Identification and cloning of a connective tissue growth factor-like cDNA from human osteoblasts encoding a novel regulator of osteoblast functions

WISP-2 modulates the induction of inflammatory mediators and cartilage catabolism in chondrocytes

Wnt-1 inducible signaling pathway protein 2 (WISP-2/CCN5) is a recently identified adipokine that has been described as an important mediator of canonical Wnt activation in adipogenic precursor cells. In osteoarthritis (OA), the most common form of arthritis, chondrocytes exhibit aberrant and increased production of pro-inflammatory mediators and matrix degrading enzymes such as IL-1β and MMP-13. Although recent evidence suggests a role for Wnt signaling in OA physiopathology, little is known about the involvement of WISP-2 in cartilage degradation. In the present study, we determined the expression of WISP-2 in healthy and OA human chondrocytes. WISP-2 expression is modulated along chondrocyte differentiation and downregulated at the onset of hypertrophy by inflammatory mediators. We also investigated the effect of WISP-2 on cartilage catabolism and performed WISP-2 loss-of-function experiments using RNA interference technology in human T/C-28a2 immortalized chondrocytes. We demonstrated that recombinant human WISP-2 protein reduced IL-1β-mediated chondrocyte catabolism, that IL-1β and WNT/b-catenin signaling pathways are involved in rhWISP-2 protein and IL-1β effects in human chondrocytes, and that WISP-2 has a regulatory role in attenuating the catabolic effects of IL-1β in chondrocytes. Gene silencing of WISP-2 increased the induction of the catabolic markers MMP-13 and ADAMTS-5 and the inflammatory mediators IL-6 and IL-8 triggered by IL-1β in human primary OA chondrocytes in a Wnt/β-catenin dependent manner. In conclusion, here we have shown for the first time that WISP-2 may have relevant roles in modulating the turnover of extracellular matrix in the cartilage and that its downregulation may detrimentally alter the inflammatory environment in OA cartilage. We also proved the participation of Wnt/β-catenin signaling pathway in these processes. Thus, targeting WISP-2 might represent a potential therapeutical approach for degenerative and/or inflammatory diseases of musculoskeletal system, such as osteoarthritis.

Omics Profiling of S2P Mutant Fibroblasts as a Mean to Unravel the Pathomechanism and Molecular Signatures of X-Linked MBTPS2 Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is an inherited skeletal dysplasia characterized by low bone density, bone fragility and recurrent fractures. The characterization of its heterogeneous genetic basis has allowed the identification of novel players in bone development. In 2016, we described the first X-linked recessive form of OI caused by hemizygous MBTPS2 missense variants resulting in moderate to severe phenotypes. MBTPS2 encodes site-2 protease (S2P), which activates transcription factors involved in bone (OASIS) and cartilage development (BBF2H7), ER stress response (ATF6) and lipid metabolism (SREBP) via regulated intramembrane proteolysis. In times of ER stress or sterol deficiency, the aforementioned transcription factors are sequentially cleaved by site-1 protease (S1P) and S2P. Their N-terminal fragments shuttle to the nucleus to activate gene transcription. Intriguingly, missense mutations at other positions of MBTPS2 cause the dermatological spectrum condition Ichthyosis Follicularis, Atrichia and Photophobia (IFAP) and Keratosis Follicularis Spinulosa Decalvans (KFSD) without clinical overlap with OI despite the proximity of some of the pathogenic variants. To understand how single amino acid substitutions in S2P can lead to non-overlapping phenotypes, we aimed to compare the molecular features of MBTPS2-OI and MBTPS2-IFAP/KFSD, with the ultimate goal to unravel the pathomechanisms underlying MBTPS2-OI. RNA-sequencing-based transcriptome profiling of primary skin fibroblasts from healthy controls (n = 4), MBTPS2-OI (n = 3), and MBTPS2-IFAP/KFSD (n = 2) patients was performed to identify genes that are differentially expressed in MBTPS2-OI and MBTPS2-IFAP/KFSD individuals compared to controls. We observed that SREBP-dependent genes are more downregulated in OI than in IFAP/KFSD. This is coupled to alterations in the relative abundance of fatty acids in MBTPS2-OI fibroblasts in vitro, while no consistent alterations in the sterol profile were observed. Few OASIS-dependent genes are suppressed in MBTPS2-OI, while BBF2H7- and ATF6-dependent genes are comparable between OI and IFAP/KFSD patients and control fibroblasts. Importantly, we identified genes involved in cartilage physiology that are differentially expressed in MBTPS2-OI but not in MBTPS2-IFAP/KFSD fibroblasts. In conclusion, our data provide clues to how pathogenic MBTPS2 mutations cause skeletal deformities via altered fatty acid metabolism or cartilage development that may affect bone development, mineralization and endochondral ossification.

Characterization of bone morphology in CCN5/WISP5 knockout mice

CCN5/WISP2 is part of the CCN family of matricellular proteins, but is distinct in that it lacks the C-terminal (CT) domain. Although CCN5 has been shown to impact cell proliferation and differentiation in vitro, its role in vivo is unclear. We therefore generated mice using ES cells developed by the Knockout Mouse Project (KOMP) in which exons 2-5, which encode the all of the conserved protein coding regions, are replaced by a lacZ cassette. Ccn5 ^LacZ/LacZ mice were viable and apparently normal. Based on previous studies showing that CCN5 impacts osteoblast proliferation and differentiation, we performed an analysis of adult bone phenotype. LacZ expression was examined in adult bone, and was found to be strong within the periosteum, but not in trabecular bone or bone marrow. Micro-CT analysis revealed no apparent changes in bone mineral density (BMD) or bone tissue volume (BV/TV) in Ccn5 ^LacZ/LacZ mice. These studies indicate that CCN5 is not required for normal bone formation, but they do not rule out a role in mechanotransduction or repair processes. The availability of Ccn5 ^LacZ mice enables studies of CCN5 expression and function in multiple tissues.

Role of CCN5 (WNT1 inducible signaling pathway protein 2) in pancreatic islets

In search of direct targets of insulin-like growth factor (IGF)-1 action, we discovered CCN5 (WNT1 inducible signaling pathway protein 2 [WISP2]) as a novel protein expressed in pancreatic β-cells. As a member of the "CCN" ( C ysteine-rich angiogenic inducer 61 [Cyr61], C onnective tissue growth factor [CTGF in humans], and N ephroblastoma overexpressed [Nov; in chickens]) family, the expression of CCN5/WISP2 is stimulated by IGF-1 together with Wnt signaling. When overexpressed in insulinoma cells, CCN5 promotes cell proliferation and cell survival against streptozotocin-induced cell death. The cell proliferation effect seems to be caused by AKT phosphorylation and increased cyclin D1 levels. These properties resemble those of CCN2/CTGF, another isoform of the CCN family, although CCN5 is the only one within the family of six proteins that lacks the C-terminal repeat. Treatment of primary mouse islets with recombinant CCN5 protein produced similar effects to those of gene transfection, indicating that either as a matricellular protein or a secreted growth factor, CCN5 stimulates β-cell proliferation and regeneration in a paracrine fashion. This review also discusses the regulation of CCN5/WISP2 by estrogen and its involvement in angiogenesis and tumorigenesis.

