Mast cells and oral pathologies: A Review

Role of mast cells in the pathogenesis of oral submucous fibrosis: a systematic review and meta-analysis

BACKGROUND

Oral Submucous Fibrosis (OSMF) is an oral potentially malignant disorder (OPMD) that commonly occurs in the South Asian population as there is high usage of areca nut. There has been extensive research on the pathogenesis and treatment of this condition. It is well-established in the scientific literature that mast cells (MC) have a definitive role in several inflammatory disorders. OSMF being a chronic inflammatory disorder, is also expected to have increased MCs. Hence, this review aims to evaluate the role of MCs in the pathogenesis of OSMF.

METHODS

A systematic search of articles was performed by two of the authors independently in PubMed, Scopus, Embase, Web of Science, and Google Scholar using the appropriate keywords and Boolean terms. The risk of bias was assessed using the Modified Newcastle-Ottawa Scale. The meta-analysis was performed with R studio software (Version: 4.4.0, Year: 2024, Company: The R foundation for statistical computing).

RESULTS

The search retrieved 36 studies, of which 16 were suitable for the review. There is evidence for a marked increase in the number of MCs in OSMF than the normal mucosa upon analyzing the retrieved articles. However, when comparing the grades of OSMF, there are variations in the reports. As all the retrieved articles were case-control studies, the risk of bias was analyzed using the Modified New Castle Ottawa Scale. All the studies scored in the good category (Score 6-9). The pooled effect size shows the Standard Mean Deviation (SMD) to be 0.09, 95% confidence interval (CI) [-0.18;0.37] to lie on either side of no effect. Hence the role of MCs in OSMF has not been established because of homogeneity and consistent sampling error.

CONCLUSION

Our systematic review does suggest a definitive role of mast cells in the progression of OSMF. However, there is a lack of methodological rigor in the included studies. This may contribute to diluting the results.

Histamine deficiency deteriorates LPS-induced periodontal diseases in a murine model via NLRP3/Caspase-1 pathway

Histamine is a versatile biogenic amine, generated by the unique enzyme histidine decarboxylase (Hdc). Accumulating evidence has proven that histamine plays important roles in numerous biological and pathophysiological processes. However, the role and mechanism of Hdc/Histamine signaling in periodontal diseases remain unclear. In our current study, the concentration of histamine increased in the serum, and Hdc gene expression was upregulated in the gingiva of WT mice with LPS-induced periodontal inflammation. With Hdc-GFP mice, we identified that Hdc/GFP in the periodontium was expressed in CD11b⁺ myeloid cells, rather than in tryptase-positive mast cells. Hdc-expressing CD11b⁺Gr-1⁺ neutrophils significantly increased in the peripheral blood of Hdc-GFP mice one day after LPS injection. Lack of histamine in Hdc^-/- mice not only promoted the activation and infiltration of more CD11b⁺ cells into the peripheral blood but also upregulated mRNA expression levels of IL-1β, IL-6, MCP-1and MMP9 in the gingiva compared to WT mice one day after LPS stimulation. 28 days after LPS treatment, we observed that Hdc^-/- mice exhibited more alveolar bone loss and more osteoclasts than WT mice, which was slightly ameliorated by the administration of exogenous histamine. In vivo and in vitro mechanistic studies revealed that the mRNA expression levels of proinflammatory cytokines and protein levels of NLRP3, Caspase-1, and cleaved-Caspase-1 were upregulated after blocking histamine receptor 1 and 2, especially histamine receptor 1. Taken together, CD11b⁺Gr-1⁺ neutrophils are the predominant Hdc-expressing sites in periodontal inflammation, and deficiency of endogenous histamine in Hdc^-/- mice exacerbates the destruction of the periodontium. Disruption of the histamine/H₁R/H₂R axis aggravates the inflammatory immune response via NLRP3/Casapse-1 pathway.

Efficacy of Csaba stain to demonstrate mature and immature mast cells in oral inflammatory lesions: An in-vitro study

Background

Mast cells (MCs) are immune cells of the myeloid lineage and are present in connective tissues throughout the body. Mastocytosis regulates many physiologic processes and affects the pathogenesis of allergic conditions, anaphylactic reactions, autoimmune disorders and leukemias. Toluidine blue is commonly employed as a special stain for MCs that uniformly imparts blue color to both immature and mature cells. Csaba stain that distinguishes mature from immature MCs has not been widely explored. However, its use in differentiating mature and immature cells has not been reported in the literature. The identification of mature and immature MCs may provide a major clue for the diagnosis of any unrecognized systemic pathologies.

