TY - JOUR
T1 - The enamel knot-like structure is eternally maintained in the apical bud of postnatal mouse incisors
AU - Nakatomi, Chihiro
AU - Nakatomi, Mitsushiro
AU - Saito, Kan
AU - Harada, Hidemitsu
AU - Ohshima, Hayato
N1 - Funding Information:
This work was supported by JSPS KAKENHI Grant Numbers 25293371 , 25861741 .
Publisher Copyright:
© 2015 Elsevier Ltd. All rights reserved.
PY - 2015/5/30
Y1 - 2015/5/30
N2 - Objectives The boundary where inner and outer enamel epithelia meet is referred to as the cervical loop (CL) in molar tooth germs. In contrast, rodent incisors are continuously growing: the labial side of the teeth is covered with enamel (crown-analog), and the lingual side is covered with cementum (root-analog). These results in the appearance of CL in the frontal sections apart from the apical end. However, many researchers have used the term "labial CL" to indicate the apical end of incisors. Design This study investigated the gene expression patterns for the enamel knot signaling center in tooth morphogenesis to clarify the difference between "labial CL" and molar CL. We examined the three-dimensional expression patterns of markers for the enamel knot including fibroblast growth factor 4 (Fgf4), sonic hedgehog (Shh), Msx2, and P21 in frontal sections of murine mandibular incisors. Results Serial frontal sections from the apical end of the postnatal incisor clearly demonstrated the existence of enamel knot-like structures composed of supra-inner enamel epithelium and stellate reticulum in the "labial CL". This structure includes the expression of all examined markers for enamel knots such as Fgf4, Shh, Msx2, and P21. Conclusions The molar tooth germ-like structure is maintained indefinitely in the "labial CL". Therefore, the "labial CL" is not equivalent to the molar CL. The existence of an EK-like structure in the apical end of incisors implies that the usage of "labial CL" may be inappropriate for indicating this region. The "apical bud" could be used as an alternative term.
AB - Objectives The boundary where inner and outer enamel epithelia meet is referred to as the cervical loop (CL) in molar tooth germs. In contrast, rodent incisors are continuously growing: the labial side of the teeth is covered with enamel (crown-analog), and the lingual side is covered with cementum (root-analog). These results in the appearance of CL in the frontal sections apart from the apical end. However, many researchers have used the term "labial CL" to indicate the apical end of incisors. Design This study investigated the gene expression patterns for the enamel knot signaling center in tooth morphogenesis to clarify the difference between "labial CL" and molar CL. We examined the three-dimensional expression patterns of markers for the enamel knot including fibroblast growth factor 4 (Fgf4), sonic hedgehog (Shh), Msx2, and P21 in frontal sections of murine mandibular incisors. Results Serial frontal sections from the apical end of the postnatal incisor clearly demonstrated the existence of enamel knot-like structures composed of supra-inner enamel epithelium and stellate reticulum in the "labial CL". This structure includes the expression of all examined markers for enamel knots such as Fgf4, Shh, Msx2, and P21. Conclusions The molar tooth germ-like structure is maintained indefinitely in the "labial CL". Therefore, the "labial CL" is not equivalent to the molar CL. The existence of an EK-like structure in the apical end of incisors implies that the usage of "labial CL" may be inappropriate for indicating this region. The "apical bud" could be used as an alternative term.
KW - Mice (ICR)
KW - Regeneration
KW - Rodentia
KW - Stem cells
KW - Tooth germ
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U2 - 10.1016/j.archoralbio.2015.05.001
DO - 10.1016/j.archoralbio.2015.05.001
M3 - Article
C2 - 26042621
AN - SCOPUS:84930654872
VL - 60
SP - 1122
EP - 1130
JO - Archives of Oral Biology
JF - Archives of Oral Biology
SN - 0003-9969
IS - 8
ER -