Searching for culture condition optimal for proliferation of spermatogonial stem cells

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Culturing of Spermatogonial Stem CellsIn April, 2003, it was reported that male germline stem cells, collected from neonatal mouse testes (strains of DBA/2 and ICR), were cultured for long period on feeder layer of mouse embryonic fibroblasts with 4 growth factors (EGF, bFGF, LIF, GDNF). We immediately repeated and confirmed results of the report and progressed it one step beyond by establishing germline stem cells (GS cells) from not only neonates but also from adult mice. The GS cells expanded exponentially in vitro. They produce sperm when transplanted recipient mouse testes. They did not produce tumor nor showed abnormal proliferation in the body of recipient mice. The GS cells was re-derived from recipient mouse testes, which showed that GS cells in vitro and spermatogonial stem cells in the testis were identical or mutually convertible.Fertilization of recipient mice with spermatogonial transplantationIn order to make recipient mice fertile after spermatogonial transplantation, immature mice (10-15 days old) were treated with irradiation before transplantation. The aim of irradiation was to make empty niche in the testis by removing endogenous germ cells for efficient colonization of donor stem cells. The dose of irradiation turned out to be optimal at around 12Gy for that purpose. One to Three days after the irradiation, the recipient mice received spermatogonial transplantation. Two months after the transplantation onward, the recipient mice were mated with females to test their fertility. It was confirmed that mice became fertile fathered pups of donor germ cell origin at high rate (about 70%). When we used GS cells, the fertility rate of recipient mice became higher, around 80%. The important factors for making recipient fertile with donor germ cells therefore include age of recipient, stem cell concentration of donor cell suspension.