Connective tissue growth factor: a cysteine-rich mitogen secreted by human vascular endothelial cells is related to the SRC-induced immediate early gene product CEF-10

Acupuncture combined with curcumin disrupts platelet-derived growth factor β receptor/extracellular signal-regulated kinase signalling and stimulates extracellular matrix degradation in carbon tetrachloride-induced hepatic fibrosis in rats

BACKGROUND

Acupuncture treatment has been increasingly used to treat chronic liver diseases. We previously reported that acupuncture combined with curcumin, a natural antifibrotic compound, could remarkably attenuate liver fibrosis in chemically intoxicated rats, but the underlying molecular mechanisms are poorly understood. The present study was aimed at investigating the effects of acupuncture combined with curcumin on platelet-derived growth factor (PDGF) signalling and extracellular matrix (ECM) regulation in the fibrotic liver.

METHODS

A total of 60 Sprague-Dawley male rats were randomly divided into control, model, sham, acupuncture, curcumin and combination treatment groups. During the establishment of fibrosis using carbon tetrachloride (CCl(4)), acupuncture at LR3, LR14, BL18 and ST36 and/or curcumin treatment by mouth were performed simultaneously. After treatment, serum PDGF levels were measured. Protein and mRNA expression of key effectors in PDGF pathway and fibrinolysis in the liver was determined.

RESULTS

Acupuncture combined with curcumin potently reduced serum PDGF levels and selectively disrupted the PDGF-βR/extracellular signal-regulated kinase (ERK) cascade. Combination treatment also significantly repressed expression of connective tissue growth factor and upregulated expression of matrix metalloproteinase-9, promoting fibrinolysis in the fibrotic liver.

CONCLUSIONS

The beneficial effects of acupuncture and its combination with curcumin could be attributed to the disruption of PDGF-βR/ERK pathway and stimulated ECM degradation in the fibrotic liver. Acupuncture treatment significantly enhanced curcumin effects at the molecular level. These findings may provide molecular insights into the potential of acupuncture combined with curcumin for prevention of hepatic fibrosis.

Collagen VIII influences epithelial phenotypic changes in experimental diabetic nephropathy

Epithelial-to-mesenchymal transition (EMT) is an important mechanism of renal tubulo-interstitial fibrosis in diabetic nephropathy (DN). Inducers of EMT, among others, are transforming growth factor-β(1) (TGF-β(1)) as well as extracellular collagens. In renal cells of diabetic mice and in kidneys of patients with DN, the expression of collagen VIII (gene: Col8α1/α2) is enhanced and characteristic features of DN in streptozotocin (STZ)-induced diabetic Col8α1/α2 knockout-(KO) mice are attenuated compared with diabetic wild-type mice. This study aimed to investigate whether collagen type VIII may influence the induction of EMT. DN was induced in wild-type and Col8α1/α2-KO mice using the established and widely accepted low-dose STZ model [treatment for 5 consecutive days (50 mg/kg)]. Healthy and diabetic mice were analyzed for changes in renal function and the expression of EMT-related genes and proteins. Renal morphology, fibrosis, and various EMT markers were studied in kidneys using immunohistological and molecular biological methods. Knockout of Col8α1/α2 attenuated albuminuria, extracellular matrix production, as well as fibrosis. Furthermore, the kidneys of diabetic Col8α1/α2-KO mice showed a marked reduction in interstitial myofibroblasts, and in tubular cells the inhibition of the expression of epithelial markers as well as the expression of typical mesenchymal markers was reduced. The present study demonstrates that in contrast to diabetic wild-type mice EMT-like changes were attenuated in diabetic Col8α1/α2-KO mice, which indicates that either collagen VIII may be one of the major inducers of EMT-like changes in kidneys of diabetic wild-type mice or/possibly the lack of Col8α1/α2 disrupts TGF-β(1)-induced EMT-like changes.

CTGF is a central mediator of tissue remodeling and fibrosis and its inhibition can reverse the process of fibrosis

CTGF is a secreted matricellular protein with very complex biology. It has been shown to modulate many signaling pathways leading to cell adhesion and migration, angiogenesis, myofibroblast activation, and extracellular matrix deposition and remodeling, which together lead to tissue remodeling and fibrosis. It has been reported in the literature that inhibition of CTGF expression by siRNA prevents CCl4-induced liver fibrosis and can reverse fibrosis when administered after significant collagen deposition is observed. A monoclonal antibody to CTGF that is currently in clinical development (FG-3019) has demonstrated the ability to reverse vascular stiffening and improve cardiac function in a rat model of diabetic complications. FG-3019 has also exhibited activity in a murine radiation-induced pulmonary fibrosis model. When FG-3019 was administered to mice after a significant radiation-induced increase in lung density could be observed by CT imaging, the density of the lungs was observed to decrease over the period during which the antibody was administered and to remain stable after therapy had ceased. When considered together, these data indicate that inhibition of CTGF can prevent and reverse the process of fibrosis.

A connective tissue growth factor signaling receptor in corneal fibroblasts

PURPOSE

To biochemically characterize the receptor for connective tissue growth factor (CTGF) of human corneal fibroblasts (HCF).

METHODS

Radiolabeled recombinant human CTGF was used to determine the specificity and time course of binding to low-passage cultures of HCF. The affinity and number of receptors present were calculated by Scatchard and best-fit analyses. In vitro immunoprecipitation assays with radiolabeled CTGF and soluble mannose 6-phosphate/insulin-like growth factor 2 receptor (M6P/IGF-2-R) alone, or with CTGF-related growth factors were conducted. Additionally, (125)I-CTGF-binding and CTGF-stimulated proliferation were measured in cultures of M6P/IGF-2-R knockout fibroblasts.

RESULTS

Binding of (125)I-CTGF to fibroblast cultures was significantly displaced by CTGF, but not by related growth factors. Scatchard plot analysis indicated the presence of both a high-affinity, low-abundance binding site, and a low-affinity, high-abundance binding site; whereas, the best-fit analysis suggests a single high-affinity, low-abundance binding site. A 280 kDa complex containing cross-linked (125)I-CTGF was immunoprecipitated by antibodies to CTGF or M6P/IGF-2-R. M6P/IGF-2-R knockout cells have a reduced proliferative response to TGF-β, and don't proliferate at all in response to CTGF.

CONCLUSIONS

CTGF binds to the M6P/IGF-2-R with high affinity, and the M6P/IGF-2-R is required for CTGF-stimulated proliferation in fibroblasts. These observations suggest that the M6P/IGF-2-R may be a new antifibrotic target.

The Wnt antagonist Wif-1 interacts with CTGF and inhibits CTGF activity

Wnt inhibitory factor 1 (Wif-1) is a secreted antagonist of Wnt signalling. We recently demonstrated that this molecule is expressed predominantly in superficial layers of epiphyseal cartilage but also in bone and tendon. Moreover, we showed that Wif-1 is capable of binding to several cartilage-related Wnt ligands and interferes with Wnt3a-dependent Wnt signalling in chondrogenic cells. Here we provide evidence that the biological function of Wif-1 may not be confined to the modulation of Wnt signalling but appears to include the regulation of other signalling pathways. Thus, we show that Wif-1 physically binds to connective tissue growth factor (CTGF/CCN2) in vitro, predominantly by interaction with the C-terminal cysteine knot domain of CTGF. In vivo such an interaction appears also likely since the expression patterns of these two secreted proteins overlap in peripheral zones of epiphyseal cartilage. In chondrocytes CTGF has been shown to induce the expression of cartilage matrix genes such as aggrecan (Acan) and collagen2a1 (Col2a1). In this study we demonstrate that Wif-1 is capable to interfere with CTGF-dependent induction of Acan and Col2a1 gene expression in primary murine chondrocytes. Conversely, CTGF does not interfere with Wif-1-dependent inhibition of Wnt signalling. These results indicate that Wif-1 may be a multifunctional modulator of signalling pathways in the cartilage compartment.

