Circ_0081572 inhibits the progression of periodontitis through regulating the miR-378h/RORA axis

Emerging Role of miRNAs in the Pathogenesis of Periodontitis

MicroRNAs (miRNAs) have been found to participate in the pathogenesis of several immune-related conditions through the modulation of the expression of cytokine coding genes and other molecules that affect the activity of the immune system. Periodontitis is an example of these conditions associated with the dysregulation of several miRNAs. Several miRNAs such as let-7 family, miR-125, miR-378, miR-543, miR-302, miR-214, miR-200, miR-146, miR-142, miR-30 and miR-21 have been shown to be dysregulated in patients with periodontitis. miR-146 is the most assessed miRNA in these patients, which is up-regulated in most studies in patients with periodontitis. In the present review, we describe the impact of miRNAs dysregulation on the pathoetiology of periodontitis.

Circ_0087199 depletion attenuates lipopolysaccharides-induced human periodontal ligament cell injury through the miR-527/TLR4 axis

BACKGROUND

Circular RNAs participate in the development of periodontitis. The present work aims to reveal the role and mechanism of circ_0087199 in human periodontal ligament cell (PDLC) injury during periodontitis.

METHODS

PDLCs were treated with lipopolysaccharides (LPS) to establish a periodontitis cell model. Quantitative real-time polymerase chain reaction was used to detect the expression of circ_0087199, miR-527, toll-like receptor 4 (TLR4). Western blot analysis assay was performed to assess protein expression. Cell viability, proliferation, apoptosis and inflammation were investigated by cell counting kit-8, EdU assay, flow cytometry and enzyme-linked immunosorbent assay, respectively. Oxidative stress was evaluated by malondialdehyde assay kit and superoxide dismutase activity assay kit. The interaction between miR-527 and circ_0087199 or TLR4 was confirmed by a dual-luciferase reporter assay.

RESULTS

Circ_0087199 and TLR4 expression levels were significantly increased, while miR-527 was decreased in the periodontal ligament tissues of periodontitis patients and LPS-stimulated PDLCs when compared with controls. LPS treatment inhibited cell viability and proliferation but induced cell apoptosis, inflammation and oxidative stress, whereas these effects were attenuated after circ_0087199 knockdown. Circ_0087199 bound to miR-527 and regulated LPS-caused PDLC damage by targeting miR-527. Additionally, the overexpression of TLR4, a target gene of miR-527, rescued miR-527 mimic-mediated effects on LPS-treated PDLCs. Further, the regulation of circ_0087199 toward TLR4 involved miR-527.

CONCLUSION

Circ_0087199 knockdown attenuated LPS-induced apoptosis, inflammation and oxidative stress of PDLCs by regulating the miR-527/TLR4 pathway.

Anti-apoptosis and anti-inflammation activity of circ_0097010 downregulation in lipopolysaccharide-stimulated periodontal ligament cells by miR-769-5p/Krüppel like factor 6 axis

Background/purpose

Periodontitis is a prevalent infectious inflammatory disease. Growing evidence has revealed important roles for circular RNAs (circRNAs) and circRNA sponge activity in periodontitis. Here, we elucidated the precise part of circ_0097010 in periodontitis pathogenesis.

Materials and methods

Human periodontal ligament cells (hPDLCs) were exposed to lipopolysaccharide (LPS). Cell viability, proliferation and apoptosis were evaluated by CCK-8 assay, EdU incorporation assay and flow cytometry, respectively. Circ_0097010, microRNA (miR)-769-5p and Krüppel like factor 6 (KLF6) were quantified by qRT-PCR and Western blot. Interleukin 6 (IL-6) level, tumor necrosis factor-α (TNF-α) secretion, superoxide dismutase (SOD) activity and malondialdehyde (MDA) level were detected by enzyme-linked immunosorbent assay (ELISA). Dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays were used to confirm the direct relationship between miR-769-5p and circ_0097010 or KLF6.

