Assessing LncRNA DQ786243 and IL-17 Expression in Oral Lichen Planus: A Case Control Study

Oral lichen planus (OLP) is a common chronic inflammatory disease associated with cell-mediated immunological dysfunction. OLP can be seen in different clinical presentations. It can be classified as papular (reticular), atrophic (erythematous) and erosive (ulcerative, bullous).1 Numerous predisposing factors have been blamed for causing OLP, including: stress, diabetes, drugs, dental materials, autoimmune diseases, infectious agents and genetic predisposition. 2 Regarding the pathogenesis of OLP, it is a T-cell mediated inflammatory disease where antigen- specific and non-specific mechanisms are hypothesized to be involved3. Antigen-specific mechanisms include antigen presentation by basal keratinocytes and antigen-specific keratinocyte killing by CD8+ cytotoxic T-cells. Non-specific mechanisms include mast cell degranulation, basement membrane disruption, chemokines and matrix metalloproteinase (MMP) activation in OLP lesions.4 Various treatment regimens have been proposed to improve the management of symptomatic OLP, but a permanent cure is not yet available. Treatment regimens are non-specific and directed at eliminating inflammation and immunosuppression.5 Corticosteroids constitute the main stay agent, other available treatment modalities include immunosuppressants, cyclosporin, tacrolimus, and retinoids.6 Long non-coding RNAs (lncRNAs) have been identified as new regulatory molecules. They modulate protein coding gene at the chromatin remodeling level, or the transcriptional and post- transcriptional control level. They play vital roles in cell differentiation, cell growth and apoptosis. lncRNA DQ786243 is drawing attention in the pathogenesis of a variety of inflammatory immune- mediated diseases such as Crohn's disease and OLP.7, 8 A recent study suggested that lncRNA DQ786243 exert its function through interleukins (ILs) including IL-17. T-helper 17 response and its hallmark IL-17 is gaining more evidence for its role and association with many diseases such as

5 Crohn's disease, ulcerative colitis, systemic lupus erythematosus and OLP. IL-17 has been found to participate in the development of autoimmune disease, inflammatory destruction and tumor microenvironments.9, 10

Research question:

What is the salivary expression of lncRNA DQ786243 and IL-17 in Oral Lichen Planus? Population (P): Oral lichen planus Control (C): Healthy individuals Outcome (O): Salivary expression level of lncRNA DQ786243 and IL-17

Objectives: