title: Gross cystic disease fluid protein-15/prolactin-inducible protein as a biomarker for keratoconus disease.
abstract: Keratoconus (KC) is a bilateral degenerative disease of the cornea characterized by corneal bulging, stromal thinning, and scarring. The etiology of the disease is unknown. In this study, we identified a new biomarker for KC that is present in vivo and in vitro. In vivo, tear samples were collected from age-matched controls with no eye disease (n = 36) and KC diagnosed subjects (n = 17). Samples were processed for proteomics using LC-MS/MS. In vitro, cells were isolated from controls (Human Corneal Fibroblasts-HCF) and KC subjects (Human Keratoconus Cells-HKC) and stimulated with a Vitamin C (VitC) derivative for 4 weeks, and with one of the three transforming growth factor-beta (TGF-β) isoforms. Samples were analyzed using real-time PCR and Western Blots. By using proteomics analysis, the Gross cystic disease fluid protein-15 (GCDFP-15) or prolactin-inducible protein (PIP) was found to be the best independent biomarker able to discriminate between KC and controls. The intensity of GCDFP-15/PIP was significantly higher in healthy subjects compared to KC-diagnosed. Similar findings were seen in vitro, using a 3D culture model. All three TGF-β isoforms significantly down-regulated the expression of GCDFP-15/PIP. Zinc-alpha-2-glycoprotein (AZGP1), a protein that binds to PIP, was identified by proteomics and cell culture to be highly regulated. In this study by different complementary techniques we confirmed the potential role of GCDFP-15/PIP as a novel biomarker for KC disease. It is likely that exploring the GCDFP-15/PIP-AZGP1 interactions will help better understand the mechanism of KC disease.
authors.affiliation: Ophthalmology, University of Oklahoma - Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States of America.
authors.forename: Shrestha
authors.initials: S
authors.lastname: Priyadarsini
authors.affiliation: Department of Ophthalmology, Aarhus University Hospital, Aarhus C, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Hjortdal
authors.affiliation: Ophthalmology, University of Oklahoma - Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States of America.
authors.forename: Akhee
authors.initials: A
authors.lastname: Sarker-Nag
authors.affiliation: Department of Ophthalmology, Aarhus University Hospital, Aarhus C, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Sejersen
authors.affiliation: Division of Signal Transduction/Mass Spectrometry Core, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: John M
authors.initials: JM
authors.lastname: Asara
authors.affiliation: Ophthalmology, University of Oklahoma - Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States of America.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Karamichos
mesh_terms: D054392:Adipokines; D000328:Adult; D001205:Ascorbic Acid / Q000494:pharmacology; D015415:Biomarkers / Q000378:metabolism*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D002853:Chromatography, Liquid; D003315:Cornea / Q000166:cytology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006023:Glycoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D020543:Proteome / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction; D053719:Tandem Mass Spectrometry; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D053781:Transforming Growth Factor beta2 / Q000494:pharmacology; D053782:Transforming Growth Factor beta3 / Q000494:pharmacology; D014815:Vitamins / Q000494:pharmacology; D055815:Young Adult; D000090203:Zn-Alpha-2-Glycoprotein
chemical_list: D054392:Adipokines; D001205:Ascorbic Acid; D015415:Biomarkers; D002352:Carrier Proteins; D006023:Glycoproteins; D026901:Membrane Transport Proteins; D020543:Proteome; D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2; D053782:Transforming Growth Factor beta3; D014815:Vitamins; C488891:AZGP1 protein, human; D000090203:Zn-Alpha-2-Glycoprotein; C488892:PIP protein, human