Investigation of the global protein content from healthy human tears.

Considering absence of invasiveness and side effects, tears emerge as a particularly attractive fluid for biomarker discovery and therefore for daily clinical use. However, to date this fluid remains poorly studied in healthy condition. Here, we present an updated in-depth characterisation of the human healthy tear protein composition using proteomics approach. Both eyes of 8 healthy controls (4 men and 4 women, average age: 38 ±â€¯18) were collected using the Schirmer's strip method. After liquid digestion and off-gel electrophoresis fractionation, three independent proteomics analyses were performed on a LTQ-Orbitrap Velos Pro. Globally, 1351 proteins were identified with 2 unique peptides and 1% FDR. Gene ontology analyses showed up that 39% of the tear proteins were enzymes, with high numbers of dehydrogenases, phosphatases, kinases and ligases. Immunoglobulins, serpins and 14-3-3 domains proteins also emerged as the main tear protein families. The glycolysis and the coagulation and complement cascades, which were already shown in tears as involved in ocular and systemic diseases, were highlighted performing pathway analyses. Our study therefore complements the existing data on healthy tears proteome. Nevertheless, extensive studies for deeply and definitively characterise this promising fluid are required in the near future in order to be able to routinely use this fluid in clinics. A better understanding of its protein content will probably open new avenues in the biomarker discovery and clinical practice in the near future.

Exploring the human tear fluid: discovery of new biomarkers in multiple sclerosis.

PURPOSE: Multiple sclerosis is the first cause of progressive neurological disability among young adults living in Western countries. Its diagnosis is mostly based on clinical evaluation, neuroimaging, and in some cases cerebrospinal fluid (CSF) analysis, but no definitive diagnostic test exists. We proposed here that the exploration of tears from multiple sclerosis patients could lead to the discovery of new biomarkers. EXPERIMENTAL DESIGN: Thirty multiple sclerosis patients (20% men) recruited to the Geneva University Hospitals were included in our study (mean age ± SD [years]: 42.4 ± 15.9). Twenty-five control patients (32% men) were also enrolled (mean age ± SD [years]: 42.7±15.1). Tears, CSF or blood was collected for each patient. Three independent quantitative (tandem mass tag) experiments were carried out between tears from multiple sclerosis and control patients. Protein verification was performed by Western blot on tears and CSF and by ELISA on serum samples. RESULTS: Combined proteomics analyses provided 185 identified tear proteins. Among the differential proteins, alpha-1 antichymotrypsin was the only one to be significantly increased in the three experiments with similar ratios (ratios 1.6 to 2.5, p < 0.05). Its tear, CSF and serum elevation were further confirmed by Western blot and ELISA, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: This study supports the concept that modifications of the tear proteome can reflect biological abnormalities associated with multiple sclerosis and perhaps other inflammatory conditions affecting the CNS. In addition, alpha-1 antichymotrypsin elevation in tear fluid emerges as a promising biomarker for the diagnosis of multiple sclerosis.