Impact of bisphosphonate drug burden in alveolar bone during orthodontic tooth movement in a rat model: A pilot study

Effect of bisphosphonate vs. osteoprotegerin during orthodontic tooth movement: A systematic review and meta-analysis

Objective

Orthodontic appliances are commonly used to achieve anchorage during orthodontic treatments; however, their use can contribute to oral diseases. Studies have shown that bisphosphonates and osteoprotegerin are highly effective in reducing orthodontic tooth movement. To determine the efficacy of bisphosphonates and osteoprotegerin in reducing orthodontic tooth movement.

Methods

A comprehensive search was conducted across five databases-MEDLINE-PubMed, Scopus, Google Scholar, ScienceDirect, and Taylor & Francis-up to August 2, 2023. Clinical trials conducted in healthy animals, where bisphosphonates and osteoprotegerin were administered during tooth movement, were included. The search identified 3,099 articles, which underwent a two-phase screening process, resulting in twelve studies for the systematic review and seven for the meta-analysis. Risk of bias was assessed using the SYRCLE tool, and Egger's regression was used to evaluate publication bias.

Results

The administration of bisphosphonates was more effective than osteoprotegerin in reducing mesiodistal orthodontic movement. However, osteoprotegerin did not significantly reduce orthodontic tooth movement.

Conclusions

The findings align with previous studies, confirming the superior efficacy of bisphosphonates over osteoprotegerin. Further research is required to determine the optimal dosage and mechanism of action for these drugs in clinical practice, considering the specific objectives of orthodontic treatments.

Mesenchymal stem cell-derived exosomes: a potential cell-free therapy for orthodontic tooth stability management

Orthodontic relapse (OR) occurs at a rate of over 70%. Retention is the current attempt at prevention, but it requires a considerable amount of time and cannot fully block OR. It's imperative to find a safe and effective method for managing post-orthodontic tooth stability. Periodontal bone remodeling is one crucial biological foundation of OR. Mesenchymal stem cell-derived exosomes (MSC-Exo) show promise in relapse management by regulating periodontal bone remodeling. MSC-Exo can prevent relapse by regulating periodontal ligament function, osteoclast activity, osteoblast differentiation, macrophage polarization, and periodontal microcirculation. In recent years, exosome-loaded hydrogels, which achieve controlled exosome release, have demonstrated efficacy in promoting bone regeneration and remodeling, offering promising prospects for OR management. This review aims to highlight the use of MSC-Exo-based therapy for preventing OR, offering new insights for future research focused on improving tooth stability and enhancing orthodontic anchorage.

GDF15 Modulates the Zoledronic-Acid-Induced Hyperinflammatory Mechanoresponse of Periodontal Ligament Fibroblasts

Orthodontic tooth movement (OTM) is thought to be impeded by bisphosphonate (BP) therapy, mainly due to increased osteoclast apoptosis and changes in the periodontal ligament (PdL), a connecting tissue between the alveolar bone and teeth. PdL cells, mainly fibroblasts (PdLFs), are crucial regulators in OTM by modulating force-induced local inflammatory processes. Recently, we identified the TGF-β/BMP superfamily member GDF15 as an important modulator in OTM, promoting the pro-inflammatory mechanoresponses of PdLFs. The precise impact of the highly potent BP zoledronate (ZOL) on the mechanofunctionality of PdLFs is still under-investigated. Therefore, the aim of this study was to further characterize the ZOL-induced changes in the initial inflammatory mechanoresponse of human PdLFs (hPdLFs) and to further clarify a potential interrelationship with GDF15 signaling. Thus, two-day in vitro treatment with 0.5 µM, 5 µM and 50 µM of ZOL altered the cellular properties of hPdLFs partially in a concentration-dependent manner. In particular, exposure to ZOL decreased their metabolic activity, the proliferation rate, detected using Ki-67 immunofluorescent staining, and survival, analyzed using trypan blue. An increasing occurrence of DNA strand breaks was observed using TUNEL and an activated DNA damage response was demonstrated using H2A.X (phosphoS139) staining. While the osteogenic differentiation of hPdLFs was unaffected by ZOL, increased cellular senescence was observed using enhanced p21Waf1/Cip1/Sdi1 and β-galactosidase staining. In addition, cytokine-encoding genes such as IL6, IL8, COX2 and GDF15, which are associated with a senescence-associated secretory phenotype, were up-regulated by ZOL. Subsequently, this change in the hPdLF phenotype promoted a hyperinflammatory response to applied compressive forces with an increased expression of the pro-inflammatory markers IL1β, IL6 and GDF15, as well as the activation of monocytic THP1 cells. GDF15 appeared to be particularly relevant to these changes, as siRNA-mediated down-regulation balanced these hyperinflammatory responses by reducing IL-1β and IL-6 expression (IL1B p-value < 0.0001; IL6 p-value < 0.001) and secretion (IL-1β p-value < 0.05; IL-6 p-value < 0.001), as well as immune cell activation (p-value < 0.0001). In addition, ZOL-related reduced RANKL/OPG values and inhibited osteoclast activation were enhanced in GDF15-deficient hPdLFs (both p-values < 0.0001; all statistical tests: one-way ANOVA, Tukey's post hoc test). Thus, GDF15 may become a promising new target in the personalized orthodontic treatment of bisphosphonatepatients.

