Activation-dependent contractility of rat hepatic lipocytes in culture and in vivo

The roles of orphan nuclear receptor 4 group A1 and A2 in fibrosis

Fibrosis is not a disease but rather an outcome of the pathological tissue repair response. Many myofibroblasts are activated which lead to the excessive accumulation of extracellular matrix components such as collagen and fibronectin with fibrosis. A variety of organs, including kidney, liver, lung, heart and skin, can undergo fibrosis under the stimulation of exogenous or endogenous pathogenic factors. The orphan nuclear receptor 4 group A1 (NR4A1) and nuclear receptor 4 group A2（NR4A2）are belong to the nuclear receptor subfamily and inhibit the occurrence and development of fibrosis. NR4A1 is an inhibitory factor of TGF-β signaling transduction. Overexpression of NR4A1 in fibroblasts can reduce TGF-β induced collagen deposition and fibrosis related gene expression. Here, we summarize the current research progress on the NR4A1/2 and fibrosis, providing reference for the treatment of fibrosis.

Stellate cell-specific adhesion molecule protocadherin 7 regulates sinusoidal contraction

BACKGROUND AND AIMS

Sustained inflammation and hepatocyte injury in chronic liver disease activate HSCs to transdifferentiate into fibrogenic, contractile myofibroblasts. We investigated the role of protocadherin 7 (PCDH7), a cadherin family member not previously characterized in the liver, whose expression is restricted to HSCs.

APPROACH AND RESULTS

We created a PCDH7 fl/fl mouse line, which was crossed to lecithin retinol acyltransferase-Cre mice to generate HSC-specific PCDH7 knockout animals. HSC contraction in vivo was tested in response to the HSC-selective vasoconstrictor endothelin-1 using intravital multiphoton microscopy. To establish a PCDH7 null HSC line, cells were isolated from PCDH7 fl/fl mice and infected with adenovirus-expressing Cre. Hepatic expression of PCDH7 was strictly restricted to HSCs. Knockout of PCDH7 in vivo abrogated HSC-mediated sinusoidal contraction in response to endothelin-1. In cultured HSCs, loss of PCDH7 markedly attenuated contractility within collagen gels and led to altered gene expression in pathways governing adhesion and vasoregulation. Loss of contractility in PCDH7 knockout cells was impaired Rho-GTPase signaling, as demonstrated by altered gene expression, reduced assembly of F-actin fibers, and loss of focal adhesions.

CONCLUSIONS

The stellate cell-specific cadherin, PCDH7, is a novel regulator of HSC contractility whose loss leads to cytoskeletal remodeling and sinusoidal relaxation.

KLF4 Inhibits the Activation of Human Hepatic Stellate Cell In Vitro

OBJECTIVE

Hepatic stellate cells (HSCs) play a crucial role in liver fibrosis. Early-stage liver fibrosis is reversible and intimately associated with the state of HSCs. Kruppel-like factor 4 (KLF4) plays a pivotal role in a wide array of physiological and pathological processes. This study aimed to investigate the effect of KLF4 on the proliferation, apoptosis and phenotype of quiescent HSCs METHODS: We designed a KLF4 lentiviral vector and a KLF4 siRNA lentiviral vector, to upregulate and silence KLF4 expression in human HSC LX-2 cells via transfection. Cell proliferation was assessed using the CCK-8 assay. Flow cytometry was used to detect the cell cycle distribution and apoptosis rate. Western blotting was used to determine the levels of some quiescence and activation markers of HSCs RESULTS: Overexpression of KLF4 significantly increased the levels of E-cadherin and ZO-1, which are quiescent HSC markers, while significantly decreased the levels of N-cadherin and a-SMA, known activated HSC markers. In contrast, cell proliferation and apoptosis rates were elevated in LX-2 cells in which KLF4 expression was silenced CONCLUSION: KLF4 inhibits the proliferation and activation of human LX-2 HSCs. It might be a key regulatory protein in the maintenance of HSC quiescence and may serve as a target for the inhibition of hepatic fibrosis.

Role of platelet factor 4 in arteriovenous fistula maturation failure: What do we know so far?

The rate of arteriovenous fistula (AVF) maturation failure remains unacceptably high despite continuous efforts on technique improvement and careful pre-surgery planning. In fact, half of all newly created AVFs are unable to be used for hemodialysis (HD) without a salvage procedure. While vascular stenosis in the venous limb of the access is the culprit, the underlying factors leading to vascular narrowing and AVF maturation failure are yet to be determined. We have recently demonstrated that AVF non-maturation is associated with post-operative medial fibrosis and fibrotic stenosis, and post-operative intimal hyperplasia (IH) exacerbates the situation. Multiple pathological processes and signaling pathways are underlying the stenotic remodeling of the AVF. Our group has recently indicated that a pro-inflammatory cytokine platelet factor 4 (PF4/CXCL4) is upregulated in veins that fail to mature after AVF creation. Platelet factor 4 is a fibrosis marker and can be detected in vascular stenosis tissue, suggesting that it may contribute to AVF maturation failure through stimulation of fibrosis and development of fibrotic stenosis. Here, we present an overview of the how PF4-mediated fibrosis determines AVF maturation failure.

Portal Hypertension in Nonalcoholic Fatty Liver Disease: Challenges and Paradigms

Portal hypertension in cirrhosis is defined as an increase in the portal pressure gradient (PPG) between the portal and hepatic veins and is traditionally estimated by the hepatic venous pressure gradient (HVPG), which is the difference in pressure between the free-floating and wedged positions of a balloon catheter in the hepatic vein. By convention, HVPG≥10 mmHg indicates clinically significant portal hypertension, which is associated with adverse clinical outcomes. Nonalcoholic fatty liver disease (NAFLD) is a common disorder with a heterogeneous clinical course, which includes the development of portal hypertension. There is increasing evidence that portal hypertension in NAFLD deserves special considerations. First, elevated PPG often precedes fibrosis in NAFLD, suggesting a bidirectional relationship between these pathological processes. Second, HVPG underestimates PPG in NAFLD, suggesting that portal hypertension is more prevalent in this condition than currently believed. Third, cellular mechanoresponses generated early in the pathogenesis of NAFLD provide a mechanistic explanation for the pressure-fibrosis paradigm. Finally, a better understanding of liver mechanobiology in NAFLD may aid in the development of novel pharmaceutical targets for prevention and management of this disease.

Bariatric surgery for diabetic comorbidities: A focus on hepatic, cardiac and renal fibrosis

Continuously rising trends in diabetes render this disease spectrum an epidemic proportion worldwide. As the disease progresses, the pathological effects of diabetes may impair the normal function of several vital organs, eventually leading to increase the risk of other diabetic comorbidities with advanced fibrosis such as non-alcoholic fatty liver disease, diabetic cardiomyopathy, and diabetic kidney disease. Currently, lifestyle changes and drug therapies of hypoglycemic and lipid-lowering are effective in improving multi-organ function, but therapeutic efficacy is difficult to maintain due to poor compliance and drug reactions. Bariatric surgery, including sleeve gastrectomy and Roux-en-Y gastric bypass surgery, has shown better results in terms of prognosis for diabetes through long-term follow-up. Moreover, bariatric surgery has significant long-term benefits on the function of the heart, liver, kidneys, and other organs through mechanisms associated with reversal of tissue fibrosis. The aim of this review is to describe the impact of type 2 diabetes mellitus on hepatic, cardiac and renal fibrosis and to summarize the potential mechanisms by which bariatric surgery improves multiple organ function, particularly reversal of fibrosis.

