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Naren Shetty, Rohit Shetty, Arkasubhra Ghosh, Narayana Nethralaya study group; Screening corneal epithelial gene expression patterns for predicting post PRK (Photorefractive keratectomy) corneal haze. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2045.
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© ARVO (1962-2015); The Authors (2016-present)
Post surgical corneal haze has been previously studied, but pre-surgical predisposing factors towards corneal haze remains unknown. This study aims at analyzing gene expression in corneal epithelium collected during primary surgery of patients who developed corneal haze following PRK by microarray analysis and validating them by real-time PCR.
Corneal epithelium was collected intraoperative in patients undergoing PRK. Epithelium of 4 eyes of 2 patients who developed haze postoperatively and that of 6 eyes of 3 age matched control patients who did not develop haze were analysed. Mean age of cases and controls was 26 and 28 years respectively. Mean spherical equivalent of cases and controls was -3.37D &- 2.38D respectively. Gene expression microarrays were performed for the mRNA samples followed by bioinformatics analysis of underlying molecular pathways. Validation of deregulated genes was performed using quantitative real-time PCR for inflammatory markers, corneal structure genes, fibrosis associated genes and regulators of signaling cascade.
Bioinformatic analysis revealed 1100 upregulated and 1700 downregulated genes in the post PRK haze group. Patients who developed haze demonstrated upregulation of ECM (extracellular matrix) regulatory pathways (collagen, Laminin, ITGA1, etc), inflammatory cytokines (IL11, IL6, etc) and oxidative stress(PREX1,etc). Wnt signaling pathway (JUN, SOX17, etc) responsible for cellular proliferation and CXC motif containing chemokines (CXCL10, CXCL1, etc) were found to be downregulated on microarray analysis. Indian Hedgehog (IHH) signalling independent of wnt and PI3 kinases may have a rolein corneal haze. Validation of the microarray results by real-time PCR analysis showed that inflammatory cytokines like IL6 and TNFα were upregulated. Regulators of signaling cascades EGFR and Wnt3a were reduced in haze patients. The mechanism of action of these factors is being investigated.
Our study identifies some novel corneal biomarkers that may help in screening patients prone to develop corneal haze prior to surgery. This would help in better surgical planning and in the future, targeting and preventing the process of corneal haze.
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