Spermatogonia: origin, physiology and prospects for conservation and manipulation of the male germ line.

In recent years, the scientific community has become increasingly interested in spermatogonia. Methodological breakthroughs, such as germ cell transplantation and spermatogonial culture combined with novel germ line transfection strategies, have provided interesting new opportunities for studying the physiology of spermatogonial stem cells and their interaction with the stem cell niche. Furthermore, intense research into pluripotent and adult stem cells has generated new insight into the differentiation pathway of germ line stem cells and has opened new perspectives for stem cell technologies. The present review briefly introduces the physiology of spermatogonial stem cells and discusses future directions of basic research and practical approaches applicable to livestock maintenance and animal reproduction.