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

Involvement of cis-acting repressive element(s) in the 3'-untranslated region of human connective tissue growth factor gene

To analyze the regulatory mechanism of connective tissue growth factor expression, the 3'-untranslated region (3'-UTR) of CTGF cDNA was amplified from HeLa cell RNA. Direct nucleotide sequencing revealed a single major population in the amplicon, which was nearly identical to other sequences. Subsequently, the effect of the 3'-UTR on gene expression was evaluated. When it was fused downstream of a firefly luciferase gene, the 3'-UTR strongly repressed luciferase gene expression. Interestingly, the repressive effect of the antisense 3'-UTR appeared to be more prominent than that of the sense one. Together with the fact that several consensus sequences for regulatory elements are found in it, these results suggest the involvement of multiple sets of regulatory elements in the CTGF 3'-UTR.

Connective tissue growth factor (IGFBP-rP2) expression and regulation in cultured bovine endothelial cells

Media from large vessel endothelial cells (pulmonary artery, aorta) contained intact connective tissue growth factor (CTGF) and a dominant 19-kDa band. N-terminal analysis of the 19-kDa band showed sequence corresponding to CTGF amino acid 181-190, suggesting that the 19-kDa band represented a proteolytic fragment of CTGF. Intact CTGF was increased by cAMP but not by transforming growth factor-beta (TGFbeta). CTGF messenger RNA (mRNA) was not changed by cAMP nor TGFbeta. In two microvessel endothelial cells, mRNA was found at low levels by PCR and Northern analysis, but no CTGF protein was seen on Western analysis. In the microvessel cells, TGFbeta increased and cAMP did not change CTGF mRNA levels, with neither TGFbeta nor cAMP increasing CTGF protein. The discordance between protein and mRNA levels in large vessel and microvessel endothelial cells was mostly explained by the effects of cAMP and TGFbeta on media proteolytic activity; in large vessel cells, cAMP inhibited degradation of CTGF, whereas in microvessel cells, TGFbeta and cAMP stimulated proteolytic activity against CTGF. We conclude that in large vessel endothelial cells, cAMP increased intact CTGF protein by inhibiting degradation of CTGF, whereas TGFbeta stimulated neither CTGF mRNA nor protein; in microvessel cells, TGFbeta increased CTGF mRNA, while both TGFbeta and cAMP stimulated CTGF degradation.

Fisp12/mouse connective tissue growth factor mediates endothelial cell adhesion and migration through integrin alphavbeta3, promotes endothelial cell survival, and induces angiogenesis in vivo

Fisp12 was first identified as a secreted protein encoded by a growth factor-inducible immediate-early gene in mouse fibroblasts, whereas its human ortholog, CTGF (connective tissue growth factor), was identified as a mitogenic activity in conditioned media of human umbilical vein endothelial cells. Fisp12/CTGF is a member of a family of secreted proteins that includes CYR61, Nov, Elm-1, Cop-1/WISP-2, and WISP-3. Fisp12/CTGF has been shown to promote cell adhesion and mitogenesis in both fibroblasts and endothelial cells and to stimulate cell migration in fibroblasts. These findings, together with the localization of Fisp12/CTGF in angiogenic tissues, as well as in atherosclerotic plaques, suggest a possible role for Fisp12/CTGF in the regulation of vessel growth during development, wound healing, and vascular disease. In this study, we show that purified Fisp12 (mCTGF) protein promotes the adhesion of microvascular endothelial cells through the integrin receptor alphavbeta3. Furthermore, Fisp12 stimulates the migration of microvascular endothelial cells in culture, also through an integrin-alphavbeta3-dependent mechanism. In addition, the presence of Fisp12 promotes endothelial cell survival when cells are plated on laminin and deprived of growth factors, a condition that otherwise induces apoptosis. In vivo, Fisp12 induces neovascularization in rat corneal micropocket implants. These results demonstrate that Fisp12 is a novel angiogenic inducer and suggest a direct role for Fisp12 in the adhesion, migration, and survival of endothelial cells during blood vessel growth. Taken together with the recent finding that the related protein CYR61 also induces angiogenesis, we suggest that Fisp12/mCTGF and CYR61 comprise prototypes of a new family of angiogenic regulators that function, at least in part, through integrin-alphavbeta3-dependent pathways.

Suppression subtractive hybridization identifies high glucose levels as a stimulus for expression of connective tissue growth factor and other genes in human mesangial cells

Accumulation of mesangial matrix is a pivotal event in the pathophysiology of diabetic nephropathy. The molecular triggers for matrix production are still being defined. Here, suppression subtractive hybridization identified 15 genes differentially induced when primary human mesangial cells are exposed to high glucose (30 mM versus 5 mM) in vitro. These genes included (a) known regulators of mesangial cell activation in diabetic nephropathy (fibronectin, caldesmon, thrombospondin, and plasminogen activator inhibitor-1), (b) novel genes, and (c) known genes whose induction by high glucose has not been reported. Prominent among the latter were genes encoding cytoskeleton-associated proteins and connective tissue growth factor (CTGF), a modulator of fibroblast matrix production. In parallel experiments, elevated CTGF mRNA levels were demonstrated in glomeruli of rats with streptozotocin-induced diabetic nephropathy. Mannitol provoked less mesangial cell CTGF expression in vitro than high glucose, excluding hyperosmolality as the key stimulus. The addition of recombinant CTGF to cultured mesangial cells enhanced expression of extracellular matrix proteins. High glucose stimulated expression of transforming growth factor beta1 (TGF-beta1), and addition of TGF-beta1 to mesangial cells triggered CTGF expression. CTGF expression induced by high glucose was partially suppressed by anti-TGF-beta1 antibody and by the protein kinase C inhibitor GF 109203X. Together, these data suggest that 1) high glucose stimulates mesangial CTGF expression by TGFbeta1-dependent and protein kinase C dependent pathways, and 2) CTGF may be a mediator of TGFbeta1-driven matrix production within a diabetic milieu.

The C-terminal domain of the regulatory protein NOVH is sufficient to promote interaction with fibulin 1C: a clue for a role of NOVH in cell-adhesion signaling

The NOVH protein belongs to the emerging CCN [Connective tissue growth factor (CTGF), Cyr61/Cef10, nephroblastoma overexpressed gene] family of growth regulators sharing a strikingly conserved multimodular organization but exhibiting distinctive functional features. Two members of the family (CYR61 and CTGF) are positive regulators of cell proliferation, whereas NOVH and two other members (ELM1 and RCOP-1) exhibit features of negative regulators of growth. The multimodular structure of these proteins suggests that their biological role(s) may depend on interactions with several factors as well as proteins constitutive of the extracellular matrix. To gain insight into the functionality of these domains, we have used a two-hybrid system to identify proteins interacting with NOVH. We report here that the C-terminal domain confers on the full-length NOVH protein the capacity to bind fibulin 1C, a protein of the extracellular matrix that interacts with several other regulators of cell adhesion. Furthermore, we show that a natural N-truncated isoform of NOVH produced by cells expressing the full-length NOVH protein also binds fibulin 1C with a high affinity, and we hypothesize that the production of truncated isoforms of NOVH (and probably of other CCN proteins) may be a critical aspect in the modulation of their biological activity. These results set the stage for a study of NOVH-fibulin 1C interactions and their potential significance in cell-adhesion signaling in normal and pathological conditions.

Insulin-like growth factor binding proteins: a proposed superfamily

The conventional concept is that the insulin-like growth factor binding proteins (IGFBPs) are cysteine-rich proteins, with conserved N- and C-domains, that are capable of binding insulin-like growth factors (IGFs) with high affinity. This dogma was recently challenged by the discovery of a group of cysteine-rich proteins that share important structural similarities with the IGFBPs, but have demonstrably lower affinity for IGFs. It is therefore proposed that these IGFBP-related proteins (IGFBP-rPs) and the IGFBPs constitute an IGFBP superfamily. We speculate that the IGFBP superfamily is derived from an ancestral gene/protein that was critically involved in the regulation of cell growth and was capable of binding IGF peptides. Over the course of evolution, some members (IGFBPs) evolved into high-affinity IGF binders and others (IGFBP-rPs) into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means.

