PROLIFERATING CELL NUCLEAR ANTIGEN - CONTRADICTORY RESULTS REGARDING ITS PRESENCE IN THE LENS

Background: Cell division of the normal lens is believed to occur in t he germinative zone of the lens epithelium only. The expression of pro liferating cell nuclear antigen (PCNA), at least in its insoluble form , is restricted to cells shortly after and during DNA synthesis. Metho d: To elucidate the location of the previously reported notable amount s of PCNA in lens epithelium, 6-mu m sections of 10 New Zealand rabbit corneas were stained with specific antibodies. Results: No PCNA-posit ive cells were detected in the lens epithelium, neither in the central zone nor in the germinative zone. Conclusion: As the mitotic activity of lens epithelium is physiologically low (below 0.03% in adult rabbi ts), the likelihood of detecting mitotic figures in histologic section s is very limited. We hence conclude that PCNA may be expressed in the epithelia of the lens but is only occasionally visible in histologica l sections. Our most recent studies have confirmed this. The fixation process and the use of specific antibodies are decisive factors that m ay, when used correctly, allow specific localization PCNA that is invo lved in cell replication of lens epithelium. However, it has to be poi nted out that the mitotic index of lens epithelium is age- and species -related, and hence so is the expression of PCNA, which makes comparis on with other studies more difficult.