Can Ocular Mucin Gene Levels Be Used as an Investigational Diagnostic Test for Dry Eye?

Abstract

Abstract: : Purpose: This research has two goals: 1) to evaluate mRNA levels of the ocular mucins MUC1, MUC2, MUC4, MUC5AC and MUC7 in conjunctival impression cytology (CIC) samples from patients with moderate to severe Dry Eye Syndrome (DES) compared with a population of healthy subjects; and 2) to investigative the putative use of these mucin levels as a potential investigational diagnostic test for DES. Methods: Two filters were applied to the bulbar conjunctiva of 38 DES patients and 43 healthy donors. Total RNA was extracted, and retrotranscription followed by real time PCR was performed to examine the mRNA of ocular mucin genes MUC1, MUC2, MUC4, MUC5AC and MUC7, using SYBR^® Green I dye for their detection. Levels of mucin genes were normalized for a housekeeping gene, GAPDH. The relative quantity of MUC mRNA in patients with DES in relation to that of normals was determined. In addition, sensitivity (SE) and specificity (SP) of MUC1, MUC4 and MUC2+MUC5AC mucin gene expression for the diagnosis of the DES was calculated. Results: The number of RNA transcripts for MUC1, MUC2, MUC4 and MUC5AC, but not for MUC7, was significantly lower in conjunctival epithelium of patients with DES compared to normal subjects. For MUC1, SE was 100% (CI95% 93.29–100) and SP was 100% (CI95% 92.05–100); for MUC4, SE was 95.10% (CI95% 86.2–99.3) and SP was 95.30% (CI95% 86.3–99.4), and for the gel–forming mucin genes MUC2+MUC5AC, SE was 83.70% (CI 95% 71.7–95.7) and SP was 81.10% (CI95% 68.4–93.8). Conclusions: The conjunctival epithelium of DES patients has significantly reduced levels of mRNAs for the ocular mucins MUC1, MUC2, MUC4 and MUC5AC, while levels of MUC7 remain unaltered. Our data also show that expression levels of ocular mucin genes MUC4, MUC2+MUC5AC, and specially MUC1, may be used as a new diagnostic test in DES for investigational and selective clinical trials. Support: Allergan Inc, Irvine, CA, USA (partial)

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