The role of PHF8 and TLR4 in osteogenic differentiation of periodontal ligament cells in inflammatory environment

Small extracellular vesicles derived from lipopolysaccharide-preconditioned dental follicle cells inhibit cell apoptosis and alveolar bone loss in periodontitis

OBJECTIVE

This study aimed to explore the effects of small extracellular vesicles derived from lipopolysaccharide-preconditioned dental follicle cells (L-D-sEV) on periodontal ligament cells from periodontitis affected teeth (p-PDLCs) in vitro and experimental periodontitis in mice.

DESIGN

In vitro, the biological function of p-PDLCs and the underlying molecular mechanism were investigated by flow cytometry, Western blot, and quantitative real-time PCR (qRT-PCR) analysis. Eighteen-eight-week-old male C57BL/6 mice were randomly divided into three groups: control (Con), periodontitis (Peri), and L-D-sEV groups. Mice periodontitis model was induced by placing the 5-0 silk thread (around the maxillary second molar) and P.gingivalis (1 ×107 CFUs per mouse). In vivo, the alveolar bone loss, osteoclast activity, and macrophage polarization were measured by micro-computed tomography and histological analysis.

RESULTS

In vitro, the RANKL/OPG ratio and phosphorylation of JNK and P38 protein levels of p-PDLCs were significantly decreased after L-D-sEV administration. Besides, flow cytometry and qRT-PCR analysis showed that L-D-sEV reduced apoptosis of p-PDLCs, down-regulated apoptosis-related genes Caspase-3 and BCL-2-Associated X expression, and up-regulated B-cell lymphoma-2 gene levels. In vivo, L-D-sEV administration significantly reduced alveolar bone loss, inhibited osteoclast activity, and induced M2 polarization. The histological analysis showed that iNOS/CD206, RANKL/OPG, p-JNK/JNK, and p-P38/P38 ratios were significantly lower in the L-D-sEV group than in the Peri group.

CONCLUSIONS

L-D-sEV administration alleviated alveolar bone loss by mediating RANKL/OPG-related osteoclast activity and M2 macrophage polarization, alleviating p-PDLCs apoptosis and proliferation via the JNK and P38 pathways.

Long non-coding RNA LncTUG1 regulates favourable compression force-induced cementocytes mineralization via PU.1/TLR4/SphK1 signalling

Orthodontic tooth movement (OTM) is a highly coordinated biomechanical response to orthodontic forces with active remodelling of alveolar bone but minor root resorption. Such antiresorptive properties of root relate to cementocyte mineralization, the mechanisms of which remain largely unknown. This study used the microarray analysis to explore long non-coding ribonucleic acids involved in stress-induced cementocyte mineralization. Gain- and loss-of-function experiments, including Alkaline phosphatase (ALP) activity and Alizarin Red S staining, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and immunofluorescence analyses of mineralization-associated factors, were conducted to verify long non-coding ribonucleic acids taurine-upregulated gene 1 (LncTUG1) regulation in stress-induced cementocyte mineralization, via targeting the Toll-like receptor 4 (TLR4)/SphK1 axis. The luciferase reporter assays, chromatin immunoprecipitation assays, RNA pull-down, RNA immunoprecipitation, and co-localization assays were performed to elucidate the interactions between LncTUG1, PU.1, and TLR4. Our findings indicated that LncTUG1 overexpression attenuated stress-induced cementocyte mineralization, while blocking the TLR4/SphK1 axis reversed the inhibitory effect of LncTUG1 on stress-induced cementocyte mineralization. The in vivo findings also confirmed the involvement of TLR4/SphK1 signalling in cementocyte mineralization during OTM. Mechanistically, LncTUG1 bound with PU.1 subsequently enhanced TLR4 promotor activity and thus transcriptionally elevated the expression of TLR4. In conclusion, our data revealed a critical role of LncTUG1 in regulating stress-induced cementocyte mineralization via PU.1/TLR4/SphK1 signalling, which might provide further insights for developing novel therapeutic strategies that could protect roots from resorption during OTM.

