title: Study on polymethylmethacrylate ring in protecting limbal stem cells during collagen cross-linking.
abstract: OBJECTIVE
  The UV rays used in the collagen cross-linking (CXL) procedure seem to cause potential damage to the limbal stem cells. This study was designed to evaluate the ability of polymethylmethacrylate (PMMA) hemiannulus as an alternative to protect corneal limbal stem cells during CXL.
  
  
  METHODS
  Ten freshly enucleated human cadaveric eyeballs were subjected to the corneal CXL procedure. The cadaveric eye ball was divided into 2 sectors: A and B. Sector A was left unprotected, while sector B was covered by a PMMA shield. Limbal biopsies from both sectors before and after the procedure were analyzed. Each limbal tissue was placed on human amniotic membrane (HAM) to check the cultivability and was subjected to marker studies using reverse transcriptase PCR.
  
  
  RESULTS
  Before CXL, biopsies from both sectors showed growth on HAM. After CXL, biopsies from sector A showed no growth on HAM while 2 out of the 10 from sector B covered with the PMMA ring did show growth on HAM. The putative stem-cell marker ABCG2 was negative in all the samples from sector A after CXL and was positive in 2 out of the 10 samples from sector B.
  
  
  CONCLUSIONS
  Covering the limbal region with PMMA offers partial protection of the limbus from the UV rays during the CXL procedure.
authors.affiliation: L&T Microbiology Research Centre, Vision Research Foundation, Chennai, India.
authors.forename: Vimalin
authors.initials: V
authors.lastname: Jeyalatha
authors.forename: Malathi
authors.initials: M
authors.lastname: Jambulingam
authors.forename: Nidhi
authors.initials: N
authors.lastname: Gupta
authors.forename: Prema
authors.initials: P
authors.lastname: Padmanabhan
authors.forename: Hajib N
authors.initials: HN
authors.lastname: Madhavan
mesh_terms: D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D015415:Biomarkers; D002102:Cadaver; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D004867:Equipment Design; D006801:Humans; D016850:Limbus Corneae / Q000166:cytology*; D009363:Neoplasm Proteins / Q000235:genetics; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D019904:Polymethyl Methacrylate; D011446:Prospective Studies; D012333:RNA, Messenger / Q000378:metabolism; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection / Q000295:instrumentation*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012256:Riboflavin / Q000627:therapeutic use; D013234:Stem Cells / Q000528:radiation effects*; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D015415:Biomarkers; D003432:Cross-Linking Reagents; D009363:Neoplasm Proteins; D017319:Photosensitizing Agents; D012333:RNA, Messenger; D003094:Collagen; D019904:Polymethyl Methacrylate; D012256:Riboflavin