Mechanisms of spontaneous resolution of rat liver fibrosis. Hepatic stellate cell apoptosis and reduced hepatic expression of metalloproteinase inhibitors

Smad2 increases the apoptosis of activated human hepatic stellate cells induced by TRAIL

The activation of hepatic stellate cells (HSCs) plays a critical role in the development of liver fibrosis. The induction of apoptosis in activated HSCs during the recovery phase of hepatic fibrosis represents a potential anti-fibrotic therapy. We have previously shown that Smad2 protects against hepatic fibrogenesis; however, the role of Smad2 in the regulation of activated HSC apoptosis remains unknown. We hypothesized that Smad2 regulates the apoptosis of activated HSCs, leading to the resolution of liver fibrosis. To test this hypothesis, the livers of rats were harvested at 0 and 4 weeks after hepatic fibrosis was established by CCl4 injection. Furthermore, TGF-β1-activated HSCs were treated with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) following the silencing or overexpression of Smad2. Both the phosphorylation of Smad2 and TRAIL were detected in fibrotic liver tissues. The results of TUNEL and α-SMA double-staining showed an increase in the apoptosis of activated HSCs during the spontaneous recovery phase. The knockdown of Smad2 reduced TRAIL-induced apoptosis in TGF-β1-activated human LX-2 cells and resulted in an increased expression of α-SMA and collagen I (Col. I). In contrast, the overexpression of Smad2 increased TRAIL-induced HSC apoptosis and reduced the expression of α-SMA and Col. I. The mechanisms underlying these findings were associated with the Smad2-mediated down-regulation of X-linked inhibitor of apoptosis protein (XIAP), resulting in enhanced caspase-3 activity and apoptosis. In conclusion, Smad2 enhances TRAIL-induced apoptosis in activated HSCs, which facilitates the resolution of hepatic fibrosis.

Is Western Diet-Induced Nonalcoholic Steatohepatitis in Ldlr-/- Mice Reversible?

Background

Nonalcoholic fatty liver disease (NAFLD) is a major public health burden in western societies. The progressive form of NAFLD, nonalcoholic steatohepatitis (NASH), is characterized by hepatosteatosis, inflammation, oxidative stress, and hepatic damage that can progress to fibrosis and cirrhosis; risk factors for hepatocellular carcinoma. Given the scope of NASH, validating treatment protocols (i.e., low fat diets and weight loss) is imperative.

Methods

We evaluated the efficacy of two diets, a non-purified chow (NP) and purified (low-fat low-cholesterol, LFLC) diet to reverse western diet (WD)-induced NASH and fibrosis in Ldlr^-/- mice.

Results

Mice fed WD for 22–24 weeks developed robust hepatosteatosis with mild fibrosis, while mice maintained on the WD an additional 7–8 weeks developed NASH with moderate fibrosis. Returning WD-fed mice to the NP or LFLC diets significantly reduced body weight and plasma markers of metabolic syndrome (dyslipidemia, hyperglycemia) and hepatic gene expression markers of inflammation (Mcp1), oxidative stress (Nox2), fibrosis (Col1A, LoxL2, Timp1) and collagen crosslinking (hydroxyproline). Time course analyses established that plasma triglycerides and hepatic Col1A1 mRNA were rapidly reduced following the switch from the WD to the LFLC diet. However, hepatic triglyceride content and fibrosis did not return to normal levels 8 weeks after the change to the LFLC diet. Time course studies further revealed a strong association (r² ≥ 0.52) between plasma markers of inflammation (TLR2 activators) and hepatic fibrosis markers (Col1A, Timp1, LoxL2). Inflammation and fibrosis markers were inversely associated (r² ≥ 0.32) with diet-induced changes in hepatic ω3 and ω6 polyunsaturated fatty acids (PUFA) content.

Conclusion

These studies establish a temporal link between plasma markers of inflammation and hepatic PUFA and fibrosis. Low-fat low-cholesterol diets promote reversal of many, but not all, features associated with WD-induced NASH and fibrosis in Ldlr^-/- mice.

Concise Review: Pluripotent Stem Cell-Derived Cardiac Cells, A Promising Cell Source for Therapy of Heart Failure: Where Do We Stand?

Heart failure is still a major cause of hospitalization and mortality in developed countries. Many clinical trials have tested the use of multipotent stem cells as a cardiac regenerative medicine. The benefit for the patients of this therapeutic intervention has remained limited. Herein, we review the pluripotent stem cells as a cell source for cardiac regeneration. We more specifically address the various challenges of this cell therapy approach. We question the cell delivery systems, the immune tolerance of allogenic cells, the potential proarrhythmic effects, various drug mediated interventions to facilitate cell grafting and, finally, we describe the pathological conditions that may benefit from such an innovative approach. As members of a transatlantic consortium of excellence of basic science researchers and clinicians, we propose some guidelines to be applied to cell types and modes of delivery in order to translate pluripotent stem cell cardiac derivatives into safe and effective clinical trials.

Induction of experimental obstructive cholestasis in mice

The induction of experimental obstructive cholestasis is a reliable model for cholestatic liver diseases in rodents. Bile duct ligation (BDL) in mice provokes typical time-dependent morphological and structural changes in the liver, ranging from liver cell injury and elevated serum enzyme levels after several days, to a severe inflammatory response in the liver after 5-7 days, up to an advanced hepatic fibrosis as soon as three to four weeks after surgical ligation of the common biliary duct. Upon BDL induction, hepatic stellate cells become activated and transdifferentiate into myofibroblasts that produce extracellular matrix proteins such as collagen. In principle, the periportal fibrosis induced by BDL in rat livers is reversible. After the relief of a biliary obstruction, the liver has the capacity to revert to a nearly normal histological architecture and a fully normal biochemical function. When BDL surgery is performed by an experienced scientist, this model has very high reproducibility among all fibrotic models. All these factors corroborate the outstanding value of this model for basic and translational research in biomedicine and hepatology. Nevertheless, this model can result in significant variations when surgery is carried out by untrained personnel or when unconscious modifications are implemented that affect the quality of the intervention. A detailed protocol is provided here for the provision of reliable and reproducible BDL in mice.

Fibroblast growth factor 21 attenuates hepatic fibrogenesis through TGF-β/smad2/3 and NF-κB signaling pathways

Fibroblast growth factor 21 (FGF-21) is a secreted protein, which has anti-diabetic and lipocaic effects, but its ability to protect against hepatic fibrosis has not been studied. In this study, we investigated the ability of FGF-21 to attenuate dimethylnitrosamine (DMN)-induced hepatic fibrogenesis in mice and the mechanism of its action. Hepatic fibrosis was induced by injection of DMN, FGF-21 was administered to the mice once daily in association with DMN injection till the end of the experiment. Histopathological examination, tissue 4-hydroxyproline content and expressions of smooth muscle α-actin (α-SMA) and collagen I were measured to assess hepatic fibrosis. Ethanol/PDGF-BB-activated hepatic stellate cells (HSCs) were used to understand the mechanisms of FGF-21 inhibited hepatic fibrogenesis. Results showed that FGF-21 treatment attenuated hepatic fibrogenesis and was associated with a significant decrease in intrahepatic fibrogenesis, 4-hydroxyproline accumulation, α-SMA expression and collagen I deposition. FGF-21 treatment inhibited the activation of HSCs via down-regulating the expression of TGF-β, NF-κB nuclear translocation, phosphorylation levels of smad2/3 and IκBα. Besides, FGF-21 treatment caused activated HSC apoptosis with increasing expression of Caspase-3, and decreased the ratio of Bcl-2 to Bax. In conclusion, FGF-21 attenuates hepatic fibrogenesis and inhibits the activation of HSC warranting the use of FGF-21 as a potential therapeutic agent in the treatment of hepatic fibrosis.

Protective effects of extracts from Pomegranate peels and seeds on liver fibrosis induced by carbon tetrachloride in rats

BACKGROUND

Liver fibrosis is a feature in the majority of chronic liver diseases and oxidative stress is considered to be its main pathogenic mechanism. Antioxidants including vitamin E, are effective in preventing liver fibrogenesis. Several plant-drived antioxidants, such as silymarin, baicalin, beicalein, quercetin, apigenin, were shown to interfere with liver fibrogenesis. The antioxidans above are polyphenols, flavonoids or structurally related compounds which are the main chemical components of Pomegranate peels and seeds, and the antioxidant activity of Pomegranate peels and seeds have been verified. Here we investigated whether the extracts of pomegranate peels (EPP) and seeds (EPS) have preventive efficacy on liver fibrosis induced by carbon tetrachloride (CCl4) in rats and explored its possible mechanisms.

