Scientists in Sweden announced the results of experiments using adult mouse stem cells. Such cells were taken from the brains of mature mice and transplanted into both mouse and chicken embryos. The stem cells matured into a variety of cell types-including beating heart cells.

Earlier research at other institutions, including Harvard, had clearly demonstrated that nerve stem cells of mice could mature into needed specialized nerve cells. Blood stem cells could mature into needed specialized blood cells, but the Swedish experiments were the first to show that neural stem cells could mature into a variety of needed specialized cells.

Scientists are cautiously optimistic as these experiments are the first evidence that stem cells can be prodded to become virtually any needed mature cell. Among the diseases they speculate we might eventually treat with stem cell transplants are Parkinson's disease, Alzheimer's disease, macular degeneration, stroke, type 1 diabetes, and spinal cord injuries. Could the next generation see the clock turned back, and the diseases of aging treated by stem cell transplant? Could repeated stem cell transplants serve as a virtual fountain of youth, replacing tissues worn and damaged by age? Only additional research will enable us to know if this staggering promise can be realized.