Expression and differential regulation of connective tissue growth factor in pancreatic cancer cells

CTGF is an immediate early growth responsive gene that has been shown to be a downstream mediator of TGFbeta actions in fibroblasts and vascular endothelial cells. In the present study hCTGF was isolated as immediate early target gene of EGF/TGFalpha in human pancreatic cancer cells by suppression hybridization. CTGF transcripts were found in 13/15 pancreatic cancer cell lines incubated with 10% serum. In 3/7 pancreatic cancer cell lines EGF/TGFalpha induced a significant rise of CTGF transcript levels peaking 1-2 h after the start of treatment. TGFbeta increased CTGF transcript levels in 2/7 pancreatic cancer cell lines after 4 h of treatment and this elevation was sustained after 24 h. Only treatment with TGFbeta was accompanied by a parallel induction of collagen type I transcription. 15/19 human pancreatic cancer tissues were shown to overexpress high levels of CTGF transcripts. CTGF transcript levels in pancreatic cancer tissues and nude mouse xenograft tumors showed a good correlation to the degree of fibrosis. In situ hybridization and the nude mouse experiments revealed that in pancreatic cancer tissues, fibroblasts are the predominant site of CTGF transcription, whereas the tumor cells appear to contribute to a lesser extent. We conclude that CTGF may be of paramount importance for the development of the characteristic desmoplastic reaction in pancreatic cancer tissues.

Immunohistochemical localization of connective tissue growth factor (CTGF) in the mouse embryo between days 7.5 and 14.5 of gestation

Connective tissue growth factor (CTGF) is a 38 kDa modular protein that is involved in processes such as cell proliferation, survival, migration, adhesion and extracellular matrix production. Target cells for CTGF include fibroblasts, smooth muscle cells and endothelial cells. Using a specific peptide antibody, CTGF was localized in tissue sections obtained from mouse embryos between days 7.5 and 14.5 of gestation. On day 7.5, CTGF was present at high levels in the embryonic ectoderm, mesoderm, and chorion, with weaker levels in the squamous endoderm. No CTGF was detected in Reichert's membrane, parietal endoderm, and visceral endoderm. Decidual cells of the maternal uterus stained strongly for CTGF. There was no specific staining for CTGF on day 11.5 but by day 13.5, the protein was detectable in a limited number of structures, most notably the liver, thymus, lung, and intestine. By day 14.5, staining for CTGF had become extensive and was present at high or moderate levels in the thymus, aorta, trachea, liver, lung, adrenal gland, kidney, iliac sinus, olfactory region, tongue, pharynx, esophagus, thyroglossal duct, choroid plexi, Rathke's pouch, stomach, pancreas, and midgut. Relatively weak staining was present in the heart and dorsal root ganglia. There was no staining in the vitelline duct or in the outer cortical or medullary regions of the brain. Among specific cell types, CTGF was localized at high levels in secretory and absorptive epithelial cells and liver parenchyma cells, at moderate levels in vascular endothelial cells and myoblasts and at low levels in mesenchymal and connective tissue cells. These data show that various tissues and organ systems produce CTGF in a specific temporo-spatial pattern during embryogenesis and support a role for CTGF in cellular differentiation and development during prenatal life.

A developmental study of novH gene expression in human central nervous system

The expression pattern of the human nephroblastoma overexpressed (novH) gene in the fetal human central nervous system was examined by in situ hybridization using digoxigenin-labeled novH-specific riboprobes. In the spinal cord, the nov-expressing neurons were first detected both in the ventral region at 16 weeks of gestation (G16W) and in the dorsal region at G38W. In the medulla, nov-expressing neurons were detected in the principal nucleus of the inferior olive, the hypoglossal nucleus and the dorsal motor nucleus of vagus at G16W. Nov-positive neurons were detected at G28W in the nucleus of the spinal tract of the trigeminal and cuneate nucleus, and at G38W in the abducens nucleus of pons, the red nucleus and the substantia nigra of the midbrain, the ventral posterolateral and the mediodorsal thalamic nucleus. A strong labeling was also detected in the striatum of the cerebrum and the cerebral cortex of the parietal lobe. These data established that novH is mainly expressed in somato-motor neurons in the lower central nervous system at early developmental stages and in the higher central nervous system at later stages, suggesting that nov may play an important role in neuronal differentiation.

Localization of connective tissue growth factor during the period of embryo implantation in the mouse

A role for connective tissue growth factor (CTGF) in reproductive function has been suggested from recent studies in the pig. To extend these findings, we have analyzed the immunohistochemical localization of CTGF during the estrous cycle and early pregnancy in mice. During the diestrous and early proestrous stages, CTGF was localized at high levels to both luminal and glandular uterine epithelial cells and at much lower levels in the stroma or myometrium. Epithelial expression of CTGF was considerably reduced at estrus. On Days 1.5-3.5 of pregnancy, CTGF was localized mainly to the uterine epithelial cells, which showed a substantially reduced level of CTGF on Day 4.5. On Days 5.5 and 6.5, CTGF was present at high levels in uterine decidual cells. CTGF was detected in the trophectoderm and inner cell mass of the preimplantation embryo on Day 4.5 and became preferentially localized to embryonic endoderm and mesoderm on Days 5.5-6.5. Multiple mass forms of CTGF (Mr 14 000-38 000) were present in endometrial extracts and uterine luminal flushings. Collectively, these data support a role for CTGF in uterine cell growth, migration, adhesion, and extracellular matrix production during the estrous cycle and early pregnancy, as well as in early development of the embryo.

Identification of rCop-1, a new member of the CCN protein family, as a negative regulator for cell transformation

By using a model system for cell transformation mediated by the cooperation of the activated H-ras oncogene and the inactivated p53 tumor suppressor gene, rCop-1 was identified by mRNA differential display as a gene whose expression became lost after cell transformation. Homology analysis indicates that rCop-1 belongs to an emerging cysteine-rich growth regulator family called CCN, which includes connective-tissue growth factor, CYR61, CEF10 (v-src inducible), and the product of the nov proto-oncogene. Unlike the other members of the CCN gene family, rCop-1 is not an immediate-early gene, it lacks the conserved C-terminal domain which was shown to confer both growth-stimulating and heparin-binding activities, and its expression is lost in cells transformed by a variety of mechanisms. Ectopic expression of rCop-1 by retroviral gene transfers led to cell death in a transformation-specific manner. These results suggest that rCop-1 represents a new class of CCN family proteins that have functions opposing those of the previously identified members.

Characterization of 16- to 20-kilodalton (kDa) connective tissue growth factors (CTGFs) and demonstration of proteolytic activity for 38-kDa CTGF in pig uterine luminal flushings

Connective tissue growth factor (CTGF) is a growth and chemotactic factor for fibroblasts encoded by an immediate early gene that is transcriptionally activated by transforming growth factor ss. Although the primary translational product of the pig CTGF gene is predicted to be of approximate Mr 38 000, pig uterine luminal flushings (ULF) contained 10- to 20-kDa CTGF proteins that were heparin-binding and mitogenic, whereas 38-kDa CTGF was not apparent. The N-termini of two microheterogeneous forms of 16-kDa CTGF, as well as 18-kDa and 20-kDa forms of CTGF, commenced at, respectively, Cys199, Ala197, Asp186, and Asp186 and did not correspond to intron-exon boundaries in the CTGF gene. Northern blotting revealed a single porcine (p) CTGF transcript of 2.4 kilobases in endometrium from Day 10 to 16 cycling or pregnant pigs. Ten- to twenty-kilodalton pCTGF proteins in ULF were stable for 48 h at 37 degreesC whereas native 38-kDa pCTGF was degraded within 10 min under the same conditions. CTGF-degrading activity in pig ULF was heat-sensitive and concentration- and time-dependent. Ten- to twenty-kilodalton CTGF levels in ULF peaked on Day 16 of the cycle and on Day 12 of pregnancy and were highly correlated with the levels of proteolytic activity for 38-kDa CTGF. Collectively these data suggest that bioactive 10- to 20-kDa CTGF proteins are generated in utero through limited proteolysis of the 38-kDa CTGF primary translational product.

