Recurrent aphthous ulcers--a Toll-like receptor-mediated disease?

Area of Science:

• Immunology
• Dermatology
• Oral Medicine

Background:

• Recurrent aphthous ulcer (RAU) presents as painful oral ulcerations with a tendency to recur.
• The exact cause of RAU remains unproven, with various pathogens proposed.
• RAU is hypothesized to be an autoinflammatory disorder triggered by microbial pathogen-associated molecular patterns (PAMPs).

Purpose of the Study:

• To investigate the role of PAMP-reactive Toll-like receptors (TLRs) in the oral epithelium of RAU patients compared to healthy controls.
• To determine if altered TLR expression or localization contributes to RAU pathogenesis.

Main Methods:

• Mapping of PAMP-reactive TLRs in the oral epithelium of healthy individuals and RAU patients.
• Comparative analysis of TLR distribution and expression levels between the two groups.

Main Results:

• Healthy oral epithelium exhibits a polarized TLR distribution, with a superficial non-reactive barrier and deeper reactive zones.
• RAU patients display a loss of TLR polarity, with TLRs found throughout the epithelium and increased expression of certain TLRs.
• RAU lesions show significant infiltration of TLR-expressing inflammatory cells in the connective tissue stroma.

Conclusions:

• The normal TLR organization in oral mucosa acts as a defense mechanism against microbes.
• In RAU, the TLR-reactive zone extends to the surface, becoming exposed to microbial PAMPs.
• Altered TLR organization and enhanced inflammatory cell recruitment in RAU suggest a TLR-mediated disease process.