Fig. 7. Tgfß1 stimulates proliferation of the dental mesenchymal cells as detected by BrdU incorporation from tissue sections (A,B) and whole mounts (C). The E12 mandibular mesenchyme or dental recombinant explants were cultured for 24 hours with protein-soaked agarose beads. Increased cell proliferation is seen in the mesenchymal cells next to the Tgfß1 (A-C) and control Fgf2 (D)-releasing beads, as well as cells next to the dental epithelium (E12), which also shows BrdU incorporation. Near the control BSA (1 mg/ml) bead (E), hardly any BrdU-positive cells are seen. B shows proliferating cells in A at a higher magnification. Arrows indicate the first molar mesenchyme region where the beads were located. (G,H) Induction of tubulogenesis in isolated E11 metanephric mesenchyme by Wnt4- and Wnt6-expressing cells after 5 days in culture. NIH3T3 control cells do not support survival and differentiation of the mesenchyme. (I) Stimulation of Gli1 expression in E11 mandibular mesenchyme by Shh-containing beads. b, bead; c, cell cluster; e, dental epithelium; m, dental mesenchyme. Scale bars: 200 µm in A,E,I; in C, 100 µm for C,D; 50 µm in B; in H, 500 µm for C,F,H.