Salivary biomarkers and proteomics: future diagnostic and clinical utilities

CapsNet-SSP: multilane capsule network for predicting human saliva-secretory proteins

Background

Compared with disease biomarkers in blood and urine, biomarkers in saliva have distinct advantages in clinical tests, as they can be conveniently examined through noninvasive sample collection. Therefore, identifying human saliva-secretory proteins and further detecting protein biomarkers in saliva have significant value in clinical medicine. There are only a few methods for predicting saliva-secretory proteins based on conventional machine learning algorithms, and all are highly dependent on annotated protein features. Unlike conventional machine learning algorithms, deep learning algorithms can automatically learn feature representations from input data and thus hold promise for predicting saliva-secretory proteins.

Results

We present a novel end-to-end deep learning model based on multilane capsule network (CapsNet) with differently sized convolution kernels to identify saliva-secretory proteins only from sequence information. The proposed model CapsNet-SSP outperforms existing methods based on conventional machine learning algorithms. Furthermore, the model performs better than other state-of-the-art deep learning architectures mostly used to analyze biological sequences. In addition, we further validate the effectiveness of CapsNet-SSP by comparison with human saliva-secretory proteins from existing studies and known salivary protein biomarkers of cancer.

Conclusions

The main contributions of this study are as follows: (1) an end-to-end model based on CapsNet is proposed to identify saliva-secretory proteins from the sequence information; (2) the proposed model achieves better performance and outperforms existing models; and (3) the saliva-secretory proteins predicted by our model are statistically significant compared with existing cancer biomarkers in saliva. In addition, a web server of CapsNet-SSP is developed for saliva-secretory protein identification, and it can be accessed at the following URL: http://www.csbg-jlu.info/CapsNet-SSP/. We believe that our model and web server will be useful for biomedical researchers who are interested in finding salivary protein biomarkers, especially when they have identified candidate proteins for analyzing diseased tissues near or distal to salivary glands using transcriptome or proteomics.

Alteration of cytokines in saliva of children with caries and obesity

Caries and obesity are multifactorial diseases with inflammatory components, whose processes involve cells and molecules, such as cytokines. Therefore, the objective of this work was to compare the concentrations of IL-6, IL-8, IL-15, and IL-18 in the salivary samples of children with caries and obesity. The study was carried out with 80 children: 43 with a normal weight and 37 with obesity. The diagnosis of caries was carried out using the ICDAS system. Salivary samples were used to measure the cytokine levels via the ELISA technique. Our results show that children with obesity and dental cavities have high levels of IL-6 and IL-15. Similarly, obese children have elevated levels of these two cytokines, while children with cavitated carious lesions presented alterations in their concentrations of IL-6 and IL-8. In conclusion, our data suggest that IL-6 has a significant effect on both obesity and caries, although IL-8 is more related to caries, and IL-15 is more related to obesity.

Is there a link between stress and immune biomarkers and salivary opiorphin in patients with a restrictive-type of anorexia nervosa?

Objectives: Opiorphin is a salivary peptide with analgesic and antidepressant properties. Its relationship with the hypothalamic-pituitary-adrenal, autonomic nervous and immune systems may provide understanding of chronic stress, especially in anorexia nervosa (AN). This study investigated a possible correlation between opiorphin and stress/immune biomarkers, cortisol, salivary alpha-amylase (sAA) and secretory immunoglobulin A (sIgA), in saliva of patients with restrictive-type AN.Methods: A case-control clinical trial was conducted in 92 AN patients (+75 healthy controls). Unstimulated salivary samples were taken during the acute stage of AN, measurements of cortisol, sAA, sIgA and opiorphin were performed with a quantitative assay (enzyme-linked immunosorbent assay, P < 0.05).Results: AN patients displayed an increase in cortisol (P < 0.001) and sIgA (P < 0.001) but not in sAA (P = 0.279) levels. Distinct correlation between these two parameters and body-weight indexes were observed. Opiorphin levels were neither correlated to stress and immune biomarkers, nor to salivary flow rate.Conclusions: The effect of stress responses can be reliably assessed in saliva in AN patients. The difference between sIgA and cortisol indicate that they can both be used for mental stress assessment in saliva. Modulation of opiorphin by chronic stress was not confirmed. Unchanged sAA indicates a partial adaptation of human organism to severe condition during malnutrition.

