Hepatic wound repair

Pathophysiology and Management of Variceal Bleeding

Cirrhosis is the fifth leading cause of death in adults. Advanced cirrhosis can cause significant portal hypertension (PH), which is responsible for many of the complications observed in patients with cirrhosis, such as varices. If portal pressure exceeds a certain threshold, the patient is at risk of developing life-threatening bleeding from varices. Variceal bleeding has a high incidence among patients with liver cirrhosis and carries a high risk of mortality and morbidity. The management of variceal bleeding is complex, often requiring a multidisciplinary approach involving pharmacological, endoscopic, and radiologic interventions. In terms of management, three stages can be considered: primary prophylaxis, active bleeding, and secondary prophylaxis. The main goal of primary and secondary prophylaxis is to prevent variceal bleeding. However, active variceal bleeding is a medical emergency that requires swift intervention to stop the bleeding and achieve durable hemostasis. We describe the pathophysiology of cirrhosis and PH to contextualize the formation of gastric and esophageal varices. We also discuss the currently available treatments and compare how they fare in each stage of clinical management, with a special focus on drugs that can prevent bleeding or assist in achieving hemostasis.

Elucidating Potential Profibrotic Mechanisms of Emerging Biomarkers for Early Prognosis of Hepatic Fibrosis

Hepatic fibrosis has been associated with a series of pathophysiological processes causing excessive accumulation of extracellular matrix proteins. Several cellular processes and molecular mechanisms have been implicated in the diseased liver that augments fibrogenesis, fibrogenic cytokines and associated liver complications. Liver biopsy remains an essential diagnostic tool for histological evaluation of hepatic fibrosis to establish a prognosis. In addition to being invasive, this methodology presents with several limitations including poor cost-effectiveness, prolonged hospitalizations, and risks of peritoneal bleeding, while the clinical use of this method does not reveal underlying pathogenic mechanisms. Several alternate noninvasive diagnostic strategies have been developed, to determine the extent of hepatic fibrosis, including the use of direct and indirect biomarkers. Immediate diagnosis of hepatic fibrosis by noninvasive means would be more palatable than a biopsy and could assist clinicians in taking early interventions timely, avoiding fatal complications, and improving prognosis. Therefore, we sought to review some common biomarkers of liver fibrosis along with some emerging candidates, including the oxidative stress-mediated biomarkers, epigenetic and genetic markers, exosomes, and miRNAs that needs further evaluation and would have better sensitivity and specificity. We also aim to elucidate the potential role of cardiotonic steroids (CTS) and evaluate the pro-inflammatory and profibrotic effects of CTS in exacerbating hepatic fibrosis. By understanding the underlying pathogenic processes, the efficacy of these biomarkers could allow for early diagnosis and treatment of hepatic fibrosis in chronic liver diseases, once validated.

Kupffer cells mediate the recruitment of hepatic stellate cells into the localized liver damage

Currently, there is a growing interest in understanding the cellular and molecular events of immune-cell trafficking and recruitment of hepatic stellate cells (HSCs) in liver diseases. Aberrant activation of HSCs is the key event leading to chronic liver fibrosis. However, the underlying mechanisms of the recruitment of HSCs in a locally injured liver are not clearly understood. Here, we report a new experimental approach for the study of inflammatory responses as well as the recruitment of HSCs into the localized cryolesion. We observed a significant liver damage accompanied by the up-regulation of plasma ALT and AST. In addition, we also found increased levels of MCP-1, IL-6 and IL-10 cytokines. The peak cytokine levels were detected at 8 h after injury, followed by intrahepatic infiltration of neutrophils and monocytes into the injury site (from 8 h to day 3), while the kupffer cells (KCs) and HSCs were mainly detected on day 3 after injury. Interestingly, the depletion of KCs, but not neutrophils, reduced the directional recruitment and accumulation of HSCs at the injury site. Moreover, the combinatorial recruitment of KCs and HSCs resulted in the gradual restoration of fibrotic area to almost typical histological appearance on day 14 post-injury. In conclusion, our data demonstrated a localized infiltration and accumulation of neutrophils and monocytes at a "predefined loci", and further revealed that KCs are critical for the recruitment of HSCs during injury, and thus, may play an important role in tissue repair.

Pre-hepatectomy type IV collagen 7S predicts post-hepatectomy liver failure and recovery

BACKGROUND

Liver resection is an effective treatment for benign and malignant liver tumors. However, a method for preoperative evaluation of hepatic reserve has not yet been established. Previously reported assessments of preoperative hepatic reserve focused only on liver failure in the early postoperative period and did not consider the long-term recovery of hepatic reserve. When determining eligibility for hepatectomy, the underlying pathophysiology needs to be considered to determine if the functional hepatic reserve can withstand both surgery and any postoperative therapy.

AIM

To identify pre-hepatectomy factors associated with both early postoperative liver failure and long-term postoperative liver function recovery.

METHODS

This study was a retrospective cohort study. We retrospectively investigated 215 patients who underwent hepatectomy at our hospital between May 2013 and December 2016. Early post-hepatectomy liver failure (PHLF) was defined using the International Study Group of Liver Surgery’s definition of PHLF. Long-term postoperative recovery of liver function was defined as the time taken for serum total bilirubin and albumin levels to return to levels of < 2 mg/dL and > 2.8 g/dL, respectively, and the time taken for Child-Pugh score to return to Child-Pugh class A.

RESULTS

Preoperative type IV collagen 7S was identified as a significant independent factor associated with both PHLF and postoperative long-term recovery of liver function. Further analysis revealed that the time taken for the recovery of Child-Pugh scores and serum total bilirubin and albumin levels was significantly shorter in patients with type IV collagen 7S ≤ 6 ng/mL than in those with type IV collagen 7S > 6 ng/mL. In additional analyses, similar results were observed in patients without chronic viral hepatitis associated with fibrosis.

