Connective tissue growth factor enhances TGF-β1-induced osteogenic differentiation via activation of p38 MAPK in mesenchymal stem cells

OBJECTIVES

Cellular differentiation is based on the effects of various growth factors. Transforming growth factor (TGF)-β1 plays a pivotal role in inducing osteogenic differentiation of mesenchymal stem cells (MSCs). In this study, we investigated the influence of connective tissue growth factor (CTGF), known to function synergistically with TGF-β1, on osteogenic differentiation in MSCs.

METHODS

UE7T-13 cells were treated with TGF-β1 and/or CTGF. Subsequently, protein levels of intracellular signaling pathway molecules were determined through western blot analysis. The mRNA expression levels of osteogenic differentiation markers were investigated using reverse transcription-quantitative polymerase chain reaction. Bone matrix mineralization was evaluated through alizarin red staining.

RESULTS

Co-treatment with TGF-β1 and CTGF resulted in the suppression of TGF-β1-induced phosphorylation of extracellular signal-regulated kinase 1/2, an intracellular signaling pathway molecule in MSCs, while significantly enhancing the phosphorylation of p38 mitogen-activated protein kinase (MAPK). In MSCs, co-treatment with CTGF and TGF-β1 led to increased expression levels of alkaline phosphatase and type I collagen, markers of osteogenic differentiation induced by TGF-β1. Osteopontin expression was observed only after TGF-β1 and CTGF co-treatment. Notably, bone sialoprotein and osteocalcin were significantly upregulated by treatment with CTGF alone. Furthermore, CTGF enhanced the TGF-β1-induced mineralization in MSCs, with complete suppression observed after treatment with a p38 MAPK inhibitor.

CONCLUSIONS

CTGF enhances TGF-β1-induced osteogenic differentiation and subsequent mineralization in MSCs by predominantly activating the p38 MAPK-dependent pathway.

Pien Tze Huang Inhibits Migration and Invasion of Hepatocellular Carcinoma Cells by Repressing PDGFRB/YAP/CCN2 Axis Activity

OBJECTIVE

To investigate the effects of Pien Tze Huang (PZH) on the migration and invasion of HCC cells and underlying molecular mechanism.

METHODS

Cell counting kit-8 (CCK-8) was applied to evaluate the cell viabilities of SMMC-7721, SK-Hep-1, C3A and HL-7702 (6 × 103 cells/well) co-incubated with different concentrations of PZH (0, 0.2, 0.4, 0.6, 0.8 mg/mL) for 24 h. Transwell, wound healing assay, CCK-8 and Annexin V-FITC/PI staining were conducted to investigate the effects of PZH on the migration, invasion, proliferation and apoptosis of SK-Hep-1 and SMMC-7721 cells (650 µ g/mL for SK-Hep-1 cells and 330 µ g/mL for SMMC-7721 cells), respectively. In vivo, lung metastasis mouse model constructed by tail vein injection of HCC cells was used for evaluating the anti-metastasis function of PZH. SK-Hep-1 cells (106 cells/200 µ L per mice) were injected into B-NDG mice via tail vein. Totally 8 mice were randomly divided into PZH and control groups, 4 mice in each group. After 2-d inoculation, mice in the PZH group were administered with PZH (250 mg/kg, daily) and mice in the control group received only vehicle (PBS) from the 2nd day after xenograft to day 17. Transcriptome analysis based on RNA-seq was subsequently used for deciphering anti-tumor mechanism of PZH. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were applied to verify RNA-seq results. Luciferase reporter assay was performed to examine the transcriptional activity of yes-associated protein (YAP).

RESULTS

PZH treatment significantly inhibited the migration, invasion, proliferation and promoted the apoptosis of HCC cells in vitro and in vivo (P<0.01). Transcriptome analysis indicated that Hippo signaling pathway was associated with anti-metastasis function of PZH. Mechanical study showed PZH significantly inhibited the expressions of platelet derived growth factor receptor beta (PDGFRB), YAP, connective tissue growth factor (CCN2), N-cadherin, vimentin and matrix metallopeptidase 2 (MMP2, P<0.01). Meanwhile, the phosphorylation of YAP was also enhanced by PZH treatment in vitro and in vivo. Furthermore, PZH played roles in inhibiting the transcriptional activity of YAP.

CONCLUSION

PZH restrained migration, invasion and epithelial-mesenchymal transition of HCC cells through repressing PDGFRB/YAP/CCN2 axis.

MicroRNA-19 upregulation attenuates cardiac fibrosis via targeting connective tissue growth factor

BACKGROUND

Previous studies have shown the role of microRNA (miR)-19 in aging-related heart failure. The present study aimed to verify the effects of miR-19 on cardiac fibrosis and its target.

METHODS

Cardiac fibrosis was induced by myocardial infarction (MI)-induced heart failure and angiotensin (Ang) II-treated rats in vivo, and was induced in Ang II-treated cardiac fibroblasts (CFs) in vitro.

RESULTS

The expression of miR-19 was reduced in the heart tissue of MI and Ang II-treated rats, and Ang II-treated CFs. The impaired cardiac function in rats was repaired after miR-19 administration. The levels of collagen I, collagen III and transforming growth factor-beta (TGF-β) increased in the heart tissue of MI and Ang II-treated rats, and Ang II-treated CFs. These increases were reversed by miR-19 agomiR. Moreover, the bioinformatic analysis and luciferase reporter assays demonstrated that connective tissue growth factor (CTGF) was a direct target of miR-19. MiR-19 treatment inhibited CTGF expression in CFs, while CTGF overexpression inhibited miR-19 agomiR to attenuate the Ang II-induced increases of collagen I and collagen III in CFs. The increases of p-ERK, p-JNK and p-p38 in the CFs induced by Ang II were repressed by miR-19 agomiR.

CONCLUSIONS

Upregulating miR-19 can improve cardiac function and attenuate cardiac fibrosis by inhibiting the CTGF and MAPK pathways.

Imaging Analysis of Neurotrophic Effects by CCN2 Protein in Neuronal Precursor Cells Derived from Human-Induced Pluripotent Stem Cells

Human-induced pluripotent stem cells (hiPSCs) are useful tools to examine human neuronal maturation processes. In this chapter, we describe the maturation of human neuronal precursor cells derived from hiPSCs by cellular communication network family member 2, also known as connective tissue growth factor. We describe the (1) preparation of feeder cells for undifferentiated culture of hiPSCs, (2) undifferentiated culture of hiPSCs, (3) induction of neuronal precursor cells from hiPSCs, (4) maturation of neuronal precursor cells from hiPSCs, (5) immunofluorescent staining of neuronal cells from hiPSCs, and (6) immunofluorescence analysis.

The use of connective tissue growth factor mimics for flexor tendon repair

Intrasynovial flexor tendon lacerations of the hand are clinically problematic, typically requiring operative repair and extensive rehabilitation. The small-molecule connective tissue growth factor (CTGF) mimics, oxotremorine M (Oxo-M) and 4-PPBP maleate (4-PPBP), have been shown to improve tendon healing in small animal models by stimulating the expansion and differentiation of perivascular CD146+ cells. To enhance intrasynovial flexor tendon healing, small-molecule CTGF mimics were delivered to repaired canine flexor tendons via porous sutures. In vitro studies demonstrated that Oxo-M and 4-PPBP retained their bioactivity and could be released from porous sutures in a sustained manner. However, in vivo delivery of the CTGF mimics did not improve intrasynovial tendon healing. Histologic analyses and expression of tenogenic, extracellular matrix, inflammation, and remodeling genes showed similar outcomes in treated and untreated repairs across two time points. Although in vitro experiments revealed that CTGF mimics stimulated robust responses in extrasynovial tendon cells, there was no response in intrasynovial tendon cells, explaining the lack of in vivo effects. The results of the current study indicate that therapeutic strategies for tendon repair must carefully consider the environment and cellular makeup of the particular tendon for improving the healing response.