Identifying genes for regulating osteogenic differentiation of human periodontal ligament stem cells in inflammatory environments by bioinformatics analysis

BACKGROUND AND OBJECTIVES

Periodontitis is an immuno-inflammatory disease caused by dental plaque biofilms and inflammations. The regeneration of bone tissue in inflammatory environment is of great significance for the treatment of periodontal disease, but the specific molecular mechanism of bone formation in periodontitis still needs further exploration. The objective of this study was to identify key osteogenesis-related genes (ORGs) in periodontitis.

METHODS

We used two datasets from the Gene Expression Omnibus (GEO) database to find differentially expressed mRNAs and miRNAs, further performed Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Then we predicted the downstream genes of the differentially expressed miRNAs (DEMs) by the TargetScan database and established a miRNA-mRNA regulatory network. Finally, the osteogenic mechanism of periodontitis was explored through quantitative real-time PCR (qRT-PCR) by inducing inflammatory environment and osteogenic differentiation of hPDLSCs.

RESULTS

Through differential expression analysis and prediction of downstream target genes of DEMs, we created a miRNA-mRNA regulatory network consisting of 29 DEMs and 11 differentially expressed osteogenesis-related genes (DEORGs). In addition, the qRT-PCR results demonstrated that BTBD3, PLAT, AKAP12, SGK1, and GLCE expression levels were significantly upregulated, while those of TIMP3, ZCCHC14, LIN7A, DNAH6, NNT, and ITGA6 were downregulated under the dual effects of inflammatory stimulation and osteogenic induction.

CONCLUSION

DEORGs might be important factors in the osteogenic phase of periodontitis, and the miRNA-mRNA network may shed light on the clarification of the role and mechanism of osteogenesis in periodontitis and contribute to the development of novel therapeutic strategies.

O-GlcNAcylation of TLR4 inhibits osteogenic differentiation of periodontal ligament stem cells

BACKGROUND

Toll-like receptor 4 (TLR4)-mediated inflammatory responses are associated with diabetes and periodontitis, which are dysregulated by O-GlcNAcylation.

OBJECTIVE

This study aimed to investigate the effects of O-GlcNAc transferase (OGT)-mediated TLR4 O-GlcNAcylation on the osteogenesis of periodontal ligament stem cells (PDLCs).

METHODS

PDLCs were treated with high glucose (HG) to establish a cell model. Osteogenic differentiation was evaluated using western blotting, an alkaline phosphatase activity assay, and an alizarin red S staining assay. The regulation of OGT on the O-GlcNAcylation of TLR4 was analyzed using co-immunoprecipitation, immunoprecipitation, western blotting, and immunofluorescence staining.

RESULTS

The results showed that HG inhibited osteogenic differentiation and promoted inflammatory response. Knockdown of OGT promoted osteogenic differentiation of HG-treated PDLCs. OGT interacted with TLR4 and increased the O-GlcNAcylation and protein levels of TLR4 in the cytomembrane of PDLCs. Moreover, silenced TLR4 reversed the effects on osteogenic differentiation induced by OGT in HG-treated PDLCs.

CONCLUSION

O-GlcNAcylation of TLR4 induced by OGT suppresses osteogenic differentiation of PDLCs after HG stimulation. The findings suggest a promising strategy for treating DP.

The osteogenic effects of sappanchalcone in vitro and in vivo

BACKGROUND AND OBJECTIVES

The utilization of natural products to enhance the function of periodontal ligament cells (PDLCs) has emerged as a popular area of research. Recent investigations have demonstrated that sappanchalcone (SC) possesses pharmacological properties such as anti-inflammatory and osteoprotective effects. This study aims to explore the impact of SC on the in vivo and in vitro osteogenic differentiation ability of PDLCs.

