Fig. 6. Plasmin induces branching morphogenesis of primary mammary organoids. (A) Dose response to increasing concentrations of plasmin. Mean±s.d. of three independent experiments is shown. (B) Effect of protease inhibitors on plasmin-induced branching morphogenesis. The difference with the control group (buffer) was statistically significant (^**P0.01). Inhibition by both aprotinin and GM6001 were statistically significant (^***P0.001). Mean±s.d. of three independent experiments is shown. To calculate the branching index, control values were taken as equal to 1. (C) Appearance of organoids treated for 6 days with no plasmin, or plasmin, with and without inhibitors. (D) Activation of MMPs by plasminogen. Casein zymogram (top panel) of conditioned media from organoids treated with buffer only (no GF), EGF, plasminogen (Pg) and EGF+plasminogen (EGF+Pg). When plasminogen was added to the treatment, the band corresponding to the latent form of Str1 disappeared. The bottom panel is a gelatin zymogram, using the same set of conditioned media as for the casein zymogram. Gelatinase B was activated in the presence of plasminogen. Scale bars: 150 µm in C.