Connective tissue growth factor (CCN2/CTGF) is a matricellular protein that is overexpressed in progressive human renal diseases, mainly in fibrotic areas. In vitro studies have demonstrated that CCN2 regulates the production of extracellular matrix (ECM) proteins and epithelial-mesenchymal transition (EMT), and could therefore contribute to renal fibrosis. CCN2 blockade ameliorates experimental renal damage, including diminution of ECM accumulation. We have reported that CCN2 and its C-terminal degradation product CCN2(IV) bind to epidermal growth factor receptor (EGFR) to modulate renal inflammation. However, the receptor involved in CCN2 profibrotic actions has not been described so far. Using a murine model of systemic administration of CCN2(IV), we have unveiled a fibrotic response in the kidney that was diminished by EGFR blockade. Additionally, in conditional CCN2 knockout mice, renal fibrosis elicited by folic acid-induced renal damage was prevented, and this was linked to inhibition of EGFR pathway activation. Our in vitro studies demonstrated a direct effect of CCN2 via the EGFR pathway on ECM production by fibroblasts and the induction of EMT in tubular epithelial cells. Our studies clearly show that the EGFR regulates CCN2 fibrotic signalling in the kidney, and suggest that EGFR pathway blockade could be a potential therapeutic option to block CCN2-mediated profibrotic effects in renal diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The intrinsic zone-specific properties of the menisci are determined by biomechanical environments. In this study, we examined mechanical stretch-dependent expression of multifunctional growth factor CYR61/CTGF/NOV (CCN) 2, and investigated the role of CCN2 in meniscus cells. Uni-axial cyclic tensile strain (CTS) was applied using a STB-140 system. CTS-induced expression of CCN2 and α1(I) collagen (COL1A1) was assessed by quantitative real-time PCR analysis. The distribution of CCN2 and Smad2/3 in stretched cells was investigated by immunohistochemical analysis. Smad2/3-dependent CCN2 transactivation was measured by luciferase reporter assay. The relationship between Smad2/3 and CTS-induced CCN2 transcription was investigated by chromatin immunoprecipitation. CTS stimulated gene expression of CCN2 and COL1A1 in inner meniscus cells, but not in outer meniscus cells. Recombinant CCN2 increased COL1A1 expression only in inner meniscus cells. CCN2 synthesis and nuclear translocalization of phosphorylated Smad2/3 in inner meniscus cells were stimulated by CTS. The CCN2 promoter activity was synergistically enhanced by overexpressed Smad3 in stretched inner meniscus cells, but was not by Smad2. Chromatin immunoprecipitation revealed that CTS increased the association between Smad3 and the Smad-binding element on the CCN2 proximal promoter in inner meniscus cells. Our results suggest that stretch-induced CCN2 may have a crucial role in regulating COL1A1 expression in the inner meniscus.

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

CCN family member 2 (CCN2) has been shown to promote the proliferation and differentiation of chondrocytes, osteoblasts, osteoclasts, and vascular endothelial cells. In addition, a number of growth factors and cytokines are known to work in harmony to promote the process of chondrogenesis and chondrocyte differentiation toward endochondral ossification. Earlier we showed that CCN2 physically interacts with some of them, suggesting that multiple effects of CCN2 on various differentiation stages of chondrocytes may be attributed to its interaction with these growth factors and cytokines. However, little is known about the functional interaction occurring between CCN2 and other growth factors and cytokines in promoting chondrocyte proliferation and differentiation. In this study we sought to shed light on the binding affinities between CCN2 and other essential growth factors and cytokines known to be regulators of chondrocyte differentiation. Using the surface plasmon resonance assay, we analyzed the dissociation constant between CCN2 and each of the following: TGF-β1, TGF-β3, IGF-I, IGF-II, PDGF-BB, GDF5, PTHrP, and VEGF. We found a strong association between CCN2 and VEGF, as well as a relatively high association with TGF-β1, TGF-β3, PDGF-BB, and GDF-5. However, the sensorgrams obtained for possible interaction between CCN2 and IGF-I, IGF-II or PTHrP showed no response. This study underlines the correlation between CCN2 and certain other growth factors and cytokines and suggests the possible participation of such interaction in the process of chondrogenesis and chondrocyte differentiation toward endochondral ossification.

