Mechanical force inhibited hPDLSCs proliferation with the downregulation of MIR31HG via DNA methylation

Roles of DNA methylation in influencing the functions of dental-derived mesenchymal stem cells

OBJECTIVE

DNA methylation as intensively studied epigenetic regulatory mechanism exerts pleiotropic effects on dental-derived mesenchymal stem cells (DMSCs). DMSCs have self-renewal and multidifferentiation potential. Here, this review aims at summarizing the research status about application of DMSCs in tissue engineering and clarifying the roles of DNA methylation in influencing the functions of DMSCs, with expectation of paving the way for its in-depth exploration in tissue engineering.

METHOD

The current research status about influence of DNA methylation in DMSCs was acquired by MEDLINE (through PubMed) and Web of Science using the keywords 'DNA methylation', 'dental-derived mesenchymal stem cells', 'dental pulp stem cells', 'periodontal ligament stem cells', 'dental follicle stem cells', 'stem cells from the apical papilla', 'stem cells from human exfoliated deciduous teeth', and 'gingival-derived mesenchymal stem cells'.

RESULTS

This review indicates DNA methylation affects DMSCs' differentiation and function through inhibiting or enhancing the expression of specific gene resulted by DNA methylation-related genes or relevant inhibitors.

CONCLUSION

DNA methylation can influence DMSCs in aspects of osteogenesis, adipogenesis, immunomodulatory function, and so on. Yet, the present studies about DNA methylation in DMSCs commonly focus on dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs). Little has been reported for other DMSCs.

Long non-coding RNA MIAT serves as a biomarker of fragility fracture and promotes fracture healing

BACKGROUND

Fragility fracture is common in the elderly. Osteoblast differentiation is essential for bone healing and regeneration. Expression pattern of long non-coding RNA MIAT during fracture healing was examined, and its role in osteoblast differentiation was investigated.

METHODS

90 women with simple osteoporosis and 90 women with fragility fractures were included. Another 90 age-matched women were set as the control group. mRNA levels were tested using RT-qPCR. Cell viability was detected via CCK-8, and osteoblastic biomarkers, including ALP, OCN, Collagen I, and RUNX2 were tested via ELISA. The downstream miRNAs and genes targeted by MIAT were predicted by bioinformatics analysis, whose functions and pathways were annotated via GO and KEGG analysis.

RESULTS

Serum MIAT was upregulated in osteoporosis women with high accuracy of diagnostic efficacy. Serum MIAT was even elevated in the fragility fracture group, but decreased in a time manner after operation. MIAT knockdown promoted osteogenic proliferation and differentiation of MC3T3-E1, but the influences were reversed by miR-181a-5p inhibitor. A total of 137 overlapping target genes of miR-181a-5p were predicted based on the miRDB, TargetScan and microT datasets, which were mainly enriched for terms related to signaling pathways regulating pluripotency of stem cells, cellular senescence, and osteoclast differentiation.

CONCLUSIONS

LncRNA MIAT serves as a promising biomarker for osteoporosis, and promotes osteogenic differentiation via targeting miR-181a-5p.

Effects of Improper Mechanical Force on the Production of Sonic Hedgehog, RANKL, and IL-6 in Human Periodontal Ligament Cells In Vitro

Improper mechanical stress may induce side effects during orthodontic treatment. If the roots and alveolar bones are extensively resorbed following excess mechanical stress, unplanned tooth mobility and inflammation can occur. Although multiple factors are believed to contribute to the development of side effects, the cause is still unknown. Sonic hedgehog (Shh), one of the hedgehog signals significantly associated with cell growth and cancer development, promotes osteoclast formation in the jawbone. Shh may be associated with root and bone resorptions during orthodontic treatment. In this study, we investigated the relationships between Shh, RANKL, and IL-6 in human periodontal ligament (hPDL) cells exposed to improper mechanical force. Weights were placed on hPDL cells and human gingival fibroblasts (HGFs) for an optimal orthodontic force group (1.0 g/cm2) and a heavy orthodontic force group (4.0 g/cm2). A group with no orthodontic force was used as a control group. Real-time PCR, SDS-PAGE, and Western blotting were performed to examine the effects of orthodontic forces on the expression of Shh, RANKL, and IL-6 at 2, 4, 6, 8, 12, and 24 h after the addition of pressure. The protein expression of Shh was not clearly induced by orthodontic forces of 1.0 and 4.0 g/cm2 compared with the control in HGFs and hPDL cells. In contrast, RANKL and IL-6 gene and protein expression was significantly induced by 1.0 and 4.0 g/cm2 in hPDL cells for forces lasting 6~24 h. However, neither protein was expressed in HGFs. RANKL and IL-6 expressions in response to orthodontic forces and in the control were clearly inhibited by Shh inhibitor RU-SKI 43. Shh did not directly link to RANKL and IL-6 for root and bone resorptions by orthodontic force but was associated with cell activities to be finally guided by the production of cytokines in hPDL cells.