Tensile stress stimulates the expression of osteogenic cytokines/growth factors and matricellular proteins in the mouse cranial suture at the site of osteoblast differentiation

Mechanical stress promotes osteoblast proliferation and differentiation from mesenchymal stem cells (MSCs). Although numerous growth factors and cytokines are known to regulate this process, information regarding the differentiation of mechanically stimulated osteoblasts from MSCs in in vivo microenvironment is limited. To determine the significant factors involved in this process, we performed a global analysis of differentially expressed genes, in response to tensile stress, in the mouse cranial suture wherein osteoblasts differentiate from MSCs. We found that the gene expression levels of several components involved in bone morphogenetic protein, Wnt, and epithelial growth factor signalings were elevated with tensile stress. Moreover gene expression of some extracellular matrices (ECMs), such as cysteine rich protein 61 (Cyr61)/CCN1 and galectin-9, were upregulated. These ECMs have the ability to modulate the activities of cytokines and are known as matricellular proteins. Cyr61/CCN1 expression was prominently increased in the fibroblastic cells and preosteoblasts in the suture. Thus, for the first time we demonstrated the mechanical stimulation of Cyr61/CCN1 expression in osteogenic cells in an ex vivo system. These results suggest the importance of matricellular proteins along with the cytokine-mediated signaling for the mechanical regulation of MSC proliferation and differentiation into osteoblastic cell lineage in vivo.

Identification of a Copy Number Variation on Chromosome 20q13.12 Associated with Osteoporotic Fractures in the Korean Population

Osteoporotic fractures (OFs) are critical hard outcomes of osteoporosis and are characterized by decreased bone strength induced by low bone density and microarchitectural deterioration in bone tissue. Most OFs cause acute pain, hospitalization, immobilization, and slow recovery in patients and are associated with increased mortality. A variety of genetic studies have suggested associations of genetic variants with the risk of OF. Genome-wide association studies have reported various single-nucleotide polymorphisms and copy number variations (CNVs) in European and Asian populations. To identify CNV regions associated with OF risk, we conducted a genome-wide CNV study in a Korean population. We performed logistic regression analyses in 1,537 Korean subjects (299 OF cases and 1,238 healthy controls) and identified a total of 8 CNV regions significantly associated with OF (p < 0.05). Then, one CNV region located on chromosome 20q13.12 was selected for experimental validation. The selected CNV region was experimentally validated by quantitative polymerase chain reaction. The CNV region of chromosome 20q13.12 is positioned upstream of a family of long non-coding RNAs, LINC01260. Our findings could provide new information on the genetic factors associated with the risk of OF.

Regulation of the CCN genes by vitamin D: A possible adjuvant therapy in the treatment of cancer and fibrosis

The CCN family is composed of six cysteine-rich, modular, and conserved proteins whose functions span a variety of tissues and include cell proliferation, adhesion, angiogenesis, and wound healing. Roles for the CCN proteins throughout the entire body including the skin, kidney, brain, blood vessels, hematopoietic compartment and others, are continuously being elucidated. Likewise, an understanding of the regulation of this important gene family is constantly becoming clearer, through identification of transcription factors that directly activate, repress, or respond to upstream cell signaling pathways, as well as other forms of gene expression control. Vitamin D (1,25-dihydroxyvitamin D3 or calcitriol), a vitamin essential for numerous biological processes, acts as a potent gene expression modulator. The regulation of the CCN gene family members by calcitriol has been described in many contexts. Here, we provide a concise and thorough overview of what is known about calcitriol and its regulation of the CCN genes, and argue that its regulation is of physiological importance in a wide breadth of tissues in which CCN genes function. In addition, we highlight the effects of vitamin D on CCN gene expression in the setting of two common pathologic conditions, fibrosis and cancer, and propose that the therapeutic effects of vitamin D3 described in these disease states may in part be attributable to CCN gene modulation. As vitamin D is perfectly safe in a wide range of doses and already showing promise as an adjuvant therapeutic agent, a deeper understanding of its control of CCN gene expression may have profound implications in clinical management of disease.

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

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

Wnt1 inducible signalling pathway protein-2 (WISP‑2/CCN5): roles and regulation in human cancers (review)

Wnt1 inducible signalling pathway protein-2 (WISP‑2), also known as CCN5, CT58, CTGF-L, CTGF-3, HICP and Cop1, is one of the 3 WNT1 inducible proteins that belongs to the CCN family. This family of members has been shown to play multiple roles in a number of pathophysiological processes, including cell proliferation, adhesion, wound healing, extracellular matrix regulation, epithelial-mesenchymal transition, angiogenesis, fibrosis, skeletal development and embryo implantation. Recent results suggest that WISP-2 is relevant to tumorigenesis and malignant transformation, particularly in breast cancer, colorectal cancer and hepatocarcinoma. Notably, its roles in cancer appear to vary depending on cell/tumour type and the microenvironment. The striking difference in the structure of WISP-2 in comparison with the other 2 family members may contribute to its difference in functions, which leads to the hypothesis that WISP-2 may act as a dominant-negative regulator of other CCN family members. In the present review, we summarise the roles, regulation and underlying mechanism of WISP-2 in human cancers.

CCN5 Expression in mammals. III. Early embryonic mouse development

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

A human embryonic stem cell-derived clonal progenitor cell line with chondrogenic potential and markers of craniofacial mesenchyme

AIMS

We screened 100 diverse human embryonic stem-derived progenitor cell lines to identify novel lines with chondrogenic potential.

MATERIALS & METHODS

The 4D20.8 cell line was compared with mesenchymal stem cells and dental pulp stem cells by assessing osteochondral markers using immunohistochemical methods, gene expression microarrays, quantitative real-time PCR and in vivo repair of rat articular condyles.

RESULTS

4D20.8 expressed the site-specific gene markers LHX8 and BARX1 and robustly upregulated chondrocyte markers upon differentiation. Differentiated 4D20.8 cells expressed relatively low levels of COL10A1 and lacked IHH and CD74 expression. Transplantation of 4D20.8 cells into experimentally induced defects in the femoral condyle of athymic rats resulted in cartilage and bone differentiation approximating that of the original tissue architecture. Relatively high COL2A1 and minimal COL10A1 expression occurred during differentiation in HyStem-C hydrogel with TGF-β3 and GDF-5.

CONCLUSION

Human embryonic stem cell-derived embryonic progenitor cell lines may provide a novel means of generating purified site-specific osteochondral progenitor cell lines that are useful in research and therapy.

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

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

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

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

CCN5: biology and pathophysiology

CCN5 is one of six proteins in the CCN family. This family of proteins has been shown to play important roles in many processes, including proliferation, migration, adhesion, extracellular matrix regulation, angiogenesis, tumorigenesis, fibrosis, and implantation. In this review, we focus on the biological and putative pathophysiological roles of CCN5. This intriguing protein is structurally unique among the CCN family members, and has a unique biological activity profile as well.

CCN5: biology and pathophysiology

CCN5 is one of six proteins in the CCN family. This family of proteins has been shown to play important roles in many processes, including proliferation, migration, adhesion, extracellular matrix regulation, angiogenesis, tumorigenesis, fibrosis, and implantation. In this review, we focus on the biological and putative pathophysiological roles of CCN5. This intriguing protein is structurally unique among the CCN family members, and has a unique biological activity profile as well.

