Enamel biomineralization; the role of pH cycling

项目摘要/摘要 矿化牙釉质是人体内最坚硬的组织，其适当的形成对保护牙釉质至关重要 并终生保持牙齿健康。釉质的生物矿化是由上皮源性的 成釉细胞。成釉细胞分泌釉质基质蛋白，然后被水解并被 羟基磷灰石晶体。成熟期成釉细胞以波的形式调制，使大约80%的成釉细胞酸化 矿化成熟期基质，其余约20%的基质保持中性。 当pH循环被打乱时，釉质的形成就会失调，由此产生的釉质基质就会 矿化程度低。虽然酸性环境不利于生物矿化，但基质酸化 牙釉质的形成被认为对羟基磷灰石(HAP)牙釉质晶体的细化有一定的作用。 然而，控制pH循环的机制(S)仍不清楚。 在这个项目中，我们将使用我们的新型极化成釉细胞培养系统，以及wdr72-/-和cftr-/-小鼠。 模型，以验证我们的中心假设，即成釉细胞直接调节釉质基质中的pH循环，以 优化釉质基质矿化。我们将通过以下具体目标来检验这一中心假设。1)至 确定成釉细胞在酸化釉质基质中的作用；2)确定 细胞外pH对成釉细胞钙转运的影响；确定基质酸化在以下方面的作用 蛋白质的水解和羟基磷灰石晶体的形成。这些研究将使我们能够更好地了解病因。 这将有助于减少牙釉质矿化不足的风险，并将使我们能够应用这一知识来降低牙釉质缺陷的风险。 我们研究的长期目标是确定成釉细胞的pH循环如何引导釉质基质 生物矿化作用合成形成牙釉质的独特的棱柱状矿化结构。

PROJECT SUMMARY/ABSTRACT Mineralized enamel is the hardest tissue in the human body, and its proper formation is critical for the protection and maintenance of healthy teeth for a lifetime. Enamel biomineralization is directed by the epithelial derived ameloblasts. Ameloblasts secrete enamel matrix proteins, which are then hydrolyzed and replaced by hydroxyapatite crystals. Maturation stage ameloblasts modulate in waves to acidify approximately 80% of the mineralizing maturation stage matrix, with the remaining approximately 20% of the matrix remaining neutral. When pH cycling is disrupted, enamel formation is dysregulated, and the resulting enamel matrix is hypomineralized. Though an acidic environment is unfavorable to biomineralization, matrix acidification in enamel formation has been presumed to have a role in refinement of the hydroxyapatite (HAP) enamel crystals. However the mechanism(s) that control pH cycling remain unclear. In this project, we will use our novel polarized ameloblast culture system, along with Wdr72-/- and Cftr-/- mouse models, to test our central hypothesis that ameloblasts directly regulate pH cycling in the enamel matrix, to optimize enamel matrix mineralization. We will test this central hypothesis with the following specific aims. 1) To determine the role of ameloblasts in acidifying the enamel matrix; 2) To determine the effects of extracellular pH on calcium transport by ameloblasts; 3). To determine the role of matrix acidification on protein hydrolysis and HAP crystal formation. These studies will allow us to better understand the etiology of enamel hypomineralization, and will allow us to apply this knowledge to reduce the risk for of enamel defects. The long-term goal of our research is to determine how pH cycling by ameloblasts directs enamel matrix biomineralization to synthesize the unique prismatic mineralized structure that forms tooth enamel.