Mast cells of the human gingiva

By way of degranulation, the mast cells release a number of biologically active substances into the connective tissue. The present study is concerned with the relation of the gingival mast cells to the pathogenesis of gingivitis. Following fixation in Newcomer's fluid and non-aqueous staining at pH 0.5 in acridine orange¹, topographically defined zones of sections of normal and inflamed marginal gingiva, histologically classified with regard to degree of inflammation, of 56 different individuals have been studied in the fluorescence microscope. The human gingiva was found to be comparatively rich in mast cells. Three main morphological variants were observed and their topographical distribution within the tissue have been described. Marked differences in stainability between mast cells of different areas of the connective tissue have been recorded, and correlated to the state of inflammation, In spite of individual variations in mast cell density, definite patterns of frequency and distribution were observed. The number of mast cells appeared inversely correlated to the density and distribution of the inflammatory cellular exudate within the pocket area of the connective tissue. Consequently, normal gingivae generally contained more mast cells per tissue unit than the moderately inflamed tissue, which, in turn, contained more than the severely inflamed gingivae. Exceptions were found in some moderately inflamed, fibrous gingiva with evidence of strong fibroblastic activity, where there was an increased number of mast cells. On basis of the distribution, frequency and stainability of the mast cells of the gingiva, it is suggested that the mast cells of the regions adjacent to the tooth are subject to an enzymatic degranulation as elicited by products elaborated by the gingival bacterial plaque or possibly by local antigen-antibody interactions. Substances released by degranulation may then act as mediators during the course of the inflammatory process as well as contribute to the local resistance against injury.     

Mast cell distribution in oral tissues of germ-free vs. conventional beagle dogs.

Light microscopic examination of the mast cell distribution in various oral tissues in germ-free and conventional beagle dogs revealed no differences between the two animals. Mast cells were observed in all tissues examined, with an increasing order of incidence as follows: cervical lymph node, parotid and submandibular glands, marginal gingivae, buccal mucosa and the middle one-third of the tongue. All four types (round, oval, elongated, and pseudopodial) of mast cells cell shapes previously described in the literature were observed. The marginal gingivae associated with the mandibular, second bicuspids was examined by light microscopy and was classified as to degree of inflammatory involvement. In a comparison of germ-free and conventional animals, the distribution of the degree of inflammation proved to be random. Correlation between mast cell densities and the degree of inflammatory infiltration was not statistically significant. However, mast cells tended to decrease as the inflammation became more severe. Electron microscopic examination of mast cells in the buccal mucosa revealed no difference in morphology of cells from germ-free or conventional animals. Cytoplasmic granules were of two basic types, one exhibited an amorphous matrix of uniform density and the other consisted of laminated coils of various sizes and densities.     

Mast cells in human odontogenic cysts

Mast cells have been shown to be present in substantial numbers in both nonkeratinizing and keratinizing odontogenic cysts and could be seen in the connective tissue capsule and the epithelial lining. Within the cyst capsule, mast cells were more prevalent just beneath the epithelium than in deeper areas. This distribution pattern for mast cells is in accord with the histochemical picture for heparin staining in odontogenic cysts. In the non-keratinizing cysts, there appeared to be some trend towards mast cells being associated with increasing inflammation but not in the odontogenic keratocyst. No evidence could be found for distinct mast cell subpopulations in odontogenic cysts. The presence of mast cells in odontogenic cyst could contribute to their pathogenesis in several ways.     

Quantification of mast cells in different stages of human periodontal disease

OBJECTIVE AND METHODS: Among the cells involved in immune and inflammatory responses in periodontal disease, mast cells have been shown to be capable of generating a large number of biologically active substances. The present study was undertaken to identify and quantify the presence of mast cells in different stages of human periodontal disease using histochemical (toluidine blue) and immunohistochemical (tryptase-positive mast cells) techniques. RESULTS: Mast cell densities (cells per mm(2)) were significantly increased in chronic periodontitis/gingivitis lesions compared with clinically healthy gingival tissues (Health) uniquely by immunohistochemical technique. Interestingly, mast cells were distributed specially in close apposition to mononuclear cells. CONCLUSIONS: In human periodontal disease there is an increase in the number of mast cells that may be participating either in the destructive events or in the defense mechanism of periodontal disease via secretion of cytokines, including perpetuation of the Th2 response, and cellular migration and healing processes.     