Breaking down bone: new insight into site-specific mechanisms of breast cancer osteolysis mediated by metalloproteinases

Bone metastases are the most common skeletal complication of malignancy. Tumor cells disrupt normal bone remodeling to promote bone destruction and its associated morbidity. In the August 15, 2009, issue of Genes & Development, Lu and colleagues (pp. 1882-1894) propose a novel molecular mechanism by which tumor-produced metalloproteinases release epidermal growth factor (EGF) ligands to activate the central osteoclastogenic pathway receptor activator of NF-kappaB ligand (RANKL) to promote breast cancer osteolysis. This work has important therapeutic applications that may quickly translate to more effective treatment for bone metastases.

A histone map of human chromosome 20q13.12

Background

We present a systematic search for regulatory elements in a 3.5 Mb region on human chromosome 20q13.12, a region associated with a number of medical conditions such as type II diabetes and obesity.

Methodology/Principal Findings

We profiled six histone modifications alongside RNA polymerase II (PolII) and CTCF in two cell lines, HeLa S3 and NTERA-2 clone D1 (NT2/D1), by chromatin immunoprecipitation using an in-house spotted DNA array, constructed with 1.8 kb overlapping plasmid clones. In both cells, more than 90% of transcription start sites (TSSs) of expressed genes showed enrichments with PolII, di-methylated lysine 4 of histone H3 (H3K4me2), tri-methylated lysine 4 of histone H3 (H3K4me3) or acetylated H3 (H3Ac), whereas mono-methylated lysine 4 of histone H3 (H3K4me1) signals did not correlate with expression. No TSSs were enriched with tri-methylated lysine 27 of histone H3 (H3K27me3) in HeLa S3, while eight TSSs (4 expressed) showed enrichments in NT2/D1. We have also located several CTCF binding sites that are potential insulator elements.

Conclusions/Significance

In summary, we annotated a number of putative regulatory elements in 20q13.12 and went on to verify experimentally a subset of them using dual luciferase reporter assays. Correlating this data to sequence variation can aid identification of disease causing variants.

Effect of Wnt-1 inducible signaling pathway protein-2 (WISP-2/CCN5), a downstream protein of Wnt signaling, on adipocyte differentiation

Wnt signaling negatively regulates adipocyte differentiation, and ectopic expression of Wnt-1 in 3T3-L1 cells induces several downstream molecules of Wnt signaling, including Wnt-1 inducible signaling pathway protein (WISP)-2. In this study, we examined the role of WISP-2 in the process of adipocyte differentiation using an in vitro cell culture system. In the differentiation of 3T3-L1 cells, WISP-2 expression was observed in growing cells and declined thereafter. In the mitotic clonal expansion phase of adipocyte differentiation, WISP-2 expression was transiently down-regulated concurrently with up-regulation of CCAAT/enhancer-binding protein delta expression. Treatment of 3T3-L1 cells in the differentiation medium with lithium, an activator of Wnt signaling, inhibited the differentiation process with concomitant induction of WISP-2. Treatment of differentiated cells with lithium induced de-differentiation as evidenced by profound reduction of peroxisome proliferator-activator receptor gamma expression and concomitant induction of WISP-2. However, de-differentiation of differentiated cells induced by tumor necrosis factor-alpha did not induce WISP-2 expression. To directly examine the effect of WISP-2 on adipocyte differentiation, 3T3-L1 cells were infected with a retrovirus carrying WISP-2. Although forced expression of WISP-2 inhibited preadipocyte proliferation, it had no effect on adipocyte differentiation. Thus, although WISP-2 is a downstream protein of Wnt signaling, the role of WISP-2 on adipocyte differentiation may be marginal, at least in this in vitro culture model.

TGF-beta1 and WISP-1/CCN-4 can regulate each other's activity to cooperatively control osteoblast function

Wnt-induced secreted protein-1 (WISP-1), like other members of the CCN family, is expressed in skeletal tissues. Its mechanism of action remains unknown. Expression of WISP-1 was analyzed in human bone marrow stroma cells (hBMSC) by RT-PCR. We identified two major transcripts corresponding to those of full-length WISP-1, and of the splice variant WISP-1va which lacks a putative BMP/TGF-beta binding site. To investigate the function of WISP-1 in bone, hBMSC cultures were treated with recombinant human (rh)WISP-1 and analyzed for proliferation and osteogenic differentiation. WISP-1 treatment increased both BrdU incorporation and alkaline phosphatase (AP) activity. Considering the known functional synergy found between the TGF-beta super-family and members of the CCN family, we next tested the effect of WISP-1 on TGF-beta1 activity. We found that rhWISP-1 could reduce rhTGF-beta1 induced BrdU incorporation. Similarly, rhTGF-beta1 inhibited rhWISP-1 induction of AP activity. To explore functional differences between the WISP-1 variants, WISP-1 or WISP-1va were transfected into hBMSC. Both variants could strongly induce BrdU incorporation. However, there were no effects of either variant on AP activity without an additional osteogenic stimulus such as TGF-beta1. Taken together our results suggest a functional relationship between WISP-1 and TGF-beta1. To further define this relationship we analyzed the effect of WISP-1 on TGF-beta signaling. rhWISP-1 significantly reduced TGF-beta1 induced phosphorylation of Smad-2. Our data indicates that full-length WISP-1 and its variant WISP-1va are modulators of proliferation and osteogenic differentiation, and may be novel regulators of TGF-beta1 signaling in osteoblast-like cells.

Hepatic differentiation of human bone marrow-derived UE7T-13 cells: Effects of cytokines and CCN family gene expression

AIM

Bone marrow-derived mesenchymal stem cells (MSC) are expected to be an excellent source of cells for transplantation. We aimed to study the culture conditions and involved genes to differentiate MSC into hepatocytes.

METHODS

The culture conditions to induce the efficient differentiation of human bone marrow-derived UE7T-13 cells were examined using cytokines, hormones, 5-azacytidine and type IV collagen.

RESULTS

We found that combination of acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF) and hepatocyte growth factor (HGF) with type IV collagen coating induced hepatic differentiation of UE7T-13 cells at over 30% frequency, where expression of albumin mRNA was increased over 20-fold. The differentiated cells had functions of albumin production, glycogen synthesis and urea secretion as well as expressing hepatocyte-specific genes. In addition, these cellshave binuclear and cuboidal morphology, which is a characteristic feature of hepatocytes. During hepatic differentiation, UE7T-13 cells showed depressed expression of WISP1 and WISP2 genes, members of the CCN family. Conversely, knockdown of WISP1 or WISP2 gene by siRNA stimulated hepatic differentiation. The effect of aFGF/bFGF/HGF/type IV collagen coating and WISP1-siRNA on hepatic differentiation was additive.

CONCLUSION

The present study suggests that aFGF/bFGF/HGF/type IV collagen coating is the efficient condition for hepatic differentiation of UE7T-13 cells, and that WISP1 and WISP2 play an important role in hepatic transdifferentiation of these cells.