Results

Our data showed that LPS repressed cell proliferation and induced cell apoptosis and inflammation in hPDLCs. Circ_0097010 was upregulated in periodontitis samples and LPS-exposed hPDLCs. Downregulation of circ_0097010 exerted anti-apoptosis and anti-inflammation functions in LPS-exposed hPDLCs. Mechanistically, circ_0097010 acted as a miR-769-5p sponge, and reduced abundance of miR-769-5p reversed the anti-apoptosis and anti-inflammation effects of circ_0097010 suppression. KLF6 was a direct miR-769-5p target, and miR-769-5p-mediated inhibition of KLF6 possessed anti-apoptosis and anti-inflammation functions in LPS-induced hPDLCs. Moreover, circ_0097010 controlled KLF6 expression by miR-769-5p.

Conclusion

These data identify circ_0097010 as a key regulator of LPS-induced inflammation and apoptosis in hPDLCs and highlight a novel mechanism of circ_0097010 regulation through miR-769-5p/KLF6 axis.

Circ_0138960 contributes to lipopolysaccharide-induced periodontal ligament cell dysfunction

BACKGROUND

Periodontitis is a common oral inflammatory disease, and lipopolysaccharide (LPS) is a key risk factor in periodontitis pathology. Here, we used LPS-induced periodontal ligament cells (PDLCs) to explore the molecular mechanism of periodontitis.

METHODS

Cell viability, proliferation, and apoptosis were analyzed by Cell Counting Kit-8, 5-ethynyl-20-deoxyuridine (EDU), and flow cytometry assays, respectively. Apart from that, their targeting relationship was validated using dual-luciferase reporter and RNA-pull down.

RESULTS

Circular RNA_0138960 (circ_0138960) was notably upregulated in periodontitis sufferers (p < .001) and LPS-disposed PDLCs (p < .05). LPS exposure dampened PDLC proliferation, and promoted apoptosis and inflammation (p < .05). Circ_0138960 acted as a microRNA sponge for miR-518a-5p to affect histone deacetylase 6 (HDAC6) expression. Circ_0138960 absence-mediated protective effects in LPS-induced PDLCs were largely abrogated via silencing miR-518a-5p or HDAC6 overexpression (p < .05).

CONCLUSION

Circ_0138960 promoted LPS-induced dysfunction in PDLCs by targeting miR-518a-5p/HDAC6 axis, which provided novel potential therapeutic targets for periodontitis.

Epigenetics in susceptibility, progression, and diagnosis of periodontitis

Periodontitis is characterized by irreversible destruction of periodontal tissue. At present, the accepted etiology of periodontitis is based on a three-factor theory including pathogenic bacteria, host factors, and acquired factors. Periodontitis development usually takes a decade or longer and is therefore called chronic periodontitis (CP). To search for genetic factors associated with CP, several genome-wide association study (GWAS) analyses were conducted; however, polymorphisms associated with CP have not been identified. Epigenetics, on the other hand, involves acquired transcriptional regulatory mechanisms due to reversibly altered chromatin accessibility. Epigenetic status is a condition specific to each tissue and cell, mostly determined by the responses of host cells to stimulations by local factors, like bacterial inflammation, and systemic factors such as nutrition status, metabolic diseases, and health conditions. Significantly, epigenetic status has been linked with the onset and progression of several acquired diseases. Thus, epigenetic factors in periodontal tissues are attractive targets for periodontitis diagnosis and treatments. In this review, we introduce accumulating evidence to reveal the epigenetic background effects related to periodontitis caused by genetic factors, systemic diseases, and local environmental factors, such as smoking, and clarify the underlying mechanisms by which epigenetic alteration influences the susceptibility of periodontitis.

Circ_0062491 alleviates LPS-induced apoptosis and inflammation in periodontitis by regulating miR-498/SOCS6 axis

