Connective Tissue Growth Factor siRNA Research Articles

Inhibition of connective tissue growth factor suppresses hepatic stellate cell activation in vitro and prevents liver fibrosis in vivo

Activation of hepatic stellate cells (HSC) represents a critical event in fibrosis, and connective tissue growth factor (CTGF) plays a profibrotic activity and a key factor in the pathogenesis of tissue fibrosis. The current study aimed to determine whether lentivirus-mediated short hairpin RNA (shRNA)-targeted CTGF downregulates the CTGF expression and furthermore whether it suppresses the activation and proliferation of HSC in vitro and prevents liver fibrosis in vivo. HSC-T6 cells were treated with recombinant lentivirus carrying CTGF siRNA. Real-time PCR, Western blotting, MTT, and flow cytometry were performed to investigate the activation and proliferation of HSC-T6 cells in response to CTGF silence. CCl4-induced rats were received lentivirus containing CTGF siRNA by intraportal vein injection. Levels of liver fibrosis were assessed by biochemical and histopathologic examinations. Recombinant lentivirus containing CTGF siRNA could effectively and specifically downregulate the expression of CTGF in both HSC-T6 cells and CCl4-induced rats with liver fibrosis. Blockade of CTGF resulted in significant inhibition of HSC activation and proliferation with decrease in TIMPs, MMP2, MMP9, and collagen I, as well as increase in cells in S phase. Silencing CTGF expression with siRNA prevented liver fibrosis in CCl4-induced rat model. These findings indicated that CTGF plays a key role in the pathogenesis of liver fibrosis and lentiviral-mediated CTGF siRNA has the potential to be an effective treatment for liver fibrosis.

Noncovalenly PEGylated CTGF siRNA/PDMAEMA complex for pulmonary treatment of bleomycin-induced lung fibrosis

On the basis of wide biomedical applications of methacrylate polymers, we previously developed noncovalently post-PEGylated ternary complex of siRNA using poly(dimethylamino)ethylmethacrylate (PDMAEMA) and its copolymer with poly(α-methylether-ω-methacrylate-ethyleneglycol) [PMAPEG]. In this work, we investigated the antifibrotic effect of connective tissue growth factor siRNA (siCTGF)/PDMAEMA/PDMAEMA-b-PMAPEG complex for the treatment of bleomycin-induced pulmonary fibrosis. After orotracheal administration to fibrotic Sprague Dawley (SD) model rats, FAM-labeled siCTGF complex was effectively delivered to the cells in the lung. The siCTGF ternary complex resulted in a significant reduction in target gene expression, collagen deposition, inflammatory cytokines production, and drastic attenuation of pulmonary fibrosis in pathophysiological analysis. Furthermore, the survival rate was remarkably increased to the statistically significant level in comparison with the scrambled siCTGF treatment group.

Cationic solid lipid nanoparticles derived from apolipoprotein-free LDLs for target specific systemic treatment of liver fibrosis

Low density lipoprotein (LDL) plays an important role in transporting fat molecules including cholesterols in the body. In this work, cationic solid lipid nanoparticles (CSLNs), bioinspired and reconstituted from natural LDLs, were designed and applied to target specific systemic delivery of connective tissue growth factor siRNA (siCTGF) for the treatment of liver fibrosis. They could form a nuclease-resistant stable nano-complex with siRNA, which was efficiently internalized into cells achieving targeted gene silencing in the presence of serum with a remarkably low cytotoxicity. After intravenous injection, CSLN/siCTGF complex was target specifically delivered to the liver and resulted in a significant reduction in collagen content and pro-fibrogenic factors like tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-β), interleukin-6 (IL-6), and CTGF with the dramatic improvement of patho-physiological symptoms in liver fibrosis model rats. The bio-distribution study by fluorescence bioimaging and single-photon emission computed tomography (SPECT) confirmed the target specific delivery and accumulation of CSLN/siCTGF complexes to the liver tissues.

