Comparative study on differentiation of cervical-loop cells and Hertwig\u2019s epithelial root sheath cells under the induction of dental follicle cells in rat

Yongwen Guo,Ding Bai,Ye Tian,Jie Chen,Guoqing Chen,Weihua Guo,Weidong Tian

doi:10.1038/s41598-018-24973-0

Yongwen Guo, Ding Bai + Show 5 more

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https://doi.org/10.1038/s41598-018-24973-0

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Abstract

Cervical loop cells (CLC) and Hertwig’s epithelial root sheath (HERS) cells are believed to play critical roles in distinct developmental patterns between rodent incisors and molars, respectively. However, the differences in differentiation between CLC and HERS cells, and their response to inductions from dental follicle cells, remain largely unknown. In present study, CLC and HERS cells, as well as incisor dental follicle (IF) cells and molar dental follicle (MF) cells were isolated from post-natal 7-day rats. IF and MF cell derived conditioned medium (CM) was obtained for induction of CLC and HERS cells. In vitro experiments, we found that, under the induction of dental follicle cell derived CM, CLC cells maintained the epithelial polygonal-shapes and formed massive minerals, while part of HERS cells underwent shape transformation and generated granular minerals. CLC cells expressed higher enamel-forming and mineralization related genes, while HERS cells showed opposite expression patterns of BMP2, BMP4, AMBN and AMGN. In vivo, CLC cells generated enamel-like tissues while HERS cells formed cementum-periodontal ligament-like structures. Taken together, CLC and HERS cells present distinct differentiation patterns under the inductions from dental follicle cells.

Highlights

Rodent incisors and molars present two totally different developmental patterns
incisor dental follicle (IF) and molar dental follicle (MF) cells were characterized by a typical fibroblast-like morphology of spindle or stellate shape. Both Cervical loop cells (CLC) and Hertwig’s epithelial root sheath (HERS) cells were positive for the epithelial cell marker CK14, but negative for the mesenchymal cell marker vimentin, while the IF and MF cells showed the opposite (Fig. 1)
These results indicated that the methods to isolate CLC, HERS, IF and MF cells are effective with a high purification

Summary

Introduction

Rodent incisors and molars present two totally different developmental patterns. The incisors grow and erupt continuously the whole life without the formation of typical root, while the molars form typical roots after the completion of crown and stop erupting spontaneously after the completion of root development[1]. The cervical loop is constantly maintained at the labial aspect of the rodent incisor apex and is the reservoir of stem cells It consists of a core of stellate reticulum cells surrounded by inner and outer enamel epithelial cells that contact the dental mesenchyme. In human teeth and rodent molars, after completion of crown, the inner and outer epithelium of enamel organ proliferate at the cervical loop and the stratum intermedium and stellate reticulum disappear to form HERS It migrates apically and participates in root formation. Regarding the mechanisms of HERS in the formation of periodontium, some researchers conclude that HERS indirectly involves in the development of periodontal structures by interacting with the surrounding dental follicles, which contain precursors that give rise to the components of the periodontium including cementum, periodontal ligament and alveolar bone[7,8,9]. The implementation of the investigation would further contribute to elucidate the mechanism of tooth development and provide experimental evidence for potential clinical application in tooth regeneration

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