Heparin-binding epidermal growth factor-like growth factor suppresses experimental liver fibrosis in mice

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a cytoprotective agent in several organ systems but its roles in liver fibrosis are unclear. We studied the roles of HB-EGF in experimental liver fibrosis in mice and during hepatic stellate cell (HSC) activation. Thioacetamide (TAA; 100 mg/kg) was administered by intraperitoneal injection three times a week for 4 weeks to wild-type HB-EGF(+/+) or HB-EGF-null (HB-EGF(-/-)) male mice. Livers were examined for histology and expression of key fibrotic markers. Primary cultured HSCs isolated from untreated HB-EGF(+/+) or HB-EGF(-/-) mice were examined for fibrotic markers and/or cell migration either during culture-induced activation or after exogenous HB-EGF (100 ng/ml) treatment. TAA induced liver fibrosis in both HB-EGF(+/+) and HB-EGF(-/-) mice. Hepatic HB-EGF expression was decreased in TAA-treated HB-EGF(+/+) mice by 37.6% (P<0.05) as compared with animals receiving saline alone. HB-EGF(-/-) mice treated with TAA showed increased hepatic α-smooth muscle actin-positive cells and collagen deposition, and, as compared with HB-EGF(+/+) mice, TAA-stimulated hepatic mRNA levels in HB-EGF(-/-) mice were, respectively, 2.1-, 1.7-, 1.8-, 2.2-, 1.2- or 3.3-fold greater for α-smooth muscle actin, α1 chain of collagen I or III (COL1A1 or COL3A1), transforming growth factor-β1, connective tissue growth factor or tissue inhibitor of metalloproteinase-1 (P<0.05). HB-EGF expression was detectable in primary cultured HSCs from HB-EGF(+/+) mice. Both endogenous and exogenous HB-EGF inhibited HSC activation in primary culture, and HB-EGF enhanced HSC migration. These findings suggest that HB-EGF gene knockout in mice increases susceptibility to chronic TAA-induced hepatic fibrosis and that HB-EGF expression or action is associated with suppression of fibrogenic pathways in HSCs.

Increased fibroblast functionality on CNN2-loaded titania nanotubes

Infection and epithelial downgrowth are major problems associated with maxillofacial percutaneous implants. These complications are mainly due to the improper closure of the implant–skin interface. Therefore, designing a percutaneous implant that better promotes the formation of a stable soft tissue biologic seal around percutaneous sites is highly desirable. Additionally, the fibroblast has been proven to play an important role in the formation of biologic seals. In this study, titania nanotubes were filled with 11.2 kDa C-terminal CCN2 (connective tissue growth factor) fragment, which could exert full CCN2 activity to increase the biological functionality of fibroblasts. This drug delivery system was fabricated on a titanium implant surface. CCN2 was loaded into anodized titania nanotubes using a simplified lyophilization method and the loading efficiency was approximately 80%. Then, the release kinetics of CCN2 from these nanotubes was investigated. Furthermore, the influence of CCN2-loaded titania nanotubes on fibroblast functionality was examined. The results revealed increased fibroblast adhesion at 0.25, 0.5, 1, 2, 4, and 24 hours, increased fibroblast viability over the course of 5 days, as well as enhanced actin cytoskeleton organization on CCN2-loaded titania nanotubes surfaces compared to uncoated, unmodified counterparts. Therefore, the results from this in vitro study demonstrate that CCN2-loaded titania nanotubes have the ability to increase fibroblast functionality and should be further studied as a method of promoting the formation of a stable soft tissue biologic seal around percutaneous sites.

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

Background:

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

Purpose:

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

Methods:

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

Results:

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

Conclusion:

