Holmes, AM; (2007) Regulation of connective tissue growth factor/CCN2 gene expression in systematic sclerosis fibroblasts. Doctoral thesis , UCL (University College London).

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Abstract

Systemic sclerosis (Scleroderma, SSc) is a chronic, connective tissue disease of unknown etiology, characterised by vascular dysfunction, iriflarnmation and organ fibrosis. Involving both genetic and environmental components, the specific mechanisms which result in fibrosis remain largely unknown. A cardinal feature of SSc is increased synthesis of extracellular matrix (ECM). Dermal fibroblasts cultured from SSc patients maintain many of the abnormal properties seen in vivo, including excess production of collagen type I, and growth factors such as connective tissue growth factor (CTGF/CCN2). CTGF, like many genes dysregulated in SSc, is induced by TGF- p in normal fibroblasts. The overall aim of my studies was to determine the mechanism(s) controlling CTGF over-expression in SSc dermal fibroblasts (SDF). Induction of CTGF by TGF-p was found to be dependent upon elements in the proximal portion of the CTGF promoter, distinct from those of the previously characterised TGF- P response element (TRE). The TRE acts, in NIH/3T3 and HFF cells, as a regulator of basal expression, and is not essential for TGF-P induction of CTGF. Instead TGF-p induces CTGF expression via a Smad3 complex, binding to a bona fide SMAD transcription factor binding site. Over-expression CTGF in SDF is independent of autocrine expression of TGF-P and the SMAD binding element and rather dependent on a functional Sp-binding site. Inhibition of Spl-like DNA binding reduces excessive CTGF expression in SDF. Consistent with this Spl-DNA binding activity is elevated in SDF nuclear extracts. Investigation of the mechanism of elevated Spl-like binding found that SDF exhibited constitunVely active ERK1/2 and JNK1. Inhibition of ERK1/2 repressed elevated Sp-binding and CTGF over-expression observed in SDF. In summary, the data presented in this thesis provide evidence that dysregulation of ERK1/2 in SDF is involved in CTGF over-expression via a Spl-like DNA binding. Thus repression of ERK may represent a candidate in targeting fibrosis in SSc.

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