HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (10) Citing Articles via Google Scholar Google Scholar Articles by Kanzaki, H. Articles by Mitani, H. Search for Related Content PubMed PubMed Citation Articles by Kanzaki, H. Articles by Mitani, H.

Local OPG Gene Transfer to Periodontal Tissue Inhibits Orthodontic Tooth Movement

¹ Division of Orthodontics and Dentofacial Orthopedics, and ² Division of Oral Dysfunction Science, Department of Oral Health and Development Sciences, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan;

^* corresponsing author, kanzaki{at}mail.tains.tohoku.ac.jp

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
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.

KEY WORDS: gene transfer • osteoprotegerin • tooth movement • mechanical stress • osteoclastogenesis

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
Orthodontic tooth movement occurs during the bone remodeling sequence that is induced by therapeutic mechanical stress (Roberts et al., 1981). Osteoclasts form on the compressed side of an orthodontically moving tooth and resorb the alveolar bone, changing the position of the tooth (Storey, 1973; Davidovitch, 1988; Brudvik and Rygh, 1994). It has been reported that osteoclastogenesis is primarily activated by the receptor activator of nuclear factor kappa B ligand (RANKL) and inhibited by osteoprotegerin (OPG) (Simonet et al., 1997; Udagawa et al., 1999; Yasuda et al., 1999). Previously, we discovered that periodontal ligament (PDL) cells, which exist between teeth and alveolar bone, induce osteoclastogenesis in vitro through the up-regulation of RANKL expression via PGE₂ synthesis when subjected to mechanical-compressive force (Kanzaki et al., 2002). Furthermore, it has been reported that RANKL expression was induced on the compressed side of an orthodontically moving tooth (Oshiro et al., 2002). Combining this information, we hypothesized that local OPG induction at the compressive site of the periodontium might neutralize the RANKL activity induced by the mechanical compressive force, inhibiting osteoclastogenesis and diminishing orthodontic tooth movement.

To test our hypothesis, we used experimental tooth movement in rats with or without local OPG gene transfer via a hemagglutinating virus of Japan (HVJ; Sendai virus) envelope vector gene delivery system.

	MATERIALS & METHODS

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
Animals and Orthodontic Appliance
Twenty six-week-old male Wistar rats with an average weight of 147 g were used in this study. The 20 animals were divided into 3 groups: Three rats were used as controls (control group); 8 rats were subjected to an applied orthodontic force (tooth-movement group), and 9 rats were subjected to an applied orthodontic force together with local OPG gene transfer, as described below (OPG-transfection group). In addition, for the purpose of testing transfection, we transfected a mock vector to 4 rats (mock group). The method used for the application of orthodontic force has been described previously in detail (Saitoh et al., 2000). Briefly, a uniform standardized compressive spring, made of 0.012-inch nickel-titanium wire (Nitinol Classic, 3M Unitek, Monrovia, CA, USA), was placed between the right and left upper first molars, causing them to move palatally. The spring initially generated an average compressive force of 167 mN (17 gram-force) on each side. The appliances were introduced into the experimental animals under pentobarbital (WAKO Jun-yaku, Tokyo, Japan) anesthesia.

All animals were treated ethically, in compliance with the regulations of Tohoku University.

