Immunohistochemical expression of heat shock proteins in the mouse periodontal tissues due to orthodontic mechanical stress

Ribosomal Stress Couples with the Hypoxia Response in Dec1-Dependent Orthodontic Tooth Movement

This study characterized the effects of a deficiency of the hypoxia-responsive gene, differentiated embryonic chondrocyte gene 1 (Dec1), in attenuating the biological function of orthodontic tooth movement (OTM) and examined the roles of ribosomal proteins in the hypoxic environment during OTM. HIF-1α transgenic mice and control mice were used for hypoxic regulation of periodontal ligament (PDL) fibroblasts. Dec1 knockout (Dec1KO) and wild-type (WT) littermate C57BL/6 mice were used as in vivo models of OTM. The unstimulated contralateral side served as a control. In vitro, human PDL fibroblasts were exposed to compression forces for 2, 4, 6, 24, and 48 h. HIF-1α transgenic mice had high expression levels of Dec1, HSP105, and ribosomal proteins compared to control mice. The WT OTM mice displayed increased Dec1 expression in the PDL fibroblasts. Micro-CT analysis showed slower OTM in Dec1KO mice compared to WT mice. Increased immunostaining of ribosomal proteins was observed in WT OTM mice compared to Dec1KO OTM mice. Under hypoxia, Dec1 knockdown caused a significant suppression of ribosomal protein expression in PDL fibroblasts. These results reveal that the hypoxic environment in OTM could have implications for the functions of Dec1 and ribosomal proteins to rejuvenate periodontal tissue homeostasis.

Impact of phosphorylation of heat shock protein 27 on the expression profile of periodontal ligament fibroblasts during mechanical strain

PURPOSE

Orthodontic tooth movement is a complex process involving the remodeling of extracellular matrix and bone as well as inflammatory processes. During orthodontic treatment, sterile inflammation and mechanical loading favor the production of receptor activator of NF-κB ligand (RANKL). Simultaneously, expression of osteoprotegerin (OPG) is inhibited. This stimulates bone resorption on the pressure side. Recently, heat shock protein 27 (HSP27) was shown to be expressed in the periodontal ligament after force application and to interfere with inflammatory processes.

METHODS

We investigated the effects of phosphorylated HSP27 on collagen synthesis (COL1A2 mRNA), inflammation (IL1B mRNA, IL6 mRNA, PTGS2 protein) and bone remodeling (RANKL protein, OPG protein) in human periodontal ligament fibroblasts (PDLF) without and with transfection of a plasmid mimicking permanent phosphorylation of HSP27 using real-time quantitative polymerase chain reaction (RT-qPCR), western blot and enzyme-linked immunosorbent assays (ELISAs). Furthermore, we investigated PDLF-induced osteoclastogenesis after compressive strain in a co-culture model with human macrophages.

RESULTS

In particular, phosphorylated HSP27 increased gene expression of COL1A2 and protein expression of PTGS2, while IL6 mRNA levels were reduced. Furthermore, we observed an increasing effect on the RANKL/OPG ratio and osteoclastogenesis mediated by PDLF.

CONCLUSION

Phosphorylation of HSP27 may therefore be involved in the regulation of orthodontic tooth movement by impairment of the sterile inflammation response and osteoclastogenesis.

Heat Shock Protein Overexpression-Mediated Periodontal Ligament Regeneration: A Fundamental Approach to Generate a Potential Biomaterial

The periodontal ligament (PDL) is a cell-rich fibrous connective tissue supporting the tooth roots. The tissue helps to maintain homeostasis and exhibits regenerative and repairing ability, which is mediated by the heat shock protein (HSP). Here, we experimentally created PDL tissue with notable ability to regenerate hard tissue and evaluated it as a potential biomaterial. We immunohistochemically examined the mechanical load-induced HSP overexpression in mouse PDL. Following mechanical load application and release, HSP70 localization in the PDL was altered immediately, suggesting that the HSP70 function may differ with the timing of its expression in PDL. HSP70 expressed in the cytoplasm and nucleus of fibroblasts in PDL on the tension side not only participated in periodontium repair, but also functioned as a molecular chaperone during protein expression involved in osteogenesis to restructure injured tissue. This study highlights the potential of artificially created highly functional PDL tissues as biomaterials.

