Proteomic analysis of tear fluid and aqueous humor of children with and without uveitis

Abstract

Purpose : Changes in biochemical and protein composition of ocular fluid may reflect inflammation due to disruption of the blood-retinal barrier (BRB), as in uveitis. Tear fluid is studied for biomarker discovery in ocular and non-ocular diseases. Tear sampling is non-invasive and tolerated by children. We aim to compare proteins in tears and aqueous humor (AH) of patients with and without uveitis.

Methods : Our cross-sectional study collected tears and AH in 4 patients with uveitis (1 JIA-uveitis, 1 chronic anterior uveitis, 2 ADNIV) and 3 pediatric non-inflammatory controls. Tears were collected by Schirmer strip, and AH during routine eye surgery. Advanced proteomic strategies (TMT labeling and nanoLC-MS/MS) quantified proteins, normalized by total peptide amount. A log transformed average of 2 abundance readings per protein/subject were used to compare proteins in tears and AH of patients and controls using a Wilcoxon rank sum test (p-value<0.05).

Results : Seven patients (71% females, median age 17y [R 2-59] at collection) contributed 10 paired tear and AH samples. 145 proteins were identified at medium 95% or higher FDR confidence with at least 1 high confidence peptide. Protein abundance was significantly different in tears vs AH of uveitis patients (median 608 vs 5012, P value 0.009), but not controls (median 634 vs 121, P value 0.175) (Figure 1A/1B). Further analysis only included proteins detected in 100% of samples. Proteomic analysis showed significantly different expression of 31/63 (49%) proteins in tears and AH of uveitis patients, and of 10/18 proteins (45%) in controls (Figure 2A/2B).

Conclusions : Uveitis is vision-threatening and warrants exploration of techniques for early detection. The eye is an immune-privileged organ immunologically shielded by the BRB. ~50% of proteins overlapped in tears and AH. Of those differentially expressed, mammoglobin-B, cystatin-S, and secretoglobin family 1D member are reported in pediatric uveitis tear biomarker studies. Lysozyme, lactoferrin, lipocalin, albumin, and lacritin are common major tear proteins. Tear sampling is feasible in children compared to AH. Use of tears in uveitis biomarker studies is promising.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1: Differences in protein abundance in children without uveitis 1A and with uveitis 1B

 

Figure 2: Significant different protein expression in tears and aqueous humor in children with and without uveitis