CCN5 Expression in mammals. II. Adult rodent tissues

CCN5 is a secreted heparin- and estrogen-regulated matricellular protein that inhibits vertebrate smooth muscle cell proliferation and motility. CCN5 is expressed throughout murine embryonic development in most organs and tissues. However, after embryonic development is complete, we hypothesized that CCN5 distribution would be largely restricted to small set of tissues, including smooth muscle cells of the arteries, uterus, airway, and digestive tract. Because CCN5 inhibits proliferation of smooth muscle cells in vitro, it might function to prevent excessive growth in vivo. In contrast, another member of the CCN family, CCN2, promotes smooth muscle cell proliferation in vitro, and thus it was expected that its expression levels would be low in uninjured normal adult tissues. Frozen sections from adult tissues and organs were analyzed immunohistochemically using anti-CCN5 and anti-CCN2 antibodies. Both proteins were detected in arteries, the uterus, bronchioles, and the digestive tract as expected, and also in many other tissues including the pancreas, spleen, liver, skeletal muscle, ovary, testis, thymus, brain, olfactory epithelium, and kidney. CCN5 and CCN2 protein was found in smooth muscle, endothelial cells, epithelial cells, skeletal muscle, cells of the nervous system, and numerous other cell types. In many cells, both CCN5 and CCN2 was present in the nucleus. Rather than having opposite patterns of localization, CCN5 and CCN2 often had similar sites of expression. The wide distribution of both CCN5 and CCN2 suggests that both proteins have additional biological functions beyond those previously identified in specific cellular and pathological models.

Connective tissue growth factor is an indicator of bone involvement in multiple myeloma, but matrix metalloproteinase-9 is not

Bone disease (BD) in multiple myeloma (MM) is because of the activation of osteoclasts and impairment of osteoblast differentiation. Connective tissue growth factor (CTGF) is known to participate in the differentiation of mesenchymal stem cells to committed osteoprogenitor cells. We analysed the concentration of circulating CTGF in 35 MM patients and 22 malignant lymphoma (ML) patients and 14 normal individuals. CTGF is protease-sensitive and thus is found as both an N-terminal half fragment (N-half CTGF) and whole (W-CTGF). Serum levels of W-CTGF and N-half CTGF + W-CTGF were determined by separate sandwich enzyme-linked immunosorbent assays. The level of W-CTGF was significantly lower (P < 0.005) in MM patients compared with ML patients and normal individuals, while N-half + W-CTGF was similar in all groups. Furthermore, W-CTGF was significantly lower in MM patients with BD compared with those without BD (P < 0.005) and this was independent of previous treatment. Matrix metalloproteinase (MMP)-9 is produced by myeloma cells and is thought to be related to BD in MM. However, MMP-9 does not cleave CTGF and serum MMP-9 level was not related to BD in MM. Thus, CTGF is an indicator of BD in MM; its metabolism and function in MM should be clarified.

CCN5 expression in mammals : I. Embryonic and fetal tissues of mouse and human

The six proteins of the CCN family have important roles in development, angiogenesis, cell motility, proliferation, and other fundamental cell processes. To date, CCN5 distribution in developing rodents and humans has not been mapped comprehensively. CCN5 strongly inhibits adult smooth muscle cell proliferation and motility. Its anti-proliferative action predicts that CCN5 would not be present in developing tissues until the proliferation phase of tissue morphogenesis is complete. However, estrogen induces CCN5 expression in epithelial and smooth muscle cells, suggesting that CCN5 might be widely expressed in embryonic tissues exposed to high levels of estrogen. 9-16 day murine embryos and fetuses and 3-7 month human fetal tissues were analyzed by immunohistochemistry. CCN5 was detected in nearly all developing tissues. CCN5 protein expression was initially present in most tissues, and at later times in development tissue-specific expression differences were observed. CCN5 expression was particularly strong in vascular tissues, cardiac muscle, bronchioles, myotendinous junctions, and intestinal smooth muscle and epithelium. CCN5 expression was initially absent in bone cartilaginous forms but was increasingly expressed during bone endochondral ossification. Widespread CCN5 mRNA expression was detected in GD14.5 mice. Although CCN2 and CCN5 protein expression patterns in some adult pathologic conditions are inversely expressed, this expression pattern was not found in developing mouse and human tissues. The widespread expression pattern of CCN5 in most embryonic and fetal tissues suggests a diverse range of functions for CCN5.

Role of CCN2/CTGF/Hcs24 in bone growth

Our bones mostly develop through a process called endochondral ossification. This process is initiated in the cartilage prototype of each bone and continues through embryonic and postnatal development until the end of skeletal growth. Therefore, the central regulator of endochondral ossification is the director of body construction, which is, in other words, the determinant of skeletal size and shape. We suggest that CCN2/CTGF/Hcs24 (CCN2) is a molecule that conducts all of the procedures of endochondral ossification. CCN2, a member of the CCN family of novel modulator proteins, displays multiple functions by manipulating the local information network, using its conserved modules as an interface with a variety of other biomolecules. Under a precisely designed four-dimensional genetic program, CCN2 is produced from a limited population of chondrocytes and acts on all of the mesenchymal cells inside the bone callus to promote the integrated growth of the bone. Furthermore, the utility of CCN2 as regenerative therapeutics against connective tissue disorders, such as bone and cartilage defects and osteoarthritis, has been suggested. Over the years, the pathological action of CCN2 has been suggested. Nevertheless, it can also be regarded as another aspect of the physiological and regenerative function of CCN2, which is discussed as well.

CCN family proteins and angiogenesis: from embryo to adulthood

The CCN family is a novel class of extracellular signal modulators that has been recently established. Typical members are composed of four conserved modules connected tandem, each of which is rich in cysteines and highly interactive with other molecules. The mammalian CCN family consists of six members, most of which have been described as multifunctional factors for the developmental process of mesenchymal tissue including blood vessel formation/induction. Particularly, the angiogenic properties of the three classical members, CCN1, 2 and 3 have so far been characterized, and their physiological and pathological significance has thus been indicated. Recent research has uncovered a unique mechanism regarding these proteins in promoting and/or modulating developmental, physiological and pathological angiogenic events. Namely, CCN proteins exert their ability to drive angiogenesis, not by stimulating a particular behavior of a particular type of cells, but by manipulating the cell communication networks that integrate most of the associated molecules/cells toward angiogenesis. In this article, the role of the CCN proteins in a variety of angiogenic events as an organizer of microenvironmental cell society is comprehensively described, together with a brief summary of the recent findings on each CCN family member relevant to angiogenesis including cardiovascular development and diseases.

NOV/CCN3 induces adhesion of muscle skeletal cells and cooperates with FGF2 and IGF-1 to promote proliferation and survival

During mammalian development, expression of the Nephroblastoma overexpressed gene (NOV/CCN3) is tightly regulated in skeletal muscles. Ex vivo, ectopic expression of NOV blocks myogenic differentiation. NOV also supports endothelial cell adhesion and angiogenesis through interactions with integrins. Integrins play fundamental roles during myogenesis. In this study, we show that NOV mediates adhesion and spreading of myoblasts. Myoblasts adhesion to NOV does not require proteoglycans and is dependent on integrin beta1, whereas spreading involves another RGD-sensitive integrin. The C-Terminal part of NOV as well as full-length is able to support adhesion of myoblasts; in addition, both increase focal-adhesion kinase (FAK) phosphorylation. Furthermore, NOV is an adhesive substrate that, combined with FGF2 or IGF-1, promotes cell specific proliferation and survival, respectively, in a better way than fibronectin. Taken together, these results identify NOV as an adhesion substrate for myoblasts which, in concert with growth factors, could play a role in the physiology of muscle cells.

