Initial signaling of the fibronectin receptor (alpha5beta1 integrin) in hepatic stellate cells is independent of tyrosine phosphorylation

SPOCK1 overexpression induced by platelet-derived growth factor-BB promotes hepatic stellate cell activation and liver fibrosis through the integrin α5β1/PI3K/Akt signaling pathway

Sparc/osteonectin, cwcv, and kazal-like domain proteoglycan 1 (SPOCK1) is a matricellular protein which regulates cell proliferation, invasion, and survival but the function of SPOCK1 in liver fibrosis is obscure. In this study, we found that SPOCK1 expression increased significantly in fibrotic liver tissues and activated primary rat hepatic stellate cells (R-HSCs). SPOCK1 co-localized with α-smooth muscle actin (α-SMA) in the cytoplasm. Mechanistically, we found platelet-derived growth factor-BB (PDGF-BB) induced SPOCK1 expression by activating the PI3K/Akt/forkhead box M1 (FoxM1) signaling pathway. Intracellular SPOCK1 downregulation decreased the HSC activation, proliferation, and migration induced by PDGF-BB. Furthermore, intracellular SPOCK1 overexpression or recombinant SPOCK1 treatment promoted HSC activation, proliferation, and migration by activating the PI3K/Akt signaling pathway. Co-immunoprecipitation, double immunofluorescence staining indicated that SPOCK1 interacted with integrin α5β1, and neutralization of integrin α5β1 significantly reduced the role of recombinant SPOCK1 in HSCs. In vivo HSC-specific SPOCK1 knockdown following lentivirus administration dramatically ameliorated thioacetamide (TAA)-induced collagen deposition in rat livers. Collectively, our study indicates that SPOCK1 is crucial for hepatic fibrosis and it might be a promising therapeutic target.

Dynamic Changes in Function and Proteomic Composition of Extracellular Vesicles from Hepatic Stellate Cells during Cellular Activation

During chronic liver injury, hepatic stellate cells (HSC) undergo activation and are the principal cellular source of collagenous scar. In this study, we found that activation of mouse HSC (mHSC) was associated with a 4.5-fold increase in extracellular vesicle (EV) production and that fibrogenic gene expression (CCN2, Col1a1) was suppressed in Passage 1 (P1; activated) mHSC exposed to EVs from Day 4 (D4; relatively quiescent) mHSC but not to EVs from P1 mHSC. Conversely, gene expression (CCN2, Col1a1, αSMA) in D4 mHSC was stimulated by EVs from P1 mHSC but not by EVs from D4 mHSC. EVs from Day 4 mHSC contained only 46 proteins in which histones and keratins predominated, while EVs from P1 mHSC contained 337 proteins and these were principally associated with extracellular spaces or matrix, proteasome, collagens, vesicular transport, metabolic enzymes, ribosomes and chaperones. EVs from the activated LX-2 human HSC (hHSC) line also promoted fibrogenic gene expression in D4 mHSC in vitro and contained 524 proteins, many of which shared identity or had functional overlap with those in P1 mHSC EVs. The activation-associated changes in production, function and protein content of EVs from HSC likely contribute to the regulation of HSC function in vivo and to the fine-tuning of fibrogenic pathways in the liver.

Integrins in wound healing, fibrosis and tumor stroma: High potential targets for therapeutics and drug delivery

Wound healing is a complex process, which ultimately leads to fibrosis if not repaired well. Pathologically very similar to fibrosis is the tumor stroma, found in several solid tumors which are regarded as wounds that do not heal. Integrins are heterodimeric surface receptors which control various physiological cellular functions. Additionally, integrins also sense ECM-induced extracellular changes during pathological events, leading to cellular responses, which influence ECM remodeling. The purpose and scope of this review is to introduce integrins as key targets for therapeutics and drug delivery within the scope of wound healing, fibrosis and the tumor stroma. This review provides a general introduction to the biology of integrins including their types, ligands, means of signaling and interaction with growth factor receptors. Furthermore, we highlight integrins as key targets for therapeutics and drug delivery, based on their biological role, expression pattern within human tissues and at cellular level. Next, therapeutic approaches targeting integrins, with a focus on clinical studies, and targeted drug delivery strategies based on ligands are described.