Efficacy of the systemic co-administration of vitamin D3 in reversing the inhibitory effects of sodium alendronate on orthodontic tooth movement: A preliminary experimental animal study

INTRODUCTION

Bisphosphonates can severely slow down orthodontic tooth movement (OTM) by reducing bone turnover. This calls for materials and methods to reverse or neutralize their effects on OTM. We propose systemic vitamin D3 (D3) for this purpose.

METHODS

Thirty-two male Wistar rats were randomized into 4 groups of 8 each. Three groups were administered D3 (3 systemic doses of 24,000 IU/kg each), alendronate (ALN) (5 doses of 7 mg/kg each), and ALN+D3 (same doses as mentioned above). One group served as the negative control. The incisors were distalized at 30 g of force for 2 weeks. OTMs were measured blindly. Radicular pressure areas were searched histologically (blindly) for capillaries, Howship's lacunae, osteoclasts, and osteoblasts. Data were analyzed statistically (α = 0.05, α = 0.0083, β <0.1).

RESULTS

OTMs in the groups D3, ALN+D3, ALN, and control were 1.900 ± 0.237, 1.629 ± 0.219, 0.975 ± 0.145, and 1.565 ± 0.324 mm (analysis of variance, P <0.001), respectively. OTM in the ALN group was smaller than all other groups (Tukey, P <0.001). OTM in the D3 group was greater than in the control group (P = 0.054). The ALN+D3 group had greater OTM than the ALN group (P <0.001) but was not significantly different from the D3 (P = 0.153) or control (P = 0.951) groups. All histologic variables were significantly different across groups (Kruskal-Wallis, P <0.001). All the markers in the D3 group were more frequent than those of the other groups (Mann-Whitney U, P <0.001). There were fewer markers in the ALN group than in the control group (P ≤0.001). The ALN+D3 group had more markers than the ALN group in terms of capillaries, osteoclasts, and osteoblasts (P ≤0.007). The ALN+D3 group was similar to the control group regarding capillaries, osteoclasts, and osteoblasts (P ≥0.382).

CONCLUSIONS

Systemic vitamin D3 may accelerate OTM and increase histologic biomarkers of bone turnover. ALN reduces OTM and its histologic biomarkers. Systemic vitamin D3 can reverse this inhibitory effect of ALN on OTM back to normal.

Effect of local administration of bisphosphonate on orthodontic anchorage – A systematic review of animal studies

BACKGROUND:

Pharmacological means of anchorage control can improve patient compliance. Bisphosphonates could be helpful in orthodontic anchorage control if their actions could be localized to limit (or control) unwanted tooth movement while not interfering with the desired tooth movement.

OBJECTIVE:

This systematic review aimed to examine and evaluate the quality of all animal studies that reported the effect of locally administered bisphosphonate on limiting orthodontic tooth movement.

DATA SOURCES:

An electronic search was conducted in the PubMed-Medline, Scopus, Google Scholar, and Cochrane databases till May 2022, using the keywords anchorage, anchorage loss, molar movement, posterior tooth movement, incisor movement, incisor retraction, anterior retraction, unwanted tooth movement, tooth displacement, tooth movement forward, bisphosphonate, local bisphosphonate administration, bisphosphonate injection, and bbisphosphonate vestibular induction. Only studies involving localized bisphosphonate administration for anchorage purposes were taken into account.

DATA SELECTION:

Animal studies that simulated orthodontic tooth movement after localized injection of bisphosphonate and evaluated the rate of tooth movement were included in the review.

DATA EXTRACTION AND ANALYSIS:

The quality of the studies was assessed by using ARRIVE guidelines (Animal Research: Reporting of In Vivo Experiments). Bias in the studies was analyzed by SYRCLE's tool (Systematic Review Centre for Laboratory Animal Experimentation) for risk of bias.

RESULTS:

The search strategy yielded 925 titles. After screening, 908 articles were discarded because they did not fulfill the inclusion/exclusion criteria based on the title and abstract. The remaining 16 articles were read entirely, of which nine were excluded as they involved systemic administration of bisphosphonates. Finally, after careful consideration, seven papers that met our inclusion criteria were included in the qualitative analysis. The majority of studies were assessed to have an uncertain risk of bias, with just one deemed low risk of bias.

CONCLUSION:

This systematic review found that bisphosphonates limit orthodontic tooth movement around the application site without affecting adjacent sites. More potent bisphosphonates in smaller doses or less potent bisphosphonates in higher frequencies have been proposed to improve outcomes. However, the data quality is insufficient to recommend a protocol for bisphosphonate administration for anchoring control. Long-term studies evaluating various types, frequencies, and dosages of bisphosphonates are required to clarify the effects on orthodontic tooth movement.