Novel angiogenic inhibitor DN-9693 that inhibits post-transcriptional induction of connective tissue growth factor (CTGF/CCN2) by vascular endothelial growth factor in human endothelial cells

Connective tissue growth factor (CTGF/CCN2) is a potent angiogenic factor. In this report, we describe for the first time that vascular endothelial growth factor (VEGF)-mediated induction of the ctgf/ccn2 gene was a post-transcriptional event that was inhibited by a novel angiogenic inhibitor, DN-9693, in human umbilical vein endothelial cells. Steady-state mRNA levels of ctgf/ccn2 were remarkably increased by VEGF in a concentration-dependent manner, whereas the activity of the ctgf/ccn2 promoter was not responsive to VEGF as confirmed by a reporter gene assay and quantitative real-time PCR analysis. By employing a RNA degradation assay, we eventually found that the observed increase in the ctgf/ccn2 mRNA level was due to an increased stability of the mRNA induced by VEGF. DN-9693 at a dose of 0.1 to 2 ng/mL did not affect basal levels of ctgf/ccn2 mRNA; however, enhancement of ctgf/ccn2 mRNA expression by VEGF was specifically inhibited by DN-9693. Of importance, the inhibitory effects could be also ascribed to post-transcriptional regulation, because the VEGF-mediated increase in stability of ctgf/ccn2 mRNA was suppressed by DN-9693. Furthermore, we investigated the effects of DN-9693 on VEGF-induced activation of three subgroups of mitogen-activated protein kinase pathways and found that DN-9693 blocked the activation of these pathways by VEGF. These results suggest that VEGF increases ctgf/ccn2 mRNA stability through mitogen-activated protein kinase-mediated intracellular signaling cascade(s), which can be inhibited posttranscriptionally by a novel angiogenic inhibitor, DN-9693, in human umbilical vein endothelial cells.

Selenium, the thyroid, and the endocrine system

Recent identification of new selenocysteine-containing proteins has revealed relationships between the two trace elements selenium (Se) and iodine and the hormone network. Several selenoproteins participate in the protection of thyrocytes from damage by H(2)O(2) produced for thyroid hormone biosynthesis. Iodothyronine deiodinases are selenoproteins contributing to systemic or local thyroid hormone homeostasis. The Se content in endocrine tissues (thyroid, adrenals, pituitary, testes, ovary) is higher than in many other organs. Nutritional Se depletion results in retention, whereas Se repletion is followed by a rapid accumulation of Se in endocrine tissues, reproductive organs, and the brain. Selenoproteins such as thioredoxin reductases constitute the link between the Se metabolism and the regulation of transcription by redox sensitive ligand-modulated nuclear hormone receptors. Hormones and growth factors regulate the expression of selenoproteins and, conversely, Se supply modulates hormone actions. Selenoproteins are involved in bone metabolism as well as functions of the endocrine pancreas and adrenal glands. Furthermore, spermatogenesis depends on adequate Se supply, whereas Se excess may impair ovarian function. Comparative analysis of the genomes of several life forms reveals that higher mammals contain a limited number of identical genes encoding newly detected selenocysteine-containing proteins.

New target genes for NOV/CCN3 in chondrocytes: TGF-beta2 and type X collagen

We studied the involvement of NOV/CCN3, whose function is poorly understood, in chondrocyte differentiation. NOV was found to upregulate TGF-beta2 and type X collagen and to act as a downstream effector of TGF-beta1 in ATDC5 and primary chondrocytes. Thus, NOV is a positive modulator of chondrogenesis.

INTRODUCTION

NOV/CCN3 is a matricellular protein that belongs to the CCN family. A growing body of evidence indicates that NOV could play a role in cell differentiation, particularly in chondrogenesis. During chick embryo development, NOV expression is tightly regulated in cartilage, and a high expression of NOV has been associated with cartilage differentiation in Wilms' tumors. However, a precise role for NOV and potential target genes of NOV in chondrogenesis are unknown.

MATERIALS AND METHODS

ATDC5 cells and primary chondrocytes were either treated with NOV recombinant protein or transfected with a NOV-specific siRNA to determine, using quantitative RT-PCR, the effect of NOV on the expression of several molecules involved in chondrocyte differentiation. Stable ATDC5 clones expressing NOV were also established to show that NOV was a downstream effector of TGF-beta1.

RESULTS

We established that NOV/CCN3 expression increases in ATDC5 cells at early stages of chondrogenic differentiation and precedes the appearance of TGF-beta2 and of several chondrocytic markers such as SOX9 or type X collagen. When exogenously administered, NOV recombinant protein up-regulates TGF-beta2 and type X collagen mRNA levels both in ATDC5 cells and in primary mouse chondrocytes but does not influence SOX9 expression. This regulation also occurs at the endogenous level because downregulation of NOV expression is correlated with an inhibition of TGF-beta2 and type X collagen in primary chondrocytes. Furthermore, we found that NOV expression is downregulated when chondrocytes are exposed to TGF-beta1-dedifferentiating treatment in chondrocytes, further providing evidence that NOV may counteract TGF-beta1 effects on chondrocytes.

CONCLUSIONS

This study provides the first characterization of two new targets of NOV involved in chondrocyte differentiation, shows that NOV acts with TGF-beta1 in a cascade of gene regulation, and indicates that NOV is a positive modulator of chondrogenesis.

Hypoxic regulation of stability of connective tissue growth factor/CCN2 mRNA by 3′-untranslated region interacting with a cellular protein in human chondrosarcoma cells

Connective tissue growth factor (CTGF/CCN2) can be induced by various forms of stress such as exposure to high glucose, mechanical load, or hypoxia. Here, we investigated the molecular mechanism involved in the induction of ctgf/ccn2 by hypoxia in a human chondrosarcoma cell line, HCS-2/8. Hypoxia increased the ctgf/ccn2 mRNA level by altering the 3'-untranslated region (UTR)-mediated mRNA stability without requiring de novo protein synthesis. After a series of extensive analyses, we eventually found that the cis-repressive element of 84 bases within the 3'-UTR specifically bound to a cytoplasmic/nuclear protein. By conducting a UV crosslinking assay, we found the cytoplasmic/nuclear protein to be a 35 kDa molecule that bound to the cis-element in a hypoxia-inducible manner. These results suggest that a cis-element in the 3'-UTR of ctgf/ccn2 mRNA and trans-factor counterpart(s) play an important role in the post-transcriptional regulation by determining the stability of ctgf/ccn2 mRNA.

Collaborative action of M-CSF and CTGF/CCN2 in articular chondrocytes: possible regenerative roles in articular cartilage metabolism

It is known that expression of the macrophage colony-stimulating factor (M-CSF) gene is induced in articular chondrocytes upon inflammation. However, the functional role of M-CSF in cartilage has been unclear. In this study, we describe possible roles of M-CSF in the protection and maintenance of the articular cartilage based on the results of experiments using human chondrocytic cells and rat primary chondrocytes. Connective tissue growth factor (CTGF/CCN2) is known to be a potent molecule to regenerate damaged cartilage by promoting the growth and differentiation of articular chondrocytes. Here, we uncovered the fact that M-CSF induced the mRNA expression of the ctgf/ccn2 gene in those cells. Enhanced production of CTGF/CCN2 protein by M-CSF was also confirmed. Furthermore, M-CSF could autoactivate the m-csf gene, forming a positive feed-back network to amplify and prolong the observed effects. Finally, promotion of proteoglycan synthesis was observed by the addition of M-CSF. These findings taken together indicate novel roles of M-CSF in articular cartilage metabolism in collaboration with CTGF/CCN2, particularly during an inflammatory response. Such roles of M-CSF were further supported by the distribution of M-CSF producing chondrocytes in experimentally induced rat osteoarthritis cartilage in vivo.

