Mass spectrometry analysis of gingival crevicular fluid in the presence of external root resorption

A simplified protocol for deep quantitative proteomic analysis of gingival crevicular fluid for skeletal maturity indicators

Assessment of craniofacial skeletal maturity is of great importance in orthodontic diagnosis and treatment planning. Traditional radiographic methods suffer from clinician subjectivity and low reproducibility. Recent biochemical methods, such as the use of gingival crevicular fluid (GCF) protein biomarkers involved in bone metabolism, have provided new opportunities to assess skeletal maturity. However, mass spectrometry (MS)-based GCF proteomic analysis still faces significant challenges, including the interference of high abundance proteins, laborious sample prefractionation and relatively limited coverage of GCF proteome. To improve GCF sample processing and further discover novel biomarkers, we herein developed a single-pot, solid-phase-enhanced sample-preparation (SP3)-based high-field asymmetric waveform ion mobility spectrometry (FAIMS)-MS protocol for deep quantitative analysis of the GCF proteome for skeletal maturity indicators. SP3 combined with FAIMS could minimize sample loss and eliminate tedious and time-consuming offline fractionation, thereby simplifying GCF sample preparation and improving analytical coverage and reproducibility of the GCF proteome. A total of 5407 proteins were identified in GCF samples from prepubertal and circumpubertal groups, representing the largest dataset of human GCF proteome to date. Compared to the prepubertal group, 61 proteins were differentially expressed (31 up-regulated, 30 down-regulated) in the circumpubertal group. The six-protein marker panel, including ATP5D, CLTA, CLTB, DNM2, HSPA8 and NCK1, showed great potential to predict the circumpubertal stage (ROC-AUC 0.937), which provided new insights into skeletal maturity assessment.

Understanding exosomes: Part 3-therapeutic + diagnostic potential in dentistry

Exosomes are the smallest subset of extracellular signaling vesicles secreted by most cells with the ability to communicate with other tissues and cell types over long distances. Their use in regenerative medicine has gained tremendous momentum recently due to their ability to be utilized as therapeutic options for a wide array of various diseases. Over 5000 publications are currently being published on this topic yearly, many of which in the dental space. This extensive review article is the first scoping review aimed at summarizing all therapeutic uses of exosomes in regenerative dentistry. A total of 944 articles were identified as using exosomes in the dental field for either their regenerative/therapeutic potential or for diagnostic purposes derived from the oral cavity. In total, 113 research articles were selected for their regenerative potential (102 in vitro, 60 in vivo, 50 studies included both). Therapeutic exosomes were most commonly derived from dental pulps, periodontal ligament cells, gingival fibroblasts, stem cells from exfoliated deciduous teeth, and the apical papilla which have all been shown to facilitate the regenerative potential of a number of tissues including bone, cementum, the periodontal ligament, nerves, aid in orthodontic tooth movement, and relieve temporomandibular joint disorders, among others. Results demonstrate that the use of exosomes led to positive outcomes in 100% of studies. In the bone field, exosomes were found to perform equally as well or better than rhBMP2 while significantly reducing inflammation. Periodontitis animal models were treated with simple gingival injections of exosomes and benefits were even observed when the exosomes were administered intravenously. Exosomes are much more stable than growth factors and were shown to be far more resistant against degradation by periodontal pathogens found routinely in a periodontitis environment. Comparative studies in the field of periodontal regeneration found better outcomes for exosomes even when compared to their native parent stem cells. In total 47 diagnostic studies revealed a role for salivary/crevicular fluid exosomes for the diagnosis of birth defects, cardiovascular disease, diabetes, gingival recession detection, gingivitis, irritable bowel syndrome, neurodegenerative disease, oral lichen planus, oral squamous cell carcinoma, oropharyngeal cancer detection, orthodontic root resorption, pancreatic cancer, periodontitis, peri-implantitis, Sjögren syndrome, and various systemic diseases. Hence, we characterize the exosomes as possessing "remarkable" potential, serving as a valuable tool for clinicians with significant advantages.

Metabolomic signatures distinguish extracellular vesicles from osteoclasts and odontoclasts

AIMS

Pathological dental root resorption and alveolar bone loss are often detected only after irreversible damage. Biomarkers in the gingival crevicular fluid or saliva could provide a means for early detection; however, such biomarkers have proven elusive. We hypothesize that a multiomic approach might yield reliable diagnostic signatures for root resorption and alveolar bone loss. Previously, we showed that extracellular vesicles (EVs) from osteoclasts and odontoclasts differ in their protein composition. In this study, we investigated the metabolome of EVs from osteoclasts, odontoclasts and clasts (non-resorbing clastic cells).

