Salivary biomarkers for periodontal disease diagnostics

Tumour Necrosis Factor Alpha (TNF-α) and Oral Squamous Cell Carcinoma

Uncovering the inflammatory mechanisms underpinning initiation, progression, and promotion of oral squamous cell carcinoma (OSCC) development is fundamental to the rational pursuit of targeted therapeutics. Here we present a review of the current knowledge of the role of TNF-α in the aetiology, pathogenesis, and potential therapies with regards to OSCC. TNF-α is worthy of particular attention in OSCC, with its presence demonstrated to enhance cell proliferation and its downregulation demonstrated to inhibit proliferation and migration in other carcinomas in both in vitro and in vivo models and oral cancer patients. Increased TNF-α in the OSCC tumour microenvironment has been demonstrated to favour invasion through promotion of firstly the pro-inflammatory, pro-invasive phenotypes of OSCC cells and secondly its paracrine mechanism mediating recruitment and activation of inflammatory cells. Polymorphisms affecting the gene expression of TNF-α have been strongly associated with an increased risk for oral squamous cell carcinoma. A number of studies have considered TNF-α within biofluids, including saliva and serum, as a potential biomarker for the early detection of OSCC, as well as its staging, differentiation, and prognosis. The broad and multifaceted role that TNF-α plays in many inflammatory states presents an obvious confounder, particularly with demonstrated increased TNF-α levels in common oral disease states. Lastly, biologic agents targeting TNF-α are currently in clinical use for immune-mediated inflammatory rheumatological and gastrointestinal diseases. There is the potential that these biological agents might have an adjunctive role in OSCC prevention and treatment.

Saliva as a Source of Biomarkers for Periodontitis and Periimplantitis

Saliva has the potential to be used as a diagnostic and monitoring tool for various diseases if biomarkers of an adequate sensitivity and specificity could be identified. Several reviews and even meta-analyses have been performed in recent years, which have found some candidate biomarkers for periodontitis, like macrophage inflammatory protein-1 alpha, interleukin-1ß, interleukin-6, matrix metalloproteinase-8, or hemoglobin. However, none of those are currently in use to replace conventional periodontal diagnostics with a periodontal probe. For periimplantitis, to date, heterogeneity of different study protocols and implant types did not permit to discover clear biomarkers, which were able to distinguish between healthy and diseased implants. Few proinflammatory cytokines, similar to periodontitis, have been characterized as adjunct tools to clinical diagnosis. The additional determination of antimicrobial peptides, bone turnover markers, and bacteria could help to enhance sensitivity and specificity in a combined model for periodontitis and periimplantitis. Furthermore, proteomic approaches might be preferred over single biomarker determinations. A global consensus is also needed to harmonize salivary sampling methods as well as procedures of biomarker analysis to ensure future comparability.

Biosensor and Lab-on-a-chip Biomarker-identifying Technologies for Oral and Periodontal Diseases

Periodontitis is a complex multifactorial disease that can lead to destruction of tooth supporting tissues and subsequent tooth loss. The most recent global burden of disease studies highlight that severe periodontitis is one of the most prevalent chronic inflammatory conditions affecting humans. Periodontitis risk is attributed to genetics, host-microbiome and environmental factors. Empirical diagnostic and prognostic systems have yet to be validated in the field of periodontics. Early diagnosis and intervention prevents periodontitis progression in most patients. Increased susceptibility and suboptimal control of modifiable risk factors can result in poor response to therapy, and relapse. The chronic immune-inflammatory response to microbial biofilms at the tooth or dental implant surface is associated with systemic conditions such as cardiovascular disease, diabetes or gastrointestinal diseases. Oral fluid-based biomarkers have demonstrated easy accessibility and potential as diagnostics for oral and systemic diseases, including the identification of SARS-CoV-2 in saliva. Advances in biotechnology have led to innovations in lab-on-a-chip and biosensors to interface with oral-based biomarker assessment. This review highlights new developments in oral biomarker discovery and their validation for clinical application to advance precision oral medicine through improved diagnosis, prognosis and patient stratification. Their potential to improve clinical outcomes of periodontitis and associated chronic conditions will benefit the dental and overall public health.

