Label free LC-MS/MS quantitative analysis of aqueous humor proteome from keratoconus and myopic controls patients

Abstract

Purpose: The etiology and the factors governing keratoconus (KC) progression remain to be elucidated. It has been reported to arise as a consequence of biochemical alterations in the cornea. It is known that the expression profile for some proteins in the aqueous humor (hAH) changes in some diseases. Our purpose was to identify the possible implication of hAH in the development of KC disease based on hAH protein expression differences among patients with KC and control subjects by a high-throughput mass spectrometry approach.

Methods: Aqueous humor samples were acquired from 5 patients with keratoconus and 5 myopic control subjects. Spectral counting mass spectrometry analysis was performed to determine the relative amounts of hAH proteins in keratokonus and controls patients.

Results: All patients included in the study presented severe keratoconus (K2>52D), and slit lamp examination revealed microfolds in Descemets membrane without clinical signs of hydrops. As a result of mass spectrometry analysis a total of 242 distinct proteins were significantly identified. Eleven proteins exhibited inter-group significant protein expression differences, seven of which were overexpressed whereas four exhibited decreased expression levels. Gene ontology analyses revealed that deregulated proteins are implicated in biological processes such as regulation of proteolysis, response to hypoxia, response to hydrogen peroxide and regulation of collagen biosynthesis, among others.

Conclusions: The protein expression profile in hAH from KC patients varies from that of myopic control subjects evidencing the implication, direct or indirect, of hAH in keratoconus disease. In consequence, this study demonstrates that in-deep analysis of hAH proteome will lead to a greater understanding of the pathophysiology of keratoconus disease.

Keywords: 663 proteomics • 574 keratoconus • 427 aqueous