Ultrastructure of Hertwig's epithelial root sheath during early root development in premolar teeth in dogs

Hertwig’s epithelial root sheath (HERS) is important for tooth root formation, but the molecular basis for the signaling of root development remains uncertain. We hypothesized that Sonic hedgehog (Shh) signaling is involved in the HERS function, because it mediates epithelial-mesenchymal interactions during embryonic odontogenesis. We examined the gene expression patterns of Shh signaling in murine developing molar roots. Shh and Patched2 transcripts were identified in the HERS, whereas Patched1, Smoothened, and Gli1 were expressed in the proliferative dental mesenchyme in addition to the HERS. To confirm whether Shh signaling physiologically functions in vivo, we analyzed mesenchymal dysplasia ( mes) mice carrying an abnormal C-terminus of the PATCHED1 protein. In the mutant, cell proliferation was repressed around the HERS at 1 wk. Moreover, the molar eruption was disturbed, and all roots were shorter than those in control littermates at 4 wks. These results indicate that Shh signaling is important in tooth root development. Abbreviations used: BrdU, 5-bromo-2′-deoxyuridine; HERS, Hertwig’s epithelial root sheath; NFI-C/CTF, nuclear factor Ic/CAAT box transcription factor; PCNA, proliferating cell nuclear antigen; Ptc, patched; Shh, sonic hedgehog; Smo, smoothened.

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Cell dynamics in Hertwig's epithelial root sheath are regulated by β‐catenin activity during tooth root development

Journal of Cellular Physiology ◽

10.1002/jcp.30243 ◽

2020 ◽

Author(s):

Siqin Yang ◽

Hwajung Choi ◽

Tak‐Heun Kim ◽

Ju‐Kyung Jeong ◽

Yudong Liu ◽

...

Keyword(s):

Root Development ◽

Tooth Root ◽

Cell Dynamics ◽

Hertwig’S Epithelial Root Sheath ◽

Root Sheath

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Role of Hertwig's epithelial root sheath cells in tooth root development

Developmental Dynamics ◽

10.1002/dvdy.10404 ◽

2003 ◽

Vol 228 (4) ◽

pp. 651-663 ◽

Cited By ~ 145

Author(s):

Margarita Zeichner-David ◽

Keiji Oishi ◽

Zhengyan Su ◽

Vassili Zakartchenko ◽

Li-Sha Chen ◽

...

Keyword(s):

Root Development ◽

Tooth Root ◽

Hertwig’S Epithelial Root Sheath ◽

Root Sheath ◽

Sheath Cells

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BMP4 signaling regulates formation of Hertwig’s epithelial root sheath during tooth root development

Cell and Tissue Research ◽

10.1007/s00441-008-0655-z ◽

2008 ◽

Vol 333 (3) ◽

pp. 503-509 ◽

Cited By ~ 42

Author(s):

Akihiro Hosoya ◽

Ji-Youn Kim ◽

Sung-Won Cho ◽

Han-Sung Jung

Keyword(s):

Root Development ◽

Tooth Root ◽

Hertwig’S Epithelial Root Sheath ◽

Root Sheath

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Local Irradiation of Mouse Tooth Germ Gives Insight into the Direct Effects of Irradiation on Root Development

Radiation Research ◽

10.1667/rade-20-00081.1 ◽

2021 ◽

Author(s):

Yoshiaki Ide ◽

Taka Nakahara ◽

Tetsuya Fukada ◽

Masanori Nasu

Keyword(s):

Root Development ◽

Root Formation ◽

Tooth Germ ◽

Lead Glass ◽

Local Irradiation ◽

Root Sheath ◽

Calcified Tissue ◽

Radiation Induced ◽

Dentin Formation ◽

Root Apices

To elucidate the mechanism underlying the failure of root formation after irradiation, we established a method of local irradiation of the molar tooth germ and demonstrated that radiation directly affected dental root development. In the current study, to locally irradiate the lower first molars of 5-day-old C57BL/6J mice, we used lead glass containing a hole as a collimator. We confirmed that our local irradiation method targeted only the tooth germ. The irradiated root was immature in terms of apical growth, and dentin formation was irregular along the outside of the root apices. Moreover, calcified tissue apically surrounded Hertwig's epithelial root sheath, which disappeared abnormally early. This method using a local irradiation experimental model will facilitate research into radiation-induced disorders of dental root formation.

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