Structural and functional properties of CCN proteins

The matricellular protein CCN5 regulates podosome function via interaction with integrin αvβ 3

CCN proteins play crucial roles in cell motility, matrix turnover, and proliferation. In particular, CCN5 plays a role in cell motility and proliferation in several cell types; however, no functional binding proteins for CCN5 have been identified. In this study we report that CCN5 binds to the cell surface receptor integrin αvβ3 in vascular smooth muscle cells. Furthermore, this interaction takes place in podosomes, organelles known to degrade matrix and mediate motility. We show that CCN5 regulates the ability of podosomes to degrade matrix, but does not affect podosome formation. The level of CCN5 present in a podosome negatively correlates with its ability to degrade matrix. Conversely, knockdown of CCN5 greatly enhances the matrix-degrading ability of podosomes. These findings suggest that the antimotility effects of CCN5 may be mediated through the direct interaction of CCN5 and integrin αvβ3 in podosomes and the concomitant suppression of matrix degradation that is required for cell migration.

The CCN family proteins: modulators of bone development and novel targets in bone-associated tumors

The CCN family of proteins is composed of six extracellular matrix-associated proteins that play crucial roles in skeletal development, wound healing, fibrosis, and cancer. Members of the CCN family share four conserved cysteine-rich modular domains that trigger signal transduction in cell adhesion, migration, proliferation, differentiation, and survival through direct binding to specific integrin receptors and heparan sulfate proteoglycans. In the present review, we discuss the roles of the CCN family proteins in regulating resident cells of the bone microenvironment. In vertebrate development, the CCN family plays a critical role in osteo/chondrogenesis and vasculo/angiogenesis. These effects are regulated through signaling via integrins, bone morphogenetic protein, vascular endothelial growth factor, Wnt, and Notch via direct binding to CCN family proteins. Due to the important roles of CCN family proteins in skeletal development, abnormal expression of CCN proteins is related to the tumorigenesis of primary bone tumors such as osteosarcoma, Ewing sarcoma, and chondrosarcoma. Additionally, emerging studies have suggested that CCN proteins may affect progression of secondary metastatic bone tumors by moderating the bone microenvironment. CCN proteins could therefore serve as potential therapeutic targets for drug development against primary and metastatic bone tumors.

CCN2 modulates hair follicle cycling in mice

Mesenchymal cells play a role in controlling the number of hair follicles. However, the precise molecules involved are unclear. Absence in mesenchymal cells of the expression of the secreted matricellular protein CTGF/CCN2 results in an increased number of hair follicles, concomitant with increased β-catenin activity.

It is critical to understand how stem cell activity is regulated during regeneration. Hair follicles constitute an important model for organ regeneration because, throughout adult life, they undergo cyclical regeneration. Hair follicle stem cells—epithelial cells located in the follicle bulge—are activated by periodic β-catenin activity, which is regulated not only by epithelial-derived Wnt, but also, through as-yet-undefined mechanisms, the surrounding dermal microenvironment. The matricellular protein connective tissue growth factor (CCN2) is secreted into the microenvironment and acts as a multifunctional signaling modifier. In adult skin, CCN2 is largely absent but is unexpectedly restricted to the dermal papillae and outer root sheath. Deletion of CCN2 in dermal papillae and the outer root sheath results in a shortened telogen-phase length and elevated number of hair follicles. Recombinant CCN2 causes decreased β-catenin stability in keratinocytes. In vivo, loss of CCN2 results in elevated numbers of K15-positive epidermal stem cells that possess elevated β-catenin levels and β-catenin–dependent reporter gene expression. These results indicate that CCN2 expression by dermal papillae cells is a physiologically relevant suppressor of hair follicle formation by destabilization of β-catenin and suggest that CCN2 normally acts to maintain stem cell quiescence.

Connective tissue growth factor (CTGF/CCN2): diagnostic and prognostic value in acute heart failure

BACKGROUND

As a mediator of ECM homeostasis, connective tissue growth factor (CTGF) appears to be involved in adverse structural remodeling processes in the heart. However, the diagnostic and prognostic value of CTGF levels in acute heart failure (AHF) in addition to natriuretic peptide testing has not yet been evaluated.

METHODS AND RESULTS

A total of 212 patients presenting with acute dyspnea and/or peripheral edema to the Emergency Department were evaluated. CTGF and NT-proBNP plasma levels were measured at the initial presentation. All patients were followed up to 1 and 5 years. The first endpoint tested was the diagnostic non-inferiority of combined CTGF plus NT-proBNP compared to NT-proBNP alone for AHF diagnosis. Afterwards, the additional diagnostic value of CTGF plus NT-proBNP was tested. CTGF levels were higher in NYHA class III/IV and AHA/ACC class C/D patients compared to lower class patients (p = 0.04). Patients with HFREF revealed highest CTGF levels (median 93.3 pg/ml, IQR 18.2-972 pg/ml, n = 48) compared to patients with a normal heart function (i.e., without HFREF and HFPEF) (median 25.9, IQR <1-82.2 pg/ml, n = 37) (p < 0.05), followed by patients with HFPEF (median 82.2 pg/ml, IQR 11.5-447 pg/ml, n = 32) as assessed by echocardiography. Finally, CTGF levels were higher in patients with AHF (median 77.3 pg/ml, IQR 22.5-1012 pg/ml, n = 66) compared to those without (p = 0.002). CTGF plus NT-proBNP was non-inferior to NT-proBNP testing alone for AHF diagnosis (AUC difference 0.01, p > 0.05). CTGF plus NT-proBNP improved the diagnostic capacity for AHF (accuracy 82 %, specificity 83 %, positive predictive value 66 %, net reclassification improvement +0.11) compared to NT-proBNP alone (p = 0.0001). CTGF levels were not able to differentiate prognostic outcomes after 1 and 5 years.

CONCLUSIONS

Additional CTGF measurements might lead to a better discrimination of higher functional and structural heart failure stages and might identify patients of an increased risk for an acute cardiac decompensation.

Connective tissue growth factor (CTGF) expression modulates response to high glucose

Connective tissue growth factor (CTGF) is an important mediator of fibrosis; emerging evidence link changes in plasma and urinary CTGF levels to diabetic kidney disease. To further ascertain the role of CTGF in responses to high glucose, we assessed the consequence of 4 months of streptozotocin-induced diabetes in wild type (+/+) and CTGF heterozygous (+/−) mice. Subsequently, we studied the influence of glucose on gene expression and protein in mice embryonic fibroblasts (MEF) cells derived from wildtype and heterozygous mice. At study initiation, plasma glucose, creatinine, triglyceride and cholesterol levels were similar between non-diabetic CTGF+/+ and CTGF+/− mice. In the diabetic state, plasma glucose levels were increased in CTGF+/+ and CTGF+/− mice (28.2 3.3 mmol/L vs 27.0 3.1 mmol/L), plasma triglyceride levels were lower in CTGF+/− mice than in CTGF+/+ (0.7 0.2 mmol/L vs 0.5 0.1 mmol/L, p<0.05), but cholesterol was essentially unchanged in both groups. Plasma creatinine was higher in diabetic CTGF+/+ group (11.7±1.2 vs 7.9±0.6 µmol/L p<0.01), while urinary albumin excretion and mesangial expansion were reduced in diabetic CTGF+/− animals. Cortices from diabetic mice (both CTGF +/+ and CTGF +/−) manifested higher expression of CTGF and thrombospondin 1 (TSP1). Expression of nephrin was reduced in CTGF +/+ animals; this reduction was attenuated in CTGF+/− group. In cultured MEF from CTGF+/+ mice, glucose (25 mM) increased expression of pro-collagens 1, IV and XVIII as well as fibronectin and thrombospondin 1 (TSP1). In contrast, activation of these genes by high glucose was attenuated in CTGF+/− MEF. We conclude that induction of Ctgf mediates expression of extracellular matrix proteins in diabetic kidney. Thus, genetic variability in CTGF expression directly modulates the severity of diabetic nephropathy.

Connective tissue growth factor is a new ligand of epidermal growth factor receptor

Chronic kidney disease is reaching epidemic proportions worldwide and there is no effective treatment. Connective tissue growth factor (CCN2) has been suggested as a risk biomarker and a potential therapeutic target for renal diseases, but its specific receptor has not been identified. Epidermal growth factor receptor (EGFR) participates in kidney damage, but whether CCN2 activates the EGFR pathway is unknown. Here, we show that CCN2 is a novel EGFR ligand. CCN2 binding to EGFR extracellular domain was demonstrated by surface plasmon resonance. CCN2 contains four distinct structural modules. The carboxyl-terminal module (CCN2(IV)) showed a clear interaction with soluble EGFR, suggesting that EGFR-binding site is located in this module. Injection of CCN2(IV) in mice increased EGFR phosphorylation in the kidney, mainly in tubular epithelial cells. EGFR kinase inhibition decreased CCN2(IV)-induced renal changes (ERK activation and inflammation). Studies in cultured tubular epithelial cells showed that CCN2(IV) binds to EGFR leading to ERK activation and proinflammatory factors overexpression. CCN2 interacts with the neurotrophin receptor TrkA, and EGFR/TrkA receptor crosstalk was found in response to CCN2(IV) stimulation. Moreover, endogenous CCN2 blockade inhibited TGF-β-induced EGFR activation. These findings indicate that CCN2 is a novel EGFR ligand that contributes to renal damage through EGFR signalling.