CONCLUSION

Preoperative type IV collagen 7S is a preoperative predictor of PHLF and long-term postoperative liver function recovery. It can also be used in patients without chronic hepatitis virus.

Influence of resveratrol on liver fibrosis induced by dimethylnitrosamine in male rats

Liver fibrosis is a significant health problem which represents the liver’s scarring process and response to injury through deposition of collagen and extracellular matrix, and ultimately leads to cirrhosis. Resveratrol is a naturally occurring phytoalexin found predominantly in grapes. This study aimed to investigate the antifibrotic role of resveratrol on dimethylnitrosamine (DMN)-induced liver fibrosis in rats. Rats were divided into four groups and treated for three weeks; control, resveratrol administered orally (20 mg/kg daily), DMN intraperitoneally injected (10 mg/kg 3 days/week), and the last group was pre-treated daily with resveratrol then injected with DMN, 3 days/week. DMN administration induced severe liver pathological alterations. However, oral administration of resveratrol before DMN significantly prevented the induced loss in body weight, as well as the increase in liver weight which arise from DMN administration. Resveratrol has also inhibited the elevation of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin levels. Furthermore, resveratrol significantly increased hepatic reduced glutathione (GSH) levels and reduced the levels of malondialdehyde (MDA) due to its antioxidants effect as well as increased serum protein levels. In addition, DMN induced elevation in hydroxyproline content. On the other hand, hydroxyproline level was significantly reduced in the resveratrol pretreated rats. Resveratrol has also remarkably maintained the normal liver lobular architecture. Moreover, resveratrol had displayed potent potentials to prevent collagen deposition, lymphocytic infiltration, necrosis, steatosis, vascular damage, blood hypertention, cholangiocyte proliferation. It can be concluded that resveratrol has a marked protective role on DMN-induced liver fibrosis in rats, and can be considered as antiproliferative, antihypertensive, as well as antifibrotic agent and may be used to block the development of liver fibrosis.

Caracterização do imunofenótipo das células envolvidas no processo fibrótico de fígados bovinos cronicamente infectados por Fasciola hepatica

RESUMO A fasciolose é uma doença parasitária causada por trematódeo do gênero Fasciola sp., que pode ocasionar fibrose hepática. Objetivou-se caracterizar o imunofenótipo das células que participam da fibrogênese de fígados bovinos frente à infecção por F. hepatica. Foram utilizados fragmentos dos lobos direito e esquerdo de 74 fígados bovinos com fasciolose. Os fragmentos foram submetidos a processamento histológico, coloração com tricrômico de Masson e imuno-histoquímica. Utilizaram-se análise estatística descritiva e teste de correlação de Spearmann com 5% de probabilidade. Na classificação do grau de fibrose, observou-se prevalência do grau 1, com associação positiva e significativa entre o grau de fibrose e o lobo hepático esquerdo (ρ=0,41; P<0,0001). Os imunofenótipos observados foram células estreladas hepáticas (CEHs) no parênquima e miofibroblastos (MFs) no espaço porta (EP). Não foram encontrados fibroblastos. Não houve correlação significativa entre o grau de fibrose e a quantidade de CEH nos lobos hepáticos, direito e esquerdo. Verificou-se aumento do número de estruturas portais, bem como do número de camadas circundando cada estrutura no EP, contudo não houve influência de qualquer estrutura sobre o grau de fibrose hepática (P>0,05). Concluiu-se que as células CEH e os MFs participam da fibrogênese de fígados bovinos com fasciolose crônica.

Embrionary way to create a fatty liver in portal hypertension

Portal hypertension in the rat by triple partial portal vein ligation produces an array of splanchnic and systemic disorders, including hepatic steatosis. In the current review these alterations are considered components of a systemic inflammatory response that would develop through three overlapping phenotypes: The neurogenic, the immune and the endocrine. These three inflammatory phenotypes could resemble the functions expressed during embryonic development of mammals. In turn, the inflammatory phenotypes would be represented in the embryo by two functional axes, that is, a coelomic-amniotic axis and a trophoblastic yolk-sac or vitelline axis. In this sense, the inflammatory response developed after triple partial portal vein ligation in the rat would integrate both functional embryonic axes on the liver interstitial space of Disse. If so, this fact would favor the successive development of steatosis, steatohepatitis and fibrosis. Firstly, these recapitulated embryonic functions would produce the evolution of liver steatosis. In this way, this fat liver could represent a yolk-sac-like in portal hypertensive rats. After that, the systemic recapitulation of these embryonic functions in experimental prehepatic portal hypertension would consequently induce a gastrulation-like response in which a hepatic wound healing reaction or fibrosis occur. In conclusion, studying the mechanisms involved in embryonic development could provide key results for a better understanding of the nonalcoholic fatty liver disease etiopathogeny.

