Storage media enhance osteoclastogenic potential of human periodontal ligament cells via RANKL-independent signaling

The effect of soy and whole milk as a means to store avulsed teeth: A histometric study

BACKGROUND/AIM

An adequate storage medium can help preserve the viability of periodontal ligament cells, favoring the periodontal ligament repair process. The aim of this study was to evaluate the repair process following the delayed replantation of teeth stored in soy milk and whole milk.

MATERIAL AND METHODS

The maxillary right incisors of 27 rats were divided into three equally sized groups: Group SM (delayed replantation with storage in soy milk), whose teeth were immersed in 50 mL of soy milk for 60 minutes; Group WM (delayed replantation with whole milk), teeth were kept for 60 minutes in 50 mL of whole milk; and Group D (delayed replantation with dry storage), teeth were kept in dry conditions for the same period (negative control). Next, the teeth of the animals of all groups were replanted into their sockets. Systemic antibiotics were given to all the animals, and then, they were euthanized after 60 days. Sections were obtained and stained with hematoxylin and eosin for histomorphometric study. The presence and location of acute and chronic inflammatory processes in the epithelial insertion of the protective and insertion periodontium were evaluated, as well as the presence, extension, depth, and repair of root resorption, and the resorption and ankylosis with bone. Statistical differences between groups were analyzed using the Dunn test.

RESULTS

Groups SM and WM showed similar patterns in the repair of the periodontal ligament following delayed replantation, in relation to the inflammatory process in the proximities of the epithelial insertion, inflammation and organization of the periodontal ligament, plus root and bone resorption. However, in group WM, more ankylosis was observed than in group SM.

CONCLUSION

The teeth stored in soy milk and whole milk had similar periodontal repair, which shows the potential of soy milk as a storage medium before tooth replantation.

Engineering of L-Plastin Peptide-Loaded Biodegradable Nanoparticles for Sustained Delivery and Suppression of Osteoclast Function In Vitro

We have recently demonstrated that a small molecular weight amino-terminal peptide of L-plastin (10 amino acids; “MARGSVSDEE”) suppressed the phosphorylation of endogenous L-plastin. Therefore, the formation of nascent sealing zones (NSZs) and bone resorption are reduced. The aim of this study was to develop a biodegradable and biocompatible PLGA nanocarrier that could be loaded with the L-plastin peptide of interest and determine the efficacy in vitro in osteoclast cultures. L-plastin MARGSVSDEE (P1) and scrambled control (P3) peptide-loaded PLGA-PEG nanoparticles (NP1 and NP3, respectively) were synthesized by double emulsion technique. The biological effect of nanoparticles on osteoclasts was evaluated by immunoprecipitation, immunoblotting, rhodamine-phalloidin staining of actin filaments, and pit forming assays. Physical characterization of well-dispersed NP1 and NP3 demonstrated ~130-150 nm size, < 0.07 polydispersity index, ~-3 mV ζ-potential, and a sustained release of the peptide for three weeks. Biological characterization in osteoclast cultures demonstrated the following: NP1 significantly reduced (a) endogenous L-plastin phosphorylation; (b) formation of NSZs and sealing rings; (c) resorption. However, the assembly of podosomes which are critical for cell adhesion was not affected. L-plastin peptide-loaded PLGA-PEG nanocarriers have promising potential for the treatment of diseases associated with bone loss. Future studies will use this sustained release of peptide strategy to systematically suppress osteoclast bone resorption activity in vivo in mouse models demonstrating bone loss.

Effects of the cathepsin K inhibitor with mineral trioxide aggregate cements on osteoclastic activity

Objectives

Root resorption is an unexpected complication after replantation procedures. Combining anti-osteoclastic medicaments with retrograde root filling materials may avert this resorptive activity. The purpose of this study was to assess effects of a cathepsin K inhibitor with calcium silicate-based cements on osteoclastic activity.

Methods

MC3T3-E1 cells were cultured for biocompatibility analyses. RAW 264.7 cells were cultured in the presence of the receptor activator of nuclear factor-kappa B and lipopolysaccharide, followed by treatment with Biodentine (BIOD) or ProRoot MTA with or without medicaments (Odanacatib [ODN], a cathepsin inhibitor and alendronate, a bisphosphonate). After drug treatment, the cell counting kit-8 assay and Alizarin red staining were performed to evaluate biocompatibility in MC3T3-E1 cells. Reverse-transcription polymerase chain reaction, tartrate-resistant acid phosphatase (TRAP) staining and enzyme-linked immunosorbent assays were performed in RAW 264.7 cells to determine the expression levels of inflammatory cytokines, interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and prostaglandin E2 (PGE2). Data were analyzed by one-way analysis of variance and Tukey's post hoc test (p < 0.05).

