Inducing muscle hypertrophy as a therapeutic strategy for muscular dystrophies

Eighteen participants from 5 countries (France, Germany, Italy, UK and USA) participated in an ENMC workshop on the topic of “Inducing muscle hypertrophy as a therapeutic strategy for muscular dystrophies”.

Muscle atrophy is observed both in muscular dystrophies and aging. Numerous approaches have been demonstrated to induce muscle hypertrophy that could be used as a mean to reverse muscle atrophy. This workshop brought together scientists and clinicians  working on cellular and molecular aspects of this process that could be exploited as a treatment for these muscle wasting conditions.

Four aspects were discussed in detail. The first topic concentrated on cellular aspects of muscle hypertrophy and in particular on the role of satellite cells. Satellite cells are a reservoir of precursors that lay in a dormant state in muscle and are recruited during phases of muscle growth and to repair damaged tissue. An important new concept to emerge from this meeting was that not all satellite cells are able to participate to the muscle regeneration. This raises the possibility of isolating those cells which are particularly able to participate to the regeneration process. In addition, evidence was presented that the efficiency of satellite cells recruitment can differ in different neuromuscular conditions. A new therapeutic avenue was presented raising the possibility of using cells other than satellite cells as a mean of addressing muscle atrophy. In particular cells from the circulatory system were shown to be able to cross the capillary bed into muscle and participate in muscle growth and repair of an animal model of muscular dystrophy.

The second topic concentrated on the mechanism by which muscles enlarge and how they undergo atrophy. Work was presented that showed that the two processes are linked by a molecule, called Akt that not only regulates protein synthesis, but also inhibits molecules involved in protein breakdown (atrofin-1 and FOXO). The role that this pathway plays in a number of conditions characterized by muscle atrophy will now have to be explored.

The third topic concentrated on secreted factors that regulate muscle growth. Particular attention was paid to a molecule called IGF-1 and similar proteins that were shown to induce muscle hypertrophy. A variant of one of these was shown to play a significant role in muscle growth following exercise.

The last session concentrated on the novel discovery of a factor that prevents muscle development, myostatin. Gene targeting that removes this protein showed massive increase in muscle formation. Strategies were discussed aimed at developing molecules that would antagonize the function of this protein as a therapeutic means to address muscle wasting. Similarities were drawn between the development of muscle during embryonic and adult life and the role of myostatin.
A discussion consolidated the four topics in this workshop and brought together the molecules and mechanisms by which muscle atrophy develops and how can be alleviate. Collaborative strategies were set up to evaluate these hypothesis.

An extended report of this meeting has been published in Neuromuscular Disorders. To access the full report, please click here.

Prof. Francesco Muntoni and Dr. Ketan Patel, London, UK

DESMIN and Protein Aggregate MyopathiesDESMIN and Protein Aggregate Myopathies

Over the past decade, altoghether four ENMC-sponsored multinational, multidisciplinary workshops were devoted to desmin (“Desmin in myology” in 1995; “Familial desmin-related myopathies and cardiomyopathies – from myopathology to molecular and clinical genetics” in 1996; “Desmin – protein surplus myopathies” in 2001), desmin-related myopathies and other protein aggregate myopathies. The last one convened 16 researchers from 6 European countries (France, Germany, Poland, Spain, Sweden and the U.K.) and the U.S.A.

The term “protein aggregate myopathies” indicates that proteins aggregate within muscle fibres as an important nosological feature. Desmin and other proteins accrue in desminopathies owing to mutations in the desmin, alpha B crystalline and unknown genes. A recently identified subgroup is caused by mutations in the selenoprotein 1 (SEPN1) gene.

The ENMC participants discussed the mutational spectrum of desmin, mutant desmin in in-vitro and in transgenic mice as well as the role of desmin-associated proteins. The spectrum of mutations in the desmin gene has been broadened considerably since the last workshop, two years ago. Now more than 19 missense and 5 other mutations have been identified, but 60% of patients with the phenotype of desmin-related myopathies do not show mutations in desmin or alpha B crystallin. The significance of cardiac involvement has also become more apparent as reported at this workshop. A new class of myopathies, Myosin myopathies, now encompasses myosin storage myopathies (formerly hyaline body myopathy) due to mutations in the myosin heavy chain I and IIa (formerly IBM3). While the pathogenesis of aggregation of mutant and non-mutant proteins is still incompletely clarified, the proteasome pathway appears to be involved.