Quantitative Assessment of Liver Impairment in Chronic Viral Hepatitis with [99mTc]Tc-Mebrofenin: A Noninvasive Attempt to Stage Viral Hepatitis-Associated Liver Fibrosis

Background and objectives—Chronic viral hepatitis B and C infections are one of the leading causes of chronic liver impairment, resulting in liver fibrosis and liver cirrhosis. An early diagnosis with accurate liver fibrosis staging leads to a proper diagnosis, thus tailoring correct treatment. Both invasive and noninvasive techniques are used in the diagnosis and staging of chronic liver impairment. Those techniques include liver biopsy, multiple serological markers (as either single tests or combined panels), and imaging examinations, such as ultrasound or magnetic resonance elastography. Nuclear medicine probes may also be employed in staging liver fibrosis, although the literature scarcely reports this. The purpose of our study was to investigate whether a dynamic liver scintigraphy with [^99mTc]Tc-mebrofenin has any value in staging or grading chronic liver damage. Materials and Methods—We prospectively enrolled patients with chronic viral hepatitis B and C infection referred for liver biopsy. All patient underwent dynamic liver scintigraphy with 99mTc-mebrofenin prior to liver biopsy. Dynamic liver scintigraphy was performed immediately after intravenous tracer injection for 30 min scanning time. Multiple scintigraphy parameters were calculated (whole liver lobe and focal area time to peak (TTP), 30 min to peak ratio (30/peak), whole lobe and focal area slope index in 350 s (slope_350). Liver biopsy took place shortly after imaging. Results—We found that many dynamic scintigraphic parameters are positively or negatively associated with different stages of liver fibrosis. The main parameters that showed most value are the ratio between 30 min and the peak of the dynamic curve (30/peak_dex (ratio)), and liver clearance corrected for body surface area and liver area (LCL_m²_dm² (%/min/m²/dm²)). Conclusions—Our present study proves that conducting dynamic liver scintigraphies with [^99mTc]Tc-mebrofenin has potential value in staging liver fibrosis. The benefits of this method, including whole liver imaging and direct imaging of the liver function, provide an advantage over presently used quantitative imaging modalities.

Hepatitis C virus treatment with direct-acting antivirals induces rapid changes in the hepatic proteome

Treatment of chronic hepatitis C virus with direct-acting antivirals usually eradicates infection, but liver fibrosis does not resolve concurrently. In patients who develop cirrhosis prior to hepatitis C virus treatment, hepatic decompensation and hepatocellular carcinoma can still occur after viral elimination due to residual fibrosis. We hypothesized the liver proteome would exhibit meaningful changes in inflammatory and fibrinogenic pathways change upon hepatitis C virus eradication, which could impact subsequent fibrosis regression. We analysed the liver proteome and phosphoproteome of paired liver biopsies obtained from 8 hepatitis C virus-infected patients before or immediately after treatment with direct-acting antivirals. Proteins in interferon signalling and antiviral pathways decreased concurrent with hepatitis C virus treatment, consistent with prior transcriptomic analyses. Expression of extracellular matrix proteins associated with liver fibrosis did not change with treatment, but the phosphorylation pattern of proteins present within signalling pathways implicated in hepatic fibrinogenesis, including the ERK1/2 pathway, was altered concurrent with hepatitis C virus treatment. Hepatitis C virus treatment leads to reduced expression of hepatic proteins involved in interferon and antiviral signalling. Additionally, changes in fibrosis signalling pathways are detectable before alteration in extracellular matrix proteins, identifying a putative chronology for the dynamic processes involved in fibrosis reversal.

Targeting myosin 1c inhibits murine hepatic fibrogenesis

Myosin 1c (Myo1c) is an unconventional myosin that modulates signaling pathways involved in tissue injury and repair. In this study, we observed that Myo1c expression is significantly upregulated in human chronic liver disease such as nonalcoholic steatohepatitis (NASH) and in animal models of liver fibrosis. High throughput data from the GEO-database identified similar Myo1c upregulation in mice and human liver fibrosis. Notably, transforming growth factor-β1 (TGF-β1) stimulation to hepatic stellate cells (HSCs), the liver pericyte and key cell type responsible for the deposition of extracellular matrix, upregulates Myo1c expression, whereas genetic depletion or pharmacological inhibition of Myo1c blunted TGF-β-induced fibrogenic responses, resulting in repression of α-smooth muscle actin (α-SMA) and collagen type I α 1 chain (Col1α1) mRNA. Myo1c deletion also decreased fibrogenic processes such as cell proliferation, wound healing response, and contractility when compared with vehicle-treated HSCs. Importantly, phosphorylation of mothers against decapentaplegic homolog 2 (SMAD2) and mothers against decapentaplegic homolog 3 (SMAD3) were significantly blunted upon Myo1c inhibition in GRX cells as well as Myo1c knockout (Myo1c-KO) mouse embryonic fibroblasts (MEFs) upon TGF-β stimulation. Using the genetic Myo1c-KO mice, we confirmed that Myo1c is critical for fibrogenesis, as Myo1c-KO mice were resistant to carbon tetrachloride (CCl4)-induced liver fibrosis. Histological and immunostaining analysis of liver sections showed that deposition of collagen fibers and α-SMA expression were significantly reduced in Myo1c-KO mice upon liver injury. Collectively, these results demonstrate that Myo1c mediates hepatic fibrogenesis by modulating TGF-β signaling and suggest that inhibiting this process may have clinical application in treating liver fibrosis.NEW & NOTEWORTHY The incidences of liver fibrosis are growing at a rapid pace and have become one of the leading causes of end-stage liver disease. Although TGF-β1 is known to play a prominent role in transforming cells to produce excessive extracellular matrix that lead to hepatic fibrosis, the therapies targeting TGF-β1 have achieved very limited clinical impact. This study highlights motor protein myosin-1c-mediated mechanisms that serve as novel regulators of TGF-β1 signaling and fibrosis.

Synergic effect of atorvastatin and ambrisentan on sinusoidal and hemodynamic alterations in a rat model of NASH

In non-alcoholic steatohepatitis (NASH), decreased nitric oxide and increased endothelin-1 (ET-1, also known as EDN1) released by sinusoidal endothelial cells (LSEC) induce hepatic stellate cell (HSC) contraction and contribute to portal hypertension (PH). Statins improve LSEC function, and ambrisentan is a selective endothelin-receptor-A antagonist. We aimed to analyse the combined effects of atorvastatin and ambrisentan on liver histopathology and hemodynamics, together with assessing the underlying mechanism in a rat NASH model. Diet-induced NASH rats were treated with atorvastatin (10 mg/kg/day), ambrisentan (30 mg/kg/day or 2 mg/kg/day) or a combination of both for 2 weeks. Hemodynamic parameters were registered and liver histology and serum biochemical determinations analysed. Expression of proteins were studied by immunoblotting. Conditioned media experiments were performed with LSEC. HSCs were characterized by RT-PCR, and a collagen lattice contraction assay was performed. Atorvastatin and ambrisentan act synergistically in combination to completely normalize liver hemodynamics and reverse histological NASH by 75%. Atorvastatin reversed the sinusoidal contractile phenotype, thus improving endothelial function, whereas ambrisentan prevented the contractile response in HSCs by blocking ET-1 response. Additionally, ambrisentan also increased eNOS (also known as Nos3) phosphorylation levels in LSEC, via facilitating the stimulation of endothelin-receptor-B in these cells. Furthermore, the serum alanine aminotransferase of the combined treatment group decreased to normal levels, and this group exhibited a restoration of the HSC quiescent phenotype. The combination of atorvastatin and ambrisentan remarkably improves liver histology and PH in a diet-induced NASH model. By recovering LSEC function, together with inhibiting the activation and contraction of HSC, this combined treatment may be an effective treatment for NASH patients.

Summary: Combining atorvastatin with ambrisentan is safe and effective in reducing intrahepatic resistance and portal hypertension in an experimental model of NASH. This liver histology amelioration highlights a promising therapeutic strategy.

Fibrosis Regression After Eradication of Hepatitis C Virus: From Bench to Bedside

Hepatitis C virus (HCV) infection and its complications have been the major cause of cirrhosis and its complications for several decades in the Western world. Until recently, treatment for HCV with interferon-based regimens was associated with moderate success but was difficult to tolerate. More recently, however, an arsenal of novel and highly effective direct-acting antiviral (DAA) drugs has transformed the landscape by curing HCV in a broad range of patients, including those with established advanced fibrosis, cirrhosis, comorbidities, and even those with complications of cirrhosis. Fibrosis is a dynamic process comprising both extracellular matrix deposition, as well as its degradation. With almost universal sustained virologic response (SVR) (ie, elimination of HCV), it is timely to explore whether HCV eradication can reverse fibrosis and cirrhosis. Indeed, fibrosis in several types of liver disease is reversible, including HCV. However, we do not know with certainty in whom fibrosis regression can be expected after HCV elimination, how quickly it occurs, and whether antifibrotic therapies will be indicated in those with persistent cirrhosis. This review summarizes the evidence for reversibility of fibrosis and cirrhosis after HCV eradication, its impact on clinical outcomes, and therapeutic prospects for directly promoting fibrosis regression in patients whose fibrosis persists after SVR.

