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 A 1 spermatogonia and resting primary spermatocytes decreased after injection. After about 24 days normal numbers of A 1 spermatogonia were found again. Thereafter a substantial overshoot in the number of A 1 spermatogonia was found. While normally most of the A pr and A al cells differentiate into A 1 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 A 1 spermatogonia is delayed from stage 3 or 4 to stage 8, i.e. still before stage 9, in which A 1 spermatogonia divide. From 16 days after the injection onwards the extra division takes place less generally and more and more cells transform into A 1 spermatogonia at the normal time.