Salivary Exosomes: Emerging Roles in Systemic Disease

Examination of Oral Squamous Cell Carcinoma and Precancerous Lesions Using Proximity Extension Assay and Salivary RNA Quantification

Saliva is an easy-to access body fluid with high diagnostic potential. The utilization of saliva for oral cancer diagnosis can be an attractive possibility. Besides the oral cancer, it is important to better understand the precancerous lesions such as oral lichen planus (OLP) and leukoplakia (OLK). In order to examine the changes of salivary proteins in controls, patients with oral cancer, and patients with precancerous conditions, proximity extension assay was utilized. Some proteins and functions were characteristic to the examined groups and can serve as a starting point for further biomarker studies. The different nature of OLK and OLP was demonstrated, showing the malignant transformation and the inflammation as the prominent biological processes in the OLK and OLP, respectively. The salivary level of IL6 was verified using quantitative ELISA and the mRNA level was also studied. Elevated IL6 levels could be detected in precancerous groups compared to controls.

Stem cell-derived exosomes for wound healing: current status and promising directions

Wound healing, especially of chronic wounds, is still an unmet therapeutic area since assessment and management are extremely complicated. Although many efforts have been made to treat wounds, all strategies have achieved limited results for chronic wounds. Stem cell-based therapy is considered a promising approach for complex wounds such as those occurring in diabetics. Mesenchymal stem cell transplantation significantly improves wound closure, angiogenesis and wound healing. However, cell therapy is complex, expensive and time-consuming. Recent studies have shown that stem cell-derived exosomes can be an exciting approach to treat wounds. Exosomes derived from mesenchymal stem cells can induce benefit in almost all stages of wound healing, including control of immune responses, inhibition of inflammation, promoting cell proliferation and angiogenesis, while reducing scar formation during the wound healing process. This review aimed at offering an updated overview of the use of exosomes in biological applications, such as wound healing, and addresses not only current applications but also new directions for this next-generation approach in wound healing.

Role and mechanisms of exosomal miRNAs in IBD pathophysiology

Exosomes represent secretory membranous vesicles used for the information exchange between cells and organ-to-organ communication. Exosome crosstalk mechanisms are involved in the regulation of several inflammatory bowel disease (IBD)-associated pathophysiological intestinal processes such as barrier function, immune responses, and intestinal flora. Functional biomolecules, mainly noncoding RNAs (ncRNAs), are believed to be transmitted between the mammalian cells via exosomes that likely play important roles in cell-to-cell communication, both locally and systemically. MicroRNAs (miRNAs) encapsulated in exosomes have generated substantial interest because of their critical roles in multiple pathophysiological processes. In addition, exosomal miRNAs are implicated in the gut health. MiRNAs are selectively and actively loaded into the exosomes and then transferred to the target recipient cell where they manipulate cell function through posttranscriptional silencing of target genes. Intriguingly, miRNA profile of exosomes differs from their cellular counterparts suggesting an active sorting and packaging mechanism of exosomal miRNAs. Even more exciting is the involvement of posttranscriptional modifications in the specific loading of miRNAs into exosomes, but the underlying mechanisms of how these modifications direct ncRNA sorting have not been established. This review gives a brief overview of the status of exosomes and exosomal miRNAs in IBD and also discusses potential mechanisms of exosomal miRNA sorting and delivering.

Deep dive on the proteome of salivary extracellular vesicles: comparison between ultracentrifugation and polymer-based precipitation isolation

Salivary extracellular vesicles (EVs), as novel functional carriers and potential biomarkers, are usually obtained by ultracentrifugation (UC) and polyethylene glycol (PEG)-based precipitation methods. However, salivary EVs obtained by these two methods have not been systematically compared. Here, we perform an in-depth analysis on EVs isolated by these two methods using proteomics. Both methods obtain EVs ranging from 40 to 210 nm, with the PEG method resulting in a wider size distribution. PEG-separated products were irregularly shaped and aggregated, while UC-separated ones were monodispersed and teacup-shaped. Additionally, the expression of EV-specific markers was higher in UC-separated EVs. Using tandem mass spectrometry proteomics, we identified and quantified 1217 kinds of saliva exosomal proteins and 361 kinds of differential proteins, showing that UC can isolate more EV-related proteins. These results offer some guidance for EV separating and provide potential direction for the use of EVs in non-invasive diagnosis.