Differential expression of CCN-family members in primary human bone marrow-derived mesenchymal stem cells during osteogenic, chondrogenic and adipogenic differentiation

Background

The human cysteine rich protein 61 (CYR61, CCN1) as well as the other members of the CCN family of genes play important roles in cellular processes such as proliferation, adhesion, migration and survival. These cellular events are of special importance within the complex cellular interactions ongoing in bone remodeling. Previously, we analyzed the role of CYR61/CCN1 as an extracellular signaling molecule in human osteoblasts. Since mesenchymal stem cells of bone marrow are important progenitors for various differentiation pathways in bone and possess increasing potential for regenerative medicine, here we aimed to analyze the expression of CCN family members in bone marrow-derived human mesenchymal stem cells and along the osteogenic, the adipogenic and the chondrogenic differentiation.

Results

Primary cultures of human mesenchymal stem cells were obtained from the femoral head of patients undergoing total hip arthroplasty. Differentiation into adipocytes and osteoblasts was done in monolayer culture, differentiation into chondrocytes was induced in high density cell pellet cultures. For either pathway, established differentiation markers and CCN-members were analyzed at the mRNA level by RT-PCR and the CYR61/CCN1 protein was analyzed by immunocytochemistry.

RT-PCR and histochemical analysis revealed the appropriate phenotype of differentiated cells (Alizarin-red S, Oil Red O, Alcian blue, alkaline phosphatase; osteocalcin, collagen types I, II, IX, X, cbfa1, PPARγ, aggrecan). Mesenchymal stem cells expressed CYR61/CCN1, CTGF/CCN2, CTGF-L/WISP2/CCN5 and WISP3/CCN6. The CYR61/CCN1 expression decreased markedly during osteogenic differentiation, adipogenic differentiation and chondrogenic differentiation. These results were confirmed by immuncytochemical analyses. WISP2/CCN5 RNA expression declined during adipogenic differentiation and WISP3/CCN6 RNA expression was markedly reduced in chondrogenic differentiation.

Conclusion

The decrease in CYR61/CCN1 expression during the differentiation pathways of mesenchymal stem cells into osteoblasts, adipocytes and chondrocytes suggests a specific role of CYR61/CCN1 for maintenance of the stem cell phenotype. The differential expression of CTGF/CCN2, WISP2/CCN5, WISP3/CCN6 and mainly CYR61/CCN1 indicates, that these members of the CCN-family might be important regulators for bone marrow-derived mesenchymal stem cells in the regulation of proliferation and initiation of specific differentiation pathways.

Role of a new member of IGFBP superfamily, IGFBP-rP10, in proliferation and differentiation of osteoblastic cells

Bone regeneration is critically regulated by various molecules. To identify the new genes involved in bone regeneration, we performed microarray-based gene expression analysis using a mouse bone regeneration model. We identified a new member of the IGFBP superfamily, designated IGFBP-rP10, whose expression is up-regulated at the early phase of bone regeneration. IGFBP-rP10 consists of an IGFBP homologous domain followed by a Kazal-type protein inhibitor domain and an immunoglobulin G-like domain. A real-time-based RT-PCR analysis demonstrated that various tissues including bone expressed IGFBP-rP10 mRNA in various degrees, and confirmed an up-regulation at the early phase of bone regeneration. In situ hybridization revealed that osteoblastic cells expressed IGFPB-rP10 mRNA during bone regeneration. Bone morphogenetic protein-2 increased the expression level of IGFBP-rP10 mRNA in various cells including C3H10T1/2, MC3T3-E1, C2C12, and primary murine osteoblastic cells. The addition of recombinant mouse IGFBP-rP10 promoted the proliferation of these cells but failed to stimulate alkaline phosphatase activity. These results suggest that IGFBP-rP10 is involved in the proliferation of osteoblasts during bone formation and bone regeneration.

WISP-1 is an osteoblastic regulator expressed during skeletal development and fracture repair

Wnt-1-induced secreted protein 1 (WISP-1) is a member of the CCN (connective tissue growth factor, Cyr61, NOV) family of growth factors. Experimental evidence suggests that CCN family members are involved in skeletogenesis and bone healing. To investigate the role of WISP-1 in osteogenic processes, we characterized its tissue and cellular expression and evaluated its activity in osteoblastic and chondrocytic cell culture models. During embryonic development, WISP-1 expression was restricted to osteoblasts and to osteoblastic progenitor cells of the perichondral mesenchyme. In vitro, we showed that WISP-1 expression in differentiating osteoblasts promotes BMP-2-induced osteoblastic differentiation. Using in situ and cell binding analysis, we demonstrated WISP-1 interaction with perichondral mesenchyme and undifferentiated chondrocytes. We evaluated the effect of WISP-1 on chondrocytes by generating stably transfected mouse chondrocytic cell lines. In these cells, WISP-1 increased proliferation and saturation density but repressed chondrocytic differentiation. Because of the similarity between skeletogenesis and bone healing, we also analyzed WISP-1 spatiotemporal expression in a fracture repair model. We found that WISP-1 expression recapitulates the pattern observed during skeletal development. Our data demonstrate that WISP-1 is an osteogenic potentiating factor promoting mesenchymal cell proliferation and osteoblastic differentiation while repressing chondrocytic differentiation. Therefore, we propose that WISP-1 plays an important regulatory role during bone development and fracture repair.

Transcriptional profiling of estrogen-regulated gene expression via estrogen receptor (ER) alpha or ERbeta in human osteosarcoma cells: distinct and common target genes for these receptors

Estrogens exert many important effects in bone, a tissue that contains both estrogen receptors alpha and beta (ERalpha and ERbeta). To compare the actions of these receptors, we generated U2OS human osteosarcoma cells stably expressing ERalpha or ERbeta, at levels comparable with those in osteoblasts, and we characterized their response to 17beta-estradiol (E2) over time using Affymetrix GeneChip microarrays to determine the expression of approximately 12,000 genes, followed by quantitative PCR verification of the regulation of selected genes. Of the approximately 100 regulated genes we identified, some were stimulated by E2 equally through ERalpha and ERbeta, whereas others were selectively stimulated via ERalpha or ERbeta. The E2-regulated genes showed three distinct temporal patterns of expression over the 48-h time course studied. Of the functional categories of the E2-regulated genes, most numerous were those encoding cytokines and factors associated with immune response, signal transduction, and cell migration and cytoskeleton regulation, indicating that E2 can exert effects on multiple pathways in these osteoblast-like cell lines. Of note, E2 up-regulated several genes associated with cell motility selectively via ERbeta, in keeping with the selective E2 enhancement of the motility of ERbeta-containing cells. On genes regulated equally by E2 via ERalpha or ERbeta, the phytoestrogen genistein preferentially stimulated gene expression via ERbeta. These studies indicate both common as well as distinct target genes for these two ERs, and identify many novel genes not previously known to be under estrogen regulation.

