Connective tissue growth factor promotes the proliferation of myofibroblast through Erk-1/2 signaling pathway

Abstract

To investigate the mechanism by which connective tissue growth factor (CTGF) enhances transforming growth factor-beta(1) (TGF-beta(1))-mediated myofibroblastic activation in renal interstitial fibroblast NRK-49F. NRK-49F cells were pretreated by TGF-beta(1) so that some cells transform into myofibroblasts, and then the cells were devided into vechile, CTGF treated group, TGF-beta(1) treated group, and PD98059 intervene group. The hallmark of myofibroblast, alpha-SMA immunostaining and marker of cellular proliferation, BrdU incorporation were determined by immunocytochemistry doublestaining. The protein level of alpha-SMA was determined by Western blot analysis. CTGF induced a proliferative response in myofibroblast initiated by TGF-beta(1), whereas TGF-beta(1) had no action on proliferation. Although CTGF could not induce myofibroblastic activation in renal interstitial fibroblast, it upregulated the protein level of alpha-smooth muscle actin significantly in cells pretreated by TGF-beta1 (P < 0.05). Significant phosphorylation of Erk-1/2 was detected after incubation with CTGF for 30 min in the cells pretreated by TGF-beta(1), while TGF-beta(1) did not have this ability. Inhibition of Erk-1/2 activation by Mek kinase inhibitor PD98059 suppressed CTGF-mediated myofibroblasts proliferation and significantly down-regulated expression of alpha-SMA protein in cells pretreated by TGF-beta(1) (P < 0.05). CTGF induced a proliferative response in TGF-beta(1)-initiated myofibroblasts, and this action is likely dependent on the activation of Erk-1/2 signaling pathway.