Figure 3

TGF-β1-induced tubulogenesis in fibrin gels. (A) J3B1A cells grown in a fibrin gel in defined medium for 11 days have formed spherical cysts. (B, C) J3B1A cells grown in a fibrin gel in defined medium for 4 days and subsequently treated with 20 pg/ml (B) or 100 pg/ml (C) TGF-β1 for an additional 7 days have formed branched tubules. (D) Cells grown as in (A-C) but incubated with 500 pg/ml TGF-β1 have generated a complex network of solid anastomosing cords. Bar, 200 um. (E) Quantitative analysis of TGF-β1-induced tubulogenesis in fibrin gels. J3B1A cells were grown in a fibrin gel for 6 days to allow cyst formation and were subsequently treated with different concentrations of TGF-β1. Tube formation was evaluated as described in Materials and Methods after 2, 4 and 7 days of treatment. Data were expressed as mean number of outgrowths per colony ± s.e.m. from three independent experiments. p < 0.0005 for values of 20 pg/ml TGF-β1 at 2 days compared with control at 2 days, as well as for values of 50 pg/ml and 100 pg/ml TGF-β1 at 7 days compared with 2 days; p < 0.005 for values of 20 pg/ml TGF-β1 at 7 days compared with 2 days; p < 0.01 for values of 50 pg/ml TGF-β1 at 4 days compared with 2 days; p < 0.025 for values of 100 pg/ml TGF-β1 at 4 days compared with 2 days; p < 0.05 for values of 20 pg/ml TGF-β1 at 4 days compared with 2 days, as well as for values of 50 pg/ml TGF-β1 at 2 days compared with 20 pg/ml TGF-β1 at 2 days.