REGISTRATION NUMBER FOR PROSPERO:

CRD42021224033

Effects of Jixueteng on Experimental Periodontitis During Orthodontic Tooth Movement in Rats

Recently, natural ingredients have focused on the inhibition of bacteria-induced alveolar bone resorption in orthodontic treatment. Jixueteng (Jix), a Chinese traditional medicine, contains several kinds of flavonoids given their biological properties. We evaluated the effects of Jix on experimental periodontitis during orthodontic tooth movement (OTM) in rats. To this end, 9-week-old male Wistar rats, which were equipped with orthodontic appliance, were orally infected with Porphyromonas gingivalis (Pg), while Jix was administered in their drinking water. A total of 28 days after the beginning of OTM, alveolar bone resorption on the right side of the upper jaws was scanned with micro-computed tomography. These were also used as histological specimens and underwent tartrate-resistant acid phosphatase (TRAP) staining. TRAP-positive multinucleated cells were counted as osteoclasts. As a result, the distance of tooth movement in the OTM and Pg infection with Jix administration (OTM + Pg + Jix) group was the same as that of the sham-infected group. The amount of bone resorption and number of osteoclasts in the OTM + Pg + Jix group was more significantly decreased than that in the OTM and Pg-infected group ( P < 0.05). Hence, Jix had little effect on OTM and inhibited Pg-induced alveolar bone destruction. We suggested that the administration of Jix can support tooth movement and contribute to the prevention of periodontitis during orthodontic treatment.

The effects of mandibular osteotomy on maxillary orthodontic tooth movement and bone remodelling in a rat model

OBJECTIVES

The accelerated tooth movement phenomenon after orthognathic surgery has been observed. However, the underlying mechanism remains unclear. There is no experimental study showing the effect of orthognathic surgery on orthodontic tooth movement of the opposing jaw. Therefore, the present study aimed at investigating if mandibular osteotomy enhances maxillary tooth movement and bone remodelling.

MATERIALS AND METHODS

Fifty-four male Sprague-Dawley rats were randomly divided into two groups: maxillary tooth movement (TM) and maxillary tooth movement + mandibular surgery (TM + MS). The orthodontic force was delivered to move the left maxillary first molar mesially. The surgical intervention was performed on the left mandible. Microcomputed tomography, histological analysis, enzyme-linked immunosorbent assay, and quantitative real-time polymerase chain reaction were used to assess changes at 3, 7, and 21 days after surgery.

RESULTS

The mandibular osteotomy accelerates the rate of maxillary tooth movement with decreased bone volume fraction on the seventh day. Bone resorption was observed on the third and seventh day after mandibular osteotomy. It was found that serum interleukin-1β level increased significantly in the TM + MS group compared with the TM group, as well as the high expression level of cathepsin K and tumour necrosis factor receptor-associated factor 5 of the orthodontic tooth on the third and seventh day after mandibular osteotomy.

CONCLUSION

Data from the present study suggested that mandibular osteotomy accelerates maxillary osteoclast activity and post-operative tooth movement, providing evidence for accelerated tooth movement phenomenon after orthognathic surgery.

Alteration of tooth movement by reveromycin A in osteoprotegerin-deficient mice

INTRODUCTION

Osteoprotegerin-deficient mice develop severe high-turnover osteoporosis with porous low-density trabecular bone from an age-related increase in osteoclast activity and are useful alveolar bone models of osteoporosis or frail periodontal tissue. Bisphosphonate (BP), a first-line drug for osteoporosis, is bone-avid, causing side effects such as brittle and fragile bones and jaw osteonecrosis after tooth extraction. In orthodontics, active movement is precisely controlled by temporarily suppressing and resuming movement. BP impedes such control because of its long half-life of several years in bone. Therefore, we investigated the novel osteoclast-specific inhibitor reveromycin A (RMA), which has a short half-life in bone. We hypothesized that tooth movement could be precisely controlled through temporary discontinuation and re-administration of RMA.

METHODS

Osteoprotegerin-deficient mice and wild-type mice were developed as tooth movement models under constant orthodontic force. A constant orthodontic force of 10 g was induced using a nickel-titanium closed coil spring to move the maxillary first molar for 14 days. We administered BP (1.25 mg/kg) or RMA (1.0 mg/kg) continuously and then discontinued it to reveal how the subsequent movement of teeth and surrounding alveolar bone was affected.

RESULTS

Continuous BP or RMA administration suppressed osteoclast activity and preserved alveolar bone around the roots, apparently normalizing bone metabolism. Tooth movement remained suppressed after BP discontinuation but resumed at a higher rate after discontinuation of RMA.

CONCLUSIONS

RMA appears useful for controlling orthodontic tooth movement because it can be suppressed and resumed through administration and discontinuation, respectively.

Microtomographic analysis of the effect of sodium alendronate on orthodontic movement in rats

OBJECTIVE

To evaluate the effect of sodium alendronate on orthodontic tooth movement in rats using microtomographic analysis.

SETTINGS AND SAMPLE POPULATION

Thirty male Wistar rats (Rattus norvegicus) were divided into three groups of 10 rats and administered saline (control), 1 mg/kg sodium alendronate or 6 mg/kg sodium alendronate, respectively.

MATERIALS AND METHODS

The drug was administered once per week for 5 weeks by gavage. Orthodontic movement was induced during the last 2 weeks of medication administration by inserting a closed nickel-titanium spring between the left upper first molar and central incisors. The opposite side served as the control. Tooth movement and bone trabeculation in the furcation region were evaluated by microtomographic analysis in the first (moved) and third (static) molars. The data were subjected to one-way or two-way ANOVA and Bonferroni test (P < .05).

