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Mus musculus: how nanofluidic drug delivery could counter muscle loss in space Muscle atrophy presents a significant health risk for astronauts, who can lose around 40% of their muscle mass after six months in microgravity. Muscle atrophy presents a significant health risk for astronauts, who can lose around 40% of their muscle mass after six months in microgravity. Astronauts in space have to exercise for an average of two and a half hours per day to minimise the impacts of muscle atrophy in microgravity. This presents a significant health risk for astronauts undertaking long-haul trips into space, such as US astronaut Mike Kelly who spent 342 days aboard the International Space Station from 2015 to 2016. The mechanical unloading of the muscles in zero-gravity conditions triggers protein synthesis to decrease and protein degradation to occur, causing the muscles to start wasting. It’s the same reason patients with chronic illnesses that leave them immobile 32
or bedridden also experience muscle atrophy. Scientists at Houston Methodist Institute for Academic Medicine are now working to combat astronauts’ atrophy in outer space, using a subcutaneously implanted nanofluidic drug delivery system. The device is designed to gradually release very small doses of a drug called formoterol and has now been trialled in mice aboard the International Space Station. Formoterol is a bronchodilation drug, a type of medication that makes breathing easier by relaxing the muscles in the lungs and widening the airways. It’s a long-acting bronchodilator, meaning it’s used as a maintenance treatment to offset the symptoms of chronic lung diseases like asthma, bronchitis or emphysema. Alongside these effects, formoterol has been shown to stimulate increased muscle mass at certain doses, which could help our astronauts out. However, these doses also lead to cardiovascular side effects – increased heart rate, decreased blood pressure, reduced plasma potassium concentration –
which in the harsh conditions of outer space are far from ideal.
Mitigating side-effects through low-dose drug delivery The Houston researchers are hoping that the systematic low-dose release of formoterol permitted by the nanofluidic delivery system can prevent muscle wastage while avoiding these cardiac side effects. Houston Methodist professor of nanomedicine Dr Alessandro Grattoni says: “It may be possible that adverse effects of formoterol could be mitigated via low-dose sustained delivery. As opposed to bolus administration, which is typically associated with a ‘rollercoaster’ in drug concentration in the body, sustained low dose delivery may prove effective while limiting side effects. However, this needs to be further investigated.” “In the study subjects flown on the international space station, we observed an increase in grip strength of 11%.”