Protection against Acute Hepatocellular Injury Afforded by Liver Fibrosis Is Independent of T Lymphocytes

Collagen produced during the process of liver fibrosis can induce a hepatocellular protective response through ERK1 signalling. However, the influence of T cells and associated cytokine production on this protection is unknown. In addition, athymic mice are frequently used in hepatocellular carcinoma xenograft experiments but current methods limit our ability to study the impact of liver fibrosis in this setting due to high mortality. Therefore, a mouse model of liver fibrosis lacking T cells was developed using Foxn1 nu/nu mice and progressive oral administration of thioacetamide (TAA) [0.01–0.02%] in drinking water. Fibrosis developed over a period of 16 weeks (alpha-SMA positive area: 20.0 ± 2.2%, preCol1a1 mRNA expression: 11.7 ± 4.1 fold changes, hydroxyproline content: 1041.2 ± 77μg/g of liver) at levels comparable to that of BALB/c mice that received intraperitoneal TAA injections [200 μg/g of body weight (bw)] (alpha-SMA positive area: 20.9 ± 2.9%, preCol1a1 mRNA expression: 13.1 ± 2.3 fold changes, hydroxyproline content: 931.6 ± 14.8μg/g of liver). No mortality was observed. Athymic mice showed phosphorylation of ERK1/2 during fibrogenesis (control 0.03 ± 0.01 vs 16 weeks 0.22 ± 0.06AU; P<0.05). The fibrosis-induced hepatoprotection against cytotoxic agents, as assessed histologically and by serum AST levels, was not affected by the absence of circulating T cells (anti-Fas JO2 [0.5μg/g bw] for 6h (fibrotic 4665 ± 2596 vs non-fibrotic 13953 ± 2260 U/L; P<0.05), APAP [750 mg/kg bw] for 6 hours (fibrotic 292 ± 66 U/L vs non-fibrotic 4086 ± 2205; P<0.01) and CCl₄ [0.5mL/Kg bw] for 24h (fibrotic 888 ± 268 vs non-fibrotic 15673 ± 2782 U/L; P<0.001)). In conclusion, liver fibrosis can be induced in athymic Foxn1 nu/nu mice without early mortality. Liver fibrosis leads to ERK1/2 phosphorylation. Finally, circulating T lymphocytes and associated cytokines are not involved in the hepatocellular protection afforded by liver fibrosis.

Bridging the Gap: From 2D Cell Culture to 3D Microengineered Extracellular Matrices

Historically the culture of mammalian cells in the laboratory has been performed on planar substrates with media cocktails that are optimized to maintain phenotype. However, it is becoming increasingly clear that much of biology discerned from 2D studies does not translate well to the 3D microenvironment. Over the last several decades, 2D and 3D microengineering approaches have been developed that better recapitulate the complex architecture and properties of in vivo tissue. Inspired by the infrastructure of the microelectronics industry, lithographic patterning approaches have taken center stage because of the ease in which cell-sized features can be engineered on surfaces and within a broad range of biocompatible materials. Patterning and templating techniques enable precise control over extracellular matrix properties including: composition, mechanics, geometry, cell-cell contact, and diffusion. In this review article we explore how the field of engineered extracellular matrices has evolved with the development of new hydrogel chemistry and the maturation of micro- and nano- fabrication. Guided by the spatiotemporal regulation of cell state in developing tissues, techniques for micropatterning in 2D, pseudo-3D systems, and patterning within 3D hydrogels will be discussed in the context of translating the information gained from 2D systems to synthetic engineered 3D tissues.

Curcumin upregulates Nrf2 nuclear translocation and protects rat hepatic stellate cells against oxidative stress

The present study aimed to investigate the protective role of curcumin against oxidative stress in rat hepatic stellate cells (HSCs)-T6, and to determine the possible underlying mechanisms. HSC-T6 cells were divided into three groups: Negative control group, oxidant-treated group and curcumin-treated group. Flow cytometry and spectrophotometry were used to measure the production of reactive oxygen species (ROS), and the levels of malondialdehyde (MDA) and glutathione (GSH). Immunocytochemistry and a radioimmunoassay were used to determine the expression of smooth muscle α-actin (α-SMA) and the secretion of extracellular matrix (ECM) molecules. In addition, western blotting and immunocytochemistry were used to determine the expression levels of nuclear factor-erythroid 2-related factor (Nrf2). Treatment with glucose oxidase (GO) significantly stimulated the formation of ROS and increased the production of MDA, as compared with the control cells; however, the production of GSH was only slightly increased. In addition, treatment with GO significantly promoted the expression of α-SMA and the secretion of ECM molecules. Conversely, treatment with curcumin significantly decreased the levels of ROS and MDA, and significantly increased the levels of GSH. Curcumin significantly inhibited the expression of α-SMA and decreased the secretion of ECM molecules. Furthermore, treatment with curcumin significantly increased the nuclear expression levels of Nrf2. These results indicated that curcumin may protect rat HSCs against oxidative stress and inhibit the GO-induced activation and secretion of ECM molecules in vitro. These effects were mediated by the upregulation of Nrf2 nuclear translocation.

Role of liver progenitors in liver regeneration

During massive liver injury and hepatocyte loss, the intrinsic regenerative capacity of the liver by replication of resident hepatocytes is overwhelmed. Treatment of this condition depends on the cause of liver injury, though in many cases liver transplantation (LT) remains the only curative option. LT for end stage chronic and acute liver diseases is hampered by shortage of donor organs and requires immunosuppression. Hepatocyte transplantation is limited by yet unresolved technical difficulties. Since currently no treatment is available to facilitate liver regeneration directly, therapies involving the use of resident liver stem or progenitor cells (LPCs) or non-liver stem cells are coming to fore. LPCs are quiescent in the healthy liver, but may be activated under conditions where the regenerative capacity of mature hepatocytes is severely impaired. Non-liver stem cells include embryonic stem cells (ES cells) and mesenchymal stem cells (MSCs). In the first section, we aim to provide an overview of the role of putative cytokines, growth factors, mitogens and hormones in regulating LPC response and briefly discuss the prognostic value of the LPC response in clinical practice. In the latter section, we will highlight the role of other (non-liver) stem cells in transplantation and discuss advantages and disadvantages of ES cells, induced pluripotent stem cells (iPS), as well as MSCs.

