Anatomical differences of the protein profile in the rabbit sclera during growth

We aimed to investigate the proteome changes in anatomical regions of sclera during growth and development of the rabbit. Sclera from New Zealand white rabbits of three ages (1 month, 2 months and 6 months) was dissected into three segments - anterior, equatorial, and posterior. A total of 36 samples were divided into groups by age and anatomical region. Tryptic digests of total proteins were analyzed by liquid chromatography followed by tandem mass spectrometry (LC-MS/MS). Label-free quantification based on spectral counts was used to determine the relative protein abundance and identify proteins with statistically significant differences between age groups or anatomical regions of the sclera. Western blotting was performed to validate some of the differentially expressed proteins. A total of 840 non-redundant proteins was identified in the sclera at different ages and regions with protein and peptide false discovery rate (FDR) at ≤1.0% and ≤0.1%, respectively. Differentially expressed proteins were identified by comparing age or anatomical region. Among these, periostin showed decreasing abundance with age, while myocilin, latent-transforming growth factor beta-binding protein 2, hyaluronan, proteoglycan link protein 1 and selenbp1 showed increasing abundance with age. In mature rabbits, alcohol dehydrogenase showed region-related differences in the sclera. Periostin showed an age-related decrease while selenbp1 showed an age-related increase in abundance in the anterior region. Vitronectin and extracellular superoxide dismutase had greater expression with age in the equatorial and posterior regions, respectively. The age related differential expression of periostin and selenbp1 was confirmed by western blotting. In conclusion, the protein profile of sclera showed age- and region-related differences. The differential protein profiles provide a baseline for understanding changes in the protein expression in the young and mature rabbit that appears to show regional changes. The changes observed in the present study add to the existing knowledge about regional alterations in biomechanical properties of sclera during growth.