Single‐Cell RNA Sequencing Reveals Functional Exhaustion of T Cells in Oral Lichen Planus

Abstract Background Oral lichen planus (OLP) is a common T‐cell‐mediated chronic inflammatory disease of the oral mucosa. Different T‐cell subsets play distinct roles in the pathogenesis of OLP. This study aims to reveal the composition and heterogeneity of T cells in the immune microenvironment of OLP using single‐cell RNA sequencing (scRNA‐seq), thus providing new insights into the pathogenesis of OLP. Materials and Methods Oral mucosal tissues were collected from three OLP patients and three healthy individuals for scRNA‐seq. Data were processed using R software for dimensionality reduction, clustering, annotation, proportion analysis, gene expression visualization, and pseudotime analysis. A chronic inflammation model was established by injecting Prevotella melaninogenica bacteria solution into the buccal mucosa of mice. RT‐qPCR was used to detect the expression levels of OLP‐related inflammatory factors (Tnf‐α, Il‐1b, and Il‐6) and the exhaustion marker Pd1. HE and immunofluorescence staining were employed to assess histopathological changes in oral mucosal tissues and the quantity of CD8 + ‐exhausted T cells (CD8 + Tex). Results ScRNA‐seq results showed a significant increase in T cell numbers in the oral mucosal tissues of OLP patients compared to healthy individuals. The average expression levels of effector molecules (GZMB, PRF1, TNFA, IL2, and IFNG) in CD8 + T cells were reduced. The number of CD8 + Tex significantly increased, and these cells were in the terminal stage of CD8 + T‐cell differentiation, thereby expressing high levels of terminal exhaustion‐related genes (PDCD1, LAG3, and TIGIT). Compared to the control group, the P. melaninogenica chronic inflammation group exhibited epithelial thickening and inflammatory cell infiltration in the lamina propria, with significantly upregulated expression of OLP‐related inflammatory factors and Pd1. Immunofluorescence staining revealed increased CD8 + Tex in the oral mucosa of OLP patients and P. melaninogenica mice model. Conclusions During the pathogenesis of OLP, the overall ability of T cells to clear antigens is decreased, leading to an inadequate ability to promptly eliminate pathogens and infected cells, which may cause the chronicity of OLP inflammation.