RESULTS

The microtomographic images of the group that received 6 mg/kg sodium alendronate demonstrated significantly less tooth movement (P = .048), less space between the trabeculae (P = .031) and greater number of bone trabeculae (P = .033) compared to the other groups. There were no statistically significant differences in bone volume and mean trabecular thickness between the three groups. The static teeth did not show the same alterations (P > .05).

CONCLUSION

Sodium alendronate treatment reduced tooth movement in rats.

Effects of systematic bisphosphonate use in patients under orthodontic treatment: a systematic review

BACKGROUND

Bisphosphonates are a class of drugs prescribed for several osseous related disorders owing to their ability to regulate bone turnover, which could in turn affect orthodontic treatment outcomes.

OBJECTIVE

To examine the effect of bisphosphonate (BP) use on orthodontic patients through clinical and radiographic measurements.

SEARCH METHODS

Systematic and unrestricted search of 17 databases complemented with additional hand-searches were performed up to March 2019.

SELECTION CRITERIA

Articles reporting on human patients with a history of BPs administration that received orthodontic treatment were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Data regarding the medical profile of the patients, the specific type of malocclusion and the performed treatment plan, as well as the clinical and radiographic outcomes were extracted. Quality assessment was performed by the ROBINS-I tool for the cohort studies and by a slightly modified checklist from the original one proposed by Agbabiaka et al. for the case reports.

RESULTS

7 articles (1 retrospective cohort study and 6 case reports) were eventually included in the present review including 122 subjects (29 patients and 93 controls) reporting on the clinical and radiographic changes following orthodontic treatment of patients during or after BPs use. BPs seem to have a controversial effect on the clinical and patient-reported variables, even though the majority of the included patients presented with compromised treatment results and a rather slow rate of tooth movement. Most radiographic findings revealed mild root resorption, widened periodontal ligament spaces and sclerotic changes on the surrounding alveolar bone. However, these results should be interpreted with caution, due to the limited number of the eligible articles and their limitations.

LIMITATIONS

The included studies were of rather low quality due to study design and incomplete reporting.

CONCLUSIONS AND IMPLICATIONS

BP administration seems to be associated with compromised clinical outcomes, prolonged treatment time, and moderate changes on the roots and surrounding tissues of orthodontic patients.

REGISTRATION

Non-registered.

FUNDING

None.

Effect of local administration of simvastatin on orthodontic tooth movement in rabbits

INTRODUCTION

Maintaining tooth anchorage during orthodontic treatment has challenged orthodontists and threatening the success of some orthodontic therapy. The objective of this study was to evaluate the effect of local administration of simvastatin on orthodontic tooth movement.

METHODS

Nickel-titanium coil springs were used to induce orthodontic tooth movement in 10 white New Zealand rabbits for 21 days. A split-mouth design was implemented where one mandibular quadrant received local administration of simvastatin and the corresponding mandibular quadrant received control vehicle solution on a weekly basis. Magnitudes of tooth movement were measured on 3-dimensional models of the experimental teeth. Animals were killed at the end of the experimental period to allow histomorphometric analysis of alveolar bone modeling.

RESULTS

The total magnitude of tooth movement in the quadrant receiving simvastatin was significantly less than that in the quadrant receiving control vehicle solution. Local administration of simvastatin resulted in a significant percentage of inhibition of tooth movement of 39.8 ± 22.6%. Histomorphometric analysis revealed a significant reduction in the numbers of osteoclasts and areas of active bone-resorptive lacunae hindering bone resorption processes in the quadrant receiving simvastatin.

CONCLUSIONS

Local administration of simvastatin can reduce the rate and magnitude of orthodontic tooth movement. Moreover, local administration of simvastatin diminishes bone resorption processes associated with orthodontic tooth movement reducing the number of osteoclasts and the subsequent area of active bone resorption.

A Novel Method to Quantify Longitudinal Orthodontic Bone Changes with In Vivo Micro-CT Data

Orthodontic tooth movement (OTM) is the result of region-specific bone modeling under a load. Quantification of this change in the alveolar bone around a tooth is a basic requirement to understand the mechanism of orthodontics. The purpose of this study was to quantify subregional alveolar bone changes during orthodontic tooth movement with a novel method. In this study, 12 Sprague-Dawley (SD) rats were used as an orthodontic model, and one side of the first upper molar was used to simulate OTM. The alveolar bone around the mesial root was reconstructed from in vivo micro-CT images and separated from other parts of the alveolar bone with two semicylinder filters. The amount and rate of OTM, bone mineral density (BMD), and bone volume (BV) around the root were calculated and compared at 5 time points. The results showed that the amount of tooth movement, BMD, and BV can be evaluated dynamically with this method. The molar moved fastest during the first 3 days, and the rate decreased after day 14. BMD decreased from day 0 to day 14 and returned from day 14 to day 28. BV deceased from day 0 to day 7 and from day 14 to day 28. The method created in this study can be used to accurately quantify dynamic alveolar bone changes during OTM.

Effectiveness of Biology-Based Methods for Inhibiting Orthodontic Tooth Movement. A Systematic Review

INTRODUCTION

Several experimental studies in the literature have tested different biology-based methods for inhibiting or decreasing orthodontic tooth movement (OTM) in humans. This systematic review investigated the effects of these interventions on the rate of tooth movement.