METHODS

The animal model was established by injection with 50 % CCl4 subcutaneously in male wistar rats twice a week for four weeks. Meanwhile, EPP and EPS were administered orally every day for 4 weeks, respectively. The protective effects of EPP and EPS on biochemical metabolic parameters, liver function, oxidative markers, activities of antioxidant enzymes and liver fibrosis were determined in CCl4-induced liver toxicity in rats.

RESULTS

Compared with the sham group, the liver function was worse in CCl4 group, manifested as increased levels of serum alanine aminotransferase, aspartate aminotransferase and total bilirubin. EPP and EPS treatment significantly ameliorated these effects of CCl4. EPP and EPS attenuated CCl4-induced increase in the levels of TGF-β1, hydroxyproline, hyaluronic acid laminin and procollagen type III. They also restored the decreased superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities and inhibited the formation of lipid peroxidized products in rats treated with CCl4.

CONCLUSION

The EPP and EPS have protective effects against liver fibrosis induced by CCl4, and its mechanisms might be associated with their antioxidant activity, the ability of decreasing the level of TGF-β1 and inhibition of collagen synthesis.

Co-delivery of small molecule hedgehog inhibitor and miRNA for treating liver fibrosis

In liver fibrosis, secretion of growth factors and hedgehog (Hh) ligands by hepatic parenchyma upon repeated insults results in transdifferentiation of quiescent hepatic stellate cells (HSCs) into active myofibroblasts which secrete excessive amounts of extracellular matrix (ECM) proteins. An Hh inhibitor GDC-0449 and miR-29b1 can play an important role in treating liver fibrosis by inhibiting several pro-fibrotic genes. Our in-silico analysis indicate that miR-29b1 targets several profibrotic genes like collagen type I & IV, c-MYC, PDGF-β and PI3K/AKT which are upregulated in liver fibrosis. Common bile duct ligation (CBDL) resulted in an increase in Ptch-1, Shh and Gli-1 expression. miR-29b1 and GDC-0449 were co-formulated into micelles using methoxy poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate-graft-dodecanol-graft-tetraethylenepentamine) (mPEG-b-PCC-g-DC-g-TEPA) copolymer, and injected systemically into CBDL mice. High concentrations of GDC-0449 and miR-29b1 were delivered to liver cells as determined by in situ liver perfusion at 30 min post systemic administration of their micelle formulation. There was a significant decrease in collagen deposition in the liver and serum injury markers, leading to improvement in liver morphology. Combination therapy was more effective in providing hepatoprotection, lowering liver injury related serum enzyme levels, reducing fibrotic protein markers such as collagen, α-SMA, FN-1 and p-AKT compared to monotherapy. In conclusion, inhibition of Hh pathway and restoration of miR-29b1 have the potential to act synergistically in treating CBDL-induced liver fibrosis in mice.

Kinetin inhibits proliferation of hepatic stellate cells by interrupting cell cycle and induces apoptosis by down-regulating ratio of Bcl-2/Bax

Liver fibrosis is an important health problem that can further progress into cirrhosis or liver cancer, and result in significant morbidity and mortality. Inhibiting proliferation and inducing apoptosis of hepatic stellate cells (HSCs) may be the key point to reverse liver fibrosis. At present, anti-fibrosis drugs are rare. Kinetin is a type of plant-derived cytokinin which has been reported to control differentiation and induce apoptosis of human cells. In this study, the HSCs were incubated with different concentrations of kinetin. The proliferation of rat HSCs was measured by MTT assay, cell cycle and apoptosis were analyzed by flow cytometry, and the apoptosis was examined by TUNEL method. The expression of Bcl-2 and Bax proteins was detected by immunocytochemistry staining. It was found that kinetin could markedly inhibit proliferation of HSCs. In a concentration range of 2 to 8 μg/mL, the inhibitory effects of kinetin on proliferation of HSCs were increased with the increased concentration and the extension of time (P < 0.01). Flow cytometry indicated that kinetin could inhibit the DNA synthesis from G0/G1 to S phase in a dose-dependent manner (P < 0.01). The apoptosis rates of the HSCs treated with 8, 4 and 2 μg/mL kinetin (25.62% ± 2.21%, 15.31% ± 1.9% and 6.18% ± 1.23%, respectively) were increased significantly compared with the control group (3.81% ± 0.93%) (P < 0.01). All the DNA frequency histogram in kinetin-treated groups showed obvious hypodiploid peak (sub-G1 peak), and with the increase of kinetin concentrations, the apoptosis rate of HSCs also showed a trend of increase. It was also found that kinetin could down-regulate the expression of Bcl-2, and up-regulate the expression of Bax, leading to the decreased ratio of Bcl-2/Bax significantly. The kinetin-induced apoptosis of HSCs was positively correlated with the expression of Bax, and negatively with the expression of Bcl-2. It was concluded that kinetin can inhibit activation and proliferation of HSCs by interrupting the cell cycle at G1/S restriction point and inducing apoptosis of HSCs via reducing the ratio of Bcl-2/Bax.

Inhibition of Cyclic Adenosine Monophosphate (cAMP)-response Element-binding Protein (CREB)-binding Protein (CBP)/β-Catenin Reduces Liver Fibrosis in Mice

Wnt/β-catenin is involved in every aspect of embryonic development and in the pathogenesis of many human diseases, and is also implicated in organ fibrosis. However, the role of β-catenin-mediated signaling on liver fibrosis remains unclear. To explore this issue, the effects of PRI-724, a selective inhibitor of the cAMP-response element-binding protein-binding protein (CBP)/β-catenin interaction, on liver fibrosis were examined using carbon tetrachloride (CCl4)- or bile duct ligation (BDL)-induced mouse liver fibrosis models. Following repetitive CCl4 administrations, the nuclear translocation of β-catenin was observed only in the non-parenchymal cells in the liver. PRI-724 treatment reduced the fibrosis induced by CCl4 or BDL. C-82, an active form of PRI-724, inhibited the activation of isolated primary mouse quiescent hepatic stellate cells (HSCs) and promoted cell death in culture-activated HSCs. During the fibrosis resolution period, an increase in F4/80(+) CD11b(+) and Ly6C(low) CD11b(+) macrophages was induced by CCl4 and was sustained for two weeks thereafter, even after having stopped CCl4 treatment. PRI-724 accelerated the resolution of CCl4-induced liver fibrosis, and this was accompanied by increased matrix metalloproteinase (MMP)-9, MMP-2, and MMP-8 expression in intrahepatic leukocytes. In conclusion, targeting the CBP/β-catenin interaction may become a new therapeutic strategy in treating liver fibrosis.

Silent information regulator 1 (SIRT1) ameliorates liver fibrosis via promoting activated stellate cell apoptosis and reversion

SIRT1 (silent information regulator 1), a conserved NAD+-dependent histone deacetylase, is closely related with various biological processes. Moreover, the important role of SIRT1 in alcoholic liver disease, nonalcoholic fatty liver and HCC had been widely reported. Recently, a novel role of SIRT1 was uncovered in organ fibrosis diseases. Here, we investigated the inhibitory effect of SIRT1 in liver fibrogenesis. SIRT1 protein was dramatically decreased in CCl4-treated mice livers. Stimulation of LX-2 cells with TGF-β1 also resulted in a significant suppression of SIRT1 protein. Nevertheless, TGF-β1-induced LX-2 cell activation was inhibited by SIRT1 plasmid, and this was accompanied by up-regulation of cell apoptosis-related proteins. Overexpression of SIRT1 also attenuated TGF-β1-induced expression of myofibroblast markers α-SMA and COL1a. However, the important characteristic of the recovery of liver fibrosis is not only the apoptosis of activated stellate cells but also the reversal of the myofibroblast-like phenotype to a quiescent-like phenotype. Restoration of SIRT1 protein was observed in the in vivo spontaneously liver fibrosis reversion model and in vitro MDI (isobutylmethylxanthine, dexamethasone, and insulin)-induced reversed stellate cells, and forced expression of SIRT1 also promoted the reversal of activated stellate cells. Furthermore, lncRNA MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) was increased in liver fibrosis. RNAi-mediated suppression of MALAT1 resulted in a decrease of myofibroblast markers and restoration of SIRT1 protein. These observations suggested that SIRT1 contributed to apoptosis and reversion of activated LX-2 cells and SIRT1 might be regulated by MALAT1 in liver fibrosis. Therefore, SIRT1 could be considered as a valuable therapeutic target for translational studies of liver fibrosis.

