Fibroblast growth factor 2 and transforming growth factor beta 1 interactions in human liver myofibroblasts

Force dependent effects of chronic overuse on fibrosis-related genes and proteins in skeletal muscles

AIM

To examine the chronic effect of force on mRNA and protein expression levels of fibrosis-related genes in flexor digitorum muscles in a rat model of repetitive overuse injury that induces muscle fibrosis at high force levels.

MATERIALS AND METHODS

Two groups of rats were trained to perform a voluntary repetitive lever-pulling task at either a high (HFHR) or a low force (LFHR) for 18 weeks, while a control group (FRC) performed no task. RNA and protein were prepared from forelimb flexor digitorum muscles. Fibrosis-related gene RNA transcripts were evaluated using quantitative PCR (qPCR) and analyzed using the geometric mean of three housekeeping genes or the mean of each individually as reference. Protein levels were quantified using ELISA, western blot, or immunohistofluorescence.

RESULTS

Of eight fibrosis-related mRNAs examined, only FGF2 demonstrated a consistent significant increase in the HFHR group, compared to the FRC group. However, protein amounts of collagen type 1, collagen type 3, and TGFβ1 were significantly higher in the HFHR, compared to the FRC and LFHR groups, while CCN2 and FGF2 were higher in both HFHR and LFHR, compared to the FRC group.

CONCLUSIONS

Our results suggest that there is steady-state transcription of fibrogenic genes in muscles with established fibrosis, implying that post-transcriptional processes are responsible for the increased protein levels of fibrotic factors during muscle overuse conditions. We hypothesize that targeting such pathways represents a valid approach to treat overuse injury. Alternatively, FGF2 gene expression may represent a valid target for therapy.

TGF-β-induced activation of conjunctival fibroblasts is modulated by FGF-2 and substratum stiffness

Purpose

This study aimed to investigate the effects of substratum stiffness on the sensitivity of human conjunctival fibroblasts to transforming growth factor (TGF)-β, and to explore the molecular mechanism of action.

Methods

Human conjunctival fibroblasts were cultured on collagen-coated plastic or silicone plates. The stiffness of the silicone plates was 0.2 or 64 kPa. Cells were treated by 2.5 ng/mL TGF-β2 with or without fibroblast growth factor (FGF)-2 (0–100 ng/mL) for 24 h or 48 h. The protein expression levels were determined by Western blot analysis. Cell proliferation was assessed using the WST-8 assay.

Results

FGF-2 suppressed the TGF-β-induced expression of α-smooth muscle actin (SMA) and collagen type I (Col I), but not fibronectin (FN). Both FGF-2 and TGF-β2 increased cell proliferation without an additive effect. The induction of α-SMA by TGF-β2 was decreased on the soft substratum, without any change in the expression level or subcellular location of Yes-associated protein/transcriptional coactivator with PDZ-binding motif (YAP/TAZ). FGF-2 suppressed TGF-β-induced α-SMA expression even on the soft substratum.

Conclusions

FGF-2 treatment and a soft substratum suppressed TGF-β-induced transdifferentiation of conjunctival fibroblasts into myofibroblasts. FGF-2 attenuated the TGF-β-induced expression of α-SMA, even on a soft substratum.

Fibroblast growth factor 2 conjugated superparamagnetic iron oxide nanoparticles (FGF2-SPIONs) ameliorate hepatic stellate cells activation in vitro and acute liver injury in vivo

Liver diseases are the growing health problem with no clinically approved therapy available. Activated hepatic stellate cells (HSCs) are the key driver cells responsible for extracellular matrix deposition, the hallmark of liver fibrosis. Fibroblast growth factor 2 (FGF2) has shown to possess anti-fibrotic effects in fibrotic diseases including liver fibosis, and promote tissue regeneration. Among the fibroblast growth factor receptors (FGFRs), FGF2 interact primarily with FGFR1, highly overexpressed on activated HSCs, and inhibit HSCs activation. However, FGF2 poses several limitations including poor systemic half-life and stability owing to enzymatic degradation. The aim of this study is to improve the stability and half-life of FGF2 thereby improving the therapuetic efficacy of FGF2 for the treatment of liver fibrosis. We found that FGFR1-3 mRNA levels were overexpressed in cirrhotic human livers, while FGFR1c, 2c, 3c, 4 and FGF2 mRNA levels were overexpressed in TGFβ-activated HSCs (LX2 cells) and FGFR1 protein expression was highly increased in TGFβ-activated HSCs. Treatment with FGF2 inhibited TGFβ-induced HSCs activation, migration and contraction in vitro. FGF2 was conjugated to superparamagnetic iron-oxide nanoparticles (SPIONs) using carbodiimide chemistry, and the resulting FGF2-SPIONs were confirmed by dynamic light scattering (DLS), zeta potential, dot-blot analysis and Prussian Blue iron-staining. In vitro, treatment with FGF2-SPIONs evidenced increased therapeutic effects (attenuated TGFβ-induced HSCs activation, migration and contraction) of FGF2 in TGFβ-activated HSCs and ameliorated early liver fibrogenesis in vivo in acute carbon tetrachloride (CCl₄)-induced liver injury mouse model. In contrast, free FGF2 showed no significant effects in vivo. Altogether, this study presents a promising therapeutic approach using FGF2-SPIONs for the treatment of liver fibrosis.

Reduction of hepatic fibrosis by overexpression of von Hippel-Lindau protein in experimental models of chronic liver disease

Hypoxia-inducible factor (HIF)-1α and HIF-2α play an important role in liver fibrosis. von Hippel–Lindau protein (VHL), a key mediator of HIF-α, regulates fibrosis in an organ- and cell-specific way. In this study, human liver samples were collected from hepatitis C-, alcoholic-, and cholestatic-associated fibrotic and healthy individuals. Two mouse models of liver fibrosis were established: bile duct ligation and carbon tetrachloride injection. We constructed adenovirus vectors to overexpress VHL, normoxia-active HIF-α, and lentiviral vectors to silence HIF-α. The results showed that liver sections from fibrosis patients had a lower level of VHL and higher levels of HIF-1α and HIF-2α compared with healthy sections, a finding which was confirmed in mice. Overexpression of VHL attenuated liver fibrosis, downregulated fibrogenic genes, and inhibited liver inflammation, apoptosis, and angiogenesis. Overexpression of VHL was more successful at inhibiting fibrosis compared with silencing HIF-1α plus HIF-2α. Normoxia-active HIF-1α or HIF-2α prevented the inhibitory effect of VHL on liver fibrosis, indicating that attenuating fibrosis via VHL is HIF-1α- and HIF-2α-dependent to some extent. In addition, overexpression of VHL inhibited mouse hepatic stellate cells activation and proliferation and promoted apoptosis. Taken together, VHL may be considered a new target to inhibit liver fibrosis.

Regulation of Hepatic Stellate Cells and Fibrogenesis by Fibroblast Growth Factors

Fibroblast growth factors (FGFs) are a family of growth factors critically involved in developmental, physiological, and pathological processes, including embryogenesis, angiogenesis, wound healing, and endocrine functions. In the liver, several FGFs are produced basally by hepatocytes and hepatic stellate cells (HSCs). Upon insult to the liver, expression of FGFs in HSCs is greatly upregulated, stimulating hepatocyte regeneration and growth. Various FGF isoforms have also been shown to directly induce HSC proliferation and activation thereby enabling autocrine and paracrine regulation of HSC function. Regulation of HSCs by the endocrine FGFs, namely, FGF15/19 and FGF21, has also recently been identified. With the ability to modulate HSC proliferation and transdifferentiation, targeting FGF signaling pathways constitutes a promising new therapeutic strategy to treat hepatic fibrosis.

Process of hepatic metastasis from pancreatic cancer: biology with clinical significance

PURPOSE

Pancreatic cancer shows a remarkable preference for the liver to establish secondary tumors. Selective metastasis to the liver is attributed to the development of potential microenvironment for the survival of pancreatic cancer cells. This review aims to provide a full understanding of the hepatic metastatic process from circulating pancreatic cancer cells to their settlement in the liver, serving as a basic theory for efficient prediction and treatment of metastatic diseases.

METHODS

A systematic search of relevant original articles and reviews was performed on PubMed, EMBASE and Cochrane Library for the purpose of this review.

RESULTS

Three interrelated phases are delineated as the contributions of the interaction between pancreatic cancer cells and the liver to hepatic metastasis process. Chemotaxis of disseminated pancreatic cancer cells and simultaneous defensive formation of platelets or neutrophils facilitate specific metastasis toward the liver. Remodeling of extracellular matrix and stromal cells in hepatic lobules and angiogenesis induced by proangiogenic factors support the survival and growth of clinical micrometastasis colonizing the liver. The bimodal role of the immune system or prevalence of cancer cells over the immune system makes metastatic progression successfully proceed from micrometastasis to macrometastasis.

