In vitro formation of fibrous septa by liver connective tissue cells

Summary Active fibrous septa are a common feature in liver fibrosis and cirrhosis. Their etiology and formation were studied using cultures of tissue fragments or cells included in collagen gels. Liver fragments obtained from patients with cirrhosis or severe schistosomal fibrosis were able to reorganize the gel and to form discrete, interconnecting fibrous septa composed of parallel arrays of collagen, subsequently colonized by migrating connective tissue cells. The same was obtained in cultures of fibrogranulomatous lesions isolated from schistosome-infected mice livers. However, fragments of normal human and murine liver tissue did not show the capacity to form fibrous septa. Septa formation was also obtained in cultures of cell spheroids formed by liver connective tissue cells isolated from human fibrotic or cirrhotic liver tissues, but not with spheroids of normal skin fibroblasts or smooth muscle cells. This experimental model may represent the fibrous septa formation in vivo, depending on the activity of liver connective tissue cells. The ability of tissue fragments or cell spheroids to form septa in collagen gels might reflect the degree of fibrosis present in the liver tissue in vivo. This research was supported by FINEP and CNPq (Brazil) and CNRS (France).     

肝纤维化基因治疗的进展

肝硬化是慢性肝病晚期的组织学改变 ,以纤维组织大量增生和肝小叶结构无序化为特征 ,因此又称肝纤维化。近年来随着分子生物学的发展 ,肝纤维化的分子机制逐渐得以阐明 ,从而使肝纤维化的基因治疗成为可能。肝纤维化的基因治疗主要起到阻止纤维化发展、刺激肝细胞分裂和肝组织结构重建三方面的作用。目前 ,常用的方法一般是通过缺陷病毒 (如腺病毒 )转入特定的细胞因子和酶 (如肝细胞生长因子、转化生长因子β1受体、基质金属蛋白酶等 )的基因 ,通过靶细胞表达这些因子作用于受损的肝脏 ,达到延缓和治愈肝纤维化的目的     

Antagonistic regulation of transmembrane 4 L6 family member 5 attenuates fibrotic phenotypes in CCl(4) -treated mice

The development of liver fibrosis from chronic inflammation can involve epithelial-mesenchymal transition (EMT). Severe liver fibrosis can progress to cirrhosis, and further to hepatocellular carcinoma. Because the tetraspanin transmembrane 4 L6 family member 5 (TM4SF5) induces EMT and is highly expressed in hepatocellular carcinoma, it is of interest to investigate whether TM4SF5 expression is correlated with EMT processes during the development of fibrotic liver features. Using hepatic cells in vitro and a CCl(4) -mediated mouse liver in?vivo model, we examined whether TM4SF5 is expressed during liver fibrosis mediated by CCl(4) administration and whether treatment with anti-TM4SF5 reagent blocks the fibrotic liver features. Here, we found that TM4SF5 expression was induced by the transforming growth factor (TGF)β1 and epidermal growth factor signaling pathways in hepatocytes in vitro. In the CCl(4) -mediated mouse liver model, TM4SF5 was expressed during the liver fibrosis mediated by CCl(4) administration and correlated with α-smooth muscle actin expression, collagen I deposition, and TGFβ1 and epidermal growth factor receptor signaling activation in fibrotic septa regions. Interestingly, treatment with anti-TM4SF5 reagent blocked the TM4SF5-mediated liver fibrotic features: the formation of fibrotic septa with α-smooth muscle actin expression and collagen I deposition was attenuated by treatment with anti-TM4SF5 reagent. These results suggest that TM4SF5 expression mediated by TGFβ1 and growth factor can facilitate fibrotic processes during chronic liver injuries. TM4SF5 is thus a candidate target for prevention of liver fibrosis following chronic liver injury.     

