Ocular Mucin Gene Expression Levels as Biomarkers for the Diagnosis of Dry Eye Syndrome

PURPOSE: To evaluate mRNA levels of the ocular mucins MUC1, MUC2, MUC4, MUC5AC, and MUC7 in conjunctival impression cytology samples from patients with moderate to severe dry eye syndrome (DES) compared with a population of healthy subjects; and to investigate the use of the levels of these mucin genes as biomarkers of DES and subsequently as a potential diagnostic test for DES. METHODS: This prospective study commenced in the year 2000 and ended in the year 2009. Thirty-eight patients with DES and 43 age- and sex-matched healthy subjects completed the initial part of the study. Investigations were repeated at a later stage in 16 healthy subjects and 30 patients with DES, which were used as external validation data. Conjunctival impression cytology was performed in all subjects to test gene expression of ocular mucin genes MUC1, MUC2, MUC4, MUC5AC, and MUC7. Statistical analysis was performed to determine whether there was a difference in the levels of mucin gene expression between the two groups of subjects. Sensitivity and specificity of mucin gene expression for the diagnosis of DES was calculated. RESULTS: Expressions of MUC1, MUC2, MUC4, and MUC5AC (P < 0.0001) were significantly lower in conjunctival epithelium of patients with DES compared with that in normal subjects. These results were replicated in the external control subject and patient groups. MUC1 expression levels demonstrated the greatest sensitivity (83.3%) and specificity (87.5%) among all genes tested. CONCLUSIONS: The data strongly suggest that the expression levels of MUC1 may be used as a diagnostic test in DES for investigational and selective clinical trials.