Evaluation of Salivary Level of Heat Shock Protein 70 in Patients with Chronic Periodontitis

STATEMENT OF THE PROBLEM

Traditional clinical criteria are usually not sufficient for determining the sites of active periodontal disease, monitoring the response to treatment, or measuring the susceptibility to future disease development. Past studies have shown that heat shock protein 70 (HSP70) are involved in the etiology of periodontal disease.

PURPOSE

The aim of this study was to evaluate the level of HSP70 in saliva of patients with chronic periodontitis (CP).

MATERIALS AND METHOD

In our case-control study, the saliva samples of 45 patients with CP and 45 age- and sex-matched healthy subjects were collected. Salivary HSP70 was measured by enzyme-linked immunosorbent assay method. The results were analyzed by statistical tests using SPSS 16 and the statistically significant difference was set at p< 0.05.

RESULTS

In this study, the mean salivary HSP70 level was 2.81±0.61ng/ml in the patient group and 1.96±0.77ng/ml in the healthy group, with a significant difference (p< 0.05). In addition, the results of spearman correlation analysis showed a positive correlation between salivary HSP 70 and clinical periodontal index.

CONCLUSION

The results of this study showed that the salivary HSP70 level in patients with CP is higher than that in healthy subjects. As a result, salivary HSP70 might be considered as a marker in the pathogenesis of CP.

Heat shock protein 70 and the extent of nuclear damage in periodontal ligament compression side cells with orthodontic force application - An ex-vivo evaluation

OBJECTIVE

Increased levels of heat shock proteins after several types of stress play a central role in cellular homeostasis allowing for continued cell survival. This study was aimed at quantitatively analysing the expression pattern of major damage associated molecular patterns (DAMPs) - HSP70, and the amount of nuclear damage incident in periodontal ligament compression side cells.

MATERIAL AND METHODS

Sixteen subjects with bimaxillary dentoalveolar protrusion requiring extraction of all first premolars as part of orthodontic treatment were selected. Extractions were carried out pretreatment from control group. In the experimental group, a buccally directed spring, with force range of 70-120gms promoting bodily movement of maxillary first premolars was placed. Periodontal ligament was scraped from the middle third of the root from the compression side, the cells were isolated and cultured followed by HSP70 protein estimation with western blot analysis and the extend of nuclear damage was assessed with COMET assay.

RESULTS

Western Blot analysis of HSP70 revealed a statistically significant increased expression of HSP70 (P<0.05; CI=95%) in the force applied group compared with the control group. COMET assay could demonstrate significant amount of nuclear fragmentation in the compression side periodontal ligament cells in comparison to control group (P<0.05; CI=95%).

CONCLUSIONS

All these findings demonstrated, for the first time, that orthodontic force application augments release of HSP70 from periodontal ligament cells as a measure to restore tissue homeostasis. Further the study demonstrated that orthodontic forces induce DNA fragmentation, which is quantified more than double the amount observed in the control group.

Are teeth superior to implants? A mapping review

STATEMENT OF PROBLEM

There is a long-held assumption that teeth are superior to implants because the periodontal ligament (PDL) confers a preeminent defense against biologic and mechanical challenges. However, adequate analysis of the literature is lacking. As a result, differential treatment planning of tooth- and implant-supported restorations has been compromised.

PURPOSE

Given an abundance and diversity of research, the purpose of this mapping review was to identify basic scientific gaps in the knowledge of how teeth and implants respond to biologic and mechanical loads. The findings will offer enhanced evidence-based clinical decision-making when considering replacement of periodontally compromised teeth and the design of implant prostheses.

MATERIAL AND METHODS

The online databases PubMed, Science Direct, and Web of Science were searched. Published work from 1965 to 2020 was collected and independently analyzed by both authors for inclusion in this review.

