Effects of local administration of clodronate on orthodontic tooth movement and root resorption in rats

Clodronate, a non-N-containing bisphosphonate, strongly inhibits bone resorption and also has anti-inflammatory properties. The purpose of this study was to examine the effect of the local administration of clodronate on orthodontic tooth movement. Both the right and left upper first molars of 26 7-week-old male Wistar rats were moved buccally with a standardized expansion spring. Clodronate solution was injected into the sub-periosteum area adjacent to the left upper molar every third day during the experimental period. The right first molar served as the control. Local injection of clodronate caused a significant (P < 0.001) and dose-dependent reduction in tooth movement in the rats. The number of osteoclasts on the clodronate-injected side was significantly less (P < 0.01) than on the control side. Local clodronate also inhibited root resorption incident to tooth movement. These results suggest that localized use of clodronate could be a useful therapeutic adjunct in orthodontic treatment.     

Involvement of cyclooxygenase-2 in interleukin-1alpha-induced prostaglandin production by human periodontal ligament cells.

BACKGROUND: Human periodontal ligament (PDL) cells produce prostaglandin (PG) E2 in response to proinflammatory cytokines. However, the mechanism of PGE2 production is not well understood. The purpose of the present study was to investigate the involvement of cyclooxygenase (COX)-1 and COX-2 in PGE2 production by PDL cells stimulated with a proinflammatory cytokine, interleukin-1alpha (IL-1alpha), and to examine the regulation of PGE2 production by cell-cell interaction of human gingival keratinocytes and PDL cells. METHODS: The levels of PGE2 in the culture media of PDL cells stimulated with IL-1alpha or culture media of human gingival keratinocytes were determined by an enzyme-linked immunosorbent assay. Expression of COX-1 and -2 mRNA and protein was studied by Northern blot analysis and Western blot analysis, respectively. RESULTS: IL-1alpha-stimulated PDL cells produced PGE2 in a time-dependent manner. Indomethacin, a non-selective COX-1/COX-2 inhibitor, and NS-398, a selective COX-2 inhibitor, completely inhibited PGE2 production by the IL-1alpha-stimulated cells. COX-2 mRNA was detected after IL-1alpha stimulation, although it was not detected in unstimulated cells. There was no difference in expression of COX-1 mRNA between unstimulated cells and IL-la-stimulated cells. Expression of COX-2 protein in IL-1alpha-stimulated cells was increased, compared with that in unstimulated cells, whereas COX-1 protein expression was almost the same in both the cells. Treatment of IL-1alpha-stimulated PDL cells with dexamethasone, known to inhibit COX-2 expression, prevented PGE2 production and COX-2 mRNA expression. Addition of the culture media of human gingival keratinocytes to PDL cells increased PGE2 production. The PGE2 production was depressed by treatment of the cells with IL-1 receptor antagonist and anti- IL-1alpha antibody, not with anti-IL-1beta antibody. The PGE2 production was also inhibited by treatment with NS-398 and dexamethasone. CONCLUSIONS: We suggest that PDL cells stimulated with IL-1alpha produce PGE2 through de novo synthesis of COX-2 and that the cell interaction of gingival keratinocytes and PDL cells controls COX-2 expression and PGE2 production via IL-1alpha or 1alpha IL-la-like factor(s). Selective COX-2 inhibitors, which have the advantage of reduced gastric toxicity, may provide a useful approach to treatment of periodontal disease.     

Neuropeptides modulate RANKL and OPG expression in human periodontal ligament cells

Neuropeptides, such as substance P (SP) and calcitonin gene-related peptide (CGRP), may be associated with bone remodeling in response to mechanical stress during orthodontic tooth movement. To investigate this hypothesis, we examined the effects of neuropeptides on the expression of receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) in human periodontal ligament (PDL) cells under compression in vitro. PDL cells were subjected to compressive force (2.0 g/cm²) continuously in the presence or absence of SP or CGRP for 2–4 days. The expression of the SP receptor, neurokinin 1-receptor (NK₁-R), in PDL cells was confirmed by RT–PCR and immunofluorescent staining. The effects of neuropeptides (SP and CGRP) on the expression of RANKL and OPG mRNA were determined using RT–PCR. PDL cells constitutively expressed NK₁-R on both the mRNA and protein levels. Compressive force decreased OPG mRNA expression and increased RANKL mRNA expression. In the presence of neuropeptides, the OPG level decreased synergistically with compression. Neuropeptides stimulated RANKL expression without compression, whereas they decreased RANKL mRNA expression with compression. These results indicate that PDL cell compression induces the up-regulation of RANKL and down-regulation of OPG, whereas neuropeptides suppress the RANKL expression induced by compression. Therefore, the neuropeptides SP and CGRP may modulate bone remodeling by PDL cells during orthodontic tooth movement.     

