Saliva diagnostics - Current views and directions

Circular RNA in Saliva

Although the type and amount of salivary components are influenced by many factors, due to easy, quick, cheap, and noninvasive sampling method alongside with the existence of the vast majority of the substances found in peripheral blood and urine in it, in recent years saliva has been considered as an ideal biofluid for disease research. Salivary circular RNA (circRNA), as an endogenous RNA molecule with a great variety of regulatory potency, is becoming a novel focus for detecting wide range of local or systemic diseases. Expectantly, with characterization of many more circRNAs in saliva, their motifs, and target sites, they can be used routinely in personalized medicine.

Feasibility of the salivary transcriptome as a novel biomarker in determining disease susceptibility

BACKGROUND AND OBJECTIVE

The salivary transcriptome may present as a readily available and non-invasive source of potential biomarkers. The development of chronic periodontitis is determined by individual patient susceptibility; hence, the aim of this study was to determine the potential of the salivary transcriptome as a biomarker of disease susceptibility using chronic periodontitis as an example.

MATERIAL AND METHODS

Using an Oragene^® RNA kit, the total RNA was purified from the saliva of 10 patients with chronic periodontitis and 10 patients without chronic periodontitis. The quantity and quality of the total RNA was determined, and a measure of gene expression via cDNA was undertaken using the Affymetrix microarray system. The microarray profiling result was further validated by real-time quantitative polymerase chain reaction.

RESULTS

Spectrophotometric analysis showed the total RNA purified from each participant ranged from 0.92 μg/500 μL to 62.85 μg/500 μL. There was great variability in the quantity of total RNA obtained from the 2 groups in the study with a mean of 10.21 ± 12.71 μg/500 μL for the periodontitis group and 15.97 ± 23.47 μg/500 μL for the control group. Further the RNA purity (based on the A₂₆₀ /A₂₈₀ ratio) for the majority of participants (9 periodontitis and 6 controls) were within the acceptable limits for downstream analysis (2.0 ± 0.1). The study samples, showed 2 distinct bands at 23S (3800 bp) and 16S (1500 bp) characteristic of bacterial rRNA. Preliminary microarray analysis was performed for 4 samples (P2, P6, H5 and H9). The percentage of genes present in each of the 4 samples was not consistent with about 1.8%-18.7% of genes being detected. Quantitative real-time polymerase chain reaction confirmed that the total RNA purified from each sample was mainly bacterial RNA (Uni 16S) with minimal human mRNA.

CONCLUSION

This study showed that minimal amounts of human RNA were able to be isolated from the saliva of patients with periodontitis as well as controls. Further work is required to enhance the extraction process of human mRNA from saliva if the salivary transcriptome is to be used in determining individual patient susceptibility.

Comparison of Total Antioxidant Capacity of Saliva in Women with Gestational diabetes mellitus and Non-diabetic Pregnant Women

Background

Pregnancy is considered a stressful event, results in higher levels of oxidative stress and considerable changes in physiological and metabolic functions such as gestational diabetes mellitus (GDM). Due to the cumulative effect of antioxidants and considering the controversies in this area, this study was undertaken to investigate the total antioxidant capacity (TAC) of saliva in pregnant women whit gestational diabetes in comparison to non-diabetic pregnant women.

Material and Methods

In this cross-sectional study (2015-16), a total of 31 women with a diagnosis of GDM and 59 non-diabetic pregnant women were included in the diabetic and control groups, respectively. Salivary samples were collected by spitting method. When all samples were collected, total antioxidant capacity (TAC) was measured with the use of a commercial kit following the manufacturer's instructions. Data were analyzed with descriptive statistics and Mann-Whitney test using SPSS 18.

Results

Average TAC level in the saliva of women with gestational diabetes was 0.10 ± 0.14, with 0.04 ± 0.11 in non-diabetic pregnant women. Nonparametric Mann-Whitney test showed that this difference was statistically significant (P=0.024).