CCN4 regulates vascular smooth muscle cell migration and proliferation

The migration and proliferation of vascular smooth muscle cells (VSMCs) are essential elements during the development of atherosclerosis and restenosis. An increasing number of studies have reported that extracellular matrix (ECM) proteins, including the CCN protein family, play a significant role in VSMC migration and proliferation. CCN4 is a member of the CCN protein family, which controls cell development and survival in multiple systems of the body. Here, we sought to determine whether CCN4 is involved in VSMC migration and proliferation. We examined the effect of CCN4 using rat cultured VSMCs. In cultured VSMCs, CCN4 stimulated the adhesion and migration of VSMCs in a dose-dependent manner, and this effect was blocked by an antibody for integrin α5β1. CCN4 expression was enhanced by the pro-inflammatory cytokine tumor necrosis factor α (TNF-α). Furthermore, knockdown of CCN4 by siRNA significantly inhibited the VSMC proliferation. CCN4 also could up-regulate the expression level of marker proteins of the VSMCs phenotype. Taken together, these results suggest that CCN4 is involved in the migration and proliferation of VSMCs. Inhibition of CCN4 may provide a promising strategy for the prevention of restenosis after vascular interventions.

CTGF mediates Smad-dependent transforming growth factor β signaling to regulate mesenchymal cell proliferation during palate development

Transforming growth factor β (TGF-β) signaling plays crucial functions in the regulation of craniofacial development, including palatogenesis. Here, we have identified connective tissue growth factor (Ctgf) as a downstream target of the TGF-β signaling pathway in palatogenesis. The pattern of Ctgf expression in wild-type embryos suggests that it may be involved in key processes during palate development. We found that Ctgf expression is downregulated in both Wnt1-Cre; Tgfbr2(fl/fl) and Osr2-Cre; Smad4(fl/fl) palates. In Tgfbr2 mutant embryos, downregulation of Ctgf expression is associated with p38 mitogen-activated protein kinase (MAPK) overactivation, whereas loss of function of Smad4 itself leads to downregulation of Ctgf expression. We also found that CTGF regulates its own expression via TGF-β signaling. Osr2-Cre; Smad4(fl/fl) mice exhibit a defect in cell proliferation similar to that of Tgfbr2 mutant mice, as well as cleft palate. We detected no alteration in bone morphogenetic protein (BMP) downstream targets in Smad4 mutant palates, suggesting that the reduction in cell proliferation is due to defective transduction of TGF-β signaling via decreased Ctgf expression. Significantly, an exogenous source of CTGF was able to rescue the cell proliferation defect in both Tgfbr2 and Smad4 mutant palates. Collectively, our data suggest that CTGF regulates proliferation as a mediator of the canonical pathway of TGF-β signaling during palatogenesis.

Regulation of CCN1 via the 3'-untranslated region

The 3'-untranslated region (UTR) is known to be a critical regulator of post-transcriptional events that determine the gene expression at the RNA level. The gene CCN1 is one of the classical members of the matricellular CCN family and is involved in a number of biological processes during mammalian development. In the present study, the 600-bp 3'-UTR of CCN1 was functionally characterized. Reporter gene analysis revealed that the entire 3'-UTR profoundly repressed gene expression in cis in different types of the cells, to which both the proximal and distal-halves of the 3'-UTR segments contributed almost equally. Deletion analysis of the 3'-UTR indicated a distinct functional element in the proximal half, whereas a putative target for microRNA-181s was predicted in silico in the distal half. Of note, the repressive RNA element in the proximal half was shown to be capable of forming a stable secondary structure. However, unexpectedly, a reporter construct with a tandem repeat of the predicted miR-181 targets failed to respond to miR-181a. In addition, the other major structured element predicted in the distal half was similarly characterized. To our surprise, the second element rather enhanced the reporter gene expression in cis. These results indicate the involvement of multiple regulatory elements in the CCN1 3'-UTR and suggest the complexity of the miRNA action as well as the 3'-UTR-mediated gene regulation.

TGF-β1-induced synthesis of collagen fibers in skeletal muscle-derived stem cells

The aim of this study was to investigate the mechanism of deposition of extracellular matrix induced by TGF-β1 in skeletal muscle-derived stem cells (MDSCs). Rat skeletal MDSCs were obtained by using preplate technique, and divided into four groups: group A (control group), group B (treated with TGF-β1, 10 ng/mL), group C (treated with TGF-β1 and anti-connective tissue growth factor (CTGF), both in 10 ng/mL), and group D (treated with anti-CTGF, 10 ng/mL). The expression of CTGF, collagen type-I (COL-I) and collagen type-III (COL-III) in MDSCs was examined by using RT-PCR, Western blot and immunofluorescent stain. It was found that one day after TGF-β1 treatment, the expression of CTGF, COL-I and COL-III was increased dramatically. CTGF expression reached the peak on the day 2, and then decreased rapidly to a level of control group on the day 5. COL-I and COL-III mRNA levels were overexpresed on the day 2 and 3 respectively, while their protein expression levels were up-regulated on the day 2 and reached the peak on the day 7. In group C, anti-CTGF could partly suppress the overexpression of COL-I and COL-II induced by TGF-β1 one day after adding CTGF antibody. It was concluded that TGF-β1 could induce MDSCs to express CTGF, and promote the production of COL-I and COL-III. In contrast, CTGF antibody could partially inhibit the effect of TGF-β1 on the MDSCs by reducing the expression of COL-I and COL-III. Taken together, we demonstrated that TGF-β1-CTGF signaling played a crucial role in MDSCs synthesizing collagen proteins in vitro, which provided theoretical basis for exploring the methods postponing skeletal muscle fibrosis after nerve injury.

Genetic analysis of human predisposition to hepatosplenic disease caused by schistosomes reveals the crucial role of connective tissue growth factor in rapid progression to severe hepatic fibrosis

Schistosome worms inhabit mammalian mesenteric veins. Their eggs cause chronic inflammation, which progresses to periportal fibrosis in 5 to 30% of cases, increasing portal blood pressure and leading to esophageal varices. Episodes of bleeding cause hepatic necrosis and may ultimately lead to hepatic failure and the death of the patient. Schistosome infections can also cause pulmonary hypertension and heart failure. The mechanisms of fibrogenesis and fibrolysis are beginning to be unraveled, but it remains unclear why disease occurs only in certain subjects, as also observed for other types of chronic liver inflammation, as in hepatitis C or B. We summarize here the results that showed that fibrosis progression is determined by a genetic locus on chromosome 6. The CCN2 gene at this locus, encodes CTGF that is a crucial regulator of fibrosis. Two groups of CCN2 polymorphisms independently modulate the progression of hepatic fibrosis. These results were obtained in an Asian population, but were extended to humans living in Africa and South America and are presently tested in liver fibrosis of other etiological origins.

A physiological role for connective tissue growth factor in early wound healing

Mesenchymal stem cells (MSCs) that overexpress secreted frizzled-related protein 2 (sFRP2) exhibit an enhanced reparative phenotype. The secretomes of sFRP2-overexpressing MSCs and vector control-MSCs were compared through liquid chromatography tandem mass spectrometry. Proteomic profiling revealed that connective tissue growth factor (CTGF; CCN2) was overrepresented in the conditioned media of sFRP2-overexpressing MSCs and MSC-derived CTGF could thus be an important paracrine effector. Subcutaneously implanted, MSC-loaded polyvinyl alcohol (PVA) sponges and stented excisional wounds were used as wound models to study the dynamics of CTGF expression. Granulation tissue generated within the sponges and full-thickness skin wounds showed transient upregulation of CTGF expression by MSCs and fibroblasts, implying a role for this molecule in early tissue repair. Although collagen and COL1A2 mRNA were not increased when recombinant CTGF was administered to sponges during the early phase (day 1-6) of tissue repair, prolonged administration (>15 days) of exogenous CTGF into PVA sponges resulted in fibroblast proliferation and increased deposition of collagen within the experimental granulation tissue. In support of its physiological role, CTGF immunoinhibition during early repair (days 0-7) reduced the quantity, organizational quality and vascularity of experimental granulation tissue in the sponge model. However, CTGF haploinsufficiency was not enough to reduce collagen deposition in excisional wounds. Similar to acute murine wound models, CTGF was transiently present in the early phase of human acute burn wound healing. Together, these results further support a physiological role for CTGF in wound repair and demonstrate that when CTGF expression is confined to early tissue repair, it serves a pro-reparative role. These data also further illustrate the potential of MSC-derived paracrine modulators to enhance tissue repair.