Dual regulation of osteoclast differentiation by periodontal ligament cells through RANKL stimulation and OPG inhibition

Periodontal ligament (PDL) cells play an important role in maintaining the homeostasis of periodontal tissues. However, it is not known how PDL cells contribute to osteoclastogenesis. In this study, we examined the consequences of cell-to-cell interactions between peripheral blood mononuclear cells (PBMCs) and PDL cells during osteoclastogenesis. PBMCs were co-cultured directly or indirectly with PDL cells for two to four weeks. PBMCs that were directly co-cultured with PDL cells formed significantly more resorption pits on dentin slices than did PBMCs that were cultured alone. However, soluble factor(s) produced from PDL cells inhibited the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells. Furthermore, PDL cells expressed both receptor activator nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) mRNA. In conclusion, PDL cells support osteoclastogenesis through cell-to-cell contact. PDL cells might regulate osteoclastogenesis by opposing mechanisms--stimulation of resorptive activity by RANKL and inhibition by OPG--thus affecting processes such as periodontitis and orthodontic tooth movement.     

Intermittent force induces high RANKL expression in human periodontal ligament cells

Intermittent compressive force stimulates bone resorption in orthodontic treatment. This study examined the molecular mechanism in human periodontal ligament (PDL) cells stimulated by an intermittent force. PDL cells were subjected to compressive force (2.0 or 5.0 g/cm(2)) for 2-4 days. Continuous or intermittent force was applied all day or for 8 hrs per day, respectively. At days 3 and 4, cell damage was less with intermittent force than with continuous force. At day 4, RANKL and IL-1beta expressions were greater with intermittent force than with continuous force. An IL-1 receptor antagonist inhibited the compressive force-induced RANKL expression. These findings indicate that IL-1beta is an autocrine factor regulating compressive force-induced RANKL expression in PDL cells, and that intermittent force can effectively induce RANKL in PDL cells with less cell damage.     

Cyclooxygenase-2-dependent prostaglandin (PG) E2 downregulates matrix metalloproteinase-3 production via EP2/EP4 subtypes of PGE2 receptors in human periodontal ligament cells stimulated with interleukin-1alpha

BACKGROUND: Prostaglandin E2 (PGE2), which exerts its actions via EP receptors (EP1, EP2, EP3, and EP4), is a bioactive metabolite produced by cyclooxygenase (COX)-1 and/or COX-2 from arachidonic acid. In the present study, we investigated whether COX-2-derived PGE2 regulated matrix metalloproteinase (MMP)-3 production in human periodontal ligament (PDL) cells stimulated with interleukin (IL)-1alpha and which EP receptors were involved in PGE2 regulation of IL-1alpha-induced MMP-3 production. METHODS: Human PDL cells obtained from periodontally healthy subjects were stimulated with vehicle or IL-1alpha in the presence or absence of indomethacin (a COX-1/COX-2 inhibitor), NS-398 (a specific COX- 2 inhibitor), PGE2, EP receptor agonists, dibutyryl cAMP, and forskolin. PGE2 levels were assayed by enzyme-linked immunosorbent assay (ELISA). MMP-3 levels and caseinolytic activities were evaluated by ELISA and casein zymography, respectively. RESULTS: IL-1alpha enhanced both MMP-3 and PGE2 production. Indomethacin and NS-398 enhanced IL-1alpha-induced MMP-3 production in PDL cells, to the same extent, although both the agents completely inhibited IL-1alpha-induced PGE2 production. Exogenous PGE2 reduced IL-1alpha-induced MMP-3 production in a dose-dependent manner. Butaprost, a selective EP2 agonist, and ONO-AE1-329, a selective EP4 agonist, significantly inhibited IL-1alpha-induced MMP-3 production, although butaprost was less potent than ONO-AE-1-329. Dibutyryl cAMP, a cAMP analog, and forskolin, an adenylate cyclase activator, significantly inhibited IL-1alpha-stimulated MMP-3 production in PDL cells. CONCLUSIONS: These data suggest that COX-2-dependent PGE2 downregulates IL-1alpha-elicited MMP-3 production by cAMP-dependent pathways via EP2/EP4 receptors in human PDL cells. cAMP-elevating agents such as EP2/EP4 receptor activators may regulate the destruction of extracellular matrix components in periodontal tissue.     

