Saliva and growth factors: the fountain of youth resides in us all

Biological processes and factors involved in soft and hard tissue healing

Wound healing is a complex and iterative process involving myriad cellular and biologic processes that are highly regulated to allow satisfactory repair and regeneration of damaged tissues. This review is intended to be an introductory chapter in a volume focusing on the use of platelet concentrates for tissue regeneration. In order to fully appreciate the clinical utility of these preparations, a sound understanding of the processes and factors involved in soft and hard tissue healing. This encompasses an appreciation of the cellular and biological mediators of both soft and hard tissues in general as well as specific consideration of the periodontal tissues. In light of good advances in this basic knowledge, there have been improvements in clinical strategies and therapeutic management of wound repair and regeneration. The use of platelet concentrates for tissue regeneration offers one such strategy and is based on the principles of cellular and biologic principles of wound repair discussed in this review.

Effects of 4-hexylresorcinol administration on the submandibular glands in a growing rat model

Background

4-Hexylresorcinol (4HR) is a food additive and class I histone deacetylase inhibitor. In this study, we examined the effects of 4HR administration on the submandibular gland in a growing rat model.

Methods

Four-week-old rats were used in this study. The experimental group (nine males and eight females) received 12.8 mg/kg of 4HR weekly for 12 weeks. Ten rats (five males and five females) were used as controls. The submandibular glands of rats were collected 12 weeks after the first administration of 4HR. The weight of the glands was measured. Histological analysis, immunoprecipitation-high-performance liquid chromatography (IP-HPLC), and western blotting were performed.

Results

The weights of the rat submandibular glands were higher in the experimental groups than in the control group, especially in male rats (P < 0.05). The vascular endothelial growth factor (VEGF) and testosterone in the submandibular glands were more highly expressed in 4HR-treated male rats than in untreated rats, as detected by both western blotting and immunohistochemistry. The IP-HPLC results demonstrated that the expression levels of Ki67, epidermal growth factor, and testosterone in the submandibular glands were higher in 4HR-treated male rats than in untreated rats.

Conclusions

This study demonstrated that the systemic administration of 4HR increased the weight of submandibular glands in male rats. In addition, the testosterone and VEGF expression levels in the submandibular glands increased owing to 4HR administration.

Engineering Bioactive Scaffolds for Skin Regeneration

Large skin wounds pose a major clinical challenge. Scarcity of donor site and postsurgical scarring contribute to the incomplete or partial loss of function and aesthetic concerns in skin wound patients. Currently, a wide variety of skin grafts are being applied in clinical settings. Scaffolds are used to overcome the issues related to the misaligned architecture of the repaired skin tissues. The current review summarizes the contribution of biomaterials to wound healing and skin regeneration and addresses the existing limitations in skin grafting. Then, the clinically approved biologic and synthetic skin substitutes are extensively reviewed. Next, the techniques for modification of skin grafts aiming for enhanced tissue regeneration are outlined, and a summary of different growth factor delivery systems using biomaterials is presented. Considering the significant progress in biomaterial science and manufacturing technologies, the idea of biomaterial-based skin grafts with the ability for scarless wound healing and reconstructing full skin organ is more achievable than ever.

Macrophage Motility in Wound Healing Is Regulated by HIF-1α via S1P Signaling

Accumulating evidence indicates that the molecular pathways mediating wound healing induce cell migration and localization of cytokines to sites of injury. Macrophages are immune cells that sense and actively respond to disturbances in tissue homeostasis by initiating, and subsequently resolving, inflammation. Hypoxic conditions generated at a wound site also strongly recruit macrophages and affect their function. Hypoxia inducible factor (HIF)-1α is a transcription factor that contributes to both glycolysis and the induction of inflammatory genes, while also being critical for macrophage activation. For the latter, HIF-1α regulates sphingosine 1-phosphate (S1P) to affect the migration, activation, differentiation, and polarization of macrophages. Recently, S1P and HIF-1α have received much attention, and various studies have been performed to investigate their roles in initiating and resolving inflammation via macrophages. It is hypothesized that the HIF-1α/S1P/S1P receptor axis is an important determinant of macrophage function under inflammatory conditions and during disease pathogenesis. Therefore, in this review, biological regulation of monocytes/macrophages in response to circulating HIF-1α is summarized, including signaling by S1P/S1P receptors, which have essential roles in wound healing.

The Bigger Picture: Why Oral Mucosa Heals Better Than Skin

Wound healing is an essential process to restore tissue integrity after trauma. Large skin wounds such as burns often heal with hypertrophic scarring and contractures, resulting in disfigurements and reduced joint mobility. Such adverse healing outcomes are less common in the oral mucosa, which generally heals faster compared to skin. Several studies have identified differences between oral and skin wound healing. Most of these studies however focus only on a single stage of wound healing or a single cell type. The aim of this review is to provide an extensive overview of wound healing in skin versus oral mucosa during all stages of wound healing and including all cell types and molecules involved in the process and also taking into account environmental specific factors such as exposure to saliva and the microbiome. Next to intrinsic properties of resident cells and differential expression of cytokines and growth factors, multiple external factors have been identified that contribute to oral wound healing. It can be concluded that faster wound closure, the presence of saliva, a more rapid immune response, and increased extracellular matrix remodeling all contribute to the superior wound healing and reduced scar formation in oral mucosa, compared to skin.