The Plasticity of Nanofibrous Matrix Regulates Fibroblast Activation in Fibrosis

Natural extracellular matrix (ECM) mostly has a fibrous structure that supports and mechanically interacts with local residing cells to guide their behaviors. The effect of ECM elasticity on cell behaviors has been extensively investigated, while less attention has been paid to the effect of matrix fiber-network plasticity at microscale, although plastic remodeling of fibrous matrix is a common phenomenon in fibrosis. Here, a significant decrease is found in plasticity of native fibrotic tissues, which is associated with an increase in matrix crosslinking. To explore the role of plasticity in fibrosis development, a set of 3D collagen nanofibrous matrix with constant modulus but tunable plasticity is constructed by adjusting the crosslinking degree. Using plasticity-controlled 3D culture models, it is demonstrated that the decrease of matrix plasticity promotes fibroblast activation and spreading. Further, a coarse-grained molecular dynamic model is developed to simulate the cell-matrix interaction at microscale. Combining with molecular experiments, it is revealed that the enhanced fibroblast activation is mediated through cytoskeletal tension and nuclear translocation of Yes-associated protein. Taken together, the results clarify the effects of crosslinking-induced plasticity changes of nanofibrous matrix on the development of fibrotic diseases and highlight plasticity as an important mechanical cue in understanding cell-matrix interactions.

Induced hepatic stellate cell integrin, α8β1, enhances cellular contractility and TGFβ activity in liver fibrosis

No effective therapy exists for fatal fibrosis. New therapeutic targets are needed for hepatic fibrosis because the incidence keeps increasing. The activation and differentiation of fibroblasts into myofibroblasts that causes excessive matrix deposition is central to fibrosis. Here, we investigated whether (and which) integrin receptors for matrix proteins activate hepatic stellate cells (HSCs). First, integrin α‐subunits were investigated systematically for their expression over the course of HSC activation and their distribution on fibroblasts and other systemic primary cells. The most upregulated in plate culture‐activated HSCs and specifically expressed across fibroblast linages was the α8 subunit. An anti‐α8 neutralizing mAb was evaluated in three different murine fibrosis models: for cytotoxic (CCl₄ treatment), non‐alcoholic steatohepatitis‐associated and cholestatic fibrosis. In all models, pathology and fibrosis markers (hydroxyproline and α‐smooth muscle actin) were improved following the mAb injection. We also CCl₄‐treated mice with inducible Itga8−/−; these mice were protected from increased hydroxyproline levels. Furthermore, ITGA8 was upregulated in specimens from 90 patients with liver fibrosis, indicating the relevance of our findings to liver fibrosis in people. Mechanistically, inhibition or ligand engagement of HSC α8 suppressed and enhanced myofibroblast differentiation, respectively, and HSC/fibroblast α8 activated latent TGFβ. Finally, integrin α8β1 potentially fulfils the growing need for anti‐fibrotic drugs and is an integrin not to be ignored. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

sEVs from tonsil-derived mesenchymal stromal cells alleviate activation of hepatic stellate cells and liver fibrosis through miR-486-5p

Mesenchymal stromal cells (MSCs) are considered as a promising therapeutic tool for liver fibrosis, a main feature of chronic liver disease. Because small extracellular vesicles (sEVs) harboring a variety of proteins and RNAs are known to have similar functions with their derived cells, MSC-derived sEVs carry out the regenerative capacities of MSCs. Human tonsil-derived MSCs (T-MSCs) are reported as a novel source of MSCs, but their effects on liver fibrosis remain unclear. In the present study, we investigated the effects of T-MSC-derived sEVs on liver fibrosis. The expression of profibrotic genes decreased in human primary hepatic stellate cells (pHSCs) co-cultured with T-MSCs. Treatment of T-MSC-sEVs inactivated human and mouse pHSCs. Administration of T-MSC-sEVs ameliorated hepatic injuries and fibrosis in chronically damaged liver induced by carbon tetrachloride (CCl₄). miR-486-5p highly enriched in T-MSC-sEVs targeting the hedgehog receptor, smoothened (Smo), was upregulated, whereas Smo and Gli2, the hedgehog target gene, were downregulated in pHSCs and liver tissues treated with T-MSC-sEVs or miR-486-5p mimic, indicating that sEV-miR-486 inactivates HSCs by suppressing hedgehog signaling. Our results showed that T-MSCs attenuate HSC activation and liver fibrosis by delivering sEVs, and miR-486 in the sEVs inactivates hedgehog signaling, suggesting that T-MSCs and their sEVs are novel anti-fibrotic therapeutics for treating chronic liver disease.

The G Protein-Coupled Bile Acid Receptor TGR5 (Gpbar1) Modulates Endothelin-1 Signaling in Liver

TGR5 (Gpbar1) is a G protein-coupled receptor responsive to bile acids (BAs), which is expressed in different non-parenchymal cells of the liver, including biliary epithelial cells, liver-resident macrophages, sinusoidal endothelial cells (LSECs), and activated hepatic stellate cells (HSCs). Mice with targeted deletion of TGR5 are more susceptible towards cholestatic liver injury induced by cholic acid-feeding and bile duct ligation, resulting in a reduced proliferative response and increased liver injury. Conjugated lithocholic acid (LCA) represents the most potent TGR5 BA ligand and LCA-feeding has been used as a model to rapidly induce severe cholestatic liver injury in mice. Thus, TGR5 knockout (KO) mice and wildtype (WT) littermates were fed a diet supplemented with 1% LCA for 84 h. Liver injury and gene expression changes induced by the LCA diet revealed an enrichment of pathways associated with inflammation, proliferation, and matrix remodeling. Knockout of TGR5 in mice caused upregulation of endothelin-1 (ET-1) expression in the livers. Analysis of TGR5-dependent ET-1 signaling in isolated LSECs and HSCs demonstrated that TGR5 activation reduces ET-1 expression and secretion from LSECs and triggers internalization of the ET-1 receptor in HSCs, dampening ET-1 responsiveness. Thus, we identified two independent mechanisms by which TGR5 inhibits ET-1 signaling and modulates portal pressure.

[Real-time measurement of cell contractile force during activation of human hepatic stellate cell line LX-2]

The contractile force of hepatic stellate cells plays a very important role in liver damage, hepatitis and fibrosis. In this paper, a method based on polydimethylsiloxane (PDMS) thin micropillar arrays is proposed to measure the contractile force of human hepatic stellate cell line LX-2, which enables dynamic measurement of the subcellular distribution of force magnitude and direction. First, thin micropillar arrays on glass bottom dish were fabricated using two-step casting process in order to meet the working distance requirement of 100× objective lens. After hydrophilic treatment and protein imprint, cells were seeded on the micropillar arrays. LX-2 cells, which were quiesced by growth in serum-free medium, were activated by adding fetal bovine serum (FBS). The deflections of the micropillars were achieved by image processing technique, and then the contractile force of cells exerted on the micropillars was calculated according to mechanical simulation results, and was analyzed under both quiescent and activated conditions. The experimental results show that the average traction force of quiescent cells is about 20 nN, while the contractile force of activated cells increased to 110 nN upon adding FBS. This method can quantify the contractile force of LX-2 cell on subcellular scale in both quiescent and activated states, which may benefit pathology study and drug screen for chronic liver diseases resulted from liver fibrosis.

Stellate Cells in Tissue Repair, Inflammation, and Cancer

Stellate cells are resident lipid-storing cells of the pancreas and liver that transdifferentiate to a myofibroblastic state in the context of tissue injury. Beyond having roles in tissue homeostasis, stellate cells are increasingly implicated in pathological fibrogenic and inflammatory programs that contribute to tissue fibrosis and that constitute a growth-permissive tumor microenvironment. Although the capacity of stellate cells for extracellular matrix production and remodeling has long been appreciated, recent research efforts have demonstrated diverse roles for stellate cells in regulation of epithelial cell fate, immune modulation, and tissue health. Our present understanding of stellate cell biology in health and disease is discussed here, as are emerging means to target these multifaceted cells for therapeutic benefit.