Further understanding of pathogenetic principles in this protein aggregation will enable meaningful approaches to therapy. Future research will concentrate on those familial desmin-related myopathies (DRM) genetically not yet identified, on the connotation of sporadic DRM, and on investigations of the pathogenetic principles of protein aggregation.

It may safely be stated that this series of four ENMC-sponsored workshops on desmin and related myopathies has considerably enlarged awareness, recognition and research on desmin diseases and other protein aggregate myopathies marked by abnormal accumulation of proteins within muscle fibres. They have attested and will continue to attest to the importance and success of multidisciplinary and multinational collaborative research, being one of the reasons for ENMC workshops and one of the main aims of ENMC.

An extended report of this meeting has been published in Neuromuscular Disorders. To access the full report, please click here.

Prof. H.H. Goebel (Mainz, Germany)
Prof. M. Fardeau (Paris, France)

Clinical Trials of Minocycline in Amyotrophic Lateral Sclerosis (ALS)

An ENMC Workshop organised by the European ALS Consortium

The ENMC hosted a Workshop organised by the clinical trials group of the European ALS (Amyotrophic Lateral Sclerosis; motor neurone disease-MND) Consortium. The main aim of the Workshop was to develop a protocol for an academic-led, multi-center, multi-national trial of minocycline in ALS. The Workshop was attended by 16 participants from 7 European countries (Belgium, France, Germany, Italy, The Netherlands, Russia and the United Kingdom) with one participant from the U.S.A. Participants included neurobiologists, statisticians, a representative of an ALS user group (The MND Association), a clinical trials coordinator, and clinical neurologists. Evidence from experiments in cell lines, primary neuronal cultures, and transgenic SOD1 mice provides a convincing rationale for a trial of minocycline in ALS, although it is not possible to predict from the mouse data what dose(s) should be used in ALS patients. Pharmacokinetic studies in man suggest that doses of 100mg-200mg daily would achieve reasonable state levels of minocycline. Safety data is available from three North American phase 2 studies in patients with Huntington’s Disease and ALS. There were no major safety concerns. The Workshop decided that another phase 2 trial is not necessary. There was consensus that a pragmatic phase 3 add-on trial (i.e., riluzole plus placebo, versus minocycline plus placebo) should be undertaken, with survival (death) as the primary end-point. The ALSFRS-R and a quality of life questionnaire (probably the Euroqol) should be secondary outcome measures. It was agreed that one minocycline dose should be tested. Professors Leigh and Meininger, on behalf of the European ALS Consortium, will develop a strategy to obtain core funding with contributions from participating countries. Issues of sponsorship under the European Directive on Clinical Trials remain to be resolved.

Prof. V. Meininger, Paris, France
Prof. P.N. Leigh, London, United Kingdom


Trial design in adult idiopathic inflammatory myopathies, with the exception of inclusion body myositis

20 Participants from Belgium, Czech Republic, France, Germany, Italy, The Netherlands, Spain, Sweden, UK, and USA met in Naarden (The Netherlands) from 10-12 October, 2003. The group comprised neurologists and rheumatologists involved with research into the treatment of the idiopathic inflammatory myopathies, as well as experts in statistics and clinical trial design.
Improvements in the treatment of patients with polymyositis (PM) or dermatomyositis (DM) are hampered by difficulties in the design of randomized controlled trials (RCTs) and the low incidence and prevalence of patients. Therefore the aims of this workshop were twofold. The first was to make progress towards reaching consensus on main issues in the design of RCTs for PM/DM, notably diagnostic criteria, outcome measures, definitions of relapse and treatment failure, and trial duration. This was addressed by first reviewing and discussing the design and conduct of completed and ongoing RCTs in PM/DM, and pinpointing specific difficulties. Subsequently, we discussed proposals concerning each of these issues. It was agreed that diagnostic criteria should allow the exclusion of other diseases and also should allow a diagnosis based on the underlying pathogenesis, while at the same time these criteria should be broadly applicable in pragmatic clinical trials. Agreement was reached on major aspects of the proposed diagnostic criteria. With respect to outcome measures, we discussed the ongoing studies by the International Myositis Assessment and Clinical Study group (IMACS). We agreed on the specification of several of the IMACS core set measures and of several other relevant outcome endpoints.
The second aim was to explore the possibilities of international RCTs for PM/DM. It was emphasized that different efforts can be undertaken by specific networks (e.g., validation of outcome measures), and that the results can be made easily available to other networks or individuals through ENMC. Several organizational aspects were discussed. One session was dedicated to potentially immunosuppressive and immunomodulating therapies in myositis,including new drugs. Participants were invited to collaborate in two European RCTs which are currently running or about to start.
This was an enjoyable and fruitful workshop that will lead to new collaborations and will contribute significantly to the improvement of therapeutic RCTs for myositis in both Europe and North America.

