Role of connective tissue growth factor in renal tubular epithelial-myofibroblast transdifferentiation and extracellular matrix accumulation in vitro

Abstract

Connective tissue growth factor (CTGF) has been reported to play an important role in mediating the profibrotic effects of transforming growth factor-β (TGF-β) in the pathogenesis of renal fibrosis. To further elucidate the role of CTGF in renal tubular transdifferentiation and extracellular matrix (ECM) metabolism, we examined the time-course of CTGF, α-smooth muscle actin (α-SMA), fibronectin and plasminogen activator inhibitor-1(PAI-1) gene expression upon the stimulation of TGF-β1 (5 μg/L) in cultured human proximal tubular epithelial cell line (HKC), and further investigated the effects of endogenous CTGF blockade. On reverse transcriptional-polymerase chain reaction (RT-PCR) analysis, TGF-β1 upregulated CTGF gene expression, preceding that of α-SMA, fibronectin and PAI-1. The α-SMA, fibronectin and PAI-1 mRNA expression induced by TGF-β1 were significantly inhibited by CTGF antisense oligodeoxynucleotide (ODN) transfection. With prolonged incubation time, CTGF antisense ODN also inhibited intracellular α-SMA and PAI-1 protein synthesis, lowered the level of fibronectin and PAI-1 protein secreted into the media, as confirmed by indirect immuno-fluorescence, flow cytometry, enzyme-linked immunosorbent assay (ELISA) and Western blot methods respectively. These results suggested that CTGF may play a crucial role in the renal tubular epithelial-transdifferentiation and the following deposition/degradation process of ECM during tubulointerstitial fibrosis.