The extracellular matrix (ECM) is a deformable dynamic structure that dictates the behavior, function and integrity of blood vessels. The composition, density, chemistry and architecture of major globular and fibrillar proteins of the matrisome regulate the mechanical properties of the vasculature (i.e., stiffness/compliance). ECM proteins are linked via integrins to a protein adhesome directly connected to the actin cytoskeleton and various downstream signaling pathways that enable the cells to respond to external stimuli in a coordinated manner and maintain optimal tissue stiffness. However, cardiovascular risk factors such as diabetes, dyslipidemia, hypertension, ischemia and aging compromise the mechanical balance of the vascular wall. Stiffening of large blood vessels is associated with well-known qualitative and quantitative changes of fibrillar and fibrous macromolecules of the vascular matrisome. However, the mechanical properties of the thin-walled microvasculature are essentially defined by components of the subendothelial matrix. Cellular communication network (CCN) 1 and 2 proteins (aka Cyr61 and CTGF, respectively) of the CCN protein family localize in and act on the pericellular matrix of microvessels and constitute primary candidate markers and regulators of microvascular compliance. CCN1 and CCN2 bind various integrin and non-integrin receptors and initiate signaling pathways that regulate connective tissue remodeling and response to injury, the associated mechanoresponse of vascular cells, and the subsequent inflammatory response. The CCN1 and CCN2 genes are themselves responsive to mechanical stimuli in vascular cells, wherein mechanotransduction signaling converges into the common Rho GTPase pathway, which promotes actomyosin-based contractility and cellular stiffening. However, CCN1 and CCN2 each exhibit unique functional attributes in these processes. A better understanding of their synergistic or antagonistic effects on the maintenance (or loss) of microvascular compliance in physiological and pathological situations will assist more broadly based studies of their functional properties and translational value.

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.

Fluid flow stress (FSS) is a major mechanical stress that induces bone remodeling upon orthodontic tooth movement, whereas CCN family protein 2 (CCN2) is a potent regenerator of bone defects. In this study, we initially evaluated the effect of laminar FSS on Ccn2 expression and investigated its mechanism in osteoblastic MC3T3-E1 cells. The Ccn2 expression was drastically induced by uniform FSS in an intensity dependent manner. Of note, the observed effect was inhibited by a Rho kinase inhibitor Y27632. Moreover, the inhibition of actin polymerization blocked the FSS-induced activation of Ccn2, whereas inducing F-actin formation using cytochalasin D and jasplakinolide enhanced Ccn2 expression in the same cells. Finally, F-actin formation was found to induce osteoblastic differentiation. In addition, activation of cyclic AMP-dependent kinase, which inhibits Rho signaling, abolished the effect of FSS. Collectively, these findings indicate the critical role of actin polymerization and Rho signaling in CCN2 induction and bone remodeling provoked by FSS.

Carcinoid syndrome (CS) develops in patients with hormone-producing neuroendocrine neoplasms (NENs) when hormones reach a significant level in the systemic circulation. The classical symptoms of carcinoid syndrome are flushing, diarrhoea, abdominal pain, and wheezing. Neuroendocrine neoplasms can produce multiple hormones: 5-hydroxytryptamine (serotonin) is the most well-known one, but histamine, catecholamines, and brady/tachykinins are also released. Serotonin overproduction can lead to symptoms and also stimulates fibrosis formation which can result in development of carcinoid syndrome-associated complications such as carcinoid heart disease (CaHD) and mesenteric fibrosis. Transforming growth factor beta (TGF-β) is one of the main factors in developing fibrosis, but platelet-derived growth factor (PDGF), basic fibroblast growth factor (FGF2), and connective tissue growth factor (CTGF or CCN2) are also related to fibrosis development. Treatment of CS focuses on reducing serotonin levels with somatostatin analogues (SSA's). Telotristat ethyl and peptide receptor radionuclide therapy (PRRT) have recently become available for patients with symptoms despite being established on SSA's. Screening for CaHD is advised, and early intervention prolongs survival. Mesenteric fibrosis is often present and associated with poorer survival, but the role for prophylactic surgery of this is unclear. Depression, anxiety, and cognitive impairment are frequently present symptoms in patients with CS but not always part of their care plan. The role of antidepressants, mainly SSRIs, is debatable, but recent retrospective studies show evidence for safe use in patients with CS. Carcinoid crisis is a life-threatening complication of CS which can appear spontaneously but mostly described during surgery, anaesthesia, chemotherapy, PRRT, and radiological procedures and may be prevented by octreotide administration.