M1 Muscarinic Receptor Deficiency Attenuates Azoxymethane-Induced Chronic Liver Injury in Mice

Cholinergic nervous system regulates liver injury. However, the role of M1 muscarinic receptors (M1R) in modulating chronic liver injury is uncertain. To address this gap in knowledge we treated M1R-deficient and WT mice with azoxymethane (AOM) for six weeks and assessed liver injury responses 14 weeks after the last dose of AOM. Compared to AOM-treated WT mice, M1R-deficient mice had attenuated liver nodularity, fibrosis and ductular proliferation, α-SMA staining, and expression of α1 collagen, Tgfβ-R, Pdgf-R, Mmp-2, Timp-1 and Timp-2. In hepatocytes, these findings were associated with reductions of cleaved caspase-3 staining and Tnf-α expression. In response to AOM treatment, M1R-deficient mice mounted a vigorous anti-oxidant response by upregulating Gclc and Nqo1 expression, and attenuating peroxynitrite generation. M1R-deficient mouse livers had increased expression of Trail-R2, a promotor of stellate cell apoptosis; dual staining for TUNNEL and α-SMA revealed increased stellate cells apoptosis in livers from M1R-deficient mice compared to those from WT. Finally, pharmacological inhibition of M1R reduced H₂O₂-induced hepatocyte apoptosis in vitro. These results indicate that following liver injury, anti-oxidant response in M1R-deficient mice attenuates hepatocyte apoptosis and reduces stellate cell activation, thereby diminishing fibrosis. Therefore, targeting M1R expression and activation in chronic liver injury may provide therapeutic benefit.

Reversibility of liver fibrosis

Liver fibrosis is a serious health problem worldwide, which can be induced by a wide spectrum of chronic liver injuries. However, until today, there is no effective therapy available for liver fibrosis except the removal of underlying etiology or liver transplantation. Recent studies indicate that liver fibrosis is reversible when the causative agent(s) is removed. Understanding of mechanisms of liver fibrosis regression will lead to the identification of new therapeutic targets for liver fibrosis. This review summarizes recent research progress on mechanisms of reversibility of liver fibrosis. While most of the research has been focused on HSCs/myofibroblasts and inflammatory pathways, the crosstalk between different organs, various cell types and multiple signaling pathways should not be overlooked. Future studies that lead to fully understanding of the crosstalk between different cell types and the molecular mechanism underlying the reversibility of liver fibrosis will definitely give rise to new therapeutic strategies to treat liver fibrosis.

Sustained Isoprostane E2 Elevation, Inflammation and Fibrosis after Acute Ischaemia-Reperfusion Injury Are Reduced by Pregnane X Receptor Activation

Liver grafts donated after cardiac death are increasingly used to expand the donor pool but are prone to ischaemic-type biliary lesions. The anti-inflammatory effects of the activated pregnane X receptor have previously been shown to be beneficial in a number of inflammatory liver conditions. However, its role in reducing peri-portal inflammation and fibrosis following ischaemia-reperfusion injury has not been investigated. Hepatic injury and its response to pregnane X receptor activation was examined after partial hepatic ischaemia-reperfusion injury induced by surgically clamping the left and middle lobar blood vessels in rats. Molecular and pathological changes in the liver were examined over the following 28 days. Ischaemia-reperfusion injury resulted in transient cholestasis associated with microvillar changes in biliary epithelial cell membranes and hepatocellular injury which resolved within days after reperfusion. However, in contrast to chemically-induced acute liver injuries, this was followed by sustained elevation in isoprostane E2, peri-portal inflammation and fibrosis that remained unresolved in the ischaemic reperfused lobe for at least 28 days after clamping. Administration of pregnenolone-16α-carbonitrile—a rodent-specific pregnane X receptor activator—resulted in significant reductions in cholestasis, hepatic injury, ischaemic lobe isoprostane E2 levels, peri-portal inflammation and fibrosis. Hepatic ischaemia-reperfusion injury therefore results in inflammatory and fibrotic changes that persist well beyond the initial ischaemic insult. Drug-mediated activation of the pregnane X receptor reduced these adverse changes in rats, suggesting that the pregnane X receptor is a viable drug target to reduce ischaemic-type biliary lesions in recipients of liver transplants donated after cardiac death.

Study on the Antifibrotic Effects of Recombinant Shark Hepatical Stimulator Analogue (r-sHSA) in Vitro and in Vivo

Hepatic fibrosis is an effusive wound healing process, characterized by an excessive deposition of extracellular matrix (ECM), as the consequence of chronic liver injury of any etiology. Current therapeutic repertoire for hepatic fibrosis is limited to withdrawal of the noxious agent, which is not always feasible. Hence, in this article, the antifibrotic effects and possible mechanisms of r-sHSA, a recombinant protein with hepatoprotection potential, were investigated. Using NIH/3T3 (mouse embro-fibroblast cell line), skin fibroblasts (human skin fibroblasts, SFBs) and HSC-T6 (rat hepatic stellate cell line), the in vitro effect of r-sHSA was evaluated by measuring the expression levels of alpha-1 Type I collagen (Col1A1) and α-smooth muscle actin (α-SMA). It turned out those fibrosis indicators were typically inhibited by r-sHSA, suggesting its capacity in HSCs inactivation. The antifibrotic activity of r-sHSA was further investigated in vivo on CCl4-induced hepatic fibrosis, in view of significant improvement of the biochemical and histological indicators. More specifically, CCl4-intoxication induced a significant increase in serological biomarkers, e.g., transaminase (AST, ALT), and alkaline phosphatase (ALP), as well as disturbed hepatic antioxidative status; most of the parameters were spontaneously ameliorated to a large extent by withdrawal of CCl4, although the fibrotic lesion was observed histologically. In contrast, r-sHSA treatment markedly eliminated fibrous deposits and restored architecture of the liver in a dose dependent manner, concomitantly with the phenomena of inflammation relief and HSCs deactivation. To sum up, these findings suggest a therapeutic potential for r-sHSA in hepatic fibrosis, though further studies are required.

In vitro reversion of activated primary human hepatic stellate cells

Background

Liver fibrosis is characterized by the excessive formation and accumulation of matrix proteins as a result of wound healing in the liver. A main event during fibrogenesis is the activation of the liver resident quiescent hepatic stellate cell (qHSC). Recent studies suggest that reversion of the activated HSC (aHSC) phenotype into a quiescent-like phenotype could be a major cellular mechanism underlying fibrosis regression in the liver, thereby offering new therapeutic perspectives for the treatment of liver fibrosis. Whether human HSCs have the ability to undergo a similar reversion in phenotype is currently unknown. The aim of the present study is to identify experimental conditions that can revert the in vitro activated phenotype of primary human HSCs and consequently to map the molecular events associated with this reversion process by gene expression profiling.

Results

We find that epidermal growth factor (EGF) and fibroblast growth factor 2 (FGF2) synergistically downregulate the expression of ACTA2 and LOX in primary human aHSCs. Their combination with oleic acid, palmitic acid, and retinol further potentiates a more quiescent-like phenotype as demonstrated by the abundant presence of retinyl ester-positive intra-cytoplasmic lipid droplets, low expression levels of activation markers, and a reduced basal as well as cytokine-stimulated proliferation and matrix metalloproteinase activity. Gene expression profiling experiments reveal that these in vitro reverted primary human HSCs (rHSCs) display an intermediary phenotype that is distinct from qHSCs and aHSCs. Interestingly, this intermediary phenotype is characterized by the increased expression of several previously identified signature genes of in vivo inactivated mouse HSCs such as CXCL1, CXCL2, and CTSS, suggesting also a potential role for these genes in promoting a quiescent-like phenotype in human HSCs.

Conclusions

We provide evidence for the ability of human primary aHSCs to revert in vitro to a transitional state through synergistic action of EGF, FGF2, dietary fatty acids and retinol, and provide a first phenotypic and genomic characterization of human in vitro rHSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13069-015-0031-z) contains supplementary material, which is available to authorized users.

Plasma levels of matrix metalloproteinase-2 and -9 in male and female patients with cirrhosis of different aetiologies

BACKGROUND

Liver fibrosis and cirrhosis may be reversible in some circumstances. Reliable diagnostic tests are necessary for monitoring hepatic fibrogenesis. Matrix metalloproteinase (MMP)-2 and MMP-9 are two of the major MMPs in the circulation and may be most relevant to hepatic fibrosis. The behaviour of MMPs may be significantly different in men and women and may also differ in cases of cirrhosis of various aetiologies.

AIMS

To evaluate the manifestations of MMP-2 and MMP-9 in liver cirrhosis of different aetiologies in men and women and to compare these patterns with those of healthy controls.

METHODS

We measured MMP-2 and MMP-9 levels in plasma samples from 112 patients with cirrhosis and 112 age- and gender-matched healthy controls. We then correlated these MMP levels with gender and disease aetiology.

RESULTS

Plasma MMP-2 concentrations in patients showed a trend towards increasing values with cirrhosis severity and were markedly increased in patients regardless of gender and aetiology compared with healthy controls (p<0.0001). Plasma mean MMP-9 levels were comparable in patients with cirrhosis and controls, but increased with disease severity. They were significantly lower in patients (130.5 ng/mL), female patients (85.4 ng/mL) and male patients (150.4 ng/mL) with mild cirrhosis than in controls (163.2 ng/mL), female controls (162.5 ng/mL) and male controls (163.3 ng/mL) (p=0.001, 0.041 and 0.009, respectively). MMP-2 and MMP-9 concentrations were not significantly different between genders among controls and among various patient subgroups.

