Germ-cell degeneration in experimental unilateral cryptorchidism: role of apoptosis.

We investigated the possible involvement of apoptosis in the increased germ-cell degeneration in undescended testes (UDT). Experimental unilateral cryptorchidism was induced in 21-day-old rats, and both testes were removed for in-situ TUNEL staining of apoptotic cells at 1, 3, 7, 10, and 14 days postoperation. A gradual increase in the incidence of apoptosis was seen at 21-28 days of age in the control testes, followed by a decrease thereafter. After 10 days postoperation, the weight of the UDT was significantly lower than that of the contralateral descended testis (CDT) and the controls. However, the weight of scrotal testes in each group was similar. UDTs demonstrated a markedly increased incidence of apoptosis. By 7 days postoperation, the percentage of seminiferous tubules containing apoptotic germ cells significantly increased in UDTs compared with that in CDTs and controls (P < 0.001). Moreover, there was a significant difference in the percentage of seminiferous tubules containing apoptotic germ cells between CDTs and controls (P < 0.01). In addition, an increased incidence of seminiferous tubules containing 8-10 and >10 apoptotic germ cells from 7, 10, and 14 days postoperation in UDTs was detected. In-situ TUNEL analysis demonstrated spermatocytes to be the main type of germ cells affected in all groups. These findings suggest that spermatogenesis decreases not only in the UDT, but also in the CDT, and that the germ-cell degeneration in cryptorchidism took the form of apoptosis.