CTGF Loaded Electrospun Dual Porous Core-Shell Membrane For Diabetic Wound Healing

PURPOSE

Impairment of wound healing is a major issue in type-2 diabetes that often causes chronic infections, eventually leading to limb and/or organ amputation. Connective tissue growth factor (CTGF) is a signaling molecule with several roles in tissue repair and regeneration including promoting cell adhesion, cell migration, cell proliferation and angiogenesis. Incorporation of CTGF in a biodegradable core-shell fiber to facilitate its sustained release is a novel approach to promote angiogenesis, cell migration and facilitate wound healing. In this paper, we report the development of CTGF encapsulated electrospun dual porous PLA-PVA core-shell fiber based membranes for diabetic wound healing applications.

METHODS

The membranes were fabricated by a core-shell electrospinning technique. CTGF was entrapped within the PVA core which was coated by a thin layer of PLA. The developed membranes were characterized by techniques such as Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) analysis. In vitro cell culture studies using fibroblasts, keratinocytes and endothelial cells were performed to understand the effect of CTGF loaded membranes on cell proliferation, cell viability and cell migration. A chicken chorioallantoic membrane (CAM) assay was performed to determine the angiogenic potential of the membranes.

RESULTS

Results showed that the developed membranes were highly porous in morphology with secondary pore formation on the surface of individual fibers. In vitro cell culture studies demonstrated that CTGF loaded core-shell membranes improved cell viability, cell proliferation and cell migration. A sustained release of CTGF from the core-shell fibers was observed for an extended time period. Moreover, the CAM assay showed that core-shell membranes incorporated with CTGF can enhance angiogenesis.

CONCLUSION

Owing to the excellent cell proliferation, migration and angiogenic potential of CTGF loaded core-shell PLA-PVA fibrous membranes, they can be used as an excellent wound dressing membrane for treating diabetic wounds and other chronic ulcers.

Infrapatellar fat pad-derived MSC response to inflammation and fibrosis induces an immunomodulatory phenotype involving CD10-mediated Substance P degradation

The infrapatellar fat pad (IFP) serves as a reservoir of Mesenchymal Stem Cells (MSC), and with adjacent synovium plays key roles in joint disease including the production of Substance P (SP) affecting local inflammatory responses and transmitting nociceptive signals. Here, we interrogate human IFP-derived MSC (IFP-MSC) reaction to inflammatory and pro-fibrotic environments (cell priming by TNFα/IFNγ and TNFα/IFNγ/CTGF exposure respectively), compared with bone marrow-derived MSC (BM-MSC). Naïve IFP-MSC exhibit increased clonogenicity and chondrogenic potential compared with BM-MSC. Primed cells experienced dramatic phenotypic changes, including a sharp increase in CD10, upregulation of key immunomodulatory transcripts, and secreted growth factors/cytokines affecting key pathways (IL-10, TNF-α, MAPK, Ras and PI3K-Akt). Naïve, and more so primed MSC (both) induced SP degradation in vitro, reproduced with their supernatants and abrogated with thiorphan, a CD10 inhibitor. These findings were reproduced in vivo in a rat model of acute synovitis, where transiently engrafted human IFP-MSC induced local SP reduction. Functionally, primed IFP-MSC demonstrated sustained antagonism of activated human peripheral blood mononuclear cells (PBMC) proliferation, significantly outperforming a declining dose-dependent effect with naïve cohorts. Collectively, our in vitro and in vivo data supports cell priming as a way to enhance the immunoregulatory properties of IFP-MSC, which selectively engraft in areas of active synovitis/IFP fibrosis inducing SP degradation, resulting in a cell-based product alternative to BM-MSC to potentially treat degenerative/inflammatory joint diseases.

Supplementation with CTGF, SDF1, NGF, and HGF promotes ovine in vitro oocyte maturation and early embryo development

The strategies for improving the in vitro maturation (IVM) of domestic animal oocytes focus on promoting nuclear and cytoplasmic maturation. The identification of paracrine factors and their supplementation in the culture medium represent effective approaches for oocyte maturation and embryo development. This study investigated the effects of paracrine factor supplementation including connective tissue growth factor (CTGF), nerve growth factor (NGF), hepatocyte growth factor (HGF), and stromal derived factor 1 (SDF1) on ovine oocytes and early parthenogenetic embryos using an in vitro culture system. First, we identified the optimal concentrations of CTGF (30 ng/mL), SDF1 (10 ng/mL), NGF (3 ng/mL), and HGF (100 ng/mL) for promoting oocyte maturation, which combined, induced nuclear maturation in 94.19% of oocytes. This combination also promoted cumulus cell expansion and inhibited oocyte/cumulus apoptosis, while enabling a larger proportion (33.04%) of embryos to develop into blastocysts than in the controls and prevented embryo apoptosis. These novel findings demonstrate that the paracrine factors CTGF, SDF1, NGF, and HGF facilitate ovine oocyte and early parthenogenetic embryo development in vitro. Thus, supplementation with these factors may help optimize the IVM of ovine oocytes and early parthenogenetic embryo development strategies.

The effect of adipose-derived stem cell sheets and CTGF on early flexor tendon healing in a canine model

Intrasynovial tendon injuries are among the most challenging in orthopedics. Despite significant improvements in operative and rehabilitation methods, functional outcomes continue to be limited by adhesions, gap formation, and rupture. Adhesions result from excessive inflammation, whereas tendon gapping and rupture result from inflammation-induced matrix degradation and insufficient regeneration. Therefore, this study used a combined treatment approach to modulate inflammation with adipose-derived mesenchymal stromal cells (ASCs) while stimulating tendon regeneration with connective tissue growth factor (CTGF). ASCs were applied to the repair surface via cell sheets and CTGF was delivered to the repair center via porous sutures. The effect of the combined treatment was assessed fourteen days after repair in a canine flexor tendon injury model. CTGF, either alone or with ASCs, reduced inflammatory (IL1B and IL6) and matrix degrading (MMP3 and MMP13) gene expression, while increasing anti-inflammatory gene (IL4) expression and collagen synthesis compared to control repairs. The combined treatment was more effective than CTGF treatment alone, reducing the inflammatory IFNG and scar-associated COL3A1 gene expression and increasing CD146+ tendon stem/progenitor cells at the tendon surface and interior along the core suture tracks. Therefore, the combined approach is promising in promoting early flexor tendon healing and worthy of further investigation.

