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Figure 1. Developmental analysis of HERS with the use of in vitro culture. (a) The numbers of IEE and OEE cells were counted. The dotted yellow line shows the HERS. The red and black numbers indicate the numbers of IEE and OEE cells, respectively. (b) The HERS length was measured between the arrows, from the connection point of the IEE and OEE to the end of the HERS. (c) DiI was injected at two points (arrowheads): the connection point of OEE and IEE, and the end of the HERS. (d) After dissecting the mandible, we removed the soft tissues, including the oral epithelium above the molar, and cut one-third from the underside of the mandibular bone, including the incisor. Bone from the distal root area was also removed. The arrows show the exposed distal root. (e) After preparation, the specimens were placed on the hole-making metal grid with the use of BGJb medium. (f,g) At PN15, the cell size in both IEE and OEE in the HERS increased compared with that at PN8. (h) However, the cell size of HERS decreased at PN20. The cell sizes at PN8 and PN20 were similar. The OEE cells were much wider than the IEE cells (arrows in g-h). Yellow dotted line: HERS. Bars: a, 15 µm; b, 40 µm; c,d, 1 mm; g,h, 15 µm).
