The process of survival of denervated and freely autotransplantated skeletal muscle

The size of the myofibers in mature grafts of the mouse extensor digitorum longus muscle

The histochemical profile of stabilized orthotopically grafted mouse extensor digitorum longus muscles (EDL) and fiber type diameter distribution in the graft was compared with control muscles. Histochemical fiber typing, based on myofibrillar ATPase reactions, indicated that type 1 fiber accounted for less than 1%, type 2a fibers for 30%, and type 2b fibers for 69% of the total fiber population of the graft. In control muscles of 56-day-old and 156-day-old mice, type 1 fibers accounted for less than 1%, type 2a fibers for 36%, and type 2b fibers for 63% of the total fiber population of normal muscles. The regenerating myofibers in stabilized grafts failed to achieve the normal fiber diameter. The type 2b fibers exhibited greater growth inhibition than did type 2a fibers.

Isoenzyme studies of whole muscle grafts and movement of muscle precursor cells

Isoenzymes of glucose-6-phosphate isomerase (GPI: E.C. 5.3.1.9) were used as markers to determine the origin of cells which give rise to new muscle formed in allografts of whole intact muscle. GPI isoenzymes were also employed to see whether host precursor cells, which have been shown to contribute to muscle formation in grafts of minced muscle, can be derived from muscle lying adjacent to grafts. Excellent muscle regeneration was found in allografts of extensor digitorum longus (EDL) muscle examined after 58 days: 12 of 16 grafts contained 80% or more new muscle. Isoenzyme analysis showed that most, and in 2 instances all, new muscle was derived from implanted donor cells; however, there was strong evidence that in 5 grafts some, or all, new muscle must have resulted from host cells moving into the graft. Although hybrid isoenzyme was not detected this was attributed to factors associated with host tolerance which appear to interfere with fusion between host and donor myoblasts. Isografts of minced muscle were placed next to whole EDL muscle allografts to see if cells from allografts moved into adjacent regenerating tissue. Unfortunately, muscle regeneration in minced isografts was poor; only 3 contained 50% or more new muscle and most contained large amounts of fibrous connective tissue. Only a single isoenzyme band was detected in 11 isografts, but in five instances, the presence of a second band showed that cells from EDL allografts were also present. As no hybrid isoenzyme was detected, it is not known whether these cells which had moved into the regenerating minced grafts were muscle precursors, fibroblasts or some other cell types.

Freely transplanted peroneus longus muscle in the cat reinnervated by a single nerve: physiological properties

Physiological properties (tetanic tension, single twitch, fatigability) of free autologous muscle transplants in cats were examined in vivo five months after transplantation. After 2 weeks denervation the peroneus longus muscle was placed isometrically in the abdomen with the omentum around the muscle and with the proximal end of a cut branch of the femoral nerve attached to the muscle. (In one case a sensory nerve was used.) Five months after transplantation the function of the muscle was controlled in vivo by nerve stimulation. In the case when a sensory nerve was connected to the muscle no contraction was obtained upon indirect or direct stimulation. All the other muscles contracted when the nerve was stimulated. The mean maximum tetanic tension was 16% of the mean for the control. The twitch-time was about the same as in the control muscle but the contraction time was longer and the half relaxation time shorter compared with the control. The transplanted muscles fatigued more slowly than the normal peroneus longus muscles. In spite of the unphysiological placement of the muscles in the abdomen where they have no natural function to fulfil, they became reinnervated and contracted as late as five months after transplantation.

Formation of neuromuscular junctions in transplanted peroneus longus muscles in the rat. A quantitative comparison with reinnervation of the muscle in situ

The formation of neuromuscular junctions in free heterotopic muscle transplants in the rat has been studied quantitatively and compared with the reinnervation of the muscle in situ. The AChE-containing area and the nerve terminal were stained in the same longitudinal section and the length of end-plate, the average number of nerve terminal branch points within the end-plate and the terminal innervation ratio (TIR) were determined. In denervated muscles we noticed early disappearance of nerves whereas the AChE-stained end-plates were visible after eight weeks. The reinnervation of the muscle in situ and after transplantation showed considerable similarities. Early during reinnervation the number of AChE positive areas increased and many of them were innervated by more than one axon. Terminal axons were also seen innervating more than one end-plate situated on the same or on different muscle fibres. Later the number of end-plates decreased and they were innervated by only one axon. The end-plate length reached normal value in the reinnervated muscle in situ but remained smaller in the transplanted muscle. In all reinnervated muscles ultraterminal sprouting was found as indicated by an increased number of nerve terminal branch points within the end-plate area. The TIR was increased in all reinnervated muscles due to terminal and ultraterminal sprouting of the axon. No significant difference in reinnervation was noted between normal and predenervated transplants. The reinnervation of transplanted muscles obviously has similarities not only with the reinnervation of normal muscles but also with the development of muscular innervation during early postnatal growth. In spite of the plasticity of the peripheral nerve the transplanted muscles underwent considerable atrophy which may have been enhanced by the unphysiological placement of the muscles in the abdomen. However, this experimental model made it possible to study reinnervation of muscle fibres only originating from the graft.

Diffusion chamber cultures of muscle from patients with scoliosis

Explants from paraspinal muscles of patients with scoliosis were cultured in Millipore diffusion chambers placed in peritoneal cavities of mice. Three and four weeks of incubation produced a predominantly myogenic growth. Cell counts done on paraffin sections and on dissociated cells from the chambers showed that explants from the concavity of the spinal curvature grew better than those from the convexity. Since cells from injured muscles, when transplanted or cultured, are known to grow better than those from healthy control tissue, these findings support our previous morphologic observations that in idiopathic scoliosis concave muscles are more involved by the disease process. Secondary subculture of the chamber contents by conventional methods produced myotubes within one to two weeks. The relative ease of diffusion chamber muscle culture should make the method useful to laboratories that are not specifically equipped for tissue culture work.