Connective tissue growth factor is a positive regulator of epithelial–mesenchymal transition and promotes the adhesion with gastric cancer cells in human peritoneal mesothelial cells

Connective tissue growth factor (CTGF) is involved in human cancer development and progression. Epithelial to mesenchymal transition (EMT) plays an important role in many biological processes. In this study, we wished to investigate the role of CTGF in EMT of peritoneal mesothelial cells and the effects of CTGF on adhesion of gastric cancer cells to mesothelial cells. Human peritoneal mesothelial cells (HPMCs) were cultured with TGF-β1 or various concentrations of CTGF for different time. The EMT process was monitored by morphology. Real-time RT-PCR and Western blot were used to evaluate the expression of vimentin, α-SMA , E-cadherin and β-catenin. RNA interference was used to achieve selective and specific knockdown of CTGF. We demonstrated that CTGF induced EMT of mesothelial cells in a dose- and time-dependent manner. HPMCs were exposed to TGF-β1 also underwent EMT which was associated with the induction of CTGF expression. Transfection with CTGF siRNA was able to reverse the EMT partially after treatment of TGF-β1. Moreover, the induced EMT of HPMCs was associated with an increased adhesion of gastric cancer cells to mesothelial cells. These findings suggest that CTGF is not only an important mediator but a potent activator of EMT in peritoneal mesothelial cells, which in turn promotes gastric cancer cell adhesion to peritoneum.

Inhibition effect of small interfering RNA targeting connective tissue growth factor on liver fibrosis in rats

To design and synthesize small interfering RNA (siRNA) targeting connective tissue growth factor (CTGF) and to investigate its effect on liver fibrosis. The interference sequence of CTGF was designed and synthesized. Rat hepatic fibrosis model was induced by intraperitoneal injection of 40 % CCl4(3 ml/kg). Thirty male rats were randomly divided into 5 groups: in normal control and model groups rats received tail vein injection of normal saline every 3 days for 8 consecutive weeks; in preventive group rats received tail vein injection of CTGF siRNA (0.1 mg/kg) every 3 days for 8 weeks; in 2-w treatment group CTGF siRNA was given for 6 weeks starting from two weeks after CCl4 injection; in 4-w treatment group CTGF siRNA was given for 4 weeks starting 4 weeks after CCl4 injection. The serum and hepatic tissue samples were harvested 3 days after the last CCl4 injection. Hepatic fibrosis indices were measured. Expression of CTGF mRNA and protein in the liver was evaluated by RT-PCR and Western blot, respectively. Fibrosis in rat liver was analyzed by Masson staining. Compared with model group (0.544 0.019), the expression of CTGF mRNA and protein in liver of both preventive(0.105 ± 0.003) and 2-w treatment groups (0.190 ± 0.006) were markedly down-regulated (P<0.05). Inflammation, necrosis and fibrosis in hepatic tissue were significantly attenuated. In addition, the serum ration of liver fibrosis indices was greatly reduced(P<0.05). Compared with preventive and 2-w treatment groups, the expression of CTGF mRNA and protein in liver in 4 weeks of treatment group were up-regulated (P<0.05); inflammation, necrosis and fibrosis in hepatic tissue were relative increased; and the serum concentrations of liver fibrosis indices were relatively higher (P<0.05). The highly effective CTGF siRNA has been successfully synthesized, which can inhibit CTGF expression in liver, prevent hepatic fibrosis and its progress in rats.

Ethanol-stimulated differentiated functions of human or mouse hepatic stellate cells are mediated by connective tissue growth factor

