Role of spermatogonia in the repair of the seminiferous epithelium following X‐irradiation of the rat testis

TLDR

In the adult rat testis, type A0 spermatogonia rarely produce spermatocytes, whereas type A1 spermatogonia regularly divide to generate spermatocytes and new A1 cells. The study examined how type A0 and A1 spermatogonia respond to a single 300‑r dose of X‑ray irradiation. Researchers counted A0 and A1 cells in whole‑mount seminiferous tubules at multiple time points post‑irradiation and used 3H‑thymidine labeling to assess proliferation of surviving cells. Type A1 spermatogonia fell to 6–3 % of controls by day 13, while A0 dropped to 62 % at day 8 but both returned to normal by day 39; A0 cells were more resistant and, by day 13, had proliferated (labeling index up to 31 %) to help rebuild the spermatogonial population.

Abstract

Abstract In the normal adult rat testis, type A 0 spermatogonia do not appear to participate to a significant extent in the production of spermatocytes, while type A 1 spermatogonia periodically initiate a series of divisions resulting in the production of spermatocytes and new type A 1 spermatogonia. The behavior of type A 0 and A 1 spermatogonia was investigated following administration of a single dose of x‐rays (300 r) to the testis. Using whole mounts of seminiferous tubules, the type A 0 and A 1 cells were counted at various intervals after irradiation. At 8 and 13 days after irradiation, type A 1 spermatogonia reached lowest values, i.e., 6% and 3% of non‐irradiated control, while type A 0 reached the lowest value, i.e., 62% of control at eight days. Thereafter the numbers of type A 0 and A 1 progressively increased to return to normal at 39 days. It was thus concluded that the type A 0 were comparatively more resistant to x‐irradiation than type A 1 spermatogonia. To verify if the surviving type A 0 proliferated in the irradiated testis, animals were injected with 3 H‐thymidine three hours before they were sacrificed at various times after x‐irradiation. In irradiated testes the labeling indices of the surviving type A (A 0 , A 1 –A 4 ) were the same as in the non‐irradiated testes except in stages V‐VI of the cycle of the seminiferous epithelium. While in the controls only 2% of type A cells were labeled at these two stages of the cycle, after irradiation the labeling index of type A reached a maximum of 31% at 13 days to return to control values by 39 days. Since at 13 days after irradiation type A 0 spermatogonia were the predominant component of the spermatogonial population, it was concluded that these cells must have incorporated 3 H‐thymidine and thereby contributed to the reconstruction of the spermatogonial population partially destroyed by irradiation.