CCN2 exerts direct cytoprotective actions in adult cardiac myocytes by activation of the PI3-kinase/Akt/GSK-3β signaling pathway

We recently reported that transgenic mice with cardiac-restricted overexpression of CCN2/CTGF have substantially increased tolerance towards ischemia/reperfusion injury. The purpose of this study was to investigate to what extent fully differentiated cardiac myocytes are direct targets of CCN2, and to resolve the signaling mechanisms that convey the cardioprotective actions of CCN2. Akt and GSK-3β were identified as putative intermediaries of intracellular signaling stimulated by recombinant human CCN2 (rhCCN2). Concentration-effect experiments revealed CCN2-stimulated phosphorylation of Akt (Ser473) and downstream GSK-3β (Ser9) with EC50 ~250 nmol/L. CCN2-stimulated phosphorylation of Akt and GSK-3β was sensitive to inhibition of PI3-kinase (LY294002). Phosphorylation of GSK-3β was also sensitive to Akt-inhibition (API-2), demonstrating CCN2-engendered activation of a PI3-kinase/Akt/GSK-3β-signaling pathway. A C-terminal peptide fragment of CCN2 (11.2 kD) displayed partial agonist activity, while two short peptides derived from the Thrombospondin- and the IGFBP- homology domains of CCN2, respectively, additively inhibited rhCCN2-stimulated Akt-phosphorylation. The viability of cardiac myocytes subjected to hypoxia/reoxygenation injury or doxorubicin-induced oxidative stress was assessed by assays of adenylate kinase and lactate dehydrogenase released from dying cells. Cardiac myocytes exposed to CCN2 displayed increased tolerance towards hypoxia/reoxygenation and doxorubicin-induced oxidative stress, an effect that was abrogated by inhibition of PI3-kinase. The cytoprotective actions of CCN2 reflected in the transcriptome of CCN2-stimulated cardiac myocytes (anti-apoptosis, stress, and wound-response gene programs). In conclusion, this study discloses the novel findings that cardiac myocytes are CCN2 target cells in which CCN2 increases tolerance towards hypoxia and oxidative stress via PI3-kinase-dependent Akt/GSK-3β signaling.

The skeletal site-specific role of connective tissue growth factor in prenatal osteogenesis

BACKGROUND

Connective tissue growth factor (CTGF/CCN2) is a matricellular protein that is highly expressed during bone development. Mice with global CTGF ablation (knockout, KO) have multiple skeletal dysmorphisms and perinatal lethality. A quantitative analysis of the bone phenotype has not been conducted.

RESULTS

We demonstrated skeletal site-specific changes in growth plate organization, bone microarchitecture, and shape and gene expression levels in CTGF KO compared with wild-type mice. Growth plate malformations included reduced proliferation zone and increased hypertrophic zone lengths. Appendicular skeletal sites demonstrated decreased metaphyseal trabecular bone, while having increased mid-diaphyseal bone and osteogenic expression markers. Axial skeletal analysis showed decreased bone in caudal vertebral bodies, mandibles, and parietal bones in CTGF KO mice, with decreased expression of osteogenic markers. Analysis of skull phenotypes demonstrated global and regional differences in CTGF KO skull shape resulting from allometric (size-based) and nonallometric shape changes. Localized differences in skull morphology included increased skull width and decreased skull length. Dysregulation of the transforming growth factor-β-CTGF axis coupled with unique morphologic traits provides a potential mechanistic explanation for the skull phenotype.

CONCLUSIONS

We present novel data on a skeletal phenotype in CTGF KO mice, in which ablation of CTGF causes site-specific aberrations in bone formation.

Future prevention and treatment of chronic hepatitis B infection

Vaccination for hepatitis B virus (HBV) infection and treatment for chronic hepatitis B, while effective for primary prevention and control of the disease, still have their limitations. Global coverage of HBV immunization needs improvement. Several patient populations are noted to have suboptimal seroprotective rates after HBV vaccination. There are currently several potential new vaccines undergoing animal and human studies, most notably vaccines containing immunostimulatory DNA sequences. Long-term nucleoside analogue therapy is necessary in achieving permanent virologic suppression. Potential new treatments explore new mechanisms of action, including the inhibition of hepatitis B surface antigen release, targeting antifibrotic mechanism, and immunomodulation through novel interferons and therapeutic vaccines. The clinical application of potential new vaccines and therapies would enhance the prevention of HBV infection and treatment of chronic hepatitis B.

CCN5 Expression in mammals. III. Early embryonic mouse development

CCN proteins play crucial roles in development, angiogenesis, cell motility, matrix turnover, proliferation, and other fundamental cell processes. Early embryonic lethality in CCN5 knockout and over-expressing mice led us to characterize CCN5 distribution in early development. Previous papers in this series showed that CCN5 is expressed widely in mice from E9.5 to adult; however, its distribution before E9.5 has not been studied. To fill this gap in our knowledge of CCN5 expression in mammals, RT-PCR was performed on preimplantation murine embryos: 1 cell, 2 cell, 4 cell, early morula, late morula, and blastocyst. CCN5 mRNA was not detected in 1, 2, or 4 cell embryos. It was first detected at the early morula stage and persisted to the preimplantation blastocyst stage. Immunohistochemical staining showed widespread CCN5 expression in post-implantation blastocysts (E4.5), E5.5, E6.5, and E7.5 stage embryos. Consistent with our previous study on E9.5 embryos, this expression was not limited to a particular germ layer or cell type. The widespread distribution of CCN5 in early embryos suggests a crucial role in development.

Regulation of pancreatic function by connective tissue growth factor (CTGF, CCN2)

Connective tissue growth factor (CTGF/CCN2) is a cysteine-rich matricellular secreted protein that regulates diverse cell functions including adhesion, migration, proliferation, differentiation, survival, senescence and apoptosis. In the pancreas, CTGF/CCN2 regulates critical functions including β cell replication during embryogenesis, stimulation of fibrogenic pathways in pancreatic stellate cells during pancreatitis, and regulation of the epithelial and stromal components in pancreatic ductal adenocarcinoma. This article reviews the evidence establishing CTGF/CCN2 as an important player in pancreatic physiology and pathology, highlighting the specific cell types that are involved in each process and the importance of CTGF/CCN2 as a component of autocrine or paracrine signaling within or between these various cells. Translational applications, including the potential for CTGF/CCN2-based therapies in diabetes, fibrosis, or cancer, are discussed.

Flaws in the peer-reviewing process : a critical look at a recent paper studying the role of CCN3 in renal cell carcinoma

A critical look at a recently published manuscript reporting the role of CCN3 in the regulation of clear cell renal cell carcinoma (RCC) biology raises several scientific concerns, and reveals flaws in the reviewing process which appear to have resulted in the dissemination of conclusions that are not supported by proper experimental procedures. In the example presented here, the observed biological effects are attributed to a high molecular weight "CCN3" protein which is detected by a single commercial antibody that was not shown in the experimental conditions used by the authors to be a valid reagent capable of stringently detecting the "canonical" CCN3 protein. Experiments establishing that inhibiting the production of high molecular weight "CCN3" protein would reverse these biological effects were not performed. The case discussed here clearly demonstrates that unreliable data can go through peer reviewing and be published. As the data can end up being cited and used as a potential reference by new investigators in the field, we believe that such data can throw roadblocks across the scientific path of inquiry and mislead investigations. We therefore raise awareness for the need of a more stringent peer reviewing process in which assurance can be had that the strength and precision of the data have been thoroughly checked by experts in the CCN field, and previous work properly referenced.

Oncostatin M inhibits TGF-β1-induced CTGF expression via STAT3 in human proximal tubular cells

Matricellular proteins play a critical role in the development of tubulointerstitial fibrosis and renal disease progression. Connective tissue growth factor (CTGF/CCN2), a CCN family member of matricellular proteins, represents an important mediator during development of glomerular and tubulointerstitial fibrosis in progressive kidney disease. We have recently reported that oncostatin M (OSM) is a potent inhibitor of TGF-β1-induced CTGF expression in human proximal tubular cells (PTC). In the present study we examined the role of TGF-β1- and OSM-induced signaling mechanisms in the regulation of CTGF mRNA expression in human proximal tubular HK-2 cells. Utilizing siRNA-mediated gene silencing we found that TGF-β1-induced expression of CTGF mRNA after 2h of stimulation at least partially depends on SMAD3 but not on SMAD2. In contrast to TGF-β1, OSM seems to exert a time-dependent dual effect on CTGF mRNA expression in these cells. While OSM led to a rapid and transient induction of CTGF mRNA expression between 15 min and 1h of stimulation it markedly suppressed basal and TGF-β1-induced CTGF mRNA levels thereafter. Silencing of STAT1 or STAT3 attenuated basal CTGF mRNA levels indicating that both STAT isoforms may be involved in the regulation of basal CTGF mRNA expression. However, knockdown of STAT3 but not STAT1 prevented OSM-mediated suppression of basal and TGF-β1-induced upregulation of CTGF mRNA expression. Together these results suggest that the inhibitory effect of OSM on TGF-β1-induced CTGF mRNA expression is mainly driven by STAT3, thereby providing a signaling mechanism whereby OSM may contribute to tubulointerstitial protection.

