Comparative Analysis of Age-Associated Changes in Meibum Composition, Distribution, and Function in Mice With Altered Hyaluronan Expression.

Abstract

PURPOSE: Mice lacking hyaluronan (HA) synthase 1 and 3 (Has1-/-; Has3-/- mice) are resistant to meibomian gland (MG) atrophy and dropout. Herein, we characterized the composition and distribution of meibum in Has1-/-; Has3-/- mice as they age and verified whether they are protected from developing dry eye disease (DED). METHODS: Tarsal plates from wild-type (wt) and Has1-/-; Has3-/- mice were isolated, and meibum lipid composition and the distribution of meibum were analyzed by liquid chromatography-mass spectrometry and whole-mount Sudan IV staining, respectively. The expression of biosynthetic enzymes for major lipid populations was analyzed by real-time PCR. The efficacy of the meibum at stabilizing the tear film was assessed using the benzalkonium chloride dry eye model, and DED-related symptoms were assessed in aged mice. RESULTS: Has1-/-; Has3-/- mice do not present a decrease in meibum production with aging and express significantly more meibum at all ages when compared to wt. Has1-/-; Has3-/- mice show significantly fewer age-related changes to meibum lipid composition when compared to wt mice. Overall, Has1-/-; Has3-/- mice have significantly less corneal opacity and epithelial erosions in aged mice when compared to wt mice. Has1-/-; Has3-/- mice are protected from developing DED when compared to wt mice. CONCLUSIONS: Our findings show that in addition to preventing MG atrophy, the overexpression of an HA-rich matrix surrounding the MG supports the production of healthy meibum that can successfully stabilize the tear film and protect the ocular surface from the effects of age-related meibomian gland dysfunction and dry eye symptoms.