MATERIALS AND METHODS

Mouse haematopoietic precursors were cultured on dentine, bone or plastic, in the presence of recombinant RANKL and CSF-1 to trigger differentiation along the clastic line. On Day 7, the cells were fixed and the differentiation state and resorptive status of the clastic cells were confirmed. EVs were isolated from the conditioned media on Day 7 and characterized by nanoparticle tracking and electron microscopy to ensure quality. Global metabolomic profiling was performed using a Thermo Q-Exactive Orbitrap mass spectrometer with a Dionex UHPLC and autosampler.

RESULTS

We identified 978 metabolites in clastic EVs. Of those, 79 are potential biomarkers with Variable Interdependent Parameters scores of 2 or greater. Known metabolites cytidine, isocytosine, thymine, succinate and citrulline were found at statistically higher levels in EVs from odontoclasts compared with osteoclasts.

CONCLUSION

We conclude that numerous metabolites found in odontoclast EVs differ from those in osteoclast EVs, and thus represent potential biomarkers for root resorption and periodontal tissue destruction.

Detection of orthodontically induced inflammatory root resorption-associated biomarkers from the gingival crevicular fluid by proteomics analysis: a randomized-controlled clinical trial

Orthodontically induced inflammatory root resorption (OIIRR) is an undesirable complication of orthodontic treatment (OT) with an ambiguous aetiologic mechanism. This study aimed to identify OIIRR-associated biomarkers in the gingival crevicular fluid (GCF) using proteomic analysis. In this randomized clinical trial, the upper first premolars (UFP) were exposed either to light or heavy force. The GCF was collected at 1 h, 1 day, 7 days, 14 days, 21 days, and 28 days following force application. After extraction of UFP, roots were imaged and resorption premolar, was used to deliver either light forcecraters were measured. Proteomic analysis of GCF was performed using 2D gel electrophoresis with MALDI-TOF/TOF MS/MS. Results were further analyzed by bioinformatics analyses showing the biological functions and predicted pathways. The predicted canonical pathways showed that the expression of immunoglobulin kappa (IGKC), neutrophil gelatinase-associated lipocalin (NGAL), neurolysin mitochondrial (NEUL), keratin, type II cytoskeletal 1 (K2C1), S100-A9, and the extracellular calcium-sensing receptor (CASR) were significantly associated with a range of biological and inflammatory processes. In conclusion, up-regulation of S100A9, CASR, and K2C1 suggested a response to force-related inflammation, chemotactic activities, osteoclastogenesis, and epithelial cell breakdown. Meanwhile, the up-regulation of IGKC, NGAL, and K2C1 indicated a response to the inflammatory process, innate immunity activation, and epithelial cell breakdown.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03572-5.

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.

Periodontal ligament cells derived small extracellular vesicles are involved in orthodontic tooth movement

OBJECTIVES

Small extracellular vesicles (EVs) from human periodontal ligament cells (hPDLCs) are closely associated with periodontal homeostasis. Far less is known about EVs association with orthodontic tooth movement (OTM). This study aimed to explore the role of small EVs originated from hPDLCs during OTM.

MATERIALS AND METHODS

Adult C57BL/6 mice were used. Springs were bonded to the upper first molars of mice for 7 days to induce OTM in vivo. To block small EVs release, GW4869 was intraperitoneally injected and the efficacy of small EVs inhibition in periodontal ligament was verified by transmission electron microscope (TEM). Tooth movement distance and osteoclastic activity were studied. In vitro, hPDLCs were isolated and administered compressive force in the EV-free culture media. The cell morphologies and CD63 expression of hPDLCs were studied. Small EVs were purified and characterized using a scanning electron microscope, TEM, western blot, and nanoparticle tracking analysis. The expression of proteins in the small EVs was further processed and validated using a human immuno-regulated cytokines array and an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The small EV depletion significantly decreased the distance and osteoclastic activity of OTM in the mice. The hPDLCs displayed different morphologies under force compression and CD63 expression level decreased verified by western blot and immunofluorescence staining. Small EVs purified from supernatants of the hPDLCs showed features with <200 nm diameter, the positive EVs marker CD63, and the negative Golgi body marker GM130. The number of small EVs particles increased in hPDLCs suffering force stimuli. According to the proteome array, the level of soluble intercellular adhesion molecule-1 (sICAM-1) displayed the most significant fold change in small EVs under compressive force and this was further confirmed using an ELISA.

