Apoptosis of T cells in the hepatic fibrotic tissue of the rat: a possible inducing role of hepatic myofibroblast-like cells

Cellular Interactions and Crosstalk Facilitating Biliary Fibrosis in Cholestasis

Biliary fibrosis is seen in cholangiopathies, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). In PBC and PSC, biliary fibrosis is associated with worse outcomes and histologic scores. Within the liver, both hepatic stellate cells (HSCs) and portal fibroblasts (PFs) contribute to biliary fibrosis, but their roles can differ. PFs reside near the bile ducts and may be the first responders to biliary damage, whereas HSCs may be recruited later and initiate bridging fibrosis. Indeed, different models of biliary fibrosis can activate PFs and HSCs to varying degrees. The portal niche can be composed of cholangiocytes, HSCs, PFs, endothelial cells, and various immune cells, and interactions between these cell types drive biliary fibrosis. In this review, we discuss the mechanisms of biliary fibrosis and the roles of PFs and HSCs in this process. We will also evaluate cellular interactions and mechanisms that contribute to biliary fibrosis in different models and highlight future perspectives and potential therapeutics.

The Heterogeneity of the Tumor Microenvironment as Essential Determinant of Development, Progression and Therapy Response of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is commonly diagnosed at advanced stages and most anti-cancer therapies have failed to substantially improve prognosis of PDAC patients. As a result, PDAC is still one of the deadliest tumors. Tumor heterogeneity, manifesting at multiple levels, provides a conclusive explanation for divergent survival times and therapy responses of PDAC patients. Besides tumor cell heterogeneity, PDAC is characterized by a pronounced inflammatory stroma comprising various non-neoplastic cells such as myofibroblasts, endothelial cells and different leukocyte populations which enrich in the tumor microenvironment (TME) during pancreatic tumorigenesis. Thus, the stromal compartment also displays a high temporal and spatial heterogeneity accounting for diverse effects on the development, progression and therapy responses of PDAC. Adding to this heterogeneity and the impact of the TME, the microbiome of PDAC patients is considerably altered. Understanding this multi-level heterogeneity and considering it for the development of novel therapeutic concepts might finally improve the dismal situation of PDAC patients. Here, we outline the current knowledge on PDAC cell heterogeneity focusing on different stromal cell populations and outline their impact on PDAC progression and therapy resistance. Based on this information, we propose some novel concepts for treatment of PDAC patients.

Hepatic stellate cells - from past till present: morphology, human markers, human cell lines, behavior in normal and liver pathology

Hepatic stellate cell (HSC), initially analyzed by von Kupffer, in 1876, revealed to be an extraordinary mesenchymal cell, essential for both hepatocellular function and lesions, being the hallmark of hepatic fibrogenesis and carcinogenesis. Apart from their implications in hepatic injury, HSCs play a vital role in liver development and regeneration, xenobiotic response, intermediate metabolism, and regulation of immune response. In this review, we discuss the current state of knowledge regarding HSCs morphology, human HSCs markers and human HSC cell lines. We also summarize the latest findings concerning their roles in normal and liver pathology, focusing on their impact in fibrogenesis, chronic viral hepatitis and liver tumors.

Stellate Cell Activation and Imbalanced Expression of TGF-β1/TGF-β3 in Acute Autoimmune Liver Lesions Induced by ConA in Mice

Objective. To study the pathogenic feature of liver injury, activation of hepatic stellate cells, and dynamic expression of TGF-β1/TGF-β3 to reveal their role in liver injury induced by ConA. Methods. Mice were randomly divided into control group and ConA treatment group. ConA (20 mg/kg) was injected through vena caudalis in ConA treatment group; the controls received the same volume of saline injection. After injection for 2 h, 8 h, 24 h, and 48 h, animals were terminated. Blood, liver, and spleen were harvested. Liver function and histopathology were studied. α-SMA, vimentin, TGF-β1, and TGF-β3 were detected. Results. After ConA injection, liver damage started to increase. Expression of α-SMA, vimentin, TGF-β1, and TGF-β3 was significantly enhanced; all above indicators reached peak at 8 h; but from 24 h after ConA injection, TGF-β3 expression began to decline, while the TGF-β1/TGF-β3 ratio at 48 h was significantly lower than control. Conclusion. (1) Autoimmune liver injury induced by ConA showed time-based features, in which the most serious liver lesions happened at 8 h after ConA injection. (2) Early activation of HSC and imbalance expression of TGF-β1 and TGF-β3 existed in ConA-induced acute autoimmune liver injury, which may be associated with liver dysfunction and the mechanisms of progression to fibrosis.