Assessment of the Utility of the Oral Fluid and Plasma Proteomes for Hydrocodone Exposure

INTRODUCTION

Non-medical use and abuse of prescription opioids is a growing problem in both the civilian and military communities, with minimal technologies for detecting hydrocodone use. This study explored the proteomic changes that occur in the oral fluid and blood plasma following controlled hydrocodone administration in 20 subjects.

METHODS

The global proteomic profile was determined for samples taken at four time points per subject: pre-exposure and 4, 6, or 168 hours post-exposure. The oral fluid samples analyzed herein provided greater differentiation between baseline and response time points than was observed with blood plasma, at least partially due to significant person-to-person relative variability in the plasma proteome.

RESULTS

A total of 399 proteins were identified from oral fluid samples, and the abundance of 118 of those proteins was determined to be significantly different upon metabolism of hydrocodone (4 and 6 hour time points) as compared to baseline levels in the oral fluid (pre-dose and 168 hours).

CONCLUSIONS

We present an assessment of the oral fluid and plasma proteome following hydrocodone administration, which demonstrates the potential of oral fluid as a noninvasive sample that may reveal features of hydrocodone in opioid use, and with additional study, may be useful for other opioids and in settings of misuse.

Mapping Relative Differences in Human Salivary Gland Secretions by Dried Saliva Spot Sampling and nanoLC-MS/MS

Dried saliva spot sampling is a minimally invasive technique for the spatial mapping of salivary protein distribution in the oral cavity. In conjunction with untargeted nano-flow liquid chromatography tandem mass spectrometry (nanoLC-MS/MS) analysis, DSS is used to compare the proteomes secreted by unstimulated parotid and submandibular/sublingual salivary glands. Two hundred and twenty proteins show a statistically significant association with parotid gland secretion, while 30 proteins are at least tenfold more abundant in the submandibular/sublingual glands. Protein identifications and label-free quantifications are highly reproducible across the paired glands on three consecutive days, enabling to establish the core proteome of glandular secretions categorized into eight salivary protein groups according to their biological functions. The data suggest that the relative contributions of the salivary glands fine-tune the biological activity of human saliva via medium-abundant proteins. A number of biomarker candidates for Sjögren's syndrome are observed among the gland-specifically expressed proteins, which indicates that glandular origin is an important factor to consider in salivary biomarker discovery.

Proteomic Investigations of In Vitro and In Vivo Models of Periodontal Disease

Proteomics has currently been a developing field in periodontal diseases to obtain protein information of certain samples. Periodontal disease is an inflammatory disorder that attacks the teeth, connective tissues, and alveolar bone within the oral cavity. Proteomics information can provide proteins that are differentially expressed in diseased or healthy samples. This review provides insight into approaches researching single species, multi species, bacteria, non-human, and human models of periodontal disease for proteomics information. The approaches that have been taken include gel electrophoresis and qualitative and quantitative mass spectrometry. This review is carried out by extracting information about in vitro and in vivo studies of proteomics in models of periodontal diseases that have been carried out in the past two decades. The research has concentrated on a relatively small but well-known group of microorganisms. A wide range of models has been reviewed and conclusions across the breadth of these studies are presented in this review.