Cloning of the Mouse OPG Gene and Construction of the OPG Expression Plasmid
Total RNA was extracted from the mouse osteoblastic cell-line MC3T3-E1 by means of a QuickPrep^® Total RNA extraction kit (Pharmacia Biotech, Uppsala, Sweden). The RNA was then reverse-transcribed with the use of You-Prime First Strand Beads (Pharmacia Biotech) and Oligo(dT)₁₅ primer (Madison, WI, USA). First-strand cDNA was subjected to PCR amplification with specific PCR primers. Two primers were designed with the use of the mouse OPG cDNA plus restriction site, primer XhoI site+OPG upstream (5'-GGGCTCGAG TGAGGTTTCCCGAGGAC-3') and primer OPG downstream+XbaI site (5'-CTAGTCTAG AACAGCCCAGTGA CCATTC-3'). PCR was performed by means of a KOD-Dash DNA Polymerase-kit (Toyobo Co., Ltd., Tokyo, Japan), following the manufacturer’s instructions. Each cycle consisted of a heat-denaturation step at 94°C for 30 sec, an annealing step at 51°C for 2 sec, and an extension step at 74°C for 2 min. The amplified cloning plasmid vector containing the restriction-site-tagged OPG sequence was digested with both XhoI and XbaI restriction enzymes (Invitrogen, Carlsbad, CA, USA), and the insert was ligated into the linearized expression plasmid vector pcDNA3.1(+) with the use of a DNA Ligation-kit (Takara-Bio Inc., Shiga, Japan). The sequence was checked with the use of the ALFexpress^TMCy^TM5 Thermo Sequenase^TM Dye Terminator-kit (Amersham-Biosciences, Piscataway, NJ, USA). This OPG expression vector (pcDNA-mOPG) was driven by a cytomegalovirus (CMV) promoter: the sequence-encoded functional mouse OPG (NM_008764, 70-1317 bp). Amplified pcDNA-mOPG was purified with Triton X-114 for removal of bacterial endotoxin.

In vitro Assay of the Constructed OPG Expression Plasmid
The constructed OPG expression plasmid was transfected into NIH3T3 cells with the use of Lipofectamine Plus (Invitrogen Corporation, Carlsbad, CA, USA). At 72 hrs after transfection, total RNA, culture media, and whole protein were collected. From the total RNA, the delivery of the OPG gene was checked by RT-PCR. From the culture media and whole protein, OPG production was checked by Western blot analysis with the use of anti-OPG antibody (Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA). The functional activity of the OPG was tested with a bone-resorption assay. Briefly, we performed the bone-resorption assay by culturing cells on calcium-phosphate-coated discs (Osteologic^®, BD Biosciences, Kingston, ON, Canada). Rat bone-marrow cells were collected (Scheven et al., 1986), seeded on Osteologic^® discs, and cultured in D-MEM containing 10%FBS (Biocell Laboratories, Rancho Dominguez, CA, USA) supplemented with 1,25-(OH)₂D₃ (1 x 10^–8 M) with or without 50% of collected culture media. Medium was changed every 5 days throughout the experiment. After cultivation for 21 days, the discs were cleaned with a trypsin-EDTA solution. Photographs were taken and scanned with a Minolta Dimage-ScanDual (Minolta, Ramsey, NJ, USA). The areas of resorption pits from randomly selected fields were measured with the use of ScionImage^® (Scion Co., Frederick, MD, USA) for Windows^®.

In vivo Gene Transfer
For in vivo transfection, we used an HVJ-envelope-vector kit (GenomONE^®, Ishihara-sangyo kaisha Ltd., Osaka, Japan), according to the manufacturer’s instructions (Kaneda et al., 2002). Administration of the HVJ-envelope-vector containing pcDNA-mOPG to the animals in the OPG-transfection group was started on the initial day of force application. A 5-µL quantity of vector-solution was injected into the sub-periosteal area, adjacent to the first molars, on days 0, 3, 7, 10, 14, and 17 of the experiment, with the animals under anesthesia (Fig. 1a). The animals in the tooth-movement group were injected with 5 µL of PBS in the corresponding area.

View larger version (66K): [in this window] [in a new window]   Figure 1. Local gene transfer area and systemic effects. (a) Schema of local gene transfer. Vector-solution was injected into the sub-periosteal area, adjacent to the first molars. Bu: buccal side. Pa: palatal side. (b) Body weight curve of experimental animals. The body weights of the experimental animals were measured throughout the experiment. There were no significant differences among the 3 groups. The results are expressed as the mean ± SD. N = 3, 8, and 9, respectively (control group, tooth-movement group, OPG-transfection group). (c) X-ray photograph of proximal rat tibiae. The densitometric patterns inside the standardized white box area were measured. (d) Bone mineral density values of tibiae of both groups. The results are expressed as the mean ± SD (N = 8). There were no significant differences among the groups.