Integrins and heparan sulfate proteoglycans on hepatic stellate cells (HSC) are novel receptors for HSC-derived exosomes

Exosomes mediate intercellular microRNA delivery between hepatic stellate cells (HSC), the principal fibrosis-producing cells in the liver. The purpose of this study was to identify receptors on HSC for HSC-derived exosomes, which bind to HSC rather than to hepatocytes. Our findings indicate that exosome binding to HSC is blocked by treating HSC with RGD, EDTA, integrin αv or β1 siRNAs, integrin αvβ3 or α5β1 neutralizing antibodies, heparin, or sodium chlorate. Furthermore, exosome cargo delivery and exosome-regulated functions in HSC, including expression of fibrosis- or activation-associated genes and/or miR-214 target gene regulation, are dependent on cellular integrin αvβ3, integrin α5β1, or heparan sulfate proteolgycans (HSPG). Thus, integrins and HSPG mediate the binding of HSC-derived exosomes to HSC as well as the delivery and intracellular action of the exosomal payload.

Molecular cloning, overexpression, and an efficient one-step purification of α5β1 integrin

The α5β1 integrin heterodimer is involved in many cellular processes and is an anti-cancer therapeutic target. Therefore, access to quantities of protein suitable for studies aimed at understanding its biological functions is important. To this end, a large-scale protein expression system, utilizing the recombinant baculovirus/SF9 insect cell expression system, was created to produce the extracellular domain of the α5β1 integrin. An incorporated 8X-histidine tag enabled one-step nickel-column purification. Following sequence confirmation by LC-MS/MS, the conformation of the heterodimer was characterized by native dot blot and negative stain electron microscopy. Cellular transduction inhibition studies confirmed biological activity. The system allows expression and purification of α5β1 integrin in quantities suitable for an array of different experiments including structural biology.

Proteomic analysis of extracellular matrix from the hepatic stellate cell line LX-2 identifies CYR61 and Wnt-5a as novel constituents of fibrotic liver

Activation of hepatic stellate cells (HSCs) and subsequent uncontrolled accumulation of altered extracellular matrix (ECM) underpin liver fibrosis, a wound healing response to chronic injury, which can lead to organ failure and death. We sought to catalogue the components of fibrotic liver ECM to obtain insights into disease etiology and aid identification of new biomarkers. Cell-derived ECM was isolated from the HSC line LX-2, an in vitro model of liver fibrosis, and compared to ECM from human foreskin fibroblasts (HFFs) as a control. Mass spectrometry analyses of cell-derived ECMs identified, with ≥99% confidence, 61 structural ECM or secreted proteins (48 and 31 proteins for LX-2 and HFF, respectively). Gene ontology enrichment analysis confirmed the enrichment of ECM proteins, and hierarchical clustering coupled with protein–protein interaction network analysis revealed a subset of proteins enriched to fibrotic ECM, highlighting the existence of cell type-specific ECM niches. Thirty-six proteins were enriched to LX-2 ECM as compared to HFF ECM, of which Wnt-5a and CYR61 were validated by immunohistochemistry in human and murine fibrotic liver tissue. Future studies will determine if these and other components may play a role in the etiology of hepatic fibrosis, serve as novel disease biomarkers, or open up new avenues for drug discovery.

The role of dystroglycan in PDGF-BB-dependent migration of activated hepatic stellate cells/myofibroblasts

Hepatic stellate cells are embedded in the loose connective tissue matrix within the space of Disse. This extracellular matrix contains several basement membrane components including laminin, but its composition changes during liver injury because of the production of extracellular matrix components found in scar tissue. These changes in extracellular matrix composition and in cell-extracellular matrix interactions may play a key role in hepatic stellate cell transdifferentiation. In this communication we used early passages of mouse hepatic stellate cells (activated HSC/myofibroblasts) to study the platelet-derived growth factor BB (PDGF-BB)-dependent expression and regulation of β-dystroglycan and its role in activated HSC/myofibroblast migration. We used Northern and Western analysis to study dystroglycan expression and confocal microscopy to investigate changes in subcellular distribution of the protein. Activated HSC migration was investigated using an in vitro wound-healing assay. PDGF-BB induced significant changes in dystroglycan regulation and subcellular distribution of the protein. Whereas steady-state levels of dystroglycan mRNA remained constant, PDGF-BB increased dystroglycan transcription but shortened the t(1/2) by 50%. Moreover, PDGF-BB changed dystroglycan and α5-integrin cellular distribution. Cell migration experiments revealed that PDGF-BB-dependent migration of activated HSC/myofibroblasts was completely blocked by neutralizing antibodies to fibronectin, α5-integrin, laminin, and β-dystroglycan. Overall, these findings suggest that both laminin and fibronectin and their receptors play a key role in PDGF-BB-induced activated HSC migration.