B7-H3 participates in human salivary gland epithelial cells apoptosis through NF-κB pathway in primary Sjögren's syndrome

Background

Primary Sjögren’s syndrome (pSS) is an autoimmune disorder mainly characterized by exocrine gland injury. Costimulatory molecules play an important role in immune-regulatory networks. Although B7 family costimulatory molecules were previously discovered in human salivary gland epithelial (HSGE) cells in pSS, the effects of the B7 family member B7-H3 (CD276) have not been well elucidated. Thus, this study aimed to investigate the role and mechanism of B7-H3 in HSGE cells in pSS.

Methods

The expression of B7-H3, B7-H1, PD-1 in serum, saliva and salivary gland were examined by immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). Immunofluorescence was used to test the expression and distribution of B7-H3, AQP5 and CK-8 in salivary gland tissues. Flow cytometry, Cell Counting Kit 8 (CCK-8) and western blot (WB) were performed to research the apoptotic, proliferative and inflammatory effects of B7-H3 in primary HSGE cells and HSGE cell lines.

Results

Our results showed that the expression of PD-1, B7-H1 and B7-H3 in peripheral blood, and salivary glands in pSS patients was higher than that in healthy controls, which was positive correlation with the grade of the salivary glands. The expression of B7-H3 in saliva was higher in pSS patients than that in healthy controls, which was detected with the most significant difference of them. The expression of B7-H3 in primary HSGE cells of pSS patients was significantly higher than healthy controls. B7-H3 increased activity of NF-κB pathway and promoted inflammation of HSGE cells, decreasing the expression of AQP5. Furthermore, B7-H3 overexpression inhibited proliferation and induced apoptosis in HSGE cell lines.

Conclusion

B7-H3 could promote inflammation and induce apoptosis of HSGE cells by activating NF-κB pathway, which might be a promising therapeutic target for pSS.

Self-Assembled STrap for Global Proteomics and Salivary Biomarker Discovery

Clinical biomarkers identified by shotgun proteomics require proteins in body fluids or tissues to be enzymatically digested before being separated and sequenced by liquid chromatography-tandem mass spectrometry. How well peptide signals can be resolved and detected is largely dependent on the quality of sample preparation. Conventional approaches such as in-gel, in-solution, and filter-based digestion, despite their extensive implementation by the community, become less appealing due to their unsatisfying protein/peptide recovery rate, lengthy sample processing, and/or lowcost-effectiveness. Suspension trapping has recently been demonstrated as an ultrafast approach for proteomic analysis. Here, for the first time, we extend its application to human salivary proteome analyses. In particular, we present a simple self-assembled glass fiber filter device which can be packed with minimal difficulty, is extremely cost-effective, and maintains the same performance as commercial filters. As a proof-of-principle, we analyzed the whole saliva from 8 healthy individuals as well as a cohort of 10 subjects of oral squamous cell carcinoma (OSCC) patients and non-OSCC subjects. Label-free quantification revealed surprisingly low interindividual variability and several known markers. Our study provides the first evidence of an easy-to-use and low-cost device for clinical proteomics as well as for general proteomic sample preparation.

A Simple Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry Method for Measurement of Cortisol Level in Human Saliva

A simple ultraperformance liquid chromatography-tandem mass spectrometry assay for measurement of cortisol level in human saliva was developed and validated. Saliva samples containing cortisol were spiked with tolperisone as internal standard (IS) and extracted with a mixture of methyl tert-butyl ether and hexane (8:2, v:v). After solvent evaporation, residue was reconstituted in 100 μl mobile phase. Analysis was performed on Atlantis dC18 column (2.1 × 100 mm, 3 μm particle size) with a mobile phase composed of acetonitrile and 2 mM ammonium acetate (50:50, v:v) and delivered at a flow rate of 0.3 ml/minute. Mass spectrometry acquisition was performed with multiple reaction monitoring in positive-ion mode for cortisol and IS (m/z: 363.1 → 121.0 and 246.0 → 97.9, respectively). Retention times of cortisol and IS were about 1.35 and 2.45 minutes, respectively. The relationship between cortisol level and peak area ratio of cortisol to IS was linear in the range of 0.5-100 ng/ml. Intra- and interday coefficient of variation and bias were ≤ 9.0% and ≤12.0%, respectively. Mean extraction recoveries of cortisol and IS from saliva samples were 92% and 94%, respectively. Using the method, cortisol was found to be ≥ 86% stable in processed (24 hours at room temperature or 48 hours at -20°C) and ≥ 91% stable in unprocessed (24 hours at room temperature or 20 weeks at -20°C) saliva samples. Further, the method was successfully applied to determine daily cortisol profile in saliva samples of a healthy volunteer.