A new FGFR inhibitor disrupts the TGF‐β1‐induced fibrotic process

Pulmonary fibrosis (PF) is chronic and irreversible damage to the lung characterized by fibroblast activation and matrix deposition. Although recently approved novel anti‐fibrotic agents can improve the lung function and survival of patients with PF, the overall outcomes remain poor. In this study, a novel imidazopurine compound, 3‐(2‐chloro‐6‐fluorobenzyl)‐1,6,7‐trimethyl‐1H‐imidazo[2,1‐f]purine‐2,4(3H,8H)‐dione (IM‐1918), markedly inhibited transforming growth factor (TGF)‐β‐stimulated reporter activity and reduced the expression of representative fibrotic markers, such as connective tissue growth factor, fibronectin, collagen and α‐smooth muscle actin, on human lung fibroblasts. However, IM‐1918 neither decreased Smad‐2 and Smad‐3 nor affected p38MAPK and JNK. Instead, IM‐1918 reduced Akt and extracellular signal‐regulated kinase 1/2 phosphorylation increased by TGF‐β. Additionally, IM‐1918 inhibited the phosphorylation of fibroblast growth factor receptors 1 and 3. In a bleomycin‐induced murine lung fibrosis model, IM‐1918 profoundly reduced fibrotic areas and decreased collagen and α‐smooth muscle actin accumulation. These results suggest that IM‐1918 can be applied to treat lung fibrosis.     

The Therapeutic Effects of Bone Marrow-Derived Mesenchymal Stem Cells and Simvastatin in a Rat Model of Liver Fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix (ECM) proteins including collagen that occurs in most types of chronic liver diseases. Studies concerning the capacity of mesenchymal stem cells (MSCs) and simvasatain (SIMV) to repair fibrotic tissues through reducing inflammation, collagen deposition, are still controversial. This study aimed to investigate the therapeutic efficacy of bone marrow (BM)-derived MSCs and SIMV on carbon tetrachloride (CCl₄)-induced liver fibrosis in rats. Rats were divided into: normal, CCl₄, CCl₄/MSCs, CCl₄/SIMV, CCl₄/MSCs/SIMV, and SIMV groups. BM-derived MSCs were detected by RT-PCR of CD29 and were then infused into the tail vein of female rats that received CCl₄ injection to induce liver fibrosis. Sex-determining region Y (SRY) gene on Y-chromosome gene was assessed by PCR to confirm homing of the male stem cells in liver tissue of the female recipients. Serum liver function tests, liver procollagens I and III, tissue inhibitors of metalloproteinase-1 (TIMP-1), endoglin, matrix metalloproteinase-1 (MMP-1) gene expressions, transforming growth factor-beta (TGF-β1) immunostaining, and histopathologicl examination were performed. MSCs and SIMV decreased liver procollagens I and III, TIMP-1 and endoglin gene expressions, TGF-β1 immunostaining, and serum liver function tests compared with the CCl₄ group. MMP-1 expression was increased in the CCl₄/MSCs group. Histopathological examination as well as fibrosis score supports the biochemical and molecular findings. It can be concluded that MSCs and SIMV were effective in the treatment of hepatic CCl₄-induced fibrosis-rat model. Treatment with MSCs was superior to SIMV. This antifibrotic effect can be attributed to their effect on the MMPs/TIMPs balance which is central in fibrogenesis.     

Urokinase-type plasminogen activator gene therapy in liver cirrhosis is mediated by collagens gene expression down-regulation and up-regulation of MMPs, HGF and VEGF

Human urokinase-type plasminogen activator (uPA) gene administration via an adenoviral (Ad)-vector induced cirrhosis regression and ameliorated hepatic dysfunction in a model of experimental liver cirrhosis. The administration of a single dose of 6 x 10(11) viral particles per kilogram of a clinical-grade Ad-vector was evaluated after the onset of rat liver cirrhosis via degradation of deposited collagen and a substantial decrease of alpha-sma-positive cells. Also, gene expression for pro-fibrogenic molecules (Col I, III, IV, TIMP-1 and PAI-1) was clearly down-regulated. In contrast, gene expression for collagen-degrading enzymes such as MMP-13 and MMP-2 was up-regulated. These events correlated with increased amounts of proteic free-TIMP-1, i.e. non-complexed with metalloproteinases (MMPs), indicating the presence of higher amounts of active MMPs inside the liver of cirrhotic animals treated with Ad-huPA. The harmonized and concerted expression of HGF and c-met resulted in exacerbated hepatocyte proliferation, although these events did not induce an abnormal liver growth. Angiogenesis, i.e. formation of new blood vessels, was evaluated by vascular endothelial growth factor (VEGF) expression which was notably detected to be 10 times higher during the first 6 days after Ad-huPA-treatment in cirrhotic animals as compared with controls. These events provide a clearer rationale as to how Ad-huPA-induced liver regeneration on CCl(4)-induced liver fibrosis takes place.     