CONCLUSIONS

Plasma MMP-2 level may be a useful diagnostic marker for monitoring hepatic fibrogenesis in patients with disease of different aetiologies.

Transplantation of mesenchymal stem cells expressing TIMP-1-shRNA improves hepatic fibrosis in CCl₄-treated rats

This study was to investigate the therapeutic effect of intravenous transplantation of TIMP-1-silencing mesenchymal stem cells (MSCs) in a rat model of liver fibrosis. MSCs were transduced with a lentiviral vector expressing tissue inhibitor of metalloproteinase 1 (TIMP-1)-shRNA, and the liver cirrhosis model was established by injection of CCl4 (1 ml/kg body weight twice a week for 4 weeks) in Sprague Dawley rats. The survived 36 rats were randomly divided into 3 groups: control group, MSCs group, and TIMP-1-shRNA group. At 4 weeks after establishment of animal model, 3×10(6) MSCs were intravenously injected. In TIMP-1-shRNA group, MSCs expressing TIMP-1-shRNA were transplanted. Animals were sacrificed 4 weeks later. Blood was collected for the detection of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The livers were harvested for histological examination. At 5 days after transfection, strong fluorescence was detectable in each group. TIMP-1-shRNA group had the lowest TIMP-1 expression. Following MSCs transplantation, serum ALT and AST reduced in rats with hepatic cirrhosis, and histology showed less fibrotic areas and collagens, as compared to control group. These improvements were more obvious in the TIMP-1-shRNA group. Our study indicates that transplantation of MSCs expressing TIMP-1-shRNA is able to inhibit the progression of liver fibrosis and possibly restore the liver function in a rat model.

Cardiac fibroblasts: from development to heart failure

Cardiac fibroblasts are a major cell population of the heart and are characterized by their capacity to produce extracellular matrix (ECM). In hearts subjected to pressure overload, excessive fibroblast accumulation is responsible for fibrosis of the myocardium, a major clinical issue. Hence, understanding mechanisms generating fibroblasts in this context has become a key question in the cardiovascular field. Recent studies now point to the activation of resident fibroblasts as the underlying cause of fibrosis. However, de novo generation of fibroblasts from endothelium and circulating hematopoietic cells has also been proposed to significantly contribute to fibrosis. Here, we discuss the latest findings on fibroblast origins, with a particular emphasis on the pressure overload model, and the implication of these findings for the development of anti-fibrotic therapies that are currently lacking.

Human liver myofibroblasts during development and diseases with a focus on portal (myo)fibroblasts

Myofibroblasts are stromal cells mainly involved in tissue repair. These cells present contractile properties and play a major role in extracellular matrix deposition and remodeling. In liver, myofibroblasts are found in two critical situations. First, during fetal liver development, especially in portal tracts, myofibroblasts surround vessels and bile ducts during their maturation. After complete development of the liver, myofibroblasts disappear and are replaced in portal tracts by portal fibroblasts. Second, during liver injury, myofibroblasts re-appear principally deriving from the activation of local stromal cells such as portal fibroblasts and hepatic stellate cells or can sometimes emerge by an epithelial-mesenchymal transition process. After acute injury, myofibroblasts play also a major role during liver regeneration. While myofibroblastic precursor cells are well known, the spectrum of activation and the fate of myofibroblasts during disease evolution are not fully understood. Some data are in accordance with a possible deactivation, at least partial, or a disappearance by apoptosis. Despite these shadows, liver is definitively a pertinent model showing that myofibroblasts are pivotal cells for extracellular matrix control during morphogenesis, repair and fibrous scarring.

Sedum mexicanum Britt. Induces Apoptosis of Primary Rat Activated Hepatic Stellate Cells

Background. Liver fibrosis is a significant liver disease in Asian countries. Sedum mexicanum Britt. (SM) has been claimed to have antihepatitis efficacy. In traditional folk medicine, a solution of boiling water-extracted SM (SME) is consumed to prevent and treat hepatitis. However, its efficacy has not yet been verified. The purpose of this study was to investigate the in vitro effect of SME on hepatoprotection. Methods. Hepatic stellate cells (HSCs) and hepatocytes (HCs) were isolated from the livers of the rats by enzymatic digestion and density gradient centrifugation. Results. Treating the HCs and aHSCs with SME caused a dose-dependent decrease in the viability of aHSCs but not that of HCs. In addition, treatment with SME resulted in apoptosis of aHSCs, as determined by DAPI analysis and flow cytometry. SME also increased the amount of cleaved caspase-3, cleaved caspase-9, and cleaved poly ADP-ribose polymerase (PARP) in aHSCs. Furthermore, SME treatment induced a dose-dependent reduction in Bcl-2 expression and increased the expression of Bax in aHSCs. Conclusions. SME did not cause cytotoxicity in HCs, but it induced apoptosis in aHSCs through the mitochondria-dependent caspase-3 pathway. Therefore, SME may possess therapeutic potential for liver fibrosis.

Experimental models of liver fibrosis

Hepatic fibrosis is a wound healing response to insults and as such affects the entire world population. In industrialized countries, the main causes of liver fibrosis include alcohol abuse, chronic hepatitis virus infection and non-alcoholic steatohepatitis. A central event in liver fibrosis is the activation of hepatic stellate cells, which is triggered by a plethora of signaling pathways. Liver fibrosis can progress into more severe stages, known as cirrhosis, when liver acini are substituted by nodules, and further to hepatocellular carcinoma. Considerable efforts are currently devoted to liver fibrosis research, not only with the goal of further elucidating the molecular mechanisms that drive this disease, but equally in view of establishing effective diagnostic and therapeutic strategies. The present paper provides a state-of-the-art overview of in vivo and in vitro models used in the field of experimental liver fibrosis research.

Resolution of liver fibrosis requires myeloid cell-driven sinusoidal angiogenesis

Angiogenesis is a key feature of liver fibrosis. Although sinusoidal remodeling is believed to contribute to fibrogenesis, the impact of sinusoidal angiogenesis on the resolution of liver fibrosis remains undefined. Myeloid cells, particularly macrophages, constantly infiltrate the fibrotic liver and can profoundly contribute to remodeling of liver sinusoids. We observe that the development of fibrosis is associated with decreased hepatic vascular endothelial growth factor (VEGF) expression as well as sinusoidal rarefication of the fibrotic scar. In contrast, the resolution of fibrosis is characterized by a rise in hepatic VEGF levels and revascularization of the fibrotic tissue. Genetic ablation of VEGF in myeloid cells or pharmacological inhibition of VEGF receptor 2 signaling prevents this angiogenic response and the resolution of liver fibrosis. We observe increased expression of matrix metalloproteases as well as decreased expression of tissue inhibitor of metalloproteases confined to sinusoidal endothelial cells in response to myeloid cell VEGF. Remarkably, reintroduction of myeloid cell-derived VEGF upon recovery restores collagenolytic acitivity and the resolution of fibrosis.

CONCLUSION

We identify myeloid cell-derived VEGF as a critical regulator of extracellular matrix degradation by liver endothelial cells, thereby unmasking an unanticipated link between angiogenesis and the resolution of fibrosis.

Reversibility and heritability of liver fibrosis: Implications for research and therapy

Liver fibrosis continues to be a major health problem worldwide due to lack of effective therapy. If the etiology cannot be eliminated, liver fibrosis progresses to cirrhosis and eventually to liver failure or malignancy; both are associated with a fatal outcome. Liver transplantation, the only curative therapy, is still mostly unavailable. Liver fibrosis was shown to be a reversible process; however, complete reversibility remains debatable. Recently, the molecular markers of liver fibrosis were shown to be transmitted across generations. Epigenetic mechanisms including DNA methylation, histone posttranslational modifications and noncoding RNA have emerged as major determinants of gene expression during liver fibrogenesis and carcinogenesis. Furthermore, epigenetic mechanisms have been shown to be transmitted through mitosis and meiosis to daughter cells and subsequent generations. However, the exact epigenetic regulation of complete liver fibrosis resolution and inheritance has not been fully elucidated. This communication will highlight the recent advances in the search for delineating the mechanisms governing resolution of liver fibrosis and the potential for multigenerational and transgenerational transmission of fibrosis markers. The fact that epigenetic changes, unlike genetic mutations, are reversible and can be modulated pharmacologically underscores the unique opportunity to develop effective therapy to completely reverse liver fibrosis, to prevent the development of malignancy and to regulate heritability of fibrosis phenotype.