Periodontitis is a prevalent chronic inflammatory disease. Circular RNAs (circRNAs) have been revealed to play roles in the inflammatory response. Hence, this work aimed to explore the role and mechanism of circ_0062491 in periodontitis progression. Human periodontal ligament cells (PDLCs) were isolated from the periodontal ligament (PDL) of the healthy teeth with orthodontic requirement after tooth extraction. In vitro experiments were conducted by cell counting Kit-8 (CCK-8) assay, flow cytometry, Western blot, and ELISA to determine cell viability, apoptosis, and inflammatory response. The binding between miR-498 and circ_0062491 or SOCS6 was confirmed using dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Circ_0062491 expression was decreased in periodontitis and LPS-induced PDLCs. Restoration of circ_0062491 attenuated LPS-induced apoptosis and inflammation in PDLCs in vitro. Mechanistically, circ_0062491 functioned as a sponge for miR-498, and miR-498 directly targeted SOCS6. Rescue experiments showed that miR-498 up-regulation reversed the protective action of circ_0062491 on PDLCs under LPS treatment. Moreover, silencing of miR-498 protected PDLCs from LPS-induced apoptosis and inflammation, which were abolished by SOCS6 knockdown. Circ_0062491 protected PDLCs from LPS-induced apoptosis and inflammation, suggesting a new target for the amelioration of periodontitis patients.

Long non-coding RNA ZFY-AS1 represses periodontitis tissue inflammation and oxidative damage via modulating microRNA-129-5p/DEAD-Box helicase 3 X-linked axis

A large number of studies have manifested long non-coding RNA (lncRNA) is involved in the modulation of the development of periodontitis, but the specific mechanism has not been fully elucidated. The purpose of this study was to explore the biological function and latent molecular mechanism of lncZFY-AS1 in periodontitis. The results clarified lncZFY-AS1 and DEAD-Box Helicase 3 X-Linked (DDX3X) were up-regulated, but microRNA (miR)-129-5p was down-regulated in periodontitis. Knockdown of lncZFY-AS2 or overexpression of miR-129-5p decreased macrophage infiltration and periodontal membrane cell apoptosis, increased cell viability, repressed inflammatory factors and nuclear factor kappa B activation, reduced oxidative stress, but promoted nuclear factor-E2-related factor 2/heme oxygenase 1 expression. LncZFY-AS1 elevation further aggravated periodontitis inflammation, oxidative stress, and apoptosis. LncZFY competitively adsorbed miR-129-5p to mediate DDX3X expression. Knockdown lncZFY’s improvement effect on periodontitis was reversed by depressive miR-129-5p or enhancive DDX3X. In conclusion, these data suggest lncZFY-AS1 promotes inflammatory injury and oxidative stress in periodontitis by competitively binding to miR-129-5p and mediating DDX3X expression. LncZFY-AS1/miR-129-5p/DDX3X may serve as a novel molecular target for treatment of periodontitis in the future.

Circ_0066881 targets miR-144-5p/RORA axis to alleviate LPS-induced apoptotic and inflammatory damages in human periodontal ligament cells

Circular RNAs (circRNAs) are involved in the regulation of various diseases, including periodontitis. The objective of this study was to analyze the biological role and regulatory mechanism of circ_0066881 in LPS-induced periodontal ligament cells (PDLCs). Circ_0066881, microRNA-144-5p (miR-144-5p) and retinoid acid-related orphan receptor A (RORA) levels were determined using reverse transcription-quantitative PCR (RT-qPCR) assay. Cell viability detection was performed by Cell Counting Kit-8 assay. Cell apoptosis was assessed through flow cytometry and caspase-3 activity assay. The protein analysis was completed via Western blot. Inflammatory cytokines were measured by ELISA. The target interaction was validated by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. The level of circ_0066881 was down-regulated in periodontitis tissues. Overexpression of circ_0066881 relieved LPS-induced cell viability inhibition and apoptosis or inflammation promotion in PDLCs. Circ_0066881 could bind to miR-144-5p. The protective function of circ_0066881 was achieved by sponging miR-144-5p in PDLCs. Circ_0066881 acts as a miR-144-5p sponge to mediate the RORA level. Inhibition of miR-144-5p attenuated LPS-induced cell injury via targeting RORA. All these results demonstrated that circ_0066881 partly prevented LPS-evoked cell dysfunction in PDLCs through miR-144-5p-mediated up-regulation of RORA.