Measurement of Bone Mineral Density (BMD) of Tibiae
After the death of the experimental animals, their bilateral tibiae were excised, and the soft tissues were removed. Lateral radiographs of tibiae were taken along with hydroxyapatite standards, by means of a soft x-ray apparatus (Sohuron Inc., Tokyo, Japan) set at 5 mA, 40 cm, 40 sec, and 30 kV. The densitometric patterns of the proximal tibiae, especially the cancellous bone area, were measured by ScionImage^® (Fig. 1c).

Cytochemical Examinations
Animals were killed under pentobarbital anesthesia on day 21, and the tissues were fixed by perfusion with 4% paraformaldehyde in PBS. The upper jaw, including the molars, was dissected and further fixed overnight. Specimens were then decalcified with 10% ethylenediamine-tetraacetic acid in 0.01 M PBS (pH 7.4) for 9 wks at 4°C, dehydrated, and embedded in paraffin. Periodontal tissues from the mesiopalatal roots of the upper first molars were examined in serial cross-sections of the molars at the bifurcation level. TRAP staining of the sections (8 µm thick) was performed with a Leukocyte Acid-Phosphatase kit (Sigma-Diagnostics^®, St. Louis, MO, USA) for osteoclast detection. We counted the TRAP-positive multinucleated cells that formed resorption lacunae on the alveolar bone surface adjacent to the mesiopalatal roots of the upper first molars.

Immunohistochemical Analysis
In brief, the sections were deparaffinized, pre-incubated in 5% bovine serum albumin (Dako, Glostrup, Denmark) in PBS for 30 min, and subsequently incubated with anti-OPG antibody (1:250 dilution; sc-8468; Santa Cruz Biotechnology) overnight at 4°C. After being thoroughly rinsed, the sections were incubated with the FITC-conjugated anti-goat IgG (1:1000 dilution; sc-2024; Santa Cruz Biotechnology), washed, mounted in PBS-glycerol, and observed with a fluorescence microscope (Leica, Heidelberg, Germany).

Statistics
Data were analyzed for statistical differences by Kruskal-Wallis analysis, followed by a Bonferroni-type multiple comparison (Tukey type). Differences with P < 0.05 were considered significant. The values are expressed as the means ± SD.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
Animal Status
The orthodontic appliance and local administration of the HVJ-envelope-vector containing pcDNA-mOPG did not affect the growth of the animals (Fig. 1b). At the start, the average weight of the rats was 147 g (SD = 8.1 g). On day 21, average weights of rats in the control group, the tooth-movement group, and the OPG-transfection group were 215 g (SD = 6.5 g), 211 g (SD = 12 g), and 217 g (SD = 4.7g), respectively. The local administration of either 5 µL of vector-solution or PBS caused no appreciable macroscopic changes at the local injection site.

In addition, local gene transfer did not affect the bone mineral density (BMD) of tibiae (Fig. 1d). The average BMDs of rats in the tooth-movement and OPG-transfection groups were 1609 µg/mm² (SD = 58.5) and 1643 µg/mm² (SD = 56.7), respectively.

In vitro Assay of the Constructed OPG Expression Plasmid
After construction of the OPG expression plasmid, we assessed the function of protein produced in vitro. OPG gene delivery and OPG production in transfected cells were confirmed (Figs. 2a, 2b). Furthermore, we performed a resorption assay to determine whether the OPG produced was functionally intact (Figs. 2c, 2d). Rat bone marrow cells cultured with 1,25-(OH)₂D₃ differentiated into osteoclasts, and there were many resorbed areas (18.3 ± 3.1%) (Fig. 2d, control). However, when the medium collected from transfected cell cultures was added, osteoclastic resorption was obviously inhibited. The resorbed area of transfected samples was almost one-third that of control samples (6.2 ± 1.9%) (Fig. 2d, transfected).

