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Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation

Runt-related transcription factor 2 (Runx2) is an essential transcription factor for osteoblast differentiation, and is activated by mechanical stress to promote osteoblast function. Cleidocranial dysplasia (CCD) is caused by mutations of RUNX2, and CCD patients exhibit malocclusion and often need o...

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Autores principales: Aonuma, Tomo, Tamamura, Nagato, Fukunaga, Tomohiro, Sakai, Yuichi, Takeshita, Nobuo, Shigemi, Shohei, Yamashiro, Takashi, Thesleff, Irma, Takano-Yamamoto, Teruko
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Elsevier 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7264061/
https://www.ncbi.nlm.nih.gov/pubmed/32509933
http://dx.doi.org/10.1016/j.bonr.2020.100285
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author Aonuma, Tomo
Tamamura, Nagato
Fukunaga, Tomohiro
Sakai, Yuichi
Takeshita, Nobuo
Shigemi, Shohei
Yamashiro, Takashi
Thesleff, Irma
Takano-Yamamoto, Teruko
author_facet Aonuma, Tomo
Tamamura, Nagato
Fukunaga, Tomohiro
Sakai, Yuichi
Takeshita, Nobuo
Shigemi, Shohei
Yamashiro, Takashi
Thesleff, Irma
Takano-Yamamoto, Teruko
author_sort Aonuma, Tomo
collection PubMed
description Runt-related transcription factor 2 (Runx2) is an essential transcription factor for osteoblast differentiation, and is activated by mechanical stress to promote osteoblast function. Cleidocranial dysplasia (CCD) is caused by mutations of RUNX2, and CCD patients exhibit malocclusion and often need orthodontic treatment. However, treatment is difficult because of impaired tooth movement, the reason of which has not been clarified. We examined the amount of experimental tooth movement in Runx2(+/−) mice, the animal model of CCD, and investigated bone formation on the tension side of experimental tooth movement in vivo. Continuous stretch was conducted to bone marrow stromal cells (BMSCs) as an in vitro model of the tension side of tooth movement. Compared to wild-type littermates the Runx2(+/−) mice exhibited delayed experimental tooth movement, and osteoid formation and osteocalcin (OSC) mRNA expression were impaired in osteoblasts on the tension side of tooth movement. Runx2 heterozygous deficiency delayed stretch-induced increase of DNA content in BMSCs, and also delayed and reduced stretch-induced alkaline phosphatase (ALP) activity, OSC mRNA expression, and calcium content of BMSCs in osteogenic medium. Furthermore Runx2(+/−) mice exhibited delayed and suppressed expression of mammalian target of rapamycin (mTOR) and rapamycin-insensitive companion of mTOR (Rictor), essential factors of mTORC2, which is regulated by Runx2 to phosphorylate Akt to regulate cell proliferation and differentiation, in osteoblasts on the tension side of tooth movement in vivo and in vitro. Loss of half Runx2 gene dosage inhibited stretch-induced PI3K dependent mTORC2/Akt activity to promote BMSCs proliferation. Furthermore, Runx2(+/−) BMSCs in osteogenic medium exhibited delayed and suppressed stretch-induced expression of mTOR and Rictor. mTORC2 regulated stretch-elevated Runx2 and ALP mRNA expression in BMSCs in osteogenic medium. We conclude that Runx2(+/−) mice present a useful model of CCD patients for elucidation of the molecular mechanisms in bone remodeling during tooth movement, and that Runx2 plays a role in stretch-induced proliferation and osteogenesis in BMSCs via mTORC2 activation.
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spelling pubmed-72640612020-06-05 Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation Aonuma, Tomo Tamamura, Nagato Fukunaga, Tomohiro Sakai, Yuichi Takeshita, Nobuo Shigemi, Shohei Yamashiro, Takashi Thesleff, Irma Takano-Yamamoto, Teruko Bone Rep Article Runt-related transcription factor 2 (Runx2) is an essential transcription factor for osteoblast differentiation, and is activated by mechanical stress to promote osteoblast function. Cleidocranial dysplasia (CCD) is caused by mutations of RUNX2, and CCD patients exhibit malocclusion and often need orthodontic treatment. However, treatment is difficult because of impaired tooth movement, the reason of which has not been clarified. We examined the amount of experimental tooth movement in Runx2(+/−) mice, the animal model of CCD, and investigated bone formation on the tension side of experimental tooth movement in vivo. Continuous stretch was conducted to bone marrow stromal cells (BMSCs) as an in vitro model of the tension side of tooth movement. Compared to wild-type littermates the Runx2(+/−) mice exhibited delayed experimental tooth movement, and osteoid formation and osteocalcin (OSC) mRNA expression were impaired in osteoblasts on the tension side of tooth movement. Runx2 heterozygous deficiency delayed stretch-induced increase of DNA content in BMSCs, and also delayed and reduced stretch-induced alkaline phosphatase (ALP) activity, OSC mRNA expression, and calcium content of BMSCs in osteogenic medium. Furthermore Runx2(+/−) mice exhibited delayed and suppressed expression of mammalian target of rapamycin (mTOR) and rapamycin-insensitive companion of mTOR (Rictor), essential factors of mTORC2, which is regulated by Runx2 to phosphorylate Akt to regulate cell proliferation and differentiation, in osteoblasts on the tension side of tooth movement in vivo and in vitro. Loss of half Runx2 gene dosage inhibited stretch-induced PI3K dependent mTORC2/Akt activity to promote BMSCs proliferation. Furthermore, Runx2(+/−) BMSCs in osteogenic medium exhibited delayed and suppressed stretch-induced expression of mTOR and Rictor. mTORC2 regulated stretch-elevated Runx2 and ALP mRNA expression in BMSCs in osteogenic medium. We conclude that Runx2(+/−) mice present a useful model of CCD patients for elucidation of the molecular mechanisms in bone remodeling during tooth movement, and that Runx2 plays a role in stretch-induced proliferation and osteogenesis in BMSCs via mTORC2 activation. Elsevier 2020-05-27 /pmc/articles/PMC7264061/ /pubmed/32509933 http://dx.doi.org/10.1016/j.bonr.2020.100285 Text en © 2020 Published by Elsevier Inc. http://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Article
Aonuma, Tomo
Tamamura, Nagato
Fukunaga, Tomohiro
Sakai, Yuichi
Takeshita, Nobuo
Shigemi, Shohei
Yamashiro, Takashi
Thesleff, Irma
Takano-Yamamoto, Teruko
Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation
title Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation
title_full Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation
title_fullStr Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation
title_full_unstemmed Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation
title_short Delayed tooth movement in Runx2(+/−) mice associated with mTORC2 in stretch-induced bone formation
title_sort delayed tooth movement in runx2(+/−) mice associated with mtorc2 in stretch-induced bone formation
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7264061/
https://www.ncbi.nlm.nih.gov/pubmed/32509933
http://dx.doi.org/10.1016/j.bonr.2020.100285
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