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is a devastating complication of peritoneal dialysis (PD). The pathogenesis is not exactly known and no preventive strategy or targeted medical therapy is available. CCN2 has both pro-fibrotic and pro-angiogenic actions and appears an attractive target. Therefore, we studied peritoneal expression of CCN2, as well as TGFβ1 and VEGF, in different stages of peritoneal fibrosis.

METHODS

Sixteen PD patients were investigated and compared to 12 hemodialysis patients and four pre-emptively transplanted patients. Furthermore, expression was investigated in 12 EPS patients in comparison with 13 PD and 12 non-PD patients without EPS. Peritoneal tissue was taken during kidney transplantation procedure or during EPS surgery. In a subset of patients, CCN2 protein levels in peritoneal effluent and plasma were determined. Samples were examined by qPCR, histology, immunohistochemistry, and ELISA.

RESULTS

Peritoneal CCN2 expression was 5-fold higher in PD patients compared to pre-emptively transplanted patients (P < 0.05), but did not differ from hemodialysis patients. Peritoneal expression of TGFβ1 and VEGF were not different between the three groups; neither was peritoneal thickness. Peritoneum of EPS patients exhibited increased expression of CCN2 (35-fold, P < 0.001), TGFβ1 (24-fold, P < 0.05), and VEGF (77-fold, P < 0.001) compared to PD patients without EPS. In EPS patients, CCN2 protein was mainly localized in peritoneal endothelial cells and fibroblasts. CCN2 protein levels were significantly higher in peritoneal effluent of EPS patients compared to levels in dialysate of PD patients (12.0 ± 4.5 vs. 0.91 ± 0.92 ng/ml, P < 0.01), while plasma CCN2 levels were not increased.

CONCLUSIONS

Peritoneal expression of CCN2, TGFβ1, and VEGF are significantly increased in EPS patients. In early stages of peritoneal fibrosis, only CCN2 expression is slightly increased. Peritoneal CCN2 overexpression in EPS patients is a locally driven response. The potential of CCN2 as biomarker and target for CCN2-inhibiting agents to prevent or treat EPS warrants further study.

Appropriate trophoblast invasion into the maternal endometrium is essential for successful human implantation and placentation. Connective tissue growth factor (CTGF), also known as CCN2, is a matricellular protein that is expressed in the placenta. Interestingly, the CTGF expression levels in the placenta and serum from patients with severe preeclampsia or fetal growth restriction are higher than those from healthy controls. However, to date, the role of CTGF in the regulation of trophoblast cell invasion remains unclear. Transforming growth factor-β1 (TGF-β1) is a potent stimulator of CTGF expression and has been shown to inhibit trophoblast cell invasiveness. However, whether CTGF mediates TGF-β1-inhibited human trophoblast cell invasion is unknown. In the present study, we show that treatment with TGF-β1 upregulates CTGF expression in a human trophoblast cell line, HTR-8/SVneo, and in primary human trophoblast cells. Our results also demonstrate that the SMAD2/3 signaling pathways are required for TGF-β1-induced upregulation of CTGF. Importantly, CTGF knockdown attenuates TGF-β1-inhibited cell invasion. Furthermore, cell invasiveness is decreased by treatment with recombinant CTGF. These results provide evidence that CTGF mediates TGF-β1-inhibited human trophoblast cell invasion.

