The fate of implanted syngenic muscle precursor cells in injured striated urethral sphincter of female rats.

We studied the outcome of syngenic skeletal muscle precursor cells (MPCs) implanted in the striated urethral sphincter of the female rat. These cells were injected at the site of a longitudinal sphincterotomy performed 21 days before implantation. MPCs were isolated from the striated hindlimb muscles of syngenic adult rats and were infected with a retrovirus carrying the gene for either the green fluorescent protein (GFP) or the beta-galactosidase enzyme (beta-gal).

Mouse sectioned muscle regenerates following auto-grafting with muscle fragments: a new muscle precursor cells transfer?

It was discovered fifty years ago that a minced skeletal muscle replaced in its bed is able to regenerate. This regeneration is due to the presence of quiescent muscle precursor cells so-called satellite cells in the adult muscle which proliferate and fuse to regenerate new centronucleated fibres when the muscle is damaged. These observations open therapeutic perspectives and, in this study, we attempted to test in the mouse whether fragments of minced muscle regenerate new fibres to fill the gap resulting from the trans-section and retraction of the extensor digitorum longus muscle (EDL).

Improvement of urethral sphincter deficiency in female rats following autologous skeletal muscle myoblasts grafting.

Sphincteric deficiency is the most common cause of urinary incontinence in humans. Various treatments have lead to disappointing results due to a temporary benefit. Recent studies raised the possibility that sphincteric deficiency could be treated by implanting skeletal myoblasts.

The urethral striated sphincter in adult male rat.

This study reports the morphology of the urethral sphincter in adult male rats, mainly the histological aspects, the features of the endplates, and the heavy myosin chain distribution in the striated fibres. First, the prostate is entirely out of the striated sphincter, which is surprising when compared to man. Second, the urethral striated sphincter consists of two lateral fascicles separated by an anterior and a posterior strip of connective tissue, which extend from the prostatic urethra (i.

[Cell therapy prospects in Duchenne muscular dystrophy].

Skeletal muscle is made of multinucleated postmitotic fibers which are the agents of contraction. These fibers arise from mononuclear precursor cells which fuse after having migrated from the somites to the site of myogenesis. The cascade of events which result in muscle differentiation is well known nowadays (Sabourin & Rudnicki, 2000).

Fate of implanted syngenic muscle precursor cells in striated urethral sphincter of female rats: perspectives for treatment of urinary incontinence.

Objectives: To analyze the outcome of syngenic skeletal muscle precursor cells (MPCs) after implantation in the striated urethral sphincter of the female rat.

Methods: MPCs were isolated from the striated muscles of the lower limbs and infected with a retrovirus carrying the gene for green fluorescent protein. Approximatively 10(5) cells were injected longitudinally in the striated urethral sphincter of 24 animals using a 10-muL Hamilton syringe.

[Organization and innervation of striated muscle fibers of the striated sphincter in the rat].

Objectives: To determine the organization of striated muscle fibre (FMS) of the rat striated sphincter (SS) and to characterize the motor endplates (MEP).

Material And Methods: The urethras of 30 male and female rats were studied. Two thousand hematein-eosin stained serial sections and 800 sections simultaneously stained for MEPs and nerve endings were studied.

Dose effect relationship between the number of normal progenitor muscle cells grafted in mdx mouse skeletal striated muscle and the number of dystrophin-positive fibres.

The transplantation of progenitor muscle cells in striated skeletal muscle of mdx mice, a model of dystrophin deficiency, is well known to induce the formation of mosaic fibres expressing dystrophin near the site of injection. We tried to determine if the number of injected cells is related to the number of dystrophin-positive fibres. The grafted cells provided by 5 day-old C57Bl10 mice are syngenic to mdx mice and were cultured to select undifferentiated progenitors.

The striated urethral sphincter in female rats.

The aim of this study was to give a microscopic description of the organization, the innervation and the slow or fast type of the striated fibers of the external urethral sphincter in the female rat. Conventional methods for photonic microscopy and immunochemistry were applied to cross and longitudinal sections of snap-frozen urethra. With hematoxylin-eosin stained cross sections, striated fibers are of small diameter and attached directly to the surrounding connective tissue.

Calpain 3 mRNA expression in mice after denervation and during muscle regeneration.

Lack of functional calpain 3 in humans is a cause of limb girdle muscular dystrophy, but the function(s) of calpain 3 remain(s) unknown. Special muscle conditions in which calpain 3 is downregulated could yield valuable clues to the understanding of its function(s). We monitored calpain 3 mRNA amounts by quantitative RT-PCR and compared them with those of alpha-skeletal actin mRNA in mouse leg muscles for different types of denervation and muscle injury.

Loss of calpain 3 proteolytic activity leads to muscular dystrophy and to apoptosis-associated IkappaBalpha/nuclear factor kappaB pathway perturbation in mice.

Calpain 3 is known as the skeletal muscle-specific member of the calpains, a family of intracellular nonlysosomal cysteine proteases. It was previously shown that defects in the human calpain 3 gene are responsible for limb girdle muscular dystrophy type 2A (LGMD2A), an inherited disease affecting predominantly the proximal limb muscles. To better understand the function of calpain 3 and the pathophysiological mechanisms of LGMD2A and also to develop an adequate model for therapy research, we generated capn3-deficient mice by gene targeting.

Skeletal muscle regeneration is not impaired in Fgf6 -/- mutant mice.

FGF6 is a member of the fibroblast growth factor family. The Fgf6 gene is almost exclusively expressed in adult and developing skeletal muscle. We have obtained mice deficient in FGF6 by targeting the Fgf6 gene by homologous recombination.

Comparison of perinatal and adult multi-innervation in human laryngeal muscle fibers.

