In vitro propagation of spermatogonial stem cells from KM mice

Spermatogonial stem cells (SSCs) are a unique type of stem cells in that they transmit genetic information to the next generation by producing sperms. Studies of SSC proliferation and differentiation have been hampered by the inability of reconstructing these processes in vitro, particularly in a serum-free culture system. Several groups have reported the long term culture of SSCs during which SSCs self-renew and restore spermatogenesis when transplanted back to recipient testes. However, different protocols and mice with particular genetic background have been used by different laboratories, and the techniques have not been adopted widely. In the present study, we first established a SSC isolation and culture system composed of differential adherence selection of SSCs, serum-free medium and mouse embryonic fibroblast (MEF) feeder cells. SSCs from KM pups could be cultured on MEF feeders in StemPro-34 SFM Medium supplemented with glial cell line-derived neurotrophic factor (GDNF), soluble GDNF family receptor alpha-1 (GFRa1) and basic fibroblast growth factor (bFGF) for 1 month. These SSCs were characterized morphologically and by examining the expression of marker genes. Expression of Oct4 and Sox2, which are crucial factors in embryonic stem cell (ESC) self-renewal, were detected in our cultured SSCs, suggesting that SSCs may share with ESCs some common mechanisms in self-renewal regulation. We also found that LIF had no effect on the proliferation of cultured SSCs derived from KM mice.