UCLA

Introduction: Since the detection of Mesenchymal Stem Cells (MSCs) in dental pulp tissue, many laboratories have conducted studies associated with pulp regeneration. Recently we introduced the pulp tissue grafting, a new approach to pulp regeneration, which would diminish the inconveniences of the existing cell-based therapy. The pulp tissue grafting might be able to avoid the cell culture expansion of MSCs, a necessary step for cell-based therapy, and the associated regulatory requirements for pulp regeneration therapy. However, as the pulp tissue grafting necessitates the patient’s pulp tissue, it also renders with clinical limitations for clinical applications. In the present study, we investigated the possibility of using gingival tissue as a source of MSCs for regenerative endodontics treatment.

Materials and Methods: We cultured cells from minced gingiva (MG) explant and isolated outgrowing cells. To determine the possible MSCs of these outgrowing cells, the phenotypes of these cells were analyzed, such as replication kinetics, migration capacity, multi-differentiation potential, and immunophenotypes. Also, we examined osteogenic/odontogenic differentiation capabilities of these cells in dentin slices model with two different scaffold, PuraMatrixTM hydrogel and poly-L-lactic acid (PLLA) in situ.

Results: We found that gingival tissue explants yielded group of cells with robust replication kinetics and multi-differentiation potential to osteogenic/odontogenic and adipogenic differentiation. Inasmuch as these isolated cells demonstrated the chractyeristics of mesenchymal stem cell, we termed them the minced gingival-mesenchymal stem cells (MG-MSCs). The MG-MSCs were able to replicate up to 45 population doublings (PDs) before senescence, while gingival MSCs (GMSCs) prepared from enzyme digestion method as reported previously (25) continued to replicate beyond 60 PDs. Senescence-associated beta-galactosidase (SA beta-Gal) staining showed that MG-MSCs underwent senescence significantly earlier compared to GMSCs. Although both MG-MSCs and GMSCs were able to differentiate into adipogenic lineage, demonstrating multi-differentiation capacities, only MG-MSCs were able to differentiate to osteo/odontogenic cells. Also MG-MSCs expressed much stronger level of stem markers, e.g., Oct3/4, Sox2, and Nanog, as well as odontogenic differentiation markers, e.g., DMP-1 (Dentin matrix acidic phosphoprotein-1) and DSPP (Dentin Sialophosphoprotein), compared with GMSCs. When MG was seeded on the scaffold (poly-L-lactic acid and PuraMatrixTM) in dentin-slice model, we noticed migratory cells from the tissues that had attached on the dentin surface and expressed DSP differentiation marker, again indicating the presence of MG-MSCs in the minced gingival tissue.

Conclusion: Our data indicate that MG transplantation yield highly proliferative MG-MSCs that exhibit the features of MSCs and undergo odontogenic differentiation in contact with dentin surface. Taken together, we believe that MG-MSCs can be utilized for direct tissue transplantation purpose of pulp-dentin regeneration.