STUDY DESIGN

Electronic [MedLine; SCOPUS; Cochrane Library; OpenGrey;Web of Science] and manual searches were conducted up to January 26th, 2016 in order to identify publications of clinical trials that compared the decreasing or inhibiting effects of different biology-based methods over OTM in humans. A primary outcome (rate of OTM deceleration/inhibition) and a number of secondary outcomes were examined (clinical applicability, orthodontic force used, possible side effects). Two reviewers selected the studies complying with the eligibility criteria (PICO format) and assessed risk of bias [Cochrane Collaboration's tool]. Data collection and analysis were performed following the Cochrane recommendations.

RESULTS

From the initial electronic search, 3726 articles were retrieved and 5 studies were finally included. Two types of biology-based techniques used to reduce the rate of OTM in humans were described: pharmacological and low-level laser therapy. In the first group, human Relaxin was compared to a placebo and administered orally. It was described as having no effect on the inhibition of OTM in humans after 32 days, while the drug tenoxicam, injected locally, inhibited the rate of OTM by up to 10% in humans after 42 days. In the second group, no statistically significant differences were reported, compared to placebo, for the rate of inhibition of OTM in humans after 90 days of observation when a 860 nm continuous wave GaAlA slow-level laser was used.

CONCLUSIONS

The currently available data do not allow us to draw definitive conclusions about the use of various pharmacological substances and biology-based therapies in humans able to inhibit or decrease the OTM rate. There is an urgent need for more sound well-designed randomized clinical trials in the field.

Zoledronic acid and alendronate sodium and the implications in orthodontic movement

OBJECTIVE

To evaluate orthodontic tooth movement (OTM) in rats treated with two types of bisphosphonates (BPs), alendronate sodium (A) and zoledronic acid (Z).

DESIGN

In all, 15 male Wistar rats were randomly divided into three groups. Group OTM+A: orthodontic tooth movement and subcutaneous administration of alendronate sodium (2.5 mg/kg); Group OTM+Z: orthodontic tooth movement and subcutaneous administration of zoledronic acid (0.02 mg/kg), and Group OTM: orthodontic tooth movement and subcutaneous injection of saline. The BPs were administered once a day during 25 days before OTM started and during 10 days of OTM. The left upper first molar was moved with a stainless-steel closed coil spring which delivered an initial force of 0.4N. OTM was measured with a digital caliper comparing the moved and the contralateral side. The histomorphometric analysis counted the number of osteoclasts, inflammatory cells, blood vessels and fibroblasts (n/10⁴  m² ) in periodontal ligament (PDL) of the distobuccal root.

RESULTS

A reduction of 58.3% of OTM was found in Group OTM+A and 99.6% in Group OTM+Z, when compared with Group OTM. There was a significant decrease of osteoclasts and inflammatory cells in BP-treated groups. Blood vessels and fibroblastic cells decreased mainly in Group OTM+Z.

CONCLUSION

Alendronate sodium and zoledronic acid have similar effects on the periodontal tissue during orthodontic treatment in rats. Especially, zoledronic acid can affect orthodontic tooth movement.

Effectiveness of biologic methods of inhibiting orthodontic tooth movement in animal studies

INTRODUCTION

A number of biologic methods leading to decreased rates of orthodontic tooth movement (OTM) can be found in the recent literature. The aim of this systematic review was to provide an overview of biologic methods and their effects on OTM inhibition.

METHODS

An electronic search was performed up to January 2016. Two researchers independently selected the studies (kappa index, 0.8) using the selection criteria established in the PRISMA statement. The methodologic quality of the articles was assessed objectively according to the Methodological Index for Non-Randomized Studies scale.

RESULTS

We retrieved 861 articles in the initial electronic search, and 57 were finally analyzed. Three biologic techniques were identified as reducing the rate of OTM: chemical methods, low-level laser therapy, and gene therapy. When the experimental objective was to slow down OTM, pharmacologic modulation was the most frequently described method (53 articles). Rats were the most frequent model (38 of 57 articles), followed by mice (9 of 57), rabbits (4 of 57), guinea pigs (2 of 57), dogs (2 of 57), cats (1 of 57), and monkeys (1 of 57). The sample sizes seldom exceeded 25 subjects per group (6 of 57 articles). The application protocols, quality, and effectiveness of the different biologic methods in reducing OTM varied widely.

CONCLUSIONS

OTM inhibition was experimentally tested with various biologic methods that were notably effective at bench scale, although their clinical applicability to humans was rarely tested further. Rigorous randomized clinical trials are therefore needed to allow the orthodontist to improve the effect of translating them from bench to clinic.

RANKL release from self-assembling nanofiber hydrogels for inducing osteoclastogenesis in vitro

PURPOSE

To develop a nanofiber hydrogel (NF-hydrogel) for sustained and controlled release of the recombinant receptor activator of NF-kB ligand; (RANKL) and to characterize the release kinetics and bioactivity of the released RANKL.