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

Subplate in the developing cortex of mouse and human

The subplate is a largely transient zone containing precocious neurons involved in several key steps of cortical development. The majority of subplate neurons form a compact layer in mouse, but are dispersed throughout a much larger zone in the human. In rodent, subplate neurons are among the earliest born neocortical cells, whereas in primate, neurons are added to the subplate throughout cortical neurogenesis. Magnetic resonance imaging and histochemical studies show that the human subplate grows in size until the end of the second trimester. Previous microarray experiments in mice have shown several genes that are specifically expressed in the subplate layer of the rodent dorsal cortex. Here we examined the human subplate for some of these markers. In the human dorsal cortex, connective tissue growth factor-positive neurons can be seen in the ventricular zone at 15-22 postconceptional weeks (PCW) (most at 17 PCW) and are present in the subplate at 22 PCW. The nuclear receptor-related 1 protein is mostly expressed in the subplate in the dorsal cortex, but also in lower layer 6 in the lateral and perirhinal cortex, and can be detected from 12 PCW. Our results suggest that connective tissue growth factor- and nuclear receptor-related 1-positive cells are two distinct cell populations of the human subplate. Furthermore, our microarray analysis in rodent suggested that subplate neurons produce plasma proteins. Here we demonstrate that the human subplate also expresses α2zinc-binding globulin and Alpha-2-Heremans-Schmid glycoprotein/human fetuin. In addition, the established subplate neuron marker neuropeptide Y is expressed superficially, whereas potassium/chloride co-transporter (KCC2)-positive neurons are localized in the deep subplate at 16 PCW. These observations imply that the human subplate shares gene expression patterns with rodent, but is more compartmentalized into superficial and deep sublayers. This increased complexity of the human subplate may contribute to differential vulnerability in response to hypoxia/ischaemia across the depth of the cortex. Combining knowledge of cell-type specific subplate gene expression with modern imaging methods will enable a better understanding of neuropathologies involving the subplate.

Connective tissue growth factor production by activated pancreatic stellate cells in mouse alcoholic chronic pancreatitis

Alcoholic chronic pancreatitis (ACP) is characterized by pancreatic necrosis, inflammation, and scarring, the latter of which is due to excessive collagen deposition by activated pancreatic stellate cells (PSC). The aim of this study was to establish a model of ACP in mice, a species that is usually resistant to the toxic effects of alcohol, and to identify the cell type(s) responsible for production of connective tissue growth factor (CTGF), a pro-fibrotic molecule. C57Bl/6 male mice received intraperitoneal ethanol injections for 3 weeks against a background of cerulein-induced acute pancreatitis. Peak blood alcohol levels remained consistently high in ethanol-treated mice as compared with control mice. In mice receiving ethanol plus cerulein, there was increased collagen deposition as compared with other treatment groups as well as increased frequency of alpha-smooth muscle actin and desmin-positive PSC, which also showed significantly enhanced CTGF protein production. Expression of mRNA for collagen alpha1(I), alpha-smooth muscle actin or CTGF were all increased and co-localized exclusively to activated PSC in ACP. Pancreatic expression of mRNA for key profibrotic markers were all increased in ACP. In conclusion, a mouse model of ACP has been developed that mimics key pathophysiological features of the disease in humans and which shows that activated PSC are the principal producers of collagen and CTGF. PSC-derived CTGF is thus a candidate therapeutic target in anti-fibrotic strategies for ACP.

Strategies for blocking the fibrogenic actions of connective tissue growth factor (CCN2): From pharmacological inhibition in vitro to targeted siRNA therapy in vivo

Connective tissue growth factor (CCN2) is a major pro-fibrotic factor that frequently acts downstream of transforming growth factor beta (TGF-beta)-mediated fibrogenic pathways. Much of our knowledge of CCN2 in fibrosis has come from studies in which its production or activity have been experimentally attenuated. These studies, performed both in vitro and in animal models, have demonstrated the utility of pharmacological inhibitors (e.g. tumor necrosis factor alpha (TNF-alpha), prostaglandins, peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists, statins, kinase inhibitors), neutralizing antibodies, antisense oligonucleotides, or small interfering RNA (siRNA) to probe the role of CCN2 in fibrogenic pathways. These investigations have allowed the mechanisms regulating CCN2 production to be more clearly defined, have shown that CCN2 is a rational anti-fibrotic target, and have established a framework for developing effective modalities of therapeutic intervention in vivo.

