Article
CTGF is the fibrogenic mediator of TGF-β in PVR disease
Search Medline for
Authors
Published: | September 22, 2004 |
---|
Outline
Text
Objective
Proliferative vitreoretinopathy (PVR) is characterized by the formation of membranes. The extracellular matrix, like fibronectin, of these membranes is mainly formed by detached retinal pigment epithelial (RPE) cells. A previous study has shown that treatment of cultured RPE cells with transforming growth factor-beta2 (TGF-β2), a growth factor known to be increased in the vitreous of PVR patients, not only increased the amount of fibronectin but also lead to a irreversible crosslinking of this component by the enzyme tissue transglutaminase (tTG). As TGF-β2 is the most relevant factor for the immune privilege of the eye, a direct inhibition of TGF-β is obsolete. It is known, that the fibrogenic effect of TGF-β is mediated through connective tissue factor (CTGF). The goal of the present study was to investigate, whether the reduction of CTGF by siRNA inhibits the fibrogenic effect of TGF-β.
Methods
Monolayer cultures of RPE cells from eyes of 5 human donors were treated with 4.0 ng/ml TGF-β2, recombinant CTGF und CTGF siRNA fo 24-48 hours. Induction of fibronectin and tTG were investigated by western- and northern-blot analysis. External tTG activity was measured by incorporation of biotinylated cadaverine into fibronectin.
Results
Treatment of cultured RPE cells with TGF-β2 increased the mRNA and protein levels of fibronectin 4-8 times. Additional TGF-β treatment increased tTG about the factor 4-6x. The increased expression correlated with an increased external tTG activity and irreversible polymerization of fibronectin. This effect was not seen by parallel treatment of TGF-β and CTGF siRNA. Treatment with recombinant CTGF showed similar results for fibronectin and tTG expression as treatment with TGF-β2.
Conclusions
CTGF is the fibrogenic mediator of TGF-β in PVR disease. Therefore the clinical use of CTGF inhibitor could help to prevent the PVR formation without affecting the immune privilege of the eye.