strategies to abrogate tgf- effects provide promising antifibrotic results , however , in vivo data regarding smad activation during fibrogenesis are scarce . methods : here , liver fibrosis was assessed subsequent to bile duct ligation by determining liver enzymes in serum and collagen deposition in liver tissue . activated hepatic stellate cells were identified by immunohistochemistry and immunoblots for alpha smooth muscle actin . rtpcr for smad4 and smad7 was conducted with total rna and northern blot analysis for smad7 with mrna . results : cholestasis induces tgf- signaling via smad3 in vivo , whereas smad2 phosphorylation was only marginally increased . , negative feedback regulation of tgf- signaling by increased smad7 expression in activated hepatic stellate cells occurs , however does not interfere with fibrogenesis .