Researchers at Kyoto University have achieved a significant milestone in space biology, successfully demonstrating that mouse spermatogonial stem cells cryopreserved for six months aboard the International Space Station (ISS) can produce healthy offspring upon return to Earth. This groundbreaking study, published in Stem Cell Reports, offers crucial insights into the viability of germ cells in the space environment and paves the way for preserving reproductive capabilities during long-duration space missions.
The research team cryopreserved mouse stem cells before their journey to the ISS, where they were stored in a deep freezer. Following their six-month stay in space, the cells were thawed and cultivated in vitro. Subsequently, these cells were transplanted into the testes of recipient mice. Within three to four months, these mice naturally mated, resulting in the birth of offspring that exhibited normal gene expression and overall good health. This outcome suggests that cryopreserved germ cells can retain their fertility for at least six months in the challenging conditions of space.
Scientists initially hypothesized that space radiation would pose a greater threat to the stem cells than the cryopreservation process itself. However, the findings indicated that the cryopreservation solution, which included hydrogen peroxide, led to the loss of some cells, while the cells that survived showed minimal differences between their pre- and post-spaceflight states. This suggests that the cryopreservation method may have a more pronounced impact on these specific cells than the space environment.
This research builds upon previous studies in space-based biological preservation, including a 2024 study that successfully cryopreserved viable peripheral blood mononuclear cells on the ISS. The implications for human germline preservation during long-duration space travel are substantial, offering a potential pathway for maintaining reproductive health on future interstellar voyages. While these initial results are highly encouraging, the researchers emphasize the need for continued long-term assessments to evaluate the health and potential effects across the lifespan of the first-generation offspring and subsequent generations. Additional samples of the cryopreserved germ cells remain aboard the ISS for ongoing experiments.