One-step quantification of salivary exosomes based on combined aptamer recognition and quantum dot signal amplification

As promising fluid biomarkers for non-invasive diagnosis, naturally-occurring exosomes in saliva have attracted a wide interest for their potential application in oral diseases especially oral cancers. However, accurate quantification of salivary exosomes is still challenging due to the current difficulties in simultaneous identification and measurement of these nano-sized vesicles. In this study, we developed a novel fluorescent biosensor for one-step sensitive quantification of salivary exosomes based on magnetic and fluorescent bio-probes (MFBPs). Within the MFBPs, self-assembled DNA concatamers loaded with numerous quantum dots (QDs) were ingeniously tethered to aptamers, which were anchored on the surface of magnetic microspheres (MMs). Efficient recognition and capture of an exosome by the aptamer would simultaneously trigger the release of a DNA concatamer as the detection signal carrier, thereby generating a "one exosome-numerous QDs" amplification effect. As the result, this biosensor allowed one-step quantification with less assay time and achieved a high sensitivity with low limit of detection. Moreover, unique fluorescent properties of QDs and the superparamagnetism of MMs offered a strong anti-interference ability, enabling a robust quantification in complex matrices. Furthermore, this biosensor exhibited a good clinical feasibility with favorable accuracy comparable to nanoscale flow cytometry, and a superiority in label-free analysis and convenient operation. This study provides a novel and general strategy for one-step sensitive quantification of exosomes from body fluids, facilitating the development of exosome-based liquid biopsy for disease diagnosis.

Exosomes released from Shiga toxin 2a-treated human macrophages modulate inflammatory responses and induce cell death in toxin receptor expressing human cells

Shiga toxins (Stxs) produced by Stx-producing Escherichia coli are the primarily virulence factors of hemolytic uremic syndrome and central nervous system (CNS) impairment. Although the precise mechanisms of toxin dissemination remain unclear, Stxs bind to extracellular vesicles (EVs). Exosomes, a subset of EVs, may play a key role in Stx-mediated renal injury. To test this hypothesis, we isolated exosomes from monocyte-derived macrophages in the presence of Stx2a or Stx2 toxoids. Macrophage-like differentiated THP-1 cells treated with Stxs secreted Stx-associated exosomes (Stx-Exo) of 90-130 nm in diameter, which induced cytotoxicity in recipient cells in a toxin receptor globotriaosylceramide (Gb₃ )-dependent manner. Stx2-Exo engulfed by Gb₃ -positive cells were translocated to the endoplasmic reticulum in the human proximal tubule epithelial cell line HK-2. Stx2-Exo contained pro-inflammatory cytokine mRNAs and proteins and induced more severe inflammation than purified Stx2a accompanied by greater death of target cells such as human renal or retinal pigment epithelial cells. Blockade of exosome biogenesis using the pharmacological inhibitor GW4869 reduced Stx2-Exo-mediated human renal cell death. Stx2-Exo isolated from human primary monocyte-derived macrophages activated caspase 3/7 and resulted in significant cell death in primary human renal cortical epithelial cells. Based on these results, we speculate that Stx-containing exosomes derived from macrophages may exacerbate cytotoxicity and inflammation and trigger cell death in toxin-sensitive cells. Therapeutic interventions targeting Stx-containing exosomes may prevent or ameliorate Stx-mediated acute vascular dysfunction.

Methods for Separation and Characterization of Extracellular Vesicles: Results of a Worldwide Survey Performed by the ISEV Rigor and Standardization Subcommittee

Research on extracellular vesicles (EVs) is growing exponentially due to an increasing appreciation of EVs as disease biomarkers and therapeutics, an expanding number of EV-containing materials under study, and application of new preparation, detection, and cargo analysis methods. Diversity of both sources and methodologies imposes challenges on the comparison of measurement results between studies and laboratories. While reference guidelines and minimal requirements for EV research have achieved the important objective of assembling community consensus, it is also essential to understand which methodologies and quality controls are currently being applied, and how usage trends are evolving. As an initial response to this need, the International Society for Extracellular Vesicles (ISEV) performed a worldwide survey in 2015 on "Techniques used for the isolation and characterization of extracellular vesicles" and published the results from this survey in 2016. In 2019, a new survey was performed to assess the changing state of the field. The questionnaire received more than 600 full or partial responses, and the present manuscript summarizes the results of this second worldwide survey. The results emphasize that separation methods such as ultracentrifugation and density gradients are still the most commonly used methods, the use of size exclusion chromatography has increased, and techniques based on tangential flow and microfluidics are now being used by more than 10% of respondents. The survey also reveals that most EV researchers still do not perform sample quality controls before or after isolation of EVs. Finally, the majority of EV researchers emphasize that separation and characterization of EVs should receive more attention.

Exosomes in cancer

Exosomes are small extracellular vesicles released by cells under physiological and pathological conditions. There is emerging evidence associating exosomes with tumorigenesis. They carry cargo (DNA, RNA, miRNA and protein) pertaining to the cell of origin and play a key role in intercellular communication, influencing several cellular processes. Moreover, exosomes can be shed and found in almost all body fluids, providing a source of biomarkers for tumor diagnosis and prognosis. In addition, the use of exosomes for cancer therapeutics is another research area that is gaining attention. This book chapter aims to explore the role of exosomes in tumor biogenesis, progression and clinical applications, comprehensively compiling the research for three tumor types, namely head and neck cancer, lung cancer and glioblastoma.