Saliva as a Diagnostic Tool in Oral Squamous Cell Carcinoma - a Systematic Review with Meta Analysis

Whole saliva is mainly composed of fluid produced by major and minor salivary glands. Major salivary glands including parotid, submandibular, and sublingual glands, are known to secrete fluid transported from serum as well as surrounding glandular tissues [1]. Beside the secretions from salivary glands, oral mucosa, periodontium, as well as oral microflora also contribute to the final content of whole saliva [1]. Whole saliva therefore represents a complex balance among local and systemic sources [2]. This allows for the application of saliva in the diagnosis not only for salivary gland disorders but also for oral diseases and systemic conditions [2]. The role of saliva as a diagnostic tool in detecting Oral Squamous Cell Carcinoma. Articles published in PUBMED, EMBASE, COCHRANE, GOOGLE, manual search and back references of the articles for last 5 years extracted 77 articles. Studies which considered saliva as a diagnostic tool were included. Statistical analysis with Receivers Operating Curve to establish sensitivity and specificity of the salivary biomarkers as a diagnostic tool to detect Oral Squamous Cell Carcinoma were included for meta analysis. The measure of effect with 95% confidence interval were meta analysed for 9 articles in which 308 healthy individuals compared with 340 patients with Oral Squamous Cell Carcinoma. Highly sensitive salivary biomarkers for detecting Oral Squamous Cell Carcinoma were MMP-9, Chemerin, Choline + Betaine + Pipecolinic Acid + I - Carnitine(confidence interval ranges from 0.83-1.0). The narrow confidence interval of 0.95 + (0.88-1.00) was seen for MMP-9 followed by 1.00 + (0.78-1.00) for chemerin. Highly specific biomarkers for Oral Squamous Cell Carcinoma were MMP-9 (specificity -100%,), Chemerin(specificity-100%), over expressed mi RNA 136 with specificity of 0.88(0.69-0.97), under expressed mi RNA 27B with specificity of 1.0(0.66-1.00). Saliva can be used as a diagnostic tool with highly sensitive and specific markers namely MMP-9, Chemerin for early detection of Oral Squamous Cell Carcinoma.

Proteome Imaging: From Classic to Modern Mass Spectrometry-Based Molecular Histology

In order to overcome the limitations of classic imaging in Histology during the actually era of multiomics, the multi-color "molecular microscope" by its emerging "molecular pictures" offers quantitative and spatial information about thousands of molecular profiles without labeling of potential targets. Healthy and diseased human tissues, as well as those of diverse invertebrate and vertebrate animal models, including genetically engineered species and cultured cells, can be easily analyzed by histology-directed MALDI imaging mass spectrometry. The aims of this review are to discuss a range of proteomic information emerging from MALDI mass spectrometry imaging comparative to classic histology, histochemistry and immunohistochemistry, with applications in biology and medicine, concerning the detection and distribution of structural proteins and biological active molecules, such as antimicrobial peptides and proteins, allergens, neurotransmitters and hormones, enzymes, growth factors, toxins and others. The molecular imaging is very well suited for discovery and validation of candidate protein biomarkers in neuroproteomics, oncoproteomics, aging and age-related diseases, parasitoproteomics, forensic, and ecotoxicology. Additionally, in situ proteome imaging may help to elucidate the physiological and pathological mechanisms involved in developmental biology, reproductive research, amyloidogenesis, tumorigenesis, wound healing, neural network regeneration, matrix mineralization, apoptosis and oxidative stress, pain tolerance, cell cycle and transformation under oncogenic stress, tumor heterogeneity, behavior and aggressiveness, drugs bioaccumulation and biotransformation, organism's reaction against environmental penetrating xenobiotics, immune signaling, assessment of integrity and functionality of tissue barriers, behavioral biology, and molecular origins of diseases. MALDI MSI is certainly a valuable tool for personalized medicine and "Eco-Evo-Devo" integrative biology in the current context of global environmental challenges.

