Assay of Membrane-Associated Mucins in Conjunctiva and Tears of Postmenopausal Women With and Without Dry Eye

Abstract

Purpose: : To compare expression, protein amount and glycosylation of membrane-tethered mucins in apical conjunctival epithelial cells and mucin content in tears of postmenopausal women with or without mild to moderate non-Sjogren’s dry eye. Membrane-associated mucins are of interest in dry eye disease as these heavily glycosylated, high molecular weight glycoproteins play a role in the protective barrier at the ocular surface.

Methods: : Dry eye was determined based on symptom questionnaire, tear breakup time, mean tear volume, and ocular surface staining. Postmenopausal women aged 45 to 91 (controls=58+6yrs, dry eye=64+7) were included in this study. Conjunctival impression cytology samples from 50 normal and 108 dry eye patients were collected for assay of MUC1 and MUC16 mRNA by real-time PCR, MUC1 and 16 proteins by western blot, and MUC16 glycosylation using the H185 antibody in ELISA. Saline tear washes were collected for MUC protein assays and H185 ELISA. Statistical significance was determined by the Mann-Whitney test in Instat3 statistical software.

Results: : Data indicate a significant increase over normal subjects in the amount of MUC1 and 16 protein in conjunctival epithelial cells of dry eye patients (37%, p<0.01; 48%, p<0.0001, respectively). MUC1 and 16 mRNA also increased significantly in conjunctival impression cytology samples of dry eye patients compared to normal subjects (1.7-fold, p<0.01; 2.3-fold, p<0.05, respectively). No statistically significant difference was seen in amount of the H185 O-acetylated sialic acid epitope in cells or in amount of membrane mucin ectodomains in tears of dry eye patients.

Keywords: cornea: tears/tear film/dry eye • cornea: surface mucins • conjunctiva