circ_0062491 alleviates periodontitis via the miR-142-5p/IGF1 axis

CircularRNAs (circRNAs) are collectively involved in periodontitis. The aim of this study was to explore the roles of circ_0062491 in osteogenic differentiation of PDLSCs and provide a novel method for periodontitis treatment. mRNA and protein expression levels were measured by qRT-PCR and western blotting. Alkaline phosphatase (ALP) and alizarin red S (ARS) staining were used to detect the activity of osteogenesis. Furthermore, the interactions between miR-142-5p and circ_0062491/IGF1 were verified by a luciferase reporter assay. circ_0062491 was suppressed in PDL tissues of periodontitis patients and overexpressed in osteogenesis-induced PDLSCs. Upregulated circ_0062491 promoted osteogenic differentiation of PDLSCs. miR-142-5p was verified to be a target of circ_0062491, and the overexpression of miR-142-5p suppressed the osteogenic differentiation of PDLSCs induced by circ_0062491 Additionally, miR-142-5p targeted IGF1, and silenced IGF1 abrogated the effects of suppressed miR-142-5p on osteogenic differentiation of PDLSCs. In conclusion, circ_0062491 acted as a competing endogenous RNA to regulate osteogenic differentiation of PDLSCs via the miR-142-5p/IGF1 axis.

Identification of potentially functional circRNAs and prediction of circRNA-miRNA-mRNA regulatory network in periodontitis: Bridging the gap between bioinformatics and clinical needs

Background and Objective

Periodontitis is a multifactorial chronic inflammatory disease that can lead to the irreversible destruction of dental support tissues. As an epigenetic factor, the expression of circRNA is tissue‐dependent and disease‐dependent. This study aimed to identify novel periodontitis‐associated circRNAs and predict relevant circRNA‐periodontitis regulatory network by using recently developed bioinformatic tools and integrating sequencing profiling with clinical information for getting a better and more thorough image of periodontitis pathogenesis, from gene to clinic.

Material and Methods

High‐throughput sequencing and RT‐qPCR were conducted to identify differentially expressed circRNAs in gingival tissues from periodontitis patients. The relationship between upregulated circRNAs expression and probing depth (PD) was performed using Spearman's correlation analysis. Bioinformatic analyses including GO analysis, circRNA‐disease association prediction, and circRNA‐miRNA‐mRNA network prediction were performed to clarify potential regulatory functions of identified circRNAs in periodontitis. A receiver‐operating characteristic (ROC) curve was established to assess the diagnostic significance of identified circRNAs.

Results

High‐throughput sequencing identified 70 differentially expressed circRNAs (68 upregulated and 2 downregulated circRNAs) in human periodontitis (fold change >2.0 and p < .05). The top five upregulated circRNAs were validated by RT‐qPCR that had strong associations with multiple human diseases, including periodontitis. The upregulation of circRNAs were positively correlated with PD (R = .40–.69, p < .05, moderate). A circRNA‐miRNA‐mRNA network with the top five upregulated circRNAs, differentially expressed mRNAs, and overlapped predicted miRNAs indicated potential roles of circRNAs in immune response, cell apoptosis, migration, adhesion, and reaction to oxidative stress. The ROC curve showed that circRNAs had potential value in periodontitis diagnosis (AUC = 0.7321–0.8667, p < .05).

Conclusion

CircRNA‐disease associations were predicted by online bioinformatic tools. Positive correlation between upregulated circRNAs, circPTP4A2, chr22:23101560‐23135351+, circARHGEF28, circBARD1 and circRASA2, and PD suggested function of circRNAs in periodontitis. Network prediction further focused on downstream targets regulated by circRNAs during periodontitis pathogenesis.

Circ_0138959/miR-495-3p/TRAF6 axis regulates proliferation, wound healing and osteoblastic differentiation of periodontal ligament cells in periodontitis

Background/purpose

Periodontitis is a chronic inflammatory disease, and periodontal ligament cells (PDLCs) are pivotal for osteogenesis. Circular RNAs (circRNAs) can regulate disease progression via targeting miRNA/mRNA axis. The purposes of this study were to explore the function and mechanism of circ_0138959 in periodontitis.

