Abstract: Objective: To investigate the expression patterns of hyaluronic acid (HA) in the first mandibular molar tooth germs, and to explore its role during the tooth development of mouse. Methods: Serial paraffin sections of the first mandibular embryonic molars at different stages were made. The expression patterns of HA were analyzed by immunohistochemistry. Results: The expression patterns of HA in the first lower molars varied among the different stages. It slightly expressed in the dental epithelium at tooth initiation stage. And it could be detected in the central areas of the tooth bud during the bud stage, while in the underlying dental mesenchyme the immunostaining was slight. From the cap stage to the late bell stage, the expression of HA at the stellate reticulum cells and dental papillae increased gradually. However, it never expressed in basement membrane, outer and inner enamel epithelium, and the areas where the ameloblast or the odontoblast located. Conclusion: The expression of HA was in a temporal-spatial specific pattern. Particularly, its expression in the stellate reticulum and dental papillae increased gradually with the development of tooth germ. This result implies that HA may be involved in tooth morphogenesis of the mouse molars.

Key words: Hyaluronic acid, Tooth germ, Tooth development, Molar