Immunolocalization of calbindin D28k and vitamin D receptor during root formation of murine molar teeth

Cells in the epithelial rest of Malassez (ERM cells) express calbindin D28k (CB); however, the hormonal regulation of CB in ERM cells remains to be elucidated. We investigated the immunohistochemical localization of CB and 1,25-dihydroxyvitamin D3 receptor (VDR) during root formation of mouse molar teeth in order to clarify whether the expression of CB in ERM cells is dependent on vitamin D. At the early stage of root formation (postnatal (PN) days 10-14), both CB- and VDR-immunoreactive cells were observed intermittently along the root surface. In the apical portion, almost all CB-immunoreactive cells showed VDR immunoreactivity; however, VDR-immunoreactive cells in the most apical portion were immunonegative for CB. In the middle and cervical portions, the distributions of the two proteins were completely different. At the late stage of root formation (PN28d) and in adult animals, CB immunoreactivity was distributed in cells found along the acellular cementum at the bifurcation region, as well as between the dentin and cellular cementum in the apical portion (although these lacked immunoreactivity for VDR). The present results indicate that CB expression in newly disrupted cells from Hertwig's epithelial root sheath occurs in a vitamin-D dependent manner, whereas the expression of CB in mature ERM cells may be independent of vitamin D.