Connective tissue growth factor is necessary for retinal capillary basal lamina thickening in diabetic mice

Experimental prevention of basal lamina (BL) thickening of retinal capillaries ameliorates early vascular changes caused by diabetes. Connective tissue growth factor (CTGF) is upregulated early in diabetes in the human retina and is a potent inducer of expression of BL components. We hypothesize that CTGF is causally involved in diabetes-induced BL thickening of retinal capillaries. To test this hypothesis, we compared the effects of streptozotocin (STZ)-induced diabetes on retinal capillary BL thickness between wild-type mice (CTGF+/+) and mice lacking one functional CTGF allele (CTGF+/-). Differences in BL thickness were calculated by quantitative analysis of electron microscopic images of transversally sectioned capillaries in and around the inner nuclear layer of the retina. We show that BL thickening was significant in diabetic CTGF+/+ mice compared with control CTGF+/+ mice, whereas diabetes did not significantly induce BL thickening in CTGF+/- mice. We conclude that CTGF expression is necessary for diabetes-induced BL thickening and suggest that reduction of CTGF levels may be protective against the development of diabetic retinopathy.

Advanced glycation end products cause increased CCN family and extracellular matrix gene expression in the diabetic rodent retina

AIMS/HYPOTHESIS

Referred to as CCN, the family of growth factors consisting of cystein-rich protein 61 (CYR61, also known as CCN1), connective tissue growth factor (CTGF, also known as CCN2), nephroblastoma overexpressed gene (NOV, also known as CCN3) and WNT1-inducible signalling pathway proteins 1, 2 and 3 (WISP1, -2 and -3; also known as CCN4, -5 and -6) affects cellular growth, differentiation, adhesion and locomotion in wound repair, fibrotic disorders, inflammation and angiogenesis. AGEs formed in the diabetic milieu affect the same processes, leading to diabetic complications including diabetic retinopathy. We hypothesised that pathological effects of AGEs in the diabetic retina are a consequence of AGE-induced alterations in CCN family expression.

MATERIALS AND METHODS

CCN gene expression levels were studied at the mRNA and protein level in retinas of control and diabetic rats using real-time quantitative PCR, western blotting and immunohistochemistry at 6 and 12 weeks of streptozotocin-induced diabetes in the presence or absence of aminoguanidine, an AGE inhibitor. In addition, C57BL/6 mice were repeatedly injected with exogenously formed AGE to establish whether AGE modulate retinal CCN growth factors in vivo.

RESULTS

After 6 weeks of diabetes, Cyr61 expression levels were increased more than threefold. At 12 weeks of diabetes, Ctgf expression levels were increased twofold. Treatment with aminoguanidine inhibited Cyr61 and Ctgf expression in diabetic rats, with reductions of 31 and 36%, respectively, compared with untreated animals. Western blotting showed a twofold increase in CTGF production, which was prevented by aminoguanidine treatment. In mice infused with exogenous AGE, Cyr61 expression increased fourfold and Ctgf expression increased twofold in the retina.

CONCLUSIONS/INTERPRETATION

CTGF and CYR61 are downstream effectors of AGE in the diabetic retina, implicating them as possible targets for future intervention strategies against the development of diabetic retinopathy.

A novel integrin alpha5beta1 binding domain in module 4 of connective tissue growth factor (CCN2/CTGF) promotes adhesion and migration of activated pancreatic stellate cells

BACKGROUND

Connective tissue growth factor (CCN2) is upregulated in pancreatic fibrosis and desmoplastic pancreatic tumours. CCN2 interacts with integrin alpha5beta1 on pancreatic stellate cells (PSC) in which it stimulates fibrogenesis, adhesion, migration, and proliferation.

AIM

To determine the structural domain(s) in CCN2 that interact with integrin alpha5beta1 to regulation PSC functions.

METHODS

Primary activated rat PSC were tested for their adherence to isoforms of CCN2 comprising modules 1-4 (CCN2(1-4)), modules 3-4 (CCN2(3-4)), module 3 alone (CCN2(3)), or module 4 alone (CCN2(4)). Adhesion studies were performed in the presence of EDTA, divalent cations, anti-integrin alpha5beta1 antibodies, CCN2 synthetic peptides, or heparin, or after pretreatment of the cells with heparinase, chondroitinase, or sodium chlorate. CCN2 integrin alpha5beta1 binding was analysed in cell free systems. The ability of CCN2(1-4), CCN2(3-4), or CCN2(4) to stimulate PSC migration was evaluated in the presence of anti-integrin alpha5beta1 or heparin.