Plasmin overcomes resistance to prostaglandin E2 in fibrotic lung fibroblasts by reorganizing protein kinase A signaling

Collagen deposition by fibroblasts contributes to scarring in fibrotic diseases. Activation of protein kinase A (PKA) by cAMP represents a pivotal brake on fibroblast activation, and the lipid mediator prostaglandin E(2) (PGE(2)) exerts its well known anti-fibrotic actions through cAMP signaling. However, fibrotic fibroblasts from the lungs of patients with idiopathic pulmonary fibrosis, or of mice with bleomycin-induced fibrosis, are resistant to the normal collagen-inhibiting action of PGE(2). In this study, we demonstrate that plasminogen activation to plasmin restores PGE(2) sensitivity in fibrotic lung fibroblasts from human and mouse. This involves amplified PKA signaling resulting from the promotion of new interactions between AKAP9 and PKA regulatory subunit II in the perinuclear region as well as from the inhibition of protein phosphatase 2A. This is the first report to show that an extracellular mediator can dramatically reorganize and amplify the intracellular PKA-A-kinase anchoring protein signaling network and suggests a new strategy to control collagen deposition by fibrotic fibroblasts.     

CDH11 promotes liver fibrosis via activation of hepatic stellate cells

Liver fibrosis, an important health condition associated with chronic liver injury that provides a permissive environment for cancer development, is characterized by the persistent deposition of extracellular matrix components that are mainly derived from activated hepatic stellate cells (HSCs). CDH11 belongs to a group of transmembrane proteins that are principally located in adherens junctions. CDH11 mediates homophilic cell-to-cell adhesion, which may promote the development of cirrhosis. The goal of this study was to determine whether CDH11 regulates liver fibrosis and to examine its mechanism by focusing on HSC activation. Here we demonstrate that CDH11 expression is elevated in human and mouse fibrotic liver tissues and that CDH11 mediates the profibrotic response in activated HSCs. Our data indicate that CDH11 regulates the TGFβ-induced activation of HSCs. Moreover, cells from CDH11 deficient mice displayed decreased HSC activation in vitro, and CDH11 deficient mice developed liver fibrogenesis in response to chronic damage induced by CCl₄ administration. In addition, CDH11 expression was positively correlated with liver fibrosis in patients with cirrhosis, and could therefore be a prognostic factor in patients with liver fibrosis. Collectively, our findings demonstrate that CDH11 promotes liver fibrosis by activating HSCs and may represent a potential target for anti-fibrotic therapies.     

Enhanced hepatic differentiation of mesenchymal stem cells after pretreatment with injured liver tissue

Liver failure represents a serious challenge for cell based therapies. Mesenchymal stem cells (MSCs) possess potential for regeneration of fibrotic liver; however, there is a dire need to improve their hepatic differentiation. This study examines a pretreatment strategy to augment the differentiation potential of MSCs towards hepatic lineage. MSCs were isolated from C57BL/6 wild type mice and were characterized by flow cytometry for CD44 (92.4%), CD90 (96.6%), CD105 (94.7%), CD45 (0.8%) and CD34 (1.4%) markers. To improve the differentiation potential of MSCs towards hepatic lineage, cells were pretreated with injured liver tissue in an in-vitro model, which resulted in high expression of albumin, cytokeratin 8, 18, TAT and HNF1α as compared to untreated MSCs. The efficacy of pretreated MSCs was evaluated by preparing in-vivo mouse model with liver fibrosis by intraperitoneal administration of CCl(4). Pretreated MSCs were transplanted in the left lateral lobe of mice with liver fibrosis and showed enhanced localization and differentiation abilities after 1 month. The expression for cytokeratin 8, 18, albumin and Bcl-xl was up-regulated and that of HGF, Bax and Caspase- 3 was down-regulated in animals transplanted with pretreated MSCs. Sirus red staining also confirmed a significant reduction in the fibrotic area in liver tissue transplanted with pretreated MSCs as compared to untreated MSCs and was concomitant with improved serum levels of bilirubin and alkaline phosphatase (ALP). Therefore, it was concluded that pretreatment with injured liver tissue augment homing and hepatic differentiation abilities of MSCs and provides an improved procedure for the treatment of liver fibrosis.     

