Efficacy of Photobiomodulation and Metformin on Diabetic Cell Line of Human Periodontal Ligament Stem Cells through Keap1/Nrf2/Ho-1 Pathway

Autophagy, a double-edged sword for oral tissue regeneration

BACKGROUND

Oral health is of fundamental importance to maintain systemic health in humans. Stem cell-based oral tissue regeneration is a promising strategy to achieve the recovery of impaired oral tissue. As a highly conserved process of lysosomal degradation, autophagy induction regulates stem cell function physiologically and pathologically. Autophagy activation can serve as a cytoprotective mechanism in stressful environments, while insufficient or over-activation may also lead to cell function dysregulation and cell death.

AIM OF REVIEW

This review focuses on the effects of autophagy on stem cell function and oral tissue regeneration, with particular emphasis on diverse roles of autophagy in different oral tissues, including periodontal tissue, bone tissue, dentin pulp tissue, oral mucosa, salivary gland, maxillofacial muscle, temporomandibular joint, etc. Additionally, this review introduces the molecular mechanisms involved in autophagy during the regeneration of different parts of oral tissue, and how autophagy can be regulated by small molecule drugs, biomaterials, exosomes/RNAs or other specific treatments. Finally, this review discusses new perspectives for autophagy manipulation and oral tissue regeneration.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Overall, this review emphasizes the contribution of autophagy to oral tissue regeneration and highlights the possible approaches for regulating autophagy to promote the regeneration of human oral tissue.

Photo biomodulation of dental derived stem cells to ameliorate regenerative capacity: In vitro study

Background

Dental regeneration benefits from improving the features of dental derived stem cells. Gallium-aluminum-arsenide laser had a significant role in modification of cell behavior in different cell lines and culture conditions. Hence, exploring its mechanism and effect on dental derived stem cells would benefit prospective regenerative dental therapies.

Objectives

To assess the impact of photo biomodulation by Low-Level-Laser on isolated Dental Pulp derived Stem Cells and Periodontal Ligament derived Stem Cells regarding their proliferation and osteogenic differentiation.

Methods

Isolated DPSCs and PDLSCs from impacted third molars were subjected to Gallium-aluminum-arsenide laser for 12 sec and 3.6 J/cm2. The proliferative capacity was evaluated via 3-(4,5-dimethylthiazol-2-yl),2,5-diphenyltetrazolium bromide (MTT) Assay and Trypan blue stain. Cell osteogenic differentiation potentials were assessed by alkaline phosphatase assay and alizarin red stain, polymerase chain reaction was performed to quantify Nuclear factor Kappa gene expression.

Results

DPSCs subjected to laser bio-stimulation showed the best results regarding cell viability (MTT) and osteogenic differentiation (ALP assay), and calcium deposition at 3 intervals (3, 7, 14 days), meanwhile, PDLSCs subjected to laser bio-stimulation showed better result than control but less than DPSCs. While NF-KB gene expression was proven to be approximately comparable for both groups. Generally, the Photo-bio modulated groups showed better results than their control groups.

Conclusion

Low-level laser bio-stimulation (LLL) therapy improves DPSC and PDLSC osteogenic differentiation and proliferation via the activation of the NF-KB pathway. Also, the DPSCs outperformed PDLSCs in terms of performance.

Clinical significance

These results can be beneficial information and a reference database for more research in tissue engineering, dental therapy, and regeneration.

The effect of adjunctive LASER application on periodontal ligament stem cells

Periodontal regeneration involves the composite action of cell, scaffolds and signaling molecules. There are numerous autologous sources of regenerative cells which are present close to the vicinity of the periodontally debilitated site, the primary one being the periodontal ligament stem cell, which is believed to have a key role in regeneration. Various methods can be harnessed to optimize and enhance the regenerative potential of PDLSCs such as the application of LASERs. In the last few years there have been various studies which have evaluated the effect of different types of LASERs on PDLSCs and the present review summarizes the photo-biomodulative activity of LASERs in general and its beneficial role in the stimulation of PDLSC specifically.

The Role of Photobiomodulation on Dental-Derived Stem Cells in Regenerative Dentistry: A Comprehensive Systematic Review

BACKGROUND

Photobiomodulation therapy involves exposing tissues to light sources, including light-emitting diodes or low-level lasers, which results in cellular function modulation. The molecular mechanism of this treatment is revealed, demonstrating that depending on the light settings utilized, it has the potential to elicit both stimulatory and inhibitory reactions.