Inhibition of TGF-beta-stimulated CTGF gene expression and anchorage-independent growth by cAMP identifies a CTGF-dependent restriction point in the cell cycle

CTGF is a 38 kDa cysteine-rich peptide whose synthesis and secretion are selectively induced by transforming growth factor beta (TGF-beta) in connective tissue cells. We have investigated the signaling pathways controlling the TGF-beta induction of connective tissue growth factor (CTGF) gene expression. Our studies indicate that inhibitors of tyrosine kinases and protein kinase C do not block the signaling pathway used by TGF-beta to induce CTGF gene expression. In contrast, elevation of cAMP levels within the target cells by a variety of methods blocked the induction of CTGF by TGF-beta. Furthermore, agents that elevate cAMP blocked the induction of anchorage-independent growth (AIG) by TGF-beta. Inhibition of AIG could be overcome by the addition of CTGF, indicating that it was not a general inhibition of growth but a selective inhibition of CTGF synthesis that is responsible for the inhibition of TGF-beta-induced AIG by cAMP. Kinetic studies of the induction of DNA synthesis by CTGF in cells arrested by cAMP indicate that the block occurs in very late G1. These and other studies in monolayer cultures suggest that the CTGF restriction point in the cell cycle is distinct from the adhesion-dependent arrest point.

Connective tissue growth factor: a novel regulator of mucosal repair and fibrosis in inflammatory bowel disease?

Inflammatory bowel disease (IBD) is a multifactorial disorder which is characterized by massive damage of the epithelium and the underlying mesenchyme of the intestine. Due to the potent effect of connective tissue growth factor (CTGF) on fibroblast proliferation and connective tissue deposition we speculated about a possible role of this mitogen in IBD. Here we demonstrate a strikingly increased expression of CTGF mRNA in surgical specimens of patients suffering from two forms of IBD, Crohn's disease and ulcerative colitis. In most specimens, the levels of CTGF mRNA correlated with the degree of inflammation as assessed by histological analysis of adjacent tissue samples and by expression analysis of the pro-inflammatory cytokine interleukin-1 beta. However, areas of little inflammation which were characterized by severe fibrosis also revealed high levels of CTGF mRNA. Expression of transforming growth factor beta-1 (TGF-beta 1), the only known inducer of CTGF so far, as well as of the CTGF target genes collagen I alpha 1, fibronectin and integrin alpha 5 revealed a strong correlation with the expression of CTGF. These data suggest a prominent role of CTGF in the repair of mucosal injury in IBD and in the aberrant deposition of extracellular matrix leading to fibrosis and stenosis, one major complication in IBD, especially in Crohn's disease.

Expression of fibrogenic cytokines in desmoplastic malignant melanoma

Desmoplastic malignant melanoma (DMM) consists of amelanotic spindle-shaped melanoma cells and is accompanied by desmoplasia with fibrous stromata. It has a strong tendency for local infiltrative growth and recurrence and a propensity for neurotropism. It is not yet known which cytokine is responsible for the desmoplasia in DMM. In the present study, we investigated the roles of several fibrogenic cytokines and cytokine receptors in DMM: basic fibroblast growth factor (bFGF), connective tissue growth factor (CTGF), transforming growth factor-beta, platelet-derived growth factor (PDGF) and PDGF receptors. Immunostaining and in situ hybridization were conducted in four cases of DMM and four cases of amelanotic malignant melanoma (AMM) as negative controls for desmoplasia. PDGF-beta receptor, bFGF and CTGF were intensely expressed in the DMM specimens in comparison with the AMM specimens. The reaction of PDGF-B ligand and CTGF to PDGF-beta receptor, in addition to the expression of bFGF, may contribute to the desmoplasia in DMM.

Connective tissue growth factor mRNA expression is upregulated in bleomycin-induced lung fibrosis

Connective tissue growth factor (CTGF) is a newly described 38-kDa peptide mitogen for fibroblasts and a promoter of connective tissue deposition in the skin. The CTGF gene promotor contains a transforming growth factor-beta1 (TGF-beta1) response element. Because TGF-beta1 expression is upregulated in several models of fibroproliferative lung disease, we asked whether CTGF is also upregulated in a murine lung fibrosis model and whether CTGF could mediate some of the fibrogenic effects associated with TGF-beta1. A portion of the rat CTGF gene was cloned and used to show that primary isolates of both murine and human lung fibroblasts express CTGF mRNA in vitro. There was a greater than twofold increase in CTGF expression in both human and murine lung fibroblasts 2, 4, and 24 h after the addition of TGF-beta1 in vitro. A bleomycin-sensitive mouse strain (C57BL/6) and a bleomycin-resistant mouse strain (BALB/c) were given bleomycin, a known lung fibrogenic agent. CTGF mRNA expression was upregulated in the sensitive, but not in the resistant, mouse strain after administration of bleomycin. In vivo differences in the CTGF expression between the two mouse strains were not due to an inherent inability of BALB/c lung fibroblasts to respond to TGF-beta1 because fibroblasts from untreated BALB/c mouse lung upregulated their CTGF message when treated with TGF-beta1 in vitro. These data demonstrate that CTGF is expressed in lung fibroblasts and may play a role in the pathogenesis of lung fibrosis.

Dexamethasone is a novel potent inducer of connective tissue growth factor expression. Implications for glucocorticoid therapy

Due to its potent effect on fibroblast proliferation and extracellular matrix deposition, connective tissue growth factor (CTGF) seems to play an important role in the pathogenesis of fibrotic disease. Since glucocorticoids are frequently used for the therapy of these disorders, we determined a potential effect of these steroids on CTGF expression. In cultured fibroblasts, a striking induction of CTGF expression was observed after dexamethasone treatment and occurred in a time- and dose-dependent manner. This effect was obviously not mediated by the CTGF inducer transforming growth factor-beta1, since expression of this factor was down-regulated by the glucocorticoid. Most importantly, CTGF expression levels also increased substantially in various tissues and organs by systemic glucocorticoid treatment of mice. After cutaneous injury, a strong induction of CTGF expression was seen in the wounds of nontreated mice. However, no further increase in the levels of CTGF mRNA occurred in wounded skin compared with unwounded skin of glucocorticoid-treated animals, suggesting the presence of other factors in the wound that might compensate for the effect of the steroids. Tumor necrosis factor-alpha was identified as a possible mediator of this effect because this factor suppressed CTGF expression in cultured fibroblasts and also blocked the glucocorticoid-induced CTGF production by these cells. These findings indicate that glucocorticoids stimulate CTGF expression in normal tissues and organs but not in highly inflamed areas.

