Department of Orthodontics and Pediatric Dentistry, University of Michigan School of Dentistry, Ann Arbor, MI, USA.
Orthod Craniofac Res. 2017 Jun;20 Suppl 1(Suppl 1):39-43. doi: 10.1111/ocr.12167.
Osterix (Osx)-expressing mesenchymal cells are progenitors for tooth root forming cells. The aim of this study was to reveal the fates of Osx-expressing cells during and after root formation using a lineage tracing experiment.
To reveal the fates of Osx-expressing dental mesenchymal progenitors, we took advantage of tamoxifen-inducible Cre reporter system. Osx-creER; R26R-tdTomato mice received tamoxifen (0.1 mg/body) at postnatal day 3 (P3). In this system, Osx-expressing at P3 (Osx-P3) cells undergo recombination, and they and their descendants continue to express Tomato red fluorescence protein permanently. Mandibles were dissected at serial time points ranging from P4 to P116 to investigate how Osx-P3 cells participated in root formation. Tomato cells on frozen sections were imaged under fluorescence microscopy.
Osx-P3 cells and their descendants differentiated into all kinds of cells that contributed to the root and periodontal tissues, such as odontoblasts, cementoblasts, alveolar bone osteoblasts and periodontal ligament (PDL) cells during root formation. Even after root formation was completed, they persisted in dental pulp and PDL to provide progenitor cells for odontoblasts and cementoblasts.
Osx-expressing cells play important roles in the entire processes of tooth root formation; their progeny continue to contribute to maintenance of tooth root even after root formation is complete.
骨形成蛋白 2 型受体（BMP2R）表达的间充质细胞是牙根管形成细胞的祖细胞。本研究旨在通过谱系追踪实验揭示根形成过程中和根形成后 BMP2R 表达细胞的命运。
为了揭示 BMP2R 表达的牙间充质祖细胞的命运，我们利用了他莫昔芬诱导型 Cre 报告系统。Osx-creER；R26R-tdTomato 小鼠在出生后第 3 天（P3）接受他莫昔芬（0.1mg/只）。在该系统中，P3 时表达 BMP2R（BMP2R-P3）的细胞经历重组，它们及其后代会持续永久表达红色荧光蛋白 Tomato。从 P4 到 P116 ，在多个时间点切取下颌骨，以研究 BMP2R-P3 细胞如何参与根形成。在荧光显微镜下对冷冻切片上的 Tomato 细胞进行成像。
BMP2R-P3 细胞及其后代分化为参与根和牙周组织形成的各种细胞，如成牙本质细胞、成牙骨质细胞、牙槽骨成骨细胞和牙周膜（PDL）细胞。即使在根形成完成后，它们仍存在于牙髓和 PDL 中，为成牙本质细胞和成牙骨质细胞提供祖细胞。
BMP2R 表达细胞在整个牙根形成过程中发挥重要作用；其后代在牙根形成完成后仍继续为牙根维持提供祖细胞。
