Production of osteopontin by cultured porcine epithelial cell rests of Malassez

Background: The epithelial cell rests of Malassez (ERM) are derived from Hertwig's epithelial root sheath (HERS). During development the cells of HERS deposit a variety of molecules on the newly forming root surface. The possibility that ERM retain this potential after root development is completed and secrete bone or cementum-related proteins needs to be investigated. The purpose of this study was to determine the expression of the non-collagenous proteins osteopontin (OPN) and bone sialoprotein (BSP) by cells derived from the epithelial cell rests of porcine periodontium. Methods: ERM and fibroblasts were cultured from porcine periodontal ligament. The cells were identified and characterized using transmission electron microscopy, immunohistochemistry, western blot analysis of proteins, reverse transcription-polymerase chain reaction and ability to form mineralized nodules in culture. In particular the expression of the mineralized tissue-related proteins, BSP and OPN, was studied. Results: Cells from porcine periodontal ligaments were successfully cultured; separated and characterized as being of either an epithelial or fibroblastic phenotype. Although the ERM did not form mineralized nodules in culture, they did express a significant amount of mRNA for OPN. Conclusions: The results from this study provide evidence that ERM express mRNA for at least one bone/cementum-related protein. Whether this function would be consistent with a role for ERM in tissue formation, inflammation and regeneration remains to be established.