Role of integrins in fibrosing liver diseases

Integrins and other cell adhesion molecules regulate numerous physiological and pathological mechanisms by mediating the interaction between cells and their extracellular environment. Although the significance of integrins in the evolution and progression of certain cancers is well recognized, their involvement in nonmalignant processes, such as organ fibrosis or inflammation, is only beginning to emerge. However, accumulating evidence points to an instrumental role of integrin-mediated signaling in a variety of chronic and acute noncancerous diseases, particularly of the liver.

Down-regulation of focal adhesion kinase by short hairpin RNA increased apoptosis of rat hepatic stellate cells

Focal adhesion kinase (FAK) plays an essential role in the activation of hepatic stellate cells (HSC). The role of FAK on proliferation and apoptosis of fibronectin (FN)-stimulated HSC was investigated using short hairpin RNA (shRNA)-mediated gene silencing technology. FAK shRNA decreased the expressions of FAK, p-FAK (Tyr(397)), ERK(1), and p-ERK(1). FAK gene silencing also inhibited HSC proliferation by 11.08% at 12-h, 15.12% at 24-h, and 28.62% at 48-h post-transfection. Flow cytometric analysis (FACS) revealed that the apoptotic rate at 24 h was increased in the FAK shRNA plasmid group compared with the HK group (8.29 ± 0.79% vs 2.70 ± 0.31%, p < 0.01). TUNEL also confirmed the increase in the rate of apoptosis (19.00 ± 0.92% vs 7.63 ± 0.70%, p < 0.01), and studies showed that the caspase-3 expression was increased while the ratio of Bcl-2 to Bax was decreased. Together, these data show that FAK regulates HSC proliferation and induces the apoptosis of HSC via the caspase-3 and Bcl-2/Bax pathway.

Integrin expression and function in the response of primary culture hepatic stellate cells to connective tissue growth factor (CCN2)

Production of connective tissue growth factor (CCN2, also known as CTGF) is a hallmark of hepatic fibrosis. This study examined early primary cultures of hepatic stellate cells (HSC) for (i) CCN2 regulation of its cognate receptor integrin subunits; and (ii) interactions between CCN2 and integrin α(5)β(1), heparan sulphate proteoglycans (HSPG) or fibronectin (FN) in supporting cell adhesion. HSC were isolated from healthy male Balb/c mice. mRNA levels of CCN2 or α(5), β(1), αv or β(3) integrin subunits were measured in days 1-7 primary culture HSC, and day 3 or day 7 cells treated with recombinant CCN2 or CCN2 small interfering RNA. Interactions between CCN2 and integrin α(5)β(1), HSPG or FN were investigated using an in vitro cell adhesion assay. Co-incident with autonomous activation over the first 7 days, primary culture HSC increasingly expressed mRNA for CCN2 or integrin subunits. Addition of exogenous CCN2 or knockdown of endogenous CCN2 differentially regulated integrin gene expression in day 3 versus day 7 cells. Either full length CCN2 ('CCN2(1-4)') or residues 247-349 containing module 4 alone ('CCN2(4)') supported day 3 cell adhesion in an integrin α(5)β(1) - and HSPG-dependent fashion. Adhesion of day 3 cells to FN was promoted in an integrin α(5) β(1)-dependent manner by CCN2(1-4) or CCN2(4), whereas FN promoted HSPG-dependent HSC adhesion to CCN2(1-4) or CCN2(4). These findings suggest CCN2 regulates integrin expression in primary culture HSC and supports HSC adhesion via its binding of cell surface integrin α(5)β(1), a novel CCN2 receptor in primary culture HSC which interacts co-operatively with HSPG or FN.

Biochemical characterization of the binding of cyclic RGDyK to hepatic stellate cells

Activated hepatic stellate cells (HSCs) play a crucial role in the development of liver fibrosis. Noninvasive monitoring of the activation of HSCs has been challenging due to the lack of specific receptors or motifs on the cells. The present study provides the evidence that integrin alpha v beta 3 expressed on HSCs is a biomarker reflecting the activation of HSCs. Solid-phase synthesis of cRGDyK (Arg-Gly-Asp-(D)Tyr-Lys) peptide and FAM-conjugated peptide were employed for binding to integrin alpha v beta 3. The increased expression of integrin alpha v and beta 3 at mRNA and protein levels was detected during HSC activation. The affinity of cRGDyK to integrin alpha v beta 3 was examined by both radioligand binding assay and FAM-conjugated peptide binding measurements. Quantitative RT-PCR and Western blotting showed a less dramatic, but significant increase in alpha v and beta 3 integrin mRNA and protein expression following activation of rat HSCs. Radioiodinated cRGDyK binds to both purified and membrane-bound integrin alpha v beta 3 with high affinity in a dissociable manner. FAM-conjugated cRGDyK was coupled to activated HSCs in a time- and dose-dependent, receptor-mediated manner. Activated HSCs express sufficient number of integrin alpha v beta 3 receptor. cRGDyK peptide binds to both purified and membrane-bound integrin alpha v beta 3 with high affinity in a reversible fashion. Thus, the cRGDyK peptide represented a new agent potentially useful for the diagnosis of liver fibrosis.