RESULTS

PSC adhesion was stimulated by CCN2(1-4), CCN2(3-4), or CCN2(4) and supported by Mg2+ but not Ca2+. CCN2(4) supported PSC adhesion or migration were blocked by anti-integrin alpha5beta1 antibodies or by treatment of cells with heparinase or sodium chlorate. A direct interaction between CCN2(4) and integrin alpha5beta1 was demonstrated in cell free assays. The sequence GVCTDGR in module 4 mediated the binding between CCN2(4) and integrin alpha5beta1 as well as CCN2(4) mediated PSC adhesion and migration.

CONCLUSIONS

A GVCTDGR sequence in module 4 of CCN2 is a novel integrin alpha5beta1 binding site that is essential for CCN2 stimulated functions in PSC and which represents a new therapeutic target in PSC mediated fibrogenesis.

Inhibition of Rho kinase modulates radiation induced fibrogenic phenotype in intestinal smooth muscle cells through alteration of the cytoskeleton and connective tissue growth factor expression

BACKGROUND

Late radiation enteritis in humans is associated with accumulation of extracellular matrix and increased connective tissue growth factor (CTGF) expression that may involve intestinal muscular layers.

AIMS

We investigated the molecular pathways involved in maintenance of radiation induced fibrosis by gene profiling and postulated that alteration of the Rho pathway could be associated with radiation induced fibrogenic signals and CTGF sustained expression.

PATIENTS AND METHODS

Ileal biopsies from individuals with and without radiation enteritis were analysed by cDNA array, and primary cultures of intestinal smooth muscle cells were established. Then, the effect of pharmacological inhibition of p160 Rho kinase, using Y-27632, was studied by real time reverse transcription-polymerase chain reaction, western blot, and electrophoretic mobility shift assay.

RESULTS

Molecular profile analysis of late radiation enteritis showed alterations in expression of genes coding for the Rho proteins. To investigate further the involvement of the Rho pathway in intestinal radiation induced fibrosis, primary intestinal smooth muscle cells were isolated from radiation enteritis. They retained their fibrogenic differentiation in vitro, exhibited a typical cytoskeletal network, a high constitutive CTGF level, increased collagen secretory capacity, and altered expression of genes coding for the Rho family. Rho kinase blockade induced a simultaneous decrease in the number of actin stress fibres, alpha smooth muscle actin, and heat shock protein 27 levels. It also decreased CTGF levels, probably through nuclear factor kappaB inhibition, and caused decreased expression of the type I collagen gene.

CONCLUSION

This study is the first showing involvement of the Rho/Rho kinase pathway in radiation fibrosis and intestinal smooth muscle cell fibrogenic differentiation. It suggests that specific inhibition of Rho kinase may be a promising approach for the development of antifibrotic therapies.

Aldosterone upregulates connective tissue growth factor gene expression via p38 MAPK pathway and mineralocorticoid receptor in ventricular myocytes

The effect of aldosterone on connective tissue growth factor (CTGF) was examined in rat embryonic ventricular myocytes. Upon aldosterone treatment, CTGF expression was significantly increased in a dose and time-dependent manner. To explore the molecular mechanism for this upregulation, we examined the role of mineralocorticoid receptor. Pre-treatment of an antagonist (spironolactone) at 5-fold excess of aldosterone blocked the CTGF induction by aldosterone, suggesting that the upregulation was mediated by mineralocorticoid receptor. Aldosterone treatment resulted in activation of ERK1/2, p38 MAPK, and JNK pathways with a more transient pattern in p38 MAPK. Blocking studies using pretreatment of the inhibitor of each pathway revealed that p38 MAPK cascade may be important for aldosterone-mediated CTGF upregulation as evidenced by the blocking of CTGF induction by SB203580 (p38 MAPK inhibitor), but not by PD098059 (ERK1/2 inhibitor) and JNK inhibitor I. Interestingly, JNK inhibitor I and PD098059 decreased the basal level of CTGF expression. On the other hand, pretreatment of spironolactone abrogated the p38 MAPK activation, indicating that mineralocorticoid receptor mechanism is linked to p38 MAPK pathway. Taken together, our findings suggest that aldosterone induces CTGF expression via both p38 MAPK cascade and mineralocorticoid receptor and that cross-talk exists between the two pathways.

