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M. Frost, T.T. Norton; Differential Protein Expression in Tree Shrew Sclera During the Development of Lens–Induced Myopia . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1148.
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The tree shrew model of refractive development is particularly useful because, like humans, tree shrews have a fibrous sclera. When myopia is induced with monocular minus–lens wear, the scleral biomechanical property ‘creep rate’ increases in the treated eye, allowing expansion of the globe by normal IOP. Changes in some candidate extracellular matrix proteins and mRNAs have been found in the sclera during the development of an induced myopia. We undertook a more neutral proteomic analysis using two–dimensional gel electrophoresis and mass spectrometry to identify scleral proteins that change during myopia development.
Five tree shrews (Tupaia glis belangeri) wore a monocular –5 D lens for 4 days, starting 24 days after natural eye opening. At the end of this time, all treated eyes had partially compensated for the minus lens and were –3.5 ± 1.5 D myopic relative to the untreated fellow control eyes. This lens–wear period was chosen because mRNA studies had previously shown significant expression changes at this time–point. Scleral proteins were then isolated and resolved by two–dimensional gel electrophoresis. The resulting protein profiles were compared using ProgenesisTM 2D analysis software to identify protein spots that were differentially represented between fellow treated and control eyes.
The scleral protein profile typically displayed ∼600 distinct protein spots within the pH 5–8 range. Comparison of the five treated eye and control eye scleras revealed 6 spots that were significantly differentially expressed in all five pairs of eyes, all slightly down–regulated in the treated eye by between 1.2 and 1.7 fold.
Because the use of a minus lens to induce myopia is a relatively mild stimulus, within the physiologically normal range of the eye, there may be few high–magnitude changes in the scleral protein levels. Rather, one would expect normal processes to be slightly up– or down–regulated under retinal control.
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