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Protection of corneal epithelial stem cells prevents ultraviolet A damage during corneal collagen cross-linking treatment for keratoconus
  1. Jonathan E Moore1,2,
  2. Sarah D Atkinson1,
  3. Dimitri T Azar3,
  4. Jenny Worthington1,
  5. C Stephen Downes1,
  6. David G Courtney1,
  7. C B Tara Moore1,2
  1. 1School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland
  2. 2Cathedral Eye Clinic, Belfast, Northern Ireland
  3. 3Department of Ophthalmology and Visual Sciences, University of Illinois College of Medicine at Chicago, Chicago, Illinois, USA
  1. Correspondence to Professor Jonathan E Moore, University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland; johnnymoorebal{at}gmail.com

Abstract

Background/aims Cross-linking of the cornea is usually carried out at a young age as a treatment to manage ectasia. The corneal limbal region contains delicate long-lived stem cells, which could potentially be deleteriously affected by Ultraviolet A (UV-A) radiation. Damage to these stem cells may not demonstrate as a clinical problem for many years subsequent to cross-linking treatment. UV-A radiation is known to have potential mutagenic effects upon mammalian DNA and can result in cancer.

Methods Cultured corneal epithelial cells and ex vivo corneal tissue were treated with the standard clinical cross-linking protocol for UV-A irradiation. 8-hydroxydeoxyguansoine (8-OHdG) and cyclin-dependent kinase inhibitor genes (CDKN1A and CDKN2A) were assayed as markers of DNA damage using immunohistochemistry, ELISA and quantitative real time PCR.

Results Staining of treated limbal tissue demonstrated the presence of 8-OHdG within p63 positive basal limbal cells. Levels of 8-OHdG and CDKN1A mRNA were found to be significantly increased in cultured corneal epithelial cells and limbal epithelial cells but no increase was demonstrated with the use of a polymethyl methylacrylate protective cover.

Conclusions This study provides evidence that oxidative nuclear DNA damage can occur through cross-linking in layers of corneal epithelial cells at the limbus and that this can be easily prevented by covering the limbus.

  • Cornea
  • Vision
  • Treatment Lasers
  • Stem Cells

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