The miR-17-92 cluster and its target THBS1 are differentially expressed in angiosarcomas dependent on MYC amplification

Angiosarcomas (ASs) represent a heterogeneous group of malignant vascular tumors that may occur spontaneously as primary tumors or secondarily after radiation therapy or in the context of chronic lymphedema. Most secondary ASs have been associated with MYC oncogene amplification, whereas the role of MYC abnormalities in primary AS is not well defined. Twenty-two primary and secondary ASs were analyzed by array-comparative genomic hybridization (aCGH) and by deep sequencing of small RNA libraries. By aCGH and subsequently confirmed by fluorescence in situ hybridization, MYC amplification was identified in three out of six primary tumors and in 8 out of 12 secondary AS. We have also found MAML1 as a new potential oncogene in MYC-amplified AS. Significant upregulation of the miR-17-92 cluster was observed in MYC-amplified AS compared to AS lacking MYC amplification and the control group (other vascular tumors, nonvascular sarcomas). Moreover, MYC-amplified ASs were associated with a significantly lower expression of thrombospondin-1 (THBS1) than AS without MYC amplification or controls. Altogether, our study implicates MYC amplification not only in the pathogenesis of secondary AS but also in a subset of primary AS. Thus, MYC amplification may play a crucial role in the angiogenic phenotype of AS through upregulation of the miR-17-92 cluster, which subsequently downregulates THBS1, a potent endogenous inhibitor of angiogenesis. © 2012 Wiley Periodicals, Inc.

Prostaglandins in cancer cell adhesion, migration, and invasion

Prostaglandins exert a profound influence over the adhesive, migratory, and invasive behavior of cells during the development and progression of cancer. Cyclooxygenase-2 (COX-2) and microsomal prostaglandin E₂ synthase-1 (mPGES-1) are upregulated in inflammation and cancer. This results in the production of prostaglandin E₂ (PGE₂), which binds to and activates G-protein-coupled prostaglandin E_1–4 receptors (EP_1–4). Selectively targeting the COX-2/mPGES-1/PGE₂/EP_1–4 axis of the prostaglandin pathway can reduce the adhesion, migration, invasion, and angiogenesis. Once stimulated by prostaglandins, cadherin adhesive connections between epithelial or endothelial cells are lost. This enables cells to invade through the underlying basement membrane and extracellular matrix (ECM). Interactions with the ECM are mediated by cell surface integrins by “outside-in signaling” through Src and focal adhesion kinase (FAK) and/or “inside-out signaling” through talins and kindlins. Combining the use of COX-2/mPGES-1/PGE₂/EP_1–4 axis-targeted molecules with those targeting cell surface adhesion receptors or their downstream signaling molecules may enhance cancer therapy.

Cyr61 is a potential prognostic marker for prostate cancer

Cysteine-rich angiogenic inducer 61 (Cyr61) is an extracellular matrix protein involved in the transduction of growth factor and hormone signaling that is frequently altered in expression in several types of cancers. In prostate cancer (PCa), Cyr61 is highly expressed in organ-confined disease. Further, Cyr61 expression levels are associated with a lower risk of disease recurrence, and can be quantitatively measured in the serum. Considered together, these results indicate that Cyr61 is a potential and clinically useful tissue, as well as serum-based biomarker for differentiating lethal and non-lethal PCa.

CCN2/connective tissue growth factor is essential for pericyte adhesion and endothelial basement membrane formation during angiogenesis

CCN2/Connective Tissue Growth Factor (CTGF) is a matricellular protein that regulates cell adhesion, migration, and survival. CCN2 is best known for its ability to promote fibrosis by mediating the ability of transforming growth factor β (TGFβ) to induce excess extracellular matrix production. In addition to its role in pathological processes, CCN2 is required for chondrogenesis. CCN2 is also highly expressed during development in endothelial cells, suggesting a role in angiogenesis. The potential role of CCN2 in angiogenesis is unclear, however, as both pro- and anti-angiogenic effects have been reported. Here, through analysis of Ccn2-deficient mice, we show that CCN2 is required for stable association and retention of pericytes by endothelial cells. PDGF signaling and the establishment of the endothelial basement membrane are required for pericytes recruitment and retention. CCN2 induced PDGF-B expression in endothelial cells, and potentiated PDGF-B-mediated Akt signaling in mural (vascular smooth muscle/pericyte) cells. In addition, CCN2 induced the production of endothelial basement membrane components in vitro, and was required for their expression in vivo. Overall, these results highlight CCN2 as an essential mediator of vascular remodeling by regulating endothelial-pericyte interactions. Although most studies of CCN2 function have focused on effects of CCN2 overexpression on the interstitial extracellular matrix, the results presented here show that CCN2 is required for the normal production of vascular basement membranes.

Connective tissue growth factor antagonizes transforming growth factor-β1/Smad signalling in renal mesangial cells

The critical involvement of TGF-β1 (transforming growth factor-β1) in DN (diabetic nephropathy) is well established. However, the role of CTGF (connective tissue growth factor) in regulating the complex interplay of TGF-β1 signalling networks is poorly understood. The purpose of the present study was to investigate co-operative signalling between CTGF and TGF-β1 and its physiological significance. CTGF was determined to bind directly to the TβRIII (TGF-β type III receptor) and antagonize TGF-β1-induced Smad phosphorylation and transcriptional responses via its N-terminal half. Furthermore, TGF-β1 binding to its receptor was inhibited by CTGF. A consequent shift towards non-canonical TGF-β1 signalling and expression of a unique profile of differentially regulated genes was observed in CTGF/TGF-β1-treated mesangial cells. Decreased levels of Smad2/3 phosphorylation were evident in STZ (streptozotocin)-induced diabetic mice, concomitant with increased levels of CTGF. Knockdown of TβRIII restored TGF-β1-mediated Smad signalling and cell contractility, suggesting that TβRIII is key for CTGF-mediated regulation of TGF-β1. Comparison of gene expression profiles from CTGF/TGF-β1-treated mesangial cells and human renal biopsy material with histological diagnosis of DN revealed significant correlation among gene clusters. In summary, mesangial cell responses to TGF-β1 are regulated by cross-talk with CTGF, emphasizing the potential utility of targeting CTGF in DN.

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.

Novel peptide targeting integrin αvβ3-rich tumor cells by magnetic resonance imaging

PURPOSE

To investigate the targeting activity of the peptide (named P1c) derived from connective tissue growth factor (CTGF) to αvβ3-rich tumor cells.

MATERIALS AND METHODS

P1c was synthesized and conjugated with ultrasuperparamagnetic iron oxide particles (USPIOs) coated with meso-2,3-dimercaptosuccinic acid (DMSA). The specific binding activity of P1c-USPIOs to αvβ3 was verified by solid phase binding assay. The combination of P1c-USPIOs with a human primary liver cancer cell (Bel 7402) with αvβ3-positive expression and uptake of P1c-USPIOs by cells was investigated by Prussian blue staining, transmission electron microscopy (TEM), and magnetic resonance imaging (MRI). The targeting activity of the probe in vivo was also evaluated using a small-animal tumor model by MRI.

RESULTS

The cell uptake of P1c-USPIOs was observed in a dose-dependent manner, whereas no significant particle uptake was found in the plain USPIOs group. The differences on T2*-weighted imaging were also found by MRI and the signal intensity (SI) was statistically reduced after coculture of Bel 7402 cells with P1c-USPIOs at a concentration of 20-80 μg/mL compared with plain USPIOs (P < 0.05). The in vivo study showed that the signal reduction was distributed mainly in the periphery and some central areas of the tumor. The tumor-to-muscle CNR (contrast-to-noise ratio) at 12 hours after the administration of the P1c-USPIOs was statistically significantly different compared to those at 0 hour, 1 hour, or the plain USPIO group (P < 0.05).

CONCLUSION

The peptide P1c might be a good candidate as a targeting carrier for drugs or tracers.

Thrombin induced connective tissue growth factor expression in rat vascular smooth muscle cells via the PAR-1/JNK/AP-1 pathway

AIM

To investigate the signaling pathways involved in thrombin-induced connective tissue growth factor (CTGF) expression in rat vascular smooth muscle cells (VSMCs).

