Assessing the human lid margin epithelium using impression cytology

Abstract

To establish if impression cytology combined with histochemical and immunocytochemical staining can be used to assess epithelium of the human upper lid margin. Following an initial eye examination of 40 healthy subjects (19 soft contact lens wearers and 21 non-contact lens wearers, aged 18-57 years), lid margin staining was assessed with lissamine green using slit lamp biomicroscopy and graded (grade 0-3). Impression cytology of the upper lid margin of both eyes was collected, fixed and stained with periodic acid Schiff (PAS) and haematoxylin for cell morphology analysis (Nelson grade) or for immunocytochemistry (keratinization-related proteins: filaggrin, transglutaminase1 (TGase1) and cytokeratin 1/10). In 57% of all subjects, grade 0 lissamine green staining showed a thin line (the Marx line), just posterior to the meibomian gland ducts. Grade 2 or 3 lissamine green staining was observed in 17% of all subjects. There was no difference between contact lens and non-contact lens wearers for lid margin staining or Nelson grade (p = 0.4, Fisher's exact test). PAS/haematoxylin staining and immunocytochemistry showed transition in epithelial cell morphology, with marginal conjunctival epithelium, mucocutaneous junction and squamous epithelium, adjacent to meibomian gland ducts. This transition in epithelium was associated with differential expression of keratinization-related proteins (filaggrin, cytokeratin 1/10 and TGase1). Lid margin epithelium can be successfully sampled using impression cytology and further characterized using histochemistry and immunocytochemistry staining techniques. This approach can be applied to assess lid margin changes in conditions such as dry eye and meibomian gland dysfunction.