TGFβ1 induces myofibroblast transdifferentiation via increasing Smad-mediated RhoGDI-RhoGTPase signaling

This study serves to investigate the effects of the Smad pathway on TGFβ1-mediated RhoGDI expression and its binding to RhoGTPases in myofibroblast transdifferentiation. Myofibroblast transdifferentiation was induced by TGFβ1 in vitro. Cells were pretreated with different siRNAs or inhibitors. Myofibroblast transdifferentiation was detected by immunohistochemistry. Immunofluorescence was used to observe the nuclear translocation of Smad4, and PSR (Picrositius Red) staining was used to measure collagen concentration. TGFβ1 induced the phosphorylation of Smad2/3 and the nuclear translocation of Smad4 in human aortic adventitial fibroblasts (HAAFs). Furthermore, TGFβ1 increased the expression of RhoGDI and its binding to RhoGTPases. Nevertheless, inhibition of Smad2/3 phosphorylation decreased TGFβ1-induced RhoGDI1/2 expressions and RhoGDI2-RhoGTPases interactions. These data suggested that the inhibition of Smad phosphorylation attenuates myofibroblast transdifferentiation by inhibiting TGFβ1-induced RhoGDI1/2 expressions and RhoGDI-RhoGTPases signaling.