Abstract
The lacrimal film has attracted increasing interest in the last decades as a potential source of biomarkers of physiopathological states, due to its accessibility, moderate complexity, and responsiveness to ocular and systemic diseases. High‐performance liquid chromatography‐mass spectrometry (LC‐MS) has led to effective approaches to tear proteomics, despite the intrinsic limitations in sample amounts. This review focuses on the recent progress in strategy and technology, with an emphasis on the potential for personalized medicine. After an introduction on lacrimal‐film composition, examples of applications to biomarker discovery are discussed, comparing approaches based on pooled‐sample and single‐tear analysis. Then, the most critical steps of the experimental pipeline, that is, tear collection, sample fractionation, and LC‐MS implementation, are discussed with reference to proteome‐coverage optimization. Advantages and challenges of the alternative procedures are highlighted. Despite the still limited number of studies, tear quantitative proteomics, including single‐tear investigation, could offer unique contributions to the identification of low‐invasiveness, sustained‐accessibility biomarkers, and to the development of personalized approaches to therapy and diagnosis.
Highlights
Clinical investigation based on proteomics has made great strides, moving from the discovery of single biomarkers for early disease diagnosis to the comprehensive characterization of protein‐ expression profiles, able to identify both the specific disease and its subtyping (Hovestadt et al, 2020; Tyler & Bunyavanich, 2019)
The offline strong cation exchange chromatography (SCX) fractionation is the fastest alternative among the three reported methods for a pre‐ fractionation in tear fluid analysis, but its effectiveness in proteome coverage improvement is controversial: SCX seems to offer the highest proteome coverage when compared with IEF and GeLC (Mostovenko et al, 2013), Both SCX and off‐gel electrophoresis (OGE) separation are usually performed at the peptide level and exploit the peptide pIs, but they lead to different subsets of identified proteins (Antberg et al, 2012)
This review summarizes the most relevant differences in mass spectrometry (MS)‐based approaches to tear proteome characterization
Summary
Clinical investigation based on proteomics (clinical proteomics) has made great strides, moving from the discovery of single biomarkers for early disease diagnosis to the comprehensive characterization of protein‐ expression profiles, able to identify both the specific disease and its subtyping (Hovestadt et al, 2020; Tyler & Bunyavanich, 2019). Studies on other body fluids as alternative sources of biomarkers have seen a major impulse Peripheral fluids such as urine, saliva, sweat, fat aspirate, and tears have elicited a growing interest, thanks to their sustainable accessibility and relatively low complexity (Azkargorta et al, 2017; Beasley‐ Green, 2016; Brambilla et al, 2012; Castagnola et al, 2011; Csősz et al, 2017; Gerner et al, 2020; Katsani & Sakellari, 2019). These samples are usually simple to collect and contain potential disease‐related signals.
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