Functional Immune Anatomy of the Liver-As an Allograft

The liver is an immunoregulatory organ in which a tolerogenic microenvironment mitigates the relative "strength" of local immune responses. Paradoxically, necro-inflammatory diseases create the need for most liver transplants. Treatment of hepatitis B virus, hepatitis C virus, and acute T cell-mediated rejection have redirected focus on long-term allograft structural integrity. Understanding of insults should enable decades of morbidity-free survival after liver replacement because of these tolerogenic properties. Studies of long-term survivors show low-grade chronic inflammatory, fibrotic, and microvascular lesions, likely related to some combination of environment insults (i.e. abnormal physiology), donor-specific antibodies, and T cell-mediated immunity. The resultant conundrum is familiar in transplantation: adequate immunosuppression produces chronic toxicities, while lightened immunosuppression leads to sensitization, immunological injury, and structural deterioration. The "balance" is more favorable for liver than other solid organ allografts. This occurs because of unique hepatic immune physiology and provides unintended benefits for allografts by modulating various afferent and efferent limbs of allogenic immune responses. This review is intended to provide a better understanding of liver immune microanatomy and physiology and thereby (a) the potential structural consequences of low-level, including allo-antibody-mediated injury; and (b) how liver allografts modulate immune reactions. Special attention is given to the microvasculature and hepatic mononuclear phagocytic system.

Activated rat hepatic stellate cells influence Th1/Th2 profile in vitro

AIM: To investigate the effects of activated rat hepatic stellate cells (HSCs) on rat Th1/Th2 profile in vitro.

METHODS: Growth and survival of activated HSCs and CD4⁺ T lymphocytes cultured alone or together was assessed after 24 or 48 h. CD4⁺ T lymphocytes were then cultured with or without activated HSCs for 24 or 48 h and the proportion of Th1 [interferon (IFN)-γ⁺] and Th2 [interleukin (IL)-4⁺] cells was assessed by flow cytometry. Th1 and Th2 cell apoptosis was assessed after 24 h of co-culture using a caspase-3 staining procedure. Differentiation rates of Th1 and Th2 cells from CD4⁺ T lymphocytes that were positive for CD25 but did not express IFN-γ or IL-4 were also assessed after 48 h of co-culture with activated HSCs. Galectin-9 expression in HSCs was determined by immunofluorescence and Western blotting. ELISA was performed to assess galectin-9 secretion from activated HSCs.

RESULTS: Co-culture of CD4⁺ T lymphocytes with activated rat HSCs for 48 h significantly reduced the proportion of Th1 cells compared to culture-alone conditions (-1.73% ± 0.71%; P < 0.05), whereas the proportion of Th2 cells was not altered; the Th1/Th2 ratio was significantly decreased (-0.44 ± 0.13; P < 0.05). In addition, the level of IFN-γ in Th1 cells was decreased (-65.71 ± 9.67; P < 0.01), whereas the level of IL-4 in Th2 cells was increased (82.79 ± 25.12; P < 0.05) by co-culturing, as measured by mean fluorescence intensity by flow cytometry. Apoptosis rates in Th1 (12.27% ± 0.99%; P < 0.01) and Th2 (1.71% ± 0.185%; P < 0.01) cells were increased 24 h after co-culturing with activated HSCs; the Th1 cell apoptosis rate was significantly higher than in Th2 cells (P < 0.01). Galectin-9 protein expression was significantly decreased in HSCs only 24 h after co-culturing (P < 0.05) but not after 48 h. Co-culture for 48 h significantly increased the differentiation of Th1 and Th2 cells; however, the increase in the proportion of Th2 cells was significantly higher than that of Th1 cells (1.85% ± 0.48%; P < 0.05).

