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William Ngo, Cameron Postnikoff, Andrew Pucker, Jason J Nichols; Detection of Extracellular Vesicles in the Human Tear Film. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4915. doi: https://doi.org/.
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Extracellular vesicles (EVs) play key roles in cell-to-cell communication in various systems in the body. It is currently unknown whether this mode of communication exists at the ocular surface. The purpose of this study was to develop an understanding of the presence of EVs in the human tear film.
This was a cross-sectional study that enrolled eight healthy, non-contact lens-wearing subjects who were ocular disease free. In order to include non-diseased subjects, ocular symptoms were evaluated with the Ocular Surface Disease Index (OSDI) and tear film stability was assessed with the OCULUS Keratograph 5M (NIKBUT). Tears from both eyes of each participant were collected using an eyewash method, whereby a sterile disposable transfer pipette was used to administer 1 mL of sterile phosphate-buffered saline (PBS) into each eye, and the run-off from each eye was collected and combined. Samples were then centrifuged to remove cells and debris. The supernatant was collected and analyzed with nanoparticle tracking analysis (NanoSight 300, Malvern Instruments Ltd, UK). Nanoparticle tracking was conducted by infusing samples into the flow chamber using a syringe pump motor at a rate of 50 units. Five videos (1 minute each) per sample were obtained and analyzed with the accompanying NTA 3.0 software using the built-in standard protocol.
The mean ± SD age of the subjects was 36 ± 7 years. Subjects had a mean OSDI score of 8.3 ± 7.5, and a NIKBUT (both eyes averaged) of 9.60 ± 6.01 s. The 10th, 50th, and 90th percentiles of the particle sizes were 101.2 ± 10.9 nm, 154.9 ± 28.7, and 352.1 ± 94.4 nm, respectively. The mode particle size, averaged across subjects was 128.0 ± 20.7 nm. The mean particle concentration was 7.91x108 ± 6.81x108 particles/mL.
Nano-sized particles were detected in tears with appropriate size characteristics. This suggests that the ocular surface may contain EVs and could be a medium for which cell-to-cell communication is taking place through these vesicles. Future studies will employ imaging flow cytometry to confirm the presence of CD63 on the exosomes.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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