title: Differential Molecular Expression of Extracellular Matrix and Inflammatory Genes at the Corneal Cone Apex Drives Focal Weakening in Keratoconus.
abstract: OBJECTIVE
  In this study, we elucidated the differential expression of a set of local molecular factors in ectatic cone area of the cornea to uncover a functional cause for focal corneal weakening characteristic of the keratoconus (KC) disease.
  
  
  METHODS
  All human corneal samples were collected after approval of Institutional Ethics Committee and informed consent. Keratoconus patients were classified based on clinical parameters, topographical features, and structural deformity. Epithelial cells were collected from KC patients (n = 66) undergoing corneal cross-linking procedures from cone apex and periphery. Nonectatic refractive surgery patients (n = 23) served as controls. The ratio of epithelial gene expression in cone and periphery of each eye was estimated by quantitative PCR and correlated with clinical data. Similar cone versus periphery analysis was done from the KC stroma and from KC patients with Bowman's layer (BL) breach observed by anterior segment optical coherence tomography (OCT).
  
  
  RESULTS
  Epithelium from the cone apex of KC patients had elevated levels of inflammatory factors TNF-α, IL-6, and matrix metalloproteinase 9 (MMP-9) but reduced Lysyl oxidase (LOX) and Collagen IVA1, which also demonstrated correlation with corneal curvature and deformity parameters. Stromal gene expression from KC patients showed trends similar to epithelium. Epithelium collected from the cone apex of BL breached KC patients showed significantly elevated MMP-9, TNF-α, and IL-6 levels but reduced IL-10, tissue inhibitor of metalloproteinases 1 (TIMP-1), and Collagen IVA1 expression.
  
  
  CONCLUSIONS
  This study provides the first evidence that altered corneal epithelial and stromal expression of specific genes at the corneal cone apex drives focal structural weakness in KC.
authors.affiliation: Cornea Department, Narayana Nethralaya, Bangalore, India.
authors.forename: Natasha
authors.initials: N
authors.lastname: Pahuja
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India.
authors.forename: Nimisha R
authors.initials: NR
authors.lastname: Kumar
authors.affiliation: Cornea Department, Narayana Nethralaya, Bangalore, India.
authors.forename: Rushad
authors.initials: R
authors.lastname: Shroff
authors.affiliation: Cornea Department, Narayana Nethralaya, Bangalore, India.
authors.forename: Rohit
authors.initials: R
authors.lastname: Shetty
authors.affiliation: Cornea Clinic, Department of Ophthalmology, Maastricht University Medical Center, the Netherlands.
authors.forename: Rudy M M A
authors.initials: RM
authors.lastname: Nuijts
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India.
authors.forename: Anuprita
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Sinha-Roy
authors.affiliation: Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, Missouri, United States.
authors.forename: Shyam S
authors.initials: SS
authors.lastname: Chaurasia
authors.affiliation: Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, Missouri, United States 5Mason Eye Institute, School of Medicine, University of Missouri, Columbia, Missouri, United States 6Harry S. Truman Veterans' Memorial Hospital, Columbia, Missouri, United States.
authors.forename: Rajiv R
authors.initials: RR
authors.lastname: Mohan
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India 7Singapore Eye Research Institute, Singapore.
authors.forename: Arkasubhra
authors.initials: A
authors.lastname: Ghosh
mesh_terms: D000328:Adult; D003315:Cornea / Q000378:metabolism* / Q000473:pathology; D019781:Corneal Topography; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics*; D004247:DNA / Q000235:genetics*; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism; D007640:Keratoconus / Q000175:diagnosis / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D060888:Real-Time Polymerase Chain Reaction; D041623:Tomography, Optical Coherence
chemical_list: D016207:Cytokines; D016326:Extracellular Matrix Proteins; D004247:DNA