Heterotopic Transplantation of Entire Muscles in Mammals

Abstract

During the period under review, the following series of experiments were carried out. 1. STUDIES ON NORMAL EDL MUSCLES IN RATS: Various morphological, morphometric, histological and biochemical characteristics of the normal extensor digitorum longus (EDL) muscle in the rats were studied. The study of all these parameters of a normal muscle was essential for comparing these with the experimentally transplanted muscle. It was discovered that the number of muscle fibres in a normal rat EDL muscle had a mean number of 1514. The mean Sarcomere number of the muscle fibres was calculated to be 3302, with a mean Sarcomere length of 0.02mm. the mean weight of the muscle was discovered to be 0.06% of total body weight. Histologically there was seen very little of connective tissue and almost no adipose tissue within a normal EDL muscle. Biochemically, it was discovered that the control muscle contained an average of 4.55 + 0.15 mg DNA/gm muscle weight and 5.34 + 0.18 mg RNA/mg muscle weight. 2. STUDIES ON THE NORMAL TRANSPLANTATION OF ENTIRE EDL MUSCLES IN THE RATS: EDL muscles were transplanted heterotopically in the contralateral leg. It was discovered that even without any pretreatment, these muscles were grafted successfully. There was a degeneration of almost all of the original muscle fibres followed by a regeneration of a new population of myotubes within the graft. Cross sectional area of the EDL muscle decreased following various transplantation days and never reached normal value. In the experiment group, the RNA and DNA content of the muscle first decreased and then after seven days it increased. 3. EFFECTS OF DERIVATION ON EDL MUSCLE: Effects of short and long term denervation on normal EDL muscles were investigated. It was seen that denervation apparently brings about an atrophy of the muscle fibres, but there are seems to be an increase in the number of muscle fibres as well as in the nuclear number within the muscle. 4. EFFECTS OF LIGNOCAING PRE-TREATMENT ON EDL MUSCLE TRANSPLANTATION: Effects of various doses of a local anesthetic agent lignocaine, on normal muscle were studied. It was discovered that this drug is myotoxic in nature. Following application of doses of .5ml of 2% strength. There was an initial phase of muscle destruction and degeneration which was not followed by any phase of muscle regeneration. Lignocaine was then applied, in various doses, to the EDL muscle as a special pre-treatment of the muscle which was then transplanted. In concentrations of 2% it was seen that there was a partial regeneration. In lower cases, rations of 1% or 0.5%, the drug brought about mostly the atrophy of the muscle fibres with little muscle degeneration and almost no muscle regeneration. 5. STUDIES OF THE EFFECTS OF MECHANICAL INJURY PRE-TREATMENT ON MSUCLE TRANSPLANTATION: Effects of severe mechanical injury in the form of cross or longitudinal incisions on the EDL muscle were examined. It was discovered that both cross and longitudinal incisions resulted into more or less complete degeneration of the original muscle fibres with an eventual replacement by a population of regeneration myotubes. From these results it seems that mechanical injury should be a good pretreatment of the muscle meant for transplantation. 6. TRANSPLANTATION ON EDL MUSCLES IN FEMURECTONIZED ANIMALS: Transplantation of normal EDL muscle in a femurectomized leg resulted into a more or less normal muscle regeneration for an initial period of about 2 weeks. There were seen distinct atrophic changes within the transplant. This indicates that a proper physical activity of the leg bearing the transplant is essential for a successful muscle transplantation. 7. MUSCLES REGENRATION FOLLOWING TRANSPLANTATION IN A DENERVATED CONDITION: In another group of rats, the EDL muscles were transplanted in a denervated condition, there was an initial phase of muscle regeneration within such grafts, but there was an eventual atrophy and degeneration of the regenerating muscle fibres resulting into a very poor regenerate. These results indicated that for a proper growth and maturation of the regenerating fibres, within the transplant, proper innervation is necessary. 8. TRANSPLANTATION OF ANTERIOR TIBIALS MUSCLES IN MICE: Anterior tibialis muscles in mice were transplanted orthophically. The results indicate that mouse ant, tibialis does not possess an appreciable ability to regenerate in a transplanted condition. The transplantation was marked by degeneration and elimination of the original muscle fibres. There were no indications of viable myoblasts of myotubes even by the end of one week. By about the end of one month following transplantation, the implant had not only been reduced greatly in size but was also almost completely composed of connective tissue fibres and a lot of adipose tissue. 9. EDL MUSCLES TRANSPLANTATION IN RABBITS: In rabbits, EDL muscles transplanted heterotopically showed typical regenerative activity, quite similar to that found in the rats. 10. EFFECTS OF HORMONES ON MUSCLES REGENERATION IN RABBITS (INSULIN, TESTOSTERONE): Insulin effect not only on regeneration process but also effect on the diameter of muscles fibres. The diameter of insulin treated regenerating muscle fibres is larger than the normal regenerating muscle fibres, with an increase in concentration of insulin, regeneration process is rapid but pattern of degeneration-regeneration is similar to normal regenerating skeleton muscle in rabbits. On the other hand, Testosterone effect only on target muscle. It accelerate the rate of regeneration of target muscle. Limb muscles do not respond to an increase in testosterone.