title: Quantification of MUCIN 1, cell surface associated and MUCIN16, cell surface associated proteins in tears and conjunctival epithelial cells collected from postmenopausal women.
abstract: OBJECTIVE
  To quantify the expression of mucin 1, cell surface associated (MUC1) and mucin 16, cell surface associated (MUC16) proteins and messenger ribonucleic acid (mRNA) in a cohort of postmenopausal women (PMW), to explore the relationship between mucin expression, dry eye symptomology, and tear stability.
  
  
  METHODS
  Thirty-nine healthy PMW (>50 years of age) were enrolled in this study. No specific inclusion criteria were used to define dry eye; instead, a range of subjects were recruited based on responses to the Allergan Ocular Surface Disease Index (OSDI) questionnaire and tear stability measurements as assessed by non-invasive tear breakup time (NITBUT). Tears were collected from the inferior tear meniscus using a disposable glass capillary tube, and total RNA and total protein were isolated from conjunctival epithelial cells collected via impression cytology. Expression of membrane-bound and soluble MUC1 and MUC16 were quantified with western blotting, and expression of MUC1 and MUC16 mRNA was assessed with real-time PCR.
  
  
  RESULTS
  OSDI responses ranged from 0 to 60, and NITBUT ranged from 18.5 to 2.9 s. Only two statistically significant correlations were found: soluble MUC16 protein concentration and MUC16 mRNA expression with OSDI vision related (-0.47; p=0.01) and ocular symptom (0.39; p=0.02) subscores, respectively. Post hoc exploratory analysis on absolute expression values was performed on two subsets of subjects defined as asymptomatic (OSDI≤6, n=12) and moderate to severe symptomatic (OSDI≥20, n=12). The only significant difference between the two subgroups was a significant reduction in MUC16 mRNA expression found in the symptomatic dry eye group (1.52±1.19 versus 0.57±0.44; p=0.03).
  
  
  CONCLUSIONS
  A broad exploration of mucin expression compared to either a sign (NITBUT) or symptoms of dry eye failed to reveal compelling evidence supporting a significant relationship, other than a potential association between MUC16 with specific symptoms. Furthermore, comparison of mucin protein and expression levels between the asymptomatic and moderate to severe symptomatic subgroups revealed only one significant difference, a reduction in MUC16 mRNA expression in the symptomatic subgroup.
authors.affiliation: Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada. s2sriniv@uwaterloo.ca
authors.forename: Sruthi
authors.initials: S
authors.lastname: Srinivasan
authors.forename: Miriam L
authors.initials: ML
authors.lastname: Heynen
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Martell
authors.forename: Robert
authors.initials: R
authors.lastname: Ritter
authors.forename: Lyndon
authors.initials: L
authors.lastname: Jones
authors.forename: Michelle
authors.initials: M
authors.lastname: Senchyna
mesh_terms: D000368:Aged; D015153:Blotting, Western; D018394:CA-125 Antigen / Q000235:genetics / Q000378:metabolism*; D015331:Cohort Studies; D003228:Conjunctiva / Q000473:pathology*; D004847:Epithelial Cells / Q000378:metabolism*; D005128:Eye Diseases / Q000235:genetics / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D018396:Mucin-1 / Q000235:genetics / Q000378:metabolism*; D017698:Postmenopause / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D013048:Specimen Handling; D013666:Tears / Q000378:metabolism*; D013997:Time Factors
chemical_list: D018394:CA-125 Antigen; C060192:MUC1 protein, human; C451759:MUC16 protein, human; D008565:Membrane Proteins; D018396:Mucin-1; D012333:RNA, Messenger