Int J Oral Biol.  2011 Sep;36(3):135-141.

The Epithelial-Mesenchymal Transition During Tooth Root Development

Affiliations
  • 1Dental Science Research Institute, 2nd Stage Brain Korea, School of Dentistry, Chonnam National University, Korea. greatone@chonnam.ac.kr

Abstract

Hertwig's epithelial root sheath (HERS) consists of bilayered cells derived from the inner and outer dental epithelia and plays important roles in tooth root formation as well as in the maintenance and regeneration of periodontal tissues. With regards to the fate of HERS, and although previous reports have suggested that this entails the formation of epithelial rests of Malassez, apoptosis or an epithelialmesenchymal transformation (EMT), it is unclear what changes occur in the epithelial cells in this structure. This study examined whether HERS cells undergo EMT using a keratin-14 (K14) cre:ROSA 26 transgenic reporter mouse. The K14 transgene is expressed by many epithelial tissues, including the oral epithelium and the enamel organ. A distinct K14 expression pattern was found in the continuous HERS bi-layer and the epithelial diaphragm were visualized by detecting the beta-galactosidase (lacZ) activity in 1 week postnatal mice. The 2 and 4 week old mice showed a fragmented HERS with cell aggregation along the root surface. However, some of the lacZ-positive dissociated cells along the root surface were not positive for pan-cytokeratin. These results suggest that the K14 transgene is a valuable marker of HERS. In addition, the current data suggest that some of the HERS cells may lose their epithelial properties after fragmentation and subsequently undergo EMT.

Keyword

HERS; EMT; K14 cre mice; tooth development

MeSH Terms

Animals
Apoptosis
beta-Galactosidase
Cell Aggregation
Diaphragm
Enamel Organ
Epithelial Cells
Epithelial-Mesenchymal Transition
Epithelium
Keratin-14
Mice
Regeneration
Tooth
Tooth Root
Transgenes
Keratin-14
beta-Galactosidase
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