Precious tears: Mass spectrometry pipeline comparison of tear proteomic analysis to find biomarkers of health and disease

Using Schirmer strips non-invasively and painlessly placed on the eye can capture enough tear fluid for detailed protein analysis, Georgia researchers report in the International Journal of Molecular Scienc.

Thesis

The tear film is a multi-layered fluid that coats the corneal and conjunctival epithelium of the eye, providing lubrication, nutrition, and protection from the external environme.

The background tear film is a 2-6 µm stratified fluid composed of mucous and lipid layers that covers the corneal and conjunctival epithelium of the ocular surfa.

In the past, proteomic analysis of tears has been challenging due to its small si.

Discussion In this study, the authors compared four different workflows, including two digestion methods and two fragmentation methods, to establish an optimized workflow for proteomic analysis of human tear sampl.

Using the selected workflow, a total of 3370 unique proteins were identified, with an average of 678 unique proteins identified per samp.

Since ocular surface disease is not always bilateral and each eye has different properties, more accurate correlations can be established between disease status and tear proteomic signatur.

The most abundant proteins in tears were identified as members of the immunoglobulin, keratin, and complement famili.

Seventeen complement family proteins were also present in most tear sampl.

In addition to the immunomodulatory family, the apolipoprotein family is also highly represented in tears, with 11 apolipoproteins found in the analys.

Structural proteins on the ocular surface, such as keratin and myosin, are commonly found in tears in both healthy and diseased conditio.

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CONCLUSIONS: The study demonstrates that tear proteomics can be used to discover diagnostic and prognostic biomarkers for a variety of ocular and systemic diseases, including dry eye, pterygium, keratoconus, glaucoma, diabetic retinopathy, cancer, systemic sclerosis disease and cystic fibros.

The authors say -- it is expected that one day tear tests could be as routine as blood tests at physical exams and used to diagnose conditions ranging from dry eye to Alzheimer.

"Our findings further our understanding of the tear film by identifying pathways and families of proteins involved in a healthy tear film and its barrier integrity," said Ashok Shar.

Their goals include developing a protein database of healthy individuals that is freely available to other scientists working to identify abnormal protein biomarkers for disease and to pursue biomarker development of their own intere.

"What's the scope of what we're trying to do to create a health profile of these proteins," he said, adding that they're also using their technology to objectively diagnose common dry eye conditions, including sub-classifying the disease to be able to identify, which pain , Dry eyes are caused by autoimmune diseas.

They are also comparing the distribution of proteins within the eye that help shape the aqueous humor and tear fi.

In collaboration with MCG ophthalmologists and optometrists, Ashok Sharma has been trying to find biomarkers of glaucoma in aqueous humor, a larger but more difficult-to-collect fluid, although most people might think that glaucoma is not always caused by the eyeball The higher pressure within is determin.

He wondered whether tears and aqueous humor could provide similar clues, even though it was clear that the two fluids came from different sourc.

Although there is a lot of protein in tears, it has been technically difficult to obtain sufficient quantities of tears to analyze th.

The study introduces a method for collecting tears that promises to clear a major hurdle to the future of tear testing -- they're not talking about collecting the tears that run down our cheeks when we're sad, because they're diluted, not a biomarker good sour.

Instead, place the Schirmer strip in the far corner of the eye, away from the tear duct, for about 5 minutes, until the tears wet, cover and protect our ey.

This has collected about 10 to 15 microliters of tear fluid, far less than a dr.

"This method is noninvasive," says Shruti Shar.

Now, Sharma is applying to the National Eye Institute for funding to build a database of healthy, diverse populations, with a proposal to build the database with a representative population of 1,600 peop.

It takes about an hour to run a sample, and it can take about a year to build the database, Ashok Sharma sa.