Immunolocalization of FGF-2 and VEGF in rat periodontal ligament during experimental tooth movement

Pulsed electromagnetic field prevents tooth relapse after orthodontic tooth movement in rat models

Objective

Relapse after orthodontic treatment remains a crucial problem. Pulsed electromagnetic fields (PEMFs) accelerate osteoblastogenesis and inhibit osteoclastogenesis. However, their effect on tooth movement during the retention phase of orthodontic treatment has not been studied. This study investigated the role of PEMF stimulation in preventing tooth relapse after orthodontic tooth movement (OTM) in rat models.

Methods

Thirty-six male Wistar rats were divided into control, PEMF 7, and PEMF 14 groups. The maxillary first molar was moved mesially with a 50 g force of a Nickel Titanium closed coil spring for 21 days. Therefore, PEMF stimulations, including a frequency of 15 Hz and intensity of 2.0 mT, were applied to a retention phase for 2 h daily for 7 and 14 days. The tooth relapse distance was evaluated on days 1, 3, 7, and 14; the number of osteoblasts, osteoclasts, and fibroblasts was assessed by hematoxylin and eosin staining; and the expression of fibroblast growth factor 2 (FGF-2) and type I collagen (Col-I) was evaluated by immunohistochemistry. The data were analyzed using one-way analysis of variance and post hoc test with p < 0.05 considered statistically significant.

Results

Tooth relapse distance was significantly decreased in the PEMF 7 and PEMF 14 groups compared to the control group. A significant increase was detected in osteoblasts, fibroblasts, FGF-2, and Col-I in both PEMF groups, while osteoclasts decreased (p < 0.05).

Conclusion

The reduction of tooth relapse could be attributed to PEMF stimulation for 7 and 14 days by accelerating alveolar bone formation and periodontal ligament remodeling.

The effect of cacao bean extracts on the prevention of periodontal tissue breakdown in diabetic rats with orthodontic tooth movements

Objective

Proper management of orthodontic treatment in diabetic patients is essential due to the heightened risk of periodontal tissue breakdown associated with hyperglycemia. Cacao bean extracts (CBE) are known to reduce the inflammatory response and increase synthesis and angiogenesis in periodontitis. Therefore, this study aims to examine the effect of CBE on preventing periodontal tissue breakdown in diabetes with orthodontic force.

Methods

A total of 25 Wistar rats were divided randomly into 5 groups, including non-diabetes, diabetes, diabetes cacao 125, 250, and 500 mg/kg BW. Diabetic rats were induced with the stratified dose of Streptozotocin, and a 30-g-force from orthodontic device was applied in all groups. Diabetes cacao group was given CBE for 7 days using a gastric probe. GCF samples were used to analyze the eNOS level through the ELISA method. NFκB, Collagen-1, and FGF-2 expression were then assessed using the immunohistochemical method, while the number of fibroblasts and blood vessels was observed using hematoxylin-eosin stained tissue. The data obtained were analyzed with one-way ANOVA and post hoc tests, with p < 0.05.

Results

CBE at a dose of 250 mg/kg BW significantly increased eNOS level, Collagen-1, and FGF-2 expression, and the number of fibroblasts and blood vessels in diabetes groups. Meanwhile, the treatment decreased NFκB expression in diabetes groups (p < 0.05).

Conclusion

This study proved that CBE increased periodontal ligament synthesis and angiogenesis and decreased inflammatory response, thereby preventing periodontal tissue breakdown in diabetic rat models with tooth movement.

The number of osteoblasts and osteoclasts in hypofunctional teeth during orthodontic tooth movement in rats

Background: When moved orthodontically, hypofunctional teeth will have a decreased tooth movement rate compared to normal teeth. This study aimed to determine the number of osteoblasts in the tension side and the number of osteoclasts in the pressure side of the hypofunctional teeth during orthodontic tooth movement. Method: 18 male Wistar rats were given a palatal coil spring application on the maxillary incisors. Rats were divided into two groups, the orthodontic group with normal occlusion (NO) and hypofunctional occlusion (HO). The number of osteoblasts on the tension side and osteoclasts on the pressure side on days zero (D 0), five (D 5), and 10 (D 10) were tested with two-way ANOVA. Observations were made by hematoxylin eosin staining. Result: The results showed that the number of osteoblasts on the tension side of the HO group was the same at the NO group (p> 0.05). The number of osteoblasts on the tension side in the NO and HO groups at D 5 was the same at D 10 (p = 0.99), but significantly higher (p = 0.002), than D 0. The number of osteoclasts on the pressure side in the HO group was significantly lower than the NO group (p <0.05). The number of osteoclasts in the NO D 5 group was significantly higher than the other groups (p <0.05). Conclusions: The number of osteoblasts on the tension side was not affected by the hypofunctional state but decreased the number of osteoclasts on the pressure side during orthodontic tooth movement.

