Emerging therapies for liver fibrosis

Liver fibrosis occurs as a result of a wide range of injurious processes and in its end-stage results in cirrhosis. This gross disruption of liver architecture is associated with impaired hepatic function, portal hypertension and significant resultant morbidity and mortality. Indeed, liver fibrosis and cirrhosis represent a major worldwide healthcare burden. Recent progress in liver transplantation, the management of portal hypertension and the treatment of chronic viral hepatitis have had an important impact. However, these approaches are not without their limitations - in particular, issues regarding organ availability for transplantation - and serve to highlight the urgent requirement to influence pharmacologically the underlying fibrotic process in many patients. Liver fibrosis has been shown to be a bidirectional process and increasing data from laboratory and clinical studies reveal that even advanced fibrosis and cirrhosis are potentially reversible. Exploration of the molecular mechanisms underlying this bi-directionality will lead to char acterisation of the essential attributes of an antifibrotic therapy. In this review, these mechanisms are highlighted and the growing number of emerging antifibrotic agents discussed.     

Investigation of liver fibrosis in clinical practice.

The liver is composed of different hepatic fibrogenic cells: hepatic stellate cells, portal fibroblasts, fibroblasts of the Glisson capsule surrounding the liver and vascular smooth muscle cells and the second layer cells present around centrolobular veins. During liver disease, one or several populations of these cells are activated, transformed into myofibroblasts and secrete the extra-cellular matrix. There are markers to identify hepatic stellate cells either quiescent (CRBP-1) or activated (alpha-smooth muscle actin). Liver biopsy, the current "gold-standard" to estimate liver fibrosis cannot be used anymore as a "gold standard". Furthermore, it is a costly procedure with adverse effects feared by patients and clinicians. Alternative to liver biopsy using non-invasive-tests or technics include FibroTest-ActiTest, transient-elastography, hepatic vein transit time using contrast ultrasonography, magnetic resonance imaging. As a routine test, the FibroTest-ActiTest is a validated one for patients with chronic hepatitis C. The advantage of the non-invasive tests or technics is that they provide a rapid and quantitative estimation of fibrosis. With these new methods, it is possible to follow the progression of the disease and its regression either spontaneously or under treatment. In conclusion, clinicians have in their hands several painless tools to explore liver fibrosis that can be easily repeated.     

Recent advancement of molecular mechanisms of liver fibrosis

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

What's new in liver fibrosis? The origin of myofibroblasts in liver fibrosis

Chronic liver injury of many etiologies produces liver fibrosis and may eventually lead to the formation of cirrhosis. Fibrosis is part of a dynamic process associated with the continuous deposition and resorption of extracellular matrix, mainly fibrillar collagen. Studies of fibrogenesis conducted in many organs including the liver demonstrate that the primary source of the extracellular matrix in fibrosis is the myofibroblast. Hepatic myofibroblasts are not present in the normal liver but transdifferentiate from heterogeneous cell populations in response to a variety of fibrogenic stimuli. Debate still exists regarding the origin of hepatic myofibroblasts. It is considered that hepatic stellate cells and portal fibroblasts have fibrogenic potential and are the major origin of hepatic myofibroblasts. Depending on the primary site of injury the fibrosis may be present in the hepatic parenchyma as seen in chronic hepatitis or may be restricted to the portal areas as in most biliary diseases. It is suggested that hepatic injury of different etiology triggers the transdifferentiation to myofibroblasts from distinct cell populations. Here we discuss the origin and fate of myofibroblast in liver fibrosis.     