Early to Phase II drugs currently under investigation for the treatment of liver fibrosis

INTRODUCTION

Chronic liver diseases represent a high unmet medical need and are characterized by persistent inflammation, parenchymal damage and fibrotic remodeling, leading eventually to cirrhosis and hepatic failure. Besides the persisting high prevalence of chronic viral hepatitis B and C, the dramatic increase in nonalcoholic steatohepatitis is now considered to be a major pathophysiologic driver for fibrosis development and subsequently cirrhosis. Increasing evidence suggests that also liver cirrhosis can regress when treated adequately.

AREAS COVERED

Herein, the authors review the underlying pathophysiologic mechanisms leading to fibrotic remodeling in the liver. They also highlight the options for novel treatment strategies by using molecular targeted agents.

EXPERT OPINION

New in vitro and preclinical animal models, and the careful selection of patients with high disease dynamics for clinical studies, provide a sound basis for the clinical development of antifibrotic agents in humans. Surrogate parameters of liver function, inflammation, tissue remodeling and damage, as well as noninvasive imaging techniques, can be applied in clinical trials to provide fast readouts and novel and reliable endpoints for trial design, and provide an attractive regulatory environment for this emerging disease area.

Small RNA- and DNA-based gene therapy for the treatment of liver cirrhosis, where we are?

Chronic liver diseases with different aetiologies rely on the chronic activation of liver injuries which result in a fibrogenesis progression to the end stage of cirrhosis and liver failure. Based on the underlying cellular and molecular mechanisms of a liver fibrosis, there has been proposed several kinds of approaches for the treatment of liver fibrosis. Recently, liver gene therapy has been developed as an alternative way to liver transplantation, which is the only effective therapy for chronic liver diseases. The activation of hepatic stellate cells, a subsequent release of inflammatory cytokines and an accumulation of extracellular matrix during the liver fibrogenesis are the major obstacles to the treatment of liver fibrosis. Several targeted strategies have been developed, such as antisense oligodeoxynucleotides, RNA interference and decoy oligodeoxynucleotides to overcome this barriers. With this report an overview will be provided of targeted strategies for the treatment of liver cirrhosis, and particularly, of the targeted gene therapy using short RNA and DNA segments.

Hepatic stellate cells and extracellular matrix in hepatocellular carcinoma: more complicated than ever

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and the third leading cause of cancer death. Recent epidemiological data indicate that the mortality rate of HCC will double over the next decades in the USA and Europe. Liver cancer progresses in a large percentage of cases during the clinical course of chronic fibro-inflammatory liver diseases leading to cirrhosis. Therefore, HCC development is regarded as the result of different environmental risk factors each involving different genetic, epigenetic- and chromosomal alterations and gene mutations. During tumour progression, the malignant hepatocytes and the activated hepatic stellate cells are accompanied by cancer-associated fibroblasts, myofibroblasts and immune cells generally called tumour stromal cells. This new and dynamic milieu further enhances the responsiveness of tumour cells towards soluble mediators secreted by tumour stromal cells, thus directly affecting the malignant hepatocytes. This results in altered molecular pathways with cell proliferation as the most important mechanism of liver cancer progression. Given this contextual complexity, it is of utmost importance to characterize the molecular pathogenesis of HCC, and to identify the dominant pathways/drivers and aberrant signalling pathways. This will allow an effective therapy for HCC that should combine strategies affecting both cancer and the tumour stromal cells. This review provides an overview of the recent challenges and issues regarding hepatic stellate cells, extracellular matrix dynamics, liver fibrosis/cirrhosis and therapy, tumour microenvironment and HCC.

BMP-7 attenuates liver fibrosis via regulation of epidermal growth factor receptor

The aim of this study was to elucidate the effect of bone morphogenetic protein-7 (BMP-7) on liver fibrosis induced by carbon tetrachloride (CCl4) in vivo and on the hepatic stellate cells (HSC) activation in vitro. In vivo, thirty male ICR mice were randomly allocated to three groups, the control group (n = 6), the CCl4 group (n = 18) and the BMP-7+CCl4 group (n = 6). The model of liver fibrosis was induced by intraperitoneal injection with CCl4 three times per week lasting for 12 weeks in CCl4 group and the BMP-7+CCl4 group. After 8 weeks injection with CCl4, mice were intraperitoneal injected with human recombinant BMP-7 in BMP-7+CCl4 group. Meanwhile, mice in the CCl4 group were only intraperitoneal injection with equal amount of saline. The degree of liver fibrosis was assessed by HE and Masson's staining. PCR and western blot were used to detect mRNA and protein levels. In BMP-7+CCl4 group, serum levels of alanine aminotransferase (ALT) and aminotransferase (AST) were decreased and serum albumin (Alb) was increased. Meanwhile, the expressions of transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) were down-regulated by BMP-7 intervention as compared to the CCl4 group (P < 0.05). Furthermore, BMP-7 also suppressed the expression of epidermal growth factor receptor (EGFR) and phosphorylated-epidermal growth factor receptor (pEGFR). HE and Masson stain showed that liver damage was alleviated in BMP-7+CCl4 group. In vitro study, expression of EGFR, TGF-β1 and α-SMA were down regulated by BMP-7 dose-dependently, indicating it might effect on suppression of HSC activation. Therefore, our data indicate BMP-7 was capable of inhibiting liver fibrosis and suppressing HSCs activation, and these effects might rely on its crosstalk with EGFR and TGF-β1. We suggest that BMP-7 may be a potential reagentfor the prevention and treatment of liver fibrosis.

Side population in LX2 cells decreased by transforming growth factor-β

AIM

Side population (SP) cells are known to be enriched in stem/progenitor-like cells. Transforming growth factor (TGF)-β signaling is associated with extracellular matrix (ECM) production in hepatic stellate cells. We hypothesized that the SP fraction in LX2 cells is associated with ECM deposition, which is regulated through TGF-β signaling.

