Fibroblast stimulation in schistosomiasis. IX. Schistosomal egg granulomas from congenitally athymic mice are deficient in production of fibrogenic factors

Schistosomal egg granulomas spontaneously secrete fibrogenic factors, suggesting that there exists a molecular link between granulomatous inflammation and hepatic fibrosis in schistosomiasis. To further assess this possibility, we compared elaboration of fibrogenic factors by egg granulomas isolated from Schistosoma mansoni-infected euthymic mice that develop substantial liver fibrosis, with those elaborated by similarly infected congenitally athymic mice that develop minimal fibrosis. Conditioned medium from cultures of granulomas from euthymic mice stimulated fibroblast proliferation, chemotaxis, and synthesis of collagen, collagenase, tissue inhibitor of metalloproteinases, and hyaluronate, whereas those prepared from cultures of granulomas isolated from athymic mice were relatively or absolutely deficient in such activities. These observations provide a correlation between the presence of fibrosis in vivo and the production of fibrogenic factors and reinforce our hypothesis that granuloma-derived fibrogenic factors play a role in the pathogenesis of liver fibrosis in schistosomiasis. Furthermore, the results of this study suggest a central role of T lymphocytes in the fibrogenic process.     

Strategies to improve the efficiency of mesenchymal stem cell transplantation for reversal of liver fibrosis

End‐stage liver fibrosis frequently progresses to portal vein thrombosis, formation of oesophageal varices, hepatic encephalopathy, ascites, hepatocellular carcinoma and liver failure. Mesenchymal stem cells (MSCs), when transplanted in vivo, migrate into fibrogenic livers and then differentiate into hepatocyte‐like cells or fuse with hepatocytes to protect liver function. Moreover, they can produce various growth factors and cytokines with anti‐inflammatory effects to reverse the fibrotic state of the liver. In addition, only a small number of MSCs migrate to the injured tissue after cell transplantation; consequently, multiple studies have investigated effective strategies to improve the survival rate and activity of MSCs for the treatment of liver fibrosis. In this review, we intend to arrange and analyse the current evidence related to MSC transplantation in liver fibrosis, to summarize the detailed mechanisms of MSC transplantation for the reversal of liver fibrosis and to discuss new strategies for this treatment. Finally, and most importantly, we will identify the current problems with MSC‐based therapies to repair liver fibrosis that must be addressed in order to develop safer and more effective routes for MSC transplantation. In this way, it will soon be possible to significantly improve the therapeutic effects of MSC transplantation for liver regeneration, as well as enhance the quality of life and prolong the survival time of patients with liver fibrosis.     

Why does liver fibrosis occur in schistosomiasis?

Schistosomiasis is one of the most prevalent of several chronic inflammatory diseases in which morbidity results primarily from tissue scarring. New concepts regarding the molecular pathogenesis of scar formation are being applied in research efforts to define the basis of liver fibrosis in schistosomiasis. Such investigations have led to the identification of an apparently novel lymphokine, fibroblast stimulating factor-I (FsF-I), produced in the egg granulomas. FsF-1 and other granulomo-derived fibrogenic cytokines may represent the molecular links between periovular granulomotous inflammation and hepatic fibrosis. Here, David Wyler postulates that the unmodified production of these f brogenic signals may be responsible for the development of severe hepatic fibrosis in the subpopulotion of infected individuals who develop this complication.     

Endocannabinoids and liver disease. II. Endocannabinoids in the pathogenesis and treatment of liver fibrosis

Hepatic fibrosis is the response of the liver to chronic injury and is associated with portal hypertension, progression to hepatic cirrhosis, liver failure, and high incidence of hepatocellular carcinoma. On a molecular level, a large number of signaling pathways have been shown to contribute to the activation of fibrogenic cell types and the subsequent accumulation of extracellular matrix in the liver. Recent evidence suggests that the endocannabinoid system is an important part of this complex signaling network. In the injured liver, the endocannabinoid system is upregulated both at the level of endocannabinoids and at the endocannabinoid receptors CB1 and CB2. The hepatic endocannabinoid system mediates both pro- and antifibrogenic effects by activating distinct signaling pathways that differentially affect proliferation and death of fibrogenic cell types. Here we will summarize current findings on the role of the hepatic endocannabinoid system in liver fibrosis and discuss emerging options for its therapeutic exploitation.     