An angiotensin II type 1 receptor antagonist, olmesartan medoxomil, improves experimental liver fibrosis by suppression of proliferation and collagen synthesis in activated hepatic stellate cells

1. We studied the effect of a new angiotensin II type 1 (AT(1)) receptor antagonist, olmesartan medoxomil (olmesartan), on the fibrogenic responses in rat hepatic stellate cells (HSCs) and liver fibrogenesis. 2. Olmesartan (1 mg kg(-1) per day) was orally administered to fibrotic rats, induced by bile duct ligation. Liver hydroxyproline content, the mRNA expression of collagen alpha1(I) and alpha-smooth muscle actin (alpha-SMA), and plasma levels of transforming growth factor-beta1 (TGF-beta1) were significantly reduced by olmesartan treatment, suggesting that olmesartan improved liver fibrosis. Interestingly, AT(1) receptors were found to be expressed in alpha-SMA-positive cells in the fibrotic area of livers in bile duct-ligated rats by immunohistochemical analysis. Olmesartan treatment reduced the number of these cells. 3. In vitro experiments showed that angiotensin II (Ang II) treatment induced proliferation and collagen synthesis, and upregulated the profibrogenic cytokines, TGF-beta1 and connective tissue growth factor (CTGF), in rat primary HSCs. Olmesartan blocked all these effects of Ang II. 4. Based on these results, since activated HSCs were found to express AT(1) receptors and Ang II is thought to play an important role in the pathogenesis of liver fibrosis by binding to these receptors, olmesartan may act as a potent antifibrotic drug to suppress the proliferation, collagen synthesis and the expression of profibrogenic cytokines in activated HSCs by blocking these receptors.

Median nerve trauma in a rat model of work-related musculoskeletal disorder

Anatomical and physiological changes were evaluated in the median nerves of rats trained to perform repetitive reaching. Motor degradation was evident after 4 weeks. ED1-immunoreactive macrophages were seen in the transcarpal region of the median nerve of both forelimbs by 5-6 weeks. Fibrosis, characterized by increased immunoexpression of collagen type I by 8 weeks and connective tissue growth factor by 12 weeks, was evident. The conduction velocity (NCV) within the carpal tunnel showed a modest but significant decline after 9-12 weeks. The lowest NCV values were found in animals that refused to participate in the task for the full time available. Thus, both anatomical and physiological signs of progressive tissue damage were present in this model. These results, together with other recent findings indicate that work-related carpal tunnel syndrome develops through mechanisms that include injury, inflammation, fibrosis and subsequent nerve compression.

A role for CCN3 (NOV) in calcium signalling

AIMS

In animals and humans increased expression of CCN3 (NOV) is detected in tissues where calcium is a key regulator, such as the adrenal gland, central nervous system, bone and cartilage, heart muscle, and kidney. Because the multimodular structure of the CCN proteins strongly suggests that these cell growth regulators are metalloproteins, this study investigated the possible role of CCN3 in ion flux and transport during development, control of cell proliferation, differentiation, and pathobiology.

METHODS

The isolation of CCN3 partners was performed by means of the two hybrid system. Yeasts were cotransfected with an HL60 cDNA library fused to the transactivation domain of the GAL4 transcription factor, and with a plasmid expressing CCN3 fused to the DNA binding domain of GAL4. Screening of the recombinant clones selected on the basis of leucine, histidine, and tryptophan prototrophy was performed with a beta-galactosidase assay. After the interaction between CCN3 and its putative partners was checked with a GST (glutathione S-transferase) pull down assay, the positive clones were identified by cloning. To establish whether the CCN3 protein affected calcium ion flux, a dynamic imaging microscopy system was used, which allowed the fluorometric measurement of the intracellular calcium concentration. The proteins used in the assays were GST fused with either CCN3 or CCN2 (CTGF) and GST alone as a control.

RESULTS

The two hybrid system identified the S100A4 (mts1) calcium binding protein as a partner of CCN3 and the use of the GST fusion proteins showed that the addition of CCN3 and CCN2 to G59 glioblastoma and SK-N-SH neuroblastoma cells caused a pronounced but transient increase of intracellular calcium, originating from both the entry of extracellular calcium and the mobilisation of intracellular stores.