Modulating microfibrillar alignment and growth factor stimulation to regulate mesenchymal stem cell differentiation

The ideal tissue engineering (TE) strategy for ligament regeneration should recapitulate the bone - calcified cartilage - fibrocartilage - soft tissue interface. Aligned electrospun-fibers have been shown to guide the deposition of a highly organized extracellular matrix (ECM) necessary for ligament TE. However, recapitulating the different tissues observed in the bone-ligament interface using such constructs remains a challenge. This study aimed to explore how fiber alignment and growth factor stimulation interact to regulate the chondrogenic and ligamentous differentiation of mesenchymal stem cells (MSCs). To this end aligned and randomly-aligned electrospun microfibrillar scaffolds were seeded with bone marrow derived MSCs and stimulated with transforming growth factor β3 (TGFβ3) or connective tissue growth factor (CTGF), either individually or sequentially. Without growth factor stimulation, MSCs on aligned-microfibers showed higher levels of tenomodulin (TNMD) and aggrecan gene expression compared to MSCs on randomly-oriented fibers. MSCs on aligned-microfibers stimulated with TGFβ3 formed cellular aggregates and underwent robust chondrogenesis, evidenced by increased type II collagen expression and sulphated glycosaminoglycans (sGAG) synthesis compared to MSCs on randomly-oriented scaffolds. Bone morphogenetic protein 2 (BMP2) and type I collagen gene expression were higher on randomly-oriented scaffolds stimulated with TGFβ3, suggesting this substrate was more supportive of an endochondral phenotype. In the presence of CTGF, MSCs underwent ligamentous differentiation, with increased TNMD expression on aligned compared to randomly aligned scaffolds. Upon sequential growth factor stimulation, MSCs expressed types I and II collagen and deposited higher overall levels of collagen compared to scaffolds stimulated with either growth factor in isolation. These findings demonstrate that modulating the alignment of microfibrillar scaffolds can be used to promote either an endochondral, chondrogenic, fibrochondrogenic or ligamentous MSC phenotype upon presentation of appropriate biochemical cues.

STATEMENT OF SIGNIFICANCE

Polymeric electrospun fibers can be tuned to match the fibrillar size and anisotropy of collagen fibers in ligaments, and can be mechanically competent. Therefore, their use is attractive when attempting to tissue engineer the bone-ligament interface. A central challenge in this field is recapitulating the cellular phenotypes observed across the bone-ligament interface. Here we demonstrated that it is possible to direct MSCs seeded onto aligned electrospun fibres towards either a ligamentogenic, chondrogenic or fibrochondrogenic phenotype upon presentation of appropriate biochemical cues. This opens the possibility of using aligned microfibrillar scaffolds that are spatially functionalized with specific growth factors to direct MSC differentiation for engineering the bone-ligament interface.

Cell Biological Assays for Measuring Chondrogenic Activities of CCN2 Protein

Growth-plate chondrocytes undergo proliferation, maturation, hypertrophic differentiation, and calcification; and these processes can be reproduced in vitro in a chondrocyte culture system. Using this system, we have shown that CCN family protein 2/connective tissue growth factor (CCN2/CTGF) promotes all stages of proliferation, maturation, hypertrophic differentiation, and calcification, thus suggesting that CCN2 is a multifunctional growth factor for chondrocytes and plays important roles in chondrocyte proliferation and differentiation. In this chapter, we describe how to evaluate CCN2 functions in these processes occurring in cultured chondrocytes. Evaluation strategies for cell proliferation include measuring DNA synthesis by [³H]-thymidine incorporation, cellular metabolic activity, and cell number with a hemocytometer. Next, evaluation strategies to assess maturation are analysis of the gene expression of markers of mature chondrocytes, and examination of proteoglycan and collagen synthesis by using radioactive compounds. In addition, cytohistochemical detection of glycosaminoglycans (GAGs), such as chondroitin sulfate, by use of alcian blue and toluidine blue staining is useful to evaluate chondrocyte maturation. These methods can be also used for evaluation of physiological functions of CCN2 in permanent chondrocytes such as articular and auricular chondrocytes, which do not calcify under physiological conditions. Next, evaluation of hypertrophic differentiation is performed by detecting type X collagen, which is specific marker of hypertrophic chondrocytes, and by measuring alkaline phosphatase (ALP) activity. Finally, evaluation of calcification is performed by detecting matrix calcification by use of alizarin red staining and by examining the incorporation of ⁴⁵Ca into cartilaginous matrix. These methods would be useful for the evaluation not only of CCN2 but also of its derivatives and other CCN proteins.

TGF-β1- and CCN2-Stimulated Sirius Red Assay for Collagen Accumulation in Cultured Cells

A simple method for the determination of relative levels of insoluble collagen accumulation in fibroblast cultures is presented. Confluent cell cultures are provided with sodium ascorbate which is then permissive for collagen deposition. At intervals, cultures are fixed and stained successively with sirius red and then crystal Violet to, respectively, assess for relative changes in collagen accumulation in response to factors such as TGF-β1 or matricellular CCN2 and changes in DNA content as an index of changes in cell density.

Transcriptional and posttranscriptional regulation of CXCL8/IL-8 gene expression induced by connective tissue growth factor

Connective tissue growth factor (CTGF), a CCN family member, is a secreted protein regulating cellular functions, including fibrosis, apoptosis, adhesion, migration, differentiation, proliferation, angiogenesis, and chondrogenesis. CTGF increases proinflammatory factor production; however, inflammatory cytokine regulation by CTGF is poorly understood. The aim of this study was to identify novel biological functions and elucidate the functional mechanisms of CTGF. Specifically, the study focused on the ability of CTGF-primed monocytes to secrete interleukin 8 (CXCL8/IL-8) and determined the signaling pathways involved in CTGF-induced CXCL8/IL-8 gene regulation during inflammation. We transfected wild-type or mutant CXCL8/IL-8 promoter-derived luciferase reporter constructs into 293T cells to examine the effect of CTGF on the CXCL8/IL-8 promoter. The results showed that the activator protein-1 and nuclear factor κB binding sites of the CXCL8/IL-8 promoter are essential for CTGF-induced CXCL8/IL-8 transcription. Moreover, the CTGF-induced activation of p38 mitogen-activated protein kinase (MAPK), c-Jun-N-terminal kinase, and extracellular signal-regulated kinase (ERK) is involved in this process. In addition, adenosine-uridine-rich elements (AREs) of the CXCL8/IL-8 3'-untranslated region (3'-UTR) reduce CXCL8/IL-8 mRNA stability. To investigate whether CTGF regulates CXCL8/IL-8 gene expression at the posttranscriptional level, we transfected 293 cells with serial luciferase constructs containing different segments of the CXCL8/IL-8 3'-UTR and then stimulated the cells with CTGF. The results suggested that CTGF stabilized luciferase mRNA and increased luciferase activity by regulating the CXCL8/IL-8 3'-UTR. Moreover, the p38 MAPK pathway may contribute to CTGF-induced CXCL8/IL-8 mRNA stabilization.

Intrinsic Deregulation of Vascular Smooth Muscle and Myofibroblast Differentiation in Mesenchymal Stromal Cells from Patients with Systemic Sclerosis

Introduction

Obliterative vasculopathy and fibrosis are hallmarks of systemic sclerosis (SSc), a severe systemic autoimmune disease. Bone marrow-derived mesenchymal stromal cells (MSCs) from SSc patients may harbor disease-specific abnormalities. We hypothesized disturbed vascular smooth muscle cell (VSMC) differentiation with increased propensity towards myofibroblast differentiation in response to SSc-microenvironment defining growth factors and determined responsible mechanisms.

Methods

We studied responses of multipotent MSCs from SSc-patients (SSc-MSCs) and healthy controls (H-MSCs) to long-term exposure to CTGF, b-FGF, PDGF-BB or TGF-β1. Differentiation towards VSMC and myofibroblast lineages was analyzed on phenotypic, biochemical, and functional levels. Intracellular signaling studies included analysis of TGF-β receptor regulation, SMAD, AKT, ERK1/2 and autocrine loops.

Results

VSMC differentiation towards both, contractile and synthetic VSMC phenotypes in response to CTGF and b-FGF was disturbed in SSc-MSCs. H-MSCs and SSc-MSCs responded equally to PDGF-BB with prototypic fibroblastic differentiation. TGF-β1 initiated myofibroblast differentiation in both cell types, yet with striking phenotypic and functional differences: In relation to H-MSC-derived myofibroblasts induced by TGF-β1, those obtained from SSc-MSCs expressed more contractile proteins, migrated towards TGF-β1, had low proliferative capacity, and secreted higher amounts of collagen paralleled by reduced MMP expression. Higher levels of TGF-β receptor 1 and enhanced canonical and noncanonical TGF-β signaling in SSc-MSCs accompanied aberrant differentiation response of SSc-MSCs in comparison to H-MSCs.