肝纤维化发病机制中细胞和分子机制的研究进展

关于肝纤维化形成的复杂的细胞和分子联系已经有了相当多的研究进展。最近的数据表明,纤维化进程的终止和纤维分解途径的恢复可以逆转晚期肝纤维化甚至肝硬化。因此,需要更好地阐明参与肝纤维化的细胞和分子机制。HSC(肝星状细胞)的激活是肝纤维化发生的中心事件,此外还有产生基质的其他细胞来源,包括肝门区的成纤维细胞,纤维细胞和骨髓来源的肌纤维母细胞。这些细胞与其邻近细胞通过多种联系聚集产生纤维疤痕并造成持续性损伤。阐明不同类型的细胞的相互作用,揭示细胞因子对这些细胞的影响,理清活化HSC基因表达的调控,将有助于我们探索新的肝纤维化治疗靶点。此外,不同的病因有不同的致病途径,弄清这一点有助于针对特异性疾病治疗方法的发现。本文概述了肝纤维化的细胞和分子机制的最新研究进展,可能为未来治疗方法带来新的突破。     

Autophagy fuels tissue fibrogenesis

Activation of hepatic stellate cells (HSC), a resident pericytic cell in liver, into a proliferative and fibrogenic cell type, is the principal event underlying hepatic fibrosis following injury. Release of lipid droplets (LD) containing retinyl esters and triglyceride is a defining feature of HSC activation, yet the basis for this release has remained mysterious. Here we offer a surprising discovery that autophagy is the missing link underlying LD release, by stimulating metabolism of their contents to provide the energy vital to fuel HSC activation. By specifically inhibiting the autophagic pathway in activated HSC, LD release is impaired and cellular ATP levels are decreased. Moreover, animals with HSC-specific deletion of Atg7 display attenuated activation following liver injury, leading to reduced fibrosis in vivo. We further demonstrate that fibrogenic cells from other organs, including kidney and lung, also rely on autophagy as a core pathway driving the scarring response. Our results provide a novel framework for understanding pathways underlying fibrogenic cell responses to tissue injury.     

Autophagy fuels tissue fibrogenesis

Activation of hepatic stellate cells (HSC), a resident pericytic cell in liver, into a proliferative and fibrogenic cell type, is the principal event underlying hepatic fibrosis following injury. Release of lipid droplets (LD) containing retinyl esters and triglyceride is a defining feature of HSC activation, yet the basis for this release has remained mysterious. Here we offer a surprising discovery that autophagy is the missing link underlying LD release, by stimulating metabolism of their contents to provide the energy vital to fuel HSC activation. By specifically inhibiting the autophagic pathway in activated HSC, LD release is impaired and cellular ATP levels are decreased. Moreover, animals with HSC-specific deletion of Atg7 display attenuated activation following liver injury, leading to reduced fibrosis in vivo. We further demonstrate that fibrogenic cells from other organs, including kidney and lung, also rely on autophagy as a core pathway driving the scarring response. Our results provide a novel framework for understanding pathways underlying fibrogenic cell responses to tissue injury.     

Hepatic fibrosis and cirrhosis: the (myo)fibroblastic cell subpopulations involved

Fibrosis, defined as the excessive deposition of extracellular matrix in an organ, is the main complication of chronic liver damage. Its endpoint is cirrhosis, which is responsible for significant morbidity and mortality. The accumulation of extracellular matrix observed in fibrosis and cirrhosis is due to the activation of fibroblasts, which acquire a myofibroblastic phenotype. Myofibroblasts are absent from normal liver. They are produced by the activation of precursor cells, such as hepatic stellate cells and portal fibroblasts. These fibrogenic cells are distributed differently in the hepatic lobule: the hepatic stellate cells resemble pericytes and are located along the sinusoids, in the Disse space between the endothelium and the hepatocytes, whereas the portal fibroblasts are embedded in the portal tract connective tissue around portal structures (vessels and biliary structures). Differences have been reported between these two fibrogenic cell populations, in the mechanisms leading to myofibroblastic differentiation, activation and "deactivation", but confirmation is required. Second-layer cells surrounding centrolobular veins, fibroblasts present in the Glisson capsule surrounding the liver, and vascular smooth muscle cells may also express a myofibroblastic phenotype and may be involved in fibrogenesis. It is now widely accepted that the various types of lesion (e.g., lesions caused by alcohol abuse and viral hepatitis) leading to liver fibrosis involve specific fibrogenic cell subpopulations. The biological and biochemical characterisation of these cells is thus essential if we are to understand the mechanisms underlying the progressive development of excessive scarring in the liver. These cells also differ in proliferative and apoptotic capacity, at least in vitro. All this information is required for the development of treatments specifically and efficiently targeting the cells responsible for the development of fibrosis/cirrhosis.     