CCN5 modulates the antiproliferative effect of heparin and regulates cell motility in vascular smooth muscle cells

Background

Vascular smooth muscle cell (VSMC) hyperplasia plays an important role in both chronic and acute vascular pathologies including atherosclerosis and restenosis. Considerable work has focused on the mechanisms regulating VSMC proliferation and motility. Earlier work in our lab revealed a novel growth arrest-specific (gas) gene induced in VSMC exposed to the antiproliferative agent heparin. This gene is a member of the CCN family and has been given the name CCN5. The objective of the present study is to elucidate the function of CCN5 protein and to explore its mechanism of action in VSMC.

Results

Using RNA interference (RNAi), we first demonstrate that CCN5 is required for the antiproliferative effect of heparin in VSMC. We also use this gene knockdown approach to show that CCN5 is an important negative regulator of motility. To explore the mechanism of action of CCN5 on VSMC motility, we use RNAi to demonstrate that knock down of CCN5 up regulates expression of matrix metalloproteinase-2 (MMP-2), an important stimulator of motility in VSMC. In addition, forced expression of CCN5 via adenovirus results in reduced MMP-2 activity, this also corroborates the gene knock down results. Finally, we show that loss of CCN5 expression in VSMC causes changes in VSMC morphology and cytoskeletal organization, including a reduction in the amount and macromolecular assembly of smooth muscle cell α-actin.

Conclusions

This work provides important new insights into the regulation of smooth muscle cell proliferation and motility by CCN5 and may aid the development of therapies for vascular diseases.

Transcriptional induction of connective tissue growth factor/hypertrophic chondrocyte-specific 24 gene by dexamethasone in human chondrocytic cells

Connective tissue growth factor (CTGF/Hcs24) is a critical growth factor for chondrocytic growth and differentiation. In this report, we describe for the first time glucocorticoid-mediated induction of the CTGF/Hcs24 gene in a chondrocytic cell line, HCS-2/8. Steady-state mRNA levels of CTGF/Hcs24 were remarkably increased after treatment with 50 nM dexamethasone, as confirmed by Northern blotting and quantitative real-time polymerase chain reaction (PCR) analysis. Corresponding to the increase in mRNA, production of CTGF/Hcs24 protein was remarkably enhanced, following a time course of up to 6 h. The observed increase in mRNA can be ascribed to transcriptional enhancement, since the stability of CTGF/Hcs24 mRNA was not affected by the same concentration of dexamethasone, which was indicated by the results of an mRNA degradation assay. However, unexpectedly, the prototypic ctgf/hcs24 promoter was not responsible for the dexamethasone stimulation, suggesting the glucocorticoid receptor binding site(s) to be elsewhere in the CTGF/Hcs24 gene. Enhancement of the prototypic promoter activity by dexamethasone was observed in murine fibroblastic cells, demonstrating the complexity of the regulatory mechanism of ctgf/hcs24 gene expression. Of importance, dexamethasone at the same concentration significantly stimulated proteoglycan synthesis in HCS-2/8 cells up to the same levels as exogenously added CTGF/Hcs24. These findings represent a novel effect of glucocorticoid on the production of CTGF/Hcs24 by chondrocytic cells, and indicate that CTGF/Hcs24 may mediate the stimulative effect of dexamethasone on chondrocytic phenotypes. Also, our results shed light on the complex mechanism of CTGF/Hcs24 induction by glucocorticoids.

A structural approach to the role of CCN (CYR61/CTGF/NOV) proteins in tumourigenesis

The CCN (CYR61 [Cystein-rich61]/CTGF [connective tissue growth factor]/NOV [Nephroblastoma overexpressed]) proteins constitute a family of regulatory factors involved in many aspects of cell proliferation and differentiation. An increasing body of evidence indicates that abnormal expression of the CCN proteins is associated to tumourgenesis. The multimodular architecture of the CCN proteins, and the production of truncated isoforms in tumours, raise interesting questions regarding the participation of each individual module to the various biological properties of these proteins. In this article, we review the current data regarding the involvement of CCN proteins in tumourigenesis. We also attempt to provide structural basis for the stimulatory and inhibitory functions of the full length and truncated CCN proteins that are expressed in various tumour tissues.

Human WISP1v, a member of the CCN family, is associated with invasive cholangiocarcinoma

Family members of the connective tissue growth factor, cysteine-rich 61, nephroblastoma over-expressed gene (CCN) encode cysteine-rich secreted proteins with roles in human fibrotic disorders and tumor progression. In this study, we identified a CCN family member, WISP1v, as over-expressed in human cholangiocarcinomas. Genetic analysis of WISP1v was performed on surgically resected specimens of cholangiocarcinoma. The WISP1v biological effects were analyzed using the HuCCT1 human cholangiocarcinoma cell line. The WISP1v gene was expressed in 19 of 39 cholangiocarcinoma tissues (49%) but not in normal livers. Expression of WISP1v was significantly associated with lymphatic and perineural invasion of tumor cells (P <.05), as well as a poor clinical prognosis (P <.01). In the intraductal papillary cholangiocarcinomas, WISP1v was detected only in the cases with duct wall invasion but not in the cases without duct wall invasion (P <.05). No mutation of WISP1v gene was detected in the examined samples. In vitro analysis revealed that WISP1v stimulated the invasive phenotype of cholangiocarcinoma cells with activation of both p38 and p42/p44 mitogen-activated protein kinases (MAPKs). Furthermore, WISP1v-induced cholangiocarcinoma invasion was significantly suppressed by the p38 MAPK inhibitor SB203580 but not by the p42/p44 MAPK kinase (MEK) inhibitor PD98059. Our findings suggest that WISP1v-mediated signaling is involved in the generation of invasive cellular properties and leads to progression of cholangiocarcinoma.

Adhesion of endothelial cells to NOV is mediated by the integrins alphavbeta3 and alpha5beta1

NOV is a member of the CCN family of matricellular proteins. We have shown previously that NOV is strongly expressed by vascular smooth muscle cells (VSMCs) of the rat carotid artery. However, 7 days after injury, NOV expression is down-regulated, except near the luminal surface of the developing intima, where it is strongly expressed. These data suggested that NOV might be involved in the regulation of endothelial cell adhesion. NOV promoted the adhesion of human umbilical vein endothelial cells (HUVECs), which was abolished by anti-NOV antibody. HUVEC adhesion to NOV required divalent cations and was inhibited by GRGDS peptide, implicating integrins in the adhesion mechanism. Monoclonal antibodies (mAbs) against alphavbeta3 inhibited adhesion of HUVECs to NOV, and NOV was shown to bind to alphavbeta3. Anti-alpha5beta1 mAbs also inhibited HUVEC adhesion to NOV, but adhesion via alpha5beta1 was mediated by fibronectin. HUVEC adhesion to NOV caused intracellular signalling, as evidenced by increased phosphotyrosine content of focal adhesion kinase. Together with evidence that NOV expression in a variety of tissues is restricted to blood vessels containing VSMCs, these data are consistent with a role for NOV in endothelial cell adhesion in vascular homeostasis and in the response to injury.