Objectives

To evaluate the staining efficacy of Csaba stain, toluidine blue and Leishman's stains in the identification of MCsTo compare the effectiveness of Csaba stain, toluidine blue and Leishman's stains to identify MCs in inflammatory pathologic lesions.

Materials and Methods

Fifty sections of inflammatory lesions were subjected to Csaba stain, toluidine blue and Leishman's stains each for studying MCs. The staining efficacy of the three stains was compared for parameters such as homogeneity, specificity, staining intensity, granular staining property and differentiation between mature and immature cells.

Results

The Csaba, toluidine blue and Leishman's stains showed statistically insignificant P = 0.50, 0.95, 0.29, 0.48 for homogeneity, specificity, staining intensity and granular staining property respectively, but Csaba stain showed statistically significant P = 0.0001* in differentiating mature from immature cells.

Conclusion

Csaba stain is more effective in differentiating mature from immature MCs compared to the other special stains.

Oral wound healing models and emerging regenerative therapies

Following injury, the oral mucosa undergoes complex sequences of biological healing processes to restore homeostasis. While general similarities exist, there are marked differences in the genomics and kinetics of wound healing between the oral cavity and cutaneous epithelium. The lack of successful therapy for oral mucosal wounds has influenced clinicians to explore alternative treatments and potential autotherapies to enhance intraoral healing. The present in-depth review discusses current gold standards for oral mucosal wound healing and compares endogenous factors that dictate the quality of tissue remodeling. We conducted a review of the literature on in vivo oral wound healing models and emerging regenerative therapies published during the past twenty years. Studies were evaluated by injury models, therapy interventions, and outcome measures. The success of therapeutic approaches was assessed, and research outcomes were compared based on current hallmarks of oral wound healing. By leveraging therapeutic advancements, particularly within in cell-based biomaterials and immunoregulation, there is great potential for translational therapy in oral tissue regeneration.

Evaluation of Mast Cells in Oral Potentially Malignant Disorders and Oral Squamous Cell Carcinoma

Background

Oral squamous cell carcinoma (OSCC) and oral potentially malignant disorders (OPMDs) are epithelial-derived pathologies which share inflammation as a common initial pathogenic-inducing state. Mast cell is a key immune modulating cell which is primarily involved in initiation and propagation of inflammation. The role of mast cell in OPMDs and OSCC has been an established fact; however, its definitive pathogenic correlation is still under study. The objective of the study was to evaluate the number of mast cell in OPMDs and OSCC using special stain correlating its probable role as a promoter or retarder of OSCC.

Materials and Methods

Forty-five archival histopathologically confirmed cases each of OPMD and OSCC were studied for mast cells using toluidine blue and Alcian blue-safranin stain and compared with 10 normal oral mucosal tissues. Comparisons between the mast cells count was also performed between the two special stains.

Results

Among 100 cases, 67% were males and 33% were females. The mean age was 41.68 ± 13.39; 55.06 ± 12.55; and 18.4 ± 2.54 years for OPMDs, OSCC, and normal, respectively. A statistically significant increase in mast cells among OPMDs (9.88 ± 7.9) and OSCC (6.711 ± 3.94) was observed compared to normal oral mucosa. The mast cell count reduced among OSCC in comparison to OPMDs which was significant as well. The mean mast cell count for Alcian blue-safranin stain was higher than toluidine blue stain.

Conclusion

There is a decrease in mean mast cell count from OPMDs to OSCC which is suggestive of protective role of mast cell. Proper quantification of mast cells using specific stains can guide to define prognosis in oral potentially malignant disorders and oral cancer.

Quantification of mast cells in nonreactive and reactive lesions of gingiva: A comparative study using toluidine blue and immunohistochemical marker mast cell tryptase

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High mast cell density indicates a longer overall survival in oral squamous cell carcinoma

This study evaluates the effects of tumour-associated mast cells on the prognosis of patients suffering from oral squamous cell carcinoma (OSCC). Tryptase-positive (MCT⁺) and CD117-positive (CD117⁺) mast cells were immunohistochemically evaluated in tissue samples of 118 OSCC patients. Besides, various clinicopathological parameters, the influence of the MCT⁺ and CD117⁺ mast cell density on overall survival and the incidence of first local recurrence was analysed by Cox regression and competing risk regression. Among all investigated parameters, multiple Cox regression revealed a significant influence of the MCT⁺ (cut-off at 14.87 mast cells/mm² stroma; p = 0.0027) and CD117⁺ mast cell density (cut-off at 33.19 mast cells/mm² stroma; p = 0.004), the age at primary diagnosis, and the T and N stage (all p-values < 0.05) on overall survival. Patients with a low mast cell density showed a significantly poorer overall survival rate compared to those with a high mast cell density in the tumour-associated stroma. Competing risk regression revealed a significant influence of the resection status (R) on the incidence of first local recurrence (p = 0.0023). A high mast cell density in the tumour-associated stroma of oral squamous cell carcinoma indicates a longer patient survival.

