through sympathetic fibres and adrenaline from the adrenal glands through the blood. When there is liver damage, the sympathetic nervous system is activated locally and systemically through proinflammatory cytokines that induce the production of epinephrine and norepinephrine. These neurotransmitters bind to cells through α-adrenergic receptors, triggering a cellular response that secretes inflammatory factors that stimulate and activate hepatic stellate cells. Hepatic stellate cells are key in the fibrotic process. They initiate the overproduction of extracellular matrix components in an active state that progresses from fibrosis to liver cirrhosis. It has also been shown that they can be directly activated by norepinephrine. Alpha and beta adrenoblockers, such as carvedilol, prazosin, and doxazosin, have recently been used to reverse CCl₄-induced liver cirrhosis in rodent and murine models.KEY MESSAGESNeurotransmitters from the sympathetic nervous system activate and increase the proliferation of hepatic stellate cells.Hepatic fibrosis and cirrhosis treatment might depend on neurotransmitter and hepatic nervous system regulation.Strategies to reduce hepatic stellate cell activation and fibrosis are based on experimentation with α-adrenoblockers.

Hepatic stellate cell-intrinsic role of SOCS1 in controlling hepatic fibrogenic response and the pro-inflammatory macrophage compartment during liver fibrosis

Introduction

Hepatic stellate cells (HSC) become activated, differentiate to myofibroblasts and produce extracellular fibrillar matrix during liver fibrosis. The hepatic fibrogenic response is orchestrated by reciprocal interactions between HSCs and macrophages and their secreted products. SOCS1 can regulate several cytokines and growth factors implicated in liver fibrosis. Here we investigated the role of SOCS1 in regulating HSC activation.

Methods

Mice lacking SOCS1 in HSCs (Socs1ΔHSC) were generated by crossing Socs1fl/fl and LratCre mice. Liver fibrosis was induced by carbon tetrachloride and evaluated by Sirius red staining, hydroxyproline content and immunostaining of myofibroblasts. Gene expression of pro-fibrogenic factors, cytokines, growth factors and chemokines were quantified by RT-qPCR. The phenotype and the numbers of intrahepatic leukocyte subsets were studied by flow cytometry. The impact of fibrosis on the development of diethyl nitrosamine-induced hepatocellular carcinoma was evaluated.

Results

Socs1ΔHSC mice developed more severe liver fibrosis than control Socs1fl/fl mice that was characterized by increased collagen deposition and myofibroblast differentiation. Socs1ΔHSC mice showed a significant increase in the expression of smooth muscle actin, collagens, matrix metalloproteases, cytokines, growth factors and chemokines in the liver following fibrosis induction. The fibrotic livers of Socs1ΔHSC mice displayed heightened inflammatory cell infiltration with increased proportion and numbers of Ly6ChiCCR2+ pro-inflammatory macrophages. This macrophage population contained elevated numbers of CCR2+CX3CR1+ cells, suggesting impaired transition towards restorative macrophages. Fibrosis induction following exposure to diethyl nitrosamine resulted in more numerous and larger liver tumor nodules in Socs1ΔHSC mice than in Socs1fl/fl mice.

Discussion

Our findings indicate that (i) SOCS1 expression in HSCs is a critical to control liver fibrosis and development of hepatocaellular carcinoma, and (ii) attenuation of HSC activation by SOCS1 regulates pro-inflammatory macrophage recruitment and differentiation during liver fibrosis.

Single-cell RNA sequencing reveals the heterogeneity and intercellular communication of hepatic stellate cells and macrophages during liver fibrosis

Uncontrolled and excessive progression of liver fibrosis is thought to be the prevalent pathophysiological cause of liver cirrhosis and hepatocellular cancer, and there are currently no effective antifibrotic therapeutic options available. Intercellular communication and cellular heterogeneity in the liver are involved in the progression of liver fibrosis, but the exact nature of the cellular phenotypic changes and patterns of interregulatory remain unclear. Here, we performed single-cell RNA sequencing on nonparenchymal cells (NPCs) isolated from normal and fibrotic mouse livers. We identified eight main types of cells, including endothelial cells, hepatocytes, dendritic cells, B cells, natural killer/T (NK/T) cells, hepatic stellate cells (HSCs), cholangiocytes and macrophages, and revealed that macrophages and HSCs exhibit the most variance in transcriptional profile. Further analyses of HSCs and macrophage subpopulations and ligand-receptor interaction revealed a high heterogeneity characterization and tightly interregulated network of these two groups of cells in liver fibrosis. Finally, we uncovered a profibrotic Thbs1+ macrophage subcluster, which expands in mouse and human fibrotic livers, activating HSCs via PI3K/AKT/mTOR signaling pathway. Our findings decode unanticipated insights into the heterogeneity of HSCs and macrophages and their intercellular crosstalk at a single-cell level, and may provide potential therapeutic strategies in liver fibrosis.

Hydroxyurea attenuates hepatic stellate cell proliferation in vitro and liver fibrogenesis in vivo

Liver fibrosis results from excessive proliferation of, and collagen production by hepatic stellate cells (HSCs) that is caused by chronic liver injury. No drugs are available to cure liver fibrosis. Hydroxyurea is an anti-proliferative drug that is used in benign and malignant disorders. Here, we studied the effect of hydroxyurea on primary HSCs and its anti-fibrotic effect in the CCl4 mouse model of liver fibrosis. Primary rat HSCs were cultured in the absence or presence of hydroxyurea (0.1-1.0 mmol/L). CCl4 or vehicle was administered to C57BL/6/J mice for 4 weeks, with or without hydroxyurea (100 mg/kg/day) co-treatment. We used real-time cell proliferation analysis, Oil Red O (lipid droplet) staining, immunohistochemistry, Acridine Orange staining (apoptosis), Sytox green staining (necrosis), RT-qPCR, ELISA, and Western Blotting for analysis. Hydroxyurea dose-dependently suppressed lipid droplet-loss and mRNA levels of Col1α1 and Acta2 in transdifferentiating HSCs. In fully-activated HSCs, hydroxyurea dose-dependently attenuated PCNA protein levels and BrdU incorporation, but did not reverse Col1α1 and Acta2 mRNA expression. Hydroxyurea did not induce apoptosis or necrosis in HSCs or hepatocytes. Hydroxyurea suppressed accumulation of desmin-positive HSCs and hepatic collagen deposition after CCl4 treatment. CCl4 -induced regenerative hepatocyte proliferation, Col1α1 and Acta2 mRNA expression and α-SMA protein levels were not affected. This study demonstrates that hydroxyurea inhibits HSC proliferation in vitro and attenuates early development of liver fibrosis in vivo, while preserving hepatocyte regeneration after toxic insults by CCl4. Thus, hydroxyurea may have therapeutic value against liver fibrosis.

Research progress on the role of PDGF/PDGFR in type 2 diabetes

Platelet-derived growth factors (PDGFs) are basic proteins stored in the α granules of platelets. PDGFs and their receptors (PDGFRs) are widely expressed in platelets, fibroblasts, vascular endothelial cells, platelets, pericytes, smooth muscle cells and tumor cells. The activation of PDGFR plays a number of critical roles in physiological functions and diseases, including normal embryonic development, cellular differentiation, and responses to tissue damage. In recent years, emerging experimental evidence has shown that activation of the PDGF/PDGFR pathway is involved in the development of diabetes and its complications, such as atherosclerosis, diabetic foot ulcers, diabetic nephropathy, and retinopathy. Research on targeting PDGF/PDGFR as a treatment has also made great progress. In this mini-review, we summarized the role of PDGF in diabetes, as well as the research progress on targeted diabetes therapy, which provides a new strategy for the treatment of type 2 diabetes.

Hepatocyte Ninjurin2 promotes hepatic stellate cell activation and liver fibrosis through the IGF1R/EGR1/PDGF-BB signaling pathway

BACKGROUND

Liver fibrogenesis is orchestrated by the paracrine signaling interaction between several resident cell types regulating the activation of hepatic stellate cells (HSCs). However, the molecular mechanisms underlying paracrine regulation are largely unknown. The aim of this study is to elucidate the role of Ninjurin2 in the crosstalk between hepatocytes and HSCs and better understand the implications of Ninjurin2 in liver fibrosis.

