Pathways and fate of epithelial root sheath cells during cementogenesis in rat incisors

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It is well known that the epithelial root sheath is greatly involved in the root dentin formation and the development of periodontium. Two possibilities on the fate of epithelial root sheath cells are proposed, the pathway to be extinguished by the apoptosis, and the pathway to transform into cementblasts by epithelio-mesenchymal transformation. Phenotypic transformation from the epithelial cell into the mesenchymal cell is reported in developing Muellerian duct and the epithelial cells in the median palatine suture, and recognized in the transformation from cancer cells into invasive metastatic cells in a pathogenic case.The origin of cementblastic cells remains controversial. Mature cementblasts produce matrix proteins common to osteoblasts, such as Type I collagen, osteocalcin, and osteopontin. These features led to the suggestion that the cementblasts are uniquely positioned osteoblasts. On the other hand, morphological data and the expression in some cementblasts of dental epithel … More ium markers, such as karatin, E-cadherin and amelin/ameloblastion/sheathlin, support the hypothesis that root epithelium-derived cells also persist during cementum formation. These findings support the epithelial-mesenchymal transformation hypothesis that epithelial root sheath cells differentiate into cementoblasts. However, to date, the spatial-temporal behavior of epithelial root sheath cells and its mechanism has not been elucidated.The immunohistochemisty demonstrated that a certain kind of heat shock protein was expressed continuously from the epithelial cells to the cementblasts on the root dentin and that a certain kind of aquapolin and S100 protein were expressed in the cementoblasts in the rat incisor. The expression pattern of these proteins during cementum formation illustrates the complex origin of cementblasts and the fate of epithelial root sheath cells. These results suggest mesenchymal transition in odontogenic epithelium and the importance of these proteins during the cement genesis. Less