OBJECTIVE

The current systematic review aimed to evaluate the impact of photobiomodulation therapy on dental stem cells and provide an evidence-based conclusion in this regard.

METHODS

This systematic review was performed and reported based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) revised guidelines. PICO(S) components were employed to define the inclusion criteria. Web of Science, Scopus, Medline as well as grey literature, and google scholar were searched up to September 2021 to retrieve relevant papers.

RESULTS

Photobiomodulation therapy showed promising effects on the proliferation, viability, and differentiation of dental stem cells. This finding was based on reviewing related articles with a low risk of bias.

CONCLUSION

Despite the positive benefits of photobiomodulation therapy on dental stem cells, the current data do not provide a definitive conclusion on the best physical parameters for enhancing cell viability, proliferation, and differentiation.

Photobiomodulation Effects on Periodontal Ligament Stem Cells: A Systematic Review of In Vitro Studies

BACKGROUND

Stem cell therapy has been considered to play a paramount role in the treatment modalities available for regenerative dentistry. The established beneficial effects of photobiomodulation (PBM) at the cellular level have led to the combined use of these two factors (PBM and stem cells). The main goal of this study was firstly to critically appraise the effects of PBM on periodontal ligament stem cells (PDLSCs), and secondly to explore the most effective PBM protocols applied.

METHODS

Pubmed, Cochrane, Scopus, Science Direct, and Google Scholar search engines were used to identify experimental in vitro studies in which PBM was applied to cultured PDLSCs. After applying specific keywords, additional filters, and inclusion/exclusion criteria, a preliminary number of 245 articles were narrowed down to 11 in which lasers and LEDs were used within the 630 - 1064 nm wavelength range. Selected articles were further assessed by three independent reviewers for strict compliance with PRISMA guidelines, and a modified Cochrane risk of bias to determine eligibility.

STATISTICAL ANALYSIS

The dataset analysed was extracted from the studies with sufficient and clearly presented PBM protocols. Simple univariate regression analysis was performed to explore the significance of contributions of potential quantitative predictor variables toward study outcomes, and a one-way ANOVA model was employed for testing differences between the laser or LED sources of the treatments. The significance level for testing was set at α = 0.05.

RESULTS

The proliferation rate, osteogenic differentiation, and expression of different indicative genes for osteogenesis and inflammation suppression were found to be positively affected by the application of various types of lasers and LEDs. With regard to the PBM protocol, only the wavelength variable appeared to affect the treatment outcome; indeed, the 940 nm wavelength parameter was found not to exert a favourable effect.

CONCLUSIONS

Photobiomodulation can enhance the stemness and differentiation capacities of periodontal ligament stem cells. Therefore, for PBM protocols, there remains no consensus amongst the scientific community. Statistical analyses performed here indicated that the employment of a near-infrared (NIR) wavelength of 940 nm may not yield a significant favourable outcome, although those within the 630 - 830 nm range did so. Concerning the fluence, it should not exceed 8 J/cm2 when therapy is applied by LED devices, and 4 J/cm2 when applied by lasers, respectively.

Protective role of metformin in preeclampsia via the regulation of NF-κB/sFlt-1 and Nrf2/HO-1 signaling pathways by activating AMPK

INTRODUCTION

Preeclampsia (PE) is a pregnancy complication that leads to hypertension and proteinuria and causes maternal mortality. Metformin (MET) is an oral hypoglycemic agent that activates AMPK-regulated signaling pathways and inhibits inflammation and oxidative stress responses. This study explored MET's roles and molecular mechanisms in PE.

METHODS

The protein or mRNA expression of signaling pathways and inflammation-related genes were detected by Western blotting and RT-qPCR and cell viability was analyzed with MTT. In addition, flow cytometry was used to assess apoptosis, and mitochondrial membrane potential was detected using JC-1 staining with flow cytometry. Moreover, LDH Cytotoxicity Assay Kit detected the release of LDH, and ROS, MDA, or SOD kits detected oxidative stress-related factors.

RESULTS

MET significantly inhibited inflammatory damage and oxidative stress responses in LPS-induced HTR-8/SVneo cells. Besides, MET could activate AMPK and then affect NF-κB/sFlt-1 and Nrf2/HO-1 signaling pathways in LPS-induced HTR-8/SVneo cells. Compound C (an AMPK inhibitor) significantly reversed MET's effects on LPS-stimulated HTR-8/SVneo cells.