Illuminating the Gateway of Gene Silencing: Perspective of RNA Interference Technology in Clinical Therapeutics

A novel laboratory revolution for disease therapy, the RNA interference (RNAi) technology, has adopted a new era of molecular research as the next generation "Gene-targeted prophylaxis." In this review, we have focused on the chief technological challenges associated with the efforts to develop RNAi-based therapeutics that may guide the biomedical researchers. Many non-curable maladies, like neurodegenerative diseases and cancers have effectively been cured using this technology. Rapid advances are still in progress for the development of RNAi-based technologies that will be having a major impact on medical research. We have highlighted the recent discoveries associated with the phenomenon of RNAi, expression of silencing molecules in mammals along with the vector systems used for disease therapeutics.     

Targeting secreted cytokine BMP9 gates the attenuation of hepatic fibrosis

Liver fibrosis is overly exuberant wound healing that leads to portal hypertension or liver cirrhosis. Recent studies have demonstrated the functions of bone morphogenetic protein 9 (BMP9) in liver fibrosis, and thus, targeting liver-specific BMP9 abnormalities will become an attractive approach for developing therapeutics to treat liver fibrosis. Here, we reveal that BMP9 serves as a valuable serum diagnostic indicator and efficient therapeutic target to attenuate liver fibrogenesis. Our analysis of biopsies from liver fibrotic patients revealed that higher BMP9 levels accompanied advanced stages of liver fibrosis. In mouse models, recombinant Bmp9 overexpression accelerated liver fibrosis, and adenovirus-mediated Bmp9 knockdown attenuated liver fibrogenesis. Intriguingly, BMP9 directly stimulated hepatic stellate cell activation via the SMAD signaling pathway to enhance hepatic fibrosis. Moreover, an inhibitory monoclonal antibody targeting Bmp9 was efficacious in treatment of mice with liver fibrosis. These observations delineate a novel model in which BMP9 directly drives SMAD/ID1 signaling in hepatic stellate cells, which modulates liver fibrogenesis development. Moreover, the findings unveil a promising surrogate biomarker for the diagnosis of hepatic fibrosis, thereby representing an efficient “BMP9 neutralization” approach in alleviating hepatic fibrosis.     

Elevated mitochondrial activity distinguishes fibrogenic hepatic stellate cells and sensitizes for selective inhibition by mitotropic doxorubicin

Activation of hepatic stellate cells (HSCs) is an integral component of the wound‐healing process in liver injury/inflammation. However, uncontrolled activation of HSCs leads to constant secretion of collagen‐rich extracellular matrix (ECM) proteins, resulting in liver fibrosis. The enhanced ECM synthesis/secretion demands an uninterrupted supply of intracellular energy; however, there is a paucity of data on the bioenergetics, particularly the mitochondrial (mito) metabolism of fibrogenic HSCs. Here, using human and rat HSCs in vitro, we show that the mito‐respiration, mito‐membrane potential (Δψm) and cellular ‘bioenergetic signature’ distinguish fibrogenic HSCs from normal, less‐active HSCs. Ex vivo, HSCs from mouse and rat models of liver fibrosis further confirmed the altered ‘bioenergetic signature’ of fibrogenic HSCs. Importantly, the distinctive elevation in mito‐Δψm sensitized fibrogenic HSCs for selective inhibition by mitotropic doxorubicin while normal, less‐active HSCs and healthy human primary hepatocytes remained minimally affected if not, unaffected. Thus, the increased mito‐Δψm may provide an opportunity to selectively target fibrogenic HSCs in liver fibrosis.     