Compression Promotes the Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Regulating METTL14-mediated IGF1

BACKGROUND AND OBJECTIVES

Orthodontic treatment involves the application of mechanical force to induce periodontal tissue remodeling and ultimately promote tooth movement. It is essential to study the response mechanisms of human periodontal ligament stem cells (hPDLSCs) to improve orthodontic treatment.

METHODS

In this study, hPDLSCs treated with compressive force were used to simulate orthodontic treatment. Cell viability and cell death were assessed using the CCK-8 assay and TUNEL staining. Alkaline phosphatase (ALP) and alizarin red staining were performed to evaluate osteogenic differentiation. The binding relationship between IGF1 and METTL14 was assessed using RIP and dual-luciferase reporter assays.

RESULTS

The compressive force treatment promoted the viability and osteogenic differentiation of hPDLSCs. Additionally, m6A and METTL14 levels in hPDLSCs increased after compressive force treatment, whereas METTL14 knockdown decreased cell viability and inhibited the osteogenic differentiation of hPDLSCs treated with compressive force. Furthermore, the upregulation of METTL14 increased m6A levels, mRNA stability, and IGF1 expression. RIP and dual-luciferase reporter assays confirmed the interaction between METTL14 and IGF1. Furthermore, rescue experiments demonstrated that IGF1 overexpression reversed the effects of METTL14 knockdown in hPDLSCs treated with compressive force.

CONCLUSIONS

In conclusion, this study demonstrated that compressive force promotes cell viability and osteogenic differentiation of hPDLSCs by regulating IGF1 levels mediated by METTL14.

Role of noncoding RNAs in orthodontic tooth movement: new insights into periodontium remodeling

Orthodontic tooth movement (OTM) is biologically based on the spatiotemporal remodeling process in periodontium, the mechanisms of which remain obscure. Noncoding RNAs (ncRNAs), especially microRNAs and long noncoding RNAs, play a pivotal role in maintaining periodontal homeostasis at the transcriptional, post-transcriptional, and epigenetic levels. Under force stimuli, mechanosensitive ncRNAs with altered expression levels transduce mechanical load to modulate intracellular genes. These ncRNAs regulate the biomechanical responses of periodontium in the catabolic, anabolic, and coupling phases throughout OTM. To achieve this, down or upregulated ncRNAs actively participate in cell proliferation, differentiation, autophagy, inflammatory, immune, and neurovascular responses. This review highlights the regulatory mechanism of fine-tuning ncRNAs in periodontium remodeling during OTM, laying the foundation for safe, precise, and personalized orthodontic treatment.

Epigenetic regulation of dental-derived stem cells and their application in pulp and periodontal regeneration

Dental-derived stem cells have excellent proliferation ability and multi-directional differentiation potential, making them an important research target in tissue engineering. An increasing number of dental-derived stem cells have been discovered recently, including dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHEDs), stem cells from apical papilla (SCAPs), dental follicle precursor cells (DFPCs), and periodontal ligament stem cells (PDLSCs). These stem cells have significant application prospects in tissue regeneration because they are found in an abundance of sources, and they have good biocompatibility and are highly effective. The biological functions of dental-derived stem cells are regulated in many ways. Epigenetic regulation means changing the expression level and function of a gene without changing its sequence. Epigenetic regulation is involved in many biological processes, such as embryonic development, bone homeostasis, and the fate of stem cells. Existing studies have shown that dental-derived stem cells are also regulated by epigenetic modifications. Pulp and periodontal regeneration refers to the practice of replacing damaged pulp and periodontal tissue and restoring the tissue structure and function under normal physiological conditions. This treatment has better therapeutic effects than traditional treatments. This article reviews the recent research on the mechanism of epigenetic regulation of dental-derived stem cells, and the core issues surrounding the practical application and future use of pulp and periodontal regeneration.