RESULTS

A total of 108 articles met the inclusion criteria of clinical, in vivo, and in vitro studies in the English language on the periradicular and peri-implant bone response to biologic and mechanical loads. The qualitative analysis found that the PDL's enhanced vascularity, stem cell ability, and resident cells that respond to inflammation allow for a more robust defense against biologic threats compared with implants. While the suspensory PDL acts to mediate moderate loads to the bone, higher compressive stress and strain within the PDL itself can initiate a biologic sequence of osteoclastic activity that can affect changes in the adjacent bone. Conversely, the peri-implant bone is more resistant to similar loads and the threshold for overload is higher because of the absence of a stress or strain sensitivity inherent in the PDL.

CONCLUSIONS

Based on this mapping review, teeth are superior to implants in their ability to resist biologic challenges, but implants are superior to teeth in managing higher compressive loads without prompting bone resorption.

Experimental animal study on BMP-3 expression in periodontal tissues in the process of orthodontic tooth movement

Expression characteristics of bone morphogenetic protein-3 (BMP-3) in the process of orthodontic tooth movement was investigated. Forty-eight rats were randomly divided into the 3-day group (n=12), the 7-day group (n=12), the 14-day group (n=12) and the 21-day group (n=12). The maxillary left molar of each rat was used as the experimental tooth, the orthodontic tooth model was established, and the contralateral molar was used as the control tooth. The tooth movement distance was measured using a vernier caliper at day 1, 3, 7 and 14 after modeling, and rats in each group were sacrificed and sampled at the corresponding time-point. The tissue morphology was observed via hematoxylin and eosin (H&E) staining, and the expression of BMP-3 was detected via immunohistochemistry. The protein expression of BMP-3 was detected via western blotting, and the messenger ribonucleic acid (mRNA) expression of BMP-3 was detected via quantitative polymerase chain reaction (qPCR). At day 14 after modeling, the periodontal space was significantly uneven, the form of periodontal tissues was disordered, and a large number of multinucleated osteoclasts could be seen. The expression levels of BMP-3 in other groups were significantly increased compared with that in the control group (P<0.05). The expression level of BMP-3 reached the peak at day 14 after modeling, and differences were statistically significant compared with those in other time points after modeling (P<0.05). The orthodontic tooth movement distance after modeling was significantly longer with the extension of time (P<0.05). In the process of orthodontic tooth movement, the expression level of BMP-3 is gradually increased and reaches the peak at day 14, promoting the increase of osteoclasts and benefiting the orthodontic tooth movement.

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.

Functional Role of HSP47 in the Periodontal Ligament Subjected to Occlusal Overload in Mice

We carried out an experiment to induce traumatic occlusion in mice periodontal tissue and analyzed the expression of HSP47. Continuous traumatic occlusion resulted to damage and remodeling of periodontal ligament as well as increase in osteoclasts and bone resorption. Four days after traumatic occlusion, osteoclasts did not increase but Howship's lacunae became enlarged. That is, the persistent occlusal overload can destroy collagen fibers in the periodontal ligament. This was evident by the increased in HSP47 expression with the occlusal overload. HSP47 is maintained in fibroblasts for repair of damaged collagen fibers. On the other hand, osteoclasts continue to increase although the load was released. The osteoclasts that appeared on the alveolar bone surface were likely due to sustained activity. The increase in osteoclasts was estimated to occur after load application at day 4. HSP47 continued to increase until day 6 in experiment 2 but then reduced at day 10. Therefore, HSP47 appears after a period of certain activities to repair damaged collagen fibers, and the activity was returned to a state of equilibrium at day 30 with significantly diminished expression. Thus, the results suggest that HSP47 is actively involved in homeostasis of periodontal tissue subjected to occlusal overload.