Extracellular and intracellular sphingosine-1-phosphate in cancer

Sphingosine-1-phosphate (S1P) was first described as a signaling molecule over 20 years ago. Since then, great strides have been made to reveal its vital roles in vastly different cellular and disease processes. Initially, S1P was considered nothing more than the terminal point of sphingolipid metabolism; however, over the past two decades, a large number of reports have helped unveil its full potential as an important regulatory, bioactive sphingolipid metabolite. S1P has a plethora of physiological functions, due in part to its many sites of actions and its different pools, which are both intra- and extracellular. S1P plays pivotal roles in many physiological processes, including the regulation of cell growth, migration, autophagy, angiogenesis, and survival, and thus, not surprisingly, S1P has been linked to cancer. In this review, we will summarize the vast body of knowledge, highlighting the connection between S1P and cancer. We will also suggest new avenues for future research.

Endogenous migration modulators as parent compounds for the development of novel cardiovascular and anti-inflammatory drugs

Development of novel cell migration modulators for anti-inflammatory and cardiovascular therapy is a complex task since any modulator will necessarily interfere with a balanced system of physiological regulators directing proper positioning of diverse immune cell types within the body. Whereas this shall serve efficient pathogen elimination, lack of proper control over these processes may result in counterproductive chronic inflammation and progressive tissue injury instead of healing. Prediction of the therapeutic potential or side effects of any migration modulator is not possible based on theoretical considerations alone but needs to be experimentally evaluated in preclinical disease models and by clinical studies. Here, we briefly summarize basic mechanism of cell migration, and groups of synthetic drugs currently in use for migration modulation. We then discuss one fundamental problem encountered with single-target approaches that arises from the complexity of any inflammation, with multiple interacting and often redundant factors being involved. This issue is likely to arise for any class of therapeutic agent (small molecules, peptides, antibodies, regulatory RNAs) addressing a single gene or protein. Against this background of studies on synthetic migration modulators addressing single targets, we then discuss the potential of endogenous proteins as therapeutic migration modulators, or as parent compounds for the development of mimetic drugs. Regulatory proteins of this type commonly address multiple receptors and signalling pathways and act upon the immune response in a phase-specific manner. Based on recent evidence, we suggest investigation of such endogenous migration modulators as novel starting points for anti-inflammatory and cardiovascular drug development.

CCN3: the-pain-killer inside me

There is increasing evidence that metalloproteinases are involved in neuropathic pain [Dev et al., Expert Opin Investig Drugs 19:455-468 2010] Hence, the identification of molecules that can regulate MMP9 and MMP2 is warranted. In a recent publication, Kular et al. (2012) claim that CCN3 functions to decrease inflammatory pain via the regulation of two metalloproteinases, MMP2 and MMP9, in response to experimentally-induced inflammation. Their conclusion is based on the following observations : i) the expression of CCN3 was reduced following induction of pain by subcutaneous injection of complete Freund's adjuvent in rat's paw, ii) an inhibition of MMP9 decreased CFA-associated mechanical allodynia, iii) inhibition of CCN3 expression by siRNA led to an upregulation of MMP2 in the dorsal horn of the spinal cord (DHSC) and MMP9 in the dorsal root ganglia (DRG), iv) a partial effect of CCN3 on CFA-induced expression of MMP9 and MMP2 in DRG and DHSC following intrathecal injection of CCN3. Unfortunately, the conclusion of this study is weakened by the lack of experimental evidence showing a direct relationship between the expression of CCN3 and MMPs. Furthermore, several results contained in this manuscript only confirm data that were previously established by others. Owing to the wide range of activities which have been attributed to CCN3 (Perbal, Mol Pathol 54:57-79 2001, Brigstock, J Endocrinol 178:169-175 2003, Perbal, Lancet 363(9402):62-64 2004, Perbal, Cell Commun Signal 4:6 2006, Holbourn et al. Trends Biochem Sci. 33:461-473 2008, Leask and Abraham, J Cell Sci 119:4803-4810 2006, Jun and Lau, Nat Rev Drug Discov 10:945-963 2011, Rachfal and Brigstock, Vitam Horm 70:69-103 2005), the mechanisms underlying the potential role of CCN3 in the expression of these MMPs in the context of inflammatory pain must be thoroughly studied before a meaningful conclusion can be reached. Indeed, Kular et al. description of variations in CCN3, MMP9 and MMP2 levels occurring simultaneously is not sufficient to draw a functional relationship between these three proteins. It should be noted that the expression of CCN3 was already reported to repress MMP9 (Benini et al., Oncogene 24:4349-4361 2005, Fukunaga-Kalabis et al., Oncogene 27:2552-2560 2008) and the roles of CCN3 in inflammatory processes has been extensively documented in the past few years (Bleau et al., Front Biosci 10:998-1009 2005, Lin et al., J Biol Chem 280:8229-8237 2005, Perbal, Cell Commun Signal 4:6 2006, Hughes et al., Diabetologia 50:1089-1098 2007, Lin et al., J Cell Commun Signal 4:141-153 2010, Pasmant et al., J Neuropathol Exp Neurol 69:60-69 2010, Shimoyama et al., Thromb Vasc Biol 30:675-682 2010, Lemaire et al., J Invest Dermatol 130:2517 2010, Chen and Lau, J Cell Commun Signal 4:63-69 2010, Le Dréau et al., Glia 58:1510-1521 2010, Rittié et al. J Cell Commun Signal 5:69-80 2011, Janune et al., J Cell Commun Signal 5:167-171 2011). In addition, the expression of CCN3 in the neurons of dorsal root ganglia and dorsal horn of the spinal horn in rat and human has also been documented (Su et al., C R Acad Sci III 321:883-892 1998, Mol Pathol 54:184-191 2001, Kocialkowski et al., Anat Embryol (Berl) 203:417-427 2001). Implication of CCN3 in cognitive functions (Su et al., Sheng Li Xue Bao 52:290-294 2000) and the possible involvement of CCN3 in the regulation of pain was already suggested almost a decade ago (Perbal, Expert Rev Mol Diagn 3:597-604 2003, Perbal et al., Mol Pathol 56:80-85 2003) with the demonstration of cell-specific effects of CCN3 on intracellular calcium stores and inhibition of anionic channels by CCN3 (Li et al., Mol Pathol 55:250-261 2002, Lombet et al., Cell Commun Signal 1:1 2003, Perbal, Expert Rev Mol Diagn 3:597-604 2003, Perbal et al., Mol Pathol 56:80-85 2003). Aside from these general aspects, and in the light of the potential participation of CCN3 in the whole process of pain sensing, the reader would have appreciated the discussion in this manuscript not being essentially a flat summary of the data presented, but a more thorough discussion of the possible role for CCN3 in the regulation of MMPs and its significance in the context of the wide biological functions of CCN3.

The role of connective tissue growth factor (CTGF/CCN2) in skeletogenesis

Connective tissue growth factor (CTGF) is a 38 kDa, cysteine rich, extracellular matrix protein composed of 4 domains or modules. CTGF has been shown to regulate a diverse array of cellular functions and has been implicated in more complex biological processes such as angiogenesis, chondrogenesis, and osteogenesis. A role for CTGF in the development and maintenance of skeletal tissues first came to light in studies demonstrating its expression in cartilage and bone cells, which was dramatically increased during skeletal repair or regeneration. The physiological significance of CTGF in skeletogenesis was confirmed in CTGF-null mice, which exhibited multiple skeletal dysmorphisms as a result of impaired growth plate chondrogenesis, angiogenesis, and bone formation/mineralization. Given the emerging importance of CTGF in osteogenesis and chondrogenesis, this review will focus on its expression in skeletal tissues, its effects on osteoblast and chondrocyte differentiation and function, and the skeletal implications of ablation or over-expression of CTGF in knockout or transgenic mouse models, respectively. In addition, this review will examine the role of integrin-mediated signaling and the regulation of CTGF expression as it relates to skeletogenesis. We will emphasize CTGF studies in bone or bone cells, and will identify opportunities for future investigations concerning CTGF and chondrogenesis/osteogenesis.

Cysteine-rich 61 (CYR61) is up-regulated in proliferative diabetic retinopathy

BACKGROUND

To investigate the role of CYR61 as a retinal angiogenic factor in proliferative diabetic retinopathy (PDR).

METHODS

Effects of CYR61 on RF/6A cell proliferation, migration and angiogenesis were observed by MTT assay, Transwell assay, and tube formation assay. The expression and distribution of CYR61 on retina layers of diabetic mouse were demonstrated by immunohistochemistry. The expression of Cyr61 mRNA in diabetic mouse retina was evaluated by reverse transcription-polymerase chain reaction (RT-PCR). Vitreous CYR61 levels of PDR and non-diabetic patients were measured by enzyme-linked immunosorbent assay (ELISA). Expression and distribution of CYR61 on epiretinal membrane of PDR, proliferative vitreoretinopathy (PVR) and idiopathic epiretinal membrane were evaluated by immunohistochemistry.

