Dystrophin has been successfully delivered to diseased muscle using intravenous injection of engineered stem cells. The approach represents an alternative to gene delivery via viral/synthetic vector or direct injection into muscle. Scientists at Children's Hospital and Harvard Medical School (Boston, MA) used bone marrow and muscle-derived stem cells to partially restore dystrophin expression in the mdx mouse model of Duchenne muscular dystrophy (Nature 401, 390–393, 1999). Richard Mulligan, a Howard Hughes investigator and senior author on the study, explains that "the use of stem cells for transplantation appears to result in the disseminated delivery of cells, a critical requirement for the effective treatment of. . .muscular dystrophy, where the afflicted cells are found throughout the body." By irradiating the mice and injecting stem cells engineered to express dystrophin, Mulligan and his colleagues showed that dystrophin-positive muscle cells could successfully engraft into diseased tissue. The approach was successful not only for hematopoietic stem cells, but also for putative muscle tissue stem cells. Although the restorative effects were well below what would be required for clinical efficacy, the findings suggest that adult stem cells from a variety of sources might be manipulated for use in gene therapy protocols.