Ever since the Apollo missions, the health of astronauts have suffered long after their time in space was over. From reduced bone density to weakened muscles to cardiovascular damage, low gravity environments take a toll on the human body. Many of the astronauts’ ailments closely resemble conditions suffered by those of advanced age, from back pain to osteoporosis, the research of low gravity healthcare goes beyond astronauts alone.
Fortunately, the University of California at San Francisco (UCSF) researchers are working to understand, develop protocols and treatments that can help astronauts and the general population.
Even with exercise routines developed to maintain muscle mass and bone density, many astronauts complain of back pain lasting for years after their low gravity exposure. Dr. Jeffrey Lotz of UCSF has been studying the vertebrae of astronauts to understand the source of the problem and was surprised by his results.
Although he thought the cause of pain would be water retention in disks, what would normally be pressed out of them by bone compression due to gravity, instead he found a deterioration in the muscles that support the back bone called the multifidus muscles.
Now, he is working in coordination with NASA to design a series of exercises that target these muscles while also considering the limitations of room on a spaceship and low gravity.
The exercises are not for muscle health alone but include improving bone health. However, as Dr. Daniel Bickle discovered in mouse studies exercise alone is not enough to maintain bone density in space.
According to his studies, the low gravity environment disturbs the signal process between osteoclasts and osteoblasts. In normal bone processes, bone is reinforced when damaged or put under the repetitive stress of walking around in Earth’s gravity. With those stressors gone in low-gravity, osteocyte cells in bone tissue detect decreased stress in certain areas, then sends an activation signal to reabsorb the extra bone tissue that’s no longer need to the osteoclasts. Once the work of the osteoclasts is done, another signal is sent to osteoblasts, which then rebuilds necessary bone.
Because the signal interruption is occurring in the later stage of the process, between the osteoclasts and osteoblasts, bone continues being absorbed but does not get rebuilt while in space.
Astronauts with only six months spent on ISS have a reduced bone density loss of six to nine percent, a loss equal to that typically seen annually in postmenopausal women. Although the astronauts may regain the bone density after a year spent in normal gravity, the bone material is redistributed in such a way that their skeletal structures resemble that of an older adult.
Dr. Bickle thinks that further study into why this happens would not only aid astronauts and deep space travel but could also unlock treatments for osteoporosis.
Another factor leading to reduced bone density in astronauts is radiation exposure, but Dr. Bernard Halloran has discovered an interesting solution for this cause of bone loss.
Although it is unclear why Dr. Halloran’s experiments with mice have proven that plum powder reduces the loss of bone due to radiation exposure. While further study is needed to concentrate the mysterious active ingredient into pill form, it is a promising discovery for low-gravity healthcare.
Perhaps the most detrimental of all the effects of spaceflight, and aging is the effect on the cardiovascular system. Over the years, Dr. Marlene Grenon has studied the effects of microgravity on astronauts, who often suffer from circulatory issues after returning to Earth and increases the risk of heart attack as they age.
Dr. Grenon and colleagues, Dr. Sonja Schrepfer and Dr. Tobias Deuse, have found multiple factors influenced by the low gravity environment of space, including gene expression, cell function interference, and thinning vascular walls, which contribute to the declining cardiovascular health of astronauts. Similar issues are evident in normal gravity cardiovascular disease sufferers.
Although not a problem on ISS, as astronauts return to normal life on Earth, the effect on their health is detrimental (damaging) and long term. But Dr. Schrepfer’s team has discovered a molecule that may stop the thinning of vascular walls and hope to begin human trials soon.
Additionally, Dr. Schrepfer will be studying the effects of space on the human immune system similar to the work done by Dr. Millie Hughes-Fulford, who’s been studying the subject since 2003.
Currently, Dr. Hughes-Fulford has been studying gene expression in T-cells. Her studies have found that in low gravity five different miRNAs (microRNA), normally responsible for activating the genes of T-cells, were not functioning. These alterations, normally seen in the elderly over a period of 30 years, starting in astronauts, typically at the height of health, after only 30 minutes in space.
So far, the only cell function researchers can find that is not negatively affected by time spent in space is the process by which DNA repairs itself. Dr. Faith Karouia of USCF and Dr. Honglu Wu of NASA’s Johnson Space Center, have studied fibroblast cells from micro gravity environments compared to Earth bound cells and found no change despite the change in gravity or radiation.
Although more data is needed for a full conclusion, scientists hope the discovery can aid research into how cancer cells survive and self-heal through radiation treatment as well as help bolster astronaut health during space flight.
Overall, low-gravity healthcare is a multidisciplinary endeavor across many medical fields and is necessary to protect the long-term health of astronauts, especially as various agencies aim for deeper exploratory space travel. In addition, the same medical breakthroughs have the potential to improve medical care for the general population too significantly.
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