Intraindividual Proteomic Comparison of Human Tears and Vitreous in Patients With Different Vitreoretinal Diseases by Means of Antibody Microarrays

Abstract

Purpose: : To develop an intraindividual proteome analysis of human tears and vitreous samples in patients with various vitreoretinal diseases.

Methods: : Tear fluid was collected using Schirmer strips and corresponding vitreous samples were taken from 24 patients during pars plana vitrectomy of patients with macular pucker (n=7), idiopathic macular hole (n=4), proliferative diabetic retinopathy (n=4), rhegmatogenous (n=3) or tractional (n=3) retinal detachment and neovascular age-related macular degeneration (n=3). Protein expression levels were estimated using customized antibody microarrays. Signal intensities obtained from microarray analysis were normalized using Z-score algorithms. To estimate changes in protein expression, mean intensities of proteins in tears and vitreous were compared by calculating the z-ratio. In order to determine the proportion of mean protein intensity in the different clinical groups, we calculated the percental difference of mean protein levels between tears and vitreous on the basis of values for patients with macular pucker (control group). Differences of mean protein level between tears and vitreous greater than 150% were considered as significant.

Results: : Complex patterns of proteins and peptides were detected in all clinical groups in tears as well as in vitreous. Furthermore, significant differences in mean protein intensity were detected in tears and vitreous in all groups. Mean intensities of some proteins, e.g. Interleukin 2, HSP27, Cystatin and Protein S100A8 were significantly higher in tears in all clinical groups compared to the intensities in vitreous. Mean intensities of e.g. PDGF A and ß2-Microglobulin in all clinical groups were significantly higher in vitreous compared to protein expression in tears (z-ratio of ±1,96 is inferred as significant, p<0.05).With respect to the control subjects with macular pucker, protein abundance of complement factors C5-C7 and C9 was significantly higher in vitreous especially in the group of patients with neovascular age-related macular degeneration (protein expression in vitreous compared to tears greater than 150%).

Conclusions: : Our study provides an intraindividual analysis of the human tear and vitreous proteome and reveals protein alterations in the included clinical groups compared to the group of patients with macular pucker. Each vitreoretinal disease corresponded with a unique set of proteins in tears and in vitreous. Significant differences in protein expression in tears and vitreous could be observed in all clinical groups. Furthermore some proteins are almost solely expressed in tears or vitreous, respectively.

Keywords: proteomics • vitreous • vitreoretinal surgery