The effect of riboflavin-UV-A treatment on corneal limbal epithelial cells--a study on human cadaver eyes.
OBJECTIVE
To determine the effect of riboflavin-UV-A treatment on the corneal limbal epithelial cells during a corneal collagen cross-linking (CXL) procedure.


METHODS
Thirty freshly enucleated human cadaveric eyeballs were subjected to a CXL procedure, mimicking the clinical protocol. During the UV-A exposure, one half of the limbus (sector A) was left unprotected, whereas the other half (sector B) was covered by a metal shield. Limbal biopsies from both sectors before and after the procedure were analyzed. Each strip of tissue was divided into 3 segments, for cell count of viable cells, for cultivation on human amniotic membrane (HAM), and for stem cell and differentiated corneal epithelial cell marker studies using reverse transcriptase-polymerase chain reaction.


RESULTS
Compared with the cell count before CXL, there was a statistically significant drop in the mean number of viable cells after CXL in sector A but not in sector B. Biopsies from both sectors before CXL and from sector B after CXL showed good growth on HAM. Biopsies from sector A after CXL showed no growth on HAM. The putative stem cell marker ABCG2 was absent in all samples and p63 was absent in 3 of 10 samples taken from sector A after CXL. All markers were present in all samples from sector B after CXL.


CONCLUSIONS
Riboflavin-UV-A treatment can result in damage to limbal epithelial cells, particularly the stem cells. Covering the limbal region with a metal shield effectively prevents this damage.
L and T Microbiology Research Centre, Vision Research Foundation, Chennai, India.
Jeyalatha
J
Vimalin
Nidhi
N
Gupta
Malathi
M
Jambulingam
Prema
P
Padmanabhan
Hajib N
HN
Madhavan
D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D015415:Biomarkers; D002452:Cell Count; D003094:Collagen / Q000378:metabolism; D003319:Corneal Stroma / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D016850:Limbus Corneae / Q000473:pathology*; D009363:Neoplasm Proteins / Q000378:metabolism; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012256:Riboflavin / Q000494:pharmacology*; D013234:Stem Cells / Q000187:drug effects* / Q000378:metabolism; D014019:Tissue Donors; D014157:Transcription Factors / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
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; C115051:TP63 protein, human; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D003094:Collagen; D012256:Riboflavin