A research team led by Dr. Se-Jin Lee of the Jackson Laboratory in Connecticut sent 40 young female black mice to the International Space Station in December, to study muscle loss:
In a paper published in the Proceedings of the National Academy of Sciences, Lee said the 24 regular untreated mice lost considerable muscle and bone mass in weightlessness as expected — up to 18%. But the eight genetically engineered “mighty mice” launched with double the muscle maintained their bulk. Their muscles appeared to be comparable to similar “mighty mice” that stayed behind at NASA’s Kennedy Space Center.
The PNAS abstract explains:
Among the physiological consequences of extended spaceflight are loss of skeletal muscle and bone mass. One signaling pathway that plays an important role in maintaining muscle and bone homeostasis is that regulated by the secreted signaling proteins, myostatin (MSTN) and activin A.
Here, we used both genetic and pharmacological approaches to investigate the effect of targeting MSTN/activin A signaling in mice that were sent to the International Space Station.
Wild type mice lost significant muscle and bone mass during the 33 d spent in microgravity. Muscle weights of Mstn -/- mice, which are about twice those of wild type mice, were largely maintained during spaceflight.
Systemic inhibition of MSTN/activin A signaling using a soluble form of the activin type IIB receptor (ACVR2B), which can bind each of these ligands, led to dramatic increases in both muscle and bone mass, with effects being comparable in ground and flight mice.
It’s not just mice who have muscle-building myostatin-related mutations, but Belgian Blue cattle, Flex Wheeler, a German toddler, a Michigan toddler, and “bully” whippets.
“bully” whippets
They also call them Whoppets. I like that better.