RESULTS

RF/6A cell proliferation, migration and tube formation capacity increased with increased concentration of CYR61 (p = 0.000). Anti-CYR61 antibody could inhibit cell migration and tube formation promoted by CYR61. In diabetic mouse, CYR61 was expressed in retina layers just as normal mouse, but the staining was stronger than normal in ganglion cell layer and inner plexiform layer. The Cyr61 mRNA expression in retina of diabetic mouse was more than that in normal mouse (p = 0.009). Vitreous CYR61 level was higher in patients with PDR than non-diabetic patients (p = 0.000). PDR patients with plenty of neovasculature on retina and epiretinal membranes had higher level of vitreous CYR61 than patients with little neovasculature (p = 0.001). CYR61 expressed in the cytoplasm of epiretinal membranes in PDR, especially in the wall cells of the tube-like structure.

CONCLUSIONS

CYR61 are likely to be involved in the pathogenesis of diabetic retinopathy, and may play a role in the course of neovasculation.

Cigarette smoke-induced early growth response-1 regulates the expression of the cysteine-rich 61 in human skin dermal fibroblasts

Tobacco smoke is known to be an element contributing to accelerate premature skin ageing. Cysteine-rich 61 (Cyr61) is a member of the connective tissue factor CCN (Cyr61, CTGF and Nov) family, and early growth response-1 (Egr-1) is a generally expressed member of the zinc-finger family of transcription factors. To investigate the regulatory potential of Egr-1 on expression of Cyr61 by smoking, this study examined the hypothesis that cigarette smoke-induced Egr-1 induces expression of Cyr61 in human skin dermal fibroblasts (HSDF). HSDF were exposed to different concentrations of cigarette smoke extract (CSE) for 24 h; a cytotoxicity assay was then performed for the detection of cell proliferation. Results of Western blot and reverse transcription-polymerase chain reaction (RT-PCR) showed that CSE induces a transient synthesis of Egr-1 in HSDF. Cyr61 mRNA and protein levels showed a marked increase in a time-dependent manner after CSE exposure. Following transfection with an Egr-1 overexpression vector, HSDF showed increased activity of the Cyr61 promoter in a dose-dependent manner. Using Egr-1 interfering RNA, we confirmed that CSE-induced Cyr61 expression was dependent on Egr-1 expression. Findings of this study indicate that Egr-1-dependent induction of Cyr61 may contribute to premature skin ageing by smoking.

Effect of prednisone on transforming growth factor-β1, connective tissue growth factor, nuclear factor-κBp65 and tumor necrosis factor-α expression in a murine model of hepatic sinusoidal obstruction syndrome induced by Gynura segetum

AIM

  One major cause of hepatic sinusoidal obstruction syndrome (HSOS) is the consumption of products containing pyrrolizidine alkaloids (PA). As the use of herbal preparations has increased in China, so has the number of reports of HSOS induced by ingesting PA-containing herbs. The aim of the present study was to investigate the mechanisms by which prednisone and the related factors, transforming growth factor (TGF)-β1 and connective tissue growth factor (CTGF), prevent liver fibrosis and the pathogenesis of HSOS.

METHODS

  A murine model of HSOS was created by oral gavage with Gynura segetum with or without prednisone for 30 days. Histological changes in liver tissue were evaluated by a scoring system in tissue slices subjected to hematoxylin-eosin and Masson trichrome staining. Hepatic expression of TGF-β1 and CTGF mRNA and protein was detected by immunohistochemistry, reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. RT-PCR was also used to detect tumor necrosis factor (TNF)-α and nuclear factor (NF)-κBp65 mRNA expression. Activation of NF-κBp65 was detected by immunohistochemistry.

RESULTS

  Intervention with prednisone diminished the symptoms of HSOS in mice treated with G. segetum. Prednisone treatment significantly inhibited expression of TGF-β1 and CTGF mRNA and protein (P < 0.05), and inhibited expression of TNF-α and NF-κBp65 mRNA (P < 0.05) in the liver tissue of HSOS mice.

CONCLUSION

  Prednisone suppresses the development of liver fibrosis in HSOS mice by inhibiting TGF-β1, CTGF, TNF-α and NF-κBp65 expression.

CCN2 is required for the TGF-β induced activation of Smad1-Erk1/2 signaling network

Connective tissue growth factor (CCN2) is a multifunctional matricellular protein, which is frequently overexpressed during organ fibrosis. CCN2 is a mediator of the pro-fibrotic effects of TGF-β in cultured cells, but the specific function of CCN2 in the fibrotic process has not been elucidated. In this study we characterized the CCN2-dependent signaling pathways that are required for the TGF-β induced fibrogenic response. By depleting endogenous CCN2 we show that CCN2 is indispensable for the TGF-β-induced phosphorylation of Smad1 and Erk1/2, but it is unnecessary for the activation of Smad3. TGF-β stimulation triggered formation of the CCN2/β₃ integrin protein complexes and activation of Src signaling. Furthermore, we demonstrated that signaling through the α_vβ₃ integrin receptor and Src was required for the TGF-β induced Smad1 phosphorylation. Recombinant CCN2 activated Src and Erk1/2 signaling, and induced phosphorylation of Fli1, but was unable to stimulate Smad1 or Smad3 phosphorylation. Additional experiments were performed to investigate the role of CCN2 in collagen production. Consistent with the previous studies, blockade of CCN2 abrogated TGF-β-induced collagen mRNA and protein levels. Recombinant CCN2 potently stimulated collagen mRNA levels and upregulated activity of the COL1A2 promoter, however CCN2 was a weak inducer of collagen protein levels. CCN2 stimulation of collagen was dose-dependent with the lower doses (<50 ng/ml) having a stimulatory effect and higher doses having an inhibitory effect on collagen gene expression. In conclusion, our study defines a novel CCN2/α_vβ₃ integrin/Src/Smad1 axis that contributes to the pro-fibrotic TGF-β signaling and suggests that blockade of this pathway may be beneficial for the treatment of fibrosis.

Gene expression profiles in rat mesenteric lymph nodes upon supplementation with conjugated linoleic acid during gestation and suckling

Background

Diet plays a role on the development of the immune system, and polyunsaturated fatty acids can modulate the expression of a variety of genes. Human milk contains conjugated linoleic acid (CLA), a fatty acid that seems to contribute to immune development. Indeed, recent studies carried out in our group in suckling animals have shown that the immune function is enhanced after feeding them with an 80:20 isomer mix composed of c9,t11 and t10,c12 CLA. However, little work has been done on the effects of CLA on gene expression, and even less regarding immune system development in early life.

Results

The expression profile of mesenteric lymph nodes from animals supplemented with CLA during gestation and suckling through dam's milk (Group A) or by oral gavage (Group B), supplemented just during suckling (Group C) and control animals (Group D) was determined with the aid of the specific GeneChip^® Rat Genome 230 2.0 (Affymettrix). Bioinformatics analyses were performed using the GeneSpring GX software package v10.0.2 and lead to the identification of 89 genes differentially expressed in all three dietary approaches. Generation of a biological association network evidenced several genes, such as connective tissue growth factor (Ctgf), tissue inhibitor of metalloproteinase 1 (Timp1), galanin (Gal), synaptotagmin 1 (Syt1), growth factor receptor bound protein 2 (Grb2), actin gamma 2 (Actg2) and smooth muscle alpha actin (Acta2), as highly interconnected nodes of the resulting network. Gene underexpression was confirmed by Real-Time RT-PCR.

Conclusions

Ctgf, Timp1, Gal and Syt1, among others, are genes modulated by CLA supplementation that may have a role on mucosal immune responses in early life.

Connective tissue growth factor (CTGF/CCN2) mediates angiogenic effect of S1P in human dermal microvascular endothelial cells

OBJECTIVE

The primary objective of this study was to examine the potential interaction between S1P, a pleiotropic lipid mediator, and CTGF/CCN2, a secreted multimodular protein, in the process of endothelial cell migration. The secondary objective was to determine whether C- and N-terminal domains of CTGF/CCN2 have a specific function in cell migration.

MATERIALS AND METHODS

Migration of HDMECs was examined in monolayer wound healing "scratch" assay, whereas capillary-like tube formation was examined in three-dimensional collagen co-culture assays.

RESULTS

We observed that S1P stimulates migration of HDMECs concomitant with upregulation of CTGF/CCN2 expression. Furthermore, the blockade of endogenous CTGF/CCN2 via siRNA abrogated S1P-induced HDMEC migration and capillary-like tube formation. Full-length CTGF induced cell migration and capillary-like tube formation with a potency similar to that of S1P, while C-terminal domain of CTGF was slightly less effective. However, N-terminal domain had only a residual activity in inducing capillary-like tube formation.