Enhanced Molecular Appreciation of Psychiatric Disorders Through High-Dimensionality Data Acquisition and Analytics

The initial diagnosis, molecular investigation, treatment, and posttreatment care of major psychiatric disorders (schizophrenia and bipolar depression) are all still significantly hindered by the current inability to define these disorders in an explicit molecular signaling manner. High-dimensionality data analytics, using large datastreams from transcriptomic, proteomic, or metabolomic investigations, will likely advance both the appreciation of the molecular nature of major psychiatric disorders and simultaneously enhance our ability to more efficiently diagnose and treat these debilitating conditions. High-dimensionality data analysis in psychiatric research has been heterogeneous in aims and methods and limited by insufficient sample sizes, poorly defined case definitions, methodological inhomogeneity, and confounding results. All of these issues combine to constrain the conclusions that can be extracted from them. Here, we discuss possibilities for overcoming methodological challenges through the implementation of transcriptomic, proteomic, or metabolomics signatures in psychiatric diagnosis and offer an outlook for future investigations. To fulfill the promise of intelligent high-dimensionality data-based differential diagnosis in mental disease diagnosis and treatment, future research will need large, well-defined cohorts in combination with state-of-the-art technologies.

Orthognathic surgery induces genomewide changes longitudinally in DNA methylation in saliva

OBJECTIVE

Orthognathic surgery dramatically changes morphology of the maxillofacial deformity and improves the malocclusion morphologically and functionally. We investigated the influence of orthognathic surgery on genomewide DNA methylation in saliva.

METHODS

Saliva was obtained from nine patients undergoing orthognathic surgery and two healthy reference individuals before and 3 months after orthognathic surgery. Genomewide DNA methylation profiling of saliva (341,482 CpG dinucleotides) was conducted using Infinium HumanMethylation450 BeadChips.

RESULTS

Comparison between pre- and postsurgery saliva samples revealed significant changes in DNA methylation patterns at 2,381 CpG sites (p < 0.01) with suggestive significance. The differentially methylated probe sets were significantly associated with the cancer pathway (p = 2.8 × 10^-7 ; a false discovery rate q-value = 3.7 × 10^-4 ) and PI3K-Akt signalling pathway (p = 2.4 × 10^-5 ; a false discovery rate q-value = 3.1 × 10^-2 ).

CONCLUSION

Pathway enrichment analysis of genes with suggestive significance demonstrated that altered DNA methylation in saliva of patients undergoing orthognathic surgery, possibly as a response to surgical stress or bone injury. Further studies with a large sample size and long-term observation are needed to validate the phenomena identified in this study.

Salivary secretion in health and disease

Saliva is a complex fluid produced by 3 pairs of major salivary glands and by hundreds of minor salivary glands. It comprises a large variety of constituents and physicochemical properties, which are important for the maintenance of oral health. Saliva not only protects the teeth and the oropharyngeal mucosa, it also facilitates articulation of speech, and is imperative for mastication and swallowing. Furthermore, saliva plays an important role in maintaining a balanced microbiota. Thus, the multiple functions provided by saliva are essential for proper protection and functioning of the body as a whole and for the general health. A large number of diseases and medications can affect salivary secretion through different mechanisms, leading to salivary gland dysfunction and associated oral problems, including xerostomia, dental caries and fungal infections. The first part of this review article provides an updated insight into our understanding of salivary gland structure, the neural regulation of salivary gland secretion, the mechanisms underlying the formation of saliva, the various functions of saliva and factors that influence salivary secretion under normal physiological conditions. The second part focuses on how various diseases and medical treatment including commonly prescribed medications and cancer therapies can affect salivary gland structure and function. We also provide a brief insight into how to diagnose salivary gland dysfunction.

