Expression Of Osteopontin By Porcine Epithelial Cell Rests of Malassez

Epithelial cell rests of Malassez (ERM) are small groups of epithelial cells within the periodontal ligament closely approximated to the radicular cementum surface. The function of the ERM is unknown and their participation in some dental pathological conditions is still controversial. Objectives: The aim of this study is to characterise porcine ERM and determine their expression of bone matrix related proteins comparing other periodontal cells Methods: ERM were cultured and isolated from porcine periodontal ligaments. An immunohistochemical study was carried out in rat porcine and human periodontal sections using AE1/AE3 antibody. The expression of cytokeratins by ERM was demonstrated in all species. Characterization and identification of ERM was achieved by TEM, immunohistochemistry and Western blot. The results demonstrated the epithelial nature of these cells obtained from the mid radicular third of porcine first deciduous molars. An in vitro study using a semi quantitative RT-PCR technique was carried out in four different types of porcine periodontal cells (GF, PDLF, ERM and alveolar bone cells). These cell types were compared for the expression of the bone related proteins osteopontin and bone sialoprotein. Results: The strongest expression of osteopontin was for the ERM compared to alveolar bone cells, PDLF and GF. These results demonstrated for the first time the expression of osteopontin by cultured porcine ERM suggesting a possible role of these cells in cementogenesis. Under mineralizing culture conditions, mineralization was only detected in OB and PDLF, not in ERM and GF cell lines. These findings indicate that ERM produce early signals for hard tissue formation and possibly not involved in tissue mineralization. Conclusion: The findings of this study contribute to a broader understanding of possible functions of the ERM and suggests a role for these cells in cementogenesis by their strong OPN expression. Study supported by University of Queensland Graduate School.