METHODS

We investigated the relationship between SP cells and TGF-β signaling in the hepatic stellate cell line LX2. The effects of TGF-β and SB431542 on the SP fraction and expression of collagen type I and phospho-Smad2 was determined.

RESULTS

We identified 0.8-3% SP cells in LX2 cells. The growth rate of sorted SP and non-SP cells was similar to that of the original LX2 population, but population of the G0/G1 phase was increased in SP cells. Treatment of LX2 cells with TGF-β decreased the SP fraction in a dose-dependent manner and increased the production of collagen type I. Treatment of LX2 cells with SB431542 blocked the effect of TGF-β on the SP fraction and the expression of collagen type I. We cultured LX2 cells on collagen-coated dishes to observe the effect of ECM deposition on the SP fraction. The growth rate and cell cycle distribution was similar to that observed on normal tissue culture dishes, but the SP fraction was decreased when LX2 cells were cultured on collagen-coated plates.

CONCLUSION

These results show that LX2 cells contain an SP fraction and that TGF-β signaling is involved in the induction of ECM deposition as well as the number of SP cells.

Microenvironment-induced myofibroblast-like conversion of engrafted keratinocytes

Myofibroblasts, recognized classically by α-smooth muscle actin (α-SMA) expression, play a key role in the wound-healing process, promoting wound closure and matrix deposition. Although a body of evidence shows that keratinocytes explanted onto a wound bed promote closure of a skin injury, the underlying mechanisms are not well understood. The basal layer of epidermis is rich in undifferentiated keratinocytes (UKs). We showed that UKs injected into granulation tissue could switch into α-SMA positive cells, and accelerate the rate of skin wound healing. In addition, when the epidermis sheets isolated from foreskin cover up the wound bed or are induced in vitro, keratinocytes located at the basal layers or adjacent sites were observed to convert into myofibroblast-like cells. Thus, UKs have a potential for myofibroblastic transition, which provides a novel mechanism by which keratinocyte explants accelerate skin wound healing.

Role of liver progenitors in acute liver injury

Acute liver failure (ALF) results from the acute and rapid loss of hepatocyte function and frequently exhibits a fulminant course, characterized by high mortality in the absence of immediate state-of-the-art intensive care and/or emergency liver transplantation (ELT). The role of hepatocyte-mediated liver regeneration during acute and chronic liver injury has been extensively investigated, and recent studies suggest that hepatocytes are not exclusively responsible for the regeneration of the injured liver during fulminant liver injury. Liver progenitor cells (LPC) (or resident liver stem cells) are quiescent in the healthy liver, but may be activated under conditions where the regenerative capacity of mature hepatocytes is severely impaired. This review aims to provide an overview of the role of the LPC population during ALF, and the role of putative cytokines, growth factors, mitogens, and hormones in the LPC response. We will highlight the potential interaction among cellular compartments during ALF, and discuss the possible prognostic value of the LPC response on ALF outcomes.

Recent progress in understanding pathogenesis and liver pathology in biliary atresia

Biliary atresia is an infantile destructive inflammatory cholangiopathy that causes obliteration of both intrahepatic and extrahepatic bile ducts and eventually liver cirrhosis. So far, the exact etiology and pathogenesis of biliary atresia remain unclear, and possible etiologies include congenital and genetic factors, infection, inflammation, immune reaction, maternal factors, and vascular factors. Immunoinflammatory theory has been accepted by most researchers, which is supported by liver pathological changes. This review focuses on the recent progress in understanding pathogenesis and liver pathology in biliary atresia.

Myofibroblasts and their resistance to apoptosis: a possible mechanism of osteoradionecrosis

Osteoradionecrosis (ORN) in the head and neck area is the most devastating long-term complication of radiotherapy, with slow progression and inability to heal spontaneously. ORN can lead to intolerable pain, fractures, and sequestration of devitalized bone and fistulae, making oral feeding impossible and causing facial deformation. In spite of its notorious reputation over at least 90 years, the precise pathogenesis of ORN has not been fully clarified, which has led to obstacles in the management of the disease. Several theories about its pathogenesis have been formulated, and radiation-induced fibrosis is the newest one. According to this theory, ORN is essentially a type of fibrosis induced by radiotherapy, and antifibrosis therapy has been shown to be effective in its treatment. We assumed that ORN, like fibrosis in other organs, is the result of a process of fibrogenesis in which myofibroblasts are the key effector cells. The uninterrupted accumulation of myofibroblasts and consequent persistent excess production of collagenous extracellular matrix and tensile force result in loss of normal function and ultimately radiation-induced fibrosis. During this process, myofibroblasts may be protected from apoptosis by acquiring an immune-privileged capacity, which allows continuous matrix synthesis. If this hypothesis proves to be correct, it would enable better understanding of the cellular and molecular mechanisms underlying the pathogenesis and progression of ORN, and would help improve our ability to prevent occurrence of ORN, give an earlier diagnosis, and treat it more effectively.

Anti-fibrotic activity and enhanced interleukin-6 production by hepatic stellate cells in response to imatinib mesylate

OBJECTIVE

To examine imatinib mesylate's effects on stellate cell responses in vivo and in vitro. The hepatic stellate cell (HSC) is a key target of anti-fibrotic therapies. Imatinib mesylate is a small molecule receptor tyrosine kinase inhibitor indicated for treatment of chronic myelogenous leukaemia and GI stromal tumours.

DESIGN

Because imatinib inhibits β-PDGFR signalling, which stimulates HSC proliferation, we assessed its activity in culture and in vivo, and examined downstream targets in a human stellate cell line (LX-2) using cDNA microarray.

