Abstract
Summary-The present study was undertaken to investigate the amelogenin gene expression in the ameloblasts of rat incisors suffering from enamel hypoplasia which was experimentaly induced by successive injections of the bisphosphonate.
Male Wistar rats, weighing 150-160g, were subcutaneously injected with 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) once a day for a week. As a control experiment, physiological saline was injected in the animals in the same way as HEBP. Twenty four hours after the last injection, they were sacrificed under general anesthesia. Their maxillary incisors and surrounding tissues were resected out. They were used for histological examination and in situ hybridization of amelogenin mRNA. In the HEBP injected rats, several islets of enamel were formed along the dentin-enamel junction, and enamel-free zones were observed between these islets. In situ hybridization of amelogenin mRNA showed that amelogenin gene expression was uniformly observed in ameloblasts of the secretory stage in the control rats. In the HEBP injected rats, amelogenin gene expression was observed not only in the ameloblasts on the enamel islets but also in the ameloblasts in the enamel-free zones. The signals of amelogenin mRNA expression in the HEBP injected rats were as intense as those in the control rats. These results indicated that successive injections of HEBP in rats did not alter the amelogenin gene expression in the ameloblasts, although they caused enamel hypoplasia in the forming ends of incisors.
