Connective tissue growth factor and igf-I are produced by human renal fibroblasts and cooperate in the induction of collagen production by high glucose.

Tubulointerstitial fibrosis is an important component in the development of diabetic nephropathy. Various renal cell types, including fibroblasts, contribute to the excessive matrix deposition in the kidney. Although transforming growth factor-beta (TGF-beta) has been thought to play a major role during fibrosis, other growth factors are also involved. Here we examined the effects of connective tissue growth factor (CTGF) and IGF-I on collagen type I and III production by human renal fibroblasts and their involvement in glucose-induced matrix accumulation. We have demonstrated that both CTGF and IGF-I expressions were increased in renal fibroblasts under hyperglycemic conditions, also in the absence of TGF-beta signaling. Although CTGF alone had no effect on collagen secretion, combined stimulation with IGF-I enhanced collagen accumulation. Furthermore, IGF-I also had a synergistic effect with glucose on the induction of collagens. Moreover, we observed a partial inhibition in glucose-induced collagen secretion with neutralizing anti-CTGF antibodies, thereby demonstrating for the first time the involvement of endogenous CTGF in glucose-induced effects in human renal fibroblasts. Therefore, the cooperation between CTGF and IGF-I might be involved in glucose-induced matrix accumulation in tubulointerstitial fibrosis and might contribute to the pathogenesis of diabetic nephropathy.

Gene regulation of connective tissue growth factor: new targets for antifibrotic therapy?

Connective tissue growth factor (CTGF) has recently received much attention as a possible key determinant of progressive fibrosis and excessive scarring and also of wound repair, neoangiogenesis, bone formation and embryonic development. CTGF is also up regulated in numerous fibrotic diseases, including atherosclerosis and lung-, skin-, pancreas-, liver- and kidney-fibrosis. TGFbeta induces CTGF through different signaling pathways and a specific TGFbeta responsive element in the CTGF promoter. CTGF is thought to act both as a profibrotic marker and as a downstream effector of TGFbeta by mediating at least some of its profibrotic activities. CTGF is an interesting target for future antifibrotic therapies as it is conceivable that inhibition of CTGF might block the profibrotic effects of TGFbeta, without affecting TGFbeta's anti-proliferative and immunosuppressive effects. In addition to TGFbeta, a number of other regulators of CTGF expression have been identified, including vascular endothelial growth factor, tumor necrosis factor alpha, shear stress, cell stretch and static pressure, H(2)O(2), O(2) and NO. In addition to trans-regulatory mechanisms, specific transcription factor binding sites in the CTGF promoter, as well as 3'untranslated region (UTR) regulatory sequences have been identified that are important for basal and induced CTGF expression. Outlining the mechanisms that underlie CTGF gene regulation in normal and fibrotic cells, might help design of future intervention strategies aiming at targeted specific interference with CTGF expression at sites of progressive fibrosis. In addition, alternative therapies targeting CTGF effects are proposed which might lead to a favorable outcome of wound repair and fibrosis.

CTGF expression in mesangial cells: involvement of SMADs, MAP kinase, and PKC.

BACKGROUND: The induction of excess matrix in renal fibrosis seems to be mediated, at least in part, by the transforming growth factor-beta (TGF-beta)-mediated induction of connective tissue growth factor (CTGF) in mesangial cells. METHODS: By examining CTGF protein and mRNA expression and promoter activity in the presence or absence of TGF-beta or inhibitors, the signaling pathways controlling basal and TGF-beta-induced CTGF expression in mesangial cells were investigated. RESULTS: TGF-beta enhances CTGF mRNA and protein expression in mesangial cells. Mutation of a consensus SMAD binding element in the CTGF promoter completely abolished TGF-beta-induced CTGF expression and reduced basal CTGF expression. The previously identified basal control element-1 (BCE-1) site, but not Sp1 contributes to basal CTGF promoter activity. Ras/MEK/ERK, protein kinase C (PKC) and tyrosine kinase activity also contribute to basal and TGF-beta-induced CTGF promoter activity in cultured mesangial cells. CONCLUSIONS: The TGF-beta-induction of CTGF in mesangial cells requires SMADs and PKC/ras/MEK/ERK pathways. SMADs are involved in basal CTGF expression, which presumably reflects the fact that mesangial cells express TGF-beta endogenously. TGF-beta also induces CTGF through ras/MEK/ERK. Inhibiting ras/MEK/ERK seems not to reduce phosphorylation (that is, activation) of SMADs, suggesting that SMADs, although necessary, are insufficient for the TGF-beta-stimulation of the CTGF promoter through ras/MEK/ERK. Thus, maximal TGF-beta induction of CTGF requires synergy between SMAD and ras/MEK/ERK signaling.

