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Qianru Zhang, Ying-Bo Shui, Anne Kettler, James Malone, Robert Townsend, David Beebe; Initial proteomic analysis of structural changes in the aging human vitreous. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1585. doi: https://doi.org/.
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A substantial proportion of vision-threatening retinal damage in older age is caused by degeneration of the vitreous body, including rhegmatogenous retinal detachment, macular hole, epiretinal membrane formation and macular traction syndrome. To prevent these conditions we need to understand the changes in vitreous structure that occur with age. We identify the structural proteins of the human vitreous, setting the stage for identification of changes in these proteins during aging.
Vitreous bodies were carefully dissected from donor eyes. Each vitreous body was divided into two portions. One was washed overnight in a mesh screen suspended in 1 L of PBS, while the other sample was analyzed in its native state. Samples were subjected to proteomic analysis by HPLC/high resolution mass spectroscopy or western blotting to identify and quantify the structural proteins of the vitreous.
A total of 407 proteins were identified in the vitreous samples. Levels of most proteins decreased dramatically after washing, including alphaA- and alphaB-crystallins, Ig gamma-3 chain C region, serum albumin, and glucose-6-phosphate isomerase. These proteins were considered as soluble components of the vitreous. Proteins that increased in relative abundance in washed, compared to whole vitreous were considered to be structural components of the vitreous. In addition to well-known vitreous structural proteins, such as collagen alpha-1(II), collagen alpha-2(IX), opticin and chondromodulin-1, we identified fibrillin-1, collagen alpha-1 (XXII) and latent-transforming growth factor beta-binding protein 2. Using western blotting, we are measuring age-related changes in the levels of collagen II, opticin and chondromodulin-1 and will extend this analysis to each of the structural components of the vitreous.
Using high-throughput proteomic analysis, we obtained the first comprehensive list of vitreous structural proteins. Quantification of changes in protein abundance and post-translational modifications, like proteolysis or glycation, should provide insight into the cause and prevention of vitreous liquefaction and its impact on age-related retinal damage.
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