[Muscular reconstruction by myogenic cell graft]

We have developed an experimental model to test the ability of cultured satellite cells to form new muscle fibers when grafted in an irreversibly injured muscle. Association of X-irradiation to autotransplantation reduced extensor digitorum longus muscles of adult rats to a cystic structure formed by a peripheral rim of surviving muscle fibers surrounding a central space devoid of myofibers. Grafting autologous satellite cells, multiplied and labelled in vitro, into this central space gave rise to new myotubes which developed and matured to form fully differentiated myofibers. Mecanophysiological recordings confirmed the improvement of functional parameters particularly a 4 fold increase of twitch and tetanic tensions in grafted muscles. Furthermore, we examined the role of old basal lamina in architectural organisation of the reconstituted muscle by electron microscopy and immunofluorescence using antibodies to laminin, fibronectin, type IV collagen and heparan sulfate proteoglycan. We observed the persistence of immunoreactivity to all components; anti-laminin antibodies for example, evidenced a clear fascicular organization of ghost basal lamina which are progressively repopulated by the grafted cells. We finally investigated in vivo proliferation of the grafted cells by an autoradiographic study of H3-thymidine incorporation in the regenerated fibers and demonstrate that grafted cells proliferate for, at least, 1 week after cell grafting.