Two-Dimensional Gel-Based Proteomic Analysis of Salivary Proteins in Oral Lichen Planus

Objectives: Oral lichen planus (OLP) is a relatively common chronic inflammatory disease of established immune-mediated pathogenesis, affecting oral mucosal tissues. Human saliva proteomics has been proven to be an innovative approach in finding protein biomarkers for human diseases. Identification of potential salivary protein biomarkers is a crucial step in the development of effective screening and diagnosis of OLP.
The aim of this study was to identify potential salivary biomarkers for diagnosis of OLP using two-dimensional gel-based proteomic approach.
Methods: Whole unstimulated saliva was collected according to the method described by Navazesh (1) from 5 OLP patients and 5 normal subjects at Faculty of Dentistry, Mahidol University. Saliva was immediately placed on ice and centrifuged at 2,600 g, 4°C for 15 minutes. The protease inhibitor was added to the supernatant and stored at -80°C until used. Two-dimensional gel electrophoresis was performed using 250 μg of pooled salivary protein from each group of subjects and stained with Coomassie Brilliant Blue for protein separation and visualization. The interesting spots were picked up for further analyzed by tandem mass spectrometry for protein identification.
Results: ImageMaster^TM 2D Platinum analysis identified 31 protein spots exhibited at least 1.5-fold difference in intensity or found only in OLP or normal group. Of these 31 protein spots, 14 protein spots were found in both groups, 11 protein spots were detected only in OLP and other 6 protein spots were presented only in normal. Interestingly, fibrinogen fragment D and complement C3c were upregulated whereas cystatin SA was downregulated in OLP group compared to normal group.
Conclusions: Fibrinogen fragment D, complement C3c and cystatin SA might be the new potentially salivary protein biomarkers for diagnosis of OLP.