Abstract
Purpose :
To investigate differences in lipid composition of meibum extracted from meibomian glands displaying different morphological characteristics in humans
Methods :
Participants aged 18 years and over, with or without symptoms of dry eye, and with evidence of meibomian gland shortening were enrolled. Glands were observed using infrared meibography, and one short gland (length typically half of the everted lower eyelid) and one long gland (full eyelid length) were marked from the same eye. Meibum from the marked glands was collected using a glass micro-capillary tube. Lipid analysis was performed using Liquid Chromatography Mass-Spectrometry. Non-polar lipids including wax esters (WEs), cholesterol esters (CE), triacylglycerides (TAG), diheptadecanoin (DAG), ceramide (Cer), and polar lipids including (O-acyl)-ω-hydroxy fatty acids (OAHFA), phosphatidylcholines (PC), phosphatidylethanolamines (PE), phosphatidylserines (PS), sphingomyelins (SM), lysophosphatidylcholines (LPC) and lysophosphatidylethanolamines (LPE) were quantified and compared between short and long glands. Data were normalised to the level of total lipid in each sample and reported as mean (mole % of total lipid) ± standard error of the mean (SEM). The distribution of these lipids between glands was compared using a Wilcoxon signed-rank test.
Results :
Fifteen participants (8 females, 7 males) completed the study (mean age: 34.7 ± 7.7 years). Mean meibum volumes of 0.02 ± 0.01µL and 0.05 ± 0.03µL (p=0.02) were collected from short and long glands respectively. WEs were the major lipids secreted with no significant difference between short and long glands (40.3 vs 47.8%, p=0.06). Among the non-polar lipids, the proportion of CE (9.6 vs 17.8%, p=0.02), TAG (1.8 vs 4.3%, p=0.04), and Cer (0.9 vs 3.5%, p=0.03) were significantly reduced in short glands compared with long glands. Among the polar lipids, the proportions of OAHFA (0.8 vs 2.7%, p=0.01) was significantly reduced in short glands whereas, PC (1.4 vs 0.8%, p=0.02) and SM (0.1 vs 0.06%, p=0.01) were significantly higher in short glands than long glands.
Conclusions :
Compositional differences in lipids between short and long meibomian glands may exist. The basis for these differences is unclear but may reflect altered meibocyte function associated with processes of intra-gland atrophy. The data generated in this study can inform appropriate sample sizes for future investigations
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.