CONCLUSIONS

Pancreatic cancer is an appropriate research object of cancer metastasis representing more than a straight cascade. If any of the successive or simultaneous phases, especially tumor-induced immunosuppression, is totally disrupted, hepatic metastasis will be temporarily under control or even cancelled forever. To shrink cancers on multiple fronts and prolong survival for patients, novel oral or intravenous anti-cancer agents covering one or different phases of metastatic pancreatic cancer are expected to be integrated into innovative strategies on the premise of safety and efficacious biostability.

In vitro reversion of activated primary human hepatic stellate cells

Background

Liver fibrosis is characterized by the excessive formation and accumulation of matrix proteins as a result of wound healing in the liver. A main event during fibrogenesis is the activation of the liver resident quiescent hepatic stellate cell (qHSC). Recent studies suggest that reversion of the activated HSC (aHSC) phenotype into a quiescent-like phenotype could be a major cellular mechanism underlying fibrosis regression in the liver, thereby offering new therapeutic perspectives for the treatment of liver fibrosis. Whether human HSCs have the ability to undergo a similar reversion in phenotype is currently unknown. The aim of the present study is to identify experimental conditions that can revert the in vitro activated phenotype of primary human HSCs and consequently to map the molecular events associated with this reversion process by gene expression profiling.

Results

We find that epidermal growth factor (EGF) and fibroblast growth factor 2 (FGF2) synergistically downregulate the expression of ACTA2 and LOX in primary human aHSCs. Their combination with oleic acid, palmitic acid, and retinol further potentiates a more quiescent-like phenotype as demonstrated by the abundant presence of retinyl ester-positive intra-cytoplasmic lipid droplets, low expression levels of activation markers, and a reduced basal as well as cytokine-stimulated proliferation and matrix metalloproteinase activity. Gene expression profiling experiments reveal that these in vitro reverted primary human HSCs (rHSCs) display an intermediary phenotype that is distinct from qHSCs and aHSCs. Interestingly, this intermediary phenotype is characterized by the increased expression of several previously identified signature genes of in vivo inactivated mouse HSCs such as CXCL1, CXCL2, and CTSS, suggesting also a potential role for these genes in promoting a quiescent-like phenotype in human HSCs.

Conclusions

We provide evidence for the ability of human primary aHSCs to revert in vitro to a transitional state through synergistic action of EGF, FGF2, dietary fatty acids and retinol, and provide a first phenotypic and genomic characterization of human in vitro rHSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13069-015-0031-z) contains supplementary material, which is available to authorized users.

SMAD-independent down-regulation of caveolin-1 by TGF-β: effects on proliferation and survival of myofibroblasts

Transforming growth factor-β (TGF-β) mediates growth-inhibitory effects on most target cells via activation of the canonical SMAD signaling pathway. This growth-inhibitory activity may be coupled with cellular differentiation. Our studies demonstrate that TGF-β1 inhibits proliferation of primary, non-transformed human lung fibroblasts in association with the induction of myofibroblast differentiation. Differentiated myofibroblasts maintain the capacity to proliferate in response to exogenous mitogenic stimuli and are resistant to serum deprivation-induced apoptosis. These proliferative and anti-apoptotic properties of myofibroblasts are related, in part, to the down-regulation of caveolin-1 (Cav-1) by TGF-β1. Cav-1 down-regulation is mediated by early activation of p38 MAPK and does not require SMAD signaling. In contrast, myofibroblast differentiation is dependent on activation of the SMAD pathway, but not on p38 MAPK. Thus, combinatorial signaling by TGF-β1 of myofibroblast differentiation and down-regulation of Cav-1 by SMAD and p38 MAPK pathways, respectively, confer proliferative and apoptosis-resistant properties to myofibroblasts. Selective targeting of this SMAD-independent, p38-MAPK/Cav-1-dependent pathway is likely to be effective in the treatment of pathological conditions characterized by TGF-β signaling and myofibroblast activation.

Hepatic stellate cells and liver fibrosis

Hepatic stellate cells are resident perisinusoidal cells distributed throughout the liver, with a remarkable range of functions in normal and injured liver. Derived embryologically from septum transversum mesenchyme, their precursors include submesothelial cells that invade the liver parenchyma from the hepatic capsule. In normal adult liver, their most characteristic feature is the presence of cytoplasmic perinuclear droplets that are laden with retinyl (vitamin A) esters. Normal stellate cells display several patterns of intermediate filaments expression (e.g., desmin, vimentin, and/or glial fibrillary acidic protein) suggesting that there are subpopulations within this parental cell type. In the normal liver, stellate cells participate in retinoid storage, vasoregulation through endothelial cell interactions, extracellular matrix homeostasis, drug detoxification, immunotolerance, and possibly the preservation of hepatocyte mass through secretion of mitogens including hepatocyte growth factor. During liver injury, stellate cells activate into alpha smooth muscle actin-expressing contractile myofibroblasts, which contribute to vascular distortion and increased vascular resistance, thereby promoting portal hypertension. Other features of stellate cell activation include mitogen-mediated proliferation, increased fibrogenesis driven by connective tissue growth factor, and transforming growth factor beta 1, amplified inflammation and immunoregulation, and altered matrix degradation. Evolving areas of interest in stellate cell biology seek to understand mechanisms of their clearance during fibrosis resolution by either apoptosis, senescence, or reversion, and their contribution to hepatic stem cell amplification, regeneration, and hepatocellular cancer.

Response of fibroblasts to transforming growth factor-β1 on two-dimensional and in three-dimensional hyaluronan hydrogels

Transforming growth factor-β1 (TGF-β1), an important cytokine with multiple functions, is secreted during wound healing. Previous studies have utilized two-dimensional (2D) cell culture to elucidate the functions of TGF-β1; however, 2D culture does not represent the complex three-dimensional (3D) in vivo environment. Using a synthetic hyaluronan (HA) extracellular matrix (ECM) hydrogel, we investigated the effect of TGF-β1 on fibroblasts cultured in three conditions--on tissue culture polystyrene (TCP), on HA (2D), and in HA (3D). After TGF-β1 treatment (0.1 to 20 ng/mL), morphological features and ECM regulation were analyzed by immunocytochemistry, Western blot, quantitative polymerase chain reaction, and zymogram assays. On TCP, cells showed the typical spindle shape with strong alpha smooth muscle actin (α-SMA) staining of cytoplasmic myofilaments along the cell axes after TGF-β1 treatment; on HA (2D), spindle-shape cells showed little α-SMA staining; in HA (3D), cells were smaller and rounded with less α-SMA deposition. The α-SMA gene and protein expression on TCP were significantly upregulated by TGF-β1, but TGF-β1 did not induce α-SMA expression in the presence of HA (both 2D and 3D). 3D HA culture significantly downregulated collagen I, III, and fibronectin expression, increased matrix metalloproteinase 1 and 2 (MMP1/MMP2) activity, upregulated MMP1 mRNA and downregulated TIMP3 mRNA expression. This study suggested that exogenous HA, particularly in 3D culture, appears to suppress ECM production, enhances ECM degradation and remodeling, and inhibits myofibroblast differentiation without decreasing TGF-β receptor expression.

NP603, a novel and potent inhibitor of FGFR1 tyrosine kinase, inhibits hepatic stellate cell proliferation and ameliorates hepatic fibrosis in rats

Fibroblast growth factor 2 (FGF-2) and its main receptor FGFR1 have been shown to promote hepatic stellate cell (HSC) activation and proliferation. However, scant information is available on the anti-fibrogenic activity of FGFR1 inhibitors. The aim of this study was to assess the impact of a selective FGFR1 tyrosine kinase inhibitor NP603 on HSC proliferation and hepatic fibrosis. We demonstrated that rat primary HSCs secreted significant amounts of FGF-2, and its tyrosine phosphorylation of FGFR1 was attenuated by NP603. NP603 inhibited HSC activaton by measuring the expression of α-smooth muscle actin (α-SMA) and the production of type I collagen using ELISA. Furthermore, NP603 (25 μM) in vitro strongly suppressed HSC growth induced by FGF-2 (10 ng/ml) and FCS. This effect correlated with the suppression of extracellular-regulated kinase (ERK) activity and its downstream targets cyclin D1 and p21. In addition, PO NP603 (20 mg·kg(-1)·day(-1)) administration significantly decreased hepatic collagen deposition and α-SMA expression in CCl(4)-treated rats. Collectively, these studies suggest that selective blocking of the FGFR1-mediated pathway could be a promising therapeutic approach for the treatment of hepatic fibrosis.

Pancreatic carcinoma cells stimulate proliferation and matrix synthesis of hepatic stellate cells

BACKGROUND/AIMS

Pancreatic ductal carcinoma cells induce fibrosis by stimulating pancreatic stellate cells to proliferate and synthesize matrix. Desmoplastic reaction has also been observed in liver metastases of pancreatic carcinoma. Hepatic stellate cells are similar to pancreatic stellate cells and may contribute to the desmoplasia associated with liver metastases of pancreatic cancer. The aim of this study was to determine the role of hepatic stellate cells in metastasis.

