Efficacy of orchidopexy on spermatogenesis in the immature mutant ‘trans-scrotal’ rat as a cryptorchid model by quantitative cytological analysis

Objectives  To determine whether cryptorchidism is a congenital malformation and whether the impaired spermatogenesis in immature testes can be reversed by early orchidopexy, using the mutant trans-scrotal (T-S) rat which is normally masculinized but has cryptorchidism in 85% of males. Materials and methods  First, T-S rats (six per group) with ectopic testes destined to be undescended were investigated histologically at 4, 7 and 14 days after birth. Secondly, 12-day-old T-S rats were divided into four groups which underwent different procedures, i.e. 1, with normally descending testes (normal control, 10 rats); 2, with undescended testes (UDT) treated by orchidopexy (treated UDT, eight rats); 3, with UDT treated by a sham operation (sham-operated UDT, six rats); and 4, with UDT left untreated (untreated UDT, six rats). Thirty days after operation the testicular anatomy was recorded; excised testes were examined histologically and different types of germ cells were counted per tubule cross-section microscopically. Results  There were no quantitative or morphological differences in the numbers of gonocytes, type-A spermatogonia or Leydig cells in the seminiferous tubules between normal and ectopic testes in the first 14 days after birth. However, by 21 days of age spermatogenesis in the UDT had declined with transformation from primary leptotene spermatocytes to spermatids. There were significantly more Leydig cells in the untreated UDT at 30 days than in normal control testes. The impaired spermatogenesis in UDT was restored by early orchidopexy and there were significantly more seminiferous tubules at stage 3 (pachytene spermatocytes) and stage 4 (spermatids) than in the untreated or sham-operated groups (P<0.001). Conclusions  These results show that in the T-S rat with cryptorchidism, the testicular damage is not a congenital malformation and can be reversed with early surgical correction.