Microenvironmental regulation of the progression of oral potentially malignant disorders towards malignancy

Oral potentially malignant disorders (OPMD) develop in a complex tissue microenvironment where they grow sustainably, acquiring oral squamous cell carcinoma (OSCC) characteristics. The malignant tumor depends on interactions with the surrounding microenvironment to achieve loco-regional invasion and distant metastases. Unlike abnormal cells, the multiple cell types in the tissue microenvironment are relatively stable at the genomic level and, thus, become therapeutic targets with lower risk of resistance, decreasing the risk of OPMD acquiring cancer characteristics and carcinoma recurrence. However, deciding how to disrupt the OPMD and OSCC microenvironments is itself a daunting challenge, since their microenvironments present opposite capacities, resulting in diverse consequences. Furthermore, recent studies revealed that tumor-associated immune cells also participate in the process of differentiation from OPMD to OSCC, suggesting that reeducating stromal cells may be a new strategy to prevent OPMD from acquiring OSCC characteristics and to treat OSCC. In this review, we discuss the characteristics of the microenvironment of OPMD and OSCC as well as new therapeutic strategies.

Clinical and Histopathologic Characterization of Canine Chronic Ulcerative Stomatitis

Canine chronic ulcerative stomatitis, also known as chronic ulcerative paradental stomatitis, is a painful condition of the oral cavity. The purpose of this study was to determine if there are commonalities in clinical and radiographic features among patients, whether the histopathologic evaluation might inform the pathogenesis, and whether the condition appears similar to human oral mucosal diseases. To do this, we prospectively collected clinical, radiographic, and histopathologic data from 20 dogs diagnosed with the disease. Clinical data were based on a clinical disease activity index, oral and periodontal examination parameters, and full-mouth dental radiographs. The histopathological and immunohistochemical data were based on oral mucosal samples obtained from erosive or ulcerated areas. Our findings revealed that canine chronic stomatitis is clinically characterized by painful oral mucosal ulcers of varying size, pattern, appearance, and distribution, most often associated with teeth with early periodontitis. Histologic examination revealed a subepithelial lichenoid band (interface mucositis) where B cells, T cells, and Forkhead-box protein 3 (FoxP3)- and interleukin-17-expressing cells were present. These cells might play a role in the underlying immune response and an immune-mediated pathogenesis is suspected. The clinical and histopathologic features of this chronic inflammatory mucosal disease in dogs resemble those of oral lichen planus in humans.

Targeting mast cells: Uncovering prolific therapeutic role in myriad diseases

The mast cells are integral part of immune system and they have pleiotropic physiological functions in our body. Any type of abnormal stimuli causes the mast cells receptors to spur the otherwise innocuous mast cells to degranulate and release inflammatory mediators like histamine, cytokines, chemokines and prostaglandins. These mediators are involved in various diseases like allergy, asthma, mastocytosis, cardiovascular disorders, etc. Herein, we describe the receptors involved in degranulation of mast cells and are broadly divided into four categories: G-protein coupled receptors, ligand gated ion channels, immunoreceptors and pattern recognition receptors. Although, activation of pattern recognition receptors do not cause mast cell degranulation, but result in cytokines production. Degranulation itself is a complex process involving cascade of events like membrane fusion events and various proteins like VAMP, Syntaxins, DOCK5, SNAP-23, MARCKS. Furthermore, we described these mast cell receptors antagonists or agonists useful in treatment of myriad diseases. Like, omalizumab anti-IgE antibody is highly effective in asthma, allergic disorders treatment and recently mechanistic insight of IgE uncovered; matrix mettaloprotease inhibitor marimistat is under phase III trial for inflammation, muscular dystrophy diseases; ZPL-389 (H4 receptor antagonist) is in Phase 2a Clinical Trial for atopic dermatitis and psoriasis; JNJ3851868 an oral H4 receptor antagonist is in phase II clinical development for asthma, rheumatoid arthritis. Therefore, research is still in inchoate stage to uncover mast cell biology, mast cell receptors, their therapeutic role in myriad diseases.