Relationship between mast cell degranulation and inflammation in the oral cavity

Mast cells are granule-containing secretory cells which are distributed preferentially about the microvascular bed in oral mucosa. This work examined the contribution of mast cell mediators to inflammation in the oral cavity. Mast cells in oral tissues expressed the serine proteases, tryptase and chymase, with a minor subpopulation being chymase-negative. Mast cells contained the cytokine tumour necrosis factor-α (TNF) in their granules. Degranulation of mast cells was a consistent feature of inflammation lesions (lichen planus, gingivitis, pulpitis, periapical inflammation). In lichen planus, intracellular stores of TNF were depleted, and expression of mRNA for TNF was upregulated, indicating ongoing production and release of the cytokine. The density of mast cells in tissue compartments was related to the level of expression of E-selectin, an endothelial adhesion molecule which is known to be induced in skin by TNF derived from degranulating mast cells. Further attention should be directed toward the role of mast cell products, particularly TNF, in inflammation in the oral cavity.     

Substance P and mast cells: preliminary histologic analysis of the human temporomandibular joint

PURPOSE: Neuropeptide-containing nerves can serve as a mechanism for nervous system regulation of host defense responses. Because bacteria associated with reactive arthritis have been identified in the temporomandibular joint (TMJ), this study investigates whether the presence of substance P (SP) neuropeptide-containing nerves and mast cells can be identified in the TMJ. MATERIAL AND METHODS: Posterior bilaminar tissue removed during TMJ surgery from 9 women was evaluated for the presence of neuropeptide-containing nerves by staining with a monoclonal antibody to SP. Staining of the TMJ tissue sections with 0.5% toluidine blue was performed to identify the presence of mast cells. RESULTS: SP-containing nerves and mast cells were identified within the posterior bilaminar tissue associated with the vasculature. CONCLUSIONS: The presence of neuropeptide nerves and mast cells within the TMJ has been shown. Mast cell degranulation products and SP release can contribute to TMJ inflammation.     

Comparative immunohistochemical study of the presence of mast cells in apical granulomas and periapical cysts: possible role of mast cells in the course of human periapical lesions

Cells other than macrophages and lymphocytes have recently been shown capable of producing cytokines and mediators. Among these are mast cells, a cell population now recognized for its immunoregulatory properties. Little is known about the complex interactions between cells, cytokines, and other inflammatory elements in periapical lesions. The objective of this investigation was to determine the immunohistochemical pattern of expression of mast cells tryptase in periapical lesions based on study of 20 apical granulomas and 20 periapical cysts. Microscopic analysis revealed mast cells to be present in greater numbers in periapical cysts than in apical granulomas, and in cysts were more numerous in regions of active inflammation. Mast cells tended to be more common in the peripheral regions of both periapical lesions, and were often found in close proximity to lymphocytes. These findings lead us to propose a functional relationship between these two cell populations that may facilitate elicitation of an immune response contributory to the pathogenesis of periapical lesions.     

Burning mouth syndrome and mast cell activation disorder

Burning mouth syndrome (BMS), a chronic diffuse oral pain syndrome affecting ～1% of the general population, is diagnosed when explanatory oral pathology and other identifiable causes are absent. BMS has been recognized for decades, but its etiology remains unknown and has not previously been attributed to mast cell disease. Three cases of BMS are reported in which evidence of an underlying mast cell activation disorder (MCAD) was found; all 3 patients' oral pain responded well to MCAD-directed therapy. Mediators released from mast cells have a wide range of local and remote effects and potentially may cause the neuropathic changes and/or inflammation thought to lead to the symptoms of BMS. Mast cell disease either in oral tissue or at sites remote from the mouth should be considered in the differential diagnosis of BMS.     