METHODS

Various concentrations of fluorescently-labelled RANKL protein were added to NF-hydrogels, composed of Acetyl-(Arg-Ala-Asp-Ala)₄-CONH₂ [(RADA)₄] of different concentrations, to investigate the resulting in vitro release rates. The nano-structures of NF-hydrogel, with and without RANKL, were determined using atomic force microscopy (AFM). Released RANKL was further analyzed for changes in secondary and tertiary structure using CD spectroscopy and fluorescent emission spectroscopy, respectively. Bioactivity of released RANKL protein was determined using NFATc1 gene expression and tartrate resistant acid phosphatase (TRAP) activity of osteoclast cells as biomarkers.

RESULTS

NF-hydrogel concentration dependent sustained release of RANKL protein was measured at concentrations between 0.5 and 2%(w/v). NF-hydrogel at 2%(w/v) concentration exhibited a sustained and slow-release of RANKL protein up to 48h. Secondary and tertiary structure analyses confirmed no changes to the RANKL protein released from NF-hydrogel in comparison to native RANKL. The results of NFATc1 gene mRNA expression and TRAP activities of osteoclast, showed that the release process did not affect the bioactivity of released RANKL.

CONCLUSIONS

This novel study is the first of its kind to attempt in vitro characterization of NF-hydrogel based delivery of RANKL protein to induce osteoclastogenesis. We have shown the self-assembling NF-hydrogel peptide system is amenable to the sustained and controlled release of RANKL locally; that could in turn increase local concentration of RANKL to induce osteoclastogenesis, for application to the controlled mobilization of tooth movement in orthodontic procedures.

STATEMENT OF SIGNIFICANCE

Orthodontic tooth movement (OTM) occurs through controlled application of light forces to teeth, facilitating the required changes in the surrounding alveolar bone through the process of bone remodelling. The RANKL system regulates alveolar bone remodelling and controls root resorption during OTM. The use of exogenous RANKL to accelerate OTM has not been attempted to date because large quantities of RANKL for systemic therapy may subsequently cause serious systemic loss of skeletal bone. The controlled and sustained local release of RANKL from a carrier matrix could maximize its therapeutic benefit whilst minimizing systemic side effects. In this study a NF-hydrogel was used for sustained and controlled release of RANKL and the release kinetics and biofunctionality of the released RANKL was characterized. Our results provide fundamental insight for further investigating the role of RANKL NF-hydrogel release systems for inducing osteoclastogenesis in vivo.

MicroRNA-503-5p inhibits stretch-induced osteogenic differentiation and bone formation

Cyclical stretch-induced bone formation during orthodontic treatment is a complex biological process modulated by various factors including miRNAs and their targeted-gene network. However, the miRNA expression profile and their roles in osteogenic differentiation of bone mesenchymal stem cells (BMSCs) exposed to mechanical stretch remains unclear. Here, we use the miRNA microarray assay to screen for mechano-sensitive miRNAs during stretch-induced osteogenic differentiation of BMSCs and identified that nine miRNAs were differentially expressed between stretched and control BMSCs. Furthermore, miR-503-5p, which was markedly downregulated in both microarray assay and qRT-PCR assay were selected for further functional verification. We found that overexpression of miR-503-5p in BMSCs attenuated stretch-induced osteogenic differentiation while the effect was reversed by miR-503-5p inhibition treatment. In vivo studies, overexpression of miR-503-5p with specific agomir decreased Runx2, ALP mRNA, and protein expression, decreased osteoblast numbers and osteoblastic bone formation in the OTM tension sides. In conclusion, our study revealed that miR-503-5p functions as the mechano-sensitive miRNA and inhibits BMSCs osteogenic differentiation subjected to mechanical stretch and bone formation in OTM tension sides.

3-D localization of non-radioactive strontium in osteoarthritic bone: Role in the dynamic labeling of bone pathological changes

The study objective was to visualize regions of bone that undergo pathological mineralization and/or remodeling during pathogenesis of osteoarthritis, by employing non-radioactive strontium as a dynamic tracer of bone turnover. Post traumatic osteoarthritis was surgically induced in skeletally mature rats, followed by in vivo micro-CT imaging for 12 weeks to assess bone micro-structural changes. Rats either received strontium ranelate daily for the entire course of study or only last 10 days before euthanization. Distribution of strontium in bone was assessed in two and three dimensions, using electron probe micro-analysis (EPMA) and synchrotron dual energy K-edge subtraction micro-CT (SRμCT), respectively. Considerable early formation of osteophytes around the collateral ligament attachments and margins of articulating surfaces were observed, followed by subchondral sclerosis at the later stages. Accordingly, strontium was heavily incorporated by mineralizing osteophytes at 4, 8, and 12 weeks post-surgery, whereas subchondral bone only incorporated strontium between weeks 8-12.This study showed low dose stable strontium can effectively serve as a dynamic tracer of bone turnover to study pathological bone micro-structural changes, at resolution higher than nuclear medicine. Co-administration of strontium during therapeutic drug intervention may show enormous utility in assessing the efficacy of those compounds upon adaptive bone physiology.

Osteoprotegerin and zoledronate bone effects during orthodontic tooth movement

OBJECTIVES

To assess the effects of local delivery of recombinant fusion protein osteoprotegerin (OPG-Fc) and bisphosphonate zoledronate on bone and periodontal ligament in a rat tooth movement model.