METHODS

Markers of the desmoplastic reaction in tumors induced in nude mice (n=6) by subcutaneously injecting pancreatic carcinoma cells with and without hepatic stellate cells were monitored immunohistochemically. Paracrine stimulation was studied by measuring matrix synthesis (collagen type I and c-fibronectin protein) and cell proliferation.

RESULTS

Supernatants of pancreatic carcinoma cells stimulated proliferation of cultured hepatic stellate cells and synthesis of collagen I and c-fibronectin. Preincubation of the supernatants with neutralizing antibodies against fibroblast growth factor 2, transforming growth factor-beta1, and platelet-derived growth factor significantly reduced these stimulatory effects. Subcutaneous injection of hepatic stellate cells induced earlier onset and faster-growth of subcutaneous fibrotic pancreatic tumors in nude mice.

CONCLUSIONS

Hepatic stellate cells enhance tumor growth in nude mouse and may play an important role in metastasis formation.

Hepatic stellate cells: protean, multifunctional, and enigmatic cells of the liver

The hepatic stellate cell has surprised and engaged physiologists, pathologists, and hepatologists for over 130 years, yet clear evidence of its role in hepatic injury and fibrosis only emerged following the refinement of methods for its isolation and characterization. The paradigm in liver injury of activation of quiescent vitamin A-rich stellate cells into proliferative, contractile, and fibrogenic myofibroblasts has launched an era of astonishing progress in understanding the mechanistic basis of hepatic fibrosis progression and regression. But this simple paradigm has now yielded to a remarkably broad appreciation of the cell's functions not only in liver injury, but also in hepatic development, regeneration, xenobiotic responses, intermediary metabolism, and immunoregulation. Among the most exciting prospects is that stellate cells are essential for hepatic progenitor cell amplification and differentiation. Equally intriguing is the remarkable plasticity of stellate cells, not only in their variable intermediate filament phenotype, but also in their functions. Stellate cells can be viewed as the nexus in a complex sinusoidal milieu that requires tightly regulated autocrine and paracrine cross-talk, rapid responses to evolving extracellular matrix content, and exquisite responsiveness to the metabolic needs imposed by liver growth and repair. Moreover, roles vital to systemic homeostasis include their storage and mobilization of retinoids, their emerging capacity for antigen presentation and induction of tolerance, as well as their emerging relationship to bone marrow-derived cells. As interest in this cell type intensifies, more surprises and mysteries are sure to unfold that will ultimately benefit our understanding of liver physiology and the diagnosis and treatment of liver disease.

Increased Smad1 expression and transcriptional activity enhances trans-differentiation of hepatic stellate cells

Smad1 is a receptor-activated intracellular signaling protein, which mediates signal transduction of bone morphogenetic proteins. Current study investigated the expression and transcriptional activity of Smad1 during hepatic stellate cell (HSC) activation. Rat HSCs were isolated from rats at 1, 2, 3 and 4 days after gavaged with carbon tetrachloride (CCl(4)) or corn oil. RT-PCR, Western blot, gel-shift assay and luciferase assay were employed to examine Smad1 expression and transcriptional activity, respectively. CCl(4)-cirrhotic liver fat-storing cells-8B (CFSC-8B) cells were infected with recombinant adenoviruses of Smad1 and/or Smad1 shRNA. Both mRNA and protein levels of Smad1 were significantly increased at 48 h after gavage of CCl(4). Gel shift assays demonstrated a significant increase in nuclear Smad1 in day 9 HSCs. Transfection of HSCs with Smad1 responsible luciferase indicated an increase in Smad1 transcriptional activity in day 6 HSCs (1.563 +/- 0.229 in day 6 versus 0.785 +/- 0.192 in day 3). When CFSC-8B cells were infected with adenoviruses with Smad1 or Smad1 short hairpin RNA (shRNA), there was an increase or decrease in Smad1 mRNA and protein, respectively. Smooth muscle alpha-actin expression was increased or decreased according to induction or reduction of Smad1. In conclusion, there were significantly increases in Smad1 expression and transcriptional activity during in vivo activation of hepatic stellate cells.

Interferon-beta reduces the mouse liver fibrosis induced by repeated administration of concanavalin A via the direct and indirect effects

Type I interferons (IFNs), IFN-alpha and IFN-beta, are widely used for treating chronic hepatitis C. Although retrospective studies have suggested that type I IFNs have direct antifibrotic effects, little is known about these mechanisms. The present study was designed to clarify the preventive mechanisms of type I IFNs in the progression of fibrosis for the establishment of a more effective therapy. A murine fibrosis model comprising immunological reactions was induced by the administration of concanavalin A (0.3 mg/body) into mice once a week for 4 weeks. Liver injury and the degree of fibrosis were determined by measuring the serum alanine aminotransferase activities and liver hydroxyproline contents with or without IFN-beta pretreatment. IFN-beta suppressed the hepatocellular injury and increased the hydroxyproline content induced by repeated concanavalin A injections, but had no effect on established fibrosis. Furthermore, IFN-beta reduced the expressions of transforming growth factor-beta, basic fibroblast growth factor, collagen type I A2 and tissue inhibitor of metalloproteinase 1 messenger RNAs, which are related to the progression of liver fibrosis. The IFN-beta reduced the liver injury and fibrosis induced by immunological reactions. These data suggest that type I IFNs suppress the progression of cirrhosis through inhibition of repeated hepatocellular injury and/or factors that promote the liver fibrosis induced by hepatitis virus infection.

Differential regulated expression of keratinocyte growth factor and its receptor in experimental and human liver fibrosis

BACKGROUND AND AIM

Immunomodulatory and protective properties have been identified for the keratinocyte growth factor (KGF). For hepatocytes, pro-proliferative and anti-apoptotic effects of this growth factor have been reported in vitro. This study was designed to characterize a putative role of KGF in observed histomorphological changes in both, human and experimental liver fibrosis.

METHODS

Liver fibrosis and cirrhosis was induced in rats by repetitive exposure to phenobarbitone and increasing doses of carbon tetrachloride. Human samples were obtained from patients undergoing surgery for partial hepatectomy or transplantation. Organ samples were scored for inflammation and morphological changes. Expression of KGF and its receptor (KGFR) mRNA was quantified by real-time RT-PCR. Protein expression and receptor phosphorylation was determined by Western blot analysis. In-situ hybridization and immunohistochemistry were utilized to determine distribution of KGF and KGFR in the liver.

RESULTS

Expression of KGF was significantly increased in damaged liver tissue in correlation to the degree of fibrosis, whereas expression of the receptor was up-regulated in early stages of liver fibrosis and down-regulated in cirrhotic organs. Protein expression of this growth factor and its receptor correlated with the alterations in mRNA. KGF expression was restricted to mesenchymal cells, whereas expression of KGFR was detected on hepatocytes only.

CONCLUSION

The expression of KGF and KGFR is differentially and significantly regulated in damaged liver tissue. This growth factor might therefore not only contribute to morphological alterations but also regeneration of liver parenchyma most likely mediated by indirect mechanisms of action.

Fibrosis in heart disease: understanding the role of transforming growth factor-beta in cardiomyopathy, valvular disease and arrhythmia

The importance of fibrosis in organ pathology and dysfunction appears to be increasingly relevant to a variety of distinct diseases. In particular, a number of different cardiac pathologies seem to be caused by a common fibrotic process. Within the heart, this fibrosis is thought to be partially mediated by transforming growth factor-beta1 (TGF-beta1), a potent stimulator of collagen-producing cardiac fibroblasts. Previously, TGF-beta1 had been implicated solely as a modulator of the myocardial remodelling seen after infarction. However, recent studies indicate that dilated, ischaemic and hypertrophic cardiomyopathies are all associated with raised levels of TGF-beta1. In fact, the pathogenic effects of TGF-beta1 have now been suggested to play a major role in valvular disease and arrhythmia, particularly atrial fibrillation. Thus far, medical therapy targeting TGF-beta1 has shown promise in a multitude of heart diseases. These therapies provide great hope, not only for treatment of symptoms but also for prevention of cardiac pathology as well. As is stated in the introduction, most reviews have focused on the effects of cytokines in remodelling after myocardial infarction. This article attempts to underline the significance of TGF-beta1 not only in the post-ischaemic setting, but also in dilated and hypertrophic cardiomyopathies, valvular diseases and arrhythmias (focusing on atrial fibrillation). It also aims to show that TGF-beta1 is an appropriate target for therapy in a variety of cardiovascular diseases.

