Adelaide University researchers reported on Mar. 26 that microgravity conditions reduce the ability of sperm to navigate reproductive tracts, potentially affecting fertilization and embryo development in space. The findings come from a study conducted by the University's Robinson Research Institute, School of Biomedicine, and Freemasons Centre for Male Health and Wellbeing.
The research is significant as it highlights challenges for human reproduction during long-term space missions or future settlements beyond Earth. Understanding how gravity affects reproduction is important as humanity considers extended stays on the Moon, Mars, or other off-Earth environments.
Scientists used a 3D clinostat machine developed by Dr Giles Kirby at Firefly Biotech to simulate zero gravity by flipping cells and disorienting them. Sperm samples from three mammals, including humans, were then observed navigating through a maze designed to mimic the female reproductive tract. "We observed a significant reduction in the number of sperm that were able to successfully find their way through the chamber maze in microgravity conditions compared to normal gravity," said Dr McPherson. "This was experienced right across all models, despite no changes to the way sperm physically move. This indicates that their loss of direction was not due to a change in motility but other elements."
The addition of progesterone helped more human sperm overcome these negative effects under simulated microgravity conditions. "We believe this is because progesterone is also released from the egg and can help guide sperm to the site of fertilisation, but this warrants further exploration as a potential solution," said Dr McPherson.
Further experiments showed that exposure to microgravity during fertilization led to a 30 percent reduction in successful mouse egg fertilizations after four hours compared with normal Earth conditions. Prolonged exposure caused developmental delays and fewer cells forming embryos at early stages. "These insights show how complex reproductive success in space is and the critical need for more research across all early stages of development," said Dr McPherson.
The work was published in Communications Biology (Nature Portfolio) and involved collaboration with Adelaide University's Andy Thomas Centre for Space Resources. Associate Professor John Culton, Director of the Centre, said: "As we progress toward becoming a spacefaring or multi-planetary species, understanding how microgravity affects the earliest stages of reproduction is critical." Researchers plan next-phase studies on varying gravitational environments such as those found on Mars or artificial gravity systems.
Dr McPherson concluded: "In our most recent study, many healthy embryos were still able to form even when fertilized under these conditions. This gives us hope that reproducing in space may one day be possible."
