Region-specific differential corneal and scleral mRNA expressions of MMP2, TIMP2, and TGFB2 in highly myopic-astigmatic chicks

Myopia and astigmatism, two common refractive errors frequently co-exist, are affecting vision at all working distances in the affected populations worldwide. Eyeballs having these refractive errors are known to exhibit abnormal eye shape at the anterior and posterior eye segments, but whether the outer coats of these abnormal eyeballs, cornea anteriorly and sclera posteriorly, are regulated by region-specific molecular mechanism remains unclear. Here we presented the changes in mRNA expression levels of three genes (MMP2, TIMP2, and TGFB2), all known to participate in extracellular matrix organization, at five regions of the cornea and sclera in chickens developing high myopia and astigmatism induced by form deprivation. We found that, compared to normal chicks, the highly myopic-astigmatic chicks had significantly higher expression of all three genes in the superior sclera (Mann-Whitney tests, all p ≤ 0.05), as well as higher TIMP2 expression in the central cornea and nasal sclera (Mann-Whitney tests, both p ≤ 0.05). Strikingly, the superior scleral region stood out as showing the strongest and most widespread correlations between mRNA expression and biometry parameters including axial and astigmatic components (r = + 0.52~ + 0.85, all p < 0.05). These results imply that local molecular mechanism may manipulate the eye shape remodeling across the globe during refractive-error development.