title: Tear levels of SFRP1 are significantly reduced in keratoconus patients.
abstract: OBJECTIVE
  To measure secreted frizzled-related protein 1 (SFRP1) levels in human tears and to investigate tear SFRP1 as a potential biomarker for keratoconus (KC).
  
  
  METHODS
  Tears were collected from control (n = 33) and KC patients (n = 33) using micropipette tubes. Total tear protein was measured using a FluoroProfile Protein Quantification kit. An in-house enzyme-linked immunosorbent assay (ELISA) was developed to measure SFRP1 in control and KC tears. Statistical analyses of age, gender, the association of SFRP1, and total tear protein with KC were conducted.
  
  
  RESULTS
  Tear SFRP1 was significantly decreased in KC, compared to age-matched controls (3.41 ng/μl ± 3.12 versus 5.55 ng/μl ± 5.62, respectively; p = 0.039). Conversely, total tear protein was significantly increased in KC, compared to age-matched controls (12.38 μg/μl ± 4.76 versus 9.40 μg/μl ± 3.88, respectively; p = 0.038). The ratio of SFRP1/total tear protein was also found to be significantly decreased in the KC group (p = 0.007). No significant association between tear SFRP1 and total tear protein was detected.
  
  
  CONCLUSIONS
  Tear SFRP1 was significantly decreased in age-matched KC versus control patients, and may be further reduced in moderate KC. Tear-SFRP1 levels alone do not provide an obvious biomarker for KC; however, our results provide further evidence that tear-protein profiles are altered in KC, and suggest the involvement of SFRPs in the pathogenesis of KC.
authors: Save Sight Institute, Discipline of Clinical Ophthalmology, The University of Sydney, Australia. jing.you@sydney.edu.au
authors: Jingjing
authors: J
authors: You
authors: Chris
authors: C
authors: Hodge
authors: Li
authors: L
authors: Wen
authors: John W
authors: JW
authors: McAvoy
authors: Michele C
authors: MC
authors: Madigan
authors: Gerard
authors: G
authors: Sutton
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D016022:Case-Control Studies; D005136:Eye Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000378:metabolism*; D007640:Keratoconus / Q000209:etiology* / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000378:metabolism*; D013666:Tears / Q000378:metabolism*; D055815:Young Adult; D000094742:Secreted Frizzled-Related Proteins
chemical_list: D015415:Biomarkers; D005136:Eye Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C117636:SFRP1 protein, human; D000094742:Secreted Frizzled-Related Proteins; C042434:tear proteins