Depletion of testis cell populations in pre-pubertal Bos indicus cattle by irradiation

Recovery of spermatogenesis following a single dose of irradiation was evaluated in pre-pubertal Brahman bulls, after receiving a single dose of 3, 6, 9 or 12 Gray (Gy) irradiation. Biopsy samples of testis tissue were collected and processed for immunohistology at various times following irradiation. Spermatogenic recovery was defined by the changes in tubule diameter, and absolute numbers of undifferentiated spermatogonia (PLZF positive cells) and Sertoli cells (GATA-4 positive cells) per tubule cross section. The effect of irradiation on the depletion of testicular cells was dose-dependent. Immunohistological results from both the 9 and 12 Gy group showed degeneration of seminiferous tubules, compared with other doses and controls. From 2 weeks after the treatment, irradiation resulted in a significant and dramatic reduction in tubule diameter (up to 40%), number of undifferentiated spermatogonia (up to 90%) and Sertoli cells (up to 70%), which was sustained for up to 16 weeks post-irradiation in 9 and 12 Gy groups (P < 0.0001). However, a moderate depletion effect was observed in the 6 Gy treatment groups, compared with 9 and 12 Gy doses. The 6 Gy treatment had significant effects on spermatogonia (up to 79% reduction) and Sertoli cell (30% reduction) numbers following irradiation (P < 0.0001). In contrast, the 3 Gy dose had no significant effect at either 3 or 5 weeks post-irradiation on tubule diameter, spermatogonia or Sertoli cells. In conclusion, the results from the current study suggest that treatment of recipient testes with a single dose of 6 Gy irradiation can temporarily deplete spermatogonial cells in pre-pubertal Brahman bulls, whilst minimising the impact on Sertoli cells and tubule morphology.