Acknowledgments We thank Dr Hiroshi Kubota (University of Pennsylvania School of Veterinary Medicine, USA) for his kind help in setting up mSPG culture through E-mail communications. This study was supported by the National Basic Research Program of China (2006CB944004) and the National Natural Science Foundation of China (30300182, 30871406).
Dear Editor, The in vitro propagation (IVP) of animal spermatogonial stem cells (SSCs) provides materials for studying the mechanism of spermatogenesis and for developing novel animal transgenesis and human thera...