Standardization of a protocol for shotgun proteomic analysis of saliva

INTRODUCTION

Saliva contains numerous proteins and peptides, each of them carries a number of biological functions that are very important in maintaining the oral cavity health and also yields information about both local and systemic diseases. Currently, proteomic analysis is the basis for large-scale identification of these proteins and discovery of new biomarkers for distinct diseases.

OBJECTIVE

This study compared methodologies to extract salivary proteins for proteomic analysis.

MATERIAL AND METHODS

Saliva samples were collected from 10 healthy volunteers. In the first test, the necessity for using an albumin and IgG depletion column was evaluated, employing pooled samples from the 10 volunteers. In the second test, the analysis of the pooled samples was compared with individual analysis of one sample. Salivary proteins were extracted and processed for analysis by LC-ESI-MS/MS.

RESULTS

In the first test, we identified only 35 proteins using the albumin and IgG depletion column, while we identified 248 proteins without using the column. In the second test, the pooled sample identified 212 proteins, such as carbonic anhydrase 6, cystatin isoforms, histatins 1 and 3, lysozyme C, mucin 7, protein S100A8 and S100A9, and statherin, while individual analysis identified 239 proteins, among which are carbonic anhydrase 6, cystatin isoforms, histatin 1 and 3, lactotransferrin, lyzozyme C, mucin 7, protein S100A8 and S100A9, serotransferrin, and statherin.

CONCLUSIONS

The standardization of protocol for salivary proteomic analysis was satisfactory, since the identification detected typical salivary proteins, among others. The results indicate that using the column for depletion of albumin and IgG is not necessary and that performing individual analysis of saliva samples is possible.

The Effect of Breed, Gender, and Acid Stimulation in Dog Saliva Proteome

Saliva gained interest as a potential noninvasive source of biomarkers in humans and that interest starts to be extended also to other animal species. For this purpose, the knowledge of the salivary proteome in healthy conditions and the factors that affect it and how they affect it are necessary. The aim of the present study was to assess the effect that gender and breed have in saliva proteome and the changes in it induced by stimulation with acid. Saliva from 4 different purebred dogs (Portuguese Podengo, Greyhound, Rafeiro Alentejano, and Beagle) of both genders was collected without and after stimulation with lemon juice. SDS-PAGE and two-dimensional gel electrophoresis (2-DE) profiles were compared and the proteins of interest in-gel digested and identified by mass spectrometry. Acid stimulation decreased total protein concentration and the relative amounts of some protein bands/spots. Gender appeared to have minimal effect in saliva proteome, whereas the influence of breed varies. Beagles and Portuguese Podengos were the two breeds with higher differences. In conclusion, stimulation procedures and dog breed should be considered in data analysis when using salivary proteins for diagnostic purposes.

Putative salivary protein biomarkers for the diagnosis of oral lichen planus: a case-control study

BACKGROUND

Salivary protein biomarkers for screening and diagnosis of oral lichen planus (OLP) are not well-defined. The objective of this study was to identify putative protein biomarkers for OLP using proteomic approaches.

METHODS

Pooled unstimulated whole saliva was collected from five OLP patients and five healthy control participants. Saliva samples were then subjected to two-dimensional gel electrophoresis, followed by mass spectrometry to identify putative protein biomarkers. Subsequently, a subset of these putative biomarkers were validated in 24 OLP patients and 24 age-matched healthy control subjects, using an enzyme-linked immunosorbent assay (ELISA). Immunoblotting analyses were then performed in 3 pairs of age- and sex-matched OLP patients and healthy controls to confirm results from the ELISA study.