Connective tissue growth factor (CTGF) expression is intimately associated with hepatic fibrotic pathophysiology. In this study, CTGF production and action was investigated in ethanol-treated mouse primary hepatic stellate cells (HSC) or human LX-2 cells. CTGF, transforming growth factor-beta1 (TGF-β1), alpha-smooth muscle actin (α-SMA) or collagen α1(I) mRNA were quantified by real-time PCR after treatment of HSC with ethanol or acetaldehyde. CTGF protein production was assessed by immunoprecipitation or ELISA. Ethanol-stimulated CTGF transcription was investigated using CTGF promoter reporter constructs. The TGF-β1- or CTGF-dependency of ethanol-induced CTGF, α-SMA, or collagen α1(I) was determined using small interfering RNA (siRNA) to TGF-β1 or CTGF. In human steatohepatitis, CTGF was produced by presumptive activated HSC. In cultured human or mouse HSC, production of CTGF, α-SMA and/or collagen was increased by ethanol treatment, an effect mimicked by acetaldehyde and blocked by 4-methylpyrazole (4-MP) or N-acetylcysteine (NAC). CTGF promoter activity was stimulated in a sustained fashion by ethanol or TGF-β1. Mutation of the Smad site or basal control element (BCE-1) in the CTGF promoter caused a 5-fold reduction in ethanol-stimulated CTGF promoter activity. Administration of TGF-β1 siRNA or CTGF siRNA significantly decreased ethanol- or acetaldehyde-stimulated mRNA or protein levels of CTGF, α-SMA or collagen I in LX-2 cells. In mouse HSC, TGF-β1- or ethanol-stimulated CTGF, α-SMA or collagen I were significantly attenuated by CTGF siRNA. Ethanol-induced α-SMA or collagen α1(I) in HSC are mediated via TGF-β-dependent CTGF production, highlighting potential therapeutic benefits of targeting CTGF in alcoholic liver disease.

Effect of silencing connective tissue growth factor on the liver fibrosis in rats

To investigate the anti-fibrogenesis property of intraportal vein small interfering RNA (siRNA) injection targeting connective tissue growth factor (CTGF) in a rat model of liver fibrosis induced by carbon tetrachloride (CCl4) and its effect on hepatic stellate cell (HSC) activation. 24 male rats were randomly divided into four group. rats received CCl4 by subcutaneous injections every three days for 6 consecutive weeks, and meantime they also obtained either siRNA targeting CTGF (as CTGF siRNA group), saline (as model group) or a control siRNA (as control siRNA group) by intraportal vein injection to rats liver at the same approach. Other rats received saline intraportal vein injection for 6 weeks (as normal control group). The expressions of CTGF and a-SMA protein were detected by Western blot. Hepatic histology was evaluated by HE staining and Sirius red staining. The collagen staining areas were measured quantitatively using a computer-aided manipulator with slight modifications. The number of active HSC were evaluated by immunohistochemistry. Six weeks after CCl4 injection, prominent upregulations were observed in the expressions of CTGF and a-SMA protein in saline or control siRNA-treated rats livers. In rats with CTGF siRNA treatment, the protein expressions of CTGF and a-SMA in liver decreased by 95%+/-2% and 86%+/-11% (F=21.234 and 12.473, P<0.01) respectively, the number of active HSC in liver decreased by 76%+/-9% (F=9.179, P<0.01) as compared to the model group. The attenuation of liver fibrosis was also observed in rats with CTGF siRNA treatment. Intraportal vein siRNA injection targeting CTGF could significantly inhibit CTGF gene expression in rats, thereby attenuate liver fibrosis by decreasing the number of active HSCs.

Effects of small interfering RNA approach to silence the connective tissue growth factor gene on the expression of the protein p27

To investigate the effects of the small interfering RNA (siRNA) approach to silence the expression of connective tissue growth factor (CTGF) gene expression on the expression of the protein p27. Experimental research. The specific siRNA of CTGF was designed and synthesized, then transfected into cultured bovine corneal endothelial cells by liposomes. The blank control group was only treated with the culture medium and not be transfected with siRNA. Reverse transfection-polymerase chain reaction (RT-PCR) was applied to show the effect of gene-silencing, and western blot was used to observe the protein p27 expression of bovine corneal endothelial cells, which were treated with 1.00 µg/L transforming growth factor β(2) (TGF-β(2)). The results were analyzed by one-factor analysis of variance. CTGF siRNA was successfully transfected into cultured bovine corneal endothelial cells and effectively silence the expression of CTGF mRNA. The CTGF mRNA expression decreased to 17.3%, 24.4% and 41.7% of control values at 24, 48 and 72 h after transfection, there was significant difference between these groups (F = 389.9, P < 0.05). Significant decrease of protein p27 expression was detected at 36 h after transfection (F = 299.3, P < 0.05). CTGF-specific siRNA was able to inhibit the expression of CTGF mRNA effectively and down-regulate the expression of p27.

