MicroRNA Expression Profiles in External Cervical Resorption

Emerging therapeutic strategies targeting bone signaling pathways in periodontitis

Periodontitis is a multifactorial immune-mediated disease exacerbated by dysregulated alveolar bone homeostasis. Timely intervention is crucial for disease management to prevent tooth loss. To successfully manage periodontitis, it is imperative to understand the cellular and molecular mechanisms involved in its pathogenesis to develop novel treatment modalities. Non-surgical periodontal therapy (NSPT) such as subgingival instrumentation/debridement has been the underlying treatment strategy over the past decades. However, new NSPT approaches that target key signaling pathways regulating alveolar bone homeostasis have shown positive clinical outcomes. This narrative review aims to discuss endogenous bone homeostasis mechanisms impaired in periodontitis and highlight the clinical outcomes of preventive periodontal therapy to avoid invasive periodontal therapies. Although the anti-resorptive therapeutic adjuncts have demonstrated beneficial outcomes, adverse events have been reported. Diverse immunomodulatory therapies targeting the osteoblast/osteoclast (OB/OC) axis have shown promising outcomes in vivo. Future controlled randomized clinical trials (RCT) would help clinicians and patients in the selection of novel preventing therapies targeting key molecules to effectively treat or prevent periodontitis.

Downregulation of miRNA-26 in chronic periodontitis interferes with innate immune responses and cell migration by targeting phospholipase C beta 1

AIM

To evaluate the potential role of miR-26 family members in periodontal pathogenesis by assessing innate immune responses to periopathic bacteria and regulation of cytoskeletal organization.

MATERIALS AND METHODS

Expression of miR-26a-5p and miR-26b-5p was quantified in gingival biopsies derived from healthy and periodontally diseased subjects before and after non-surgical (scaling and root planing) therapy by RT-qPCR. Global pathway analysis and luciferase assays were performed for target identification and validation. Cytokine expression was assessed in miR-26a-5p transfected human oral keratinocytes upon stimulation with either live Porphyromonas gingivalis (Pg), Aggregatibacter actinomycetemcomitans or Pg lipopolysaccharide (LPS). Wound closure assays were performed in cells transfected with miR-26a-5p, while the impact on cytoskeletal organization was assessed by F-actin staining.

RESULTS

miR-26a-5p and miR-26b-5p were downregulated in diseased gingiva and restored 4-6 weeks post-therapy to levels comparable with healthy subjects. Target validation assays identified phospholipase C beta 1 as a bona fide novel target exhibiting antagonistic expression pattern in disease and post-therapy cohorts. miR-26a-5p transfected cells secreted higher levels of cytokine/chemokines upon stimulation with periopathogens and demonstrated impaired cell migration and cytoskeletal rearrangement.

CONCLUSIONS

Downregulated miR-26a-5p levels in periodontal inflammation may interfere with key cellular functions that may have significant implications for host defence and wound healing.

Biomarkers in External Apical Root Resorption: An Evidence-based Scoping Review in Biofluids

BACKGROUND

External apical root resorption (EARR), an unwanted sequela of orthodontic treatment, is difficult to diagnose radiographically. Hence, the current scoping review was planned to generate critical evidence related to biomarkers in oral fluids, i.e. gingival crevicular fluid (GCF), saliva, and blood, of patients showing root resorption, compared to no-resorption or physiologic resorption.

METHODS

A literature search was conducted in major databases along with a manual search of relevant articles in the library, and further search from references of the related articles in March 2021. The initial search was subjected to strict inclusion and exclusion criteria according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines.