Connective tissue growth factor (CTGF/CCN2) is a matricellular protein that belongs to the CCN family of proteins. Since its discovery, it has been linked to cellular processes such as cell proliferation, differentiation, adhesion, migration, and synthesis of extracellular matrix (ECM) components, among others. The pro-fibrotic role of CTGF/CCN2 has been well-studied in several pathologies characterized by the development of fibrosis. Reduction of CTGF/CCN2 levels in mdx mice, a murine model for Duchenne muscular dystrophy (DMD), decreases fibrosis and improves skeletal muscle phenotype and function. Recently, it has been shown that skeletal muscle of symptomatic hSOD1^G93A mice, a model for Amyotrophic lateral sclerosis (ALS), shows up-regulation of CTGF/CCN2 accompanied by excessive deposition ECM molecules. Elevated levels of CTGF/CCN2 in spinal cord from ALS patients have been previously reported. However, there is no evidence regarding the role of CTGF/CCN2 in neurodegenerative diseases such as ALS, in which alterations in skeletal muscle seem to be the consequence of early pathological denervation. In this regard, the emerging evidence shows that CTGF/CCN2 also exerts non-fibrotic roles in the central nervous system (CNS), specifically impairing oligodendrocyte maturation and regeneration, and inhibiting axon myelination. Despite these striking observations, there is no evidence showing the role of CTGF/CCN2 in peripheral nerves. Therefore, even though more studies are needed to elucidate its precise role, CTGF/CCN2 is starting to emerge as a novel therapeutic target for the treatment of neurodegenerative diseases where demyelination and axonal degeneration occurs.

Fibrosis is a pathological situation in which excessive amounts of extracellular matrix (ECM) are deposited in the tissue. Myofibroblasts play a crucial role in the development and progress of fibrosis as they actively synthesize ECM components such as collagen I, fibronectin and connective tissue growth factor (CTGF) and cause organ fibrosis. Transforming growth factor beta 1 (TGF-β1) plays a major role in tissue fibrosis. Activin receptor-like kinase 1 (ALK1) is a type I receptor of TGF-β1 with an important role in angiogenesis whose function in cellular biology and TGF-β signaling is well known in endothelial cells, but its role in fibroblast biology and its contribution to fibrosis is poorly studied. We have recently demonstrated that ALK1 regulates ECM protein expression in a mouse model of obstructive nephropathy. Our aim was to evaluate the role of ALK1 in several processes involved in fibrosis such as ECM protein expression, proliferation and migration in ALK1(+/+) and ALK1(+/-) mouse embryonic fibroblasts (MEFs) after TGF-β1 stimulations and inhibitors. ALK1 heterozygous MEFs show increased expression of ECM proteins (collagen I, fibronectin and CTGF/CCN2), cell proliferation and migration due to an alteration of TGF-β/Smad signaling. ALK1 heterozygous disruption shows an increase of Smad2 and Smad3 phosphorylation that explains the increases in CTGF/CCN2, fibronectin and collagen I, proliferation and cell motility observed in these cells. Therefore, we suggest that ALK1 plays an important role in the regulation of ECM protein expression, proliferation and migration.

OBJECTIVE

Transforming growth factor (TGF) beta is strongly implicated in the progression of renal fibrosis. TGFbeta1 is reported to cause epithelial-mesenchymal transition, inhibition of epithelial cell proliferation, increased apoptosis, auto-induction of TGFbeta production and induction of secondary mediators of tissue fibrosis such as connective tissue growth factor (CTGF, CCN2). The aims of this study were to investigate the role of the Ras/MAP kinase pathway in TGFbeta1 inhibition of proliferation, TGFbeta auto-induction and TGFbeta1-induced CTGF expression in HKC human renal tubule epithelial cells.

RESULTS

TGFbeta1 (0-25 ng/ml) inhibited proliferation of HKC cells and at 25 ng/ml also induced apoptosis. After 5-10 min of incubation, TGFbeta1 increased cellular levels of phospho-ERK1/2 and phospho-AKT with a bell-shaped dose-response curve with a maximally effective concentration of 2.5 ng/ml. TGFbeta3 caused an increase in extracellular TGFbeta1, which was significantly reduced in the presence of PD 98059. TGFbeta1 increased cellular and secreted CTGF protein in HKC cells in a MEK-dependent manner. To identify the Ras isoform involved, specific antisense oligonucleotides targeted to Ha-Ras, Ki-Ras and N-Ras were employed. Only inhibition of N-Ras resulted in a significant reduction of auto-induced TGFbeta1 secretion and TGFbeta1-induced cellular and secreted CTGF.

CONCLUSIONS

These results establish that the Ras/MAP kinase pathway, specifically through N-Ras, mediates TGFbeta1 auto-induction and TGFbeta1-induced CTGF expression in human renal tubule epithelial cells.