An extended report of this meeting is published in Neuromuscular Disorders, Volume 14, No. 5, May 2004.

Dr. J.E. Hoogendijk, The Netherlands
Dr. A.A. Amato, U.S.A.
Dr. B.R.F. Lecky, United Kingdom


Advances in Myotubular Myopathy

The ENMC consortium on advances in myotubular myopathy (MTM) held its 6th Workshop in Naarden, the Netherlands, the weekend from 26-28th September 2003. It was attended by 19 active participants from Australia, Finland, France, Germany, Italy, Switzerland, the United Kingdom and the USA. The meeting opened with an overview on the genotype-phenotype correlation on 340 families and 196 different mutations in the myotubularin gene (MTM1) in order to predict severity of manifestations with the type of mutation and domain position. Most were private mutations but 7 mutations were more recurrent and most were found in exons 4-8-12. Direct exon sequencing improves molecular diagnosis in relation to other screening methods. Manifesting carriers of MTM1 are rare (3 out of 43 studied).
In addition to mutation analysis the protein status can be studied by immunoprecipitation but not yet routinely.
A whole morning was concentrated on studies that try to unravel the subcellular localization and the function of MTM1 and myotubularin related proteins (MTMRs), highlighting the specific substrates, the catalytic activities and the crystallographic structure of MTMR2. Preliminary observations show that MTMRs are expressed ubiquitously but their amount of expression varies differently among tissues. Two MTMRs are responsible for 2 forms of demyelinating Charcot-Marie-Tooth neuropathies (CMT) type 4B1 (MTMR2) and CMT4B2 (MTMR13/SBF2), showing characteristic myelin outfoldings at the nerve biopsy. The knock out mouse model of MTM1 showed many similarities with the human disorder. There was a moderate growth deficiency at birth and progressive muscle weakness together with appearance of muscle fibers showing central nuclei. Fibers were normally differentiated and showed no significant necrosis and regeneration, but fiber atrophy with structural disorganization was found. This model seems promising for therapeutic strategies.
A review on clinical and histopathological aspects of autosomal dominant and autosomal recessive centronuclear myopathies was presented. Following the chromosomal localization of a canine model to chromosome 2 and searching on the syntenic human region on chromosome 10, a candidate gene coding for a tyrosine phosphatase-like protein was chosen but yielded no mutations in some autosomal dominant and recessive patients with centronuclear myopathy. Moreover a genome wide search on a few autosomal dominant families indicated a new chromosomal locus but further confirmation is required adding other informative families. In patients with no mutations in MTM1 and in the myotonic dystrophy gene a candidate gene approach is on-going to find new disease genes for centronuclear myopathies.
A few patients with pathogenetic mutations in the MTM1 gene showed an overgrowth syndrome which may be related to abnormally increased levels of IGFs. The workshop consortium agreed to collect serum from MTM1 patients to confirm these trophic factor abnormalities.

An extended report of the meeting will be submitted for publication in Neuromuscular Disorders.

Prof. Enrico Bertini (Rome, Italy)
Dr. Wolfram Kress (Würzburg, Germany)


Ventilatory Support in Congenital Neuromuscular Disorders: Congenital Myopathies, Congenital Muscular Dystrophies, Congenital Myotonic Dystrophy and SMA (II)

Eighteen participants from Austria, Denmark, Finland, France, Germany, The Netherlands, the UK, and the USA met in Naarden, representing a variety of disciplines with experience in the respiratory management of patients with neuromuscular diseases. As much data exist on the natural history and management of respiratory impairment in DMD, this meeting concentrated on other childhood neuromuscular diseases including the congenital muscular dystrophies, spinal muscular atrophy type 2 and the congenital myopathies. The accumulated experience of the group included over 500 patients with these disorders, of whom overall around one third were receiving some kind of ventilatory support.
The aims of this workshop were two-fold. The first was to improve the situation for patients around the world with respiratory problems due to neuromuscular disorders who may not currently be receiving adequate medical attention. This was addressed by defining the scope of the respiratory problems in these disorders and by developing practically applicable guidelines for the diagnosis and treatment of respiratory insufficiency in this group of patients. The guidelines were developed at the workshop based on review of the published evidence base and the experience and current clinical practise of the assembled expert group. A set of guidelines for the assessment and treatment of these diseases was generated and will be published in Neuromuscular Disorders. An important message of the workshop was that patients with these disorders may be at risk of respiratory problems but proper management of these problems can be very effective.
The second aim was to address the current shortages of sound scientific data on the efficacy of assessment techniques, prophylactic measures and various modes of treatment for respiratory insufficiency due to neuromuscular disorders, in particular for children with congenital conditions.

