Sheep Helping NASA Prepares for Trip to Mars
February 21, 2014

Colorado State University, NASA and a herd of sheep have teamed up to make human space travel safer.The federal space agency hopes to send astronauts to Mars by 2030, but it needs more information about the impact of weightlessness on the body first. The use of sheep in these studies has been important for the researchers to determine how the results could translate to astronauts, and eventually to older people and others with osteoporosis, said Christopher Puttlitz, associate professor of mechanical engineering and head of the CSU research team. 
Adult sheep, have bones that are similar in size and skeletal architecture to humans, making them desirable candidates for investigating orthopedic-related conditions. Traditionally, mice and rats have been used in research experiment, but the findings are not as readily translatable to human outcomes because of major anatomic and physiologic differences between the two species, such as bone microarchitecture and healing rates. 
Use of animals in a research study, though, is not taken lightly. 
"We have to provide extensive literature research to establish that the use of animals for a research project is the only reasonable way and practical means to get the information necessary," Palmer said. "It's easy to look at it from an outside angle, until the information we discovered with animal research can be used for yourself or a family member." 
According to NASA's Human Research Roadmap, astronauts can lose 1 percent to 2 percent of their bone density each month in space. This loss, coupled with the high-impact forces astronauts may encounter, can put them at risk of fracturing bones. So Puttlitz and Ross Palmer, a CSU professor and veterinary orthopedic surgeon, are using living sheep to mimic the impact of space travel on bones to better understand bone health and healing. 
The model was developed by observing the results of placing a protection frame, or brace, on the back leg of a sheep and isolating the metatarsal bone from the impact of normal daily activity over an eight-week period. The brace kept the sheep from bearing weight, simulating the effects of microgravity. Because the bone was isolated from any gravitational forces, the research team was able to discern that the sheep's bone density decreased - as did the load required to fracture the bone. The weakened bone could break more easily, Puttlitz reported in the Journal of Biomedical Engineering.