"Mighty mice" sent to space offer hope of maintaining muscle mass

What they did: The nonprofit Jackson Laboratory provided 40 black, female mice that were placed on a SpaceX rocket that traveled to the space station for the "Rodent Research-19" experiment.

What they found: 24 mice that were left untreated experienced muscle and bone mass loss of up to 18%.

• But eight "mighty mice" lost none of their brawn after being modified to lack the protein myostatin, which blocks a molecular signaling pathway.
• The muscles increased noticeably in eight other mice given the "mighty mouse" treatment in space after they returned to Earth in a SpaceX Dragon capsule on Jan. 7.

What they're saying: Lead researcher Se-Jin Lee, of the Jackson Laboratory, and wife Emily Germain-Lee, of Connecticut Children's Medical Center, who also took part in the study, told AP the results were encouraging.

• But Germain-Lee added researchers were "years away" from testing the drug in people without concerns about "serious side effects."
• Lee said they were looking at possibly sending more "mighty mice" to space for a longer duration.

Of note: NASA astronauts Andrew Morgan and Jessica Meir and Christina Koch — who made history with the first female spacewalk last October — cared for the mice on the ISS, and they're listed as study co-authors.