The innervation of human laryngeal myofibers appears distinct from that of skeletal myofibers, because some of them exhibit multiple neuromuscular junctions. We attempted to understand the significance of the multi-innervation phenomenon by comparing intrinsic laryngeal muscles obtained from autopsies of a fetus, a stillbirth, and a 7-month-old infant to muscles from adults. In longitudinal sections (40 to 60 microm thick) the cholinesterase sites and the nerve terminals were stained simultaneously for light microscopy.

Successful myoblast transplantation in fibrotic muscles: no increased impairment by the connective tissue.

Background: Implantation of normal myoblasts may eventually be a treatment for inherited myopathies such as Duchenne muscular dystrophy.

Methods: We report a comparative study of the effectiveness on myoblast implantation: (1) into the muscles of young (2 months) mdx mice nonirradiated and noninjected with notexin (group 1), (2) into muscles of old mdx mice (15 months) nonirradiated and noninjected with notexin (group 2), and (3) into muscles of 5 months mdx mice irradiated 3 months before the transplantation (group 3). Roughly 3 million cells were injected with bFGF in the Tibialis anterior.

Hindlimb immobilization applied to 21-day-old mdx mice prevents the occurrence of muscle degeneration.

Dystrophin-deficient skeletal muscles of mdx mice undergo their first rounds of degeneration-regeneration at the age of 14-28 days. This feature is thought to result from an increase in motor activity at weaning. In this study, we hypothesize that if the muscle is prevented from contracting, it will avoid the degenerative changes that normally occur.

Mouse muscle regeneration: an in vivo 2D 1H magnetic resonance spectroscopy (MRS) study.

Muscle degeneration and regeneration were studied by 2D 1H magnetic resonance spectroscopy (MRS) and histological examination, in an experimental model of muscle injury using a myotoxic snake venom, notexin. The injured muscles produced a very specific MRS signal, corresponding to a tri-unsaturated fatty acid (linolenic acid-like) signal, from day 2 to day 9 after injury. The combination of MRS with histology showed that this signal was associated with a mechanism occurring during myoblast fusion to form myotubes.

Apparent normal phenotype of Fgf6-/- mice.

To study the role of the sixth member of the FGF (fibroblast growth factor) family whose expression is restricted to skeletal muscle, we have derived mouse mutants with a homozygous disruption of the Fgf6 gene. The animals are viable, fertile and apparently normal, indicating that FGF6 is not required for vital functions in the laboratory mouse.

Selective motor hyperreinnervation using motor rootlet transfer: an experimental study in rat brachial plexus.

Misdirection of sensory fibers into motor pathways is, in part, responsible for the poor results obtained after peripheral nerve repair. After avulsion of the C-5 root in rats, the authors connected a C-4 ventral rootlet to the musculocutaneous nerve by means of a sural nerve graft. In this way, they were able to increase the number of regenerating motor fibers and avoid growth of sensory fibers into the nerve grafts.

Innervation of adult human laryngeal muscle fibers.

The innervation of laryngeal muscle fibers was appraised in adult humans. Sixteen intrinsic laryngeal muscles were dissected during the autopsy of 4 adults (41-71 years old). Longitudinal serial frozen sections, 60 microm thick, of the whole muscles were double-stained for cholinesterase activity and axonal visualization.

Angiogenic and inflammatory responses following skeletal muscle injury are altered by immune neutralization of endogenous basic fibroblast growth factor, insulin-like growth factor-1 and transforming growth factor-beta 1.

Injured skeletal muscle degeneration comprises early microvascular changes and inflammatory cell infiltration, possibly under the control of several growth factors. We have studied the role of basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF1), and transforming growth factor beta-1 (TGF beta 1), by injecting specific anti-growth factor neutralizing antibodies into mouse extensor digitorum longus muscle at the time of injury (denervation and devascularization). Four days later, at the height of damaged myofiber phagocytosis, we assessed quantitatively revascularization, phagocytic activity, and inflammation.

Factors inducing mast cell accumulation in skeletal muscle.

It has been suggested that mast cells contribute to the phenotype of dystrophinopathies, but the mechanisms of their recruitment into the skeletal muscle remain hypothetical. The aim of this study is to quantify the presence of mast cells in muscle during the cellular events of myofibre degeneration and regeneration. For this purpose, we compare the mast cell profile in dystrophin-deficient mdx mice in which muscles exhibit spontaneous cycles of degeneration-regeneration from 3 weeks of age, with that in Swiss mice in which muscles were injured either by ischaemia or by notexin injection.

Basic fibroblast growth factor promotes in vivo muscle regeneration in murine muscular dystrophy.

Due to the lack of dystrophin, a subsarcolemmal protein, mdx mutant mice undergo spontaneous rounds of myofiber necrosis-regeneration from the age of weaning. Muscle regeneration is likely to be controlled by basic fibroblast growth factor (bFGF) which is detectable in regenerating areas of mdx muscles. Moreover, the proliferation of mdx satellite cells seems to be particularly sensitive to bFGF in culture.

The cellular events of injured muscle regeneration depend on the nature of the injury.

The cellular events of muscle degeneration and regeneration and their time course were studied in two experimental models of muscle injury mice; (i) the denervation-devascularization (DD) of the extensor digitorum longus (EDL) muscle, which is an ischaemic lesion; (ii) the injection of notexin (NOT), a snake venom, in the tibialis anterior (TA) muscle, resulting in a toxic lesion. Compared to the ischaemic lesion, the toxic lesion was characterized by a more extensive inflammatory infiltrate and a shortened phase of phagocytosis of the damaged myofibres. This allowed the proliferation and differentiation of muscle precursor cells (mpc) to take place earlier and may be further promoted by growth factors released by inflammatory cells.