The effect of connective tissue growth factor RNA interference on keloid-derived fibroblasts

Objective To investigate the impact of connective tissue growth factor (CTGF) RNA interference on the proliferation and type I collagen synthesis of keloid-derived fibroblasts (KFs). Methods Three CTGF small interference RNA (siRNA) sequences were cloned into pRNAT-6.1/Neo vector, and transfected into KFs. The expression of CTGF and type I collagen was detected by using quantitative real-time PCR (q RT-PCR). The cell number of KFs was counted. Results All of the three CTGF siRNA vectors showed inhibitory effects on CTGF mRNA expression in KFs. Among them,the CTGF siRNA3 vector was the most potent one,which decreased CTGF relative expression level from 3.13 ±0. 17 to 0. 71 ± 0.02 (P<0.01). Meanwhile, the expression of type I collagen was decreased from 2.04 ± 0. 10 to 0. 60 ± 0.04 (P<0.01).The cell number of KF on the day 5 was (10.50 ±0.25) × 10~4 in the control group, while decreased to (6. 83 ± 0. 29) × 10~4 in the CTGF siRNA3 group (P<0. 01). Conclusion CTGF RNAi inhibits the CTGF expression in KFs,therefore decreases type I collagen expression and cell proliferation of KFs. Key words: Keloid; Fibroblast; Connective tissue growth factor

Resolution of experimental liver fibrosis in mice by targeted delivery of connective tissue growth factor siRNA

Resolution of experimental liver fibrosis in mice by targeted delivery of connective tissue growth factor siRNAConnective tissue growth factor (CTGF) promotes liver fibrosis by stimulating collagen production in activated hepatic stellate cells (HSC). Here, we investigated the curative properties of CTGF siRNA delivered to activated HSC in acute or chronic models of CCl4‐induced liver fibrosis. Modified liposomes containing CTGF siRNA were coated with a collagen Type VI receptor‐binding peptide. Balb/c mice received daily injections of CCl4 or oil control for either 3 or 5 weeks. During the last 2 weeks of these regimens, some mice also received concurrent daily injections of CTGF siRNA in targeted liposomes ("CTGF siRNA‐TL") or scrambled CTGF siRNA in targeted liposomes ("CTGF SsiRNA‐TL"). Administration of CCl4 for 3 or 5 weeks resulted in high levels of α‐SMA‐positive cells and deposition of collagen. Whereas this response was unaffected by administration of CTGF SsiRNA‐TL, neither α‐SMA‐positive cells nor collagen deposits were present in CTGF siRNA‐TL‐treated livers. Real‐time PCR showed that the CCl4‐induced mRNA expression of α‐SMA, collagen Type I α1, TGF‐β, or CTGF was restored to baseline values by CTGF siRNA‐TL (p&lt; 0.01) but not by CTGF SsiRNA‐TL. Thus, this targeted liposomal delivery system designed to deliver CTGF siRNA to activated HSC was effective in either preventing or reversing fibrosis even in the continued presence of the fibrotic insult.

Inhibition of Connective Tissue Growth Factor by Small Interfering RNA Prevents Renal Fibrosis in Rats Undergoing Chronic Allograft Nephropathy