CONCLUSION: Activated rat HSCs lower the Th1/Th2 profile, inhibiting the Th1 response and enhancing the Th2 response, and this may be a novel pathway for liver fibrogenesis.

Fenofibrate A peroxisome proliferator activated receptor-α agonist treatment ameliorates Concanavalin A-induced hepatitis in rats

Peroxisome proliferator-activated receptor-α (PPARα) is physiologically highly expressed by hepatocytes, where it plays a pivotal anti-inflammatory and metabolic role. The decrease expression and functional activity of PPARα in hepatocytes during hepatitis C virus infection may contribute to the pathogenesis of the disease in humans. This study aims at evaluating the effects of PPARα activation with fenofibrate (FF) on liver inflammation, fibrosis and portal pressure (PP) in Concanavalin A (Con A)- induced hepatitis in rats. The rats were randomly divided to 3 groups; control (1 ml saline iv/wk) group, Con A (20mg/kg/iv/wk) group and Con A with FF (100mg/kg/day p.o) group. Blood samples and livers were collected by the end of the first, second, fourth and eighth injections of Con A for biochemical, histopathological and immunohistochemistry studies for α-smooth muscle actin (α SMA). Measurement of PP was performed by the end of the 8th week. FF group had a significant (P<0.05) decrease of serum alanine and aspartate aminotransferases with significant reduction of hepatic tumor necrosis factor alpha and malondialdehyde levels than Con A group. Histopathological examination revealed that treatment with FF significantly suppressed early inflammation, reduced α SMA, and apoptosis of hepatocytes induced by Con A, thereby preventing the progression of chronic liver injury and fibrosis. In addition FF group had a significantly lower PP (-89.0%) than Con A group. In conclusion PPARα activation significantly reduced liver inflammation, fibrosis and PP in Con A model of hepatitis that may represent a new therapeutic strategy for hepatitis and its complications.

T-cell apoptosis induced by intratumoral activated hepatic stellate cells is associated with lung metastasis in hepatocellular carcinoma

Profound T cell inhibitory activity of hepatic stellate cells (HSCs) in vitro has recently been described in hepatocellular carcinoma (HCC). In the present study, we investigated the immune inhibitory activity of HSCs in vivo in an orthotopic rat HCC model with lung metastasis. Rats (n=24) were randomly sacrificed on days 7, 14, 21 and 28 (n=4 each). Lung tissues were stained with hematoxylin and eosin. Liver sections were stained for immunofluorescence analysis. T-cell apoptosis was detected using double staining for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Staining revealed marked and continuous accumulation of α-smooth muscle actin with tumor progression after orthotopic tumor implantation in rat liver. T lymphocyte numbers gradually increased following tumor progression, and subset analysis revealed an increase in the distribution of liver CD8+ and CD4+ T cells. Double staining for CD3 and TUNEL demonstrated T-cell apoptosis. Apoptotic T cells were more frequent in the HCC livers compared to the normal livers, and were spatially associated with intratumoral activated HSCs (tHSCs), suggesting a direct interaction. T-cell apoptosis was more frequently induced in the co-cultures of activated splenic T cells(aT)/tHSCs compared to aT/quiescent (q) HSCs or qT/tHSCs. tHSCs were positively correlated with T-cell apoptosis, and the percentage of T-cells undergoing apoptosis was positively correlated with the number of lung metastasis nodules. T-cell apoptosis may be promoted via an interaction with tHSCs, suggesting that tHSCs regulate T cells and contribute to lung metastasis in HCC.