DISCUSSION

MET attenuated inflammatory and oxidative stress of HTR-8/SVneo cells in PE by activating AMPK to regulate NF-κB/sFlt-1 and Nrf2/HO-1 signaling pathways, suggesting that MET was a potential therapeutic drug for PE.

Metformin modulates mitochondrial autophagy in renal tubular epithelial injury induced by high glucose via the Keap1/Nrf2 pathway

The current study aimed to explore the role and underpinning molecular mechanisms of metformin in renal cellular injury induced by high glucose levels. Male C57BL/KsJ (db/db) and (db/m +) mice were utilized in this study. The experimental group was administered 1 mg/mL of metformin through drinking water. Renal tissues were harvested for hematoxylin and eosin (HE) staining, superoxide dismutase (SOD) activity detection, biochemical indices analysis, Western blotting, and qRT-PCR. HK-2 cells were utilized for Nrf2 siRNA transfection and to establish a high level of glucose-induced cell models. Metformin was administered at a concentration of 1 mmol/L in the experimental group. Cellular viability was assessed using CCK-8, whereas acridine orange (AO) staining and LC3-mitotracker co-localization staining were employed to evaluate autophagy. The expression of Nrf2, P21, LC3, PTEN-induced putative kinase 1 (PINK1), translocase of outer mitochondrial membrane 20 (TOMM20), and Kelch-like ECH-associated protein 1 (Keap1) were determined through Western blotting and qRT-PCR. Metformin mitigated renal tissue inflammatory damage in diabetic mice, as indicated by upregulated expression of Nrf2, PINK1, LC3, and TOMM20, and downregulated expression of Keap1 and P21. High level of glucose treatment in HK-2 cells resulted in decreased autophagy, and reduced expression of Nrf2, PINK1, LC3, and TOMM20 alongside elevated the expression of Keap1 and P21. Notably, metformin treatment partially counteracted these effects. Nrf2 knockdown intensified these phenomena in the high level of glucose-induced model. Protein-protein interaction network analysis indicated that Nrf2 could regulate the majority autophagy-related proteins via Keap1. Metformin modulates mitochondrial autophagy in high glucose-induced renal tubular epithelial senescence via the Keap1/Nrf2 pathway.

Validation of a physiological type 2 diabetes model in human periodontal ligament stem cells

OBJECTIVES

Type 2 diabetes (T2DM), a recognized risk factor for periodontitis, is characterized by insulin resistance. However, the molecular mechanisms concerning the role of insulin resistance in linking T2DM and periodontitis remain poorly elucidated due to the absence of an appropriate T2DM cell model. We aimed to explore an appropriate model of T2DM in human periodontal ligament stem cells (hPDLSCs) and uncover the involved mechanisms.

MATERIALS AND METHODS

hPDLSCs were incubated with common reagents for recapitulating insulin resistance state including high glucose (HG) (15, 25, 35, 45 mM), glucosamine (0.8, 8, 18, 28, 38 mM), or palmitic acid (PA; 100, 200, 400, 800 μM), combined with LPS for 48 h. The insulin signaling pathway, inflammation, and pyroptosis were detected by western blots and quantitative real-time polymerase chain reaction (RT-qPCR). The effects on osteogenesis were evaluated by alkaline phosphatase staining, alizarin red S staining, RT-qPCR, and western blots.

RESULTS

HG failed to recapitulate insulin resistance. Glucosamine was sufficient to induce insulin resistance but failed to trigger inflammation. In total, 100 and 200 μM PA exhibited the most proinflammatory, insulin resistance, and pyroptosis induced role, and inhibited the osteogenic differentiation of hPDLSCs.

CONCLUSION

Palmitic acid is a promising candidate for developing T2DM model in hPDLSCs.

Photobiomodulation at molecular, cellular, and systemic levels

Since the reporting of Endre Mester's results, researchers have investigated the biological effects induced by non-ionizing radiation emitted from low-power lasers. Recently, owing to the use of light-emitting diodes (LEDs), the term photobiomodulation (PBM) has been used. However, the molecular, cellular, and systemic effects involved in PBM are still under investigation, and a better understanding of these effects could improve clinical safety and efficacy. Our aim was to review the molecular, cellular, and systemic effects involved in PBM to elucidate the levels of biological complexity. PBM occurs as a consequence of photon-photoacceptor interactions, which lead to the production of trigger molecules capable of inducing signaling, effector molecules, and transcription factors, which feature it at the molecular level. These molecules and factors are responsible for cellular effects, such as cell proliferation, migration, differentiation, and apoptosis, which feature PBM at the cellular level. Finally, molecular and cellular effects are responsible for systemic effects, such as modulation of the inflammatory process, promotion of tissue repair and wound healing, reduction of edema and pain, and improvement of muscle performance, which features PBM at the systemic level.

