The effect of airborne particulate matter 2.5 (PM) on meibomian gland.

Exposure to particulate matters in air pollution of 2.5 μm or less (PM) was associated with loss of meibomian glands. The aim of this study was to verify that PM could directly impact meibomian gland epithelial cells and damage their function. To investigate the impact of PM on meibomian gland, immortalized human meibomian gland epithelial cells were treated with various concentrations of PMin vitro. Meibomian gland cell microstructure, cell viability, expression of proliferating cell nuclear antigen and IL-1β, and intracellular accumulation of acidic vesicles were measured by transmission electron microscopy, cell counting, Western blot and LysoTracker staining, respectively. To further study the effect of PMin vivo, male C57BL/6J mice were treated with 5 mg/ml PM or vehicle for 3 months. Corneal fluorescein staining and ocular examinations were done before and after the treatment. Eyelids tissues were processed for morphological studies, immunostaining and Oil Red O staining. Our data suggest that exposure to PM caused significant meibomian gland dropout, clogged gland orifice and increased corneal fluorescein staining that were consistent with the clinical presentations of meibomian gland dysfunction. Prominent changes in the morphology and ultrastructure of meibomian glands was observed with PM treatment. PM promoted ductal keratinization, inhibited cell proliferation, induced cell apoptosis and increased Interleukin-1β production in meibomian gland epithelial cells. This study may explain the association between PM exposure and meibomian gland dropout observed in clinic. PM resuspension instillation could be used to induce a meibomian gland dysfunction animal model.