METHODS AND RESULTS

Imatinib inhibited proliferation of LX-2 cells (0.5-10 mM) but not primary human stellate cells, with no effect on viability, associated with attenuated β-PDGFR phosphorylation. Mitochondrial activity and superoxide anion production were decreased in response to imatinib. cDNA microarray uncovered up-regulation of 29 genes in response to imatinib, including interleukin-6 (IL-6) mRNA, which was correlated with progressive IL-6 secretion. Imatinib also decreased gene expression of collagen α(1) (I), alpha smooth muscle actin, β-PDGFR, transforming growth factor β receptor type 1, matrix metalloproteinase 2 and tissue inhibitor of metalloproteinase 2. In vivo, imatinib administered to rats beginning 4 weeks after starting thioacetamide (TAA) led to reduced collagen content, with significant reductions in portal pressure and down-regulation of fibrogenic genes in whole liver. Importantly, hepatic IL-6 mRNA levels were significantly increased in TAA-treated animals receiving imatinib.

CONCLUSIONS

These findings reinforce the anti-fibrotic activity of imatinib and uncover an unexpected link between inhibition of HSC activation by imatinib and enhanced secretion of IL-6, a regenerative cytokine.

Organotypic liver culture models: meeting current challenges in toxicity testing

Prediction of chemical-induced hepatotoxicity in humans from in vitro data continues to be a significant challenge for the pharmaceutical and chemical industries. Generally, conventional in vitro hepatic model systems (i.e. 2-D static monocultures of primary or immortalized hepatocytes) are limited by their inability to maintain histotypic and phenotypic characteristics over time in culture, including stable expression of clearance and bioactivation pathways, as well as complex adaptive responses to chemical exposure. These systems are less than ideal for longer-term toxicity evaluations and elucidation of key cellular and molecular events involved in primary and secondary adaptation to chemical exposure, or for identification of important mediators of inflammation, proliferation and apoptosis. Progress in implementing a more effective strategy for in vitro-in vivo extrapolation and human risk assessment depends on significant advances in tissue culture technology and increasing their level of biological complexity. This article describes the current and ongoing need for more relevant, organotypic in vitro surrogate systems of human liver and recent efforts to recreate the multicellular architecture and hemodynamic properties of the liver using novel culture platforms. As these systems become more widely used for chemical and drug toxicity testing, there will be a corresponding need to establish standardized testing conditions, endpoint analyses and acceptance criteria. In the future, a balanced approach between sample throughput and biological relevance should provide better in vitro tools that are complementary with animal testing and assist in conducting more predictive human risk assessment.

Anti-fibrotic therapy: lost in translation?

While preclinical development of potential anti-fibrotics is far advanced, with numerous pharmacological targets and promising agents, almost none has entered clinical validation. Reasons are manifold, including the usually slow progression of liver fibrosis, requiring high numbers of well-stratified patients undergoing long-term treatment when conventional liver biopsy based parameters or hard liver-related endpoints are used. Importantly, there is a notorious lack of sensitive and specific surrogate markers or imaging technologies for liver fibrosis progression or regression that would permit a rapid clinical screening for potential anti-fibrotics. Nonetheless, in view of an urgent need for anti-fibrotics that positively impact morbidity and mortality from chronic liver diseases, the field is now moving more quickly towards clinical translation. This development is driven by thoughtful preclinical validation, a better study design and improved surrogate readouts using currently available methodologies. Moreover, upcoming novel biomarkers and imaging technologies will soon permit a more exact and efficient assessment of fibrosis progression and regression.

Interleukin-30: a novel antiinflammatory cytokine candidate for prevention and treatment of inflammatory cytokine-induced liver injury

The liver is the major metabolic organ and is subjected to constant attacks from chronic viral infection, uptake of therapeutic drugs, life behavior (alcoholic), and environmental contaminants, all of which result in chronic inflammation, fibrosis, and, ultimately, cancer. Therefore, there is an urgent need to discover effective therapeutic agents for the prevention and treatment of liver injury, the ideal drug being a naturally occurring biological inhibitor. Here we establish the role of IL30 as a potent antiinflammatory cytokine that can inhibit inflammation-induced liver injury. In contrast, interleukin (IL)27, which contains IL30 as a subunit, is not hepatoprotective. Interestingly, IL30 is induced by the proinflammatory signal such as IL12 through interferon-gamma (IFN-γ)/signal transducer and activator of transcription 1 signaling. In animal models, administration of IL30 by way of a gene therapy approach prevents and treats both IL12-, IFN-γ-, and concanavalin A-induced liver toxicity. Likewise, immunohistochemistry analysis of human tissue samples revealed that IL30 is highly expressed in hepatocytes, yet barely expressed in inflammation-induced tissue such as fibrous/connective tissue.

CONCLUSION

These novel observations reveal a novel role of IL30 as a therapeutic cytokine that suppresses proinflammatory cytokine-associated liver toxicity.