Conclusions

Deregulated VSMC differentiation with a shift towards myofibroblast differentiation expands the concept of disturbed endogenous regenerative capacity of MSCs from SSc patients. Disease related intrinsic hyperresponsiveness to TGF-β1 with increased collagen production may represent one responsible mechanism. Better understanding of repair barriers and harnessing beneficial differentiation processes in MSCs could widen options of autologous MSC application in SSc patients.

Connective-Tissue Growth Factor (CTGF/CCN2) Induces Astrogenesis and Fibronectin Expression of Embryonic Neural Cells In Vitro

Connective-tissue growth factor (CTGF) is a modular secreted protein implicated in multiple cellular events such as chondrogenesis, skeletogenesis, angiogenesis and wound healing. CTGF contains four different structural modules. This modular organization is characteristic of members of the CCN family. The acronym was derived from the first three members discovered, cysteine-rich 61 (CYR61), CTGF and nephroblastoma overexpressed (NOV). CTGF is implicated as a mediator of important cell processes such as adhesion, migration, proliferation and differentiation. Extensive data have shown that CTGF interacts particularly with the TGFβ, WNT and MAPK signaling pathways. The capacity of CTGF to interact with different growth factors lends it an important role during early and late development, especially in the anterior region of the embryo. ctgf knockout mice have several cranio-facial defects, and the skeletal system is also greatly affected due to an impairment of the vascular-system development during chondrogenesis. This study, for the first time, indicated that CTGF is a potent inductor of gliogenesis during development. Our results showed that in vitro addition of recombinant CTGF protein to an embryonic mouse neural precursor cell culture increased the number of GFAP- and GFAP/Nestin-positive cells. Surprisingly, CTGF also increased the number of Sox2-positive cells. Moreover, this induction seemed not to involve cell proliferation. In addition, exogenous CTGF activated p44/42 but not p38 or JNK MAPK signaling, and increased the expression and deposition of the fibronectin extracellular matrix protein. Finally, CTGF was also able to induce GFAP as well as Nestin expression in a human malignant glioma stem cell line, suggesting a possible role in the differentiation process of gliomas. These results implicate ctgf as a key gene for astrogenesis during development, and suggest that its mechanism may involve activation of p44/42 MAPK signaling. Additionally, CTGF-induced differentiation of glioblastoma stem cells into a less-tumorigenic state could increase the chances of successful intervention, since differentiated cells are more vulnerable to cancer treatments.

Connective tissue growth factor modulates adult β-cell maturity and proliferation to promote β-cell regeneration in mice

Stimulation of endogenous β-cell expansion could facilitate regeneration in patients with diabetes. In mice, connective tissue growth factor (CTGF) is expressed in embryonic β-cells and in adult β-cells during periods of expansion. We discovered that in embryos CTGF is necessary for β-cell proliferation, and increased CTGF in β-cells promotes proliferation of immature (MafA(-)) insulin-positive cells. CTGF overexpression, under nonstimulatory conditions, does not increase adult β-cell proliferation. In this study, we tested the ability of CTGF to promote β-cell proliferation and regeneration after partial β-cell destruction. β-Cell mass reaches 50% recovery after 4 weeks of CTGF treatment, primarily via increased β-cell proliferation, which is enhanced as early as 2 days of treatment. CTGF treatment increases the number of immature β-cells but promotes proliferation of both mature and immature β-cells. A shortened β-cell replication refractory period is also observed. CTGF treatment upregulates positive cell-cycle regulators and factors involved in β-cell proliferation, including hepatocyte growth factor, serotonin synthesis, and integrin β1. Ex vivo treatment of whole islets with recombinant human CTGF induces β-cell replication and gene expression changes consistent with those observed in vivo, demonstrating that CTGF acts directly on islets to promote β-cell replication. Thus, CTGF can induce replication of adult mouse β-cells given a permissive microenvironment.

Directed differentiation of skin-derived precursors into fibroblast-like cells

Skin-derived precursors (SKPs), which are located at skin's dermis, display multi-lineage potential and can produce both neural and mesodermal progeny in vitro. SKPs are considered to take part in dermal reconstruction and may be an important source of fibroblast during wound repairing. To explore the possibility of differentiation of SKPs into fibroblasts, the 3(rd) passage SKPs were treated with 0, 20, 40, 100, or 500 ng/ml human recombinant connective tissue growth factor (CTGF) for 48 h or treated with 100 ng/ml CTGF for 0, 24, 48, 72, or 96 h. Subsequently, a series of methods were to be used to observe cells immunocytochemistry changes under fluorescence microscope, to validate the mRNA expression change of collagen I, collagen III, fibroblast-specific protein 1 (FSP-1) and alpha smooth muscle actin (α-SMA) by quantitative real-time reverse transcriptase polymerase chain reaction (QRT-PCR), to analyze the expression of collagen I and collagen III protein by Enzyme-linked immunosorbent assay (ELISA), to semiquantitatively measure the expression of FSP-1 and α-SMA by western-blot. After differentiation, cells showed that positively staining for collagen I, collagen III, α-SMA, and FSP-1, which are markers for fibroblasts, but negative expression for neural precursors. The effects of CTGF on collagen I, collagen III, FSP-1 and α-SMA in SKPs were detected both on the transcriptional and posttranscriptional levels. These findings indicate that SKPs can be induced to differentiate into fibroblast-like cells with CTGF treatment that may be a key source of fibroblast in wound healing.

Connective tissue growth factor induces collagen I expression in human lung fibroblasts through the Rac1/MLK3/JNK/AP-1 pathway

Connective tissue growth factor (CTGF) plays an important role in lung fibrosis. In this study, we investigated the role of Rac1, mixed-lineage kinase 3 (MLK3), c-Jun N-terminal kinase (JNK), and activator protein-1 (AP-1) in CTGF-induced collagen I expression in human lung fibroblasts. CTGF caused concentration- and time-dependent increases in collagen I expression. CTGF-induced collagen I expression was inhibited by the dominant negative mutant (DN) of Rac1 (RacN17), MLK3DN, MLK3 inhibitor (K252a), JNK1DN, JNK2DN, a JNK inhibitor (SP600125), and an AP-1 inhibitor (curcumin). Treatment of cells with CTGF caused activation of Rac1, MLK3, JNK, and AP-1. The CTGF-induced increase in MLK3 phosphorylation was inhibited by RacN17. Treatment with RacN17 and the MLK3DN inhibited CTGF-induced JNK phosphorylation. CTGF caused increases in c-Jun phosphorylation and the recruitment of c-Jun and c-Fos to the collagen I promoter. Furthermore, stimulation of cells with the CTGF resulted in increases in AP-1-luciferase activity; this effect was inhibited by Rac1N17, MLK3DN, JNK1DN, and JNK2DN. Moreover, CTGF-induced α-smooth muscle actin (α-SMA) expression was inhibited by the procollagen I small interfering RNA (siRNA). These results suggest for the first time that CTGF acting through Rac1 activates the MLK3/JNK signaling pathway, which in turn initiates AP-1 activation and recruitment of c-Jun and c-Fos to the collagen I promoter and ultimately induces collagen I expression in human lung fibroblasts.

