Evolution of the distribution, proliferation and ultraviolet repair capacity of rat lens epithelial cells as a function of maturation and aging.

The symmetrical organization of lens epithelium was a determining factor in this study whose purpose was to investigate the growth of this tissue during development, maturation and aging. By direct observation it was possible to score all the nuclei, to determine four different zones of cellular density and to monitor them during the whole lifespan. The central zone is mainly quiescent and the proliferation at the periphery accounts for the low steady growth rate of the tissue. With aging there is a continuous decrease in the mitotic index and a cell size enlargement. These cells were able to perform unscheduled DNA synthesis in vitro after ultraviolet irradiation. There is an age-related decrease in DNA repair, but most of it occurs during development (until 59 weeks of age) and then remains constant (59-173 weeks). These results mean that in a differentiated pure cell population aging is not directly related to decline in unscheduled DNA synthesis.