Traditionally, space medicine has tackled medical problems associated with the space environment. Increasingly, however, space medicine also encompasses research conducted aboard space stations and vehicles. Medical research conducted in microgravity is making significant contributions to the understanding of the molecular structure of living things—a key to the development of new disease-fighting drugs. The scope of biological molecules includes proteins, polysaccharides and other carbohydrates, lipids and nucleic acids of biological origin, and those expressed in plant, animal, fungal, or bacteria systems. The precise structure of proteins and some other biologic molecules can be determined by diffracting X rays off crystalline forms of these molecules to create a visual image of the molecular structure. Determining the structure of these macromolecules—which allow livingorganisms to function—is essential to the design of new, more effective drugs against infectious diseases and other afflictions, such as AIDS, heart disease, cancer, diabetes, sickle-cell anemia, hepatitis, and rheumatoid arthritis.
A researcher examines images of insulin crystals grown on a space shuttle.
Medical Advances from Space Research
Space-based crystal growth facilitates the study of how macromolecules work in the human body, which has important implications for medicine. For example, through protein crystal growth research, scientists have made an important step toward developing a treatment for respiratory syncytial virus—a life-threatening virus that causes pneumonia and severe upper respiratory infection in infants and young children. Investigators have determined the structure of a potentially important antibody to the virus, allowing scientists to understand key interactions between the antibody and the virus, thus, facilitating development of treatments. Factor D protein crystals have also been grown in space, leading to development of a drug that may aid patients recovering from heart surgery by inhibiting the body's inflammatory responses. Experiments in protein crystallization research have also yielded detailed structural data on proteins associated with Chagas' disease, a deadly illness that afflicts more than 20 million people in Latin America and parts of the United States.
Medical research in space has likewise yielded precise images of insulin proteins—mapped from space-grown crystals—which can aid the development of new insulin treatments for diabetes. Such treatments would greatly improve the quality of life of insulin-dependent diabetics by reducing the number of injections they require. In addition, a space-based study of the HIV protease-inhibitor complex has resulted in improved resolution of the protein's structure, which has important implications for designing new drugs for AIDS therapies. Microgravity research has also provided insight into an enzyme called neuraminidase, which is a target for the treatment and prevention of the flu. Meanwhile, influenza protein crystals grown aboard several space shuttle flights have had a significant impact on the progress for a flu medicine. As a result, several potent inhibitors of viral influenza (types A and B) have been developed. Medical research in space has also provided insight into fundamental physiologic processes in the human body. A protein crystal growth study conducted during a space shuttle flight shed new light on antithrombin—a protein that controls coagulation of blood.
Research on the International Space Station
Equipped with a dedicated research laboratory, the International Space Station (ISS) will support longer-duration experiments in a more research-friendly, acceleration-free, dedicated laboratory than the space shuttle can allow. Onboard ISS, astronauts and cosmonauts will use the Microgravity Science Glovebox to support investigations and demonstrations in all of the microgravity research disciplines. When it is sealed, the Glovebox serves as a single level of containment by providing a physical barrier. A planned protein crystal growth facility will be used to expose a pure protein solution to a substrate, which draws the liquid out of the protein solution, leaving crystallized proteins behind.
Plans for the ISS also call for a "bioreactor" onboard that will be used in experiments to grow cells and tissues in a controlled environment. OnEarth, bioreactors have to rotate to allow cell growth in three dimensions, very similar to the way cells grow naturally within an organism. However, this works only up to a certain sample size because the larger the sample gets, the faster the bioreactor has to spin to keep the cells suspended. In the microgravity environment of the International Space Station, the cells will remain suspended on their own because there is virtually no gravity to cause sedimentation. As a result, samples can be grown larger and be kept alive for longer periods.
Blood is drawn from astronaut John Glenn as part of the Protein Turnover Experiment (PTO), which examined muscle atrophy during exposure to microgravity.
With these cells and tissues, new medicines in the fight against AIDS, cancer, and diabetes can be safely tested, without harming animal or human test subjects, and long-term exposure to microgravity and its effects on human bones, muscles, cartilage, and immunity can be studied effectively. Bioreactor research will also be valuable in the study of potential cartilage and liver tissue transplantation.
