Fig. 5

Induction of coronoid secondary cartilage in mice. a–c Alizarin red/alcian blue staining of E14.5–E15.5 dentary explant cultures shows that the condylar and angular process cartilages seen in vivo grow after 5 days culture in serum free conditions whereas no coronoid process cartilage is observed (a), addition of foetal bovine serum results in the formation of coronoid process secondary cartilage in explants of E14.5 dentary tissue (b), but not of E15.5 (c). Blue arrowheads show location of secondary cartilages. d–f Immunofluorescence of Sox9 in histological section of explants demonstrates that Sox9 expression is not expressed within the coronoid position of E14.5 explants without serum (d), but is highly expressed in E14.5 explants with serum where cartilage develops (e). Sox9 was not expressed in E15.5 explants with serum (f). g–i. In postnatal day 4 mouse coronoid process immunofluorescence shows Sox9 + cells to be reduced in periosteal cells and irregular within the ossified process (arrow in g). A few cells in the ossified domain also express Col2a, as shown by in situ hybridisation (arrow in h). No alcian blue stained cartilage is observed in sirius red/alcian blue trichrome staining (i); C.P. coronoid process; Scale bar in a–c is 1000 µm, and d–i is 100 µm