Demonstration of receptors specific for connective tissue growth factor on a human chondrocytic cell line (HCS-2/8)

The presence of receptors specific for connective tissue growth factor (CTGF) was demonstrated on a human chondrosarcoma-derived chondrocytic cell line, HCS-2/8. The binding of 125I-labeled recombinant CTGF to HCS-2/8 cells was inhibited by unlabeled CTGF but not by PDGF-BB or bFGF. Scatchard analysis revealed the presence of two classes of binding sites with Kd values of 18.6 and 259 nM on cells. A cross-linking study revealed the formation of 125I-CTGF-receptor complex with an apparent molecular weight of 280 kDa. The 125I-CTGF-receptor complex disappeared almost completely on the addition of unlabeled CTGF but not PDGF-BB or bFGF. In addition, the 125I-CTGF-receptor complex was immunoprecipitated with anti-CTGF antiserum but not with anti-PDGF receptor antiserum. These findings suggest that CTGF directly binds to specific receptor molecules on HCS-2/8 cells.

novH: differential expression in developing kidney and Wilm's tumors

We previously established that the expression of the human nov gene (novH) was altered in Wilms' tumors and that levels of novH and WT1 mRNA were inversely correlated in individual Wilms' tumors. Insofar as novH has been shown to be a target for WT1 regulation, novH might play an important role during normal nephrogenesis and in the development of Wilms' tumors. We now show that during normal nephrogenesis novH protein is tightly associated with differentiation of glomerular podocytes. NovH expression is not restricted to renal differentiation but is also detected in endothelium and neural tissue of the kidney. Our results establish that alteration of novH expression in sporadic and heritable Wilms' tumors is associated with dysregulated expression of both novH mRNA and protein. In general, the highest novH expression was noted in the Wilms' tumor, genitourinary anomalies, aniridia, and mental retardation (WAGR)-associated Wilms' tumors. Expression in the Denys-Drash syndrome (DDS)-associated Wilms' tumors fell within the variable spectrum observed in sporadic Wilms' tumor cases. As in developing kidney podocytes, novH protein was also prominent in the abnormal hypoplastic podocytes from DDS cases and in kidney podocytes adjoining Wilms' tumors. In Wilms' tumors exhibiting heterotypic differentiation, novH protein was expressed at high levels in tumor-derived striated muscle and at lower levels in tumor-derived cartilage. These observations taken together indicate that novH may represent both a marker of podocytic differentiation in kidney and a marker of heterotypic mesenchymal differentiation in Wilms' tumors. In addition, absence or very low levels of WT1 are correlated with higher novH expression, and its variable expression in cases with mutant WT1 (sporadic and DDS) suggests that the potential activation and repression transcriptional functions possessed by WT1 are likely dependent on the specific mutation incurred.

ADAMTS-1 protein anchors at the extracellular matrix through the thrombospondin type I motifs and its spacing region

Cellular disintegrin and metalloproteinases (ADAMs) are a family of genes with a sequence similar to those of snake venom metalloproteinases and disintegrins. The ADAMTS-1 gene encodes a new type of ADAM protein with respect to possessing the thrombospondin (TSP) type I motifs. Expression of the gene is induced in kidney and heart by in vivo administration of lipopolysaccharide, suggesting a possible role in the inflammatory reaction. In this study, we characterized the ADAMTS-1 gene product by using a transient expression system in COS-7 cells. We found that the precursor and processed forms of ADAMTS-1 were secreted from cells. Under normal growth conditions, little or none of both forms was detected in the cell culture medium, and instead the majority was found associated with the extracellular matrix (ECM). In addition, when cells were cultured in the presence of heparin, the mature form of ADAMTS-1 protein was detected in the cell culture medium, suggesting that binding of ADAMTS-1 to the ECM is mediated through sulfated glycosaminoglycans such as heparan sulfate. Analyses of deletion mutants of the ADAMTS-1 protein revealed that the spacer region as well as three TSP type I motifs in the carboxyl-terminal region of the ADAMTS-1 protein are important for a tight interaction with the ECM. These results suggest that the ADAMTS-1 is a unique ADAM family protein that anchors at the ECM.

How many insulin-like growth factor binding proteins?

Mac25, connective tissue growth factor, the nov-oncogene and cyr61 have been proposed as insulin-like growth factor binding proteins (IGFBPs) although they bind the ligand with very low affinity. Sequence similarity between the candidate proteins and the recognised IGFBPs is restricted to a single cysteine-rich N-terminal domain. The cysteine-rich domain (CRD) can be found in other vertebrate and invertebrate proteins that are associated with the extracellular matrix but otherwise have vastly different functions. Characteristically, the proteins with the CRD have a modular architecture suggesting that exon shuffling has played a significant role in their evolution. Although the proposed candidate proteins may not be IGFBPs, linkage relationships of the latter suggest that two other IGFBPs may indeed exist.

The human analog of murine cystein rich protein 61 [correction of 16] is a 1alpha,25-dihydroxyvitamin D3 responsive immediate early gene in human fetal osteoblasts: regulation by cytokines, growth factors, and serum

1Alpha,25-dihydroxyvitamin D3 (1,25-(OH)2D3) is a potent mediator of differentiation and maintenance of specific functions of osteoblasts. To detect novel targets for 1,25-(OH)2D3 action, we applied differential display PCR to human fetal osteoblast-like cells and identified the human analog of murine cystein rich protein 61 (hCYR61) as a 1,25-(OH)2D3-responsive immediate early gene in differentiated fetal osteoblast-like cells. The murine gene CYR61 is important for cell-cell and cell-matrix interactions, and it belongs to an emerging gene family of cysteine-rich proteins. hCYR61 messenger RNA (mRNA) steady-state levels were stimulated 11-fold by 10 nM 1,25-(OH)2D3 by 1 h and declined to control levels by 4 h. This transient stimulation of hCYR61 mRNA was not inhibited by cycloheximide but was prevented by actinomycin D, indicating that the 1,25-(OH)2D3 effect involves transcriptional events and does not require de novo protein synthesis. hCYR61 mRNA stability was not influenced by 1,25(OH)2D3, whereas cycloheximide treatment stabilized hCYR61 mRNA. FCS, as well as growth factors and cytokines such as basic fibroblast growth factor, epidermal growth factor, tumor necrosis factor alpha, and interleukin-1, strongly elevated hCYR61 mRNA steady-state levels within 1 h. hCYR61 mRNA was expressed also in primary human osteoblasts and osteosarcoma cell lines. Using a commercial tissue blot, hCYR61 mRNA was only observed in skeletal muscle. The fast and transient response of hCYR 61 to 1,25-(OH)2D3, serum, growth factors, and cytokines suggests an important role of hCYR61 for osteoblast function and differentiation.

Expression of connective tissue growth factor in human renal fibrosis

Chronic renal failure may occur in etiologically diverse renal diseases and can be caused by hemodynamic, immunologic and metabolic factors. Initial damage may evoke irreversible scarring, which involves production of a number of proinflammatory and fibrogenic cytokines, including platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF-beta). Connective tissue growth factor (CTGF), a cytokine of the family of growth regulators comprising sef10, cyr61, CTGF and nov, has recently been described in association with scleroderma and other scarring conditions. We investigated CTGF mRNA expression in 65 human renal biopsy specimens of various renal diseases by in situ hybridization. In control human kidney CTFG mRNA was mainly expressed in visceral epithelial cells, parietal epithelial cells, and some interstitial cells. Connective tissue growth factor was strongly up-regulated in the extracapillary and severe mesangial proliferative lesions of crescentic glomerulonephritis, IgA nephropathy, focal and segmental glomerulosclerosis and diabetic nephropathy. An increase in the number of cells expressing CTGF mRNA was observed at sites of chronic tubulointerstitial damage, which correlated with the degree of damage. in the tubulointerstitial area the majority of the CTGF mRNA positive cells coexpressed alpha-smooth muscle actin, and were negative for macrophage markers. Our results indicate that CTGF may be a common growth factor involved in renal fibrosis.

Differential expression of connective tissue growth factor gene in cutaneous fibrohistiocytic and vascular tumors

Connective tissue growth factor (CTGF) is a member of a family of immediate early gene products that may play an important role during tissue regeneration, wound repair and skin fibrosis. In this study, CTGF gene expression in mesenchymal tumors was investigated by in situ hybridization and CD34 antigen expression was studied by means of immunohistochemical staining. CTGF mRNA was expressed in fibroblasts of all nine dermatofibromas examined, but five of seven dermatofibrosarcoma protuberans (DFSP) or two cases of malignant fibrous histiocytoma were negative for its expression. In contrast, CD34 antigen was expressed only in DFSP. In vascular tumors, CTGF mRNA was expressed in pyogenic granuloma but not in angiosarcoma. In addition, the endothelial cells in angiolipoma and angioleiomyoma, but not in venous lake, expressed CTGF mRNA. These vascular lesions were all positive for CD34 expression. Tumors of other origins were negative for CTGF mRNA. Our findings indicated that benign fibroblasts and/or vascular endothelial cells have the capability to express CTGF mRNA when activated, but these cells lose this ability when they achieve malignant potency. Thus, examination of CTGF gene expression may be useful for differentiating between benign and malignant mesenchymal tumors, or to determine the origin of the tumors in connective tissue.

