Biomedical subjects

Gillian S Butler-Browne

Publications and source records attributed to Gillian S Butler-Browne.

9 recordsLinked to original sources

PubMed2006

Human muscle stem cells.

Stem cells are unspecialized cells that have been defined in many different ways but they have two important characteristics that distinguish them from other cells in the body. First, they can replenish their numbers for long periods through cell division. Second, after receiving certain chemical signals, they can produce, through asymmetric cell division, a progeny that can differentiate or transform into specialized cells with specific functions, such as heart, nerve or muscle. In recent years, stem cells have received much attention owing to their potential use in cell-based therapies for human neurodegenerative diseases such as Parkinson's disease, stroke and muscular dystrophies. However, many questions need to be resolved before stem cells with myogenic potential are used in clinical standard protocols.

Animals↗

PubMed2005

Comparative analysis of genetically engineered immunodeficient mouse strains as recipients for human myoblast transplantation.

The development of an optimized animal model for the in vivo analysis of human muscle cells remains an important goal in the search of therapy for muscular dystrophy. Here we examined the efficiency of human myoblast xenografts in three distinct immunodeficient mouse models. We found that different conditioning regimes used to provoke host muscle regeneration (i.e., cardiotoxin versus cryodamage) had a marked impact on xenograft success. Tibialis anterior muscle of Rag2-, Rag-/gammac-, and Rag-/gammac-/C5- mice was treated by cardiotoxin or cryodamage, submitted to enzymatic digestion, and analyzed by cytofluorometry to quantitate inflammatory cells. Human myoblasts were injected into pretreated muscles from immunodeficient recipients and the cell engraftment evaluated by immunocytochemistry, 4-8 weeks after transplantation. Donor cell differentiation and dispersion within the host muscles was also investigated. Host regeneration in cardiotoxin-treated mice was accompanied by a higher inflammatory cell infiltration when compared to that induced by cryodamage. Accordingly, when compared to the cardiotoxin group, more human myogenic cells were found after cryodamage. When the distinct immunodeficient mice were compared, we found that the alymphoid strain lacking the complement component C5 (Rag-/gammac-/C5- mice) was the most efficient host for human muscle xenografts, when compared with C5(+)Rag-/gammac- mice or Rag- mice. Our results demonstrate that cryolesion-conditioned muscles of Rag-/gammac-/C5- mice provide the best environment for long-term in vivo human myoblast differentiation, opening the way for a novel approach to study the pathophysiology of human muscle disorders.

Animals↗

PubMed2004

Human circulating AC133(+) stem cells restore dystrophin expression and ameliorate function in dystrophic skeletal muscle.

Duchenne muscular dystrophy (DMD) is a common X-linked disease characterized by widespread muscle damage that invariably leads to paralysis and death. There is currently no therapy for this disease. Here we report that a subpopulation of circulating cells expressing AC133, a well-characterized marker of hematopoietic stem cells, also expresses early myogenic markers. Freshly isolated, circulating AC133(+) cells were induced to undergo myogenesis when cocultured with myogenic cells or exposed to Wnt-producing cells in vitro and when delivered in vivo through the arterial circulation or directly into the muscles of transgenic scid/mdx mice (which allow survival of human cells). Injected cells also localized under the basal lamina of host muscle fibers and expressed satellite cell markers such as M-cadherin and MYF5. Furthermore, functional tests of injected muscles revealed a substantial recovery of force after treatment. As these cells can be isolated from the blood, manipulated in vitro, and delivered through the circulation, they represent a possible tool for future cell therapy applications in DMD disease or other muscular dystrophies.

AC133 Antigen↗

PubMed2003

Changes in myotonic dystrophy protein kinase levels and muscle development in congenital myotonic dystrophy.

Myotonic dystrophy (DM1) is caused by the expansion of a CTG repeat in the noncoding region of a protein kinase, DMPK, expressed in skeletal and cardiac muscles. The aim of the present study was to determine the effects of very large CTG expansions on DMPK expression and skeletal muscle development. In fetuses suffering from the severe congenital form of DM1 with large CTG expansions (1800 to 3700 repeats), the skeletal muscle level of DMPK was reduced to 57% of control levels and a similar reduction was observed in cultured DM1 muscle cells relative to control cultures. These results are consistent with greatly reduced DMPK expression from the mutant allele and normal expression from the unaffected allele in this autosomal dominant disorder. In normal fetuses, DMPK protein levels increased dramatically between 9 and 16 weeks and remained high throughout the remaining gestation period. DM1 fetuses showed impaired skeletal muscle development, characterized by a persistence of embryonic and fetal myosin heavy chains and almost total absence of slow myosin heavy chains at the end of gestation. DMPK expression, however, was similar in both fast and slow fibers from normal adult muscle. The reduced DMPK and the delayed slow fiber maturation in congenital DM1 may be two separate consequences of nuclear retention of DMPK RNA transcripts with expanded CUG repeats.