Hepatic fibrogenesis using chronic arsenic ingestion: studies in a murine model

Chronic oral arsenic (As) ingestion has been alleged to cause hepatic fibrosis, non-cirrhotic portal fibrosis and cirrhosis of the liver. The present study was aimed to investigate if hepatic fibrogenesis and non-cirrhotic portal fibrosis (NCPF) is caused by arsenic. A significant increase in the hepatic protein and collagen was seen compared with controls; hepatic 4-hydroxyproline levels, indicative of fibrogenesis, were increased 4-14 folds with different dosages of arsenic compared to the controls. Hepatocellular necrosis and inflammation were negligible to mild in all the groups. None of the animals developed significant splenomegaly or features of non-cirrhotic portal hypertension. The results suggest that (i) prolonged oral arsenic ingestion in mice leads to significant hepatic fibrogenesis and collagen synthesis with minimal hepato-cellular injury; (ii) arsenic ingestion alone is unlikely to cause non-cirrhotic portal fibrosis or cirrhosis of liver. This murine model of arsenic feeding could be used for the evaluation of new antifibrotic agents for the liver.     

Effect of nitric oxide on the differentiation of fibroblasts into myofibroblasts in the Peyronie’s fibrotic plaque and in its rat model

The myofibroblast shares phenotypic features of both fibroblasts and smooth muscle cells. It plays a critical role in collagen deposition and wound healing and disappears by apoptosis when the wound is closed. Its abnormal persistence leads to hypertrophic scar formation and other fibrotic conditions. Myofibroblasts are present in the fibrotic plaque of the tunica albuginea (TA) of the penis in men with Peyronie's disease (PD), a localized fibrosis that is accompanied by a spontaneous induction of the inducible nitric oxide synthase (iNOS), also observed in the TGFbeta1-elicited, PD-like lesion in the rat model. iNOS expression counteracts fibrosis, by producing nitric oxide (NO) that reduces collagen deposition in part by neutralization of profibrotic reactive oxygen species. In this study we investigated whether fibroblast differentiation into myofibroblasts is enhanced in the human and rat PD-like plaque and in cultures of human tissue fibroblasts. We also examined whether NO reduces this cell differentiation and collagen synthesis. The myofibroblast content in the fibroblast population was measured by quantitative immunohistochemistry as the ratio between alpha-smooth muscle actin (ASMA; myofibroblast marker) and vimentin (general fibroblast marker) levels. We found that myofibroblast content was considerably increased in the human and TGFbeta1-induced rat plaques as compared to control TA. Inhibition of iNOS activity by chronic administration of L-iminoethyl-L-lysine to rats with TGFbeta1-induced TA lesion increased myofibroblast abundance and collagen I synthesis measured in plaque and TA homogenates from animals injected with a collagen I promoter construct driving the expression of beta-galactosidase. Fibroblast differentiation into myofibroblasts occurred with passage in the cell cultures from the human PD plaque, but was minimal in cultures from the TA. Induction of iNOS in PD and TA cultures with a cytokine cocktail and a NO donor, S-nitroso-N-acetyl penicillamine (SNAP), was detected by immunohistochemistry. Both treatments reduced the total number of cells and the number of ASMA positive cells, whereas only SNAP decreased collagen I immunostaining. These results support the hypotheses that myofibroblasts play a role in the development of the PD plaque and that the antifibrotic effects of NO may be mediated at least in part by the reduction of myofibroblast abundance and lead to a reduction in collagen I synthesis.     

Myofibroblast - like cells and liver fibrogenesis: Emerging concepts in a rapidly moving scenario

Fibrotic progression of chronic liver diseases of different aetiology to the common advanced-stage of cirrhosis can be envisaged as a dynamic and highly integrated cellular response to chronic liver injury. Liver fibrosis is accompanied by perpetuation of liver injury, chronic hepatitis and persisting activation of tissue repair mechanisms, leading eventually to excess deposition of ECM components. Liver fibrogenesis (i.e., the process) is sustained by populations of highly proliferative, pro-fibrogenic and contractile MFs that, according to current literature, originate by a process of activation involving perisinusoidal HSC, portal fibroblasts and even bone marrow-derived MSC. In this short review emerging concepts in hepatic fibrogenesis and related molecular mechanisms, as provided by recent experimental and clinical studies, are presented.     

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.     