Expression of the Elm1 gene, a novel gene of the CCN (connective tissue growth factor, Cyr61/Cef10, and neuroblastoma overexpressed gene) family, suppresses In vivo tumor growth and metastasis of K-1735 murine melanoma cells

We previously isolated a partial cDNA fragment of a novel gene, Elm1 (expressed in low-metastatic cells), that is expressed in low-metastatic but not in high-metastatic K-1735 mouse melanoma cells. Here we determined the full-length cDNA structure of Elm1 and investigated the effect of Elm1 expression on growth and metastatic potential of K-1735 cells. The Elm1 gene encodes a predicted protein of 367 amino acids showing approximately 40% amino acid identity with the CCN (connective tissue growth factor [CTGF], Cyr61/Cef10, neuroblastoma overexpressed gene [Nov]) family proteins, which consist of secreted cysteine-rich proteins with growth regulatory functions. Elm1 is also a cysteine-rich protein and contains a signal peptide and four domains conserved in the CCN family proteins. Elm1 was highly conserved, expressed ubiquitously in diverse organs, and mapped to mouse chromosome 15. High-metastatic K-1735 M-2 cells, which did not express Elm1, were transfected with an Elm1 expression vector, and several stable clones with Elm1 expression were established. The in vivo growth rates of cells expressing a high level of Elm1 were remarkably slower than those of cells expressing a low level of Elm1. Metastatic potential of transfectants was reduced in proportion to the level of Elm1 expression. Thus, Elm1 is a novel gene of CCN family that can suppress the in vivo growth and metastatic potential of K-1735 mouse melanoma cells.

Characterization of cell-associated and soluble forms of connective tissue growth factor (CTGF) produced by fibroblast cells in vitro

Connective tissue growth factor (CTGF) is a mitogenic and chemotactic factor for cultured fibroblasts that has been implicated in wound healing, fibrotic disorders and uterine function. Although the primary translational products of the mouse, human and pig CTGF (mCTGF, hCTGF, pCTGF) genes are predicted to be secreted and of approximate M(r) 38,000, 10 kDa biologically active forms of pCTGF have recently been described. In this report, we show that human foreskin fibroblasts (HFFs) and mouse connective tissue fibroblasts contained 2.4 kb CTGF transcripts, stained positively with an anti-CTGF[81-94] peptide antiserum, and produced a 38 kDa protein that was immunoprecipitated by an anti-CTGF[247-260] peptide antiserum. While 38 kDa CTGF was readily detected in cell lysates, it was non- or barely detectable in conditioned medium. 38 kDa CTGF remained cell-associated for at least 5 days after synthesis and was not releasable by treatment of the cells with trypsin, heparin, 1 M NaCl or low pH. Purification of CTGF from human or mouse fibroblast conditioned medium resulted in the isolation of 10-12 kDa CTGF proteins that were heparin-binding, bioactive, and reactive with anti-CTGF[247-260] on Western blots. Whereas 10 kDa CTGF stimulated DNA synthesis in 3T3 cells to the same extent as platelet-derived growth factor (PDGF)-AA, -AB, or -BB, it did not compete with 125I-PDGF-BB for binding to alpha alpha, alpha beta or beta beta PDGF receptors (PDGF-R), did not stimulate tyrosine phosphorylation of PDGF-alpha-R or -beta-R, and was not antagonized by a neutralizing PDGF-R-alpha antiserum. These data show that, in cultured fibroblasts, 38 kDa CTGF is principally cell-associated whereas low mass forms of CTGF are soluble and biologically active. They further demonstrate that, contrary to the previously proposed properties of 38 kDa CTGF, 10 kDa CTGF does not bind to PDGF-R and stimulates Balb/c 3T3 cell mitosis via a PDGF-R-independent mechanism.

Cyr61, product of a growth factor-inducible immediate-early gene, regulates chondrogenesis in mouse limb bud mesenchymal cells

Chondrogenesis during embryonic skeletal development involves the condensation of mesenchymal cells followed by their differentiation into chondrocytes. We describe herein a previously unrecognized regulator of mammalian chondrogenesis encoded by a murine growth factor-inducible immediate-early gene, cyr61. The Cyr61 protein is a secreted, heparin-binding protein (379 amino acids with 38 conserved cysteines) that promotes cell adhesion, migration, and proliferation. The expression pattern of the cyr61 gene during embryogenesis is tissue specific and temporally regulated. Most notably, cyr61 is transiently expressed in mesenchymal cells of both mesodermal and neuroectodermal origins undergoing chondrogenesis, suggesting that Cyr61 may play a role in the development of the embryonic skeleton. In this communication, we demonstrate that the Cyr61 protein promotes chondrogenesis in micromass cultures of limb bud mesenchymal cells in vitro and is likely to play a similar role in vivo based on the following observations: (1) Cyr61 is present in the embryonic limb mesenchyme during chondrogenesis in vivo and in vitro; (2) purified recombinant Cyr61 protein added exogenously to micromass cultures promotes chondrogenesis as judged by precocious expression of type II collagen, increased [35S]sulfate incorporation, and larger Alcian blue-staining cartilage nodules; (3) Cyr61 enhances cell-cell aggregation, an initial step in chondrogenesis, and promotes chondrogenic differentiation in cultures plated at subthreshold cell densities that are otherwise unable to support differentiation; and (4) neutralization of the endogenous Cyr61 with specific antibodies inhibits chondrogenesis. Taken together, these results identify Cyr61 as a novel player in chondrogenesis that contributes to the development of the mammalian embryonic skeleton.

Chromosomal mapping and expression of the human cyr61 gene in tumour cells from the nervous system

AIMS

To characterise the human cyr61 gene (cyr61H) and determine its chromosomal locality. To compare expression of cyr61H in human tumour cell lines with that of two other structurally related genes, novH (nephroblastoma overexpressed gene) and CTGF (connective tissue growth factor), that are likely to play a role in the control of cell proliferation and differentiation.

METHODS

To isolate the human cyr61 gene, placental genomic and HeLa cDNA libraries were screened with murine cyr61 cDNA. The nucleotide sequence of the complete cyr61H cDNA was established. Both Southern blotting of a panel of somatic cell hybrids and in situ hybridisation on chromosomes were performed to map the cyr61H gene. Expression of cyr61H, novH, CTGF, and novH was analysed by northern blotting in both human neuroblastomas and glioblastoma cell lines.

RESULTS

Genomic and cDNA clones encompassing the cyr61H gene were isolated and characterised. Comparison of mouse and human cyr61 sequences indicated that their genomic organisation is highly conserved. Alignment of coding sequences highlighted the conservation of cyr61 regions that might be critical for its biological function. The data showed that the cyr61H gene is assigned to chromosome 1p22.3 and that different levels of cyr61H, CTGF, and novH mRNA have been detected in several human tumour cell lines derived from the nervous system.

CONCLUSIONS

The human cyr61 gene belongs to an emerging family of genes including CTGF/fisp12 and nov. The murine cyr61 encodes an extracellular cysteine rich protein that exhibits chemotactic activity, promotes attachment and spreading of cells, and potentiates the mitogenic effect of growth factors. Assignment of the cyr61H gene to chromosome 1p22.3 will allow studies to determine whether human pathologies derived from the nervous system or from other tissues are associated with chromosomal abnormalities involving this region. Although the coding regions of cyr61H, CTGF, and novH are highly homologous, a growing body of evidence suggests that expression of these genes is regulated differentially, and that a balance between expression of these genes might represent a key element in determining the stage of differentiation and/or the malignant potential of tumour cells.