Liver fibrosis and hepatic stellate cells: Etiology,pathological hallmarks and therapeutic targets

Liver fibrosis is a reversible wound-healing process aimed at maintaining organ integrity, and presents as the critical pre-stage of liver cirrhosis, which will eventually progress to hepatocellular carcinoma in the absence of liver transplantation. Fibrosis generally results from chronic hepatic injury caused by various factors, mainly viral infection, schistosomiasis, and alcoholism; however, the exact pathological mechanisms are still unknown. Although numerous drugs have been shown to have antifibrotic activity in vitro and in animal models, none of these drugs have been shown to be efficacious in the clinic. Importantly, hepatic stellate cells(HSCs) play a key role in the initiation, progression, and regression of liver fibrosis by secreting fibrogenic factors that encourage portal fibrocytes, fibroblasts, and bone marrow-derived myofibroblasts to produce collagen and thereby propagate fibrosis. These cells are subject to intricate cross-talk with adjacent cells, resulting in scarring and subsequent liver damage. Thus, an understanding of the molecular mechanisms of liver fibrosis and their relationships with HSCs is essential for the discovery of new therapeutic targets. This comprehensive review outlines the role of HSCs in liver fibrosis and details novel strategies to suppress HSC activity, thereby providing new insights into potential treatments for liver fibrosis.     

Liver transplantation for cirrhosis in cystic fibrosis.

BACKGROUND: Liver disease is the third most common cause of death in children with cystic fibrosis (CF). Liver transplantation is an effective treatment in children with hepatic failure. AIMS: The objective of the present study was to review the indications and postoperative course of hepatic transplantation in a cystic fibrosis population. PATIENTS: Five children with CF, at a mean age of 16.5 years, underwent liver transplantation. RESULTS: All patients showed cirrhosis, portal hypertension and hepatic failure. The main postoperative complication was ascites refractory to treatment in two patients. No significant deterioration of the pulmonary function was noted. Two patients died, one of Hodgkin lymphoma and the other of progressive pulmonary failure. CONCLUSION: Liver transplantation was indicated in children with CF when hepatic failure and/or severe portal hypertension was present with well-preserved pulmonary function.     

肝纤维化内科治疗的研究

肝纤维化是各种慢性肝病向肝硬化发展的中间病理过程.此过程是一动态过程,是可逆性的.目前许多学者研究发现给予药物治疗、基因治疗、干细胞移植等方法 能有效预防肝纤维化的发生、延缓肝纤维化的进展或使肝纤维化逆转.     

Fibrogenese – Zirrhose

Liver fibrosis is defined as an excessive deposition of extracellular matrix. It is the main complication in chronic liver damage and its endpoint, liver cirrhosis, is responsible for impressive morbidity and mortality. The accumulation of extracellular matrix proteins in liver fibrosis and cirrhosis is due to different cell types which acquire a myofibroblastic phenotype – the hepatic stellate cells, located in the space of Disse, portal fibroblasts as well as myofibroblasts of the portal and pericentral area and bone marrow derived myofibroblasts. Differences have been reported between the two cell populations with respect to myofibroblastic differentiation, activation and “deactivation”, proliferation and apoptosis. However, in most cases additional confirmation may be required. Thus, the biological and biochemical characterization of these cells, their interactions with inflammatory cells and the cytokine environment leading to their activation or cell death are essential to understand the mechanisms underlying the progressive development of excessive scarring in the liver as well as the ability of the liver to repair tissue and regenerate.     

Inflammation, damage repair and liver fibrosis--role of cytokines and different cell types

Liver fibrosis is defined as an excessive deposition of extracellular matrix. It is the main complication of chronic liver damage and its endpoint, the liver cirrhosis, is responsible for impressive morbidity and mortality. The accumulation of extracellular matrix proteins in liver fibrosis and cirrhosis is due to different cell types which acquire a myofibroblastic phenotype--the hepatic stellate cells, located in the space of Disse, portal fibroblasts as well as myofibroblasts of the portal and pericentral areas. Further studies also suggest an impressive role of bone marrow-derived myofibroblasts. Differences have been reported between the two cell populations with respect to myofibroblastic differentiation, activation and "deactivation", proliferation and apoptosis. However, in most cases additional confirmation may be required; thus the biological and biochemical characterization of these cells, their interactions with inflammatory cells and the cytokine environment leading to their activation or cell death are essential to understand the mechanisms underlying the progressive development of excessive scarring in the liver as well as the ability of the liver for tissue repair and regeneration. All this information is required to estimate the value of already suggested possible treatments to specifically and efficiently target the cells responsible for the development of liver fibrosis/cirrhosis and as well as for liver regeneration.     