A Scarless Healing Tale: Comparing Homeostasis and Wound Healing of Oral Mucosa With Skin and Oesophagus

Epithelial tissues are the most rapidly dividing tissues in the body, holding a natural ability for renewal and regeneration. This ability is crucial for survival as epithelia are essential to provide the ultimate barrier against the external environment, protecting the underlying tissues. Tissue stem and progenitor cells are responsible for self-renewal and repair during homeostasis and following injury. Upon wounding, epithelial tissues undergo different phases of haemostasis, inflammation, proliferation and remodelling, often resulting in fibrosis and scarring. In this review, we explore the phenotypic differences between the skin, the oesophagus and the oral mucosa. We discuss the plasticity of these epithelial stem cells and contribution of different fibroblast subpopulations for tissue regeneration and wound healing. While these epithelial tissues share global mechanisms of stem cell behaviour for tissue renewal and regeneration, the oral mucosa is known for its outstanding healing potential with minimal scarring. We aim to provide an updated review of recent studies that combined cell therapy with bioengineering exporting the unique scarless properties of the oral mucosa to improve skin and oesophageal wound healing and to reduce fibrotic tissue formation. These advances open new avenues toward the ultimate goal of achieving scarless wound healing.

Cimetidine-induced androgenic failure causes cell death and changes in actin, EGF and V-ATPase immunoexpression in rat submandibular glands

Submandibular gland (SMG) is responsive to androgens via androgen receptor (AR). We verified whether cimetidine induces androgenic dysfunction in SMG, and evaluated the structural integrity, cell death and immunoexpression of actin, EGF and V-ATPase in androgen-deficient SMG. Male rats received cimetidine (CMTG) and control animals (CG) received saline. Granular convoluted tubules (GCTs) diameter and number of acinar cell nuclei were evaluated. TUNEL and immunofluorescence reactions for detection of AR, testosterone, actin, EGF and V-ATPase were quantitatively analysed. In CG, testosterone immunolabelling was detected in acinar and ductal cells cytoplasm. AR-immunolabelled nuclei were observed in acinar cells whereas ductal cells showed AR-immunostained cytoplasm, indicating a non-genomic AR action. In CMTG, the weak testosterone and AR immunoexpression confirmed cimetidine-induced androgenic failure. A high cell death index was correlated with decreased number of acinar cells, GCTs diameter and EGF immunoexpression under androgenic dysfunction. Actin immunofluorescence decreased in the SMG cells, but an increased and diffuse cytoplasmic V-ATPase immunolabelling was observed in striated ducts, suggesting a disruption in the actin-dependent V-ATPase recycling due to androgenic failure. Our findings reinforce the androgenic role in the maintenance of SMG histophysiology, and point to a potential clinical use of cimetidine against androgen-dependent glandular tumour cells.

Electrical stimulation enhances early palatal wound healing in mice

BACKGROUND/OBJECTIVE

Electrical stimulation (ES) has been used to treat chronic wound and other clinical applications, showing favorable results in wound closure. It was hypothesized that ES can present a positive effect on oral mucosa healing. The aim of this study was to investigate the effects of ES during the palatal mucosa early healing process in Swiss mice.

METHODS

Ninety animals were divided into two groups: Control (C; n = 45), which received Sham ES applications, and Test (ES; n = 45), which received ES (100 μA; 9 kHz; 660 mVpp) once a day for 3 days. A full thickness wound was performed with a 1.5 mm diameter biopsy punch in the hard palate. Histologically, the following parameters were evaluated: palatal wound closure and epithelial and connective wound edge distance (EED and CED). Furthermore, IL-1β, IL-6, IL-10 TNF-α, and VEGF cytokine levels were evaluated by multiplex assay. The percentage of collagen fibers was assessed using the polarization method and the Smad proteins using the immunofluorescence method.

RESULTS

Palatal wound closure presented a significant reduction on day 5 in the ES group (p = 0.01). Additionally, both EED and CED were shorter for all time points in the ES group (p < 0.05), and the inflammatory markers IL-6, IL-10, TNF-α, and VEGF were reduced (p < 0.05). There were no differences in collagen fibers and phospho-Smad2 between the groups.

CONCLUSION

ES had a positive effect on early palatal wound closure outcomes, as well as on inflammatory markers.

The reliability and validity of the European League Against Rheumatism Sjögren Syndrome Patient Reported Index in patients with primary Sjögren syndrome: A Turkish version study

Objectives

This study aims to assess the reliability and validity of the Turkish version of the European League Against Rheumatism (EULAR) Sjögren Syndrome Patient Reported Index (ESSPRI) (TR) in patients with primary Sjögren syndrome (pSS).

Materials and methods

A cross-sectional survey study design and analysis were used to assess the reliability and validity of the ESSPRI (TR) between March 2019 and July 2019. A total of 30 patients (5 males, 25 females; mean age 54.1±10.5 years; range, 18 to 75 years) diagnosed as pSS according to revised American College of Rheumatology (ACR)/EULAR classification criteria were included. ESSPRI (TR) was applied to the patients with face-to-face interviews twice: on their first visit and after an interval of 15 days. The test-retest reliability was assessed with the intraclass correlation coefficient (ICC), and the internal consistency of the multi-item subscales by calculating Cronbach alpha values. The correlations between basal and stimulated salivary flow (BSF and SSF), Oral Health Impact Profile-14 (OHIP-14) and Oral Health-Related Quality of Life-UK (OHRQOL-UK) questionnaires were evaluated to determine the construct validity.

Results

The ICC value for the test/retest reliability of ESSPRI (TR) was 0.925. The internal consistency was 0.682. There were low to moderate correlations between the ESSPRI (TR) total score and BSF (-0.39), SSF (-0.50), OHIP-14 total (0.57) and OHRQOL-UK total (-0.67).

Conclusion

The Turkish version of the ESSPRI was found to be clinically valid and reliable to be used in clinical evaluations and rehabilitation interventions in patients with pSS.

