D'Errico J A, Berry J E, Ouyang H, Strayhorn C L, Windle J J, Somerman M J
Department of Periodontics/Prevention/Geriatrics, University of Michigan, Ann Arbor 48109-1078, USA.
J Periodontol. 2000 Jan;71(1):63-72. doi: 10.1902/jop.2000.71.1.63.
Proper formation of cementum, a mineralized tissue lining the tooth root surface, is required for development of a functional periodontal ligament. Further, the presence of healthy cementum is considered to be an important criterion for predictable restoration of periodontal tissues lost as a consequence of disease. Despite the significance of cementum to general oral health, the mechanisms controlling development and regeneration of this tissue are not well understood and research has been hampered by the lack of adequate in vitro experimental models.
In an effort to establish cementoblast cell populations, without the trappings of a heterogeneous population containing periodontal ligament (PDL) cells, cells were obtained from the root surface of first mandibular molars of OC-TAg transgenic mice. These mice contain the SV40 large T-antigen (TAg) under control of the osteocalcin (OC) promoter. Therefore, only cells that express OC also express TAg and are immortalized in vitro. Based on results of prior in situ studies, OC is expressed by cementoblasts during root development, but not by cells within the PDL. Consequently, when populations are isolated from developing molars using collagenase/trypsin digestion, only cementoblasts, not PDL cells, are immortalized and thus, will survive in culture.
The resulting immortalized cementoblast population (OC/CM) expressed bone sialoprotein (BSP), osteopontin (OPN), and OC, markers selective to cells lining the root surface. These cells also expressed type I and XII collagen and type I PTH/PTHrP receptor (PTH1R). In addition to expression of genes associated with cementoblasts, OC/CM cells promoted mineral nodule formation and exhibited a PTHrP mediated cAMP response.
This approach for establishing cementoblasts in vitro provides a model to study cementogenesis as required to enhance our knowledge of the mechanisms controlling development, maintenance, and regeneration of periodontal tissues.
牙骨质是衬于牙根表面的矿化组织，其正常形成是功能性牙周韧带发育所必需的。此外，健康牙骨质的存在被认为是可预测性修复因疾病而丧失的牙周组织的重要标准。尽管牙骨质对口腔整体健康具有重要意义，但控制该组织发育和再生的机制尚未完全明确，且由于缺乏合适的体外实验模型，相关研究受到了阻碍。
为了建立成牙骨质细胞群体，且不包含含有牙周韧带（PDL）细胞的异质群体，从OC-TAg转基因小鼠的第一下颌磨牙根表面获取细胞。这些小鼠在骨钙素（OC）启动子的控制下含有SV40大T抗原（TAg）。因此，只有表达OC的细胞也表达TAg，并在体外永生化。基于先前原位研究的结果，OC在牙根发育过程中由成牙骨质细胞表达，但PDL内的细胞不表达。因此，当使用胶原酶/胰蛋白酶消化从发育中的磨牙中分离细胞群体时，只有成牙骨质细胞，而非PDL细胞，会永生化，从而能够在培养中存活。
所得的永生化成牙骨质细胞群体（OC/CM）表达骨唾液蛋白（BSP）、骨桥蛋白（OPN）和OC，这些是牙根表面细胞特有的标志物。这些细胞还表达I型和XII型胶原蛋白以及I型甲状旁腺激素/甲状旁腺激素相关蛋白受体（PTH1R）。除了表达与成牙骨质细胞相关的基因外，OC/CM细胞还促进矿化结节形成，并表现出PTHrP介导的cAMP反应。
这种体外建立成牙骨质细胞的方法提供了一个模型，可用于研究牙骨质形成，以增进我们对控制牙周组织发育、维持和再生机制的了解。
