Role of connective tissue growth factor (CTGF) module 4 in regulating epithelial mesenchymal transition (EMT) in HK-2 cells

Background: Recent studies have suggested that connective tissue growth factor (CTGF) plays a key role in tissue fibrosis including renal scarring. While studies showed several forms of CTGF with 10-38 kDa in the body fluids, little is known about these small molecule species. We investigated the effect of a 10 kDa CTGF molecule consisting of module 4, on the epithelial mesenchymal transition (EMT) in human proximal tubular cell line (HK-2). Methods: HK2 cells were cultured in DMEM medium. The response of cytokeratin (CK) and vimentin (VIM) mRNA and protein expression to the stimulation of rhCTGF(C) were observed by real-time PCR and immunocytochemistry. At the same time, the morphologic changes were observed by microscopy, and expression of alpha-smooth muscle actin (alpha-SMA) and fibronectin (FN) was detected by laser confocal microscope. These effects were compared with CTGF N-terminal [rhCTGF(N)], consisting of module 1-3, and observed in a condition with the addition of anti-CTGF antibody. Results: RhCTGF(C) induced striking changes in epithelial cells, including changes in cellular morphology, loss of CK, gain VIM and alpha-SMA, and increased levels of fibronectin. Cocultured with anti-CTGF antibody could abrogate most of these effects, while cells treated with rhCTGF(N) showed no significant phenotypic changes comparing to control group. Conclusions: Our results suggest that module 4 could induce HK-2 cells EMT, whereas the residual fragment has no similar effect in spite of consisting of 3 modules of CTGF molecule. (c) 2006 Elsevier B.V. All rights reserved.