Aim Connective tissue growth factor (CTGF) is a highly profibrogenic molecule implicated in renal fibrogenesis. Small interfering RNA (siRNA) is an effective tool to silence gene expression. This study determined whether caudal vein injection of siRNA targeting CTGF inhibited its expression in rat kidneys in vivo, and furthermore whether it protected the kidney from renal fibrosis in chronic allograft nephropathy (CAN). Methods Male inbred Fischer (F344, RT1 lv1) rat renal grafts were orthotopically transplanted into Lewis (LEW, RT1 1) rats following the procedure of Kamada with our modification. At 6 weeks, recipients were divided into siRNA, normal saline (NS), and control siRNA groups, using daily siRNA-targeting CTGF (0.1 mg/kg), or NS, or a control siRNA via caudal vein injection for 14 days. At 4, 6, and 8 weeks, we observed the pathologic changes, expression of CTGF, E-cadherin, collagen I and IV, and anti-smooth muscle actin (α-SMA). Results Serum creatinine level, Banff score, and the expression of CTGF were significantly lower among the siRNA than the NS or the control siRNA groups at 8 weeks ( P < .05). The expressions of collagen I and IV, and α-SMA were also significantly downregulated and E-cadherin was lost in the siRNA versus the NS and control siRNA groups at 8 weeks. Conclusions This study showed that delivery of CTGF siRNA via the caudal vein significantly inhibited expression of CTGF in rat kidneys, effectively preventing fibrosis in CAN. The results suggest that siRNA-targeting of CTGF has the potential to be a novel strategy for amelioration of CAN.

RNA interfering connective tissue growth factor prevents rat hepatic stellate cell activation and extracellular matrix production

Connective tissue growth factor (CTGF) is a possible key determinant of progressive fibrosis. Small interfering RNA (siRNA) is a powerful tool for silencing gene expression post-transcriptionally. Therefore, the present study aimed to determine whether synthetic siRNA target CTGF down-regulates the expression of the CTGF gene in primary rat hepatic stellate cells (HSC) and HSC T6, and, furthermore, whether it prevents rat HSC activation and extracellular matrix (ECM) production. Primary HSC were obtained by enzymatic perfusion of rat liver. HSC T6, primary HSC were treated with siRNAs that target CTGF or a control siRNA by addition to the culture medium. We obtained one siRNA that could sequence-specifically reduce target gene expression by over 90% at a concentration of 200 nM in the cell culture medium for a total of three siRNAs targeting CTGF genes. In HSC T6 cells, the effect of CTGF siRNA was dose-dependent (50-200 nM) and time-limited to a 24-72-h period. The siRNA knockdown of CTGF significantly reduced the expression of alpha-smooth muscle actin protein, increased the number of cells, upregulated the ratios of G0/G1 stage in rat HSC at 7 days of culture after plating, and attenuated the expression of type I and III collagen mRNA with a supernatant concentration of hyaluronic acid, and type III procollagen in an activated HSC of culture for 24-72 h. CTGF siRNA could effectively and sequence-specifically down-regulate the expression of CTGF in rat HSC, resulting in significant inhibition of HSC activation and proliferation as well as ECM production. These findings indicate that synthetic siRNA targeting CTGF could prove to be a useful treatment of liver fibrosis.

SiRNA-mediated knockdown of connective tissue growth factor prevents N-nitrosodimethylamine-induced hepatic fibrosis in rats

Hepatic fibrosis is a dynamic process that involves the interplay of different cell types in the hepatic tissue. Connective tissue growth factor (CTGF) is a highly profibrogenic molecule and plays a crucial role in the pathogenesis of hepatic fibrosis. The aim of the present investigation was three-fold. First, we studied the expression of CTGF in the cultured hepatic stellate cells using immunohistochemical technique. Second, we induced hepatic fibrosis in rats through serial intraperitoneal injections of N-nitrosodimethylamine (NDMA; dimethylnitrosamine, DMN) and studied the upregulation of CTGF and TGF-beta1 during hepatic fibrogenesis. Third, we downregulated CTGF expression using CTGF siRNA and examined the role of CTGF siRNA to prevent the progression of NDMA-induced hepatic fibrosis. The results depicted strong staining of CTGF in the transformed hepatic stellate cells in culture. Serial administrations of NDMA resulted in activation of hepatic stellate cells, upregulation of CTGF and TGF-beta1 both at mRNA and protein levels and well-developed fibrosis in the liver. Immunostaining, Western blot analysis, semiquantitative and real-time RT-PCR studies showed downregulation of CTGF and TGF-beta1 after treatment with CTGF siRNA. The results of the present study demonstrated that CTGF gene silencing through siRNA reduces activation of hepatic stellate cells, prevents the upregulation of CTGF and TGF-beta1 gene expression and inhibits accumulation of connective tissue proteins in the liver. The data further suggest that knockdown of CTGF upregulation using siRNA has potential therapeutic application to prevent hepatic fibrogenesis.