CONCLUSIONS

The interaction of CCN3 with S100A4 may account, in part, for the association of CCN3 with carcinogenesis and its pattern of expression in normal conditions. The increased intracellular calcium concentrations induced by CCN3 and CCN2 both involve different processes, among which voltage independent calcium channels might be of considerable importance in regulating the calcium flux associated with cell growth control, motility, and spreading. These observations assign for the first time a biological function to the CCN3 protein and point out a broader role for the CCN proteins in calcium ion signalling.

Pentoxifylline downregulates profibrogenic cytokines and procollagen I expression in rat secondary biliary fibrosis

BACKGROUND

The trisubstituted methylxanthine derivative pentoxifylline inhibits hepatic stellate cell proliferation and collagen synthesis in vitro. The antifibrotic effect of pentoxifylline in a suitable in vivo model of chronic liver fibrogenesis remains to be tested.

METHODS

Groups of adult rats (n=20-23) received oral pentoxifylline at a dose of 8 mg/kg/day from week 1 to week 6, and 16 mg/kg/day from week 1 to week 6 or week 4 to week 6 after complete bile duct occlusion. Animals who underwent sham operation that received 16 mg/kg/day pentoxifylline and untreated rats with bile duct occlusion alone served as controls. After six weeks, animals were sacrificed and parameters of fibrogenesis determined.

RESULTS

Bile duct occlusion caused portal cirrhosis with a 10-fold increased hepatic collagen content in the absence of inflammation or necrosis. This was accompanied by an 11-fold elevated serum aminoterminal procollagen III peptide (PIIINP). The drug induced a dramatic eightfold downregulation of procollagen I mRNA, and suppression of the fibrogenic factors transforming growth factor beta1 and connective tissue growth factor by 60-70%. However, profibrogenic tissue inhibitor of metalloproteinase 1 (TIMP-1) mRNA was increased twofold, resulting in only a moderate decrease in liver collagen, fibrosis score, and PIIINP.

CONCLUSIONS

We conclude that targeting pentoxifylline to the fibrogenic cells, thereby avoiding upregulation of TIMP-1, could become a potent antifibrogenic tool in chronic liver disease.

Steroidal regulation of connective tissue growth factor (CCN2; CTGF) synthesis in the mouse uterus

AIMS

To determine mechanisms regulating the production of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta1 (TGF-beta1) in the mouse uterus.

METHODS

In situ hybridisation and immunohistochemistry were used to localise CCN2 (CTGF) and TGF-beta1 in uteri from sexually mature female mice that had either been (1) mated with sterile males to induce pseudopregnancy or (2) ovariectomised (OVX) and administered estradiol-17beta (E2) or progesterone (P4), either alone or in combination. Uteri collected on days 0.5, 1.5, 2.5, 3.5, 4.5, or 5.5 of pseudopregnancy or at one, three, six, 12, or 24 hours after steroid administration were fixed, sectioned, and incubated with specific riboprobes or antibodies to permit detection and localisation of mRNA or protein for CTGF and TGF-beta1.

RESULTS

On days 0.5-2.5 of pseudopregnancy, CCN2 (CTGF) and TGF-beta1 were principally colocalised to uterine epithelial cells, with much smaller amounts in the stroma. On days 3.5-4.5, there was a reduction of CCN2 (CTGF) and TGF-beta1 in the epithelium but an increase in stromal and endothelial cells, corresponding to a period of extracellular matrix remodelling and neovascularisation within the endometrium. In OVX mice, epithelial cells were weakly positive for both CCN2 (CTGF) and TGF-beta1 in the absence of steroid hormones. Epithelial CTGF mRNA production were strongly but transiently stimulated in OVX mice cells by E2. These effects were antagonised by P4, which itself transiently stimulated epithelial CCN2 (CTGF) production, although less robustly than E2. CTGF and TGF-beta1 protein amounts were high in epithelial cells throughout steroid treatment and were increased in the stroma, where they were relatively long lived. Stromal CCN2 (CTGF) and TGF-beta1 were lower after co-administration of E2 and P4 than in response to each hormone individually. Although ccn2 (ctgf) is a TGF-beta1 inducible gene in other systems, and both growth factors were often co-localised in uterine tissues in these studies, several treatment regimens resulted in high amounts of TGF-beta1 protein in stromal cells without the concomitant production of ccn2 (ctgf) mRNA.