The cis-acting element of structure-anchored repression (CAESAR) is a post-transcriptional regulatory element of gene expression, which is located in the 3'-untranslated region (UTR) of the human ccn2 gene (ctgf/ccn2). In this report, the repression mechanism of CAESAR, as well as the structural requirement, was investigated. Removal of minor stem-loops from CAESAR resulted in proportional attenuation of the repressive function, whereas removal of the single bulge or modification of primary nucleotide sequence did not affect its functionality. In light of functional mechanism, CAESAR exerted no significant effects on stability or nuclear export of the cis-linked mRNA. However, this element significantly interfered with the association of such mRNA on ribosome and slowed down the translation process thereafter in vitro. A translation repression mechanism by RNA secondary structure to determine the basal ctgf/ccn2 expression level was uncovered herein.

Connective tissue growth factor (Ctgf) or CCN2 is a protein synthesized by osteoblasts necessary for skeletal homeostasis, although its overexpression inhibits osteogenic signals and bone formation. Ctgf is induced by bone morphogenetic proteins, transforming growth factor β and Wnt; and in the present studies, we explored whether Notch regulated Ctgf expression in osteoblasts. We employed Rosa(Notch) mice, where the Notch intracellular domain (NICD) is expressed following the excision of a STOP cassette, placed between the Rosa26 promoter and NICD. Notch was activated by transduction of adenoviral vectors expressing Cre recombinase (Ad-CMV-Cre). Notch induced Ctgf mRNA levels in a time dependent manner and increased Ctgf heterogeneous nuclear RNA. Notch also destabilized Ctgf mRNA shortening its half-life from 13h to 3h. The effect of Notch on Ctgf expression was lost following Rbpjκ downregulation, demonstrating that it was mediated by Notch canonical signaling. However, downregulation of the classic Notch target genes Hes1, Hey1 and Hey2 did not modify the effect of Notch on Ctgf expression. Wild type osteoblasts exposed to immobilized Delta-like 1 displayed enhanced Notch signaling and increased Ctgf expression. In addition to the effects of Notch in vitro, Notch induced Ctgf in vivo, and calvariae and femurs from Rosa(Notch) mice mated with transgenics expressing the Cre recombinase in cells of the osteoblastic lineage exhibited increased expression of Ctgf. In conclusion, Ctgf is a target of Notch canonical signaling in osteoblasts, and may act in concert with Notch to regulate skeletal homeostasis.

Connective tissue growth factor (CTGF/CCN2) is a member of the CCN family of secreted proteins that are believed to play an important role in the development of neoplasia. In particular, CTGF has been reported to play an important role in mammary tumorigenesis and to have prognostic value in female breast cancer (FBC). The aim of the present study was to investigate clinicopathologic correlations and prognostic value of CTGF in male breast cancer (MBC) and to compare these findings with FBC. For this, we studied CTGF protein expression by immunohistochemistry in 109 MBC cases and 75 FBC cases. In MBC, stromal CTGF expression was seen in the majority of the cases 78% (85/109) with high expression in 31/109 cases (28.4%), but expression in tumor cells was only seen in 9.2% (10/109) of cases. High stromal CTGF expression correlated with high grade and high proliferation index (>15%) assessed by MIB-1 immunohistochemical staining. CTGF expression in tumor epithelial cells did not correlate with any of the clinicopathologic features. In FBC, stromal CTGF expression positively correlated with mitotic count and tumor CTGF expression was associated with triple negative status of the tumor (p = 0.002). Neither stromal nor tumor epithelial cell CTGF expression had prognostic value in MBC and FBC. In conclusion, stromal CTGF expression was seen in a high percentage of MBC and was correlated with high grade and high proliferation index. In view of the important role of the microenvironment in cancer progression, this might suggest that stromal CTGF could be an interesting target for novel therapies and molecular imaging. However, the lack of association with prognosis warrants caution. The potential role of CTGF as a therapeutic target for triple negative FBC deserves to be further studied.

Connective tissue growth factor (CTGF/CCN2) is a cysteine-rich matricellular protein that belongs to the CCN (CYR61, CTGF, NOV) protein family. It is highly expressed by human rhabdomyosarcoma cells and sustains their survival. In this study we investigated CCN2 expression in a mouse model of spontaneous rhabdomyosarcomagenesis that combines HER-2/neu oncogene activation and p53 oncosuppressor gene inactivation (BALB-p53neu mice). Murine rhabdomyosarcoma cells showed a 4-26 fold increase in CCN2 mRNA expression regarding to normal thigh muscle. Moreover, they expressed CCN2 protein at levels comparable to human rhabdomyosarcoma cells. Therefore BALBp53neu mice might be useful for the evaluation of the role played by CCN2 in rhabdomyosarcoma in vivo.

