Assessment of tear derived extracellular vesicles as a minimally source of novel biomarkers for subconjunctival glaucoma surgery

Abstract

Aims/purpose: Glaucoma is a highly prevalent pathology causing avoidable blindness. Topical treatments used to stabilize intraocular pressure (IOP) may produce several side effects including inflammatory reactions. Patients who fail to control IOP or suffer significant side effects undergo subconjunctival glaucoma surgery (SGS). Estimations point to 30–40% of these patients will develop local scarring and fibrosis, which are the main complications of SGS. Thus, predicting the surgical outcome and starting preemptively fibrosis treatment are crucial. The aim of this study was to determine whether tears, and specifically tear‐derived extracellular vesicles (L‐EVs), can be used as liquid biopsy source, as a previous step for identifying new biomarkers for SGS outcome.Methods: Tear samples were obtained from patients (no surgical treatment, n = 11) by Schirmer's test. L‐EVs were enriched by size‐exclusion chromatography. Protein quantification was measured by microBCA assay and miRNA extraction (both from whole tear and L‐EVs) was performed using commercial kits.Results: Whole tear samples displayed variable miRNA and protein concentrations among patients (range 222.0–1388.1 ng miRNAs and 5.6–27.2 μg protein). Levels of miRNA and protein were also highly variable but considerably reduced in L‐EVS (0.14–46.78 ng miRNAs and 0.5–4.2 μg protein). Yet, in most patients, both types of samples (whole tears and L‐EVs) rendered sufficient quantity of protein and miRNA to perform proteomic and transcriptomic analysis.Conclusions: Concentration of miRNAs and Protein in tears and L‐EVs is highly variable among patients. As expected by their higher enrichment, miRNA and protein concentrations in L‐EVs are reduced compared to whole tears, yet quantities may be still enough to perform mic analyses. This higher purification of L‐EVS may help identifying specific biomarkers related to SGS outcome in a minimally invasive manner.