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Developmental Properties of the Hertwig’s Epithelial Root Sheath in Mice
H. Yamamoto1,
S.-W. Cho1,
E.-J. Kim1,
J.-Y. Kim1,
N. Fujiwara2 and
H.-S. Jung1,*
1 Division in Anatomy and Developmental Biology, Department of Oral Biology, Research Center for Orofacial Hard Tissue Regeneration, Oral Science Research Center, College of Dentistry, Brain Korea 21 project for Medical Science, Yonsei Center of Biotechnology, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Korea; and
2 Department of Oral Anatomy, School of Dentistry, Iwate Medical University, 1-3-27 Chuo-dori, Morioka city, Iwate 090-8505, Japan;
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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).
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Figure 2. Several signaling factors are mutually coordinated in HERS development. (a) At PN10, an immunopositive reaction for PCNA was observed, not only in many HERS cells, but also in the cells of the dental pulp and dental follicle. (b) At PN18, some HERS cells showed an immunopositive reaction. However, the number of immunopositive cells decreased compared with that at PN10. Moreover, clusters of 3-4 PCNA-positive cells could be seen in the HERS. (c) At PN10, no TUNEL-positive cells could be detected in the HERS. In the dental pulp and dental follicle, a few cells showed a positive reaction. (d) At PN18, although the numbers of IEE and OEE cells decreased dramatically, a small number of HERS cells showed a TUNEL-positive reaction. (e) In the underside view of the specimen, DiI labeling could be observed on the base (orange dotted line) and end (yellow dotted line) of the HERS (arrows) after 3 days of culture. (f) In this section, the HERS is indicated as a yellow dotted line. The DiI-labeled cells did not move during tooth root formation. The blue line shows dentin. (g) At PN10, an immunopositive reaction for laminin beta-3 localized in HERS cells. The dental pulp and dental follicle cells show a negative reaction. (h) At PN10, syndecan-1 immunoreactivity could be observed in the HERS cells, although the cells of the dental pulp and dental follicle did not show a positive reaction. (i) Bmp-2 was detected in the HERS at PN10. Positive signals were also observed in the cells of the dental pulp and dental follicle. (j) At PN10, Bmp-4 was expressed in the HERS. However, the expression was weak compared with that of the Bmp-2. (k) Compared with the mesenchyme, there was strong expression for Msx-2 in the HERS. Black dotted line, HERS; F, dental follicle, P, dental pulp. Bars: a-d, 15 µm; e, 100 µm; f, 50 µm; g-k, 15 µm.
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Journal of Dental Research, Vol. 83, No. 9,
688-692 (2004)
DOI: 10.1177/154405910408300906
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