Hormonal Influences on Skeletal Muscle Grafts

Abstract

The effects of various hormones on the regeneration of muscle fibres within rat EDL muscle graft were studied under various experimental conditions. Primarily three hormones, Testosterone, Insulin and Thyroid hormones, were examined in the present study. It was discovered that EDL muscle graft reacted negatively to lack of androgens. In such androgen deprived conditions the muscle graft underwent considerable degree of atrophy and degeneration. On the other hand, following exogenous administration of Testosterone, it developed normally or even better than in control animals. It, therefore seems that mammalian skeletal muscle may be, in general, more sensitive to the presence of androgens during development growth and regeneration than what has been previously proposed. In another series of experiments the Insulin production was inhibited by Allaxon treatment. In such rats, EDL grafts showed very poor regenerative activity, as compared to the control grafts. On the contrary, in Hyperinsulinaemic rats, prepared through exogenous administration on insulin, EDL muscle grafts regenerated much better. In such grafts the hypertrophy of the individual muscle fibres was evident as exhibited in significantly higher cross-sectional area. These observations indicate that Insulin also plays an important role in the regeneration and growth of mammalian skeletal muscle. When thyroid activity was inhibited through the administration of Thiourea, it was once again noticed that EDL muscle grafts in such conditions underwent almost complete atrophy. However, the EDL transplants in rats made Hyperthroid through Thyroxine administration showed a considerable degree of hypertrophy. Thus it ca be stated with a certain degree of confidence that these three anabolic hormones i.e., Testosterone, Insulin and Thyroxine play a very important role in the regeneration of EDL muscle grafts. Complete absence or physiologically lower concentrations of these hormones resulted in atrophy and degeneration of the muscle fibres within the graft. On the other hand, higher concentrations of these hormones affected the EDL muscle grafts positively, as is apparent by higher average cross-sectional area of muscle fibres in such trans-plants. These findings are not only helpful in the management of muscle transplantation in patients with endocrine disorders, but are also of great importance in solving the problems of obtaining better regenerates with better structural and functional parameters.