Diagnostic model of saliva peptide finger print analysis of primary Sjögren's syndrome patients by using weak cation exchange magnetic beads

Sjögren's syndrome: novel insights from proteomics and miRNA expression analysis

Introduction

Sjögren's syndrome (SS) is a systemic autoimmune disease, which affects the exocrine glands leading to glandular dysfunction and, particularly, symptoms of oral and ocular dryness. The aetiology of SS remains unclear, and the disease lacks distinctive clinical features. The current diagnostic work-up is complex, invasive and often time-consuming. Thus, there is an emerging need for identifying disease-specific and, ideally, non-invasive immunological and molecular biomarkers that can simplify the diagnostic process, allow stratification of patients, and assist in monitoring the disease course and outcome of therapeutic intervention in SS.

Methods

This systematic review addresses the use of proteomics and miRNA-expression profile analyses in this regard.

Results and discussion

Out of 272 papers that were identified and 108 reviewed, a total of 42 papers on proteomics and 23 papers on miRNA analyses in saliva, blood and salivary gland tissue were included in this review. Overall, the proteomic and miRNA studies revealed considerable variations with regard to candidate biomarker proteins and miRNAs, most likely due to variation in sample size, processing and analytical methods, but also reflecting the complexity of SS and patient heterogeneity. However, interesting novel knowledge has emerged and further validation is needed to confirm their potential role as biomarkers in SS.

Peptidomic changes of saliva after nonsurgical treatment of stage I / II generalized periodontitis

OBJECTIVE

To explore the changes of peptidome profiles of saliva, serum and gingival crevicular fluid (GCF) before and after nonsurgical periodontal treatment in patients with generalized periodontitis (stage I / II).

SUBJECTS AND METHODS

Saliva, serum and GCF samples were collected from 17 patients at baseline (T₀ ), one week after ultrasonic supragingival scaling (T₁ ) and eight weeks after subgingival scaling and root planning (T₂ ). Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) was carried out to detect changes in peptidomic profiles. Then nano-liquid chromatography-electrospray ionization-tandem mass spectrometry (nano-LC/ESI-MS/MS) was performed to identify potential peptide biomarkers.

RESULTS

Most of the peptides from the patients exhibited a decreasing trend from the time point of pre-treatment to that of post-treatment. Cluster analysis and scatter plots using these peptides indicated that salivary peptidome has an acceptable capability of reflecting the status of stage I / II generalized periodontitis. Seven of these peptides were successfully identified as α-1-antitrypsin, immunoglobulin κ variable 4-1, haptoglobin and immunoglobulin heavy constant γ2.

CONCLUSIONS

Certain peptides in saliva, serum and GCF were down-regulated after nonsurgical periodontal treatment, demonstrating the application prospects of saliva in monitoring and surveillance of periodontal diseases in both clinical settings and communities.

Saliva proteomics from children with caries at different severity stages

OBJECTIVE

To perform a comparative analysis of saliva protein profile of patients with early childhood caries at different levels of severity and caries-free individuals.

MATERIALS AND METHODS

Stimulated saliva samples were collected from 126 children (2-6 years old), classified according to the ICDAS II, and divided into 3 groups (n = 42): caries-free (CF), enamel caries (EC), and dentine caries (DC). Samples were digested and analyzed by nanoUPLC coupled with a mass spectrometry. Data analyses were conducted with Progenesis QI for Proteomics Software v2.0. Gene Ontology (GO) terms and protein-protein interaction analysis were obtained.

RESULTS

A total of 306 proteins (≈6 peptides) were identified. Among them, 122 were differentially expressed in comparisons among children with different caries status. Out of the 122 proteins, the proteins E2AK4 and SH3L2 were exclusively present in groups CF and EC, respectively, and 8 proteins (HAUS4, CAH1, IL36A, IL36G, AIMP1, KLHL8, KLH13, and SAA1) were considered caries-related proteins when compared to caries-free children; they were up-regulated proteins in the caries groups (EC and DC).

CONCLUSION

The identification of exclusive proteins for caries-free or carious-related conditions may help in understanding the mechanisms of caries and predicting risk as well as advancing in caries control or anti-caries approaches.

Nanotechnology: a promising method for oral cancer detection and diagnosis

Oral cancer is a common and aggressive cancer with high morbidity, mortality, and recurrence rate globally. Early detection is of utmost importance for cancer prevention and disease management. Currently, tissue biopsy remains the gold standard for oral cancer diagnosis, but it is invasive, which may cause patient discomfort. The application of traditional noninvasive methods-such as vital staining, exfoliative cytology, and molecular imaging-is limited by insufficient sensitivity and specificity. Thus, there is an urgent need for exploring noninvasive, highly sensitive, and specific diagnostic techniques. Nano detection systems are known as new emerging noninvasive strategies that bring the detection sensitivity of biomarkers to nano-scale. Moreover, compared to current imaging contrast agents, nanoparticles are more biocompatible, easier to synthesize, and able to target specific surface molecules. Nanoparticles generate localized surface plasmon resonances at near-infrared wavelengths, providing higher image contrast and resolution. Therefore, using nano-based techniques can help clinicians to detect and better monitor diseases during different phases of oral malignancy. Here, we review the progress of nanotechnology-based methods in oral cancer detection and diagnosis.

