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 cry ptorchidism was induced in 21-day-old rats, and both testes were removed fo r in-situ TUNEL staining of apoptotic cells at 1, 3, 7, 10, and 14 days pos toperation. 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. A fter 10 days postoperation, the weight of the UDT was significantly lower t han that of the contralateral descended testis (CDT) and the controls. Howe ver, the weight of scrotal testes in each group was similar. UDTs demonstra ted a markedly increased incidence of apoptosis. By 7 days postoperation, t he percentage of seminiferous tubules containing apoptotic germ cells signi ficantly increased in UDTs compared with that in CDTs and controls (P < 0.0 01). Moreover, there was a significant difference in the percentage of semi niferous tubules containing apoptotic germ cells between CDTs and controls (P < 0.01). In addition, an increased incidence of seminiferous tubules con taining 8-10 and > 10 apoptotic germ cells from 7, 10, and 14 days postoper ation in UDTs was detected. In-situ TUNEL analysis demonstrated spermatocyt es 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 th e CDT, and that the germ-cell degeneration in cryptorchidism took the form of apoptosis.