Staining mast cells in human gingiva

This study was undertaken to select a specific, consistent stain-fixative combination which permits easy identification of all mast cells in human gingiva in order that meaningful studies of alterations in mast cell populations and distributions in periodontal disease could be performed. Previous investigators have employed a variety of metachromatic or non-specific stains for such studies with highly variable and conflicting results. In this study, a number of stain-fixative combinations were investigated. The metachromatic stains (i.e. toluidine blue, methylene blue, etc.) gave inconsistent or unreliable results and were difficult to read. In the presence of inflammation mast cells were frequently indistinguishable from other cells. Other nonspecific stains (i.e. aldehyde fuchsin, Giemsa, etc.) presented similar difficulties. The use of aqueous as compared with non-aqueous fixatives had no consistent effect on numbers of mast cells which could be visualized. For reliable, specific, easily readable staining of human gingival mast cells, the histochemical technique for the demonstration of the trypsin-like esterase activity in mast cells devised by and (1962) proved to be vastly superior to all other techniques studied.     

Mast cells in human periodontal disease

Recently, mast cells have been shown to produce cytokines which can direct the development of T-cell subsets. The aim of the present study was to determine the relationship between mast cells and the Th1/Th2 response in human periodontal disease. Tryptase+ mast cell numbers were decreased in chronic periodontitis tissues compared with healthy/gingivitis lesions. Lower numbers of c-kit+ cells, which remained constant regardless of clinical status, indicate that there may be no increased migration of mast cells into periodontal disease lesions. While there were no differences in IgG2+ or IgG4+ cell numbers in healthy/gingivitis samples, there was an increase in IgG4+ cells compared with IgG2+ cells in periodontitis lesions, numbers increasing with disease severity. This suggests a predominance of Th2 cells in periodontitis, although mast cells may not be the source of Th2-inducing cytokines.     

Mast Cell Degranulation in Human Periodontitis

Background: Mast cells are tissue‐resident immune cells that participate in a variety of allergic and inflammatory conditions. Limited attention has been given to the role of mast cells in periodontal diseases, and the effects of mast cell degranulation on the chronic stages of non‐allergic inflammation, particularly in periodontitis, are not known. The present study analyzes the relationship between the mast cell degranulation and human periodontal disease progression. Methods: A total of 50 clinical specimens including moderate periodontitis (n = 17), advanced periodontitis (n = 18), and healthy control tissues (n = 15) were used in this study. All specimens were fixed in 10% buffered formalin and stained with hematoxylin and eosin for histopathology, with toluidine blue for identifying mast cells, and by immunohistochemistry for the expressions of mast cell tryptase in periodontal tissues. The total and degranulated mast cell densities (per high‐power field) were quantified in the specimens. Results: Compared with healthy controls, there were significantly increased both total and degranulated mast cell densities in human moderate (P <0.01) and advanced (P <0.01) periodontitis groups by toluidine blue staining, and there were significantly higher densities of both total and degranulated tryptase‐positive mast cell subpopulation in the moderate periodontitis group (P <0.01) and even significantly higher subpopulation densities in the advanced periodontitis group by immunohistochemical staining, in which both total and degranulated mast cell densities were significantly higher in the advanced periodontitis group than those in the moderate periodontitis group (P <0.01) by both toluidine blue staining and immunohistochemical staining. There was significantly more severe periodontal inflammatory pathology in the advanced periodontitis group than in the moderate periodontitis group (P <0.01). Conclusion: These findings indicate a significant correlation among tryptase‐positive mast cell density, the degree of their degranulation, and the human periodontitis severity, and the results of this study further indicate that mast cell degranulation appears to be associated with human periodontal disease.     

