Abstract
Abstract: :
Purpose: Irritancy and inflammation have been shown to be associated with changes in mucin expression in the respiratory system. Since contact lens (CL) wear can be associated with irritancy and inflammation on the ocular surface, there may be changes in the character of the ocular surface after CL wear. The purpose of this study was to determine if long–term CL wear causes changes in the expression of mucin mRNA by the ocular surface epithelium or mucin protein content in tears. Methods: Twenty long–term (5 years or more), tolerant CL wearers (2 with hard, and 18 with soft contact lenses) were compared with 20 non–CL wearers. One hour after removing lenses, tear fluid was collected from the inferior fornix after instillation of 60 ul sterile water onto the ocular surface. After tear fluid collection, impression cytology was performed on the bulbar temporal region for RNA isolation. After reverse transcription of total RNA (1 ug), real–time PCR was performed using TaqMan primer and probes for MUC1, 4, 5AC, and 16. Enzyme–linked immunosorbent assay (ELISA) was performed on the collected tears (5 ug of total protein) using antibodies against MUC5AC and a carbohydrate epitope on MUC16 (H185). For the analysis of adherent mucins on CL, discarded daily–wear (8 hours) contact lenses (etafilcon A) of 3 subjects were collected and incubated overnight at 4 oC in Mucin Isolation Buffer. CL–adsorbed protein was further extracted by sonication for 30 minutes. Immunoblot analysis of extracted proteins, separated in a 1% agarose gel and transferred to nitrocellulose membrane, was performed using antibodies against MUC1 (HMFG–2), MUC4 (1G8), MUC5AC (791), and MUC16 (OC125). Results: No significant change was detected for any of the mucins (MUC1, 4, 5AC, and 16) when analyzing the expression of mRNA from CL and non–CL wearers. The amount of total protein in tears collected from CL wearers (35.4 ± 33.0 ug) was significantly less than that from non–CL wearers (85.8 ± 86.3 ug, p = 0.015). By ELISA, protein levels of MUC5AC and MUC16 (H185) in tears of CL wearers were not significantly different from non–CL wearers. The amount of total protein extracted from the discarded contact lenses was 131.7 ± 27.7 ug. By immunoblot analysis, three membrane–associated mucins, MUC1, 4 and 16, and the secreted mucin MUC5AC were detected in protein extracted from the discarded contact lenses. Conclusions: The expression of neither mucin mRNA in conjunctival epithelium nor mucin proteins in tears was altered in tolerant CL wearers even by long–term CL wear. Shed membrane–associated mucins, MUC1, 4, and 16, and the goblet cell mucin MUC5AC may be adsorbed onto contact lenses.
Keywords: cornea: surface mucins • cornea: tears/tear film/dry eye • contact lens