title: Beneficial effect of the antioxidant riboflavin on gene expression of extracellular matrix elements, antioxidants and oxidases in keratoconic stromal cells.
abstract: BACKGROUND
  Keratoconus manifests as a conical protrusion of the cornea and is characterised by stromal thinning. This causes debilitating visual impairment which may necessitate corneal transplantation. Therapeutic targets related to disease mechanisms are currently lacking, as the pathobiology remains unclear. Many pathological features may be manifestations of defects in wound healing and reactive oxygen species (ROS)-associated functions. In a wide range of tissue and cell types, antioxidant exposure has beneficial effects on both of these pathways. This study investigated the effect of treatment with the antioxidant riboflavin on wound healing and ROS-associated functions in keratoconus.
  
  
  METHODS
  Stromal cells were isolated from human central keratoconic (n = 3) and normal (n = 3) corneas. Total RNA was extracted and reverse-transcribed into complementary DNA. The gene expression of 22 genes involved in repair (eight normal and four repair-type extracellular matrix constituents) and ROS-associated processes (eight antioxidants and two ROS-synthesising oxidases) was quantified using quantitative polymerase chain reaction. This was also performed on keratoconic stromal cells treated in vitro with riboflavin (n = 3).
  
  
  RESULTS
  In stromal cells from untreated keratoconic corneas (compared with untreated normal corneas), there was an up-regulation of 7/12 extracellular matrix elements. Four of eight antioxidants and two of two oxidases were also increased. In treated keratoconic corneas (compared with untreated keratoconic corneas), six out of eight normal extracellular matrix constituents were up-regulated and two of four repair-type molecules were reduced. An increase was also observed in seven out of eight antioxidants and there was a diminution in two out of two oxidases.
  
  
  CONCLUSIONS
  Riboflavin encourages the synthesis of a normal extracellular matrix and reduces reactive oxygen species levels in keratoconus. This supports the occurrence of wound healing and ROS-associated abnormalities in keratoconus. By targeting the causative disease mechanisms, riboflavin may have therapeutic potential in the clinical management of keratoconus.
authors: Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. i.cheung@auckland.ac.nz.
authors: Isabella M Y
authors: IM
authors: Cheung
authors: Charles N J
authors: CN
authors: McGhee
authors: Trevor
authors: T
authors: Sherwin
mesh_terms: D003319:Corneal Stroma / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007640:Keratoconus / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012256:Riboflavin / Q000627:therapeutic use*; D014803:Vitamin B Complex / Q000627:therapeutic use
chemical_list: D016326:Extracellular Matrix Proteins; D017382:Reactive Oxygen Species; D014803:Vitamin B Complex; D012313:RNA; D012256:Riboflavin
keywords: antioxidant; keratoconus; oxidative damage; wound healing