View larger version (79K): [in this window] [in a new window]   Figure 2. In vitro assay of pcDNA-mOPG. (a) RT-PCR analysis of NIH3T3 cells. RT-PCR analysis was performed with cDNA from OPG-transfected NIH3T3 cells and control NIH3T3 cells. The results shown are from 1 representative independent experiment out of 3. C, control NIH3T3 cells; T, OPG-transfected NIH3T3 cells; L, DNA ladder. (b) Western blot analysis with antibody against OPG. L, protein ladder; Control, cell lysate from control NIH3T3 cells; Transfect, cell lysate from OPG-transfected NIH3T3 cells. The results shown are from 1 representative independent experiment out of 3. (c) Resorption assay (photos). Upper panel: Osteologic® discs cultured with normal culture medium and 1,25-(OH)2D3. Lower panel: Osteologic® discs cultured with 50% collected culture medium and 1,25-(OH)2D3. Arrowhead indicates resorption pit. The areas of the resorption pits from randomly selected fields were measured. The results shown are from 1 representative experiment out of 8. Bar = 100 µm. (d) Resorption assay (resorbed area of Osteologic® discs). The areas of the resorption pits from randomly selected fields were measured. The resorbed areas of 24 fields were measured. * p < 0.05.

View larger version (107K): [in this window] [in a new window]   Figure 3. Immunohistochemical analysis of OPG. Immunofluorescence analyses of serial sections were performed with anti-OPG antibodies. Images (a) to (c) are photographs of the palatal sides of first molars. Fluorescence image and phase-contrast image were superimposed on the software (Adobe Photoshop 5.0, San Jose, CA, USA). (a) Photograph of the tooth-movement group. Representative photographs of 6 sections are shown. (b) Photograph of the OPG-transfection group. Representative photographs of 5 sections are shown. (c) Photograph of the mock group. Representative photographs of 4 sections are shown. Bar = 100 µm. Bu, buccal side. Pa, palatal side. (d) Combined photograph of the OPG-transfection group. Series of the fluorescent photographs taken under the same exposure conditions were combined. Strong OPG expression was observed at M1. (e) Photograph of the OPG-transfection group stained with hematoxylin-eosin. About the same field as shown in Fig. 3d is presented. Bar = 1 mm.

View larger version (58K): [in this window] [in a new window]   Figure 4. Osteoclastogenesis and tooth movement. Photo images of osteoclasts. TRAP-positive multinucleated cells were observed around the teeth in the tooth-movement group (a) and in the OPG-transfection group (b). Periodontal tissues of the mesiopalatal roots of the upper first molars were examined in serial cross-sections of the molars at a bifurcation level. TRAP-positive multinucleated cells that formed resorption lacunae on the alveolar bone surface adjacent to the mesiopalatal roots of the upper first molars were counted. Representative photographs of 6 sections of both groups are shown. Bar = 100 µm. (c) Number of osteoclasts in the periodontium. TRAP-positive multinucleated cells that formed resorption lacunae on the alveolar bone surface adjacent to the mesiopalatal roots of the upper first molars were counted. The results are expressed as the mean ± SD (N = 6). (d) Time course of changes in tooth movement. N = 8 and 9, respectively (tooth-movement group, OPG-transfection group). No tooth movement to the palatal side was observed in both control and mock groups (data not shown). (e) Data are presented as percent inhibition of tooth movement (OPG-transfection group/tooth-movement group) in each day. *P < 0.05; **P < 0.01; ***P < 0.001.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
In this study, we adopted an experimental tooth movement system, using a fixed orthodontic appliance that constantly generated a lightly effective orthodontic force on the upper first molars (Igarashi et al., 1994; Saitoh et al., 2000). The amount of tooth movement was measured by an enlarged tracing method (Igarashi et al., 1994). This method provided precise measurements, with 0.011 mm of measurement error. The application of orthodontic force did not affect the rats’ body weights (Fig. 1b). Local OPG gene transfer to the periodontal tissue was performed with an HVJ-envelope-vector gene-delivery system containing pcDNA-mOPG, and resulted in OPG protein production in the periodontal tissue (Fig. 3) and significant inhibition of osteoclastogenesis (Figs. 4a–4c). The adjusted vector-solution included an introduction enhancer to inhibit the incorporation of vector solution into the blood circulation; we assumed that this agent enabled the expression plasmid to produce OPG locally.

