Immunolocalization of interleukin-1 alpha in rat mandibular molars and its enhancement after in vivo injection of epidermal growth factor.

Immunolocalization of interleukin-1 alpha in the first mandibular molars of rats from day 0-12 postnatally showed that the protein was localized in the epithelial stellate reticulum adjacent to the dental follicle. Staining of the stellate reticulum was most prominent in the early days postnatally and was absent by postnatal day 11. Injection of epidermal growth factor into rats at day 0 greatly increased the intensity of the staining for interleukin-1 alpha in the stellate reticulum. Epidermal growth factor (EGF) enhanced the gene expression of interleukin-1 alpha in stellate reticulum cells in vitro, and this study suggests there is enhanced translation of interleukin-1 alpha messenger RNA in the stellate reticulum following EGF injection. In turn, the interleukin-1 alpha may exert its effect on the dental follicle cells adjacent to the stellate reticulum because EGF also enhanced expression of the interleukin-1 receptor type I messenger RNA in cultured dental follicle cells as well as enhancing its expression in vivo. In view of the fact that injection of EGF will stimulate precocious eruption of teeth, its stimulus of interleukin-1 alpha synthesis in the stellate reticulum may be the mechanism by which EGF initiates a cascade of molecular events to signal the onset of tooth eruption.