Abstract
Purpose:
To identify changes to the retinal proteome following branch retinal vein occlusion (BRVO)
Methods:
Experimental BRVO<br /> In 5 Danish Landrace pigs BRVO was induced in the right eyes. With an argon laser (532 nm) laser burns were applied directly on an inferior branch vein until stagnation of the venous blood flow was observed. In the left eyes that served as controls an identical area of laser burns was created in the inferior retina in an area devoid of vessels.<br /> <br /> Mass spectrometry and bioinformatics<br /> After fifteen days the eyes were enucleated and the retinas were excised and prepared for label-free liquid chromatography tandem mass spectrometry by using a filter aided sample preparation method. Mass spectrometry data were searched against a pig isoform database optimized from Uniprot using MaxQuant (v. 1.5.0.22). Standard settings included a false discovery rate of 1% and unique peptides ≥ 2 peptides. In Perseus (version 1.5.0.9) technical replicates were averaged by mean and proteins were filtered by requiring at least 2 unique peptides and at least 3 valid entries. The resulting matrix was exported to Excel for statistic analysis by paired t-test. The Panther Classification System (Version 9.0) was used for GeneOntology analysis and pathway identification.
Results:
A total of 1974 proteins were identified. A number of 114 proteins were significantly expressed (p < 0.05). A total of 77 proteins were significantly upregulated whilst 37 proteins were significantly downregulated. A number of annexin proteins including annexin A1, annexin A2, annexin A4, annexin A11 were found to be significantly upregulated. Proteins involved in the integrin signaling pathway accounted for 20.8% of all pathway hits for upregulated proteins. Proteins with transporter functions accounted for 27.0% of all function hits in the GeneOntology analysis of the molecular functions related to significantly downregulated proteins.
Conclusions:
BRVO resulted in an upregulation of annexin A1, annexin A2, annexin A4, annexin A11 as well as proteins involved in the integrin signalling pathway. Annexin A2 and the integrin signalling pathway may be driving forces in BRVO-induced angiogenesis and neovascularisation. BRVO induced a downregulation of proteins with transporter functions which may compromise maintenance of the retinal ion and water homeostasis.