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A. Acera, T. Suarez, E. Vecino, J. A. Duran; Molecular Changes in the Proteomic Profile of Keratoconus Patient Tears. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4312. doi: https://doi.org/.
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The aim of this study was to identify tear proteins which differentially expressed in keratoconus vs. normal tears.
Tears from six normal subjects and six patients with keratoconus were analyzed by two-dimensional gel electrophoresis. Total protein from tears was separated in the first dimension by isoelectric focusing (IPG strips), and the second dimension was carried out using 8-16% SDS-PAGE. Gel images were analyzed using Progenesis software. Spots of interest were manually excised from gels and the corresponding proteins were identified by MALDI-TOF
Approximately 200 protein spots were detected in each gel. Four spots were identified from the total proteome as being differentially expressed between keratoconus and control tear samples; three of these proteins were overexpressed including cystatin-S (1.7 fold; p=0.018), immunoglobulin kappa chain C (1.6 fold; p=0.01) and immunoglobulin J chain (1.5 fold; p=0.006). Only lipocalin 1 was found to be down-regulated (-1.2 fold; p<0.001).
Our results revealed relatively low levels of lipocalin-1 in the tears of keratoconus patients compared to controls, which could contribute to an unwettable and unstable surface. High levels of cystatin-S indicate elevated concentrations of cysteine proteinases in tears. These enzymes may play important roles in ocular defense mechanisms activated under pathological conditions. Our findings suggest that the proteins identified in this study may contribute to the progression of keratoconus and should be studied in conjunction with proteins which have also been found to be altered on the ocular surface.
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