Study on iTRAQ-based differential expression protein analysis in nuclear cataract lens with different axial length

Objective\r\nTo identify and verify differentially expressed proteins in lens of nuclear cataract eyes with different axial lengths.\r\n\r\n\r\nMethods\r\nForty-eight nuclear cataract patients with the hardness grade Ⅲ to Ⅳ were enrolled from January 2016 to December 2017 in the east area of Xining city.The lens nucleus was obtained during extracapsular cataract extraction (ECCE) surgery.The samples were divided into six groups according to age and axial length, with 8 samples in each group.Seven normal transparent human lens nuclei were obtained from donors during corneal transplantation surgery and served as normal control.Water-soluble, water-insoluble and water-insoluble-urea-soluble protein fractions were extracted separately and merged to analyze by using 8-plex isobaric tags for relative and absolute quantitation (iTRAQ) labeling combined with 2D-LC/MS/MS.The data were processed with ProteinPilot software.Two technical replicates of iTRAQ analyses were carried out.Up-regulated and down-regulated proteins were selected in two replicates as candidate biomarkers.Twenty lens nuclei from 20 nulear cataract patients were divided into long axis young age group, normal axis young age group, long axis old age group and normal axis old age group.Western blot was used to confirm the most different proteins.This study protocol was approved by the Ethics Committee of TangDu Hospital of Air Force Medical University (TDLL2015046). Written consent was obtained from each participant.\r\n\r\n\r\nResults\r\nEighty proteins were identified.Six proteins were selected as differentially-expressed proteins.Sorbitol dehydrogenase (SDH) was elevated whereas beta-crystallin B2 (CRYBB2) was decreased in the long axis groups.The relative expression of SDH protein in the long axis low age group was 1.204±0.142, which was significantly higher than 0.711±0.072 in the normal axis low age group, the relative expression level of SDH in the long axis old age group was 1.092±0.334, which was significantly higher than 0.617±0.089 in the normal axis old age group, the difference was statistically significant (all at P\u003c0.05).\r\n\r\n\r\nConclusions\r\nThe expression levels of SDH in the nuclear cataract were elevated with long axial length.SDH may be involved in the pathogenesis of axial myopia-associated nuclear cataract.\r\n\r\n\r\nKey words: \r\nAxial lengths, eye; Human lens, crystalline; Nuclear cataract; Isotope labeling; Proteomics