March 1st marked the end to NASA Astronaut Scott Kelly’s 340-day space mission on the International Space Station (ISS). The overall goal of Kelly’s mission was to study behavioral and physiological effects of prolonged exposure to space in order to better understand how NASA can better prepare for a mission to Mars.

Recent media has been most interested in telling us how he is “younger”, grew 2 inches (temporarily), and has a twin (Mark Kelly) who served as a ground based control here on Earth. More scientifically geared media discuss how NASA is studying the effects of microgravity on Kelly’s vision, cognitive functioning, muscle atrophy, bone loss, cardiovascular function, gut microbes, epigenetic and genetic changes to name a few. Although Kelly’s time in space is telling us quite a bit, much research is also being done on the ISS using rodents as a model of humans.

NASA’s experiments using rodents are geared towards understanding the mechanistic underpinnings of various biological processes following extended periods of time in space. These experiments form the groundwork for future missions, and investigate above and beyond the biological effects that NASA can measure in Scott Kelly.

Current research is specifically investigating:

Mechanisms of bone mass regulation

Mechanisms regulating skeletal muscle protein balance in microgravity

Fracture repair and wound healing

Evaluation of new drugs to preserve and reverse bone loss

Effects of long-term exposure to microgravity, radiation, and closed systems

Effects of space on processes of development, reproduction, and aging

Effects of microgravity on cardiovascular function and fluid balance

and more…

NASA Research Announcement, 2013 (NRA, NNH14ZTT001N)

Using rodents in space is most interesting because scientists can measure some long-term developmental and aging effects of time spent in space in much shorter periods of time than would be needed to document such developmental and aging effects with humans. Over 26 rodent spaceflights have housed and studied rodents for periods less than 20 days, most recent studies have been focused on extended periods of 35 days, and future studies are aimed at 90 days in space. But how does time in days for rodents compare to the life of a human? Many experimental studies would suggest that 35 days in space for a rodent is comparable to about 3 years in the life of a human. Although the maturity phases vary for mice and rats and are not directly comparable to humans, 35 days in space for a rodent can tell us a lot about long-term exposure to space.

Rat’s Age Rat’s Age in Human Years 1.5 months 12.5 years (puberty) 6 months 18 years (social maturity) 1 year 30 years 1.5 years 45 years 2 years 60 years 2.5 years 75 years

*These comparisons are all estimations

It is also important to note that similar to NASA’s utilization of Scott Kelly’s twin, NASA scientists typically run ground based control studies of genetically identical and similarly housed rodents here on Earth in synchrony with ISS experiments in space. Furthermore, all experiments are optimized to test specific hypotheses where the variable of space would be necessary. Otherwise, scientists make use of standardized microgravity analogs, and hyper-gravity models to investigate questions where the variable of space is not necessary.

In addition to rodent research, there is other animal and human research currently underway at NASA and the ISS. However, rodent research provides an interesting model for studying the biological effects of space. Rodents enable us to better investigate specific mechanisms behind problems astronauts will face during prolonged missions. Therefore, we can better prepare for issues that may arise, potentially compensate for these issues, and make the most out of the future Scott Kellys exploring space and beyond.

Justin

Additional information on rodent research:

Recapturing a Future for Space Exploration: Life and Physical Sciences for a New Era (2011)

International Space Station Rodent Research mini-book