Splicing Factor Transcript Abundance in Saliva as a Diagnostic Tool for Breast Cancer

Breast cancer is the second leading cause of death in women above 60 years in the US. Screening mammography is recommended for women above 50 years; however, 22% of breast cancer cases are diagnosed in women below this age. We set out to develop a test based on the detection of cell-free RNA from saliva. To this end, we sequenced RNA from a pool of ten women. The 1254 transcripts identified were enriched for genes with an annotation of alternative pre-mRNA splicing. Pre-mRNA splicing is a tightly regulated process and its misregulation in cancer cells promotes the formation of cancer-driving isoforms. For these reasons, we chose to focus on splicing factors as biomarkers for the early detection of breast cancer. We found that the level of the splicing factors is unique to each woman and consistent in the same woman at different time points. Next, we extracted RNA from 36 healthy subjects and 31 breast cancer patients. Recording the mRNA level of seven splicing factors in these samples demonstrated that the combination of all these factors is different in the two groups (p value = 0.005). Our results demonstrate a differential abundance of splicing factor mRNA in the saliva of breast cancer patients.

Salivary exosomes: properties, medical applications, and isolation methods

Salivary exosomes are extracellular vesicles (EVs) with abundant CD63 immunoreactivity on their surface. Based on their size and protein composition, these exosomes can be categorized into two classes of exosomes I (mean diameter of 83.5 nm) and II (mean diameter of 40.5 nm). We have attempted to review the features of these exosomes, including origin, composition, separation methods, and their application in medicine. Not only the composition of salivary exosomes is invaluable in term of diagnosis, but can also afford an understanding in roles of the contents and components of these exosomes in the fundamental pathophysiologic processes of different diseases. since these EVs can cross the epithelial barriers they may be essential for transporting of multifarious components from the blood into saliva. Thus, in comparison to other bodily fluids, salivary exosomes are probably a better and accessible tool to examine the function of exosomes in the diagnosis and treatment of disease.

Exosome-like Nanoparticles: A New Type of Nanocarrier

Nanoparticles are one of the most commonly used systems for imaging or therapeutic drug delivery. Exosomes are nanovesicular carriers that transport cargo for intercellular communication. These nanovesicles are linked to the pathology of some major diseases, in some cases with a central role in their progression. The use of these carriers to transport therapeutic drugs is a recent and promising approach to treat diseases such as cancer and Alzheimer disease. The physiological production of these structures is limited impairing its collection and subsequent purification. These drawbacks inspired the search for mimetic alternatives. The collection of exosome-like nanoparticles from plants can be a good alternative, since they are easier to extract and do not have the drawbacks of those produced in animal cells. Both natural and synthetic exosome-like nanoparticles, produced from serial extrusion of cells or by bottom up synthesis, are currently some of the most promising, biocompatible, high efficiency systems for drug delivery.

ADSC-Exos containing MALAT1 promotes wound healing by targeting miR-124 through activating Wnt/β-catenin pathway

Cutaneous wound is a soft tissue injury that is difficult to heal during aging. It has been demonstrated that adipose-derived stem cells (ADSCs) and its secreted exosomes exert crucial functions in cutaneous wound healing. The present study aimed to elucidate the mechanism of exosomes derived from ADSCs (ADSC-Exos) containing MALAT1 in wound healing. ADSCs were isolated from human normal subcutaneous adipose tissues and identified by flow cytometry analysis. Exosomes were extracted from ADSC supernatants and MALAT1 expression was determined using qRT-PCR analysis. HaCaT and HDF cells were exposed to hydrogen peroxide (H2O2) for simulating the skin lesion model. Subsequently, CCK-8, flow cytometry, wound healing and transwell assays were employed to validate the role of ADSC-Exos containing MALAT1 in the skin lesion model. Besides, cells were transfected with sh-MALAT1 to verify the protective role of MALAT1 in wound healing. The binding relationship between MALAT1 and miR-124 were measured by dual-luciferase reporter assay. ADSC-Exos promoted cell proliferation, migration, and inhibited cell apoptosis of HaCaT and HDF cells impaired by H2O2. However, the depletion of MALAT1 in ADSC-Exos lose these protective effects on HaCaT and HDF cells. Moreover, miR-124 was identified to be a target of MALAT1. Furthermore, ADSC-Exos containing MALAT1 could mediate H2O2-induced wound healing by targeting miR-124 and activating Wnt/β-catenin pathway. ADSC-Exos containing MALAT1 play a positive role in cutaneous wound healing possibly via targeting miR-124 through activating the Wnt/β-catenin pathway, which may provide novel insights into the therapeutic target for cutaneous wound healing.

Milk-Derived Extracellular Vesicles in Inter-Organism, Cross-Species Communication and Drug Delivery

Milk is considered as more than a source of nutrition for infants and is a vector involved in the transfer of bioactive compounds and cells. Milk contains abundant quantities of extracellular vesicles (EVs) that may originate from multiple cellular sources. These nanosized vesicles have been well characterized and are known to carry a diverse cargo of proteins, nucleic acids, lipids and other biomolecules. Milk-derived EVs have been demonstrated to survive harsh and degrading conditions in gut, taken up by various cell types, cross biological barriers and reach peripheral tissues. The cargo carried by these dietary EVs has been suggested to have a role in cell growth, development, immune modulation and regulation. Hence, there is considerable interest in understanding the role of milk-derived EVs in mediating inter-organismal and cross-species communication. Furthermore, various attributes such as it being a natural source, as well as its abundance, scalability, economic viability and lack of unwarranted immunologic reactions, has generated significant interest in deploying milk-derived EVs for clinical applications such as drug delivery and disease therapy. In this review, the role of milk-derived EVs in inter-organismal, cross-species communication and in drug delivery is discussed.

