Germline transmission of cryopreserved mouse spermatogonial stem cells maintained on the International Space Station.

Despite growing interest in space exploration, the effects of spaceflight on stem cells remain largely unknown. Damages to germline cells are especially crucial, as spaceflight poses risks to gametogenesis, with abnormalities observed in multiple species. While embryonic stem (ES) cells show genomic instability after space exposure and have not yet produced offspring, this study demonstrates successful offspring production from cryopreserved mouse spermatogonial stem cells (SSCs) stored on the International Space Station for 6 months. Spaceflight did not increase apoptosis or DNA damage in SSCs. After thawing, SSCs proliferated comparably to those cryopreserved on Earth, showing no significant phenotypic or functional differences. Offspring were produced via spermatogonial transplantation followed by natural mating. Since SSCs from many species can be cryopreserved like somatic cells and still produce sperm, they offer a promising resource for germline preservation during space exploration.