Host gene and its guest: short story about relation of long-noncoding MIR31HG transcript and microRNA miR-31

Epigenetics is the changes in a cellular phenotype without changes in the genotype. This term is not limited only to the modification of chromatin and DNA but also relates to some RNAs, like non-coding RNAs (ncRNAs), both short and long RNAs (lncRNAs) acting as molecular modifiers. Mobile RNAs, as a free form or encapsulated in exosomes, can regulate neighboring cells or be placed in distant locations. It underlines the vast capacity of ncRNAs as epigenetic elements of transmission information and message of life. One of the amazing phenomena is long non-coding microRNA-host-genes (lnc-MIRHGs) whose processed transcripts function as lncRNAs and also as short RNAs named microRNAs (miRNAs). MIR31HG functions as a modulator of important biological and cellular processes including cell proliferation, apoptosis, cell cycle regulation, EMT process, metastasis, angiogenesis, hypoxia, senescence, and inflammation. However, in most cases, the role of MIR31HG is documented only by one study and there is a lack of exact description of molecular pathways implicated in these processes, and for some of them, such as response to irradiation, no studies have been done. In this review, MIR31HG, as an example of lnc-MIRHGs, was described in the context of its known function and its potential uses as a biomarker in oncology.

Compressive force regulates orthodontic tooth movement via activating the NLRP3 inflammasome

Mechanical stress regulates various cellular functions like cell inflammation, immune responses, proliferation, and differentiation to maintain tissue homeostasis. However, the impact of mechanical signals on macrophages and the underlying mechanisms by which mechanical force regulates bone remodeling during orthodontic tooth movement remain unclear. NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome has been reported to promote osteoclastic differentiation to regulate alveolar bone resorption. But the relationship between the compressive force and NLRP3 inflammasome in macrophages remains unknown. In this study, immunohistochemical staining results showed elevated expression of NLRP3 and interleukin-1β, as well as an increased number of macrophages expressing NLRP3, on the compression side of the periodontal tissues, after force application for 7 days. Furthermore, the number of tartrate-resistant acid phosphatase-positive osteoclasts, and the mRNA and protein expression levels of osteoclast-related genes in the periodontal tissue decreased in the Nlrp3^-/- mice compared to the WT mice group after orthodontic movement. In vitro mechanical force activates the NLRP3 inflammasome and inhibits autophagy. Intraperitoneal injection of the autophagy inhibitor 3-methyladenine in Nlrp3^-/- mice promoted orthodontic tooth movement. This result indicates that the absence of NLRP3 inflammasome activation can be partially compensated for by autophagy inhibitors. Mechanistically, force-induced activation of the NLRP3 inflammasome in macrophages via the cGAS/P2X7R axis. In conclusion, compressive force regulates orthodontic tooth movement via activating the NLRP3 inflammasome.

Long non-coding RNA SNHG5 mediates periodontal inflammation through the NF-κB signaling pathway

AIM

We investigated the role of the long non-coding RNA (lncRNA), small nucleolar RNA host gene 5 (SNHG5), in the pathogenesis of periodontitis.

MATERIALS AND METHODS

A ligature-induced periodontitis mouse model was established, and gingival tissues from patients with periodontitis and healthy controls were collected. Inflammatory cytokines were detected using qRT-PCR and western blotting analyses. Direct interactions between SNHG5 and p65 were detected by RNA pull-down and RNA immunoprecipitation assays. Micro-computed tomography, hematoxylin and eosin staining, and immunohistochemical staining were used to measure periodontal bone loss.

RESULTS

SNHG5 expression was downregulated in human and mouse periodontal tissues compared to that in the healthy controls. In vitro experiments demonstrated that SNHG5 significantly ameliorated tumor necrosis factor-α (TNFα)-induced inflammation. Mechanistically, SNHG5 directly binds to the nuclear factor-kappa B (NF-κB) p65 subunit and inhibits its translocation, thereby suppressing the NF-κB signaling pathway activation and reducing the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 inflammasome expression. Locally injecting si-SNHG5 aggravated the periodontal destruction.

CONCLUSION

This study revealed that SNHG5 mediates periodontal inflammation through the NF-κB signaling pathway, providing a potential therapeutic target for periodontitis treatment. This article is protected by copyright. All rights reserved.