METHODS

Ninj2 knockout mice (Ninj2^-/-) and hepatocyte-specific Ninj2 overexpression mice (Ninj2^Hep-tg) were constructed and followed by the induction of liver fibrosis using methionine- and choline-deficient (MCD) diet. The relationship between Ninjurin2 and liver fibrosis phenotype was evaluated in vivo by measurement of fibrotic markers and related genes. We used an in vitro transwell cell co-culture model to examine the impact of Ninjurin2 in hepatocytes on the crosstalk to HSCs. The interaction of Ninjurin2 and IGF1R and the regulation of PI3K-AKT-EGR1 were analyzed in vivo and in vitro. Finally, an inhibitory Ninjurin2 peptide was injected intravenously via the tail vein to investigate whether inhibiting of Ninjurin2 cascade can attenuate MCD diet-induced liver fibrosis in mice.

RESULTS

We found that hepatic Ninjurin2 expression was significantly increased in fibrotic human liver and MCD diet-induced liver injury mouse models. In the mouse model, hepatocyte-specific overexpression of Ninj2 exacerbates MCD-induced liver fibrosis, while global Ninj2 knockout reverses the phenotype. To mimic hepatocyte-HSC crosstalk during liver fibrosis, we used co-culture systems containing hepatocytes and HSCs and determined that Ninjurin2 overexpression in hepatocytes directly activates HSCs in vitro. Mechanistically, Ninjurin2 directly interacts with insulin-like growth factor 1 receptor (IGF1R) and increases the hepatocyte secretion of the fibrogenic cytokine, platelet-derived growth factor-BB (PDGF-BB) through IGF1R-PI3K-AKT-EGR1 cascade. Inhibition of PDGFRB signaling in HSCs can abolish the profibrogenic effect of Ninjurin2. In addition, we demonstrated that a specific inhibitory Ninjurin2 peptide containing an N-terminal adhesion motif mitigates liver fibrosis and improves hepatic function in the mouse models by negatively regulating the sensitivity of IGF1R to IGF1 in hepatocytes.

CONCLUSION

Hepatic Ninjurin2 plays a key role in liver fibrosis through paracrine regulation of PDGF-BB/PDGFRB signaling in HSCs, and the results suggesting Ninjurin2 may be a potential therapeutic target.

Hepatic Stellate Cells: Dictating Outcome in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a fast growing, chronic liver disease affecting ∼25% of the global population. Nonalcoholic fatty liver disease severity ranges from the less severe simple hepatic steatosis to the more advanced nonalcoholic steatohepatitis (NASH). The presence of NASH predisposes individuals to liver fibrosis, which can further progress to cirrhosis and hepatocellular carcinoma. This makes hepatic fibrosis an important indicator of clinical outcomes in patients with NASH. Hepatic stellate cell activation dictates fibrosis development during NASH. Here, we discuss recent advances in the analysis of the profibrogenic pathways and mediators of hepatic stellate cell activation and inactivation, which ultimately determine the course of disease in nonalcoholic fatty liver disease/NASH.

The Preventive and Therapeutic Potential of the Flavonoids in Liver Cirrhosis: Current and Future Perspectives

Non-alcoholic fatty liver disease (NAFLD) may vary from moderately mild non-alcohol fatty liver (NAFL) towards the malignant variant known as non-alcoholic steatohepatitis (NASH), which is marked by fatty liver inflammation and may progress to liver cirrhosis (LC), liver cancer, fibrosis, or liver failure. Flavonoids can protect the liver from toxins through their anti-inflammatory, antioxidant, anti-cancer, and antifibrogenic pharmacological activities. Furthermore, flavonoids protect against LC by regulation of hepatic stellate cells (HSCs) trans-differentiation, inhibiting growth factors like TGF-β and platelets-derived growth factor (PDGF), vascular epithelial growth factor (VEGF), viral infections like hepatitis-B, C and D viruses (HBV, HCV & HDV), autoimmune-induced, alcohol-induced, metabolic disorder-induced, causing by apoptosis, and regulating MAPK pathways. These flavonoids may be explored in the future as a therapeutic solution for hepatic diseases.

Self-homing nanocarriers for mRNA delivery to the activated hepatic stellate cells in liver fibrosis

Herein, we report on the development of a platform for the selective delivery of mRNA to the hard-to-transfect Activated Hepatic Stellate Cells (aHSCs), the fundamental player in the progression of liver fibrosis. Using a microfluidic device (iLiNP), we prepared a series of lipid nanoparticles (LNPs) based on a diverse library of pH-sensitive lipids. After an in-depth in vivo optimization of the LNPs, their mRNA delivery efficiency, selectivity, potency, robustness, and biosafety were confirmed. Furthermore, some mechanistic aspects of their selective delivery to aHSCs were investigated. We identified a promising lipid candidate, CL15A6, that has a high affinity to aHSCs. Tweaking the composition and physico-chemical properties of the LNPs enabled the robust and ligand-free mRNA delivery to aHSCs in vivo post intravenous administration, with a high biosafety at mRNA doses of up to 2 mg/Kg, upon either acute or chronic administrations. The mechanistic investigation suggested that CL15A6 LNPs were taken up by aHSCs via Clathrin-mediated endocytosis through the Platelet-derived growth factor receptor beta (PDGFRβ) and showed a pKa-dependent cellular uptake. The novel and scalable platform reported in this study is highly promising for clinical applications.

Multi-omics characterization reveals the pathogenesis of liver focal nodular hyperplasia

The molecular landscape and pathogenesis of focal nodular hyperplasia (FNH) have yet to be elucidated. We performed multi-omics approaches on FNH and paired normal liver tissues from 22 patients, followed by multi-level bioinformatic analyses and experimental validations. Generally, FNH had low mutation burden with low variant allele frequencies, and the mutation frequency significantly correlated with proliferation rate. Although no recurrently deleterious genomic events were found, some putative tumor suppressors or oncogenes were involved. Mutational signatures indicated potential impaired mismatch function and possible poison contact. Integrated analyses unveiled a group of FNH specific endothelial cells that uniquely expressed SOST and probably had strong interaction with fibroblasts through PDGFB/PDGFRB pathway to promote fibrosis. Notably, in one atypical FNH (patient No.11) with pronounced copy number variations, we observed a unique immune module. Most FNH are benign, but molecularly atypical FNH still exist; endothelial cell derived PDGFB probably promotes the fibrogenic process in FNH.

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FNHs are genetically stable, but high mutation cases exist

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FNHs have unique transcriptomic modules, and they alter in atypical FNH

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FNH has a unique type of SOST-expressing endothelial cells that may promote fibrosis

Macrophages evoke autophagy of hepatic stellate cells to promote liver fibrosis in NAFLD mice via the PGE2/EP4 pathway

The pathogenesis of liver fibrosis in nonalcoholic fatty liver disease (NAFLD) remains unclear and the effective treatments have not been explored yet. The activation of hepatic stellate cells (HSCs) is considered as the most critical factor in the progression of liver fibrosis and cirrhosis. Autophagy has recently been identified as a new mechanism to regulate HSC activation. Here, we found that liver macrophages were polarized toward type 2 (M2) during the progression of nonalcoholic steatohepatitis (NASH) and liver fibrosis in both patients and NAFLD mice. Using the methionine-choline-deficient (MCD) diet NAFLD murine model and the in vitro cell culture system, we identified that the M2 macrophages promoted HSC autophagy by secreting prostaglandin E2 (PGE2) and binding its receptor EP4 on the surface of HSCs, which consequently enhanced HSC activation, extracellular matrix deposition, and liver fibrosis. Mechanistically, PGE2/EP4 signals enhanced HSC autophagy through the Erk pathway. A specific PGE2/EP4 antagonist E7046 significantly inhibited M2 macrophage-mediated HSC autophagy and improved liver fibrosis and histopathology in NAFLD mice. Our study provides novel mechanistic insights into the regulation of HSC activation and liver fibrosis. Our findings suggest that the PGE2/EP4 pathway is a promising therapeutic target to prevent NASH progression into cirrhosis.

Therapeutic potential of targeting regulatory mechanisms of hepatic stellate cell activation in liver fibrosis

Hepatic fibrosis is a manifestation of different etiologies of liver disease with the involvement of multiple mediators in complex network interactions. Activated hepatic stellate cells (aHSCs) are the central driver of hepatic fibrosis, given their potential to induce connective tissue formation and extracellular matrix (ECM) protein accumulation. Therefore, identifying the cellular and molecular pathways involved in the activation of HSCs is crucial in gaining mechanistic and therapeutic perspectives to more effectively target the disease. In addition to a comprehensive summary of our current understanding of the role of HSCs in liver fibrosis, we also discuss here the proposed therapeutic strategies based on targeting HSCs.