Salivary peptidome profiling analysis for occurrence of new carious lesions in patients with severe early childhood caries

This study aimed to identify differences of peptide profiles in stimulated whole saliva among children with and without occurrence of new carious lesions, and to provide a simple way for early diagnosis and prevention of the relapse of severe early childhood caries (s-ECC). Overall, 26 children aged 3–4 years were selected out from all the children in the kindergarten to be involved in the present study, among them 13 were diagnosed as s-ECC and underwent dental treatment, whilst the other 13 were matched by age and sex as control. Stimulated whole saliva samples were collected before treatment, and at 10 days and 4 months after treatment. During follow-up, 7 of the 13 children with s-ECC showed a relapse, and the new carious lesions were then treated. Salivary peptides were detected using the technique of magnetic beads combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Fifteen peptides showed significant differences in the group without occurrence of new carious lesions (CH group). On comparing the CH group and the other group with occurrence of new carious lesions (CR group), no significant differences were observed before treatment, whereas certain peptides showed significant differences at both 10 days and 4 months after treatment. Two peptides (experimental m/z values: 3162.0 Da and 3290.4 Da) exhibited a consistent tendency in cross-sectional and longitudinal comparisons among these groups; these may be associated with recurrence of s-ECC. Based on our findings, it is concluded that different saliva peptide peaks can be detected in s-ECC using MALDI-TOF MS combined with magnetic beads. Moreover, 2 specific peptides with m/z values 3162.0 Da and 3290.4 Da could be promising salivary protein biomarkers for diagnosis of recurrence of s-ECC.

Longitudinal investigation of salivary proteomic profiles in the development of early childhood caries

OBJECTIVES

To investigate differentially expressed salivary peptides in the development of early childhood caries (ECC) in 3-4 year-old children.

MATERIALS AND METHODS

Eighty-two caries-free children at baseline were followed-up for 1year, during which period 15 of them had developed ECC (Group C), whilst another 15 cases out of the 31 individuals who remained healthy were marked as Group H. Stimulated whole saliva samples were collected at 0, 6 and 12 months, and analyzed using weak cation exchange magnetic beads combined with matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Corresponding peptide mass fingerprints were obtained to develop a discriminating model for ECC development. Q-Exactive mass spectrometry was then performed to identify the possible proteins where these peptides might derive from.

RESULTS

Nine peptide peaks were found to be significantly different in Group C among the three sampling time points and might correlate with development of caries. Levels of three of them increased over time, whilst that of the other six decreased gradually. We chose three peptides (1346.6, 2603.5 and 3192.8Da) which exhibited the best capability of classification, to establish a model for children at high risk of caries. One peptide (1346.6Da) was identified to be salivary histatin-rich peptide.

CONCLUSIONS

Our results indicate that peptidomic methods can be applied to help identify new candidate biomarkers for the occurrence and development of ECC.

CLINICAL SIGNIFICANCE

The change of salivary peptides may be an indicator of ECC, facilitating more effective measures to be taken in prevention of this disease.

Salivary peptidome profiling for diagnosis of severe early childhood caries

BACKGROUND

Severe early childhood caries (s-ECC), which has quite high prevalence among children, is a widespread problem with significant impacts among both developing and developed countries. At present, it is widely known that no early detective techniques and diagnostic tests could have high sensitivity and specificity when using for clinical screening of s-ECC. In this study, we had applied magnetic bead (MB)-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to screen distinctive candidate biomarkers of this disease, so as to establish protein profiles and diagnostic models of s-ECC.

METHODS

Firstly, we used the technique mentioned above to detect specifically expressed peptides in saliva samples from ten children with s-ECC, separately at the time point of before, 1 and 4 weeks after dental treatment. Then a diagnostic model for s-ECC was established with the K nearest-neighbour method, which was validated in another six children in the next stage of study. After that, linear ion trap-orbitrap-mass spectrometry (LTQ-Orbitrap-MS) was performed to identify which of the proteins in saliva might be the origination of these peptides.

RESULTS

We found that seven peptide peaks were significantly different when comparing the three time points, among them two were higher, while other five were lower in the pre-treatment s-ECC group compared with post-treatment. The sensitivity and specificity of the diagnostic model we built were both 83.3 %. Two of these peptides were identified to be segments of histatin-1, which was one important secretory protein in saliva.

CONCLUSIONS

Hereby we confirmed that MB-based MALDI-TOF MS is an effective method for screening distinctive peptides from the saliva of junior patients with s-ECC, and histatin-1 may probably be one important candidate biomarker of this common dental disease. These findings might have bright prospect in future in establishing new diagnostic methods for s-ECC.