Influence of clodronate and compressive force on IL-1ß-stimulated human periodontal ligament fibroblasts

Objectives

The aim of this study was to investigate in vitro the effect of clodronate on interleukin-1ß (IL-1ß)–stimulated human periodontal ligament fibroblasts (HPdLFs) with the focus on inflammatory factors of orthodontic tooth movement with and without compressive force.

Materials and methods

HPdLFs were incubated with 5 μM clodronate and 10 ng/mL IL-1ß. After 48 h, cells were exposed to 3 h of compressive force using a centrifuge. The gene expression of cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), matrix metalloproteinase 8 (MMP-8), and the tissue inhibitor of MMP (TIMP-1) was analyzed using RT-PCR. Prostaglandin E2 (PGE-2), IL-6, and TIMP-1 protein syntheses were quantified via ELISA.

Results

Compressive force and IL-1ß induced an overexpression of COX-2 gene expression (61.8-fold; p < 0.05 compared with control), diminished by clodronate (41.1-fold; p < 0.05 compared with control). Clodronate slowed down the compression and IL-1ß induced IL-6 gene expression (161-fold vs. 85.6-fold; p < 0.05 compared with control). TNF-α was only slightly affected without statistical significance. Clodronate reduced IL-1ß-stimulated MMP-8 expression with and without compressive force. TIMP-1 on gene and protein level was downregulated in all groups. Analyzing the MMP-8/TIMP-1 ratio, the highest ratio was detected in IL-1ß-stimulated HPdLFs with compressive force (21.2-fold; p < 0.05 compared with control). Clodronate diminished IL-1ß-induced upregulation of MMP-8/TIMP-1 ratio with (11.5-fold; p < 0.05 compared with control) and without (12.5-fold; p < 0.05 compared with control) compressive force.

Conclusion

Our study demonstrates a slightly anti-inflammatory effect by clodronate under compressive force in vitro. Additionally, the periodontal remodeling presented by the MMP-8/TIMP-1 ratio seems to be diminished by clodronate.

Clinical relevance

Reduction of pro-inflammatory factors and reduction of periodontal remodeling might explain reduced orthodontic tooth movement under clodronate intake.

     

增龄因素对鼠正畸牙齿移动中牙周组织骨保护素（OPG）表达的影响

目的 比较在正畸牙齿移动中幼年鼠和成年鼠牙周组织骨保护素(osteoprotegerin,OPG)信使RNA(mRNA)表达的不同,以探讨增龄因素影响正畸骨改建的分子机制。方法以4周(幼年鼠)和24周(成年鼠)雄性大鼠为实验动物,牵引左上第一磨牙近中移动为正畸牙齿移动模型,原位杂交检测牙周膜组织OPG mRNA的表达。结果 1.幼年鼠正畸牙齿移动中加力后3小时张力侧近牙槽骨表面可见OPG表达阳性细胞排列;与幼年鼠相比,成年鼠加力后牵张侧牙周膜细胞的OPG mRNA表达没有明显改变。2.幼年鼠加力后6小时开始压力侧即可观察到破骨细胞的数目明显增多,成年鼠加力后,压力侧加力24小时可见破骨细胞;无论幼年和成年鼠压力侧牙周膜细胞的OPG mRNA表达在加力前后均未见明显改变。结论 增龄因素使牙周组织内OPG表达明显增强;成年牙周组织中较强的OPG表达可能与成人正畸出现的牙槽骨吸收、牙齿移动迟缓相关。     

Lactoferrin inhibits infection-related osteoclastogenesis without interrupting compressive force-related osteoclastogenesis