CONCLUSIONS

Maternal factors are principal cues for CCN2 (CTGF) and TGF-beta1 production in the uterus because (1) their expression during pseudopregnancy is comparable to that seen in pregnancy and (2) they are regulated by ovarian steroids. TGF-beta dependent and independent mechanisms of ccn2 (ctgf) gene transcription exist in the uterus that are variably regulated by steroid hormones. Collectively, the data support a role for CCN2 (CTGF) in mediating the effects of steroid hormones and TGF-beta on endometrial function.

Rho-dependent inhibition of the induction of connective tissue growth factor (CTGF) by HMG CoA reductase inhibitors (statins)

It was supposed that inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) reductase (statins) might inhibit the expression of the fibrosis-related factor CTGF (connective tissue growth factor) by interfering with the isoprenylation of Rho proteins. The human renal fibroblast cell line TK173 was used as an in vitro model system to study the statin-mediated modulation of the structure of the actin cytoskeleton and of the expression of CTGF mRNA. Incubation of the cells with simvastatin or lovastatin time-dependently and reversibly changed cell morphology and the actin cytoskeleton with maximal effects observed after about 18 h. Within the same time period, statins reduced the basal expression of CTGF and interfered with CTGF induction by lysophosphatidic acid (LPA) or transforming growth factor beta. Simvastatin and lovastatin proved to be much more potent than pravastatin (IC(50) 1 - 3 microM compared to 500 microM). The inhibition of CTGF expression was prevented when the cells were incubated with mevalonate or geranylgeranylpyrophosphate (GGPP) but not by farnesylpyrophosphate (FPP). Specific inhibition of geranylgeranyltransferase-I by GTI-286 inhibited LPA-mediated CTGF expression whereas an inhibitor of farnesyltransferases FTI-276 was ineffective. Simvastatin reduced the binding of the small GTPase RhoA to cellular membranes. The effect was prevented by mevalonate and GGPP, but not FPP. These data are in agreement with the hypothesis that interference of statins with the expression of CTGF mRNA is primarily due to interference with the isoprenylation of RhoA, in line with previous studies, which have shown that RhoA is an essential mediator of CTGF induction. The direct interference of statins with the synthesis of CTGF, a protein functionally related to the development of fibrosis, may thus be a novel mechanism underlying the beneficial effects of statins observed in renal diseases.

Regulation of connective tissue growth factor (ccn2; ctgf) gene expression in human mesangial cells: modulation by HMG CoA reductase inhibitors (statins)

AIM

Connective tissue growth factor (ccn; ctgf) gene expression is upregulated in fibrotic renal glomeruli. Therefore, the regulation and pharmacological modulation of ccn2 (ctgf) mRNA expression was investigated in a human renal mesangial cell line.

METHODS

A human renal mesangial cell line was cultured in vitro under standard conditions. After stimulation, RNA was extracted and ccn2 (ctgf) mRNA expression assessed by northern blot analysis.

RESULTS

The expression of ccn2 (ctgf) mRNA was transiently upregulated by fetal calf serum. Very rapid onset but short lasting ccn2 (ctgf) mRNA expression was observed after stimulation with lysophosphatidic acid, a bioactive lipid, which activates G protein coupled receptors. Induction of ccn2 (ctgf) mRNA expression by transforming growth factor beta (TGF-beta) was more prolonged and lasted for more than one day. The small GTPases of the Rho family were essential for basal as well as induced ccn2 (ctgf) expression: preincubation of the cells with toxin B from Clostridium difficile abrogated ccn2 (ctgf) mRNA expression. HMG CoA reductase inhibitors, which are therapeutically used as lipid lowering drugs, interfere with the isoprenylation and thus activation of Rho proteins. Simvastatin, an HMG CoA reductase inhibitor, inhibited ccn2 (ctgf) mRNA expression in a concentration dependent manner (IC(50): 1-2 microM).

CONCLUSION

Statins were identified as potent inhibitors of ccn2 (ctgf) mRNA expression in mesangial cells, and therefore might be of potential use to modulate the excessive ccn2 (ctgf) expression in mesangial cells related to glomerular fibrosis.