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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

Sections stained for keratin. (A) Section 1. Only intact epithelial root sheath is stained positive for keratin. DF, dental follicle; DP, dental papilla. Bar=10 μm (common in A–C). (B) Sections 1 and 2 are partitioned by the dotted line. In section 2, a few epithelial cells (arrow) are lost from the surface of dentin (asterisk) simultaneously with epithelial sheath fragmentation. The total number of epithelial cells appears smaller than in section 1. (C) Section 3. Many keratin-positive epithelial cells (black arrows) are incorporated in the deep region of cementum (double asterisk), whereas only a few epithelial cells (white arrows) are located on the cementum.
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Figure 2: Sections stained for keratin. (A) Section 1. Only intact epithelial root sheath is stained positive for keratin. DF, dental follicle; DP, dental papilla. Bar=10 μm (common in A–C). (B) Sections 1 and 2 are partitioned by the dotted line. In section 2, a few epithelial cells (arrow) are lost from the surface of dentin (asterisk) simultaneously with epithelial sheath fragmentation. The total number of epithelial cells appears smaller than in section 1. (C) Section 3. Many keratin-positive epithelial cells (black arrows) are incorporated in the deep region of cementum (double asterisk), whereas only a few epithelial cells (white arrows) are located on the cementum.

Mentions: In section 1 (Fig. 2A, B), the intact epithelial sheath stained positive for keratin. In section 2 (Fig. 2B), where the epithelial sheath was disrupted, only a few epithelial cells had migrated away from the dentin surface. At this point, the total number of epithelial cells appeared to be fewer than in the intact epithelial sheath. In section 3 (Fig. 2C), cells or cellular debris (see Fig. 1E) in the deep region of the cementum stained positive for keratin, indicating that they are the progeny of epithelial sheath cells. These embedded epithelial remnants were much more than unembedded epithelial cells, i.e., epithelial cell rests of Malassez.


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)

Sections stained for keratin. (A) Section 1. Only intact epithelial root sheath is stained positive for keratin. DF, dental follicle; DP, dental papilla. Bar=10 μm (common in A–C). (B) Sections 1 and 2 are partitioned by the dotted line. In section 2, a few epithelial cells (arrow) are lost from the surface of dentin (asterisk) simultaneously with epithelial sheath fragmentation. The total number of epithelial cells appears smaller than in section 1. (C) Section 3. Many keratin-positive epithelial cells (black arrows) are incorporated in the deep region of cementum (double asterisk), whereas only a few epithelial cells (white arrows) are located on the cementum.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Sections stained for keratin. (A) Section 1. Only intact epithelial root sheath is stained positive for keratin. DF, dental follicle; DP, dental papilla. Bar=10 μm (common in A–C). (B) Sections 1 and 2 are partitioned by the dotted line. In section 2, a few epithelial cells (arrow) are lost from the surface of dentin (asterisk) simultaneously with epithelial sheath fragmentation. The total number of epithelial cells appears smaller than in section 1. (C) Section 3. Many keratin-positive epithelial cells (black arrows) are incorporated in the deep region of cementum (double asterisk), whereas only a few epithelial cells (white arrows) are located on the cementum.
Mentions: In section 1 (Fig. 2A, B), the intact epithelial sheath stained positive for keratin. In section 2 (Fig. 2B), where the epithelial sheath was disrupted, only a few epithelial cells had migrated away from the dentin surface. At this point, the total number of epithelial cells appeared to be fewer than in the intact epithelial sheath. In section 3 (Fig. 2C), cells or cellular debris (see Fig. 1E) in the deep region of the cementum stained positive for keratin, indicating that they are the progeny of epithelial sheath cells. These embedded epithelial remnants were much more than unembedded epithelial cells, i.e., epithelial cell rests of Malassez.

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