PROLIFERATING CELL NUCLEAR ANTIGEN COLOCALIZATION WITH CORNEAL EPITHELIAL STEM-CELLS AND INVOLVEMENT IN PHYSIOLOGICAL CELL TURNOVER

Corneal integrity is dependent on a constant turnover of epithelial ce lls. According to the current hypothesis essential contributors to thi s process, the so-called stem-cells, are localized in the limbal area of the cornea, However, histological identification of stem cells of t he cornea is thus far not possible, In the present study,ve have used specific antibodies against proliferating cell nuclear antigen (PCNA). The nuclear protein is expressed in cells during replication, Prior t o establishment of staining indices the optimal fixation procedure was found to be of major importance for the results and standardized for fixation in 4% formaldehyde, This procedure also gave the best preserv ation of the morphology. In the corneas often New Zealand rabbits the staining index for PCNA was found to be on average 23% (SD +/- 13%) fo r the basal layer of the limbal epithelium. In the mid-peripheral and central corneal epithelium only occasional staining of PCNA was detect ed with a 2% staining index (SD +/- 2%), The agglomeration of PCNA-pos itive cells in the basal layer of the limbal epithelium together with their colocalization with the known location of stem cells strongly su ggests that PCNA could serve as a reliable indicator for the proximity of proliferating corneal epithelial stem cells in histological sectio ns, which would be of significant clinical importance.