bone marrow transplantation attenuates the myopathic phenotype of a muscular mouse model of spinal muscular atrophy bone marrow bm transplantation was performed on a muscular mouse model of spinal muscular atrophy that had been created by mutating the survival of motor neuron gene smn in myofibers only this model is characterized by a severe myopathy and progressive loss of muscle fibers leading to paralysis transplantation of wildtype bm cells following irradiation at a low dose 6 gy improved motor capacity 85 this correlated with a normalization of myofiber number associated with a higher number of regenerating myofibers 16fold increase and an activation of cd34 and pax7 satellite cells however bm cells had a very limited capacity to replace or fuse to mutant myofibers 2 these data suggest that bm transplantation was able to attenuate the myopathic phenotype through an improvement of skeletal muscle regeneration of recipient mutant mice a process likely mediated by a biological activity of bmderived cells this hypothesis was further supported by the capacity of muscle protein extracts from transplanted mutant mice to promote myoblast proliferation in vitro 16fold increase in addition a tremendous upregulation of hepatocyte growth factor hgf which activates quiescent satellite cells was found in skeletal muscle of transplanted mutants compared with nontransplanted mutants eventually thanks to the creloxp system we show that bmderived muscle cells were strong candidates harboring this biological activity taken together our data suggest that a biological activity is likely involved in muscle regeneration improvement mediated by bm transplantation hgf may represent an attractive paracrine mechanism to support this activity