Ten differentially expressed proteins in the tear film of dogs with diabetic retinopathy

Purpose A common early lesion of diabetic retinopathy in human patients and a diverse range of animal models is retinal capillary basement membrane thickening occur within 6 months of induction of diabetes. This hallmark pathology of diabetic microvascular disease is used in the evaluation of drug‐mediated modulation of diabetic retinopathy in a range of animal models. Moreover results from published clinical practice have shown that more than 22% of dogs with naturally contracted diabetes mellitus develop ophtalmoscopic signs of retinal hemorrhages or microaneurysms in a relatively short time from onset of the disease. Therefore, we hypothesize that changes in the retina in such dogs results in changes in the protein profile of tear fluid, that can be of the diagnostic or therapeutic value and can contribute to the better understanding the pathophysiology mechanisms underlying that disease. The objective of this study was to identify the protein content of tear film in dogs with naturally contracted diabetes mellitus with and/ without retinopathy, and its comparison with the content of control group. That approach results with mapping out the comprehensive proteome of tear film in diabetic dog and the may contribute to development a noninvasive method to detect potential protein candidates for diabetic retinopathy biomarkers in tear film. Methods Tear film was collected with Schirmer strips from the canine diabetic patients with/ and without retinopathy and sex‐ and age‐matched control group.The study was conducted on 24 dogs (8 dogs in each group).Two‐dimensional electrophoresis was performed followed by MALDI‐TOF mass spectrometry identification of differential proteins. Quantitative analysis of the differentiating electrophoretic spots was done with 2Delta software. Metabolic pathways associated with those proteins were identified with Panther GO software. Results Altogether, 5 significantly differentially expressed proteins were identified. Of those, 4 were downregulated, and 1 was upregulated in the tear film of diabetic patients with retinopathy. Pathway analysis revealed that the proteins were associated with multiple pathways involved in biological regulation, cellular and metabolic process and cellular component organization. Conclusions Tear film protein analysis provides a novel way to screen diabetic retinopathy biomarkers in dogs.