Scientists are taking animal research to new heights—literally. Since 2014, researchers have been conducting various experiments with rodents in outer space aboard the International Space Station.
Living organisms experience various changes in the environment of space, including to the bones, muscles, heart, and circulatory and immune systems.
Given their genetic similarities to humans, studying how the bodies of rodents react to being in space can help answer fundamental questions about human health, both in space and on Earth.
Rodent Research Missions
Rodent Research-1
Launched in 2014, Rodent Research-1 was a joint operation between NASA and the Center for the Advancement of Science in Space (CASIS). It was the first mission in NASA’s rodent research project to use the Rodent Research Hardware System, a three-module system for transport, transfer, and long-term housing. The hardware was found to be effective and safe to use in space. The mice transported to the space station using the system lived in the “habitat” module for one month and were healthy and active. In addition to testing the Rodent Research Hardware System, Rodent Research-1 also included a CASIS commercial research project studying muscle loss or atrophy. Using a bone densitometer, the team measured the bone loss, soft-tissue density, lean/fat muscle mass, and total animal mass of the mice, which will help to team determine the effects of microgravity on rodent bone and muscle.
Rodent Research-2
Launched in 2015, the primary goal of Rodent Research-2 was to examine how the space environment affected the musculoskeletal and neurological systems of mice. The tissue collected in Rodent Research-2, a CASIS-sponsored commercial research mission, may help scientists discover new therapies for muscle- and bone-related diseases.
Rodent Research-3
The 2016 mission was the result of a commercial partnership between CASIS and the pharmaceutical company Eli Lilly to evaluate a potential new treatment for skeletal muscle wasting and weakness by evaluating its ability to prevent these conditions in mice exposed to extended time in space.
Rodent Research-4
Launched in April 2017, this mission focused on bones, including how they grow and heal and how microgravity affects these processes. The results could have applications not only for astronauts and future space travelers but also for patients with severe bone injuries.
Rodent Research-5
Launched just two months after the previous Rodent Research mission, Rodent Research-5 was a joint effort between the University of California, Los Angeles (UCLA), CASIS, NASA, and BioServe. The mission tested a new treatment designed to not only prevent bone loss but also rebuild it. A total of 40 mice were treated with NELL-1, a protein critical for normal bone growth and development, and transferred to the space station. Half the mice were returned to Earth after one month and the remaining 20 stayed for two months, allowing researchers to study the effects of the therapy.
Rodent Research-6
Rodent Research-6, launched in December 2017, shifted the study from bone to muscle. The goal of the mission was to test whether formoterol, a drug typically used to treat asthma, could prevent muscle wasting in mice. The study, conducted by researchers from Novartis, NanoMedical Systems, and Houston Methodist Research Institute, implanted a chip under the skin of the mice, which delivered a constant, low dose of either the drug or a control solution. Half of the 60 mice were returned to Earth after 30 days, with the rest remaining for an additional month.
Rodent Research-7
This mission explored how the reduced-gravity environment of the International Space Station affects the community of microorganisms in the gut and their impact on multiple body systems. The results will help scientists create solutions to keep astronauts healthy on long-duration spaceflights and improve treatments for gastrointestinal, immune, metabolic, and sleep disorders on Earth.
Rodent Research-8
The next study, launched in December 2018, explored the physiology of aging and how age affects disease progression. The investigation, sponsored by the International Space Station U.S. National Laboratory and Taconic Bioscience, was designed to provide a better understanding of aging-related immune, bone, and muscle disease processes.
Rodent Research-9
Rodent Research-9 was the first to focus on NASA-sponsored experiments as opposed to commercial projects. The study examined the effects of microgravity on blood vessels in the brain and eye and on cartilage loss in joints to better understand the visual impairment and joint tissue degradation that affect astronauts living in space for extended periods. The results could provide potential treatments for these health problems, both in astronauts and in people on Earth with vision loss, eye disorders, and arthritis.
Rodent Research-10
Rodent Research-10, launched in December 2020, investigated how microgravity affects bone tissue regeneration, with a specific focus on the cell cycle inhibitor Cdkn1a gene encoding the CDKN1A/p21 protein, which on Earth can be induced by oxidative stress and radiation.
Rodent Research-11
Rodent Research-11 was designed to evaluate how vascular miRNAs respond and adapt to microgravity.
Rodent Research-12
The focus of Rodent Research-12 was the immune system, with researchers from Loma Linda University and Kansas State University examining the effects of spaceflight on antibody production and immune memory.
Rodent Research-14
This mission targeted the body’s internal clock and key organs, using mice to examine how microgravity affects the biological circadian rhythm and whether disruptions in microgravity affect the colon, heart, lung, liver, kidney, and hypothalamus. It also investigated how cellular adaptation due to changes in the daily clock can affect behavior.
Rodent Research-15
The purpose of Rodent Research-15 was to study bone loss due to the weightlessness of space. It examined changes in the DNA, RNA, and protein of mice, investigating changes in bone mass, turnover dynamics, and material properties.
Rodent Research-17
Aging was the focus of this mission, with researchers investigating the physiology of aging in response to microgravity and biological age at the onset of disease progression. To test the hypothesis that spaceflight accelerates or magnifies the aging process, 40 female mice, 20 young and 20 old, were flown to the space station to determine whether they exhibited changes in the progression of cellular and metabolic dysfunction associated with aging and senescence on Earth.
Rodent Research-18
Rodent Research-18 investigated how spaceflight affects visual function, based on visual problems reported by astronauts after spaceflight. The study examined changes in the vascular system of the retina and the interactions of specific cells, and tested the antioxidant metalloporphyrin as a potential treatment.
Rodent Research-19
Rodent Research-19, dubbed “Mighty Mice in Space,” investigated myostatin and activin, molecular signaling pathways that affect the breakdown of muscles and bones. The study, led by researchers from the University of Connecticut School of Medicine, looked into myostatin and activin as possible targets for maintaining muscle and bone health during spaceflight, and improving recovery after return to Earth.
Rodent Research-20
Rodent Research-20, launched in November 2023, focused on reproduction. The female mice on previous missions had exhibited changes in ovarian function, so this mission was launched to investigate whether these changes would lead to temporary or permanent fertility issues.
Rodent Research-21
Using transgenic mice, Rodent Research-21 investigated the parallels between the adverse physiological effects of spaceflight on astronauts, such as cardiovascular and musculoskeletal deconditioning, and the effects of normal aging on Earth. The study could establish links between aging and gravity at the molecular level.
Rodent Research-23
Rodent Research-23 studied how spaceflight affects vision, including the structure and function of the associated arteries, veins, and lymphatic vessels. The mission could help scientists develop methods of protecting astronauts from spaceflight-associated eye conditions and shed light on eye diseases on Earth. After the five-week mission, ocular vasculature experts at Texas A&M University will examine the eyes of the mice for changes caused by their time in weightlessness
