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

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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.