Fibronectin stimulates endothelin-1 synthesis in rat hepatic myofibroblasts via a Src/ERK-regulated signaling pathway

BACKGROUND & AIMS

Liver injury serves as an excellent model of wound healing, characterized by increased synthesis of various cytokines and peptides, including the vasoactive peptide endothelin-1. In the liver, wound healing is mediated by effector cells such as hepatic stellate cells, which cause tissue contraction. Endothelin-1 has autocrine effects on stellate cells and induces their contractile activities. We explored the role of various extracellular matrix components, particularly of fibronectin, in regulating endothelin-1 production during liver injury.

METHODS

Hepatic stellate cells were isolated from normal and injured rats. Real-time polymerase chain reaction immunoblot and enzyme-linked immunosorbent assay analyses were used to measure specific variables, including endothelin-1 production. Preproendothelin-1 promoter activity was determined by a luciferase assay. Stellate cell contraction was measured by a gel contraction assay.

RESULTS

Fibronectin stimulated transcription of preproendothelin-1 messenger RNA and expression of endothelin through an integrin-dependent pathway in activated hepatic stellate cells. In these cells, fibronectin induced phosphorylation/activation of extracellular signal-regulated kinase (ERK) through a Shc- and Src-dependent mechanism; ERK activation was required for fibronectin-induced endothelin-1 expression. Fibronectin stimulation by stellate cells induced expression of smooth muscle alpha-actin and endothelin-1-mediated autocrine stellate cell contraction. Stellate cells isolated from injured livers of rats exhibited increased basal phosphorylation levels of Src, Shc, and ERK, as well as increased endothelin-1 synthesis.

CONCLUSIONS

Fibronectin stimulates activated stellate cells to produce endothelin-1 and contract, via an ERK-dependent signaling pathway. The resulting autocrine functional effects of endothelin-1 are likely to be important in the wound-healing process in injured liver.

The predictive value of CD38 positive hepatic stellate cell count for assessing disease activity and fibrosis in patients with chronic hepatitis

The activation of hepatic stellate cells (HSCs) is a critical event in hepatic fibrosis. The objectives of this study were to find out if cluster of differentiation 38 (CD38) can be demonstrated immunohistochemically on HSCs in liver biopsies from patients with chronic liver disease and if CD38 immunopositive HSC count is correlated with METAVIR inflammatory and fibrosis scores. Immunohistochemical labelling for CD38 was performed on 100 liver biopsies from patients with chronic liver disease. The CD38 immunopositive HSCs were identified and counted. The CD38 immunopositive HSC count was found to be associated with both the METAVIR score and the fibrosis scores. The CD38 immunopositive HSC count was able to discriminate between no fibrosis and stages 2, 3 or 4 fibrosis, but could not discriminate between no fibrosis and stage 1 fibrosis. Using receiver operating characteristic (ROC) curves, a cut-off point of 10 HSCs per 10 high power field (hpf), or 25 per 100 hepatocytes, is 80% sensitive and 70% specific for predicting fibrosis. The specificity rose to 100% in patients with hepatitis C viral (HCV) infection. We conclude that CD38 positive HSCs can be demonstrated immunohistochemically and that the count is highly predictive of moderate to severe hepatic fibrosis.

Proliferation and adhesion of periodontal ligament cells on synthetic biominerals

OBJECTIVE

Hydroxiapatite (HA) has been suggested as a useful biomaterial to support the regeneration of tissues. In this study, we investigated the adhesion of periodontal ligament (PDL) cells on octacalcium phosphate (OCP) and its hydrolyzed apatitic product (HL), which are known precursors of HA.

METHODS

Rat PDL cells were cultured on OCP or HL-coated dishes. Cell proliferation and adhesion and mRNA expression of collagen I, fibronectin integrin subunits were examined. Cell adhesion inhibition assays were carried out by GRGDSPK (Gly-Arg-Gly-Asp-Ser-Pro-Lys).