Tenofovir disoproxil fumarate directly ameliorates liver fibrosis by inducing hepatic stellate cell apoptosis via downregulation of PI3K/Akt/mTOR signaling pathway

Background

Antifibrotic agent for the treatment of liver fibrosis has not been developed so far. Long term treatment of chronic hepatitis B patients with antiviral drugs tenofovir disoproxil fumarate (TDF) and entecavir (ETV) results in the regression of liver fibrosis, but the underlying mechanism has not been clarified. Therefore, we aimed to investigate the direct impact of TDF and ETV on liver fibrosis.

Methods

Activated hepatic stellate cell (HSC) cell lines were used to evaluate the effects of TDF and ETV. After treatment with each antiviral agent, cell viability, morphology, apoptotic features, autophagy and antifibrosis signalling pathways were examined. Then, collagen deposition, fibrosis markers and activated HSCs were measured in liver tissues of the liver fibrosis model mice.

Results

After TDF treatment, the viabilities of LX2 and HSC-T6 cells were decreased, and the cells exhibited apoptotic features, but ETV did not induce these effects. Cleavage of PARP and Caspase-3 and the inhibition of the antiapoptotic gene Bcl-xl indicated activated HSC apoptosis following TDF treatment. TDF simultaneously increased autophagy, which also regulated apoptosis through crosstalk. TDF inactivated the PI3K/Akt/mTOR signalling pathway, which was associated with the activation of both apoptosis and autophagy. In the liver fibrosis mouse model, the fibrotic area and activated HSC markers were decreased by TDF but not ETV treatment. Additionally, apoptotic cells were concentrated in the periportal fibrotic area after TDF treatment, which indicated the specific antifibrotic effect of TDF.

Conclusions

TDF directly ameliorates liver fibrosis by downregulating the PI3K/Akt/mTOR signalling pathway, which results in the apoptosis of activated HSCs. The antifibrotic effects of TDF indicate that it may be a therapeutic agent for the treatment of liver fibrosis.

TGF-β-induced fibrosis: A review on the underlying mechanism and potential therapeutic strategies

Transforming growth factor-beta (TGF-β) plays multiple homeostatic roles in the regulation of inflammation, proliferation, differentiation and would healing of various tissues. Many studies have demonstrated that TGF-β stimulates activation and proliferation of fibroblasts, which result in extracellular matrix deposition. Its increased expression can result in many fibrotic diseases, and the level of expression is often correlated with disease severity. On this basis, inhibition of TGF-β and its activity has great therapeutic potential for the treatment of various fibrotic diseases such as pulmonary fibrosis, renal fibrosis, systemic sclerosis and etc. By understanding the molecular mechanism of TGF-β signaling and activity, researchers were able to develop different strategies in order to modulate the activity of TGF-β. Antisense oligonucleotide was developed to target the mRNA of TGF-β to inhibit its expression. There are also neutralizing monoclonal antibodies that can target the TGF-β ligands or α_vβ₆ integrin to prevent binding to receptor or activation of latent TGF-β respectively. Soluble TGF-β receptors act as ligand traps that competitively bind to the TGF-β ligands. Many small molecule inhibitors have been developed to inhibit the TGF-β receptor at its cytoplasmic domain and also intracellular signaling molecules. Peptide aptamer technology has been used to target downstream TGF-β signaling. Here, we summarize the underlying mechanism of TGF-β-induced fibrosis and also review various strategies of inhibiting TGF-β in both preclinical and clinical studies.

Curc-mPEG454, a PEGylated curcumin derivative, as a multi-target anti-fibrotic prodrug

Our previous studies demonstrated that Curc-mPEG454, a curcumin derivative modified with short-chain polyethylene glycol (PEG), not only increased the blood concentration of curcumin, but also retained its anti-inflammatory activity. Here, we aimed to evaluate the anti-fibrotic effect of Curc-mPEG454 on a rat liver fibrosis model induced by carbon tetrachloride (CCl₄), and to explore the underlying mechanisms by integrating our total liver RNA sequencing (RNA-seq) data with recent liver single-cell sequencing (scRNA-seq) studies. 50 mg/kg and 100 mg/kg Curc-mPEG454 treatment significantly reduced the elevation of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) induced by CCl₄, and the incidence of liver cirrhosis decreased from 75% to 37% and 35%, respectively. RNA-seq analysis revealed that Curc-mPEG454 significantly upregulated aldehyde oxidase 1 (AOX1) while downregulated cytochrome p450 26A1 (CYP26A1) and cytochrome p450 26B1 (CYP26B1) resulting in restoring liver retinoic acid (RA) level, increased glutamate-cysteine ligase catalytic subunit (GCLC) and glutamate-cysteine ligase modifier subunit (GCLM) expression to synthesize hepatic glutathione (GSH), and inhibited liver inflammation via down-regulating the Prostaglandin E Synthase 2 (PTGES2)/prostacyclin E2 (PGE2) signaling. Integrating scRNA-seq data revealed that Curc-mPEG454 effectively inhibited the expansion of scar-associated macrophage subpopulation and scar-producing myofibroblasts in the damaged liver, and remodeled the fibrotic niche via regulation of ligand-receptor interactions including platelet-derived growth factor-B (PDGF-B)/platelet-derived growth factor receptor-α (PDGFR-α) signaling. As a multi-target prodrug, PEGylated curcumin deserves further attention and research.

Systemic cytokines, chemokines and growth factors reveal specific and shared immunological characteristics in infectious cardiomyopathies

Heart disease is a major cause of death worldwide. Chronic Chagas cardiomyopathy (CCC) caused by infection with Trypanosoma cruzi leading to high mortality in adults, and rheumatic heart disease (RHD), resulting from infection by Streptococcus pyogenes affecting mainly children and young adults, are amongst the deadliest heart diseases in low-middle income countries. Despite distinct etiology, the pathology associated with both diseases is a consequence of inflammation. Here we compare systemic immune profile in patients with these cardiopathies, to identify particular and common characteristics in these infectious heart diseases. We evaluated the expression of 27 soluble factors, employing single and multivariate analysis combined with machine-learning approaches. We observed that, while RHD and CCC display higher levels of circulating mediators than healthy individuals, CCC is associated with stronger immune activation as compared to RHD. Despite distinct etiologies, univariate analysis showed that expression of TNF, IL-17, IFN-gamma, IL-4, CCL4, CCL3, CXCL8, CCL11, CCL2, PDGF-BB were similar between CCC and RHD, consistent with their inflammatory nature. Network analysis revealed common inflammatory pathways between CCC and RHD, while highlighting the broader reach of the inflammatory response in CCC. The final multivariate model showed a 100% discrimination power for the combination of the cytokines IL-12p70, IL-1Ra, IL-4, and IL-7 between CCC and RHD groups. Thus, while clear immunological distinctions were identified between CCC and RHD, similarities indicate shared inflammatory pathways in these infectious heart diseases. These results contribute to understanding the pathogenesis of CCC and RHD and may impact the design of immune-based therapies for these and other inflammatory cardiopathies that may also share immunological characteristics.

Targeting Dermal Fibroblast Subtypes in Antifibrotic Therapy: Surface Marker as a Cellular Identity or a Functional Entity?

Fibroblasts are the chief effector cells in fibrotic diseases and have been discovered to be highly heterogeneous. Recently, fibroblast heterogeneity in human skin has been studied extensively and several surface markers for dermal fibroblast subtypes have been identified, holding promise for future antifibrotic therapies. However, it has yet to be confirmed whether surface markers should be looked upon as merely lineage landmarks or as functional entities of fibroblast subtypes, which may further complicate the interpretation of cellular function of these fibroblast subtypes. This review aims to provide an update on current evidence on fibroblast surface markers in fibrotic disorders of skin as well as of other organ systems. Specifically, studies where surface markers were treated as lineage markers and manipulated as functional membrane proteins are both evaluated in parallel, hoping to reveal the underlying mechanism behind the pathogenesis of tissue fibrosis contributed by various fibroblast subtypes from multiple angles, shedding lights on future translational researches.