Effects of mechanical force on proliferation and apoptosis of stem cells from human exfoliated deciduous teeth

OBJECTIVES

This study was designed to explore the effects of mechanical force on the proliferation, apoptosis, and morphology of stem cells from human exfoliated deciduous tooth pulp (SHEDs).

MATERIALS AND METHODS

Caries-free stranded deciduous teeth were extracted, and SHEDs were isolated through enzymatic digestion. The cultured SHEDs were subjected to different levels of mechanical stimuli (0, 100, 200, and 300 g) for 7 days (30 min/day) using external centrifugal force. Cell proliferation was evaluated with the CCK-8 assay, and the cell cycle and apoptosis were assessed by flow cytometry. The cell morphology was examined using transmission electron microscopy.

RESULTS

Cell proliferation assay showed no differences between the three stimulation groups and the control group in day 1 to day 3. From the 4th day, cell proliferation was significantly lower in the mechanical force groups than in the control group, but no significant difference was observed among the three mechanical force groups. Besides, there was no significant difference in cell apoptosis among the four groups for 7 days. On day 7 after stimulation, the SHEDs were shrunken, with significantly increased isochromosome in the nucleus and an increase in lysosomes.

CONCLUSIONS

Mechanical force can inhibit the proliferation and affect morphology of SHEDs, but it has no effect on cell apoptosis.

CLINICAL RELEVANCE

Mechanical force stimulation significantly inhibited cell proliferation of SHEDs. Mechanical force stimulation had no significant effect on cell apoptosis of SHEDs. The morphology and ultrastructure of SHEDs changed after mechanical force stimulation.

Long non-coding RNA SNHG5 promotes the osteogenic differentiation of bone marrow mesenchymal stem cells via the miR-212-3p/GDF5/SMAD pathway

Background

The treatment of bone loss has posed a challenge to clinicians for decades. Thus, it is of great significance to identify more effective methods for bone regeneration. However, the role and mechanisms of long non-coding RNA small nucleolar RNA host gene 5 (SNHG5) during osteogenic differentiation remain unclear.

Methods

We investigated the function of SNHG5, Yin Yang 1 (YY1), miR-212-3p and growth differentiation factor 5 (GDF5) in osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) in vitro and in vivo. Molecular mechanisms were clarified by chromatin immunoprecipitation assay and dual luciferase reporter assay.

Results

We found SNHG5 expression was upregulated during osteogenesis of hBMSCs. Knockdown of SNHG5 in hBMSCs inhibited osteogenic differentiation while overexpression of SNHG5 promoted osteogenesis. Moreover, YY1 transcription factor directly bound to the promoter region of SNHG5 and regulated SNHG5 expression to promote osteogenesis. Dual luciferase reporter assay confirmed that SNHG5 acted as a miR-212-3p sponge and miR-212-3p directly targeted GDF5 and further activated Smad1/5/8 phosphorylation. miR-212-3p inhibited osteogenic differentiation, while GDF5 promoted osteogenic differentiation of hBMSCs. In addition, calvarial defect experiments showed knockdown of SNHG5 and GDF5 inhibited new bone formation in vivo.

Conclusion

Our results demonstrated that the novel pathway YY1/SNHG5/miR-212-3p/GDF5/Smad regulates osteogenic differentiation of hBMSCs and may serve as a potential target for the treatment of bone loss.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02781-8.

The Expression and Regulatory Roles of Long Non-Coding RNAs in Periodontal Ligament Cells: A Systematic Review

Periodontal ligament (PDL) cells play a pivotal role in periodontal and bone homeostasis and have promising potential for regenerative medicine and tissue engineering. There is compelling evidence that long non-coding RNAs (lncRNAs) are differentially expressed in PDL cells compared to other cell types and that these lncRNAs are involved in a variety of biological processes. This study systematically reviews the current evidence regarding the expression and regulatory functions of lncRNAs in PDL cells during various biological processes. A systematic search was conducted on PubMed, the Web of Science, Embase, and Google Scholar to include articles published up to 1 July 2021. Original research articles that investigated the expression or regulation of lncRNAs in PDL cells were selected and evaluated for a systematic review. Fifty studies were ultimately included, based on our eligibility criteria. Thirteen of these studies broadly explored the expression profiles of lncRNAs in PDL cells using microarray or RNA sequencing. Nineteen studies investigated the mechanisms by which lncRNAs regulate osteogenic differentiation in PDL cells. The remaining 18 studies investigated the mechanism by which lncRNAs regulate the responses of PDL cells to various stimuli, namely, lipopolysaccharide-induced inflammation, tumor necrosis factor alpha-induced inflammation, mechanical stress, oxidative stress, or hypoxia. We systematically reviewed studies on the expression and regulatory roles of lncRNAs in diverse biological processes in PDL cells, including osteogenic differentiation and cellular responses to inflammation, mechanical stress, and other stimuli. These results provide new insights that may guide the development of lncRNA-based therapeutics for periodontal and bone regeneration.