RESULTS

In early culture period, the cell number of PDL cells was lower on OCP and HL than that on control without any coating. However, the cell number on OCP or HL caught up with control later period. mRNA expression level of collagen I and fibronectin on OCP and HL were similar among OCP HL and control, although they differed early in the culture period. Integrin subunits were expressed on both OCP and HL as well as on control. Cell adhesion was inhibited by RGD inhibitor peptide.

CONCLUSION

Our findings indicated that rat PDL cells produce collagen I and fibronectin on OCP and HL, and then show increased cell numbers depending on adhesion to the matrices through integrins.

Pharmacological inhibition of the vitronectin receptor abrogates PDGF-BB-induced hepatic stellate cell migration and activation in vitro

BACKGROUND/AIMS

Activated hepatic stellate cells (HSC) play a central role in the development of liver fibrosis. Platelet-derived growth factor (PDGF)-BB and the integrin alphavbeta3 mediate mesenchymal cell migration and proliferation. However, their contribution and interaction during fibrogenic activation of HSC remains unclear. To this aim we investigated if PDFGF-BB and alphavbeta3 interact, and how far small molecular inhibitors of alphavbeta3 modulate PDGF-BB and serum-induced migration, proliferation and fibrogenic activation of HSC.

METHODS

Rat and human HSC were subjected to migration and proliferation assays in the presence or absence of a peptide or a nonpeptide alphavbeta3 inhibitor. Activation of mitogen-activated protein kinases (ERK1/2, p38), Akt, focal adhesion kinase (FAK), paxillin and beta3 integrin was evaluated by phospho-specific Western blotting. Fibrosis related transcripts were determined by quantitative real-time PCR.

RESULTS

PDGF-BB-stimulated HSC migration which was blocked dose-dependently by the alphavbeta3 antagonists, with complete inhibition at 10(-6)M. alphavbeta3 blockage did not affect cell viability or proliferation, while it decreased phosphorylation of FAK, paxillin, beta3 integrin and p38, but not of ERK1/2 or Akt. alphavbeta3 inhibition led to downregulation of certain profibrogenic transcripts, while it upregulated fibrolytic MMP-13 mRNA.

CONCLUSIONS

Inhibition of integrin alphavbeta3 leads to abrogation of migration of HSC stimulated with PDGF-BB and to an antifibrogenic gene expression pattern.

Gene expression profiling of extracellular matrix as an effector of human hepatocyte phenotype in primary cell culture

Previously, we demonstrated that primary cultures of rat hepatocytes evidence higher levels of differentiated function when cultured in the presence of a dilute overlay of extracellular matrix (Matrigel). In this investigation, we used DNA microarrays, quantitative RT-PCR, immunoblotting, and cell morphology analyses to evaluate the biological responses imparted by Matrigel overlays on primary cultures of human hepatocytes from five independent donors. Although interindividual variability in responses was evident, our results demonstrated that Matrigel additions typically improved hepatocyte morphology and differentiation character. Results from RNA-profiling experiments indicated that Matrigel additions enhanced hepatocyte RNA expression levels associated with a battery of differentiated features, to levels comparable to those seen in vivo, for genes such as the cytochrome P450s, solute carrier family members, sulfotransferases, certain nuclear transcription factors, and other liver-specific markers, such as albumin, transferrin, and response to the inducer, phenobarbital. In contrast, Matrigel additions were generally associated with reduced RNA expression levels for several cytokeratins, integrins, and a number of stress-related pathways. Decreases in integrin protein expression were similarly detected, although enhanced levels of the gap junction-associated protein, connexin 32, were detected in Matrigel-treated cultures. These data support the concept that ECM functions mechanistically to augment the differentiation character of primary human hepatocytes in culture by mediating a reduction in cellular stress response signaling and by enhancing gap junctional cell-cell communication.

Identification and functional characterization of the hepatic stellate cell CD38 cell surface molecule

The activation of hepatic stellate cells (HSCs) is a critical event in hepatic fibrosis, because these cells are the main producers of extracellular matrix proteins in the liver and contribute to the modulation of inflammatory responses via the secretion of several cytokines and the expression of adhesion molecules. The goal of the present study was to characterize cell surface proteins that regulate HSC activation. To this end, a panel of monoclonal antibodies (mAbs) was generated. mAb 14.27 recognized a protein of 45 kd that was highly expressed on HSCs. Affinity purification of this protein followed by sequencing revealed that protein to be CD38. We subsequently demonstrated that CD38 was constitutively expressed by HSCs and that its expression increased after in vitro and in vivo activation. mAb 14.27 induced an increase in cytosolic Ca2+ levels in HSCs, showing that it functions as an agonistic antibody. Moreover, the effects mediated by the CD38 mAb included induction of the proinflammatory cytokine interleukin-6 and up-regulation of the adhesion molecules intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and neural cell adhesion molecule. Collectively, our data suggest that CD38 can act as a regulator of HSC activation and effector functions.

