Reduction of Egf Signaling Decides Transition From Crown to Root in the Development of Mouse Molars
Reduction of Egf Signaling Decides Transition From Crown to Root in the Development of Mouse Molars
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DOI：
10.1002/jez.b.21268
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发表时间：
2009-07-15
影响因子：
2.2
通讯作者：
Harada, Hidemitsu
中科院分区：
文献类型：
--
作者：
Fujiwara, Naoki;Akimoto, Tadashi;Harada, Hidemitsu
小鼠、大鼠和人类磨牙在牙冠形态发生完成后开始形成牙根。虽然有几个信号通路和转录因子已被牵连在臼齿冠发育的调节，相对较少的是知道的调控机制，参与从冠到根的发展。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。在这项研究中，我们检查了在这个转变过程中表皮生长因子（Egf）信号的变化。免疫组化结果显示，EGF受体在成釉器中的表达逐渐消失，在HERS中未见表达。在这里，为了检验EGF对转化的影响，我们使用器官培养方法来检查根的发育。在Egf的存在下，成釉器内外上皮层之间的星状网状细胞（SR）活跃增殖并维持成釉器，未观察到HERS的形成。另一方面，在没有EGF或存在EGF受体抑制剂的情况下，SR细胞消失，HERS开始形成。随后，在培养期间进行根的形成。因此，SR区的消失可能是控制HERS发生时间的关键事件，EGF可能是参与牙根发育过程中宫颈袢上皮向HERS转变的调节因子之一。J. Exp. Zool.（Mol. Dev. Evol.）312 B：486-494，2009. (C)2008威利利斯公司
Mouse, rat, and human molars begin to form their roots after the completion of crown morphogenesis. Though several signaling pathways and transcription factors have been implicated in the regulation of molar crown development, relatively little is known about the regulatory mechanisms involved in the transition from crown to root development. Tooth root formation is initiated by the development of Hertwig's epithelial root sheath (HERS) from the cervical loop in the enamel organ. In this study we examined the change in epidermal growth factor (Egf) signaling during this transition process. Immunohistochemical studies showed that the expression of Egf receptors in the enamel organ disappear gradually in the process and are not observed in HERS. Here, to examine the effect of Egf on the transition, we used the organ culture method to examine the root development. In the presence of Egf, stellate reticulum (SR) cells between the inner and outer epithelial layers in the enamel organ actively proliferated and maintained the enamel organ, and the formation of HERS was not observed. On the other hand, in either the absence of Egf or the presence of the inhibitor of Egf receptors, the SR cells disappeared and HERS formation started. Subsequently, root formation proceeded in the culture period. Therefore, disappearance of SR area may be a key event that controls the timing of onset of HERS formation, and Egf may be one of regulatory factors involved in the change from cervical loop epithelium to HERS during root development. J. Exp. Zool. (Mol. Dev. Evol.) 312B:486-494, 2009. (C) 2008 Wiley-Liss, Inc.