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From the Department of Physiological Optics, School of Optometry, University of Alabama at Birmingham.
PURPOSE. In tree shrews, visual form deprivation induces myopia and tissue remodeling in the sclera, characterized by decreased levels of collagen and glycosaminoglycans (GAGs) and increased levels of matrix metalloproteinases (MMPs). Removal of the visual deprivation allows recovery. This study investigated whether these changes are accompanied by changes in steady state mRNA levels in the sclera.
METHODS. Quantitative competitive reverse transcriptionpolymerase chain
reaction (RT-PCR) was used to measure steady state levels of mRNA for
collagen (
1(I) chain), decorin (core protein), gelatinase-A (MMP-2),
stromelysin-1 (MMP-3), and a tissue inhibitor of metalloproteinase
(TIMP-1) in the scleras of tree shrews that received either 11 days of
monocular form deprivation (MD) or 11 days of MD followed by 4 days of
recovery. A group of age-matched normal animals was also measured.
RESULTS. After 11 days of MD,
1(I) collagen mRNA levels were 34% lower, and
MMP-2 mRNA levels were 66% higher in the deprived eyes than in the
control eyes. After 4 days of recovery, collagen mRNA levels were 33%
higher, MMP-2 levels were 20% lower, and TIMP-1 levels were 43%
higher in the recovering eyes than in the control eyes. Decorin and
MMP-3 mRNA levels were not significantly different between the treated
and control eyes after MD or after recovery.
CONCLUSIONS. The tissue remodeling in mammalian sclera induced by altering the visual environment is accompanied by modulation of mRNA levels in the sclera. The levels of collagen and MMP-2 mRNA were modulated in a pattern generally consistent with observed changes in protein levels, suggesting that visual regulation of the levels of these scleral proteins may involve modulation of gene expression at the transcriptional level.
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