Structural Differences in Meibum From Donors After Hematopoietic Stem Cell Transplantations

Abstract

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 (C) increased from 30.3 (0.4) to 34.2 (0.9), and the magnitude of the phase transition (cm) 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.

FIGURE 1.

A) Infrared spectra of the CH stretching region at 22 °C of a typical 36 year-old Caucasian adolescent female without dry eye (top), and a typical 31 year-old Caucasian adolescent female with dry eye and Graft-versus-host disease (bottom). B) Schematic showing trans and gauche conformations in lipid hydrocarbon chains. The greater the number of trans rotamers, the tighter the lipids pack, the stronger the van der Wall’s forces, the greater the lipid order and higher the lipid phase transition temperature. C) Typical lipid phase transitions of meibum from a 13 year-old Caucasian adolescent female without dry eye (●) and a 14 year-old Caucasian adolescent female with dry eye and Graft-versus-host disease (○). The CH₂ symmetric stretching frequency is related to lipid structural order. The higher the value for the frequency, the more disordered the lipid. (─) Curve fit of data using the sigmoidal equation 1 (Experimental Section). D) Correlation between the lipid phase transition temperature and lipid order at 33.4 °C for human meibum. (●) Meibum from donors without dry eye. (o) Meibum from donors with dry eye and graft versus host disease. (★) Meibum from donors with meibomian gland dysfunction. Data are average ± the standard error of the mean.

FIGURE 2.

Key lipid phase transition parameters from Table 1. All bars are statistically different from each other, P < 0.05 (Table 1). Data are average ± the standard error of the mean.