CB1 cannabinoid receptor antagonism: a new strategy for the treatment of liver fibrosis

Hepatic fibrosis, the common response associated with chronic liver diseases, ultimately leads to cirrhosis, a major public health problem worldwide. We recently showed that activation of hepatic cannabinoid CB2 receptors limits progression of experimental liver fibrosis. We also found that during the course of chronic hepatitis C, daily cannabis use is an independent predictor of fibrosis progression. Overall, these results suggest that endocannabinoids may drive both CB2-mediated antifibrogenic effects and CB2-independent profibrogenic effects. Here we investigated whether activation of cannabinoid CB1 receptors (encoded by Cnr1) promotes progression of fibrosis. CB1 receptors were highly induced in human cirrhotic samples and in liver fibrogenic cells. Treatment with the CB1 receptor antagonist SR141716A decreased the wound-healing response to acute liver injury and inhibited progression of fibrosis in three models of chronic liver injury. We saw similar changes in Cnr1-/- mice as compared to wild-type mice. Genetic or pharmacological inactivation of CB1 receptors decreased fibrogenesis by lowering hepatic transforming growth factor (TGF)-beta1 and reducing accumulation of fibrogenic cells in the liver after apoptosis and growth inhibition of hepatic myofibroblasts. In conclusion, our study shows that CB1 receptor antagonists hold promise for the treatment of liver fibrosis.     

Induction of cell death in activated hepatic stellate cells by targeted gene expression of the thymidine kinase/ganciclovir system

Liver fibrosis is the result from a relative imbalance between synthesis and degradation of matrix proteins. Following liver injury of any etiology, hepatic stellate cells undergo a response known as activation, which is the transition of quiescent cells into proliferative, fibrogenic, and contractile myofibroblasts. Upon this cellular transdifferentiation the effector cell becomes the major source of fibrillar and non-fibrillar matrix proteins resulting in excessive scar formation and cirrhosis, the end stage of fibrosis. Concomitant with progressive liver fibrosis, the tissue inhibitor of metalloproteinases-1 (TIMP-1) is strongly activated in hepatic stellate cells. We have developed a recombinant replication-defective adenovirus in which the TIMP-1 promoter is coupled to the herpes simplex virus thymidine kinase gene rendering activated hepatic stellate cells susceptible to ganciclovir. This novel targeted suicide gene approach was validated in a culture model considered to reflect an accelerated time course of the cellular and molecular events that occur during liver fibrosis. We demonstrate that transfer of the suicide gene to culture-activated hepatic stellate cells results in a strong expression of the respective transgene as assessed by Northern blot and Western blot analyses. The enzyme catalyzed the proper conversion of its prodrug subsequently initiating programmed cell death as estimated by caspase-3 assay and Annexin V-Fluos staining. Altogether, these results indicate that induction of programmed cell death is a promising approach to eliminate fibrogenic HSC.     

Endoplasmic reticulum stress and autophagy are involved in adipocyte-induced fibrosis in hepatic stellate cells

Liver fibrosis, with the characterization of progressive accumulation of extracellular matrix (ECM), is the common pathologic feature in the process of chronic liver disease. Hepatic stellate cells (HSCs) which are activated and differentiate into proliferative and contractile myofibroblasts are recognized as the main drivers of fibrosis. Obesity-related adipocytokine dysregulation is known to accelerate liver fibrosis progression, but the direct fibrogenic effect of mature adipocytes on HSCs has been rarely reported. Therefore, the purpose of this study was to explore the fibrogenic effect of adipocyte 3T3-L1 cells on hepatic stellate LX-2 cells. The results showed that incubating LX-2 cells with the supernatant of 3T3-L1 adipocytes triggered the expression of ECM related proteins, such as α-smooth muscle actin (α-SMA), type I collagen (CO-I), and activated TGF β/Smad2/3 signaling pathway in LX-2 cells. In addition, 3T3-L1 cells inhibited insulin sensitivity, activated endoplasmic reticulum stress and autophagy to promote the development of fibrosis. These results supported the notion that mature adipocytes can directly activate hepatic stellate cells, and the establishment of an in vitro model of adipocytes on HSCs provides an insight into screening of drugs for liver diseases, such as nonalcoholic fatty liver disease.

