The long-term objective of this proposal is to determine how the cells of the dental follicle and stellate reticulum (SR) may regulate tooth eruption. Previous studies have shown that the dental follicle (DF), a loose connective tissue sac surrounding the developing tooth, is necessary for tooth eruption - possibly by regulating concurrent events of tooth eruption; namely, bone resorption, bone formation and tooth movement. My laboratory has shown that there is an influx of mononuclear cells (monocytes?) into the DF prior to tooth eruption and they may be precursors of osteoclasts that are necessary to erode the bony crypt in order fro eruption to occur. In conjunction with this, changes occur in the extracellular matrix content of the DF prior to eruption. Hence, it is the hypothesis of this proposal that the initiation and regulation of the cellular/extracellular events of tooth eruption are controlled by growth factors, primarily epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGF-beta1). Thus, this study first will use light and EM immunocytochemical techniques to determine the spatial and temporal localization of EGF and TGF-beta1 in the DF and SR, as well as using a monoclonal antibody to the EGF receptor to determine its localization. Next, the factors will be injected into rats to determine their effects on the DF in terms of monocyte influx and extracellular matrix changes. This effect on rate of tooth eruption also will be assessed and correlated with any cellular/extracellular changes in the DF. To determine if the growth factors act indirectly by stimulating cells of the DF or SR to secrete a protein, a pure population of cultured DF cells or another population of cultured SR cells will be incubated with the growth factors. The serum - free medium will then be assayed to determine if new proteins are secreted by the cells or if there is an increase in amount of a given protein normally secreted by the cells. If a new protein is secreted, it will be purified and injected in rats to determine its effects on rates of tooth eruption and on cellular events in the DF. Elucidating the cell and molecular basis of tooth eruption could lead to methods for facilitating the eruption of impacted teeth, or prevent loss of deciduous teeth if there were no permanent successors. Equally attractive, new techniques might be developed in orthodontics once a cellular understanding of tooth eruption is obtained.
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