Connective tissue growth factor: a fibrogenic master switch in fibrotic liver diseases

Authors


Correspondence
Axel M. Gressner, Institute of Clinical Chemistry and Pathobiochemistry, RWTH-University Hospital, Pauwelsstraße 30, 52074 Aachen, Germany
Tel: 0049-241-8088678
Fax: 0049-241-8082512
e-mail: agressner@ukaachen.de

Abstract

Connective tissue growth factor (CTGF=CCN2), one of six members of cysteine-rich, secreted, heparin-binding proteins with a modular structure, is recognized as an important player in fibrogenic pathways as deduced from findings in non-hepatic tissues and emerging results from liver fibrosis. Collectively, the data show strongly increased expression in fibrosing tissues and transforming growth factor (TGF-β)-stimulated expression in hepatocytes, biliary epithelial cells and stellate cells. Functional activity as a mediator of fibre–fibre, fibre–matrix and matrix–matrix interactions, as an enhancer of profibrogenic TGF-β and several secondary effects owing to TGF-β enhancement, and as a down-modulator of the bioactivity of bone morphogenetic protein-7 has been proposed. By changing the activity ratio of TGF-β to its antagonist bone-morphogenetic protein-7, CTGF is proposed as a fibrogenic master switch for epithelial–mesenchymal transition. Consequently, knockdown of CTGF considerably attenuates experimental liver fibrosis. The spill-over of CTGF from the liver into the blood stream proposes this protein as a non-invasive reporter of TGF-β bioactivity in this organ. Indeed, CTGF-levels in sera correlate significantly with fibrogenic activity. The data suggest CTGF as a multifaceted regulatory protein in fibrosis, which offers important translational aspects for diagnosis and follow-up of hepatic fibrogenesis and as a target for therapeutic interventions. In addition, CTGF-promoter polymorphism might be of importance as a prognostic genetic marker to predict the progression of fibrosis.

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