Inhibition of T-cell responses by intratumoral hepatic stellate cells contribute to migration and invasion of hepatocellular carcinoma

The stroma of hepatocellular carcinoma (HCC) is markedly infiltrated with activated hepatic stellate cells (HSCs), and associated invasion and metastasis of HCC. However, little is known of the role of HSCs in immune responses in HCC. The Buffalo rat HCC model was established. Quiescent HSCs (qHSCs) and intratumoral HSCs (tHSCs) were isolated. Surface molecules of tHSC were detected by flow cytometry, and gene expression was analyzed by fluorescence quantitative RT-PCR. T cell proliferation was monitored by [(3)H]-thymidine ((3)H-TdR) incorporation into DNA, and cytotoxic activity was assessed by measuring the release of (51)Cr. The level of cytokine expression by T cells was measured by enzyme-linked immunosorbent assay. T cell apoptosis was detected by double-stained terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and anti-CD3 antibodies. The migration and invasion of HCC was observed by transwell experiments. tHSCs express low levels of major histocompatibility complex (MHC) class I, MHC class II, and costimulatory molecules, and produce varying levels of cytokines. Addition of the tHSCs suppressed thymidine uptake by T cells that were stimulated by alloantigens or by anti-CD3-mediated T-cell receptor ligation. The tHSC-induced T-cell hyporesponsiveness was associated with enhanced T-cell apoptosis, and contributed to the migration and invasion of hepatoma cell. tHSCs was associated with markedly enhanced expression of B7-H1. Blockade of B7-H1/PD-1 ligation significantly reduced HSC immunomodulatory activity, and hepatoma cell migration and invasion. tHSCs can induce T cell apoptosis, suggesting an important role for B7-H1. The interactions between tHSCs and T cells may contribute to hepatic immune tolerance and invasion and migration of HCC.

Mononuclear cells in liver fibrosis

Fibrosis is a multicellular wound healing process, where myofibroblasts that express extracellular matrix components extensively cross-talk with other cells resident in the liver or recruited from the bloodstream. Macrophages and infiltrating monocytes participate in the development of fibrosis via several mechanisms, including secretion of cytokines and generation of oxidative stress-related products. However, macrophages are also pivotal in the process of fibrosis resolution, where they contribute to matrix degradation. T lymphocytes modulate the fibrogenic process by direct interaction with myofibroblasts and secreting cytokines. In general, Th2 polarized responses promote fibrosis, while Th1 cytokines may be antifibrogenic. NK cells limit the development of fibrosis and favor its resolution, at least in part via killing of fibrogenic cells. The possible role of NKT cells and B cells is emerging in recent studies. Thus, mononuclear cells represent a critical regulatory system during fibrogenesis and may become an appealing target for therapy.

Systematic review: hepatic fibrosis - regression with therapy

BACKGROUND

Hepatic fibrosis occurs in response to chronic liver injury, regardless of the cause. An impressive amount of knowledge concerning the pathogenesis and treatment of liver fibrosis has emerged over the past few years. The hallmark of this event is the activation of the hepatic stellate cell. The latter event causes accumulation of extracellular matrix and formation of scar, leading to deterioration in hepatic function.

AIM

To assess chronic liver injury, many invasive and non-invasive methods have been suggested.

METHODS

Although transient elastography, image analysis of fractal geometry and fibrotest with actitest have been used in clinical practice, liver biopsy remains the recommended choice, especially when histological staging of fibrosis or response to treatment is needed.

CONCLUSIONS

The recent advances in anti-viral therapy have resulted in many reports on fibrosis and even on cirrhosis regression, especially early and in young people. A number of new agents have been suggested for the treatment of fibrosis, with promising results in animals; however, their efficacy in humans remains to be elucidated. The investigation of heterogeneity and plasticity of hepatic stellate cells is a topic of scientific interest and may result in improvements in patient management.

Mononuclear cells modulate the activity of pancreatic stellate cells which in turn promote fibrosis and inflammation in chronic pancreatitis

Background

Interactions between mononuclear cells and activated pancreatic myofibroblasts (pancreatic stellate cells; PSC) may contribute to inflammation and fibrosis in chronic pancreatitis (CP).

Methods

Markers of fibrosis and inflammation were concomitantly analysed by immunohistochemistry in chronic pancreatitis tissues. In vitro, PSC were stimulated with TNFalpha and LPS. Primary human blood mononuclear cells (PBMC) and PSC were cocultured, followed by analysis of cytokines and extracellular matrix (ECM) proteins. PBMC were derived from healthy donors and CP and septic shock patients.