A Switch from Cell-Associated to Soluble PDGF-B Protects against Atherosclerosis, despite Driving Extramedullary Hematopoiesis

Platelet-derived growth factor B (PDGF-B) is a mitogenic, migratory and survival factor. Cell-associated PDGF-B recruits stabilizing pericytes towards blood vessels through retention in extracellular matrix. We hypothesized that the genetic ablation of cell-associated PDGF-B by retention motif deletion would reduce the local availability of PDGF-B, resulting in microvascular pericyte loss, microvascular permeability and exacerbated atherosclerosis. Therefore, Ldlr-/-Pdgfbret/ret mice were fed a high cholesterol diet. Although plaque size was increased in the aortic root of Pdgfbret/ret mice, microvessel density and intraplaque hemorrhage were unexpectedly unaffected. Plaque macrophage content was reduced, which is likely attributable to increased apoptosis, as judged by increased TUNEL+ cells in Pdgfbret/ret plaques (2.1-fold) and increased Pdgfbret/ret macrophage apoptosis upon 7-ketocholesterol or oxidized LDL incubation in vitro. Moreover, Pdgfbret/ret plaque collagen content increased independent of mesenchymal cell density. The decreased macrophage matrix metalloproteinase activity could partly explain Pdgfbret/ret collagen content. In addition to the beneficial vascular effects, we observed reduced body weight gain related to smaller fat deposition in Pdgfbret/ret liver and adipose tissue. While dampening plaque inflammation, Pdgfbret/ret paradoxically induced systemic leukocytosis. The increased incorporation of 5-ethynyl-2'-deoxyuridine indicated increased extramedullary hematopoiesis and the increased proliferation of circulating leukocytes. We concluded that Pdgfbret/ret confers vascular and metabolic effects, which appeared to be protective against diet-induced cardiovascular burden. These effects were unrelated to arterial mesenchymal cell content or adventitial microvessel density and leakage. In contrast, the deletion drives splenic hematopoiesis and subsequent leukocytosis in hypercholesterolemia.

2021 ISHEN guidelines on animal models of hepatic encephalopathy

This working group of the International Society of Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) was commissioned to summarize and update current efforts in the development and characterization of animal models of hepatic encephalopathy (HE). As defined in humans, HE in animal models is based on the underlying degree and severity of liver pathology. Although hyperammonemia remains the key focus in the pathogenesis of HE, other factors associated with HE have been identified, together with recommended animal models, to help explore the pathogenesis and pathophysiological mechanisms of HE. While numerous methods to induce liver failure and disease exist, less have been characterized with neurological and neurobehavioural impairments. Moreover, there still remains a paucity of adequate animal models of Type C HE induced by alcohol, viruses and non-alcoholic fatty liver disease; the most common etiologies of chronic liver disease.

Cross-talk between hepatic stellate cells and T lymphocytes in liver fibrosis

BACKGROUND

Fibrosis results from inflammation and healing following injury. The imbalance between extracellular matrix (ECM) secretion and degradation leads to the ECM accumulation and liver fibrosis. This process is regulated by immune cells. T lymphocytes, including alpha beta (αβ) T cells, which have adaptive immune functions, and gamma delta (γδ) T cells, which have innate immune functions, are considered regulators of liver fibrosis. This review aimed to present the current understanding of the cross-talk between T lymphocytes and hepatic stellate cells (HSCs), which are the key cells in liver fibrosis.

DATA SOURCES

The keywords "liver fibrosis", "immune", and "T cells" were used to retrieve articles published in PubMed database before January 31, 2020.

RESULTS

The ratio of CD8+ (suppressor) T cells to CD4+ (helper) T cells is significantly higher in the liver than in the peripheral blood. T cells secrete a series of cytokines and chemokines to regulate the inflammation in the liver and the activation of HSCs to influence the course of liver fibrosis. In addition, HSCs also regulate the differentiation and proliferation of T cells.

CONCLUSIONS

The cross-talk between T cells and HSCs regulates liver fibrosis progression. The elucidation of this communication process will help us to understand the pathological process of liver fibrosis.

PDGF-BB induces conversion, proliferation, migration, and collagen synthesis of oral mucosal fibroblasts through PDGFR-β/PI3K/ AKT signaling pathway

OBJECTIVE

To explore the pathogenesis of oral submucosal fibrosis (OSF) by analyzing the impact of Platelet Derived Growth Factor (PDGF)-BB on oral mucosal fibroblasts (FB) and PDGFR-β/Phosphoinositide 3-kinase (PI3K)/serine/threonine protein kinase (AKT) signaling pathway.

METHODS

The isolated and purified oral mucosal fibroblasts were divided into four groups: the control group (CON, 10% FBS DMEM), the PDGF-BB group (40 ng/ml PDGF-BB), the PDGF-BB+IMA group (40 ng/ml PDGF-BB and 60 μmol/L IMA), and the PDGF-BB+LY294002 group (40 ng/ml PDGF-BB and 48 μmol/L LY294002). Primary human FB cells were isolated and cultured for detecting the effects of PDGF-BB on α-smooth muscle actin (α-SMA) by indirect immunofluorescence. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, Thiazolyl Blue Tetrazolium Bromide (MTT) method and scratch test were used to detect the proliferation and migration of FB. Western blots were used to detect the synthesis of type I collagen (Col I) and the expression of PDGFR-β/PI3K/AKT signaling pathway-related proteins. The effects of PDGFR-β inhibitor and PI3K inhibitor were observed.

RESULTS

Compared with group CON, group IMA, and group LY294002, α-SMA was upregulated in group PDGF-BB (p< 0.05), with higher OD490 nm value (p< 0.05), narrower average scratch width, and higher relative cell migration rate (p< 0.05). The expression levels of Col I, p-PDGFR-β, p-PI3K, and p-AKT were higher in group PDGF-BB (p< 0.05).

CONCLUSIONS

PDGF-BB induces FB to transform into myofibroblasts (MFB) through the PDGFR-β/PI3K/AKT signaling pathway, and promotes the proliferation, migration, and collagen synthesis.

A dietary ketone ester mitigates histological outcomes of NAFLD and markers of fibrosis in high-fat diet fed mice

Nutritional ketosis as a therapeutic tool has been extended to the treatment of metabolic diseases, including obesity, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD). The purpose of this study was to determine whether dietary administration of the ketone ester (KE) R,S-1,3-butanediol diacetoacetate (BD-AcAc2) attenuates markers of hepatic stellate cell (HSC) activation and hepatic fibrosis in the context of high-fat diet (HFD)-induced obesity. Six-week-old male C57BL/6J mice were placed on a 10-wk ad libitum HFD (45% fat, 32% carbohydrates, 23% proteins). Mice were then randomized to one of three groups (n = 10 per group) for an additional 12 wk: 1) control (CON), continuous HFD; 2) pair-fed (PF) to KE, and 3) KE (HFD + 30% energy from BD-AcAc2, KE). KE feeding significantly reduced histological steatosis, inflammation, and total NAFLD activity score versus CON, beyond improvements observed for calorie restriction alone (PF). Dietary KE supplementation also reduced the protein content and gene expression of profibrotic markers (α-SMA, COL1A1, PDGF-β, MMP9) versus CON (P < 0.05), beyond reductions observed for PF versus CON. Furthermore, KE feeding increased hepatic markers of anti-inflammatory M2 macrophages (CD163) and also reduced proinflammatory markers [tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and cellular communication network factor 1 (CCN1)] versus CON and PF (P ≤ 0.05), in the absence of changes in markers of total hepatic macrophage content (F4/80 and CD68; P > 0.05). These data highlight that the dietary ketone ester BD-AcAc2 ameliorates histological NAFLD and inflammation and reduces profibrotic and proinflammatory markers. Future studies to further explore potential mechanisms are warranted.NEW & NOTEWORTHY To our knowledge, this is the first study focusing on hepatic outcomes in response to dietary ketone ester feeding in male mice with HFD-induced NAFLD. Novel findings include that dietary ketone ester feeding ameliorates NAFLD outcomes via reductions in histological steatosis and inflammation. These improvements were beyond those observed for caloric restriction alone. Furthermore, dietary ketone ester feeding was associated with greater reductions in markers of hepatic fibrogenesis and inflammation compared with control and calorie-restricted mice.

Hepatic stellate cells - from past till present: morphology, human markers, human cell lines, behavior in normal and liver pathology

Hepatic stellate cell (HSC), initially analyzed by von Kupffer, in 1876, revealed to be an extraordinary mesenchymal cell, essential for both hepatocellular function and lesions, being the hallmark of hepatic fibrogenesis and carcinogenesis. Apart from their implications in hepatic injury, HSCs play a vital role in liver development and regeneration, xenobiotic response, intermediate metabolism, and regulation of immune response. In this review, we discuss the current state of knowledge regarding HSCs morphology, human HSCs markers and human HSC cell lines. We also summarize the latest findings concerning their roles in normal and liver pathology, focusing on their impact in fibrogenesis, chronic viral hepatitis and liver tumors.

