Figure 1.

Establishment of mouse spermatogonial cultures in vitro. (a) Single spermatogonium or small spermatogonial clumps (red arrow) were observed 36 hours after culture in vitro. (b) At Passage 3 (P3), cells began to form stable colonies (red arrow) on MEF. (c) Spermatogonial clumps formed on MEF at day 180 in vitro. (d) Proliferation curves of spermatogonial cultures. Within 7-week period, spermatogonia expanded approximately 750-fold with 40 ng/mL GDNF and 500-fold with 10 ng/mL GDNF. Scale bar: 20 μm.