Non-neoplastic Portal Vein Thrombosis in HCV Cirrhosis Patients: Is it an Immuno-Inflammatory Disorder?

BACKGROUND AND AIMS

Portal vein thrombosis (PVT) is a critical complication in cirrhotic patients. We explored the role of the activated factor VII-antithrombin (FVIIa-AT) complex and enhanced monocytic tissue factor (TF) expression in the development and prediction of non-neoplastic PVT in cirrhotic patients.

MATERIAL AND METHODS

A total of 30 HCV-cirrhosis patients were included in our study. They were compared to 35 cirrhotic patients without PVT, 15 non-cirrhotic patients with PVT, and 15 healthy controls. The plasma level of the FVIIa-AT complexes was analyzed by ELISA. MIF CD142, CD86, and HLA-DR on monocytes (CD14) were determined by flow cytometry.

RESULTS

Compared with cirrhotic patients without PVT, cirrhotic patients with PVT had comparable plasma values of FVIIa, AT, and the FVIIa-AT complex. However, they had significantly lower values compared to non-cirrhotic patients with PVT and healthy controls. Cirrhotic patients with PVT had increased monocytic TF expression (MIF CD142) compared to non-PVT cirrhotic patients and healthy controls [86.5 (93.5) vs. 18 (32.0) and 11.0 (6.0), respectively; p < 0.001 for each]. However, cirrhosis PVT could not be distinguished from non-cirrhosis PVT. The area under the ROC curve of MIF CD142 was 0.759 (0.641- 0.876; p = 0.000) at an optimal cut-off value of 45, which yielded a sensitivity of 60% and a specificity of 77.1%, as well as a PPV and NPV of 69.2% for each.

CONCLUSION

Enhanced expression of monocytic TF may have a role in the development and prediction of non-neoplastic PVT in HCV-cirrhosis patients. Large multicenter studies are necessary to validate our results.

Biology of portal hypertension

Portal hypertension develops as a result of increased intrahepatic vascular resistance often caused by chronic liver disease that leads to structural distortion by fibrosis, microvascular thrombosis, dysfunction of liver sinusoidal endothelial cells (LSECs), and hepatic stellate cell (HSC) activation. While the basic mechanisms of LSEC and HSC dysregulation have been extensively studied, the role of microvascular thrombosis and platelet function in the pathogenesis of portal hypertension remains to be clearly characterized. As a secondary event, portal hypertension results in splanchnic and systemic arterial vasodilation, leading to the development of a hyperdynamic circulatory syndrome and subsequently to clinically devastating complications including gastroesophageal varices and variceal hemorrhage, hepatic encephalopathy from the formation of portosystemic shunts, ascites, and renal failure due to the hepatorenal syndrome. This review article discusses: (1) mechanisms of sinusoidal portal hypertension, focusing on HSC and LSEC biology, pathological angiogenesis, and the role of microvascular thrombosis and platelets, (2) the mesenteric vasculature in portal hypertension, and (3) future directions for vascular biology research in portal hypertension.

Serial Analysis of Tracheal Restenosis After 3D-Printed Scaffold Implantation: Recruited Inflammatory Cells and Associated Tissue Changes

Tracheal restenosis is a major obstacle to successful tracheal replacement, and remains the greatest challenge in tracheal regeneration. However, there have been no detailed investigations of restenosis. The present study was performed to analyze the serial changes in recruited inflammatory cells and associated histological changes after tracheal scaffold implantation. Asymmetrically porous scaffolds, which successfully prevented tracheal stenosis in a partial trachea defect model, designed with a tubular shape by electrospinning and reinforced by 3D-printing to reconstruct 2-cm circumferential tracheal defect. Serial rigid bronchoscopy, micro-computed tomography, and histology [H&E, Masson's Trichrome, IHC against α-smooth muscle actin (α-SMA)] were performed 1, 4, and 8 weeks after transplantation. Progressive stenosis developed especially at the site of anastomosis. Neutrophils were the main inflammatory cells recruited in the early stage, while macrophage infiltration increased with time. Recruitment of fibroblasts peaked at 4 weeks and deposition of α-SMA increased from 4 weeks and was maintained through 8 weeks. During the first 8 weeks post-transplantation, neutrophils and macrophages played significant roles in restenosis of the trachea. Antagonists to these would be ideal targets to reduce restenosis and thus play a pivotal role in successful tracheal regeneration.

Bovine milk-derived α-lactalbumin prevents hepatic fibrosis induced by dimethylnitrosamine via nitric oxide pathway in rats

The present study was designed to evaluate the hepatoprotective potential of α-lactalbumin (αLA) against dimethylnitrosamine (DMN)-induced toxic insults in the rat liver. The liver damage was induced in rats by the repeated administration of DMN (10 mg/kg, i.p.) on three consecutive days per week for three weeks. The rats were maintained on either a standard AIN-93 M or αLA-enriched diet starting one week before the DMN injection until the termination of the experiment. The DMN treatment produced a progressive increase in the plasma markers (aspartate aminotransferase, alanine aminotransferase, total bililbin, hyarulonic acid, and matrix metalloproteinase-2) in 28 days after the first DMN injection. Dietary treatment with αLA significantly reduced the DMN-induced damage toward normalcy. N^Ｇ-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, significantly attenuated the hepatoprotective effect of αLA. These findings show that αLA has a marked suppressive effect on hepetic fibrosis through a nitric oxide-mediated mechanism.

Muscle-relevant genes marked by stable H3K4me2/3 profiles and enriched MyoD binding during myogenic differentiation

Post-translational modifications of histones play a key role in the regulation of gene expression during development and differentiation. Numerous studies have shown the dynamics of combinatorial regulation by transcription factors and histone modifications, in the sense that different combinations lead to distinct expression outcomes. Here, we investigated gene regulation by stable enrichment patterns of histone marks H3K4me2 and H3K4me3 in combination with the chromatin binding of the muscle tissue-specific transcription factor MyoD during myogenic differentiation of C2C12 cells. Using k-means clustering, we found that specific combinations of H3K4me2/3 profiles over and towards the gene body impact on gene expression and marks a subset of genes important for muscle development and differentiation. By further analysis, we found that the muscle key regulator MyoD was significantly enriched on this subset of genes and played a repressive role during myogenic differentiation. Among these genes, we identified the pluripotency gene Patz1, which is repressed during myogenic differentiation through direct binding of MyoD to promoter elements. These results point to the importance of integrating histone modifications and MyoD chromatin binding for coordinated gene activation and repression during myogenic differentiation.

Fibroblasts in Hypoxic Conditions Mimic Laryngotracheal Stenosis

Objective To elucidate the role of hypoxia and inflammatory pathways in the pathogenesis of iatrogenic laryngotracheal stenosis (iLTS). Study Design (1) Examination of mucosal surface gene expression in human iLTS. (2) In vitro comparison of normal and scar laryngotracheal fibroblasts under normoxic and hypoxic conditions. Setting Tertiary care hospital in a research university (2012-2016). Subjects and Methods Brush biopsies were obtained from normal laryngotracheal tissue and scar in iLTS patients; gene expression was compared. Fibroblasts were isolated from normal and scarred trachea and grown in vitro in either a 1% O₂ or normoxic environment. Cell growth and gene and protein expression were compared. Statistical analysis utilized a multilevel mixed effects model. Results Expression of IL-6 (fold change = 2.8, P < .01), myofibroblast marker αSMA (fold change = 3.0, P = .01), and MMP13 (fold change = 5.4, P = .02) was significantly increased in scar biopsy samples as compared to normal. Under hypoxic conditions in vitro, normal laryngotracheal fibroblasts proliferated significantly faster (n = 8, P < .01 each day). Expression of IL-6 (n = 8, fold change = 2.6, P < .01) increased significantly after 12 hours under hypoxia. Expression of αSMA (n = 8, fold change= 2.0, P = .03), COL1 (n = 8, fold change = 1.1, P = .03), and MMP13 (n = 8, fold change = 1.6, P = .01) increased significantly after 48 hours under hypoxia. Scar fibroblasts also proliferated significantly faster under hypoxic conditions but did not display the same expression profile. Conclusion Human iLTS scar has a myofibroblast phenotype. Under hypoxic conditions in vitro, normal laryngotracheal fibroblasts can transdifferentiate into a similar phenotype. These changes may be mediated by IL-6, a fibrosis-related cytokine.