CCN family member 2/connective tissue growth factor (CCN2/CTGF) has anti-aging effects that protect articular cartilage from age-related degenerative changes

To examine the role of connective tissue growth factor CCN2/CTGF (CCN2) in the maintenance of the articular cartilaginous phenotype, we analyzed knee joints from aging transgenic mice (TG) overexpressing CCN2 driven by the Col2a1 promoter. Knee joints from 3-, 14-, 40-, and 60-day-old and 5-, 12-, 18-, 21-, and 24-month-old littermates were analyzed. Ccn2-LacZ transgene expression in articular cartilage was followed by X-gal staining until 5 months of age. Overexpression of CCN2 protein was confirmed through all ages in TG articular cartilage and in growth plates. Radiographic analysis of knee joints showed a narrowing joint space and other features of osteoarthritis in 50% of WT, but not in any of the TG mice. Transgenic articular cartilage showed enhanced toluidine blue and safranin-O staining as well as chondrocyte proliferation but reduced staining for type X and I collagen and MMP-13 as compared with those parameters for WT cartilage. Staining for aggrecan neoepitope, a marker of aggrecan degradation in WT articular cartilage, increased at 5 and 12 months, but disappeared at 24 months due to loss of cartilage; whereas it was reduced in TG articular cartilage after 12 months. Expression of cartilage genes and MMPs under cyclic tension stress (CTS) was measured by using primary cultures of chondrocytes obtained from wild-type (WT) rib cartilage and TG or WT epiphyseal cartilage. CTS applied to primary cultures of mock-transfected rib chondrocytes from WT cartilage and WT epiphyseal cartilage induced expression of Col1a1, ColXa1, Mmp-13, and Mmp-9 mRNAs; however, their levels were not affected in CCN2-overexpressing chondrocytes and TG epiphyseal cartilage. In conclusion, cartilage-specific overexpression of CCN2 during the developmental and growth periods reduced age-related changes in articular cartilage. Thus CCN2 may play a role as an anti-aging factor by stabilizing articular cartilage.

[Connective tissue growth factor induced differentiation of placenta mesenchymal stem cell into dermal fibroblast]

OBJECTIVE

To investigate the possibility of placenta mesenchymal stem cells (PMSCs) differentiation into dermal fibroblast, and the potency of PMSCs used in cutaneous wound healing and stored as seed cells.

METHODS

Enzyme digestion method was used to obtain PMSCs, and PMSCs were amplified after culture in vitro. Flow cytometry assay, osteogenic and adipogenic differentiation were done for MSCs identification. The induction medium composed of DMEM/F12 + 50 microg/ml VC + 100 ng/ml connective tissue growth factor (CTGF) was added into the 24-well plate for 16 days induction period. Pictures were taken to record morphologic change. Immunofluorescence tests were performed to detect Vimentin, FSP-1, collagen I , collagen III, desmin and laminin expression before and after induction. At the same time osteogenic and adipogenic differentiation were used to assay the differentiation ability change after induction. The induced dermal fibroblasts were frozen in liquid nitrogen and recovery and trypan blue was used to detect cell viability.

RESULTS

After CTGF induction, PMSCs got obvious fibroblasts morphology, the protein level of Vimentin, FSP-1, collagen I, collagen III and Laminin increased, PMSCs started to express Desmin, the dermal fibroblasts specific proteins, and osteogenic and adipogenic differentiation ability was diminished. PMSCs were successfully induced into dermal fibroblasts, and these induced cells could get a high cell viability ( more than 90% ) after recovery.

CONCLUSIONS

PMSCs could be induced into dermal fibroblasts by CTGF in vitro. PMSCs have the potential application in skin wound healing, and can be used as seed cells of dermal fibroblasts.

[Functions of exogenous application of connective tissue growth factor in stimulating human dermal papilla cells and human hair follicle outer root sheath cells for reconstructive tissue-engineering hair follicles]

OBJECTIVE

To explore the functions of connective tissue growth factor (CTGF) in the restoration of hair follicles with a mixture of human dermal papilla cells and human hair follicle outer root sheath cells in vitro in nude mice.

METHODS

Human hair follicle outer root sheath cells (hfORS) and human hair dermal papilla cells (hDP) were cultured in vitro and mixed in a fixed ratio (hfORS: hDP = 5:1). Flow cytometry was used to detect the content of CD200(+) cells in human hair follicle outer root sheath cells.And 8 nude mice were divided randomly into 2 groups according to a random number table and back wounds produced. Group A was transplanted with cell mixture plus 20 µg/L CTGF. Group B was transplanted with cell mixture alone. After 8 weeks of transplantation, the development of hair follicle formation was observed histologically.PCR was used to detect the expression of human specific DNA and mice DNA in transplants.

RESULTS

The portion of CD200(+) cells in cultured hfORS was 19.65%. At 8 weeks after implantation, hair follicle formation could be observed in Group A (268 ± 96) more than Group B (62 ± 20). The difference was statistically significant (P < 0.05). And PCR showed that there was human composition in transplant.

CONCLUSION

CTGF can induce the formation of hair follicle by promoting the interference between hDP and hfORS.

Enhancement of meniscal repair in the avascular zone using connective tissue growth factor in a rabbit model

BACKGROUND

Connective tissue growth factor (CTGF) is a secreted protein containing several domains that mediate interactions with growth factors, integrins and extracellular matrix components. CTGF plays an important role in extracellular matrix production by its ability to mediate collagen deposition during wound healing. CTGF also induces neovascularization in vitro, suggesting a role in angiogenesis in vivo. We herein evaluated whether CTGF was required for extracellular matrix synthesis of meniscal fibrochondrocytes and/or angiogenesis during the repair of meniscal tears.

METHODS

Meniscal fibrochondrocytes were isolated from the inner-1/2 of rabbit meniscus by trypsin collagenase treatment and further treated with 100 ng/ml CTGF in vitro. Characterization of fibrochondrocytes was identified by flow cytometry analyzing CD31, CD44, CD45 and CD105, and was further tested by type II collagen immunocytochemistry. Changes in gene expression of meniscal fibrochondrocytes were monitored by quantitative real-time polymerase chain reaction. Histological sections prepared from a 3-mm portion of a longitudinal tearing defect in the middle of the rabbit meniscus were subjected to fluorescence-immunohistochemistry analysis at 1, 4 and 10 weeks following surgical treatment with 1.5 µg of CTGF/fibrin-glue composites.

RESULTS

Quantitative RT-PCR assay showed that types I and II collagen and vascular endothelial growth factor mRNA expression in the 100 ng/ml CTGF group were remarkably enhanced as compared to levels in the no-dose group at 14 days ((2.38 ± 0.63) fold, (2.96 ± 0.87) fold, (2.14 ± 0.56) fold, respectively). Likewise, fluorescence-immunohistochemical analysis revealed that in the group implanted with CTGF-fibrin glue, types I and II collagen, as well as the capillaries, completely filled the defect by 10 weeks, postoperatively. In contrast, only soft tissue repair occurred when PBS-fibrin glue was implanted.

CONCLUSIONS

These findings suggest that CTGF can significantly promote extracellular matrix deposition (types I and II collagen) within the meniscal avascular zone; CTGF can greatly heighten the expression of vascular endothelial growth factor activity simultaneously in vivo, further enhancing the repair of meniscal tears in the avascular zone.

[Integrin β3 pathway mediated connective tissue growth factor-induced proliferation, migration and extracellular matrix deposition of pulmonary arterial smooth muscle cells]

OBJECTIVE

To explore the effects of integrin β3 pathway on the proliferation, migration and extracellular matrix deposition of pulmonary arterial smooth muscle cells (PASMCs) induced by connective tissue growth factor (CTGF).