Examination of the Therapeutic Potential of Mouse Oral Mucosa Stem Cells in a Wound-Healing Diabetic Mice Model

Diabetic wounds' delayed healing response is still considered a major therapeutic challenge. Stem cells and derived cellular products have been an active field of research for novel therapies referred to as regenerative medicine. It has recently been shown that human oral mucosa stem cells (hOMSCs) are a readily accessible source for obtaining large quantities of stem cells. This study evaluates the potential of mouse oral mucosa stem cells (mOMSCs) to enhance wound healing in a diabetic (db/db) mouse model by morphological and histological analysis. We show that mOMSCs-treated wounds displayed a significantly faster wound-healing response (p ≤ 0.0001), featuring faster re-epithelialization and a larger area of granulation tissue (p ≤ 0.05). Taken together, these results suggest that oral mucosa stem cells might have therapeutic potential in diabetic wound healing.

A salivary metabolite signature that reflects gingival host-microbe interactions: instability predicts gingivitis susceptibility

Several proteins and peptides in saliva were shown to stimulate gingival wound repair, but the role of salivary metabolites in this process remains unexplored. In vitro gingival re-epithelialization kinetics were determined using unstimulated saliva samples from healthy individuals collected during an experimental gingivitis study. Elastic net regression with stability selection identified a specific metabolite signature in a training dataset that was associated with the observed re-epithelialization kinetics and enabled its prediction for all saliva samples obtained in the clinical study. This signature encompassed ten metabolites, including plasmalogens, diacylglycerol and amino acid derivatives, which reflect enhanced host-microbe interactions. This association is in agreement with the positive correlation of the metabolite signature with the individual’s gingival bleeding index. Remarkably, intra-individual signature-variation over time was associated with elevated risk for gingivitis development. Unravelling how these metabolites stimulate wound repair could provide novel avenues towards therapeutic approaches in patients with impaired wound healing capacity.

Wearable Lab on Body: Combining Sensing of Biochemical and Digital Markers in a Wearable Device

Wearables are being widely researched for monitoring individual's health and wellbeing. Current generation wearable devices sense an individual's physiological data such as heart rate, respiration, electrodermal activity, and EEG, but lack in sensing their biological counterparts, which drive the majority of individual's physiological signals. On the other hand, biosensors for detecting biochemical markers are currently limited to one-time use, are non-continuous and don't provide flexibility in choosing which biomarker they sense. We present "wearable lab on body", a platform for active continuous monitoring of human biomarkers from the biological fluid. Our platform contains both digital sensors such as IMU for activity recognition, as well as an automated system for continuous sampling of biomarkers from saliva by leveraging already existing paper-based biochemical sensors. The platform could aid with longitudinal studies of biomarkers and early diagnosis of diseases.

Scarless wound healing: From development to senescence

An essential element of tissue homeostasis is the response to injuries, cutaneous wound healing being the most studied example. In the adults, wound healing aims at quickly restoring the barrier function of the skin, leading however to scar, a dysfunctional fibrotic tissue. On the other hand, in fetuses a scarless tissue regeneration takes place. During ageing, the wound healing capacity declines; however, in the absence of comorbidities a higher quality in tissue repair is observed. Senescent cells have been found to accumulate in chronic unhealed wounds, but more recent reports indicate that their transient presence may be beneficial for tissue repair. In this review data on skin wound healing and scarring are presented, covering the whole spectrum from early embryonic development to adulthood, and furthermore until ageing of the organism.

Salivary protease spectrum biomarkers of oral cancer

Proteases are important molecules that are involved in many physiological and pathological processes of the human body, such as growth, apoptosis and metastasis cancer cells. They are potential targets in cancer diagnosis and biotherapy. In this study, we analyzed the salivary protease spectrum of patients with oral squamous cell carcinoma (OSCC), oral benign masses and chronic periodontitis, as well as that of health, using human protease array kits, enzyme-linked immunosorbent assay, western blot and immunofluorescence. The salivary protease spectrum was found to be associated with oral diseases. For example, the saliva of patients with OSCC contained increased numbers of proteases than those of other oral diseases and health. The levels of matrix metalloproteinase (MMP)-1, MMP-2, MMP-10, MMP-12, A disintegrin and metalloprotease (ADAM)9, A disintegrin and metalloprotease with thrombospondin type 13 motifs (ADAMST13), cathepsin V and kallikrein 5 in the saliva of patients with OSCC were significantly increased compared with those of other groups. Taking MMP-1, cathepsin V, kallikrein 5 and ADAM9 as biomarkers of OSCC, cutoff values were199, 11.34, 9.29 and 202.55 pg·mL^-1, respectively. From the area under the curve, sensitivity and specificity, the combination of cathepsin V/kallikrein5/ADAM9 was an optimal biomarker for diagnosing OSCC. Thus, analysis of the salivary protease spectrum may be an innovative and cost-efficient approach to evaluating the health status of the oral cavity. Specifically, increases in cathepsin V, kallikrein 5 and ADAM9 may be useful biomarkers in the screening and diagnosis of OSCC.

Humic Acid Enhances Wound Healing in the Rat Palate

Introduction

Humic acid was previously shown to enhance cutaneous wound healing and show antibacterial properties; however, it has not been used for wound healing in the oral cavity. Thus, the goal of this study was the evaluation of the effect of the humic acid on the healing of excisional wounds in an experimental rat study.

Materials and Methods

A circular wound on mid-palatal surfaces was made on a total of 77 Wistar rats by using a 3-mm biopsy punch under anesthesia. The animals were divided into 4 groups as baseline, saline control (0.09%), chlorhexidine gluconate (0.05%), and humic acid (80 mg/kg) and were treated with these materials for 7 days.

Results

The rats were observed for 3 weeks in order to track the wound closure rates. Both humic acid treatment and chlorhexidine gluconate treatment resulted in statistically significant enhanced rate of wound closure compared to the saline control on both the 1st and 2nd weeks of treatment. Humic acid treatment for the wounds in the palate resulted in enhanced recovery compared to not only saline control but also chlorhexidine gluconate treatment.

