Cementogenesis is inhibited under a mechanical static compressive force via Piezo1

Exploring biological mechanisms in orthodontic tooth movement: Bridging the gap between basic research experiments and clinical applications - A comprehensive review

OBJECTIVES

The molecular mechanisms behind orthodontic tooth movements (OTM) were investigated by clarifying the role of chemical messengers released by cells.

METHODS

Using the Cochrane library, Google scholar, and PubMed databases, a literature search was conducted, and studies published from 1984-2024 were considered.

RESULTS

Both bone growth and remodeling may occur when a tooth is subjected to mechanical stress. These chemicals have a significant effect on the stimulation and regulation of osteoblasts, osteoclasts, and osteocytes during alveolar bone remodeling. This regulation can take place in pathological conditions, such as periodontal diseases, or during OTM alone. This comprehensive review outlines key molecular mechanisms underlying OTM and explores various clinical assumptions associated with specific molecules and their functional domains during this process. Furthermore, clinical applications of certain molecules such as relaxin, prostaglandin E (PGE), and interleukin-1β (IL-1β) in accelerating OTM have been reported. Our findings underscore the existing gap between OTM clinical applications and basic research investigations.

CONCLUSION

A comprehensive understanding of orthodontic treatment is enriched by insights into biological systems. We reported the activation of osteoblasts, osteoclast precursor cells, osteoclasts, and osteocytes in response to mechanical stress, leading to targeted cellular and molecular interventions and facilitating rapid and regulated alveolar bone remodeling during tooth movement. Despite the shortcomings of clinical studies in accelerating OTM, this review highlights the crucial role of biological agents in this process and advocates for prioritizing high-quality human studies in future research to gain further insights from clinical trials.

Mitochondrial ROS participates in Porphyromonas gingivalis-induced pyroptosis in cementoblasts

This study aimed to investigate correlation between mitochondrial reactive oxygen species and Porphyromonas gingivalis in the process of cementoblast pyroptosis. Lactate dehydrogenase activity assay, enzyme-linked immunosorbent assay, western blotting and flow cytometry analysis were utilized to explore whether Porphyromonas gingivalis triggered pyroptosis in cementoblasts. Reactive oxygen species and mitochondrial reactive oxygen species were detected using flow cytometry and fluorescence staining. The effect of mitochondrial reactive oxygen species on the Porphyromonas gingivalis-induced pyroptosis of cementoblasts was assessed by Mito-Tempo, mitochondrion-targeted superoxide dismutase mimetic. Phosphorylation levels of p65 were measured by western blotting. SC75741, a nuclear factor-kappa B inhibitor, was added to block the nuclear factor-kappa B in the Porphyromonas gingivalis-infected cementoblasts. Porphyromonas gingivalis triggered pyroptosis of cementoblasts, and an elevation in reactive oxygen species generation in the mitochondria was observed. Inhibition of mitochondrial reactive oxygen species reduced pyroptosis and nuclear factor-kappa B signaling pathway mediated the pyroptotic cell death in Porphyromonas gingivalis-infected cementoblasts. Together, our findings demonstrate that mitochondrial reactive oxygen species increased by Porphyromonas gingivalis participated in the pyroptosis of cementoblasts. Targeting mitochondrial reactive oxygen species may offer therapeutic strategies for root surface remodeling or periodontal regeneration.

Nociceptor mechanisms underlying pain and bone remodeling via orthodontic forces: toward no pain, big gain

Orthodontic forces are strongly associated with pain, the primary complaint among patients wearing orthodontic braces. Compared to other side effects of orthodontic treatment, orthodontic pain is often overlooked, with limited clinical management. Orthodontic forces lead to inflammatory responses in the periodontium, which triggers bone remodeling and eventually induces tooth movement. Mechanical forces and subsequent inflammation in the periodontium activate and sensitize periodontal nociceptors and produce orthodontic pain. Nociceptive afferents expressing transient receptor potential vanilloid subtype 1 (TRPV1) play central roles in transducing nociceptive signals, leading to transcriptional changes in the trigeminal ganglia. Nociceptive molecules, such as TRPV1, transient receptor potential ankyrin subtype 1, acid-sensing ion channel 3, and the P2X3 receptor, are believed to mediate orthodontic pain. Neuropeptides such as calcitonin gene-related peptides and substance P can also regulate orthodontic pain. While periodontal nociceptors transmit nociceptive signals to the brain, they are also known to modulate alveolar bone remodeling in periodontitis. Therefore, periodontal nociceptors and nociceptive molecules may contribute to the modulation of orthodontic tooth movement, which currently remains undetermined. Future studies are needed to better understand the fundamental mechanisms underlying neuroskeletal interactions in orthodontics to improve orthodontic treatment by developing novel methods to reduce pain and accelerate orthodontic tooth movement-thereby achieving "big gains with no pain" in clinical orthodontics.