The demonstration and automatic quantitation of mast cells by image analyzing computer

In order to investigate the significance and possible modes of action of mast cells in gingiva, it was necessary to have available consistent methods for their identification and quantitation in tissue samples. It was found that the Padawer (1959) technique known as a highly selective method for staining mast cells in various vertebrate sdid not consistently stain these cells in rhesus monkey gingiva. An attempt was made to modify and control the different steps of the technique to stain mast cells consistently, to shorten the time necessary and to have as little background stain as possible in order to utilize a Quantimet 720 Image Analyzer for automatic quantitation of mast cells. The staining system adopted has the following advantages over other methods. The results consist of an intense metachromasia of mast cell granules with a very faint orthochromatic background; the final product is produced in 2.5 hours and furnishes an intense contrast between mast cell granules and all other constituents of the tissue. Having established the technique, the accuracy and applicability of automatic counts using a Quantimet 720 Image Analyzing Computer was investigated. Results revealed that the mean counts of mast cells of two hundred sections obtained by manual and Quantimet methods were comparable.     

Human gingival mast cells

The literature concerning changes in mast cell populations in human gingiva associated with inflammation is contradictory. No reports of the effects of therapy on these populations have been published.This study was designed to determine whether gingival mast cell populations are altered by inflammation and whether these populations change following routine therapy. Twenty systemically healthy patients, age 20 to 40, ten with normal gingiva and ten with periodontitis of similar severity bilaterally, were selected for study. Biopsies of interdental papillae from premolar regions were utilized. In the periodontitis group, one papilla was obtained prior to therapy, the second from the ipsilateral quadrant two weeks after root planing and curettage.
Mast cell populations were determined from frozen sections stained with EACNAS-GBC Hematoxylin (Hall, 1966). Granule estimates were obtained from photographic negatives of frozen sections stained with EACNAS-GBC alone, using a photoelectric assaying device. Mast cell counts and granule estimates were made separately for beneath col and beneath keratinized tissue. Results show a larger mast cell population and a greater granule estimate under keratinized tissue than beneath the col. Mast cell counts and granule estimates show a decrease during periodontitis and a return to "normal" limits following routine therapy. These results support the concept that mast cell numbers are decreased in the presence of chronic inflammation but return to "normal" levels following resolution of the inflammatory process.     

Sequential histological changes and mast cell response in skin during chemically-induced carcinogenesis

Skin tumors experimentally induced by dimethylbenzathracene (DMBA) are associated with dense subepithelial accumulations of mast cells. To investigate the sequential changes of the mast cell population during carcinogenesis, and to provide a model with which to examine mast cell proliferation, the back skin of 48 Swiss Webster mice was painted with 0.5% DMBA in benzene twice weekly for 12 weeks. Control and DMBA-treated tissues were processed for histological examination. The observed pattern of tissue changes fell into four phases: a) inflammation and necrosis followed by epithelial regeneration and hyperplasia, b) development of localized regions of acanthosis, c) loss of normal organization with downgrowth of epithelial cells and formation of keratin pearls, d) appearance of well-defined nodules resembling verrucous carcinoma. Subepithelial mast cells varied greatly in number during the above sequence of changes. Dense foci of cells were seen, particularly beneath the regions of hyperplastic epithelium. Mast cells may play a role in abnormal epithelial proliferation and, further, DMBA treatment may provide a suitable model with which to examine the origin and kinetics of mast cells.     

Mast cells – a role in periodontal diseases?

OBJECTIVES: Limited attention has been given to the role mast cells may play in periodontal diseases. BACKGROUND: Mast cells are indeed found abundantly below and within several types of mucosal epithelia. On the basis of their proteinase content, mast cells are divided into connective tissue (CT) and mucosal phenotypes. The CT phenotype contains both tryptase and chymase (MC(TC)), while the mucosal phenotype contains only tryptase (MC(T)). The in vivo significance of different mast cell phenotypes has not yet been fully established. Mast cells are able to phagocytose, process and present antigens as effectively as macrophages. RESULTS: Recently mast cells were found in high numbers in chronically inflamed gingival tissue taken from patients with chronic marginal periodontitis (CMP). The number of mast cells was found to be even higher in HIV(+) patients with CMP. Furthermore, mast cells also express strongly matrix metalloproteinases (MMPs), which are key enzymes in degradation of gingival extracellular matrix. Mast cells may release preformed cytokines directing local innate and adaptive immune responses. The present review will focus on possible roles for mast cells in periodontal diseases. CONCLUSIONS: We certainly feel that this is a key cell in inflamed periodontal tissue and its role in periodontitis needs to be revisited.     

