The effect of riboflavin-UV-A treatment on corneal limbal epithelial cells--a study on human cadaver eyes.

PURPOSE: 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.