Results

In areas of mononuclear cell infiltration in chronic pancreatitis tissues, there was decreased immunoreactivity for collagen1 and fibronectin, in contrast to areas with sparse mononuclear cells, although PSC were detectable in both areas. LPS and TNFalpha induced collagen1 and fibronectin levels as well as the matrix degradation enzyme MMP-1. Coculture experiments with PSC and PBMC revealed increased fibronectin secretion induced by PBMC. In addition, donor and CP PBMC significantly induced an increase in IL-6, MCP-1 and TGFbeta levels under coculture conditions. Determination of the source of cytokines and ECM proteins by mRNA expression analysis confirmed PSC as major contributors of ECM production. The increase in cytokine expression was PBMC- and also PSC-derived.

Conclusion

Mononuclear cells modulate the activity of pancreatic stellate cells, which may in turn promote fibrosis and inflammation.

Cotransplanted hepatic stellate cells enhance vascularization of islet allografts

Islet transplantation is an alternative to whole pancreas transplantation in curative therapy of diabetics. The outcome of engraftment of islet, however, remains disappointing. Rapid and adequate islet revascularization is crucial for the survival and function of transplanted islets. In this study, hepatic stellate cells (HSC) were cotransplanted with islet allografts, achieving marked prolongation of islet allografts. This was associated with enhanced revascularization within islet grafts as determined by anti-CD31 antibody staining.

The Mechanism of How Anti-IL-18 Prevents Concanavalin-A-Induced Hepatic Fibrosis on a Mouse Model

BACKGROUND

The administration of concanavalin A (ConA) induces severe hepatic fibrosis in mice. Tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) and interleukin 4 (IL-4) were the key cytokines involved in the process. The aim of this research was to explore the effects and the mechanisms of IL-18 and anti-IL-18 on hepatic fibrosis in a ConA induced hepatic fibrosis model in BABL-C mice.

MATERIALS AND METHODS

One hundred eighty BABL-C mice were randomly divided into five groups (Group a, b, c, d, e). The mice were administered saline, immunoglobulin G, ConA, IL-18 + ConA, Anti-IL-18 + ConA, respectively. At 1, 7, 14, 21 wk, the levels of serum alanine aminotransferase, TNF-alpha, IFN-gamma, IL-4, matrix metalloproteinase (MMP)-2-RNA, and tissue inhibitor of metalloproteinase-1-mRNA were measured.

RESULTS

The levels of serum TNF-alpha and IFN-gamma detected in the IL-18 + ConA group was higher than in the anti-IL-18 + ConA group (P < 0.05). Similarly, the levels of MMP-2-RNA and tissue inhibitor of metalloproteinase-1-mRNA expressed in IL-18 + ConA group was higher than in the anti-IL-18 + ConA group (P < 0.05). A majority of these cytokines was secreted by CD4(+)T cells.

CONCLUSIONS

The immunological response to hepatic fibrosis by repeated injection of ConA in the mouse model was aggravated by IL-18 and blocked by anti-IL-18.

Erythrophagocytosis by liver macrophages (Kupffer cells) promotes oxidative stress, inflammation, and fibrosis in a rabbit model of steatohepatitis: implications for the pathogenesis of human nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. Here, we report a molecular aspect of this disease elucidated using rabbits fed a cholesterol-rich high-fat diet and exhibiting insulin resistance. The liver in this model showed steatohepatitis with fibrosis and high mRNA expression for some cytokines, heme oxygenase-1, transforming growth factor-beta1, and collagen alpha1(I). Erythrocytes isolated from the model showed marked fragility and the externalization of phosphatidylserine (PS) on the outer leaflet of the membrane and were frequently engulfed by Kupffer cells/macrophages in the hepatic sinusoids. Expression of milk fat globule-epidermal growth factor (EGF)-factor 8, a PS-binding protein, was augmented in the liver. In culture, RAW 264.7 cells engulfed erythrocytes oxidized by tert-butyl hydroperoxide, a process that was inhibited by anti-milk fat globule-EGF-factor 8 antibody. In addition, PS-positive erythrocytes appeared entrapped in the model liver in ex vivo perfusion experiments. Finally, in specimens from NASH patients, the aggregation of erythrocytes in inflammatory hepatic sinusoids was notable. These results indicate that the engulfment of PS-externalized, apoptotic signal-positive, erythrocytes by hepatic macrophages may lead to the deposition of iron derived from hemoglobin in the liver and be involved in the pathogenesis of steatohepatitis.

