Muscle precursor cells injected into irradiated mdx mouse muscle persist after serial injury.

Muscle of donor origin was formed after implantation of H-2Kb-tsA58 muscle precursor cells (mpc) into irradiated mdx nu/nu mouse muscles. A series of injections of the myotoxin, notexin, which destroys mature muscle fibers but spares muscle precursor cells and other tissues, was made into the mpc-injected muscles, leaving time for regeneration to occur between each injection. New muscle fibers of donor origin were formed after up to four notexin treatments, providing evidence that some of the implanted mpc reentered an undifferentiated, quiescent, stem cell-like state and were capable of myogenesis after further injuries to the muscle. A similar model could be used to assay whether preparations of human mpc contain long-lasting precursor cells, prior to their implantation into patients. In control mdx muscles, which had been irradiated, injected with tissue culture medium, and given three notexin injections, regeneration also occurred, indicating that radiation-resistant mpc were present, presumably within the treated muscle.