Abstract

SA.17.07

Contribution of keratinisation to Meibomian Gland Disease (MGD)

Erich Knop1, Nadja Knop2
1Forschungslabor der Augenklinik, CVK, Charité - Universitätsmedizin Berlin, Berlin, 2Abt. Zellbiologie in der Anatomie, Medizinische Hochschule Hannover, Hannover

Objective
Meibomian gland disease (MGD) is an increasingly recognized factor in the pathogenesis of keratokonjunctivitis and dry eye disease. Low delivery of Meibomian lipids due to simple obstructive MGD caused by various underlying reasons is the most frequent form of MGD and abnormal keratinisation is potentially a major causative factor.
Methods
Conjunctival whole-mount specimens including the lid margin from ten normal human body donors of older age (average age in the mid seventies) were embedded in paraffin. Serial sections were stained with different histological stains (including HE and Masson Goldner´s trichrome stain) and by immunohistochemistry for cytokeratins in order to investigate the histology and degree of keratinisation.
Results
The excretory duct of the Meibomian gland opened onto the free lid margin close to the inner lid border. This region was still covered by the stratified squamous cornified epithelium of the skin. It terminated in about the middle line between the Meibomian gland orifices but typically encircled the orifice. Later the cornified epidermis terminated abruptly and gave rise to the muco-cutaneous junction. In histology, the opening of the Meibomian gland was typically 100µm in diameter. A 6-layered cornified squamous epithelium continued into the terminal segment of the Meibomian gland excretory duct. It often formed shed luminal keratin lamellae lying inside the lumen. Further inside the gland, the central Meibomian duct typically formed a widened ampulla lined by a three to four layered squamous epithelium that contained single keratohyalin granules. In immunohistochemistry the conjunctival cytokeratins CK19 and CK4 terminated before the muco-cutaneous junction. The skin keratin CK10 continued from the surface of the free lid margin into the excretory duct and on the proximal side onto the inner lid border and hence encircled the Meibomian orifice.
Conclusions
In older age, where an increased incidence of obstructive MGD occurs, the terminal part of the Meibomian gland excretory duct often contains keratinised epithelial cell lamellae and the upstream epithelium shows a potency for keratinisation which may contribute to stasis of Meibum inside the gland.

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