Purpose
Dry eye (DE) and meibomian gland dysfunction (MGD) are the most common ocular surface diseases. Discrimination between these conditions is difficult because of the overlapping signs and symptoms and the lack of correlation between these symptoms and clinical parameters. We searched for the differences between tear proteomes in these two conditions.
Methods
Tear samples were collected from 37 individuals: 7 with DE disease, 12 with MGD, and 18 control subjects. Diagnosis was based on clinical examination including the Schirmer test with anesthesia to measure only the basal secretion, slit-lamp examination of the lid margin and meibomian glands, fluorescein staining, and subjective symptoms. Each patient answered a modified “National Eye Institute Visual Functioning Questionnaire 25” (VFQ-25), which included some statements about problems with their vision or wellbeing .<br /> The samples were analyzed using spectral counting-based LC-MS/MS quantitation.
Results
Comparative analysis of tear protein profiles revealed discriminating changes in the expression levels of 26 proteins, including protein S100A6, annexin A1, cystatin-S, thioredoxin, phospholipase A2, antileukoproteinase, and lactoperoxidase. Some of the proteins with altered expression have been reported and validated previously. Comparative studies conducted using other proteomics technologies have already discovered some tear biomarkers for DE and MGD.
Conclusions
Our study confirmed S100A6, cystatin-S, annexin A1, and phospholipase A2 as valid tear biomarkers for these conditions. Subsequent functional network analysis revealed the main biological processes that should be examined to improve our understanding of ocular surface diseases and identify new candidate therapeutic targets.