BackgroundControl of periodontal tissue inflammation during orthodontic treatment is very important in achieving a favourable therapeutic goal. We previously demonstrated that orally applied bovine lactoferrin (bLF) inhibited LPS-induced bone resorption but not orthodontic force-induced tooth movement in vivo. This study is designed to examine the underlying mechanism of it.MethodsWe examined the inhibitory effects of bLF on the expression of RANKL, OPG, TNF-α and COX-2 in osteoblasts loaded with compressive stress (CS) in comparison with LPS stimulated osteoblasts. Formation of osteoclasts was evaluated by co-culture system.ResultsBoth CS- and LPS-applications upregulated COX-2 and RANKL but downregulated OPG. TNF-α was upregulated in LPS-stimulated osteoblasts but downregulated in CS-loaded osteoblasts. NS398 (a specific inhibitor of COX-2) significantly inhibited CS-induced RANKL-upregulation but not LPS-induced RANKL upregulation, indicating a critical role of COX-2/PGE₂ pathway in CS-induced osteoclastogenesis. bLF significantly downregulated LPS-induced upregulation of RANKL and eliminated OPG suppression but not affected in CS-induced changes. Moreover, bLF significantly decreased LPS-induced osteoclast formation, whereas bLF had no effect on PGE₂-induced osteoclast formation.ConclusionsbLF can effectively suppress harmful bone destruction associated with periodontitis without inhibiting bone remodelling by CS-loading. Therefore, oral administration of bLF may be highly beneficial for control of periodontitis in orthodontic patients.     

Expression of heat shock protein 47 in the periodontal ligament during orthodontic tooth movement

The aim of this study was to investigate the kinetics of heat shock protein 47 (HSP47) and proliferating cell nuclear antigen (PCNA) immunohistochemistry in periodontal ligament (PDL) cells during orthodontic tooth movement in a mouse model. An orthodontic appliance was set between the upper incisors and the upper left first molar. The mice were killed 2, 6 and 10 days after initiation of orthodontic tooth movement. Computer-assisted image analysis was used to compare the quantitative expression of HSP47 in the PDL. HSP47 expression was significantly higher on the tension side 2 days after application of the appliance, whereas no significant change was observed on the pressure side at any time point. Furthermore, the PCNA labelling indices of PDL cells were increased significantly on the tension side 6 and 10 days after application of the appliance, and on the pressure side 2, 6 and 10 days after application of the appliance. These data suggest that collagen is metabolised predominantly on the tension side, and that PDL cells actively proliferate on both the tension and pressure sides during orthodontic tooth movement.     

Human interleukin-1 beta and interleukin-1 receptor antagonist secretion and velocity of tooth movement

The cytokines interleukin-1 beta (IL-1 beta) and IL-1 receptor antagonist (IL-1RA) probably play a part in orthodontic tooth movement. Here, the force magnitudes and the area of force application in the compressed periodontal ligament (PDL) were controlled and the velocity of tooth movement correlated with concentrations of IL-1 beta and IL-1RA in the gingival crevicular fluid (GCF). Seven individuals undergoing orthodontic treatment involving maxillary first premolar extractions and distal movement (bodily retraction) of the maxillary canines participated in the 84-day study. For each participant, continuous retraction forces were applied so that they received equivalent PDL stresses of 13 kPa for one canine and 4 kPa for the other. GCF cytokine concentrations from experimental and control teeth were expressed relative to total protein in the GCF and compared using an 'Activity Index' (AI)=Experimental (IL-1 beta/IL-1RA)/Control (IL-1 beta/IL-1RA). The results showed that the velocity of tooth movement in an individual was related to their AI. The correlation between AI and tooth movement was stronger from the distal (R(d)=0.78) than from the mesial (R(m)=0.65) of retracted teeth. The results demonstrate that equivalent force systems produce individual differences in cytokine production, which correlate with interindividual differences in the velocity of canine retraction.     

Force-induced IL-8 from periodontal ligament cells requires IL-1beta

During orthodontic tooth movement, mechanical stresses induce inflammatory reactions in the periodontal ligament (PDL). We hypothesized that chemokines released from PDL cells under mechanical stress regulate osteoclastogenesis, and investigated the profiles and mechanisms of chemokine expression by human PDL cells in response to mechanical stress. In vitro, shear stress and pressure force rapidly increased the gene and protein expressions of IL-8/CXCL8 by PDL cells. Consistently, amounts of IL-8 in the gingival crevicular fluid of healthy individuals increased within 2 to 4 days of orthodontic force application. The PDL cells constitutively expressed low levels of IL-1beta, which were not further increased by mechanical stress. Interestingly, neutralization of IL-1beta abolished IL-8 induction by mechanical stresses, indicating that IL-1beta is essential for IL-8 induction, presumably though autocrine or paracrine mechanisms. Finally, experiments with signal-specific inhibitors indicated that MAP kinase activation is essential for IL-8 induction.     

