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Persistent Muscle Fiber Regeneration in Long Term Denervation. Past, Present, Future.

Carraro U, Boncompagni S, Gobbo V, Rossini K, Zampieri S, Mosole S, Ravara B, Nori A, Stramare R, Ambrosio F, Piccione F, Masiero S, Vindigni V, Gargiulo P, Protasi F, Kern H, Pond A, Marcante A - Eur J Transl Myol (2015)

Bottom Line: Whether in mammals, humans included, this is a result of persistent de novo formation of muscle fibers is an open issue we would like to explore in this review.Although embryonic isoforms of acetylcholine receptors are known to be re-expressed and to spread from the end-plate to the sarcolemma of muscle fibers in early phases of muscle denervation, we suggest that the MHCemb positive muscle fibers we observe result from the activation, proliferation and fusion of satellite cells, the myogenic precursors present under the basal lamina of the muscle fibers.Some of the mandatory procedures, are ready to be translated from animal experiments to clinical studies to meet the needs of persons with long-term irreversible muscle denervation.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurorehabilitation, Foundation San Camillo Hospital , I.R.C.C.S., Venice, Italy.

ABSTRACT
Despite the ravages of long term denervation there is structural and ultrastructural evidence for survival of muscle fibers in mammals, with some fibers surviving at least ten months in rodents and 3-6 years in humans. Further, in rodents there is evidence that muscle fibers may regenerate even after repeated damage in the absence of the nerve, and that this potential is maintained for several months after denervation. While in animal models permanently denervated muscle sooner or later loses the ability to contract, the muscles may maintain their size and ability to function if electrically stimulated soon after denervation. Whether in mammals, humans included, this is a result of persistent de novo formation of muscle fibers is an open issue we would like to explore in this review. During the past decade, we have studied muscle biopsies from the quadriceps muscle of Spinal Cord Injury (SCI) patients suffering with Conus and Cauda Equina syndrome, a condition that fully and irreversibly disconnects skeletal muscle fibers from their damaged innervating motor neurons. We have demonstrated that human denervated muscle fibers survive years of denervation and can be rescued from severe atrophy by home-based Functional Electrical Stimulation (h-bFES). Using immunohistochemistry with both non-stimulated and the h-bFES stimulated human muscle biopsies, we have observed the persistent presence of muscle fibers which are positive to labeling by an antibody which specifically recognizes the embryonic myosin heavy chain (MHCemb). Relative to the total number of fibers present, only a small percentage of these MHCemb positive fibers are detected, suggesting that they are regenerating muscle fibers and not pre-existing myofibers re-expressing embryonic isoforms. Although embryonic isoforms of acetylcholine receptors are known to be re-expressed and to spread from the end-plate to the sarcolemma of muscle fibers in early phases of muscle denervation, we suggest that the MHCemb positive muscle fibers we observe result from the activation, proliferation and fusion of satellite cells, the myogenic precursors present under the basal lamina of the muscle fibers. Using morphological features and molecular biomarkers, we show that severely atrophic muscle fibers, with a peculiar cluster reorganization of myonuclei, are present in rodent muscle seven-months after neurectomy and in human muscles 30-months after complete Conus-Cauda Equina Syndrome and that these are structurally distinct from early myotubes. Beyond reviewing evidence from rodent and human studies, we add some ultrastructural evidence of muscle fiber regeneration in long-term denervated human muscles and discuss the options to substantially increase the regenerative potential of severely denervated human muscles not having been treated with h-bFES. Some of the mandatory procedures, are ready to be translated from animal experiments to clinical studies to meet the needs of persons with long-term irreversible muscle denervation. An European Project, the trial Rise4EU (Rise for You, a personalized treatment for recovery of function of denervated muscle in long-term stable SCI) will hopefully follow.

No MeSH data available.


Related in: MedlinePlus

Four-year LMN human denervated quadriceps muscle. Immunohistochemical staining with anti-MHCslow shows that both the green-labeled slow type muscle fibers (white arrows) and the fast (larger, not stained muscle fibers noted by black arrowheads) present several central nuclei. Scale bar: 100 μm.
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fig007: Four-year LMN human denervated quadriceps muscle. Immunohistochemical staining with anti-MHCslow shows that both the green-labeled slow type muscle fibers (white arrows) and the fast (larger, not stained muscle fibers noted by black arrowheads) present several central nuclei. Scale bar: 100 μm.

