Effects of Fluorosis on Osteoclast Activity and RANK/RANKL/OPG Pathway Expression during Orthodontic Tooth Movement in Mice

doi:10.13701/j.cnki.kqyxyj.2025.07.007

Abstract

Abstract: Objective: To investigate the impact of chronic fluorosis on orthodontic tooth movement (OTM) in rats by assessing alterations in osteoclast activity and the expression levels of receptor activator of nuclear factor-κB (RANK)/receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG). Methods: Eighty SD rats were evenly divided into four groups using a random number table: control group, orthodontic group, fluoridated group, and fluoridated orthodontic group with each group divided into 3-day, 7-day, 14-day, and 21-day subgroups (n=5/subgroup). After establishing the fluorosis and OTM models, osteoclast counts were determined via tartrate-resistant acid phosphatase (TRAP) staining. Protein and mRNA expression levels of RANKL, OPG, and RANK were analyzed using immunohistochemistry and real-time fluorescence quantitative PCR. Results: Rats in the fluoridated group exhibited grade Ⅱ-Ⅲ dental fluorosis, with fluoride levels higher than control group (P<0.05). After orthodontic treatment, a significant gap appeared between the first and second molars of the mice, indicating the successful establishment of chronic fluorosis and OTM models. TRAP-positive osteoclasts were significantly increased in mice after orthodontic treatment (P<0.05), while fluoridated orthodontic group had significantly fewer osteoclasts than the orthodontic group (P<0.05). RANK expression in fluoridated orthodontic group was higher than that in fluoridated group (P<0.05), but not significantly different from that in orthodontic group (P>0.05). RANKL expression was the highest in orthodontic group, and higher than that in fluoridated orthodontic group (P<0.05). OPG expression was the highest in orthodontic group, particularly in the initial stage (P<0.05). The RANKL/OPG ratio in fluoridated group was lower than that in control group (P<0.05), and orthodontic group had a higher ratio than fluoridated orthodontic group. Mice with chronic fluorosis exhibited a typical "fast-slow-rebound" cycle of orthodontic tooth movement, with fluoridated orthodontic group featuring lower initial velocity than orthodontic group (P<0.05), and no significant difference in later stages. Conclusion: Fluoride accumulation affects the expression of RANK/RANKL/OPG, reduces osteoclast activity, and ultimately restricts orthodontic tooth movement.

Key words: fluorosis, orthodontic tooth movement, osteoclast, RANK/RANKL/OPG pathway

LIANG Huimin, JIA Ying, DING Xue, LIU Chun. Effects of Fluorosis on Osteoclast Activity and RANK/RANKL/OPG Pathway Expression during Orthodontic Tooth Movement in Mice[J]. Journal of Oral Science Research, 2025, 41(7): 581-588.