Results

Biocompatibility results showed that there were no significant differences among any of the groups. RAW 264.7 cells treated with BIOD and ODN showed the lowest levels of TNF-α and PGE2. Treatments with BIOD + ODN were more potent suppressors of inflammatory cytokine expression (p < 0.05).

Conclusion

The cathepsin K inhibitor with calcium silicate-based cement inhibits osteoclastic activity. This may have clinical application in preventing inflammatory root resorption in replanted teeth.

Transcriptional activation of glucose transporter 1 in orthodontic tooth movement-associated mechanical response

The interplay between mechanoresponses and a broad range of fundamental biological processes, such as cell cycle progression, growth and differentiation, has been extensively investigated. However, metabolic regulation in mechanobiology remains largely unexplored. Here, we identified glucose transporter 1 (GLUT1)—the primary glucose transporter in various cells—as a novel mechanosensitive gene in orthodontic tooth movement (OTM). Using an in vivo rat OTM model, we demonstrated the specific induction of Glut1 proteins on the compressive side of a physically strained periodontal ligament. This transcriptional activation could be recapitulated in in vitro cultured human periodontal ligament cells (PDLCs), showing a time- and dose-dependent mechanoresponse. Importantly, application of GLUT1 specific inhibitor WZB117 greatly suppressed the efficiency of orthodontic tooth movement in a mouse OTM model, and this reduction was associated with a decline in osteoclastic activities. A mechanistic study suggested that GLUT1 inhibition affected the receptor activator for nuclear factor-κ B Ligand (RANKL)/osteoprotegerin (OPG) system by impairing compressive force-mediated RANKL upregulation. Consistently, pretreatment of PDLCs with WZB117 severely impeded the osteoclastic differentiation of co-cultured RAW264.7 cells. Further biochemical analysis indicated mutual regulation between GLUT1 and the MEK/ERK cascade to relay potential communication between glucose uptake and mechanical stress response. Together, these cross-species experiments revealed the transcriptional activation of GLUT1 as a novel and conserved linkage between metabolism and bone remodelling.

A glucose-transporting protein is key to helping teeth respond to orthodontic implants, say researchers in China. Implants apply forces to teeth and the periodontal ligament (PDL) that holds them in place, causing bone to grow on one side and be absorbed into the body on the other. Yanheng Zhou and co-workers at Peking University in Beijing showed that GLUT1, a protein that transports glucose through cell membranes, was greatly upregulated in rat, mouse and human PDL cells subjected to mechanical force. They also injected some of the mice with a GLUT1 inhibitor and found that the treatment greatly decreased the distance moved by the teeth. This could be attributed to a decline in the activity of cells that break down bone tissue and a failure in signalling channels when GLUT1 is inhibited.

Efficacy of Hank's balanced salt solution compared to other solutions in the preservation of the periodontal ligament. A systematic review and meta-analysis

This systematic review and meta-analysis (MA) aimed to verify the capacity of different storage media to preserve viability of periodontal ligament cells in comparison to Hank’s Balanced Salt Solution. The searches, selection process, data extraction and Risk of Bias control were conducted according to Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. Five MA were conducted to compare the cell viability between milk versus Hank's balanced salt solution (HBSS) in a dichotomous (1) or continuous (2) data model; tap water versus HBSS (3); medicinal herbals versus HBSS (4); and saline solution versus HBSS (5). 693 potentially studies were identified, with 18 studies included in the qualitative and 8 studies included in the quantitative analysis. Most of the articles presented a low risk of bias. HBSS medium showed a superior ratio of cell viability compared to tap water (RR 0.26; 95% CI [0.21, 0.32]; p < 0.00001; I2 = 96%) and saline solution (RR 0.76; 95% CI [0.69, 0.84]; p < 0.0001; I2 = 99%). Herbal medicines showed a similar ratio of cell viability when compared to HBSS (RR 0.97; 95% CI [0.94, 1.00]; p = 0.08; I² = 50%). Mixed results were observed between milk and HBSS: a superior ratio of HBSS was observed in an overall evaluation (RR 0.26; 95% CI [0.21, 0.32]; p < 0.00001; I² = 96%), and a similar ratio was achieved when periodontal ligament (PDL) cells were removed prior to immersion in the solution (RR 0.94; 95% CI [0.87, 1.01]; p = 0.10; I2 = 0%) or rinsed in tap water or maintained in open air prior to immersion (RR 0.63; 95% CI [0.35, 1.12]; p = 0.11; I2 = not applicable). This systematic review and MA suggests that milk and herbal medicines could represent an alternative to HBSS. However, more studies are necessary to obtain a reliable conclusion.

