Bae Cheol-Hyeon, Kim Tak-Heun, Chu Jung-Yob, Cho Eui-Sic
Cluster for Craniofacial Development and Regeneration Research, Institute of Oral Biosciences, Chonbuk National University, School of Dentistry, Jeonju 561-756, South Korea.
Gene Expr Patterns. 2013 Jun-Jul;13(5-6):197-202. doi: 10.1016/j.gep.2013.04.001. Epub 2013 Apr 18.
Root formation is initiated with the extension of Hertwig's epithelial root sheath (HERS) after crown morphogenesis. To date, little is known about the molecular and cellular mechanisms controlling root formation. Recently we found rootless molars are formed in the dental mesenchyme-specific β-catenin conditional knockout mice. The striking root phenotypes of these mutant mice result from the disrupted differentiation of differentiating odontoblasts, caused by ablation of β-catenin during initiation of root formation. Here we show the cellular and molecular characteristics of differentiating odontoblasts using histochemistry and immunohistochemistry. These cells were not found in crown formation, but appeared only in the apical end of developing tooth, thus we have named these cells "apical odontoblasts" (AOds). AOds appeared immediately after HERS formation and were always present on the apical side of developing roots until root formation was complete. These findings indicate that AOds are closely associated with the transition from crown to root and with root elongation. In AOds, several transcription factors, including Nfic, Creb3l1, and Osx, as well as β-catenin and alkaline phosphatase were expressed but Phex and Dspp were not expressed. Taken together, our results indicate that AOds are the principal cells responsible for tooth root formation. These findings may contribute to the further understanding of the mechanisms underlying tooth root formation and root regeneration.
在牙冠形态发生后，赫特维希上皮根鞘（HERS）的延伸启动了牙根的形成。迄今为止，关于控制牙根形成的分子和细胞机制知之甚少。最近我们发现，在牙间充质特异性β-连环蛋白条件性敲除小鼠中形成了无根磨牙。这些突变小鼠显著的牙根表型是由于在牙根形成起始阶段β-连环蛋白缺失导致成牙本质细胞分化中断所致。在这里，我们使用组织化学和免疫组织化学展示了成牙本质细胞分化的细胞和分子特征。这些细胞在牙冠形成过程中未被发现，仅出现在发育中牙齿的根尖，因此我们将这些细胞命名为“根尖成牙本质细胞”（AOds）。AOds在HERS形成后立即出现，并始终存在于发育中牙根的根尖侧，直至牙根形成完成。这些发现表明，AOds与从牙冠到牙根的转变以及牙根伸长密切相关。在AOds中，表达了几种转录因子，包括Nfic、Creb3l1和Osx，以及β-连环蛋白和碱性磷酸酶，但未表达Phex和Dspp。综上所述，我们的结果表明，AOds是负责牙根形成的主要细胞。这些发现可能有助于进一步了解牙根形成和牙根再生的潜在机制。
