The Inverted U-Curve Association of Fluoride and Osteoclast Formation in Mice
- 12 Downloads
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.
KeywordsFluoride Fluorosis Osteoclast Osteoblast
We gratefully thank Andrew M. Driscoll (651 Huntington Ave., Boston MA 02115 USA) for English editing of this manuscript.
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.
- 4.Pei J, Li B, Liu Y, Liu X, Li M, Chu Y, Yang Q, Jiang W, Chen F, Darko GM, Yang Y, Gao Y (2017) Matrix metallopeptidase-2 gene rs2287074 polymorphism is associated with brick tea skeletal fluorosis in Tibetans and Kazaks, China. Sci Rep 7:40086. https://doi.org/10.1038/srep40086 CrossRefPubMedPubMedCentralGoogle Scholar
- 5.Chavassieux P, Seeman E, Delmas PD (2007) Insights into material and structural basis of bone fragility from diseases associated with fractures: how determinants of the biomechanical properties of bone are compromised by disease. Endocr Rev 28(2):151–164. https://doi.org/10.1210/er.2006-0029 CrossRefPubMedGoogle Scholar
- 8.Hua K, Bu LS, Li GS (2003) Effects of fluoride on osteoclastic activity of rats in vitro. Chin J Prev Med 37(4):256–258Google Scholar
- 10.Abdelmagid SM, Sondag GR, Moussa FM, Belcher JY, Yu B, Stinnett H, Novak K, Mbimba T, Khol M, Hankenson KD, Malcuit C, Safadi FF (2015) Mutation in osteoactivin promotes receptor activator of NFκB ligand (RANKL)-mediated osteoclast differentiation and survival but inhibits osteoclast function. J Biol Chem 290(33):20128–20146. https://doi.org/10.1074/jbc.M114.624270 CrossRefPubMedPubMedCentralGoogle Scholar
- 12.Pei J, Yao Y, Li B, Wei W, Gao Y, Darko GM, Sun D (2017) Excessive fluoride stimulated osteoclast formation through up-regulation of receptor activator for nuclear factor-κB ligand (RANKL) in C57BL/6 mice. Int J Clin Exp Med 10(11):15260–15268Google Scholar
- 13.Linkhart TA, Linkhart SG, Kodama Y, Farley JR, Dimai HP, Wright KR, Wergedal JE, Sheng M, Beamer WG, Donahue LR, Rosen CJ, Baylink DJ (1999) Osteoclast formation in bone marrow cultures from two inbred strains of mice with different bone densities. J Bone Miner Res Off J Am Soc Bone Miner Res 14(1):39–46. https://doi.org/10.1359/jbmr.19126.96.36.199 CrossRefGoogle Scholar
- 14.Boyce BF, Wright K, Reddy SV, Koop BA, Story B, Devlin R, Leach RJ, Roodman GD, Windle JJ (1995) Targeting simian virus 40 T antigen to the osteoclast in transgenic mice causes osteoclast tumors and transformation and apoptosis of osteoclasts. Endocrinology 136(12):5751–5759. https://doi.org/10.1210/endo.136.12.7588333 CrossRefPubMedGoogle Scholar
- 19.Li G (2000) Some conceptual problems in pathology of skeletal fluorosis. Chin J Endemiol 19(6):479–481. https://doi.org/10.3760/cma.j.issn.1000-4955.2000.06.029 CrossRefGoogle Scholar
- 22.Huo L, Liu K, Pei J, Yang Y, Ye Y, Liu Y, Sun J, Han H, Xu W, Gao Y (2013) Fluoride promotes viability and differentiation of osteoblast-like Saos-2 cells via BMP/Smads signaling pathway. Biol Trace Elem Res 155(1):142–149. https://doi.org/10.1007/s12011-013-9770-0 CrossRefPubMedPubMedCentralGoogle Scholar
- 23.Chen S, Li B, Lin S, Huang Y, Zhao X, Zhang M, Xia Y, Fang X, Wang J, Hwang SA, Yu S (2013) Change of urinary fluoride and bone metabolism indicators in the endemic fluorosis areas of southern China after supplying low fluoride public water. BMC Public Health 13:156. https://doi.org/10.1186/1471-2458-13-156 CrossRefPubMedPubMedCentralGoogle Scholar
- 26.Pei J, Gao Y, Li B, Zhou L, Zhang Z, Sun D (2012) Effect of fluoride on osteoclast formation at various levels of receptor activator of nuclear factor kappa-B ligand (RANKL). Fluoride 45(2):86–93Google Scholar