MATERIALS

Cell proliferation was quantified using the CCK-8 assay, while gene expression levels were assessed through qRT-PCR analysis. Osteoblast differentiation capacity was evaluated by employing Alizarin red staining (ARS), alkaline phosphatase (ALP) staining and western blot (WB) analysis. A rat model of periodontitis was established utilizing the tether-wire method. Micro-CT imaging and hematoxylin and eosin (HE) staining were employed to evaluate alveolar bone resorption. Masson's trichrome staining was utilized to observe fiber alignment, whereas immunohistochemistry (IHC) techniques were applied for detecting osteogenic and inflammatory factors.

RESULTS

The results from the CCK-8 assay indicate no observed cytotoxicity for concentrations of 1, 5, or 10 nM for SC treatment (p < .05), while qRT-PCR analysis demonstrates a significant decrease in inflammatory factors such as MMP-1 and IL-6 with treatment by SC (p < .05). Additionally, western blotting reveals an increase in protein expression levels of Runx2 and OPN within PDLCs treated with SC compared to control groups (p < .05), which is further supported by ARS and ALP staining indicating an increase in mineralized nodules formation along with elevated ALP content within these cells following treatment with this compound (p < .05). Finally, both HE staining as well as micro-CT imaging suggest potential benefits associated with using this compound including slowing alveolar bone resorption while simultaneously promoting junctional epithelium proliferation.

CONCLUSIONS

Our in vitro and in vivo findings suggest that SC can effectively enhance the inflammatory response of PDLCs and promote their osteogenic differentiation ability under inflammatory conditions, indicating its potential as a promising therapeutic agent for improving periodontal inflammation and bone formation.

MiR-155 Negatively Regulates Anti-Viral Innate Responses among HIV-Infected Progressors

HIV infection impairs host immunity, leading to progressive disease. An anti-retroviral treatment efficiently controls viremia but cannot completely restore the immune dysfunction in HIV-infected individuals. Both host and viral factors determine the rate of disease progression. Among the host factors, innate immunity plays a critical role; however, the mechanism(s) associated with dysfunctional innate responses are poorly understood among HIV disease progressors, which was investigated here. The gene expression profiles of TLRs and innate cytokines in HIV-infected (LTNPs and progressors) and HIV-uninfected individuals were examined. Since the progressors showed a dysregulated TLR-mediated innate response, we investigated the role of TLR agonists in restoring the innate functions of the progressors. The stimulation of PBMCs with TLR3 agonist-poly:(I:C), TLR7 agonist-GS-9620 and TLR9 agonist-ODN 2216 resulted in an increased expression of IFN-α, IFN-β and IL-6. Interestingly, the expression of IFITM3, BST-2, IFITM-3, IFI-16 was also increased upon stimulation with TLR3 and TLR7 agonists, respectively. To further understand the molecular mechanism involved, the role of miR-155 was explored. Increased miR-155 expression was noted among the progressors. MiR-155 inhibition upregulated the expression of TLR3, NF-κB, IRF-3, TNF-α and the APOBEC-3G, IFITM-3, IFI-16 and BST-2 genes in the PBMCs of the progressors. To conclude, miR-155 negatively regulates TLR-mediated cytokines as wel l as the expression of host restriction factors, which play an important role in mounting anti-HIV responses; hence, targeting miR-155 might be helpful in devising strategic approaches towards alleviating HIV disease progression.

Effect of LSD1 on osteogenic differentiation of human periodontal ligament stem cells in periodontitis

OBJECTIVE

Periodontitis is a chronic inflammation of periodontal tissues. This study is expected to assess the effect of LSD1 on the osteogenic differentiation of hPDLSCs in periodontitis.

METHODS

hPDLSCs were separated, cultivated, and identified, and then treated by LPS to induce inflammatory microenvironment and subjected to osteogenic differentiation. Subsequently, LSD1 expression was determined, and then silenced to assess its effect on hPDLSCs. Next, the binding relation between LSD1 and miR-590-3p was analyzed. miR-590-3p expression was detected and then overexpressed to evaluate its role in hPDLSCs in periodontitis. Afterward, the relation between LSD1 and OSX was analyzed. H3K4me2 level and OSX transcription were measured, and the role of H3K4me2 was determined. Additionally, the role of OSX in hPDLSCs was verified.

