The Inverted U-Curve Association of Fluoride and Osteoclast Formation in Mice

  • Yingjie Yao
  • Yongzheng Ma
  • Nan Zhong
  • Junrui PeiEmail author


The effect of fluoride on osteoclasts is still controversial. In the past, researchers thought that the effects of fluoride on osteoclast and osteoblast formation occurred in a dose-dependent pattern. However, our previous in vitro study showed fluoride elicited a notably different effect on osteoclast formation. To further verify the relationship between fluoride and osteoclast formation in vivo, 60 male C57BL/6 mice were randomly divided into three groups: two treatment groups consuming water supplemented with 50 and 100 mg/L of fluoride, and a third control group with nonsupplemented water. Ion selective electrode method analysis was used to detect bone fluoride content, and the effects of fluoride on bone tissue were assessed with hematoxylin and eosin (HE) staining. Additionally, the expression of BGP and ALP were examined by Western blot analysis, and tartrate-resistant acid phosphatase (TRAP) was assessed with immunohistochemistry. Osteoclasts in bone tissue were identified with a combination method of TRAP staining and cell morphology assessment. Results showed increasing expression of BGP among treatment groups as fluoride exposure increased, and ALP expression in the 100 mg/L treatment group was significantly higher than that for both the 50 mg/L treatment and control groups. The number of osteoclasts in the 50 mg/L group was highest amongst the three groups, followed by the 100 mg/L treatment and then by the control group, with the latter showing significantly fewer osteoclasts than in either treatment group. These results suggest that fluoride enhances bone formation at increasing levels of fluoride exposure. However, the inverted U-curve association was found between fluoride exposure and osteoclast formation, with the higher dose of fluoride having slightly reduced osteoclast formation. The results from this study may provide key insights towards understanding the role of osteoclasts in the progression of skeletal fluorosis.


Fluoride Fluorosis Osteoclast Osteoblast 



We gratefully thank Andrew M. Driscoll (651 Huntington Ave., Boston MA 02115 USA) for English editing of this manuscript.

Funding Information

This study was supported by the Nation Natural Science Foundation of China (Nos. 81773468 and 81302389), the Wu Liande Science Foundation of Harbin Medical University (Grant No. WLD-QN1703), and Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province (LBH-Q17092).

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.


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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Key Lab of Etiology and Epidemiology, Education Bureau of Heilongjiang Province & National Health Commission (23618504), Center for Endemic Disease Control, Chinese Center for Disease Control and PreventionHarbin Medical UniversityHarbinChina

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