Conclusion

In this study, humic acid was shown to enhance healing of oral wounds for the first time in the literature. These findings indicate that humic acid can be used as an alternative to current treatment methods for oral wounds.

Glycan recognition at the saliva - oral microbiome interface

The mouth is a first critical interface where most potentially harmful substances or pathogens contact the host environment. Adaptive and innate immune defense mechanisms are established there to inactivate or eliminate pathogenic microbes that traverse the oral environment on the way to their target organs and tissues. Protein and glycoprotein components of saliva play a particularly important role in modulating the oral microbiota and helping with the clearance of pathogens. It has long been acknowledged that glycobiological and glycoimmunological aspects play a pivotal role in oral host-microbe, microbe-host, and microbe-microbe interactions in the mouth. In this review, we aim to delineate how glycan-mediated host defense mechanisms in the oral cavity support human health. We will describe the role of glycans attached to large molecular size salivary glycoproteins which act as a first line of primordial host defense in the human mouth. We will further discuss how glycan recognition contributes to both colonization and clearance of oral microbes.

Realising the Potential of Urine and Saliva as Diagnostic Tools in Sport and Exercise Medicine

Accurate monitoring of homeostatic perturbations following various psychophysiological stressors is essential in sports and exercise medicine. Various biomarkers are routinely used as monitoring tools in both clinical and elite sport settings. Blood collection and muscle biopsies, both invasive in nature, are considered the gold standard for the analysis of these biomarkers in exercise science. Exploring non-invasive methods of collecting and analysing biomarkers that are capable of providing accurate information regarding exercise-induced physiological and psychological stress is of obvious practical importance. This review describes the potential benefits, and the limitations, of using saliva and urine to ascertain biomarkers capable of identifying important stressors that are routinely encountered before, during, or after intense or unaccustomed exercise, competition, over-training, and inappropriate recovery. In particular, we focus on urinary and saliva biomarkers that have previously been used to monitor muscle damage, inflammation, cardiovascular stress, oxidative stress, hydration status, and brain distress. Evidence is provided from a range of empirical studies suggesting that urine and saliva are both capable of identifying various stressors. Although additional research regarding the efficacy of using urine and/or saliva to indicate the severity of exercise-induced psychophysiological stress is required, it is likely that these non-invasive biomarkers will represent "the future" in sports and exercise medicine.

Post-weaning xenohormone intake affects adult rat submandibular gland in a sex-dependent manner

OBJECTIVES

We previously reported that maternal exposure to genistein and vinclozolin, ingested alone or in combination, affects submandibular salivary glands of rat offspring. Here, we investigated the responsiveness of submandibular gland when such xenohormone exposure occurs later in life.

MATERIALS AND METHODS

Chemicals were given orally to male and female Wistar rats (1 mg/kg body weight per day), from weaning to adulthood. Submandibular glands and plasma were collected at postnatal day 100 for histologic and molecular analysis.

RESULTS

Whereas no effect was observed in females, increases in granular convoluted tubules area coupled with a modification of salivary secretions were found in male submandibular glands. Genistein and vinclozolin similarly increased the mRNA expression of Cystatin C, Mucin 10, Growth factors, and plasmatic EGF. Negative correlations were found between the expressions of androgen receptor and EGF (-0.34; p < 0.05), TGFα (-0.52; p < 0.01), Mucin 10 (-0.43; p < 0.05), and Cystatin C (-0.42; p < 0.05) as well as between progesterone receptor and EGF (-0.56; p < 0.01). The Spearman correlation test revealed also a positive correlation between salivary EGF-mRNA expression and EGF in plasma (+0.32; p < 0.05).

CONCLUSION

Our findings confirm the sex-dependent sensitivity of submandibular salivary glands to dietary xenohormones and underline the influence of the exposure period.

Facile derivatization of ultratrace carboxylic acids in saliva for quantification by HPLC-MS/MS

It remains an issue to directly quantify trace biologically important carboxyl compounds in body fluids. Herein we propose an innovative method to determine α-lipoic acid, 2-(β-carboxyethyl)-6-hydroxy-2,7,8-trimethylchroman, prostaglandin E₂, cholic acid, and chenodeoxycholic acid in saliva. The method consists of two successive steps: fast and direct labeling of the target analytes with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide followed by ultrahigh-performance liquid chromatography-tandem mass spectrometry analysis. The method exhibited a wide linear range from 2.5 to 2500 pg/mL, with linear coefficients greater than 0.9963 and limits of detection and quantification as low as 0.10 and 0.33 pg/mL, respectively. The method precision was evaluated, with relative standard deviations ranging from 2.12% to 10.63% for intraday assays and from 2.98% to 12.88% for interday assays. The recoveries were measured by our spiking saliva samples with standards at three different levels, and ranged from 72.5% to 98.0%. Real applicability was validated by direct quantification of trace target analytes in human saliva, with simple pretreatment, use of a small sample volume, and a short analysis time. Graphical abstract Sequential steps to extract, label, and determine the ultratrace carboxylic acids in saliva. CDCA chenodeoxycholic acid, γ-CEHC 2-(β-carboxyethyl)-6-hydroxy-2,7,8-trimethylchroman, α-LA α-lipoic acid, PGE₂ prostaglandin E₂, UHPLC-MS/MS ultrahigh-performance liquid chromatography-tandem mass spectrometry.

