Study of roles of epithelial cell rests of Malassez in periodontal regeneration

为阐明牙周膜上皮细胞在牙骨质修复中的作用，采用形态学和免疫组织化学方法，对实验性牙根吸收过程中牙周膜中存在的eCRM进行了研究。机械损伤后第7天，牙根可见吸收，吸收陷窝附近可见eCRM。在邻近吸收陷窝部位的牙周韧带中可观察到它们。这些eCRM对骨形态发生蛋白-2呈免疫反应。在早期牙骨质修复阶段，eCRM呈骨桥蛋白和成釉蛋白免疫反应阳性。这些结果提示eCRM可能通过激活它们分泌已在牙齿发育中表达的基质蛋白的能力而与牙骨质修复有关。在体外，我们研究了碱性磷酸酶(ALPase)、骨桥蛋白(OPN)、骨形态发生蛋白(BMP)-2和BMP-4在人牙周膜上皮细胞(E细胞)和成纤维细胞(F细胞)中的表达。逆转录聚合酶链式反应分析显示，E细胞的ALPase和BMP-4基因表达水平低于F细胞。而骨桥蛋白基因在E细胞中的表达强于F细胞。因此，它们具有不同的ALPase、BMP-4和OPN的表达模式，提示牙周膜中的ERM和间充质细胞可能协同参与牙骨质修复。

n vivo, to clarify the roles of epithelial cell rests of Malassez (ECRM), ECRM existed in periodontal ligament during cementum repair was investigated using morphological and immunohistochemicai approaches in experimental root resorption. At day 7, after mechanical injury, root resorption was observed and ECRM were present adjacent to the site of resorption lacunae. They were observed in periodontal ligament adjacent to site of the resorption lacunae. These ECRM were immunoreactive for bone morphogenetic protein-2. During the stage of early cementum repair, the ECRM were immunoreactive for osteopontin and ameloblastin. These findings suggested that ECRM may be related to cementum repair by activating their potential to secrete matrix proteins which have been expressed in tooth development.In vitro, we investigated the expression of alkaline phosphatase (ALPase), osteopontin (OPN), bone morphogenetic protein (BMP)-2 and BMP-4 in epithelial cells (E cells) and fibroblastic cells (F cells) derived from human periodontal ligament. Reverse transcription-polymerase chain reaction analysis showed that E cells have lower ALPase and BMP-4 mRNA levels than F cells. On the other hand, the expression of OPN mRNA in E cells was stronger than in F cells. Thus, they have different expression patterns of ALPase, BMP-4 and OPN, suggesting that ERM and mesenchymal cells in periodontal ligament may be cooperatively involved in cementum repair.