Isolation of three different sizes of exosomes in an Asian population with different retinal diseases before and after treatment

Exosomes are membranous structures measuring between 40–120 nm that are secreted by various cells of the human body into the body fluid system. Exosomes contain proteins, mRNA, miRNA, and signaling molecules, and physiologically they assist in the intercellular transport of proteins and RNA molecules. In this study, we used an immunoaffinity filter paper platform combined with scanning electron microscopy and microfluidic systems to detect the size of exosomes within the aqueous humor. Eight aqueous humor samples showed three distinct sizes of exosomes that were significantly different on scanning electron microscopy(P < 0.01). We further used nanoparticle tracking analysis to assess the size distribution of exosomes within the aqueous humor. We found significantly different distributions of exosomes between patients with three different ocular diseases and patients with normal cataracts as controls. An obvious peak of exomeres(size around 35 nm)was found in the patients with central retinal vein occlusion and vitreous hemorrhage. Flare-ups of large exosomes(size 90–120 nm)were found in the patients with the inflammatory ocular disease pars planitis. No obvious peaks in exomeres or large exosomes were found in the control group. There was a high association between the distribution of exosomes and the pathogenesis of ocular diseases. After intravitreal anti-vascular endothelial growth factor treatment, the aqueous humor from the patients with neovascular diseases showed a significant reduction in exosomes in nanoparticle tracking analysis. These findings suggest that at least three distinct sizes of exosomes exist in the aqueous humor:(1)exomeres:<35 nm;(2)small exosomes:60–80 nm; and (3)large exosomes:90–120 nm. Different sizes of exosomes may have different implications in normal or diseased eyes.