Effect of propolis on preserving human periodontal ligament cells and regulating pro-inflammatory cytokines

BACKGROUND/AIM

Propolis has been suggested as a storage medium for avulsed teeth. The aim of this study was to compare the effectiveness of Brazilian propolis with Hank's balanced salt solution and milk in maintaining the viability of human periodontal ligament cells, their osteogenic differentiation potential, and pro-inflammatory cytokine expression.

MATERIAL AND METHODS

Cell Counting Kit 8 assays were performed to test human periodontal ligament cell viability in different storage media. The preservative effect on osteogenic differentiation was evaluated using alkaline phosphatase staining and activity assays, Alizarin Red S staining, and western blotting. Quantification of pro-inflammatory cytokines was performed using real-time PCR and enzyme-linked immunosorbent assays.

RESULTS

Brazilian propolis at 10 μg/ml was not cytotoxic toward human periodontal ligament cells. The milk group showed the highest cell viability. Brazilian propolis and Hank's balanced salt solution groups showed similar cell viabilities. Alkaline phosphatase staining and activity were similar in all groups. Calcium deposition and mineralization nodule formation were similar in the Brazilian propolis and Hank's balanced salt solution groups, but were higher in the milk group. Osteogenic marker gene and protein levels were similar in all groups. The genes and protein expression levels of IL1β, IL6, and IL8 decreased significantly after treatment with Brazilian propolis. TNFα mRNA expression showed no significant difference among the experimental groups. Pro-inflammatory cytokine levels in the milk group were higher than in the Brazilian propolis and Hank's balanced salt solution groups.

CONCLUSIONS

Brazilian propolis, Hank's balanced salt solution, and milk maintained the viability of human periodontal ligament cells and preserved their osteogenic differentiation ability similarly. However, Brazilian propolis showed a better anti-inflammatory effect. This article is protected by copyright. All rights reserved.

Histological evaluation of the repair process of replanted rat teeth after storage in resveratrol dissolved in dimethyl sulphoxide

BACKGROUND/AIM

The storage media is directly related to the prognosis of avulsed teeth, with resveratrol drawing attention due to its antioxidant and anti-inflammatory proprieties. The aim of this study was to evaluate the repair process in rat teeth following delayed replantation after storage in resveratrol (R) dissolved in dimethyl sulphoxide (DMSO).

MATERIALS AND METHODS

The upper right central incisors of 36 rats were divided into 4 groups. In group I, the teeth were extracted and immediately replanted. Group II teeth were stored in 50 mL R+DMSO (0.0512 g/mL), whereas group III teeth were stored in 50 mL pure DMSO, both for a period of 60 minutes. The teeth of group IV were stored dry for 60 minutes. The teeth of groups II, III and IV were then replanted, and the animals were euthanized after 60 days. Longitudinal histological cuts were HE stained for histomorphometric analysis of the periodontal ligament, alveolar bone, cementum and dentin.

RESULTS

The analysis of HE stained histological sections showed the following statistical differences: the acute inflammatory process in the epithelial insertion was less prominent in group II than in group III; the organization of the periodontal ligament was better in group I, while the intensity and extension of acute inflammation in the periodontal ligament were better in group I, and worse in group III; the chronic inflammatory infiltrate was less in groups I and IV, and the depth and extent of resorption, as well as the repair of root resorption, were better in group I.

CONCLUSIONS

Storage in R+DMSO solution did not inhibit root resorption after delayed replantation in rat teeth. It is concluded that pure DMSO is not a suitable transport medium for avulsed teeth.

Mechanism of NF-κB signaling pathway and autophagy in the regulation of osteoblast differentiation

OBJECTIVE

The objective of the present work was to investigate a possible mechanism of NF-κB signaling pathway and autophagy in the regulation of osteoblast differentiation, and provide experimental basis for the study of tooth eruption disorder.

METHODS

Mouse osteoblast-like (MC3T3-E1) cells were inoculated with a cell density of 70%. According to the grouping experimental design, Western blot and monodansylcadaverine (MDC) detection were conducted after dosing for 24 h. The cells were divided into the following five groups: blank control group; 6.25 µg/mL SN50 group; 12.5 µg/mL SN50 group; 25 µg/mL SN50 group and 50 µg/mL SN50 group.

RESULTS

Western blot analysis revealed that the expression of LC3 protein was present in the blank control group; 6.25 µg/mL SN50 group; 12.5 µg/mL SN50 group and 50 µg/mL SN50 group, with no significant differences among these groups. However, the expression of LC3 protein was significantly lower in the 25 µg/mL SN50 group. MDC detection showed that, in the blank control group; 6.25 µg/mL SN50 group; 12.5 µg/mL SN50 group and 50 µg/mL SN50 group, there was obvious green fluorescence in the cytoplasm of the osteoblasts. However, in the 25 µg/mL SN50 group, it was found that there were significantly fewer green fluorescent particles.