Conclusions

Under the limitations of the present study it can be concluded that there is an increase in oxidative stresses during pregnancy, followed by an increase in the total levels of salivary antioxidants to counteract such stresses. Therefore, it is expected that determining the salivary antioxidant levels during pregnancy can be an alternative technique for the early diagnosis of diabetes. Key words:Gestational diabetes mellitus, pregnancy, saliva, total antioxidant capacity.

Cell-free nucleic acids in body fluids as biomarkers for the prediction and early detection of recurrent head and neck cancer: A systematic review of the literature

Liquid biopsy is a minimally invasive detection method for molecular biomarkers in body fluids which may serve as a novel tool in management of head and neck cancer. The purpose of this systematic review is to outline the current status of liquid biopsy in head and neck squamous cell carcinoma (HNSCC) patients by systematically identifying and qualifying all published studies on the diagnostic or prognostic value of cell-free nucleic acids detection for posttreatment disease monitoring and/or disease outcome. A search was performed in PubMed, EMBASE, and Cochrane Library. Thirty articles met the inclusion criteria for further analysis. Study and patient characteristics, molecular analysis method and treatment or prognostic outcomes were extracted. Seventeen studies investigated circulating miRNAs in blood. Of these studies, 16 found statistically significant results for a total of 24 different candidate miRNAs for prognostication or treatment monitoring. The remaining studies investigated circulating tumor DNA by targeting somatic mutations, allelic imbalances, hypermethylation, or HPV-DNA. Of these studies, 2 found a statistically significant association between nucleic acid levels (tumor DNA targeted by allelic imbalances and HPV-DNA) in blood and/or saliva and prognostic outcome. One study found significantly different pre- and posttreatment levels of mitochondrial DNA in serum. Despite large differences among these studies in both design and results, individual results are promising and provide ground for more large-scale studies with standardized serial assessment of patient samples in the future.

Gut Microbiota and Salivary Diagnostics: The Mouth Is Salivating to Tell Us Something

The microbiome of the human body represents a symbiosis of microbial networks spanning multiple organ systems. Bacteria predominantly represent the diversity of human microbiota, but not to be forgotten are fungi, viruses, and protists. Mounting evidence points to the fact that the "microbial signature" is host-specific and relatively stable over time. As our understanding of the human microbiome and its relationship to the health of the host increases, it is becoming clear that many and perhaps most chronic conditions have a microbial involvement. The oral and gastrointestinal tract microbiome constitutes the bulk of the overall human microbial load, and thus presents unique opportunities for advancing human health prognosis, diagnosis, and therapy development. This review is an attempt to catalog a broad diversity of recent evidence and focus it toward opportunities for prevention and treatment of debilitating illnesses.

Oral Health: The Need for Both Conventional Microbial and Molecular Characterization

This study aims to consider the microbial distribution in oral disease, as well as gene analysis and expression, in elucidating: 1, the fundamental underpinnings of oral disease, and 2, the potential relationship between oral diseases and systemic health. A key focus is identifying the microbiota associated with oral disease manifestations characterized by both conventional microbiological and molecular methods. Variations in the observed microbial populations characterized by conventional and molecular approaches have been identified for caries, periodontitis, peri-implantitis, and stomatitis. The discovery of therapeutic approaches for oral disease will require comprehensive microbial and genomic analysis. This study evaluated the current state of the relevant microbial and genomic information for several prevalent oral diseases.

Advancing Point-of-Care (PoC) Testing Using Human Saliva as Liquid Biopsy

Salivary diagnostics is an emerging field for the encroachment of point of care technology (PoCT). The necessity of the development of point-of-care (PoC) technology, the potential of saliva, identification and validation of biomarkers through salivary diagnostic toolboxes, and a broad overview of emerging technologies is discussed in this review. Furthermore, novel advanced techniques incorporated in devices for the early detection and diagnosis of several oral and systemic diseases in a non-invasive, easily-monitored, less time consuming, and in a personalised way is explicated. The latest technology detection systems and clinical utilities of saliva as a liquid biopsy, electric field-induced release and measurement (EFIRM), biosensors, smartphone technology, microfluidics, paper-based technology, and how their futuristic perspectives can improve salivary diagnostics and reduce hospital stays by replacing it with chairside screening is also highlighted.