Proliferation of Pulmonary Interstitial Fibroblasts Is Mediated by Transforming Growth Factor-β1-induced Release of Extracellular Fibroblast Growth Factor-2 and Phosphorylation of p38 MAPK and JNK

Idiopathic pulmonary fibrosis (IPF; a progressive lung disease) is characterized by parenchymal remodeling with enlarged air spaces called honeycomb cysts and palisades of fibroblasts called fibroblast foci. In IPF, lung epithelial cells covering honeycomb cysts and fibroblast foci aberrantly express the active conformation of the potent fibrogenic cytokine transforming growth factor-beta1 (TGF-beta1). Using explanted rat lung slices, we transfected alveolar epithelial cells with the retrovirus pMX containing a site-directed mutation in which Cys223 and Cys225 were substituted with serines, resulting in release of biologically active TGF-beta1 and fibroblast proliferation and remodeling that resembled IPF. Fibroblasts obtained from transfected explants and in culture for 6 weeks incorporated 6.59 +/- 1.55-fold more [3H]thymidine compared with control fibroblasts without transfection or fibroblasts obtained from transfected explants cultured with antibody to fibroblast growth factor-2 (FGF-2). Primary lung fibroblasts obtained from normal rat lungs cultured with TGF-beta1 expressed increased levels of phosphorylated p38 MAPK and JNK, but not ERK1/2. The presence of TGF-beta1 caused an immediate release of extracellular FGF-2 from primary pulmonary fibroblasts; and in the presence of anti-FGF-2 antibody, phosphorylated p38 MAPK and JNK were abrogated. TGF-beta inhibits cell proliferation by suppression of c-Myc and induction of p15INK46, p21CIP1, or p27KIP. Fibroblasts cultured with TGF-beta1 showed no regulation of c-Myc or induction of p15INK46, p21CIP1,or p27KIP. These findings suggest that pulmonary fibroblasts may not respond to the anti-proliferative effects of TGF-beta1, but proliferate in response to TGF-beta1 indirectly by the release of FGF-2, which induces phosphorylation of p38 MAPK and JNK.

Hepatocyte transplantation activates hepatic stellate cells with beneficial modulation of cell engraftment in the rat

We investigated whether transplanted hepatocytes interact with hepatic stellate cells, as cell-cell interactions could modulate their engraftment in the liver. We transplanted Fischer 344 rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient rats. Activation of hepatic stellate cells was analyzed by changes in gene expression, including desmin and alpha-smooth muscle actin, matrix proteases and their inhibitors, growth factors, and other stellate cell-associated genes with histological methods or polymerase chain reaction. Furthermore, the potential role of hepatic ischemia, Kupffer cells, and cytokine release in hepatic stellate cell activation was investigated. Hepatocyte transplantation activated desmin-positive hepatic stellate cells, as well as Kupffer cells, including in proximity with transplanted cells. Inhibition of Kupffer cells by gadolinium chloride, blockade of tumor necrosis factor alpha (TNF-alpha) activity with etanercept or attenuation of liver ischemia with nitroglycerin did not decrease this hepatic stellate cell perturbation. After cell transplantation, soluble signals capable of activating hepatic stellate cells were rapidly induced, along with early upregulated expression of matrix metalloproteinases-2, -3, -9, -13, -14, and their inhibitors. Moreover, prior depletion of activated hepatic stellate cells with gliotoxin decreased transplanted cell engraftment. In conclusion, cell transplantation activated hepatic stellate cells, which, in turn, contributed to transplanted cell engraftment in the liver. Manipulation of hepatic stellate cells might provide new strategies to improve liver repopulation after enhanced transplanted cell engraftment.

Idiopathic pulmonary fibrosis: emerging concepts on pharmacotherapy

Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrosing disease of the distal air spaces of the lung of unknown aetiology. IPF is usually fatal with a median survival of < 3 years. There are currently no effective pharmacotherapeutic agents for the treatment of IPF. In this review, unifying concepts on the pathogenesis of IPF based on understanding of host responses to tissue injury are presented. These host responses involve tightly regulated and contextually orchestrated inflammatory and repair processes. Dysregulation of either of these processes can lead to pathological outcomes. Fibrosis results from an exaggerated or dysregulated repair process that proceeds 'uncontrolled' even after inflammatory responses have subsided. Disease heterogeneity may arise when inflammation and repair are in different (dys)regulatory phases, thus accounting for regional disparity. Usual interstitial pneumonia (UIP), the histopathological correlate of clinical IPF, represents a more fibrotic tissue reaction pattern and for which anti-inflammatory agents are ineffective. Emerging 'antifibrotic' drugs and strategies for UIP/IPF are discussed. The importance of accurately phenotyping a highly heterogeneous disease process that may require individualised and 'combined' therapies is emphasised.

Effects of TGF-beta s on the growth, collagen synthesis and collagen lattice contraction of human dental pulp fibroblasts in vitro

Transforming growth factor-beta (TGF-beta) is important in regulating the repair and regeneration of damaged dental pulp. For further elucidating the roles of different isoforms of TGF-beta in the healing and inflammatory processes of human dental pulp, we found that TGF-beta1, TGF-beta2 and TGF-beta3 inhibited the growth of two human dental pulp cell strains in vitro by 19-29, 18-25 and 23-26%, respectively, at a concentration of 0.5 ng/ml. TGF-beta also differentially stimulated the collagen synthesis of pulp cells. Collagen synthesis increased by 1 ng/ml of TGF-beta1 and TGF-beta2 by 42 and 51%, respectively. TGF-beta3 (0.1-1 ng/ml) lacked of stimulatory effect on collagen synthesis of pulp cells. Pulp cells have the intrinsic capacity to contract collagen lattice, leading to decreasing of lattice diameter. An 8 h exposure to TGF-beta1 and TGF-beta2 enhanced the pulp cell-populated collagen lattice contraction at concentrations ranging from 0.2 to 3 ng/ml. At similar concentrations, TGF-beta3 lacked of this stimulatory effect. When collagen lattice were detached after 24 h of exposure, TGF-beta1 and TGF-beta2 (0.6-3 ng/ml) induced the pulp cells-populated collagen lattice contraction within 4-8h of gel detachment. These results indicate that TGF-beta-induced collagen lattice contraction is a late cellular event. These in vitro results indicate that effects of TGF-beta isoforms on the growth, collagen synthesis and collagen lattice contraction of pulp cells may play crucial roles in the pathobiological processes of dental pulp.

Cytomegalovirus and chronic allograft rejection in liver transplantation

Cytomegalovirus (CMV) remains one of the most frequent viral infections and the most common cause of death after liver transplantation (LT). Chronic allograft liver rejection remains the major obstacle to long-term allograft survival and CMV infection is one of the suggested risk factors for chronic allograft rejection. The precise relationship between cytomegalovirus and chronic rejection remains uncertain. This review addresses the morbidity of cytomegalovirus infection and the risk factors associated with it, the relationship between cytomegalovirus and chronic allograft liver rejection and the potential mechanisms of it.

Autocrine release of TGF-beta by portal fibroblasts regulates cell growth

Portal fibroblasts (PF) are a newly isolated population of fibrogenic cells in the liver postulated to play a significant role in early biliary fibrosis. Because transforming growth factor-beta (TGF)-beta is a key growth factor in fibrosis, we characterized the response of PF to TGF-beta. We demonstrate that PF produce significant amounts of TGF-beta2 and, unlike activated hepatic stellate cells (HSC), express all three TGF-beta receptors and are growth inhibited by TGF-beta1 and TGF-beta2. Fibroblast growth factor (FGF)-2, but not platelet derived growth factor (PDGF), causes PF proliferation. These data suggest a mechanism whereby HSC eclipse PF as the dominant myofibroblast population in biliary fibrosis.

Role of fibroblast growth factor type 1 and 2 in carbon tetrachloride-induced hepatic injury and fibrogenesis

Genomic ablation of hepatocyte-specific fibroblast growth factor receptor (FGFR)4 in mice revealed a role of FGF signaling in cholesterol and bile acid metabolism and hepatolobular restoration in response to injury without effect on liver development or hepatocyte proliferation. Although the potential role of all 23 FGF polypeptides in the liver is still unclear, the most widely studied prototypes, FGF1 and FGF2, are present and have been implicated in liver cell growth and function in vitro. To determine whether FGF1 and FGF2 play a role in response to injury and fibrosis, we examined the impact of both acute and chronic exposure to carbon tetrachloride (CCl(4)) in the livers of FGF1- and FGF2-deficient mice. After acute CCl(4) exposure, FGF1(-/-)FGF2(-/-) mice exhibited an accelerated release of serum alanine aminotransferase similar to FGFR4 deficiency, but no effect on overall hepatolobular restoration or bile acid metabolism. FGF1(-/-)FGF2(-/-) mice exhibited a normal increase in alpha-smooth muscle actin and desmin associated with activation and migration of hepatic stellate cells to damage, but a reduced level of hepatic stellate cell-derived matrix collagen alpha1(I) synthesis. Liver fibrosis resulting from chronic CCl(4) exposure was markedly decreased in the livers of FGF1/FGF2-deficient mice. These results suggest an agonist role for FGF1 and FGF2 in specifically insult-induced liver matrix deposition and hepatic fibrogenesis and a potential target for the prevention of hepatic fibrosis.

