Altered expression of tenascin C in pericoronal tissues by odontogenic epithelial cells during tooth eruption.

Abstract

<h4>Objectives</h4>We aimed to elucidate the role of odontogenic epithelium in pericoronal tissue during tooth eruption by investigating the morphology of epithelial cells and expression of tenascin C.<h4>Methods</h4>Biopsy samples from human patients diagnosed with lower first molar eruption disorders, along with mandibular molar tissues from ICR mice, collected between postnatal day 10 (PN10) and PN15, were examined. Immunohistochemical analyses were performed to evaluate the expression of cytokeratin, tenascin C, E-cadherin, pSmads, and Ki67. In situ hybridization was used to detect expression of tenascin C mRNA.<h4>Results</h4>In human lower first molar specimens, a band-like configuration of epithelial islands was observed in the pericoronal connective tissue, with and without expression of tenascin C. In one patient, a high level of tenascin C mRNA was detected in the continuous epithelial layer covering the crown of impacted first molars, and the expression of tenascin C correlated with Ki67, a marker of cell proliferation. During lower molar tooth eruption in mice, odontogenic epithelial cells transformed from a mesh-like to a sheet-like configuration, accompanied by a reduction in the expression of tenascin C protein and mRNA. There was no proliferation or expression of pSmads in the epithelial component.<h4>Conclusions</h4>Persistent secretion of tenascin C by odontogenic epithelial cells may promote proliferation of the cells and increase accumulation of tenascin C in the pericoronal tissue. These findings suggest that sustained expression of tenascin C suppresses the progression of tooth eruption.