Recent advancement of molecular mechanisms of liver fibrosis

Liver fibrosis occurs in response to any etiology of chronic liver injury including hepatitis B and C, alcohol consumption, fatty liver disease, cholestasis, and autoimmune hepatitis. Hepatic stellate cells (HSCs) are the primary source of activated myofibroblasts that produce extracellular matrix (ECM) in the liver. Various inflammatory and fibrogenic pathways contribute to the activation of HSCs. Recent studies also discovered that liver fibrosis is reversible and activated HSCs can revert to quiescent HSCs when causative agents are removed. Although the basic research for liver fibrosis has progressed remarkably, sensitive and specific biomarkers as non-invasive diagnostic tools, and effective anti-fibrotic agents have not been developed yet. This review highlights the recent advances in cellular and molecular mechanisms of liver fibrosis, especially focusing on origin of myofibroblasts, inflammatory signaling, autophagy, cellular senescence, HSC inactivation, angiogenesis, and reversibility of liver fibrosis.

1,25-(OH)₂-vitamin D₃ prevents activation of hepatic stellate cells in vitro and ameliorates inflammatory liver damage but not fibrosis in the Abcb4(-/-) model

BACKGROUND/PURPOSE OF THE STUDY

Vitamin D3-deficiency is common in patients with chronic liver-disease and may promote disease progression. Vitamin D3-administration has thus been proposed as a therapeutic approach. Vitamin D3 has immunomodulatory effects and may modulate autoimmune liver-disease such as primary sclerosing cholangitis. Although various mechanisms of action have been proposed, experimental evidence is limited. Here we test the hypothesis that active 1,25-(OH)2-vitamin D3 inhibits activation of hepatic stellate cells (HSC) in vitro and modulates liver-injury in vivo.

METHODS

Proliferation and activation of primary murine HSC were assessed by BrdU- and PicoGreen(®)-assays, immunoblotting, immunofluorescence-microscopy, quantitative-PCR, and zymography following calcitriol-treatment. Wild-type and ATP-binding cassette transporter b4(-/-) (Abcb4(-/-))-mice received calcitriol for 4 weeks. Liver-damage, inflammation, and fibrosis were assessed by serum liver-tests, Sirius-red staining, quantitative-PCR, immunoblotting, immunohistochemistry and hydroxyproline quantification.

RESULTS

In vitro, calcitriol inhibited activation and proliferation of murine HSC as shown by reduced α-smooth muscle actin and platelet-derived growth factor-receptor-β-protein-levels, BrdU and PicoGreen®-assays. Furthermore, mRNA-levels and activity of matrix metalloproteinase 13 were profoundly increased. In vivo, calcitriol ameliorated inflammatory liver-injury reflected by reduced levels of alanine aminotransferase in Abcb4(-/-)-mice. In accordance, their livers had lower mRNA-levels of F4/80, tumor necrosis factor-receptor 1 and a lower count of portal CD11b positive cells. In contrast, no effect on overall fibrosis was observed.

CONCLUSION

Calcitriol inhibits activation and proliferation of HSCs in vitro. In Abcb4(-/-)-mice, administration of calcitriol ameliorates inflammatory liver-damage but has no effect on biliary fibrosis after 4 weeks of treatment.

A glimpse of matrix metalloproteinases in diabetic nephropathy

Matrix metalloproteinases (MMPs) are proteolytic enzymes belonging to the family of zinc-dependent endopeptidases that are capable of degrading almost all the proteinaceous components of the extracellular matrix (ECM). It is known that MMPs play a role in a number of renal diseases, such as, various forms of glomerulonephritis and tubular diseases, including some of the inherited kidney diseases. In this regard, ECM accumulation is considered to be a hallmark morphologic finding of diabetic nephropathy, which not only is related to the excessive synthesis of matrix proteins, but also to their decreased degradation by the MMPs. In recent years, increasing evidence suggest that there is a good correlation between the activity or expression of MMPs and progression of renal disease in patients with diabetic nephropathy and in various experimental animal models. In such a diabetic milieu, the expression of MMPs is modulated by high glucose, advanced glycation end products (AGEs), TGF-β, reactive oxygen species (ROS), transcription factors and some of the microRNAs. In this review, we focused on the structure and functions of MMPs, and their role in the pathogenesis of diabetic nephropathy.

Antifibrotic effects of luteolin on hepatic stellate cells and liver fibrosis by targeting AKT/mTOR/p70S6K and TGFβ/Smad signalling pathways

BACKGROUND & AIMS

Luteolin has been reported to exert antifibrogenic effects in CCl4 -induced hepatic fibrosis in mice. However, limited information is available on the cellular and molecular events responsible for this effect. This study focused on the action of luteolin on hepatic stellate cells (HSCs) and the relevant signalling molecules and pathways as well as the antifibrotic efficacy in multiple models of fibrosis.

METHODS

The in vitro effect of luteolin on rat HSCs and HSC-T6 cells was assessed using proliferation assays, invasion chamber, quantitative real-time PCR analysis and Western blotting. The in vivo effect of luteolin on progression of fibrosis was assessed in three experimental rat models induced by CCl4 , dimethylnitrosamine (DMN) and bile duct ligation (BDL).

RESULTS

Luteolin inhibited proliferation, migration, collagen synthesis as well as expression of fibrosis-related genes in the activated HSCs and HSC-T6 cells stimulated with or without transforming growth factor-β1(TGFβ1) or platelet-derived growth factor (PDGF). Luteolin induced HSC apoptosis associated with the increased caspase 3 activity and p53 expression, and induced G1 arrest with the decreased expression of bcl-2, Cyclin E and p-Cdk-2. Moreover, luteolin significantly inhibited PDGF and TGFβ1-simulated phosphorylation of AKT and Smad pathway. In vivo study showed that luteolin administration markedly alleviated hepatic fibrosis along with reduced elevations of alanine aminotransferase and aspartate aminotransferase. HSCs were found to undergo apoptosis and decreased expression of p-Smad2 and p-AKT in luteolin-treated animals.

CONCLUSIONS

This study demonstrates that luteolin prevents the progression of liver fibrosis through multiple mechanisms and indicates that luteolin has potential for effective treatment of liver fibrosis.

Animal Models for Fibrotic Liver Diseases: What We Have, What We Need, and What Is under Development

Liver fibrosis is part of the wound-healing response to liver damage of various origins and represents a major health problem. Although our understanding of the pathogenesis of liver fibrosis has grown considerably over the last 20 years, effective antifibrotic therapies are still lacking. The use of animal models is crucial for determining mechanisms underlying initiation, progression, and resolution of fibrosis and for developing novel therapies. To date, no animal model can recapitulate all the hepatic and extra-hepatic features of liver disease. In this review, we will discuss the current rodent models of liver injuries. We will then focus on the available ways to target specifically particular compounds of fibrogenesis and on the new models of liver diseases like the humanized liver mouse model.

Nitric oxide is a potential mediator of hepatic inflammation and fibrogenesis in autoimmune hepatitis

BACKGROUND

Despite advances in the understanding of the pathophysiological basis of autoimmune hepatitis (AIH), it is still difficult to delineate the mechanisms involved in progression from hepatic inflammation toward fibrosis. Our aim was to study serum concentrations of NO in AIH of different histological severity and possible effects of immunosuppressive therapy on NO production.

MATERIALS AND METHODS

We studied serum NO metabolites (NOx) in 47 consecutive patients with AIH and in 28 age- and sex-matched controls.

RESULTS

Serum NOx concentrations were higher in AIH patients than in controls (10.3 (4.5-27.3 µmol/L) vs. 4.3 (1.6-14.3 µmol/L), p < 0.001). According to liver histology, median NOx concentrations were significantly higher in patients with severe interface hepatitis compared to patients with mild-moderate interface hepatitis (12.3 (4.5-27.3 µmol/L) vs. 9.3 (4.6-20.3 µmol/L), p = 0.029). Similarly, serum NOx concentrations were significantly higher in patients with advanced fibrosis than in those with early fibrosis (12.2 (4.6-27.3 µmol/L) vs. 9.3 (6.6-12.8 µmol/L), p = 0.018). NOx concentrations decreased in 16 AIH patients who were tested also after biochemical remission was achieved (12.6 (4.5-22.8 µmol/L) at baseline and 5.9 (2.8-10.5 µmol/L) after remission, p = 0.001).

CONCLUSION

This study shows that serum NOx levels are associated with the histological severity of AIH. Hepatocyte inflammation and injury may activate hepatic stellate cells and kupffer cells, and the consequences may include release of NO, which ultimately promotes hepatic fibrosis. Immunosuppressive therapy inhibits this process and the production of NO.