METHODS

Experiments were preformed on primary rat aortic smooth muscle cells (RASMCs) and a rat VSMC line (A10). CTGF protein levels were measured using Western blotting. Luciferase reporter genes and dominant negative mutants (DNs) were used to investigate the signaling pathways mediating the induction of CTGF expression by thrombin.

RESULTS

Thrombin (0.3-3.0 U/mL) caused a concentration- and time-dependent increase in CTGF expression in both RASMCs and A10 cells. Pretreating A10 cells with the protease-activated receptor 1 (PAR-1) antagonist SCH79797 (0.1 μmol/L) significantly blocked thrombin-induced CTGF expression, while the PAR-4 antagonist tcY-NH(2) (30 μmol/L) had no effect. The PAR-1 agonist SFLLRN-NH(2) (300 μmol/L) induced CTGF expression, while the PAR-4 agonist GYPGQV-NH(2) (300 μmol/L) had no effect. Thrombin (1 U/mL) caused time-dependent phosphorylation of c-Jun N-terminal kinase (JNK). Pretreating with the JNK inhibitor SP600125 (3-30 μmol/L) or transfection with DNs of JNK1/2 significantly attenuated thrombin-induced CTGF expression. Thrombin (0.3-3.0 U/mL) increased activator protein-1 (AP-1)-luciferase activity, which was inhibited by the JNK inhibitor SP600125. The AP-1 inhibitor curcumin (1-10 μmol/L) concentration-dependently attenuated thrombin-induced CTGF expression.

CONCLUSION

Thrombin acts on PAR-1 to activate the JNK signaling pathway, which in turn initiates AP-1 activation and ultimately induces CTGF expression in VSMCs.

CCN2 promotes cigarette smoke-induced proliferation of rat pulmonary artery smooth muscle cells through upregulating cyclin D1 expression

Cigarette smoke has been demonstrated to induce pulmonary vascular remodeling, which is characterized by medial thickening of the pulmonary arteries mainly resulting from the abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs). However, the molecular mechanism underlying this process is still unclear. In the present study, we investigated whether CCN2 regulated rat PASMCs (rPASMCs) proliferation induced by cigarette smoke extract (CSE) and nicotine by upregulating cyclin D1 in vitro. CCN2 siRNA or cyclin D1 siRNA were transfected to rPASMCs which were then exposed to CSE and nicotine. Both mRNA and protein expressions of CCN2 were significantly increased in rPASMCs treated with 2% CSE or 1 µM nicotine, which markedly promoted the proliferation of rPASMCs. CCN2 siRNA inhibited the proliferation of rPASMCs induced by CSE or nicotine. Furthermore, CCN2 siRNA markedly suppressed the mRNA and protein expressions of cyclin D1 in rPASMCs and led to cell cycle arrest in G0/G1 phase resulting in reduced rPASMCs proliferation. These findings suggest that CCN2 contributes to the CSE and nicotine-induced proliferation of rPASMCs at least in part by upregulating cyclin D1 expression.

Differential roles of CCN family proteins during osteoblast differentiation: Involvement of Smad and MAPK signaling pathways

CCN family proteins play diverse roles in many aspects of cellular processes such as proliferation, differentiation, adhesion, migration, angiogenesis and survival. In the bone tissue of vertebrate species, the expression of most CCN family members has been observed in osteoblasts. However, their spatial and temporal distributions, as well as their functions, are still only partially understood. In this study, we evaluated the localization of CCN family members in skeletal tissue in vivo and comparatively analyzed the gene expression patterns and functions of the members in murine osteoblasts in primary culture. Immunofluorescent analyses revealed that the CCN family members were differentially produced in osteoblasts and osteocytes. The presence of all Ccn transcripts was confirmed in those osteoblasts. Among the members, CCN1, CCN2, CCN4 and CCN5 were found in osteocytes. CCN4 and CCN5 were distributed in osteocytes located inside of bone matrix as well. Next, we investigated the expression pattern of Ccn family members during osteoblast differentiation. Along with differentiation, most of the members followed proper gene expression patterns; whereas, Ccn4 and Ccn5 showed quite similar patterns. Furthermore, we evaluated the effects of CCN family members on the osteoblastic activities by using recombinant CCN proteins and RNA interference method. Five members of this family displayed positive effects on osteoblast proliferation or differentiation. Of note, CCN3 drastically inhibited the osteoblast activities. Each Ccn specific siRNA could modulate osteoblast activities in a manner expected by the observed effect of respective recombinant CCN protein. In addition, we found that extracellular signal-regulated kinase1/2 and p38 mitogen-activated protein kinase pathways were critically involved in the CCN family member-mediated modification of osteoblast activities. Collectively, all Ccn family members were found to be differentially expressed along with differentiation and therefore could participate in progression of the osteoblast lineage.

Runx2/Smad3 complex negatively regulates TGF-β-induced connective tissue growth factor gene expression in vascular smooth muscle cells

AIM

Connective tissue growth factor (CTGF), a direct target gene of transforming growth factor-β (TGF-β) signaling, plays an important role in the development of atherosclerosis. We previously showed that Runx2, a key transcription factor in osteoblast differentiation, regulates osteogenic conversion and dedifferentiation of vascular smooth muscle cells (VSMCs). In this study, we investigated the hypothesis that Runx2 modulates CTGF gene expression via the regulation of TGF-β signaling.

METHODS AND RESULTS

Expression of the Runx2 gene was decreased, and CTGF mRNA levels were reciprocally increased by TGF-β in a time-dependent manner in cultured human aortic smooth muscle cells (HASMCs) and C3H10T1/2 cells. Forced expression of Runx2 decreased and the reduction of Runx2 expression by small interfering RNA enhanced both basal and TGF-β-stimulated CTGF gene expression in HASMCs. Site-directed mutation analysis of the CTGF promoter indicated that transcriptional repression by Runx2 was mediated by the Smad-binding element (SBE) under basal and TGF-β-stimulated conditions. Data obtained from immunoblots of Runx2-, Smad3- or Smad4-transfected cells and chromatin immunoprecipitation analysis indicated that Runx2 interacts with Smad3 at the SBE. Immunohistochemistry revealed that the expression of Runx2 and CTGF was distinct and almost mutually exclusive in human atherosclerotic plaque.

CONCLUSIONS

These results for the first time demonstrate that Runx2/Smad3 complex negatively regulates endogenous and TGF-β-induced CTGF gene expression in VSMCs. Thus, the induction of Runx2 expression contributes to the phenotypic modulation of VSMCs, in which the TGF-β/Smad pathway plays a major role.

Hypertrophy of ligamentum flavum in lumbar spine stenosis associated with the increased expression of connective tissue growth factor

Hypertrophy of the ligamentum flavum (LF) contributes to lumbar spinal stenosis (LSS), and results mainly from fibrosis. Connective tissue growth factor (CTGF) is a profibrotic factor involved in the fibrotic process. This study aimed to evaluate CTGF expression in hypertrophied lumbar LF and the involvement of CTGF in LF hypertrophy. Ten patients with LSS were enrolled in this study. The control group included 10 patients with lumbar disc herniation. LF thickness was measured on the preoperative axial T1-weighted MRI. LF samples were collected during surgery. LF fibrosis was scored by Masson's trichrome staining. CTGF expression was determined by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. Correlation between LF thickness and CTGF expression was analyzed. Human LF cells were cultured and treated with recombinant human (rh) CTGF. Expression of types I and III collagen was determined by real-time PCR and ELISA. The thickness and fibrosis scores of LF in the LSS group were higher than that in the control group (all P < 0.001). CTGF was expressed in the extracellular matrix of all ligament samples, and was significantly higher in the LSS group than that in the control group (P < 0.001). The increase of CTGF expression was positive correlation with the LF thickness (r = 0.969, P = 0.000). rhCTGF treatment increased the mRNA expression and protein synthesis of types I and III collagen of the LF cells (all P < 0.001). Our results suggest that the increased expression of CTGF is associated with hypertrophy of the LF in patients with LSS.

