Myogenic stem cells from the bone marrow: a therapeutic alternative for muscular dystrophy?

Differentiated muscle fibres can be formed by transplanted haematopoietic stem cells in models of acute or chronic muscle regeneration, including the dystrophin-deficient mdx mouse. Muscle-forming activity can be found in adult, foetal and embryonic haematopoietic tissues. The blood-to-muscle transition may be due to transdifferentiation of haematopoietic progenitors in response to local signals provided by the regenerating muscle. These signals are only poorly provided by the muscle of the mdx mouse, since transplantation into these mice of normal C57Bl/6 bone marrow gives rise only to a minimal number of muscle fibres expressing the normal dystrophin protein (<1%) throughout the animal life span. Expansion and active recruitment to myogenic differentiation of transplanted haematopoietic cells are therefore critical factors for a future use of bone marrow transplantation in cell/gene therapy of muscular dystrophy.