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

为探讨Malassez上皮细胞残余物（epithelial cell rests of Malassez，ECRM）在牙骨质修复过程中的作用，在实验性牙根吸收的基础上，采用形态学和组织化学方法研究了ECRM在牙骨质修复过程中牙周膜中的作用。机械性损伤后第7天，可见牙根吸收，吸收陷窝附近可见ECRM。在吸收陷窝附近的牙周膜中观察到它们。这些ECRM的骨形态发生蛋白-2免疫反应。在牙骨质修复早期，ECRM表达成釉蛋白和骨桥蛋白。本研究采用体外培养的方法，观察了人牙周膜上皮细胞（E细胞）和成纤维细胞（F细胞）中碱性磷酸酶（ALP）、骨桥蛋白（OPN）、骨形态发生蛋白（BMP）-2和BMP-4的表达。逆转录-聚合酶链反应分析表明，E细胞具有较低的ALTH和BMP-4的mRNA水平比F细胞。E细胞OPN mRNA的表达强于F细胞。因此，它们具有不同的表达模式的ALP 3，BMP-4和OPN，这表明ERM和牙周膜间充质细胞可能是合作参与牙骨质修复。

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.