The Regulation of Bone Resorption in Tooth Formation and Eruption Processes in Mouse Alveolar Crest Devoid of Cathepsin K

• Published in: Journal of Pharmacological Sciences 2003, Vol.91(4), pp.285-294
• Main Authors: Okaji, Masayo, Sakai, Hideaki, Sakai, Eiko, Shibata, Mitsue, Hashimoto, Fumio, Kobayashi, Yasuhiro, Yoshida, Noriaki, Okamoto, Kuniaki, Yamamoto, Kenji, Kato, Yuzo
• Format: Article
• Language: English
• Subjects: Alveolar Bone Loss - genetics; Alveolar Bone Loss - metabolism; Animals; Bone Resorption - genetics; Cathepsin K; Cathepsins - deficiency; Cathepsins - genetics; Cathepsins - physiology; knockout mice; matrix metalloproteinase-9; Mice; Mice, Inbred C57BL; Mice, Knockout; osteoclast; Osteoclasts - metabolism; Tooth - growth & development; Tooth - metabolism; Tooth - physiology; tooth development; Tooth Eruption - genetics; Tooth Eruption - physiology
• ISSN: 1347-8613; 1347-8648
• DOI: 10.1254/jphs.91.285

Osteoclastic bone resorption has recently been implicated in the tooth formation and eruption in alveolar bone. Cathepsin K (CK) is a cysteine proteinase expressed predominantly in osteoclasts and is believed to play a critical role in degradation of bone matrix proteins. Here we present evidence that the alveolar bone resorption is essential for the tooth formation and that eruption proceeds normally in CK-deficient (CK−/−) mice. Radiographic and histological analyses revealed that the alveolar bone from these animals had no significant abnormalities during the tooth development between 5 and 28 days after birth. The tooth crown was normally erupted through the alveolar bone layer at 28 days after birth. The number of tartrate-resistant acid phosphatase-positive multinuclear cells in the alveolar bone around the tooth germ was apparently increased in 5-day-old CK−/− mice compared with age-matched littermates. More important, however, the immunohistochemical localization of matrix metalloproteinase-9 (MMP-9) was clearly increased in the CK−/− osteoclasts. In contrast, no significant difference in the immunoreactivity for cathepsin D was observed between the CK−/− osteoclasts and the wild-type ones. These results indicate that CK−/− osteoclasts are fully differentiated and are capable of degrading the organic phase of alveolar bone during the tooth formation and eruption, which may result from the compensatory action by MMP-9 increasingly expressed in the osteoclasts.