The Molecular Basis of Portal Hypertension

Cirrhosis leads to portal hypertension and vascular abnormalities in multiple vascular beds. There is intense vasoconstriction in the liver and the kidneys, but also vasodilation in the other vascular beds, including the periphery, lungs, brain, and mesentery. The derangement in each of these beds leads to specific clinical disease. The vasoconstrictive phenotype in the liver ultimately leads to clinical portal hypertension, and is caused by an imbalance of vasoconstrictive and vasorelaxing molecules, which will be the focus of this review.

Relationship between chronic liver disease and liver hypoxia

The liver is an organ that metabolizes various substances very vigorously. During hepatic metabolism a large amount of oxygen needs to be provided for the liver, so the liver is vulnerable to hypoxia. Many chronic liver diseases are accompanied by liver cell hypoxia. In turn, liver cell hypoxia not only worsens liver tissue damage on the basis of primary liver lesion and inhibits hepatocellular regeneration but also accelerates liver fibrosis, cirrhosis, and even primary liver carcinoma. With chronic liver diseases exacerbating, liver hypoxia becomes more and more serious, and vice versa. This is an important mechanism by which chronic liver diseases gradually get worse and worse. As the most important hypoxia signal transduction factor in vivo, hypoxia inducible factor-1α (HIF-1α) plays an indispensable key role in the process of adaptive responses of the liver to hypoxia stimulus. Some progress in therapy for chronic liver diseases has been being made as the relationship between chronic liver diseases and liver hypoxia has been revealed and understood more deeply, especially by regulating and controlling HIF-1α and its downstream target to treat liver fibrosis. In addition, it has been found that some medicines have positive therapeutic effects on patients with chronic liver diseases through improving liver microcirculation and ameliorating liver hypoxia. However, the very complicated mechanism of interaction between chronic liver diseases and liver hypoxia, which involves a number of complex signal pathways, has not been completely elucidated, and therefore more basic and clinical studies need to be carried out for the clarification of their interaction.

Murine junctional adhesion molecules JAM-B and JAM-C mediate endothelial and stellate cell interactions during hepatic fibrosis

Classical junctional adhesion molecules JAM-A, JAM-B and JAM-C influence vascular permeability, cell polarity as well as leukocyte recruitment and immigration into inflamed tissue. As the vasculature becomes remodelled in chronically injured, fibrotic livers we aimed to determine distribution and role of junctional adhesion molecules during this pathological process. Therefore, livers of naïve or carbon tetrachloride-treated mice were analyzed by immunohistochemistry to localize all 3 classical junctional adhesion molecules. Hepatic stellate cells and endothelial cells were isolated and subjected to immunocytochemistry and flow cytometry to determine localization and functionality of JAM-B and JAM-C. Cells were further used to perform contractility and migration assays and to study endothelial tubulogenesis and pericytic coverage by hepatic stellate cells. We found that in healthy tissue, JAM-A was ubiquitously expressed whereas JAM-B and JAM-C were restricted to the vasculature. During fibrosis, JAM-B and JAM-C levels increased in endothelial cells and JAM-C was de novo generated in myofibroblastic hepatic stellate cells. Soluble JAM-C blocked contractility but increased motility in hepatic stellate cells. Furthermore, soluble JAM-C reduced endothelial tubulogenesis and endothelial cell/stellate cell interaction. Thus, during liver fibrogenesis, JAM-B and JAM-C expression increase on the vascular endothelium. More importantly, JAM-C appears on myofibroblastic hepatic stellate cells linking them as pericytes to JAM-B positive endothelial cells. This JAM-B/JAM-C mediated interaction between endothelial cells and stellate cells stabilizes vessel walls and may control the sinusoidal diameter. Increased hepatic stellate cell contraction mediated by JAM-C/JAM-C interaction may cause intrahepatic vasoconstriction, which is a major complication in liver cirrhosis.

Ammonia produces pathological changes in human hepatic stellate cells and is a target for therapy of portal hypertension

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are vital to hepatocellular function and the liver response to injury. They share a phenotypic homology with astrocytes that are central in the pathogenesis of hepatic encephalopathy, a condition in which hyperammonemia plays a pathogenic role. This study tested the hypothesis that ammonia modulates human HSC activation in vitro and in vivo, and evaluated whether ammonia lowering, by using l-ornithine phenylacetate (OP), modifies HSC activation in vivo and reduces portal pressure in a bile duct ligation (BDL) model.

METHODS

Primary human HSCs were isolated and cultured. Proliferation (BrdU), metabolic activity (MTS), morphology (transmission electron, light and immunofluorescence microscopy), HSC activation markers, ability to contract, changes in oxidative status (ROS) and endoplasmic reticulum (ER) were evaluated to identify effects of ammonia challenge (50 μM, 100 μM, 300 μM) over 24-72 h. Changes in plasma ammonia levels, markers of HSC activation, portal pressure and hepatic eNOS activity were quantified in hyperammonemic BDL animals, and after OP treatment.

RESULTS

Pathophysiological ammonia concentrations caused significant and reversible changes in cell proliferation, metabolic activity and activation markers of hHSC in vitro. Ammonia also induced significant alterations in cellular morphology, characterised by cytoplasmic vacuolisation, ER enlargement, ROS production, hHSC contraction and changes in pro-inflammatory gene expression together with HSC-related activation markers such as α-SMA, myosin IIa, IIb, and PDGF-Rβ. Treatment with OP significantly reduced plasma ammonia (BDL 199.1 μmol/L±43.65 vs. BDL+OP 149.27 μmol/L±51.1, p<0.05) and portal pressure (BDL 14±0.6 vs. BDL+OP 11±0.3 mmHg, p<0.01), which was associated with increased eNOS activity and abrogation of HSC activation markers.

CONCLUSIONS

The results show for the first time that ammonia produces deleterious morphological and functional effects on HSCs in vitro. Targeting ammonia with the ammonia lowering drug OP reduces portal pressure and deactivates hHSC in vivo, highlighting the opportunity for evaluating ammonia lowering as a potential therapy in cirrhotic patients with portal hypertension.

Reversible Human TGF-β Signal Shifting between Tumor Suppression and Fibro-Carcinogenesis: Implications of Smad Phospho-Isoforms for Hepatic Epithelial-Mesenchymal Transitions

Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are observed during both physiological liver wound healing and the pathological fibrotic/carcinogenic (fibro-carcinogenetic) process. TGF-β and pro-inflammatory cytokine are considered to be the major factors accelerating liver fibrosis and promoting liver carcinogenesis. Smads, consisting of intermediate linker regions connecting Mad homology domains, act as the intracellular mediators of the TGF-β signal transduction pathway. As the TGF-β receptors, c-Jun N-terminal kinase and cyclin-dependent kinase, differentially phosphorylate Smad2/3, we have generated numerous antibodies against linker (L) and C-terminal (C) phosphorylation sites in Smad2/3 and identified four types of phosphorylated forms: cytostatic COOH-terminally-phosphorylated Smad3 (pSmad3C), mitogenic pSmad3L (Ser-213) signaling, fibrogenic pSmad2L (Ser-245/250/255)/C signaling and migratory pSmad2/3L (Thr-220/179)/C signaling. After acute liver injury, TGF-β upregulates pSmad3C signaling and terminates pSmad3L (Ser-213)-mediated hepatocyte proliferation. TGF-β and pro-inflammatory cytokines cooperatively enhance collagen synthesis by upregulating pSmad2L (Thr-220)/C and pSmad3L (Thr-179)/C pathways in activated hepatic stellate cells. During chronic liver injuries, hepatocytes persistently affected by TGF-β and pro-inflammatory cytokines eventually become pre-neoplastic hepatocytes. Both myofibroblasts and pre-neoplastic hepatocyte exhibit the same carcinogenic (mitogenic) pSmad3L (Ser-213) and fibrogenic pSmad2L (Ser-245/250/255)/C signaling, with acquisition of fibro-carcinogenic properties and increasing risk of hepatocellular carcinoma (HCC). Firstly, we review phospho-Smad-isoform signalings in epithelial and mesenchymal cells in physiological and pathological conditions and then consider Smad linker phosphorylation as a potential target for pathological EMT during human fibro-carcinogenesis, because human Smad phospho-isoform signals can reverse from fibro-carcinogenesis to tumor-suppression in a process of MET after therapy.

