title: Biophysical and morphological evaluation of human normal and dry eye meibum using hot stage polarized light microscopy.
abstract: OBJECTIVE
  To study melting characteristics and the morphology of human and mouse meibum.
  
  
  METHODS
  Hot stage cross-polarized light microscopy (HSPM) and immunohistochemical approaches were used.
  
  
  RESULTS
  Isolated human meibum, and meibum of mice (either isolated or within the meibomian ducts of mice), were found to be in liquid-crystal state at physiological temperatures. Melting of both types of meibum started at approximately 10°C and was completed at approximately 40°C. Melting curves of isolated meibum and meibum inside the meibomian ducts were multiphasic with at least two or three clearly defined phase transition temperatures, typically at approximately 12 ± 2°C (minor transition), 21 ± 3°C, and 32 ± 3°C, regardless the source of meibum. Melting was highly cooperative in nature. Samples of abnormal human meibum collected from dry eye patients with meibomian gland dysfunction often showed an increased presence of nonlipid, nonmelting, nonbirefringent, chloroform-insoluble inclusions of a protein nature. The inclusions were positively stained for cytokeratins. The presence of these inclusions was semiquantitatively characterized using a newly proposed 0 to 4 scale. In the presence of large amounts of these inclusions, melting characteristics of meibum and its structural integrity were altered.
  
  
  CONCLUSIONS
  HSPM is an effective tool that is suitable for biophysical and morphological evaluation of meibum. Morphological properties and melting characteristics of human meibum were found to be similar to those of mice. Abnormal meibum of many dry eye patients contained large quantities of nonlipid, protein-like inclusions, which were routinely absent in meibum of normal controls.
authors.affiliation: Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Igor A
authors.initials: IA
authors.lastname: Butovich
authors.forename: Hua
authors.initials: H
authors.lastname: Lu
authors.forename: Anne
authors.initials: A
authors.lastname: McMahon
authors.forename: Howard
authors.initials: H
authors.lastname: Ketelson
authors.forename: Michelle
authors.initials: M
authors.lastname: Senchyna
authors.forename: David
authors.initials: D
authors.lastname: Meadows
authors.forename: Elaine
authors.initials: E
authors.lastname: Campbell
authors.forename: Mike
authors.initials: M
authors.lastname: Molai
authors.forename: Emily
authors.initials: E
authors.lastname: Linsenbardt
mesh_terms: D000328:Adult; D000818:Animals; D015352:Dry Eye Syndromes / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D050356:Lipid Metabolism; D008055:Lipids / Q000032:analysis*; D008297:Male; D008537:Meibomian Glands / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008859:Microscopy, Polarization / Q000379:methods; D013666:Tears / Q000737:chemistry*
chemical_list: D008055:Lipids
keywords: biophysics; hot stage polarized light microscopy; lipids; meibomian glands; phase transitions; rheology