Identification of a family of low-affinity insulin-like growth factor binding proteins (IGFBPs): characterization of connective tissue growth factor as a member of the IGFBP superfamily

The insulin-like growth factor (IGF) binding proteins (IGFBPs) modulate the actions of the insulin-like growth factors in endocrine, paracrine, and autocrine settings. Additionally, some IGFBPs appear to exhibit biological effects that are IGF independent. The six high-affinity IGFBPs that have been characterized to date exhibit 40-60% amino acid sequence identity overall, with the most conserved sequences in their NH2 and COOH termini. We have recently demonstrated that the product of the mac25/IGFBP-7 gene, which shows significant conservation in the NH2 terminus, including an "IGFBP motif' (GCGCCXXC), exhibits low-affinity IGF binding. The closely related mammalian genes connective tissue growth factor (CTGF) gene, nov, and cyr61 encode secreted proteins that also contain the conserved sequences and IGFBP motifs in their NH2 termini. To ascertain if these genes, along with mac25/IGFBP-7, encode a family of low-affinity IGFBPs, we assessed the IGF binding characteristics of recombinant human CTGF (rhCTGF). The ability of baculovirus-synthesized rhCTGF to bind IGFs was demonstrated by Western ligand blotting, affinity cross-linking, and competitive affinity binding assays using 125I-labeled IGF-I or IGF-II and unlabeled IGFs. CTGF, like mac25/IGFBP-7, specifically binds IGFs, although with relatively low affinity. On the basis of these data, we propose that CTGF represents another member of the IGFBP family (IGFBP-8) and that the CTGF gene, mac25/IGFBP-7, nov, and cyr61 are members of a family of low-affinity IGFBP genes. These genes, along with those encoding the high-affinity IGFBPs 1-6, together constitute an IGFBP superfamily whose products function in IGF-dependent or IGF-independent modes to regulate normal and neoplastic cell growth.

Serum- and polypeptide growth factor-inducible gene expression in mouse fibroblasts

Complex cellular processes such as proliferation, differentiation, and apoptosis are regulated in part by extracellular signaling molecules: for example, polypeptide growth factors, cytokines, and peptide hormones. Many polypeptide growth factors exert their mitogenic effects by binding to specific cell surface receptor protein tyrosine kinases. This interaction triggers numerous biochemical responses, including changes in phospholipid metabolism, the activation of a protein phosphorylation cascade, and the enhanced expression of specific immediate-early, delayed-early, or late response genes. In this review, I summarize the major findings obtained from studies investigating the effects of serum or individual polypeptide growth factors on gene expression in murine fibroblasts. Several experimental approaches, including differential hybridization screening of cDNA libraries and differential display, have been employed to identify mRNA species that are expressed at elevated levels in serum- or polypeptide growth factor-stimulated cells. These studies have demonstrated that serum- and growth factor-inducible genes encode a diverse family of proteins, including DNA-binding transcription factors, cytoskeletal and extracellular matrix proteins, metabolic enzymes, secreted chemokines, and serine-threonine kinases. Some of these gene products act as effectors of specific cell cycle functions (e.g., enzymes involved in nucleotide and DNA synthesis), others are required to successfully convert a metabolically inactive cell to a metabolically active cell that will eventually increase in size and then divide (e.g., glucose-metabolizing enzymes), and some actually function as positive or negative regulators of cell cycle progression. In conclusion, research conducted during the past 15 years on serum- and growth factor-regulated gene expression in murine fibroblasts has provided significant insight into mitogenic signal transduction and cell growth control.

Connective tissue growth factor: a mediator of TGF-beta action on fibroblasts

Connective tissue growth factor (CTGF) is a cysteine-rich mitogenic peptide that binds heparin and is secreted by fibroblasts after activation with transforming growth factor beta (TGF-beta). CTGF is a member of a highly conserved family of peptides that include immediate early gene products cef10, cyr61, fisp12; a putative avian proto-oncogene, nov; and a drosophila gene, twisted gastrulation, tsg, that controls medial mesoderm induction during dorsal-ventral axis pattern formation, a process also controlled by TGF-beta related peptides (dpp, scw). In the adult mammal, CTGF functions as a downstream mediator of TGF-beta action on connective tissue cells, where it stimulates cell proliferation and extracellular matrix synthesis. CTGF does not appear to act on epithelial cells or immune cells. Because the biological actions of TGF-beta are complex and affect many different cell types, CTGF may serve as a more specific target for selective intervention in processes involving connective tissue formation during wound repair or fibrotic disorders. Northern blot and in situ hybridization studies have demonstrated that CTGF is coordinately expressed with TGF-beta in every fibrotic disorder examined to date. Agents that inhibit CTGF production or action could lead to the development of new therapeutic approaches for the control of fibrotic disorders in humans.

Induction of subcutaneous tissue fibrosis in newborn mice by transforming growth factor beta-simultaneous application with basic fibroblast growth factor causes persistent fibrosis

To establish an appropriate animal model of skin fibrosis by exogenous application of growth factors, we investigated the in vivo effects of transforming growth factor-beta by injection into subcutaneous tissue of newborn mice. Histological examination revealed that TGF-beta1, beta2, and beta3 induced granulation tissue formation after 3 days of injection, while these changes had disappeared after 7 days. The changes after 3 days of injection were more pronounced in the tissue injected with TGF-beta2 or beta3 than that with TGF-beta1. In situ hybridization analysis indicated that connective tissue growth factor mRNA was strongly expressed in the fibroblasts at the site of TGF-beta injection, which suggested that fibroblasts were activated by TGF-beta. Next, we investigated the cooperative effects of TGF-beta and other growth factors including basic fibroblast growth factor (bFGF). The simultaneous application of TGF-beta and bFGF caused apparent tissue fibrosis which persisted for at least 2 weeks, while bFGF alone caused slight fibrotic changes after 7 days of injection. Thus, we succeeded in establishing an animal model of skin fibrotic disorders by the exogenous addition of growth factors, and this animal model will be useful for future studies in this area.

Purification and characterization of novel heparin-binding growth factors in uterine secretory fluids. Identification as heparin-regulated Mr 10,000 forms of connective tissue growth factor

Uterine growth factors are potential effector molecules in embryo growth signaling pathways. Pig uterine luminal flushings contained a heparin-binding growth factor (HBGF) that required 0.8 M NaCl for elution from heparin columns and was termed HBGF-0.8. This factor, which was heat- and acid-labile and of Mr 10,000 as assessed by gel filtration, stimulated DNA synthesis in fibroblasts and smooth muscle cells but not endothelial cells. Two forms of HBGF-0.8, termed HBGF-0.8-P1 and HBGF-0.8-P2, exhibited differential heparin-binding properties. SDS-polyacrylamide gel electrophoresis showed that each form of HBGF-0.8 migrated with an apparent Mr of 10, 000 under reducing conditions. Amino acid sequencing revealed the N-terminal sequence EENIKKGKKXIRTPKI for HBGF-0.8-P1 and ENIKKGKKXIRT for HBGF-0.8-P2. These sequences corresponded, respectively, to residues 247-262 and 248-259 of the 349-residue predicted primary translation product of porcine connective tissue growth factor (pCTGF). 10-kDa CTGF-mediated fibroblast DNA synthesis was modulated by exogenous heparin, and CTGF-immunoreactive proteins of 10, 16, and 20 kDa were present in unfractionated uterine luminal flushings. These data reveal the identity of a novel growth factor in uterine fluids as a highly truncated form of CTGF and show that the N-terminal two-thirds of the CTGF primary translation product is not required for mitogenic activity or heparin binding.

Connective tissue growth factor. Friend or foe?

