Expression of SFRP Family Proteins in Human Keratoconus Corneas

PLoS One. 2013 Jun 18;8(6):e66770. doi: 10.1371/journal.pone.0066770. Print 2013.

Abstract

We investigated the expression of the secreted frizzled-related proteins (SFRPs) in keratoconus (KC) and control corneas. KC buttons (∼8 mm diameter) (n = 15) and whole control corneas (n = 7) were fixed in 10% formalin or 2% paraformaldehyde and subsequently paraffin embedded and sectioned. Sections for histopathology were stained with hematoxylin and eosin, or Periodic Acid Schiff's reagent. A series of sections was also immunolabelled with SFRP 1 to 5 antibodies, visualised using immunofluorescence, and examined with a Zeiss LSM700 scanning laser confocal microscope. Semi-quantitative grading was used to compare SFRP immunostaining in KC and control corneas. Overall, KC corneas showed increased immunostaining for SFRP1 to 5, compared to controls. Corneal epithelium in all KC corneas displayed heterogeneous moderate to strong immunoreactivity for SFRP1 to 4, particularly in the basal epithelium adjacent to cone area. SFRP3 and 5 were localised to epithelial cell membranes in KC and control corneas, with increased SFRP3 cytoplasmic expression observed in KC. Strong stromal expression of SFRP5, including extracellular matrix, was seen in both KC and control corneas. In control corneas we observed differential expression of SFRP family proteins in the limbus compared to more central cornea. Taken together, our results support a role for SFRPs in maintaining a healthy cornea and in the pathogenesis of epithelial and anterior stromal disruption observed in KC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cornea / metabolism*
  • Cornea / pathology
  • Humans
  • Immunohistochemistry
  • Keratoconus / metabolism*
  • Keratoconus / pathology
  • Membrane Proteins / metabolism*
  • Middle Aged
  • Young Adult

Substances

  • Membrane Proteins

Grants and funding

The research was funded by grants from The Sydney Eye Hospital Foundation, Sydney Foundation for Medical Research (MCM), Sydney Medical Foundation (GS) and Sydnovate, University of Sydney. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.