GelMA combined with sustained release of HUVECs derived exosomes for promoting cutaneous wound healing and facilitating skin regeneration

It remains a clinical challenge for cutaneous wound healing and skin regeneration. Endothelial cells participate in the formation of blood vessels and play an important role in the whole process of wound healing. Recent studies suggested that exosomes contribute to the intercellular communication through paracrine pathways, and sustained release of exosomes from hydrogel-based materials provide a promising strategy for curing wound defects. In this study, we isolated exosomes derived from human umbilical vein endothelial cells (HUVECs) and found that HUVECs derived exosomes (HUVECs-Exos) could promote the proliferation and migration activities of keratinocytes and fibroblasts, which are two important effector cells for skin regeneration. Then we developed gelatin methacryloyl (GelMA) hydrogel as the wound dressing to incorporate HUVECs-Exos and applied it to the full-thickness cutaneous wounds. It demonstrated that GelMA scaffold could not only repair the wound defect, but also achieve sustained release of exosomes. The in vivo results showed accelerated re-epithelialization, promotion of collagen maturity and improvement of angiogenesis. Collectively, our findings suggested that HUVECs-Exos could accelerate wound healing and GelMA mediated controlled release of HUVECs-Exos might offer a new method for repairing cutaneous wound defects.

Comparability of the small RNA secretome across human biofluids concomitantly collected from healthy adults

Small extracellular vesicles (sEV) are nano-sized (40–150 nm), membrane-encapsulated vesicles that are released by essentially all cells into the extracellular space and function as intercellular signaling vectors through the horizontal transfer of biologic molecules, including microRNA (miRNA) and other small non-coding RNA (ncRNA), that can alter the phenotype of recipient cells. sEV are present in essentially all extracellular biofluids, including serum, urine and saliva, and offer a new avenue for discovery and development of novel biomarkers of various disease states and exposures. The objective of this study was to systematically interrogate similarities and differences between sEV ncRNA derived from saliva, serum and urine, as well as cell-free small ncRNA (cf-ncRNA) from serum. Saliva, urine and serum were concomitantly collected from 4 healthy donors to mitigate potential bias that can stem from interpersonal and temporal variability. sEV were isolated from each respective biofluid, along with cf-RNA from serum. sEV were isolated from the respective biofluids via differential ultracentrifugation with a 30% sucrose cushion to minimize protein contamination. Small RNA-sequencing was performed on each sample, and cluster analysis was performed based on ncRNA profiles. While some similarities existed in terms of sEV ncRNA cargo across biofluids, there are also notable differences in ncRNA class and ncRNA secretion, with sEV in each biofluid bearing a unique ncRNA profile, including major differences in composition by ncRNA class. We conclude that sEV ncRNA cargo varies according to biofluid, so thus should be carefully selected and interpreted when designing or contrasting translational or epidemiological studies.

A comprehensive analysis of sialolith proteins and the clinical implications

BACKGROUND

Sialolithiasis or salivary gland stones are associated with high clinical morbidity. The advances in the treatment of sialolithiasis has been limited, however, by our understanding of their composition. More specifically, there is little information regarding the formation and composition of the protein matrix, the role of mineralogical deposition, or the contributions of cell epithelium and secretions from the salivary glands. A better understanding of these stone characteristics could pave the way for future non-invasive treatment strategies.

METHODS

Twenty-nine high-quality ductal stone samples were analyzed. The preparation included successive washings to avoid contamination from saliva and blood. The sialoliths were macerated in liquid nitrogen and the maceration was subjected to a sequential, four-step, protein extraction. The four fractions were pooled together, and a standardized aliquot was subjected to tandem liquid chromatography mass spectrometry (LCMS). The data output was subjected to a basic descriptive statistical analysis for parametric confirmation and a subsequent G.O.-KEGG data base functional analysis and classification for biological interpretation.

RESULTS

The LC-MS output detected 6934 proteins, 824 of which were unique for individual stones. An example of our sialolith protein data is available via ProteomeXchange with the identifier PXD012422. More important, the sialoliths averaged 53% homology with bone-forming proteins that served as a standard comparison, which favorably compared with 62% homology identified among all sialolith sample proteins. The non-homologous protein fraction had a highly variable protein identity. The G.O.-KEGG functional analysis indicated that extracellular exosomes are a primary cellular component in sialolithiasis. Light and electron microscopy also confirmed the presence of exosomal-like features and the presence of intracellular microcrystals.

CONCLUSION

Sialolith formation presents similarities with the hyperoxaluria that forms kidney stones, which suggests the possibility of a common origin. Further verification of a common origin could fundamentally change the way in which lithiasis is studied and treated.

