Transitory alkali exposure on meibomian gland orifices induces meibomian gland dysfunction

Purpose: To determine pathological changes of meibomian glands (MGs) after transient exposure of the rat eyelid margin to alkali solution.Methods: Filter paper infiltrated with 1 N sodium hydroxide solution was applied to the eyelid margin of SpragueDawley rats for 30 s under general anesthesia, without touching the conjunctiva, after which the ocular surface and eyelid margin were examined by slit-lamp microscopy. In vivo confocal microscopy and stereomicroscopy were subsequently applied to observe MG morphology on day 5, day 10 and day 30 post alkali injury. Eyelid cross-sections were processed for H & E staining, Oil red O staining and immunofluorescent staining. Results: After alkali injury, there was marked plugging of MG orifices, telangiectasia and hypertrophy of the eyelid margin, while corneal epithelium was intact at post-injury days 5 and 10. However, 30 days after alkali injury, mild corneal epithelial damage was observed. Degeneration of MG acini was observed at days 5 and became aggravated at days 10 and 30, along with MG duct dilation and acini loss. Oil red O staining showed lipid accumulation in the dilated duct. Inflammatory cell infiltration and the presence of apoptotic cells was seen in the MG loci 5 days post injury, but diminished at days 10 and 30. Cytokeratin 10 expression was increased in dilated duct, while cytokeratin 14, PPAR-& gamma;, Ki67 and LRIG1 expression were decreased in the acini of injured loci.Conclusions: Transitory alkali exposure of the rat eyelid margin obstructs the MG orifice and induces pathological changes of MG dysfunction.