METHODS

PASMCs of SD Rats were cultured in M199 culture system in vitro and the 3rd-7th passages of PASMCs were used in the experiments. The cells were randomly divided into three groups: (1) CONTROL GROUP: culture system contained no any stimulation factor; (2) CTGF group: culture system was added into 50 ng/ml CTGF; (3) CTGF+ anti-integrin β3 antibody group:culture system was added with 50 ng/ml CTGF and 10 mg/L anti-integrin β3 antibody. The PASMCs were cultured with 50 ng/ml CTGF and anti-integrin β3 antibody (0, 5, 10, 15, 20 mg/L) for 24, 48, 72 and 96 h, the proliferation of PASMCs was detected by WST-1 Cell Proliferation Assay Kit. The migration of PASMCs was observed by Transwell cell test under the phase contrast microscope. RT-PCR assay was applied to detect the mRNA expression of collagenI-α1, collagen III-α1 and fibronectin-1 gene of PASMCs. The expression of fibronectin protein was examined by Western blotting and immunohistochemistry.

RESULTS

The results of WST-1 test showed that the anti-integrin β3 antibody inhibited significantly the proliferation of PASMCs induced by CTGF (P < 0.05), among which the inhibition rate of anti-integrin β3 antibody (10 mg/L) was the most significant. Transwell test results showed that CTGF group of PASMCs migration numbers (25 ± 1.57) were higher than that of the control group (11 ± 2.08, P < 0.01); PASMCs migration numbers of CTGF+ integrin β3 antibody group (17 ± 4.16) were less than that of the CTGF group (P < 0.05). Compared with the control group, the mRNA expression of collagen typeI-α1 (4.28 ± 0.33), collagen typeIII-α1 (4.41 ± 0.35), fibronectin-1 (4.05 ± 0.33) of PASMCs was increased in CTGF group, with a time-dependence (P < 0.01); Compared with the CTGF group, the mRNA expression of collagen typeI-α1 (3.38 ± 0.30), collagen typeIII-α1 (3.40 ± 0.30), fibronectin-1 (3.12 ± 0.29) of PASMCs was reduced in CTGF+ anti-integrin β3 antibody group (P < 0.05), which was higher than that of the control group (P < 0.05); Western blot and immunohistochemical tests showed that compared with the control group, CTGF group could stimulate the expression of fibronectin protein of PASMCs (P < 0.01); the anti-integrin β3 antibody could inhibit the expression of fibronectin protein induced by CTGF(P < 0.01), which was more remarkable than that in the control group (P < 0.01).

CONCLUSION

Integrin β3 pathway can mediate CTGF-induced proliferation, migration and extracellular matrix deposition of PASMCs, CTGF-integrin β3 signaling pathway may play an important role in pulmonary vascular remodeling.

Effect of CCN2 on FGF2-induced proliferation and MMP9 and MMP13 productions by chondrocytes

CCN2 (also known as connective tissue growth factor) interacts with several growth factors involved in endochondral ossification via its characteristic four modules and modifies the effect of such growth factors. Presently we investigated whether CCN2 interacts with fibroblast growth factor 2 (FGF2). Solid-phase binding assay, immunoprecipitation-Western blot analysis, and surface plasmon resonance (SPR) spectroscopy revealed that the C-terminal module of CCN2 (CT) directly bound to FGF2 with a dissociation constant of 5.5 nm. Next, we examined the combinational effects of CCN2 and FGF2 on the proliferation of and matrix metalloproteinase (MMP)-9 and -13 productions by cultured chondrocytes. FGF2 promoted not only the proliferation but also the production of MMP9 and -13, however, combined of FGF2 with CT module nullified the enhancement of both MMP productions and proliferation. To clarify the mechanism, we investigated the binding of CCN2 or its CT module to FGF receptor 1. As a result, we found that CCN2 bound to FGF receptor 1 with a dissociation constant of 362 nm, whereas the CT module did not. In addition, when we tested FGF signaling in chondrocytic HCS-2/8 cells stimulated by the combination of FGF2 with CT module, the level of ERK1/2, p38 MAPK, and c-Jun N-terminal kinase phosphorylation was decreased compared with that found with FGF2 alone. These findings suggest that CCN2 may regulate the proliferation and matrix degradation of chondrocytes by forming a complex with FGF2 as a novel modulator of FGF2 functions.

[Biomechanical research of SOX9, CTGF in bone tendon junction healing]

AIM

To investigate the biomechanical effect of SOX9, CTGF in bone tendon junction healing.

METHODS

36 adult New Zealand rabbits were randomly divided into A, B and C groups(each group were 12 rab-bits). Group A with SOX9 inject into bone tendon junction;Group B with CTGF inject into bone tendon junction; C group was inject nothing. The animal of three groups were used surgery and all of the animals were faced with biomechanical test after 4 weeks, 8 weeks and 12 weeks; The result were used statistical analysis.

RESULTS

group A and group B's cross-sectional area were lower than group C during 4 weeks, 12 weeks postoperative; there were statistical difference between each groups ( P < 0. 05). group Aand group B's pulled off load and ultimate tensile stress were higher than group C during 4 weeks, 8 weeks, 12 weeks postoperative, the result were statistical difference between each groups ( P < 0. 05).

CONCLUSION

SOX9 and CTGF group can not only promote the early bone ten-don junction healing, But also increased the biomechanical strength of bone tendon junction.

[Inducing of epithelial mesenchymal transition of HK-2 cells by connective tissue growth factor in vitro]

OBJECTIVE

To investigate the role of connective tissue growth factor (CTGF) in epithelial mesenchymal transition of HK-2 cells in vitro.

METHODS

HK-2 cells were randomly divided into two groups: (1) control group including cells cultured in DMEM medium supplemented with 10% fetal bovine serum only; and (2) experimental group including cells cultured in DMEM medium supplemented with 10% fetal bovine serum and recombinant CTGF at a final concentration of 5 microg/L. The cells were collected at 72 h time points. Direct immunofluorescence staining and immunohistochemistry were used to evaluate the E-cadherin, Vimentin, alpha-SMA and ERK2 in cells. Western-blotting was used to detect the E-cadherin, Vimentin and ERK2 protein expression. Boyden Chamber was used to detect the migration of tubular endothelium at 1 d, 3 d and 5 d.

RESULTS

There were less E-cadherin but more Vimentin expressed in cells of the experimental group. The presence of alpha-SMA was detected at 48 h with peak at 72 h in the cells of the experimental group. On the first day, the cellular migration in the two groups showed no difference. However, after 3 days, the transformed cells migrated surpassed the control group with peak at the 5th day [(45.0+/-1.1):(14.0+/-1.2), P<0.05)].

CONCLUSION

Connective tissue growth factor induces mesenchymal transformation of HK-2 cells, in which the ERK2 signaling pathway may play an important role.

[Function of STAT1 in proliferation and differentiation of human hypertrophic scar fibroblast induced by connective tissue growth factor]

OBJECTIVE

To validate whether STAT1 participated in the process of CTGF-induced proliferation and differentiation of human hypertrophic scar fibroblast (hHSF) on account of past research.

METHODS

To cultivate hHSF with 6 patients' hypertrophic scar specimens together. Electrophoretic mobility shift assay (EMSA) was used to verify binding ability between DNA and STAT1 with the stimulus of different concentration CTGF (0, 5, 7.5, 10, 15 ng/ml) at 45th min and the stimulus of 10 ng/ml CTGF at different phase point (0, 10, 20, 30, 45, 60, 90, and 120 min). We divided cells into CTGF group, STAT1 ASODN group. STAT1 ASODN + CTGF group. control group. And MTT was used to detect the proliferation of hHSF on days1, 2 and 3, and RT-PCR to detect alpha-smooth muscle actin mRNA to follow the differentiation.