Enhanced deposition of cartilage oligomeric matrix protein is a common feature in fibrotic skin pathologies

Skin fibrosis is characterized by activated fibroblasts and an altered architecture of the extracellular matrix. Excessive deposition of extracellular matrix proteins and altered cytokine levels in the dermal collagen matrix are common to several pathological situations such as localized scleroderma and systemic sclerosis, keloids, dermatosclerosis associated with venous ulcers and the fibroproliferative tissue surrounding invasively growing tumors. Which factors contribute to altered organization of dermal collagen matrix in skin fibrosis is not well understood. We recently demonstrated that cartilage oligomeric matrix protein (COMP) functions as organizer of the dermal collagen I network in healthy human skin (Agarwal et al., 2012). Here we show that COMP deposition is enhanced in the dermis in various fibrotic conditions. COMP levels were significantly increased in fibrotic lesions derived from patients with localized scleroderma, in wound tissue and exudates of patients with venous leg ulcers and in the fibrotic stroma of biopsies from patients with basal cell carcinoma. We postulate enhanced deposition of COMP as one of the common factors altering the supramolecular architecture of collagen matrix in fibrotic skin pathologies. Interestingly, COMP remained nearly undetectable in normally healing wounds where myofibroblasts transiently accumulate in the granulation tissue. We conclude that COMP expression is restricted to a fibroblast differentiation state not identical to myofibroblasts which is induced by TGFβ and biomechanical forces.     

Estimation of collagen content of liver specimens. Variation among animals and among hepatic lobes in cirrhotic rats

We undertook a study to evaluate the correlation between morphometric evaluation and colorimetric determination of hepatic collagen content, and to analyze the variation among animals as well as among lobes of the same liver in hepatic collagen content after CCl4-induced micronodular cirrhosis. The results revealed a significant correlation (r = 0.9458; p less than 0.001) between the morphometric and colorimetric methods of collagen evaluation of liver specimens; both methods also significantly distinguished data obtained from controls and from cirrhotic rats (p less than 0.0005). After induction of micronodular cirrhosis by chronic CCl4 administration, a highly significant variation in hepatic collagen content was observed among animals (p less than 0.0001). By contrast, no significant difference in collagen content was observed (p less than 0.05) among hepatic lobes of a given animal. These results indicate that in this animal model of liver cirrhosis, interpretation of biochemical data would benefit by being related to the severity of the hepatic collagen infiltration of each animal. Our data also show that representative values for total hepatic collagen infiltration can be obtained from a single liver specimen; we suggest, however, that the specimen be taken from a major lobe of the liver and that a sufficiently large number of animals be used to avoid occasional sampling errors.     

A novel acetyltransferase p300 inhibitor ameliorates hypertension-associated cardio-renal fibrosis

Hypertension-associated end-organ damage commonly leads to cardiac and renal fibrosis. As no effective anti-fibrotic therapy currently exists, the unchecked progression of fibrogenesis manifests as cardio-renal failure and early death. We have previously shown that FATp300—p300 with intrinsic factor acetyltransferase activity—is an essential epigenetic regulator of fibrogenesis, and is elevated in several fibrotic tissues. In this report, we investigate the therapeutic efficacy of a novel FATp300 inhibitor, L002, in a murine model of hypertensive cardio-renal fibrosis. Additionally, we examine the effects of L002 on cellular pro-fibrogenic processes and provide mechanistic insights into its antifibrogenic action. Utilizing cardiac fibroblasts, podocytes, and mesangial cells, we demonstrate that L002 blunts FATp300-mediated acetylation of specific histones. Further, incubating cells with L002 suppresses several pro-fibrogenic processes including cellular proliferation, migration, myofibroblast differentiation and collagen synthesis. Importantly, systemic administration of L002 in mice reduces hypertension-associated pathological hypertrophy, cardiac fibrosis and renal fibrosis. The anti-hypertrophic and anti-fibrotic effects of L002 were independent of blood pressure regulation. Our work solidifies the role of epigenetic regulator FATp300 in fibrogenesis and establishes it as a pharmacological target for reducing pathological matrix remodeling and associated pathologies. Additionally, we discover a new therapeutic role of L002, as it ameliorates hypertension-induced cardio-renal fibrosis and antagonizes pro-fibrogenic responses in fibroblasts, podocytes and mesangial cells.