A nanomembrane system that rapidly harvests exosomes from tears with high yield and purity has been developed. Dubbed iTEARS, the system could enable clinicians to diagnose many diseases and conditions more efficiently and less invasively.
Luke Lee, PhD, and Fei Liu, PhD, led the development of the platform, “Incorporated Tear Exosomes Analysis via Rapid-isolation System.” It is detailed in an ACS Nano article (“Discovering the Secret of Diseases by Incorporated Tear Exosomes Analysis via Rapid-Isolation System: iTEARS”).
Exosomes are small vesicles that are generated by cells in the body. They contain various proteins, lipids, nucleic acids, and metabolites that reflect their tissue of origin. During disease, the contents of exosomes may reflect the altered cell or tissue states and can serve as useful biomarkers for diagnosis.
“Since exosomes are recognized as attractive sources of diagnostic biomarkers, we assume that the tear exosomal cargos could also reflect the variations in physiology and pathology conditions,” the researchers wrote. Indeed, tear exosomes were previously reported to contain molecules associated with immune responses, dry eyes, diseases such as multiple sclerosis, and breast cancer testing and treatment.
Furthermore, tears are well-suited for sample collection because the fluid can be collected quickly and noninvasively, though only tiny amounts can be harvested at a time.
Until now, progress in harnessing tear exosomes for clinical purposes had been minimal because of practical limitations related to sample handling and analysis. To overcome these limitations, the research team adapted a nanomembrane system that they previously developed for isolating and analyzing exosomes from urine and plasma.
The new system, iTEARS, was designed to handle the low volume of tears. It separated out exosomes in just five minutes by filtering tear solutions over nanoporous membranes with an oscillating pressure flow to reduce clogging. Proteins from the exosomes could be tagged with fluorescent probes while they were still on the device and then transferred to other instruments for further analysis. Nucleic acids were also extracted from the exosomes and analyzed.
Based on proteomic analysis of the extracted proteins, the researchers successfully distinguished between healthy controls and patients with various types of dry eye disease. Notably, they showed that CALML5, KRT6A, and S100P were particularly useful for the classification of dry eye disease.
Similarly, they also investigated microRNAs in tear exosomes from patients with diabetic retinopathy and those without. They showed that miR-145-5p, miR-214-3p, miR-218-5p, and miR-9-5p were dysregulated during diabetic retinopathy development, suggesting that iTEARS could help track disease progression.
The team said that this work could lead to a more sensitive, faster, and less invasive molecular diagnosis of a variety of diseases—using only tears.
“Our iTEARS will be a powerful platform for discovering biomarkers of various diseases via exosomes from tears and understanding the clinical pathogenesis to establish tear-exosome-based precision medicine,” the researchers wrote. “We also believe iTEARS can be used for improving molecular diagnostics using tears to investigate ocular disorders, systemic diseases, and numerous other neurodegenerative diseases and cancer.”