This project will study the risk of seriously damaging knee joints because of exposure to weightlessness and radiation during long duration spaceflights. The knee joint consists of articular cartilage lining bone, the meniscus which distributes forces through the joint, the ligaments joining bones, and the underlying bone. Maintaining health of all joint structures is necessary for proper knee function. Both exposure to space radiation and weightlessness during long spaceflights has the potential to damage these structures, increasing the risk of bone fracture or developing arthritis during spaceflight or after returning to earth. However, spaceflight effects on these tissues (besides bone) are largely unstudied.
To study this problem, we will remove the forces applied to the knees of rats through hind limb unloading. After determining how weightlessness can cause erosion of these structures, we will characterize how combined weightlessness and space radiation can damage the knee. Rats that have been exposed to weightlessness and/or radiation will be allowed to recover under normal weight-bearing conditions. Damage to and repair of the knee joint structures will be measured using noninvasive imaging techniques and stained tissue sections. We will identify proteins that are produced and can lead to joint tissue erosion during unloading radiation. Also, cells from the knee joint will be grown and their properties studied in tissue culture systems, further identifying the cause of knee joint damage.
Our goal is to determine the extent of and cause for knee joint damage during weightlessness and radiation characteristic of the spaceflight environment. Once we understand how the tissues in the knee are damaged during modeled spaceflight, we can develop and test ways to prevent this knee joint damage for future missions. We also will gain insights into how arthritis develops on earth, and how it can be prevented.