Protective effects of Selenium-enriched probiotics on carbon tetrachloride-induced liver fibrosis in rats

This study aimed to investigate the effects of Se-enriched probiotics (SP) on the liver fibrosis induced by CCl4 in rats. The results showed that SP significantly decreased serum alanine aminotransferase (87.0 ± 1.96 U/L), aspartate aminotransferase (101 ± 3.13 U/L), hepatic hydroxyproline (898 ± 72.5 μg/g), and malondialdehyde (2.39 ± 0.34 nmol/mg) levels, but increased glutathione peroxidase (37.2 ± 3.19 U/mg), superoxide dismutase (201 ± 19.2 U/mg), and glutathione levels (3.32 ± 0.25 mg/g) (P < 0.05) in rats treated by CCl4. SP suppressed hepatic inflammation and necrosis induced by CCl4. Moreover, SP significantly reduced the expression of α-smooth muscle actin, collagen, TGF-β1, TIMP-1, and inflammation-related gene and induced apoptosis of activated hepatic stellate cells (P < 0.05) in rats treated by CCl4. Our results suggest that SP could protect the liver from fibrosis by attenuating hepatic oxidative stress, suppressing hepatic inflammation, and inducing apoptosis of hepatic stellate cells.

Adiponectin reduces hepatic stellate cell migration by promoting tissue inhibitor of metalloproteinase-1 (TIMP-1) secretion

Hepatic stellate cells (HSC) are central players in liver fibrosis that when activated, proliferate, migrate to sites of liver injury, and secrete extracellular matrix. Obesity, a known risk factor for liver fibrosis is associated with reduced levels of adiponectin, a protein that inhibits liver fibrosis in vivo and limits HSC proliferation and migration in vitro. Adiponectin-mediated activation of adenosine monophosphate-activated kinase (AMPK) inhibits HSC proliferation, but the mechanism by which it limits HSC migration to sites of injury is unknown. Here we sought to elucidate how adiponectin regulates HSC motility. Primary rat HSCs were isolated and treated with adiponectin in migration assays. The in vivo actions of adiponectin were examined by treating mice with carbon tetrachloride for 12 weeks and then injecting them with adiponectin. Cell and tissue samples were collected and analyzed for gene expression, signaling, and histology. Serum from patients with liver fibrosis was examined for adiponectin and tissue inhibitor of metalloproteinase-1 (TIMP-1) protein. Adiponectin administration into mice increased TIMP-1 gene and protein expression. In cultured HSCs, adiponectin promoted TIMP-1 expression and through binding of TIMP-1 to the CD63/β1-integrin complex reduced phosphorylation of focal adhesion kinase to limit HSC migration. In mice with liver fibrosis, adiponectin had similar effects and limited focal adhesion kinase phosphorylation. Finally, in patients with advanced fibrosis, there was a positive correlation between serum adiponectin and TIMP-1 levels. In sum, these data show that adiponectin stimulates TIMP-1 secretion by HSCs to retard their migration and contributes to the anti-fibrotic effects of adiponectin.

Resolution of chronic bacterial-induced prostatic inflammation reverses established fibrosis

BACKGROUND

Prostatic inflammation has been suggested to contribute to the etiology of lower urinary tract symptoms by inducing fibrosis. We previously used a well-characterized mouse model of bacterial-induced prostate inflammation to demonstrate that chronic prostatic inflammation induces collagen deposition. Here, we examined stability of the newly synthesized collagen in bacterial-induced prostatic inflammation and the reversibility of fibrosis after resolution of infection and inflammation.

METHODS

Uropathogenic Escherichia coli 1677 was instilled transurethrally into adult C3H/HeOuJ male mice to induce chronic prostatic inflammation. Collagen was labeled by (3) H-proline administration for 28 days post-inoculation and (3) H-hydroxyproline incorporation measured to determine stability of the newly synthesized collagen. Inflammation score was graded using a previously established system and total collagen content was measured by picrosirius red staining quantitation and hydroxyproline content. Resolution of inflammation and reversal of collagen deposition was assessed after treatment with antibiotic enrofloxacin for 2 weeks on day 28 post-inoculation followed by an 8-week recovery period.

RESULTS

Decay analysis of incorporated (3) H-hydroxyproline revealed the half-life of newly synthesized collagen to be significantly shorter in infected/inflamed prostates than in controls. Treatment with antibiotic enrofloxacin completely eradicated bacterial infection and allowed resolution of inflammation. This was followed by marked attenuation of collagen content and correlation analysis verified a positive association between the resolution of inflammation and the reversal of collagen deposition.

CONCLUSIONS

These data demonstrate, for the first time, that inflammation-induced prostatic fibrosis is a reversible process.

Antiviral therapy leads to histological improvement of HBeAg-negative chronic hepatitis B patients

BACKGROUND

We investigated hepatic histological changes in a cohort of HBeAg-negative chronic hepatitis B (CHB) patients (n=50) under long-term antiviral treatment in clinical practice.

METHODS

Liver biopsies were obtained at baseline and after prolonged antiviral treatment with lamivudine (42/50), entecavir (6/50), telbivudine (1/50), or tenofovir (1/50). Due to viral resistance to lamivudine a nucleotide analog was added in 17 patients (adefovir n=11; tenofovir n=6). Twenty-two patients had initially received a 12-month course of pegylated interferon-α, followed by nucleos(t)ide analogs. Necroinflammatory activity was graded as 1-minimal (histological activity index [HAI]: 0-3), 2-mild (HAI: 4-8), 3-moderate (HAI: 9-12), or 4-severe (HAI: 13-18); staging was performed according to the METAVIR system.

RESULTS

Twenty-seven patients were male and 23 female; mean age was 46.9±10.7 years. Mean interval between biopsies was 72.6±27.8 months. Improvement in activity was observed in 31/42 patients (74%) (mean drop -1.1 grade, SD=1.0), and in histological staging in 24/50 patients (48%) (mean drop -0.56 stage, SD=0.73). Importantly, the repeat biopsies of 5/10 patients with initial stage F4 were classified as F3 (n=3), F2 (n=1) or F1 (n=1). Worsening of staging was observed in only one patient. Development of resistance to lamivudine had no significant effect on stage improvement.

CONCLUSIONS

Sustained hepatitis B virus suppression with antiviral treatment in HBeAg-negative CHB patients leads to reduction in necroinflammatory activity and improvement in staging, regardless of transient viral breakthrough. Potent antivirals in common clinical use for CHB can even lead to regression of fibrous septa and architectural improvement of cirrhotic livers.

Reversibility of hepatitis B virus cirrhosis after therapy: who and why?

The end point of liver fibrosis in almost all chronic liver diseases including HBV chronic hepatitis is cirrhosis. Progression to cirrhosis is associated with annular deposition of fibrous tissue and vascular remodeling with a shift from a lobular to nodular organization. Although advanced liver fibrosis was previously thought to be irreversible, today there is compelling evidence that cirrhosis can be reversed if the underlying cause of liver injury is eliminated. Indeed, most clinical trials with antiviral therapy and histological follow-up have shown that fibrosis can regress and that in some cases even cirrhosis can reverse following long-term HBV-DNA suppression, although the return to a fully normal liver is rarely observed and difficult to prove. Nevertheless, a marked percentage of cirrhosis will not reverse even after effective antiviral therapy. Generally cirrhosis is more likely to regress if it is recent, there is effective and long-lasting viral suppression, an internal capacity to regenerate and no vascular thrombosis. HBV treatment in patients with cirrhosis is associated with an improved clinical outcome although there may still be a risk of hepatocellular carcinoma. Nevertheless it has not yet been determined if a favorable outcome depends on histological regression or whether the reversal of cirrhosis is merely a surrogate marker of viral suppression. The significance of the reversal of cirrhosis is still a subject of debate because neither the histological scoring systems nor non-invasive markers to evaluate the reversal of cirrhosis have been validated.

The influence of astragalus polysaccharide and β-elemene on LX-2 cell growth, apoptosis and activation

Background

Activated hepatic stellate cells are the main source of excessive collagen deposition in liver fibrosis. Here we report the inhibitory effects of the combinational treatment of two natural products, astragalus polysaccharide (APS) and β-elemene (ELE) on the activation of human liver hepatic stellate cell line LX-2 cells.

Methods

Cultured LX-2 cells were treated with different concentrations of APS or ELE for 24 or 48 hours. Cell viability/apoptosis was measured by MTT assay and Annexin V/PI staining , activation related genes including α-SMA and CD44 expressions were measured by real-time PCR and western blot respectively.

Results

The majority of LX-2 cells showed morphological change in the presence of APS or ELE for 24 hours. Treatment with APS + ELE for 24 or 48 hours significantly inhabited the cell proliferation compared with APS or ELE treatment alone on LX-2 cells. APS + ELE may block the up-regulation of α-SMA and CD44 both in mRNA and protein levels through TGF-β pathway in LX-2 cells.