Salivary levels of specialized pro-resolving lipid mediators as indicators of periodontal health/disease status

AIM

This cross-sectional case-control study aimed to determine if salivary levels of lipoxin A4 (LXA4), protectin D1 (PD1), resolvin E1 (RvE1) and maresin 1 (MaR1) might constitute a reflection of periodontal health/disease status.

MATERIALS AND METHODS

One hundred and two periodontitis patients and 61 healthy controls were recruited. Periodontal clinical status was determined by criteria based on full-mouth clinico-radiographical data. Salivary concentration of the analytes was calculated by enzyme-linked immunosorbent assay. The association between the biomarkers with disease status was assessed individually and adjusted for confounding using multivariate binary logistic regression models.

RESULTS

Significantly decreased LXA4 and increased PD1/MaR1 salivary levels were detected in periodontitis patients in comparison with healthy controls. However, no significant differences were observed for RvE1 levels between clinical groups. Clinical parameters such as probing depth, clinical attachment loss and extent were negatively correlated with LXA4, positively correlated with PD1/MaR1 and not correlated with RvE1 salivary levels. Logistic regression analyses revealed a strong/independent association of LXA4, PD1 and MaR1 salivary levels regarding disease status. Interaction effects between demographic predictor variables and salivary concentration of LXA4, PD1 and MaR1 were also identified.

CONCLUSION

The results of this study demonstrated a strong/independent association between reduced LXA4 and increased PD1/MaR1 salivary levels with periodontitis suggesting an imbalance in the specialized pro-resolving lipid mediators (SPMs) in periodontal disease.

Decreased salivary concentration of CD9 and CD81 exosome-related tetraspanins may be associated with the periodontal clinical status

AIM

This cross-sectional case-control study was designed to determine the association of the salivary concentration of CD9/CD81 exosome-related tetraspanins with the periodontal clinical status.

MATERIALS AND METHODS

Saliva samples from 104 periodontitis patients and 45 healthy controls were collected. Periodontal status was assessed based on full-mouth clinico-radiographical data, and salivary concentration of the analytes was calculated by ELISA. The association between the biomarkers with disease status was analysed using multivariate binary logistic regression models.

RESULTS

Significantly decreased salivary levels of CD9 and CD81 exosomes were detected in periodontitis patients in comparison with healthy controls. Also, negative significant correlations between salivary concentrations of CD9/CD81 exosomes regarding clinical measurements were observed. Likewise, a significant downward trend of the concentration of these two biomarkers concerning the stage and grade of disease could be identified. Logistic regression analyses revealed a strong/independent association for decreased salivary concentration of CD81 exosomes regarding disease status. Confounding and interaction effects between age and salivary concentration of CD9 exosomes were also noted.

CONCLUSION

Reduced salivary concentration of CD9/CD81 exosomes might be of significance in the context of periodontal disease pathogenesis.

A New Approach for the Diagnosis of Systemic and Oral Diseases Based on Salivary Biomolecules

Early diagnosis represents the target of contemporary medicine and has an important role in the prognosis and further treatment. Saliva is a biofluid that generated a high interest among researchers due to its multiple advantages over other body fluids. The multitude of components that can act as biomarkers influenced the existing technologies to develop protocols that could allow saliva to become the new noninvasive diagnostic method. Saliva as a diagnostic tool can bring substantial addition to the diagnostic armamentarium, providing important information about oral and general health. The diagnostic applications of saliva extended and had a rapid evolution due to the advancement in salivaomics. The present review summarizes the latest researches in saliva-related studies and explores the information and correlations that saliva can offer regarding the systemic and oral diseases, highlighting its great potential of diagnosis. It is expected that in the future specific guidelines and results regarding the salivary diagnostics are to be available, together with high-sensitivity and specificity tests for multiple systemic and oral diseases.

Assessing a multiplex-targeted proteomics approach for the clinical diagnosis of periodontitis using saliva samples

AIM

The present study focused on the research of new biomarkers based on the liquid chromatography-multiple-reaction monitoring (MRM) proteomic profile in whole saliva of patients with periodontitis compared with periodontal healthy patients.

METHODS

A 30-min multiplexed liquid chromatography-MRM method was used for absolute quantification of 35 plasma biomarkers in saliva from control patients and patients with periodontitis.

