Almost every function of the human body is affected by exposure to microgravity and typically involves complex changes in human tissues and organs. However, in most cases, the adaptions induced by microgravity are only temporary and typically return to normal after returning to Earth.

It uses a validated mouse model to investigate the genetic mechanisms underlying bone mass loss and other microgravity effect on different tissues such as muscles, glands, brain, and provide mouse tissues for many different researchers studying the effects microgravity has on the body at the organ and cellular levels. Pleiotrophin transgenic mice (PTN-Tg) were selected because this transgene (a foreign gene that has been inserted into its genome to exhibit a particular trait) plays an important role in bone metabolism. MDS tests the hypothesis that mice with an overexpression of the PTN gene will be protected from the osteoporosis-like effects due to microgravity.

MDS set the longest permanence in space for rodents (91 days).