Spaceflight May Cause Hereditary Reproductive Damage: New Study

Spaceflight Effects on Female Mouse Reproduction and Offspring Health

Researchers examined female mice after extended periods aboard the International Space Station to determine how microgravity impacts the female reproductive system, according to the PNAS study. Upon coming back to Earth, the space-traveling mice maintained fertility levels comparable to control groups kept on the ground, but study co-author Lane Christenson—a professor of cell biology and physiology at the University of Kansas Medical Center—pointed out that their offspring exhibited distinct behavioral and physiological variations. “The offspring of those that came back from space were altered in their behavior, their muscle, their ability to reproduce further,” Christenson told Live Science, noting that “just about every marker we looked at had some differences.”

The second generation of mice born to the spacefaring mothers exhibited about 15% less muscle strength than control groups, alongside a heightened proneness to stress in female offspring during behavioral experiments. Furthermore, these descendants produced fewer and smaller litters. Testing revealed that both the second and third generations of mice possessed lower levels of anti-müllerian hormone (AMH) than control groups, a key metric that correlates directly with overall egg counts.

Comparing Past Space Research With New Reproductive Findings

Past investigations into the physiological impacts of space travel largely focused on short-term missions or male subjects. The well-known NASA Twins Study compared astronaut Scott Kelly to his identical twin brother, Mark Kelly, after a year-long mission on the ISS, suggesting modest overall health effects from short-term spaceflight. A separate 2019 study examined male mice aboard the ISS and determined they could still father healthy offspring. The new PNAS research was specifically designed to fill a research gap concerning the female reproductive system, according to Christenson. Because hormones like estrogen regulate nearly all organ systems in the female body—including bone maintenance—understanding these shifts remains a priority for long-term space exploration planning.

Deep-Space Radiation and Cellular Aging Concerns

Scientists theorize that the observed transgenerational changes may stem from an acceleration of aging triggered by microgravity exposure. Previous studies on mice and human tissue suggest that a lack of gravitational force leaves cells more vulnerable to stress, which connects to dysfunction in mitochondria—the cellular powerhouses containing DNA passed exclusively from mother to child. On the other hand, Dr. Ulrike Luderer—who serves as the director of the Center for Occupational and Environmental Health at the University of California, Irvine, and took no part in the study—pointed out that cosmic radiation levels on the ISS are lower than those found in deep space.

Earlier this year, Luderer published research demonstrating that exposing mice to radiation levels comparable to a journey to Mars results in a very significant decrease in egg and follicle numbers in the ovaries. As space agencies plan extended missions and potential planetary colonization, researchers emphasize the need to study how combined microgravity and deep-space radiation affect human reproductive markers and hormonal levels over generations.

Frequently Asked Questions

Did the spacefaring mice lose their fertility?

No. According to the study published in PNAS, female mice that spent 42 days on the ISS could still get pregnant and give birth to live offspring upon returning to Earth, though their immediate litters were slightly smaller.

How did space travel affect the offspring of the mice?

The offspring of the spacefaring mice exhibited about 15% less muscle strength, lower levels of anti-müllerian hormone (AMH), reduced litter sizes, and increased stress susceptibility in females, according to researchers.

Can these mouse study results apply to humans?

Experts note that mice serve as effective biological models for human reproduction because they are mammals with very similar reproductive systems and molecular hormone backgrounds, though direct translation to human astronauts requires further study.