Expression of NCAM in activated portal fibroblasts during regeneration of the rat liver after partial hepatectomy

In the portal tract of the regenerating liver after partial hepatectomy, vascular and bile ductular remodeling takes place in response to the portal hyperdynamic state and parenchymal hyperplasia. In order to reveal phenotypical changes in the portal fibroblasts, we immunohistochemically investigated neural cell adhesion molecules (NCAM) and alpha smooth muscle actin (alphaSMA) expression and the ultrastructural changes in them during liver regeneration. In the control rat liver, portal fibroblasts were negative for both NCAM and alphaSMA. They became positive for both markers two days after partial hepatectomy, increased in staining intensity, reached a maximum at three to four days, then decreased, being still clearly positive at 14 days. Under an electron microscope, portal fibroblasts from the regenerating liver had larger amounts of cytoplasm and rough endoplasmic reticulum than those from the control liver; thus they might be activated. Additionally, periportal hepatic stellate cells in the regenerating liver were activated with alphaSMA, but without NCAM. The present study has demonstrated that portal fibroblasts express NCAM and alphaSMA in the regenerating liver after partial hepatectomy via transformation into myofibroblasts following reconstruction of the portal tracts.

Mechanisms of Disease: mechanisms of hepatic fibrosis and therapeutic implications

Hepatic fibrosis, or scarring of the liver, is emerging as a treatable complication of advanced liver disease, following significant progress in understanding its underlying mechanisms. Efforts have focused on the hepatic stellate cell, as these cells can undergo 'activation' into proliferative and fibrogenic myofibroblast-like cells during liver injury. Stimuli driving stellate cell activation include hepatocellular necrosis due to oxidant stress, apoptosis, and soluble growth factors. Specific lymphocyte subsets can also stimulate fibrogenesis. A cascade of signaling and transcriptional events in stellate cells underlies the fibrogenic response to liver injury, with each step in the cascade being a potential target for antifibrotic therapy. Disease-specific fibrogenic mechanisms have also been uncovered: in hepatitis C, this may include direct stimulation of stellate cell activation by viral infection; in nonalcoholic steatohepatitis, elevated levels of leptin and increased leptin signaling by stellate cells increase fibrogenesis. Determinants of fibrosis progression include both environmental and genetic factors, with ongoing efforts to define specific polymorphisms correlating with fibrosis progression rates. Human studies now indicate that fibrosis and even cirrhosis could be reversible, especially if the underlying disease is eradicated. A key challenge is to establish noninvasive means of assessing fibrosis stage and progression using either serum tests and/or imaging. In addition, endpoints of antifibrotic clinical trials need to be established so that reliable evidence of benefit can be identified. We are on the cusp of a new era in which antifibrotic therapies could become important in treating chronic fibrosing liver disease.

Inhibition of T-cell responses by hepatic stellate cells via B7-H1-mediated T-cell apoptosis in mice