RESULTS

EMSA showed that the binding ability between STAT1 and DNA depended on the concentration of CTGF and peaked with the stimulation of 10ng/ml CTGF. And at the same time, it peaked at 45 - 60 min with 10 ng/ml CTGF. MTT showed that cell proliferation of CTGF group was much higher than that of control group (all P < 0.05). And those of STAT1 ASODN group and STAT1 ASODN + CTGF group were much lower than those of control group and CTGF group (all P < 0.05). RT-PCR showed that differentiation activation from fibroblast to myofibroblast of CTGF group, STAT1 ASODN group, STAT1 ASODN + CTGF group and control group were 0.78 +/- 0.08, 0.38 +/- 0.09, 0.76 +/- 0.10, and 0.40 +/- 0.12, respectively. Differentiation activation of STAT1 ASODN group and control group were much lower than those of CTGF group and STAT1 ASODN + CTGF group (all P < 0.05).

CONCLUSION

STAT1 ASODN is important in the process of proliferation of hHSF and it blocks the stimulation of CTGF on hHSF proliferation. The above result revealed that STAT1 participates in the process of hHSF proliferation induced by connective tissue growth factor.

Connective tissue growth factor confers drug resistance in breast cancer through concomitant up-regulation of Bcl-xL and cIAP1

Connective tissue growth factor (CTGF) expression is elevated in advanced breast cancer and promotes metastasis. Chemotherapy response is only transient in most metastatic diseases. In the present study, we examined whether CTGF expression could confer drug resistance in human breast cancer. In breast cancer patients who received neoadjuvant chemotherapy, CTGF expression was inversely associated with chemotherapy response. Overexpression of CTGF in MCF7 cells (MCF7/CTGF) enhanced clonogenic ability, cell viability, and resistance to apoptosis on exposure to doxorubicin and paclitaxel. Reducing the CTGF level in MDA-MB-231 (MDA231) cells by antisense CTGF cDNA (MDA231/AS cells) mitigated this drug resistance capacity. CTGF overexpression resulted in resistance to doxorubicin- and paclitaxel-induced apoptosis by up-regulation of Bcl-xL and cellular inhibitor of apoptosis protein 1 (cIAP1). Knockdown of Bcl-xL or cIAP1 with specific small interfering RNAs abolished the CTGF-mediated resistance to apoptosis induced by the chemotherapeutic agents in MCF7/CTGF cells. Inhibition of extracellular signal-regulated kinase (ERK)-1/2 effectively reversed the resistance to apoptosis as well as the up-regulation of Bcl-xL and cIAP1 in MCF7/CTGF cells. A neutralizing antibody against integrin alpha(v)beta(3) significantly attenuated CTGF-mediated ERK1/2 activation and up-regulation of Bcl-xL and cIAP1, indicating that the integrin alpha(v)beta(3)/ERK1/2 signaling pathway is essential for CTGF functions. The Bcl-xL level also correlated with the CTGF level in breast cancer patients. We also found that a COOH-terminal domain peptide from CTGF could exert activities similar to full-length CTGF, in activation of ERK1/2, up-regulation of Bcl-xL/cIAP1, and resistance to apoptosis. We conclude that CTGF expression could confer resistance to chemotherapeutic agents through augmenting a survival pathway through ERK1/2-dependent Bcl-xL/cIAP1 up-regulation.

Connective tissue growth factor: context-dependent functions and mechanisms of regulation

Connective tissue growth factor (CTGF, CCN2) is a secreted matricellular protein, the functions of which depend on the interactions with other molecules in the microcellular environment. As an example of context-dependent activity of CTGF, this review will outline different aspects of CTGF function in relation to angiogenesis. CTGF is barely expressed in normal adult tissue, but is strongly upregulated in fibrotic tissue and is also increased during development, in wound healing, or in certain types of cancer. Accordingly, gene expression of CTGF is tightly regulated. To highlight the complexity of the regulation of CTGF gene expression, we discuss here the mechanisms involved in CTGF regulation by TGFbeta in different cell types, and the mechanisms related to CTGF gene expression in cells exposed to mechanical forces. Finally, we will touch upon novel aspects of epigenetic regulation of CTGF gene expression. (c) 2009 International Union of Biochemistry and Molecular Biology, Inc.

[To transdifferentiate human hypertrophic scar fibroblasts induced by connective tissue growth factor mediated transforming growth factor-beta 1 in vitro]

OBJECTIVE

To investigate the role of connective tissue growth factor (CTGF) induced TGF-beta 1 in the transdifferentiation of human hypertrophic scar fibroblast (HSFb).

METHODS

Human hypertrophic scar fibroblasts were cultured in vitro, 5 cell samples were stimulated with TGF-beta 1 (0, 2.5, 5.0, 7.5, 10.0 ng/mL, respectively) for 48 hours; other cell samples were divided into: normal control (NC) group, CTGF group (with addition of 10 ng/mL rhCTGF into culture medium), TGF-beta 1 group (with addition of 10 ng/mL TGF-beta 1 into culture medium), CTGF ASODN group (with addition of 10% FBS-DMEM after transfection of CTGF ASODN), CTGF ASODN + TGF-beta 1group (with addition of 10 ng/mL TGF-beta 1 after transfection of CTGF ASODN). Expression of CTGF was determined by Western blotting with stimulation of different concentration of TGF-beta 1. Expression of alpha-smooth muscle actin (alpha-SMA) was measured by Western blotting. Positive cell rate of alpha-SMA was examined by flow cytometry.

RESULTS

With stimulation of 10.0 ng/mL TGF-beta 1, the expression of CTGF was obviously higher than that of non-stimulation (P < 0.05). Expression of alpha-SMA in the CTGF group and the TGF-beta 1 group was obviously higher than that in NC group (P < 0.01), while there was no obvious difference among NC, CTGF ASODN, CTGF ASODN + TGF-beta 1 groups (P > 0.05). The positive cell rate of alpha-SMA in NC, CTGF, TGF-beta 1, CTGF ASODN, CTGF ASODN + TGF-beta 1 groups was (10.8 +/- 2.8)%, (29.1 +/- 4.0)%, (28.7 +/- 4.8)%, (10.7 +/- 2.3)%, (14.3 +/- 2.9)%, respectively, which was similar to expression of alpha-SMA on statistic analysis.

CONCLUSIONS

CTGF is one of the most important downstream efforts for TGF-beta 1 in inducing the transdifferentiation of HSFb.

CCN family 2/connective tissue growth factor (CCN2/CTGF) regulates the expression of Vegf through Hif-1alpha expression in a chondrocytic cell line, HCS-2/8, under hypoxic condition

Vascular endothelial growth factor (VEGF) is essential for establishing vascularization and regulating chondrocyte development and survival. We have demonstrated that VEGF regulates the expression of CCN2/connective tissue growth factor (CCN2/CTGF) an essential mediator of cartilage development and angiogenesis, suggesting that CCN2 functions in down-stream of VEGF, and that VEGF function is mediated in part by CCN2. On the other hand, the phenotype of Ccn2 mutant growth plates, which exhibit decreased expression of VEGF in the hypertrophic zone, indicates that Vegf expression is dependent on Ccn2 expression as well. Therefore, we investigated the molecular mechanisms underlying the induction of VEGF by CCN2 using a human chondrocytic cell line, HCS-2/8. Hypoxic stimulation (5% O(2)) of HCS-2/8 cells increased VEGF mRNA levels by approximately 8 fold within 6 h as compared with the cells cultured under normoxia. In addition, VEGF expression was further up-regulated under hypoxia in HCS-2/8 cells transfected with a Ccn2 expression plasmid. Hypoxia-inducible factor (HIF)-1alpha mRNA and protein levels were increased by stimulation with recombinant CCN2 (rCCN2). Furthermore, the activity of a VEGF promoter that contained a HIF-1 binding site was increased in HCS-2/8, when the cells were stimulated by rCCN2. These results suggest that CCN2 regulates the expression of VEGF at a transcriptional level by promoting HIF-1alpha activity. In fact, HIF-1alpha was detected in the nuclei of proliferative and pre-hypertrophic chondrocytes of wild-type mice, whereas it was not detected in Ccn2 mutant chondrocytes in vivo. This activation cascade from CCN2 to VEGF may therefore play a critical role in chondrocyte development and survival.

