Clarification of the disintegration of Hertwig's epithelial root sheath by using a real time imaging

牙根的形成是由成釉器中的颈环的Hertwig上皮根鞘（HERS）的发育开始的。然而，HERS形成过程中的细胞动力学尚不清楚。本研究的目的是建立一个可视化HERS细胞动态变化的实验系统，以阐明EMT对HERS细胞的崩解机制。我们建立了真实的时间切片培养成像系统，可以观察HERS细胞的迁移、分裂和肌动蛋白启动子活性。我们还建立了小鼠磨牙HERS细胞系。细胞表达间充质细胞标志物，TGF-β刺激后表达增强。HGF可促进牙根的伸长，促进细胞增殖，提示HGF信号通路与牙根的形成有关。

Tooth root formation is initiated by the development of Hertwig's epithelial root sheath(HERS) from the cervical loop in the enamel organ. However, the cellular dynamics during HERS formation is not well known yet. In This study, we aimed to establish the experimental system to visualize the dynamics of HERS cells in order to elucidate the mechanism of HERS disintegration by EMT. We established the real time slice culture imaging system, which could observe the migration, division, and actin promoter activity in HERS cell. We also established HERS cell line from mouse molars. The cells expressed mesenchymal cell markers, and the expressions were increased to the stimulation of TGF-β. The root elongation was intensified by HGF with the increased cell proliferation, indicating the implication between HGF signaling and tooth root formation.