Transitory alkali exposure on meibomian gland orifices induces meibomian gland dysfunction

To determine pathological changes of meibomian glands (MGs) after transient exposure of the rat eyelid margin to alkali solution. Filter paper infiltrated with 1 N sodium hydroxide solution was applied to the eyelid margin of Sprague-Dawley 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. 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-γ, Ki67 and LRIG1 expression were decreased in the acini of injured loci. Transitory alkali exposure of the rat eyelid margin obstructs the MG orifice and induces pathological changes of MG dysfunction.