Monitoring Salivary Levels of Interleukin 1 Beta (IL-1β) and Vascular Endothelial Growth Factor (VEGF) for Two Years of Orthodontic Treatment: A Prospective Pilot Study

Results

A gradual increase in IL-1β and VEGF was observed at alignment, reaching significance at space closure (p = 0.002 and p = 0.025, respectively). At finishing, both IL-1β and VEGF declined, however, without reverting to baseline values (p = 0.172 and p = 0.207, respectively). Bland-Altman analysis showed the agreement between IL-1β and VEGF in terms of a systematic increase, with a higher percentage difference for VEGF.

Conclusions

The salivary levels of both IL-1β and VEGF increased following orthodontic treatment and reached their peaks during the treatment stage of space closure. This novel approach provides a hint on how and when to sample saliva during orthodontic treatment to analyse bone remodelling.

Effect of Caffeic Acid Phenethyl Ester Provision on Fibroblast Growth Factor-2, Matrix Metalloproteinase-9 Expression, Osteoclast and Osteoblast Numbers during Experimental Tooth Movement in Wistar Rats (Rattus norvegicus)

Objectives  To investigate the effect of caffeic acid phenethyl ester (CAPE) provision on matrix metalloproteinase-9 (MMP-9), fibroblast growth factor-2 (FGF-2) expression, osteoclast and osteoblast numbers during experimental orthodontic tooth movement (OTM) in male Wistar rats ( Rattus norvegicus ).

Materials and Methods  Forty-eight healthy male Wistar rats ( R. norvegicus ), 16 to 20 weeks old with 200 to 250 g body weight (bw) were divided into several groups as follows: K1: OTM for 3 days; K2: OTM for 7 days; K3: OTM for 14 days; KP1: OTM and CAPE for 3 days; KP2: OTM and CAPE for 7 days; and KP3: OTM and CAPE for 14 days. A nickel titanium closed coil spring 8.0 mm long with 10 g/mm ² was installed between the upper left first molar and upper central incisor to move molar mesially. CAPE provision with a dose of 20 mg/kg bw of animal studies was done per orally. Immunohistochemistry was done to examine MMP-9 expression and osteoclast number in compression side as well as FGF-2 expression and osteoblast number in tensile side of the OTM.

Statistical Analysis  One-way analysis of variance test and Tukey’s honest significant difference test were performed to determine the difference between the groups ( p < 0.05).

Results  MMP-9 expression and osteoclast numbers in the compression side were significantly different between the groups. Similarly, FGF-2 expression and osteoclast numbers in the tensile side were significantly different between the groups.

Conclusions  CAPE provision during OTM increases the number of osteoblasts and the FGF-2 expression significantly in the tensile side. Osteoclast numbers and MMP-9 expression significantly decrease in the compression side.

TGF-β-induced activation of conjunctival fibroblasts is modulated by FGF-2 and substratum stiffness

Purpose

This study aimed to investigate the effects of substratum stiffness on the sensitivity of human conjunctival fibroblasts to transforming growth factor (TGF)-β, and to explore the molecular mechanism of action.

Methods

Human conjunctival fibroblasts were cultured on collagen-coated plastic or silicone plates. The stiffness of the silicone plates was 0.2 or 64 kPa. Cells were treated by 2.5 ng/mL TGF-β2 with or without fibroblast growth factor (FGF)-2 (0–100 ng/mL) for 24 h or 48 h. The protein expression levels were determined by Western blot analysis. Cell proliferation was assessed using the WST-8 assay.

Results

FGF-2 suppressed the TGF-β-induced expression of α-smooth muscle actin (SMA) and collagen type I (Col I), but not fibronectin (FN). Both FGF-2 and TGF-β2 increased cell proliferation without an additive effect. The induction of α-SMA by TGF-β2 was decreased on the soft substratum, without any change in the expression level or subcellular location of Yes-associated protein/transcriptional coactivator with PDZ-binding motif (YAP/TAZ). FGF-2 suppressed TGF-β-induced α-SMA expression even on the soft substratum.

Conclusions

FGF-2 treatment and a soft substratum suppressed TGF-β-induced transdifferentiation of conjunctival fibroblasts into myofibroblasts. FGF-2 attenuated the TGF-β-induced expression of α-SMA, even on a soft substratum.