Inhibition effect of small interfering RNA of connective tissue growth factor on the expression of vascular endothelial growth factor and connective tissue growth factor in cultured human peritoneal mesothelial cells

The peritoneum response to peritoneal dialysis can lead to fibrosis. The transforming growth factor beta1 (TGF-beta1) plays a key role in regulating tissue repair and remodelling after injury. Connective tissue growth factor (CTGF), a downstream mediator of TGF-beta1 inducing fibrosis, has been implicated in peritoneal fibrosis. Vascular endothelial growth factor (VEGF) plays a key role in angiogenesis that can hasten peritoneal fibrosis. In this study, we investigated the effect of small interfering RNA (siRNA) of CTGF by pRETRO-SUPER (PRS) retrovirus vector on the expression of CTGF and VEGF in human peritoneal mesothelial cells. Retrovirus producing CTGF siRNA were constructed from the inverted oligonucleotides and transferred into packaging cell line PT67 with lipofectamine, and the virus supernatant was used to infect human peritoneal mesothelial cell (HPMC). The cells were divided into seven groups: low glucose DMEM, low glucose DMEM + TGF-beta1 5 ng/ml, low glucose DMEM + TGF-beta1 5 ng/ml + PRS-CTGF-siRNA(1-4) and low glucose DMEM + TGF-beta1 5 ng/ml + PRS. The expression of CTGF and VEGF were measured by semiquantitative RT-PCR and Western blot. Low levels of CTGF and VEGF were detected in confluent HPMCs. Following stimulation with TGF-beta1, the levels of CTGF and VEGF were significantly upregulated (P < 0.01). Introduction of PRS-CTGF-siRNA(1-4) resulted in the significant reduction of CTGF mRNA and protein, and VEGF mRNA (P < 0.01), especially in groups PRS-CTGF-siRNA1 and PRS-CTGF-siRNA4. The introduction of PRS void vector did not have these effects (P > 0.05). The expression of CTGF siRNA mediated by PRS retrovirus vector can effectively reduce the level of CTGF and VEGF induced by TGF-beta1 in cultured HPMCs. This study may provide potential therapeutic strategies to prevent the peritoneal fibrosis.

SPARC, an upstream regulator of connective tissue growth factor in response to transforming growth factor β stimulation

To differentiate the effects of inhibition of specific small interfering RNA (siRNA) of SPARC (secreted protein, acidic and rich in cysteine) and siRNA of connective tissue growth factor (CTGF) in cultured human fibroblasts, and to identify potential interrelationships between SPARC and CTGF. Fibroblasts from skin biopsy specimens of 2 normal individuals were transfected with siRNA of SPARC and siRNA of CTGF. The fibroblasts were stimulated with or without transforming growth factor beta1 (TGFbeta1) and examined by real-time quantitative reverse transcription-polymerase chain reaction to determine the transcription levels of several extracellular matrix genes. After exogenous TGFbeta1 stimulation, both SPARC siRNA and CTGF siRNA showed a protective role against overexpression of collagen genes. Following TGFbeta1 stimulation, SPARC siRNA-transfected fibroblasts showed a greater reduction in expression of the collagen genes compared with CTGF siRNA-transfected fibroblasts, as well as a significantly decreased expression of CTGF (P < 0.05). Using linear structure equations to quantitatively model a genetic network based on expression levels of each gene, a positive regulatory role of SPARC on CTGF, COL1A2, COL3A1, COL11A1, and TIMP3 was observed. However, the regulatory role of CTGF on SPARC appeared to be negative and very small, while the positive regulatory effects of CTGF on COL1A2, COL3A1, COL11A1, and TIMP3 were less than those of SPARC. The results of this quantitative comparison support the hypothesis that in these cultured fibroblasts, the regulatory effects of SPARC on some major extracellular matrix structural components are greater than those of CTGF. In addition, SPARC appears to regulate CTGF in a predominantly positive manner, while CTGF may act as a negative feedback control on SPARC following TGFbeta stimulation.