Actinobacillus actinomycetemcomitans outer membrane protein 100 triggers innate immunity and production of beta-defensin and the 18-kilodalton cationic antimicrobial protein through the fibronectin-integrin pathway in human gingival epithelial cells

Antimicrobial peptides, human beta-defensin (hBD), and the 18-kDa cationic antimicrobial protein (CAP18) are components of innate immunity. These peptides have antimicrobial activity against bacteria, fungi, and viruses. Actinobacillus actinomycetemcomitans is a gram-negative facultative anaerobe implicated in the initiation of periodontitis. The innate immunity peptides have antibacterial activity against A. actinomycetemcomitans. We investigated the molecular mechanism of human gingival epithelial cells (HGEC) responding to exposure to A. actinomycetemcomitans. HGEC constitutively express hBD1 and inducibly express hBD2, hBD3, and CAP18 on exposure to A. actinomycetemcomitans. The level of expression varies among clinical isolates. In the signaling pathway for hBD2 induction by the bacterial contact, we demonstrate that the mitogen-activated protein (MAP) kinase and not the NF-kappaB transcription factor pathway is used. We found the outer membrane protein 100 (Omp100; identified by molecular mass) is the component inducing the hBD2 response. Omp100 binds to fibronectin, an extracellular matrix inducing hBD2 via the MAP kinase pathway. Anti-integrin alpha(5)beta(1), antifibronectin, genistein, and PP2 suppress the Omp100-induced expression of hBD2, suggesting that Src kinase is involved through integrin alpha(5)beta(1). The inflammatory cytokines, tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-6 and IL-8, produced by HGEC on contact with A. actinomycetemcomitans also stimulate expression of hBD2. Further, neutralizing antibody against TNF-alpha or IL-8 partially inhibits the induction of hBD2 on bacterial contact. Therefore, we found that the induction of the antimicrobial peptides is mediated by a direct response principally through an Omp100-fibronectin interaction, and using secondary stimulation by inflammatory cytokines induced by the bacterial exposure.

Effects of rhDecorin on TGF-beta1 induced human hepatic stellate cells LX-2 activation

Decorin is a small leucine-rich extracellular matrix proteoglycan composed of a core protein with a single glycosaminoglycan (GAG) chain near the N-terminus and N-glycosylated at three potential sites. Decorin is involved in the regulation of formation and organization of collagen fibrils, modulation of the activity of growth factors such as transforming growth factor beta (TGF-beta), and exerts other effects on cell proliferation and behavior. Increasing evidences show that decorin plays an important role in fibrogenesis by regulating TGF-beta, a key stimulator of fibrosis, and by directly modulating the degradation of extracellular matrix (ECM) from activated hepatic stellate cells (HSCs). In this study, the core protein of human decorin was cloned and expressed in Escherichia coli. The purified recombinant human decorin (rhDecorin) significantly inhibited the proliferation of LX-2 cells, a human HSC cell line, stimulated by TGF-beta1. RT-PCR result showed that the expression of metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were reduced by rhDecorin in LX-2 cells stimulated by TGF-beta1. Furthermore, the protein expression of smooth muscle-alpha-actin (alpha-SMA), collagen type III and phosphorylated Smad2 (p-Smad2) was significantly decreased in the presence of rhDecorin. rhDecorin also reduced fibrillogenesis of collagen type I in a dose-dependent manner. Gene expression profiles of LX-2 cells stimulated by TGF-beta1 in the presence and the absence of rhDecorin were obtained by using cDNA microarray technique and differentially expressed genes were identified to provide further insight into the molecular action mechanism of decorin on LX-2 cells.

Differential cell adhesion to vocal fold extracellular matrix constituents

The human vocal folds are a complex layering of cells and extracellular matrix. Vocal fold extracellular matrix uniquely contributes to the biomechanical viscoelasticity required for human phonation. We investigated the adhesion of vocal fold stellate cells, a novel cell type first cultured by our laboratory, and fibroblasts to eight vocal fold extracellular matrix components: elastin, decorin, fibronectin, hyaluronic acid, laminin and collagen types I, III and IV. Our data demonstrate that these cells adhere differentially to said substrates at 5 to 120 min. Cells were treated with hyaluronidase and Y-27632, a p160ROCK-specific inhibitor, to test the role of pericellular hyaluronan and Rho-ROCK activation in early and mature adhesion. Reduced adhesion resulted; greater inhibition of fibroblast adhesion was observed. We modulated the fibronectin affinity exhibited by both cell types using Nimesulide, an inhibitor of fibronectin integrin receptors alpha5beta1 and alphavbeta3. Our results are important in understanding vocal fold pathologies, wound healing, scarring, and in developing an accurate organotypic model of the vocal folds.