Hepatic Stellate Cell Activation and Inactivation in NASH-Fibrosis-Roles as Putative Treatment Targets?

Hepatic fibrosis is the primary predictor of mortality in patients with non-alcoholic steatohepatitis (NASH). In this process, the activated hepatic stellate cells (HSCs) constitute the principal cells responsible for the deposition of a fibrous extracellular matrix, thereby driving the hepatic scarring. HSC activation, migration, and proliferation are controlled by a complex signaling network involving growth factors, lipotoxicity, inflammation, and cellular stress. Conversely, the clearance of activated HSCs is a prerequisite for the resolution of the extracellular fibrosis. Hence, pathways regulating the fate of the HSCs may represent attractive therapeutic targets for the treatment and prevention of NASH-associated hepatic fibrosis. However, the development of anti-fibrotic drugs for NASH patients has not yet resulted in clinically approved therapeutics, underscoring the complex biology and challenges involved when targeting the intricate cellular signaling mechanisms. This narrative review investigated the mechanisms of activation and inactivation of HSCs with a focus on NASH-associated hepatic fibrosis. Presenting an updated overview, this review highlights key cellular pathways with potential value for the development of future treatment modalities.

Lenvatinib prevents liver fibrosis by inhibiting hepatic stellate cell activation and sinusoidal capillarization in experimental liver fibrosis

Molecular targeted agents are pharmacologically used to treat liver fibrosis and have gained increased attention. The present study examined the preventive effect of lenvatinib on experimental liver fibrosis and sinusoidal capillarization as well as the in vitro phenotypes of hepatic stellate cells. LX-2, a human stellate cell line, was used for in vitro studies. In vivo liver fibrosis was induced in F344 rats using carbon tetrachloride by intraperitoneal injection for 8 weeks, and oral administration of lenvatinib was started two weeks after initial injection of carbon tetrachloride. Lenvatinib restrained proliferation and promoted apoptosis of LX-2 with suppressed phosphorylation of extracellular signal-regulated kinase 1/2 and AKT. It also down-regulated COL1A1, ACTA2 and TGFB1 expressions by inhibiting the transforming growth factor-β1/Smad2/3 pathway. Treatment with lenvatinib also suppressed platelet-derived growth factor-BB-stimulated proliferation, chemotaxis and vascular endothelial growth factor-A production, as well as basic fibroblast growth factor-induced LX-2 proliferation. In vivo study showed that lenvatinib attenuated liver fibrosis development with reduction in activated hepatic stellate cells and mRNA expression of profibrogenic markers. Intrahepatic neovascularization was ameliorated with reduced hepatic expressions of Vegf1, Vegf2 and Vegfa in lenvatinib-treated rats. Collectively, these results suggest the potential use of lenvatinib as a novel therapeutic strategy for liver fibrosis.

Endothelial GATA4 controls liver fibrosis and regeneration by preventing a pathogenic switch in angiocrine signaling

BACKGROUND & AIMS

Angiocrine signaling by liver sinusoidal endothelial cells (LSECs) regulates hepatic functions such as growth, metabolic maturation, and regeneration. Recently, we identified GATA4 as the master regulator of LSEC specification during development. Herein, we studied the role of endothelial GATA4 in the adult liver and in hepatic pathogenesis.

METHODS

We generated adult Clec4g-icre^tg/0xGata4^fl/fl (Gata4^LSEC-KO) mice with LSEC-specific depletion of Gata4. Livers were analyzed by histology, electron microscopy, immunohistochemistry/immunofluorescence, in situ hybridization, and LSECs were isolated for gene expression profiling, ChIP- and ATAC-sequencing. Partial hepatectomy was performed to assess regeneration. We used choline-deficient, l-amino acid-defined (CDAA) diet and chronic carbon tetrachloride exposure to model liver fibrosis. Human single cell RNA-seq data sets were analyzed for endothelial alterations in healthy and cirrhotic livers.

RESULTS

Genetic Gata4 deficiency in LSECs of adult mice caused perisinusoidal liver fibrosis, hepatopathy and impaired liver regeneration. Sinusoidal capillarization and LSEC-to-continuous endothelial transdifferentiation were accompanied by a profibrotic angiocrine switch involving de novo endothelial expression of hepatic stellate cell-activating cytokine PDGFB. Increased chromatin accessibility and amplification by activated MYC mediated angiocrine Pdgfb expression. As observed in Gata4^LSEC-KO livers, CDAA diet-induced perisinusoidal liver fibrosis was associated with GATA4 repression, MYC activation and a profibrotic angiocrine switch in LSECs. Comparison of CDAA-fed Gata4^LSEC-KO and control mice demonstrated that endothelial GATA4 indeed protects against dietary-induced perisinusoidal liver fibrosis. In human cirrhotic livers, GATA4-positive LSECs and endothelial GATA4 target genes were reduced, while non-LSEC endothelial cells and MYC target genes including PDGFB were enriched.

CONCLUSIONS

Endothelial GATA4 protects against perisinusoidal liver fibrosis by repressing MYC activation and profibrotic angiocrine signaling at the chromatin level. Therapies targeting the GATA4/MYC/PDGFB/PDGFRβ axis offer a promising strategy for prevention and treatment of liver fibrosis.

LAY SUMMARY

The liver vasculature is supposed to play a major role in the development of liver fibrosis and cirrhosis, which can lead to liver failure and liver cancer. Herein, we discovered that structural and transcriptional changes induced by genetic deletion of the transcription factor GATA4 in the hepatic endothelium were sufficient to cause liver fibrosis. Activation of the transcription factor MYC and de novo expression of the "angiocrine" growth factor PDGFB were identified as downstream drivers of fibrosis and as potential therapeutic targets for this potentially fatal disease.

Liver Fibrosis in Non-alcoholic Fatty Liver Disease: From Liver Biopsy to Non-invasive Biomarkers in Diagnosis and Treatment

An increasing percentage of people have or are at risk to develop non-alcoholic fatty liver disease (NAFLD) worldwide. NAFLD comprises different stadia going from isolated steatosis to non-alcoholic steatohepatitis (NASH). NASH is a chronic state of liver inflammation that leads to the transformation of hepatic stellate cells to myofibroblasts. These cells produce extra-cellular matrix that results in liver fibrosis. In a normal situation, fibrogenesis is a wound healing process that preserves tissue integrity. However, sustained and progressive fibrosis can become pathogenic. This process takes many years and is often asymptomatic. Therefore, patients usually present themselves with end-stage liver disease e.g., liver cirrhosis, decompensated liver disease or even hepatocellular carcinoma. Fibrosis has also been identified as the most important predictor of prognosis in patients with NAFLD. Currently, only a minority of patients with liver fibrosis are identified to be at risk and hence referred for treatment. This is not only because the disease is largely asymptomatic, but also due to the fact that currently liver biopsy is still the golden standard for accurate detection of liver fibrosis. However, performing a liver biopsy harbors some risks and requires resources and expertise, hence is not applicable in every clinical setting and is unsuitable for screening. Consequently, different non-invasive diagnostic tools, mainly based on analysis of blood or other specimens or based on imaging have been developed or are in development. In this review, we will first give an overview of the pathogenic mechanisms of the evolution from isolated steatosis to fibrosis. This serves as the basis for the subsequent discussion of the current and future diagnostic biomarkers and anti-fibrotic drugs.

Emerging Roles of SIRT1 in Alcoholic Liver Disease

Alcoholic liver disease (ALD) is the most prevalent type of chronic liver disease worldwide with a wide spectrum of liver pathologies ranging from simple steatosis to steatohepatitis, cirrhosis, and even hepatocellular carcinoma. It has been demonstrated that ALD is mediated in whole or in part by a central signaling molecule sirtuin 1 (SIRT1), a conserved class III histone deacetylase.SIRT1 plays beneficial roles in regulating hepatic lipid metabolism, inhibiting hepatic inflammation, controlling hepatic fibrosis and mediating hepatocellular carcinoma in ALD. However, underlying molecular mechanisms are complex and remain incompletely understood. The aim of this review was to highlight the latest advances in understanding of SIRT1 regulatory mechanisms in ALD and discuss their unique potential role as novel therapeutic target for ALD treatment.