RESULTS

LSD1 was poorly expressed after osteogenic differentiation of hPDLSCs while it was rescued upon LPS induction. The osteogenic differentiation of hPDLSC in periodontitis was strengthened upon LSD1 downregulation. Besides, miR-590-3p targeted LSD1 transcription, and LSD1 inhibited OSX transcription via H3K4me2 demethylation. miR-590-3p overexpression improved osteogenic differentiation of hPDLSCs in periodontitis. But this improvement was annulled by OSX inhibition.

CONCLUSION

miR-590-3p targeted LSD1 transcription and upregulated H3K4me2 methylation to promote OSX transcription, thereby encouraging osteogenic differentiation of hPDLSCs in periodontitis.

Long non-coding RNA APDC plays important regulatory roles in metabolism of bone and adipose tissues

The long noncoding RNA (lncR) ANRIL in the human genome is an established genetic risk factor for atherosclerosis, periodontitis, diabetes, and cancer. However, the regulatory role of lncR-ANRIL in bone and adipose tissue metabolism remains unclear. To elucidate the function of lncRNA ANRIL in a mouse model, we investigated its ortholog, AK148321 (referred to as lncR-APDC), located on chr4 of the mouse genome, which is hypothesized to have similar biological functions to ANRIL. We initially revealed that lncR-APDC in mouse bone marrow cells (BMSCs) and lncR-ANRIL in human osteoblasts (hFOBs) are both increased during early osteogenesis. Subsequently, we examined the osteogenesis, adipogenesis, osteoclastogenesis function with lncR-APDC deletion/overexpression cell models. In vivo, we compared the phenotypic differences in bone and adipose tissue between APDC-KO and wild-type mice. Our findings demonstrated that lncR-APDC deficiency impaired osteogenesis while promoting adipogenesis and osteoclastogenesis. Conversely, the overexpression of lncR-APDC stimulated osteogenesis, but impaired adipogenesis and osteoclastogenesis. Furthermore, KDM6B was downregulated with lncR-APDC deficiency and upregulated with overexpression. Through binding-site analysis, we identified miR-99a as a potential target of lncR-APDC. The results suggest that lncR-APDC exerts its osteogenic function via miR-99a/KDM6B/Hox pathways. Additionally, osteoclasto-osteogenic imbalance was mediated by lncR-APDC through MAPK/p38 and TLR4/MyD88 activation. These findings highlight the pivotal role of lncR-APDC as a key regulator in bone and fat tissue metabolism. It shows potential therapeutic for addressing imbalances in osteogenesis, adipogenesis, and osteoclastogenesis.

LIPUS as a potential strategy for periodontitis treatment: A review of the mechanisms

Periodontitis is a chronic inflammatory condition triggered by oral bacteria. A sustained inflammatory state in periodontitis could eventually destroy the alveolar bone. The key objective of periodontal therapy is to terminate the inflammatory process and reconstruct the periodontal tissues. The traditional Guided tissue regeneration (GTR) procedure has unstable results due to multiple factors such as the inflammatory environment, the immune response caused by the implant, and the operator's technique. Low-intensity pulsed ultrasound (LIPUS), as acoustic energy, transmits the mechanical signals to the target tissue to provide non-invasive physical stimulation. LIPUS has positive effects in promoting bone regeneration, soft-tissue regeneration, inflammation inhibition, and neuromodulation. LIPUS can maintain and regenerate alveolar bone during an inflammatory state by suppressing the expression of inflammatory factors. LIPUS also affects the cellular behavior of periodontal ligament cells (PDLCs), thereby protecting the regenerative potential of bone tissue in an inflammatory state. However, the underlying mechanisms of the LIPUS therapy are still yet to be summarized. The goal of this review is to outline the potential cellular and molecular mechanisms of periodontitis-related LIPUS therapy, as well as to explain how LIPUS manages to transmit mechanical stimulation into the signaling pathway to achieve inflammatory control and periodontal bone regeneration.