Collagen binding alpha2beta1 and alpha1beta1 integrins play contrasting roles in regulation of Ets-1 expression in human liver myofibroblasts

Activation of hepatic stellate cells from quiescence to myofibroblast-like cells (MFBs) is a pivotal event in hepatic fibrogenesis. Plastic-cultured stellate cells (an established in vitro model of the activated phenotype) recultured on Matrigel revert to quiescence. In the present study we analyzed the molecular mechanism underlying this process, focusing on the effect of collagen receptors alpha(2)beta(1) and alpha(1)beta(1) integrin signaling on the expression of Ets-1 transcription factor and its target gene MMP1 in cultured human MFBs. Cells grown in 3-dimensional (3D) substrates (Matrigel) or collagen type I gel) markedly upregulated Ets-1 and MMP1 messages, in comparison to cells cultured on plastic. A similar effect but less intense was mimicked by stimulation of alpha(2)beta(1) or blocking of alpha(1)beta(1) integrin in cells grown on plastic. We observed increased expression of MMP1 transcripts with parallel changes in MMP1 promoter activity, and in mRNA and protein levels of upstream transcription factors Ets-1 and c-Jun. Interference with alpha(2)beta(1) and alpha(1)beta(1) integrin function in cells cultured in a 3D collagen substrate resulted in an even greater effect. Morphologically, stimulation of alpha(2)beta(1) integrin resulted in formation of multicellular networks, probably by facilitation of cell migration. Thus, we report the novel observation that in cultured human MFBs reverting to quiescence, the expression of transcription factor Ets-1 and its downstream target MMP1 can be modulated by changes in the microenvironment, which are mediated, at least in part, by the balance between collagen receptor integrin alpha(2)beta(1) and alpha(1)beta(1) activities.

Immunohistochemical assessment of fibronectin and tenascin and their integrin receptors alpha5beta1 and alpha9beta1 in gastric and colorectal cancers with lymph node and liver metastases

The aim of the current study was to assess immunohistochemically and compare the level of expression of tenascin (TN) and fibronectin (FN) and their integrin receptors alpha9beta1 and alpha5beta1 in the primary colorectal and gastric tumors, and in corresponding lymph node and liver metastases from 53 patients. We detected similar high deposition of the studied ECM proteins and their receptors in the stroma of primary tumors and in liver metastases and a lower deposition in lymph node metastases. Cytoplasmic immune reaction for FN and TN was also seen in the tumor cells. A pronounced co-localization of immune deposits for FN and TN and their receptors was found in the stroma of the center and the invasion front (IF) (p<0.0001). A significant decrease of FN immune signal was observed in the IF in primary tumors and liver metastases (p<0.0001). The levels of immunolabeling of FN and TN correlated with the differentiation grade of primary tumors (p<0.0001). In conclusion, we may say that there is heterogeneous deposition of TN, FN and their integrin receptors in the different areas of primary colorectal and gastric tumors and of their metastases. These findings imply that the studied proteins may be involved in cell processes such as growth, adhesion, migration and apoptosis.

Immortalization of pancreatic stellate cells as an in vitro model of pancreatic fibrosis: deactivation is induced by matrigel and N-acetylcysteine

Tissue fibrosis is one of the characteristics of chronic pancreatitis and pancreatic adenocarcinoma. Activated pancreatic stellate cells (PSC) play a central role in this process. However, analysis of the molecular mechanisms leading to PSC activation is hampered by the lack of an established human PSC line. To overcome this problem, we immortalized and characterized primary human PSC. The cells were isolated by the outgrowth method and were immortalized by transfection with SV40 large T antigen and human telomerase (hTERT). Primary human PSC served as controls. An immortalized line, RLT-PSC, was analyzed for the expression of stellate cell markers. Moreover, the effects of transforming growth factor beta 1(TGFbeta1) or platelet-derived growth factor stimulation and of cultivation on basement membrane components or N-acetylcysteine (NAC) treatment on gene and protein expression and proliferation were analyzed. Immortal RLT-PSC cells retained the phenotype of activated PSC proven by the expression of alpha-smooth muscle actin (alphaSMA), vimentin, desmin and glial fibrillary acidic protein (GFAP). TGFbeta1 treatment upregulated the expression of alphaSMA, collagen type I (Col I), fibronectin and TGFbeta1. Incubation of RLT-PSC cells and primary human activated PSC on Matrigel plus NAC treatment resulted in a deactivated phenotype as evidenced by a decrease of alphaSMA, connective tissue growth factor and Col I expression and by a decreased proliferation of the cells. Moreover, this treatment restored the ability of the cells to store vitamin A in cytoplasmic vesicles. In conclusion, we have established an immortal pancreatic stellate cell line, without changing the characteristic phenotype. Importantly, we were able to demonstrate that besides soluble factors, the matrix surrounding PSC plays a pivotal role in the maintenance of the activation process of PSC. Cultivation of activated PSC on a reconstituted basement membrane plus treatment with NAC was able to deactivate the cells, thus pointing to the possibility of an antifibrosis therapy in chronic pancreatitis.