Materials and methods

Periodontitis cell model was established by lipopolysaccharide (LPS) treatment in PDLCs. RNA expression was determined by quantitative reverse transcription-polymerase chain reaction assay. Cell proliferation was detected using 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide assay. Wound healing and cell apoptosis were examined by wound healing assay and flow cytometry. Inflammatory cytokines were measured via Enzyme-linked immunosorbent assay. Osteogenic differentiation was assessed by Alkaline phosphatase and Alizarin red S staining assays. Western blot was used for protein detection. The target interaction was validated by dual-luciferase reporter assay.

Results

Circ_0138959 was overexpressed in periodontitis tissues and LPS-treated PDLCs. Downregulation of circ_0138959 attenuated LPS-induced inhibition of proliferation, wound healing and osteogenic differentiation but promotion of apoptosis and inflammation. Circ_0138959 acted as a miR-495-3p sponge, and the regulatory role of circ_0138959 in LPS-induced cell injury was achieved by sponging miR-495-3p. Additionally, miR-495-3p targeted TNF Receptor Associated Factor 6 (TRAF6) and miR-495-3p protected against LPS-induced cell dysfunction by targeting TRAF6. Circ_0138959 upregulated TRAF6 level via inhibiting miR-495-3p.

Conclusion

This study suggested that circ_0138959 upregulated the TRAF6 expression by binding to miR-495-3p, consequently aggravating LPS-induced cell damages in PDLCs. Circ_0138959 might be a probable target for treatment of periodontitis.

Redondoviridae infection regulates circRNAome in periodontitis

Redondoviridae is a recently identified family of DNA viruses associated with periodontitis. Circular RNAs (circRNAs) are novel endogenous, conserved noncoding RNAs contributing to the virus-related immune-inflammatory response. The present study aimed to analyze the expression profiles of circRNAs in the gingival tissues of periodontitis patients with and without Redondoviridae-infection and healthy controls using high-throughput RNA sequencing combined with experimental validation. Out of 17819 circRNAs, 175 were dysregulated. Functional annotation and enrichment analysis of the differential circRNA host genes demonstrated potential alterations in the molecular and cellular components and metabolism in individuals suffering from periodontitis with Redondoviridae infection. Moreover, "axon guidance", "lysine biosynthesis", and "vascular endothelial growth factor signaling pathways" were significantly enriched in Redondoviridae-infected gingivitis tissues. Furthermore, the key circRNAs (circCOL1A1, circAASS, circPTK2, circATP2B4, circDOCK1, circTTBK2, and circMCTP2) associated with the pathobiology of Redondoviridae-related periodontitis were identified by constructing circRNA-miRNA-mRNA networks. Bioinformatics analyses demonstrated that abnormally expressed circRNAs might contribute to the etiopathogenesis and development of Redondoviridae-related periodontitis. The present study's findings have enhanced the current understanding ofthe Redondoviridae-related periodontitis mechanism and provide insights into further applications for diagnostic markers and therapeutic uses. This article is protected by copyright. All rights reserved.

Pyroptosis-Mediated Periodontal Disease

Pyroptosis is a caspase-dependent process relevant to the understanding of beneficial host responses and medical conditions for which inflammation is central to the pathophysiology of the disease. Pyroptosis has been recently suggested as one of the pathways of exacerbated inflammation of periodontal tissues. Hence, this focused review aims to discuss pyroptosis as a pathological mechanism in the cause of periodontitis. The included articles presented similarities regarding methods, type of cells applied, and cell stimulation, as the outcomes also point to the same direction considering the cellular events. The collected data indicate that virulence factors present in the diseased periodontal tissues initiate the inflammasome route of tissue destruction with caspase activation, cleavage of gasdermin D, and secretion of interleukins IL-1β and IL-18. Consequently, removing periopathogens’ virulence factors that trigger pyroptosis is a potential strategy to combat periodontal disease and regain tissue homeostasis.