Nitric oxide down-regulates connective tissue growth factor in rat mesangial cells.

BACKGROUND: Nitric oxide (NO) exerts complex regulatory actions on mesangial cell (MC) biology, such as inhibition of proliferation, adhesion or contractility and induction of apoptosis. In our previous studies the NO-donor S-nitroso-glutathione (GSNO) was found to be a potent inhibitor of MC growth. This effect was mediated at least in part by inhibitory effects of GSNO on the transcription factor early growth response gene-1 (Egr-1) [10]. We therefore were interested in the regulation of gene expression in MC after treatment with NO. METHODS: To identify the genes that are regulated by NO in MC, gene expression was analyzed by representational difference analysis. Expression of connective tissue growth factor (CTGF) was studied by Northern and Western blot analyses. RESULTS: Cultured rat MCs treated with GSNO for 8 hours were compared with unstimulated MCs and the CTGF mRNA was found to be down-regulated. The down-regulation was dose-dependent and transient, with a maximum inhibition seen after 6 hours. In parallel, down-regulation of CTGF protein by GSNO was observed by Western blot analysis. Other NO-donors such as S-nitroso-N-acetyl-D,L-penicillamine and spermine-NO showed similar effects. The induction of the inducible NO-synthase by TNF-alpha, IL-1beta and LPS provoked a transient down-regulation of CTGF mRNA, an effect that could be partially overcome by pretreatment with the NOS-inhibitor Nomega-nitro-l-arginine methyl ester. The observed NO-effect could be simulated by treatment with the stable cGMP analog 8br-cGMP, and was abolished by blocking the guanylyl cyclase with the inhibitor NS2028. CONCLUSION: NO acts as a strong repressor of CTGF expression in cultured rat MC. Thus, in addition to its antiproliferative effects, NO potentially exerts antifibrotic activity by down-regulation of CTGF.

Prognosis of haemorrhagic stroke in childhood: a long-term follow-up study.

Little is known about long-term physical sequelae, cognitive functioning, and quality of life of children who have had a haemorrhagic stroke. Fifty-six patients (29 females, 27 males) under 16 years of age at time of the bleeding were studied. Mean age at time of bleeding was 7.7 years (range 1 month to 15.9 years). The primary site and cause of the bleeding at baseline were determined. Occurrences of death, re-bleedings, and seizures during follow-up were recorded. Patients who survived were invited for a follow-up examination including physical check-up, general screening of cognition, and an inventory of subjective health perception. Thirteen children died directly as a result of the haemorrhage; nine experienced a recurrent bleeding, which was fatal in three; six children developed epileptic seizures. At follow-up 36 of 56 patients were still alive. Mean follow-up time was 10.3 years (range 1.3 to 19.9 years) and mean age was 18.6 years (range 1.8 to 34.1 years). There was no patient lost to follow-up. Five patients declined to visit the hospital. In 15 out of 31 patients who could be examined, no physical impairment was observed, 11 had a hemiparesis of varying severity, and three had symptoms of cerebellar ataxia. One child had persisting tetraparesis and one persisting paraparesis. Signs of cognitive deficits were found in 15 patients. Of the children who survive haemorrhagic stroke, the physical and functional prognosis is relatively good, as almost all children were independent at follow-up. However, only a quarter of the surviving children had no physical or cognitive deficit after a mean follow-up period of 10 years. The majority had low self-esteem as well as emotional, behavioural, and health problems.

Long-term prognosis of cerebral venous sinus thrombosis in childhood.

Cerebral venous sinus thrombosis (CVST) is a rare but potentially serious disorder in children. There is no literature on the long-term neuropsychological and emotional sequelae and implications for quality of life. We studied 17 children who had CVST after the neonatal period, aged between 1 month and 16 years at the time of CVST (mean age at CVST was 6 years, median 4 years 8 months). Five children died during follow-up. The cause of death was related to CVST in one child. Twelve children participated in a clinical follow-up assessment. Mean follow-up was 2 years 8 months. One child had physical sequelae with impairment of skilled movement. All children had average or high intelligence scores. Two children with CVST due to an uncomplicated mastoiditis had mild cognitive deficits: one child had difficulty with written language; the other had diminished cognitive efficiency with concentration and attention problems associated with decreased psychosocial functioning. Decreased physical well-being was reported in three of 12 children. We conclude that children who had survived CVST had a fair prognosis. Most had normal cognitive and physical development, although mild cognitive deficits or decreased physical and psychosocial well-being can occur.