Meibomian glands are a modified type of sebaceous glands within the eye lid, which produce an oily secretion important for the stabilization and the prevention of evaporation of the tear film. The holocrine secretory mode of Meibomian glands is characterized by the centripetal movement, the maturation and finally degeneration of the acinar epithelial cells. The process of maturation and degeneration is paralleled by altered expression pattern of certain proteins and the intracellular accumulation of Meibomian gland lipids. In this study, we investigated the correlation between the differentiation status of Meibomian acinus cells and the presence of adhesive junctions. By ultrastructural analyses, we showed for the first time that the frequency of desmosomes increased with the degree of differentiation. Importantly, we detected a differentiation-dependent distribution pattern of desmosomes within the Meibomian gland cells of the acinus, whereas molecules of other cell junctions, e.g., adherens junctions, are equally distributed. Together, these findings provide new insights into the processes of Meibomian gland secretion and may be important for the interpretation of Meibomian gland dysfunction causing diseases like the dry eye syndrome.
Keywords: Adhesion junctions; Desmosomes; Dry eye syndrome; Electron microscopy; Human eye lid; Meibomian glands; Pemphigus.