MATERIALS AND METHODS

Maxillary first molars of 36 male Sprague-Dawley rats were displaced mesially using a calibrated spring connected to an anterior mini-screw. Two different drugs were used: a single dose of Zoledronate (16 μg) and a twice-weekly dose of OPG-Fc (5.0 mg/kg) were injected. Tooth movement was measured on scanned plaster casts. Structural and immunohistochemical analysis of the orthodontic-induced changes in bone included receptor activator of nuclear factor ĸ (RANK), Runx, type 1 collagen, matrix metalloproteinases (MMPs) 2 and 9, tissue inhibitors of metalloproteinases (TIMPs) 1 and 2, and vimentin.

RESULTS

Both groups showed a reduction in mesial molar displacement. Animals receiving OPG-Fc demonstrated only 52%, 31%, and 21% of the total mesial molar displacement compared to control rats at 7, 14, and 21 days, respectively (*p < 0.001). For rats receiving zoledronate tooth displacement decreased significantly with 52%, 46% and 30%, respectively (*p < 0.001). At 14 and 21 days, OPG-Fc group showed significantly less molar displacement than the zoledronate group (*p < 0.001). RANK, Runx, vimentin, MMP-9 and tissues-inhibitor metalloproteinase 1 immunoreactivity were reduced in zoledronate treated animals and even more in OPG treated animals.

CONCLUSION

Local delivery of OPG-Fc or zoledronate inhibits bone resorption and therefore tooth movement. OPG-Fc was more effective than zoledronate in blocking the action of osteoclasts.

Experimental evidence of pharmacological management of anchorage in Orthodontics: A systematic review

INTRODUCTION

Orthodontic anchorage is one of the most challenging aspects of Orthodontics. Preventing undesired movement of teeth could result in safer and less complicated orthodontic treatment. Recently, several reviews have been published about the effects of different molecules on bone physiology and the clinical side effects in Orthodontics. However, the effects of local application of these substances on the rate of orthodontic tooth movement have not been assessed.

OBJECTIVES

The aim of this research was to analyze the scientific evidence published in the literature about the effects of different molecules on orthodontic anchorage.

METHODS

The literature was systematically reviewed using PubMed/Medline, Scopus and Cochrane databases from 2000 up to July 31st, 2014. Articles were independently selected by two different researchers based on previously established inclusion and exclusion criteria, with a concordance Kappa index of 0.86. The methodological quality of the reviewed papers was performed.

RESULTS

Search strategy identified 270 articles. Twenty-five of them were selected after application of inclusion/exclusion criteria, and only 11 qualified for final analysis. Molecules involved in orthodontic anchorage were divided into three main groups: osteoprotegerin (OPG), bisphosphonates (BPs) and other molecules (OMs).

CONCLUSIONS

Different drugs are able to alter the bone remodeling cycle, influencing osteoclast function and, therefore, tooth movement. Thus, they could be used in order to provide maximal anchorage while preventing undesired movements. OPG was found the most effective molecule in blocking the action of osteoclasts, thereby reducing undesired movements.

Recombinant osteoprotegerin effects during orthodontic movement in a rat model

BACKGROUND AND OBJECTIVES

Anchorage is one of the most challenging sides in orthodontics. The use of biological modulators that inhibit osteoclasts could be a solution to address these problems and provide new adjunctive approaches. The aim of this study was to assess the effectiveness of recombinant osteoprotegerin fusion protein (OPG-Fc) in orthodontic anchorage.

MATERIALS AND METHODS

Two groups of male Sprague-Dawley rats were utilized. The animals in the experimental group received twice-weekly injections with high dose of OPG-Fc (5.0mg/kg) in mesial and distal mucosa of the first molars, and those in the control group received no drugs. Right first maxillary molars were mesialized using a calibrated nickel-titanium spring connected to an anterior mini-screw. Tooth movement was measured by two blinded observers using scanned and magnified stone casts. Receptor activator of nuclear factor κB (RANK), run-related transcription factor 2 (Runx2), type I collagen, vimentin, matrix metalloproteinases 2 and 9, S100 protein and the putative mechanoproteins acid-sensing ion channel (ASIC2) and transient receptor potential vainilloid 4 (TRPV4) were evaluated using immunohistochemistry.

RESULTS

OPG-Fc group showed an important decreased in mesial molar movement with only 52%, 31%, and 22% of the total mesial molar movement compared with control group at Days 7, 14, and 21, respectively (P < 0.001). RANK ligand and Runx2 positive cells were severely reduced after OPG-Fc treatment. Periodontal ligament architecture, cell arrangement, and immunohistochemical patter for vimentin, type I collagen and the mechanoproteins TRPV4 and ASIC2 were altered by tooth movement and all these parameters altered by the applied treatment.

CONCLUSIONS

OPG-Fc effectively inhibits osteoclastogenesis resulting in improved bone quantity and orthodontic anchorage. Based on present results, OPG-Fc could have clinical utility in preventing undesired tooth movements.

