ABSTRACT
Objective To study whether the expression Smad 7 protein by the recombinant adenovirus with Egr-1 promoter and Smad 7 cDNA in fibroblast cell can block the signal transduction pathway of transforming growth factor-beta1 (TGF-?1) under irradiation thereby inhibiting collagen synthesis in vitro. Methods The location of endogenous Smad 7 and exogenous Smad 7 protein in recombinant adenovirus infected fibroblast cells(3T6) were determined by immunocytochemical method. The infected 3T6 cells were irradiated and then cultured with TGF-?1 4 hours after irradiation. The activity of preventing radiation-induced fibrosis by expression Smad 7 protein was evaluated by the amount of collagen synthesis and proliferation of 3T6 cells. The amount of collagen synthesis was shown by the coruscant per minute (cmp) through the 3?H-Proline incorporation technique. Results The endogenous Smad 7 and exogenous Smad 7 protein both were located in the cytoplasm. When cultured with TGF-?1 4 hours after irradiation, the amount of collagen synthesis in the 3T6 cells infected with the recombinant adenovirus was significantly less than that in the cells without infecting adenovirus after irradiation(P=0.001), But, there was no difference in the proliferation of 3T6 cells between those with and without adenovirus infection (P= 0.312 ). Conclusions The Egr-1 promoter in the recombinant adenovirus can regulate the expression of downstream Smad 7 cDNA in 3T6 cells. The expression Smad 7 protein could block the TGF-?1 signal transduction pathway thereby inhibiting the collagen synthesis. The mechanism of inhibiting the collagen synthesis may be accomplished at the transcription level.