title: Hydroxyapatite promotes superior keratocyte adhesion and proliferation in comparison with current keratoprosthesis skirt materials.
abstract: OBJECTIVE
  Published clinical series suggest the osteoodontokeratoprosthesis (OOKP) may have a lower extrusion rate than current synthetic keratoprostheses. The OOKP is anchored in the eye wall by autologous tooth. The authors' aim was to compare adhesion, proliferation, and morphology for telomerase transformed keratocytes seeded on calcium hydroxyapatite (the principal mineral constituent of tooth) and materials used in the anchoring elements of commercially available synthetic keratoprostheses.
  
  
  METHODS
  Test materials were hydroxyapatite, polytetrafluoroethylene (PTFE), polyhydroxyethyl methacrylate (HEMA), and glass (control). Cell adhesion and viability were quantified at 4 hours, 24 hours, and 1 week using a calcein-AM/EthD-1 viability/cytotoxicity assay. Focal contact expression and cytoskeletal organisation were studied at 24 hours by confocal microscopy with immunoflourescent labelling. Further studies of cell morphology were performed using light and scanning electron microscopy.
  
  
  RESULTS
  Live cell counts were significantly greater on hydroxyapatite surfaces at each time point (p<0.04). Dead cell counts were significantly higher for PTFE at 7 days (p<0.002). ss(1) integrin expression was highest on hydroxyapatite. Adhesion structures were well expressed in flat, spread out keratocytes on both HA and glass. Keratocytes tended to be thinner and spindle shaped on PTFE. The relatively few keratocytes visible on HEMA test surfaces were rounded and poorly adherent.
  
  
  CONCLUSIONS
  Keratocyte adhesion, spreading, and viability on hydroxyapatite test surfaces is superior to that seen on PTFE and HEMA. Improving the initial cell adhesion environment in the skirt element of keratoprostheses may enhance tissue integration and reduce device failure rates.
authors.affiliation: Cornea & External Disease Service, Moorfields Eye Hospital, London, UK. jodmehta@gmail.com
authors.forename: J S
authors.initials: JS
authors.lastname: Mehta
authors.forename: C E
authors.initials: CE
authors.lastname: Futter
authors.forename: S R
authors.initials: SR
authors.lastname: Sandeman
authors.forename: R G A F
authors.initials: RG
authors.lastname: Faragher
authors.forename: K A
authors.initials: KA
authors.lastname: Hing
authors.forename: K E
authors.initials: KE
authors.lastname: Tanner
authors.forename: B D S
authors.initials: BD
authors.lastname: Allan
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002448:Cell Adhesion; D049109:Cell Proliferation; D002470:Cell Survival; D003315:Cornea / Q000601:surgery* / Q000648:ultrastructure; D017886:Durapatite / Q000737:chemistry*; D006801:Humans; D019012:Integrin beta1 / Q000032:analysis; D008422:Materials Testing / Q000379:methods; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D010590:Phalloidine / Q000032:analysis; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D016596:Vinculin / Q000032:analysis
chemical_list: D001672:Biocompatible Materials; D019012:Integrin beta1; D016596:Vinculin; D010590:Phalloidine; D017886:Durapatite