title: Attenuation of lysyl oxidase and collagen gene expression in keratoconus patient corneal epithelium corresponds to disease severity.
abstract: OBJECTIVE
  Keratoconus (KC) is characterized by progressive vision loss due to corneal thinning and structural abnormalities. It is hypothesized that KC is caused by deregulated collagen levels and collagen fibril-maturating enzyme lysyl oxidase (LOX). Further, it is currently not understood whether the gene expression deregulated by the corneal epithelium influences KC pathogenesis. We studied (i) the expressions of the LOX, collagen I (COL IA1), collagen IV (COL IVA1), MMP9, and IL6 genes in KC corneal epithelia, (ii) validated their expression levels in patient tissues, and (iii) correlated expression levels with KC disease severity. The primary goal of this study was to evaluate the importance of these genes in the progression of KC.
  
  
  METHODS
  We analyzed the gene expression levels of the key proteins LOX, collagens (COL IA1 and COL IVA1), MMP9, and IL6 in debrided corneal epithelia from a large cohort of KC patients (90 eyes) and compared them to control patients (52 eyes) without KC. We measured the total LOX activity in the tears of KC patients compared to controls. We also correlated the protein expression levels of LOX and collagens by immunohistochemistry (IHC) in primary tissues from KC patients (27 eyes) undergoing keratoplasty compared to healthy donor corneas (15 eyes).
  
  
  RESULTS
  We observed a significant reduction in LOX transcript levels in KC corneal epithelia, and LOX activity in KC tears correlated with disease severity. Collagen transcripts were also reduced in KC while MMP9 transcript levels were upregulated and correlated with disease severity. IL6 was moderately increased in KC patients. IHC demonstrated a reduction in the protein expression levels of LOX in the epithelium and collagen IV in the basement membrane of KC patients compared to healthy donor corneas.
  
  
  CONCLUSIONS
  The data demonstrates that the structural deformity of the KC cornea may be dependent on reduced expressions of collagens and LOX, as well as on MMP9 elevated by the corneal epithelium.
authors.affiliation: Cornea Department, Narayana Nethralaya, Bangalore, India.
authors.forename: Rohit
authors.initials: R
authors.lastname: Shetty
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India.
authors.forename: Arunapriya
authors.initials: A
authors.lastname: Sathyanarayanamoorthy
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India.
authors.forename: Reshma Airody
authors.initials: RA
authors.lastname: Ramachandra
authors.affiliation: Cornea Department, Narayana Nethralaya, Bangalore, India.
authors.forename: Vishal
authors.initials: V
authors.lastname: Arora
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India.
authors.forename: Anuprita
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: Cornea Department, Narayana Nethralaya, Bangalore, India.
authors.forename: Purnima Raman
authors.initials: PR
authors.lastname: Srivatsa
authors.affiliation: Cornea Department, Narayana Nethralaya, Bangalore, India.
authors.forename: Natasha
authors.initials: N
authors.lastname: Pahuja
authors.affiliation: Cornea Clinic, Department of Ophthalmology, Maastricht University Medical Center, 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: Abhijit
authors.initials: A
authors.lastname: Sinha-Roy
authors.affiliation: Mason Eye Institute, School of Medicine, University of Missouri-Columbia, Columbia, NY.
authors.forename: Rajiv R
authors.initials: RR
authors.lastname: Mohan
authors.affiliation: GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India ; Singapore Eye Research Institute, Singapore.
authors.forename: Arkasubhra
authors.initials: A
authors.lastname: Ghosh
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D024042:Collagen Type I / Q000235:genetics* / Q000378:metabolism; D024141:Collagen Type IV / Q000235:genetics* / Q000378:metabolism; D019573:Epithelium, Corneal / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D007640:Keratoconus / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism; D008249:Protein-Lysine 6-Oxidase / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012720:Severity of Illness Index; D013666:Tears / Q000737:chemistry
chemical_list: D024042:Collagen Type I; D024141:Collagen Type IV; C508600:IL6 protein, human; D015850:Interleukin-6; D012333:RNA, Messenger; D008249:Protein-Lysine 6-Oxidase; C579270:MMP9 protein, human; D020780:Matrix Metalloproteinase 9