CONCLUSIONS

This study revealed that CTGF/CCN2 is required for the S1P-induced endothelial cell migration, which suggests that CTGF/CCN2 may be an important mediator of S1P-induced physiological and pathological angiogenesis. Moreover, this study shows that the pro-migratory activity of CTGF/CCN2 is located in the C-terminal domain.

Mechanisms of novel cardioprotective functions of CCN2/CTGF in myocardial ischemia-reperfusion injury

CCN2/connective tissue growth factor (CTGF), a CCN family matricellular protein repressed in healthy hearts after birth, is induced in heart failure of various etiologies. Multiple cellular and biological functions have been assigned to CCN2/CTGF depending on cellular context. However, the functions and mechanisms of action of CCN2/CTGF in the heart as well as its roles in cardiac physiology and pathophysiology remain unknown. Transgenic mice with cardiac-restricted overexpression of CTGF (Tg-CTGF) were generated and compared with nontransgenic littermate control (NLC) mice. Tg-CTGF mice displayed slightly lower cardiac mass and inconspicuous increase of myocardial collagen compared with NLC mice but no evidence of contractile dysfunction. Analysis of the myocardial transcriptome by DNA microarray revealed activation of several distinct gene programs in Tg-CTGF hearts involved in cardioprotection and growth inhibition. Indeed, Tg-CTGF mice subjected to ischemia-reperfusion injury by in situ transient occlusion of the left anterior descending coronary artery in vivo displayed reduced vulnerability with markedly diminished infarct size. These findings were recapitulated in isolated hearts perfused with recombinant human (h)CTGF before the ischemia-reperfusion procedure. Consistently, Tg-CTGF hearts, as well as isolated adult cardiac myocytes exposed to recombinant hCTGF, displayed enhanced phosphorylation and activity of the Akt/p70S6 kinase/GSK-3β salvage kinase pathway and induction of several genes with reported cardioprotective functions. Inhibition of Akt activities also prevented the cardioprotective phenotype of hearts from Tg-CTGF mice. This report provides novel evidence that CTGF confers cardioprotection by salvage phosphokinase signaling leading to inhibition of GSK-3β activities, activation of phospho-SMAD2, and reprogramming of gene expression.

Effects of streptolysin o on extracellular matrix gene expression in normal human epidermal keratinocytes

ML-05 is a non-hemolytic form of streptolysin O, the membrane-damaging extracellular toxin produced by certain streptococci. ML-05 stimulates keratinocyte migration and proliferation in wound-healing scratch assays and promotes wound healing in a human skin organ culture wound model. Pathway-focused DNA microarrays were used to elucidate ML-05's mechanism of action in wound healing processes. Normal human epidermal keratinocytes (NHEK) were treated with varying concentrations of ML-05 for 24 hours, followed by RNA extraction and cRNA production. Gene expression profiling utilized microarrays containing nucleic acid probes for 113 extracellular matrix (ECM) genes. Microarrays yielded 6 upregulated and 4 downregulated genes with ≥2-fold changes and p<0.05 in t-tests. Quantitative real-time polymerase chain reactions (qPCR) were used to verify gene regulation. Upregulated genes of interest were VCAN (formerly CSPG2, encoding versican), CD44 (encoding hyaluronan receptor), ICAM1 (encoding intercellular adhesion molecule-1) and CTGF (encoding connective tissue growth factor). All four upregulated genes encode proteins involved in promoting keratinocyte migration and proliferation. Downregulated genes of interest were MMP9 (encoding matrix metalloproteinase 9) and SPP1 (encoding osteopontin). ML-05 may enhance wound healing through the expression of specific genes encoding proteins capable of promoting keratinocyte migration, proliferation, and other activities related to maintaining ECM structure and function.

CCN5, a novel transcriptional repressor of the transforming growth factor β signaling pathway

CCN5 is a member of the CCN (connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed) family and was identified as an estrogen-inducible gene in estrogen receptor-positive cell lines. However, the role of CCN5 in breast carcinogenesis remains unclear. We report here that the CCN5 protein is localized mostly in the cytoplasm and in part in the nucleus of human tumor breast tissue. Using a heterologous transcription assay, we demonstrate that CCN5 can act as a transcriptional repressor presumably through association with histone deacetylase 1 (HDAC1). Microarray gene expression analysis showed that CCN5 represses expression of genes associated with epithelial-mesenchymal transition (EMT) as well as expression of key components of the transforming growth factor β (TGF-β) signaling pathway, prominent among them TGF-βRII receptor. We show that CCN5 is recruited to the TGF-βRII promoter, thereby providing a mechanism by which CCN5 restricts transcription of the TGF-βRII gene. Consistent with this finding, CCN5, we found, functions to suppress TGF-β-induced transcriptional responses and invasion that is concomitant with EMT. Thus, our data uncovered CCN5 as a novel transcriptional repressor that plays an important role in regulating tumor progression functioning, at least in part, by inhibiting the expression of genes involved in the TGF-β signaling cascade that is known to promote EMT.

Global transcriptome analysis of human bone marrow stromal cells (BMSC) reveals proliferative, mobile and interactive cells that produce abundant extracellular matrix proteins, some of which may affect BMSC potency

BACKGROUND AIMS

Bone marrow stromal cells (BMSC) are being used for immune modulatory, anti-inflammatory and tissue engineering applications, but the properties responsible for these effects are not completely understood. Human BMSC were characterized to identify factors that might be responsible for their clinical effects and biomarkers for assessing their quality.

METHODS

Early passage BMSC prepared from marrow aspirates of seven healthy subjects were compared with three human embryonic stem cell (hESC) samples, CD34(+) cells from three healthy subjects and three fibroblast cell lines. The cells were analyzed with oligonucleotide expression microarrays with more than 35 000 probes.

RESULTS

BMSC gene expression signatures of BMSC differed from those of hematopoietic stem cells (HSC), hESC and fibroblasts. Genes upregulated in BMSC were involved with cell movement, cell-to-cell signaling and interaction and proliferation. The upregulated genes most probably belonged to pathways for integrin signaling, integrin-linked kinase (ILK) signaling, NF-E2-related factor-2 (NFR2)-mediated oxidative stress response, regulation of actin-based motility by Rho, actin cytoskeletal signaling, caveolar-mediated endocytosis, clathrin-mediated endocytosis and Wingless-type MMTV integration site (Wnt/β catenin signaling. Among the most highly upregulated genes were structural extracellular matrix (ECM) proteins (α5 and β5 integrin chains, fibronectin and collagen type IIIα1 and Vα1) and functional EMC proteins [connective tissue growth factor (CTGF), transforming growth factor beta-induced protein (TGFBI) and A disintegrin and metalloproteinase (ADAM12)].

CONCLUSIONS

Global analysis of human BMSC suggests that they are mobile, metabolically active, proliferative and interactive cells that make use of integrins and integrin signaling. They produce abundant ECM proteins that may contribute to their clinical immune modulatory and anti-inflammatory effects.

Regulation of cancer cell migration and invasion by sphingosine-1-phosphate

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid that has been implicated in regulation of a number of cancer cell malignant behaviors, including cell proliferation, survival, chemotherapeutic resistance and angiogenesis. However, the effects of S1P on cancer cell migration, invasion and metastasis, are perhaps its most complex, due to the fact that, depending upon the S1P receptors that mediate its responses and the crosstalk with other signaling pathways, S1P can either positively or negatively regulate invasion. This review summarizes the effects of S1P on cancer cell invasion and the mechanisms by which it affects this important aspect of cancer cell behavior.

The impact of Fli1 deficiency on the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune inflammatory disease with unknown etiology characterized by microvascular injury and fibrosis of the skin and internal organs. A growing body of evidence suggests that deficiency of the transcription factor Fli1 (Friend leukemia integration-1) has a pivotal role in the pathogenesis of SSc. Fli1 is expressed in fibroblasts, endothelial cells, and immune cells, and has important roles in the activation, differentiation, development, and survival of these cells. Previous studies demonstrated that Fli1 is downregulated in SSc fibroblasts by an epigenetic mechanism and a series of experiments with Fli1-deficient animal models revealed that Fli1 deficiency in fibroblasts and endothelial cells reproduces the histopathologic features of fibrosis and vasculopathy in SSc, respectively. In this article, we review the impact of Fli1 deficiency on the pathogenesis of SSc and discuss a new therapeutic strategy for SSc by targeting the transcription factor Fli1.