LIMITATIONS

Further mechanism studies are warranted to validate the hPDLC-originated small EVs function in OTM through proteins delivery.

CONCLUSIONS

The notable decrease in the OTM distance after small EV blocking and the significant alteration of the sICAM-1 level in the hPDLC-originated small EVs under compression provide a new vista into small EV-related OTM biology.

Tooth root resorption: A review

Tooth root resorption is multifactorial, leading to progressive destruction and eventual loss of tooth root dentin and cement. There are internal and external types of root resorption, each having its variety. The etiology and pathogenesis of tooth root resorption are poorly understood, and the most significant etiological factors are trauma, pulpal infection, tooth bleaching, and orthodontic treatment. Tooth root resorption is primarily asymptomatic; thus, it is revealed accidentally by radiographic examination. Progressive clinical manifestations are pain, tooth discoloration, tooth mobility, and other conditions. Awareness of the causes and risk factors allowing tooth root resorption, and regular radiographic examination, in case of necessity, make it possible to reveal resorption at an early stage and to prevent its further development. Thus, the aim of this study is to present etiopathogenesis, a clinical course, and diagnostic peculiarities of internal and external types of tooth root resorption, enabling practicing dentists to timely diagnose root resorption and take appropriate measures to avoid further complications. Within the limitation of this review, even though the etiopathogenesis of tooth root resorption is yet not fully understood, it is suggested that the etiological factors fall into two groups (endogenic and exogenic) to enhance further understanding of the possible causes and mechanisms of root resorption and allow practitioners to monitor high-risk patients and make timely diagnoses. Moreover, radiographic examination and CBCT are indispensable for the diagnosis of root resorption.

Obesity affects the proteome profile of periodontal ligament submitted to mechanical forces induced by orthodontic tooth movement in rats

The prevalence of obesity has increased significantly worldwide. Therefore, this study aimed to evaluate the influence of obesity on the proteomic profile of periodontal ligament (PDL) tissues of rat first maxillary molars (1 M) submitted to orthodontic tooth movement (OTM). Ten Holtzman rats were distributed into two groups (n = 5): the M group (OTM), and the OM group (obesity induction plus OTM). Obesity was induced by a high-fat diet for the entire experimental periods After that period, the animals were euthanized and the hemimaxillae removed and processed for laser capture microdissection of the PDL tissues of the 1 M. Peptide extracts were obtained and analyzed by LC-MS/MS. Data are available via ProteomeXchange with identifier PXD033647. Out of the 109 proteins with differential abundance, 49 were identified in the OM group, including Vinculin, Cathepsin D, and Osteopontin, which were selected for in situ localization by immunohistochemistry analysis (IHC). Overall, Gene Ontology (GO) analysis indicated that enriched proteins were related to the GO component cellular category. IHC validated the trends for selected proteins. Our study highlights the differences in the PDL proteome profiling of healthy and obese subjects undergoing OTM. These findings may provide valuable information needed to better understand the mechanisms involved in tissue remodeling in obese patients submitted to orthodontic treatment. SIGNIFICANCE: The prevalence of obesity is increasing worldwide. Emerging findings in the field of dentistry suggest that obesity influences the tissues around the teeth, especially those in the periodontal ligament. Therefore, evaluation of the effect of obesity on periodontal tissues remodeling during orthodontic tooth movement is a relevant research topic. To our knowledge, this is the first study to evaluate proteomic changes in periodontal ligament tissue in response to the association between orthodontic tooth movement and obesity. Our study identified a novel protein profile associated with obesity by using laser microdissection and proteomic analysis, providing new information to increase understanding of the mechanisms involved in obese patients undergoing orthodontic treatment which can lead to a more personalized orthodontic treatment approach.

Systems Biology in Periodontitis

Systems biology is a promising scientific discipline that allows an integrated investigation of host factors, microbial composition, biomarkers, immune response and inflammatory mediators in many conditions such as chronic diseases, cancer, neurological disorders, and periodontitis. This concept utilizes genetic decoding, bioinformatic, flux-balance analysis in a comprehensive approach. The aim of this review is to better understand the current literature on systems biology and identify a clear applicability of it to periodontitis. We will mostly focus on the association between this condition and topics such as genomics, transcriptomics, proteomics, metabolomics, as well as contextualize delivery systems for periodontitis treatment, biomarker detection in oral fluids and associated systemic conditions.