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.

Connective tissue growth factor (CTGF; CCN2) plays a role in the development of diabetic nephropathy (DN). Urinary CTGF (uCTGF) is elevated in DN patients and has been proposed as a biomarker for disease progression, but it is unknown which pathophysiological factors contribute to elevated uCTGF. We studied renal handling of CTGF by infusion of recombinant CTGF in diabetic mice. In addition, uCTGF was measured in type 1 DN patients and compared with glomerular and tubular dysfunction and damage markers. In diabetic mice, uCTGF was increased and fractional excretion (FE) of recombinant CTGF was substantially elevated indicating reduced tubular reabsorption. FE of recombinant CTGF correlated with excretion of endogenous CTGF. CTGF mRNA was mainly localized in glomeruli and medullary tubules. Comparison of FE of endogenous and recombinant CTGF indicated that 60% of uCTGF had a direct renal source, while 40% originated from plasma CTGF. In DN patients, uCTGF was independently associated with markers of proximal and distal tubular dysfunction and damage. In conclusion, uCTGF in DN is elevated as a result of both increased local production and reduced reabsorption due to tubular dysfunction. We submit that uCTGF is a biomarker reflecting both glomerular and tubulointerstitial hallmarks of diabetic kidney disease.

OBJECTIVE

Oral submucous fibrosis (OSF) is a premalignant condition caused by the chewing of areca nut (AN). Transforming growth factor β (TGFβ) plays a central role in the pathogenesis of OSF. Connective tissue growth factor (CTGF or CCN2) and early growth response-1 (Egr-1) are important mediators in the fibrotic response to TGFβ in several fibrotic disorders including OSF. Arecoline, a major AN alkaloid, induced the synthesis of CCN2 and Egr-1 in human buccal mucosal fibroblast (BMFs). The aims of this study were to investigate whether arecoline-induced CCN2 and Egr-1 syntheses are mediated through TGFβ1 signaling and to inspect the detailed mechanisms involved.

METHODS

Western blot and TGFβ1 Emax® ImmunoAssay were used to measure the effect of arecoline on the TGFβ signaling pathways. 2',7'-dichlorodihydrofluorescein diacetate and MitoSOX™ Red were used to measure the effect of arecoline on the cellular and mitochondrial reactive oxygen species (ROS).

RESULTS

Arecoline induced latent TGFβ1 activation, Smad2 phosphorylation, and mitochondrial and total cellular ROS in BMFs. TGFβ-neutralizing antibody completely inhibited the arecoline-induced synthesis of CCN2 and Egr-1. Mito-TEMPO, a mitochondria-targeted antioxidant, completely suppressed arecoline-induced latent TGFβ1 activation and mitochondrial and total cellular ROS. Epigallocatechin-3-gallate (EGCG) dose-dependently inhibited arecoline-induced TGFβ1 activation and mitochondrial ROS in BMFs.

CONCLUSIONS

Our results indicated that arecoline-induced mitochondrial ROS plays pivotal roles in the activation of latent TGFβ1 leading to the initiation of TGFβ1 signaling and subsequent increase in the synthesis of CCN2 and Egr-1. EGCG can be a useful agent in the chemoprevention and treatment of OSF.

Mice lacking the pro-adhesive matricellular protein connective tissue growth factor (CTGF/CCN2) display an embryonic lethal phenotype due to defects in bone and cartilage. However, the specific role of CCN2 in skin development is unknown. Here, we generated mice deleted for CCN2 in the entire body (using a cre/lox system in which CCN2 is deleted in the entire body due to the presence of a constitutively expressed cre recombinase). We found that CCN2 was not required for the development of skin as defined by skin thickness measurements, trichrome staining and immunostaining with anti-CD31 (to detect endothelial cells) and anti-α-SMA (to detect smooth muscle cells and pericytes) antibodies. Thus, although recently we have shown that CCN2 is required for fibrogenesis in postnatal mice, CCN2 is not required for skin development during embryogenesis.

