Abstract
Purpose :
Sjogren's syndrome (SS) is a chronic autoimmune rheumatic disease affecting 3 million individuals in the United States. About 80 % of people with SS have dry eye, keratoconjunctivitis sicca. We measured the composition and conformation of meibum in donors with SS and donors without SS or dry eye since meibum lipid has been associated with dry eye and meibomian gland dysfunction.
Methods :
Meibum was collected using an ILUX instrument (Alcon, Fort Worth, TX). Infrared spectroscopy was used to measure meibum lipid conformation (structure). 1H-NMR spectroscopy was used to measure meibum composition.
Results :
Meibum was collected from 35 donors without dry eye (Mn) and without SS and eight donors with dry eye and with SS (Mss). The cholesterylester/wax ester ratio was significantly, P = 0.003. higher for Mss 0.51 ± 0.02 compared with Mss, 0.70 ± 0.06. Mss contained significantly, P = 0.02, more straight chains, 67 ± 5 %, compared with Mn, 57 ± 1 %. No statistical difference was apparent, P > 0.05, between the Anteiso Branched, 20 ± 1, 15 ± 1 or Iso Branched chains 23 ± 1, 19 ± 4 of Mn or Mss, respectively. There was no statistical difference, P > 0.05, between the eight phase transition parameters measured for Mss or Mn.: Transition Temperature ( oC), Mn : 30.3 ± 0.4, Mss: 29.9 ± 0.9; Cooperativity, Mn : 7.9 ± 0.4, Mss: 7.6 ± 0.6; Order 36.0 oC (% trans), Mn : 35 ± 1, Mss: 38.4 ± 3.6; Order 33.4 oC (% trans), Mn : 40 ± 1, Mss: 43.3 ± 3.7; Δ enthalpy (kcal/mol), Mn : 142 ± 6, Mss :135 ± 25; Δ entropy (kcal.mol/degree), Mn : 0.48 ± 0.02, Mss: 0.45 ± 0.03; Minimum Frequency (cm-1), Mn : 2849.71 ± 0.06, Mss: 2849.5 ± 0.1; Maximum Frequency (cm-1), Mn : 2853.69 ± 0.09, Mss: 2853.3 ± 0.1.
Conclusions :
Inspite of having a higher cholesterylester/wax ester ratio and more straight chains, the compositional differences between Mss and Mn did not affect their phase transition parameters. A higher CE/WE ratio and straight chain composition of Mss compared with Mn, could be a marker for SS and/or contribute to dry eye in patients with SS. Studies are planned to measure the rheology of Mss to test this idea.
This is a 2021 ARVO Annual Meeting abstract.