Growth factors essential for self-renewal and expansion of mouse spermatogonial stem cells

Spermatogonial stem cells (SSCs) self-renew and produce large numbers of committed progenitors that are destined to differentiate into spermatozoa throughout life. However, the growth factors essential for self-renewal of SSCs remain unclear. In this study, a serum-free culture system and a transplantation assay for SSCs were used to identify exogenous soluble factors that promote proliferation of SSCs. Mouse pup testis cells were enriched for SSCs by selection with an anti-Thy-1 antibody and cultured on STO (SIM mouse embryo-derived thioguanine and ouabain resistant) feeders in a serum-free defined medium. In the presence of glial cell line-derived neurotrophic factor (GDNF), SSCs from DBA/2J strain mice…