CCN2/CTGF is a multifunctional growth factor. Our previous studies have revealed that CCN2 plays important roles in both growth and differentiation of chondrocytes and that the 3'-untranslated region (3'-UTR) of ccn2 mRNA contains a cis-repressive element of gene expression. In the present study, we found that the stability of chicken ccn2 mRNA is regulated in a differentiation stage-dependent manner in chondrocytes. We also found that stimulation by bone morphogenetic protein 2, platelet-derived growth factor, and CCN2 stabilized ccn2 mRNA in proliferating chondrocytes but that it destabilized the mRNA in prehypertrophic-hypertrophic chondrocytes. The results of a reporter gene assay revealed that the minimal repressive cis-element of the 3'-UTR of chicken ccn2 mRNA was located within the area between 100 and 150 bases from the polyadenylation tail. Moreover, the stability of ccn2 mRNA was correlated with the interaction between this cis-element and a putative 40-kDa trans-factor in nuclei and cytoplasm. In fact, the binding between them was prominent in proliferating chondrocytes and attenuated in (pre)hypertrophic chondrocytes. Stimulation by the growth factors repressed the binding in proliferating chondrocytes; however, it enhanced it in (pre)hypertrophic chondrocytes. Therefore, gene expression of ccn2 mRNA during endochondral ossification is properly regulated, at least in part, by changing the stability of the mRNA, which arises from the interaction between the RNA cis-element and putative trans-factor.

Diabetes mellitus is characterized by hyperglycemia, which induces oxidative stress and perturbs a number of pathways, leading to tissue injury. One of the pathological responses to tissue injury is the development of fibrosis and cell death. Enalapril is a non-thiol angiotensin-converting enzyme inhibitor that is commonly used in the treatment of diabetes-associated hypertension. The present study examines the possible beneficial effects of enalapril on the development of diabetes associated fibrosis and DNA damage in rats. Sprague-Dawley rats (250 ± 10 g) were used in the study. Enalapril (10 mg kg(-1) per oral) was administered for four consecutive weeks to the streptozotocin (STZ)-induced diabetic rats. After 4 weeks, all the animals were sacrificed and comet assay (normal and modified) was performed to detect the normal as well as oxidative DNA damage. Expression of profibrotic marker CCN2 and fibrosis was examined in the heart, kidney and liver of diabetic rats. Enalapril treatment significantly restored the malondialdehyde and glutathione content as well as the DNA damage in the heart, kidney and liver of diabetic rat. Significant decrease in the expression of CCN2 was observed in the heart, kidney and liver of diabetic rat receiving enalapril treatment as compared with the diabetic group. Further, the enalapril treatment led to significant decrease in the fibrosis and CCN2 expression in the diabetic group as compared with control. The results of the present study clearly demonstrate that enalapril ameliorates the DNA damage, cell death and expression of CCN2 in the heart, kidney and liver of the STZ-induced diabetic rat.

BACKGROUND

Gingival squamous cell carcinoma (SCC) cells frequently invade mandibular bone, and this destruction is associated with a worse prognosis. However, the relationship between bone destruction and associated factors is unclear. In this study, the role and diagnostic utility of transforming growth factor-beta (TGF-beta) type I receptor (TbetaRI) in bone destruction of the mandible was investigated.

METHODS

The expression of TbetaRI was explored by using an immunohistochemical method on paraffin-embedded tissues from 21 cases of mandibular SCC. An inhibitor of the kinase activity of the TbetaRI (TbetaRI-I) was used to assess the role of TbetaRI in bone destruction by a human oral SCC cell line (HSC-2) that highly expresses TbetaRI.

RESULTS

TbetaRI-positive signals were closely associated with destructive invasion of the mandible by oral SCC cells. Consistent with these results, TbetaRI-I greatly reduced HSC-2 cell-induced bone destruction and osteoclast formation in vivo and in vitro. TbetaRI-I treatment reduced the expression of TNF-alpha, RANKL and connective tissue growth factor (CTGF/CCN2), all of which were up-regulated by TGF-beta in HSC-2 cells.

CONCLUSIONS

These data demonstrated an important role for TGF-beta signalling in bone invasion by oral SCC cells, and suggest that the bone destruction is mediated by RANKL, TNF-alpha and CCN2.