Oral epithelial stem cells in tissue maintenance and disease:the first steps in a long journey

The identification and characterization of stem cells is a major focus of developmental biology and regenerative medicine.The advent of genetic inducible fate mapping techniques has made it possible to precisely label specific cell populations and to follow their progeny over time.When combined with advanced mathematical and statistical methods,stem cell division dynamics can be studied in new and exciting ways.Despite advances in a number of tissues,relatively little attention has been paid to stem cells in the oral epithelium.This review will focus on current knowledge about adult oral epithelial stem cells,paradigms in other epithelial stem cell systems that could facilitate new discoveries in this area and the potential roles of epithelial stem cells in oral disease.     

Diagnostic aids for detection of oral precancerous conditions

Oral cancer has a tendency to be detected at late stage which is detrimental to the patients because of its high mortality and morbidity rates. Early detection of oral cancer is therefore important to reduce the burden of this devastating disease. In this review article, the most common oral precancerous lesions are discussed and the importance of early diagnosis is emphasized. In addition, the most common non-invasive oral cancer devices that can aid the general practitioners in early diagnosis are also discussed.     

Loss of Ab-nerve endings associated with the Merkel cell-neurite complex in the lesional oral mucosa epithelium of lichen planus and hyperkeratosis

The Merkel cell-neurite complex initiates the perception of touch and mediates Ab slowly adapting type I responses. Lichen planus is a chronic inflammatory autoimmune disease with T-cell-mediated inflammation, whereas hyperkeratosis is characterized with or without epithelial dysplasia in the oral mucosa. To determine the effects of lichen planus and hyperkeratosis on the Merkel cell-neurite complex, healthy oral mucosal epithelium and lesional oral mucosal epithelium of lichen planus and hyperkeratosis patients were stained by immunohistochemistry (the avidin-biotin-peroxidase complex and double immunofluorescence methods) using pan cytokeratin, 20 (K20, a Merkel cell marker), and neurofilament 200 (NF200, a myelinated Ab- and Ad-nerve fibre marker) antibodies. NF200-immunoreactive (ir) nerve fibres in healthy tissues and in the lesional oralmucosa epitheliumof lichen planus and hyperkeratosis were counted and statistically analysed. In the healthy oral mucosa, K20-positive Merkel cells with and without close association to the intraepithelial NF200-ir nerve fibres were detected. In the lesional oral mucosa of lichen planus and hyperkeratosis patients, extremely rare NF200-ir nerve fibres were detected only in the lamina propria. Compared with healthy tissues, lichen planus and hyperkeratosis tissues had significantly decreased numbers of NF200-ir nerve fibres in the oral mucosal epithelium. Lichen planus and hyperkeratosis were associated with the absence of Ab-nerve endings in the oral mucosal epithelium. Thus, we conclude that mechanosensation mediated by the Merkel cell-neurite complex in the oral mucosal epithelium is impaired in lichen planus and hyperkeratosis.     

Spindle cell lipoma of the mandibular mucogingival junction:a case report of unusual oral neoplasm

Spindle cell lipoma (SCL) is a benign lipomatous neoplasm typically located in the posterior neck and back of older males. It presents as a well-circumscribed mass in the buccal mucosa, tongue, floor o...     

Investigation of basement membrane proteins in a case of granular cell ameloblastoma

Granular cell ameloblastoma is a rare,benign neoplasm of the odontogenic epithelium.A case of massive granular cell ameloblastoma in a 44-year-old Thai female is reported.Histopathological features displayed a follicular type of ameloblastoma with an accumulation of granular cells residing within the tumor follicles.After treatment by partial mandibulectomy,the patient showed a good prognosis without recurrence in a 2-year follow-up.To characterize the granular cells in ameloblastoma,we examined the expression of basement membrane(BM) proteins,including collagen type IV,laminins 1 and 5 and fibronectin using immunohistochemistry.Except for the granular cells,the tumor cells demonstrated a similar expression of BM proteins compared to follicular and plexiform ameloblastomas in our previous study,whereas the granular cells showed strong positivity to laminins 1 and 5 and fibronectin.The increased fibronectin expression in granular cells suggests a possibility of age-related transformation of granular cells in ameloblastoma.     