CNS-Derived Blood Exosomes as a Promising Source of Biomarkers: Opportunities and Challenges

Eukaryotic cells release different types of extracellular vesicles (EVs) including exosomes, ectosomes, and microvesicles. Exosomes are nanovesicles, 30–200 nm in diameter, that carry cell- and cell-state-specific cargo of proteins, lipids, and nucleic acids, including mRNA and miRNA. Recent studies have shown that central nervous system (CNS)-derived exosomes may carry amyloidogenic proteins and facilitate their cell-to-cell transfer, thus playing a critical role in the progression of neurodegenerative diseases, such as tauopathies and synucleinopathies. CNS-derived exosomes also have been shown to cross the blood-brain-barrier into the bloodstream and therefore have drawn substantial attention as a source of biomarkers for various neurodegenerative diseases as they can be isolated via a minimally invasive blood draw and report on the biochemical status of the CNS. However, although isolating specific brain-cell-derived exosomes from the blood is theoretically simple and the approach has great promise, practical details are of crucial importance and may compromise the reproducibility and utility of this approach, especially when different laboratories use different protocols. In this review we discuss the role of exosomes in neurodegenerative diseases, the usefulness of CNS-derived blood exosomes as a source of biomarkers for these diseases, and practical challenges associated with the methodology of CNS-derived blood exosomes and subsequent biomarker analysis.

Salivary MicroRNA for Diagnosis of Cancer and Systemic Diseases: A Systematic Review

: Background: The aberrant expression of microRNAs (miRNAs) has been associated with several diseases, including cancer, inflammatory, and autoimmune conditions. Interest in salivary miRNAs as non-invasive tools for the diagnosis of malignancies and systemic diseases is rapidly increasing. The present systematic review was developed for answering the question: "Are salivary microRNAs reliable biomarkers for diagnosis of cancer and systemic diseases?"

METHODS

The application of inclusion and exclusion criteria led to the selection of 11 papers. Critical appraisals and quality assessments of the selected studies were performed through the National Institute of Health "Study Quality Assessment Tool" and the classification of the Oxford Center for Evidence-Based Medicine.

RESULTS

Seven studies reported statistically significant correlations between one or more salivary miRNAs and the investigated disease. The critical analysis allowed us to classify only two studies (18.2%) as having "good" quality, the rest being scored as "intermediate" (8; 73%) and "poor" (1; 9%). Evidence exists that salivary miR-940 and miR-3679-5p are reliable markers for pancreatic cancer and that miR140-5p and miR301a are promising molecules for the salivary diagnosis of gastric cancer.

CONCLUSIONS

Further studies, possibly avoiding the risk of bias highlighted here, are necessary to consolidate these findings and to identify new reliable salivary biomarkers.

A Role for Exosomes in Craniofacial Tissue Engineering and Regeneration

Tissue engineering and regenerative medicine utilize mesenchymal stem cells (MSCs) and their secretome in efforts to create or induce functional tissue replacement. Exosomes are specific extracellular vesicles (EVs) secreted by MSCs and other cells that carry informative cargo from the MSC to targeted cells that influence fundamental cellular processes including apoptosis, proliferation, migration, and lineage-specific differentiation. In this report, we review the current knowledge regarding MSC exosome biogenesis, cargo and function. This review summarizes the use of MSC exosomes to control or induce bone, cartilage, dentin, mucosa, and pulp tissue formation. The next-step engineering of exosomes provides additional avenues to enhance oral and craniofacial tissue engineering and regeneration.

Exosomes in head and neck cancer. Updating and revisiting

Exosomes have gone from being considered simple containers of intracellular waste substances to be considered important carriers of cellular signals. Its broad capacity to promote tumour growth, both in situ and metastatic, has greatly intensified scientific research on them. In the same way and depending on its content, its tumour suppressive properties have opened a window of light and hope in the fight against cancer. In the present review we try to gather in a simple and understandable way the most relevant knowledge to date on the role of exosomes in oral squamous cell carcinoma, helping to understand their process of formation, release and activity on the tumour microenvironment.

Interests of Exosomes in Bone and Periodontal Regeneration: A Systematic Review

Periodontitis is an infectious inflammatory disease characterized by clinical attachment loss and tooth supporting tissue destruction. As exosomes demonstrated pro-regenerative ability, their use in periodontal treatment has been suggested. The aim of this systematic review is to gather and summarize the most recent data regarding exosomes to determine their potential impact in bone and periodontal regeneration. Electronic databases (Pubmed, Web of Science) were searched up to February 2020. Studies assessing the impact of exosomes administration in experimental bone and periodontal defects have been identified according to PRISMA guidelines. Among the 183 identified articles, 16 met the inclusion criteria and were included in this systematic review. Experimental bone defects were mainly surgically induced with a dental bur or distraction tools. All studies considered bone healing after exosomes administration as the primary outcome. Results showed that mesenchymal stem cells derived exosomes administration promoted bone healing and neovascularization. Nevertheless, a dose-effect relationship was observed. Exosomes administration appears to promote significantly the bone healing and periodontal regeneration. However, only a limited number of studies have been carried out so far and the optimized protocols in this context need to be evaluated.

