There is a need to better understand the cause of different health problems suffered by the astronauts who spend an extended time away from the earth. The health issues faced by them include loss of bone and muscle mass, immune dysfunction, heart and liver problems.
Data was collected from different sources by a multidisciplinary team led by NASA scientists who reported that mitochondrial dysfunction is the reason for the damage. A systematic approach was used by the researchers to look at the widespread alterations which affect the biological function.
The study was published in the journal Cell.
Mitochondria are cell organelles that generate energy the cells need for various biochemical reactions which is needed for the different life processes. This energy is stored in small molecule called ATP (Adenosine Triphoshphate) which drives biological contraction and nerve impulse propagation.
Data was analyzed from NASA's GeneLab platform which contains a comprehensive database including data from animal studies, NASA Twin study and samples of 59 astronauts who have travelled to space over a decade. The database also contains a range of biological data related to changes in tissues and cells that occur due to the combined effects of space radiation and microgravity.
Beheshti said, "We compared all these different tissues from mice that were flown in space on two different missions, and we saw that mitochondrial dysfunction kept popping up. We looked at problems in the liver, and saw they were caused by pathways related to the mitochondria. Then we looked at problems in the eyes and saw the same pathways. This is when we became interested in taking a deeper look."
Co-senior author of the paper Jonathan Schisler, PhD, assistant professor of pharmacology and pathology and laboratory medicine at the UNC School of Medicine and also a member of the UNC McAllister Heart Institute said, "This particular study is a great example of what team science can accomplish. My lab focuses on the integration of complex genomic-biologic data to elucidate the relationship between complex biological functions and disease. So our expertise was a great fit for this collaboration with NASA."
Mitochondrial suppression as well as overcompensation which occurs due to mitochondrial suppression can cause many systemic organ responses as well as the common changes which are observed in the immune system.
The researchers started their discoveries from mice and then looked at whether the same mechanisms could be involved with humans in space. From the NASA Twin study, in which identical twins Scott on the International Space Station and Mark Kelly on the ground were followed over time, they saw many changes in mitochondrial activity.
During Scott's time in space, alterations in his distribution of immune cells occurred which could be explained by the changes in the mitochondrial activity. Physiological data like blood and urine samples were collected from dozens of astronauts to confirm the suppression of the mitochondria in different cells.
Beheshti said, "I was completely surprised to see that mitochondria are so important, because they weren't on our radar. We were focusing on all the downstream components but hadn't made this connection." Other common problems with extended space travel like disrupted circadian rhythm and cardiovascular problems can also be explained by mitochondrial dysfunction. Schisler added,"We can now ask more specific questions regarding the relationship between mitochondrial function and space flight. One challenging aspect of mitochondrial biology is the chicken and egg discussion. Are the changes in mitochondrial function resulting from other parts of the cell not working correctly, or do the elements of space directly impact the mitochondria? It's exciting that our study opens the door for the design of mitochondrial-specific countermeasures that could negate the impact of microgravity and radiation on our body's cells to generate energy."
Now that the mitochondrial dysfunction is identified as a reason behind so many health issues related to space travel, there is hope to develop counter measures to address them. Beheshti said,"There are already many approved drugs for various mitochondrial disorders, which would make it easier to move them toward this application. The low-hanging fruit now would be to test some of these drugs with animal and cell models in space."