Alanine racemase is essential for the growth and interspecies competitiveness of Streptococcus mutans

D-alanine (D-Ala) is an essential amino acid that has a key role in bacterial cell wall synthesis. Alanine racemase (Alr) is a unique enzyme that interconverts L-alanine and D-alanine in most bacteria, making this enzyme a potential target for antimicrobial drug development. Streptococcus mutans is a major causative factor of dental caries. The factors involved in the survival, virulence and interspecies interactions of S. mutans could be exploited as potential targets for caries control. The current study aimed to investigate the physiological role of Alr in S. mutans. We constructed alr mutant strain of S. mutans and evaluated its phenotypic traits and interspecies competitiveness compared with the wild-type strain. We found that alr deletion was lethal to S. mutans. A minimal supplement of D-Ala (150μg·mL?1) was required for the optimal growth of the alr mutant. The depletion of D-alanine in the growth medium resulted in cell wall perforation and cell lysis in the alr mutant strain. We also determined the compromised competitiveness of the alr mutant strain relative to the wild-type S. mutans against other oral streptococci (S. sanguinis or S. gordonii), demonstrated using either conditioned medium assays or dual-species fluorescent in situ hybridization analysis. Given the importance and necessity of alr to the growth and competitiveness of S. mutans, Alr may represent a promising target to modulate the cariogenicity of oral biofilms and to benefit the management of dental caries.     

A post-classical theory of enamel biomineralization… and why we need one

Enamel crystals are unique in shape,orientation and organization.They are hundreds of thousands times longer than they are wide,run parallel to each other,are oriented with respect to the ameloblast membrane at the mineralization front and are organized into rod or interrod enamel.The classical theory of amelogenesis postulates that extracellular matrix proteins shape crystallites by specifically inhibiting ion deposition on the crystal sides,orient them by binding multiple crystallites and establish higher levels of crystal organization.Elements of the classical theory are supported in principle by in vitro studies;however,the classical theory does not explain how enamel forms in vivo.In this review,we describe how amelogenesis is highly integrated with ameloblast cell activities and how the shape,orientation and organization of enamel mineral ribbons are established by a mineralization front apparatus along the secretory surface of the ameloblast cell membrane.     

The clinical effectiveness of reflectance optical spectroscopy for the in vivo diagnosis of oral lesions

Optical spectroscopy devices are being developed and tested for the screening and diagnosis of oral precancer and cancer lesions. This study reports a device that uses white light for detection of suspicious lesions and green–amber light at 545 nm that detect tissue vascularity on patients with several suspicious oral lesions. The clinical grading of vascularity was compared to the histological grading of the biopsied lesions using specific biomarkers. Such a device, in the hands of dentists and other health professionals, could greatly increase the number of oral cancerous lesions detected in early phase. The purpose of this study is to correlate the clinical grading of tissue vascularity in several oral suspicious lesions using the IdentafiH system with the histological grading of the biopsied lesions using specific vascular markers. Twenty-one patients with various oral lesions were enrolled in the study. The lesions were visualized using IdentafiH device with white light illumination, followed by visualization of tissue autofluorescence and tissue reflectance. Tissue biopsied was obtained from the all lesions and both histopathological and immunohistochemical studies using a vascular endothelial biomarker（CD34） were performed on these tissue samples. The clinical vascular grading using the green–amber light at 545 nm and the expression pattern and intensity of staining for CD34 in the different biopsies varied depending on lesions, grading ranged from 1 to3. The increase in vascularity was observed in abnormal tissues when compared to normal mucosa, but this increase was not limited to carcinoma only as hyperkeratosis and other oral diseases, such as lichen planus, also showed increase in vascularity. Optical spectroscopy is a promising technology for the detection of oral mucosal abnormalities; however, further investigations with a larger population group is required to evaluate the usefulness of these devices in differentiating benign lesions from potentially malignant lesions.     

