Microgravity floating may seem like a blissful restoration of the skeleton, bearing the weight of the human body, but when astronauts spend months in space, the density of their bones takes a serious blow that can never be fully recovered from.
A study of mice on board the International Space Station gives NASA scientists a better idea of why this significant and unresolved health risk exists.
As it turns out, bones may not be related to cosmic radiation, lack of sunlight or a similar, systemic factor. After spending 37 days in orbit, some parts of the skeletons showed more damage than others.
Compared to the mice “Control of the Earth”, which were not transferred from our planet, the back thigh mice in space were numb with large holes, especially at their edges, where they join the hip and knee joints. In contrast, the lumbar part of the mouse spikes remained remarkably intact.
“A specific focus of our study is the femur because of its main role in weight in the mouse,” explains NASA researchers and the Blue Marble Science Institute.
In two legs, the lumbar spine mostly carries the weight of the upper body, but in four-legged rodents the horizontal structure does not serve the same role of weight.
This suggests that the bones of mammals carrying weight on the ground are those that are most affected by the microgravity in the orbit.
It may be like the concept “Use it or lose it” in the neuroscience. If the bones carrying weights are not “developed” as usual, they may begin to deteriorate.
When the mice on the earth were kept in cells that restrict movement, they showed losses of density in the supporting weights, but to a lesser extent than the microgravity mice.
To take into account the tension of launching the rocket, the ground control mice were also exposed to flight simulations.
“If space radiation in low Earth or other systemic factors were the main effectors of bone loss during space flight, we would expect systemic changes in the skeletal system,” the researchers explain.
If the loss is caused by ionizing radiation, for example, researchers would expect to see the dense outer bones of the bones, which somewhat protect the internal cavity of the brain. But this is not the case. The deterioration occurs from the inside out of mice.
The femur neck, for example, has a significant external bone coating and yet shows significant loss of internal, mushroom bone marrow when exposed to microgravity for 37 days.
After that a lot of time in orbit with low earth orbit, the authors of the study led by bio -engineer Rukmani Cahill, they say that on board the ISs are only exposed to a small daily dose of radiation.
In simulated studies showing radiation, it can cause bone loss, the dose is much, much higher, equivalent to about 13 years of life on board the ISS.
However, for less than half a year in low orbit, astronauts can experience bone loss so that they can never completely recover. Each month, travelers in the human space lose 1 % or more of their bone density, about 10 times larger than the speed of osteoporosis on the ground. This decline significantly increases the risk of fractures in long bones such as the femur.
Unlike human astronauts, mice tested in this study are young in the late stages of skeletal maturation. In microgravity, their thighs, who had to continue to grow for a while, show signs of premature ossification, turning cartilage to a bone earlier than typical. This could possibly limit bone growth, stunning development.
These warning results come from the NASA space hiking study so far.
The space agency says this is the first of many experiments to study how to protect the health of astronauts during space travel.
If their bone density hypothesis is correct, it suggests that tactics as a diet may not improve the health of the astronaut bones. Running paths with bundles holding a consumer of the Earth or devices that mimic lifting weight in space can be more efficient.
The study has been published in Plos oneS