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. Conclusion:  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

Dexamethasone enhances the effects of parathyroid hormone on human periodontal ligament cells in vitro

Periodontal ligament cells (PDL) are thought to play a major role in promoting periodontal regeneration. Recent studies, focused on characterizing PDL cells, have been directed at establishing their osteoblast-like properties and determining biological mediators and/or factors that induce osteoblastic cell populations in the PDL. The glucocorticoid, dexamethasone (Dex), has been shown to selectively stimulate osteoprogenitor cell proliferation and to induce osteoblastic cell differentiation in many cell systems. In the present study the ability of Dex to modulate parathyroid hormone (PTH)-stimulated cAMP synthesis in cultured human PDL cells was examined. PDL cells, obtained from premolar teeth extracted for orthodontic reasons, were cultured with Dex (0–1000 nM) for 7 days prior to PTH (1–34) stimulation. The exposure of PDL cells to Dex resulted in a dose-dependent increase in cAMP production in response to PTH stimulation. This response was seen in cells obtained from three different patients. The first significant Dex effect was seen on day 7 when compared to day 1 for 100 nM Dex. PTH (1–34) stimulation caused a dose-dependent increase in cAMP synthesis after Dex (1000 nM) treatment for 7 days. Conversely, stimulation of the cells with PTH (7–34) (0–1000 nM) did not increase cAMP production in PDL cells after Dex treatment. Forskolin- (1 μM) and isoproterenol- (1 μM) stimulated cAMP synthesis was not augmented by Dex treatment. Dex treatment did not alter calcitonin-(1 μM) stimulated cAMP production in PDL cells. Glucocorticoid enhancement of PTH-stimulated cAMP synthesis in these cells supports the presence of an osteoblast-like population in the PDL, in vitro .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48007/1/223_2004_Article_BF00298592.pd