Connective tissue growth factor (CTGF) is a novel cysteine-rich, secreted peptide, which is implicated in human atherosclerosis and fibrotic disorders such as systemic scleroderma. CTGF is a member of the peptide family that includes serum-induced immediate early gene products, a v-src-induced peptide, and a putative proto-oncogene. The CTGF gene family is a modular protein and is conserved throughout evolution. CTGF mRNA has been found in the human, mouse, chicken, frog, and fly. The functions of the CTGF gene family include embryogenesis, wound healing, and regulation of extracellular matrix production. Human CTGF is undetectable in normal blood vessels but overexpressed in atherosclerotic lesions, suggesting an important role in atherogenesis.

Combinatorial signaling by Twisted Gastrulation and Decapentaplegic

The Twisted Gastrulation (TSG) protein is one of five secreted proteins required to pattern the dorsal part of the early Drosophila embryo. Unlike the Decapentaplegic (DPP) protein that is required to pattern the entire dorsal half of the embryo, TSG is needed only to specify the fate of the dorsal midline cells. Here we have misexpressed the tsg gene with different promoters to address its mechanism of action and relationship to DPP. When expressed in a ventral stripe of cells, TSG protein can diffuse to the dorsalmost cells and can rescue the dorsal midline cells in tsg mutant embryos. Despite elevated levels that exceed that exceed those needed for biological activity, there was no change in dorsal midline or lateral cell fates under any conditions tested. We conclude that TSG does not modulate an activity gradient of DPP. Instead, it functions in a permissive rather than instructive role to elaborate cell fates along the dorsal midline after peak levels of DPP activity have 'primed' cells to respond to TSG. The interaction between TSG and DPP defines a novel type of combinatorial synergism.

Cyr61 and Fisp12 are both ECM-associated signaling molecules: activities, metabolism, and localization during development

cyr61 and fisp12 are homologous immediate-early genes that are transcriptionally activated upon growth factor stimulation in fibroblasts. Their gene products belong to an emerging family of secreted proteins with a high degree of sequence homology, including conservation of all 38 cysteine residues in their secreted portions. We have recently shown that Cyr61 is an extracellular matrix (ECM) signaling molecule that promotes cell proliferation, migration, and adhesion. We describe herein the first purification of the Fisp12 protein and we compare the activities of purified Cyr61 and Fisp12, their metabolism, targeting, and their localization during development. Although Fisp12 is the mouse homolog of the human connective tissue growth factor (CTGF), it has no detectable mitogenic activity by itself. Rather, Fisp12 enhances fibroblast growth factor-induced DNA synthesis. The activities of Fisp12 and Cyr61 are nearly indistinguishable in three cell types tested: fibroblasts, endothelial, and epithelial cells. Both proteins are found in the ECM, although Cyr61 associates with the ECM more strongly and binds heparin with higher affinity. Fisp12, but not Cyr61, is also found in the culture medium, suggesting that Fisp12 might be able to act at a distance from its site of secretion, whereas Cyr61 might act more locally. Both secreted proteins are internalized and degraded through the lysosomal pathway, suggesting interaction with cell surface receptors. Both Cyr61 and Fisp12 are found in the placenta and the circulatory system as detected by immunohistochemistry, whereas Cyr61, but not Fisp12, is found in the skeletal and nervous systems. Fisp12, but not Cyr61, is found in secretory organs. Taken together, we propose that Cyr61 and Fisp12 are both signaling cell adhesion molecules that have similar or overlapping activities, and their differential sites of localization and targeting may dictate specificity in their biological roles.

Cloning of a mRNA preferentially expressed in chondrocytes by differential display-PCR from a human chondrocytic cell line that is identical with connective tissue growth factor (CTGF) mRNA

Chondrocyte- or chondrosarcoma cell line (HCS)-specific DNA fragments were obtained using differential display-PCR. Nucleotide sequences of 32 species derived from HCS cells were determined. One of the sequence tags (tag no. 24) corresponded to the nucleotide sequence of connective tissue growth factor (CTGF). Northern blot analysis showed that CTGF was highly expressed in HCS cells and rabbit growth cartilage cells in culture but was not expressed in osteoblastic cells in culture. In situ hybridization revealed that CTGF was expressed only in the hypertrophic chondrocytes of costal cartilage and the vertebral column in embryonic mice. The expression of CTGF in HCS cells was up-regulated by the addition of TGF-beta or BMP-2. These findings suggest that CTGF participates in endochondral ossification.

Human connective tissue growth factor is expressed in advanced atherosclerotic lesions

BACKGROUND

Atherosclerosis affects certain but not all vascular beds of the human circulation. Its molecular mechanisms are only partially understood. Human connective tissue growth factor (hCTGF) is a novel cysteine-rich, secreted polypeptide. hCTGF is implicated in connective tissue formation, which may play an important role in atherosclerosis.

METHODS AND RESULTS

By using a differential cloning technique, we isolated a cDNA clone from a human aorta cDNA library, which is identical to hCTGF. Northern analysis shows that hCTGF mRNA was expressed at 50- to 100-fold higher levels in atherosclerotic blood vessels compared with normal arteries. In vascular smooth muscle cells, high-level expression of hCTGF mRNA was induced by transforming growth factor-beta 1. Using in situ hybridization and immunohistochemistry, we found that all advanced atherosclerotic lesions of human carotid arteries (eight patients; mean age, 69; age range, 57 to 85 years) and femoral arteries (two patients; mean age, 71.5 years) that we tested expressed high levels of both hCTGF mRNA and protein. hCTGF expression was localized mainly to smooth muscle cells in the plaque lesions that are negative for proliferating cell nuclear antigen staining. In addition, some CD-31-positive endothelial cells of plaque vessels expressed high levels of hCTGF mRNA and protein. hCTGF-positive cells were found predominantly in areas with extracellular matrix accumulation and fibrosis. In contrast, in normal arteries, we were unable to detect either hCTGF mRNA or immunoreactive hCTGF protein.

CONCLUSIONS

In the present study, we have shown for the first time that both hCTGF mRNA and protein are expressed in human arteries in vivo and that hCTGF may represent a novel factor expressed at high levels specifically in advanced lesions and may play a role in the development and progression of atherosclerosis.

Endothelial cell-conditioned medium downregulates smooth muscle contractile protein expression

Smooth muscle cells (SMC) within atherosclerotic lesions proliferate and exhibit phenotypic modulation, but the contribution of vascular endothelium to this process is poorly understood. Our aim was to examine the effects of endothelial cell-conditioned medium (ECCM) on vascular SMC growth and differentiation. Rat aortic ECCM stimulated a ninefold increase in [3H]thymidine incorporation and downregulated smooth muscle-specific myosin heavy chain and alpha-actin synthesis in rat aortic SMC. These effects were not inhibited by antibodies to platelet-derived growth factor (PDGF)-BB or PDGF-AB or with a PDGF beta-receptor subunit. Treatment with PDGF-BB (at a concentration found in ECCM), PDGF-AA, basic fibroblast growth factor, endothelin-1, or transforming growth factor-beta did not reproduce these effects. The ECCM activities were sensitive to heat and trypsinization, were >30 kDa in molecular mass, and bound weakly to heparin-Sepharose. Our data indicate that cultured endothelial cells produce a factor(s) that downregulates contractile protein expression in SMC, which may contribute to SMC dedifferentiation and proliferation.

Regulation of differentiation/maturation in vascular smooth muscle cells by hormones and growth factors

Smooth muscle cells (SMC) within atherosclerotic lesions show marked alterations in their differentiated properties as compared to normal medial SMC. This process of de-differentiation of SMC has been referred to as "phenotypic modulation", and is characterized by increased growth responsiveness, altered lipid metabolism, increased matrix production, and loss of contractile proteins, all of which can contribute to the development and/or progression of atherosclerotic disease. As such there has been much interest in understanding mechanisms and factors that control the differentiation of the vascular SMC. This paper reviews the effects of growth factors, growth inhibitors, and other extrinsic factors on differentiation/maturation of SMC, with a particular emphasis on consideration of factors that may contribute to abnormal control of SMC differentiation in vascular disease. In addition, we will briefly summarize what is currently known regarding molecular mechanisms that control the coordinate expression of genes encoding for SMC-selective/specific proteins that are required for the differentiated function of the vascular SMC.

