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L. He, M. R. Frost, J. T. Siegwart, Jr., T. T. Norton; Adhesion-Related Protein and Vitamin D Receptor mRNA Levels in Tree Shrew Sclera During Minus Lens Treatment and During Recovery. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3681.
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© ARVO (1962-2015); The Authors (2016-present)
To examine differential changes in mRNA levels for 8 focal adhesion-related proteins and vitamin D receptor (VDR) in tree shrew sclera during the development of minus lens induced myopia and during recovery.
Real-time PCR was used to measure the levels of mRNA for adhesion-related proteins ARHGEF 12 (Rho guanine nucleotide exchange factor 12), Talin 1, Talin 2, Kindlin 2, Calpain 1, Calpain 2, Calpain 4, Syndecan 2 and for vitamin D receptor in the scleras of five groups of tree shrews. Three groups of tree shrews (n=5/group) received 1, 4, or 11 days of monocular -5 D lens treatment starting at 24 days of visual experience respectively; two groups of tree shrews (n=5/group) received 1 or 4 days of recovery after 11 days of lens wear. The untreated fellow eyes served as a control. Non-cycloplegic refractive measures (Nidek autorefractor) were performed on awake animals to monitor myopia development (lens compensation) and recovery.
After 1 day of lens wear, none of the genes showed significant differential changes between treated and control eyes. After 4 days of -5 D lens wear, four mRNA levels were significantly down-regulated in the treated eyes compared with the control eyes: Calpain 2 (-1.36 fold), Calpain 4 (-1.34 fold), Syndecan 2 (-1.36 fold), and VDR (-1.66 fold) [paired t-test, p<0.05]. After 11 days of lens wear, when the eyes had compensated for the -5D lens, there were no significant differences between the treated- and control-eye mRNA levels. After 1 day of recovery, there were no significant differences between treated and control eyes. After 4 days of recovery, the Calpain 4 mRNA level in the treated eyes was up-regulated by 1.23 fold compared with control eyes (p<0.05).
The Calpains appear to be signaling intermediates acting on cell migration and regulating focal adhesion structure and turnover. Syndecan 2 is also involved in cell-matrix interactions. If translated into protein levels, the down-regulation of Calpain 2, Calpain 4 and Syndecan 2 may play a role in focal adhesion turnover and allow increased extensibility in the sclera during myopia development by increasing slippage of the scleral layers across each other. Outdoor activity recently has been found to be protective against myopia (Jones et al., IOVS 48:3524, 2007; Rose et al., Ophthalmol. 115:1279, 2008). Thus, it is interesting to find that VDR mRNA levels decreased during myopia and were unaffected during recovery. How VDR levels in the sclera might be involved in myopia remains to be identified.
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