Role of CTGF/HCS24/ecogenin in skeletal growth control

Connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) is a multifunctional growth factor for chondrocytes, osteoblasts, and vascular endothelial cells. CTGF/Hcs24 promotes the proliferation and maturation of growth cartilage cells and articular cartilage cells in culture and hypertrophy of growth cartilage cells in culture. The factor also stimulates the proliferation and differentiation of cultured osteoblastic cells. Moreover, CTGF/Hcs24 promotes the adhesion, proliferation, and migration of vascular endothelial cells, as well as induces tube formation by the cells and strong angiogenesis in vivo. Because angiogenesis is critical for the replacement of cartilage with bone at the final stage of endochondral ossification and because gene expression of CTGF/Hcs24 predominates in hypertrophic chondrocytes in the physiological state, a major physiological role for this factor should be the promotion of the entire process of endochondral ossification, with the factor acting on the above three types of cells as a paracrine factor. Thus, CTGF/Hcs24 should be called "ecogenin: endochondral ossification genetic factor." In addition to hypertrophic chondrocytes, osteoblasts activated by various stimuli including wounding also express a significantly high level of CTGF/Hcs24. These findings in conjunction with in vitro findings about osteoblasts mentioned above suggest the involvement of CTGF/Hcs24 in intramembranous ossification and bone modeling/remodeling. Because angiogenesis is also critical for intramembranous ossification and bone remodeling, CTGF/Hcs24 expressed in endothelial cells activated by various stimuli including wounding may also play important roles in direct bone formation. In conclusion, although the most important physiological role of CTGF/Hcs24 is ecogenin action, the factors also play important roles in skeletal growth and modeling/remodeling via its direct action on osteoblasts under both physiological and pathological conditions.

CCN5 is a growth arrest-specific gene that regulates smooth muscle cell proliferation and motility

Vascular smooth muscle cell (VSMC) hyperplasia plays an important role in both chronic and acute vascular pathologies. Considerable work has focused on the mechanisms regulating VSMC growth and the search for agents that could suppress VSMC hyperproliferation. One of the several inhibitors studied is the glycosaminoglycan heparin, which inhibits VSMC proliferation and migration both in cell culture and in animal models (Mishra-Gorur K, Delmolino LM, Castellot Jr JJ: Biological functions of heparan sulfate and heparan sulfate proteoglycans. Trends Glycosci Glycotechnol 1998, 10:193-210). To aid our understanding of the anti-proliferative mechanism of action of heparin, we used a subtractive hybridization approach to isolate and characterize a novel growth arrest-specific (gas) gene induced in VSMCs exposed to heparin (Delmolino LM, Stearns NA, Castellot Jr JJ: Heparin induces a member of the CCN family which has characteristics of a growth arrest specific gene. Mol Biol Cell 1997, 8:287a and Delmolino LM, Stearns NA, Castellot Jr JJ: COP-1, a member of the CCN family, is a heparin-induced growth arrest specific gene in vascular smooth muscle cells. J Cell Physiol 2001, 188:45-55). This gene is a member of the cysteine-rich 61/connective tissue growth factor/nephroblastoma-overexpressed (CCN) family and has been given the name CCN5. In this report, we provide functional evidence that CCN5 can inhibit VSMC proliferation, motility, and invasiveness. In contrast, adhesion and apoptosis are unaffected by CCN5 in this cell type. We also significantly extend previous data from our laboratory that suggests CCN5 is a growth arrest-specific (gas) gene. Furthermore, we map for the first time the cellular localization of CCN5 protein in cultured VSMCs. We also examine uninjured and balloon-injured rat carotid arteries for CCN5 expression. The results from the in vitro and in vivo localization studies show that CCN5 is temporally and spatially expressed in a manner consistent with a role in regulating proliferation, motility, and invasiveness of VSMCs.

CTGF/Hcs24 interacts with the cytoskeletal protein actin in chondrocytes

Connective tissue growth factor/hypertrophic chondrocyte-specific gene product 24 (CTGF/Hcs24) displays multiple functions in several types of mesenchymal cells, including the promotion of proliferation and differentiation of chondrocytes. Recently, the internalization and intracellular function of CTGF/Hcs24 were indicated as well. In this study, a binding protein for this factor was purified from the cytosolic fraction of human chondrosarcoma-derived chondrocytic cell line (HCS-2/8) by CTGF/Hcs24-affinity chromatography. The apparent molecular weight of the protein was 42kDa and determination of the internal amino acid sequence revealed this protein to be beta- or gamma-actin. An in vitro competitive binding assay of 125I-labeled recombinant CTGF/Hcs24 with cold-rCTGF/Hcs24 showed that the binding between actin and 125I-CTGF/Hcs24 was specific. Immunoprecipitation analysis also showed that CTGF/Hcs24 bound to actin in HCS-2/8 cells. However, rCTGF/Hcs24 had no effects on the expression level of gamma-actin mRNA or total actin protein. These findings suggest that a significant portion of intracellular CTGF/Hcs24 may regulate certain cell biological events in chondrocytes through the interaction with this particular cytoskeletal protein.

The expression of novH in adrenocortical cells is down-regulated by TGFbeta 1 through c-Jun in a Smad-independent manner

The human NOV secreted glycoprotein (NOVH) is abundant in the fetal and adult adrenal cortex. The amount of NOVH increases in benign adrenocortical tumors and decreases in malignant adrenocortical tumors, suggesting that NOVH plays a role in tumorigenesis in the adrenal cortex. Transforming growth factor beta1 (TGFbeta1), fibroblast growth factor 2 (FGF2), and insulin growth factors (IGFs) play crucial roles in the physiology of the adrenal cortex. We investigated the effects of these factors on the expression of novH in the NCI H295R adrenocortical cell line. The amounts of NOVH protein and novH transcripts were down-regulated by TGFbeta1 and up-regulated by FGF2, whereas IGFs had no effect. Furthermore, the TGFbeta1-dependent inhibition of novH promoter activity was completely abrogated following site-directed mutation of two activating protein (AP-1) sequences (positions -473 and -447), whereas the stimulatory effect of FGF2 was not affected. Co-transfection with dominant negative forms of c-Jun and MEKK1 also abrogated novH-targeted regulation by TGFbeta1, whereas the overproduction of Smad proteins or dominant negative forms of Smad had no effect. Taken together, these results suggest that c-Jun and MEKK1 signaling but not Smad signaling are involved in the TGFbeta1-dependent decrease in NOVH in NCI H295R cells. In conclusion, our data provide evidence that novH is a new target of TGFbeta1; unlike other members of the CCN (cyr61, ctgf, nov) family, however, its expression is repressed rather than induced.

Tyrosine kinase-type receptor ErbB4 in chondrocytes: interaction with connective tissue growth factor and distribution in cartilage

In order to identify receptor molecules that participate in the growth and differentiation of chondrocytes, we cloned a number of cDNA fragments from HCS-2/8 chondrocytic cells, by using tyrosine kinase-specific primers for amplification. The mRNA expression of one such receptor, ErbB4, was increased by connective tissue growth factor/hypertrophic chondrocyte-specific gene product (CTGF/Hcs24), which promotes all stages of the endochondral ossification in vitro. ErbB4 expression was observed through all stages of chondrocytic differentiation in vitro, corresponding to the wide distribution of CTGF/Hcs24 target cells. Furthermore, positive signals for erbB4 mRNA were detectable throughout most populations of chondrocytes, in growth and articular cartilage in vivo. These results demonstrate for the first time that ErbB4 is expressed in chondrocytes and may play some roles in chondrocytic growth and differentiation along with CTGF/Hcs24.