Mentions: Fig. 6, B and Fig. 7 show cryosections from 4.0-year and 5.4-year LMN denervated human muscle biopsies, respectively, after staining (in green) with an anti-MHCslow antibody. In Fig. 7 the white arrows point to slow-type (green) atrophic muscle fibers with centralized nuclei labeled in blue by Hoechst 33258. The black arrowheads indicate two less atrophic fast type muscle fibers (not stained by the anti-MHCslow antibody), which contain several centralized nuclei. The immunohistochemical analyses presented in panel B of Fig. 6 and in Fig 7 show that both fast and slow muscle fibers undergo severe atrophy and nuclear relocation and that this relocation of nuclei precedes the disappearance of all the contractile proteins. On the other hand, only a few (1% of the muscle fibers we were able to count) small muscle fibers from the longer term denervated muscles stain in green with an anti-MHCemb anti-body (Fig 7, C). These morphological aspects suggest that severe atrophy with consequent nuclear redistribution is the result of the incremental disorganization of the sarcomeric structures of the denervated muscle fibers, which meantime lose the normal coil distribution of subsarcolemmal myonuclei. Whatever the mechanisms of their rearrangement, the muscle nuclei are for many months (or years) regrouped into clusters of tens that fill the severely atrophic muscle fibers and are separated by long stretches of amyofibrillar myoplasm.23,24 The size of nuclear clumps is better evaluated in 1 μm semi-thin longitudinally sectioned myofibers (Fig. 8). Here, stretches of amyofibrillar sarcoplasm (15-20 μm wide and 50-100 μm long) alternate with groups of tens of nuclei that fill 20-30 μm long portions of the fibers. These two 0.3 mm long portions of severely atrophic muscle fiber contain 10-30 myonuclei, suggesting that loss of nuclei is substantial at these late stages of muscle atrophy (in normal muscle there are 1000-2000 nuclei per mm of myofiber).25,26


Persistent Muscle Fiber Regeneration in Long Term Denervation. Past, Present, Future.

Carraro U, Boncompagni S, Gobbo V, Rossini K, Zampieri S, Mosole S, Ravara B, Nori A, Stramare R, Ambrosio F, Piccione F, Masiero S, Vindigni V, Gargiulo P, Protasi F, Kern H, Pond A, Marcante A - Eur J Transl Myol (2015)

Four-year LMN human denervated quadriceps muscle. Immunohistochemical staining with anti-MHCslow shows that both the green-labeled slow type muscle fibers (white arrows) and the fast (larger, not stained muscle fibers noted by black arrowheads) present several central nuclei. Scale bar: 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383182&req=5

fig007: Four-year LMN human denervated quadriceps muscle. Immunohistochemical staining with anti-MHCslow shows that both the green-labeled slow type muscle fibers (white arrows) and the fast (larger, not stained muscle fibers noted by black arrowheads) present several central nuclei. Scale bar: 100 μm.
Mentions: Fig. 6, B and Fig. 7 show cryosections from 4.0-year and 5.4-year LMN denervated human muscle biopsies, respectively, after staining (in green) with an anti-MHCslow antibody. In Fig. 7 the white arrows point to slow-type (green) atrophic muscle fibers with centralized nuclei labeled in blue by Hoechst 33258. The black arrowheads indicate two less atrophic fast type muscle fibers (not stained by the anti-MHCslow antibody), which contain several centralized nuclei. The immunohistochemical analyses presented in panel B of Fig. 6 and in Fig 7 show that both fast and slow muscle fibers undergo severe atrophy and nuclear relocation and that this relocation of nuclei precedes the disappearance of all the contractile proteins. On the other hand, only a few (1% of the muscle fibers we were able to count) small muscle fibers from the longer term denervated muscles stain in green with an anti-MHCemb anti-body (Fig 7, C). These morphological aspects suggest that severe atrophy with consequent nuclear redistribution is the result of the incremental disorganization of the sarcomeric structures of the denervated muscle fibers, which meantime lose the normal coil distribution of subsarcolemmal myonuclei. Whatever the mechanisms of their rearrangement, the muscle nuclei are for many months (or years) regrouped into clusters of tens that fill the severely atrophic muscle fibers and are separated by long stretches of amyofibrillar myoplasm.23,24 The size of nuclear clumps is better evaluated in 1 μm semi-thin longitudinally sectioned myofibers (Fig. 8). Here, stretches of amyofibrillar sarcoplasm (15-20 μm wide and 50-100 μm long) alternate with groups of tens of nuclei that fill 20-30 μm long portions of the fibers. These two 0.3 mm long portions of severely atrophic muscle fiber contain 10-30 myonuclei, suggesting that loss of nuclei is substantial at these late stages of muscle atrophy (in normal muscle there are 1000-2000 nuclei per mm of myofiber).25,26