CircRNA FAT1 Regulates Osteoblastic Differentiation of Periodontal Ligament Stem Cells via miR-4781-3p/SMAD5 Pathway

The ability of human periodontal ligament stem cells (PDLSCs) to differentiate into osteoblasts is significant in periodontal regeneration tissue engineering. In this study, we explored the role and mechanism of circRNA FAT1 (circFAT1) in the osteogenic differentiation of human PDLSCs. The proliferation capacity of PDLSCs was evaluated by EdU and CCK-8 assay. The abilities of circFAT1 and miR-4781-3p in regulating PDLSC differentiation were analyzed by western blot, reverse transcription-polymerase chain reaction (RT-PCR), alkaline phosphatase (ALP), and Alizarin red staining (ARS). A nucleocytoplasmic separation experiment was utilized for circFAT1 localization. A dual-luciferase reporter assay confirmed the binding relationship between miR-4781-3p and circFAT1. It was showed that circFAT1 does not affect the proliferation of PDLSCs. The osteogenic differentiation of PDLSCs was benefited from circFAT1, which serves as a miRNA sponge for miR-4781-3p targeting SMAD5. Both knockdown of circFAT1 and overexpression of miR-4781-3p suppressed the osteogenic differentiation of PDLSCs. Thus, circFAT1 might be considered as a potential target of PDLSCs mediated periodontal bone regeneration.

Abnormal hsa_circ_0003948 expression affects chronic periodontitis development by regulating miR-144-3p/NR2F2/PTEN signaling

BACKGROUND AND OBJECTIVE

This study aimed to investigate the correlation between chronic periodontitis (CP) and abnormal circular RNA (circRNA) expression and to identify the role of hsa_circ_0003948 in the progression of CP.

METHODS

Next-generation sequencing was utilized to investigate abnormal expression of circRNA in gingival tissues from CP patients and healthy control subjects. Bioinformatics and luciferase reporting analyses were used to clarify the interactive relationship among circRNA, miRNA, and mRNA. Periodontal ligament cells (PDLCs) were employed to analyze proliferation and apoptosis after lipopolysaccharide (LPS) treatment using the cell counting kit 8 (CCK8) assay and flow cytometry detection.

RESULTS

High-throughput sequencing and RT-qPCR analyses confirmed that hsa_circ_0003948 expression decreased dramatically in gingival samples of CP patients. Overexpression of hsa_circ_0003948 alleviated LPS-induced PDLC injury by regulating NR2F2/PTEN signaling. The miR-144-3p and NR2F2 were determined to be hsa_circ_0003948 downstream targets. NR2F2 downregulation or miR-144-3p overexpression reversed the protective effect of hsa_circ_0003948 in PDLCs after treatment with LPS. Upregulation of NR2F2 reversed the inhibitory effect of miR-144-3p on surviving PDLCs after LPS treatment.

CONCLUSION

Overexpression of hsa_circ_0003948 exerts a protective effect in CP via miR-144-3p/NR2F2/PTEN signaling regulation.

The Emerging Regulatory Role of Circular RNAs in Periodontal Tissues and Cells

Periodontitis is a chronic complex inflammatory disease associated with a destructive host immune response to microbial dysbiosis, leading to irreversible loss of tooth-supporting tissues. Regeneration of functional periodontal soft (periodontal ligament and gingiva) and hard tissue components (cementum and alveolar bone) to replace lost tissues is the ultimate goal of periodontal treatment, but clinically predictable treatments are lacking. Similarly, the identification of biomarkers that can be used to accurately diagnose periodontitis activity is lacking. A relatively novel category of molecules found in oral tissue, circular RNAs (circRNAs) are single-stranded endogenous, long, non-coding RNA molecules, with covalently circular-closed structures without a 5' cap and a 3' tail via non-classic backsplicing. Emerging research indicates that circRNAs are tissue and disease-specific expressed and have crucial regulatory functions in various diseases. CircRNAs can function as microRNA or RNA binding sites or can regulate mRNA. In this review, we explore the biogenesis and function of circRNAs in the context of the emerging role of circRNAs in periodontitis pathogenesis and the differentiation of periodontal cells. CircMAP3K11, circCDK8, circCDR1as, circ_0062491, and circ_0095812 are associated with pathological periodontitis tissues. Furthermore, circRNAs are expressed in periodontal cells in a cell-specific manner. They can function as microRNA sponges and can form circRNA-miRNA-mRNA networks during osteogenic differentiation for periodontal-tissue (or dental pulp)-derived progenitor cells.