Deterioration in saliva quality in patients with Sjögren's syndrome: impact of decrease in salivary epidermal growth factor on the severity of intraoral manifestations

Background

Sjögren’s syndrome (SS) is a chronic inflammatory autoimmune disease characterized by lymphocytic infiltration of the exocrine glands, especially the salivary and lacrimal glands. As a result of salivary gland dysfunction, most patients with SS have xerostomia related to a reduced salivary flow rate. In addition to the discomfort due to xerostomia, dry mouth can cause various intraoral manifestations such as refractory stomatitis, ulcer, and atrophic changes in the oral mucosa and tongue, and the patient’s quality of life (QoL) is severely impaired. These manifestations are believed to be caused mainly by a decrease in the clearance in the oral cavity owing to hyposalivation. However, because saliva has several beneficial physiological effects on the intraoral environment, qualitative changes in sialochemistry should also be considered a cause of the refractory intraoral manifestations in SS.

Main text

Salivary epidermal growth factor (EGF) is considered an important cytoprotective factor against injuries. It contributes to wound healing in the oral cavity and to maintenance of mucosal integrity in the oral cavity and gastrointestinal tract. We evaluated changes in salivary EGF levels and assessed the association between salivary EGF levels and the severity of intraoral manifestations in patients with SS. The following novel findings were obtained: (1) salivary EGF levels in SS patients were significantly lower than those in non-SS patients; (2) salivary EGF levels as well as the salivary flow rate decreased with the progression of SS; (3) with prolonged SS disease duration, salivary EGF levels decreased more rapidly than the salivary flow rate; and (4) decreases in salivary EGF levels significantly correlated with exacerbation of the oral health-related QoL in patients with SS.

Conclusions

The deterioration in saliva quality as well as lower intraoral clearance by hyposalivation could play a role in the pathogenesis of refractory intraoral manifestations in patients with SS. Our findings suggest a new target for therapeutic intervention for SS.

Histatins, wound healing, and cell migration

Wounds in the oral mucosa heal faster and more efficiently than those in the skin, although the mechanisms underlying these differences are not completely clear. In the last 10 years, a group of salivary peptides, the histatins, has gained attention on behalf of their ability to improve several phases of the wound-healing process. In addition to their roles as anti-microbial agents and in enamel maintenance, histatins elicit other biological effects, namely by promoting the migration of different cell types contained in the oral mucosa and in non-oral tissues. Histatins, and specifically histatin-1, promote cell adhesion and migration in oral keratinocytes, gingival and dermal fibroblasts, non-oral epithelial cells, and endothelial cells. This is particularly relevant, as histatin-1 promotes the re-epithelialization phase and the angiogenic responses by increasing epithelial and endothelial cell migration. Although the molecular mechanisms associated with histatin-dependent cell migration remain poorly understood, recent studies have pointed to the control of signaling endosomes and the balance of small GTPases. This review aimed to update the literature on the effects of histatins in cell migration, with a focus on wound healing. We will also discuss the consequences that this increasing field will have in disease and therapy design.

Oral Biofluid Biomarker Research: Current Status and Emerging Frontiers

Salivary diagnostics is a rapidly advancing field that offers clinicians and patients the potential of rapid, noninvasive diagnostics with excellent accuracy. In order for the complete realization of the potential of saliva, however, extensive profiling of constituents must be conducted and diagnostic biomarkers must be thoroughly validated. This article briefly overviews the process of conducting a study of salivary biomarkers in a patient cohort and highlights the studies that have been conducted on different classes of molecules in the saliva. Emerging frontiers in salivary diagnostics research that may significantly advance the field will also be highlighted.

Salivary and serum insulin-like growth factor (IGF-1) assays in anorexic patients

OBJECTIVES

The purpose of this study was to measure the salivary and serum free IGF-1 concentration of patients with anorexia nervosa (AN) in comparison to an average population.

METHODS

A controlled clinical trial was designed for an age- and gender-matched group of 121 AN patients and 77 healthy individuals. A clinical examination was made and blood and salivary samples were taken during the acute stage of AN (BMI < 15 kg/m²) in the first week of hospitalization. An enzyme immunoassay (ELISA) suitable for measuring free IGF-1 was used.

RESULTS

Anorexic patients had significant reductions in salivary unstimulated flow rate (UFR), pH and free IGF-1 levels in their saliva and serum. Significant correlations between serum IGF-1 and BMI; salivary IGF-1 and UFR and pH were detected.

CONCLUSIONS

Salivary and serum IGF-1 analyses appear to be a reliable biochemical indicator of malnutrition in AN patients. Measurement of salivary IGF-1 levels would allow new perspectives in monitoring AN in its early stages.

Myofibroblasts in Palatal Wound Healing: Prospects for the Reduction of Wound Contraction after Cleft Palate Repair

The surgical closure of orofacial clefts is considered to impair maxillary growth and dento-alveolar development. Wound contraction and subsequent scar tissue formation, during healing of these surgical wounds, contribute largely to these growth disturbances. The potential to minimize wound contraction and subsequent scarring by clinical interventions depends on the surgeon’s knowledge of the events responsible for these phenomena. Fibroblasts initiate wound contraction, but proto-myofibroblasts and mature myofibroblasts are by far the most important cells in this process. Myofibroblasts are characterized by their cytoskeleton, which contains alpha-smooth-muscle actin. Additionally, their contractile apparatus contains bundles of actin microfilaments and associated contractile proteins, such as non-muscle myosin. This contractile apparatus is thought to be the major force-generating element involved in wound contraction. After closure of the wound, the myofibroblasts disappear by apoptosis, and a less cellular scar is formed. A reduction of contraction and scarring might be obtained by inhibition of myofibroblast differentiation, stimulation of their de-differentiation, stimulation of myofibroblast apoptosis, or impairment of myofibroblast function. In this review, we will discuss all of these possibilities, which ultimately may lead to a better outcome of cleft palate surgery.