Impaired intracellular signaling may allow up-regulation of CTGF-synthesis and secondary peri-retinal fibrosis in human retinal pigment epithelial cells from patients with age-related macular degeneration

Age-related macular degeneration (AMD) is a major sight-threatening ocular disorder in the United States of America and the world, yet its etiology is not clearly understood, preventing the development of effective prevention or therapy. Connective tissue growth factor (CTGF) has been implicated in the pathological synthesis of peri-retinal fibrous tissue in patients with AMD. Very little is known about the mechanism of this interaction. In this study, the authors demonstrate that insulin like growth factor-1 (IGF-1) and glucose-stimulated CTGF production are not blocked by the MAP kinase pathway inhibitor, PD98059 in hRPE cells obtained from eyes of a patient with AMD in contrast to hRPE cells obtained from normal human eyes. This suggests that there may be abnormal CTGF synthesis regulation in AMD, which may play a role in fibrous peri-retinal membrane formation in patients with AMD-related proliferative vitreoretinopathy.

Assembly of the prothrombinase complex on the surface of human foreskin fibroblasts: Implications for connective tissue growth factor

Activated factor X (FXa) and thrombin can up-regulate gene expression of connective tissue growth factor (CTGF/CCN2) on fibroblasts. Since tissue factor (TF) is expressed on these cells, we hypothesized that they may assemble the prothrombinase complex leading to CTGF/CCN2 upregulation. In addition, the effect of thrombospondin-1 (TSP1) on this reaction was evaluated. Human foreskin fibroblasts were incubated with purified factor VII (FVII), factor X (FX), factor V (FV), prothrombin and calcium in the presence and absence of TSP1. Generation of FXa and of thrombin were assessed using chromogenic substrates. SMAD pathway phosphorylation was detected via Western-blot analysis. Pre-incubation of fibroblasts with FVII led to its auto-activation by cell-surface expressed TF, which in turn in the presence of FX, FVa, prothrombin and calcium led to FXa (9.7±0.8nM) and thrombin (7.9±0.04 U/mL×10-3) generation. Addition of TSP1 significantly enhanced thrombin (23.3±0.7 U/mL×10-3) but not FXa (8.5±0.6nM) generation. FXa and thrombin generation leads to upregulation of CTGF/CCN2. TSP1 alone upregulated CTGF/CCN2, an effect mediated via activation of transforming growth factor beta (TGFβ) as shown by phosphorylation of the SMAD pathway, an event blunted by using a TGFβ receptor I inhibitor (TGFβRI). FXa- and thrombin-induced upregulation of CTGF/CCN2 was not blocked by TGFβRI. In summary, assembly of the prothrombinase complex occurs on fibroblast's surface leading to serine proteases generation, an event enhanced by TSP1 and associated with CTGF/CCN2 upregulation. These mechanisms may play an important role in human diseases associated with fibrosis.

Extracellular acidification induces connective tissue growth factor production through proton-sensing receptor OGR1 in human airway smooth muscle cells

Asthma is characterized by airway inflammation, hyper-responsiveness and remodeling. Extracellular acidification is known to be associated with severe asthma; however, the role of extracellular acidification in airway remodeling remains elusive. In the present study, the effects of acidification on the expression of connective tissue growth factor (CTGF), a critical factor involved in the formation of extracellular matrix proteins and hence airway remodeling, were examined in human airway smooth muscle cells (ASMCs). Acidic pH alone induced a substantial production of CTGF, and enhanced transforming growth factor (TGF)-β-induced CTGF mRNA and protein expression. The extracellular acidic pH-induced effects were inhibited by knockdown of a proton-sensing ovarian cancer G-protein-coupled receptor (OGR1) with its specific small interfering RNA and by addition of the G(q/11) protein-specific inhibitor, YM-254890, or the inositol-1,4,5-trisphosphate (IP(3)) receptor antagonist, 2-APB. In conclusion, extracellular acidification induces CTGF production through the OGR1/G(q/11) protein and inositol-1,4,5-trisphosphate-induced Ca(2+) mobilization in human ASMCs.

Connective tissue growth factor is required for normal follicle development and ovulation

Connective tissue growth factor (CTGF) is a cysteine-rich protein the synthesis and secretion of which are hypothesized to be selectively regulated by activins and other members of the TGF-β superfamily. To investigate the in vivo roles of CTGF in female reproduction, we generated Ctgf ovarian and uterine conditional knockout (cKO) mice. Ctgf cKO mice exhibit severe subfertility and multiple reproductive defects including disrupted follicle development, decreased ovulation rates, increased numbers of corpus luteum, and smaller but functionally normal uterine horns. Steroidogenesis is disrupted in the Ctgf cKO mice, leading to increased levels of serum progesterone. We show that disrupted follicle development is accompanied by a significant increase in granulosa cell apoptosis. Moreover, despite normal cumulus expansion, Ctgf cKO mice exhibit a significant decrease in oocytes ovulated, likely due to impaired ovulatory process. During analyses of mRNA expression, we discovered that Ctgf cKO granulosa cells show gene expression changes similar to our previously reported granulosa cell-specific knockouts of activin and Smad4, the common TGF-β family intracellular signaling protein. We also discovered a significant down-regulation of Adamts1, a progesterone-regulated gene that is critical for the remodeling of extracellular matrix surrounding granulosa cells of preovulatory follicles. These findings demonstrate that CTGF is a downstream mediator in TGF-β and progesterone signaling cascades and is necessary for normal follicle development and ovulation.

Stretch-inducible expression of connective tissue growth factor (CTGF) in human osteoblasts-like cells is mediated by PI3K-JNK pathway

To explore the possible role for connective tissue growth factor (CTGF) during tooth movement, we evaluated CTGF gene and protein expression in MG-63 cells subjected to cyclic stretch. Cyclic stretch caused a time-dependent increase in CTGF mRNA and protein levels.Inhibition of p38 MAP kinase or ERK activation did not affect cyclic stretch-induced CTGF expression. Specific inhibitors of PI3K suppressed stretch -induced CTGF expression in a time-dependent manner. cyclic stretch activated JNK and ERK, but not p38 MAP kinase in osteoblast-like cells. PI3K inhibitors suppressed cyclic stretch-induced JNK, but not p38 MAP kinase activation. Finally, SP600125, a Specific Inhibitor of JNK, suppressed stretch -induced CTGF Expression. These results suggest that stretch-induced CTGF expression is mediated through the PI3K-JNK -dependent pathway, not by p38 MAP kinase and ERK pathways.

Plasma CCN2 (connective tissue growth factor; CTGF) is a potential biomarker in idiopathic pulmonary fibrosis (IPF)

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal pulmonary fibrotic disease and useful biomarkers are required to diagnose and predict disease activity. CCN2 (connective tissue growth factor; CTGF) has been reported as one of the key profibrotic factors associated with transforming growth factor-β (TGF-β), and its assay has potential as a non-invasive measure in various fibrotic diseases. Recently, we developed a new subtraction method for determination of plasma CCN2 levels. We examined the utility of plasma CCN2 levels as a surrogate marker in IPF.

METHODS

Plasma CCN2 levels were calculated in 33 patients with IPF, 14 patients with non-IPF idiopathic interstitial pneumonias (IIPs) and 101 healthy volunteers by sandwich enzyme-linked immunosorbent assay (ELISA) using specific monoclonal antibodies for two distinct epitopes of human CCN2. We evaluated the utility of plasma CCN2 levels by comparison with clinical parameters.

RESULTS

Plasma CCN2 levels were significantly higher in patients with IPF than in those with non-IPF IIPs and healthy volunteers. Importantly, plasma CCN2 levels showed significantly negative correlation with 6-month change of forced vital capacity (FVC) in patients with IPF.

CONCLUSIONS

Plasma CCN2 is a potential biomarker for IPF.

Effect of brain- and tumor-derived connective tissue growth factor on glioma invasion

BACKGROUND

Tumor cell invasion is the principal cause of treatment failure and death among patients with malignant gliomas. Connective tissue growth factor (CTGF) has been previously implicated in cancer metastasis and invasion in various tumors. We explored the mechanism of CTGF-mediated glioma cell infiltration and examined potential therapeutic targets.

