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Y. Izawa, T. Matsuo, T. Uchida, K. Shimamura, H. Ohtsuki; Atomic Force Microscopic Observation of Trehalose–Treated and Dried Corneal Surface . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5574.
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Trehalose is a disaccharide and present in organisms such as yeasts and seeds. It confers anhydrobiosis, the resistance to dryness and capability of surviving in drying conditions. Trehalose is shown to protect human corneal epithelial cells in culture from death by desiccation (BJO 2001;85:610–612). Furthermore, trehalose eye drops are proven effective to improve signs and symptoms of moderate–to–severe dry eye syndrome (Ophthalmology 2002;109:2024–2029, JJO 2004;48:321–327). To search for the mechanism of the effect of trehalose, we observed the trehalose–treated corneal surface of porcine eyes with atomic force microscopy in this study.
Enucleated porcine eyes were obtained from a local slaughterhouse, stored at 4 C, and used within 6 hours. Full–thickness corneal pieces in 5 x 5 mm size were cut out with a razor blade. Three kinds of disaccharide, trehalose, maltose, and sucrose, dissolved in saline at 100 mM concentration, and saline as a control, were applied to the surface of the full–thickness corneal pieces, and stood for 15 minutes at room temperature. Excess fluid was then absorbed by cotton tips at the edge of the pieces, and the corneal pieces were dried naturally at room temperature and in room humidity for 72 hours. The dried corneal pieces were observed first with a dissecting microscope and then fixed on the observation platform for atomic force microscopy.
By dissecting microscopic observation, trehalose–treated corneal surface appeared smoother than saline, maltose, and sucrose–treated surface. By atomic force microscopic observation in a tapping mode, saline, maltose, and sucrose–treated corneal surface had a larger number of pits in a greater size than trehalose–treated surface. The number of pits in the size of 0.14 micrometer or greater was significantly smaller in trehalose–treated corneal surface than in saline–treated surface (P=0.0017, n=28, Mann–Whitney U test). No significant difference was found in pits between maltose or sucrose–treated surface and saline–treated surface. Mean roughness index, an indicator for surface roughness, was significantly lower in trehalose–treated surface than in saline–treated surface (P=0.0027, n=28, Mann–Whitney U test).
Trehalose–treated corneal surface is smoother than saline, maltose, or sucrose–treated surface. One effect of trehalose is to keep the corneal surface smooth in drying condition.
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