Engineered three-dimensional rabbit oral epithelial-mesenchymal-muscular hybrid sheets

Regenerative muscles are required for swallowing and mastication, and are important for functional recovery from diseases involving oral muscular defects. Therefore, we generated three-layer hybrid sheets, similar to oral mucosal structures containing submucosal muscles, using rabbit oral mucosa epithelial, mesenchymal, and myoblastic progenitor cells, and examined the structural proteins. Each cell type was obtained from rabbit oral mucosa using enzymatic digestion. Isolated mesenchymal and myoblastic cells were multi-differentiated into osteoblasts, adipocytes, and chondrocytes or myotubes. Isolated epithelial cells were cultured on collagen gels containing isolated mesenchymal cells for 2 weeks, and these epithelial–mesenchymal cell sheets were laminated onto myoblastic cell sheets. The engineered hybrid sheets were multi-stratified in the epithelial and myoblastic layers in a time-dependent manner, expressing intermediate cytoskeletal filament proteins of epithelium and muscle. Hybrid sheets also expressed extracellular matrix basement membrane proteins. Immature cell markers for epithelial and myoblastic cells were observed continuously in hybrid sheet cultures. We established engineered three-dimensional rabbit oral mucosa hybrid sheets containing each immature cell type in vitro.     

Progress toward understanding the contribution of alkali generation in dental biofilms to inhibition of dental caries

Alkali production by oral bacteria is believed to have a major impact on oral microbial ecology and to be inibitory to the initiation and progression of dental caries.A substantial body of evidence is beginning to accumulate that indicates the modulation of the alkalinogenic potential of dental biofilms may be a promising strategy for caries control.This brief review highlights recent progress toward understanding molecular genetic and physiologic aspects of important alkali-generating pathways in oral bacteria,and the role of alkali production in the ecology of dental biofilms in health and disease.     

Oral mucosal lipids are antibacterial against Porphyromonas gingivalis, induce ultrastructural damage, and alter bacterial lipid and protein compositions

Oral mucosal and salivary lipids exhibit potent antimicrobial activity for a variety of Gram-positive and Gram-negative bacteria;however,little is known about their spectrum of antimicrobial activity or mechanisms of action against oral bacteria.In this study,we examine the activity of two fatty acids and three sphingoid bases against Porphyromonas gingivalis,an important colonizer of the oral cavity implicated in periodontitis.Minimal inhibitory concentrations,minimal bactericidal concentrations,and kill kinetics revealed variable,but potent,activity of oral mucosal and salivary lipids against P.gingivalis,indicating that lipid structure may be an important determinant in lipid mechanisms of activity against bacteria,although specific components of bacterial membranes are also likely important.Electron micrographs showed ultrastructural damage induced by sapienic acid and phytosphingosine and confirmed disruption of the bacterial plasma membrane.This information,coupled with the association of treatment lipids with P.gingivalis lipids revealed via thin layer chromatography,suggests that the plasma membrane is a likely target of lipid antibacterial activity.Utilizing a combination of two-dimensional in-gel electrophoresis and Western blot followed by mass spectroscopy and N-terminus degradation sequencing we also show that treatment with sapienic acid induces upregulation of a set of proteins comprising a unique P.gingivalis stress response,including proteins important in fatty acid biosynthesis,metabolism and energy production,protein processing,cell adhesion and virulence.Prophylactic or therapeutic lipid treatments may be beneficial for intervention of infection by supplementing the natural immune function of endogenous lipids on mucosal surfaces.     

Mesenchymal Stem Cells and Tooth Engineering

Tooth loss compromises human oral health. Although several prosthetic methods, such as artificial denture and dental implants, are clinical therapies to tooth loss problems, they are thought to have safety and usage time issues. Recently, tooth tissue engineering has attracted more and more attention. Stem cell based tissue engineering is thought to be a promising way to replace the missing tooth. Mesenchymal stem cells （MSCs） are multipotent stem cells which can differentiate into a variety of cell types. The potential MSCs for tooth regeneration mainly include stem cells from human exfoliated deciduous teeth （SHEDs）, adult dental pulp stem cells （DPSCs）, stem cells from the apical part of the papilla （SCAPs）, stem cells from the dental follicle （DFSCs）, periodontal ligament stem cells （PDLSCs） and bone marrow derived mesenchymal stem cells （BMSCs）. This review outlines the recent progress in the mesenchymal stem cells used in tooth regeneration.     