Autophagy mediates cementoblast mineralization under compression through periostin/β-catenin axis

Repair of orthodontic external root resorption and periodontal tissue dysfunction induced by mechanical force remains a clinical challenge. Cementoblasts are vital in cementum mineralization, a process important for restoring damaged cementum. Despite autophagy plays a role in mineralization under various environmental stimuli, the underlying mechanism of autophagy in mediating cementoblast mineralization remains unclear. Here we verified that murine cementoblasts exhibit compromised mineralization under compressive force. Autophagy was indispensable for cementoblast mineralization, and autophagic activation markedly reversed cementoblast mineralization and prevented cementum damage in mice during tooth movement. Subsequently, messenger RNA sequencing analyses identified periostin (Postn) as a mediator of autophagy and mineralization in cementoblasts. Cementoblast mineralization was significantly inhibited following the knockdown of Postn. Furthermore, Postn silencing suppressed Wnt signaling by modulating the stability of β-catenin. Together our results highlight the role of autophagy in cementoblast mineralization via Postn/β-catenin signaling under compressive force and may provide a new strategy for the remineralization of cementum and regeneration of periodontal tissue.

A regulatory role of Piezo1 in apoptosis of periodontal tissue and periodontal ligament fibroblasts during orthodontic tooth movement

Investigation on the effect of Piezo1 on periodontal tissue and periodontal ligament fibroblasts (PDLFs) under mechanical stress and the underlying mechanism. The orthodontic tooth movement rat model was established via an orthodontic spiral tension spring. PDLFs were cultured and subjected to 2.0 g/cm2 static compressive loading. Blocked the Piezo1 via Piezo1 inhibitor, GsMTx4. TUNEL staining and flow cytometry determined the apoptosis rate of periodontal tissue and PDLFs in rats. Expression of Piezo1, p-p38 and ERK1/2 was analysed by immunofluorescence assay and western blotting. Piezo1 inhibitor GsMTx4 relieved the increased expression of Piezo1, ERK1/2 and p-p38, and alleviated apoptosis in periodontal tissue and PDLFs under compressive loading. Piezo1 inhibition can alleviate force-induced apoptosis and damage in rats' periodontal tissue and PDLFs, and regulate the p38/ERK1/2 signalling pathway.

Knockout of Bone Sialoprotein in Cementoblasts Cell Lines Affects Specific Gene Expression in Unstimulated and Mechanically Stimulated Conditions

One of the major components in cementum extracellular matrix is bone sialoprotein (BSP). BSP knockout (Ibsp) mice were reported to have a nonfunctional hypo-mineralized cementum, as well as detachment and disorganization of the periodontal ligament tissue. However, studies investigating the influence of Ibsp in cementoblasts are missing yet. This study investigates the influences of Bsp in three cementoblasts cell lines (OCCM.30-WT,Ibsp^ΔNterm, and Ibsp^KAE). The mRNA expression of cementoblast and osteoclast markers (Col1a1, Alpl, Ocn, Runx2, Ctsk, Rankl and Opg) and the cell morphology were compared. Additionally, a functional monocyte adhesion assay was performed. To understand the influence of external stimuli, the effect of Ibsp was investigated under static compressive force, mimicking the compression side of orthodontic tooth movement. Cementoblasts with genotype Ibsp^ΔNterm and Ibsp^KAE showed slight differences in cell morphology compared to OCCM.30-WT, as well as different gene expression. Under compressive force, the Ibsp cell lines presented expression pattern markers similar to the OCCM.30-WT cell line. However, Cathepsin K was strongly upregulated in Ibsp^ΔNterm cementoblasts under compressive force. This study provides insight into the role of BSP in cementoblasts and explores the influence of BSP on periodontal ligament tissues. BSP markers in cementoblasts seem to be involved in the regulation of cementum organization as an important factor for a functional periodontium. In summary, our findings provide a basis for investigations regarding molecular biology interactions of BSP in cementoblasts, and a supporting input for understanding the periodontal and cellular cementum remodeling.

