REGENERATION OF SKELETAL MUSCLE IN THE ROTTNEST QUOKKA

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Abstract
Summary: The reversal of the nutritional myopathy of the captive Rottnest quokka (Setonix brachyurus) with vitamin E provided a model for the study of regenerative processes in skeletal muscle. Seventeen quokkas recovering from myopathy following treatment with α‐to opherol were studied by means of 2 to 7 serial biopsies from each animal. As the debris within necrotic muscle fibres was removed by macrophages, proliferation of sarcolemmal nuclei occurred. Cells with basophilic cytoplasm, due to a high content of ribonucleic acid (RNA), appeared and showed mitotic activity. Myofibrillar markings identified these cells as myoblasts. Later in the sequence multi‐nucleated masses and young muscle fibres developed, probably by fusion of myoblasts. Cross striations became obvious and the sarcoplasm eosinophilic, due to increased content of protein. Lastly, sarcolemmal nuclei centrally or randomly distributed underwent marginal migration and the muscle fibre became fully reconstituted. With acrolein‐Schiff staining necrotic fibres were rarefied, due to loss of protein, but during maturation staining became deeper as the protein content increased. The early phases occupied several days, while complete restoration required 5 to 8 weeks. There were many features of similarity between the morphology of regeneration in vivo and the growth and differentiation of skeletal muscle in vitro. Regenerative activity is prominent in the histopathological lesion of human polymyositis, and increased attention has been recently given to regenerative phenomena in case of human progressive muscular dystrophy, so that clarification of this property of muscle may improve understanding of these diseases.