Early quantitative profiling of differential retinal protein expression in lens-induced myopia in Guinea pig using fluorescence difference two-dimensional gel electrophoresis

The current study aimed to investigate the differential protein expression in Guinea pig retinas in response to lens-induced myopia (LIM) before fully compensated eye growth. Four days old Guinea pigs (n=5) were subjected to -4D LIM for 8 days. Refractive errors were measured before and at the end of the lens wear period. Ocular dimensions were also recorded using high-frequency A-scan ultrasonography. After the LIM treatment, retinas of both eyes were harvested and soluble proteins were extracted. Paired retinal protein expressions in each animal were profiled and compared using a sensitive fluorescence difference two-dimensional gel electrophoresis. The quantitative retinal proteomes of myopic and control eye were analysed using computerised DeCyder software. Those proteins that were consistently changed with at least 1.2-fold difference (P<0.05) in the same direction in all five animals were extracted, trypsin digested and identified by tandem mass spectrometry. Significant myopia was induced in Guinea pigs after 8 days of lens wear. The vitreous chamber depth in lens-treated eyes was found to be significantly elongated. Typically, more than 1,000 protein spots could be detected from each retina. Thirty-two of them showed differential expression between myopic and untreated retina. Among these proteins, 21 spots were upregulated and 11 were downregulated. Eight protein spots could be successfully identified which included β-actin, enolase 1, cytosolic malate dehydrogenase, Ras-related protein Rab-11B, protein-L-isoaspartate (D-aspartate) O-methyltransferase, PKM2 protein, X-linked eukaryotic translation initiation factor 1A and ACP1 protein. The present study serves as the first report to uncover the retinal 2D proteome expressions in mammalian Guinea pig myopia model using a top-down fluorescent dyes labelling gel approach. The results showed a downregulation in glycolytic enzymes that may suggest a significant alteration of glycolysis during myopia development. Other protein candidates also suggested multiple pathways which could provide new insights for further study of the myopic eye growth.