Developmental regulation and ultrastructure of glycogen deposits during murine tooth morphogenesis |
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Authors: | Hayato Ohshima Jorma Wartiovaara Irma Thesleff |
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Institution: | (1) Institute of Biotechnology, Viikki Biocenter, University of Helsinki, PO Box 56, FIN-00014, Finland, FI;(2) Second Department of Oral Anatomy, Niigata University School of Dentistry, 2–5274 Gakkocho-dori, Niigata 951–8514, Japan e-mail: histoman@dent.niigata-u.ac.jp; Tel: +81 25 227 2816; Fax: +81 25 223 6499, JP |
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Abstract: | The distribution and ultrastructure of glycogen deposits were investigated in the murine tooth germ by histochemical periodic
acid-Schiff (PAS) staining and transmission electron microscopy. Lower and upper first molars were examined in mouse embryos
at embryonic days 11.5–17 (E11.5–E17) and in 2-day-old postnatal (P2) mice. The oral and dental epithelia and the mesenchymal
cells were generally PAS-positive during tooth morphogenesis. PAS-negative cells were present at E13 in the distal tip of
the tooth bud epithelium and in the contacting mesenchyme, and this complete lack of PAS reactivity continued in the dental
papilla mesenchyme and inner enamel epithelium during the cap and bell stages. The lack of glycogen deposits in the interacting
epithelium and mesenchyme during early morphogenesis may be associated with their demonstrated high signaling activities.
Mesenchymal cells in the dental follicle consistently possessed small clusters or large pools of glycogen, which disappeared
by P2. Since an intense PAS reaction was seen in mesenchymal cells at future bone sites, the glycogen in the dental follicle
cells may be associated with their development into hard-tissue-forming cells. Ultrastructural observation of the enamel organ
cells from the cap to early bell stages (E14–E15) revealed the occurrence of glycogen pools, which were associated with the
Golgi apparatus and with vesicles having amorphous contents. Glycogen particles were also occasionally present inside vesicles
or in the extracellular matrix. These may be associated with the exocytosis of glycosaminoglycan components into extracellular
spaces and the formation of the stellate reticulum.
Received: 9 November 1998 / Accepted: 17 January 1999 |
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Keywords: | Dental follicle Dental papilla Enamel organ Glycogen PAS reaction Tooth development Epithelial-mesenchymal interactions Mouse (CBA × NMRI) |
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