Abstract
Purpose :
There is a need for a rapid non-invasive method to detect and monitor progression of age-related macular degeneration (AMD). Our laboratory has recently developed techniques for isolation and analysis of extracellular vesicles (EVs) present in tears. We hypothesized that tear EV size and concentration would be greater in AMD, compared with controls.
Methods :
We collected tears from patients with AMD (n=6) and controls (n= 20) using Schirmer tear strips. Extracellular vesicles (EVs) were eluted from the strips in PBS overnight at 4°C. EVs were isolated through a series of ultracentrifugation steps (1000xg/4°C/10min, 25000xg/4°C/30min) followed by final wash and isolation at 115,000xg/4°C/90min. The isolated EVs underwent analysis using ZetaView® ParticleMetrix to determine their size and concentration, which were compared using generalized estimating equation methods to account for correlation between right and left eyes. To examine the bulk protein content of the exosomes, we used unbiased silver stain analysis.
Results :
Mean EV concentration was lower in tears of eyes with AMD than those of controls (14,930,000 particles/ml vs 33,577,777 particles/ml; difference = -1864778 particles/ml; 95% CI= -977384 particles/ml to -36318171 particles/ml; p = 0.039). However, mean exosome size was not significantly different in the tears of eyes with AMD compared with controls (206.81nm vs 198.97nm; difference 7.84 nm; 95% CI= -9.62nm to 25.3nm; p = 0.38). Silver stain analysis illustrated no global difference in exosome protein cargo.
Conclusions :
Paradoxically, we found eyes with AMD had lower concentration of EVs in tears than in controls. Further characterization of the content of tear exosomes in AMD is warranted.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.