RESULTS

Three proteins namely hemopexin, plasminogen and α-fibrinogen were shown to be clearly related to the presence of periodontitis compared with healthy patients. Apolipoprotein H was found to discriminate for the first time chronic and aggressive periodontitis.

CONCLUSION

Our results indicate that this innovative MRM method could be used to screen for periodontitis in clinical environment. Furthermore, apolipoprotein H was found to be a discriminant biomarker of aggressive periodontitis.

Salivary Levels of NLRP3 Inflammasome-Related Proteins as Potential Biomarkers of Periodontal Clinical Status

BACKGROUND

Emerging evidence suggests that activation of inflammasomes plays a central mechanism in pathogenesis of periodontitis. This study aims to compare salivary levels of nod-like receptor family pyrin domain containing protein (NLRP) 3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), cysteine aspartase (caspase)-1, and interleukin (IL)-1β from individuals with aggressive (AgP) or chronic periodontitis (CP) and healthy controls (HC), as well as elucidate its association with periodontal clinical status.

METHODS

Saliva samples from individuals with CP (n = 75), AgP (n = 20), and HC (n = 69) were collected. Periodontal status was assessed by measurement of probing depth, clinical attachment level, and extent and severity of disease. Salivary levels of analytes were analyzed by enzyme-linked immunosorbent assay. Association between biomarkers with CP or AgP was analyzed using multivariate binary logistic regression models.

RESULTS

Significantly higher levels of NLRP3, ASC, and IL-1β were detected in periodontitis groups in comparison to the periodontally HC group. However, no significant differences were observed for caspase-1 levels between clinical groups, and only NLRP3 salivary concentration was significantly higher in AgP compared with CP patients. Also, positive significant correlations among NLRP3, ASC, and IL-1β salivary concentrations and clinical parameters were observed. Logistic regression analyses revealed a strong/independent association of NLRP3, ASC, and IL-1β salivary levels with CP and AgP.

CONCLUSION

Although the concentration of caspase-1 in saliva samples makes its determination useless for detection of periodontal disease and/or its severity, salivary levels of NLRP3, ASC, and IL-1β may act as strong/independent indicators of amount and extent of periodontal breakdown in both CP and AgP and could potentially be used for prevention and therapy of this group of diseases.

Salivary and serum adiponectin and C-reactive protein levels in acute myocardial infarction related to body mass index and oral health

BACKGROUND AND OBJECTIVE

Adiponectin is produced by adipose cells and is considered an anti-inflammatory molecule. In contrast, C-reactive protein (CRP) has been identified as a hallmark of systemic inflammation and used as a risk marker of cardiovascular disease (CVD). Of interest was the relationship of these two biomarkers to oral health and CVD risk.

MATERIAL AND METHODS

This investigation examined these two molecules in serum and unstimulated whole saliva of patients within 48 h of an acute myocardial infarction (AMI) compared to control subjects. We hypothesized a differential response in these biomolecules resulting from the heart attack that would be affected by both the body mass index and oral health characteristics of the individuals.

RESULTS

Significantly lower adiponectin levels were observed in the serum of patients with AMI. Serum adiponectin in both groups and salivary adiponectin in patients with AMI decreased with increasing body mass index. Oral health was significantly worse in patients with AMI, and both serum and salivary adiponectin were elevated with better oral health in control subjects. Serum CRP levels were increased in patients with AMI regardless of their oral health, and both serum and salivary CRP were significantly elevated in S-T wave elevated patients with MI.

CONCLUSIONS

These initial data provide evidence relating obesity and oral health to salivary and serum analyte levels that occur in association with cardiac events. Relationships have been described between CVD risk and periodontal disease. Additionally, various systemic inflammatory biomarkers appear to reflect both the CVD risk and the extent/severity of periodontitis. Our findings indicated that oral health and obesity contribute to altering levels of these salivary and serum analytes in association with cardiac events. The potential that serum and/or salivary biomarkers could aid in evaluating CVD risk requires knowledge regarding how the oral health of the individual would impact the effectiveness of these biological measures.

Influence of Periodontal Clinical Status on Salivary Levels of Glutathione Reductase

BACKGROUND

Inadequate antioxidant balance may play a role in the excessive tissue breakdown in periodontitis. Because aggressive periodontitis (AgP) not only differs from chronic periodontitis (CP) in terms of clinical manifestations, this study investigates whether the salivary levels of glutathione reductase (GR) may be linked with periodontal status.

