Micro-RNA Profiles in Saliva, Plasma and Tissue in Sjögren’s Syndrome

Objectives: Increasing evidence suggests that aberrant expression of micro-RNAs (miRNAs) is involved in the progression of autoimmunity including primary Sjögren’s syndrome (pSS). The aim of this study was to investigate if whole saliva, plasma, and salivary gland tissue from patients with pSS display distinct miRNA expression profiles, and if these profiles differ from those of patients having symptoms of pSS, but not fulfilling the classification criteria.
Methods: miRNA real-time qPCR was performed on whole saliva, plasma and labial salivary gland tissue from 24 patients with pSS and 16 non-Sjögren sicca controls (non-pSS) using miRCURY LNA™ Universal RT microRNA PCR, Polyadenylation and cDNA synthesis kit (Exiqon). The amplification was performed in a LightCycler® 480 RealTime PCR System (Roche) in 384 well plates. Two-sided t-test was used as comparative analysis, followed by Benjamini-Hochberg correction for multiple dependent analysis. For correlation analysis, Pearson correlation coefficient was calculated.
Results: On average, 158 miRNAs were identified in saliva, 155 in plasma, and 274 in salivary gland tissue. Fourteen miRNAs were significantly differentially expressed in saliva from patients with pSS compared to the non-pSS patients (p <0.05). In saliva of patients with pSS, hsa-miR-17-5p, hsa-miR-328-3p, hsa-miR-7-5p, hsa-miR-30c-5p, hsa-miR-191-5p, hsa-miR-106a-5p, hsa-miR-154-5p, hsa-miR-215-5p, hsa-miR-106b-5p, hsa-miR-409-3p, and hsa-miR-20b-5p were downregulated, and hsa-let-7i-5p, hsa-miR-222-3p, and hsa-let-7e-5p upregulated. In salivary gland tissue of patients with pSS, hsa-miR-29a-3p was upregulated. Plasma miRNAs did not differ between the two groups. Positive or negative correlations (r >0.6; p <0.01) were found between 10 of the 14 differently expressed miRNAs in saliva.
Conclusions: Our findings indicate that the miRNA expression profile in whole saliva enables discrimination between pSS and non-pSS patients. Salivary miRNAs represent potentially novel diagnostic biomarkers in pSS. The miRNA profile in saliva was superior to miRNAs in plasma and salivary gland tissue to discriminate between pSS and non-pSS.