Serum- and feeder-free culture of mouse germline stem cells.

Spermatogonial stem cells (SSCs) undergo self-renewal divisions to support spermatogenesis. Although several in vitro SSC culture systems have been developed, these systems include serum or fibroblast feeders, which complicate SSC self-renewal analyses. Here, we developed a serum- and feeder-free culture system for long-term propagation of SSCs. In addition to the SSC self-renewal factors, including glial cell line-derived neurotrophic factor, supplementation with fetuin and lipid-associated molecules was required to drive SSC proliferation in vitro. Cultured cells proliferated for at least 6 mo at a rate comparable to that of serum-supplemented cultured cells. However, germline potential was reduced under serum- and feeder-free conditions, as indicated by a lower SSC frequency after germ cell transplantation. Nevertheless, the cultured cells completed spermatogenesis and produced offspring following spermatogonial transplantation into seminiferous tubules of infertile mice. This culture system provides a basic platform for understanding the regulation of SSC fate commitment in vitro and for improving SSC culture medium.