Oxidative Stress Induced Age Dependent Meibomian Gland Dysfunction in Cu, Zn-Superoxide Dismutase-1 (Sod1) Knockout Mice

PURPOSE The purpose of our study was to investigate alterations in the meibomian gland (MG) in Cu, Zn-Superoxide Dismutase-1 knockout (Sod1-/-) mouse. METHODS Tear function tests [Break up time (BUT) and cotton thread] and ocular vital staining test were performed on Sod1-/- male mice (n = 24) aged 10 and 50 weeks, and age and sex matched wild-type (+/+) mice (n = 25). Tear and serum samples were collected at sacrifice for inflammatory cytokine assays. MG specimens underwent Hematoxylin and Eosin staining, Mallory staining for fibrosis, Oil Red O lipid staining, TUNEL staining, immunohistochemistry stainings for 4HNE, 8-OHdG and CD45. Transmission electron microscopic examination (TEM) was also performed. RESULTS Corneal vital staining scores in the Sod1-/- mice were significantly higher compared with the wild type mice throughout the follow-up. Tear and serum IL-6 and TNF-α levels also showed significant elevations in the 10 to 50 week Sod1-/- mice. Oil Red O staining showed an accumulation of large lipid droplets in the Sod1-/- mice at 50 weeks. Immunohistochemistry revealed both increased TUNEL and oxidative stress marker stainings of the MG acinar epithelium in the Sod1-/- mice compared to the wild type mice. Immunohistochemistry staining for CD45 showed increasing inflammatory cell infiltrates from 10 to 50 weeks in the Sod1-/- mice compared to the wild type mice. TEM revealed prominent mitochondrial changes in 50 week Sod1-/- mice. CONCLUSIONS Our results suggest that reactive oxygen species might play a vital role in the pathogensis of meibomian gland dysfunction. The Sod1-/- mouse appears to be a promising model for the study of reactive oxygen species associated MG alterations.