Th2-associated alternative Kupffer cell activation promotes liver fibrosis without inducing local inflammation

Cirrhosis is the final outcome of liver fibrosis. Kupffer cell-mediated hepatic inflammation is considered to aggravate liver injury and fibrosis. Alternatively-activated macrophages are able to control chronic inflammatory events and trigger wound healing processes. Nevertheless, the role of alternative Kupffer cell activation in liver harm is largely unclear. Thus, we evaluated the participation of alternatively-activated Kupffer cells during liver inflammation and fibrosis in the murine model of carbon tetrachloride-induced hepatic damage. To stimulate alternative activation in Kupffer cells, 20 Taenia crassiceps (Tc) larvae were inoculated into BALBc/AnN female mice. Six weeks post-inoculation, carbon tetrachloride or olive oil were orally administered to Tc-inoculated and non-inoculated mice twice per week during other six weeks. The initial exposure of animals to T. crassiceps resulted in high serum concentrations of IL-4 accompanied by a significant increase in the hepatic mRNA levels of Ym-1, with no alteration in iNOS expression. In response to carbon tetrachloride, recruitment of inflammatory cell populations into the hepatic parenchyma was 5-fold higher in non-inoculated animals than Tc-inoculated mice. In contrast, carbon tetrachloride-induced liver fibrosis was significantly less in non-inoculated animals than in the Tc-inoculated group. The latter showed elevated IL-4 serum levels and low IFN-γ concentrations during the whole experiment, associated with hepatic expression of IL-4, TGF-β, desmin and α-sma, as well as increased mRNA levels of Arg-1, Ym-1, FIZZ-1 and MMR in Kupffer cells. These results suggest that alternative Kupffer cell activation is favored in a Th2 microenvironment, whereby such liver resident macrophages could exhibit a dichotomic role during chronic hepatic damage, being involved in attenuation of the inflammatory response but at the same time exacerbation of liver fibrosis.

Pathophysiologic role of hepatocyte nuclear factor 6

Hepatocyte nuclear factor 6 (HNF6) is one of liver-enriched transcription factors. HNF6 utilizes the bipartite onecut-homeodomain sequence to localize the HNF6 protein to the nuclear compartment and binds to specific DNA sequences of numerous target gene promoters. HNF6 regulates an intricate network and mediates complex biological processes that are best known in the liver and pancreas. The function of HNF6 is correlated to cell proliferation, cell cycle regulation, cell differentiation and organogenesis, cell migration and cell-matrix adhesion, glucose metabolism, bile homeostasis, inflammation and so on. HNF6 controls the transcription of its target genes in different ways. The details of the regulatory pathways and their mechanisms are still under investigation. Future study will explore HNF6 novel functions associated with apoptosis, oncogenesis, and modulation of the inflammatory response. This review highlights recent progression pertaining to the pathophysiologic role of HNF6 and summarizes the potential mechanisms in preclinical animal models. HNF6-mediated pathways represent attractive therapeutic targets for the treatment of the relative diseases such as cholestasis.

Epithelial-mesenchymal transition in chronic liver disease: fibrogenesis or escape from death?

The possibility that epithelial-mesenchymal transition (EMT) could contribute to hepatic fibrogenesis in chronic liver diseases as reported in other organs, particularly the kidney, reinforced the concept that activated hepatic stellate cells were not the only key players in the hepatic fibrogenic process and that other cell types, either hepatic (i.e. portal fibroblast) or extrahepatic (bone marrow-derived cells and circulating fibrocytes) could contribute to this process. The possibility of the rapid mobilization of a large amount of fibrogenic cells by EMT after liver tissue injury made this phenomenon a relevant and suitable target for anti-fibrogenic strategies. Following an initial enthusiasm for the discovery of this novel pathway in fibrogenesis and the publication of a several highly quoted papers, more recent research has started to cast serious doubts upon the real relevance of this phenomenon in human fibrogenetic disorders. The debate on the authenticity of EMT or at least on its real contribution to the fibrogenic process has become very animated, sometimes reaching levels of "religious" integralism. The overall result is a general confusion on the meaning and on the definition of several key aspects. The aim of this article is to analyze and discuss the evidence supporting or confuting this possibility in order to reach reasonable and useful conclusions.

Non-invasive oxidative stress markers for liver fibrosis development in the evolution of toxic hepatitis

Oxidative stress is related to the liver fibrosis, anticipating the hepatic stellate cells' (HSC) activation. Our aim was to correlate oxidative stress markers with the histological liver alterations in order to identify predictive, noninvasive parameters of fibrosis progression in the evolution of toxic hepatitis.CCl4 in sunflower oil was administered to rats intragastrically, twice a week. After 2, 3, 4 and 8 weeks of treatment, plasma levels of malondialdehyde (MDA), protein carbonyls (PC), hydrogen donor capacity (HD), sulfhydryl groups (SH), and glutathione (GSH) were measured and histological examination of the liver slides was performed. Dynamics of histological disorders was assessed by The Knodell score. Significant elevation of inflammation grade was obtained after the second week of the experiment only (p=0.001), while fibrosis started to become significant (p=0.001) after 1 month of CCl4 administration. Between plasma MDA and liver fibrosis development a good correlation was obtained (r=0.877, p=0.05). Correlation between PC dynamics and liver alterations was marginally significant for inflammation grade (r=0.756, p=0.138). HD evolution revealed a marginally inverse correlation with inflammation grade (r=-0.794, p=0.108). No correlations could be established for other parameters with either inflammation grade or fibrosis stage.Our study shows that MDA elevation offers the best prediction potential for fibrosis, while marginal prediction fiability could be attributed to high levels of plasma PC and low levels of HD.

Liver fibrogenic cells

Liver fibrogenic cells are a heterogenous population of cells that include α-smooth muscle actin positive myofibroblasts (MFs). MFs promote the progression of chronic liver diseases (CLDs) towards cirrhosis. MFs are highly proliferative and contractile and promote fibrogenesis by means of their multiple phenotypic responses to injury. These include: excess deposition and altered remodelling of extracellular matrix; the synthesis and release of growth factor which sustain and perpetuate fibrogenesis; chronic inflammatory response and neo-angiogenesis. MFs mainly originate from hepatic stellate cells or portal fibroblasts through activation and transdifferentiation. MFs may also potentially differentiate from bone marrow-derived stem cells. It has been suggested that MFs can be derived from hepatocytes or cholangiocytes through a process of epithelial to mesenchymal transition in the liver, however this is controversial. Hepatic MFs may also modulate the immune responses to hepatocellular carcinomas and metastatic cancers through cross talk with hepatic progenitor and tumour cells.