METHODS

Highly infiltrative patient-derived glioma tumor-initiating or tumor stem cells (TIC/TSCs) were harvested and used to explore a CTGF-induced signal transduction pathway via luciferase reporter assays, chromatin immunoprecipitation (ChIP), real-time polymerase chain reaction, and immunoblotting. Treatment of TIC/TSCs with small-molecule inhibitors targeting integrin β1 (ITGB1) and the tyrosine kinase receptor type A (TrkA), and short hairpin RNAs targeting CTGF directly were used to reduce the levels of key protein components of CTGF-induced cancer infiltration. TIC/TSC infiltration was examined in real-time cell migration and invasion assays in vitro and by immunohistochemistry and in situ hybridization in TIC/TSC orthotopic xenograft mouse models (n = 30; six mice per group). All statistical tests were two-sided.

RESULTS

Treatment of TIC/TSCs with CTGF resulted in CTGF binding to ITGB1-TrkA receptor complexes and nuclear factor kappa B (NF-κB) transcriptional activation as measured by luciferase reporter assays (mean relative luciferase activity, untreated vs CTGF(200 ng/mL): 0.53 vs 1.87, difference = 1.34, 95% confidence interval [CI] = 0.69 to 2, P < .001). NF-κB activation resulted in binding of ZEB-1 to the E-cadherin promoter as demonstrated by ChIP analysis with subsequent E-cadherin suppression (fold increase in ZEB-1 binding to the E-cadherin promoter region: untreated + ZEB-1 antibody vs CTGF(200 ng/mL) + ZEB-1 antibody: 1.5 vs 6.4, difference = 4.9, 95% CI = 4.8 to 5.0, P < .001). Immunohistochemistry and in situ hybridization revealed that TrkA is selectively expressed in the most infiltrative glioma cells in situ and that the surrounding reactive astrocytes secrete CTGF.

CONCLUSION

A CTGF-rich microenvironment facilitates CTGF-ITGB1-TrkA complex activation in TIC/TSCs, thereby increasing the invasiveness of malignant gliomas.

CCN3/NOV small interfering RNA enhances fibrogenic gene expression in primary hepatic stellate cells and cirrhotic fat storing cell line CFSC

Nephroblastoma overexpressed gene encodes a matricellular protein (CCN3/NOV) of the CCN family, comprising CCN1 (CYR61), CCN2 (CTGF), CCN4 (WISP-1), CCN5 (WISP-2), and CCN6 (WISP-3). CCN proteins are involved in the regulation of mitosis, adhesion, apoptosis, extracellular matrix production, growth arrest and migration in multiple cell types. Compared to CCN2/CTGF, known as a profibrotic protein, the biological role of CCN3/NOV in liver fibrosis remains obscure. In this study we showed ccn3/nov mRNA to increase dramatically following hepatic stellate cell activation, reaching peak levels in fully transdifferentiated myofibroblasts. In models of experimental hepatic fibrosis, CCN3/NOV increased significantly at the mRNA and protein levels. CCN3/NOV was found mainly in non-parenchymal cells along the areas of tissue damage and repair. In the bile-duct ligation model, CCN3/NOV was localized mainly along portal tracts, while the repeated application of carbon tetrachloride resulted in CCN3/NOV expression mainly in the centrilobular areas. In contrast to CCN2/CTGF, the profibrotic cytokines platelet-derived growth factor-B and -D as well as transforming growth factor-β suppressed CCN3/NOV expression. In vitro, CCN3/NOV siRNA attenuated migration in the cirrhotic fat storing cell line CFSC well in line with in vivo findings that various types of cells expressing CCN3/NOV migrate into the area of tissue damage and regeneration. The suppression of CCN3/NOV enhanced expression of profibrotic marker proteins, such as α-smooth muscle actin, collagen type I, fibronectin, CCN2/CTGF and TIMP-1 in primary rat hepatic stellate cells and in CFSC. We further found that adenoviral overexpression of CCN2/CTGF suppressed CCN3/NOV expression, while the overexpression of CCN3/NOV as well as the suppression of CCN3/NOV by targeting siRNAs both resulted in enhanced CCN2/CTGF expression. These results indicate the complexity of CCN actions that are far beyond the classic Yin/Yang interplay.

Relationship between hepatic CTGF expression and routine blood tests at the time of liver transplantation for biliary atresia: hope or hype for a biomarker of hepatic fibrosis

Background:

Progressive hepatic fibrosis (HF) is a prominent feature of biliary atresia (BA), the most common indication for liver transplantation (LT) in children. Despite its importance in BA, HF is not evaluated in routine patient care because the invasiveness of liver biopsy makes histologic monitoring of fibrosis unfeasible. Therefore, the identification of noninvasive markers to assess HF is desirable especially in children.

Purpose:

The main goal of this pilot project was to establish an investigational framework correlating hepatic expression of fibrogenic markers with routine blood tests in BA.

Methods:

Using liver explants from patients with BA (n = 26), immune-expression of connective tissue growth factor (CTGF), a key fibrogenic cytokine was determined using horseradish-labeled antibodies. Expression intensities of lobular (L-CTGF) and portal (P-CTGF) CTGF were determined by using ImageJ software. These CTGF intensities were correlated with blood tests performed at the time of LT. Correlation coefficients were determined for each blood test variable versus mean L-CTGF and P-CTGF expression intensities. A P-value of less than 0.05 was considered statistically significant.

Results:

All patients had end-stage liver disease and persistent cholestasis at the time of LT. Kendall tau (τ) rank correlation coefficient for L-CTGF and white blood cell (WBC) was inversed (−0.52; P ≤ 0.02). Similar but statistically nonsignificant inverse relationships were noted between L-CTGF and prothrombin time (PT) (−0.15; P ≤ 0.4), international normalized ratio (INR) (−0.14; P ≤ 0.5), and platelet count (−0.36; P ≤ 0.09). Inversed (τ) rank correlation coefficients were also evident between P-CTGF expression and gamma-glutamyl transpeptidase (GGT), PT, INR, and platelet count. Pearson correlation coefficients for combinational analysis of standardized total bilirubin (TB), alkaline phosphatase, GGT, and platelet count with L-CTGF (0.33; P = 0.3) and P-CTGF (0.06; P = 0.8), were not significant. Similar analysis for alanine aminotransferase, TB, and GGT combination (L-CTGF, 0.16; P = 0.5; P-CTGF −0.3; P = 0.2) as well as WBC, platelet count, and TB (L-CTGF: −0.36; P = 0.09; P-CTGF −0.33; P = 0.13) also revealed nonsignificant results.

Conclusion:

Hepatic expression of fibrogenic markers can be correlated with routinely performed blood tests in patients with BA. We document that although a trend of inverse relationship is noted, hepatic CTGF expression does not correlate well with routinely performed blood tests in advanced BA. Further work is required to determine more reliable ways of noninvasive diagnosis of HF.

CTGF is overexpressed in malignant melanoma and promotes cell invasion and migration

BACKGROUND

Malignant melanoma cells are known to have altered expression of growth factors compared with normal human melanocytes. These changes most likely favour tumour growth and progression, and influence tumour environment. The induction of transforming growth factor beta1, 2 and 3 as well as BMP4 and BMP7 expression in malignant melanoma has been reported before, whereas the expression of an important modulator of these molecules, connective tissue growth factor (CTGF), has not been investigated in melanomas until now.

METHODS

Expression of CTGF was analysed in melanoma cell lines and tissue samples by qRT-PCR and immunohistochemistry. To determine the regulation of CTGF expression in malignant melanoma, specific siRNA was used. Additionally, migration, invasion and attachment assays were carried out.

RESULTS

We were able to demonstrate that CTGF expression is upregulated in nine melanoma cell lines and in primary and metastatic melanoma in situ. The transcription factor HIF-1α was revealed as a positive regulator for CTGF expression. Melanoma cells, in which CTGF expression is diminished, show a strong reduction of migratory and invasive properties when compared with controls. Further, treatment of normal human epidermal melanocytes with recombinant CTGF leads to an increase of migratory and invasive behaviour of these cells.

