Salivary mir-27b Expression in Oral Lichen Planus Patients: A Series of Cases and a Narrative Review of Literature

Background: microRNAs play a critical role in auto-immunity, cell proliferation, differentiation and cell death. miRNAs are present in all biological fluids, and their expression is essential in maintaining regular immune functions and preventing autoimmunity, whereas miRNA dysregulation may be associated with the pathogenesis of autoimmune and inflammatory diseases. Oral lichen planus (OLP) is an inflammatory disease mediated by cytotoxic T cells attack against epithelial cells. The present study aims to perform a specific microRNA expression profile through the analysis of saliva in this disease. Methods: The study group was formed by five patients (mean age 62.8 +/- 1.98 years; 3 females/2 males) affected by oral lichen planus and control group by five healthy subjects (mean age 59.8 years +/- 2.3; 3 females/ 2 males); using a low-density microarray analysis, we recorded a total of 98 differentially expressed miRNAs in the saliva of patients with oral lichen planus compared to the control group. The validation was performed for miR-27b with qRT-PCR in all saliva samples of oral lichen planus group. Results: 89 miRNAs were up-regulated and nine down-regulated. In details, levels of miR-21, miR-125b, miR-203 and miR15b were increased (p<0.001) in study group while levels of miR-27b were about 3.0-fold decreased compared to controls (p<0.001) of miR-27b expression in OLP saliva. QRT-PCR validation confirmed the down regulation of miR-27b in all saliva samples. Conclusion: Collecting saliva samples is a non-invasive procedure and is well accepted by all patients. microRNAs can be readily isolated and identified and can represent useful biomarkers of OLP.