Expression of connective tissue growth factor mRNA in the fibrous stroma of mammary tumors

Desmoplasia, the formation of highly cellular, excessive connective tissue stroma associated with some cancers, shares many features with the wound healing response. Since connective tissue growth factor (CTGF) has previously been demonstrated to play a role in wound repair, we wanted to determine if it might be involved in the pathogenesis of stromal demoplasia in mammary cancer. We assayed 11 human invasive mammary ductal carcinomas by Northern blot and 7 out of 11 were positive for both CTGF expression and transforming growth factor-beta 1 (TGF-beta 1, a principal CTGF inducer). One specimen was positive only for TGF-beta 1. The remaining 3 tumors lacked significant stromal involvement and were negative for either factor. In every case we assayed, in which there was marked connective tissue involvement, both CTGF and TGF-beta 1 messages were found. We also assayed 3 murine mammary tumor models. The GI-101 xenograft model had marked stroma and was positive for both factors in-vivo, but positive for only TGF-beta 1 mRNA expression in culture where fibroblasts were absent. The DMBA murine tumor lacked significant stroma and was negative for CTGF and TGF-beta 1 expression by Northern blot, while the stromal rich DMBA-MMTV tumor contained multifocal desmoplasia and was positive for both factors. We performed in-situ hybridization for CTGF and TGF-beta 1 on the GI-101 and DMBA-MMTV tumors. CTGF message was observed only in the fibroblasts of the stroma, while TGF-beta 1 mRNA hybridization was present in tumor epithelial cells and leukocytes. These results suggest that cancer stroma formation involves induction of similar fibroproliferative growth factors (TGF-beta 1 and CTGF) as wound repair.

Particle-mediated gene transfer with transforming growth factor-beta1 cDNAs enhances wound repair in rat skin

Based on preliminary but variable results with direct DNA transfer into wounds, we evaluated in vivo gene transfer by particle-mediated DNA delivery to rat skin to determine whether overexpression of TGF-beta1 at the site of skin incisions would result in a significant improvement in repair. Optimization of the method with viral promoter-luciferase reporter constructs indicated that expression of luciferase activity persisted up to 5 d and was promoter, pressure, and site dependent (ventral > dorsal). Using cytomegalovirus (CMV)-driven human alpha1-antitrypsin, transgene expression was immunolocalized within keratinocytes of the stratum granulosum at 24 h. We measured tensile strength of skin incisions at 11-21 d in both normal and diabetic rats transfected with TGF-beta1 expression vectors at surgery. Native murine TGF-beta1 under an SV40 promoter produced positive effects, while wound strengthening was more pronounced in diabetic animals using a CMV-driven construct. Transfection of rat skin with constitutively active, mutant porcine TGF-beta1 under the control of the CMV and Moloney murine leukemia virus promoters significantly increased tensile strength up to 80% for 14-21 d after surgery. Transfection 24 h before surgery was more effective. Particle-mediated gene delivery can be used to deliver viral promoter-cytokine expression constructs into rat skin in a safe, efficient, and reproducible fashion. The extent of wound repair, as evidenced by enhanced tensile strength, can be markedly improved in tissues transfected with TGF-beta1 expression constructs.

Stimulation of fibroblast cell growth, matrix production, and granulation tissue formation by connective tissue growth factor

Connective tissue growth factor (CTGF) is a 36-to 38-kDa peptide that is selectively induced by transforming growth factor-beta (TGF-beta) in fibroblastic cell types. We compared the biologic activities of CTGF with TGF-beta on fibroblasts in culture and in animal models of fibroplasia. CTGF was active as a mitogen in monolayer cultures of normal rat kidney fibroblasts. CTGF did not stimulate anchorage-independent growth of NRK fibroblasts, however, or inhibit the growth of mink lung epithelial cells, distinguishing CTGF's growth-regulatory activities from those of TGF-beta. In NRK fibroblasts, both TGF-beta and CTGF significantly increased the transcripts encoding alpha 1 type I collagen, alpha 5 integrin, and fibronectin. Stimulation of type I collagen and fibronectin protein synthesis by TGF-beta and CTGF was confirmed by pulse labeling of cells with [35S]methionine. Subcutaneous injection of TGF-beta and CTGF into neonatal NIH Swiss mice resulted in a large stimulation of granulation tissue and fibrosis at the site of injection. In situ hybridization studies revealed that TGF-beta injection induced high levels of CTGF mRNA in the dermal fibroblasts at the injection site, demonstrating that TGF-beta can induce the expression of CTGF in connective tissue cells in vivo. No CTGF transcripts were detected in the epidermal cells in either control or TGF-beta-injected skin or in fibroblasts in control (saline-injected) skin. These results demonstrate that, like TGF-beta, CTGF can induce connective tissue cell proliferation and extracellular matrix synthesis.

Immunohistochemical analysis of platelet-derived growth factor and basic fibroblast growth factor in cardiac biopsy and autopsy specimens of heart transplant patients

The purposes of this study were to examine 250 heart biopsy specimens and 20 autopsy specimens from heart transplant patients for the presence and localization of platelet-derived growth factor (PDGF)and basic fibroblast growth factor (bFGF) and to correlate these findings with the histologic features of rejection and the autopsy findings of graft coronary vasculopathy and global ischemia. Positive specimen staining was significantly more prevalent for PDGF (78% of specimens) than for bFGF (54% of specimens) (p< 0.001). PDGF was distributed more in an interstitial (53%) than a vascular (28%) pattern and was associated with macrophages, whereas bFGF was distributed more in a vascular (50%) than an interstitial (12%) pattern. The prevalence of PDGF (but not bFGF) staining was significantly greater in biopsy specimens with at least grade 2 vascular rejection changes (81%) than in those without vascular rejection changes (58%) (p<0.001). In autopsy specimens, PDGF staining was present in the hearts of all 5 patients (100%) who died of graft failure from coronary vasculopathy and was present in all 11 hearts (100%) with global ischemic changes, but in only 4 of 9 (44%) of the hearts without global ischemia (p<0.01). PDGF staining was absent in nontransplanted heart specimens, whereas bFGF staining in nontransplanted heart specimen was similar to that in transplanted hearts. We conclude that PDGF is increased in transplanted hearts, is distributed more in an interstitial pattern, and is associated with macrophages. Furthermore, PDGF staining is increased in transplanted hearts with evidence of vascular rejection, coronary vasculopathy, or global ischemia.

Isolation and characterization of xnov, a Xenopus laevis ortholog of the chicken nov gene

We have isolated an ortholog (xnov) of the chicken nov gene (for nephroblastoma overexpressed; encoding a putative avian proto-oncogene) from Xenopus laevis (Xl) by screening an Xl ovary cDNA library and genomic library using the entire coding region of human CTGF (encoding connective tissue growth factor) as a probe and by 5'RACE (rapid amplification of cDNA ends). xnov has the same genomic organization as chicken nov, mouse fisp12 and cyr61, but has a unique promoter sequence. The Xl open reading frame (ORF) encodes a 343-amino-acid (aa) polypeptide of 37.9 kDa. Xnov shows 62.9, 60.5, 52.2, 52.1, 47.6 and 45.8% identity with the chicken Nov, human NovH, human CTGF, mouse Fisp12, chicken Cef10 and mouse Cyr61 proteins, respectively. Xnov contains four aa domains which characterize the CTGF family. RT-PCR (reverse transcription-polymerase chain reaction) analysis shows that the xnov mRNA is very low in abundance and appears to be present throughout early Xl development. Our results also indicate that xnov and nov are not orthologs of human CTGF.