A comparative proteomic analysis to define the influencing factors on gingival crevicular fluid using LC-MS/MS

Gingival crevicular fluid (GCF) is a promising biofluid for disease identification and biomarker searching in periodontology. This study aimed to investigate the possible influencing factors, including tooth site, sex and age, on the normal GCF proteome. Forty periodontal healthy adults were randomly divided into a training group and a testing group. In the training group, GCF samples from 12 adults were analyzed using the iTRAQ 2D LC-MS/MS method. The influencing factors, tooth site (including periodontitis-susceptible and -insusceptible tooth sites), sex and age, and related differential proteins were defined and functionally annotated. The important differential proteins from 28 adults in the testing group were then validated by PRM analysis. An average of approximately 5 differential proteins were found between tooth sites of periodontitis-susceptible and -insusceptible sites. Eighty-five differentially expressed proteins were obtained between sexes in the young group, while only 7 sex-associated proteins were found in the old group. A total of 203 and 235 age-associated proteins were found in the male and female groups, respectively. The differential protein functional annotation showed that sex-related proteins were mainly related to immune function and metabolism, and age-related proteins were primarily associated with inflammation, lipid metabolism and immune function. In the testing group, a total of 4 sex-related proteins and 12 age-related proteins were validated by PRM analysis. SIGNIFICANCE: The influences of tooth site, sex and age in GCF proteomics in periodontal health were firstly analyzed using LC-MS/MS. Tooth site showed a small influence on the GCF proteome. The sex effect was significant in young adults, but its influence in old adults is small. Age is an important impact factor for the GCF proteome. These findings enrich the knowledge about the normal GCF proteome and might benefit future disease analyses.

A qualitative and quantitative analysis of the human gingival crevicular fluid proteome and metaproteome

Gingival crevicular fluid (GCF) is an integral part of oral fluid that plays a special role in maintaining the structure of junctional epithelium and defending against bacterial infection. In this study, we comprehensively analysed the composition of the human GCF proteome and metaproteome simultaneously to obtain multidimensional information about GCF. A total of 3680 human proteins (2540 with at least two unique peptides) were identified in the normal GCF sample, and their functions were mainly associated with immune function and inflammation. Among these proteins, 1874 proteins could be quantified by the iBAQ algorithm, and their abundances spanned a dynamic range of six orders of magnitude. For the GCF metaproteome, a total of 3082 proteins and 69 genera were found. In addition, 16 genera were not identified by GCF metagenomic analysis. Compared to the saliva metaproteome, 32 genera were found to be in common. The protein quantitative analysis showed that the abundance of GCF metaproteome contributed to approximately 4.17% of the total GCF proteome. The top three most abundant genera were Fusobacterium, Corynebacterium, and Leptotrichia. The above data will be useful for future research on GCF-related diseases.

Expression of biological markers in gingival crevicular fluid of teeth with orthodontically induced root resorption

AIM

The goal was to investigate interleukin‑1 receptor antagonist (IL-1ra) and dentin sialophosphoprotein (DSPP) levels in gingival crevicular fluid (GCF) as potential biomarkers for orthodontically induced root resorption (OIRR) using enzyme-linked immunosorbent immunoassay (ELISA).

MATERIALS AND METHODS

In all, 74 subjects were assigned to one of three groups: (1) orthodontic group included orthodontic patients who showed radiographic evidence of 1-3 mm root resorption of a maxillary central incisor, (2) pediatric group included pediatric patients who showed radiographic evidence of physiologic root resorption of a lower second primary molar, and (3) control group included subjects who had no orthodontic treatment and showed no radiographic evidence of root resorption. Samples from the GCF were collected with endodontic absorbent paper points inserted 1 mm below the gingival margin of the tooth. The IL-1ra and DSPP levels were evaluated using ELISA.

RESULTS

The IL-1ra levels were 657.5 ± 51.5, 319.9 ± 181.3, and 129.4 ± 54.9 pg/ml for the control, orthodontic, and pediatric groups, respectively. The DSPP levels were 1.6 ± 1.0, 30.1 ± 9.6, and 39.2 ± 3.3 pg/ml for the control, orthodontic, and pediatric groups, respectively. Post hoc analyses revealed significant differences for IL-1ra and DSPP between any two groups. Sensitivity and specificity of IL-1ra for the diagnosis of OIRR showed 80% reliability and a cutoff value of ≤432.6 pg/ml, while the analysis of DSPP showed 100% reliability and a cutoff value of ≥7.33 pg/ml.