Hepatic Stellate Cell-Macrophage Crosstalk in Liver Fibrosis and Carcinogenesis

Chronic liver injury due to viral hepatitis, alcohol abuse, and metabolic disorders is a worldwide health concern. Insufficient treatment of chronic liver injury leads to fibrosis, causing liver dysfunction and carcinogenesis. Most cases of hepatocellular carcinoma (HCC) develop in the fibrotic liver. Pathological features of liver fibrosis include extracellular matrix (ECM) accumulation, mesenchymal cell activation, immune deregulation, and angiogenesis, all of which contribute to the precancerous environment, supporting tumor development. Among liver cells, hepatic stellate cells (HSCs) and macrophages play critical roles in fibrosis and HCC. These two cell types interplay and remodel the ECM and immune microenvironment in the fibrotic liver. Once HCC develops, HCC-derived factors influence HSCs and macrophages to switch to protumorigenic cell populations, cancer-associated fibroblasts and tumor-associated macrophages, respectively. This review aims to summarize currently available data on the roles of HSCs and macrophages in liver fibrosis and HCC, with a focus on their interaction.

PDGFA gene rs9690350 polymorphism increases biliary atresia risk in Chinese children

Biliary atresia (BA) is a genetic and severe fibro-inflammatory obliterative cholangiopathy of neonates. Platelet-derived growth factor subunit A (PDGFA), as one of participants in liver fibrosis, the overexpression of PDGFA through DNA hypomethylation may lead to the development of BA, but the pathogenesis is still unclear. We conducted a large case-control cohort to investigate the association of genetic variants in PDGFA with BA susceptibility in the Southern Chinese population (506 cases and 1473 controls). We observed that the G allele of rs9690350(G>C) in PDGFA was significantly associated with an increased risk of BA (OR = 1.24, 95% CI = 1.04-1.49, P=0.02). Additionally, the rs9690350 G allele increased the risk of non-cystic biliary atresia (OR = 1.26, 95% CI = 1.04-1.52, P=0.02) and was a genetic biomarker of severe manifestations after surgery. These findings indicate that the rs9690350 G allele is a PDGFA polymorphism associated with the risk of BA that may confer increased disease susceptibility.

Liver fibrosis: Pathophysiology and clinical implications

Liver fibrosis is a clinically significant finding that has major impacts on patient morbidity and mortality. The mechanism of fibrosis involves many different cellular pathways, but the major cell type involved appears to be hepatic stellate cells. Many liver diseases, including Hepatitis B, C, and fatty liver disease cause ongoing hepatocellular damage leading to liver fibrosis. No matter the cause of liver disease, liver-related mortality increases exponentially with increasing fibrosis. The progression to cirrhosis brings more dramatic mortality and higher incidence of hepatocellular carcinoma. Fibrosis can also affect outcomes following liver transplantation in adult and pediatric patients and require retransplantation. Drugs exist to treat Hepatitis B and C that reverse fibrosis in patients with those viral diseases, but there are currently no therapies to directly treat liver fibrosis. Several mouse models of chronic liver diseases have been successfully reversed using novel drug targets with current therapies focusing mostly on prevention of myofibroblast activation. Further research in these areas could lead to development of drugs to treat fibrosis, which will have invaluable impact on patient survival. This article is categorized under: Metabolic Diseases > Molecular and Cellular Physiology.

Hepatic microenvironment underlies fibrosis in chronic hepatitis B patients

BACKGROUND

Chronic hepatitis B virus (HBV) infection is a leading cause of liver morbidity and mortality worldwide. Liver fibrosis resulting from viral infection-associated inflammation and direct liver damage plays an important role in disease management and prognostication. The mechanisms underlying the contribution of the liver microenvironment to fibrosis in HBV patients are not fully understood. There is an absence of effective clinical treatments for liver fibrosis progression; thus, establishing a suitable in vitro microenvironment in order to design novel therapeutics and identify molecular biomarkers to stratify patients is urgently required.

AIM

To examine a subset of pre-selected microenvironment factors of chronic HBV patients that may underlie fibrosis, with a focus on fibroblast activation.

METHODS

We examined the gene expression of key microenvironment factors in liver samples from patients with more advanced fibrosis compared with those with less severe fibrosis. We also used the human stellate cell line LX-2 in the in vitro study. Using different recombinant cytokines and growth factors or their combination, we studied how these factors interacted with LX-2 cells and pinpointed the cross-talk between the aforementioned factors and screened the most important factors.

RESULTS

Of the secreted factors examined, transforming growth factor (TGF)-β1, interleukin (IL)-1β and tumor necrosis factor (TNF)-α were increased in patients with advanced fibrosis. We found that besides TGF-β1, IL-1β can also induce a profibrotic cascade by stimulating the expression of connective tissue growth factor and platelet-derived growth factor (PDGF) in LX-2 cells. Furthermore, the proinflammatory response can be elicited in LX-2 cells following treatment with IL-1β and TNF-α, suggesting that stellate cells can respond to proinflammatory stimuli. By combining IL-1β and TGF-β1, we observed not only fibroblast activation as shown by αlpha-smooth muscle actin and PDGF induction, but also the inflammatory response as shown by increased expression of IL-1β.

CONCLUSION

Collectively, our data from HBV patients and in vitro studies demonstrate that the hepatic microenvironment plays an important role in mediating the crosstalk between profibrotic and proinflammatory responses and modulating fibrosis in chronic HBV patients. For the establishment of a suitable in vitro microenvironment for HBV-induced liver fibrosis, not only TGF-β1 but also IL-1β should be considered as a necessary environmental factor.

The liver fibrosis niche: Novel insights into the interplay between fibrosis-composing mesenchymal cells, immune cells, endothelial cells, and extracellular matrix

Liver fibrosis is a hepatic wound-healing response caused by chronic liver diseases that include viral hepatitis, alcoholic liver disease, non-alcoholic steatohepatitis, and cholestatic liver disease. Liver fibrosis eventually progresses to cirrhosis that is histologically characterized by an abnormal liver architecture that includes distortion of liver parenchyma, formation of regenerative nodules, and a massive accumulation of extracellular matrix (ECM). Despite intensive investigations into the underlying mechanisms of liver fibrosis, developments of anti-fibrotic therapies for liver fibrosis are still unsatisfactory. Recent novel experimental approaches, such as single-cell RNA sequencing and proteomics, have revealed the heterogeneity of ECM-producing cells (mesenchymal cells) and ECM-regulating cells (immune cells and endothelial cells). These approaches have accelerated the identification of fibrosis-specific subpopulations among these cell types. The ECM also consists of heterogenous components. Their production, degradation, deposition, and remodeling are dynamically regulated in liver fibrosis, further affecting the functions of cells responsible for fibrosis. These cellular and ECM elements cooperatively form a unique microenvironment: a fibrotic niche. Understanding the complex interplay between these elements could lead to a better understanding of underlying fibrosis mechanisms and to the development of effective therapies.

Metabolic inflammation as an instigator of fibrosis during non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive storage of fatty acids in the form of triglycerides in hepatocytes. It is most prevalent in western countries and includes a wide range of clinical and histopathological findings, namely from simple steatosis to steatohepatitis and fibrosis, which may lead to cirrhosis and hepatocellular cancer. The key event for the transition from steatosis to fibrosis is the activation of quiescent hepatic stellate cells (qHSC) and their differentiation to myofibroblasts. Pattern recognition receptors (PRRs), expressed by a plethora of immune cells, serve as essential components of the innate immune system whose function is to stimulate phagocytosis and mediate inflammation upon binding to them of various molecules released from damaged, apoptotic and necrotic cells. The activation of PRRs on hepatocytes, Kupffer cells, the resident macrophages of the liver, and other immune cells results in the production of proinflammatory cytokines and chemokines, as well as profibrotic factors in the liver microenvironment leading to qHSC activation and subsequent fibrogenesis. Thus, elucidation of the inflammatory pathways associated with the pathogenesis and progression of NAFLD may lead to a better understanding of its pathophysiology and new therapeutic approaches.

