Secreted frizzled-related protein 1 (SFRP1) is highly upregulated in keratoconus epithelium: a novel finding highlighting a new potential focus for keratoconus research and treatment.
OBJECTIVE
To investigate the expression of Wnt signalling pathway genes in keratoconic (KC) epithelium.


METHODS
RNA was extracted from the epithelium of four KC patients undergoing corneal transplantation and five age-matched controls. The expression of 84 genes known to be involved in the Wnt signalling pathway was tested by reverse transcription-polymerase chain reaction (RT-PCR) with a pathway-targeted array (Human Wnt RT(2) Profiler PCR Array, Superarray).


RESULTS
Using RT-PCR arrays, LEF1, PITX2 and secreted frizzled-related protein 1 (SFRP1) were upregulated more than twofold in KC compared with control epithelium. Only SFRP1 was significantly upregulated, approximately 25-fold compared with pooled controls (range 9.12-fold to 98.6-fold; P = 0.019). SFRP1 expression was associated with patient age and possibly the rate of progression of the keratoconus. Immunohistochemistry was used to assess SFRP1 protein distribution and confirm the SFRP1 microarray result (n = 3 KC and n = 2 control corneas). SFRP1 immunolablelling was seen in all KC corneas, mostly in the basal epithelium; however, control corneas showed minimal SFRP1 immunoreactivity.


CONCLUSIONS
SFRP1 is highly upregulated in the epithelium of these KC patients, suggesting a role in the pathogenesis and progression of keratoconus. Future investigations are required to establish if SFRP1 may be a potential marker of KC progression or if manipulation of its expression can be used to therapeutic effect in this disease.
Sutton
Gerard
G
Save Sight Institute, Sydney Medical School, New South Wales, Australia. gerard.sutton@vgaustralia.com <gerard.sutton@vgaustralia.com>
Madigan
Michele
M
Roufas
Athena
A
McAvoy
John
J
D000328:Adult; D016039:Corneal Transplantation; D019573:Epithelium, Corneal / Q000378:metabolism*; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D007640:Keratoconus / Q000235:genetics* / Q000378:metabolism / Q000601:surgery; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000235:genetics; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D018613:Microscopy, Confocal; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics; D015854:Up-Regulation / Q000502:physiology*; D051153:Wnt Proteins / Q000235:genetics; D055815:Young Adult; D000097577:Homeobox Protein PITX2; D000094742:Secreted Frizzled-Related Proteins
D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D051821:Lymphoid Enhancer-Binding Factor 1; D008565:Membrane Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D051153:Wnt Proteins; D000097577:Homeobox Protein PITX2; C497573:LEF1 protein, human; C117636:SFRP1 protein, human; D000094742:Secreted Frizzled-Related Proteins