Synergistic Effect of Polydatin and Polygonatum sibiricum Polysaccharides in Combating Atherosclerosis via Suppressing TLR4-Mediated NF-κB Activation in ApoE-Deficient Mice

Objective

Atherosclerosis is a chronic inflammatory disease, which is closely related to hyperlipidemia, inflammatory responses, and oxidative stress. As natural products, polydatin (PD) and Polygonatum sibiricum polysaccharides (PSP) have remarkable pharmacological effects in anti-inflammatory, antioxidant stress, and lipid regulation. In this study, we sought to investigate whether the combination of polydatin and P. sibiricum polysaccharides play an anti-atherosclerotic role in alleviating inflammatory responses by inhibiting the toll-like receptor4 (TLR4)/myeloid differentiation factor88(MyD88)/nuclear factor-kappa B(NF-κB) signaling pathway.

Methods

Thirty-two ApoE-/- mice were fed with a high-fat diet (HFD) starting at the age of 8 weeks. Mice were randomly divided into four groups; (1) model group, (2) PD (100 mg/kg) + PSP (50 mg/kg) group, (3) TAK-242 (3 mg/kg) (TLR4 inhibitor) group, (4) PD (100 mg/kg) + PSP (50 mg/kg) + TAK-242 (3 mg/kg) group. Eight age-matched wild-type C57BL/6J mice fed an ordinary diet were used as a control group. Blood lipid levels were measured with an automatic biochemical analyzer. The lipid accumulation and histopathological changes in the aorta and liver were observed by Oil Red O and hematoxylin and eosin (H&E) staining, respectively. ELISA was performed to measure the serum levels of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). Western blot analysis was performed to analyze the expression of key proteins in the TLR4/MyD88/NF-κB signaling pathway.

Results

Compared with the model group, the combination of PD and PSP significantly inhibit serum lipids (low-density lipoprotein cholesterol, total cholesterol, and triglyceride) and cell adhesion molecules (VCAM-1, ICAM-1). Oil Red O staining indicated that the combination of PD and PSP decrease lipid accumulation in the aorta and liver. Moreover, H&E staining suggested that the combination of PD and PSP alleviate aortic intimal hyperplasia, inflammatory cell infiltration, and hepatic steatosis. Finally, the combination of PD and PSP inhibit the expression of TLR4, MyD88, and the phosphorylation level of NF-κB p65 protein in the aorta.

Conclusions

Polydatin synergizes with P. sibiricum polysaccharides in preventing the development of atherosclerosis in ApoE-/- mice by inhibiting the TLR4/MyD88/NF-κB signaling pathway.

MicroRNA-203 mediates P. gingivalis LPS-induced inflammation and differentiation of periodontal ligament cells

AIM

In this study, we aimed to explore the effects of microRNA-203 (miR-203) on P. gingivalis lipopolysaccharide (P.g. LPS)-stimulated periodontal ligament cells (PDLCs) and identify potential molecular targets for periodontitis treatment.

METHODS

PDLCs were stimulated by P.g. LPS, followed by quantification of miR-203 and AP-1 expression. Next, loss- and gain-of-function experiments were applied in P.g. LPS-induced PDLCs. The proliferation, apoptosis, and differentiation of PDLCs were determined and mineralized nodule numbers were counted. Functional assays were used to identify interactions among miR-203, activator protein 1 (AP-1), and intercellular adhesion molecule 1 (ICAM-1). In addition, expression of osteogenesis-related genes and release of proinflammatory factors were analyzed.