Liver Fibrosis: Mechanistic Concepts and Therapeutic Perspectives

Liver fibrosis due to viral or metabolic chronic liver diseases is a major challenge of global health. Correlating with liver disease progression, fibrosis is a key factor for liver disease outcome and risk of hepatocellular carcinoma (HCC). Despite different mechanism of primary liver injury and disease-specific cell responses, the progression of fibrotic liver disease follows shared patterns across the main liver disease etiologies. Scientific discoveries within the last decade have transformed the understanding of the mechanisms of liver fibrosis. Removal or elimination of the causative agent such as control or cure of viral infection has shown that liver fibrosis is reversible. However, reversal often occurs too slowly or too infrequent to avoid life-threatening complications particularly in advanced fibrosis. Thus, there is a huge unmet medical need for anti-fibrotic therapies to prevent liver disease progression and HCC development. However, while many anti-fibrotic candidate agents have shown robust effects in experimental animal models, their anti-fibrotic effects in clinical trials have been limited or absent. Thus, no approved therapy exists for liver fibrosis. In this review we summarize cellular drivers and molecular mechanisms of fibrogenesis in chronic liver diseases and discuss their impact for the development of urgently needed anti-fibrotic therapies.

Thymosinβ4 alleviates cholestatic liver fibrosis in mice through downregulating PDGF/PDGFR and TGFβ/Smad pathways

Liver fibrosis is an important health problem without adequate and effective therapeutics. In this study, effects of thymosinβ4 (Tβ4) on hepatic fibrogenesis and the underlying molecular mechanisms were explored in bile duct ligation (BDL)-induced mice cholestatic liver fibrosis model. Results showed exogenous Tβ4 significantly reduced the mortality and liver/body weight ratio in BDL mice. Histological examinations and biochemical analyses demonstrated that BDL induced evident portal fibrosis and a significant increase in hepatic collagen contents. However, these changes were significantly attenuated by exogenous Tβ4. Quantitative real-time PCR assays showed that Tβ4 suppressed BDL-induced increases in many fibrotic genes expression including α-smooth muscle actin (α-SMA), collagen I, III and fibronectin, TGFβ1, TGFβR II, Smad2, Smad3, and PDGFRβ. Results from immunohistochemistry and Western blots also showed that Tβ4 reduced TGFβ1 and PDGFRβ protein levels in the liver tissues of BDL mice. In vitro studies using LX-2 cells demonstrated that Tβ4 could decrease PDGFRβ and TGFβR II levels in hepatic stellate cells. Taken together, findings in our present studies suggested that exogenous Tβ4 alleviated BDL-induced cholestatic liver fibrosis through downregulating PDGF/PDGFR and TGFβ/Smad pathways.

Hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein (HIP/PAP) confers protection against hepatic fibrosis through downregulation of transforming growth factor β receptor II

Hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein (HIP/PAP) has antimicrobial, antioxidant, anti-inflammatory, mitogenic, and antiapoptotic effects and thus exerts important functions in the maintenance of integrity and homeostasis of several organs, such as the gastrointestinal tract, pancreas, and liver. Although the potent hepatoprotective effect of HIP/PAP has been validated, its impact on liver fibrosis has not been reported. In this study, we evaluated the role of HIP/PAP on hepatic fibrosis and explored the possible underlying mechanisms. We found that the expression of HIP/PAP and its mouse counterpart, Reg3B, was markedly upregulated in fibrotic human or mouse livers. Intraperitoneal (i.p.) interleukin (IL)-10, IL-6, and TNF-α but not TGF-β1 significantly induced hepatic overexpression of Reg3B in mice. In both CCl₄ and BDL liver fibrosis models, adenovirus-mediated ectopic expression of HIP/PAP markedly alleviated liver injury, inflammation, collagen deposition, hepatic stellate cell activation, and the overexpression of profibrotic cytokines, including transforming growth factor β1 (TGF-β1), platelet-derived growth factor (PDGF)-A, B, connective tissue growth factor (CTGF), and plasminogen activator inhibitor-1 (PAI-1), in mice. In vitro experiments demonstrated that, in addition to suppressing hepatic stellate cell proliferation and accelerating hepatocyte proliferation, HIP/PAP mitigated TGF-β1-induced hepatic stellate cell activation, hepatocyte epithelial-mesenchymal transition (EMT) and upregulated expression of profibrotic cytokines in both hepatic stellate cells and hepatocytes. Moreover, HIP/PAP attenuated the overexpression of TGF-β receptor II (TGF-βRII) in fibrotic mouse livers and decreased the basal expression of TGF-βRII in nonfibrotic mouse livers as well as in cultured hepatocytes and hepatic stellate cells, which is at least partly attributable to the TGF-β1-antagonizing function of HIP/PAP. This study indicates that increased expression of hepatic HIP/PAP serves as a countermeasure against liver injury and fibrosis. Exogenous supplementation of HIP/PAP might be a promising therapeutic agent for hepatic fibrosis as well as liver injury.

Macrophage MerTK Promotes Liver Fibrosis in Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is emerging as a leading cause of chronic liver disease. However, therapeutic options are limited by incomplete understanding of the mechanisms of NASH fibrosis, which is mediated by activation of hepatic stellate cells (HSCs). In humans, human genetic studies have shown that hypomorphic variations in MERTK, encoding the macrophage c-mer tyrosine kinase (MerTK) receptor, provide protection against liver fibrosis, but the mechanisms remain unknown. We now show that holo- or myeloid-specific Mertk targeting in NASH mice decreases liver fibrosis, congruent with the human genetic data. Furthermore, ADAM metallopeptidase domain 17 (ADAM17)-mediated MerTK cleavage in liver macrophages decreases during steatosis to NASH transition, and mice with a cleavage-resistant MerTK mutant have increased NASH fibrosis. Macrophage MerTK promotes an ERK-TGFβ1 pathway that activates HSCs and induces liver fibrosis. These data provide insights into the role of liver macrophages in NASH fibrosis and provide a plausible mechanism underlying MERTK as a genetic risk factor for NASH fibrosis.

Mechanisms of liver fibrosis and its role in liver cancer

Hepatic fibrogenesis is a pathophysiological outcome of chronic liver injury hallmarked by excessive accumulation of extracellular matrix proteins. Fibrosis is a dynamic process that involves cross-talk between parenchymal cells (hepatocytes), hepatic stellate cells, sinusoidal endothelial cells and both resident and infiltrating immune cells. In this review, we focus on key cell-types that contribute to liver fibrosis, cytokines, and chemokines influencing this process and what it takes for fibrosis to regress. We discuss how mitochondria and metabolic changes in hepatic stellate cells modulate the fibrogenic process. We also briefly review how the presence of fibrosis affects development of hepatocellular carcinoma.

Ameliorating liver fibrosis in an animal model using the secretome released from miR-122-transfected adipose-derived stem cells

BACKGROUND

Recently, the exclusive use of mesenchymal stem cell (MSC)-secreted molecules, called secretome, rather than cells, has been evaluated for overcoming the limitations of cell-based therapy, while maintaining its advantages. However, the use of naïve secretome may not fully satisfy the specificity of each disease. Therefore, it appears to be more advantageous to use the functionally reinforced secretome through a series of processes involving physico-chemical adjustments or genetic manipulation rather than to the use naïve secretome.

AIM

To determine the therapeutic potential of the secretome released from miR-122-transfected adipose-derived stromal cells (ASCs).

METHODS

We collected secretory materials released from ASCs that had been transfected with antifibrotic miR-122 (MCM) and compared their antifibrotic effects with those of the naïve secretome (CM). MCM and CM were intravenously administered to the mouse model of thioacetamide-induced liver fibrosis, and their therapeutic potentials were compared.

RESULTS

MCM infusion provided higher therapeutic potential in terms of: (A) Reducing collagen content in the liver; (B) Inhibiting proinflammatory cytokines; and (C) Reducing abnormally elevated liver enzymes than the infusion of the naïve secretome. The proteomic analysis of MCM also indicated that the contents of antifibrotic proteins were significantly elevated compared to those in the naïve secretome.

CONCLUSION

We could, thus, conclude that the secretome released from miR-122-transfected ASCs has higher antifibrotic and anti-inflammatory properties than the naïve secretome. Because miR-122 transfection into ASCs provides a specific way of potentiating the antifibrotic properties of ASC secretome, it could be considered as an enhanced method for reinforcing secretome effectiveness.