Living-related liver transplantation in patients with variceal bleeding: outcome and prognostic factors

BACKGROUND:Liver transplantation currently represents the ultimate therapy for bleeding esophageal varices in patients with liver cirrhosis.It is the only therapy that cures both portal hypertension and the underlying liver disease.The outcome of liver transplantation is thought to be correlated with several factors.In this study,the clinical outcome of living-related liver transplantation(LRLT) was evaluated in patients with variceal bleeding,and the prognostic indicators of short-term survival in these pa...     

Liver transplantation in cystic fibrosis.

Liver disease is the second most common cause of death in patients with cystic fibrosis (CF). Improvement in surgical techniques, medical management, and imaging modalities has broadened the range of options for treatment of these patients. Medical management with ursodeoxycholic acid and nutritional support may help decelerate the progression of liver disease. A timely evaluation of CF patients with liver involvement for transplantation is important. Such evaluation should not be delayed until signs of hepatic decompensation occur. Combined lung-liver transplant can be considered for patients with advanced pulmonary disease. Pretransplant management of portal hypertension with a portosystemic shunt procedure is an option for patients with well-preserved synthetic liver function. Improvement in lung function after liver transplantation and no significant risk of pulmonary infection with immunosuppressive therapy have been reported. Review of individual center experiences have shown satisfactory survival and improved quality of life for CF patients undergoing liver transplant.     

The phenotypic fate and functional role for bone marrow-derived stem cells in liver fibrosis

Liver fibrosis is an outcome of chronic liver injury of any etiology. It is manifested by extensive deposition of extracellular matrix (ECM) proteins that produce a fibrous scar in the injured liver. Bone marrow (BM) cells may play an important role in pathogenesis and resolution of liver fibrosis. BM cells contribute to the inflammatory response by TGF-β1 secretion and activation of liver resident myofibroblasts. Moreover, BM itself can serve as a source of collagen expressing cells, e.g. BM-derived fibrocytes and mesenchymal progenitors, which in turn, have a potential to in situ differentiate into fibrogenic myofibroblasts and facilitate fibrosis. Finally, BM cells play an active part in resolution of liver fibrosis after cessation of fibrogenic stimuli. While natural killer (NK) cells are implicated in apoptosis of activated hepatic stellate cells/myofibroblasts, cells of myelo-monocitic lineage secrete matrix metalloproteinases to actively degrade the fibrous scar. The focus of this review is on the current understanding of the role of different subsets of BM cells in the onset, development and resolution of liver fibrosis.     

Cirrhosis and autoimmune liver disease:Current understanding

Primary biliary cirrhosis(PBC),primary sclerosing cholangitis(PSC) and autoimmune hepatitis(AIH) constitute the classic autoimmune liver diseases(AILDs).While AIH target the hepatocytes,in PBC and PSC the targets of the autoimmune attack are the biliary epithelial cells.Persistent liver injury,associated with chronic AILD,leads to un-resolving inflammation,cell proliferation and the deposition of extracellular matrix proteins by hepatic stellate cells and portal myofibroblasts.Liver cirrhosis,and the resultant loss of normal liver function,inevitably ensues.Patients with cirrhosis have higher risks or morbidity and mortality,and that in the decompensated phase,complications of portal hypertension and/or liver dysfunction lead to rapid deterioration.Accurate diagnosis and monitoring of cirrhosis is,therefore of upmost importance.Liver biopsy is currently the gold standard technique,but highly promising non-invasive methodology is under development.Liver transplantation(LT) is an effective therapeutic option for the management of endstage liver disease secondary to AIH,PBC and PSC.LT is indicated for AILD patients who have progressed to end-stage chronic liver disease or developed intractable symptoms or hepatic malignancy;in addition,LT may also be indicated for patients presenting with acute liver disease due to AIH who do not respond to steroids.     