Discovery of cytoglobin and its roles in physiology and pathology of hepatic stellate cells

Cytoglobin (CYGB), a new member of the globin family, was discovered in 2001 as a protein associated with stellate cell activation (stellate cell activation-associated protein [STAP]). Knowledge of CYGB, including its crystal, gene, and protein structures as well as its physiological and pathological importance, has increased progressively. We investigated the roles of oxygen (O2)-binding CYGB as STAP in hepatic stellate cells (HSCs) to understand the part played by this protein in their pathophysiological activities. Studies involving CYGB-gene-deleted mice have led us to suppose that CYGB functions as a regulator of O2 homeostasis; when O2 homeostasis is disrupted, HSCs are activated and play a key role(s) in hepatic fibrogenesis. In this review, we discuss the rationale for this hypothesis.

Macrophages During the Fibrotic Process: M2 as Friend and Foe

Macrophages play essential activities in homeostasis maintenance during different organism’s conditions. They may be polarized according to various stimuli, which subsequently subdivide them into distinct populations. Macrophages with inflammatory activity function mainly during pathological context, while those with regulatory activity control inflammation and also remodel the repairing process. Here, we propose to review and to present a concise discuss on the role of different components during tissue repair, including those related to innate immune receptors and metabolic modifications. The scar formation is directly related to the degree of inflammation, but also with the appearance of M2 macrophages. In spite of greater numbers of macrophages in the fibrotic phase, regulatory macrophages present some characteristics related to promotion of fibrosis but also with the control of scar formation. These regulatory macrophages present an oxidative metabolism, and differ from the initial inflammatory macrophages, which in turn, present a glycolytic characteristic, which allow regulatory ones to optimize the oxygen consumption and minimizing their ROS production. We will emphasize the difference in macrophage subpopulations and the origin and plasticity of these cells during fibrotic processes.

Evolution in the understanding of the pathophysiological basis of portal hypertension: How changes in paradigm are leading to successful new treatments

Among the common complication of cirrhosis portal hypertension witnessed a major improvement of prognosis during the past decades. Principally due to the introduction of rational treatments based on new pathophysiological paradigms (concepts of thought) developed in the 1980s. The best example being the use of non-selective beta-blockers and of vasopressin analogs, somatostatin, and its analogs. Further refinement in the knowledge of the molecular mechanisms involved in the regulation of both the splanchnic and hepatic circulation has led to the emergence of new treatments, which are based on evidence that show not only structural but also vasoactive components increase the hepatic vascular resistance, as well as of angiogenesis. This knowledge and future improvements will most likely result in more effective treatment of portal hypertension and effective prevention of its complications in early stages.

Vascular pathobiology in chronic liver disease and cirrhosis - current status and future directions

Chronic liver disease is associated with remarkable alterations in the intra- and extrahepatic vasculature. Because of these changes, the fields of liver vasculature and portal hypertension have recently become closely integrated within the broader vascular biology discipline. As developments in vascular biology have evolved, a deeper understanding of vascular processes has led to a better understanding of the mechanisms of the dynamic vascular changes associated with portal hypertension and chronic liver disease. In this context, hepatic vascular cells, such as sinusoidal endothelial cells and pericyte-like hepatic stellate cells, are closely associated with one another, where they have paracrine and autocrine effects on each other and themselves. These cells play important roles in the pathogenesis of liver fibrosis/cirrhosis and portal hypertension. Further, a variety of signaling pathways have recently come to light. These include growth factor pathways involving cytokines such as transforming growth factor β, platelet derived growth factor, and others as well as a variety of vasoactive peptides and other molecules. An early and consistent feature of liver injury is the development of an increase in intra-hepatic resistance; this is associated with changes in hepatic vascular cells and their signaling pathway that cause portal hypertension. A critical concept is that this process aggregates signals to the extrahepatic circulation, causing derangement in this system's cells and signaling pathways, which ultimately leads to the collateral vessel formation and arterial vasodilation in the splanchnic and systemic circulation, which by virtue of the hydraulic derivation of Ohm's law (pressure = resistance × flow), worsens portal hypertension. This review provides a detailed review of the current status and future direction of the basic biology of portal hypertension with a focus on the physiology, pathophysiology, and signaling of cells within the liver, as well as those in the mesenteric vascular circulation. Translational implications of recent research and the future directions that it points to are also highlighted.

TGF-β/Smad signaling during hepatic fibro-carcinogenesis (review)

After hepatitis virus infection, plasma transforming growth factor (TGF)-β increases in either the acute or chronic inflammatory microenvironment. Although TGF-β is upregulated in patients with hepatocellular carcinoma, it is one of the most potent growth inhibitors for hepatocytes. This cytokine also upregulates extracellular matrix (ECM) production of hepatic stellate cells. Therefore, TGF-β is considered to be the major factor regulating liver carcinogenesis and accelerating liver fibrosis. Smad2 and Smad3 act as the intracellular mediators of TGF-β signal transduction pathway. We have generated numerous antibodies against individual phosphorylation sites in Smad2/3, and identified 3 types of phosphorylated forms (phospho-isoforms): COOH-terminally phosphorylated Smad2/3 (pSmad2C and pSmad3C), linker phosphorylated Smad2/3 (pSmad2L and pSmad3L) and dually phosphorylated Smad2/3 (pSmad2L/C and pSmad3L/C). These Smad phospho-isoforms are categorized into 3 groups: cytostatic pSmad3C signaling, mitogenic pSmad3L signaling and invasive/fibrogenic pSmad2L/C signaling. In this review, we describe differential regulation of TGF-β/Smad signaling after acute or chronic liver injuries. In addition, we consider how chronic inflammation associated with hepatitis virus infection promotes hepatic fibrosis and carcinogenesis (fibro-carcinogenesis), focusing on alteration of Smad phospho-isoform signaling. Finally, we show reversibility of Smad phospho-isoform signaling after therapy against hepatitis virus infection.

Cicletanine stimulates eNOS phosphorylation and NO production via Akt and MAP kinase/Erk signaling in sinusoidal endothelial cells

The function of the endothelial isoform of nitric oxide synthase (eNOS) and production of nitric oxide (NO) is altered in a number of disease states. Pharmacological approaches to enhancing NO synthesis and thus perhaps endothelial function could have substantial benefits in patients. We analyzed the effect of cicletanine, a synthetic pyridine with potent vasodilatory characteristics, on eNOS function and NO production in normal (liver) and injured rat sinusoidal endothelial cells, and we studied the effect of cicletanine-induced NO on stellate cell contraction and portal pressure in an in vivo model of liver injury. Sinusoidal endothelial cells were isolated from normal and injured rat livers. After exposure to cicletanine, eNOS phosphorylation, NO synthesis, and the signaling pathway regulating eNOS activation were measured. Cicletanine led to an increase in eNOS (Ser¹¹⁷⁷) phosphorylation, cytochrome c reductase activity, L-arginine conversion to L-citrulline, as well as NO production. The mechanism of the effect of cicletanine appeared to be via the protein kinase B (Akt) and MAP kinase/Erk signaling pathways. Additionally, cicletanine improved NO synthesis in injured sinusoidal endothelial cells. NO production induced by cicletanine in sinusoidal endothelial cells increased protein kinase G (PKG) activity as well as relaxation of stellate cells. Finally, administration of cicletanine to mice with portal hypertension induced by bile duct ligation led to reduction of portal pressure. The data indicate that cicletanine might improve eNOS activity in injured sinusoidal endothelial cells and likely activates hepatic stellate cell NO/PKG signaling. It raises the possibility that cicletanine could improve intrahepatic vascular function in portal hypertensive patients.

