Three-dimensional configuration of apical epithelial compartments including stem cell niches in guinea pig cheek teeth

Publication date: Available online 21 January 2019

Source: Journal of Oral Biosciences

Author(s): Yuta Seino, Mitsushiro Nakatomi, Hiroko Ida-Yonemochi, Daisuke Koga, Tatsuo Ushiki, Hayato Ohshima

Abstract

Objectives

Continuously growing rodent incisors have an apically located epithelial stem cell compartment, known as an "apical bud" (AB). Few studies have described the morphological features of ABs and stem cell niches in continuously growing premolars/molars. We attempted to clarify the relationship between the three-dimensional configuration of ABs and the stem cell niches in guinea pig cheek teeth.

Methods

We perfusion-fixed four-week-old guinea pigs, then decalcified their premolars/molars to produce serial paraffin sections, which we immunostained for Sox2. We reconstructed the serial sections using image processing and analysis software. We processed undecalcified samples for scanning electron microscopy by KOH digestion.

Results

Two types of epithelia with M and Δ shapes surrounded the S-shaped dental papilla in the apical region of the premolars/molars, and there were three Sox2-positive epithelial bulges above the M- and Δ-shaped epithelia. Sox2-positive epithelial stem cell niches were restricted to the apical side, and cell proliferation and differentiation immediately proceeded in the crown-analogue dentin. The Sox2-positive epithelial stem cell niches were sparsely distributed and extended to the occlusal side. We also detected continuously proliferating cells in the cervical loop and Hertwig's epithelial root sheath of the root-analogue dentin.

Conclusions

Our findings suggest that guinea pig cheek teeth have three ABs, and the complex configuration of these types of teeth may be attributed to the prompt formation of crown-analogue dentin followed by the long-term formation of root-analogue dentin.

Graphical abstract

http://bit.ly/2FKWMxV