METHODS

Saliva samples from patients with CP (n = 121), patients with AgP (n = 18), and healthy controls (n = 69) were collected. Periodontal status was assessed by criteria based on probing depth, clinical attachment level, and extent and severity of periodontal breakdown. GR salivary levels were analyzed by spectrophotometry. The association among GR concentration and CP or AgP was analyzed individually and adjusted for confounding using multivariate binary logistic regression models.

RESULTS

GR levels not only differed significantly between the two periodontitis groups, being significantly greater in patients with AgP, but also were significantly greater than those observed in healthy controls. Synchronously, positive significant correlations between salivary GR concentration and clinical parameters were observed. After binary logistic regression analysis, both GR salivary levels ≥15.38 and ≥24.20 mU/mL were associated independently with CP and AgP, respectively. A significant interaction effect was also detected between increased GR salivary concentration and aging in the CP group.

CONCLUSIONS

Increased GR salivary concentration may be a strong/independent prognostic indicator of the amount and extent of oxidative stress-induced periodontal damage in both CP and AgP. Likewise, saliva samples might reflect an interactive effect of GR levels associated with the aging-related cumulative characteristics of periodontal damage in CP.

Comparative performance analyses of commercially available products for salivary collection and nucleic acid processing in the newborn

Analysis of saliva for clinical monitoring and biomarker detection holds great promise for improving health care. Commercially available assays are not intended for use with neonates, however, and collection and processing of saliva for subsequent transcriptomic analysis presents unique challenges in this population. We compared RNA yield, quality, stability and RT-qPCR performance for two commonly used commercial systems: the Qiagen RNeasy Protect Saliva Mini Kit(®) and the DNA Genotek Oragene•RNA(®) assay. Two 10 μl saliva samples were collected from ten newborns and stabilized for each assay. Total RNA was extracted following incubation for 3, 10, 15 or 20 days. Total RNA extracted from each assay was analyzed for integrity, quality and quantity using the Agilent BioAnalyzer 2100. RT-qPCR was performed for the reference gene, GAPDH, to assess subsequent performance of the extracted RNA. Although the DNA Genotek extraction protocol required nearly twice the time of the Qiagen protocol, RNA integrity did not differ between the kits. RNA concentration using the DNA Genotek assay, however, was 3,264 pg/μl (range: 262 - 10,336 pg/μl) compared to 822.4 pg/μl (range: 0 - 1,856 pg/μl) for the Qiagen protocol. Linear regression analysis showed a stronger correlation between the threshold cycle and RNA concentration using DNA Genotek (r(2) = 0.356) compared to Qiagen (r(2) = 0.0331). Our results suggest that although the Qiagen assay may reduce overall extraction time, RNA yield and performance in subsequent transcriptomic analysis is more robust using the DNA Genotek assay.

A Filifactor alocis-centered co-occurrence group associates with periodontitis across different oral habitats

Periodontitis is a highly prevalent polymicrobial disease worldwide, yet the synergistic pattern of the multiple oral pathogens involved is still poorly characterized. Here, saliva, supragingival and subgingival plaque samples from periodontitis patients and periodontally healthy volunteers were collected and profiled with 16S rRNA gene pyrosequencing. Different oral habitats harbored significantly different microbiota, and segregation of microbiota composition between periodontitis and health was observed as well. Two-step redundancy analysis identified twenty-one OTUs, including Porphyromonas gingivalis, Tannerella forsythia and Filifactor alocis, as potential pathogens that were significantly associated with periodontitis and with two periodontitis diagnostic parameters (pocket depth and attachment loss) in both saliva and supragingival plaque habitats. Interestingly, pairwise correlation analysis among the 21 OTUs revealed that Filifactor alocis was positively correlated with seven other putative pathogens (R > 0.6, P < 0.05), forming a co-occurrence group that was remarkably enriched in all three habitats of periodontitis patients. This bacterial cluster showed a higher diagnostic value for periodontitis than did any individual potential pathogens, especially in saliva. Thus, our study identified a potential synergistic ecological pattern involving eight co-infecting pathogens across various oral habitats, providing a new framework for understanding the etiology of periodontitis and developing new diagnoses and therapies.