Mechanosensitive Piezo1 and Piezo2 ion channels in craniofacial development and dentistry: Recent advances and prospects

Mechanical forces play important roles in many biological processes and there is increasing interest and understanding of these roles. Mechanotransduction is the process by which mechanical stimuli are converted to biochemical signals through specific mechanisms, and this results in the activation of downstream signaling pathways with specific effects on cell behaviors. This review systematically summarizes the current understanding of the mechanosensitive Piezo1 and Piezo2 ion channels in craniofacial bone, tooth, and periodontal tissue, presenting the latest relevant evidence with implications for potential treatments and managements of dental and orofacial diseases and deformities. The mechanosensitive ion channels Piezo1 and Piezo2 are widely expressed in various cells and tissues and have essential functions in mechanosensation and mechanotransduction. These channels play an active role in many physiological and pathological processes, such as growth and development, mechano-stimulated bone homeostasis and the mediation of inflammatory responses. Emerging evidence indicates the expression of Piezo1 and Piezo2 in bone, dental tissues and dental tissue-derived stem cells and suggests that they function in dental sensation transduction, dentin mineralization and periodontal bone remodeling and modulate orthodontic tooth movement.

Effects of mechanosensitive ion channel Piezo1 on proliferation and osteogenic differentiation of human dental follicle cells

BACKGROUND

To explore the role of the mechanosensitive ion channel Piezo1 in the proliferation and osteogenic differentiation of human dental follicle cells (hDFCs), and its mechanism, so as to provide the basis for the use of hDFCs to achieve bone regeneration.

METHODS

hDFCs were obtained from fresh dental follicle tissues by enzymatic digestion, and cell phenotype and multipotential differentiation were identified. Identification of the expression of mechanosensitive ion channel Piezo1 was performed by immunofluorescence and immunohistochemistry. CCK-8 was used to determine the optimal concentration of the Piezo1 agonist, Yoda1. Then, according to the obtained results, Alizarin red staining, RT-PCR quantitative analysis and Western blot were used to further observe the osteogenic differentiation of hDFCs and its probable mechanism via Wnt/β-catenin signalling. The data were analysed by SPSS 22.0 software.

RESULTS

The results of the concentration gradient experiments indicated that 0.5 µM Piezo1 agonist (Yoda1) enhanced the proliferation of hDFCs. Compared with the control group, a considerable number of calcium nodules showed that activating Piezo1 could promote the osteogenic differentiation of hDFCs. The relative mRNA and protein expression of Piezo1, ALP, RUNX2, OCN and BMP2 in the Piezo1 agonist group were higher than that of the control group. Furthermore, the expression of Wnt3a and β-catenin related to the classical osteogenic pathway were significantly up-regulated in the Piezo1 agonist group.

CONCLUSION

Activating mechanosensitive ion channel Piezo1 with an appropriate concentration of Yoda1 has a positive effect on the proliferation and osteogenic differentiation of hDFCs. This mechanism of promoting osteogenic differentiation may be mediated by the Wnt/β-catenin pathway.

Compressive force regulates cementoblast migration via downregulation of autophagy

BACKGROUND

Migration of cementoblasts to resorption lacunae is the foundation for repairing root resorption during orthodontic tooth movement. Previous studies reported that autophagy was activated by compression in periodontal ligament cells. The aim of this study was to investigate the migration of cementoblasts and determine whether autophagy is involved in the regulation of cementoblast migration under compressive force.

