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Hertwig's Epithelial Root Sheath Fate during Initial Cellular Cementogenesis in Rat Molars.

Yamamoto T, Yamada T, Yamamoto T, Hasegawa T, Hongo H, Oda K, Amizuka N - Acta Histochem Cytochem (2015)

Bottom Line: The advancing root end was divided into three sections, which follow three distinct stages of initial cellular cementogenesis: section 1, where the epithelial sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where initial cellular cementogenesis begins.Dental follicle cells, precementoblasts, and cementoblasts showed immunoreactivity for vimentin and TNALP.Taken together, these findings suggest that: (1) epithelial sheath cells divide into two groups; one group is embedded in the cementum and thereafter dies by apoptosis, and the other survives on the cementum surface as epithelial cell rests of Malassez; and (2) epithelial sheath cells do not undergo epithelial-mesenchymal transition during initial cellular cementogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental Biology of Hard Tissue, Hokkaido University Graduate School of Dental Medicine , Sapporo, Japan.

ABSTRACT
To elucidate the fate of the epithelial root sheath during initial cellular cementogenesis, we examined developing maxillary first molars of rats by immunohistochemistry for keratin, vimentin, and tissue non-specific alkaline phosphatase (TNALP) and by TdT-mediated dUTP nick end labeling (TUNEL). The advancing root end was divided into three sections, which follow three distinct stages of initial cellular cementogenesis: section 1, where the epithelial sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where initial cellular cementogenesis begins. After fragmentation of the epithelial sheath, many keratin-positive epithelial sheath cells were embedded in the rapidly growing cellular cementum. A few unembedded epithelial cells located on the cementum surface. Dental follicle cells, precementoblasts, and cementoblasts showed immunoreactivity for vimentin and TNALP. In all three sections, there were virtually no cells possessing double immunoreactivity for vimentin-keratin or TNALP-keratin and only embedded epithelial cells showed TUNEL reactivity. Taken together, these findings suggest that: (1) epithelial sheath cells divide into two groups; one group is embedded in the cementum and thereafter dies by apoptosis, and the other survives on the cementum surface as epithelial cell rests of Malassez; and (2) epithelial sheath cells do not undergo epithelial-mesenchymal transition during initial cellular cementogenesis.

No MeSH data available.


Related in: MedlinePlus

H&E-stained sections showing a 35-day-old rat maxillary first molar. (A) Full view of the tooth. Asterisk indicates a mesial root. Bar=0.5 mm. (B) Magnification of boxed area in A. Two lines demarcate sections 1 to 3. Arrow and asterisk indicate Hertwig’s epithelial root sheath and cellular cementum, respectively. The intact epithelial sheath bends towards the dental pulp (DP). PL, periodontal ligament; AB, alveolar bone. Bar=50 μm. (C) Section 1. Intact epithelial root sheath (between arrows) demarcates dental follicle (DF) and dental papilla (DP). Bar=10 μm (common in C–E). (D) Sections 1 and 2 are partitioned by the dotted line. In section 1, odontoblasts (black arrow) start to form dentin (asterisk). In section 2, the epithelial sheath becomes fragmented and precementoblasts (white arrows) appear. (E) Section 3. Cementoblasts (white arrows) form the initial cellular cementum (double asterisk). Some cementoblasts are embedded as cementocytes (black arrow). Cells or cellular debris (yellow arrows) are seen in the deep region of cementum.
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Figure 1: H&E-stained sections showing a 35-day-old rat maxillary first molar. (A) Full view of the tooth. Asterisk indicates a mesial root. Bar=0.5 mm. (B) Magnification of boxed area in A. Two lines demarcate sections 1 to 3. Arrow and asterisk indicate Hertwig’s epithelial root sheath and cellular cementum, respectively. The intact epithelial sheath bends towards the dental pulp (DP). PL, periodontal ligament; AB, alveolar bone. Bar=50 μm. (C) Section 1. Intact epithelial root sheath (between arrows) demarcates dental follicle (DF) and dental papilla (DP). Bar=10 μm (common in C–E). (D) Sections 1 and 2 are partitioned by the dotted line. In section 1, odontoblasts (black arrow) start to form dentin (asterisk). In section 2, the epithelial sheath becomes fragmented and precementoblasts (white arrows) appear. (E) Section 3. Cementoblasts (white arrows) form the initial cellular cementum (double asterisk). Some cementoblasts are embedded as cementocytes (black arrow). Cells or cellular debris (yellow arrows) are seen in the deep region of cementum.

Mentions: Cellular cementogenesis had just begun on the mesial side of the mesial root of the maxillary first molars at postnatal day 35. The apical section of these sides was used to examine the process of initial cellular cementogenesis (Fig. 1A, B). For descriptive convenience, we divided the initial cellular cementogenesis into three stages, which correspond to three distinct sections: section 1, where Hertwig’s epithelial root sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where cellular cementogenesis begins.