An extended report of this meeting is published in Neuromuscular Disorders, Volume 14, No. 1, January 2004.

Dr. C. Wallgren-Pettersson (Finland)
Prof. K. Bushby (United Kingdom)
Dr. U. Mellies (Germany

Treatment of mitochondrial disease

Eighteen participants from Denmark, Finland, France, Germany, Italy, Norway, Spain, Sweden, The Netherlands, the U.K. and the U.S.A. met in Naarden to discuss the treatment of mitochondrial disorders in children and adults. The group included adult and paediatric neurologists, metabolic paediatricians, an ophthalmologist, an endocrinologist, and other clinical scientists. The workshop concentrated on disorders that result from mitochondrial respiratory chain (MRC) dysfunction.
Since we know that MRC dysfunction may produce a great variety of different diseases, one of the first topics discussed was the nature and size of the problem. Figures from Sweden have shown an incidence in children under 6 years of 1/11,000. The same study showed prevalence figures of 1/21,000 in the paediatric population (<16). Studies from the UK looking at adults gave a potential prevalence of 1/8,000 and combining the figures for children and adults suggests that MRC disease is far from rare, and may occur as frequently as 1/8,500.
The next topic discussed was methods of assessing disease severity. This is an extremely difficult but essential area if we are to find methods with which to assess treatment response. It was clear from the discussions that we lack clear data concerning the natural history of MRC disease. Participants discussed their use of clinical investigations, such as the measurement of lactate in blood, imaging modalities and MRS, as well as biochemical and genetic methods of analysis. Whilst indirect measures of disease, such as lactate are used often, these were not felt to be good enough to measure disease severity. Biochemical measurement of MRC activity, including histochemistry, established the diagnosis, but could not be used to follow the disease. The same applied to genetic analysis, such as measurement of mutation load. For certain manifestations such as hearing impairment and ophthalmoplegia, it appears possible to use existing technologies to follow progression or indeed treatment response. In addition, the use of non-invasive techniques based on exercise testing offers an exciting possibility of follow disease progression or treatment in those patients having muscle manifestations.
The third major area of discussion concerned the current best practice for the treatment of mitochondrial disease. It appears that much of our management of patients with MRC disease is based on anecdotes or case-reports of single or small numbers of patients. Whilst many of the participants used a variety of supplements, including ubiquinone, nicotinamide, riboflavin, vitamin E and carnitine, with varying degrees of success, it was generally accepted that there was insufficient data to know whether response was real or simply natural fluctuation in disease severity. Dichloroacetate treatment is being evaluated in larger clinical trials, but individual experience suggested that this had little impact on disease and should be confined to acute use where lowering of lactate concentration and thus improvement of acidosis is the goal. The treatment of specific manifestations such as seizures, cardiac dysfunction, hearing loss and general nutrition was felt to be extremely valuable in appropriate individuals and something that should be stressed since these interventions improve quality of life significantly. A number of novel treatments including genetic manipulations were also discussed and experience with these techniques is growing. Apart from gene-shifting experiments, where satellite cell proliferation is induced in the hope that this will replace diseased with normal muscle, none are yet at the point where they can be used on patients.
From our discussions we were able to produce two documents, a consensus statement on the current best practice for the treatment of mitochondrial disorders and a draft clinical rating scale for mitochondrial disorders. The rating scale will hopefully form the basis of future joint clinical studies. The participants stressed the importance of the European collaboration and it was agreed that the group should form an ENMC consortium with the aim to meet again in 12 to 18 months to consolidate the links and compare prospectively collected natural history data and treatment experiences.

An extended report of this meeting is published in Neuromuscular Disorders, Volume 13, No. 9, November 2003.

