title: UV cross-linking of donor corneas confers resistance to keratolysis.
abstract: OBJECTIVE
  The aim of this study was to develop a modified ex vivo corneal cross-linking method that increases stromal resistance to enzymatic degradation for use as a carrier for the Boston keratoprosthesis.
  
  
  METHODS
  Ex vivo cross-linking of human corneas was performed using Barron artificial anterior chambers. The corneas were deepithelialized, pretreated with riboflavin solution (0.1% riboflavin/20% dextran), and irradiated with ultraviolet A (UV-A) light (λ = 370 nm, irradiance = 3 mW/cm) for various durations. The combined effect of UV-A and gamma (γ) irradiation was also assessed using the commercially available γ-irradiated corneal donors. The corneas were then trephined and incubated at 37°C with 0.3% collagenase A solution. The time to dissolution of each cornea was compared across treatments.
  
  
  RESULTS
  Deepithelialized corneas (no UV light, no riboflavin) dissolved in 5.8 ± 0.6 hours. Cross-linked corneas demonstrated increased resistance to dissolution, with a time to dissolution of 17.8 ± 2.6 hours (P < 0.0001). The corneal tissues' resistance to collagenase increased with longer UV-A exposure, reaching a plateau at 30 minutes. Cross-linking both the anterior and posterior corneas did not provide added resistance when compared with cross-linking the anterior corneas only (P > 0.05). γ-irradiated corneas dissolved as readily as deepithelialized controls regardless of whether they were further cross-linked (5.6 ± 1.2 hours) or not (6.1 ± 0.6 hours) (P = 0.43).
  
  
  CONCLUSIONS
  Collagen cross-linking of the deepithelialized anterior corneal surface for 30 minutes conferred optimal resistance to in vitro keratolysis by collagenase A.
authors.affiliation: *Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA; and †Schepens Eye Research Institute, Harvard Medical School, Boston, MA.
authors.forename: Samer N
authors.initials: SN
authors.lastname: Arafat
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Robert
authors.forename: Anita N
authors.initials: AN
authors.lastname: Shukla
authors.forename: Claes H
authors.initials: CH
authors.lastname: Dohlman
authors.forename: James
authors.initials: J
authors.lastname: Chodosh
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Ciolino
mesh_terms: D003094:Collagen / Q000378:metabolism*; D017364:Collagenases / Q000633:toxicity; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism; D003316:Corneal Diseases / Q000139:chemically induced / Q000517:prevention & control*; D003319:Corneal Stroma / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D006801:Humans; D017319:Photosensitizing Agents / Q000494:pharmacology*; D012256:Riboflavin / Q000494:pharmacology*; D014019:Tissue Donors; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D017364:Collagenases; D012256:Riboflavin