Bottom Line: Whether in mammals, humans included, this is a result of persistent de novo formation of muscle fibers is an open issue we would like to explore in this review.Although embryonic isoforms of acetylcholine receptors are known to be re-expressed and to spread from the end-plate to the sarcolemma of muscle fibers in early phases of muscle denervation, we suggest that the MHCemb positive muscle fibers we observe result from the activation, proliferation and fusion of satellite cells, the myogenic precursors present under the basal lamina of the muscle fibers.Some of the mandatory procedures, are ready to be translated from animal experiments to clinical studies to meet the needs of persons with long-term irreversible muscle denervation.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurorehabilitation, Foundation San Camillo Hospital , I.R.C.C.S., Venice, Italy.

ABSTRACT
Despite the ravages of long term denervation there is structural and ultrastructural evidence for survival of muscle fibers in mammals, with some fibers surviving at least ten months in rodents and 3-6 years in humans. Further, in rodents there is evidence that muscle fibers may regenerate even after repeated damage in the absence of the nerve, and that this potential is maintained for several months after denervation. While in animal models permanently denervated muscle sooner or later loses the ability to contract, the muscles may maintain their size and ability to function if electrically stimulated soon after denervation. Whether in mammals, humans included, this is a result of persistent de novo formation of muscle fibers is an open issue we would like to explore in this review. During the past decade, we have studied muscle biopsies from the quadriceps muscle of Spinal Cord Injury (SCI) patients suffering with Conus and Cauda Equina syndrome, a condition that fully and irreversibly disconnects skeletal muscle fibers from their damaged innervating motor neurons. We have demonstrated that human denervated muscle fibers survive years of denervation and can be rescued from severe atrophy by home-based Functional Electrical Stimulation (h-bFES). Using immunohistochemistry with both non-stimulated and the h-bFES stimulated human muscle biopsies, we have observed the persistent presence of muscle fibers which are positive to labeling by an antibody which specifically recognizes the embryonic myosin heavy chain (MHCemb). Relative to the total number of fibers present, only a small percentage of these MHCemb positive fibers are detected, suggesting that they are regenerating muscle fibers and not pre-existing myofibers re-expressing embryonic isoforms. Although embryonic isoforms of acetylcholine receptors are known to be re-expressed and to spread from the end-plate to the sarcolemma of muscle fibers in early phases of muscle denervation, we suggest that the MHCemb positive muscle fibers we observe result from the activation, proliferation and fusion of satellite cells, the myogenic precursors present under the basal lamina of the muscle fibers. Using morphological features and molecular biomarkers, we show that severely atrophic muscle fibers, with a peculiar cluster reorganization of myonuclei, are present in rodent muscle seven-months after neurectomy and in human muscles 30-months after complete Conus-Cauda Equina Syndrome and that these are structurally distinct from early myotubes. Beyond reviewing evidence from rodent and human studies, we add some ultrastructural evidence of muscle fiber regeneration in long-term denervated human muscles and discuss the options to substantially increase the regenerative potential of severely denervated human muscles not having been treated with h-bFES. Some of the mandatory procedures, are ready to be translated from animal experiments to clinical studies to meet the needs of persons with long-term irreversible muscle denervation. An European Project, the trial Rise4EU (Rise for You, a personalized treatment for recovery of function of denervated muscle in long-term stable SCI) will hopefully follow.

No MeSH data available.


Related in: MedlinePlus