REGULATION OF PERIODONTAL CELLS BY CEMENTUM COMPONENTS

牙骨质是覆盖在牙根上的矿化组织。牙周膜和牙龈的结缔组织通过牙骨质附着到牙齿上，这种附着对牙齿的支抗和牙齿的移动是必不可少的。牙骨质在牙齿萌出时沉积在生长的牙齿表面，对牙骨质形成的分子、细胞和机制知之甚少。新的牙骨质形成是修复牙周炎所致的结缔组织附着丧失所必需的，然而，这能否达到尚不清楚。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学活性的黏附分子和生长因子。我们已经分离并部分鉴定了其中一种黏附分子，一种56 kDa的附着蛋白，并制备了针对该蛋白的单抗。我们证明了这种蛋白，牙骨质附着蛋白(CAP)，存在于牙骨质中，在其他牙周组织中检测不到。氨基酸序列分析表明，CAP是一种新的胶原蛋白。牙周膜细胞在培养过程中形成矿化组织，并产生CAP，与CAP高特异性结合而不是低特异性结合。根据这些观察结果，我们认为CAP是一种独特的牙骨质蛋白，它通过招募成牙骨质前体细胞并调节它们的活动来参与牙骨质的形成。我们将通过筛选产生CAP的牙骨质肿瘤细胞株的cDNA文库来分离该蛋白的cDNA，并在体外表达该蛋白。利用产生CAP的牙周膜细胞，我们将研究其生物合成和成熟以及其生产是如何调节的。我们将通过研究CAP与其受体的结合来研究CAP如何与牙周细胞相互作用。我们将评估CAP是否影响矿化组织的形成和调节牙骨质基质蛋白的表达。最后，我们将评估CAP的生物学作用是否受到牙骨质衍生生长因子的影响，牙骨质中存在一种生长因子。通过这些研究，我们有望阐明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。我们期望这些研究为儿童牙骨质形成的机制提供深入的见解，并帮助设计合理的治疗程序，以形成新的牙骨质和结缔组织附着到以前患病的牙根和骨内种植体上。

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.