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Chea-Su Kee, Yan-yan Xi, Chin-Hung Geoffrey Chu, Shea Ping Yip, Jody Summers Rada; Regional variations in corneal and scleral mRNA expressions of MMP2, TIMP2, TGFβ2 in highly myopic-astigmatic chicks. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3676.
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© ARVO (1962-2015); The Authors (2016-present)
To determine MMP2, TIMP2, TGFβ2 mRNA expressions at different corneal and scleral regions in highly myopic-astigmatic chicks.
High magnitudes of myopia and astigmatism were induced by using diffuser to monocularly form-deprive chicks from P5 to P12 (n=8). Age-matched chicks without any treatment served as controls (n=8). Refractive errors and corneal biometric parameters were measured by, respectively, a modified Hartinger refractometer and a custom-made corneal videokeratography system. The refractive and corneal biometric components were expressed as interocular difference between the treated/right and fellow/left eyes. Corneal (1.5mm diameter) and posterior scleral tissues punches (5mm diameter) were obtained using a disposable trephine from five regions: central, superior, inferior, temporal and nasal. Real-time RT PCR was used to quantify the mRNA expressions of MMP2, TIMP2, TGFβ2, and 18S rRNA. Fold of change at each region was calculated by 2-ΔΔCT method, where ΔΔCT=[(CT target gene - CT 18S gene) treated eye - (CT target gene - CT 18S gene) fellow eye]. Mann-Whitney test was used to compare the changes between treated and control groups.
Compared to the control group, significantly higher mRNA expressions in MMP2, TIMP2 and TGFβ2 were found at the superior region of posterior sclera (all p≤0.014). In addition, there was higher than normal expression of MMP2 at the nasal quadrant of posterior sclera (p=0.046). When data from all birds were pooled for correlation analyses, the correlations between refractive-error components and mRNA expressions were generally higher in sclera than those in cornea. All three target genes at the superior sclera showed moderate-high correlations with refractive/corneal spherical equivalent and J45 astigmatic components (r=0.51~0.88, all p≤0.01). In addition, high correlations between TGFβ2 with MMP2 (r=0.88, p<0.001) and TIMP2 (r=0.83, p<0.001) were found at the nasal cornea, whereas high correlations between TGFβ2 with MMP2 (r=0.91, p<0.001) and TIMP2 (r=0.90, p<0.001) were found at the superior sclera.
Regional variations in mRNA expressions of the three target genes were found in corneal and scleral tissues. These results suggest that the eye shape remodeling during myopia development may be modulated by local molecular mechanism.
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