title: Subclinical keratoconus and inflammatory molecules from tears.
abstract: OBJECTIVE
  Tissue degradation in corneal thinning disorders, such as keratoconus (KC), involves the expression of inflammatory mediators. The purpose of this study was to determine the levels of proinflammatory cytokines and matrix metalloproteinase 9 (MMP-9) in tears from both eyes of unilateral keratoconus (KC) patients.
  
  
  METHODS
  Thirty patients diagnosed as having asymmetrical KC (30 KC eyes, and 30 subclinical KC eyes) and 20 normal control subjects (one eye) were studied in a prospective, cross-sectional study. Keratoconus screening programmes were performed on these participants. Ten microlitres of tears was collected from each eye. The concentrations of cytokines (interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha)) and MMP-9 were measured by ELISA.
  
  
  RESULTS
  Mean values for IL-6 levels were similar in KC and subclinical KC samples (5.5 (4.9 to 6.9) vs 5.7 (4.5 to 6.2) pg/ml, p = 0.131), but significantly higher in relation to the control group (2.2 (1.0 to 4.1) pg/ml, p<0.0001). Significant differences were found in TNF-alpha levels between KC and subclinical KC eyes (5.4 (4.1 to 6.8) vs 4.8 (4.2 to 6.0) pg/ml, p = 0.032) and control group (1.8 (1.5 to 2.3) pg/ml, p<0.0001). Increased values of MMP-9 were found in KC (59.4 (50.6 to 66.1) ng/ml) vs subclinical KC eye (7.0 (4.8 to 8.6) ng/ml) (p<0.0001). MMP-9 levels in the control group (6.1 (3.9 to 8.3) ng/ml) and subclinical KC were similar (p = 0.203).
  
  
  CONCLUSIONS
  IL-6 and TNF-alpha are overexpressed in the tears of subclinical and KC eyes. Increased MMP-9 levels were found only in the KC eye. These results indicate that the pathogenesis of KC may involve chronic inflammatory events.
authors.affiliation: Instituto Galego de Oftalmoloxía, University of Santiago de Compostela, Spain. mariaisabel.lema@usc.es
authors.forename: I
authors.initials: I
authors.lastname: Lema
authors.forename: T
authors.initials: T
authors.lastname: Sobrino
authors.forename: J A
authors.initials: JA
authors.lastname: Durán
authors.forename: D
authors.initials: D
authors.lastname: Brea
authors.forename: E
authors.initials: E
authors.lastname: Díez-Feijoo
mesh_terms: D000293:Adolescent; D000328:Adult; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000032:analysis*; D015850:Interleukin-6 / Q000032:analysis; D007640:Keratoconus / Q000378:metabolism*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000032:analysis; D013666:Tears / Q000737:chemistry*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis; D055815:Young Adult
chemical_list: D018836:Inflammation Mediators; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D020780:Matrix Metalloproteinase 9