RESUMO
BACKGROUND: Connective tissue growth factor (CTGF) is a profibrotic growth factor, which is upregulated in wound healing and renal fibrosis, including anti-Thy-1.1 nephritis. The kinetics of CTGF mRNA expression in anti-Thy-1.1 nephritis suggested that CTGF regulation might contribute to glomerular response to injury downstream of transforming growth factor-beta (TGFbeta). In anti-Thy-1.1 nephritis the initial damage is followed by mesangial repair and limited sclerosis, which involves mesangial cell (MC) activation (alpha-smooth-muscle actin (alphaSMA) expression), proliferation, migration, and extracellular matrix production. The present in vitro study addresses the possible role of CTGF in these different aspects of mesangial response to injury, and how CTGF activity might relate to effects of TGFbeta and platelet-derived growth factor-BB (PDGF-BB). METHODS AND RESULTS: Immunostaining and ELISA showed that alphaSMA expression and transformation of MC into myofibroblast-like cells was induced by TGFbeta, but not affected by PDGF-BB, CTGF, or neutralizing anti-CTGF antibodies. [(3)H]thymidine incorporation and Ki67 staining demonstrated that, unlike PDGF-BB, neither CTGF nor TGFbeta induced the proliferation of MC. In contrast, both CTGF and TGFbeta induced MC migration, as evidenced by approximation of wound edges in scrape-wounded, non-proliferating rat MC monolayers. In addition, fibronectin expression was upregulated by both CTGF and TGFbeta, as measured by dot-blot analysis. Anti-CTGF completely blocked the effect of added CTGF. Moreover, anti-CTGF significantly reduced TGFbeta-induced increase in fibronectin. CONCLUSION: It thus appears that CTGF is specifically involved in a subset of the adaptive changes of MC involved in mesangial repair and sclerosis, which makes it an interesting candidate target for future intervention strategies.
Assuntos
Regulação da Expressão Gênica/fisiologia , Mesângio Glomerular/lesões , Mesângio Glomerular/fisiologia , Substâncias de Crescimento/fisiologia , Proteínas Imediatamente Precoces/fisiologia , Peptídeos e Proteínas de Sinalização Intercelular , Fator de Crescimento Derivado de Plaquetas/farmacologia , Fator de Crescimento Transformador beta/genética , Actinas/genética , Animais , Anticorpos/farmacologia , Becaplermina , Divisão Celular/efeitos dos fármacos , Linhagem Celular , Movimento Celular/efeitos dos fármacos , Movimento Celular/fisiologia , Fator de Crescimento do Tecido Conjuntivo , Fibronectinas/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Mesângio Glomerular/citologia , Substâncias de Crescimento/genética , Substâncias de Crescimento/farmacologia , Humanos , Proteínas Imediatamente Precoces/genética , Proteínas Imediatamente Precoces/farmacologia , Antígeno Ki-67/análise , Cinética , Proteínas Proto-Oncogênicas c-sis , Ratos , Proteínas Recombinantes/farmacologia , Timidina/metabolismoRESUMO
BACKGROUND: Connective tissue growth factor (CCN2; CTGF) is a newly identified growth factor, which is involved in the regulation of wound repair and fibrosis. Because there is variation among individuals with respect to tissue response to injury, genetic factors might be involved in the final outcome of tissue repair or scarring. For example, polymorphisms in the promoter region of genes, such as those encoding transforming growth factor beta1 (TGF-beta1), interleukin 10 (IL-10), and tumour necrosis factor alpha (TNF-alpha), influence transcriptional responses and are thought to contribute to the dysregulation of these genes in pathological conditions. AIM: To investigate whether the promoter region of the ccn2 (ctgf) gene contains polymorphic sequences that might account for differential expression. MATERIALS/METHODS: Seventy seven human DNA samples were sequenced-45 were from healthy controls and 32 were from patients with ischaemic heart disease (IHD)-using M13 tailed sequence specific ccn2 (ctgf) primers for amplification of a 600 bp fragment upstream of the transcription start site. Amplicons were bidirectionally sequenced with a dye primer M13 forward and reverse sequencing kit. RESULTS: A C to G substitution was identified at position -132 in one of the patients with IHD. Moreover, in five of the 32 patients with IHD and in six of the 45 healthy controls, a G to C polymorphism was found at position -447. These substitutions at -132 and -447 are thought to lie within predicted binding domains for the transcription factors Pbx-1 and MZF1, respectively. In addition, insertions at position -43 (G), -47 (C), -71 (G) and a C to T substitution at position -198 were found in all DNA samples compared with the published ccn2 (ctgf) promoter sequence. These corrections do not involve sequences predicted to function as transcription factor binding sites. CONCLUSION: Sequence analysis of the ccn2 (ctgf) promoter of 77 human DNA samples has revealed corrections and polymorphic sites. The latter lie within putative regulatory elements.