Possible Role of Oxidative Stress and Nrf2/HO-1 Pathway in Pentylenetetrazole-induced Epilepsy in Aged Rats

Background

To examine the impact of aging on the response of rats to pentylenetetrazole (PTZ)-induction of epilepsy and the possible role of oxidative stress and nuclear factor erythroid 2-related factor 2 (Nrf2)/ heme oxygenase (HO)-1 pathway in this response.

Methods

Forty male albino rats were equally allocated into 4 groups; 1) Young control (YC) group, aged 8-12 weeks, 2) Old control (OC) group, aged 24 months, 3) PTZ-Young group: young rats received PTZ (50 mg/Kg, i.p. every other day) for 2 weeks and 4) PTZ-Old group: as group 3 but rats were old. The seizure score stage and latency to the first jerk were recorded in rats. Redox state markers in brain tissues including malondialdehyde (MDA), catalase and total antioxidant capacity (TAC) were evaluated. Also, the expression of Nrf2 and HO-1 genes were measured in the brain tissues.

Results

Old rats showed an early and a significant rise in the seizure score with PTZ administration and a significant drop in the seizure latency compared to young rats (P <0.01). Also, old rats showed a significantly higher MDA concentration and a significantly lower TAC and catalase activity than young rats (P <0.01). Moreover, the expression of Nrf2 and HO-1 was significantly lowered in old rats compared to young rats with PTZ administration (P < 0.01).

Conclusion

Aging increases the vulnerability of rats to PTZ-induced epilepsy. An effect might come down to the up-regulation of oxidative stress and the down regulation of antioxidant pathways including Nrf2 and HO-1.

Investigating the effects of Ceylon cinnamon water extract on HepG2 cells for Type 2 diabetes therapy

Cinnamon and its extracts have been used as herbal remedies for many ailments, including for reducing insulin resistance and diabetes complications. Type 2 diabetes mellitus (T2DM) is a rapidly growing health concern around the world. Although many drugs are available for T2DM treatment, side effects and costs can be considerable, and there is increasing interest in natural products for managing chronic health conditions. Cinnamon may decrease the expression of genes associated with T2DM risk. The purpose of this study was to evaluate the effects of cinnamon water extract (CWE) compared with metformin on T2DM-related gene expression. HepG2 human hepatoma cells, widely used in drug metabolism and hepatotoxicity studies, were treated with different concentrations of metformin or CWE for 24 or 48 h. Cell viability was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and glucose uptake was compared in untreated and CWE- or metformin-treated cells under high-glucose conditions. Finally, total RNA was extracted and analyzed by RNA sequencing (RNA-seq), and bioinformatics analyses were performed to compare the transcriptional effects of CWE and metformin. We found cell viability was better in cells treated with CWE than in metformin-treated cells, demonstrating that CWE was not toxic at tested doses. CWE significantly increased glucose uptake in HepG2 cells, to the same degree as metformin (1.4-fold). RNA-seq data revealed CWE and metformin both induced significantly increased (1.3- to 1.4-fold) glucose uptake gene expression compared with untreated controls. Transcriptional differences between CWE and metformin were not significant. The effects of 0.125 mg mL^-1 CWE on gene expression were comparable to 1.5 mg mL^-1 (9.5 mM) metformin. In addition, gene expression at 0.125 mg mL^-1 CWE was comparable to 1.5 mg mL^-1 (9.5 mM) metformin. Our results reveal that CWE's effects on cell viability, glucose uptake, and gene expression in HepG2 cells are comparable to those of metformin, suggesting CWE may be an effective dietary supplement for mitigating T2DM-related metabolic dysfunction.

