title: Keratocyte cytotoxicity of riboflavin/UVA-treatment in vitro.
abstract: OBJECTIVE
  Collagen crosslinking using ultraviolet- A (UVA) -irradiation combined with the photosensitizer riboflavin is a new technique for treating progressive keratoconus. It has been shown to increase effectively the biomechanical strength of the cornea and to stop or even reverse the progression of keratoconus. As part of a safety evaluation, the present study was undertaken to investigate in vitro the possible cytotoxic effect of combined riboflavin/UVA-treatment on corneal keratocytes and to compare it to UVA-irradiation alone.
  
  
  METHODS
  Cell cultures established from porcine keratocytes were treated with 0.025% riboflavin solution and various UVA (370 nm)-irradiances ranging from 0.4 to 1.0 mW/cm2 and with UVA alone between 2 and 9 mW/cm2 for 30 min. The cell cultures were evaluated for cell death 24 h after irradiation using trypan-blue and Yopro-fluorescence staining.
  
  
  RESULTS
  An abrupt cytotoxic irradiance level was found at 0.5 mW/cm2 for keratocytes after UVA-irradiation combined with the photosensitizer riboflavin, which is 10-fold lower than the cytotoxic irradiance of 5 mW/cm2 after UVA-irradiation alone.
  
  
  CONCLUSIONS
  A cytotoxic effect of combined riboflavin/UVA-treatment on keratocytes is to be expected at 0.5 mW/cm2, which is reached in the clinical setting in human corneas down to a depth of 300 microm using the standard surface UVA-irradiance of 3 mW/cm2.
authors.affiliation: Department of Ophthalmology, Technical University of Dresden, Dresden, Germany. gwollens@hotmail.com
authors.forename: G
authors.initials: G
authors.lastname: Wollensak
authors.forename: E
authors.initials: E
authors.lastname: Spoerl
authors.forename: F
authors.initials: F
authors.lastname: Reber
authors.forename: T
authors.initials: T
authors.lastname: Seiler
mesh_terms: D000818:Animals; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology / Q000187:drug effects* / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000494:pharmacology*; D012256:Riboflavin / Q000494:pharmacology*; D013552:Swine; D014466:Ultraviolet Rays
chemical_list: D017319:Photosensitizing Agents; D012256:Riboflavin