Leptin Aggravates Periodontitis by Promoting M1 Polarization via NLRP3

Periodontitis is characterized by periodontal pocket formation, loss of attachment, and alveolar bone resorption. Both innate and adaptive immunity are involved in the pathogenesis of this oral chronic inflammatory disease. Accumulating evidence indicates a critical role of leptin in periodontal diseases. However, the mechanism by which leptin promotes periodontitis pathogenesis remains unclear. In the present study, we observed an elevated expression of leptin in the serum of periodontitis mice compared to that in healthy controls. There was a higher extent of M1 phenotype macrophage infiltration in mice periodontitis samples than in healthy controls. A positive correlation was observed between the serum leptin levels and M1 macrophages. Treatment with leptin increased M1 macrophage polarization and decreased M2 macrophage polarization in RAW 264.7 cells. Moreover, leptin facilitated lipopolysaccharide (LPS)-induced M1 phenotype macrophage polarization in RAW 264.7 cells. In bone marrow-derived macrophages (BMDMs) generated from leptin-deficient obese (ob/ob) mice, M1 macrophage polarization was significantly attenuated after LPS stimulation compared to the healthy controls. With regards to the molecular mechanism, we found that leptin activated the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome and promoted M1 polarization via the NLRP3 inflammasome in vitro. In BMDMs generated from Nlrp3^-/- mice, M1 macrophage polarization was significantly attenuated after synchronous stimulation with leptin and LPS compared with BMDMs produced by healthy controls. The NLRP3 inhibitor MCC950 also prevented leptin-mediated M1 macrophage polarization in RAW 264.7 cells. Nlrp3^-/- periodontitis models indicated that leptin aggravates the periodontal response to the ligature by promoting M1 macrophage polarization via the NLRP3 inflammasome. Taken together, we show that leptin promotes the progression of periodontitis via proinflammatory M1 macrophage skewing, and targeting leptin/NLRP3 signaling may be a feasible approach for treating periodontitis.

Intermittent compressive force induces cell cycling and reduces apoptosis in embryoid bodies of mouse induced pluripotent stem cells

In vitro manipulation of induced pluripotent stem cells (iPSCs) by environmental factors is of great interest for three-dimensional (3D) tissue/organ induction. The effects of mechanical force depend on many factors, including force and cell type. However, information on such effects in iPSCs is lacking. The aim of this study was to identify a molecular mechanism in iPSCs responding to intermittent compressive force (ICF) by analyzing the global gene expression profile. Embryoid bodies of mouse iPSCs, attached on a tissue culture plate in 3D form, were subjected to ICF in serum-free culture medium for 24 h. Gene ontology analyses for RNA sequencing data demonstrated that genes differentially regulated by ICF were mainly associated with metabolic processes, membrane and protein binding. Topology-based analysis demonstrated that ICF induced genes in cell cycle categories and downregulated genes associated with metabolic processes. The Kyoto Encyclopedia of Genes and Genomes database revealed differentially regulated genes related to the p53 signaling pathway and cell cycle. qPCR analysis demonstrated significant upregulation of Ccnd1, Cdk6 and Ccng1. Flow cytometry showed that ICF induced cell cycle and proliferation, while reducing the number of apoptotic cells. ICF also upregulated transforming growth factor β1 (Tgfb1) at both mRNA and protein levels, and pretreatment with a TGF-β inhibitor (SB431542) prior to ICF abolished ICF-induced Ccnd1 and Cdk6 expression. Taken together, these findings show that TGF-β signaling in iPSCs enhances proliferation and decreases apoptosis in response to ICF, that could give rise to an efficient protocol to manipulate iPSCs for organoid fabrication.