A Study of the Variation in the Salivary Peptide Profiles of Young Healthy Adults Acquired Using MALDI-TOF MS

A cross-sectional observational study was conducted to evaluate the inter-individual variation in the MALDI-TOF MS peptide profiles of unstimulated whole saliva in a population of 268 systemically healthy adults aged 18-30 yr (150 males and 118 females) with no apparent caries lesions or periodontal disease. Using Spectral Clustering, four subgroups of individuals were identified within the study population. These subgroups were delimited by the pattern of variation in 9 peaks detected in the 2-15 kDa m/z range. An Unsupervised Feature Selection algorithm showed that P-C peptide, a 44 residue-long salivary acidic proline-rich protein, and three of its fragments (Fr. 1-25, Fr. 15-35 and Fr. 15-44) play a central role in delimiting the subgroups. Significant differences were found in the salivary biochemistry of the subgroups with regard to lysozyme and chitinase, two enzymes that are part of the salivary innate defense system (p < 0.001). These results suggest that MALDI-TOF MS salivary peptide profiles may relate information on the underlying state of the oral ecosystem and may provide a useful reference for salivary disease biomarker discovery studies.

Biomarker Characterization by MALDI-TOF/MS

Mass spectrometric techniques frequently used in clinical diagnosis, such as gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, ambient ionization mass spectrometry, and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF/MS), are discussed. Due to its ability to rapidly detect large biomolecules in trace amounts, MALDI-TOF/MS is an ideal tool for characterizing disease biomarkers in biologic samples. Clinical applications of MS for the identification and characterization of microorganisms, DNA fragments, tissues, and biofluids are introduced. Approaches for using MALDI-TOF/MS to detect various disease biomarkers including peptides, proteins, and lipids in biological fluids are further discussed. Finally, various sample pretreatment methods which improve the detection efficiency of disease biomarkers are introduced.

Top-down analytical platforms for the characterization of the human salivary proteome

Comprehensive analysis and characterization of the human salivary proteome is an important step towards the possible use of saliva for diagnostic and prognostic purposes. The contribution of the different sources to whole saliva, and the evaluation of individual variability and physiological modifications have been investigated by top-down proteomic approaches, disclosing the faceted and complex profile of the human salivary proteome. All this information is essential to develop saliva protein biomarkers. In this Review the major results obtained in the field by top-down platforms, and the improvements required to allow a more complete picture, will be discussed.

Establishment of a novel diagnostic model for Sjögren's syndrome by proteomic fingerprinting

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease that lacks sensitive and specific diagnostic methods. The aim of this study was to identify potential biomarkers specific for pSS and to establish a diagnostic model. Serum samples from patients with pSS, disease controls (DC, patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA)), and healthy controls (HC)) were randomly divided into a training set (35 pSS, 50 DC, and 26 HC) and a testing set (25 pSS, 50 DC, and 25 HC). Weak cationic exchange (WCX) magnetic beads were used to differentially capture serum proteins prior to proteomic analysis. Proteomic mass spectra were generated by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). One hundred differential M/Z peaks associated with pSS were identified, and the m/z peaks at 8,133.85, 11,972.8, 2,220.81, and 4,837.66 were used to establish a diagnostic model for pSS. This diagnostic model was able to distinguish pSS from non-pSS controls with a sensitivity of 77.1 % and a specificity of 85.5 %, and its efficacy was confirmed in our blinded testing set with good sensitivity and specificity of 95.5 and 88 %, respectively. The results indicated that the proteomic fingerprinting model was effective in the diagnosis of pSS.

Rapid screening and identification of new soluble tannin-salivary protein aggregates in saliva by mass spectrometry (MALDI-TOF-TOF and FIA-ESI-MS)

Astringency is mainly attributed to the interaction between tannins and salivary proteins. Proline-rich proteins, histatins, and statherins are supposed to be the most reactive salivary proteins. This study aims to contribute to the knowledge of the tannin-protein binding process in saliva. It was identified for the first time in several soluble tannin-human salivary protein aggregates. A rapid mass spectrometry analytical method (MALDI-TOF and FIA-ESI-MS) was developed to identify new soluble tannin-human salivary protein aggregates. Three different tannins--procyanidin B3 (B3), procyanidin B2 gallate (B2G), and pentagalloylglucoside (PGG)--were tested to elucidate the tannin selectivity toward histatins, proline-rich proteins, and statherins in human saliva. A greater number of aggregates with a higher molecular weight was found when PGG was tested while no difference in the number and molecular mass range was observed in B3 or B2G salivary protein aggregates. This study confirms for the first time the bilateral selectivity of tannins and protein to yield soluble tannin-human salivary protein complexes. The results confirm that B3 and B2G are more selective than PGG. Furthermore, the families of proteins involved in the majority of B3-salivary protein soluble aggregates were primarly histatins, followed by basic proline-rich proteins and statherins. When B2G was tested, basic proline-rich proteins were involved in a greater number of aggregates, followed by histatines and statherins. Basic proline-rich proteins were also the family of proteins that formed a greater number of PGG-salivary protein aggregates followed by statherins and histatins. Acidic proline-rich proteins and glucosilated proline-rich proteins formed fewer soluble aggregates regardless of the tannin tested. The aggregation process was also found to be influenced by tannin and protein polarity. Indeed, the protein/tannin ratio of soluble aggregates increased with the tannin polarity. On the other hand, the only amphiphilic salivary proteins studied (histatins) formed a greater number of aggregates with the least polar tannin tested (B3).