Saliva initiates the formation of pro-inflammatory macrophages in vitro

OBJECTIVES

Saliva can support oral wound healing, a process that requires a temporary inflammatory reaction. We have reported previously that saliva provokes a strong inflammatory response in oral fibroblasts. Bone marrow cells also give rise to macrophages, a heterogeneous subset of cell population involved in wound healing. Lipopolysaccharide (LPS) and interleukin 4 (IL-4) induce activation of pro-(M1), and anti-(M2) inflammatory macrophages, respectively. Yet, the impact of saliva on programming bone marrow cells into either M1 or M2 macrophages remains unclear .

DESIGN

Herein, we examined whether sterile saliva affects the in vitro process of macrophage polarization based on murine bone marrow cultures and RAW264.7 mouse macrophages.

RESULTS

We report that sterile saliva, similar to lipopolysaccharides, provoked a robust activation of the M1 phenotype which is characterized by a strong increase of the respective genes IL-12 and IL-6, based on a real-time gene expression analysis, and for IL-6 with immunoassay. Arginase-1 and Ym1, both genes characteristic for the M2 phenotype, were not considerably modulated by saliva. Inhibition of TLR4 signaling with TAK-242, blocking NFκB signaling with Bay 11-7085, but also autoclaving saliva greatly reduced the development of the M1 phenotype.

CONCLUSION

These data suggest that saliva activates the TLR4 dependent polarization into pro-inflammatory M1 macrophages in vitro.

Absolute quantification of 35 plasma biomarkers in human saliva using targeted MS

BACKGROUND

Although the use of human saliva for diagnosing disease has been known to be of great clinical potential, few attempts have been made so far to develop its use. In this work, we developed an MRM-MS approach for 35 plasma biomarkers using human saliva in a clinical environment.

METHODS & RESULTS

A 30-min micro LC-MS/MS run in MRM mode was conducted in order to quantify the 35 plasma proteins in human saliva. Sample preparation procedures were performed in quadruplicate and analyzed in duplicate. Results show that 32 of the 35 plasma proteins were quantified in human saliva using calibration curves in the 2- log10 dynamic ranges with excellent linearity.

DISCUSSION/CONCLUSION

Our MRM method is compatible with routine measurements in daily clinical practice.

Distinct phenotype and therapeutic potential of gingival fibroblasts

Gingiva of the oral mucosa provides a practical source to isolate fibroblasts for therapeutic purposes because the tissue is easily accessible, tissue discards are common during routine clinical procedures and wound healing after biopsy is fast and results in complete wound regeneration with very little morbidity or scarring. In addition, gingival fibroblasts have unique traits, including neural crest origin, distinct gene expression and synthetic properties and potent immunomodulatory functions. These characteristics may provide advantages for certain therapeutic approaches over other more commonly used cells, including skin fibroblasts, both in intraoral and extra-oral sites. However, identity and phenotype of gingival fibroblasts, like other fibroblasts, are still not completely understood. Gingival fibroblasts are phenotypically heterogeneous, and these…fibroblast subpopulations may play different roles in tissue maintenance, regeneration and pathologies. The purpose of this review is to summarize what is currently known about gingival fibroblasts, their distinct potential for tissue regeneration and their potential therapeutic uses in the future.

Saliva: A Cutting Edge in Diagnostic Procedures

The ability to monitor the health and disease status of the patient through saliva is a highly desirable goal for the health professionals. Considering the microconcentration of salivary constituents, saliva is explored to be diagnostic tool as it also meets the demands for an inexpensive, noninvasive and easy to use screening method. The incorporation of salivary diagnostics into clinical practice is gaining reality and will be of diagnostic value in the prospective future. The investigative use of saliva is not being applied only in dental health but also in various other systemic disorders. The advent of molecular techniques is gaining attention and this has triggered its application as a specific and sensitive biomarker in proteomics, genomics, and transcriptomics. This review discusses the basics of salivary diagnostics, expectoration techniques, and its application in various local and systemic disorders.

Salivary biomarkers: toward future clinical and diagnostic utilities

The pursuit of timely, cost-effective, accurate, and noninvasive diagnostic methodologies is an endeavor of urgency among clinicians and scientists alike. Detecting pathologies at their earliest stages can significantly affect patient discomfort, prognosis, therapeutic intervention, survival rates, and recurrence. Diagnosis and monitoring often require painful invasive procedures such as biopsies and repeated blood draws, adding undue stress to an already unpleasant experience. The discovery of saliva-based microbial, immunologic, and molecular biomarkers offers unique opportunities to bypass these measures by utilizing oral fluids to evaluate the condition of both healthy and diseased individuals. Here we discuss saliva and its significance as a source of indicators for local, systemic, and infectious disorders. We highlight contemporary innovations and explore recent discoveries that deem saliva a mediator of the body's physiological condition. Additionally, we examine the current state of salivary diagnostics and its associated technologies, future aspirations, and potential as the preferred route of disease detection, monitoring, and prognosis.

Expression and localization of trefoil factor family genes in rat submandibular glands

The trefoil factor (TFF) family, which comprises TFF1, TFF2 and TFF3, plays an essential role in epithelial regeneration within the gastrointestinal tract. All three TFFs are present in human saliva; TFF3 is the predominant trefoil peptide. Little is known about the expression and tissue distribution of TFFs in rats, which are commonly used as a model system for human studies. We investigated the localization of the TFF genes that encode secretory peptides in rat submandibular glands (SMG). All three TFFs were expressed in rat SMG, although their location varied. Substantial amounts of TFF1 were detected only in the cytoplasm of epithelial cells in the SMG granular convoluted tubules (GCT), while TFF2 and TFF3 were widely distributed in the cytoplasm of epithelial cells of intercalated ducts (ID), striated ducts (SD) and interlobular ducts (ILD). The three TFFs also were detected especially in the lumens of the SD and ILD. Semi-quantitative RT-PCR and in situ hybridization experiments confirmed TFF1, TFF2 and TFF3 mRNA expressions in the SMG. Greater expression of TFF peptides and mRNA was observed in male rats than in females. The broad expression of TFFs in rat SMG cells and lumens suggests that TFFs function in this organ by their secretion into the duct lumens. We also found differences in TFF expression profiles between rat and human SMG; therefore, caution should be exercised when using rats as a model for human TFF studies.