CONCLUSIONS

The levels of IL-1ra and DSPP detected in the orthodontic and pediatric groups indicate a possible association with OIRR. Efforts to develop tests for screening, diagnosis, and monitoring OIRR based on biological markers should continue.

Metaproteome and metabolome of oral microbial communities

The emergence of high-throughput technologies for the comprehensive measurement of biomolecules, also referred to as "omics" technologies, has helped us gather "big data" and characterize microbial communities. In this article, we focus on metaproteomic and metabolomic approaches that support hypothesis-driven investigations on various oral biologic samples. Proteomics reveals the working units of the oral milieu and metabolomics unveils the reactions taking place; and so these complementary techniques can unravel the functionality and underlying regulatory processes within various oral microbial communities. Current knowledge of the proteomic interplay and metabolic interactions of microorganisms within oral biofilm and salivary microbiome communities is presented and discussed, from both clinical and basic research perspectives. Communities indicative of, or from, health, caries, periodontal diseases, and endodontic lesions are represented. Challenges, future prospects, and examples of best practice are given.

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.

Top down proteomic analysis of gingival crevicular fluid in deciduous, exfoliating and permanent teeth in children

Gingival Crevicular Fluid (GCF), a plasma-derived exudate present in the gingival crevice was collected from deciduous, exfoliating and permanent teeth from 20 children (60 samples) with the aim to characterize and quantify by a mass spectrometry based top-down proteomic approach, the peptide/proteins in the fluid and verify possible variations occurring during the exfoliating process. The results obtained confirmed the presence in GCF of α-Defensins 1-4, Thymosin β4 and Thymosin β10, as described in previous works and revealed the presence of other interesting peptides never described before in GCF such as specific fragments of α-1-antitrypsin, α-1-antichymotrypsin; fragments of Thymosin β4 and Thymosin β10; Fibrinopeptide A and its fragments and Fibrinopeptide B; S100A8 and S100A9, LVV Hemorphin-7 (hemoglobin chain β fragment), as well as some other peptides deriving from α and β subunits of hemoglobin. Statistical analysis evidenced different levels in 5 proteins/peptides in the three groups. Our study demonstrate that an in-depth analysis of a biological fluid like GCF, present in small amount, can provide useful information for the understanding of different biological processes like teeth eruption. Data are available via ProteomeXchange with identifier PXD016010 and PXD016049. SIGNIFICANCE: GCF due to his site-specific nature has a great potential in containing factors that are specific for action at a given site and might have diagnostic value to detect qualitative and quantitative variations of proteins/peptides composition linked to physiological or pathological conditions.

The proteome of extracellular vesicles released by clastic cells differs based on their substrate

Extracellular vesicles (EVs) from osteoclasts are important regulators in intercellular communication. Here, we investigated the proteome of EVs from clastic cells plated on plastic (clasts), bone (osteoclasts) and dentin (odontoclasts) by two-dimensional high performance liquid chromatography mass spectrometry seeking differences attributable to distinct mineralized matrices. A total of 1,952 proteins were identified. Of the 500 most abundant proteins in EVs, osteoclast and odontoclast EVs were 83.3% identical, while clasts shared 70.7% of the proteins with osteoclasts and 74.2% of proteins with odontoclasts. For each protein, the differences between the total ion count values were mapped to an expression ratio histogram (Z-score) in order to detect proteins differentially expressed. Stabilin-1 and macrophage mannose receptor-1 were significantly-enriched in EVs from odontoclasts compared with osteoclasts (Z = 2.45, Z = 3.34) and clasts (Z = 13.86, Z = 1.81) and were abundant in odontoclast EVs. Numerous less abundant proteins were differentially-enriched. Subunits of known protein complexes were abundant in clastic EVs, and were present at levels consistent with them being in assembled protein complexes. These included the proteasome, COP1, COP9, the T complex and a novel sub-complex of vacuolar H⁺-ATPase (V-ATPase), which included the (pro) renin receptor. The (pro) renin receptor was immunoprecipitated using an anti-E-subunit antibody from detergent-solubilized EVs, supporting the idea that the V-ATPase subunits present were in the same protein complex. We conclude that the protein composition of EVs released by clastic cells changes based on the substrate. Clastic EVs are enriched in various protein complexes including a previously undescribed V-ATPase sub-complex.