Current concepts on the role of nitric oxide in portal hypertension

Portal hypertension (PHT) is defined as a pathological increase in portal venous pressure and frequently accompanies cirrhosis. Portal pressure can be increased by a rise in portal blood flow, an increase in vascular resistance, or the combination. In cirrhosis, the primary factor leading to PHT is an increase in intra-hepatic resistance to blood flow. Although much of this increase is a mechanical consequence of architectural disturbances, there is a dynamic and reversible component that represents up to a third of the increased vascular resistance in cirrhosis. Many vasoactive substances contribute to the development of PHT. Among these, nitric oxide (NO) is the key mediator that paradoxically regulates the sinusoidal (intra-hepatic) and systemic/splanchnic circulations. NO deficiency in the liver leads to increased intra-hepatic resistance while increased NO in the circulation contributes to the hyperdynamic systemic/splanchnic circulation. NO mediated-angiogenesis also plays a role in splanchnic vasodilation and collateral circulation formation. NO donors reduce PHT in animals models but the key clinical challenge is the development of an NO donor or drug delivery system that selectively targets the liver.

Translating an understanding of the pathogenesis of hepatic fibrosis to novel therapies

The response to injury is one of wound healing and fibrogenesis, which ultimately leads to fibrosis. The fibrogenic response to injury is a generalized one across virtually all organ systems. In the liver, the injury response, typically occurring over a prolonged period of time, leads to cirrhosis (although it should be pointed out that not all patients with liver injury develop cirrhosis). The fact that many different diseases result in cirrhosis suggests a common pathogenesis. The study of hepatic fibrogenesis over the past 2 decades has been remarkably active, leading to a considerable understanding of this process. It clearly has been shown that the hepatic stellate cell is a central component in the fibrogenic process. It also has been recognized that other effector cells are important in the fibrogenic process, including resident fibroblasts, bone marrow-derived cells, fibrocytes, and even perhaps cells derived from epithelial cells (ie, through epithelial to mesenchymal transition). A key aspect of the biology of fibrogenesis is that the fibrogenic process is dynamic; thus, even advanced fibrosis (or cirrhosis) is reversible. Together, an understanding of the cellular basis for liver fibrogenesis, along with multiple aspects of the basic pathogenesis of fibrosis, have highlighted many exciting potential therapeutic opportunities. Thus, although the most effective antifibrotic therapy is simply treatment of the underlying disease, in situations in which this is not possible, specific antifibrotic therapy is likely not only to become feasible, but will soon become a reality. This review highlights the mechanisms underlying fibrogenesis that may be translated into future antifibrotic therapies and to review the current state of clinical development.

Cholestasis is associated with hepatic microvascular dysfunction and aberrant energy metabolism before and during ischemia-reperfusion

AIMS

The aim was to investigate the impact of ischemia-reperfusion (I/R) on intrahepatic oxidative stress, oxidative phosphorylation, and nucleotide metabolism in relation to liver damage and inflammation in cholestatic rats to elucidate the molecular mechanisms responsible for post-I/R pathogenesis during cholestasis.

RESULTS

Pre-I/R cholestatic livers exhibited mild hepatopathology in the form of oxidative/nitrosative stress, perfusion defects, necrosis and apoptosis, inflammation, and fibrosis. Plasma bilirubin concentration in cholestatic livers was 190 μM. I/R in cholestatic livers exacerbated hepatocellular damage and leukocyte infiltration. However, myeloperoxidase activity in neutrophils at 6 h reperfusion was not elevated in cholestatic livers compared to pre-I/R levels and to control (Ctrl) livers. At 6 h reperfusion, cholestatic livers exhibited severe histological damage, which was absent in Ctrl livers. Despite a lower antioxidative capacity after I/R, no cardiolipin peroxidation and equivalent reduced glutathione/oxidized glutathione ratios and Hsp70 levels were found in cholestatic livers versus Ctrls. Bilirubin acted as a potent and protective antioxidant. Postischemic resumption of oxidative phosphorylation in Ctrl livers proceeded rapidly and encompassed reactive hyperemia, which was significantly impaired in cholestatic livers owing to extensive vasoconstriction and perfusion defects. Normalization of intrahepatic energy status and nucleotide-based metabolic cofactors was delayed in cholestatic livers during reperfusion. Innovation and

CONCLUSIONS

Cholestatic livers possess sufficient antioxidative capacity to ameliorate radical-mediated damage during I/R. I/R-induced damage in cholestatic livers is predominantly caused by microvascular perfusion defects rather than exuberant oxidative/nitrosative stress. The forestalled rate of oxidative phophorylation and recovery of bioenergetic and possibly metabolic parameters during the early reperfusion phase are responsible for extensive liver damage.

Autotaxin in liver fibrosis

Autotaxin (ATX) hydrolyzes lysophosphatidylcholine to produce lysophosphatidic acid (LPA), a multi-functional bioactive lipid mediator. ATX is a major determinant of LPA levels in the blood, and the pathophysiological functions of ATX are thought to be largely attributed to its ability to produce LPA. Liver fibrosis is one of the rare disorders exhibiting the increased ATX and LPA levels in the blood. This review summarizes the recent findings on the relation between ATX or LPA and liver fibrosis, the usefulness of serum ATX levels to predict the stages of liver fibrosis, and speculated roles of increased serum ATX and plasma LPA levels in liver fibrosis.

Sphingosine-1-phosphate as a mediator involved in development of fibrotic diseases

Fibrosis is a pathological process characterized by massive deposition of extracellular matrix (ECM) such as type I/III collagens and fibronectin that are secreted by an expanded pool of myofibroblasts, which are phenotypically altered fibroblasts with more contractile, proliferative, migratory and secretory activities. Fibrosis occurs in various organs including the lung, heart, liver and kidney, resulting in loss of normal tissue architecture and functions. Myofibroblasts could originate from multiple sources including tissue-resident fibroblasts, epithelial and endothelial cells through mechanisms of epithelial/endothelial-mesenchymal transition (EMT/EndMT), and bone marrow-derived circulating progenitors called fibrocytes. Emerging evidence in recent years shows that sphingosine-1-phosphate (S1P) acts on several types of target cells and is engaged in pro-fibrotic inflammatory process and fibrogenic process through multiple mechanisms, which include vascular permeability change, leukocyte infiltration, and migration, proliferation and myofibroblast differentiation of fibroblasts. Many of these S1P actions are receptor subtype-specific. In these actions, S1P has multiple cross-talks with other cytokines, particularly transforming growth factor-β (TGFβ), which plays a major role in fibrosis. The cross-talks include the regulation of S1P production through altered expression and activity of sphingosine kinases in fibrotic lesions, altered expression of S1P receptors, and S1P receptor-mediated transactivation of TGFβ signaling pathway. These cross-talks may give rise to a feed-forward, amplifying loop between S1P and TGFβ, and possibly with other cytokines in stimulating fibrogenesis. Another lysophospholipid mediator lysophosphatidic acid has also been recently implicated in fibrosis. The lysophospholipid signaling pathways represent novel, promising therapeutic targets for treating refractory fibrotic diseases. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.

Effect of recombinant human growth hormone and interferon gamma on hepatic collagen synthesis and proliferation of hepatic stellate cells in cirrhotic rats

BACKGROUND

Fibrosis plays a key role in the development of liver cirrhosis. In this study, we investigated the effect of growth hormone and interferon gamma on hepatic collagen synthesis and the proliferation of hepatic stellate cells in a cirrhotic rat model.

METHODS

Cirrhosis was induced in rats using carbon tetrachloride. Rats were simultaneously treated with daily subcutaneous injections of recombinant human growth hormone or interferon gamma combined with recombinant human growth hormone. The control group was given saline. The relative content of type I and type IV collagen was assessed by indirect immunofluorescence analysis. Activated hepatic stellate cells were prepared from cirrhotic rats. The 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) method was used to assess the effects of recombinant human growth hormone and interferon gamma on these cells in vitro.

RESULTS

Both qualitative and quantitative analysis showed that type I and type IV collagen secretion increased with time after recombinant human growth hormone administration and was significantly higher than control and recombinant human growth hormone combined with interferon gamma administration. In vitro, recombinant human growth hormone significantly stimulated hepatic stellate cell proliferation in a concentration-dependent manner (10(-3)-10(-1) mg/100 μL), and interferon gamma (10(-2)-10(-1) μg/100 μL) significantly inhibited their growth compared to the control group. Interferon gamma combined with recombinant human growth hormone eliminated this growth-promoting effect to a certain degree in a concentration-dependent manner (10(-1) μg/100 μL, P<0.05, 10(-2)-10(-3) μg/100 μL, P>0.05) and a time-dependent manner (P<0.05).