Dr. P. Chinnery (Newcastle, U.K.)
Dr. L. Bindoff (Bergen, Norway)

DM2/PROMM and other myotonic dystrophies

The ENMC consortium on myotonic dystrophy type 2 (=DM2/PROMM) held its 3rd workshop in Naarden, the Netherlands, 14-16th February 2003. It was attended by 22 active participants from Finland, France, Germany, Italy, the Netherlands, Spain, the United Kingdom and the USA. The meeting opened with an overview of the main scientific progress in the molecular genetics since its 2nd workshop held in 2000: The identification of the mutation responsible for the myotonic dystrophy type 2 disease. Participants now reported on the occurrence of the mutation in the previously DM2-linked and unlinked families. The results of these analyses show that all DM2-linked families harbor the same mutation defect, an unusually large CCTG-repeat expansion of the DNA on chromosome 3q21. Morover, all families previously reported as DM2-unlinked PROMM families also proved to have the same CCTG-repeat expansion mutation. The diagnosis does not yet provide possibilities for therapy, but it is of great importance for the patients to correctly understand their symptoms and to get the best possible management. However, the DNA analysis for definite mutation detection is difficult, and not yet largely available as a routine diagnostic procedure. The workshop consortium agreed on sharing methological protocols in order to find the optimal molecular diagnostic procedure. For the routine diagnostic work-up, the identification of muscle fiber type 2 atrophy on muscle biopsy specimens may be helpful in selecting patients for molecular genetic testing. Some new diagnostic methods based on tissue in situ hybridization were also introduced. Much of the workshop was advocated to the next task for the scientific research efforts: the understanding of the abnormal events taking place in the muscles and other affected organs caused and directed by the DM2 mutation, in order to answer scientific questions like: Why is there no detectable correlation between the expansion size of the DM2 mutation and the clinical severity of the disease? Why is the reproductive system so much better protected against the consequences of the DM2 mutation in comparison to myotonic dystrophy type 1 (=Steinert’s disease)? The identification of the DM2 mutation has greatly improved the understanding of the basic molecular abnormalities also in Steinert’s disease.

An extended report of this meeting is published in Neuromuscular Disorders, Volume 13, No. 7-8, September 2003.

Dr. B. Udd (Finland)
Dr. R. Krahe (U.S.A.)

Congenital Muscular Dystrophy (CMD)

9th Workshop of the International consortium on CMD/3rd Workshop of the MYO CLUSTER project GENRE

The ENMC Consortium on Congenital muscular dystrophy (CMD) held its 8th meeting in Narden during the weekend of the 17th-19th January 2003. It was attended by 25 participants from 9 countries, including Austria, Finland, France, Germany, Italy, The Netherlands, Turkey, United Kingdom and USA. This workshop was sponsored by the European Community as part of the Myocluster project GENRE. The participants were basic scientists with biochemical and molecular biology background, and clinicans and muscle pathologists, all sharing a substantial expertise in neuromuscular disorders.

Congenital muscular dystrophies (CMD) are a heterogeneous group of disabling neuromuscular disorders inherited as autosomal recessive conditions. Affected children present with muscle weakness and hypotonia at birth, or within the first six months of life and motor development is delayed. The severity and progression of the disease is very variable and dependent on the disease subtype. Brain involvement in the form of mental retardation and abnormal formation of different parts of the brain is a feature of several forms of CMD.

The present meeting focused on a group of CMD syndromes characterized by deficiency in proteins with enzymatic activity (glycosyltransferases). These proteins are believed to play a role in adding sugars to dystroglycan, a molecule that plays a central role in the organisation of the muscle fibre. The involvement of several putative glycosyltransferases represents a novel mechanism of disease that is believed to be responsible for 4 subtypes of CMDs (Walker-Warburg syndrome, Fukuyama CMD, Muscle Eye Brain disease and MDC1C / LGMD2I); and a related disorder that occurs spontaneously in mice. In addition, a similar mechanism of disease is likely to play a role in a number of other CMD syndromes in which the primary defect is unknown, suggesting that deficiency of glycosyltransferases plays a major role in the pathogenesis of CMD.

The widening spectrum of the conditions due to a known gene defect was presented by various participants, together with novel data regarding the spectrum of the pathological changes in muscle and brain.

Strategies aimed at reaching a final diagnosis in each of these conditions were discussed, together with novel therapeutic approaches to animal models. A number of collaborative studies were agreed.

An extended report of this meeting is published in Neuromuscular Disorders, Volume 13, No. 7-8, September 2003.

Prof. Francesco Muntoni (London, UK)
Dr. Pascale Guicheney (Paris, France)
Chairpersons, CMD consortium