Duration of orthodontic force affecting initial response of nitric oxide synthase in rat periodontal ligaments

Clinical experience suggests that successful orthodontic tooth movement can be produced with a threshold for force duration at about 6 hours, however, the changes in the periodontal ligaments (PDL) during this period is still unclear. Nitric oxide (NO) is a marker of signal transduction relating to bone remodeling. The aim of this study was to observe the initial response of NO synthase (NOS) when PDL equilibrium would be broken against light continuous orthodontic force. Rat maxillary first molars were moved mesially with 2 gf Titanium-Nickel closed coil springs for 1, 3 and 6 hours. The number of NADPH-diaphorase positive cells in PDL was counted for investigating NOS activity. At the control group, NOS activity in the distal area of the PDL was significantly higher than that of the mesial area (P<0.001). The activity of mesial area increased at 1-hour group (P<0.01), while the activity of distal area dropped down at 3- and 6-hour groups (P 3-hour<0.05, P 6-hour<0.001), compared with the control group. These results suggest that 1-3 hours would be the threshold of force duration for tooth movement with light continuous force.     

Local OPG gene transfer to periodontal tissue inhibits orthodontic tooth movement

Previously, we discovered that RANKL expression is induced in compressed periodontal ligament cells, and that this promotes osteoclastogenesis on the compression side in orthodontic tooth movement. We hypothesized that local OPG gene transfer to the periodontium would neutralize the RANKL activity induced by mechanical compressive force, thereby inhibiting osteoclastogenesis and diminishing tooth movement. The upper first molars of six-week-old male Wistar rats were moved palatally by means of a fixed-orthodontic wire. A mouse OPG expression plasmid [pcDNA3.1(+)-mOPG] was constructed, and the production of functional OPG protein was confirmed in vitro. The inactivated HVJ envelope vector containing pcDNA3.1(+)-mOPG or PBS was injected periodically into the palatal periodontal tissue of upper first molars. When this local OPG gene transfer was performed, OPG production was induced, and osteoclastogenesis was inhibited. Local OPG gene transfer significantly diminished tooth movement. In this study, we report that OPG gene transfer to periodontal tissue inhibited RANKL-mediated osteoclastogenesis and inhibited experimental tooth movement.     

Neurotransmitters, cytokines, and the control of alveolar bone remodeling in orthodontics

This article described research aimed at testing the hypothesis that tissue remodeling during orthodontic tooth movement is modulated, at least in part, by factors derived from the nervous and vascular (immune) systems. Specifically, the neurotransmitters SP and VIP and the cytokines IL-1 alpha and IL-1 beta were localized immunohistochemically in paradental tissues of cat canines that had been treated by the application of an 80 g tipping force for 1 hour to 14 days. Increased staining (concentrations) of these agents were found in areas of PDL tension and compression at different time periods. Moreover, administration of SP and IL-1 beta to human PDL fibroblasts in vitro for 1 to 60 minutes resulted in significant increases in the levels of the intracellular "second messenger" cAMP, as well as of PGE2, a plasma membrane-associated fatty acid believed to serve as a local regulator of bone cell activity. Taken together, these results tend to support the hypothesis that neurotransmitters and cytokines play a regulatory role in orthodontic force-induced alveolar bone remodeling. Consequently, determination of the cytokine synthetic activity by leukocytes of orthodontic patients may inform about their alveolar bone remodeling potential.     

核因子-κB受体活化因子配体在大鼠正畸牙压力侧牙周组织中的表达

目的：探讨正畸牙移动中，压力侧牙周组织中核因子-κB受体活化因子配体(RANKL)的表达在破骨细胞诱导和骨改建中的作用。方法：建立大鼠正畸牙移动模型，对压力侧牙周组织中RANKL蛋白的表达及破骨细胞的生成进行检测。结果：TRAP( )破骨细胞在牙移动第3、5和7天时数量明显增多；免疫组化检测显示牙周成骨细胞、骨衬里细胞、牙周纤维细胞和位于骨陷窝内的破骨细胞，是表达RANKL的主要细胞。与对照组RANKL持续弱阳性表达比较，实验组RANKL在正畸牙移动第3、5和7天时出现强阳性表达，其表达变化与破骨细胞的数量变化较为一致。结论：在大鼠正畸牙移动中，RANKL可能在压力侧牙周组织破骨细胞的形成和骨改建中发挥了重要作用。     

Interactive effects between cytokines on PGE production by human periodontal ligament fibroblasts in vitro