Connective tissue growth factor (CTGF) acts as a downstream mediator of TGF‐β1 to induce mesenchymal cell condensation

Mesenchymal cell (MC) condensation or the aggregation of MCs precedes chondrocyte differentiation and is required for subsequent cartilage formation during endochondral ossification. In this study, we used micromass cultures of C3H10T1/2 cells as an in vitro model system for studying MC condensation and the events important for this process. Transforming growth factor beta1 (TGF-beta1) served as the initiator of MC condensation in our model system and we were interested in determining whether CTGF functions as a downstream mediator of TGF-beta1. CTGF is a matricellular protein that has been found to be expressed in MC condensations and in the perichondrium. Micromass cultures of C3H10T1/2 cells condensed under TGF-beta1 stimulation concomitant with dramatic up-regulation of CTGF mRNA and protein levels. CTGF silencing by either CTGF siRNA or CTGF antisense oligonucleotide approaches showed that TGF-beta1-induced condensation was CTGF dependent. Furthermore, silencing of CTGF expression resulted in significant reductions in cell proliferation and migration, events that are crucial during MC condensation. In addition, up-regulation of Fibronectin (FN) and suppression of Sox9 expression by TGF-beta1 was also found to be mediated by CTGF. Immunofluorescence of developing mouse vertebrae showed that CTGF, TGF-beta1 and FN were co-expressed in condensations of MCs, while Sox9 expression was low at this stage. During subsequent chondrogenesis, Sox9 expression was high in chondrocytes while CTGF expression was limited to the perichondrium. Thus, CTGF is an essential downstream mediator of TGF-beta1-induced MC condensation through its effects on cell proliferation and migration. CTGF is also involved in up-regulating FN and suppressing Sox9 expression during TGF-beta1 induced MC condensation.

Inhibition of connective tissue growth factor by siRNA prevents liver fibrosis in rats

Connective tissue growth factor (CTGF) is a highly profibrogenic molecule implicated in hepatic fibrogenesis. Small interfering RNA (siRNA) is an effective tool to silence gene expression post-transcriptionally. Therefore, we conducted an investigation to determine if intraportal vein siRNA injection targeting CTGF inhibits CTGF expression on rat liver in vivo and furthermore whether it protects the liver from liver fibrosis. Some rats received carbon tetrachloride (CCl4) by subcutaneous injections every three days for six consecutive weeks, and meantime they also obtained either siRNA (0.1 mg/kg) targeting CTGF, saline or a control siRNA by intraportal vein injection to rats' liver at the same pattern. Other rats received CCl4 by subcutaneous injection for 2 weeks, followed by CCl4 and CTGF siRNA intraportal vein injection for four more weeks. Intraportal vein injection of CTGF siRNA specifically reduced the expression of CTGF protein in rat liver, and these effects were maintained for 3 days. Six weeks after CCl4 injection, prominent upregulations were observed in the gene expressions of CTGF, type I, III collagen, laminin, tissue inhibitor metal proteinase-1 (TIMP-1) and transforming growth factor-beta1 (TGF-beta1) in saline or control siRNA-treated rats livers. Administrating CTGF siRNA for 4 or 6 weeks, by contrast, markedly attenuated the induction of CTGF, type I, III collagen, laminin, TIMP-1 and TGF-beta1 genes, whereas Smad2, 7 gene expression was not affected. The number of active hepatic stellate cells (HSCs) determined by the expression of alpha-smooth muscle actin was also significantly decreased. The CTGF siRNA treatment markedly reduced serum procollagen type III, hepatic hydroxyproline and liver fibrosis staging. Silencing CTGF expression with siRNA demonstrates therapeutic potential to prevent liver fibrosis by inhibiting HSC activation with consequent extracellular matrix accumulation and the upregulation of TGF-beta1 gene expression.

