Effect of aging and dietary restriction on rat testicular germ cell apoptosis

The purpose of this study was to determine whether apoptotic cell death of rat testicular germ cells varies with increased age or with dietary restriction. Slide-mounted cross-sections of formalin-fixed testis from 4-, 13-, and 23-month-old ad-libitum-fed and 40% dietary-restricted male F344 rats were used in an in situ assay for apoptotic germ cells. Results show that in ad-libitum-fed rats, increased age caused a significant increase in the percentage of seminiferous tubules containing apoptotic cells, but a significant decrease in the number of apoptotic cells per apoptosis-positive tubule. In the 23-month-old rats, dietary restriction significantly increased both the percentage of apoptotic positive tubules and the number of apoptotic cells per apoptosis-positive tubule above ad-libitum-fed values. Both ad-libitum and diet-restricted groups demonstrated a decrease in the percentage of apoptotic spermatogonia concomitant with a significant increase in the percentage of apoptotic primary spermatocytes with advanced age. The significant age-related increase in total numbers of apoptotic germ cells may reflect elimination of defective germ cells, which occurs with increased frequency in advanced age. Dietary restriction may induce enhanced screening against defective germ cells above that seen in the ad-libitum-fed rats. These results have potential implications in aging studies as well as research involving perturbation of normal germ cell homeostasis.