Fibrosis in autoimmune and cholestatic liver disease

Autoimmune and cholestatic liver disease account for a significant part of end-stage liver disease and are leading indications for liver transplantation. Especially cholestatic liver diseases (primary biliary cirrhosis and primary sclerosing cholangitis) appear to be different from other chronic liver diseases with regards to pathogenesis. Portal fibroblasts located in the connective tissue surrounding bile ducts appear to be different from hepatic stellate cells with regards to expression of marker proteins and response the profibrogenic and mitogenic stimuli. In addition there is increasing evidence for a cross talk between activated cholangiocytes and portal myofibroblasts. Several animal models have improved our understanding of the mechanisms underlying these chronic liver diseases. In the present review, we discuss the current concepts and ideas with regards to myofibroblastic cell populations, mechanisms of fibrosis, summarize characteristic histological findings and currently employed animal models of autoimmune and cholestatic liver disease.     

Vitamin A deficiency in chronic cholestatic liver disease: Is vitamin A therapy beneficial?

Chronic cholestatic diseases are progressive diseases of the biliary tract that cause hepatic fibrosis and ultimately lead to liver failure. Liver transplantation is the sole curative option currently available, and because of high morbidity and mortality rates of these diseases, new therapeutic approaches are needed. Vitamin A is a nutrient essential for health as it regulates many processes, including epithelial growth and immunological processes. Vitamin A is primarily stored in hepatic stellate cells, and during liver injury, through an unknown mechanism, these cells lose vitamin A and convert into collagen‐producing myofibroblasts, which contributes to hepatic fibrosis. Vitamin A deficiencies in chronic cholestatic diseases have been frequently reported, and therefore, retinoid metabolism has attracted a lot of attention. Retinoids have been shown to attenuate or even prevent hepatic fibrosis, and to regulate hepatic immunological response to cholestatic injury in different rodent models of chronic cholestasis. Recently, their potential as therapeutic drugs in primary sclerosing cholangitis patients was analyzed. The aim of this review is to summarize the existing knowledge and hypotheses about vitamin A role and the disease progression in cholestatic liver disease.     

Therapeutic efficiency of bone marrow-derived mesenchymal stem cells for liver fibrosis: A systematic review of in vivo studies

Although multiple drugs are accessible for recovering liver function in patients, none are considered efficient. Liver transplantation is the mainstay therapy for end-stage liver fibrosis. However, the worldwide shortage of healthy liver donors, organ rejection, complex surgery, and high costs are prompting researchers to develop novel approaches to deal with the overwhelming liver fibrosis cases. Mesenchymal stem cell (MSC) therapy is an emerging alternative method for treating patients with liver fibrosis. However, many aspects of this therapy remain unclear, such as the efficiency compared to conventional treatment, the ideal MSC sources, and the most effective way to use it. Because bone marrow (BM) is the largest source for MSCs, this paper used a systematic review approach to study the therapeutic efficiency of MSCs against liver fibrosis and related factors. We systematically searched multiple published articles to identify studies involving liver fibrosis and BM-MSC-based therapy. Analyzing the selected studies showed that compared with conventional treatment BM-MSC therapy may be more efficient for liver fibrosis in some cases. In contrast, the cotreatment presented a more efficient way. Nevertheless, BM-MSCs are lacking as a therapy for liver fibrosis; thus, this paper also reviews factors that affect BM-MSC efficiency, such as the implementation routes and strategies employed to enhance the potential in alleviating liver fibrosis. Ultimately, our review summarizes the recent advances in the BM-MSC therapy for liver fibrosis. It is grounded in recent developments underlying the efficiency of BM-MSCs as therapy, focusing on the preclinical in vivo experiments, and comparing to other treatments or sources and the strategies used to enhance its potential while mentioning the research gaps.     