METHODS

Flow cytometry was employed to examine the apoptosis of murine cementoblasts (OCCM-30) at different compression times (0, 6, 12, and 24 hours) and magnitudes (0, 1.0, 1.5, and 2.0 g/cm² ). Cell proliferation was examined using the CCK-8 method. Wound healing migration assays and transwell migration assays were performed to compare the migration of cementoblasts. Chloroquine (CQ) and rapamycin were used to inhibit and activate autophagy, respectively. The level of autophagy was determined using western blotting and immunofluorescence staining. The expression of matrix metalloproteinases (MMPs) was assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot analysis, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Cell apoptosis and proliferation did not significantly change in OCCM-30 cells under mechanical compression at magnitude of 1.5 g/cm² for 12 hours. However, the migration of cementoblasts was significantly inhibited after the application of compressive force. MMP2, MMP9, and MMP13 mRNA expression was decreased, and MMP9 and MMP13 protein expression and secretion level were also decreased. Further, autophagic activity was inhibited in cementoblasts under compressive force. Treatment with chloroquine reduced the cellular migration, and rapamycin partially relieved the inhibition of cementoblast migration induced by the compressive force. MMP9 and MMP13 mRNA expression, protein expression, and secretion levels showed a similar trend.

CONCLUSION

Migration of OCCM-30 cells was inhibited under compressive force partially dependent on the inhibition of MMPs, which was mediated by downregulation of autophagy. The findings provide new insights into the role of autophagy in biological behaviors of cementoblasts under compressive force and a potential therapeutic strategy for reducing external root resorption.

Gene expression and phosphorylation of ERK and AKT are regulated depending on mechanical force and cell confluence in murine cementoblasts

Cementoblasts, located on the tooth root surface covered with cementum, are considered to have tooth protecting abilities. They prevent tissue damage and secure teeth anchorage inside the periodontal ligament during mechanical stress. However, the involvement of cementoblasts in mechanical compression induced periodontal remodeling needs to be identified and better understood. Here, we investigated the effect of static compressive stimulation, simulating the compression side of orthodontic force and cell confluence on a murine cementoblast cell line (OC/CM). The influence of cell confluence in cementoblast cells was analyzed by MTS assay and immunostaining. Furthermore, mRNA and protein expression were investigated by real-time RT-PCR and western blotting at different confluence grades and after mechanical stimulation. We observed that cementoblast cell proliferation increases with increasing confluence grades, while cell viability decreases in parallel. Gene expression of remodeling markers is regulated by compressive force. In addition, cementoblast confluence plays a crucial role in this regulation. Confluent cementoblasts show a significantly higher basal expression of Bsp, Osterix, Alpl, Vegfa, Mmp9, Tlr2 and Tlr4 compared to sub-confluent cells. After compressive force of 48 h at 60% confluence, an upregulation of Bsp, Osterix, Alpl, Vegf and Mmp9 is observed. In contrast, at high confluence, all analyzed genes were downregulated through mechanical stress. We also proved a regulation of ERK, phospho-ERK and phospho-AKT dependent on compressive force. In summary, our findings provide evidence that cementoblast physiology and metabolism is highly regulated in a cell confluence-dependent manner and by mechanical stimulation.

The long non-coding RNA landscape of periodontal ligament stem cells subjected to compressive force

OBJECTIVE

The role of long non-coding ribonucleic acids (lncRNAs) during orthodontic tooth movement remains unclear. We explored the lncRNA landscape of periodontal ligament stem cells (PDLSCs) subjected to compressive force.

MATERIALS AND METHODS

PDLSCs were subjected to static compressive stress (2 g/cm2) for 12 hours. Total RNA was then extracted and sequenced to measure changes in lncRNA and messenger RNA (mRNA) expression levels. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to validate the expression levels of certain lncRNAs. Differential expression analysis as well as Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were also performed.

RESULTS

In total, 90 lncRNAs and 519 mRNAs were differentially expressed in PDLSCs under compressive stress. Of the lncRNAs, 72 were upregulated and 18 downregulated. The levels of eight lncRNAs of interest (FER1L4, HIF1A-AS2, MIAT, NEAT1, ADAMTS9-AS2, LUCAT1, MIR31HG, and DHFRP1) were measured via qRT-PCR, and the results were found to be consistent with those of RNA sequencing. GO and KEGG pathway analyses showed that a wide range of biological functions were expressed during compressive loading; most differentially expressed genes were involved in extracellular matrix organization, collagen fibril organization, and the cellular response to hypoxia.

CONCLUSIONS

The lncRNA expression profile was significantly altered in PDLSCs subjected to compressive stress. These findings expand our understanding of molecular regulation in the mechanoresponse of PDLSCs.