Saliva proteomics updates in biomedicine

In the years of personalized (or precision) medicine the 'omics' methodologies in biomedical sciences-genomics, transcriptomics, proteomics and metabolomics-are helping researchers to detect quantifiable biological characteristics, or biomarkers, that will best define the human physiology and pathologies. Proteomics use high throughput and high efficiency approaches with the support of bioinformatic tools in order to identify and quantify the total protein content of cells, tissues or biological fluids. Saliva receives a lot of attention as a rich biological specimen that offers a number of practical and physiological advantages over blood and other biological fluids in monitoring human health. The aim of this review is to present the latest advances in saliva proteomics for biomedicine.

Salivary Biomarkers for Oral Squamous Cell Carcinoma Diagnosis and Follow-Up: Current Status and Perspectives

Oral cancer is the sixth most common cancer type in the world, and 90% of it is represented by oral squamous cell carcinoma (OSCC). Despite progress in preventive and therapeutic strategies, delay in OSCC diagnosis remains one of the major causes of high morbidity and mortality; indeed the majority of OSCC has been lately identified in the advanced clinical stage (i.e., III or IV). Moreover, after primary treatment, recurrences and/or metastases are found in more than half of the patients (80% of cases within the first 2 years) and the 5-year survival rate is still lower than 50%, resulting in a serious issue for public health. Currently, histological investigation represents the “gold standard” of OSCC diagnosis; however, recent studies have evaluated the potential use of non-invasive methods, such as “liquid biopsy,” for the detection of diagnostic and prognostic biomarkers in body fluids of oral cancer patients. Saliva is a biofluid containing factors such as cytokines, DNA and RNA molecules, circulating and tissue-derived cells, and extracellular vesicles (EVs) that may be used as biomarkers; their analysis may give us useful information to do early diagnosis of OSCC and improve the prognosis. Therefore, the aim of this review is reporting the most recent data on saliva biomarker detection in saliva liquid biopsy from oral cancer patients, with particular attention to circulating tumor DNA (ctDNA), EVs, and microRNAs (miRNAs). Our results highlight that saliva liquid biopsy has several promising clinical uses in OSCC management; it is painless, accessible, and low cost and represents a very helpful source of diagnostic and prognostic biomarker detection. Even if standardized protocols for isolation, characterization, and evaluation are needed, recent data suggest that saliva may be successfully included in future clinical diagnostic processes, with a considerable impact on early treatment strategies and a favorable outcome.

Salivary extracellular vesicles can modulate purinergic signalling in oral tissues by combined ectonucleoside triphosphate diphosphohydrolases and ecto-5'-nucleotidase activities

We reported previously that the rat submandibular gland is able to release nanovesicles capable to hydrolyse millimolar concentrations of ATP, ADP and AMP in vitro. Here, we show that rat saliva also contains nanovesicles with the ability to hydrolyse ATP. Our aim was to identify and characterize vesicular nucleotidases by using kinetic, immunological and in silico approaches. Nucleotidase activity in the absence or presence of specific inhibitors allowed us to assume the participation of NTPDase1, -2 and -3, together with ecto-5'-nucleotidase, confirmed using specific antibodies. At neutral pH, initial ATPase activity would be mostly due to NTPDase2, which was thereafter inactivated, leaving NTPDase1 and NTPDase3 to hydrolyse ATP and ADP with an efficacy ATPase/ADPase around 2. Ecto-5'nucleotidase would be mainly responsible for AMP hydrolysis and adenosine accumulation. We proposed a kinetic model for NTPDase2 as a tool to isolate and analyse the turnover of this enzyme in the presence of different ATP concentrations, including those expected in extracellular media. Our study characterizes the ectonucleotidases carried by extracellular vesicles which contribute to modulate ATP and adenosine concentrations in the oral cavity, essential players in purinergic signalling.

The role of Epstein-Barr virus infection in primary Sjögren's syndrome

PURPOSE OF REVIEW

The purpose of this article is to draw attention to the role of Epstein-Barr virus (EBV) virus in the pathogenesis of the primary Sjögren's syndrome. The article introduces the problem of consequences of EBV acute infection, and its reactivation, in association with the immune response modulation by the virus and with an increased risk of developing systemic autoimmune diseases and EBV-associated cancers.

RECENT FINDINGS

The knowledge about the mechanisms by which the virus may stay for years in a latent phase, unrecognized by the host response immune cells is constantly expanding. There are several mechanisms and theories about EBV influence on the autoimmune process in Sjogren's syndrome (pSS), including the similarity (molecular mimicry) between viral EBNA-2 protein and Ro-60 antigen or EBER-1 and EBER-2 viral proteins and La antigen.

SUMMARY

The influence of EBV infection on the development and course of pSS has been proven. It has also been established that both EBV and pSS result in the increased risk of tumor (especially lymphoma) development. In the light of these findings, new ways to manage EBV infections are being sought. Optimal methods for assessing EBV infection status are being devised. Research also aims at finding therapies, which target EBV through the inhibition of the autoimmune process and of viral activity. The present article is an attempt to discuss the most important phenomena and elements linking EBV infection to the primary Sjögren's syndrome.