Intermittent claudication and muscle fiber fine structure: correlation between clinical and morphological data

Bilaterally obtained muscle biopsies (anterior tibial muscle) from 22 patients with unilateral peripheral arterial insufficiency (intermittent claudication) were qualitatively and quantitatively analyzed by means of enzyme histochemistry and electron microscopy. In a majority of the biopsies from the symptomatic legs, two different patterns of morphological deviations were seen in the abnormal muscles: one suggested primary muscle fiber damage and the other indicated denervation. Biopsies from the asymptomatic legs were often only slightly changed or normal. Significant correlations were found in both legs between the relative number of type 1 (slow twitch, highly oxidative) fibers and the age of the subjects. In symptomatic legs, furthermore, a relation could be demonstrated between the relative number of type 1 fibers and (1) the initial walking tolerance (walking distance covered before pain occurred), (2) duration of symptoms, and (3) occlusion or stenosis at high level (i.e., above the deep femoral artery). Finally, the diameters of both type 1 and type 2 fibers in the symptomatic leg were correlated to the initial walking tolerance. The importance of circulatory disturbances as differential diagnostic points (arteriovasculo-occlusive myopathy) in the diagnosis of neuromuscular diseases is stressed.

The reliability of histochemical fibre typing of human necropsy muscles

The reliability of muscle fibre typing of post mortem specimens was investigated with special reference to the influence of time and temperature. In specimens stored at +4 degrees C, muscle fibre typing could be reliably performed up to at least ten and fifteen days post mortem for the masseter and biceps brachii muscles respectively. The corresponding figures for storage at room temperature were three and six days. The difference in the preservation of enzyme activity between masticatory and limb muscles might be related to the demonstrated difference in the fibre type composition and thus the enzyme content and energy sources.

Cellular responses to free grafting of the extensor digitorum longus muscle of the rat

The cellular and subcellular responses related to the survival or destruction and subsequent regeneration of muscle fibers within the freely grafted extensor digitorum longus muscle of the rat were examined by light and electron microscopy. A small number of fibers at the periphery of the grafts survived the initial ischemia but underwent denervation changes and accumulated lipid deposits. The majority of fibers in the grafts, however, became ischemic and underwent an intrinsic degeneration within 4 hours. Cell-mediated destruction of the degenerating fibers occurred as the grafts became revascularized. The basal laminae and some of the satellite cells were the only elements of the original fibers that persisted. Regeneration began at the periphery of the graft within three days after grafting and reached the center about three days later. After phagocytosis of the original fibers, presumptive myoblasts within the grafts differentiated into myoblasts and myotubes. The formation of myotubes followed a biphasic pattern of development comparable to that of normal fetal muscle. Although most of the myotubes were formed within the basal lamina remaining from the original fiber, there was also evidence for regeneration outside the basal lamina. Myotubes matured into muscle fibers which were essentially normal in apperance when examined up to 180 days after grafting. Some fibers, however, were atrophic, presumably due to a failure to become innervated, and some fibers were joined by myo-myous junctions. Pre-denervated grafts and Marcaine-treated grafts were also examined. There were more surviving fibers in pre-denervated grafts, and cell-mediated destruction of degenerating fibers proceeded more rapidly than in normal grafts. No surviving fibers were found in Marcaine-treated grafts. The changes in these grafts were otherwise similar to normal grafts. A schematic model of the spatial and temporal sequence of degeneration and regeneration within a free muscle graft is presented.

Free autogenous muscle transplantation in the treatment of urinary incontinence in children: background, surgical technique and preliminary results

Urinary incontinence owing to epispadias or bladder exstrophy is a difficult therapeutic problem. To improve the results a new method, including free autogenous muscle transplantation, was developed. Before transplantation a skeletal muscle (extensor brevis of the foot) is denervated and, 2 weeks later, it is transplanted and placed as a U-sling around the urethra in close contact with normally innervated muscles, which act as reinnervation sources. Two patients showed improvement of continence and increasing bladder capacity from 6 weeks after transplantation. Postoperative cine-studies of micturition demonstrated clearly the functional properties of the transplanted muscle.

A new treatment of anal incontinence in children: free autogenous muscle transplantation

A new method is presented for the treatment of anal incontinence in children, including free autogenous muscle transplantation. The primary step is denervation of a skeletal muscle, which 2 wk later is transplanted and placed as a U-sling around the rectum, imitating the position and function of the puborectalis muscle. The transplant is placed in close contact with innervated muscles, which act as reinnervation sources. The results in five consecutive patients are highly promising. An early sign of improvement is the occurrence of a sensation of rectal fullness. All the patients reached an acceptable degree of continence, including abandonment of the use of napkins, 4-12 mo after surgery.

The free autografting of entire limb muscles in the cat: morphology

Normal or pre-denervated extensor digitorum longus (EDL) muscles were sucessfully grafted in place of the contralateral EDL muscles in cats. Histological preparations of 57 grafts were examined at intervals from 4 to 170 days after transplantation. The morphological sequence of events in a cat muscle graft is similar to that in the rat except that the time course of regeneration is considerably slower. Surviving original muscle fibers form a thin rim at the periphery of the graft. Beneath this rim, the original muscle fibers undergo fragmentation, starting near the periphery and progressing toward the center. Regenerating muscle fibers take the place of the degenerated muscle fibers. In pre-denervated grafts, the last of the original muscle fibers in the center of the graft have broken down by 41 days whereas in normal muscle grafts the original muscle fibers in the central region persist until 50 days. The main difference between grafts of normal and pre-denervated muscles is the rate of breakdown of the original muscle fibers. Long term grafts of both groups are morphologically very similar.