Molecular profiling of early stage liver fibrosis in patients with chronic hepatitis C virus infection

The molecular mechanisms of acute hepatitis C virus (HCV) infection, end-stage hepatitis (cirrhosis), and hepatocellular carcinoma have been extensively studied, but little is known of the changes in liver gene expression during the early stages of liver fibrosis associated with chronic HCV infection, that is, the transition from normal liver (NL) of uninfected patients to the first stage of liver fibrosis (F1-CH-C). To obtain insight into the molecular pathogenesis of F1-CH-C, we used real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to study the mRNA expression of 240 selected genes in liver tissue with F1-CH-C, in comparison with NL. The expression of 54 (22.5%) of the 240 genes was significantly different between F1-CH-C and NL; 46 genes were upregulated and 8 were downregulated in F1-CH-C. The most noteworthy changes in gene expression mainly affected the transcriptional network regulated by interferons (IFNs), including both IFN-alpha/beta-inducible genes (STAT1, STAT2, ISGF3G/IRF9, IFI27, G1P3, G1P2, OAS2, MX1) and IFN-gamma-inducible genes (CXCL9, CXCL10, CXCL11). Interesting, upregulation of IFN-alpha/beta-inducible genes (but not IFN-gamma-inducible genes) was independent of histological scores (grade and stage of fibrosis) and HCV characteristics (hepatic HCV mRNA levels and the HCV genotype), and was specific to HCV (as compared to hepatitis B virus (HBV)). Other genes dysregulated in F1-CH-C, albeit less markedly than IFN-alpha/beta- and IFN-gamma-inducible genes, were mainly involved in the activation of lymphocytes infiltrating the liver (IFNG, TNF, CXCL6, IL6, CCL8, CXCR3, CXCR4, CCR2), cell proliferation (p16/CDKN2A, MKI67, p14/ARF), extracellular matrix remodeling (MMP9, ITGA2), lymphangiogenesis (XLKD1/LYVE), oxidative stress (CYP2E1), and cytoskeleton microtubule organization (STMN2/SCG10). Thus, a limited number of signaling pathways, and particularly the transcriptional network regulated by interferons, are dysregulated in the first stage of HCV-induced liver fibrosis. Some of the genes identified here could form the basis for new approaches aimed at refining IFN-based therapies for chronic HCV infection.

Gene expression differences of regenerating rat liver in a short interval successive partial hepatectomy

AIM: To identify the genes expressed differentially in the regenerating rat liver in a short interval successive partial hepatectomy (SISPH), and to analyze their expression profiles.

METHODS: Five hundred and fifty-one elements selected from subtractive cDNA libraries were conformed to a cDNA microarray (cDNA chip). An extensive gene expression analysis following 0-36-72-96-144 h SISPH was performed by microarray.

RESULTS: Two hundred and sixteen elements were identified either up- or down-regulated more than 2-fold at one or more time points of SISPH. By cluster analysis and generalization analysis, 8 kinds of ramose gene expression clusters were generated in the SISPH. Of the 216 elements, 111 were up-regulated and 105 down-regulated. Except 99 unreported genes, 117 reported genes were categorized into 22 groups based on their biological functions. Comparison of the gene expression in SISPH with that after partial hepatectomy (PH) disclosed that 56 genes were specially altered in SISPH, and 160 genes were simultaneously up-regulated or down-regulated in SISPH and after PH, but in various amount and at different time points.

CONCLUSION: Genes expressed consistently are far less than that intermittently; the genes strikingly increased are much less than that increased only 2-5 fold; the expression trends of most genes in SISPH and in PH are similar, but the expression of 56 genes is specifically altered in SISPH. Microarray combined with suppressive subtractive hybridization can in a large scale effectively identify the genes related to liver regeneration.