REGULATION OF PERIODONTAL CELLS BY CEMENTUM COMPONENTS

牙骨质是覆盖在牙齿根部的矿化组织。牙周韧带和牙龈的结缔组织通过牙骨质附着在牙齿上，这种附着对牙齿的固定和移动是必不可少的。牙骨质在牙齿萌牙过程中沉积在生长的牙齿表面，目前对牙骨质形成的分子、细胞和机制知之甚少。新牙骨质的形成对于恢复因牙周炎而失去的结缔组织附着物是必要的，然而，这能否预测地实现尚不清楚。我们和其他人已经证明，牙骨质基质中含有影响牙周细胞生物活性的粘附分子和生长因子。我们已经分离并部分表征了其中一个粘附分子，一个56 kDa的附着蛋白，并制备了针对该蛋白的单克隆抗体。我们证明了这种蛋白，牙骨质附着蛋白（CAP），存在于牙骨质中，而在其他牙周组织中未检测到。氨基酸序列表明该蛋白是一种新型胶原蛋白。高特异性结合而非低特异性结合的牙周韧带细胞在培养中形成矿化组织并产生CAP。基于这些观察，我们提出CAP是一种独特的牙骨质蛋白，通过招募成牙骨质前体细胞并调节其活性参与牙骨质形成。我们将通过筛选产生CAP的骨骨质肿瘤细胞株的cDNA文库分离该蛋白，并在体外表达该蛋白。利用产生CAP的牙周韧带细胞，我们将研究其生物合成和成熟及其产生的调控机制。我们将通过表征其与受体的结合来研究CAP如何与牙周细胞相互作用。我们将评估CAP是否会影响矿化组织的形成并调节牙骨质基质蛋白的表达。最后，我们将评估CAP的生物作用是否受到骨质衍生生长因子（一种存在于骨质中的生长因子）的影响。通过这些研究，我们希望阐明CAP的分子结构、生物合成和功能，并了解该蛋白如何参与牙骨质的形成。我们希望这些研究能够深入了解儿童骨质形成的机制，并有助于设计合理的治疗方法，以形成新的骨质和结缔组织附着在先前患病的根和内种植体上。

Cementum is the mineralized tissue which covers the roots of the teeth. Connective tissues of the periodontal ligament and gingiva are attached to the teeth through cementum, and this attachment is essential for tooth anchorage and tooth mobility. The cementum is deposited on growing tooth surfaces during tooth eruption and very little is known about the molecules, cells and mechanisms involved in cementogenesis. New cementum formation is necessary t restore connective tissue attachment lost as a result of periodontitis, however, this can be predictably achieved is not known. We and others have shown that the cementum matrix contains adhesion molecules and growth factors which influence the biological activities of periodontal cells. We have isolated and partially characterize one of the adhesion molecules, a 56 kDa attachment protein, and produced monoclonal antibodies against this protein. We demonstrated that this protein, cementum attachment protein (CAP), is present in cementum and not detectable in other periodontal tissues. Amino acid sequence showed that the CAP is an apparently novel collagenous protein. Periodontal ligament cells which bind CAP with high specific binding, not those with low specific binding, form mineralized tissue in culture and produce CAP. Based on these observations we propose that the CAP is a distinct cementum protein which participates in cementogenesis by recruiting cementoblast precursor cells and regulating their activities. We will isolate cDNAs for this protein by screening a cDNA library made from a cementum tumor cell strain which produces CAP, and express this protein in vitro. Using periodontal ligament cells which produce the CAP, we will study its biosynthesis and maturation and how its production is regulated. We will investigate how the CAP interacts with periodontal cells by characterizing its binding to its receptors. We will assess if the CAP affects mineralized tissue formation and regulates the expression of cementum matrix proteins. Finally, we will assess if the biological actions of CAP are influenced by cementum-derived growth factor, a growth factor present in cementum. From these studies we expect to elucidate the molecular structure, biosynthesis and function of the CAP, and understand how this protein participates in cementum formation. We expect these studies to provide insights into the mechanisms of cementogenesis in children and help to design rational therapeutic procedures to form new cementum and connective tissue attachment to previously diseased roots and on endosseous implants.