Something “Strange” Happened To Mice Who Lived On The ISS for 37 Days

Space is a challenging environment, especially for the human body. Spending extended periods in microgravity can have various effects on our physiology, such as decreased blood cell count and weaker bones. However, the exact location of bone loss in space has been a bit of a mystery. Recent experiments on mice have shed some light on this, as well as the potential impact of radiation.

NASA estimates that for every month spent in space, the density of weight-bearing bones can drop by at least 1 percent. In addition, muscle mass can decrease by up to 20 percent in less than two weeks. Understanding the mechanisms behind these changes is crucial for ensuring the health of astronauts on long-duration space missions.

A recent study involved sending female mice to live on the International Space Station for 37 days to observe how their bones were affected. The researchers compared these space-traveling mice to control groups on Earth, both in standard cages and in an ISS Environmental simulator.

Interestingly, the study found that bone loss in space was not uniform across all bones. Weight-bearing bones, like the femur, experienced more significant loss compared to bones that are not heavily loaded, such as the spine. This suggests that microgravity plays a significant role in bone loss, rather than the higher radiation levels in space.

Previous experiments on medaka fish sent to the ISS revealed that microgravity alters the balance between bone-forming cells (osteoblasts) and bone-degrading cells (osteoclasts). In space, osteoclasts seem to be more active, leading to a reduction in bone mineral density.

The new findings also suggest that not all bones are affected in the same way by microgravity. While some bones lose mass, others remain unchanged, and there are even cases of certain bones becoming denser. This variation may be linked to changes in blood pressure in the upper body during the initial days in orbit, which can cause swelling in the face, headaches, and altered sense of smell in astronauts. Fortunately, these symptoms typically subside as the body adjusts to the space environment.

The results of the mice study were published in the journal PLOS One, providing valuable insights into the effects of microgravity on bone health.