Clastic cells in orthodontic treatment: Translational challenges and recent advances

OBJECTIVES

Orthodontic treatment consists of numerous appliance activations that rely on stimulation of osteoclasts at alveolar bone sites. However, the action of osteoclast-like cells on dentin ("odontoclasts") is a pathological side effect of orthodontic treatment. The aim of this article is twofold: (a) To report preliminary results from ongoing cell culture experiments to identify unique markers of dentin resorption, and (b) To discuss our work using nanoparticle tracking analysis (NTA) and exosomes for developing biological fluid-based biopsies to monitor clastic cell activity.

SETTING AND SAMPLE POPULATION

Twelve healthy volunteers in permanent dentition.

MATERIAL AND METHODS

For the in vitro experiments, murine clastic cell precursors were cultured on dentin or bone slices for 7 days and phage-display biopanning was used to identify molecular surface differences between osteoclasts and odontoclasts. In the human study, gingival crevicular fluid (GCF) samples were collected using different tools and analysed for protein and exosome recovery.

RESULTS

Biopanning generated antibody fragments that were uniquely reactive to odontoclasts. Numerous nanoparticles in the size range of exosomes were detected in all of the human GCF samples.

CONCLUSIONS

Our results support that there are molecular differences between osteoclasts and odontoclasts. Emerging technologies may allow the use of exosomes in GCF as a clinical tool to detect markers of root resorption.

Extracellular vesicle identification in tooth movement models

Extracellular vesicles (EVs) are 30-150 nm in diameter vesicles released by cells that serve important intercellular regulatory functions. EVs include exosomes and microvesicles. Exosomes form in multivesicular bodies and are released extracellularly as the multivesicular bodies fuse with the plasma membrane. Microvesicles bud directly from the plasma membrane. Here, we examine methods that are available or emerging to detect and study EVs during orthodontic tooth movement (OTM). EV's involvement in regulating bone remodelling associated with OTM may be demonstrated by adding isolated EVs to an animal model to change the rate of tooth movement. Exosomes in multivesicular bodies might be detected by immunogold labelling of markers in sections from the tooth and jaw and detection by electron microscopy. Gingival crevicular fluid (GCF) is enriched in EVs. Detection and characterization of EVs released by osteoclasts during resorption have been described, and this information could be used to analyse EVs in OTM models. Regulatory EVs may be enriched in the GCF from teeth that are being moved or are undergoing root resorption. Emerging approaches, including nanoparticle tracking, ExoView and micro- and nanofluidics, show promise for studying EVs in the GCF. Techniques that amplify signal, including polymerase chain reaction (PCR), provide the sensitivity necessary to utilize EVs from GCF as biomarkers. Studies of the role of EVs in OTM will provide fresh insight that may identify means for enhancing OTM procedures. EVs in GCF may include biomarkers for bone remodelling during OTM, orthodontic-associated root resorption, and other dental pathologies.

Current Status of Proteomic Technologies for Discovering and Identifying Gingival Crevicular Fluid Biomarkers for Periodontal Disease

Periodontal disease is caused by bacteria in dental biofilms. To eliminate the bacteria, immune system cells release substances that inflame and damage the gums, periodontal ligament, or alveolar bone, leading to swollen bleeding gums, which is a sign of gingivitis. Damage from periodontal disease can cause teeth to loosen also. Studies have demonstrated the proteomic approach to be a promising tool for the discovery and identification of biochemical markers of periodontal diseases. Recently, many studies have applied expression proteomics to identify proteins whose expression levels are altered by disease. As a fluid lying in close proximity to the periodontal tissue, the gingival crevicular fluid (GCF) is the principal target in the search for periodontal disease biomarkers because its protein composition may reflect the disease pathophysiology. Biochemical marker analysis of GCF is effective for objective diagnosis in the early and advanced stages of periodontal disease. Periodontal diseases are also promising targets for proteomics, and several groups, including ours, have applied proteomics in the search for GCF biomarkers of periodontal diseases. This search is of continuing interest in the field of experimental and clinical periodontal disease research. In this article, we summarize the current situation of proteomic technologies to discover and identify GCF biomarkers for periodontal diseases.

The use of cell culture platforms to identify novel markers of bone and dentin resorption

OBJECTIVES

1) To test the hypothesis that there would be proteomic differences in the composition of exosomes isolated from osteoclasts and odontoclasts and 2) to determine the clinical usefulness of these in vitro biomarker candidates.

MATERIALS AND METHODS

Mouse bone marrow-derived precursors were cultured on either dentin or bone slices and allowed to mature and begin resorption. Exosomes were isolated from cell culture media and characterized by mass spectrometry. The proteomic data obtained from this in vitro study were compared with the data obtained from human samples in our previous work.

