Abstract: Objective To explore the effects of blocking two sites of TGF-β/Smads signaling on the formation of scar-related proteins in human skin fibroblasts. Methods Two lentivirus vectors encoding soluble TGF-β receptor Ⅱ (sTβRⅡ) and mutant Smad 4–Smad 4ΔM4 were respectively transfected into human skin fibroblast cell line human foreskin fibroblast 1 (HFF-1) cells with the optimum multiplicity of infection (MOI) of 50. The protein expressions of sTβRⅡ and Smad 4ΔM4 of the two types of transfected cells were determined by Western blotting so as to compare with those of the untransfected cells. The HFF-1 cells were divided into 6 groups as named below according to the random number table, with 6 dishes in each group, 1×10⁴ cells per dish. Co-transfection group, transfected with the two previous lentivirus vectors, mixed with the ratio of 1∶1 and MOI of 50, and then stimulated with 5 ng/mL TGF-β₁ for 72 h; sTβRⅡ group, transfected with lenti-sTβRⅡ with MOI of 50, with the other treatment as above; Smad 4ΔM4 group, transfected with lenti-Smad 4ΔM4 with MOI of 50, with the other treatment as above; negative virus group, transfected with empty lentivirus vector, with the other treatment as above; positive control group, stimulated with 5 ng/mL TGF-β₁ for 72 h; and blank control group, conventionally cultured without any other treatment. After stimulation, Western blotting and real-time fluorescent quantitative RT-PCR were respectively used to determine the protein and mRNA expressions of fibronectin in cells of each group. ELISA and Sircol collagen assay were respectively used to determine the protein expressions of connective tissue growth factor (CTGF) and total collagen in the cell culture supernate of each group. Data were processed with one-way analysis of variance and SNK-q test. Results (1) HFF-1 cells transfected with lenti-sTβRⅡ and HFF-1 cells transfected with lenti-Smad 4ΔM4 respectively expressed higher levels of sTβRⅡ protein and Smad 4ΔM4 protein compared with those of untransfected cells, confirming that HFF-1 cells transfected with the two lentivirus vectors can efficiently express the target proteins. (2) There were statistically significant differences in the protein and mRNA expressions of fibronectin in cells of the 6 groups (with F values respectively 53.536 and 24.365, P values below 0.001). The protein and mRNA expressions of fibronectin in cells of positive control group (respectively 1.60±0.18 and 1.99±0.40) were similar with those of negative virus group (respectively 1.60±0.15 and 1.94±0.28, with q values respectively 0.091 and 0.419, P values above 0.05), and they were significantly higher than those of the rest 4 groups (with q values from 5.245 to 18.228, P values below 0.05). The protein and mRNA expressions of fibronectin in cells of co-transfection group (respectively 0.60±0.05 and 0.70±0.11) were significantly lower than those of sTβRⅡ group (respectively 0.89±0.13 and 1.24±0.17) and Smad 4ΔM4 group (respectively 0.91±0.14 and 1.28±0.19, with q values from 3.964 to 4.294, P values below 0.05). (3) There were statistically significant differences in the protein expressions of CTGF and total collagen in the cell culture supernate of the 6 groups (with F values respectively 107.680 and 38.347, P values below 0.001). The protein expressions of CTGF and total collagen in the cell culture supernate of positive control group were similar with those of negative virus group (with q values respectively 1.106 and 0.491, P values above 0.05), and they were significantly higher than those of the rest 4 groups (with q values from 6.414 to 26.420, P values below 0.05). The protein expressions of CTGF and total collagen in the cell culture supernate of co-transfection group were significantly lower than those of sTβRⅡ group and Smad 4ΔM4 group (with q values from 3.424 to 7.143, P values below 0.05). Conclusions In human skin fibroblasts, blockage of two sites of TGF-β/Smads signaling can reduce the expression of scar related proteins which are up-regulated by TGF-β₁ to a greater extent than that of blocking one single site.