The SELDI-TOF-MS technology seems to be ideally suitable for the mass screening of peptides and proteins in tears. This highly sensitive approach dramatically reduces the analysis time and provides protein profiles with great mass accuracy. Thus, it may become a very useful tool in the search for potential biomarkers for diagnosis and new therapeutics in ocular diseases such as dry eye.

Purpose: To evaluate epiretinal membranes in proliferative eye disease for the presence of vascular endothelial growth factor (VEGF) and tumor necrosis factor α (TNF-α). Methods: Membranes were surgically removed from 66 patients with proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR) and macular pucker (MP). Cytokine concentrations were determined by ELISA (VEGF) and bioassay (TNF-α). Results: VEGF was detected in all 66 membranes investigated. The highest VEGF values were found in patients with type I diabetes (mean = 5,994 pg/mg protein). In patients with type II diabetes, the values were at a mean of 1,242 pg/mg protein. When coagulation therapy was performed for longer than 3 months prior to surgery, VEGF was significantly (p < 0.05) reduced. Intermediate levels of VEGF were found in PVR membranes (mean = 1,417 pg/mg protein). The lowest activity was found in MP (mean = 216 pg/mg protein). In contrast, TNF-α was present in 16 PDR membranes, 9 PVR membranes and 8 MP membranes. Conclusion: The presence of VEGF in all membranes investigated indicates that this cytokine plays an important role in angiogenesis in ischemic retinal disease and in membrane growth in proliferative disorders.

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In-depth studies on the proteome of reflex tears are still inadequate. Hence, further studies on this subject will unravel the key proteins which are conjectured to possess vital functions in the protection of the ocular surface. Therefore, this study investigated the differences in the expression levels in proteome of reflex compared to basal tears. Basal (n = 10) and reflex (n = 10) tear samples from healthy subjects were collected employing the capillary method, subsequently pooled and the proteomes were characterized employing 1DE combined with LC-ESI-MS/MS strategy for label-free quantitative (LFQ) analysis. The differentially expressed proteins were validated by 2DE combined with LC-ESI-MS/MS and targeted-MS approach called accurate inclusion mass screening (AIMS) strategies. The analysis of the reflex tear proteome demonstrated increased abundance in proline-rich protein 4 (PRR4) and zymogen granule protein 16 homolog B (ZG16B) for the first time. Other abundant lacrimal proteins, e.g. lactotransferrin and lysozyme remained constant. Predominantly, the lacrimal gland-specific PRR4 represents the major increased protein in reflex tears in an attempt to wash out irritants that come into contact with the eye. Conversely, decreased abundance in Ig alpha-1 chain C, polymeric immunoglobulin receptor, cystatin S/SN, clusterin and mammaglobin were observed. This study had further unraveled the intricate proteome regulation during reflex tearing, especially the potential role of PRR4, which may be the key player in the protection and maintenance of dynamic balance of the ocular surface.