The role of autocrine FGF-2 in the distinctive bone marrow fibrosis of hairy-cell leukemia (HCL)

Bone marrow (BM) fibrosis is a central diagnostic and pathogenetic feature of hairy-cell leukemia (HCL). It is known that fibronectin (FN) produced and assembled by the malignant hairy cells (HCs) themselves is a major component of this fibrosis. It is also known that FN production is greatly enhanced by adhesion of HCs to hyaluronan (HA) via CD44. The aim of the present study was to establish the roles of fibrogenic autocrine cytokines (fibroblast growth factor-2 [FGF-2] and transforming growth factor beta [TGFbeta]) and of different isoforms of CD44 in this FN production. We show that HC adhesion to HA stimulates FGF-2, but not TGFbeta, production and that HCs possess FGF-2 receptor. In a range of experiments, FN production was greatly reduced by blocking FGF-2 but not TGFbeta. Moreover FN, but not FGF-2, secretion was blocked by down-regulation of the v3 isoform of CD44 and by addition of heparitinase. These results show that autocrine FGF-2 secreted by HCs is the principal cytokine responsible for FN production by these cells when cultured on HA. The central role of FGF-2 in the pathogenesis of the BM fibrosis of HCL was supported by our immunohistochemical demonstration of large amounts of this cytokine in fibrotic BM but not in HCL spleen where there is no fibrosis. As regards CD44 isoforms, the present work demonstrates that CD44v3 is essential for providing the heparan sulfate necessary for HC stimulation by FGF-2, whereas the signal for production of the cytokine was provided by HA binding to CD44H, the standard hematopoietic form of the molecule.

Heparin inhibits DNA synthesis and gene expression in alveolar type II cells

Responses of isolated type II alveolar cells to fibroblast growth factors (FGF) have been shown to be sensitive to the level of sulfation in extracellular matrix (ECM) substrata. These observations may reflect the specific in situ distribution and level of sulfation of ECM within the alveolar basement membranes (ABM) associated with type II cells. The goal of this study was to determine if the model sulfated ECM heparin modified DNA synthesis and gene expression by type II cells in a concentration dependent-manner. Isolated rat type II cells were exposed to different concentrations of heparin (0.005-500 micro g/ml) in serum-free medium for 1-3 d with or without FGF-1 or FGF-2. The effects of heparin were examined by [(3)H]thymidine incorporation into DNA, total cell protein, cell number, and selected gene expression. Results indicated that heparin inhibited [(3)H]thymidine uptake in a concentration-dependent manner. Total protein, cell number, and FGF-2 protein expression and mRNA of FGF-1, -2, and FGF receptor-2 detected by reverse transcriptase-polymerase chain reaction were decreased by heparin. These results demonstrate that sulfated molecules in the ABM may play important regulatory role(s) in selected type II cell activities during normal cell homeostasis, turnover, and repair after lung injury.

[Mechanisms of hepatic fibrogenesis]

Hepatic fibrosis is a scaring process leading to cirrhosis, a major complication of numerous chronic liver diseases. Hepatic stellate cells play a central role in the fibrotic process. After parenchymal or biliary injury, cytokines and growth factors allow the recruitment, proliferation, and activation, of stellate cells toward myofibroblasts, which secrete the extracellular matrix. Fibrosis, resulting from the failure of the balance between synthesis and degradation of extracellular matrix, is an evolutive and potentially reversible process. Histological examination is the main investigation to quantify fibrosis. Serological tests are warranted to allow a non invasive follow up of patients. Development of antifibrotic therapies should soon permit to slow down the evolution toward cirrhosis, limiting the needs for hepatic transplantation.

DDR2 receptor promotes MMP-2-mediated proliferation and invasion by hepatic stellate cells

Type I collagen provokes activation of hepatic stellate cells during liver injury through mechanisms that have been unclear. Here, we tested the role of the discoidin domain tyrosine kinase receptor 2 (DDR2), which signals in response to type I collagen, in this pathway. DDR2 mRNA and protein are induced in stellate cells activated by primary culture or in vivo during liver injury. The receptor becomes tyrosine phosphorylated in response to either endogenous or exogenous type I collagen, whereas its expression is downregulated during cellular quiescence induced by growth on Matrigel. We developed stellate cell lines stably overexpressing either wild-type DDR2, a constitutively active chimeric DDR2 receptor (Fc-DDR2), a truncated receptor expressing the extracellular domain, or a kinase-dead DDR2 Cells overexpressing DDR2 showed enhanced proliferation and invasion through Matrigel, activities that were directly related to increased expression of active matrix metalloproteinase 2 (MMP-2). These data show that DDR2 is induced during stellate cell activation and implicate the phosphorylated receptor as a mediator of MMP-2 release and growth stimulation in response to type I collagen. Moreover, type I collagen-dependent upregulation of DDR2 expression establishes a positive feedback loop in activated stellate cells, leading to further proliferation and enhanced invasive activity.

DDR2 receptor promotes MMP-2-mediated proliferation and invasion by hepatic stellate cells

Type I collagen provokes activation of hepatic stellate cells during liver injury through mechanisms that have been unclear. Here, we tested the role of the discoidin domain tyrosine kinase receptor 2 (DDR2), which signals in response to type I collagen, in this pathway. DDR2 mRNA and protein are induced in stellate cells activated by primary culture or in vivo during liver injury. The receptor becomes tyrosine phosphorylated in response to either endogenous or exogenous type I collagen, whereas its expression is downregulated during cellular quiescence induced by growth on Matrigel. We developed stellate cell lines stably overexpressing either wild-type DDR2, a constitutively active chimeric DDR2 receptor (Fc-DDR2), a truncated receptor expressing the extracellular domain, or a kinase-dead DDR2 Cells overexpressing DDR2 showed enhanced proliferation and invasion through Matrigel, activities that were directly related to increased expression of active matrix metalloproteinase 2 (MMP-2). These data show that DDR2 is induced during stellate cell activation and implicate the phosphorylated receptor as a mediator of MMP-2 release and growth stimulation in response to type I collagen. Moreover, type I collagen-dependent upregulation of DDR2 expression establishes a positive feedback loop in activated stellate cells, leading to further proliferation and enhanced invasive activity.

TGF-beta 1 induces proliferation in human renal fibroblasts via induction of basic fibroblast growth factor (FGF-2)

BACKGROUND

The prognosis of primary renal disease is often dependent on the degree of tubulointerstitial scarring. Scarring is caused by proliferation and excessive matrix production of renal fibroblasts and possibly other cellular elements. Transforming growth factor-beta (TGF-beta) is the most important cytokine for the induction of matrix synthesis in the kidney. However, its effects on renal fibroblast proliferation have not been determined. We have recently demonstrated that the expression of basic fibroblast growth factor (FGF-2) is robustly up-regulated in human kidneys with tubulointerstitial fibrosis and that FGF-2 is a potent inducer of fibroblast proliferation. The present study examined the interaction between TGF-beta 1 and FGF-2 in human renal fibroblasts.

METHODS

Experiments were performed on a transformed medullary fibroblast line and on primary cortical kidney and skin fibroblasts isolated from human biopsies. mRNA levels of FGF-2 and TGF-beta 1 were analyzed by Northern blot analyses. Changes in protein expression were examined by immunoblots and enzyme-linked immunosorbent assay (ELISA). Bromodeoxyuridine incorporation assays and cell counts were used to analyze cell proliferation. The expression of cell cycle-regulatory proteins cyclin-dependent kinase (cdk) 2 and the cdk inhibitor p27(kip1) were determined by immunoblots.

RESULTS

Stimulation of renal fibroblasts with FGF-2 resulted in no change of TGF-beta 1 mRNA expression, whereas incubation of the cells with TGF-beta 1 induced FGF-2 mRNA up to 3.51 +/- 0.21-fold after six hours. This increase could be blocked almost completely by the addition of cyclohexamide, indicating that the process is in large part dependent on protein synthesis. The up-regulation in FGF-2 mRNA expression was paralleled by de novo detection of FGF-2 protein in the supernatant, peaking after 12 to 24 hours, as determined by Western blot and ELISA, whereas cellular protein was only increased up to 2.1-fold. Interestingly, both methods detected release of FGF-2 protein to the supernatant already at three hours, indicating a role for TGF-beta1 in directly releasing preformed FGF-2. Since TGF-beta 1 induced FGF-2, which results in fibroblast proliferation, we hypothesized that TGF-beta1 may cause fibroblast proliferation mediated by FGF-2. This hypothesis was verified by cell proliferation assays demonstrating that stimulation of renal fibroblasts with TGF-beta1 resulted in an up to 3.21 +/- 0.28-fold increase in bromodeoxyuridine incorporation and a 1.95 +/- 0.16-fold increase in cell number after 72 hours. This mitogenic effect of TGF-beta1 could be blocked completely by the addition of a neutralizing antibody to FGF-2 or the tyrosine kinase inhibitor tyrphostin AG1296, which blocks FGF receptor (FGFR) tyrosine kinase activity. Conversely, a neutralizing antibody to epidermal growth factor (EGF) or the tyrphostin B42, which inhibits EGF receptor signal transduction, had no effect. Interestingly, a neutralizing antibody to PDGF had only minor effects in primary kidney fibroblasts but reduced TGF-beta 1-induced proliferation considerably in primary skin fibroblasts. Finally, TGF-beta1-induced proliferation in kidney fibroblasts was paralleled by a robust increase in cdk 2 protein expression up to 72 hours, whereas p27(kip1), whose activity is maintained by TGF-beta in epithelial cells, was down-regulated up to 48 hours.