Nrf2 activation attenuates both orthodontic tooth movement and relapse

During orthodontic tooth movement, osteoclasts resorb the alveolar bone at the compress side of periodontium. Reactive oxygen species (ROS) works as intracellular signaling molecules of RANKL during osteoclastogenesis, although ROS has cytotoxicity against cells such as lipid oxidation. To deal with oxidative stress, cells have a defense system that is scavenging ROS by augmented antioxidative stress enzymes via transcriptional regulation with nuclear factor E2-related factor 2 (Nrf2). Previously, we reported that augmented antioxidative stress enzymes by Nrf2-gene transfer inhibited bone destruction. In the present study, we examined the effects of Nrf2 activation on osteoclastogenesis and, thereby, orthodontic tooth movement and orthodontic relapse. Mouse macrophage cell line RAW264.7 cells were used as osteoclast progenitor cells and stimulated with recombinant RANKL (100 ng/mL) with or without Nrf2 activator sulforaphane (SFN) and epigallocatechin gallate (EGCG) or ROS scavenger catechin. Osteoclastogenesis, resorption activity, and osteoclast marker gene expression were examined. Intracellular ROS was analyzed by flow cytometry. Maxillary first molars of C57BL6 male mice were moved palatally with 0.012-inch NiTi wire (100-mN force); SFN or EGCG was injected into the palatal gingiva once a week; and phosphate buffered saline was injected on the contralateral side. Tooth movement was monitored using a stone model with precise impression, and the amount of the tooth movement was compared among groups. SFN and EGCG significantly, but catechin weakly, inhibited RANKL-mediated osteoclastogenesis in vitro. Western blot analysis revealed that SFN and EGCG augmented the nuclear translocation of Nrf2 and the expression of anti-oxidative stress enzymes such as HO-1, although catechin did not. SFN and EGCG significantly, but catechin weakly, attenuated the intracellular ROS. Finally, animal experiment revealed that both SFN and EGCG successfully inhibited the orthodontic tooth movement. Additionally, SFN inhibited the relapse. These results suggest that Nrf2 activation could be therapeutic target for the anchorage enforcement in orthodontic treatment and pharmacologic retention against relapse.

Administration of bisphosphonate (ibandronate) impedes molar tooth movement in rabbits: A radiographic assessment

Introduction:

Bisphosphonate (Bp)-ibandronate is a pharmacological agent, exhibits antiosteoclastic or antiresorptive activity and used to treat osteolytic or osteopenic disorders. BP-ibandronate may also interfere during orthodontic tooth movement. The aim of this study was to examine the influence of locally administered Bp-ibandronate on experimental tooth movement in rabbits.

Materials and Methods:

Twenty rabbits were divided into two groups- “10” served as Group-1 (control) and other “10” as Group-2 (experimental). Both groups received nickel-titanium closed coil springs with 100 g force between mandibular molar and incisors. Group-1 animals received 1 ml normal saline and Group-2 animals received ibandronate solution (0.3 mg/kg body weight) locally, mesial to the mandibular molar on the 1^st, 7^th, and 14^th day of the experiment. A total of “40” lateral cephalograms were taken from both groups on the 1^st and 21^st day using a digital X-ray unit (Siemens X-ray systems, 300 mA Pleomophos analog, 2008, Germany). Individually, each animal's radiograph was traced manually and superimposed. The molar tooth movement was measured with the help of a standard metric scale.

Results:

The Student's t-test has been done to compare the mean values of Group-1 (4.650 ± 0.363) and Group-2 (2.030 ± 0.291) and the difference was statistically significant (P < 0.001).

Conclusion:

The retarded molar tooth movement was noticed in local drug administered rabbits, which could be beneficial in orthodontics to control the undesired tooth movement.

Mechanical loading influences the effects of bisphosphonates on human periodontal ligament fibroblasts

OBJECTIVES

There is increasing evidence that bisphosphonates affect orthodontic tooth movement. The object of the study was to investigate the changes produced by tensile strain on human periodontal ligament fibroblasts (HPdLFs) treated with clodronate or zoledronate.

MATERIALS AND METHODS

HPdLF were cultured with 5 and 50 μM clodronate or zoledronate for 48 h and applied to tensile strain (TS) (5 and 10 %) for 12 h in vitro. Viability was verified by MTT assay and apoptosis rate via caspase 3/7 assay. Gene expression of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) was investigated using real-time PCR. OPG was also analyzed by ELISA and RANKL by immunocytochemical staining.

RESULTS

Zoledronate (50 μM) reduced the viability of HPdLF (76 vs 100 %) and combined with 5 % TS to 53 %. TS of 10 % and clodronate reduced viability to 79 % with increased caspase 3/7 activity. Clodronate (5 μM) led to a slight increase of OPG gene expression, zoledronate (5 μM) to a slight decrease. Combined with 5 % TS, both increased OPG gene expression (2-3-fold) and OPG synthesis. Zoledronate increased gene expression of RANKL (4-fold). Combined with 5 % of TS, this increase was abolished. TS of 10 % in combination amplified increase of RANKL ending up with a 9-fold gene expression by clodronate and high RANKL protein synthesis.

CONCLUSIONS

This study shows for the first time that mechanical loading alters the effects of bisphosphonates on viability, apoptosis rate, and OPG/RANKL system of HPdLF dependent on the applied strength. Low forces and bisphosphonates increase factors for bone apposition, whereas high forces combined with bisphosphonates stimulate osteoclastogenesis.

CLINICAL RELEVANCE

Mechanical loading of periodontal ligament with high strengths should be avoided during bisphosphonate therapy.