The differential regulation of Smad7 in kidney tubule cells by connective tissue growth factor and transforming growth factor-beta1

Abstract

Aims: Smad7 is an inhibitory Smad that regulates transforming growth factor-β (TGF-β) signaling. Connective tissue growth factor (CTGF) is recognized as a potent downstream mediator of the fibrogenic effects of TGF-β1. SMAD binding sites have been identified in both TGF-β and CTGF promoters. The effect of CTGF on Smad7 expression and its role in the regulation of Smad7 induced by TGF-β1 in renal tubular cells is unknown. Methods: Human model of proximal tubular cells (HK-2 cells) was used and confirmed using a diabetic rat model. RT-PCR was performed to measure Smad7, TGF-β1 and Smad2 and ELISA was performed to measure active TGF-β1. CTGF or TGF-β1 was silenced in HK-2 cells using siRNA meth..