Human Dental Pulp Tissue during Orthodontic Tooth Movement: An Immunofluorescence Study

The orthodontic tooth movement is the last step of several biological processes that take place after the application of external forces. During this process, dental pulp tissue is subjected to structural and protein expression modifications in order to maintain their integrity and functional morphology. The purpose of the present work was to perform an in vivo study, evaluating protein expression modifications in the human dental pulp of patients that have undergone orthodontic tooth movement due to pre-calibrated light force application for 30 days. Dental pulp samples were extracted from molars and premolars of the control group and after 7 and 30 days of treatment; the samples were then processed for immunofluorescence reactions using antibodies against fibronectin, collagen I and vascular endothelial growth factor (VEGF). Our results show that, after 7 days of treatment, all tested proteins change their pattern expression and will reset after 30 days. These data demonstrate that the dental pulp does not involve any irreversible iatrogenic alterations, supporting the efficacy and safety of using pre-calibrated force application to induce orthodontic tooth movement in clinical practice.

An immunofluorescence study on VEGF and extracellular matrix proteins in human periodontal ligament during tooth movement

The periodontal ligament (PDL) is a highly vascularized connective tissue surrounding the root of a tooth. In particular, the PDL is continuously exposed to mechanical stresses during the phases of mastication, and it provides physical, sensory, and trophic functions. It is known that the application of orthodontic force creates a change in periodontal structures. In fact, these forces generate a pressure on the ligament that closes the vessels. The aim of this study is to observe the modifications of vascular endothelial growth factor (VEGF) in the PDL and extracellular matrix proteins after application of a pre-calibrated and constant orthodontic force at different phases of treatment. We used a 50-g NiTi coiled spring and in vivo samples of PDL of maxillary and mandibular premolars of patients subjected to orthodontic treatment. These teeth were extracted at 1, 7, 14, 21, and 30 days, respectively, by application of force. The extraction of the PDL was effectuated by scarifying the radicular surface on the pressure and tension sides. The mechanical stress induced by the application of force caused an increase in the reactive type of metabolism of extracellular matrix proteins and modulation of neoangiogenesis until restoration.

Expression of biological mediators during orthodontic tooth movement: A systematic review

OBJECTIVES

The aim of the present systematic review was to offer a timeline of the events taking place during orthodontic tooth movement(OTM).

MATERIALS AND METHODS

Electronic databases PubMed, Web of Science and EMBASE were searched up to November 2017. All studies describing the expression of signaling proteins in the periodontal ligament(PDL) of teeth subjected to OTM or describing the expression of signaling proteins in human cells of the periodontal structures subjected to static mechanical loading were considered eligible for inclusion for respectively the in-vivo or the in-vitro part. Risk of bias assessment was conducted according to the validated SYRCLE's RoB tool for animal studies and guideline for assessing quality of in-vitro studies for in-vitro studies.

RESULTS

We retrieved 7583 articles in the initial electronic search, from which 79 and 51 were finally analyzed. From the 139 protein investigated, only the inflammatory proteins interleukin(IL)-1β, cyclooxygenase(COX)-2 and prostaglandin(PG)-E2, osteoblast markers osteocalcin and runt-related transcription factor(RUNX)2, receptor activator of nuclear factor kappa-B ligand(RANKL) and osteoprotegerin(OPG) and extracellular signal-regulated kinases(ERK)1/2 are investigated in 10 or more studies.

CONCLUSION

The investigated proteins were presented in a theoretical model of OTM. We can conclude that the cell activation and differentiation and recruitment of osteoclasts is mediated by osteocytes, osteoblasts and PDL cells, but that the osteogenic differentiation is only seen in stem cell present in the PDL. In addition, the recently discovered Ephrin/Ephs seem to play an role parallel with the thoroughly investigated RANKL/OPG system in mediating bone resorption during OTM.

