Tear stability decreases with increasing age and the same signs of instability are exacerbated with dry eye. Meibum lipid compositional changes with age provide insights into the biomolecules responsible for tear film instability. Meibum was collected from 69 normal donors ranging in age from 0.6 to 68 years of age. Infrared spectroscopy was used to measure meibum lipid phase transition parameters. Nuclear magnetic resonance spectroscopy was used to measure lipid saturation. Increasing human meibum lipid hydrocarbon chain unsaturation with age was related to a decrease in hydrocarbon chain order, cooperativity, and in the phase transition temperature. The change in these parameters was most dramatic between 1 and 20 years of age. Meibum was catalytically saturated to determine the effect of saturation on meibum lipid phase transition parameters. Hydrocarbon chain saturation was directly related to lipid order, phase transition temperature, cooperativity, changes in enthalpy and entropy, and could account for the changes in the lipid phase transition parameters observed with age. Unsaturation could contribute to decreased tear film stability with age.

Purpose: Meibum is considered to be a key component of tears that serve to protect the eye, and conformational changes in meibum have not been studied extensively within the population of patients who had hematopoietic stem cell transplantation (HSCT). The aim of this study was to determine possible lipid conformational changes in the meibum of patients who had HSCT. Methods: Participants who had HSCT were randomly sampled for this prospective comparative study. Control participants did not have dry eye or had not undergone allogeneic or autologous stem cell transplantation. Fourier-transform infrared spectroscopy was used to measure meibum phase transition. Results: Meibum was collected from both eyes of 36 donors without dry eye (Mc) and from 22 patients who had undergone HSCT (MHSCT). There were no significant differences between the phase transition parameters based on gender or race. The following were the significant differences (P < 0.0001) between the parameters for Mc compared with MHSCT : lipid order (% trans) at 33.4°C increased from 40 (1) to 54 (2), cooperativity decreased from 7.9 (0.4) to 5.4 (0.3), the phase transition temperature (oC) increased from 30.3 (0.4) to 34.2 (0.9), and the magnitude of the phase transition (cm−1) increased from 4.0 (0.1) to 4.7 (0.5) (standard error of the mean). Conclusions: Conformational and thermodynamic differences were observed between Mc and MHSCT. The changes observed in the lipid conformation of meibum from patients receiving HSCTs suggest that meibum composition changes after stem cell transplantation, and clinicians should consider treating the meibomian glands to improve the ocular surface.

PurposeGraft‐versus‐host disease (GvHD) is a common complication of allogenic hematological stem cell transplantations that is often associated with dry eye disease (DED) classified as a mixture of meibomian gland dysfunction and aqueous tear deficiency. The temperature‐dependence of conformational changes in human meibum (hM) was measured in a comparative study to elucidate the potential impact of GvHD on hM composition, structure and function with DED.MethodsDonors received full ophthalmic eye exams and DED was clinically diagnosed. A total of 28 donors without DED were separated into two pools: adolescent (age: 17 ± 1 and 63% male) and adult (age: 42 ± 4 and 73% male). Adolescent (age: 15 ± 1 and 80% male) and adult (age: 45 ± 5 and 30% male) pools from a total of 15 donors affected by both DED and GvHD were also tested. The extracted hM was placed in d‐chloroform and analyzed by Fourier Transform Infrared Spectroscopy (FTIR).ResultsAmong the measured parameters, the lipid order (% trans) in hM at 36°C increased significantly from adolescents without DED (35.3 ± 4%) to those affected by GvHD (54.7 ± 4%). A similar trend (33.3 ± 0.09% without DED to 38.0 ± 4% with DED/GvHD) was observed in hM from adults. The change in enthalpy for the order‐to‐disorder transition decreased significantly with DED/GvHD in both adolescents (from 163 ± 10 Kcal/mol without DED to 134 ± 9 Kcal/mol with DED/GvHD) and adults (141 ± 5 Kcal/mol without DED to 126 ± 11 Kcal/mol with DED/GvHD). The phase transition temperature (C°) was significantly higher in adolescents with DED/GvHD (38 ± 1°C) compared to donors without DED (30.4 ± 0.6°C), but the increase was less pronounced in adults with DED/GvHD (31 ± 1°C) relative to those without DED (30.0 ± 0.4°C).ConclusionBoth age and DED lead to conformational and thermodynamic differences in hM. Increases in lipid order and transition temperatures were observed in hM with GvHD. However, these relative increases were more pronounced in hM from adolescents than from adults. The decrease of change in enthalpy for adolescents was more pronounced compared with adults. The conformational and thermodynamic differences observed with age and, importantly, with DED/GvHD are indicative of compositional changes in hM that could impact tear film stability.Support or Funding InformationMajor support was obtained from the National Institute of Health (NIH) EYO RO126180 (DB); NIH Research Supplements to Promote Diversity in Health‐Related Research EYO RO126180S‐1 (SS); and an unrestricted grant from Research to Prevent Blindness, Inc. New York, NY, USA.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.