RESULTS

Following PRISMA guidelines, 20 studies were included in the final review. The studies included human clinical trials and cross-sectional and prospective studies with/without control groups with no date/language restriction. Various biomarkers identified in EARR included dentinal proteins, enzymes, cytokines, and salivary proteins. Severe resorption had higher dentin sialoprotein (DSP) and resorption protein concentrations as well as lower granulocyte-macrophage colony-stimulating factor (GM-CSF) as compared with mild resorption. Increased DSP and dentin phosphophoryn (DPP) expression was found in physiologic resorption. Compared to controls, resorbed teeth showed a higher receptor activator of nuclear factor kappa B ligand/osteoprotegerin (RANKL/OPG) ratio. In contrast, levels of anti-resorptive mediators (IL-1RA, IL-4) was significantly decreased. Differences in force levels (150 g and 100 g) showed no difference in resorption, but a significant rise in biomarkers (aspartate transaminase [AST] and alkaline phosphatase [ALP]) for 150 g force. Moderate to severe resorption in young patients showed a rise in specific salivary proteins, requiring further validation. Limitations of the studies were heterogeneity in study design, biomarker collection, sample selection, and confounding inflammatory conditions.

CONCLUSIONS

Various biomarkers in biofluids indicate active resorption, while resorption severity was associated with DSP and GM-CSF in GCF, and a few salivary proteins. However, a robust study design in the future is mandated.

Exploring the Expression of Pro-Inflammatory and Hypoxia-Related MicroRNA-20a, MicroRNA-30e, and MicroRNA-93 in Periodontitis and Gingival Mesenchymal Stem Cells under Hypoxia

Hypoxia associated with inflammation are common hallmarks observed in several diseases, and it plays a major role in the expression of non-coding RNAs, including microRNAs (miRNAs). In addition, the miRNA target genes for hypoxia-inducible factor-1α (HIF-1α) and nuclear factor of activated T cells-5 (NFAT5) modulate the adaptation to hypoxia. The objective of the present study was to explore hypoxia-related miRNA target genes for HIF-1α and NFAT5, as well as miRNA-20a, miRNA-30e, and miRNA-93 expression in periodontitis versus healthy gingival tissues and gingival mesenchymal stem cells (GMSCs) cultured under hypoxic conditions. Thus, a case-control study was conducted, including healthy and periodontitis subjects. Clinical data and gingival tissue biopsies were collected to analyze the expression of miRNA-20a, miRNA-30e, miRNA-93, HIF-1α, and NFAT5 by qRT-PCR. Subsequently, GMSCs were isolated and cultured under hypoxic conditions (1% O₂) to explore the expression of the HIF-1α, NFAT5, and miRNAs. The results showed a significant upregulation of miRNA-20a (p = 0.028), miRNA-30e (p = 0.035), and miRNA-93 (p = 0.026) in periodontitis tissues compared to healthy gingival biopsies. NFAT5 mRNA was downregulated in periodontitis tissues (p = 0.037), but HIF-1α was not affected (p = 0.60). Interestingly, hypoxic GMSCs upregulated the expression of miRNA-20a and HIF-1α, but they downregulated miRNA-93e. In addition, NFAT5 mRNA expression was not affected in hypoxic GMSCs. In conclusion, in periodontitis patients, the expression of miRNA-20a, miRNA-30e, and miRNA-93 increased, but a decreased expression of NFAT5 mRNA was detected. In addition, GMSCs under hypoxic conditions upregulate the HIF-1α and increase miRNA-20a (p = 0.049) expression. This study explores the role of inflammatory and hypoxia-related miRNAs and their target genes in periodontitis and GMSCs. It is crucial to determine the potential therapeutic target of these miRNAs and hypoxia during the periodontal immune–inflammatory response, which should be analyzed in greater depth in future studies.

Human and herpesvirus microRNAs in periodontal disease

Periodontitis is a multi-etiologic infection characterized clinically by pathologic loss of the periodontal ligament and alveolar bone. Herpesviruses and specific bacterial species are major periodontal pathogens that cooperate synergistically in producing severe periodontitis. Cellular immunity against herpesviruses and humoral immunity against bacteria are key periodontal host defenses. Genetic, epigenetic, and environmental factors are modifiers of periodontal disease severity. MicroRNAs are a class of noncoding, gene expression-based, posttranscriptional regulatory RNAs of great importance for maintaining tissue homeostasis. Aberrant expression of microRNAs has been associated with several medical diseases. Periodontal tissue cells and herpesviruses elaborate several microRNAs that are of current research interest. This review attempts to conceptualize the role of periodontal microRNAs in the pathogenesis of periodontitis. The diagnostic potential of salivary microRNAs is also addressed. Employment of microRNA technology in periodontics represents an interesting new preventive and therapeutic possibility.