Catastrophic microangiopathy induced by high-titre factor VIII inhibitors after liver transplantation for haemophilia A with cirrhosis

Liver transplantation may induce immune tolerance to factor VIII inhibitors but de novo development of inhibitors after transplantation may cause intractable haemorrhage. We report a patient with mild haemophilia A and high-titre FVIII inhibitors who received an orthotopic liver transplantation for complications of hepatitis C virus cirrhosis. Recombinant activated FVII was used in addition to routine haemostatic agents. Conventional immunosuppression was supplemented with antithymocyte globulin and cyclophosphamide. FVIII inhibitors disappeared from the circulation with liver transplantation but they were found to have bound to the graft endothelium, which became activated and induced catastrophic microangiopathy. A subsequent anamnestic response resulted in FVIII inhibitor titres of 1000 Bethesda Units. Uncontrollable haemorrhage persisted until the recipient's death. In patients with high-titre FVIII inhibitors resilient desensitization is required before liver transplantation.     

Other genetic liver diseases in children

Wilson disease is rare but proteiform, and should be suspected in any child with liver disease and older than 3 years of age. The treatment is very efficient, and must be taken life-long. Fifteen percent of patients with alpha-1-antitrypsin deficiency develop a neonatal jaundice, and 3% a cirrhosis in childhood. There is no specific treatment except liver transplantation. Five percent of cystic fibrosis patients develop a cirrhosis, with a very slow progression. Milder abnormalities are frequent, as well as biliary stones. Liver disease in ciliopathies may be a congenital hepatic fibrosis, with risks of portal hypertension and cholangitis, or a more variable biliary disease. Gilbert disease is frequent and benign. Crigler-Najjar syndrome is rare, severe, and may be an indication for liver or liver-cell transplantation.     

Expression of angiotensin II type 1 receptor in human cirrhotic livers: Its relation to fibrosis and portal hypertension.

Angiotensin II (ANG-II) and its receptor (AT1) have been potential targets of therapy for liver cirrhosis. However, AT1 expression in human cirrhotic livers has not been clarified. We studied AT1 and ANG-II generating enzymes in human autopsy (20 cirrhotics and 20 normal controls) and biopsy (10 cirrhotics) livers. AT1 immunoreactivity in tissue sections was quantified by computer-aided morphometry. AT1 protein and mRNA levels were assessed by Western blotting and real-time polymerase chain reaction. Concerning ANG-II generating system, angiotensin-converting enzyme (ACE) and mast cell chymase were examined. AT1 expression was seen not only in vascular smooth muscle cells, but also in activated stellate cells/myofibroblasts and liver parenchymal cells. AT1-positive vessels and myofibroblasts were significantly increased in fibrous septa of cirrhosis, although overall hepatic AT1 expression was reduced in the cirrhotic livers compared with the controls. Augmentation of AT1-positive vessels was related to severity of portal hypertension. Expressions of ACE and chymase were enhanced in the cirrhotic livers. These results suggest that hepatic AT1 expression is shifted to and concentrated in vessels and myofibroblasts in cirrhotic settings, and increased ANG-II generation by ACE and chymase contributes to portal hypertension and liver fibrosis via binding to AT1 expressed on vessels and myofibroblasts.     

肝硬化的手术与细胞治疗

肝硬化是由一种或多种病因长期或反复作用形成的弥漫性肝损害。肝移植是治疗失代偿期肝硬化的有效方法,但是由于肝源紧张等因素,多数肝硬化患者因上消化道出血、肝性脑病、继发感染、癌变等并发症危及生命。干细胞治疗可以改善肝硬化,自体骨髓经门静脉移植到肝脏,更有利于干细胞在肝内的存活和增殖。对150多例失代偿期肝硬化患者做自体骨髓经门静脉移植,结果显示肝功能好转,肝脏体积增大,弹性超声检查提示肝脏硬度减低。