Exosomes and other extracellular vesicles in oral and salivary gland cancers

Extracellular vesicles (EVs, including exosomes) are a group of heterogeneous nanometer-sized vesicles that are released by all types of cells and serve as functional mediators of cell-to-cell communication. This ability is primarily due to their capacity to package and transport various proteins, lipids, and nucleic acids-namely DNA and messenger RNA (mRNA), but also microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). These contents can influence the function and fate of both recipient and donor cells. More and more studies have shown that EVs are involved in every phase of cancer development, mediating bidirectional cross talk between cancer cells and their tissue microenvironment. More specifically, EVs can promote tumor progression by modifying vesicular contents and establishing a distant premetastatic niche with molecules that favor cancer cell proliferation, migration, invasion, metastasis, angiogenesis, and even drug resistance. Given that the packaging of these molecules is known to be tissue-specific, EVs can not only serve as novel prognostic and diagnostic markers but also be used as potential therapeutic targets and vehicles for drug delivery. The present review discusses the current understanding of the multifaceted roles of EVs in the progression of oral and salivary gland cancers, as well as their potential use in clinical applications.

The functions and clinical application potential of exosomes derived from adipose mesenchymal stem cells: a comprehensive review

Exosomes are extracellular membranous nanovesicles that mediate local and systemic intercellular communication by transporting proteins or nucleic acids (DNA and RNA) into target cells, thus altering the behaviors of recipient cells. Recent studies have revealed that these vesicles play a critical role in many biological functions, such as cell proliferation, immune regulation, nerve regeneration, and cancer. Adipose-derived stem cells (ADSCs) are now considered a multipotent and abundant tool in the field of cell therapy and regenerative medicine. ADSCs can produce and secrete many exosomes, which inherit multiple functions of cells. Therefore, in this review, we will introduce the characteristics of exosomes derived from ADSCs (ADSC-Exos), describe their functions in different biological processes, summarize the latest research achievements, describe their limitations in cell-free therapy, and provide further insights into their clinical application potential for the treatment of certain diseases.

Clinical validity of saliva and novel technology for cancer detection

Cancer, a local disease at an early stage, systemically evolves as it progresses by triggering alterations in surrounding microenvironment, disturbing immune surveillance and further disseminating its molecular contents into circulation. This pathogenic characteristic of cancer makes the use of biofluids such as blood/serum/plasma, urine, tear and cerebrospinal fluids credible surrogates harboring tumor tissue-derived molecular alterations for the detection of cancer. Most importantly, a number of recent reports have credentialed the clinical validity of saliva for the detection of systemic diseases including cancers. In this review, we discussed the validity of saliva as credible biofluid and clinical sample type for the detection of cancers. We have presented the molecular constituents of saliva that could mirror the systemic status of our body and recent findings of salivaomics associated with cancers. Recently, liquid biopsy to detect cancer-derived circulating tumor DNA has emerged as a credible cancer-detection tool with potential benefits in screening, diagnosis and also risk management of cancers. We have further presented the clinical validity of saliva for liquid biopsy of cancers and a new technology platform based on electrochemical detection of cancer-derived ctDNA in saliva with superior sensitivity and point-of-care potential. The clinical utilities of saliva for the detection of cancers have been evidenced, but biological underpinning on the existence of molecular signatures of cancer-origin in saliva, such as via exosomal distribution, should be addressed in detail.

The exosome-mediated PI3k/Akt/mTOR signaling pathway in cervical cancer

BACKGROUND

Cervical cancer is the second most common cancer and one of the leading causes of cancer deaths among women worldwide.

OBJECTIVE

To evaluate the clinical significance of the PI3k/Akt/mTOR signaling pathway in cancer tissues and exosomes extracted from vaginal secretions.

METHODS

Immunohistochemical staining was used to detect the protein expression of PI3k, Akt, and mTOR in tissue samples from the control group, the CIN (cervical intraepithelial neoplasia) group, and the cervical cancer group. qPCR (quantitative PCR) was used to detect the expressions of PI3k, Akt, and mTOR in cervical cancer tissues, the corresponding adjacent tissues, and exosomes extracted from vaginal secretions.

RESULTS

Compared with those of healthy people and CIN, the PI3k/Akt/mTOR protein levels in extracts from tissues were higher in the cervical cancer patients. The PI3k/Akt/mTOR gene and protein levels increased in the cervical cancer tissues with the increase in the degree of malignancy of the cancer. There was no significant difference in PI3k/Akt/mTOR gene expression between the cervical cancer tissues and the exosomes extracted from vaginal secretions, but both were significantly higher than the expressions of the corresponding adjacent tissues.

CONCLUSIONS

The PI3k/Akt/mTOR signaling pathway mediated by exosomes extracted from vaginal secretions may provide candidate diagnostic biomarkers or potential therapeutic targets.