Halitosis:the multidisciplinary approach

Halitosis,bad breath or oral malodour are all synonyms for the same pathology. Halitosis has a large social and economic impact. For the majority of patients suffering from bad breath,it causes embarrassment and affects their social communication and life. Moreover,halitosis can be indicative of underlying diseases. Only a limited number of scientific publications were presented in this field until 1995. Ever since,a large amount of research is published,often with lack of evidence. In general,intraoral conditions,like insufficient dental hygiene,periodontitis or tongue coating are considered to be the most important cause (85%) for halitosis. Therefore,dentists and periodontologists are the first-line professionals to be confronted with this problem. They should be well aware of the origin,the detection and especially of the treatment of this pathology. In addition,ear-nose-throat-associated (10%) or gastrointestinal/ endocrinological (5%) disorders may contribute to the problem. In the case of halitophobia,psychiatrical or psychological problems may be present. Bad breath needs a multidisciplinary team approach:dentists,periodontologists,specialists in family medicine,ear-nose-throat surgeons,internal medicine and psychiatry need to be updated in this field,which still is surrounded by a large taboo. Multidisciplinary bad breath clinics offer the best environment to examine and treat this pathology that affects around 25% of the whole population. This article describes the origin,detection and treatment of halitosis,regarded from the different etiological origins.     

Immunobiology of Facial Nerve Repair and Regeneration

Immunobiological study is a key to revealing the important basis of facial nerve repair and regeneration for both research and development of clinic treatments. The microenvironmental changes around an injuried facial motoneuron, i.e., the aggregation and expression of various types of immune cells and molecules in a dynamic equilibrium, impenetrate from the start to the end of the repair of an injured facial nerve. The concept of "immune microenvironment for facial nerve repair and regeneration", mainly concerns with the dynamic exchange between expression and regulation networks and a variaty of immune cells and immune molecules in the process of facial nerve repair and regeneration for the maintenance of a immune microenvironment favorable for nerve repair. Investigation on microglial activation and recruitment, T cell behavior, cytokine networks, and immunological cellular and molecular signaling pathways in facial nerve repair and regeneration are the current hot spots in the research on immunobiology of facial nerve injury. The current paper provides a comprehensive review of the above mentioned issues. Research of these issues will eventually make immunological interventions practicable treatments for facial nerve injury in the clinic.     

Artemisinins inhibit oral candidiasis caused by Candida albicans through the repression on its hyphal development

<正>Candida albicans is the most abundant fungal species in oral cavity.As a smart opportunistic pathogen,it increases the virulence by switching its forms from yeasts to hyphae and becomes the major pathogenic agent for oral candidiasis.However,the overuse of current clinical antifungals and lack of new types of drugs highlight the challenges in the antifungal treatments because of the drug resistance and side effects.Anti-virulence strategy is proved as a practical way to develop new type...     

Low-grade myofibroblastic sarcoma of the palate

Low-grade myofibroblastic sarcoma(LGMS) is a rare,malignant tumor with myofibroblastic differentiation.Despite it being classified as a distinct entity by the World Health Organization,a few cases were reported in the oral and maxillofacial region.Here,a LGMS developed on the palate of a 73-year-old man who presented with a 1-cm tumor on the posterior border of the palate.Based on the histological and immunohistochemical features,a diagnosis of LGMS was established.The tumor was resected,and no recurrence was observed over 2 years.Although the tongue is the most preferred site for LGMS,it may occur in any region of the oral cavity.     

Oral polymorphonuclear neutrophil characteristics in relation to oral health:a cross-sectional,observational clinical study

Polymorphonuclear neutrophils (PMNs) have a major role in the innate immune system. However, little is known about PMN contribution in relation to oral health. The objective of this study was to investigate the numbers and functional characteristics of oral PMNs (oPMNs) compared with circulatory PMNs (cPMNs). Oral rinse and venous blood samples were obtained from 268 systemically and orally healthy volunteers in a cross-sectional observational study. PMN counts, cell cycle analysis and cellular activation state were investigated. Also, reactive oxygen species (ROS) production was analyzed, with and without bacterial stimulation (Fusobacterium nucleatum). In males, 1.2 × 106 ± 1.0 × 106 oPMNs were collected, and showed a tendency to correlate with the levels of gingival bleeding (r=0.215, P=0.008). Comparable oPMNs counts were found among females (1.0 × 106 ± 0.7 × 106). More late-stage apoptotic/necrotic cells were found among the oPMNs (53.1%) compared with the cPMNs (8.5%;Po0.001). Without additional stimulation, oPMNs were more activated than cPMNs, as indicated by higher expression of CD11b, CD63 and CD66b, and higher constitutive ROS levels (Po0.001). Notably, in response to bacterial stimulation, oPMNs released comparable ROS levels as cPMNs (P=0.042). In conclusion, this study provides data on viable oPMNs showing high levels of activation in orally and systemically healthy individuals, free of apparent caries lesions and periodontal disease. These data suggests that although the oPMNs are in a more mature stage of their life cycle compared with the cPMNs, oPMNs are still responsive to stimulation, which indicates their functional potential and possible contribution to a healthy oral ecosystem.     