Numerous reports have described the pharmacological control of tooth movement through the regulation of osteoclasts. Non-steroidal anti-inflammatory drugs inhibit cyclooxygenase and result in delayed tooth movement (Chumbley and Tuncay, 1986; Kehoe et al., 1996; Roche et al., 1997). However, because these drugs are rapidly flushed by blood circulation, daily systemic administration or daily local injection is needed. Others have used bisphosphonates to control orthodontic tooth movement (Igarashi et al., 1994; Kim et al., 1999). Bisphosphonates tend to incorporate into bone tissue and directly inactivate osteoclasts; this treatment requires injection every 3 days (Adachi et al., 1994). Collins and Sinclair tested the effect of vitamin D₃ on tooth movement. They found that vitamin D₃ activated osteoclasts and observed rapid tooth movement (Collins and Sinclair, 1988). The local administration of prostaglandins (Lee, 1990), osteocalcin (Hashimoto et al., 2001), or PTH (Soma et al., 2000) also induced orthodontic tooth movement. In this study, we used local OPG gene transfer instead of OPG administration. Local gene transfer has two advantages (Blesing and Kerr, 1996): First, it can maintain a locally effective concentration and prolonged protein expression, regardless of blood circulation. Second, protein expression occurs at the local site, so that systemic effects are avoided. However, because recurrent injection of viral membrane to the experimental animals could induce immune responses, further modifications of gene transfer are required.

We were able to induce local OPG expression in the periodontal tissue without any systemic effects (Figs. 1b, 1d). However, OPG induction was not limited to the palatal sides of the first molars; OPG was also slightly increased on the buccal sides (Fig. 3d). There are two possible explanations for this: First, the vector solution might have diffused due to blood flow. Second, because the OPG protein produced from the pcDNA-mOPG gene is soluble, it might have diffused via the interstitial fluid.

Local OPG gene transfer significantly inhibited the osteoclastogenesis in the periodontium that was caused by experimental tooth movement (Figs. 4a–4c). The number of osteoclasts in the OPG-gene-transfer group was about half that in the tooth-movement group. Thus, OPG gene transfer did not completely inhibit the induction of osteoclastogenesis. The partial inhibition may have been due to a low efficiency of transfection; alternatively, osteoclastogenesis induction by orthodontic tooth movement may be controlled, in part, by other cytokines, such as vascular endothelial growth factor (VEGF) (Kaku et al., 2001; Kohno et al., 2003), IL-1 (Saito et al., 1991; Alhashimi et al., 2001; Iwasaki et al., 2001), and TNF- (Lowney et al., 1995; Lossdorfer et al., 2002).

Enforced OPG expression diminished tooth movement to almost half that observed in the tooth-movement group on day 21 (Figs. 4d, 4e). The tooth movement that occurred in the OPG-transfection group may have been the result of induced RANKL expression that was not completely inhibited by OPG gene transfer; alternatively, orthodontic tooth movement may also be controlled by other cytokines, as described above.

In this study, we demonstrated that OPG gene transfer to the periodontal tissue inhibited RANKL-mediated osteoclastogenesis induced by mechanical stress, and inhibited experimental tooth movement, without eliciting any systemic effects. In conclusion, osteoclastogenesis in response to orthodontic tooth movement appears to be regulated primarily through RANKL signaling in periodontal cells.

	ACKNOWLEDGMENTS

 
This work was supported by Grants-in-Aid for scientific research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan (12671984 and 16390602).

