EM investigation of myoblast origin in regenerating hamster skeletal muscle explants

This study attempted to dispel the confusion that exists in the understanding of the origin of myoblasts during muscle regeneration. Regenerating hamster muscle explants from cultures were studied under the EM on 4 consecutive days, after incubation. Preincubation specimens served as controls. Revelations were that euchromatic myonuclei underwent dense granulation and activation after incubation. Presumptive myoblasts (PM) lying clearly within the myofibre increased in numbers with incubation time. Some myonuclei showed partial transformation towards a PM. This study concluded that myonuclei transformed into myoblasts during the process of muscle regeneration and that the PM, produced from a myonucleus, was a stage in the development of the satellite cell (SC) in regenerating muscle. These SC, myoblasts from myonuclear origin, proliferated, fused, and formed multinucleate myotubes that matured into myofibres which replaced damaged muscle. Findings of this study may have new implications for the proposed myoblast transplant or gene transfer therapy, both of which, whilst being possible answers for muscular dystrophy, depend on a sound knowledge of muscle regeneration mechanisms.