External cervical resorption-a review of pathogenesis and potential predisposing factors

External cervical resorption (ECR) refers to a pathological state in which resorption tissues penetrate into the dentin at the cervical aspect of the root. Despite being latent in its initial phase, ECR could cause severe damage to mineralized dental tissue and even involve the pulp if not given timely diagnosis and treatment. Nevertheless, the etiology of ECR is still poorly understood, which adds to the difficulty in early diagnosis. ECR has received growing attention in recent years due to the increasing number of clinical cases. Several potential predisposing factors have been recognized in cross-sectional studies as well as case reports. In the meantime, studies on histopathology and pathogenesis have shed light on possible mechanisms of ECR. This review aims to summarize the latest findings in the pathogenesis and potential predisposing factors of ECR, so as to provide pragmatic reference for clinical practice.

A Review of External Cervical Resorption

External cervical resorption (ECR) is a relatively uncommon yet aggressive form of dental hard tissue destruction. It is initiated at the cervical aspect of the root surface and extends apicocoronally and circumferentially inside the dentin. Despite the large number of case reports and clinical studies that have investigated ECR, its etiology remains unclear. Recent advancements in clinical assessment measures, such as the use of cone-beam computed tomographic imaging, have provided additional insights into the nature of this lesion. This has facilitated the continued development and improvement of treatment methods for this condition. In this article, we provide an overview of the latest research pertaining to the etiology, histopathology, predisposing factors, diagnosis, classification, and treatment of ECR. Furthermore, we provide a summary of the different classification schemes for ECR and highlight the relevant therapeutic principles.

A meta-analysis of microRNAs expressed in human aerodigestive epithelial cultures and their role as potential biomarkers of exposure response to nicotine-containing products

The expression of some microRNAs (miRNA) is modulated in response to cigarette smoke (CS), which is a leading cause of major preventable diseases. However, whether miRNA expression is also modulated by the aerosol/extract from potentially reduced-risk products is not well studied. The present work is a meta-analysis of 12 in vitro studies in human organotypic epithelial cultures of the aerodigestive tract (buccal, gingival, bronchial, nasal, and small airway epithelia). These studies compared the effects of exposure to aerosols from electronic vapor (e-vapor) products and heated tobacco products, and to extracts from Swedish snus products (in the present work, will be referred to as reduced-risk products [RRPs]) on miRNA expression with the effects of exposure to CS or its total particulate matter fraction. This meta-analysis evaluated 12 datasets of a total of 736 detected miRNAs and 2775 exposed culture inserts. The t-distributed stochastic neighbor embedding method was used to find similarities across the diversity of miRNA responses characterized by tissue type, exposure type, and product concentration. The CS-induced changes in miRNA expression in gingival cultures were close to those in buccal cultures; similarly, the alterations in miRNA expression in small airway, bronchial, and nasal tissues resembled each other. A supervised clustering was performed to identify miRNAs exhibiting particular response patterns. The analysis identified a set of miRNAs whose expression was altered in specific tissues upon exposure to CS (e.g., miR-125b-5p, miR-132-3p, miR-99a-5p, and 146a-5p). Finally, we investigated the impact of RRPs on miRNA expression in relation to that of CS by calculating the response ratio r between the RRP- and CS-induced alterations at an individual miRNA level, showing reduced alterations in miRNA expression following RRP exposure relative to CS exposure (94 % relative reduction). No specific miRNA response pattern indicating exposure to aerosols from heated tobacco products and e-vapor products, or extracts from Swedish snus was identifiable.

Label-free quantitative proteomic analysis of gingival crevicular fluid to identify potential early markers for root resorption

Background

Orthodontically-induced root resorption is an iatrogenic effect and it cannot be examined regularly due to the harmful effects of sequential doses of radiation with more frequent radiography. This study aims to compare protein abundance (PA) of pre-treatment and during orthodontic treatment for root resorption and to determine potential early markers for root resorption.