Cell Differentiation↗

PubMed2003

Athletes with exercise-associated fatigue have abnormally short muscle DNA telomeres.

INTRODUCTION/PURPOSE: Although the beneficial health effects of regular moderate exercise are well established, there is substantial evidence that the heavy training and racing carried out by endurance athletes can cause skeletal muscle damage. This damage is repaired by satellite cells that can undergo a finite number of cell divisions. In this study, we have compared a marker of skeletal muscle regeneration of athletes with exercise-associated chronic fatigue, a condition labeled the "fatigued athlete myopathic syndrome" (FAMS), with healthy asymptomatic age- and mileage-matched control endurance athletes. METHODS: Muscle biopsies of the vastus lateralis were obtained from 13 patients diagnosed with FAMS and from 13 healthy control subjects. DNA was extracted from the muscle samples and their telomeric restriction fragment (TRF) or telomere lengths were measured by Southern blot analysis. RESULTS: All 13 symptomatic athletes reported a progressive decline in athletic performance, decreased ability to tolerate high mileage training, and excessive muscular fatigue during exercise. The minimum value of TRF lengths (4.0 +/- 1.8 kb) measured on the DNA from vastus lateralis biopsies from these athletes were significantly shorter than those from 13 age- and mileage-matched control athletes (5.4 +/- 0.6 kb, P < 0.05). Three of the FAMS patients had extremely short telomeres (1.0 +/- 0.3 kb). The minimum TRF lengths of the remaining 10 symptomatic athletes (4.9 +/- 0.5 kb, P < 0.05) were also significantly shorter that those of the control athletes. CONCLUSION: These findings suggest that skeletal muscle from symptomatic athletes with FAMS show extensive regeneration which most probably results from more frequent bouts of satellite cell proliferation in response to recurrent training- and racing-induced muscle injury.

Adult↗

PubMed2003

Telomerase can extend the proliferative capacity of human myoblasts, but does not lead to their immortalization.

Normal cells in culture display a limited capacity to divide and reach a non-proliferative state called cellular senescence. Spontaneous escape from senescence resulting in an indefinite life span is an exceptionally rare event for normal human cells and viral oncoproteins have been shown to extend the replicative life span but not to immortalize them. Telomere shortening has been proposed as a mitotic clock that regulates cellular senescence. Telomerase is capable of synthesizing telomere repeats onto chromosome ends to block telomere shortening and to maintain human fibroblasts in proliferation beyond their usual life span. However, the consequence of telomerase expression on the life span of human myoblasts and on their differentiation is unknown. In this study, the telomerase gene and the puromycin resistance gene were introduced into human satellite cells, which are the natural muscle precursors (myoblasts) in the adult and therefore, a target for cell-mediated gene therapy. Satellite cells expressing telomerase were selected, and the effects of the expression of the telomerase gene on proliferation, telomere length, and differentiation were investigated. Our results show that the telomerase-expressing cells are able to differentiate and to form multinucleated myotubes expressing mature muscle markers and do not form tumors in vivo. We also demonstrated that the expression of hTERT can extend the replicative life of muscle cells although these failed to undergo immortalization.

Cell Differentiation↗

PubMed2002

Muscle-specific alternative splicing of myotubularin-related 1 gene is impaired in DM1 muscle cells.