Degradable hydrogel fibers encapsulate and deliver metformin and periodontal ligament stem cells for dental and periodontal regeneration

Human periodontal ligament stem cells (hPDLSCs) are promising cells for dental and periodontal regeneration. This study aimed to develop novel alginate-fibrin fibers that encapsulates hPDLSCs and metformin, to investigate the effect of metformin on the osteogenic differentiation of hPDLSCs, and to determine the regulatory role of the Shh/Gli1 signaling pathway in the metformin-induced osteogenic differentiation of hPDLSCs for the first time. CCK8 assay was used to evaluate hPDLSCs. Alkaline phosphatase (ALP) staining, alizarin red S staining, and the expression of osteogenic genes were evaluated. Metformin and hPDLSCs were encapsulated in alginate-fibrinogen solutions, which were injected to form alginate-fibrin fibers. The activation of Shh/Gli1 signaling pathway was examined using qRT-PCR and western blot. A mechanistic study was conducted by inhibiting the Shh/Gli1 pathway using GANT61. The administration of 50 μM metformin resulted in a significant upregulation of osteogenic gene expression in hPDLSCs by 1.4-fold compared to the osteogenic induction group (P < 0.01), including ALP and runt-related transcription factor-2 (RUNX2). Furthermore, metformin increased ALP activity by 1.7-fold and bone mineral nodule formation by 2.6-fold (P<0.001). We observed that hPDLSCs proliferated with the degradation of alginate-fibrin fibers, and metformin induced their differentiation into the osteogenic lineage. Metformin also promoted the osteogenic differentiation of hPDLSCs by upregulating the Shh/Gli1 signaling pathway by 3- to 6- fold compared to the osteogenic induction group (P<0.001). The osteogenic differentiation ability of hPDLSCs were decreased 1.3- to 1.6-fold when the Shh/Gli1 pathway was inhibited, according to ALP staining and alizarin red S staining (P<0.01). Metformin enhanced the osteogenic differentiation of hPDLSCs via the Shh/Gli1 signaling pathway. Degradable alginate-fibrin hydrogel fibers encapsulating hPDLSCs and metformin have significant potential for use in dental and periodontal tissue engineering applications. Alginate-fibrin fibers encapsulating hPDLSCs and metformin have a great potential for use in the treatment of maxillofacial bone defects caused by trauma, tumors, and tooth extraction. Additionally, they may facilitate the regeneration of periodontal tissue in patients with periodontitis.

Influence of Nanocurcumin and Photodynamic Therapy Using Nanocurcumin in Treatment of Rat Tongue Oral Squamous Cell Carcinoma Through Histological Examination and Gene Expression of BCL2 and Caspase-3

Background

Oral squamous cell carcinoma (OSCC) is the sixth most common mouth cancer in the world. The aim of the present study is comparing the effects of using Nanocurcumin, and photodynamic therapy (PDT), alone or together in treatment of OSCC in rats.

Methods

Forty Wister male rats were divided into Control (group 1), 650 nm diode Laser only (group 2), Nanocurcumin alone (group 3), and PDT with a combination of laser with Nanocurcumin (group 4). Then, OSCC in the tongue induced by dimethylbenz anthracene (DMBA). The treatments were evaluated clinically, histopathologically, and immunohistochemically through BCL2 and Caspase-3 genes expression.

Results

Positive control with OSCC displayed significant weight loss, while PDT group gained more than nanocurcumin treated groups as well as laser groups comparing with control positive group. The histological examination of the tongue in PDT group showed improvement. In laser group, there were partial loss of surface epithelium with various ulcers and dysplasia and partial improvement by this type of treatment. The tongue in the positive control group showed ulcer in the dorsum surface with inflammatory cells, hyperplasia of the mucosa membrane around the ulcer (acanthosis) with increase of dentition, vacuolar degeneration of prickle cell layer and increase mitotic activity of basal cell layer together with dermal proliferation.

Conclusion

Under the condition of the present study, PDT using nanocurcumin photosensitizer was effective in the treatment of OSCC regarding clinical, histological and gene expression of BCL2 and Caspase-3.

Metformin suppresses Oxidative Stress induced by High Glucose via Activation of the Nrf2/HO-1 Signaling Pathway in Type 2 Diabetic Osteoporosis

BACKGROUND

Metformin (MET) is widely used as a first-line hypoglycemic agent for the treatment of type 2 diabetes mellitus (T2DM) and was also confirmed to have a therapeutic effect on type 2 diabetic osteoporosis (T2DOP). However, the potential mechanisms of MET in the treatment of T2DOP are unclear.

OBJECTIVE

To clarify the effect of MET in T2DOP and to explore the potential mechanism of MET in the treatment of T2DOP.

METHODS

In vitro, we used MC3T3-E1 cells to study the effects of MET on osteogenic differentiation and anti-oxidative stress injury in a high glucose (Glucose 25 mM) environment. In vivo, we directly used db/db mice as a T2DOP model and assessed the osteoprotective effects of MET by Micro CT and histological analysis.