Hertwig's Epithelial Root Sheath Fate during Initial Cellular Cementogenesis in Rat Molars.

Yamamoto T, Yamada T, Yamamoto T, Hasegawa T, Hongo H, Oda K, Amizuka N - Acta Histochem Cytochem (2015)

H&E-stained sections showing a 35-day-old rat maxillary first molar. (A) Full view of the tooth. Asterisk indicates a mesial root. Bar=0.5 mm. (B) Magnification of boxed area in A. Two lines demarcate sections 1 to 3. Arrow and asterisk indicate Hertwig’s epithelial root sheath and cellular cementum, respectively. The intact epithelial sheath bends towards the dental pulp (DP). PL, periodontal ligament; AB, alveolar bone. Bar=50 μm. (C) Section 1. Intact epithelial root sheath (between arrows) demarcates dental follicle (DF) and dental papilla (DP). Bar=10 μm (common in C–E). (D) Sections 1 and 2 are partitioned by the dotted line. In section 1, odontoblasts (black arrow) start to form dentin (asterisk). In section 2, the epithelial sheath becomes fragmented and precementoblasts (white arrows) appear. (E) Section 3. Cementoblasts (white arrows) form the initial cellular cementum (double asterisk). Some cementoblasts are embedded as cementocytes (black arrow). Cells or cellular debris (yellow arrows) are seen in the deep region of cementum.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4491499&req=5

Figure 1: H&E-stained sections showing a 35-day-old rat maxillary first molar. (A) Full view of the tooth. Asterisk indicates a mesial root. Bar=0.5 mm. (B) Magnification of boxed area in A. Two lines demarcate sections 1 to 3. Arrow and asterisk indicate Hertwig’s epithelial root sheath and cellular cementum, respectively. The intact epithelial sheath bends towards the dental pulp (DP). PL, periodontal ligament; AB, alveolar bone. Bar=50 μm. (C) Section 1. Intact epithelial root sheath (between arrows) demarcates dental follicle (DF) and dental papilla (DP). Bar=10 μm (common in C–E). (D) Sections 1 and 2 are partitioned by the dotted line. In section 1, odontoblasts (black arrow) start to form dentin (asterisk). In section 2, the epithelial sheath becomes fragmented and precementoblasts (white arrows) appear. (E) Section 3. Cementoblasts (white arrows) form the initial cellular cementum (double asterisk). Some cementoblasts are embedded as cementocytes (black arrow). Cells or cellular debris (yellow arrows) are seen in the deep region of cementum.
Mentions: Cellular cementogenesis had just begun on the mesial side of the mesial root of the maxillary first molars at postnatal day 35. The apical section of these sides was used to examine the process of initial cellular cementogenesis (Fig. 1A, B). For descriptive convenience, we divided the initial cellular cementogenesis into three stages, which correspond to three distinct sections: section 1, where Hertwig’s epithelial root sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where cellular cementogenesis begins.

Bottom Line: The advancing root end was divided into three sections, which follow three distinct stages of initial cellular cementogenesis: section 1, where the epithelial sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where initial cellular cementogenesis begins.Dental follicle cells, precementoblasts, and cementoblasts showed immunoreactivity for vimentin and TNALP.Taken together, these findings suggest that: (1) epithelial sheath cells divide into two groups; one group is embedded in the cementum and thereafter dies by apoptosis, and the other survives on the cementum surface as epithelial cell rests of Malassez; and (2) epithelial sheath cells do not undergo epithelial-mesenchymal transition during initial cellular cementogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental Biology of Hard Tissue, Hokkaido University Graduate School of Dental Medicine , Sapporo, Japan.

ABSTRACT
To elucidate the fate of the epithelial root sheath during initial cellular cementogenesis, we examined developing maxillary first molars of rats by immunohistochemistry for keratin, vimentin, and tissue non-specific alkaline phosphatase (TNALP) and by TdT-mediated dUTP nick end labeling (TUNEL). The advancing root end was divided into three sections, which follow three distinct stages of initial cellular cementogenesis: section 1, where the epithelial sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where initial cellular cementogenesis begins. After fragmentation of the epithelial sheath, many keratin-positive epithelial sheath cells were embedded in the rapidly growing cellular cementum. A few unembedded epithelial cells located on the cementum surface. Dental follicle cells, precementoblasts, and cementoblasts showed immunoreactivity for vimentin and TNALP. In all three sections, there were virtually no cells possessing double immunoreactivity for vimentin-keratin or TNALP-keratin and only embedded epithelial cells showed TUNEL reactivity. Taken together, these findings suggest that: (1) epithelial sheath cells divide into two groups; one group is embedded in the cementum and thereafter dies by apoptosis, and the other survives on the cementum surface as epithelial cell rests of Malassez; and (2) epithelial sheath cells do not undergo epithelial-mesenchymal transition during initial cellular cementogenesis.

No MeSH data available.


Related in: MedlinePlus