Mononuclear cell production of cytokines that stimulate fibroblast production of prostaglandin E (PGE) is an important mechanism by which mononuclear cells regulate fibroblast function. The objective of this investigation was to determine the effects of the cytokines interleukin 1 beta (IL-1 beta), interleukin 1 alpha (IL-1 alpha), tumor necrosis factor alpha (TNF-alpha), and interferon gamma (IFN-gamma), alone or in paired combinations, on PGE production by near-confluent human periodontal ligament (PDL) fibroblasts in vitro. Premolars extracted in the course of orthodontic treatment were used for this study. Fibroblast cultures, free of epithelial cells, were obtained after the fourth subculture by the use of accurately-timed trypsin treatment. Cells in the fourth to sixth passage, incubated in DMEM supplemented with 10% equine serum, were used for these experiments. Cells (1 x 10(5)) were seeded in 12- x -75-mm tissue culture tubes and incubated with various doses of IL-1 beta, IL-1 alpha, TNF-alpha, and IFN-gamma, alone or in specific combinations, for 15 min, two, 12, 24, and 72 h. PGE concentrations in the media were measured by radio-immunoassay. The results showed that human PDL fibroblasts responded to the administration of cytokines by an elevation in the synthesis of PGE in a dose- and time-related fashion. The increase in PGE production was inhibited by the addition of indomethacin. The interactions between these cytokines varied in degree, depending on the particular combinations of cytokines. In addition, the administration of cytokine combinations was found to be additive, synergistic, subtractive, or suppressive on the production of PGE by PDL fibroblasts, depending on the duration of incubation. These experiments demonstrate the importance of the consideration of the interplay between cytokines produced by mononuclear cells on the mechanisms that regulate the functions of PDL fibroblasts.     

核因子-κB受体活化因子配体在大鼠正畸牙压力侧骨改建中的作用

目的：初步探讨在正畸牙移动压力侧核因子-κB受体活化因子配基(receptor activator of nuclearfactor-κB ligand，RANKL)的表达在破骨细胞诱导和骨改建中的调节作用。方法：建立大鼠正畸牙移动模型，利用免疫组化的方法对压力侧RANKL的表达及其变化进行检测；并进一步观察了RANKL对大鼠骨髓破骨细胞形成的影响。结果：正畸牙移动压力侧组化结果显示，RANKL阳性表达位于牙周膜细胞和位于骨陷窝内的破骨细胞中，在正畸牙移动第3、5和7天时呈强阳性表达。体外破骨细胞诱导实验结果显示，在巨噬细胞集落刺激因子(macrophage clone stimulating factor，M-CSF)协同作用下，RANKL呈剂量依赖型诱导TRAP阳性细胞生成。结论：大鼠正畸牙移动中，RANKL在压力侧的表达上调有诱导破骨细胞形成的作用，并导致牙槽骨吸收。     

Osteoblast lineage cells and periodontal ligament fibroblasts regulate orthodontic tooth movement that is dependent on Nuclear Factor-kappa B (NF-kB) activation

ObjectivesTo investigate the role of NF-κB in osteoblast lineage cells and periodontal ligament (PDL) fibroblasts during orthodontic tooth movement (OTM).Materials and MethodsTransgenic mice that expressed a dominant negative mutant of the inhibitor of kB kinase (IKK-DN) with lineage specific expression in osteoblastic cells and PDL fibroblasts driven by a response element in the collagen1α1 promoter and matched wild-type (WT) mice were examined. A 10-12 g force was applied by a NiTi coil and maintained for 5 or 12 days. OTM distance, PDL width, and bone volume fraction were measured using micro computed tomography. Osteoclast numbers were counted in tartrate-resistant acid phosphatase-stained sections. Activation of nuclear factor kappa B (NF-kB) was assessed by nuclear localization of p65, and the receptor activator of nuclear factor-κB ligand (RANKL) was measured by immunofluorescence and compared to control specimens with no orthodontic force.ResultsOTM-induced NF-kB activation (p65 nuclear localization) in WT mice was largely blocked in transgenic (TG) mice. OTM was significantly reduced in the TG mice compared to WT mice along with reduced osteoclastogenesis, narrower PDL width, higher bone volume fraction, and reduced RANKL expression.ConclusionsOsteoblast lineage cells and PDL fibroblasts are key contributors to alveolar bone remodeling in OTM through IKKβ dependent NF-κB activation.