July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Lipidomic Analysis of Meibomian Gland Secretions from the Tree Shrew: Identification of Candidate Tear Lipids Critical for Reducing Evaporation
Author Affiliations & Notes
  • Jianzhong CHEN
    University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Shyam Panthi
    University of Alabama at Birmingham, Birmingham, Alabama, United States
  • Footnotes
    Commercial Relationships   Jianzhong CHEN, None; Shyam Panthi, None
  • Footnotes
    Support  P30 EY003039, S10 RR027822
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4173. doi:
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    • Get Citation

      Jianzhong CHEN, Shyam Panthi; Lipidomic Analysis of Meibomian Gland Secretions from the Tree Shrew: Identification of Candidate Tear Lipids Critical for Reducing Evaporation. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4173.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Evaporative dry eye is thought to originate from adverse changes in the outermost lipid layer of the tear film that lead to increased tear evaporation. However, the underlying mechanisms are still unclear. The aim of this study was to evaluate the tree shrew, the non-primate mammal closest to humans, as a model for evaporative dry eye.

Methods : Meibomian gland secretions (meibum) were expressed from eyelids dissected from sacrificed tree shrews and collected in microcapillary glass tubes. Meibum lipids were extracted with a chloroform-methanol solvent mixture (2:1, vol/vol) and dispensed into a glass vial using a bulb dispenser. Meibum lipid samples were diluted five-fold with methanol, and 0.025% ammonium hydroxide served as an additive. These working solutions were analyzed on a high-resolution mass spectrometer (TripleTOF 5600, SCIEX, MA) by direct infusion and electrospray ionization. Mass spectrometry (MS) and MS/MSall data were acquired in positive and negative ion modes with sequential polarity switching.

Results : The lipid profile of tree shrew meibum was similar to that of human meibum. The lipids detected, including wax esters, cholesteryl esters, diesters, triacylglycerols (TGs), and (O-acyl)-ω-hydroxyl fatty acids (OAHFAs), largely aligned with those found in human meibum. However, key differences between tree shrew and human meibum were observed. In particular, with the exception of TGs, the chain lengths of the lipids listed above were longer than those found in human meibum. These longer chain lipids may contribute to the high stability of tree shrew tear film, implied by the substantially lower blinking frequency of this mammal. The second difference was the observation of a series of lipids unique to tree shrew meibum that were identified as longer-chain OAHFAs. The third difference was that high-intensity peaks associated with phospholipids, including phosphatidylcholines, were detected in both MS and MS/MSall. These phospholipids likely originated from immature meibomian gland cells collected as a result of harsh expression procedures or from contamination from the areas surrounding the meibomian glands.

Conclusions : The lipid profile of tree shrew meibum shares many similarities with that of human meibum, but also displays interesting differences. The tree shrew may represent an effective model for the study of dry eye.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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