The research advances of exosomes in esophageal cancer

Esophageal carcinoma (EC) is one of the most common human digestive tract tumors, with high morbidity and mortality. It is necessary to elucidate the mechanism of cancer progression and seek early EC diagnostic markers for prompt detection and intervention. Exosomes are membrane nanovesicles secreted from many nucleated cells, 30-100 nm in diameter, containing various proteins, lipids and nucleic acids. They exist in peripheral blood, urine, ascites and other body fluids, widely engaged with intercellular material exchange and signal communication. Exosomes secreted from EC cells or tissues conduct important functions in tumor growth and progression. The detection and analysis of tumor-derived or tumor-associated exosomes has potential for EC early diagnosis and prognosis assessment. In the present paper, the exosomes' biological behaviors, isolation, detection and functions in EC progression - using as potential biomarkers for EC diagnosis or prognosis - are reviewed.

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.

Adipose mesenchymal stem cell-derived exosomes promote cell proliferation, migration, and inhibit cell apoptosis via Wnt/β-catenin signaling in cutaneous wound healing

Cutaneous wounds, a type of soft tissue injury, are difficult to heal in aging. Differentiation, migration, proliferation, and apoptosis of skin cells are identified as key factors during wound healing processes. Mesenchymal stem cells have been documented as possible candidates for wound healing treatment because their use could augment the regenerative capacity of many tissues. However, the effects of exosomes derived from adipose-derived stem cell (ADSC-exos) on cutaneous wound healing remain to be carefully elucidated. In this present study, HaCaT cells were exposed to hydrogen peroxide (H₂ O ₂ ) for the establishment of the skin lesion model. Cell Counting Kit-8 assay, migration assay, and flow cytometry assay were conducted to detect the biological function of ADSC-exos in skin lesion model. Finally, the possible mechanism was further investigated using Western blot assay. The successful construction of the skin lesion model was confirmed by results of the enhanced cell apoptosis of HaCaT cells induced by H ₂ O ₂ , the increased Bax expression and decreased Bcl-2 expression. CD9 and CD63 expression evidenced the existence of ADSC-exos. The results of functional experiments demonstrated that ADSC-exos could prompt cell proliferation and migration of HaCaT cells, and repress cell apoptosis of HaCaT cells. In addition, the activation of Wnt/β-catenin signaling was confirmed by the enhanced expression of β-catenin at the protein level. Collectively, our findings suggest that ADSC-exos play a positive role in cutaneous wound healing possibly via Wnt/β-catenin signaling. Our study may provide new insights into the therapeutic target for cutaneous wound healing.

Detection of Exosomal PD-L1 RNA in Saliva of Patients With Periodontitis

Periodontitis is the most prevalent inflammatory disease of the periodontium, and is related to oral and systemic health. Exosomes are emerging as non-invasive biomarker for liquid biopsy. We here evaluated the levels of programmed death-ligand 1 (PD-L1) mRNA in salivary exosomes from patients with periodontitis and non-periodontitis controls. The purposes of this study were to establish a procedure for isolation and detection of mRNA in exosomes from saliva of periodontitis patients, to characterize the level of salivary exosomal PD-L1, and to illustrate its clinical relevance. Bioinformatics analysis suggested that periodontitis was associated with an inflammation gene expression signature, that PD-L1 expression positively correlated with inflammation in periodontitis based on gene set enrichment analysis (GSEA) and that PD-L1 expression was remarkably elevated in periodontitis patients versus control subjects. Exosomal RNAs were successfully isolated from saliva of 61 patients and 30 controls and were subjected to qRT-PCR. Levels of PD-L1 mRNA in salivary exosomes were higher in periodontitis patients than controls (P < 0.01). Salivary exosomal PD-L1 mRNA showed significant difference between the stages of periodontitis. In summary, the protocols for isolating and detecting exosomal RNA from saliva of periodontitis patients were, for the first time, characterized. The current study suggests that assay of exosomes-based PD-L1 mRNA in saliva has potential to distinguish periodontitis from the healthy, and the levels correlate with the severity/stage of periodontitis.

Role of Exosomes as a Treatment and Potential Biomarker for Stroke

Approximately, 16 million strokes occur worldwide each year, causing 6 million deaths and considerable disability, implying an enormous social, individual health, and economic burden. Due to this high incidence, strategies to promote stroke recovery are urgently needed. Research into new therapeutic approaches for stroke has determined that intravenous administration of mesenchymal stem cells (MSCs) is a good strategy to improve recovery by amplifying mechanisms implicated in brain plasticity. Recent studies have demonstrated the efficacy of MSCs in stroke, with no need for them to reach the area of brain injury. Although the mechanisms by which they mediate restorative effects are still unknown, the evidence suggests that MSCs might use specialised communication by sending and receiving biological information included in elements called exosomes. Exosomes are nanosized extracellular vesicles released into physical environments, and they have recently been suggested to mediate restorative stem cell effects. Moreover, after stroke, exosomes can also be synthesised and released from brain cells, passing through the blood-brain barrier (BBB), and can be detected in peripheral blood or in cerebrospinal fluid. Thus, exosomes could possibly be biomarkers that reflect pathological progress and promote stroke recovery. This review discusses the translational aspects of MSC-derived exosomes and their various roles in brain repair and as circulating biomarkers in stroke.