     

A class of imidazolium salts is anti-oxidative and anti-fibrotic in hepatic stellate cells

A class of imidazolium salts (IMSs) is routinely used in organic synthetic chemistry as precursors to generate N-heterocyclic carbenes (NHCs) with catalytic activity. However, their biological properties are largely unknown. The current study investigates the biological activity of a typical NHC precursor DBZIM and its trimer TDBZIM in hepatic stellate cells (HSCs), which is an in vitro model for studying liver fibrosis. The results show that HSCs treated with IMSs have an enhanced GSH/GSSG ratio and a reduced level of reactive oxygen species (ROS), which may consequently contribute to the attenuation in gene expression of fibrogenic molecules such as smooth muscle actin-α (SMAA), transforming growth factor-beta 1 (TGF-β1), procollagen αI(I) and fibronectin. Further, the in vivo experiments demonstrate that DBZIM is an anti-fibrotic agent in a mouse model of liver fibrosis. These findings suggest that the versatile IMSs could be a potential source for developing novel therapeutics to treat liver fibrosis and other fibrogenic disorders caused by oxidative stress and TGF-β1 mal-signalling.     

肝纤维化发生发展及逆转过程中肝巨噬细胞亚群分类

肝纤维化是由持续性损伤修复反应引起的,导致肝组织内细胞外基质异常沉积,进一步引发肝脏结构和肝功能异常改变的一种病理过程.已有大量研究表明,肝纤维化在去除损伤因素后是可以逆转的.肝星状细胞作为主要的效应细胞,合成和分泌各种胶原和细胞外基质,一直被认为是肝纤维化发生发展的中心环节.最近的研究发现,巨噬细胞作为主要的调节细胞,能同时调节肝星状细胞的功能和基质胶原的降解,促进肝纤维化的形成.而在肝纤维化逆转过程中,促使活化的肝星状细胞凋亡和纤维胶原的降解,促进肝纤维化的逆转.目前已有研究表明,巨噬细胞亚群在肝纤维化发生发展及逆转中具有双向调控作用,但是对于动物模型体内还没有系统的研究巨噬细胞亚群的分类.本文对巨噬细胞亚群的分类研究做一个全面的综述,对肝脏巨噬细胞在肝纤维化中分子机制的进一步研究具有一定的参考价值和借鉴意义.     

Nano-regenerative medicine towards clinical outcome of stem cell and tissue engineering in humans

Nanotechnology is a fast growing area of research that aims to create nanomaterials or nanostructures development in stem cell and tissue-based therapies. Concepts and discoveries from the fields of bio nano research provide exciting opportunities of using stem cells for regeneration of tissues and organs. The application of nanotechnology to stem-cell biology would be able to address the challenges of disease therapeutics. This review covers the potential of nanotechnology approaches towards regenerative medicine. Furthermore, it focuses on current aspects of stem- and tissue-cell engineering. The magnetic nanoparticles-based applications in stem-cell research open new frontiers in cell and tissue engineering.     

Comprehensive characterization of metabolic,inflammatory and fibrotic changes in a mouse model of diet-derived nonalcoholic steatohepatitis

The objective of this study was to develop a well-characterized mouse model of nonalcoholic steatohepatitis (NASH) with a strong manifestation of liver fibrosis. The progression of metabolic, inflammatory and fibrotic features of this mouse model was monitored by performing in vivo time-course study. Male C57BL/6J mice were fed a high-fat/high-sucrose/high-cholesterol diet (34% fat, 34% sucrose and 2.0% cholesterol, by weight) for 2, 4, 6, 8, 10, 12, 14 or 16 weeks to induce obesity-associated metabolic dysfunctions, inflammation and fibrosis in the liver and white adipose tissue (WAT). Body and liver weights were gradually increased with significant hepatic triglyceride accumulation, i.e., liver steatosis, and marked elevation of serum alanine transaminase levels at week 10. While hepatic inflammation was displayed with the highest expression of macrophage markers and M1 markers at week 6, liver fibrosis determined by collagen accumulation was continuously increased to week 16. In epididymal WAT, weights and adipocyte size peaked at week 6–8. The increased expression of fibrogenic genes preceded inflammatory features (week 2 to 6 vs. week 6 to 16), suggesting that early fibrosis may trigger inflammatory events in the WAT. This study established a mouse model of diet-induced NASH with a strong manifestation of liver fibrosis. This mouse model will be a valuable in vivo tool in studying the pathophysiology of NASH and also in testing preventive and therapeutic potentials of dietary components and drugs against NASH with liver fibrosis.