References

[1] Whelton HP, Spencer AJ, Do LG, et al. Fluoride revolution and dental caries: Evolution of policies for global use [J]. J Dent Res, 2019, 98(8): 837-846.
[2] Ahmad Dar F, Kurella S. Fluoride in drinking water: An in-depth analysis of its prevalence, health effects, advances in detection and treatment [J]. Mater Today: Proc, 2024, 102: 349-360.
[3] Cao H, Xie X, Wang Y, et al. Predicting geogenic groundwater fluoride contamination throughout China [J]. J Environ Sci (China), 2022, 115: 140-148.
[4] 赵凡,郭志伟.地方性氟中毒致机体损伤的研究进展[J].中华地方病学杂志,2024,43(1): 71-76.
[5] Chiang PC, Hsin-Chung Cheng J, De-Shing Chen D, et al. Changes in smile parameters after surgical-orthodontic treatment for skeletal Class Ⅲ malocclusion [J]. J Dent Sci, 2024, 19(3): 1477-1485.
[6] Huang H, Williams RC, Kyrkanides S. Accelerated orthodontic tooth movement: molecular mechanisms [J]. Am J Orthod Dentofacial Orthop, 2014, 146(5): 620-632.
[7] Gonzales C, Hotokezaka H, Karadeniz EI, et al. Effects of fluoride intake on orthodontic tooth movement and orthodontically induced root resorption [J]. Am J Orthod Dentofacial Orthop, 2011, 139(2): 196-205.
[8] Yao Y, Ma Y, Zhong N, et al. The inverted U-curve association of fluoride and osteoclast formation in mice [J]. Biol Trace Elem Res, 2019, 191(2): 419-425.
[9] Ding X, Lai L, Jia Y, et al. Effects of chronic fluorosis on the expression of VEGF/PI3K/AKT/eNOS in the gingival tissue of rats with orthodontic tooth movement [J]. Exp Ther Med, 2024, 27(3): 121-129.
[10] Yamaguchi M. RANK/RANKL/OPG during orthodontic tooth movement [J]. Orthod Craniofac Res, 2009, 12(2): 113-119.
[11] Wu L, Su Y, Lin F, et al. MicroRNA-21 promotes orthodontic tooth movement by modulating the RANKL/OPG balance in T cells [J]. Oral Dis, 2020, 26(2): 370-380.
[12] 王梦蝶,吴虹,王荣慧,等.RANKL介导的诱导破骨细胞分化的相关经典信号通路研究进展[J].中国药理学通报,2020,36(7): 898-902.
[13] Ikebuchi Y, Aoki S, Honma M, et al. Coupling of bone resorption and formation by RANKL reverse signalling [J]. Nature, 2018, 561(7722): 195-200.
[14] Kaya S, Cifter M, Cekici A, et al. Effects of orthodontic force magnitude on cell apoptosis and RANKL-induced osteoclastogenesis : Studies in a rat model [J]. J Orofac Orthop, 2020, 81(2): 100-112.
[15] Yoshimatsu M, Kitaura H, Morita Y, et al. Effects of anti-mouse RANKL antibody on orthodontic tooth movement in mice [J]. J Dent Sci, 2022, 17(3): 1087-1095.
[16] 丁雪,贾莹,刘纯,等.慢性氟中毒SD大鼠正畸牙移动的位移及速率变化[J].中国组织工程研究,2022,26(29): 4687-4692.
[17] 刘纯,贾莹,杨世榕,等.骨微结构水平观察染氟对大鼠髁突软骨下骨生长发育的影响[J].中华地方病学杂志,2022,41(8): 626-633.
[18] 刘兴沄,李仲伟,贾莹,等.慢性氟中毒环境对大鼠正畸牙移动过程中牙周组织VEGF和eNOS表达的影响[J].口腔医学研究,2024,40(8): 727-734.
[19] 王丽华,安冬,边建朝,等.新修订Dean法氟斑牙诊断标准编制说明与图示[J].中华地方病学杂志,2013,32(2): 213-216.
[20] Zhao H, Wang X, Jin A, et al. Reducing relapse and accelerating osteogenesis in rapid maxillary expansion using an injectable mesoporous bioactive glass/fibrin glue composite hydrogel [J]. Bioact Mater, 2022, 18: 507-525.
[21] Zorlu FY, Darici H, Turkkahraman H. Histomorphometric and histopathologic evaluation of the effects of systemic fluoride intake on orthodontic tooth movement [J]. Eur J Dent, 2019, 13(3): 361-369.
[22] Marcoline FV, Ishida Y, Mindell JA, et al. A mathematical model of osteoclast acidification during bone resorption [J]. Bone, 2016, 93: 167-180.
[23] Junrui P, Bingyun L, Yanhui G, et al. Relationship between fluoride exposure and osteoclast markers during RANKL-induced osteoclast differentiation [J]. Environ Toxicol Pharmacol, 2016, 46: 241-245.
[24] Pei J, Li B, Gao Y, et al. Fluoride decreased osteoclastic bone resorption through the inhibition of NFATc1 gene expression [J]. Environ Toxicol, 2014, 29(5): 588-595.
[25] 王贺,李易,张曼,等.基于RANKL/OPG通路探讨GsMTx4对大鼠正畸牙齿移动过程中压力侧牙周组织改建的影响[J].口腔生物医学,2022,13(3): 169-174.
[26] Li Y, Zhan Q, Bao M, et al. Biomechanical and biological responses of periodontium in orthodontic tooth movement: up-date in a new decade [J]. Int J Oral Sci, 2021, 13(1): 20-38.
[27] 尹文.不同力值对偏侧咀嚼大鼠正畸牙移动及OPG、RANKL表达的影响研究[D].海南医科大学,2024.
[28] 赵娇阳,时静,李文晋.OPG/RANKL/RANK信号通路在牙槽骨代谢中研究进展[J].临床军医杂志,2022,50(2): 214-217.
[29] Jin Y, Zhou BH, Zhao J, et al. Fluoride-induced osteoporosis via interfering with the RANKL/RANK/OPG pathway in ovariectomized rats: Oophorectomy shifted skeletal fluorosis from osteosclerosis to osteoporosis [J]. Environ Pollut, 2023, 336: 122407-122429.
[30] Liu XL, Song J, Liu KJ, et al. Role of inhibition of osteogenesis function by Sema4D/Plexin-B1 signaling pathway in skeletal fluorosis in vitro [J]. J Huazhong Univ Sci Technolog Med Sci, 2015, 35(5): 712-715.
[31] 林维龙,吴晓沛,何薇薇,等.重组人转化生长因子-β1对大鼠正畸牙移动模型成骨细胞分化及ERK/MAPK信号通路的影响[J].口腔医学研究,2023,39(2): 118-123.
[32] 郭晓峰,杜艳锋,张晶,等.木犀草素对正畸牙移动模型大鼠骨改建及BMP2/Smad1信号通路的影响[J].北京口腔医学,2024,32(3): 179-183.
[33] 卢平,金婕.重组人转化生长因子-β1对正畸牙移动小鼠牙根吸收和Hippo-Yes信号通路的影响[J].河北医药,2025,47(1): 17-22.