Selection and validation of reference genes by RT-qPCR for murine cementoblasts in mechanical loading experiments simulating orthodontic forces in vitro

Different structures and cell types of the periodontium respond to orthodontic tooth movement (OTM) individually. Cementoblasts (OC/CM) located in the immediate vicinity of the fibroblasts on the cement have found way to the centre of actual research. Here, we identify and validate possible reference genes for OC/CM cells by RT-qPCR with and without static compressive loading. We investigated the suitability of 3 reference genes in an in vitro model of cementoblast cells using four different algorithms (Normfinder, geNorm, comparative delta-Ct method and BestKeeper) under different confluences and time. Comparable to our previous publications about reference genes in OTM in rats and human periodontal ligament fibroblasts (hPDLF), Rpl22 in murine OC/CM cells appears as the least regulated gene so that it represents the most appropriate reference gene. Furthermore, unlike to the expression of our recommended reference genes, the expression of additionally investigated target genes changes with confluence and under loading compression. Based on our findings for future RT-qPCR analyses in OC/CM cells, Rpl22 or the combination Rpl22/Tbp should be favored as reference gene. According to our results, although many publications propose the use of Gapdh, it does not seem to be the most suitable approach.

Lithium chloride attenuates suppressed differentiation induced by mechanical strain in cementoblasts

Aim: The purpose of this study was to investigate the influence of mechanical strain on OCCM-30 cementoblast differentiation and Wnt/β-catenin pathway activity. Materials and Methods: Mechanical tension in the form of 2500-µ strain was applied to the cells using the Forcel four-point bending system, with or without the Wnt signaling activator, lithium chloride. Changes in cell differentiation and the expression of Wnt/β-catenin pathway components in response to strain and lithium chloride were assessed by real-time PCR, immunofluorescence, and western blotting. Results: The mRNA expression levels of the cementoblastogenesis-related genes alkaline phosphatase, runt-related transcription factor 2, and collagen 1, were decreased with mechanical strain. Similarly, the Wnt signaling pathway component genes LRP5, AXIN2, and LEF1 were decreased. The immunofluorescence assay demonstrated that scant β-catenin underwent nuclear translocation after the cells were subjected to mechanical strain. Moreover, western blotting showed that the protein levels of both β-catenin and phosphorylated β-catenin were increased after mechanical strain. In the presence of lithium chloride, the differentiation that was suppressed by mechanical strain was attenuated. Conclusions: 2500-µ strain mechanical strain inhibited cementoblast differentiation activity in vitro, which could be alleviated by actviating Wnt/β-catenin signaling using lithium chloride.

PTH1R signalling regulates the mechanotransduction process of cementoblasts under cyclic tensile stress

Objective

To investigate the regulatory role of type I parathyroid hormone receptor (PTH1R) signalling in the mechanotransduction process of cementoblasts under cyclic tensile stress (CTS).

Materials and methods

Immortalized cementoblast cell line OCCM-30 were employed and subjected to cyclic tensile strain applied by a four-point bending system. The expression of PTHrP and PTH1R, as well as cementoblastic transcription factor Runx-2, Osterix, and extracellular matrix protein COL-1 and OPN were assessed by quantitative real-time polymerase chain reaction and western blot analysis. PTH1R expression was knocked down by siPTH1R transfection, and the alteration of cementoblastic biomarkers expression was examined to evaluate the function of PTH1R. Furthermore, to investigate possible downstream molecules, expression of signal molecule ERK1/2 with or without siPTH1R transfection, and the effect of ERK inhibitor PD98059 on the expression of cementoblastic biomarkers was also examined.

Results

Cyclic tensile strain elevated the expression of PTHrP and PTH1R, as well as cementoblastic biomarkers Runx-2, Osterix, COL-1, and OPN in a time-dependent manner, which was inhibited by siPTH1R transfection. The expression of phosphorylated ERK1/2 was upregulated time-dependently under cyclic stretch, which was also inhibited by siPTH1R transfection, and pretreatment of p-ERK1/2 inhibitor PD98059 undermined the increase of Runx-2, Osterix, COL-1, and OPN prominently.

Conclusion

The findings of the present study indicate that PTH1R signalling plays a regulatory role in the CTS induced cementoblastic differentiation in mature cementoblasts, and ERK1/2 is essentially involved as a downstream intracellular signal molecule in this mechanotransduction process.