CCN family 2/connective tissue growth factor (CCN2/CTGF) stimulates proliferation and differentiation of auricular chondrocytes

OBJECTIVES

CCN family 2/connective tissue growth factor (CCN2/CTGF) is an atypical growth factor for growth plate chondrocytes. It plays an important role in their proliferation and differentiation in vitro, but does not stimulate hypertrophy or calcification of articular chondrocytes. We herein report for the first time that CCN2/CTGF promotes growth and differentiation of auricular chondrocytes and maintains their molecular phenotype in vitro and in vivo.

METHODS

Auricular chondrocytes were isolated from rabbit auricular cartilage by trypsin-collagenase treatment, and treated with human recombinant CCN2/CTGF or infected with adenovirus harboring the ccn2/ctgf gene. Cell proliferation was measured by [(3)H] thymidine incorporation and MTS assay, and changes in gene expression of auricular chondrocyte markers were monitored by real-time polymerase chain reaction, Northern hybridization, and histological analysis. For in vivo studies, auricular chondrocytes were cultured as pellets and implanted subcutaneously after treatment of recombinant human CCN2/CTGF. Ectopically formed cartilage was subjected to histological analysis. Cell death was monitored by in situ TUNEL analysis.

RESULTS

CCN2/CTGF stimulated proliferation, differentiation and synthesis of elastin and proteoglycans of rabbit primary auricular chondrocytes in a dose-dependent manner. CCN2/CTGF caused a 2.5-fold increase in the expression of elastin in comparison to the control, resulting in enhanced deposition of elastin fibers in a monolayer culture of auricular chondrocytes. Mineralization was not induced; in contrast, CCN2/CTGF stimulated expression of matrix gla protein which is known to impair mineralization. Furthermore, pretreatment of pellets of auricular chondrocytes with CCN2/CTGF and subcutaneous implantation significantly enhanced the growth of ectopic auricular cartilage pieces expressing phenotypic markers of auricular chondrocytes including type II and X collagen. Notably, chondrocyte apoptosis was impaired by CCN2/CTGF.

CONCLUSIONS

These findings show that CCN2/CTGF may be a suitable agent for promoting differentiation and growth of auricular chondrocytes, while preventing mineralization and apoptosis, and suggests that CCN2/CTGF may be useful for the repair or reconstruction of elastic cartilage.

[Effects of core proteoglycan on the transdifferentiation of human renal tubular epithelial cell induced by transforming growth factor-beta1 in vitro]

OBJECTIVE

To study the effects of core proteoglycan on the transdifferentiation of human renal tubular epithelial cell induced by transforming growth factor beta1 (TGF-beta1) in vitro.

METHOD

The cultured HK-2 cells were divided into six groups: A. negative control group; B. 10 ng/ml TGF-beta1 group; C. 10 ng/ml core proteoglycan treated group; D. 100 ng/ml core proteoglycan treated group; E. 10 ng/ml TGF-beta1 + 10 ng/ml core proteoglycan group; F. 10 ng/ml TGF-beta1 + 100 ng/ml core proteoglycan group. The changes in configuration of HK-2 cells were inspected 48 hours after adding the stimulating factor. At the same time, changes in mRNA of keratin, alpha-smooth muscle actin, vimentin were analyzed.

RESULTS

Compared with group A, group B showed great changes in the morphology of cells, most cells converted into spindle shape, like fibroblast; groups E and F, especially group F showed significantly reduced spindle shape cells. Compared with group A, groups C and D had no significant changes in morphology of cells Compared with 10 ng/ml TGF-beta1 group and negative control, the mRNA expression of alpha-smooth muscle actin and vimentin had significant increase, but that of keratin reduced (P < 0.05). However, after combined treatment with TGF-beta1 and core proteoglycan, alpha-smooth muscle actin and vimentin expression were reduced significantly, while expression of keratin was up-regulated. Single core proteoglycan treated group and negative control group had no dramatic differences (P > 0.05).

CONCLUSION

TGF-beta1 can induce the transdifferentiation of human renal tubular epithelial cell and core proteoglycan has some inhibitory effect on transdifferentiation of human renal tubular epithelial cell induced by TGF-beta1 in vitro.

[Effect of synthesized polypeptide (P16) on inhibiting cell transdifferentiation and fibrosis induced by connective tissue growth factor]

OBJECTIVE

To explore the possibility of a CTGF originated hexadeca-peptide (named P16) to compete with the CTGF in binding integrin avP3 on rat tubular epithelial cells (NRK-52E) and inhibit the transdifferentiation and myofibroblasts of NRK-52E cells induced by CTGF.

METHODS

The NRK-52E cells were cultured in a condition with the existence of CTGF, P16-FITC (P16 labeled with fluorescein isothiocyanate), or both for 24h. The immunofluorescence staining and RT-PCR were employed to detect the expressions of the protein and mRNA of alpha-SMA and the collagen I and IV which indicate the cell trans-differentiation and fibrosis.

RESULTS

The P16 had stronger affinity with the NRK-52E cells than the CTGF. In a CTGF and P16 co-culture system, the P16 inhibited the expression of a-SMA, collagen I and IV up-regulated by the CTGF. However, P16 alone had no effect on cell trans-differentiation and fibrosis.

CONCLUSION

The synthesized P16 is capable of binding with NRK-52E cells and inhibiting trans-differentiation and fibrosis of the NRK-52E cells induced by CTGF in vitro. This finding offers a possibility of developing a novel antifibrosis therapy that targets CTGF receptor.

[p42/44 MAPK mediates synthesis of fractalkine by mesangial cells stimulated by connective tissue growth factor]

AIM

To examine whether connective tissue growth factor(CTGF) induces the production of fractalkine(FLK) by glomerular mesangial cells of rats, and explore the mechanism of signal pathway of CTGF actions.

METHODS

The mRNA expression of FLK was analyzed by RT-PCR in cultured mesangial cells stimulated by CTGF. The protein of FLK in the supernatants of cells was determined by ELISA. The chemotactic effect of the supernatants on monocytes was assessed by the in vitro chemotaxis assay. The phosphorylation of p42/44 MAPK was assessed by Western blot.

RESULTS

Treatment of the cells with CTGF enhanced the mRNA expression of FLK and concentration of FLK in the supernatants. Pretreatment of the supernatants of CTGF-treated cells with anti-FLK antibodies partially inhibited the chemotactic effect of the supernatants on monocytes. CTGF increased the p42/44MAPK phosphorylation. Pretreatment of the cells with PD98059 or UO126, inhibitors of phosphorylated p42/44 MAKP, decreased the CTGF-induced expression of phosphorylated p42/44 MAPK and concentration of FLK in supernatants.

CONCLUSION

CTGF-induced secretion of FLK by mesangial cells was associated with the phosphorylation of p24/p44 MAPK.