Non-collagenous Bone Proteins in Cultured Epithelial Rests of Malassez

Objective: Many studies have demonstrated that non-collagenous bone proteins such as bone sialoprotein (BSP), osteopontin (OPN) and osteocalsin (OC) are secreted on the root surface prior to cementum formation. Moreover, it has been suggested that the epithelial rests of Malassez (ERM) are involved in cementum formation. The present study was undertaken to know whether ERM cells have the ability to produce non-collagenous proteins, BSP, OPN and OC as well as alkaline phosphatase (ALPase). Methods: Human periodontal ligaments (HPDL) were sampled from the root of extracted teeth with a special care to avoid contamination of gingival epithelial cells. The outgrowth of ERM cells was produced from the explant in the modified serum-free MCDB153 medium. The second passage cultures were used for the experiments. ERM cells were confirmed to produce amelogenin by immunostaining with anti-amelogenin antibody and in situ hybridization. Human gingival epithelial (HGE) cells were used as control. The expressions of BSP, OPN and OC were analyzed by immunostaining and in situ hybridization. The expression of ALPase was analyzed by the Azo-dye method and in situ hybridization. Results: BSP, OPN, OC and ALPase as well as their mRNAs were abundant in cultured ERM cells, while either the proteins or their mRNAs were not detected in HGE cells. Conclusion: These findings indicate that ERM cells induce BSP, OPN, OC and ALPase, supporting their involvement in cementum formation. This work was supported by Grant-in-Aid for Encouragement of Young Scientists (No. 15791088) from Japan Society for the Promotion of Science, Japan.