Figure 3. Buccal-lingual sections of the M1 in an eight-week-old rat stained with Azan (A,C,D) or treated for detecting GDF-5 (E,H), -6 (F,I), and -7 (G,J) transcripts. Small rectangles of C and D (A) indicate the areas enlarged in C and D, respectively. (C) Periodontal ligament fiber bundles appear thicker and denser than in the previous stage. (D) Thick cellular cementum (cc) on the root dentin surface. (B) Fluorescent green lines of labeled calcein follow the course of mineralizing fronts of dentin (d), alveolar bone (ab), and cellular cementum (cc) in the area outlined by the red rectangle in Fig. 3A. (E-J) Cells showing GDFs gene expression are observed in the cells on the surfaces of the cementum and the alveolar wall and also on those scattered in the periodontal ligament (pdl) (arrowheads). ab, alveolar bone; cc, cellular cementum; d, dentin; pdl, periodontal ligament; pul, pulp. Bar = 500 µm (A and B), 50 µm (C-J).