Methods

Ten subjects (n = 10) who had upper and lower fixed appliances (MBT, 3 M Unitek, 0.022″ × 0.028″) were recruited for this study. Human gingival crevicular fluid (GCF) was obtained using periopaper strips at pre-treatment (T0), 1 month (T1), 3 months (T3), and 6 months (T6) of orthodontic treatment. Periapical radiographs of the upper permanent central incisors were taken at T0 and T6 to measure the amount of root resorption. Identification of changes in PA was performed using liquid chromatography-tandem mass spectrometry. Student’s t-test was then performed to determine the significance of the differences in protein abundance before and after orthodontic treatment.

Results

Our findings showed that all ten subjects had mild root resorption, with an average resorption length of 0.56 ± 0.30 mm. A total of 186 proteins were found to be commonly present at T0, T1, T3, and T6. There were significant changes in the abundance of 16 proteins (student’s t-test, p ≤ 0.05). The increased PA of S100A9, immunoglobulin J chain, heat shock protein 1A, immunoglobulin heavy variable 4–34 and vitronectin at T1 suggested a response to stress that involved inflammation during the early phase of orthodontic treatment. On the other hand, the increased PA of thymidine phosphorylase at T3 suggested growth promotion and, angiogenic and chemotactic activities.

Conclusions

The identified proteins can be potential early markers for root resorption based on the increase in their respective PA and predicted roles during the early phase of orthodontic treatment. Non-invasive detection of root resorption using protein markers as early as possible is extremely important as it can aid orthodontists in successful orthodontic treatment.

Expression of MicroRNAs in Periodontal and Peri-Implant Diseases: A Systematic Review and Meta-Analysis

AIM

The purpose of this review was to evaluate the expression patterns of miRNAs in periodontal and peri-implant diseases, while identifying potential miRNAs with the greatest diagnostic ability as an oral fluid biomarker.

MATERIALS AND METHODS

Human and animal studies were included when evaluating expression of miRNAs between health and different forms/stages of diseases, in which microarray and/or real-time polymerase chain reaction (RT-PCR) was carried out to detect fold changes in gene expression. After full-text analysis, 43 articles were considered for a qualitative assessment, and 16 miRNAs were selected to perform meta-analysis.

RESULTS

Based on human studies, results showed an overall upregulation of most of the evaluated miRNAs in periodontitis, with miRNA-142-3p and miRNA-146a being the most conclusive on both microarray and RT-PCR values and potentially serving as diagnostic biomarkers for disease activity. Conversely, miR-155 was the only miRNA revealing a statistically significant difference (SSD) (p < 0.05*) in experimental periodontitis models from RT-PCR values. Scarce scientific evidence is available from peri-implant diseases, however, most explored miRNAs in peri-implantitis were downregulated except for miR-145.

CONCLUSIONS

Although our results revealed that a distinct differential expression of specific miRNAs can be noted between the state of health and disease, future research remains necessary to explore the functional role of specific miRNAs and their potential as therapeutic targets in periodontal and peri-implant diseases. MeSH Terms: periodontitis, peri-implantitis, epigenomics, microarray analysis, real-time polymerase chain reaction, microRNAs.

CLINICAL RELEVANCE

Scientific background: Although most research identified different expression levels of miRNAs in periodontal and peri-implant diseases compared to their counterparts, their actual role in the pathogenesis of these conditions remains unclear. Therefore, we aimed to present a systematic review and meta-analysis on the expression patterns of miRNAs in periodontitis and peri-implantitis, while identifying potential miRNAs with the greatest diagnostic ability as an oral fluid biomarker.

PRINCIPAL FINDINGS

In periodontitis-related studies, miRNA-142-3p and miRNA-146a were the most conclusive on both microarray and RT-PCR values. Scarce scientific evidence is available from peri-implant diseases.

PRACTICAL IMPLICATIONS

Both miRNA-142-3p and miRNA-146a might serve as future diagnostic biomarkers for disease activity in periodontitis. Yet, future research remains necessary to explore the functional role of specific miRNAs and their potential as therapeutic targets in periodontal and peri-implant diseases.