CONCLUSION

These results suggest that CTGF promotes melanoma cell invasion and migration and, therefore, has an important role in the progression of malignant melanoma.

First structural glimpse of CCN3 and CCN5 multifunctional signaling regulators elucidated by small angle x-ray scattering

The CCN (cyr61, ctgf, nov) proteins (CCN1-6) are an important family of matricellular regulatory factors involved in internal and external cell signaling. They are central to essential biological processes such as adhesion, proliferation, angiogenesis, tumorigenesis, wound healing, and modulation of the extracellular matrix. They possess a highly conserved modular structure with four distinct modules that interact with a wide range of regulatory proteins and ligands. However, at the structural level, little is known although their biological function(s) seems to require cooperation between individual modules. Here we present for the first time structural determinants of two of the CCN family members, CCN3 and CCN5 (expressed in Escherichia coli), using small angle x-ray scattering. The results provide a description of the overall molecular shape and possible general three-dimensional modular arrangement for CCN proteins. These data unequivocally provide insight of the nature of CCN protein(s) in solution and thus important insight into their structure-function relationships.

Connective tissue growth factor cooperates with fibronectin in enhancing attachment and migration of corneal epithelial cells

Corneal wound healing is a complex process involving the integrated actions of various growth factors, cytokines and extracellular matrix produced by corneal cells and inflammatory cells. Connective tissue growth factor (CTGF) has been linked to wound healing, and fibronectin (FN) is a major component of the extracellular matrix. However, the functions of CTGF and FN in corneal epithelial cells are not well understood. We therefore investigated the coordinated function of CTGF and FN in the attachment and migration of corneal epithelial cells. Treatment of human corneal epithelial cells (HCECs) with transforming growth factor (TGF) beta1 up-regulated the expression of CTGF, but did not noticeably affect FN expression, as judged by immunoblot analysis of cell lysates. In contrast, the amount of FN accumulated in the cultured media was increased in a time-dependent manner, but CTGF was undetectable in the cultured media. The expression level of FN was decreased by the knockdown of CTGF expression with a specific short hairpin RNA, indicating that CTGF acts as an upstream mediator of FN expression. CTGF augmented the FN-mediated increase in the attachment of HCEC by about twofold, although CTGF alone did not influence the attachment. Moreover, the migration assay with rabbit corneal blocks revealed that CTGF (390 nM) alone or in combination of FN (10 microg/mL) promoted corneal epithelial migration; the mean migration distances of control, CTGF, and CTGF + FN were 272, 325, and 626, microm, respectively. In conclusion, CTGF cooperates with FN in enhancing the attachment and migration of corneal epithelial cells.

Variable behavior and complications of autologous bone marrow mesenchymal stem cells transplanted in experimental autoimmune encephalomyelitis

Autologous bone marrow stromal cells (BMSCs) offer significant practical advantages for potential clinical applications in multiple sclerosis (MS). Based on recent experimental data, a number of clinical trials have been designed for the intravenous (IV) and/or intrathecal (ITH) administration of BMSCs in MS patients. Delivery of BMSCs in the cerebrospinal fluid via intracerebroventricular (ICV) transplantation is a useful tool to identify mechanisms underlying the migration and function of these cells. In the current study, BMSCs were ICV administered in severe and mild EAE, as well as naive animals; neural precursor cells (NPCs) served as cellular controls. Our data indicated that ICV-transplanted BMSCs significantly ameliorated mild though not severe EAE. Moreover, BMSCs exerted significant anti-inflammatory effect on spinal cord with concomitant reduced axonopathy only in the mild EAE model. BMSCs migrated into the brain parenchyma and, depending on their cellular density, within brain parenchyma formed cellular masses characterized by focal inflammation, demyelination, axonal loss and increased collagen-fibronectin deposition. These masses were present in 64% of ICV BMASC-transplanted severe EAE animals whereas neither BMSCs transplanted in mild EAE cases nor the NPCs exhibited similar behavior. BMSCs possibly exerted their fibrogenic effect via both paracrine and autocrine manner, at least partly due to up-regulation of connective tissue growth factor (CTGF) under the trigger of TGFb1. Our findings are of substantial relevance for clinical trials in MS, particularly regarding the possibility that ICV transplanted BMSCs entering the inflamed central nervous system may exhibit - under conditions - a local pathology of yet unknown consequences.

Knockdown of connective tissue growth factor by plasmid-based short hairpin RNA prevented pulmonary vascular remodeling in cigarette smoke-exposed rats

Cigarette smoking may contribute to pulmonary hypertension in chronic obstructive pulmonary disease by resulting in pulmonary vascular remodeling that involves pulmonary artery smooth muscle cell proliferation. Connective tissue growth factor (CTGF) is a cysteine-rich peptide implicated in several biological processes such as cell proliferation, survival, and migration. This study investigated the potential role of CTGF in pulmonary vascular remodeling. We constructed a plasmid-based short hairpin RNA (shRNA) to knock down the expression of CTGF in primary cultured rat pulmonary artery smooth muscle cells (rPASMCs) and in rat lung vessels. Rat PASMCs were challenged with cigarette smoke extract (CSE). Rats were exposed to cigarette smoke for 3 months in the absence or in the presence of plasmid-based short hairpin RNA against CTGF which was administrated by tail vein injection. CTGFshRNA significantly prevented CTGF and cyclin D1 expression, arrested cell cycle at G0/G1 phase and suppressed cell proliferation in rPASMCs exposed to CSE. CTGFshRNA administration ameliorated pulmonary vascular remodeling, inhibited cigarette smoke-induced CTGF elevation and reversed the cyclin D1 increase in pulmonary vessels in rats. Collectively, our data demonstrated that plasmid-based shRNA against CTGF attenuated pulmonary vascular remodeling in cigarette smoke-exposed rats.

Decorin interacts with connective tissue growth factor (CTGF)/CCN2 by LRR12 inhibiting its biological activity

Fibrotic disorders are the end point of many chronic diseases in different tissues, where an accumulation of the extracellular matrix occurs, mainly because of the action of the connective tissue growth factor (CTGF/CCN2). Little is known about how this growth factor activity is regulated. We found that decorin null myoblasts are more sensitive to CTGF than wild type myoblasts, as evaluated by the accumulation of fibronectin or collagen III. Decorin added exogenously negatively regulated CTGF pro-fibrotic activity and the induction of actin stress fibers. Using co-immunoprecipitation and in vitro interaction assays, decorin and CTGF were shown to interact in a saturable manner with a K(d) of 4.4 nM. This interaction requires the core protein of decorin. Experiments using the deletion mutant decorin indicated that the leucine-rich repeats (LRR) 10-12 are important for the interaction with CTGF and the negative regulation of the cytokine activity, moreover, a peptide derived from the LRR12 was able to inhibit CTGF-decorin complex formation and CTGF activity. Finally, we showed that CTGF specifically induced the synthesis of decorin, suggesting a mechanism of autoregulation. These results suggest that decorin interacts with CTGF and regulates its biological activity.

A coding RNA segment that enhances the ribosomal recruitment of chicken ccn1 mRNA

CCN1, a member of the CCN family of proteins, plays important physiological or pathological roles in a variety of tissues. In the present study, we initially found a highly guanine-cytosine (GC)-rich region of approximately 200 bp near the 5'-end of the open reading frame, which was always truncated by amplification of the corresponding cDNA region through the conventional polymerase chain reaction. An RNA in vitro folding assay and selective ribonuclease digestion of the corresponding segment of the ccn1 mRNA confirmed the involvement of a stable secondary structure. Subsequent RNA electromobility-shift assays demonstrated the specific binding of some cytoplasmic factor(s) in chicken embryo fibroblasts to the RNA segment. Moreover, the corresponding cDNA fragment strongly enhanced the expression of the reporter gene in cis at the 5'-end, but did not do so at the 3'-end. According to the results of a ribosomal assembly test, the effect of the mRNA segment can predominantly be ascribed to the enhancement of transport and/or entry of the mRNA into the ribosome. Finally, the minimal GC-rich mRNA segment that was predicted and demonstrated to form a secondary structure was confirmed to be a functional regulatory element. Thus, we here uncover a novel dual-functionality of the mRNA segment in the ccn1 open reading frame, which segment acts as a cis-element that mediates posttranscriptional gene regulation, while retaining the information for the amino acid sequence of the resultant protein.