CONCLUSIONS

Our studies demonstrate, to our knowledge for the first time, that TGF-beta1 induces proliferation in human renal fibroblasts and that this process is mediated largely by FGF-2. The induction of proliferation by TGF-beta 1 via induction of FGF-2 may play an important role in the autonomy of renal fibroblast growth and thus in the pathogenesis of human fibrogenesis.

Neutralization of fibroblast growth factor-2 reduces intraarticular adhesions

Adhesion is a serious complication after trauma or surgery. Because adhesion formation is essentially a fibrogenetic process, a series of growth factors are assumed to be involved in its development. If this is true, it may be possible that inhibition of the growth factor activity suppresses adhesion formation. The current study was conducted to verify this hypothesis on fibroblast growth factor-2 using an intraarticular adhesion model in the rabbit knee. Forty Japanese White rabbits were used. They were divided randomly into five groups of eight animals, and in three of them, activity of endogenous fibroblast growth factor-2 was suppressed locally by a neutralizing antibody. The remaining two groups served as controls, and formation of adhesions was evaluated 4 weeks after surgery. The results showed that the administration of the antibody reduced the extent of adhesions macroscopically, whereas histologic observation and collagen content measurement suggested the adhesion tissue was not affected significantly. Corresponding to the macroscopic findings, contraction of the knee was improved in the antibody groups. The findings showed that suppression of fibroblast growth factor-2 activity reduces adhesions. It is expected that control of the cytokine activity may become a novel method for reducing adhesions.

Effects of fibrogenic mediators on the development of pancreatic fibrosis in a TGF-beta1 transgenic mouse model

The pancreas morphology of transgenic mice that overexpress transforming growth factor-beta1 (TGF-beta1) in the pancreas resembles partially morphological features of chronic pancreatitis, such as progressive accumulation of extracellular matrix (ECM). Using this transgenic mouse model, we characterized the composition of pancreatic fibrosis and involved fibrogenic mediators. On day 14 after birth, fibrotic tissue was mainly composed of collagen type I and III. At this time, mRNA levels of TGF-beta1 were increased. On day 70, the ECM composition was expanded by increased deposition of fibronectin, whereas connective tissue growth factor, fibroblast growth factor (FGF)-1, and FGF-2 mRNA expression levels were elevated in addition to TGF-beta1. In parallel, the number of pancreatic stellate cells (PSC) increased over time. In vitro, TGF-beta1 stimulated collagen type I expression but not fibronectin expression in PSC, in contrast to FGF-2, which stimulated both. This confirms that TGF-beta1 mediates pancreatic fibrosis through activation of PSC and deposition of collagen type I and III at early time points. Furthermore, this points to an indirect mechanism in which TGF-beta regulates pancreatic ECM assembly by induction of additional growth factors.

Transforming growth factor beta-1 stimulates invasivity of hepatic stellate cells by engagement of the cell-associated fibrinolytic system

The activation of hepatic stellate cells (HSC) during liver fibrogenesis has been shown to be mediated by paracrine and autocrine loops involving transforming growth factor-beta1 (TGF-beta1) as the main fibrogenic mediator secreted by activated macrophages, endothelial cells and liberated by disintegrated platelets. The cell-associated plasminogen activation system regulates extracellular matrix (ECM) catabolism and cell movement. We have studied whether TGF-beta1 could modulate the plasminogen activation system in human HSC and the role of such protease system in the activity of TGF-beta1 on HSC. Urokinase plasminogen activator receptors (u-PAR), u-PA and plasminogen activator inhibitor type 1 (PAI-1) were determined by immunoassay and RNase protection assay. Cell migration, evaluated either as chemotaxis or as chemoinvasion, was studied in Boyden chambers after addition of TGF-beta1, and inhibition with anti-u-PA and anti-u-PAR antagonists [antibodies against u-PA and u-PAR and antisense oligonucleotides (aODN) against u-PAR mRNA]. We have shown that TGF-beta1 is not mitogenic for HSC, while it is a powerful motogen either in chemotaxis or chemoinvasion assays. TGF-beta1 up-regulates the synthesis and expression of PAI-1, as well as u-PAR expression and exposure at the cell membrane, while it does not affect u-PA levels. TGF-beta1-dependent chemoinvasion of reconstituted basement membrane exploits the cell-associated plasminogen activation system, since it is blocked by monoclonal antibodies against u-PA and against various u-PAR domains, as well as by anti-u-PAR aODN. We have also observed a cumulative effect of TGF-beta1, b-FGF and PDGF in the invasion assay of HSC: in the presence of low amounts of TGF-beta1 the chemoinvasive activity of PDGF and bFGF is dramatically increased. Also this cooperation requires u-PAR and is inhibited by monoclonal antibodies against u-PAR domains I, II and III.

TGF-beta1 and fibroblast growth factor-1 modify fibroblast growth factor-2 production in type II cells

Fibroblast growth factor (FGF)-2, which stimulates DNA synthesis by type II cells in the lung, has been shown to be regulated by transforming growth factor (TGF)-beta1, an important inflammatory cytokine, in vascular epithelium. The goal of this study was to determine if FGF-2 production by alveolar type II cells is modulated by TGF-beta1 or FGF-1, which also stimulates DNA synthesis by type II cells. Isolated rat type II cells were exposed to 0-40 ng/ml of TGF-beta1 or 0-500 ng/ml of FGF-1 in serum-free medium for 1-5 days. With a specific immunoassay, significant increases of FGF-2 protein in type II cell lysates to levels above those in control cells were achieved after 1 day of exposure to 100 ng/ml of FGF-1 and after 3 days of treatment with 8 ng/ml of TGF-beta1. Similarly, transcripts for FGF-2 were dramatically increased above those in control cells with TGF-beta1 or FGF-1, as were those for FGF receptor-1. These results demonstrate important regulatory links between FGF-2 and both TGF-beta1 and FGF-1 in the alveolar epithelium that could contribute to the regulation of normal cell turnover, development, and the repair processes after injury in the lung.

Reactive oxygen species in cell signaling

Reactive oxygen species (ROS) are generated as by-products of cellular metabolism, primarily in the mitochondria. When cellular production of ROS overwhelms its antioxidant capacity, damage to cellular macromolecules such as lipids, protein, and DNA may ensue. Such a state of "oxidative stress" is thought to contribute to the pathogenesis of a number of human diseases including those of the lung. Recent studies have also implicated ROS that are generated by specialized plasma membrane oxidases in normal physiological signaling by growth factors and cytokines. In this review, we examine the evidence for ligand-induced generation of ROS, its cellular sources, and the signaling pathways that are activated. Emerging concepts on the mechanisms of signal transduction by ROS that involve alterations in cellular redox state and oxidative modifications of proteins are also discussed.

Transforming growth factor-beta 1-induced activation of the ERK pathway/activator protein-1 in human lung fibroblasts requires the autocrine induction of basic fibroblast growth factor

Transforming growth factor-beta (TGF-beta) is involved in multiple processes including cell growth and differentiation. In particular, TGF-beta has been implicated in the pathogenesis of fibrotic lung diseases. In this study, we examined regulation of the mitogen-activated protein kinase pathway by TGF-beta1 in primary human lung fibroblasts. TGF-beta1 treatment resulted in extracellular signal-regulated kinase (ERK) pathway activation in a delayed manner, with maximal activity at 16 h. ERK activation occurred concomitantly with the induction of activator protein-1 (AP-1) binding, a nuclear factor required for activation of multiple genes involved in fibrosis. AP-1 binding was dependent on ERK activation, since the MEK-1 (mitogen-activated protein kinase kinase) inhibitor PD98059 inhibited TGF-beta1-induced binding. Induction of the receptor tyrosine kinase-linked growth factor, basic fibroblast growth factor (bFGF) protein expression temporally paralleled the activation of ERK/AP-1. Induction of AP-1 by TGF-beta1-conditioned medium was observed at 2 h, similar to AP-1 induction in response to exogenous bFGF. Dependence of ERK/AP-1 activation on bFGF induction was demonstrated by inhibition of TGF-beta1-induced ERK/AP-1 activation when conditioned medium from TGF-beta1-treated cells was incubated with bFGF-neutralizing antibody. Together, these results demonstrate that TGF-beta1 regulates the autocrine induction of bFGF, resulting in activation of the ERK mitogen-activated protein kinase pathway and induction of AP-1 binding.

