The role of odontogenic genes and proteins in tooth epithelial cells and their niche cells during rat tooth root development

Objectives: The rodent incisor cervical loop and molar Hertwig's epithelial root sheath (HERS) are common models used for investigating tooth root generation. The purpose of the present study was to gain a better understanding of the molecular mechanisms mediating root development by determining the distinctive gene and protein expression profiles of each during different stages of development. Methods: In this study, we used quantitative real time reverse transcription-PCR and immunohistochemistry to analyse the expression levels of high mobility group AT-hook 2, ameloblastin, amelogenin, dentine sialoprotein, dentine matrix protein 1, osteocalcin, and bone sialoprotein in rat epithelial and mesenchymal cells isolated at postnatal days 4 and 8. Results: Results showed that the expression of these genes and proteins was up-regulated in cervical loop epithelial cells, but decreased or unchanged in other cells during development. This increase in expression in the incisor cervical loop may be due to the interaction of the inner incisor dental papilla cells, which are the niche cells of cervical loop epithelial cells and demonstrated up-regulated expression of the corresponding proteins, revealing a complex and dynamic interplay of these molecules during neonatal tooth development. Conclusion: These findings provide novel insights into the molecular processes underlying crown development of rodent incisors, and contribute to our overall understanding of the pathogenic processes of tooth root dysontogenesis. (C) 2012 Elsevier Ltd. All rights reserved.