Characterization of Fusobacterium nucleatum ATCC 23726 adhesins involved in strain-specific attachment to Porphyromonas gingivalis

Bacterial adherence is an essential virulence factor in pathogenesis and infection. Fusobacterium nucleatum has a central role in oral biofilm architecture by acting as a bridge between early Gram-positive and late Gram-negative colonizers that do not otherwise adhere to each other. In this study, we survey a key adherence interaction of F. nucleatum with Porphyromonas gingivalis, and present evidence that multiple fusobacterial adhesins have a role in the attachment of F. nucleatum ATCC 23726 to P. gingivalis in a highly strain-dependent manner. Interaction between these species displayed varying sensitivities to arginine, galactose and lactose. Arginine was found to hamper coaggregation by at least 62%and up to 89%with several P. gingivalis strains and galactose inhibition ranged from no inhibition up to 58%with the same P. gingivalis strains. Lactose consistently inhibited F. nucleatum interaction with these P. gingivalis strains ranging from 40% to 56%decrease in coaggregation. Among the adhesins involved are the previously described Fap2 and surprisingly, RadD, which was described in an earlier study for its function in attachment of F. nucleatum to Gram-positive species. We also provide evidence for the presence of at least one additional adhesin that is sensitive to arginine but unlike Fap2 and RadD, is not a member of the autotransporter family type of fusobacterial large outer membrane proteins. The strain-specific binding profile of multiple fusobacterial adhesins to P. gingivalis highlights the heterogeneity and complexity of interspecies interactions in the oral cavity.     

The progenitors of inner ear hair cells and their regulating genes

Hair cells in the mammalian inner ear are very fragile and are often injured as a result of acoustic trauma or exposure to ototoxic drugs (cisplatin, aminoglycosides, etc)[1]. In amphibians and birds, spontaneous post-injury regeneration of all inner ear sensory hair cell occurs, while in the mammalian cochlea, such hearing loss is usually permanent as there are currently no treatments that can lead to post-injury hair cell regeneration.     

transcervical approach for resection of lateral skull base tumors

Objectives Conventional approaches for removal of lateral skull base tumors, including transmandibular, infratemporal fossa, preauricular transzygmatic subtemporal approaches, are major invasive procedures that often sacrifice hearing and cause abnormal occlusion and cosmetic defects. Reports of the transcervical approach for resection of skull base tumors are rare, although it was described for resection of clival chordomas in as early as 1966. The purpose of this study is to review our experiences in management of lateral skull base tumors using the transcervical approach. Study Design Retrospective chart review. Methods Six lateral skull base tumor cases treated with transcervical approach procedures were reviewed, including the medical records. Results There were 4 males and 2 females. Age ranged from 12 through 52 years. Histopathological diagnoses included malignant schwannoma(n = 1), malignant carotid body tumor(n = 1), heamangioma(n=1), schwannoma (n=2) and pleomorphic adenoma (n = 1). Transcervical techniques were used in all cases with the use of microscope in the lateral skull base area. Complete tumor removal was achieved in all cases. Postoperative radiotherapy was implemented in 1 case of malignant schwannoma and 1 case of malignant carotid body tumor. Jugular foramen syndrome occurred as a surgical complication in 1 case of malignant Schwannoma of the vagus nerve. There was no tumor recurrence during the 10 - 42 month follow-up period. Conclusion Compared with conventional approaches, the transcervical approach provides a easy, safe, minimal invasive and effective procedure for removal of selected lateral skull base tumors.