RESULTS

There was a difference in the proteomic composition of exosomes from osteoclasts and odontoclasts. A total of 40 exosomal proteins were only present in osteoclast media, whereas six unique exosomal proteins were identified in odontoclast supernatants. Approximately 50% of exosomal proteins released by clastic cells in vitro can be found in oral fluids.

CONCLUSION

Our data suggest that the mineralized matrix type plays a role in the final phenotypic characteristics of mouse clastic cells. Many in vitro biomarker candidates of bone and dentin resorption can also be found in human oral fluids, thus indicating that this approach may be a viable alternative in biomarker discovery.

Identification of salivary protein biomarkers for orthodontically induced inflammatory root resorption

PURPOSE

Orthodontically induced inflammatory root resorption (OIIRR) is one of the most prevalent and unavoidable consequence of orthodontic tooth movement. The aim of this study was to discover potential diagnostic protein biomarkers for detection of OIIRR in whole saliva (WS).

MATERIAL AND METHODS

Unstimulated WS was collected from 72 subjects: 48 OIIRR patients and 24 untreated, generally healthy, age and gender matched controls. Radiographic assessment of periapical x-rays of four upper incisors taken before and 9 months after bonding was done. High-abundance proteins were depleted followed by two-dimensional-gel-electrophoresis and quantitative mass spectrometry (qMS). Finally, to initially validate qMS results, Western blotting was performed.

RESULTS

qMS revealed differentially expressed proteins in the moderate-to-severe OIIRR group, which have never been found in WS before. Additionally, in the moderate-to-severe young OIIRR group, the pathogenetic mechanisms related to actin cytoskeleton regulation and Fc gamma R- mediated phagocytosis were detected, while in adults- to focal adhesion. Preliminary validation by Western blotting of fetuin-A and p21-ARC indicated expression profile trends similar to those identified by qMS.

CONCLUSION

The significance of WS novel proteomic methodologies is clearly demonstrated for detecting new OIIRR biomarkers as well as for unveiling possible novel pathogenetic mechanisms in both young and adult patients.

Human Gingival Crevicular Fluids (GCF) Proteomics: An Overview

Like other fluids of the human body, a gingival crevicular fluid (GCF) contains proteins, a diverse population of cells, desquamated epithelial cells, and bacteria from adjacent plaque. Proteomic tools have revolutionized the characterization of proteins and peptides and the detection of early disease changes in the human body. Gingival crevicular fluids (GCFs) are a very specific oral cavity fluid that represents periodontal health. Due to their non-invasive sampling, they have attracted proteome research and are used as diagnostic fluids for periodontal diseases and drug analysis. The aim of this review is to explore the proteomic science of gingival crevicular fluids (GCFs), their physiology, and their role in disease detection.

Effect of intraoral mechanical stress application on the expression of a force-responsive prognostic marker associated with system disease progression

OBJECTIVES

Malocclusion may be corrected nonsurgically by mechanical tooth movement. The plasma protein profiles of human subjects receiving the first phase of orthodontic treatment were examined to test the hypothesis that application of mechanical stresses to teeth induces systemic proteomic alterations.

METHODS

Tandem mass tag-based liquid chromatography-mass spectrometry (LC-MS/MS) was used to examine systemic proteomic alterations in subjects undergoing controlled stress application (N=10) and in volunteers not receiving treatment (N=7) at 3 time intervals within 24h. Proteins differentially expressed by the tooth movement group were functionally analyzed with "Gene Ontology" (GO) and "Search Tool to Retrieve Interacting Genes/proteins" (STRING) softwares. Enzyme-Linked Immunosorbent Assay and Western-blot were used to validate the in vivo protein alterations. An in vitro model consisting of human periodontal ligament cells (hPDLCs) under compression was used to validate the force-responsive characteristics of galectin-3 binding protein (LGALS3BP).

RESULTS

Sixteen out of the 294 proteins identified by LC-MS/MS were differentially expressed in the plasma of subjects receiving controlled mechanical stresses for moving teeth. Those proteins were clustered in biological processes related to acute inflammatory response and vesicle-related transportation. Serotransferrin, fibronectin and LGALS3BP were processed for confirmation in vivo; LGALS3BP was significantly increased in the tooth movement group. In vitro secretion of LGALS3BP in PDLCs was force-responsive.