Platelet-derived growth factor receptor tyrosine kinase inhibitor AG1295 attenuates rat hepatic stellate cell growth

Enhanced activity of receptor tyrosine kinases such as the platelet-derived growth factor-receptorbeta (PDGF-Rbeta) has been implicated as a contributing factor in the development of hepatic fibrosis. In this study we have used tyrosine kinase inhibitors of the tyrphostin class (AG1295) to specifically block autophosphorylation of PDGF-Rbeta and proliferation of rat hepatic stellate cells. We also examined the effect of AG1295 on the PDGF-BB-induced activation of the 44 kd and 42 kd mitogen-activated protein (MAP) kinase isoforms (p44mapk/p42mapk). Rat hepatic stellate cells were treated with AG1295 (10 micromol/L) for 24 hours and stimulated with PDGF-BB for 5 minutes. AG1295 specifically inhibited autophosphorylation of PDGF-Rbeta and caused a 20% decrease in PDGF-BB-stimulated bromodeoxyuridine incorporation by rat hepatic stellate cells. Treatment of rat hepatic stellate cells with AG1295 resulted in an inhibition of the PDGF-BB-induced activation of MAP kinase isoforms. Quantification of the immunoprecipitated tyrosine-phosphorylated phosphatidylinositol 3-kinase, phospholipase C-gamma, and p21ras guanosine triphosphatase-activating protein by Western blotting revealed that AG1295 treatment effectively inhibits tyrosine phosphorylation of these kinases in hepatic stellate cells. Our findings demonstrate that AG1295 is a selective inhibitor of the tyrosine phosphorylation of PDGF-Rbeta and its downstream signaling pathway, and this compound could offer a strategy for the treatment of fibrotic liver diseases.

Basic fibroblast growth factor expression is increased in human renal fibrogenesis and may mediate autocrine fibroblast proliferation

BACKGROUND

Interstitial fibroblasts play a critical role in renal fibrogenesis, and autocrine proliferation of these cells may account for continuous matrix synthesis. Basic fibroblast growth factor (FGF-2) is mitogenic for most cells and exerts intracrine, autocrine, and paracrine effects on epithelial and mesenchymal cells. The aims of the present studies were to localize and quantitate the expression of FGF-2 in normal and pathologic human kidneys and to study the in vitro effects of FGF-2 on proliferation, differentiation, and matrix production of isolated cortical kidney fibroblasts.

METHODS

FGF-2 protein expression was localized by immunofluoresence double labelings in normal and fibrotic human kidneys. Subsequently, interstitial FGF-2 labeling was determined semiquantitatively in 8 normal kidneys and 39 kidneys with variable degrees of interstitial fibrosis and was correlated with the morphometrically determined interstitial cortical volume. In addition, FGF-2 expression was quantitated by immunoblot analysis in three normal and six fibrotic kidneys. FGF-2 mRNA was localized by in situ hybridizations. Seven primary cortical fibroblast lines were established, and expression of FGF-2 and FGF receptor-1 (FGFR-1) were examined. The effects of FGF-2 on cell proliferation were determined by bromodeoxyuridine incorporation and cell counts, those on differentiation into myofibroblasts by staining for alpha-smooth muscle actin, and those on matrix synthesis by enzyme-linked immunosorbent assay for collagen type I and fibronectin. Finally, proliferative activity in vivo was evaluated by expression of MIB-1 (Ki-67 antigen).

RESULTS

In normal kidneys, FGF-2 expression was confined to glomerular, vascular, and a few tubular as well as interstitial fibroblast-like cells. The expression of FGF-2 protein was increased in human kidneys, with tubulointerstitial scarring correlating with the degree of interstitial fibrosis (r = 0.84, P < 0.01). Immunoblot analyses confirmed a significant increase in FGF-2 protein expression in kidneys with interstitial scarring. In situ hybridization studies demonstrated low-level detection of FGF-2 mRNA in normal kidneys. However, FGF-2 mRNA expression was robustly up-regulated in interstitial and tubular cells in end-stage kidneys, indicating that these cells are the source of excess FGF-2 protein. Primary cortical fibroblasts express FGF-2 and FGFR-1 in vitro. FGF-2 induced a robust growth response in these cells that could be blocked specifically by a neutralizing FGF-2 antibody. Interestingly, the addition of the neutralizing antibody alone did reduce basal proliferation up to 31.5%. In addition, FGF-2 induced expression of alpha-smooth muscle actin up to 1.6-fold, but no significant effect was observed on the synthesis of collagen type I and fibronectin. Finally, staining for MIB-1 revealed a good correlation of interstitial FGF-2 positivity with interstitial and tubular proliferative activity (r = 0.71, P < 0.01 for interstitial proliferation, N = 30).

CONCLUSIONS

Interstitial FGF-2 protein and mRNA expression correlate with interstitial scarring. FGF-2 is a strong mitogen for cortical kidney fibroblasts and may promote autocrine fibroblast growth. Expression of FGF-2 correlates with interstitial and tubular proliferation in vivo.

Transforming growth factor beta2, but not beta1 and beta3, is critical for early rat lung branching

Mesenchymal-epithelial tissue interactions are critical for lung branching morphogenesis, and polypeptide growth factors are likely involved in these tissue interactions. Transforming growth factorbetas (TGFbetas) have been implicated in lung development, but their involvement in early lung branching morphogenesis is unclear. In the present study, we investigated the role of the three mammalian TGFbeta subtypes (beta1, beta2, and beta3) and their receptors (type III (TbetaR-III), type II (TbetaR-II), and two types I (TbetaR-I), ALK-1 and ALK-5) in early rat lung organogenesis by using an embryonic rat lung explant culture. Transcripts and proteins for all three TGFbetas and their receptors were detected during the embryonic period of fetal rat lung development. Inhibition of TGFbeta2, but not beta1 and beta3, with antisense oligonucleotides and neutralizing antibodies resulted in significant inhibition of early lung branching in culture. Addition of minute amounts (</=1 ng/ml) of exogenous TGFbeta2, but not beta1 and beta3, restored the branching of TGFbeta2 antisense-treated explants. Higher concentrations of TGFbeta2 were inhibitory. BrdU labeling of lung explants was not altered by antisense TGFbeta2 treatment, but low concentrations of TGFbeta2 increased thymidine uptake by isolated epithelial cells. Fibronectin and metallogelatinase activities of embryonic lung cells were not affected by any TGFbeta isoform but TGFbeta2 specifically decreased mesenchymal hyaluronan synthesis. Antisense inhibition of ALK-5 and TbetaR-II showed a similar reduction in early lung branching as observed with antisense TGFbeta2. Incubation of lung explants with soluble TbetaR-II receptors also abrogated lung branching. ALK-1 antisense treatment did not affect early branching. Administration of neither activin A, which can act via ALK-1, nor follistatin, the natural inhibitor of activin, to the explants cultures had any significant effect on lung branching. Antisense inhibition of the activin receptor-II (Act-RII) also did not affect lung branching. These results are consistent with TGFbeta2, but not beta1 and beta3, regulating pattern formation during early rat lung organogenesis. This TGFbeta signaling in rat lung branching in vitro appears to be predominantly mediated via the TbetaR-I(ALK-5)/TbetaR-II heteromeric complex.

New prognostic histological parameter of invasive ductal carcinoma of the breast: clinicopathological significance of fibrotic focus

Immunohistochemistry, DNA ploidy analysis and molecular genetics have made it possible to predict the outcome of breast cancer more precisely than routine histological examination alone. However, in routine practice, it is difficult to incorporate these methodologies in all cases. If certain histological parameters can accurately predict the outcome of patients with breast cancer, they would be more practical for routine use. We showed that the presence of fibrotic focus (FF) in invasive ductal carcinoma (IDC) is closely associated with c-erbB-2 or p53 protein expression, high proliferative activity, and high angiogenesis of the tumors. Furthermore, multivariate analyses with well-known prognostic parameters for IDC demonstrated that the presence of FF is the most useful independent parameter to predict IDC patient outcome. In addition, our data suggested that the interaction between tumor cells and stromal fibroblasts may play an important role in the formation of FF in IDC based on growth factor and growth factor receptor protein expression in the tumor cells and fibroblasts forming FF. Based on the results of our clinicopathological studies, we propose a new prognostic classification scheme for the prediction of IDC patient outcome, which consists of FF, nuclear atypia, and fat invasion. This classification has superior predicting power to existing prognostic classifications.