CONCLUSIONS

Recombinant human growth hormone increased collagen secretion in cirrhotic rats in vivo and promoted the proliferation of hepatic stellate cells from cirrhotic rats in vitro. It is possible that concurrent interferon gamma therapy can offset these side-effects of recombinant human growth hormone.

Differential Regulation of TGF-β/Smad Signaling in Hepatic Stellate Cells between Acute and Chronic Liver Injuries

Current evidence suggests that regulation of extracellular matrix (ECM) accumulation by fibrogenic transforming growth factor (TGF)-β and platelet-derived growth factor (PDGF) signals involves different mechanisms in acute and chronic liver injuries, even though hepatic stellate cells (HSC) are the principal effecter in both cases. As a result of chronic liver damage, HSC undergo progressive activation to become myofibroblasts (MFB)-like cells. Our current review will discuss the differential regulation of TGF-β signaling between HSC and MFB in vitro and in vivo. Smad proteins, which convey signals from TGF-β receptors to the nucleus, have intermediate linker regions between conserved Mad-homology (MH) 1 and MH2 domains. TGF-β type I receptor and Ras-associated kinases differentially phosphorylate Smad2 and Smad3 to create COOH-terminally (C), linker (L), or dually (L/C) phosphorylated (p) isoforms. After acute liver injury, TGF-β and PDGF synergistically promote collagen synthesis in the activated HSC via pSmad2L/C and pSmad3L/C pathways. To avoid unlimited ECM deposition, Smad7 induced by TGF-β negatively regulates the fibrogenic TGF-β signaling. In contrast, TGF-β and PDGF can transmit the fibrogenic pSmad2L/C and mitogenic pSmad3L signals in MFB throughout chronic liver injury, because Smad7 cannot be induced by the pSmad3L pathway. This lack of Smad7 induction might lead to constitutive fibrogenesis in MFB, which eventually develop into accelerated liver fibrosis.

Differential Regulation of TGF-β/Smad Signaling in Hepatic Stellate Cells between Acute and Chronic Liver Injuries

Current evidence suggests that regulation of extracellular matrix (ECM) accumulation by fibrogenic transforming growth factor (TGF)-β and platelet-derived growth factor (PDGF) signals involves different mechanisms in acute and chronic liver injuries, even though hepatic stellate cells (HSC) are the principal effecter in both cases. As a result of chronic liver damage, HSC undergo progressive activation to become myofibroblasts (MFB)-like cells. Our current review will discuss the differential regulation of TGF-β signaling between HSC and MFB in vitro and in vivo. Smad proteins, which convey signals from TGF-β receptors to the nucleus, have intermediate linker regions between conserved Mad-homology (MH) 1 and MH2 domains. TGF-β type I receptor and Ras-associated kinases differentially phosphorylate Smad2 and Smad3 to create COOH-terminally (C), linker (L), or dually (L/C) phosphorylated (p) isoforms. After acute liver injury, TGF-β and PDGF synergistically promote collagen synthesis in the activated HSC via pSmad2L/C and pSmad3L/C pathways. To avoid unlimited ECM deposition, Smad7 induced by TGF-β negatively regulates the fibrogenic TGF-β signaling. In contrast, TGF-β and PDGF can transmit the fibrogenic pSmad2L/C and mitogenic pSmad3L signals in MFB throughout chronic liver injury, because Smad7 cannot be induced by the pSmad3L pathway. This lack of Smad7 induction might lead to constitutive fibrogenesis in MFB, which eventually develop into accelerated liver fibrosis.

The function of integrin-linked kinase in normal and activated stellate cells: implications for fibrogenesis in wound healing

Integrin-linked kinase (ILK) is a multidomain focal adhesion protein implicated in signal transduction between integrins and growth factor/extracellular receptors. We have previously shown that ILK expression is increased in liver fibrosis and that ILK appears to be a key regulator of fibrogenesis in rat hepatic stellate cells, effectors of the fibrogenic response. Here we hypothesized that the mechanism by which ILK mediates the fibrogenic phenotype is by engaging the small GTPase, Rho in a signal transduction pathway linked to fibrogenesis. ILK function in quiescent (non-fibrogenic) and activated (fibrogenic) stellate cells was examined in cells isolated from rat livers. ILK, Rho, and Gα(12/13) signaling were manipulated using established chemical agents or specific adenoviral constructs. ILK activity was minimal in quiescent stellate cells, but prominent in activated stellate cells; inhibition of ILK activity had no effect in quiescent cells, but had prominent effects in activated cells. Overexpression of ILK in activated stellate cells increased Rho activity, but had no effect in quiescent cells. Further, endothelin-1 stimulated Rho activity in activated stellate cells, but not in quiescent cells. Rho, Rho guanine nucleotide exchange factors, and Gα(12/13) expression were increased after stellate cell activation. Inhibition of Gα(12/13) signaling, by expression of the RGS domain of the p115-Rho-specific GEF (p115-RGS) in activated stellate cells, significantly inhibited type I collagen and smooth muscle α-actin expression, both classically upregulated after stellate cell activation. The data suggest that ILK mediates Rho-dependent functional effects in activated stellate cells, and raise the possibility that ILK is important in cross-talk with the G-protein-coupled receptor system.

"Normal" liver stiffness measure (LSM) values are higher in both lean and obese individuals: a population-based study from a developing country

The liver stiffness measure (LSM) needs to be explored in ethnically and anthropometrically diverse healthy subjects (to derive an acceptable normal range) and also in patients with liver disease. In view of this objective, LSM was performed by transient elastography (TE) using FibroScan in 437 healthy subjects with normal alanine aminotransferase (ALT) levels, recruited from a free-living population of the Birbhum Population Project (BIRPOP; www.shds.in), a Health and Demographic Surveillance System (HDSS), and from 274 patients with liver disease attending the Hepatology Clinic of the School of Digestive and Liver Diseases (SDLD; Institute of Post Graduate Medical Education & Research [IPGME&R], Kolkata, India) including 188 with nonalcoholic fatty liver disease (NAFLD) and 86 with chronic hepatitis of viral and other etiologies. Liver biopsy was performed in 125 patients. The range of normal values for LSM, defined by 5th and 95th percentile values in healthy subjects, was 3.2 and 8.5 kPa, respectively. Healthy subjects with a lower body mass index (BMI; < <18.5 kg/m(2)) had a higher LSM compared with subjects who had a normal BMI; this LSM value was comparable to that of obese subjects (6.05 ± 1.78 versus 5.51 ± 1.59 and 6.60 ± 1.21, P = 0.016 and 0.349, respectively). Liver disease patients without histologic fibrosis had significantly higher LSM values compared with healthy subjects (7.52 ± 5.49 versus 5.63 ± 1.64, P < 0.001). Among the histologic variables, stage of fibrosis was the only predictor for LSM. LSM did not correlate with inflammatory activity and ALT in both NAFLD and chronic hepatitis groups.

CONCLUSION

LSM varies between 3.2 and 8.5 kPa in healthy subjects of South Asian origin. Both lean and obese healthy subjects have higher LSM values compared with subjects with normal BMI. Liver stiffness begins to increase even before fibrosis appears in patients with liver disease.

Update on hepatic stellate cells: pathogenic role in liver fibrosis and novel isolation techniques

Hepatic stellate cells (HSCs), also called Ito cells or lipocytes, are vitamin A-storing cells located in the Dissé space between hepatocytes and sinusoidal endothelial cells. Upon liver injury, these cells transdifferentiate into extracellular matrix-producing, highly proliferative myofibroblasts that promote hepatic fibrogenesis. Other possible collagen-producing cells in liver fibrosis include portal fibroblasts, bone marrow-derived cells (mesenchymal stem cells, fibrocytes and hematopoietic cells) and parenchymal cells undergoing epithelial-to-mesenchymal transition. Important factors and signaling pathways for HSC activation, as well as different functions of HSC during homeostasis and fibrosis, such as collagen production, secretion of cytokines and chemokines, immune modulation and changes in contractile features, as well as vitamin A storage capacity, have been identified in vitro and in vivo. Novel isolation techniques, specifically HSC sorting by FACS via autofluorescence and antibodies, will provide us with further opportunities to advance our understanding of HSC biology in health and disease.