Impact of aging and diabetes mellitus on the expression of the proliferating cell nuclear antigen in rat testicular tissue

This study evaluated the expression of proliferating cell nuclear antigen (PCNA), which is one of the important markers of cell proliferation, in testicular tissue with aging and progress of diabetes mellitus (DM). OLETF rats were used as animal models for non-insulin-dependent DM. They were 12, 30, 50, and 70 weeks old. The controls were age-matched nondiabetic LEIO rats. Testes were taken from all the rats and paraffin-embedded sections were cut and stained with PC 10 monoclonal AB (x50). Labeled cells were assessed in randomly selected fields. Labeling index (LI) for each stage of spermatogenesis was estimated and total LI for each specimen was calculated. In control rats, the 12-week-old animals showed the highest PCNA-LI. The indexes started to decrease in other older animals, with an increase in the number of suppressed stages as the animals aged, leading to significant differences among groups except between the 12- and 30-week-old groups. The same features were also seen in DM animals as the disease progressed. The total LI of controls were significantly higher and the number of suppressed stages was lower than those of DM animals, except among the 12-week-old group. Both aging and DM have depressing effects on the expression of PCNA in testicular tissue. The decline in PCNA expression is parallel with advancement of age and progress of DM. However, DM has a more suppressing effect than aging on that expression. This suppression could explain the decrease in male fertility potential that may be associated with both conditions.