Promotion of transplanted bone marrow-derived cell migration into the periodontal tissues due to orthodontic mechanical stress

BACKGROUND

Bone marrow-derived cells (BMCs) have abilities of cell migration and differentiation into tissues/organs in the body and related with the differentiation of teeth or periodontal tissue including fibroblasts. Then, we examined the effect of orthodontic mechanical stress to the transplanted BMC migration into periodontal tissues using BMC transplantation model.

MATERIAL AND METHOD

BMC from green fluorescence protein (GFP) transgenic mice were transplanted into 8-week-old female C57BL/6 immunocompromised recipient mice, which had undergone 10 Gy of lethal whole-body-irradiation. Five mice as experimental group were received orthodontic mechanical stress using separator between first molar (M1) and second molar (M2) 1 time per week for 5 weeks and 5 mice as control group were not received mechanical stress. The maxilla with M1 and M2 was removed and was immunohistochemically analyzed using a Dako Envision + Kit-K4006 and a primary anti-GFP-polyclonal rabbit antibody. Immunohistochemically stained was defined as positive area and the pixel number of positive area in the periodontal tissue was compared with the previously calculated total pixel number of the periodontal tissue.

RESULTS

The immunohistochemistry revealed that GFP positive cells were detected in the periodontal tissues, both in the experimental and control specimens. The ratio of pixel number in the examination group showed 5.77 ± 3.24 % (mean ± SD); and that in the control group, 0.71 ± 0.45 % (mean ± SD). The examination group was significantly greater than that of control group (Mann-Whitney U test: p<0.001).

CONCLUSION

These results suggest that orthodontic mechanical stress accelerates transplanted BMC migration into periodontal tissues.

Immunohistochemical expression of heat shock protein27 in the mouse dental pulp after immediate teeth separation

Aim

After immediate teeth separation, expression of HSP27 in the mouse dental pulp was examined. Immunohistochemistry was performed to examine the incidence of HSP27 expression.

Materials and methods

A total of 36 8-week-old ddY mice were used as experimental subjects and a wedge was inserted in between maxillary right molars. The wedge was removed 30 min or 3 h after insertion. Animals were immediately sacrificed after the removal of wedge or until 1 week later and serial sections from paraffin-embedded tissues were prepared. Immunohistochemistry was carried out to examine the expression of HSP27. The untreated side served as the control.

Results

In the control group, the endothelial cells and some pulp fibroblasts weakly expressed HSP27 suggesting that the expression is due to mechanical stress brought about by physiological masticatory force and pressure from the tongue. In both 30 min and 3 h experimental groups, HSP27 expression was highest at 24 h after wedge removal and the expression remained the same or started to decrease thereafter. The expression decreased at the same level as that of the control group 1 week after wedge removal.

Conclusion

HSP27 may serve as an indicator of stimulus strong enough to show its expression.

Immunohistochemical expression of hard tissue related factors in the mouse dental pulp after immediate teeth separation

We examined change of Runx2 and ALP expression in mouse tooth pulp which exposed to teeth separation experiment by immunohistochemistry as a model for conservative dentistry treatment. 8-week-old 36 male ddY mice were used and wedge was inserted between upper 1st and 2nd molars. The wedge was removed 30 minutes as well as 3 hours after the insertion and the samples were prepared extending up to 1 week of time period for regular histopathological and immunohistochemical examinations for ALP and Runx2 expression. The opposite sides without wedge insertion were taken as controls. In the control group pulp, weak expressions of Runx2 and ALP in the vessel endothelial cells as well as the pulp cells were revealed, suggesting the appearance of these genes upon mechanical stress induced by mastication and tongue pressure etc. On the other hand in the experiment group, Runx2 expression increased both in 30-minute and 3-hour teeth separation group. The expression became maximum at 24 hours. Then it gradually decreased and became similar level with the control group at 1-week after the wedge insertion. Similarly ALP expression increased after the wedge insertion and was maximum at 24 hours and then gradually decreased to the levels similar with the control group. These results suggest that when immunohistochemical expression of Runx2 as well as ALP was used as an index, no severe damage occur upon clinical application of wedge insertion.