Long-term culture and transplantation of spermatogonial stem cells from BALB/c mice.

Development of a culture system that supports self-renewal and proliferation of spermatogonial stem cells (SSCs) is enormously valuable for experimental research and potential treatment for male infertility. Although several research groups had reported their successes in SSC isolation and culture, the two current accepted culture systems are different in cell enrichment methods, serum and growth factors. Previous researches also indicated SSCs from different mouse strains required different culture conditions. Here we report for the first time that SSCs from BALB/c mice could be cultured in an improved culture system for 3 months. The modified culture system consisted of an improved enzymatic procedure, the enrichment of undifferentiated spermatogonia by differential adherence selection of isolated SSCs, mouse embryonic fibroblast feeder cells, StemPro-34 SFM medium supplemented with glial cell line-derived neurotrophic factor (GDNF), basic fibroblast growth factor and GDNF-family receptor alpha1 (GFRalpha1). The improved digestion method increased the viability and enrichment efficiency of isolated testis cells. Furthermore, basal culture medium with 10% fetal bovine serum as selected medium could increase the number of germ cell colonies in the initiation stage of culture. Cultured SSCs were characterized morphologically and formed typical colonies. Immunocytochemical staining and RT-PCR showed that cultured SSCs expressed Oct-4, GFRalpha1, Sox2 and several other special genes resembling undifferentiated spermatogonia. Spermatogonia transplantation further confirmed that cultured SSCs were functionally normal and could restore complete spermatogenesis. The culture methods described here could serve as a paradigm to establish conditions for the culture of SSCs from other species, allowing identification of universal factors necessary for proliferation of SSCs.