The CCN proteins: important signaling mediators in stem cell differentiation and tumorigenesis

The CCN proteins contain six members, namely CCN1 to CCN6, which are small secreted cysteine-rich proteins. The CCN proteins are modular proteins, containing up to four functional domains. Many of the CCN members are induced by growth factors, cytokines, or cellular stress. The CCNs show a wide and highly variable expression pattern in adult and in embryonic tissues. The CCN proteins can integrate and modulate the signals of integrins, BMPs, VEGF, Wnts, and Notch. The involvement of integrins in mediating CCN signaling may provide diverse context-dependent responses in distinct cell types. CCN1 and CCN2 play an important role in development, angiogenesis and cell adhesion, whereas CCN3 is critical to skeletal and cardiac development. CCN4, CCN5 and CCN6 usually inhibit cell growth. Mutations of Ccn6 are associated with the progressive pseudorheumatoid dysplasia and spondyloepiphyseal dysplasia tarda. In stem cell differentiation, CCN1, CCN2, and CCN3 play a principal role in osteogenesis, chondrogenesis, and angiogenesis. Elevated expression of CCN1 is associated with more aggressive phenotypes of human cancer, while the roles of CCN2 and CCN3 in tumorigenesis are tumor type-dependent. CCN4, CCN5 and CCN6 function as tumor suppressors. Although CCN proteins may play important roles in fine-tuning other major signaling pathways, the precise function and mechanism of action of these proteins remain undefined. Understanding of the biological functions of the CCN proteins would not only provide insight into their roles in numerous cellular processes but also offer opportunities for developing therapeutics by targeting CCN functions.

Phase 1 study of anti-CTGF monoclonal antibody in patients with diabetes and microalbuminuria

BACKGROUND AND OBJECTIVES

This report summarizes the first phase 1 trial treating patients with microalbuminuric diabetic kidney disease (DKD) using FG-3019, a human monoclonal antibody to connective tissue growth factor (CTGF). CTGF is critically involved in processes of progressive fibrosis, including DKD. This phase 1, open-label, dose-escalation trial evaluated safety, pharmacokinetics, and possible therapeutic effects of FG-3019 on albuminuria, proteinuria, and tubular proteins.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

Microalbuminuric subjects (n = 24) with type 2 (79%) or type 1 (21%) diabetes received 3 or 10 mg/kg FG-3019 dosed intravenously every 14 days for four doses. Albuminuria and safety follow-up were to days 62 and 365, respectively.

RESULTS

No infusion was interrupted for symptoms, although 5 of 24 subjects had mild infusion-day adverse events thought to be possibly drug-related. No subject developed anti-FG-3019 antibodies. FG-3019 clearance was lower at 10 mg/kg than at 3 mg/kg, suggesting a saturable elimination pathway. Although this study was not designed for efficacy testing, it was notable that urinary albumin/creatinine ratio (ACR) decreased significantly from mean pretreatment ACR of 48 mg/g to mean post-treatment (day 56) ACR of 20 mg/g (P = 0.027) without evidence for a dose-response relationship.

CONCLUSIONS

Treatment of microalbuminuric DKD subjects using FG-3019 was well tolerated and associated with a decrease in albuminuria. The data demonstrate a saturable pathway for drug elimination, minimal infusion adverse events, and no significant drug-attributable adverse effects over the year of follow-up. Changes in albuminuria were promising but require validation in a prospective, randomized, blinded study.

TGF-β-stimulated CTGF production enhanced by collagen and associated with biogenesis of a novel 31-kDa CTGF form in human corneal fibroblasts

PURPOSE

Connective tissue growth factor (CTGF) is induced by transforming growth factor-beta (TGF-β) after corneal wounding. This study addressed the role of the extracellular matrix in the induction of CTGF by TGF-β.

METHODS

Human corneal fibroblasts (HCFs) were grown on fibronectin (FN), vitronectin (VN), or collagen (CL) in supplemented serum-free media alone or with TGF-β1 or fibroblast growth factor plus heparin. CTGF mRNA was analyzed by qPCR and protein expression by Western blot analysis of Triton X-100 (TX-100)-soluble and TX-100-insoluble cell lysates using antibodies to N-terminal, mid, and C-terminal CTGF regions. Immunocytochemistry was performed on nonconfluent or scrape-wounded confluent HCFs.

RESULTS

TGF-β-treated HCFs grown on CL produced five times more 38-kDa CTGF than untreated controls (72 hours). TGF-β-treated HCFs on CL secreted twofold more CTGF than those on FN or VN. Furthermore, a 31-kDa CTGF form, lacking the N-terminal domain, was detected in Triton X-100 insoluble fractions in Western blot analysis. Immunodetectable extracellular CTGF formed linear arrays parallel to, but not colocalized with, CL or FN. It also did not colocalize with FAK, vinculin, or integrins α(v)β(3) and α(5)β(1). Intracellular CTGF was detected in the Golgi apparatus and vesicles, including endosomes.

CONCLUSIONS

Enhanced CTGF secretion induced by TGF-β in CL-grown cells may contribute to positive feedback in which CL is overexpressed in CTGF-induced fibrosis. N-terminal CTGF fragments in the plasma of patients with severe fibrotic disease may be a product of CTGF proteolysis that also produces the newly identified 31-kDa CTGF that remains cell associated and may have its impact by non-integrin signaling pathways.

CCN3/CCN2 regulation and the fibrosis of diabetic renal disease

Prior work in the CCN field, including our own, suggested to us that there might be co-regulatory activity and function as part of the actions of this family of cysteine rich cytokines. CCN2 is now regarded as a major pro-fibrotic molecule acting both down-stream and independent of TGF-beta1, and appears causal in the disease afflicting multiple organs. Since diabetic renal fibrosis is a common complication of diabetes, and a major cause of end stage renal disease (ESRD), we examined the possibility that CCN3 (NOV), might act as an endogenous negative regulator of CCN2 with the capacity to limit the overproduction of extracellular matrix (ECM), and thus prevent, or ameliorate fibrosis. We demonstrate, using an in vitro model of diabetic renal fibrosis, that both exogenous treatment with CCN3 and transfection with the over-expression of the CCN3 gene in mesangial cells markedly down-regulates CCN2 activity and blocks ECM over-accumulation stimulated by TGF-beta1. Conversely, TGF-beta1 treatment reduces endogenous CCN3 expression and increases CCN2 activity and matrix accumulation, indicating an important, novel yin/yang effect. Using the db/db mouse model of diabetic nephropathy, we confirm the expression of CCN3 in the kidney, with temporal localization that supports these in vitro findings. In summary, the results corroborate our hypothesis that one function of CCN3 is to regulate CCN2 activity and at the concentrations and conditions used down-regulates the effects of TGF-beta1, acting to limit ECM turnover and fibrosis in vivo. The findings suggest opportunities for novel endogenous-based therapy either by the administration, or the upregulation of CCN3.

Influence and mechanism of He-Ne laser on scar formation of filtration canal after trabeculectomy in rabbit

AIM

To investigate the influence of He-Ne laser on connective tissue growth factor (CTGF) expression and collagen formation of fibroblast in filtration site after trabeculectomy in rabbit, and to discuss the mechanism for preventing scar formation with He-Ne laser in vivo.

METHODS

The upper nasal limbus area next to the upper rectus muscle in right eyes received 10 minutes He-Ne laser irradiation (200mW/cm(2)) every day for three days, the left eyes served as control. Twenty-four hours after the last irradiation, both eyes of the rabbits were took trabeculectomy surgery. The expressions of CTGF in the filtration area were tested on the 7(th), 14(th) and 28(th) day after surgery and collagen density was tested on the 14(th) and 28(th) day after surgery. Each of the time point had 7 rabbits.

RESULTS

The expression of CTGF was lower than that of the control group's on the 7(th) and 14(th) day after trabeculectomy surgery (P=0.01, P=0.005). When examined on the 14(th) and 28(th) day, the collagen density of irradiation group were significantly lower than that of the control group's (P=0.013, P=0.01).

CONCLUSION

Pretreating the filtration area with 200mW/cm(2) He-Ne laser may be helpful in preventing scar formation after trabeculectomy in rabbit, possibly due to downregulation of the expression of CTGF and collagen synthesis in fibroblasts. He-Ne laser may be developed into a new scar preventing method in filtration surgery.

Connective tissue growth factor (CCN2, CTGF) and organ fibrosis: lessons from transgenic animals

In recent months, four different systems have been reported in the literature in which CCN2 transgenes were individually expressed in podocytes, hepatocytes, cardiomyocytes or respiratory epithelial cells to achieve overexpression in, respectively, the kidney, liver, heart, or lung. These transgenic systems have provided valuable information about the contribution of CCN2 to fibrosis in vivo and have begun to reveal the complexities of the underlying mechanisms involved. On the one hand, studies of these animals have revealed that CCN2 overexpression does not necessarily lead directly to fibrotic pathology but may cause severe non-fibrotic tissue damage due to its other effects on cell function (e.g. heart). On the other hand, overexpression of CCN2 in concert with signaling pathways associated with development (e.g. lung) or fibrosing injuries (e.g. kidney, liver) can lead to the initiation or exacerbation of fibrosis. The significance of these studies is discussed in the context of the requirement for interactions between CCN2 and co-stimulatory factors in the microenvironment for the manifestation of CCN2-dependent fibrosis.

