Hematopoietic stem cell transplantation does not restore dystrophin expression in Duchenne muscular dystrophy dogs

Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene on the X-chromosome that result in skeletal and cardiac muscle damage and premature death. Studies in mice, including the mdx mouse model of DMD, have demonstrated that circulating bone marrow-derived cells can participate in skeletal muscle regeneration, but the potential clinical utility of treating human DMD by allogeneic marrow transplantation from a healthy donor remains unknown. To assess whether allogeneic hematopoietic cell transplantation (HCT) provides clinically relevant levels of donor muscle cell contribution in dogs with canine X-linked muscular dystrophy (c-xmd), 7 xmd dogs were given hematopoietic cell (HC) transplants from nonaffected littermates. Compared with the pretransplantation baseline, the number of dystrophin-positive fibers and the amount of wild-type dystrophin RNA did not increase after HCT, with observation periods ranging from 28 to 417 days. Similar results were obtained when the recipient dogs were given granulocyte colony-stimulating factor (G-CSF) after their initial transplantation to mobilize the cells. Despite successful allogeneic HCT and a permissive environment for donor muscle engraftment, there was no detectable contribution of bone marrow-derived cells to either skeletal muscle or muscle precursor cells assayed by clonal analyses at a level of sensitivity that should detect as little as 0.1% donor contribution.