Received November 6, 2003; Last revision September 5, 2004; Accepted September 28, 2004

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS & METHODS RESULTS DISCUSSION REFERENCES

 
Adachi H, Igarashi K, Mitani H, Shinoda H, (1994). Effects of topical administration of a bisphosphonate (risedronate) on orthodontic tooth movements in rats. J Dent Res 73:1478–1486.[Abstract/Free Full Text]

Alhashimi N, Frithiof L, Brudvik P, Bakhiet M (2001). Orthodontic tooth movement and de novo synthesis of proinflammatory cytokines. Am J Orthod Dentofacial Orthop 119:307–312.[ISI][Medline]

Blesing CH, Kerr DJ (1996). Intra-hepatic arterial drug delivery. J Drug Target 3:341–347.[ISI][Medline]

Brudvik P, Rygh P (1994). Multi-nucleated cells remove the main hyalinized tissue and start resorption of adjacent root surfaces. Eur J Orthod 16:265–273.[Abstract/Free Full Text]

Chumbley AB, Tuncay OC (1986). The effect of indomethacin (an aspirin-like drug) on the rate of orthodontic tooth movement. Am J Orthod 89:312–314.[ISI][Medline]

Collins MK, Sinclair PM (1988). The local use of vitamin D to increase the rate of orthodontic tooth movement. Am J Orthod Dentofacial Orthop 94:278–284.[ISI][Medline]

Davidovitch Z (1988). Neurotransmitters, cytokines, and the control of alveolar bone remodeling in orthodontics. Dent Clin North Am 32:411–435.

Hashimoto F, Kobayashi Y, Mataki S, Kobayashi K, Kato Y, Sakai H (2001). Administration of osteocalcin accelerates orthodontic tooth movement induced by a closed coil spring in rats. Eur J Orthod 23:535–545.[Abstract/Free Full Text]

Igarashi K, Mitani H, Adachi H, Shinoda H (1994). Anchorage and retentive effects of a bisphosphonate (AHBuBP) on tooth movements in rats. Am J Orthod Dentofacial Orthop 106:279–289.[ISI][Medline]

Iwasaki LR, Haack JE, Nickel JC, Reinhardt RA, Petro TM (2001). Human interleukin-1 beta and interleukin-1 receptor antagonist secretion and velocity of tooth movement, Arch Oral Biol 46:185–189.[ISI][Medline]

Kaku M, Kohno S, Kawata T, Fujita I, Tokimasa C, Tsutsui K, et al. (2001). Effects of vascular endothelial growth factor on osteoclast induction during tooth movement in mice. J Dent Res 80:1880–1883.[Abstract/Free Full Text]

Kaneda Y, Nakajima T, Nishikawa T, Yamamoto S, Ikegami H, Suzuki N, et al. (2002). Hemagglutinating virus of Japan (HVJ) envelope vector as a versatile gene delivery system. Mol Ther 6:219–226.[ISI][Medline]

Kanzaki H, Chiba M, Shimizu Y, Mitani H (2002). Periodontal ligament cells under mechanical stress induce osteoclastogenesis by receptor activator of nuclear factor kappa B ligand up-regulation via prostaglandin E₂ synthesis. J Bone Miner Res 17:210–220.[ISI][Medline]

Kehoe MJ, Cohen SM, Zarrinnia K, Cowan A (1996). The effect of acetaminophen, ibuprofen, and misoprostol on prostaglandin E₂ synthesis and the degree and rate of orthodontic tooth movement, Angle Orthod 66:339–349.[ISI][Medline]

Kim TW, Yoshida Y, Yokoya K, Sasaki T (1999). An ultrastructural study of the effects of bisphosphonate administration on osteoclastic bone resorption during relapse of experimentally moved rat molars. Am J Orthod Dentofacial Orthop 115:645–653.[ISI][Medline]

Kohno S, Kaku M, Tsutsui K, Motokawa M, Ohtani J, Tenjo K, et al. (2003). Expression of vascular endothelial growth factor and the effects on bone remodeling during experimental tooth movement. J Dent Res 82:177–182.[Abstract/Free Full Text]

Lee WC (1990). Experimental study of the effect of prostaglandin administration on tooth movement—with particular emphasis on the relationship to the method of PGE₁ administration. Am J Orthod Dentofacial Orthop 98:231–241.[ISI][Medline]

