Transfection efficiency along the regenerating soleus muscle of the rat.

We investigated the efficiency of a single plasmid transfection along the longitudinal axis of the regenerating soleus of young rats. This also reflected transfection efficiency along the fibers because the soleus is a nearly fusiform muscle in young animals. The complete regeneration was induced by notexin and the transfection was made by intramuscular injection of enhanced green fluorescent protein- or Discosoma red-coding plasmids after 4 days. One week after transfection the number of transfected fibers was higher at the place of injection (i.e., in the muscle belly) and lower or absent at the ends of the muscle. The inspection of longitudinal sections and neuromuscular endplates indicated that one of the reasons of uneven transfection might be the shortness of transfected myotubes and the other reason might be the limit of diffusion of transgenic proteins from the expressing nuclei. As a result, the efficiency of transfection in the whole regenerating muscle was much lower than it could be estimated from the most successfully transfected part.