CONCLUSION

The osteoblast itself had a strong function of autophagy. The appropriate concentration of SN50 in blocking the NF-κB pathway of the osteoblast was associated with the obvious inhibition of autophagy. However, the relationship between NF-κB signaling pathway and autophagy in the process of tooth eruption requires further study.

Histomorphometric analysis of the healing process after the replantation of rat teeth maintained in bovine milk whey and whole milk

BACKGROUND/AIM

In cases of tooth avulsion, a minimal extra-alveolar dry storage period or the use of a suitable storage medium is crucial to maintaining the vitality of the periodontal ligament. Whey has similar properties to milk and has therefore been investigated as a storage medium for avulsed teeth. The aim of this study was to evaluate the repair process after replantation of rat teeth kept in whey and whole milk.

MATERIALS AND METHODS

Thirty-six male rats were divided into four groups of nine animals. The upper right incisor was extracted under general anesthesia. In Group I, the teeth were immediately replanted without treatment (positive control). In Group II, the teeth were stored in 50 mL of sweet whey. In Group III, the teeth were kept in 50 mL of long-shelf-life whole milk (UHT, Parmalat^® ). In Group IV, the teeth were kept dry (negative control). After 60 minutes, the teeth in Groups II, III, and IV were replanted into their sockets. The animals were subjected to euthanasia 60 days after replantation. The specimens were stained with hematoxylin and eosin for histomorphometric analysis.

RESULTS

The organization of the periodontal ligament in Group II (whey) was similar to that in Groups I (immediate replantation) and III (whole milk) (P > .05). However, some specimens in this group exhibited periodontal fibers inserted into the bone and cementum throughout the entire length of the periodontal ligament. This occurred in the group submitted to immediate replantation, whereas this histological aspect was not seen in whole milk group. Group IV (late replantation) had a higher rate of root resorption. Regarding the root repair process, it was expected that Group I (immediate) would demonstrate more favorable repair than the other groups. However, Group III (whole milk) had better results when compared to Groups II (whey) and IV (late) (P < .05).

CONCLUSION

Whey and whole milk achieved similar results and were adequate storage media for avulsed teeth.

Enterococcus faecalis promotes osteoclast differentiation within an osteoblast/osteoclast co-culture system

OBJECTIVE

To investigate the effects of heat-killed Enterococcus faecalis ATCC 29212 and P25RC clinical strain (derived from an obturated root canal with apical periodontitis) on osteoclast differentiation within an osteoblast/osteoclast co-culture system.

RESULTS

Heat-killed E. faecalis significantly increased the proportion of multinucleated osteoclastic cells (MNCs) within the co-culture system. The IL-6 level was significantly increased upon exposure to heat-killed E. faecalis. Gene expression levels of NFATc1 and cathepsin K were significantly up-regulated compared to the untreated control. EphrinB2 and EphB4 expressions at both the mRNA and protein levels were also significantly upregulated compared to the untreated control.

CONCLUSIONS

Heat-killed E. faecalis can induce osteoclast differentiation within the osteoblast/osteoclast co-culture system in vitro, possibly through ephrinB2-EphB4 bidirectional signaling.

The effect of cathepsin K inhibitor on osteoclastic activity compared to alendronate and enamel matrix protein

BACKGROUND/AIM

There have been several attempts to treat delayed replantation with agents that inhibit root resorption. The purpose of this study was to assess the effectiveness of cathepsin K inhibitor in inhibiting osteoclastic activity compared to that of alendronate and enamel matrix protein.

MATERIALS AND METHODS

Murine RAW 264.7 cells were cultured in the presence of the receptor activator of NF-kB and lipopolysaccharide, followed by treatment with odanacatib, alendronate, or Emdogain at various concentrations. After drug treatment, an MTT assay was performed to evaluate cytotoxicity, while reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assays were performed to determine the expression levels of interleukin-1β, interleukin-6, prostaglandin E2, and tumor necrosis factor-α. Data were analyzed by one-way anova and Tukey's post-hoc test (P < 0.05).

RESULTS

Of all tested agents, Emdogain resulted in the least cytotoxicity on RAW 264.7 cells, while 10(-9) M odanacatib had the largest suppressive effects on the expression levels of inflammatory cytokines.

CONCLUSIONS

Odanacatib inhibits osteoclastic activity, showing the possibility as a treatment agent for delayed replantation of avulsed teeth.