Less Smad2 is good for you! A scientific update on coffee's liver benefits

Scientists at the National Institutes of Health have reported that increased coffee consumption is associated with a slower progression of fibrogenesis in patients with chronic and particularly alcoholic liver disease and a reduced incidence of heptocellular carcinoma. However, a causal mechanistic explanation was pending. New results indicate that the methylxanthine caffeine--a major component of coffee and the most widely consumed pharmacologically active substance in the world--might be responsible for this phenomenon, because it inhibits the synthesis of connective tissue growth factor (CTGF/CCN2) in liver parenchymal and nonparenchymal cells, primarily by inducing degradation of Smad2 (and to a much lesser extent Smad3) and thus impairment of transforming growth factor beta (TGF-beta) signaling. CTGF and TGF-beta play crucial roles in the fibrotic remodeling of various organs, and, ultimately, carcinogenesis. This article summarizes the clinical-epidemiological observations as well as the pathophysiological background and provides suggestions for the therapeutic use of (methyl)xanthine derivatives in the management of fibro-/carcinogenic (liver) diseases.

Tuning cell differentiation patterns and single cell dynamics by regulating proteins' functionalities in a toggle switch

We investigate how the regulation of protein multi-functionalities affect the dynamics of a stochastic model of a toggle switch and the differentiation pattern of cell population regulated by the switch. We study the effects of loss of functionality in DNA-binding and repression and the involvement in differentiation pathway choice. First is shown how the patterns of cell differentiation differ, when each of these functionalities is fully non-functional. Next, tuning the fraction of non-functional proteins regarding the ability to bind DNA is shown to allow fine tuning of the switch and cell differentiation pattern dynamics. Finally, biasing the probability of functionality of the two proteins biases the dynamics of the switch and cell differentiation patterns, especially when transcription factors retain the ability to bind DNA but have lost the ability to repress gene expression. Our results suggest that, besides transcriptional and translational levels of regulation, activation of functionalities in multi-functional proteins are an important regulator of gene networks.

About coffee, cappuccino and connective tissue growth factor-Or how to protect your liver!?

Several epidemiological studies suggest that coffee drinking is inversely correlated with the risk of development of liver fibrosis. However, a causal, mechanistic explanation has long been pending. New results indicate that the methylxanthine caffeine, major component of coffee and the most widely consumed pharmacologically active substance in the world, might be responsible for this phenomenon as it, and even more potently its derived primary metabolite paraxanthine, inhibits transforming growth factor (TGF)-β-dependent and -independent synthesis of connective tissue growth factor (CTGF/CCN2) in liver parenchymal cells in vitro and in vivo. CTGF plays a crucial role in the fibrotic remodeling of various organs which has therefore frequently been proposed as therapeutic target in the management of fibrotic disorders. This article summarizes the clinical-epidemiological observations as well as the pathophysiological background of the antifibrotic effects of coffee consumption and provides suggestions for the therapeutic use of caffeine and its derived metabolic methylxanthines as potentially powerful drugs in patients with chronic fibrogenic liver disease by their inhibitory effect on (hepatocellular) CTGF synthesis.

Osteogenic differentiation of mesenchymal stem cells promoted by overexpression of connective tissue growth factor

OBJECTIVE

Large segmental bone defect repair remains a clinical and scientific challenge with increasing interest focusing on combining gene transfection with tissue engineering techniques. The aim of this study is to investigate the effect of connective tissue growth factor (CTGF) on the proliferation and osteogenic differentiation of the bone marrow mesenchymal stem cells (MSCs).

METHODS

A CTGF-expressing plasmid (pCTGF) was constructed and transfected into MSCs. Then expressions of bone morphogenesis-related genes, proliferation rate, alkaline phosphatase activity, and mineralization were examined to evaluate the osteogenic potential of the CTGF gene-modified MSCs.

RESULTS

Overexpression of CTGF was confirmed in pCTGF-MSCs. pCTGF transfection significantly enhanced the proliferation rates of pCTGF-MSCs (P<0.05). CTGF induced a 7.5-fold increase in cell migration over control (P<0.05). pCTGF transfection enhanced the expression of bone matrix proteins, such as bone sialoprotein, osteocalcin, and collagen type I in MSCs. The levels of alkaline phosphatase (ALP) activities of pCTGF-MSCs at the 1st and 2nd weeks were 4.0- and 3.0-fold higher than those of MSCs cultured in OS-medium, significantly higher than those of mock-MSCs and normal control MSCs (P<0.05). Overexpression of CTGF in MSCs enhanced the capability to form mineralized nodules.

CONCLUSION

Overexpression of CTGF could improve the osteogenic differentiation ability of MSCs, and the CTGF gene-modified MSCs are potential as novel cell resources of bone tissue engineering.

Normal growth and development in mice over-expressing the CCN family member WISP3

Loss-of-function mutations in the gene WISP3 cause the autosomal recessive human skeletal disease Progressive Pseudorheumatoid Dysplasia, whereas mice with knockout mutations of Wisp3 have no phenotype. The lack of a phenotype in the Wisp3 knockout mice has constrained studies of the protein’s in vivo function. Over-expression experiments in zebrafish indicated that WISP3 may function as a BMP and Wnt signaling modulator. To determine whether these biologic activities are retained in mice, we created two strains of transgenic mice that over-express WISP3 in a broad array of tissues. Despite strong and persistent protein over-expression, the transgenic mice remained phenotypically indistinguishable from their non-transgenic littermates. Surprisingly, WISP3 contained in conditioned medium recovered from transgenic mouse primary kidney cell cultures was able to bind BMP and to inhibit BMP signaling in vitro. Factors that account for the difference between the in vitro and in vivo activities of WISP3 remain unknown. At present, the mouse remains a challenging model organism in which to explore the biologic function of WISP3.

Summary of article. Transgenic mice that broadly over-express WISP3 were created to search for in vivo biologic activities, since mice that lack WISP3 were normal. Surprisingly, transgenic mice were also phenotypically indistinguishable from wild-type animals. The mouse is a challenging model organism in which to explore the biologic function of WISP3.

Domain-and species-specific monoclonal antibodies recognize the Von Willebrand Factor-C domain of CCN5

The CCN family of proteins typically consists of four distinct peptide domains: an insulin-like growth factor binding protein-type (IGFBP) domain, a Von Willebrand Factor C (VWC) domain, a thrombospondin type 1 repeat (TSP1) domain, and a carboxy-terminal (CT) domain. The six family members participate in many processes, including proliferation, motility, cell-matrix signaling, angiogenesis, and wound healing. Accumulating evidence suggests that truncated and alternatively spliced isoforms are responsible for the diverse functions of CCN proteins in both normal and pathophysiologic states. Analysis of the properties and functions of individual CCN domains further corroborates this idea. CCN5 is unique among the CCN family members because it lacks the CT-domain. To dissect the domain functions of CCN5, we are developing domain-specific mouse monoclonal antibodies. Monoclonal antibodies have the advantages of great specificity, reproducibility, and ease of long-term storage and production. In this communication, we injected mixtures of GST-fused rat CCN5 domains into mice to generate monoclonal antibodies. To identify the domains recognized by the antibodies, we constructed serial expression plasmids that express dual-tagged rat CCN5 domains. All of the monoclonal antibodies generated to date recognize the VWC domain, indicating it is the most highly immunogenic of the CCN5 domains. We characterized one particular clone, 22H10, and found that it recognizes mouse and rat CCN5, but not human recombinant CCN5. Purified 22H10 was successfully applied in Western Blot analysis, immunofluorescence of cultured cells and tissues, and immunoprecipitation, indicating that it will be a useful tool for domain analysis and studies of mouse-human tumor models.

CCN3 (NOV) is a negative regulator of CCN2 (CTGF) and a novel endogenous inhibitor of the fibrotic pathway in an in vitro model of renal disease

Fibrosis is a major cause of end-stage renal disease, and although initiation factors have been elucidated, uncertainty concerning the downstream pathways has hampered the development of anti-fibrotic therapies. CCN2 (CTGF) functions downstream of transforming growth factor (TGF)-beta, driving increased extracellular matrix (ECM) accumulation and fibrosis. We examined the possibility that CCN3 (NOV), another CCN family member with reported biological activities that differ from CCN2, might act as an endogenous negative regulator of ECM and fibrosis. We show that cultured rat mesangial cells express CCN3 mRNA and protein, and that TGF-beta treatment reduced CCN3 expression levels while increasing CCN2 and collagen type I activities. Conversely, either the addition of CCN3 or CCN3 overexpression produced a marked down-regulation of CCN2 followed by virtual blockade of both collagen type I transcription and its accumulation. This finding occurred in both growth-arrested and CCN3-transfected cells under normal growth conditions after TGF-beta treatment. These effects were not attributable to altered cellular proliferation as determined by cell cycle analysis, nor were they attributable to interference of Smad signaling as shown by analysis of phosphorylated Smad3 levels. In conclusion, both CCN2 and CCN3 appear to act in a yin/yang manner to regulate ECM metabolism. CCN3, acting downstream of TGF-beta to block CCN2 and the up-regulation of ECM, may therefore serve to naturally limit fibrosis in vivo and provide opportunities for novel, endogenous-based therapeutic treatments.