3-D neurohistology of transparent tongue in health and injury with optical clearing

Tongue receives extensive innervation to perform taste, sensory, and motor functions. Details of the tongue neuroanatomy and its plasticity in response to injury offer insights to investigate tongue neurophysiology and pathophysiology. However, due to the dispersed nature of the neural network, standard histology cannot provide a global view of the innervation. We prepared transparent mouse tongue by optical clearing to reveal the spatial features of the tongue innervation and its remodeling in injury. Immunostaining of neuronal markers, including PGP9.5 (pan-neuronal marker), calcitonin gene-related peptide (sensory nerves), tyrosine hydroxylase (sympathetic nerves), and vesicular acetylcholine transporter (cholinergic parasympathetic nerves and neuromuscular junctions), was combined with vessel painting and nuclear staining to label the tissue network and architecture. The tongue specimens were immersed in the optical-clearing solution to facilitate photon penetration for 3-dimensiontal (3-D) confocal microscopy. Taking advantage of the transparent tissue, we simultaneously revealed the tongue microstructure and innervation with subcellular-level resolution. 3-D projection of the papillary neurovascular complex and taste bud innervation was used to demonstrate the spatial features of tongue mucosa and the panoramic imaging approach. In the tongue injury induced by 4-nitroquinoline 1-oxide administration in the drinking water, we observed neural tissue remodeling in response to the changes of mucosal and muscular structures. Neural networks and the neuromuscular junctions were both found rearranged at the peri-lesional region, suggesting the nerve-lesion interactions in response to injury. Overall, this new tongue histological approach provides a useful tool for 3-D imaging of neural tissues to better characterize their roles with the mucosal and muscular components in health and disease.

Role of salivary vascular endothelial growth factor (VEGF) in palatal mucosal wound healing

The mucosa of alimentary tract heals more rapidly than cutaneous wounds. The underlying mechanisms of this enhanced healing have not been completely elucidated. Constant exposure to salivary growth factors has been shown to play a critical role in mucosal homeostasis and tissue repair. Angiogenesis also has an essential role in successful wound repair. One of the main angiogenic growth factors, vascular endothelial growth factor (VEGF), has a pleiotropic role in tissue repair via neovascularization, reepithelialization, and regulation of extracellular matrix. We have previously reported a critical role for salivary VEGF in bowel adaptation after small bowel resection. We hypothesize that salivary VEGF is an essential stimulus for oral mucosal tissue repair, and use the murine palatal wound model to test our hypothesis. In a loss-of-function experiment, we removed the primary source of VEGF production through selective submandibular gland (SMG) sialoadenectomy in a murine model and observed the effects on wound closure and neovascularization. We then performed a selective loss-of-function experiment using the protein VEGF-Trap to inhibit salivary VEGF. In a gain-of-function experiment, we supplemented oral VEGF following SMG sialoadenectomy. After SMG sialoadenectomy, there was significant reduction in salivary VEGF level, wound closure, and vessel density. Lower levels of salivary VEGF were correlated with impaired neovascularization and reepithelialization. The selective blockade of VEGF using VEGF-Trap resulted in a similar impairment in wound healing and neovascularization. The sole supplementation of oral VEGF after SMG sialoadenectomy rescued the impaired wound healing phenotype and restored neovascularization to normal levels. These data show a novel role for salivary-VEGF in mucosal wound healing, and provide a basis for the development of novel therapeutics aimed at augmenting wound repair of the oral mucosa, as well as wounds at other sites in the alimentary tract.

Endocannabinoids mediate hyposalivation induced by inflammogens in the submandibular glands and hypothalamus

OBJECTIVE

The aim of this study was to investigate the factors that could participate on salivary glands hypofunction during inflammation and the participation of endocannabinoids in hyposalivation induced by the presence of inflammogens in the submandibular gland (SMG) or in the brain.

DESIGN

Salivary secretion was assessed in the presence of inflammogens and/or the cannabinoid receptor antagonist AM251 in the SMG or in the brain of rats. At the end of the experiments, some systemic and glandular inflammatory markers were measured and histopathological analysis was performed.

RESULTS

The inhibitory effect observed 1h after lipopolysaccharide (LPS, 50μg/50μl) injection into the SMG (ig) was completely prevented by the injection of AM251 (5μg/50μl) by the same route (P<0.05). The LPS (ig)-induced increase in PGE2 content was not altered by AM251 (ig), while the glandular production of TNFα induced by the endotoxin (P<0.001) was partially blocked by it. Also, LPS injection produced no significant changes in the wet weight of the SMG neither damage to lipid membranes of its cells, nor significant microscopic changes in them, after hispopathological analysis, compared to controls. Finally, TNFα (100ng/5μl) injected intracerebro-ventricularly (icv) inhibited methacholine-induced salivary secretion evaluated 30min after (P<0.01), but the previous injection of AM251 (500ng/5μl, icv) prevented completely that effect.

CONCLUSION

We conclude that endocannabinoids mediate the hyposialia induced by inflammogens in the SMG and in the brain. The hypofunction would be due to changes on signalling pathway produced by inflammatory compounds since anatomical changes were not observed.

