AIMTo evaluate the long term effect of experimental cryptorchidism on germ cell apoptotic rate and testicular sperm content in adult rats.

METHODSBilateral cryptorchidism was created in 40 adult male Sprague-Dawley rats by surgically manipulating the testes into the abdominal cavity and closing the internal inguinal ring. The rats were sacrificed and the testes removed 6 hours and 2, 4, 7, 21, 28 and 56 days after cryptorchidism. Germ cell apoptosis was quantified by means of TUNEL assay and apoptosis was confirmed using transmission electron microscopy.

RESULTSThe rate of apoptosis peaked at 4 days of cryptorchidism and then progressively declined to a nadir at 14 days of cryptorchidism. At 56 days of cryptorchidism, the germinal epithelium was largely depleted by the apoptotic process and only a few mature sperm were seen within the testis. At this point, a few tubules were seen to be repopulating with primary spermatocytes and the level of germ cell apoptosis began to increase marginally. Testicular sperm count (TSC) began to decline rapidly at day 7 of cryptorchidism. Only a few mature sperm were found in the testes of rats following 56 days of cryptorchidism. Multinucleated giant cells (MGC) were most numerous within the seminiferous tubules at day 4. At day 7, 35 % of MGCs were TUNEL positive. At all subsequent time points, however, MGCs fail to stain positive for apoptosis. This resumption of increased apoptosis coincided with the appearance of a population of primary spermatocytes in some seminiferous tubules. Moreover, there was not a corresponding increase in the number of mature sperm after 56 days of cryptorchidism.

CONCLUSIONThe decline in germ cell apoptosis after 4 days of cryptorchidism can be attributed to be the result of an overall depletion of germ cells. It appears that after a prolonged cryptorchidism (56 days), there is a limited resumption of spermatogenesis presumably as a result of a decrease in the maturing germ cells undergoing programmed cell death.