CCN2: a bona fide target for anti-fibrotic drug intervention

CCN2 (formerly known as connective tissue growth factor) was identified by several different laboratories approximately 20 years ago. Almost since its identification as a factor induced in normal fibroblasts by transforming growth factor β and overexpressed in fibrotic disease, CCN2 has been hypothesized to be not only a marker but also a central mediator of fibrosis in vivo. Finally, in vivo data are emerging to validate this key hypothesis. For example, a neutralizing anti-CCN2 antibody was found to attenuate fibrogenesis in three separate animal models (Wang et al. in Fibrogenesis Tissue Repair 4:1-4, 2011). This commentary addresses recent data indicating that CCN2 appears to represent a key central mediator of fibrosis and a good target for anti-fibrotic drug intervention.

The role of CCN2 in cartilage and bone development

CCN2, a classical member of the CCN family of matricellular proteins, is a key molecule that conducts cartilage development in a harmonized manner through novel molecular actions. During vertebrate development, all cartilage is primarily formed by a process of mesenchymal condensation, while CCN2 is induced to promote this process. Afterwards, cartilage develops into several subtypes with different fates and missions, in which CCN2 plays its proper roles according to the corresponding microenvironments. The history of CCN2 in cartilage and bone began with its re-discovery in the growth cartilage in long bones, which determines the skeletal size through the process of endochondral ossification. CCN2 promotes physiological developmental processes not only in the growth cartilage but also in the other types of cartilages, i.e., Meckel's cartilage representing temporary cartilage without autocalcification, articular cartilage representing hyaline cartilage with physical stiffness, and auricular cartilage representing elastic cartilage. Together with its significant role in intramembranous ossification, CCN2 is regarded as a conductor of skeletogenesis. During cartilage development, the CCN2 gene is dynamically regulated to yield stage-specific production of CCN2 proteins at both transcriptional and post-transcriptional levels. New functional aspects of known biomolecules have been uncovered during the course of investigating these regulatory systems in chondrocytes. Since CCN2 promotes integrated regeneration as well as generation (=development) of these tissues, its utility in regenerative therapy targeting chondrocytes and osteoblasts is indicated, as has already been supported by experimental evidence obtained in vivo.

Epithelial-mesenchymal interactions in biliary diseases

In most cholangiopathies, liver diseases of different etiologies in which the biliary epithelium is the primary target in the pathogenic sequence, the central mechanism involves inflammation. Inflammation, characterized by pleomorphic peribiliary infiltrate containing fibroblasts, macrophages, lymphocytes, as well as endothelial cells and pericytes, is associated to the emergence of "reactive cholangiocytes." These biliary cells do not possess bile secretory functions, are in contiguity with terminal cholangioles, and are of a less-differentiated phenotype. They have acquired several mesenchymal properties, including motility and ability to secrete a vast number of proinflammatory chemo/cytokines and growth factors along with de novo expression of a rich receptor machinery. These functional properties enable reactive cholangiocytes to establish intimate contacts and to mutually exchange a variety of paracrine signals with the different mesenchymal cell types populating the portal infiltrate. The extensive crosstalk between the epithelial and mesenchymal compartments is the driver of liver repair mechanisms in cholangiopathies, ultimately evolving toward portal fibrosis. Herein, the authors first review the properties of the different cell types involved in their interaction, and then analyze the underlying molecular mechanisms as they relate to liver repair in cholangiopathies.

Induction of matrix metalloproteinase-1 by small interfering RNA targeting connective tissue growth factor in dermal fibroblasts from patients with systemic sclerosis

We aimed to evaluate the effect of small interfering RNA (siRNA) targeting CTGF on extracellular matrices (ECMs) metabolism in normal and SSc fibroblasts. Normal and SSc fibroblasts were transfected with CTGF-specific siRNAs to silence CTGF synthesis. After silencing CTGF, production of type I collagen and matrix metalloproteinase (MMP)-1 by fibroblasts stimulated with TGF-beta was examined. Then quantitative analyses of protein production or mRNA expression of type I collagen, MMP-1,-2,-9 and tissue inhibitor of metalloproteinase (TIMP)-1 with TGF-beta stimulation were carried out. Furthermore, after silencing CTGF, proliferations of normal and SSc fibroblasts were investigated. CTGF-specific siRNA significantly reduced CTGF production. The production of type I collagen was significantly reduced by CTGF silencing in normal fibroblasts. The CTGF silencing significantly increased the production of MMP-1 and decreased the production of TIMP-1 in SSc fibroblasts. The mRNA expression of MMP-1 was increased in CTGF-silenced SSc fibroblasts, but not in normal fibroblasts. There were no significant changes in the production or mRNA expression of other ECM-related genes in normal and SSc fibroblasts. Fibroblast proliferations were suppressed by CTGF silencing in normal and SSc fibroblasts. Our data showed that MMP-1 was increased by CTGF-specific siRNA transfection only in SSc fibroblasts. RNAi targeting CTGF could be a novel therapeutic strategy for SSc.

CTGF expression is up-regulated by PROK1 in early pregnancy and influences HTR-8/Svneo cell adhesion and network formation

BACKGROUND

Prokineticin-1 (PROK1) and connective tissue growth factor (CTGF) are expressed in human endometrium and first-trimester decidua and have individually been proposed to have roles in implantation and placentation. We have recently demonstrated that CTGF may be a target gene for PROK1 in gene array analysis of a prokineticin receptor-1 stably transfected Ishikawa endometrial epithelial cell line (PROKR1-Ishikawa). The first aim of the study was to determine the effect of PROK1 on CTGF expression in PROKR1-Ishikawa cells and first-trimester decidua samples. Secondly, the effect of CTGF on trophoblast-derived HTR-8/SVneo cell adhesion and network formation was investigated.

METHODS AND RESULTS

Real-time qPCR showed that CTGF expression is elevated in first-trimester decidua compared with non-pregnant endometrium. In decidua, CTGF co-localized with PROKR1 to the glandular epithelium and a subset of stromal cells. PROK1 increased CTGF mRNA and protein expression in PROKR1-Ishikawa cells and first-trimester human decidua (8-12 weeks gestation). Knock down of endogenous PROK1 using micro RNA constructs targeted at PROK1, resulted in decreased expression of CTGF mRNA and protein in decidua. Inhibitors of specific cell signalling molecules demonstrated that PROK1 regulates CTGF expression via the Gq, phospholipase C (PLC), cSrc, epidermal growth factor receptor (EGFR), mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) kinase pathway activation. Treatment of trophoblast-derived HTR-8/Svneo cells with 1 µg/ml CTGF significantly increased adhesion to collagen IV, and differentiation of the cells into tube-like structures in matrigel.

CONCLUSIONS

CTGF expression in early pregnancy decidua is regulated by PROK1, via activation of the Gq, PLC, cSrc, EGFR, MAPK/ERK kinase pathway. CTGF in turn may contribute to the regulation of trophoblast conversion of maternal spiral arteries.

