Fertility and histological studies in a unilateral cryptorchid rat model during early and late adulthood

To investigate the effect of age on fertility and testicular development in rats with untreated unilateral undescended testes.

Newborn male Wistar King-A rats were divided into two groups. In group 1, a mechanical model of unilateral undescended testis was created by performing extra-abdominal fixation of the gubernaculum in the neonatal period, and in group 2, sham-operated rats were used as controls. At 90 days old (early adulthood), the fertility of both groups was assessed by mating the rats with mature virgin females for 2 weeks. Thereafter, some of the rats were killed and their testes examined histologically, while the remaining rats were allowed to develop further. At the age of 180 days (late adulthood), fertility was re-assessed in the same way. All the rats were then killed and their testes removed for histological examination.

There was no significant difference in pregnancy rate of females mated with males from either group in early adulthood. However, in late adulthood there was a significant reduction in pregnancy rate in females coupled with cryptorchid rats compared with that of females coupled with control rats. There was a significant degeneration of the unilateral cryptorchid testes compared with control testes in both early and late adulthood. In contrast, there were no significant changes in histological development between the contralateral scrotal testes and the controls in early adulthood, although they were significantly different from the controls in late adulthood.

These results suggest that fertility is affected by ageing in untreated unilateral cryptorchidism; this may be induced by extensive damage not only in the undescended testes, but also in the contralateral scrotal testis, in this mechanically induced model of unilateral cryptorchidism.