Transforming Growth Factor-β2 Modulated Extracellular Matrix Component Expression in Cultured Human Optic Nerve Head Astrocytes

To study whether glaucomatous extracellular matrix (ECM) modifications in the lamina cribrosa might be induced by TGF-beta 2, the effect of TGF-beta 2 on the expression of collagen types I (Col1 alpha 1), III (Col3 alpha 1), and IV (Col4 alpha 2); fibronectin (FN); tissue transglutaminase (TGM2); connective tissue growth factor (CTGF); and thrombospondin (TSP-1) in cultured human optic nerve head (ONH) astrocytes was investigated. Astrocytes were isolated from eyes of five human donors, and cultured monolayers were treated with 1.0 ng/mL TGF-beta 2 for 24 and 48 hours. Expression of Col1 alpha 1, Col3 alpha 1, Col4 alpha 2, FN, TGM2, CTGF, and TSP-1 was examined by semiquantitative RT-PCR and Northern and Western blot analyses. The effect of CTGF silencing on the TGF-beta 2-modulated expression of these genes was investigated by transfection of CTGF small interfering (si)RNA before TGF-beta 2 treatment. TGF-beta 2 treatment upregulated the expression of Col1 alpha 1, Col4 alpha 2, FN, CTGF, TGM2, and TSP-1 mRNA and protein in cultured astrocytes. Inductions ranged between 1.5- and 4-fold. Expression of Col3 alpha 1 remained unaffected. Transfection of 10 nM CTGF siRNA inhibited the TGF-beta 2-induced upregulation of CTGF, Col4 alpha 2, Col1 alpha 1, TGM2, and FN, whereas TSP-1 expression was not reduced. TGF-beta 2 is capable of inducing the expression of ECM and basement membrane components in cultured ONH astrocytes via CTGF and upregulated TSP-1, a protein naturally involved in the activation of latent TGF-beta. Therefore, TGF-beta 2 could be a factor in the initiation of the modification of ECM in the glaucomatous ONH. In addition, TSP-1 induction may be a mechanism by which TGF-beta 2 amplifies its own activation.

Connective tissue growth factor siRNA modulates mRNA levels for a subset of molecules in normal and TGF‐β1–stimulated porcine skin fibroblasts

Previous studies in a pig model of skin wound healing showed a coordinate expression of transforming growth factor‐β (TGF‐β) and connective tissue growth factor (CTGF), and exposure of porcine skin fibroblasts in vitro to recombinant human CTGF significantly up‐regulated mRNA levels for a number of molecules. Therefore, based on recent reports that small interfering RNA (siRNA; double‐stranded RNA) can effect silencing of the expression of gene(s), this approach has now been used with CTGF‐specific siRNA to better understand the function of this growth factor in regulating matrix homeostasis and repair. Normal skin fibroblasts from Yorkshire pigs were treated with 0.1–0.8 µM CTGF siRNA, TGF‐β, or TGF‐β plus CTGF siRNA for 12–48 hours. Total RNA was isolated and quantified, and then mRNA levels for specific molecules were analyzed by reverse transcription‐polymerase chain reaction. Protein levels for CTGF and HSP47 were assessed by Western‐blot analysis. CTGF siRNA transfection led to significant decreases in mRNA and protein levels for CTGF in both a dose‐ and time‐dependent manner. mRNA levels for types I and III procollagen, decorin, HSP47, tissue inhibitor of metalloproteinase ‐1, ‐2, ‐3, and basic fibroblast growth factor were also significantly and uniquely decreased following exposure of cells to CTGF siRNA. Addition of TGF‐β to the cells led to increases in CTGF mRNA levels that were blocked by CTGF siRNA. CTGF siRNA exposure also significantly and selectively down‐regulated TGF‐β–mediated increases in mRNA levels for types I and III procollagen. The results indicate that CTGF can regulate extracellular matrix molecule, growth factor, and proteinase inhibitor gene expression, and that some of the TGF‐β effects on skin fibroblasts are via a CTGF‐dependent pathway. (WOUND REP REG 2004;12:–)