RESULTS

Thirty-one protein spots were identified, corresponding to 20 unique proteins. Notably, fibrinogen fragment D and complement component C3c exhibited increased expression in OLP patients, while cystatin SA exhibited decreased expression in OLP patients, compared with healthy control subjects. ELISA analyses indicated increased expression of fibrinogen fragment D and complement component C3c, and decreased expression of cystatin SA, in the saliva of OLP patients. Statistical differences in the expression of salivary complement C3c were observed between OLP patients and healthy control subjects. Immunoblotting analyses confirmed the results of our ELISA study.

CONCLUSION

Complement C3c, fibrinogen fragment D and cystatin SA may serve as salivary biomarkers for screening and/or diagnosis of OLP.

Detection of salivary protein biomarkers of saliva secretion disorder in a primary Sjögren syndrome murine model

Saliva secretion disorder is one of the most common symptoms in primary Sjögren syndrome (pSS). Salivary biomarkers related to saliva secretion disorder were identified in a pSS murine model, NOD/ShiLtJ mouse, using differential proteomic analysis. Candidate biomarkers were screened with Kyoto Encyclopedia of Genes and Genomes pathway analysis and validated in saliva and salivary glands by western blotting and immunohistochemistry (IHC). Biological functions were detected using ingenuity pathway analysis (IPA). We identified 1101 salivary proteins from NOD/ShiLtJ mice and BALB/c mice (control). Catenin alpha-3 (CTNNA3), tyrosine-protein phosphatase non-receptor type 6 (PTPN6), Ras-related C3 botulinum toxin substrate (RAC2), and intermediate conductance calcium-activated potassium channel protein 4 (KCNN4) were screened as candidate biomarkers from 225 significantly dysregulated salivary proteins. These proteins participated in adherens junction or saliva secretion pathway and may be related to saliva secretion disorder. Proteomic analysis revealed that CTNNA3, PTPN6, and RAC2 were dysregulated in saliva and salivary glands and showed satisfactory sensitivity and specificity in receiver-operating characteristic curve; KCNN4 showed no statistical difference. IHC and IPA indicated that CTNNA3 may regulate acinar cell morphology, while PTPN6 and RAC2 promoted lymphocyte adhesion in salivary glands. Thus, CTNNA3, PTPN6, and RAC2 may be related to saliva secretion disorder in pSS.

Salivary Protein Roles in Oral Health and as Predictors of Caries Risk

This work describes the current state of research on the potential relationship between protein content in human saliva and dental caries, which remains among the most common oral diseases and causes irreversible damage in the oral cavity. An understanding the whole saliva proteome in the oral cavity could serve as a prerequisite to obtaining insight into the etiology of tooth decay at early stages. To date, however, there is no comprehensive evidence showing that salivary proteins could serve as potential indicators for the early diagnosis of the risk factors causing dental caries. Therefore, proteomics indicates the promising direction of future investigations of such factors, including diagnosis and thus prevention in dental therapy.

Compliance with Saliva Collection Protocol in Healthy Volunteers: Strategies for Managing Risk and Errors

Salivary bioscience technologies such as electrophoresis are widely applied for diagnosing systemic health status. Diagnosis using a saliva sample has emerged as a preferred technique since the sample is easy to collect and the method is inexpensive and non-invasive. Salivary diagnostics have even been identified as potential substitutes for serum protein biomarkers. However, the optimal protocol for collecting saliva has not yet been established. In many scientific settings, such as randomized controlled trials, sampling and statistical errors often occur when handling samples from healthy volunteers. These errors can be due to the psychological behavior of the volunteers, subject nonadherence, questionnaire characteristics, collection methods, and/or sample processing. The purpose of the review presented here is to outline the strategies for managing the risk factors and to minimize the sampling errors during saliva collection in healthy volunteers.