Human meibomian glands: the ultrastructure of acinar cells as viewed by thin section and freeze-fracture transmission electron microscopies.

Heightened interest in meibomian glands dysfunction prompted the authors to examine the ultrastructure of the glandular epithelium in specimens of surgical origin, by thin section and freeze-fracture electron microscopies. In meibomian glands, the morphology and ultrastructure of acinar cells varies considerably according to their stage of holocrine differentiation. This study shows close interdependence between fat droplets and Golgi apparatus or endoplasmic reticulum. As the cells initiate their differentiation, the smooth endoplasmic reticulum and the Golgi apparatus become prominent and the first small lipid droplets appear in the cytoplasm. When fractured through a plane close to their surface, lipid droplets appear onion-like structured, ie made up of a variable number of irregular shaped concentric lamellae. This lamellar organization suggests that membranes are not only involved in synthesis, but also that some of their components are incorporated in the fat droplets. The authors conclude that human meibomian glands are a holocrine glandular complex that, despite great differences in type and location, present basic similarities with sebaceous glands.