Conclusion

APS or ELE treatment alone on LX-2 cells could inhibit cell proliferation and induce apoptosis. The combinational treatment using APS + ELE significantly increased the killing efficiency on LX-2 cells. α-SMA and CD44 expressions was inhibited upon APS + ELE treatment through TGF-β pathway in LX-2 cells. The results indicated a novel treatment using natural products for liver diseases with anti-fibrotic effect.

Mistletoe alkaloid fractions alleviates carbon tetrachloride-induced liver fibrosis through inhibition of hepatic stellate cell activation via TGF-β/Smad interference

ETHNOPHARMACOLOGICAL RELEVANCE

Mistletoe (Viscum coloratum (Kom.) Nakai) has long been categorized as a traditional herbal medicine in Asia. In addition to its application in cancer therapy, mistletoe has also been used in the treatment of chronic hepatic disorders in China. In the present study, we investigated the antifibrotic effect and mechanisms of action of mistletoe extracts in a rat model of carbon tetrachloride (CCl4)-induced hepatotoxicity.

MATERIALS AND METHODS

An experimental model of hepatic fibrosis was established by intraperitoneal injection of rats with CCl4 for 8 weeks. Rats were subsequently treated with a mistletoe alkaloid fraction preparation via oral administration (120mg/kg daily for 8 weeks) or with distilled water as a control. Histopathological changes were observed by hematoxylin and eosin staining and Masson׳s trichrome staining. The expression of markers relevant to hepatic stellate cell (HSC) activation in the liver was assessed by real-time reverse transcription-polymerase chain reaction, immunohistochemistry and western blotting. The anti-fibrosis activity and mechanisms of action of mistletoe alkaloid fractions were further investigated in the HSC-T6 HSC line, following treatment with mistletoe alkaloid fractions (12mg/ml) for 48h.

RESULTS

Hepatic fibrosis decreased markedly in CCl4-treated animals following treatment with mistletoe alkaloid fractions, compared to controls. The mRNA levels of transforming growth factor-β1 (TGF-β1), procollagen I and tissue inhibitors of metalloproteinases (TIMPs) were significantly downregulated, by about 40%, 40% and 45%, respectively, in liver tissues from rats treated with mistletoe alkaloid fractions. Furthermore, significant downregulation of TGF-β1, TGF-β1 receptor, phosphorylated Smad 2 and alpha smooth muscle actin (α-SMA) proteins, by about 45%, 30% and 40%, respectively, was also observed in liver tissues from mistletoe alkaloid fractions-treated rats. In contrast, Smad 7 levels were significantly increased by about 30% in mistletoe alkaloid fractions-treated rats. Treatment of HSC-T6 cells with mistletoe alkaloid fractions significantly induced Smad 7 expression and inhibited the expression of α-SMA, TGFβ1, TGF-β1 receptor, Smad 2 and TIMP-1, in vitro.

CONCLUSION

We demonstrate that mistletoe alkaloid fractions decrease extracellular matrix accumulation by inhibiting HSC activation. Mechanistically, this may occur via inhibition of TGF-β1/Smad 2 and Smad 7 signal transduction, thereby blocking the synthesis of procollagen I and TIMP-1. These findings suggest that mistletoe alkaloid fractions may be a potential therapeutic agent for the treatment of hepatic fibrosis.

Liver fibrosis and protection mechanisms action of medicinal plants targeting apoptosis of hepatocytes and hepatic stellate cells

Following chronic liver injury, hepatocytes undergo apoptosis leading to activation of hepatic stellate cells (HSC). Consequently, activated HSC proliferate and produce excessive extracellular matrix, responsible for the scar formation. The pandemic trend of obesity, combined with the high incidence of alcohol intake and viral hepatitis infections, highlights the urgent need to find accessible antifibrotic therapies. Treatment strategies should take into account the versatility of its pathogenesis and act on all the cell lines involved to reduce liver fibrosis. Medicinal plants are achieving popularity as antifibrotic agents, supported by their safety, cost-effectiveness, and versatility. This review will describe the role of hepatocytes and HSC in the pathogenesis of liver fibrosis and detail the mechanisms of modulation of apoptosis of both cell lines by twelve known hepatoprotective plants in order to reduce liver fibrosis.

Hepatic stellate cells and liver fibrosis

Hepatic stellate cells are resident perisinusoidal cells distributed throughout the liver, with a remarkable range of functions in normal and injured liver. Derived embryologically from septum transversum mesenchyme, their precursors include submesothelial cells that invade the liver parenchyma from the hepatic capsule. In normal adult liver, their most characteristic feature is the presence of cytoplasmic perinuclear droplets that are laden with retinyl (vitamin A) esters. Normal stellate cells display several patterns of intermediate filaments expression (e.g., desmin, vimentin, and/or glial fibrillary acidic protein) suggesting that there are subpopulations within this parental cell type. In the normal liver, stellate cells participate in retinoid storage, vasoregulation through endothelial cell interactions, extracellular matrix homeostasis, drug detoxification, immunotolerance, and possibly the preservation of hepatocyte mass through secretion of mitogens including hepatocyte growth factor. During liver injury, stellate cells activate into alpha smooth muscle actin-expressing contractile myofibroblasts, which contribute to vascular distortion and increased vascular resistance, thereby promoting portal hypertension. Other features of stellate cell activation include mitogen-mediated proliferation, increased fibrogenesis driven by connective tissue growth factor, and transforming growth factor beta 1, amplified inflammation and immunoregulation, and altered matrix degradation. Evolving areas of interest in stellate cell biology seek to understand mechanisms of their clearance during fibrosis resolution by either apoptosis, senescence, or reversion, and their contribution to hepatic stem cell amplification, regeneration, and hepatocellular cancer.

Mutant MMP-9 and HGF gene transfer enhance resolution of CCl4-induced liver fibrosis in rats: role of ASH1 and EZH2 methyltransferases repression

Hepatocyte growth factor (HGF) gene transfer inhibits liver fibrosis by regulating aberrant cellular functions, while mutant matrix metalloproteinase-9 (mMMP-9) enhances matrix degradation by neutralizing the elevated tissue inhibitor of metalloproteinase-1 (TIMP-1). It was shown that ASH1 and EZH2 methyltransferases are involved in development of liver fibrosis; however, their role in the resolution phase of liver fibrosis has not been investigated. This study evaluated the role of ASH1 and EZH2 in two mechanistically different therapeutic modalities, HGF and mMMP-9 gene transfer in CCl₄ induced rat liver fibrosis. Liver fibrosis was induced in rats with twice a week intraperitoneal injection of CCl₄ for 8 weeks. Adenovirus vectors encoding mMMP-9 or HGF genes were injected through tail vein at weeks six and seven and were sacrificed one week after the second injection. A healthy animal group was likewise injected with saline to serve as a negative control. Rats treated with mMMP-9 showed significantly lower fibrosis score, less Sirius red stained collagen area, reduced hydroxyproline and ALT concentration, decreased transforming growth factor beta 1 (TGF-β1) mRNA and lower labeling indices of α smooth muscle actin (α-SMA) and proliferating cell nuclear antigen (PCNA) stained cells compared with HGF- or saline-treated rats. Furthermore, TIMP-1 protein expression in mMMP-9 group was markedly reduced compared with all fibrotic groups. ASH1 and EZH2 protein expression was significantly elevated in fibrotic liver and significantly decreased in mMMP-9- and HGF-treated compared to saline-treated fibrotic livers with further reduction in the mMMP-9 group. Conclusion: Gene transfer of mMMP-9 and HGF reduced liver fibrosis in rats. ASH1 and EZH2 methyltransferases are significantly reduced in mMMP-9 and HGF treated rats which underlines the central role of these enzymes during fibrogenesis. Future studies should evaluate the role of selective pharmacologic inhibitors of ASH1 and EZH2 in resolution of liver fibrosis.

Role of Bone Marrow Mesenchymal Stem Cells in the Treatment of CCL4 Induced Liver Fibrosis in Albino Rats: A Histological and Immunohistochemical Study

BACKGROUND AND OBJECTIVES

Variety of pathological factors including viral hepatitis, alcohol and drug abuse, metabolic diseases, autoimmune diseases and congenital abnormalities can cause hepatic injury. Liver transplantation is the treatment of choice for end-stage liver diseases, however, it faces several difficulties. So the aim of the work is to evaluate the effect of bone marrow derived mesenchymal stem cells (BM-MSCs) on the liver structure in carbon tetra chloride CCL4 induced liver fibrosis in rats.