Decreased collagen types I and IV, laminin, CK-19 and α-SMA expression after bone marrow cell transplantation in rats with liver fibrosis

Bone marrow cells have frequently been tested in animal models of liver fibrosis to assess their role in hepatic regeneration. The mononuclear fraction of bone marrow cells is of particular interest, as many studies show that these cells may be beneficial to treat hepatic fibrosis. In this study, we used the bile duct ligation model to induce hepatic fibrosis in an irreversible manner, and rats were treated with bone marrow mononuclear (BMMN) cells after fibrosis was established. Analysis of collagen types I and IV, laminin and α-SMA showed a decreased expression of these proteins in fibrotic livers after 7 days of BMMN cell injection. Moreover, cytokeratin-19 analysis showed a reduction in bile ducts in the BMMN cell-treated group. These results were accompanied by ameliorated levels of hepatic enzymes GPT (Glutamic-pyruvic transaminase), GOT (glutamic-oxaloacetic transaminase) and alkaline phosphatase (AP). Therefore, we showed that BMMN cells decrease hepatic fibrosis by significantly reducing myofibroblast numbers and through reduction of the collagen and laminin-rich extracellular matrix of fibrotic septa and hepatic sinusoids.

Evolving challenges in hepatic fibrosis

Continued elucidation of the mechanisms of hepatic fibrosis has yielded a comprehensive and nuanced portrait of fibrosis progression and regression. The paradigm of hepatic stellate cell (HSC) activation remains the foundation for defining events in hepatic fibrosis and has been complemented by progress in a number of new areas. Cellular sources of extracellular matrix beyond HSCs have been identified. In addition, the role of chemokine, adipokine, neuroendocrine, angiogenic and NAPDH oxidase signaling in the pathogenesis of hepatic fibrosis has been uncovered, as has the contribution of extracellular matrix stiffness to fibrogenesis. There is also increased awareness of the contribution of innate immunity and greater understanding of the complexity of gene regulation in HSCs and myofibroblasts. Finally, both apoptosis and senescence have been recognized as orchestrated programs that eliminate fibrogenic cells during resolution of liver fibrosis. Ironically, the progress that has been made has highlighted the growing disparity between advances in the experimental setting and their translation into new diagnostic tools and treatments. As a result, focus is shifting towards overcoming key translational challenges in order to accelerate the development of new therapies for patients with chronic liver disease.

Bcl-2 overexpression in hepatic stellate cell line CFSC-2G, induces a pro-fibrotic state

BACKGROUND AND AIM

Development of hepatic fibrosis is a complex process that involves oxidative stress (OS) and an altered balance between pro- and anti-apoptotic molecules. Since Bcl-2 overexpression preserves viability against OS, our objective was to address the effect of Bcl-2 overexpression in the hepatic stellate cells (HSC) cell-line CFSC-2G under acetaldehyde and H(2)O(2) challenge, and explore if it protects these cells against OS, induces replicative senescence and/or modify extracellular matrix (ECM) remodeling potential.

METHODS

To induce Bcl-2 overexpression, HSC cell line CFSC-2G was transfected by lipofection technique. Green fluorescent protein-only CFSC-2G cells were used as a control. Cell survival after H(2)O(2) treatment and total protein oxidation were assessed. To determine cell cycle arrest, proliferation-rate, DNA synthesis and senescence were assessed. Matrix metalloproteinases (MMP), tissue-inhibitor of MMP (TIMP), transglutaminases (TG) and smooth muscle a-actin (alpha-SMA) were evaluated by western blot in response to acetaldehyde treatment as markers of ECM remodeling capacity in addition to transforming growth factor-beta (TGF-beta) mRNA.

RESULTS

Cells overexpressing Bcl-2 survived approximately 20% more than control cells when exposed to H(2)O(2) and approximately 35% proteins were protected from oxidation, but Bcl-2 did not slow proliferation or induced senescence. Bcl-2 overexpression did not change alpha-SMA levels, but it increased TIMP-1 (55%), tissue transglutaminases (tTG) (25%) and TGF-beta mRNA (49%), when exposed to acetaldehyde, while MMP-13 content decreased (47%).

CONCLUSIONS

Bcl-2 overexpression protected HSC against oxidative stress but it did not induce replicative senescence. It increased TIMP-1, tTG and TGF-beta mRNA levels and decreased MMP-13 content, suggesting that Bcl-2 overexpression may play a key role in the progression of fibrosis in chronic liver diseases.

Involvement of cholangiocyte proliferation in biliary fibrosis

Cholangiocytes are the epithelial cells that line the biliary tree. In the adult liver, they are a mitotically dormant cell population, unless ductular reaction is triggered by injury. The ability of cholangiocytes to proliferate is important in many different human pathological liver conditions that target this cell type, which are termed cholangiopathies (i.e. primary biliary cirrhosis, primary sclerosing cholangitis and biliary atresia). In our article, we provide background information on the morphological and functional heterogeneity of cholangiocytes, summarize what is currently known about their proliferative processes, and briefly describe the diseases that target these cells. In addition, we address recent findings that suggest cholangiocyte involvement in epithelial-to-mesenchymal transformation and liver fibrosis, and propose directions for future studies.

Epithelial-mesenchymal transitions and hepatocarcinogenesis

Epithelial-mesenchymal transitions (EMTs) are believed to play a role in invasion and metastasis of many types of tumors. In this issue of the JCI, Chen et al. show that a gene that has been associated with aggressive biology in hepatocellular carcinomas initiates a molecular cascade that results in EMT.