2023 年 3 巻 1 号 p. 12-21
Purpose: It has been proposed that some enamel organ-derived cells undergo an epithelial-mesenchymal transition (EMT) during tooth development, differentiate into cementoblasts, and make acellular cementum. The primary purpose of this study was to elucidate the mechanisms of cell differentiation by transplanting apical bud-derived stem cells of the epithelial lineage of tooth embryos into the bony defects around the molars and tracking their dynamics. The secondary purpose of this study was to use those tissue stem cells as a source of cell transplantation for future periodontal tissue regeneration therapy.
Methods: Apical bud cells from GFP-positive mouse incisors were isolated under a microscope, collected, dispersed, and transplanted into bone defects created around the molars of wild-type mice, and their dynamics were observed for three months. Undecalcified cryosections were made by Kawamoto’s method, and immunofluorescence staining was made using antibodies against Osteocalcin (OCN), Cementum protein 1 (CEMP1), and Cytokeratin 10 (CK10).
Results: GFP-positive cells were observed to settle in the periodontal tissue after four weeks of transplantation. Most of the GFP-positive cells showed OCN positivity throughout the observation period. In 12 weeks, some transplanted cells were aligned along the surface of the cementum, and HE images showed the development of cement matrix-like structures around the cells. Among the transplanted cells, cells in the periodontal space were mostly CK10-positive and CEMP1-negative, while cells on the cementum and near alveolar bone were mostly CEMP1-positive and CK10-negative.
Conclusion: Our observations revealed that some transplanted cells underwent EMT and became cementoblast-like on the root surface and osteoblast-like, where they were incorporated into the alveolar bone. Both cementoblast-like and osteoblast-like cells were CEMP1-positive. On the other hand, CEMP1-negative and CK10-positive cells were located in the middle of the periodontal ligament space, suggesting that they settled into the tissue as ERM without undergoing EMT. It is interesting to see how the transplanted cells migrate and settle or differentiate under the influence of surrounding cells. These results suggest that enamel organ-derived tissue stem cells may differentiate into osteoblasts and cementoblasts/cementocytes and could be the source of periodontal tissue regeneration.