MATERIALS AND RESULTS

BM-MSCs were isolated and characterized from long bones of twenty male albino rats. Sixty female rats were divided into the following two groups: Group I; thirty rats which were the control group. Group II; thirty rats were injected intra-peritoneal (IP) by CCL4 twice weekly for four weeks and was further subdivided into the following three subgroups: Subgroup IIA (CCL4 alone); included ten rats which were sacrificed after this four weeks. Subgroup IIB (CCL4/MSCs); included ten rats which were IP injected by a single dose of BM-MSCs and were sacrificed after four weeks. Subgroup IIC (CCL4/recovery); included ten rats which were left for another four weeks without any intervention. Histological examination of liver specimens showed that CCl4 caused variable pathological changes with elevated liver enzymes. Injection of BM-MSCs revealed an improvement in the histological picture of the liver and its enzymatic profile. On the other hand, most of the pathological lesion were still detected in rats of recovery group.

CONCLUSIONS

BM-MSC could restore the liver structure and function in experimental model of liver fibrosis.

Inhibition of a novel fibrogenic factor Tl1a reverses established colonic fibrosis

Intestinal fibrostenosis is among the hallmarks of severe Crohn's disease. Patients with certain TNFSF15 (gene name for TL1A) variants over-express TL1A and have a higher risk of developing strictures in the small intestine. In addition, sustained Tl1a expression in mice leads to small and large intestinal fibrostenosis under colitogenic conditions. The aim of this study was to determine whether established murine colonic fibrosis could be reversed with Tl1a antibody (Ab). Treatment with neutralizing Tl1a Ab reversed colonic fibrosis back to the original pre-inflamed levels, potentially as a result of lowered expression of connective tissue growth factor, Il31Ra, transforming growth factor β1 and insulin-like growth factor-1. In addition, blocking Tl1a function by either neutralizing Tl1a Ab or deletion of death domain receptor 3 (Dr3) reduced the number of fibroblasts and myofibroblasts, the primary cell types that mediate tissue fibrosis. Primary intestinal myofibroblasts expressed Dr3 and functionally responded to direct Tl1a signaling by increasing collagen and Il31Ra expression. These data demonstrated a direct role for TL1A-DR3 signaling in tissue fibrosis and that modulation of TL1A-DR3 signaling could inhibit gut fibrosis.

Cell death and cell death responses in liver disease: mechanisms and clinical relevance

Hepatocellular death is present in almost all types of human liver disease and is used as a sensitive parameter for the detection of acute and chronic liver disease of viral, toxic, metabolic, or autoimmune origin. Clinical data and animal models suggest that hepatocyte death is the key trigger of liver disease progression, manifested by the subsequent development of inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Modes of hepatocellular death differ substantially between liver diseases. Different modes of cell death such as apoptosis, necrosis, and necroptosis trigger specific cell death responses and promote progression of liver disease through distinct mechanisms. In this review, we first discuss molecular mechanisms by which different modes of cell death, damage-associated molecular patterns, and specific cell death responses contribute to the development of liver disease. We then review the clinical relevance of cell death, focusing on biomarkers; the contribution of cell death to drug-induced, viral, and fatty liver disease and liver cancer; and evidence for cell death pathways as therapeutic targets.

Mouse models of liver fibrosis mimic human liver fibrosis of different etiologies

The liver has the amazing capacity to repair itself after injury; however, the same processes that are involved in liver regeneration after acute injury can cause serious consequences during chronic liver injury. In an effort to repair damage, activated hepatic stellate cells trigger a cascade of events that lead to deposition and accumulation of extracellular matrix components causing the progressive replacement of the liver parenchyma by scar tissue, thus resulting in fibrosis. Although fibrosis occurs as a result of many chronic liver diseases, the molecular mechanisms involved depend on the underlying etiology. Since studying liver fibrosis in human subjects is complicated by many factors, mouse models of liver fibrosis that mimic the human conditions fill this void. This review summarizes the general mouse models of liver fibrosis and mouse models that mimic specific human disease conditions that result in liver fibrosis. Additionally, recent progress that has been made in understanding the molecular mechanisms involved in the fibrogenic processes of each of the human disease conditions is highlighted.

New Approaches for Studying Alcoholic Liver Disease

Alcoholic liver disease (ALD) is major cause of chronic liver injury which results in liver fibrosis and cirrhosis. According to the surveillance report published by the National Institute on Alcohol Abuse and Alcoholism, liver cirrhosis is the 12th leading cause of death in the United States with 48 % of these deaths being attributed to excessive alcohol consumption. ALD includes a spectrum of disorders from simple steatosis to steatohepatitis, fibrosis, and hepatocellular carcinoma. Several mechanisms play a critical role in the pathogenesis of ALD. These include ethanol-induced oxidative stress and depletion of glutathione, pathological methionine metabolism, increased gut permeability and release of endotoxins into the portal blood, recruitment and activation of inflammatory cells including bone marrow-derived and liver resident macrophages (Kupffer cells). Chronic alcohol consumption results in liver damage and activation of hepatic stellate cells (HSCs) and myofibroblasts, leading to liver fibrosis. Here we discuss the current view on factors that are specific for different stages of ALD and those that regulate its progression, including cytokines and chemokines, alcohol-responsive intracellular signaling pathways, and transcriptional factors. We also review recent studies demonstrating that alcohol-mediated changes can be regulated on an epigenetic level, including microRNAs. Finally, we discuss the reversibility of liver fibrosis and inactivation of HSCs as a potential strategy for treating alcohol-induced liver damage.

Early detection of liver fibrosis in rats using 3-D ultrasound Nakagami imaging: a feasibility evaluation

We investigated the feasibility of using 3-D ultrasound Nakagami imaging to detect the early stages of liver fibrosis in rats. Fibrosis was induced in livers of rats (n = 60) by intraperitoneal injection of 0.5% dimethylnitrosamine (DMN). Group 1 was the control group, and rats in groups 2-6 received DMN injections for 1-5 weeks, respectively. Each rat was sacrificed to perform 3-D ultrasound scanning of the liver in vitro using a single-element transducer of 6.5 MHz. The 3-D raw data acquired at a sampling rate of 50 MHz were used to construct 3-D Nakagami images. The liver specimen was further used for histologic analysis with hematoxylin and eosin and Masson staining to score the degree of liver fibrosis. The results indicate that the Metavir scores of the hematoxylin and eosin-stained sections in Groups 1-4 were 0 (defined as early liver fibrosis in this study), and those in groups 5 and 6 ranged from 1 to 2 and 2 to 3, respectively. To quantify the degree of early liver fibrosis, the histologic sections with Masson stain were analyzed to calculate the number of fiber-related blue pixels. The number of blue pixels increased from (2.36 ± 0.79) × 10(4) (group 1) to (7.68 ± 2.62) × 10(4) (group 4) after DMN injections for 3 weeks, indicating that early stages of liver fibrosis were successfully induced in rats. The Nakagami parameter increased from 0.36 ± 0.02 (group 1) to 0.55 ± 0.03 (group 4), with increasing numbers of blue pixels in the Masson-stained sections (p-value < 0.05, t-test). We concluded that 3-D Nakagami imaging has potential in the early detection of liver fibrosis in rats and may serve as an image-based pathologic model to visually track fibrosis formation and growth.

Bone marrow-derived stromal cell therapy in cirrhosis: clinical evidence, cellular mechanisms, and implications for the treatment of hepatocellular carcinoma

Current treatment options for hepatocellular carcinoma (HCC) are often limited by the presence of underlying liver disease. In patients with liver cirrhosis, surgery, chemotherapy, and radiation therapy all carry a high risk of hepatic complications, ranging from ascites to fulminant liver failure. For patients receiving radiation therapy, cirrhosis dramatically reduces the already limited radiation tolerance of the liver and represents the most important clinical risk factor for the development of radiation-induced liver disease. Although improvements in conformal radiation delivery techniques have improved our ability to safely irradiate confined areas of the liver to increasingly higher doses with excellent local disease control, patients with moderate-to-severe liver cirrhosis continue to face a shortage of treatment options for HCC. In recent years, evidence has emerged supporting the use of bone marrow-derived stromal cells (BMSCs) as a promising treatment for liver cirrhosis, with several clinical studies demonstrating sustained improvement in clinical parameters of liver function after autologous BMSC infusion. Three predominant populations of BMSCs, namely hematopoietic stem cells, mesenchymal stem cells, and endothelial progenitor cells, seem to have therapeutic potential in liver injury and cirrhosis. Preclinical studies of BMSC transplantation have identified a range of mechanisms through which these cells mediate their therapeutic effects, including hepatocyte transdifferentiation and fusion, paracrine stimulation of hepatocyte proliferation, inhibition of activated hepatic stellate cells, enhancement of fibrolytic matrix metalloproteinase activity, and neovascularization of regenerating liver. By bolstering liver function in patients with underlying Child's B or C cirrhosis, autologous BMSC infusion holds great promise as a therapy to improve the safety, efficacy, and utility of surgery, chemotherapy, and hepatic radiation therapy in the treatment of HCC.