RESULTS

In vitro, we found that MET increased ALP activity in MC3T3-E1 cells in a high-glucose environment, promoted the formation of bone mineralized nodules, and upregulated the expression of the osteogenesis-related transcription factors RUNX2, Osterix, and COL1A1-related genes. In addition, MET was able to reduce high glucose-induced reactive oxygen species (ROS) production. In studies on the underlying mechanisms, we found that MET activated the Nrf2/HO-1 signaling pathway and alleviated high-glucose-induced oxidative stress injury. In vivo results showed that MET reduced bone loss and bone microarchitecture destruction in db/db mice.

CONCLUSION

Our results suggest that MET can activate the Nrf2/HO-1 signaling pathway to regulate the inhibition of osteogenic differentiation induced by high glucose thereby protecting T2DOP.

In Vitro Differential Sensitivity of Head and Neck Squamous Cell Carcinoma to Cisplatin, Silver Nanoparticles, and Photodynamic Therapy

BACKGROUND

The clinical effect of photodynamic therapy (PDT) may be correlated with the degree of dysplasia of cancer tissues. The aim of this study was to compare the effects of cisplatin, silver nanoparticles (AgNps), and photodynamic therapy (PDT) using methylene blue (MB) photosensitizer on Head and Neck squamous cell carcinoma - cell line (HNSCC), Hep-2, through genes expression.

METHODS

Hep-2 cells were divided into four groups: group I as control and without any treatment, group II and III were treated by cisplatin and AgNps, respectively, and group IV were incubated with MB for four minutes followed by PDT using laser irradiation at 650 nm for 8 minutes. The resulting toxicity was assessed in cell lines using MTT cytotoxicity assay. Further, apoptosis and the response to treatment was examined via RT-qPCR.

RESULTS

MB-PDT inhibited the proliferation of Hep-2 cells. Following PDT, compared with AgNps cells and via MTT assay, a highly significant decrease was observed in cell proliferation in Cancer cells treated with AgNps and MB- PDT groups compared to cancer group cells and cancer cells treated with Cisplatin (p value< 0.001). Mechanistically, both the mRNA and protein expression levels of Bcl-2, Caspase-3, Cyclin-D, HIF-1, IL-8, MAPK-38, and ROS were found to be down regulated in Hep-2 cell line after MB-PDT.

DISCUSSION

MB-PDT effectively killed Hep-2 cells in vitro, however, under the same conditions, the susceptibilities of the cell line to cisplatin, AgNps, and MB-PDT were different. Further studies are necessary to confirm whether this difference is present in clinical oral cancer lesions.

Comprehensive analysis of DNA methylation for periodontitis

Background

Periodontitis is an infectious disease, and a risk factor for peri-implantitis that could result in the implant loss. DNA methylation has an essential role in the etiology and pathogenesis of inflammatory disease. However, there is lack of study on methylation status of genes in periodontitis. This study sought to explore the gene methylation profiling microarray in periodontitis.

Methods

Through searching in the Gene Expression Omnibus database, a gene methylation profiling data set GSE173081 was identified, which included 12 periodontitis samples and 12 normal samples, respectively. Thereafter, the data of GSE173081 was downloaded and analyzed to determined differentially methylated genes (DMGs), which then were used to perform Gene Ontology analysis and pathway enrichment analyses through online database. In addition, the DMGs were applied to construct the protein–protein interaction (PPI) network information, predict the hub genes in pathology of periodontitis.

Results

In total 668 DMGs were sorted and identified from the data set, which included 621 hypo-methylated genes and 47 hyper-methylated genes. Through the function and ontology analysis, these 668 genes are mainly classified into intracellular signaling pathway, cell components, cell–cell interaction, and cellular behaviors. The pathway analysis showed that the hypo-methylated genes were mostly enriched in the pathway of cGMP–PKG signaling pathway; RAF/MAP kinase; PI3K–Akt signaling pathway, while hyper-methylated genes were mostly enriched in the pathway of bacterial invasion of epithelial cells; sphingolipid signaling pathway and DCC mediated attractive signaling. The PPI network contained 630 nodes and 1790 interactions. Moreover, further analysis identified top 10 hub genes (APP; PAX6; LPAR1; WNT3A; BMP2; PI3KR2; GATA4; PLCB1; GATA6; CXCL12) as central nodes that are involved in the immune system and the inflammatory response.

Conclusions

This study provides comprehensive information of methylation status of genes to the revelation of periodontitis pathogenesis that may contribute to future research on periodontitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40729-022-00420-8.