Effect of contact lenses on the protein composition in tear film: a ProteinChip study

Background The aim of this study was to analyze and compare the effects of rigid gas permeable and soft contact lenses on the protein composition in the tear film of contact lens wearers. Methods Wearers of soft contact lenses (CL_S, n=13) and rigid gas permeable contact lenses (CL_H, n=13) were recruited for this study. Thirteen non-contact lens wearers were also included as the control. Tears were collected using Schirmer strips and frozen until use. The tears were eluted and analyzed on ProteinChips SELDI-TOF (surfaceenhanced laser desorption and ionization in time of flight mass spectrometry; Bio-Rad, USA) with different chromatographic surfaces (cationic and anionic exchanger and reversed phase surface). The SELDI spectra were analyzed by multivariate statistical analysis and artificial neural networks in order to find a biomarker panel which differentiates best between the groups. In order to identify protein/peptide peaks from SELDI spectra which showed a significant difference between groups, fractionated tear samples were analyzed using MALDI-TOF MS (matrixassisted laser desorption/ionization time-of-flight mass spectrometry). For validation of biomarkers, we used an antibody microarray approach. Results Complex patterns of tear proteins and peptides were detected in the control group and in both contact lens groups. The tear protein composition in both wearers of rigid gas permeable (CL_H) and soft contact lenses (CL_S) differed significantly from protein composition in noncontact lens wearers (p<0.01). The identification of biomarkers revealed an increase of Protein S100 A8 in the group of wearers of soft contact lenses (CL_S) and a decrease of a main tear protein, lysozyme, in both contact lens groups. The identified biomarker cystatin was upregulated in the group of rigid gas permeable lens wearers (CL_H), whereas the protein intensity of secretoglobin was significantly reduced in this group. Using the microarray approach, detected alterations could be confirmed. Conclusions Contact lens wear alters the protein profiles in a complex manner. This study demonstrates that significant changes can be found in wearers of soft contact lenses (CL_S) and rigid gas permeable contact lenses (CL_H). Some biomarker intensities are significantly altered only in the group of rigid gas permeable lens wearers (CL_H).