RESULTS

miR-203 was found to be downregulated while AP-1 was upregulated in PDLCs stimulated by P.g. LPS. The overexpression of miR-203 promoted P.g. LPS-stimulated PDLC proliferation and differentiation, inhibited apoptosis, and increased the number of mineralized nodules. miR-203 was verified to downregulate AP-1/ICAM-1 axis. miR-203 overexpression reduced the secretion of proinflammatory factors while increasing expression of osteogenesis-related genes in P.g. LPS-stimulated PDLCs, which was reversed by overexpressing AP-1 and ICAM-1.

CONCLUSION

These experimental data demonstrated the potential inhibitory effects of overexpressed miR-203 on periodontitis development by promoting PDLC differentiation and suppressing inflammatory responses through AP-1/ICAM-1 axis.

Epigenetic modifications of histones during osteoblast differentiation

In bone biology, epigenetics plays a key role in mesenchymal stem cells' (MSCs) commitment towards osteoblasts. It involves gene regulatory mechanisms governed by chromatin modulators. Predominant epigenetic mechanisms for efficient osteogenic differentiation include DNA methylation, histone modifications, and non-coding RNAs. Among these mechanisms, histone modifications critically contribute to altering chromatin configuration. Histone based epigenetic mechanisms are an essential mediator of gene expression during osteoblast differentiation as it directs the bivalency of the genome. Investigating the importance of histone modifications in osteogenesis may lead to the development of epigenetic-based remedies for genetic disorders of bone. Hence, in this review, we have highlighted the importance of epigenetic modifications such as post-translational modifications of histones, including methylation, acetylation, phosphorylation, ubiquitination, and their role in the activation or suppression of gene expression during osteoblast differentiation. Further, we have emphasized the future advancements in the field of epigenetics towards orthopaedical therapeutics.

CircMAP3K11 Contributes to Proliferation, Apoptosis and Migration of Human Periodontal Ligament Stem Cells in Inflammatory Microenvironment by Regulating TLR4 via miR-511 Sponging

Growing number of studies regarding the role of circRNAs in the development of various diseases have emerged in recent years, but the role of circRNAs in periodontitis pathogenesis remains obscure. Human periodontal ligament stem cells (hPDLSCs) play a critical role in periodontal remodeling, regeneration and repair processes, and their regenerative capacity could be prohibited in local periodontal inflammatory microenvironment. Herein, we sought to uncover the molecular mechanisms of periodontitis pathogenesis by investigating the role of circMAP3K11 (hsa_circ_002284) for regenerative capacity of hPDLSCs under an inflammatory condition. The hPDLSCs isolated from periodontitis patients were used as a cell model of inflammatory microenvironment to study the effect of the circMAP3K11/miR-511-3p/TLR4 axis on the proliferation, apoptosis and migration of hPDLSCs under inflammatory conditions. Compared to the periodontal tissues from normal subjects, those from periodontitis patients exhibited higher expression levels of circMAP3K11 and TLR4, and lower expression level of miR-511-3p. Both the expressions of circMAP3K11 and TLR4 were negatively correlated with the expressions of miR-511-3p in periodontitis. In vitro studies demonstrated that circMAP3K11 is capable of enhancing hPDLSCs proliferation and migration, and reducing the apoptosis of hPDLSCs. We also found that circMAP3K11 could up-regulate the expression of transcription factors that are closely related to periodontal regeneration (Runx2, OSX, ATF4, and BSP). RT-PCR and western blot showed that the inhibitory role of miR-511-3p on TLR4 expression could be reversed by circMAP3K11, which was in line with the results of bioinformatics tools and luciferase reporter assay. Meanwhile, both in vitro and in vivo studies indicated that circMAP3K11 could reverse the effects of miR-511-3p in periodontitis, which further confirmed that circMAP3K11 functioned as a ‘sponge’ of miR-511-3p to positively regulate the expression of TLR4. Taken together, our study preliminarily uncovered a circMAP3K11/miR-511-3p/TLR4 axis that regulates the function of hPDLSCs in periodontitis, providing novel insight and scientific base in the treatment of periodontal tissue regeneration based on stem cells.