SPERMATOGONIAL STEM CELL RENEWAL IN THE MOUSE: II AFTER CELL LOSS

The repair of the mouse seminiferous epithelium after cell loss has been studied in seminiferous tubules mounted in toto . Cell loss was inflicted by injection of Myleran in a dose of 10 mg/kg body weight. In stages 7–8, in which we mainly counted, the numbers of A_isolated (A_is), A_paired (A_pr), A_aligned (A_al) and A₁ spermatogonia and resting primary spermatocytes decreased after injection. After about 24 days normal numbers of A₁ spermatogonia were found again. Thereafter a substantial overshoot in the number of A₁ spermatogonia was found.
While normally most of the A_pr and A_al cells differentiate into A₁ spermatogonia in stages 3 and 4 and do not divide until stage 9, during repair they pass through one more division during stages 6 and 7. Normally, during these stages divisions of these spermatogonia are rare. Owing to this extra division the transformation of A_pr and A_al into A₁ spermatogonia is delayed from stage 3 or 4 to stage 8, i.e. still before stage 9, in which A₁ spermatogonia divide. From 16 days after the injection onwards the extra division takes place less generally and more and more cells transform into A₁ spermatogonia at the normal time.