Objectives: Hertwig's Epithelial Root Sheath (HERS) cells are a unique population of epithelial cells in the periodontal ligament compartment. Here we report that HERS cells are capable of promoting differentiation of periodontal ligament stem cells (PDLSCs) and undergoing epithelial-mesenchymal-transition (EMT) to convert to cementoblasts. Methods: Immunohistochemical staining, Western blot analysis, co-culture, and in vivo transplantation were used to characterize the interplay between HERS cells and periodontal ligament stem cells as well as the EMT of HERS cells. Results: Immunohistochemical staining revealed that HERS cells were positive for epithelial markers, such as cytokeratin or E-cadherin. Interestingly, HERS cells were also positive for mesenchymal/osteogenic markers, including vimentin, osteocalcin, and bone sialoprotein. HERS cells could be isolated from human PDL tissues and cultured under the preferential growth condition for epithelial cells. These cells formed colonies and showed a typical polygonal shape with a cobblestone growth pattern. When co-cultured with PDLSCs, HERS cells enhanced mineralized nodule formation of PDLSCs along with a down regulation of STRO-1 expression. TGF-beta1 induced HERS cells to change to a spindle shape and show an up-regulated expression of vimentin and N-cadherin along with a down-regulated expression of E-cadherin and beta-catenin. An inhibitor of phosphatidylinositol 3-kinase blocked TGF-beta1-induced up-regulation of phospho-AKT and vimentin. When transplanted into immunocompromised mice, HERS cells generated cementum-like mineralized tissues. Conclusion: These results suggest that HERS cells can form cementum and regulate PDLSC differentiation. EMT of HERS cells appear to be a critical process for HERS cells to convert to cementoblasts.

Back to the Mineralized Tissue Program
Back to the IADR/AADR/CADR 85th General Session and Exhibition (March 21-24, 2007)

Top Level Search