The myotubularin-related 1 (MTMR1) gene belongs to a highly conserved family of eucaryotic phosphatases, with at least 11 members in humans. The founder member of this gene family, MTM1, is mutated in X-linked myotubular myopathy, a severe congenital disorder that affects skeletal muscle, and codes for myotubularin, a specific phosphatidylinositol 3-phosphate [PI(3)P] phosphatase. MTM1 and MTMR1 are adjacent on the X chromosome, and the corresponding proteins share 59% sequence identity. In the present study, we investigated the putative role of MTMR1 in myogenesis by analysing its expression pattern in muscle cells during differentiation and in skeletal muscle throughout development. We have identified three novel coding exons in the MTMR1 intron 2 that are conserved between mouse and human, are alternatively spliced, and give rise to six mRNA isoforms. One of the transcripts is muscle-specific and is induced during myogenesis both in vitro and in vivo, and represents the major isoform in adult skeletal muscle. We show that the two main MTMR1 protein muscular isoforms, like myotubularin, efficiently dephosphorylate PI(3)P in vitro. We have also analysed whether MTMR1 alternative splicing is affected in skeletal muscle cells derived from patients with congenital myotonic dystrophy (cDM1), in which mRNA splicing disturbances of specific genes are thought to constitute an important pathogenic mechanism. We found a striking reduction in the level of the muscle-specific isoform and the appearance of an abnormal MTMR1 transcript in differentiated cDM1 muscle cells in culture and in skeletal muscle from cDM1 patients. Our results suggest that MTMR1 plays a role in muscle formation and represents a novel target for abnormal mRNA splicing in myotonic dystrophy.

Alternative Splicing↗

PubMed2002

Contractile properties, structure and fiber phenotype of intact and regenerating slow-twitch muscles of mice treated with cyclosporin A.

We have studied the contractile properties, structure, fiber-type composition, and myosin heavy chain (MyHC) expression pattern of regenerating and intact soleus muscles of adult CBA/J mice treated with cyclosporin A (CsA) or vehicle solutions (Cremophor, saline). A comparison of muscles after 4-7 weeks drug application with those receiving vehicle showed that the isometric contractile force of intact drug-treated muscles was reduced (tetanus, -21%; twitch, -34%) despite normal mass and muscle cross-sectional area. The frequency of fast-twitch fibers was increased, whereas no innervation deficits, histopathological alterations, or changes in fiber numbers were observed. Regeneration after cryolesion of the contralateral soleus proceeded more slowly in CsA-treated than in vehicle-treated animals. Despite this, when muscle properties reached mature levels (4-7 weeks), muscle mass recovery was better in CsA-treated animals (30% higher weight, 50% more fiber profiles in cross-sections). The force production per unit cross-sectional area was deficient, but not the maximum tension. Twitch time-to-peak and half-relaxation time were shorter than controls correlating with a predominance of fast-twitch fibers (98% Type II fibers versus 16%-18% in control muscles) and fast MyHC isoforms. Partial reversal of this fast phenotype and an increase in muscle force were observed when the animals were left to recover without treatment for 5-8 weeks after CsA application over 7 weeks. The high numbers of fiber profiles in CsA-treated regenerated muscles and increased mass remained unchanged after withdrawal. Thus, CsA treatment has a hyperplastic effect on regenerating muscles, and drug-induced phenotype alterations are much more prominent in regenerated muscles.

Animals↗

PubMed1998

Pathological mechanisms implicated in localized female trapezius myalgia.

Myalgia localized to the neck and shoulder in women is a growing problem both in the general population and in the industrial world. The aim of this study was to investigate the mechanisms involved in work-related myalgia. In 21 women (age, 38.7+/-5.5 years), muscle biopsies were obtained from the upper part of the trapezius and the morphologic and metabolic characteristics of muscle fibres were analyzed. The patients indicated the number of painful areas on a pain drawing and the intensity of pain was assessed using a visual analogue scale (VAS). Two groups were formed on the basis of the median values: lower pain level and higher pain level. Trapezius muscles were characterized by the large size of type I fibres and the low capillary to fibre area ratio for both type I and type IIA fibres. Patients with the highest pain scores had the lowest capillary to fibre area ratio for type I fibres (coefficient correlation r = -0.45 and P < 0.05). Moreover, the proportion of cytochrome c oxidase (COX)-negative fibres seen in the cross-sections was significantly higher in the group of patients which had the higher pain and more painful areas than in the group of patients with lower pain level and painful areas (P < 0.05). The significant increase (P < 0.05) of the size of the type I fibres in trapezius myalgia point to the special strain imposed upon type I muscle fibres during work tasks. Cytochrome oxidase c deficiency which is indicative of an energy crisis within muscle cells and the low capillary to fibre area ratio which might impair oxygen delivery and removal of metabolites in the working muscles are both associated with pain in the trapezius muscle.

Adult↗