Crosstalk between the oral microbiota, mucosal immunity, and the epithelial barrier regulates oral mucosal disease pathogenesis

Abstract

Oral mucosal disease (OMD), which is also called soft tissue oral disease, is described as a series of disorders or conditions affecting the mucosa and soft tissue in the oral cavity. Its etiology is unclear, but emerging evidence has implicated the influence of the composition of the oral mucosa and saliva-resident microbiota. In turn, this dysbiosis effects the immune response balance and epithelial barrier function, followed by the occurrence and progression of OMD. In addition, oral microbial dysbiosis is diverse in different types of diseases and different disease progressions, suggesting that key causal pathogens may exist in various oral pathologies. This narrative literature review primarily discusses the most recent findings focusing on how microbial dysbiosis communicates with mucosal adaptive immune cells and the epithelial barrier in the context of five representative OMDs, including oral candidiasis (OC), oral lichen planus (OLP), recurrent aphthous ulcer (RAU), oral leukoplakia (OLK), and oral squamous cell carcinoma (OSCC), to provide new insight into the pathogenetic mechanisms of OMDs.

Leukoplakia in the Oral Cavity and Oral Microbiota: A Comprehensive Review

“…The authors speculate on a synergistic effect of fungi and bacteria in tumour development, supported by the recent finding of a protective role of Candida albicans towards Porphyromonas gingivalis [24]. Lin et al drew the same conclusions, suggesting a tight relationship between bacteria and Candida in the regulation of mucosal immunity, particularly T-reg and Th17 cells [2]. The authors also state that significantly higher abundances of Candida and Aspergillus were observed in patients with erosive OLP.…”

“…Still, they nonetheless recommend that thorough analysis of the virome in oral malignant and potentially premalignant tissues is carried out in the future because of the unknown HPV subtypes and possibly new viral pathogens [21]. As stated by Lin et al, "to date the roles of bacterial-fungal-virus interactions in OLP pathogenesis remain largely uncharacterized" [2]. Two recent meta-analyses explored the association of HPV with OLKs, and both groups encountered considerable heterogeneity between studies.…”

“…The oral cavity is a complex biologic environment, where countless microorganisms interact continuously with one another and the mucosal epithelium, maintaining a delicate balance [1,2]. More than 700 different bacterial species have been identified in the oral cavity, and likely more will be discovered in the following years, thanks to the everevolving technologies (e.g., Next Generation Sequencing (NGS)).…”

“…The term "dysbiosis" refers to the perturbation of the microbial ecosystem, which is modified constitutionally and functionally. This perturbation could be associated with oral disease [2]. The meaning of this association has become the focus of plenty of studies in the last decade, especially as far as oral cancer is concerned.…”

Oral Microbiota: A Major Player in the Diagnosis of Systemic Diseases

“…Oral mucosal disease (OMD) is a series of disorders or conditions affecting the oral soft tissues and mucosa. OMD mainly includes oral infectious diseases such as oral candidiasis, oral lichen planus (OLP) or oral mucosal patches striae diseases, ulcerative lesions such as recurrent aphthous ulcers (RAU), oral premalignant lesions like oral leukoplakia (OLK), and oral cancers, mainly oral squamous cell carcinoma (OSCC) [227]. OMDs share multiple risk factors, including genetic predisposition, immunological disturbances, viral and bacterial infections, food allergies, and nutritional deficiencies, and also hormonal imbalance, mechanical repetitive injuries, and stress.…”