Lossdorfer S, Gotz W, Jager A (2002). Localization of IL-1alpha, IL-1 RI, TNF, TNF-RI and TNF-RII during physiological drift of rat molar teeth—an immunohistochemical and in situ hybridization study. Cytokine 20:7–16.[ISI][Medline]

Lowney JJ, Norton LA, Shafer DM, Rossomando EF (1995). Orthodontic forces increase tumor necrosis factor alpha in the human gingival sulcus. Am J Orthod Dentofacial Orthop 108:519–524.[ISI][Medline]

Oshiro T, Shiotani A, Shibasaki Y, Sasaki T (2002). Osteoclast induction in periodontal tissue during experimental movement of incisors in osteoprotegerin-deficient mice. Anat Rec 266:218–225.[Medline]

Roberts WE, Goodwin WC, Heiner SR (1981). Cellular response to orthodontic force. Dent Clin North Am 25:3–17.[ISI][Medline]

Roche JJ, Cisneros GJ, Acs G (1997). The effect of acetaminophen on tooth movement in rabbits. Angle Orthod 67:231–236.[ISI][Medline]

Saito M, Saito S, Ngan PW, Shanfeld J, Davidovitch Z (1991). Interleukin 1 beta and prostaglandin E are involved in the response of periodontal cells to mechanical stress in vivo and in vitro. Am J Orthod Dentofacial Orthop 99:226–240.[ISI][Medline]

Saitoh S, Takahashi I, Mizoguchi I, Sasano Y, Kagayama M, Mitani H (2000). Compressive force promotes chondrogenic differentiation and hypertrophy in midpalatal suture cartilage in growing rats. Anat Rec 260:392–401.[Medline]

Scheven BA, Visser JW, Nijweide PJ (1986). In vitro osteoclast generation from different bone marrow fractions, including a highly enriched haematopoietic stem cell population. Nature 321:79–81.[Medline]

Simonet WS, Lacey DL, Dunstan CR, Kelley M, Chang MS, Luthy R, et al. (1997). Osteoprotegerin: a novel secreted protein involved in the regulation of bone density, Cell 89:309–319.[ISI][Medline]

Soma S, Matsumoto S, Higashi Y, Takano-Yamamoto T, Yamashita K, Kurisu K, et al. (2000). Local and chronic application of PTH accelerates tooth movement in rats, J Dent Res 79:1717–1724.[Abstract/Free Full Text]

Storey E (1973). The nature of tooth movement. Am J Orthod 63:292–314.[ISI][Medline]

Udagawa N, Takahashi N, Jimi E, Matsuzaki K, Tsurukai T, Itoh K, et al. (1999). Osteoblasts/stromal cells stimulate osteoclast activation through expression of osteoclast differentiation factor/RANKL but not macrophage colony-stimulating factor. Bone 25:517–523.[Medline]

Yasuda H, Shima N, Nakagawa N, Yamaguchi K, Kinosaki M, Goto M, et al. (1999). A novel molecular mechanism modulating osteoclast differentiation and function. Bone 25:109–113.[Medline]

This article has been cited by other articles:

				G.E. Wise and G.J. King Mechanisms of Tooth Eruption and Orthodontic Tooth Movement J. Dent. Res., May 1, 2008; 87(5): 414 - 434. [Abstract] [Full Text] [PDF]

				M. Yamaguchi, N. Aihara, T. Kojima, and K. Kasai RANKL Increase in Compressed Periodontal Ligament Cells from Root Resorption. J. Dent. Res., August 1, 2006; 85(8): 751 - 756. [Abstract] [Full Text] [PDF]

				Relevant research from non-orthodontic journals J. Orthod., June 1, 2005; 32(2): 142 - 144. [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Services Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (10) Citing Articles via Google Scholar Google Scholar Articles by Kanzaki, H. Articles by Mitani, H. Search for Related Content PubMed PubMed Citation Articles by Kanzaki, H. Articles by Mitani, H.