CONCLUSIONS

Regional application of mechanical stresses stimulates systemic proteomic changes. Because serum LGALS3BP is over-expressed in different systemic diseases, including cancer, further work is needed to examine how systemic up-regulation of LGALS3BP affects the progression of those diseases.

Advances of Proteomic Sciences in Dentistry

Applications of proteomics tools revolutionized various biomedical disciplines such as genetics, molecular biology, medicine, and dentistry. The aim of this review is to highlight the major milestones in proteomics in dentistry during the last fifteen years. Human oral cavity contains hard and soft tissues and various biofluids including saliva and crevicular fluid. Proteomics has brought revolution in dentistry by helping in the early diagnosis of various diseases identified by the detection of numerous biomarkers present in the oral fluids. This paper covers the role of proteomics tools for the analysis of oral tissues. In addition, dental materials proteomics and their future directions are discussed.

Characterization of Regulatory Extracellular Vesicles from Osteoclasts

Extracellular vesicles (EVs), which include exosomes and ectosomes/microvesicles, have emerged as important intercellular regulators. EVs can interact with surface receptors of target cells and can transport luminal components, including messenger RNAs (mRNAs), microRNAs, and enzymes, to the cytosol of the target cell. Here, we show that hematopoietic cells grown in culture shed exosome-like EVs as they differentiate from preosteoclasts into osteoclasts. These EVs were between 25 and 120 nm (mean, 40 nm) in diameter determined by transmission electron microscopy. The exosome-associated markers CD63 and EpCAM were enriched in the isolated EVs while markers of Golgi and endoplasmic reticulum were not detected. Treatment of isolated hematopoietic cells with EVs did not affect their receptor activator of nuclear factor κB-ligand (RANKL)-stimulated differentiation into osteoclasts. However, EVs from osteoclast precursors promoted 1,25-dihydroxyvitamin D3-dependent osteoclast formation in whole mouse marrow cultures, and EVs from osteoclast-enriched cultures inhibited osteoclastogenesis in the same cultures. These data suggested that osteoclast-derived EVs are paracrine regulators of osteoclastogenesis. EVs from mature osteoclasts contained receptor activator of nuclear factor κB (RANK). Immunogold labeling showed RANK was enriched in 1 in every 32 EVs isolated from osteoclast-enriched cultures. Depletion of RANK-rich EVs relieved the ability of osteoclast-derived EVs to inhibit osteoclast formation in 1,25-dihydroxyvitamin D3-stimulated marrow cultures. In summary, we show for the first time that EVs released by osteoclasts are novel regulators of osteoclastogenesis. Our data suggest that RANK in EVs may be mechanistically linked to the inhibition of osteoclast formation. RANK present in EVs may function by competitively inhibiting the stimulation of RANK on osteoclast surfaces by RANKL similar to osteoprotegerin. RANK-rich EVs may also take advantage of the RANK/RANKL interaction to target RANK-rich EVs to RANKL-bearing cells for the delivery of other regulatory molecules.

Immunoassay analysis of proteins in gingival crevicular fluid samples from resorbing teeth

Objective: 

To carry out an immunoassay analysis of biomarkers expressed in gingival crevicular fluid (GCF) with the main goal of finding a useful diagnostic pattern to distinguish between resorbing deciduous teeth and nonresorbing controls.

Materials and Methods: 

A split-mouth design was used in this study with a total of 22 GCF samples collected from 11 patients in the mixed dentition. For each child, one deciduous molar with radiographic evidence of root resorption was used as the test tooth whereas the contralateral first permanent molar with formed roots was used as the control tooth. Samples were processed with immunoassays using a panel of selected biomarkers including interleukin-1 beta (IL-1b), interleukin-1 receptor antagonist (IL-1RA), nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG), matrix metalloproteinase-9 (MMP-9), and dentin sialoprotein (DSP).

Results: 

There were no statistically significant differences in levels of IL-1b, OPG, and MMP-9 between test and control sites (P &gt; .05). IL-1RA was the only biomarker to show a significant down-regulation (P  =  .04) in GCF samples collected from resorbing teeth. RANKL data showed a heavily skewed distribution and was deemed unreliable. Only one deciduous GCF sample had detectable levels of DSP; therefore, no further statistical calculation was applicable because of the limited amount of data for this biomarker.

Conclusions: 

This study indicated that IL1-RA is down-regulated in GCF from resorbing primary molars, thus suggesting this cytokine as a potential analyte to be included in a panel that can discriminate between resorbing and nonresorbing teeth.