MicroRNA-195-5p Regulates Osteogenic Differentiation of Periodontal Ligament Cells Under Mechanical Loading

Osteogenic differentiation and bone formation are tightly regulated by several factors, including microRNAs (miRNAs). However, miRNA expression patterns and function during mechanical loading-induced osteogenic differentiation of human periodontal ligament cells (PDLCs) remain unclear. Here, we investigated the differential expression of miRNA-195-5p in the periodontal tissues of mice under orthodontic mechanical loading and in primary human PDLCs exposed to a simulated tension strain. The miR-195-5p was observed to be down-regulated and negatively correlated with osteogenic differentiation. Overexpression of miR-195-5p significantly inhibited PDLC differentiation under cyclic tension strain (CTS), whereas the functional inhibition of miR-195-5p yielded an opposite effect. Further experiments confirmed that WNT family member 3A (WNT3A), fibroblast growth factor 2 (FGF2), and bone morphogenetic protein receptor-1A (BMPR1A), proteins important for osteogenic activity and stability, were direct targets of miR-195-5p. Mechanical loading increased the WNT3A, FGF2, and BMPR1A protein levels, while miR-195-5p inhibited WNT3A, FGF2, and BMPR1A protein expression. WNT, FGF, and BMP signaling were involved in osteogenic differentiation of PDLCs under CTS. Further study confirmed that reintroduction of WNT3A and BMPR1A can rescue the inhibition of miR-195-5p on osteogenic differentiation of PDLCs. Our findings are the first to demonstrate that miR-195-5p is a mechanosensitive gene that plays an important role in mechanical loading-induced osteogenic differentiation and bone formation.

Orthodontic tensile strain induces angiogenesis via type IV collagen degradation by matrix metalloproteinase-12

BACKGROUND AND OBJECTIVE

During orthodontic tooth movement (OTM), periodontal ligament (PDL) is remodeled dynamically, which requires sufficient blood supply for the regeneration of PDL. However, little is known about the remodeling of blood vessels during OTM. In this study, we hypothesized that the orthodontic tensile strain upregulates matrix metalloproteinase-12 (MMP-12) expression in the tension zone and induces angiogenesis via degradation of type IV collagen (Col-IV) in vascular endothelial basement membrane during the early stage of OTM.

MATERIAL AND METHODS

Temporal and spatial MMP-12 expression in the tension zone of PDL, during the early stage of OTM, were examined by immunohistochemistry in rats. Continuous tensile strain was applied to cultured human immortalized PDL cell lines (HPL cells) and MMP-12 expression was examined in vitro. Colocalization of MMP-12 and Col-IV in vivo were examined by immunohistochemistry. To investigate whether MMP-12 produced by HPL cells could degrade Col-IV, recombinant Col-IV was incubated in the culture supernatants of HPL cells. Intact Col-IV in vitro was also examined by western blot analysis. Finally, the changes in blood vessels in the PDL were examined by micro-computed tomography analysis with perfused contrast agents and by conventional histological analysis.

RESULTS

Orthodontic tensile strain induced MMP-12 expression in PDL cells in vivo and in vitro. Immunohistochemistry revealed that MMP-12-positive cells were observed adjacent to the Col-IV-positive tubular area in the tension zone of PDL. MMP-12 in culture supernatant of HPL cells degraded recombinant Col-IV, and specific MMP-12 inhibitor blocked the Col-IV degradation. Micro-computed tomography analysis and conventional histological analysis demonstrated that the areas of blood vessels were increased in the tension zone of the PDL after OTM.

CONCLUSION

We discovered that the orthodontic tensile strain upregulates MMP-12 expression in the tension zone of PDL and induces angiogenesis via degradation of Col-IV in the vascular endothelial basement membrane.

PLAP-1/Asporin Positively Regulates FGF-2 Activity

PLAP-1 is an extracellular matrix protein that is predominantly expressed in the periodontal ligament within periodontal tissue. It was previously revealed that PLAP-1 negatively regulates bone morphogenetic protein 2 and transforming growth factor β activity through direct interactions. However, the interaction between PLAP-1 and other growth factors has not been defined. Here, we revealed that PLAP-1 positively regulates the activity of fibroblast growth factor 2 (FGF-2), a critical growth factor in tissue homeostasis and repair. In this study, we isolated mouse embryonic fibroblasts (MEFs) from Plap-1(-/-) mice generated in our laboratory. Interestingly, Plap-1(-/-) MEFs exhibited enhanced responses to bone morphogenetic protein 2 but defective responses to FGF-2, and Plap-1 transfection into Plap-1(-/-) MEFs rescued these defective responses. In addition, binding assays revealed that PLAP-1 promotes FGF-2-FGF receptor 1 (FGFR1) complex formation by direct binding to FGF-2. Immunocytochemistry analyses revealed colocalization of PLAP-1 and FGF-2 in wild-type MEFs and reduced colocalization of FGF-2 and FGFR1 in Plap-1(-/-) MEFs compared with wild-type MEFs. Taken together, PLAP-1 positively regulates FGF-2 activity through a direct interaction. Extracellular matrix-growth factor interactions have considerable effects; thus, this approach may be useful in several regenerative medicine applications.