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Am J Orthod Dentofacial Orthop. 2014 Sep;146(3):337-45. doi: 10.1016/j.ajodo.2014.05.027.

Downregulation of Wnt causes root resorption.

Author information

1
Researcher, Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, Calif; associate professor, Department of Orthodontics, School of Dentistry & Dental Research Institute, Seoul National University, Seoul, Korea.
2
Research associate, Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, Calif.
3
Researcher, Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, Calif.
4
Former researcher, Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, Calif.
5
Clinical instructor, Department of Orthodontics, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
6
Professor, Division of Plastic and Reconstructive Surgery, Department of Surgery, School of Medicine, Stanford University, Stanford, Calif. Electronic address: jhelms@stanford.edu.

Abstract

INTRODUCTION:

There are multiple causes of external root resorption, but absent a disease state, it is most often observed when excessive physical force is used during orthodontic treatment. Even without mechanical stimulation, however, root resorption can still occur. The purpose of this study was to test whether Wnt signaling plays a role in pathologic root resorption, by conditionally deleting Wntless (Wls) from odontoblasts and osteoblasts and then evaluating the phenotypic effects on the maintenance of the root surface.

METHODS:

Ten (age, 1 month) and 20 (age, 3 months) OCN-Cre;Wls(fl/fl) mice and their wild-type littermates were evaluated using microcomputed tomography, histology, and immunohistochemistry. Phenotypic alterations in the alveolar bone, dentin, and cementum were characterized and quantified.

RESULTS:

In a genetic model of reduced Wnt signaling, we found that RANKL expression is upregulated, and osteoprotegerin expression is downregulated. This molecular disruption results in an increase in osteoclast activity, a decrease in osteoblast activity, and extensive, spontaneous root resorption. A genetic strain of mice in which Wnt signaling is elevated exhibits thicker cementum, whereas, even in the perinatal period, OCN-Cre;Wls(fl/fl) mice exhibit thinner cementum.

CONCLUSIONS:

Taken together, these data demonstrate that Wnts regulate cementum homeostasis, and that idiopathic cases of root resorption might have as their etiology a reduction in endogenous Wnt signaling.

PMID:
25172256
DOI:
10.1016/j.ajodo.2014.05.027
[Indexed for MEDLINE]

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