Early cellular changes following cryosurgery of oral mucosa in hamsters

Abstract Mitotic activity in the basal epithelial cells and mast cell degranulation have been studied as markers of early cellular change following experimental cryosurgery of hamster sublingual epithelium. It has been shown that mitotic activity initially increases, suggesting that freezing is a stimulus to cell division. Within a short time mitotic activity rapidly falls and this fall is preceded by a marked fall in the number of intact mast cells in the tissue. The timing of both events supports the view that early damage is apparent before vascular stasis intervenes.     

Early cellular changes following cryosurgery of oral mucosa in hamsters

Mitotic activity in the basal epithelial cells and mast cell degranulation have been studied as markers of early cellular change following experimental cryosurgery of hamster sublingual epithelium. It has been shown that mitotic activity initially increases, suggesting that freezing is a stimulus to cell division. Within a short time mitotic activity rapidly falls and this fall is preceded by a marked fall in the number of intact mast cells in the tissue. The timing of both events supports the view that early damage is apparent before vascular stasis intervenes.     

Mast cell heterogeneity in various oral mucosal sites in the rat.

Two distinct types of mast cells are recognized in the rat: connective tissue mast cells (CTMCs), found in the peritoneal cavity, skin, tongue, etc. and mucosal mast cells (MMCs), found in the intestinal mucosa. The two subsets differ functionally and can be defined by histochemical methods. The aim here was to characterize the mast cell population in various oral mucosal sites. Biopsies were taken from the tongue, buccal mucosa, gingival mucosa and intestine (jejunum) of 20 rats. For optimal preservation of the MMCs, a fixative with low aldehyde concentration and low pH was used. The biopsies were embedded in paraffin. The first of three consecutive sections (5 microns) was stained with toluidine blue for 30 s, the second with toluidine blue for 7 days and the third with astra blue/safranine. Cells positive with toluidine blue after 30 s were classified as CTMCs, and those positive after 7 days but not after 30 s as MMCs. Cells positive to safranine in the astra blue/safranine staining sequence were classified as CTMCs and those positive to astra blue as MMCs. The total number of mast cells was similar in the superficial layers of all oral tissues studied. There were more mast cells in the deeper than in the superficial portions of the tongue. Mast cells with staining characteristics and size similar to those observed in the intestinal mucosa (MMCs) were found together with 'classical' connective tissue mast cells (CTMCs). The results suggest that the mast cell population of oral mucosal tissues of the rat contains both CTMC- and MMC-like cells.     

The role of neuromodulators (substance P and calcitonin gene-related peptide) in the development of neurogenic inflammation in the oral mucosa

Vatous observations carried out in the course of the years have shown that certain neuropeptides have a possible role to play as inflammation mediators. The substances on which attention has been principally focused are: substance P, calcitonin gene-related peptide, capsaicin an histamine. Knowledge acquired in this field, however, does not yet permit us to sufficiently clarify the role, not to speak of the possible action mechanism, on the basis of which these neuropeptides act, although it is confirmed that these substances have been found first in laboratory animals and later also in human tissues in the course of experimentally induced neurogenic inflammation. The need to know more and more about inflammatory mechanisms and the increasingly complex possibilities offered by the application of technology in the field of medical research have led to many small advance in our knowledge of what is involved in inflammation. In fact it has been understood that behind the typical signs of inflammation (the famous four cardinal signs of Celsus: pain, redness, swelling, heat) no abstract entities or strange alchemies are concealed, but a series of well-known, classified substance, the so-called "inflammation mediators", namely a variety of substances of cellular or plasmatic origin united by the fact that exist, in stationary state conditions, in the form of inactive precursors, or sequestered in intracellular sites where they are unable to carry out their action. Following an inflammatory stimulus, they are activated, or their synthesis can be induced, or their release from intracellular sequestration sites in favoured; in any case they are stored in the disturbance district in concentrations that are such as to act on their respective targets, triggering event s that characterise the various stages of the inflammatory process.