In the injured liver, hepatic stellate cells (HSCs) secrete many different cytokines, recruit lymphocytes, and thus participate actively in the pathogenesis of liver disease. Little is known of the role of HSCs in immune responses. In this study, HSCs isolated from C57BL/10 (H2b) mice were found to express scant key surface molecules in the quiescent stage. Activated HSCs express major histocompatibility complex class I, costimulatory molecules, and produce a variety of cytokines. Stimulation by interferon gamma (IFN-gamma) or activated T cells enhanced expression of these molecules. Interestingly, addition of the activated (but not quiescent) HSCs suppressed thymidine uptake by T cells that were stimulated by alloantigens or by anti-CD3-mediated T-cell receptor ligation in a dose-dependent manner. High cytokine production by the T cells suggests that the inhibition was probably not a result of suppression of their activation. T-cell division was also found to be normal in a CFSE dilution assay. The HSC-induced T-cell hyporesponsiveness was associated with enhanced T-cell apoptosis. Activation of HSCs was associated with markedly enhanced expression of B7-H1. Blockade of B7-H1/PD-1 ligation significantly reduced HSC immunomodulatory activity, suggesting an important role of B7-H1. In conclusion, the bidirectional interactions between HSCs and immune cells may contribute to hepatic immune tolerance.

Immune stimulation of hepatic fibrogenesis by CD8 cells and attenuation by transgenic interleukin-10 from hepatocytes

BACKGROUNDS & AIMS

Immunomodulatory cytokines, including interleukin-10 (IL-10), may mediate hepatic fibrosis.

METHODS

We generated transgenic (TG) mice with hepatocyte expression of rat IL-10 (rIL-10) to assess its impact on lymphocyte subsets and activation of hepatic stellate cells following liver injury from carbon tetrachloride (CCl 4 ) or thioacetamide (TAA).

RESULTS

Fibrosis was reduced in the TG animals in both models, which was not explained solely by differences in liver injury. By fluorescence-activated cell sorter (FACS), there were less CD4+ T cells in naive TG mice, and, following fibrosis induction, CD4+ T cells decreased only in wild-type (WT) mice, whereas increases in CD8+ T cells seen in WT animals were significantly attenuated in TG mice. Subtotal irradiation diminished fibrosis equally in both WT and TG groups, suggesting that rIL-10's antifibrotic effect was lymphocyte mediated. To assess the role of lymphocytes on stellate cell activation, either whole splenic lymphocytes, CD4+, or CD8+ T-cell subsets from WT animals with CCl 4 fibrosis were adoptively transferred to severe combined immunodeficiency (SCID) recipients, which led to stellate cell activation and fibrogenic stimulation as assessed by expression of transforming growth factor (TGF)-beta1 and collagen I messenger RNA (mRNA) and by immunoblot of alpha-smooth muscle actin. Moreover, serum aminotransferase levels and stellate cell activation mRNA were significantly higher among the CD8+ T-cell recipients.

CONCLUSIONS

Transgenic expression of rIL-10 in liver leads to reduced fibrosis and alterations in liver lymphocyte subsets both in untreated liver and following fibrosis induction. In this model, fibrosis may be a CD8+ T-cell-mediated disease that is attenuated by rIL-10.

Cytoglobin/STAP, its unique localization in splanchnic fibroblast-like cells and function in organ fibrogenesis

Cytoglobin/stellate cell activation-associated protein (Cygb/STAP) consists of a new class of hexacoordinate globin superfamily, which was recently discovered by a proteome analysis on the rat hepatic stellate cells. Unlike haemoglobin, myoglobin, and neuroglobin, Cygb/STAP is ubiquitously expressed in several organs, although its detailed localization has not been clarified. Immunohistochemistry and immunoelectron microscopy revealed that Cygb/STAP is uniquely localized in fibroblast-like cells in splanchnic organs, namely the vitamin A-storing cell lineage, but neither in epithelial cells, endothelial cells, muscle cells, blood cells, macrophages, nor dermal fibroblasts. The expression of Cygb/STAP was upregulated in fibrotic lesions of the pancreas and kidney in which activated fibroblast-like cells or myofibroblasts are known to increase in number. In cultured hepatic stellate cells, Cygb/STAP expression was augmented by the stimulation with sera, platelet-derived growth factor-BB, and transforming growth factor-beta 1. Overexpression of Cygb/STAP in NIH 3T3 cells induced the cells to lessen migratory activities and increase the expression of collagen alpha1(I) mRNA. These results indicate that Cygb/STAP is a tissue globin uniquely localized in splanchnic fibroblastic cell lineage and may play a role in fibrotic organ disorder.