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T. Kryczka, G. Wollensak, S. Sel, A. Midelfart; Metabolic Profile of Porcine Corneas after Photodynamic Cross-linking Treatment. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5487.
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Keratoconus is a noninflammatory conelike ectasia of the cornea, which progresses over time leading to substantial reduction of vision and discomfort. Photodynamic collagen cross-linking using ultraviolet A (UVA) irradiation and the photosensitizer riboflavin has been recently introduced as a new possible treatment of this disease. The aim of this study is to examine the influence of the cross-linking treatment on metabolic profile of corneas.
36 corneal buttons with 10 mm diameter were trephined from fresh post mortem porcine eyes; the epithelium was removed completely in all samples. 12 porcine corneas were used as controls. 12 corneas were cross-linked with the photosensitizer riboflavin (1 mg riboflavin-5-phosphate in 10 ml 20% dextran T-500) and UVA irradiation for 30 minutes using a double UVA diode (370 nm, 3 mW/cm2). Another 12 were obtained after the same cross-linking procedure, just omitting dextran in the photosensitizer solution. After treatment, the samples were immediately frozen at -80 ºC. The metabolic profiles of the samples were investigated with HR MAS (High Resolution Magic Angle Spinning) 1H NMR (Nuclear Magnetic Resonance) spectroscopy (14.1 T) operating at 600.132 MHz.
20 metabolites were assigned in HR MAS 1H NMR spectra. Corneas exposed to cross-linking with riboflavin/dextran solution and UVA displayed significant differences in levels of leucine, glutathione and formate in comparison to the controls. Corneas cross-linked with riboflavin and UVA showed significant differences in levels of alanin, arginine, lactate and tryptophan in comparison to the controls.
The study presents the metabolic profiles of porcine corneas after photodynamic collagen cross-linking treatment. This treatment option seems to be safe as the levels of most of the analysed water soluble metabolites were not significantly changed after this procedure and the cross-linking process did not seem to induce major alterations in the collagen amino acid composition. Then the questions arise about the long-term effect of photodynamic collagen cross-linking on metabolic profile of corneas and the nature of the collagen cross-links. Further research could explore the above issues.
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