Mining the salivary proteome with grating-coupled surface plasmon resonance imaging and surface plasmon coupled emission microarrays

Biological indicators have numerous and widespread utility in personalized medicine, but the measurement of these indicators also poses many technological and practical challenges. Blood/plasma has typically been used as the sample source with which to measure these indicators, but the invasiveness associated with sample procurement has led to increased interest in saliva as an attractive alternative. However, there are unique issues associated with the measurement of saliva biomarkers. These issues are compounded by the imperfect correlation between saliva and plasma with respect to biomarker profiles. In this manuscript, we address the technical challenges associated with saliva biomarker quantification. We describe a high-content microarray assay that employs both grating-coupled surface plasmon resonance imaging and surface plasmon-coupled emission modalities in a highly sensitive assay with a large dynamic range. This powerful approach provides the tools to map the proteome of saliva, which in turn should greatly enhance the utility of salivary biomarker profiles in personalized medicine.

The scientific exploration of saliva in the post-proteomic era: from database back to basic function

The proteome of human saliva can be considered as being essentially completed. Diagnostic markers for a number of diseases have been identified among salivary proteins and peptides, taking advantage of saliva as an easy-to-obtain biological fluid. Yet, the majority of disease markers identified so far are serum components and not intrinsic proteins produced by the salivary glands. Furthermore, despite the fact that saliva is essential for protecting the oral integuments and dentition, little progress has been made in finding risk predictors in the salivary proteome for dental caries or periodontal disease. Since salivary proteins, and in particular the attached glycans, play an important role in interactions with the microbial world, the salivary glycoproteome and other post-translational modifications of salivary proteins need to be studied. Risk markers for microbial diseases, including dental caries, are likely to be discovered among the highly glycosylated major protein species in saliva. This review will attempt to raise new ideas and also point to under-researched areas that may hold promise for future applicability in oral diagnostics and prediction of oral disease.

Capability of tissue stem cells to organize into salivary rudiments

Branching morphogenesis (BrM), an essential step for salivary gland development, requires epithelial-mesenchymal interactions. BrM is impaired when the surrounding mesenchyme is detached from the salivary epithelium during the pseudoglandular stage. It is believed that the salivary mesenchyme is indispensable for BrM, however, an extracellular matrix gel with exogenous EGF can be used as a substitute for the mesenchyme during BrM in the developing salivary epithelium. Stem/progenitor cells isolated from salivary glands in humans and rodents can be classified as mesenchymal stem cell-like, bone-marrow-derived, duct cell-like, and embryonic epithelium-like cells. Salivary-gland-derived progenitor (SGP) cells isolated from duct-ligated rats, mice, and swine submandibular glands share similar characteristics, including intracellular laminin and α6β1-integrin expression, similar to the embryonic salivary epithelia during the pseudoglandular stage. Progenitor cells also isolated from human salivary glands (human SGP cells) having the same characteristics differentiate into hepatocyte-like cells when transplanted into the liver. Similar to the dissociated embryonic salivary epithelium, human SGP cells aggregate to self-organize into branching organ-like structures on Matrigel plus exogenous EGF. These results suggest the possibility that tissue stem cells organize rudiment-like structures, and the embryonic cells that organize into whole tissues during development are preserved even in adult tissues.

Chaperonin containing T-complex polypeptide (CCT) subunit expression in oral mucosal wounds and fibroblasts

Mucosal wound healing in adults has been reported to feature diminished scar formation compared to healing skin wounds. We sought to determine if the expression pattern of chaperonin containing T-complex polypeptide (CCT) subunits in mucosal wounds and fibroblasts is different from that observed in skin wounds and fibroblasts. We found that CCT-beta is the only subunit message to be reduced in wounded mucosa versus unwounded control, and this reduction was confirmed at the protein level. In contrast, mRNA levels of CCT-zeta, -delta, -eta, and -epsilon were significantly increased in mucosal wounds. The increase in CCT-eta was also confirmed at the protein level. Expression levels of CCT-alpha, -beta, -delta; -epsilon, and -theta mRNAs were significantly increased in adult mucosal fibroblasts in culture compared to skin-derived fibroblasts. Western blot analyses confirmed a modest increase in CCT-beta in adult mucosal fibroblasts relative to skin fibroblasts, but CCT-eta protein was unaffected. These differences may contribute to the reported difference in healing outcomes between these two tissue types.

Preferential recruitment of bone marrow-derived cells to rat palatal wounds but not to skin wounds

OBJECTIVE

To investigate the contribution of bone marrow-derived cells to oral mucosa wounds and skin wounds.

BACKGROUND

Bone marrow-derived cells are known to contribute to wound healing, and are able to differentiate in many different tissue-specific cell types. As wound healing in oral mucosa generally proceeds faster and with less scarring than in skin, we compared the bone marrow contribution in these two tissues.

DESIGN

Bone marrow cells from GFP-transgenic rats were transplanted to irradiated wild-type rats. After recovery, 4-mm wounds were made in the mucoperiosteum or the skin. Two weeks later, wound tissue with adjacent normal tissue was stained for GFP-positive cells, myofibroblasts (a-smooth muscle actin), activated fibroblasts (HSP47), and myeloid cells (CD68).

RESULTS

The fraction of GFP-positive cells in unwounded skin (19%) was larger than in unwounded mucoperiosteum (0.7%). Upon wounding, the fraction of GFP-positive cells in mucoperiosteum increased (8.1%), whilst it was unchanged in skin. About 7% of the myofibroblasts in both wounds were GFP-positive, 10% of the activated fibroblasts, and 25% of the myeloid cells.

CONCLUSIONS

The results indicate that bone marrow-derived cells are preferentially recruited to wounded oral mucosa but not to wounded skin. This might be related to the larger healing potential of oral mucosa.