Evidence for apoptosis induction in myofibroblasts during palatal mucoperiosteal repair

Apoptosis is thought to be a requisite event for maintaining kinetic homeostasis within continually renewing tissues such as the oral mucosa and skin. However, no systematic study of the apoptotic process in fibroblasts in the oral mucosa following injury has been performed. In this study, we have assessed the expression of transforming growth factor-beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF), which are among the most important modulators of wound repair, during wound healing following mucoperiosteal injury in the rat palate. In addition, we have investigated fibroblast differentiation and apoptosis by immunohistochemical analysis for alpha-smooth-muscle (alpha-SM) actin or DNA strand breaks, respectively, to clarify the mechanisms of the wound healing process. TGF-beta1-positive cells were noted in the subepithelium from Day 2 to Day 14 after injury, by which time the wounds were completely reepithelialized. Strong expression of bFGF was observed, mainly in macrophages and monocytes at the injured site, from Day 10 to Day 14 after injury. TGF-beta1 and bFGF-immunostaining was significantly lower during the later phase of wound healing. In addition, the number of myofibroblasts expressing alpha-SM actin increased (peak at Day 14), and thereafter gradually decreased. In parallel, the apoptosis in myofibroblasts was prominent on Day 14. These results suggest that TGF-beta1 and bFGF may be potential stimulators of apoptosis in myofibroblasts after re-epithelialization in the palatal wound healing process. The regulation of apoptotic phenomena during wound healing may be important in scar establishment and development of pathological scarring.

Stellate cell activation in alcoholic fibrosis--an overview

There has been remarkable progress in our understanding of how chronic alcohol ingestion may lead to hepatic injury and scarring, or fibrosis. Hepatic fibrosis represents the liver's wound healing response and is characterized by accumulation of interstitial matrix, or scar. Fibrosis in the liver results from the activation of stellate cells, or resident mesenchymal cells. Stellate cell activation is a dramatic phenotype transition whose net effect is the replacement of normal liver matrix by scar. Features of stellate cell activation include increased cell accumulation from proliferation and directed migration, increased matrix production, enhanced contractility, accelerated degradation of the normal liver matrix, release of profibrogenic cytokines, and loss of cellular vitamin A. Alcohol may enhance fibrogenesis through stimulation of stellate cells by hypoxia, generation of lipid peroxides from damaged hepatocytes, production of acetaldehyde that may have direct fibrogenic activity, and through activation of Kupffer cells or resident macrophages. Unanswered questions remain to be studied, but the clarification of underlying mechanisms of fibrosis portends continued progress in our ability to treat alcoholic liver fibrosis.

Expression of collagens type I and IV, osteonectin and transforming growth factor beta-1 (TGFbeta1) in biliary atresia and paucity of intrahepatic bile ducts during infancy

BACKGROUND/AIMS

Biliary atresia and paucity of intrahepatic bile ducts are the main causes of neonatal cholestasis leading to hepatic fibrosis. Fibrotic evolution is slow in paucity of bile ducts as compared to the rapid progression to biliary cirrhosis in biliary atresia when cholestasis persists despite hepatoportoenterostomy. Our aim was to compare the expression of collagens type I and IV, alpha-smooth muscle actin, osteonectin and transforming growth factor beta1 in biliary atresia and paucity of bile ducts.

METHODS

Liver biopsies were obtained in 12 children with biliary atresia and in five with paucity of bile ducts. Collagens type I and IV, alpha-smooth muscle actin were detected with immunostaining. Collagens type I and IV, osteonectin and transforming growth factor beta1 mRNAs were detected by in situ hybridization.

RESULTS

Expression of mRNA and proteins was roughly parallel. In ductular proliferation areas of biliary atresia: (1) the expression of collagens type I and IV and osteonectin was increased, and was localized to periductular myofibroblasts; (2) transforming growth factor beta1 was expressed around biliary ductules, probably in inflammatory cells, and also in biliary cells. Osteonectin expression was also increased in the lobules. In paucity of bile ducts, there was no overexpression of collagens type I and IV and transforming growth factor beta1, except in the only child with marked fibrosis. However, osteonectin expression was enhanced at the periphery of the lobules, even when fibrosis was mild or absent.

CONCLUSIONS

These findings suggest that in biliary atresia ductular proliferation areas are the site of a marked production of extracellular matrix proteins in periductular myofibroblasts, probably secondary to transforming growth factor beta1 production by inflammatory cells and by biliary cells. The weak expression of transforming growth factor beta1 could explain the slow progression of fibrosis in paucity of bile ducts.

Basic Fibroblast Growth Factor Is Expressed by CD19/CD11c-Positive Cells in Hairy Cell Leukemia

Several features are characteristic for hairy cell leukemia (HCL). Among those are pancytopenia, bone marrow fibrosis, and the appearance of a defined tumor cell phenotype in peripheral blood (PB), bone marrow (BM), and spleen. Hairy cells (HC) coexpress antigens specific for B lymphocytes and monocytes/macrophages and thus the malignant cell does not seem to be restricted to a defined lineage. When serum or bone marrow aspirate was screened by enzyme-linked immunosorbent assay (ELISA) for basic fibroblast growth factor (bFGF), specimen derived from HCL (serum: mean value, 29 pg/mL; BM aspirate: mean value, 641 pg/mL) contained significantly higher levels than those from healthy subjects. To study whether peripheral blood mononuclear cells (PBMC) derived from patients suffering from HCL and healthy donors (HD) were capable of producing bFGF, culture supernatant (conditioned medium, [CM]) was tested for the presence of this cytokine. While bFGF was not detectable in cell cultures from HD, HCL-derived CM contained relatively high levels of bFGF. CM was successfully used for stimulation of mesenchymal cell proliferation, which could be inhibited by a neutralizing anti-bFGF antibody. Cellular activation by pokeweed mitogen (PWM) or the combination of 12-o-tetradecanoyl-phorbol-13-acetate (TPA) plus calcium ionophore (Ca-Ip) led to an enhanced mRNA expression. Results of Western blot experiments showed that HC synthesize at least three isoforms (approximately 18, 23, and 25 kD), but only the 23-kD isoform is exported. To assess the nature of the producer cell, double immunofluorescence analysis using a bFGF-specific and an anti-CD11c monoclonal antibody (MoAb) was undertaken. The majority of cells scoring positive for CD11c were also reactive with the anti-bFGF MoAb. Furthermore, enrichment of CD19/CD11c-positive cells correlated with enhanced bFGF levels, thereby supporting the argument for HC being the producer cells of bFGF. A biological function of bFGF in HCL might be mediation of chemoresistance, as 2-chlorodeoxyadenosine (2-CdA)–induced inhibition of cell proliferation can be reversed by bFGF. Endogenous bFGF production by HC is not affected by this purine analogue and 2-CdA–induced apoptosis is diminished in bFGF-producing HC as compared with normal PBMC. Therefore, bFGF expression by HC might be important for resistance to chemotherapy and survival of the malignant cells.

Liver fibrogenesis and the role of hepatic stellate cells: new insights and prospects for therapy

Hepatic fibrosis is a wound-healing response to chronic liver injury, which if persistent leads to cirrhosis and liver failure. Exciting progress has been made in understanding the mechanisms of hepatic fibrosis. Major advances include: (i) characterization of the components of extracellular matrix (ECM) in normal and fibrotic liver; (ii) identification of hepatic stellate cells as the primary source of ECM in liver fibrosis; (iii) elucidation of key cytokines, their cellular sources, modes of regulation, and signalling pathways involved in liver fibrogenesis; (iv) characterization of key matrix proteases and their inhibitors; (v) identification of apoptotic mediators in stellate cells and exploration of their roles during the resolution of liver injury. These advances have helped delineate a more comprehensive picture of liver fibrosis in which the central event is the activation of stellate cells, a transformation from quiescent vitamin A-rich cells to proliferative, fibrogenic and contractile myofibroblasts. The progress in understanding fibrogenic mechanisms brings the development of effective therapies closer to reality. In the future, targeting of stellate cells and fibrogenic mediators will be a mainstay of antifibrotic therapy. Points of therapeutic intervention may include: (i) removing the injurious stimuli; (ii) suppressing hepatic inflammation; (iii) down-regulating stellate cell activation; and (iv) promoting matrix degradation. The future prospects for effective antifibrotic treatment are more promising than ever for the millions of patients with chronic liver disease worldwide.

Myofibroblasts. I. Paracrine cells important in health and disease

Myofibroblasts are a unique group of smooth-muscle-like fibroblasts that have a similar appearance and function regardless of their tissue of residence. Through the secretion of inflammatory and anti-inflammatory cytokines, chemokines, growth factors, both lipid and gaseous inflammatory mediators, as well as extracellular matrix proteins and proteases, they play an important role in organogenesis and oncogenesis, inflammation, repair, and fibrosis in most organs and tissues. Platelet-derived growth factor (PDGF) and stem cell factor are two secreted proteins responsible for differentiating myofibroblasts from embryological stem cells. These and other growth factors cause proliferation of myofibroblasts, and myofibroblast secretion of extracellular matrix (ECM) molecules and various cytokines and growth factors causes mobility, proliferation, and differentiation of epithelial or parenchymal cells. Repeated cycles of injury and repair lead to organ or tissue fibrosis through secretion of ECM by the myofibroblasts. Transforming growth factor-beta and the PDGF family of growth factors are the key factors in the fibrotic response. Because of their ubiquitous presence in all tissues, myofibroblasts play important roles in various organ diseases and perhaps in multisystem diseases as well.