"Let my liver rather heat with wine" - a review of hepatic fibrosis pathophysiology and emerging therapeutics

Cirrhosis is characterized by extensive hepatic fibrosis, and it is the 14th leading cause of death worldwide. Numerous contributing conditions have been implicated in its development, including infectious etiologies, medication overdose or adverse effects, ingestible toxins, autoimmunity, hemochromatosis, Wilson’s disease and primary biliary cholangitis to list a few. It is associated with portal hypertension and its stigmata (varices, ascites, hepatic encephalopathy, combined coagulopathy and thrombophilia), and it is a major risk factor for hepatocellular carcinoma. Currently, orthotopic liver transplantation has been the only curative modality to treat cirrhosis, and the scarcity of donors results in many people waiting years for a transplant. Identification of novel targets for pharmacologic therapy through elucidation of key mechanistic components to induce fibrosis reversal is the subject of intense research. Development of robust models of hepatic fibrosis to faithfully characterize the interplay between activated hepatic stellate cells (the principal fibrogenic contributor to fibrosis initiation and perpetuation), hepatocytes and extracellular matrix components has the potential to identify critical components and mechanisms that can be exploited for targeted treatment. In this review, we will highlight key cellular pathways involved in the pathophysiology of fibrosis from extracellular ligands, effectors and receptors, to nuclear receptors, epigenetic mechanisms, energy homeostasis and cytokines. Further, molecular pathways of hepatic stellate cell deactivation are discussed, including apoptosis, senescence and reversal or transdifferentiation to an inactivated state resembling quiescence. Lastly, clinical evidence of fibrosis reversal induced by biologics and small molecules is summarized, current compounds under clinical trials are described and efforts for treatment of hepatic fibrosis with mesenchymal stem cells are highlighted. An enhanced understanding of the rich tapestry of cellular processes identified in the initiation, perpetuation and resolution of hepatic fibrosis, driven principally through phenotypic switching of hepatic stellate cells, should lead to a breakthrough in potential therapeutic modalities.

Docosahexaenoic acid inhibits hepatic stellate cell activation to attenuate liver fibrosis in a PPARγ-dependent manner

Docosahexaenoic acid (DHA) has been found to have a hepatoprotective effect. In this study, we investigated the role of peroxisome proliferator-activated receptor γ (PPARγ) in DHA regulation of liver fibrosis. DHA was found to inhibit hepatic stellate cell (HSC)-LX2 cell viability and downregulate marker proteins of HSC activation. Furthermore, DHA induced cell cycle arrest at G1 phase in HSCs. Antagonism of PPARγ by GW9662 abrogated the effects of DHA on HSCs. Computer-aided molecular docking predicted that DHA bound to PPARγ via hydrogen bonding with residues Ser289, His323, Tyr473, and His499. We overexpressed Ser289 mutant PPARγ in HSC-LX2 cells and investigated fibrotic marker modulation, and found that DHA effects on HSCs were diminished. Thus, bonding with the Ser289 residue might be indispensable for DHA to activate PPARγ to exert its inhibiting effect on activated HSCs. Last, data from a CCl₄-treated mouse model confirmed that PPARγ activation was required for DHA to attenuate liver fibrosis.

Tubular GM-CSF Promotes Late MCP-1/CCR2-Mediated Fibrosis and Inflammation after Ischemia/Reperfusion Injury

BACKGROUND

After bilateral kidney ischemia/reperfusion injury (IRI), monocytes infiltrate the kidney and differentiate into proinflammatory macrophages in response to the initial kidney damage, and then transition to a form that promotes kidney repair. In the setting of unilateral IRI (U-IRI), however, we have previously shown that macrophages persist beyond the time of repair and may promote fibrosis.

METHODS

Macrophage homing/survival signals were determined at 14 days after injury in mice subjected to U-IRI and in vitro using coculture of macrophages and tubular cells. Mice genetically engineered to lack Ccr2 and wild-type mice were treated ±CCR2 antagonist RS102895 and subjected to U-IRI to quantify macrophage accumulation, kidney fibrosis, and inflammation 14 and 30 days after the injury.

RESULTS

Failure to resolve tubular injury after U-IRI results in sustained expression of granulocyte-macrophage colony-stimulating factor by renal tubular cells, which directly stimulates expression of monocyte chemoattractant protein-1 (Mcp-1) by macrophages. Analysis of CD45⁺ immune cells isolated from wild-type kidneys 14 days after U-IRI reveals high-level expression of the MCP-1 receptor Ccr2. In mice lacking Ccr2 and wild-type mice treated with RS102895, the numbers of macrophages, dendritic cells, and T cell decreased following U-IRI, as did the expression of profibrotic growth factors and proimflammatory cytokines. This results in a reduction in extracellular matrix and kidney injury markers.

CONCLUSIONS

GM-CSF-induced MCP-1/CCR2 signaling plays an important role in the cross-talk between injured tubular cells and infiltrating immune cells and myofibroblasts, and promotes sustained inflammation and tubular injury with progressive interstitial fibrosis in the late stages of U-IRI.

Protein tyrosine phosphatase 1b deficiency protects against hepatic fibrosis by modulating nadph oxidases

Inflammation is typically associated with the development of fibrosis, cirrhosis and hepatocellular carcinoma. The key role of protein tyrosine phosphatase 1B (PTP1B) in inflammatory responses has focused this study in understanding its implication in liver fibrosis. Here we show that hepatic PTP1B mRNA expression increased after bile duct ligation (BDL), while BDL-induced liver fibrosis was markedly reduced in mice lacking Ptpn1 (PTP1B^−/−) as assessed by decreased collagen deposition and α-smooth muscle actin (α-SMA) expression. PTP1B^−/− mice also showed a significant increase in mRNA levels of key markers of monocytes recruitment (Cd68, Adgre1 and Ccl2) compared to their wild-type (PTP1B^+/+) littermates at early stages of injury after BDL. Interestingly, the lack of PTP1B strongly increased the NADPH oxidase (NOX) subunits Nox1/Nox4 ratio and downregulated Cybb expression after BDL, revealing a pro-survival pattern of NADPH oxidase induction in response to liver injury. Chimeric mice generated by transplantation of PTP1B^−/− bone marrow (BM) into irradiated PTP1B^+/+ mice revealed similar hepatic expression profile of NOX subunits than PTP1B^−/− mice while these animals did not show differences in infiltration of myeloid cells at 7 days post-BDL, suggesting that PTP1B deletion in other liver cells is necessary for boosting the early inflammatory response to the BDL. PTP1B^−/− BM transplantation into PTP1B^+/+ mice also led to a blockade of TGF-β and α-SMA induction after BDL. In vitro experiments demonstrated that deficiency of PTP1B in hepatocytes protects against bile acid-induced apoptosis and abrogates hepatic stellate cells (HSC) activation, an effect ameliorated by NOX1 inhibition. In conclusion, our results have revealed that the lack of PTP1B switches NOX expression pattern in response to liver injury after BDL and reduces HSC activation and liver fibrosis.

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PTP1B deficiency in mice ameliorates liver damage induced by cholestasis.

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The increased NOX1/NOX4 ratio in livers from PTP1B^-/- mice was associated with protection against BDL-induced fibrosis.

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The lack of PTP1B exacerbates macrophage recruitment upon BDL which is dispensable for ameliorating cholestatic liver damage.

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Resistance of PTP1B^-/- hepatocytes against bile acid-induced apoptosis protects from HSC activation in a NOX1-dependent manner.

Targeted Delivery of an siRNA/PNA Hybrid Nanocomplex Reverses Carbon Tetrachloride-Induced Liver Fibrosis

Liver fibrosis is a wound healing process with excessive accumulation of extracellular matrix in the liver. We recently discovered a PCBP2 siRNA that reverses fibrogenesis in activated hepatic stellate cells (HSCs), which are the key players in liver fibrogenesis. However, targeted delivery of siRNAs to HSCs still remains a challenge. Herein, we developed a new strategy to fabricate a multicomponent nanocomplex using siRNA/PNA hybrid instead of chemically conjugated siRNA, thus increasing the scalability and feasibility of the siRNA nanocomplex for animal studies. We modified the nanocomplex with an insulin growth factor 2 receptor (IGF2R)-specific peptide, which specifically binds to activated HSCs. The siRNA nanocomplex shows a controllable size and high serum stability. The nanocomplex also demonstrates high cellular uptake in activated HSCs in vitro and in vivo. Anti-fibrotic activity of the siRNA nanocomplex was evaluated in rats with carbon tetrachloride-induced liver fibrosis. Treatment with the PCBP2 siRNA nanocomplex significantly inhibits the mRNA expressions of PCBP2 and type I collagen in fibrotic liver. Histology study revealed that the siRNA nanocomplex efficiently reduces the protein level of type I collagen and reverses liver fibrosis. Our data suggest that the nanocomplex efficiently delivers the siRNA to fibrotic liver and produces a potent anti-fibrotic effect.