Isotope-coded protein label based quantitative proteomic analysis reveals significant up-regulation of apolipoprotein A1 and ovotransferrin in the myopic chick vitreous

This study used isotope-coded protein label (ICPL) quantitative proteomics and bioinformatics analysis to examine changes in vitreous protein content and associated pathways during lens-induced eye growth. First, the vitreous protein profile of normal 7-day old chicks was characterized by nano-liquid chromatography electrospray ionization tandem mass spectrometry. A total of 341 unique proteins were identified. Next, myopia and hyperopia were induced in the same chick by attaching -10D lenses to the right eye and +10D lenses to the left eye, for 3 and 7 days. Protein expression in lens-induced ametropic eyes was analyzed using the ICPL approach coupled to LCMS. Four proteins (cystatin, apolipoprotein A1, ovotransferrin, and purpurin) were significantly up-regulated in the vitreous after 3 days of wearing -10D lenses relative to +10D lens contralateral eyes. The differences in protein expression were less pronounced after 7 days when the eyes approached full compensation. In a different group of chicks, western blot confirmed the up-regulation of apolipoprotein A1 and ovotransferrin in the myopic vitreous relative to both contralateral lens-free eyes and hyperopic eyes in separate animals wearing +10D lenses. Bioinformatics analysis suggested oxidative stress and lipid metabolism as pathways involved in compensated ocular elongation.