Recombinant expression, purification, and functional characterisation of connective tissue growth factor and nephroblastoma-overexpressed protein

The CCN family of proteins, especially its prominent member, the Connective tissue growth factor (CTGF/CCN2) has been identified as a possible biomarker for the diagnosis of fibrotic diseases. As a downstream mediator of TGF-β1 signalling, it is involved in tissue scarring, stimulates interstitial deposition of extracellular matrix proteins, and promotes proliferation of several cell types. Another member of this family, the Nephroblastoma-Overexpressed protein (NOV/CCN3), has growth-inhibiting properties. First reports further suggest that these two CCN family members act opposite to each other in regulating extracellular matrix protein expression and reciprocally influence their own expression when over-expressed. We have established stable HEK and Flp-In-293 clones as productive sources for recombinant human CCN2/CTGF. In addition, we generated an adenoviral vector for recombinant expression of rat NOV and established protocols to purify large quantities of these CCN proteins. The identity of purified human CCN2/CTGF and rat CCN3/NOV was proven by In-gel digest followed by ESI-TOF/MS mass spectrometry. The biological activity of purified proteins was demonstrated using a Smad3-sensitive reporter gene and BrdU proliferation assay in permanent cell line EA•hy 926 cells. We further demonstrate for the first time that both recombinant CCN proteins are N-glycosylated.

Genetic variant in the promoter of connective tissue growth factor gene confers susceptibility to nephropathy in type 1 diabetes

BACKGROUND The evidence for genetic susceptibility in the pathogenesis of diabetic nephropathy is well recognised, but the genes involved remain to be identified. It is hypothesised that mutations within the gene encoding connective tissue growth factor (CTGF/CCN2) will increase the propensity of diabetic subjects to develop nephropathy. METHODS AND RESULTS Genomic screening was performed for single nucleotide polymorphisms (SNPs) within the CTGF gene in 862 subjects from the DCCT/EDIC cohort of type 1 diabetes. A novel SNP was identified in the promoter region that changes a C-G at the position -20. The frequency of GG genotype in microalbuminuric patients (albumin excretion rate (AER) >40 mg/24 h) is significantly greater than diabetics with AER <40 mg/24 h, p<0.0001. The relative risk (RR) to develop microalbuminuria in diabetic subjects with the polymorphism is 3X higher than diabetic subjects without the polymorphism (RR 3.142, 95% CI 1.9238 to 5.1249; p<0.05). Kaplan-Meier survival curves demonstrated that the GG genotype group developed microalbuminuria and macroalbuminuria at a more rapid rate than the GC or CC genotypes. Functional studies demonstrated that the basal activity of the substituted allele/promoter (-20 GG allele) was significantly greater than that of the wild type promoter (-20 CC genotype). This higher level of basal activity of substituted allele CTGF/CCN2 promoter was abrogated upon suppression of Smad1 levels, indicating that SNP region in the CTGF/CCN2 promoter plays a vital role in the gene expression. CONCLUSIONS These findings provide the first evidence that variants within the promoter region of the CTGF/CCN2 gene predisposes diabetic subjects to develop albuminuria and demonstrate that Smad1 [corrected] controls the expression of CTGF/CCN2 promoter through this region.

The contribution of adhesion signaling to lactogenesis

The mammary gland undergoes hormonally controlled cycles of pubertal maturation, pregnancy, lactation, and involution, and these processes rely on complex signaling mechanisms, many of which are controlled by cell-cell and cell-matrix adhesion. The adhesion of epithelial cells to the extracellular matrix initiates signaling mechanisms that have an impact on cell proliferation, survival, and differentiation throughout lactation. The control of integrin expression on the mammary epithelial cells, the composition of the extracellular matrix and the presence of secreted matricellular proteins all contribute to essential adhesion signaling during lactogenesis. In vitro and in vivo studies, including the results from genetically engineered mice, have shed light on the regulation of these processes at the cell and tissue level and have led to increased understanding of the essential signaling components that are regulated in temporal and cell specific manner during lactogenesis. Recent studies suggest that a secreted matricellular protein, CTGF/CCN2, may play a role in lactogenic differentiation through binding to β1 integrin complexes, enhancing the production of extracellular matrix components and contributions to cell adhesion signaling.

Differential expression of novH and CTGF in human glioma cell lines

Aims-(1) To investigate the expression in human derived glioblastoma cell lines of two structurally related genes, novH (nephroblastoma overexpressed gene) and CTGF (connective tissue growth factor), which encode putative insulin-like growth factor binding proteins of a novel type. (2) To investigate whether the same transcription factors regulate CTGF and novH expression.Methods-Expression of novH and CTGF was analysed in 24 glioblastoma derived cell lines by northern blotting. The CTGF promoter region was characterised by nucleotide sequencing, RNase protection experiments, by transient transfections, and CAT assays.Results-CTGF and novH mRNA levels differed in the glioma cell lines studied. NovH and CTGF genes were not co-expressed in all cell lines. The CTGF promoter region was highly conserved compared with the corresponding region in the mouse (FISP12) and exhibited in vitro transcriptional activity.Conclusions-Although the coding regions of novH and CTGF are highly homologous, their promoter regions are substantially different, suggesting that these two genes may be regulated by different mechanisms. Considering that novH and CTGF are likely to be, respectively, negative and positive regulators of growth and that some glioma cell lines expressing novH are not tumorigenic, expression of these two genes might represent a key element in determining the stage of differentiation or the malignant potential, or both, of some tumour cell lines.

Bioscreening of phage display antibody library and expression of a humanized single-chain variable fragment antibody against human connective tissue growth factor (CTGF/CCN2)

Excessive expression of CTGF (connective tissue growth factor)/CCN2 has been observed in many fibrotic diseases. The inhibition of the CTGF/CCN2 by antibody has been shown to be clinically useful for the management of fibrosis. A phage display humanized single-chain Fv antibody library was screened using CTGF/C (CTGF/CCN2 C-terminal domain) as the target. A phage ELISA was performed after four rounds of biopanning, and ten positive clones were further evaluated by ELISA and were chosen for DNA sequencing. The DNA encoding scFv (single-chain variable fragment) containing a full-length variable domain fragment of heavy chain and light chain of human immunoglobulin was inserted into pET-32(a)+ vector, and the fusion protein (TrxA-scFv) containing a thrombin cleavage site was expressed mainly in soluble form. The scFv was obtained by purified fusion protein digested with thrombin and then separated from the fusion partner TrxA by gel-filtration chromatography. An immunological assay showed that the purified scFv reacted with CTGF/CCN2 in a concentration-dependent manner. The result of the cell migration assay demonstrated that the scFv at 100 ng/ml could effectively inhibit the migration of HUVEC (human umbilical-vein endothelial cells) caused by CTGF/C. The number of migratory cells was significantly decreased as compared with the negative control (1062+/-92 versus 3269+/-288, P<0.001) and the inhibition rate was 90.5%.

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.

A novel primate model of delayed wound healing in diabetes: dysregulation of connective tissue growth factor

AIMS/HYPOTHESIS

Chronic non-healing wounds are a common complication of diabetes. Prolonged inflammation and decreased matrix accumulation may contribute. Connective tissue growth factor (CTGF) is induced during normal wound healing, but its regulation in diabetic wounds is unknown. We developed a primate model for the study of in vivo wound healing in baboons with long diabetes duration.

METHODS

Drum implants were placed subcutaneously into thighs of diabetic and non-diabetic control baboons. After 2 and 4 weeks the skin incision sites were removed for measurement of breaking strength and epithelial thickness. Drum implants were removed for analysis of granulation tissue and inflammatory cells, CTGF and tissue inhibitor of matrix metalloproteinase (TIMP-1). Degradation of added CTGF by wound fluid was also examined.

RESULTS

Healed incision site skin was stiffer (less elastic) in diabetic baboons and epithelial remodelling was slower compared with controls. Granulation tissue from diabetic baboons was reduced at 2 and 4 weeks, with increased vessel lumen areas at 4 weeks. Macrophages were reduced while neutrophils persisted in diabetic tissue. In diabetic wound tissue at 4 weeks there was less CTGF induced, as shown by immunohistochemistry, compared with controls. In contrast, immunoreactive fragments of CTGF were significantly increased in whole tissue lysate in diabetic baboons, suggesting that CTGF is redistributed in diabetes from granulation tissue into wound fluid. When recombinant human CTGF was co-incubated with wound fluid, increased CTGF degradation products were observed in both control and diabetic samples.

CONCLUSIONS/INTERPRETATION

This baboon model of wound healing reflects the abnormal microenvironment seen in human diabetic wounds and provides insights into the dysregulation of CTGF in diabetic wounds.