RESEARCHERS at University of Colorado transplanted stem cells into the leg muscles of mice prevented the loss of muscle function and mass that normally occurs with aging - a find that could be used in treating humans with chronic, degenerative muscle diseases. The cells not only repaired the injury within days, they caused the treated muscle to double in mass and sustain itself through the lifetime of the transplanted mice. We found that the transplanted stem cells are permanently altered and reduce the aging of the transplanted muscle, maintaining strength and mass, said Professor Bradley Olwin of CU-Boulders molecular, cellular and developmental biology department. With further research we may one day be able to greatly resist the loss of muscle mass, size and strength in humans that accompanies aging, as well as chronic degenerative diseases like muscular dystrophy, he added. Stem cells have the ability to renew themselves through cell division and differentiate into specialized cell types. The environment that the stem cells are injected into is very important, because when it tells the cells there is an injury, they respond in a unique way, he said. We dont yet know why the cells we transplanted are not responding to the environment around them in the way that the cells that are already there respond. Its fascinating, and something we need to understand. Fortunately, the research team saw no increase in tumors in the transplanted mice despite the rapid, increased growth and production of muscle stem cells. But Olwin said it is important to remember that the team did not transplant young cells into old muscles, but rather transplanted young cells into young muscles. A paper on the subject was published in the Nov. 10 issue of Science Translational Medicine. YN