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Jay M. Stewart, David S. Schultz, On-Tat Lee, Monique L. Trinidad; Collagen Cross-Links Reduce Corneal Permeability. Invest. Ophthalmol. Vis. Sci. 2009;50(4):1606-1612. doi: 10.1167/iovs.08-2727.
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purpose. To investigate the relationship between corneal permeability and nonenzymatic cross-link density.
methods. Corneas were dissected from 90 cadaveric porcine eyes. Samples were incubated for 24 hours with control solution or methylglyoxal at concentrations of 0.01%, 0.10%, and 1.00%. Nonenzymatic cross-link density in treated and control groups was quantified by papain digest and fluorescence spectrophotometry. Control and treated corneas were mounted in a customized Ussing-type chamber connected to vertical tubing, and specific hydraulic conductivity was determined according to the descent of a column of degassed saline at room temperature. Permeability to diffusion of fluorescein in a static chamber was determined for a similar set of corneal samples.
results. Methylglyoxal treatment effectively increased nonenzymatic cross-link content, as indicated by the average fluorescence for each group. Specific hydraulic conductivity (m2) was reduced with increasing cross-link density. Similarly, the permeability coefficient for the fluorescein solute consistently decreased with increasing methylglyoxal concentration, indicating diffusion impedance resulting from the treatment.
conclusions. Nonenzymatic cross-link density in the cornea can be significantly increased by treatment with methylglyoxal. Porcine cornea showed a nonlinear reduction in solute permeability and specific hydraulic conductivity with increasing cross-link density. This model suggests that age-related nonenzymatic cross-link accumulation can have a substantial impact on corneal permeability.
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