RESUMEN
This study investigated the expression and localization of APin (which was previously identified and cloned from a rat odontoblast cDNA library), during ameloblast differentiation in rat incisors, by using in situ hybridization and immunohistochemistry. The subcellular localization of APin varied during ameloblast differentiation, but was stage-specific. APin mRNA was not expressed in pre-ameloblasts, was weakly expressed in secretory ameloblasts, and was strongly expressed in maturation-stage ameloblasts as well as in the junctional epithelium attached to the enamel of erupted molars. In the maturation-stage ameloblasts, APin protein was conspicuous in the supranuclear area (Golgi complex) of smooth-ended ameloblasts as well as in both the supranuclear area and the ruffle end of ruffle-ended ameloblasts. During ameloblast-lineage cell culture, APin was expressed at a low level in the early stages of culture, but at a high level in the late stage of culture, which was equivalent to the maturation stage. APin protein was efficiently secreted from transfected cells in culture. Furthermore, its overexpression and inactivation caused an increase and decrease in matrix metalloproteinase-20 (MMP-20) and tuftelin expression, respectively. These findings indicate a functional role for APin in the mineralization and maturation of enamel that is mediated by the expression of MMP-20 and tuftelin.
Asunto(s)
Ameloblastos/metabolismo , Amiloide/metabolismo , Esmalte Dental/metabolismo , Incisivo/química , Ameloblastos/citología , Amiloide/análisis , Animales , Técnicas de Cultivo de Célula , ADN Complementario/genética , Esmalte Dental/química , Esmalte Dental/embriología , Expresión Génica , Incisivo/embriología , Metaloproteinasa 20 de la Matriz/metabolismo , Ratas , Ratas Sprague-DawleyRESUMEN
Examinations of prenatal fluoride supplemented (PNF) teeth in an animal model and in a five-month human fetus find these teeth to be more developed than the non-supplemented controls. The fact that PNF allows teeth to develop to their full potential suggests that PNF could be an essential nutrient for the entire human and this could be demonstrated most easily during rapid fetal growth. A review of the recent literature, including trials by NIH and The World Health Organization, provide evidence that fluoride (F) does allow the fetus to grow and develop to its full potential. The authors conclude that PNF must be supplied in at least a 2 mg/day pulse dose, and then F must be given from shortly after birth in a daily amount appropriate for the weight of the child with some consideration for the amount of F water utilized.
Asunto(s)
Desarrollo Embrionario y Fetal/efectos de los fármacos , Fluoruros/uso terapéutico , Ameloblastos/citología , Animales , Peso Corporal , Estudios de Casos y Controles , Cricetinae , Esmalte Dental/embriología , Papila Dental/embriología , Suplementos Dietéticos , Modelos Animales de Enfermedad , Células Epiteliales/citología , Músculos Faciales/embriología , Femenino , Fluoruración , Fluoruros/administración & dosificación , Humanos , Incisivo/embriología , Mandíbula/embriología , Odontoblastos/citología , Odontogénesis/efectos de los fármacos , EmbarazoRESUMEN
The present study describes the detailed changes in mineral concentration in developing human enamel across the different stages of development from early formation to maturation. The results indicate a stage in the development of deciduous human incisor enamel in which the tissue becomes porous because of a loss of matrix protein, which is subsequently replaced by mineral during the maturation process, with the enamel finally becoming fully mineralized and hard. The importance of this stage with regard to enamel susceptibility to metabolic influences is discussed.