PURPOSE: To elucidate the mechanism of infertility caused by cryptorchidism we focused on early stage spermatogenesis and spermatogonial stem cell activity in undifferentiated spermatogonia in cryptorchid testes. MATERIALS AND METHODS: Histological findings and expression patterns of the stem cell marker undifferentiated embryonic cell transcription factor 1 were examined in a unilateral cryptorchid rat model. We removed unilateral descended testis and contralateral descended testis from cryptorchid and normal rats (control), respectively, 18 days postcoitum to 144 days postpartum. RESULTS: In descended testes gonocyte differentiation into early A spermatogonia occurred at 9 days postpartum. However, this transformation was altered in undescended testes. Furthermore, the undifferentiated embryonic cell transcription factor 1 negative early A spermatogonia-to-positive early A spermatogonia ratio was significantly higher in the undescended testis group (mean ± SD 0.69 ± 0.04) than in the control (0.46 ± 0.10, p = 0.037) and descended testis (0.44 ± 0.05, p = 0.022) groups, indicating decreased early A spermatogonia with spermatogonial stem cell activity in cryptorchid testes. CONCLUSIONS: In cryptorchid testes the differentiation from gonocytes into early A spermatogonia and the stem cell activity of early A spermatogonia were altered during the early stage of spermatogenesis, suggesting that the loss of spermatogonial stem cell activity in cryptorchid rats resulted in altered spermatogenesis, thus interfering with fertility.
PURPOSE: To elucidate the mechanism of infertility caused by cryptorchidism we focused on early stage spermatogenesis and spermatogonial stem cell activity in undifferentiated spermatogonia in cryptorchid testes. MATERIALS AND METHODS: Histological findings and expression patterns of the stem cell marker undifferentiated embryonic cell transcription factor 1 were examined in a unilateral cryptorchid rat model. We removed unilateral descended testis and contralateral descended testis from cryptorchid and normal rats (control), respectively, 18 days postcoitum to 144 days postpartum. RESULTS: In descended testes gonocyte differentiation into early A spermatogonia occurred at 9 days postpartum. However, this transformation was altered in undescended testes. Furthermore, the undifferentiated embryonic cell transcription factor 1 negative early A spermatogonia-to-positive early A spermatogonia ratio was significantly higher in the undescended testis group (mean ± SD 0.69 ± 0.04) than in the control (0.46 ± 0.10, p = 0.037) and descended testis (0.44 ± 0.05, p = 0.022) groups, indicating decreased early A spermatogonia with spermatogonial stem cell activity in cryptorchid testes. CONCLUSIONS: In cryptorchid testes the differentiation from gonocytes into early A spermatogonia and the stem cell activity of early A spermatogonia were altered during the early stage of spermatogenesis, suggesting that the loss of spermatogonial stem cell activity in cryptorchid rats resulted in altered spermatogenesis, thus interfering with fertility.