The muscular dystrophies are a heterogeneous group of genetically caused muscle degenerative disorders. The Kunkel laboratory has had a longstanding research program into the pathogenesis and treatment of these diseases. Starting with our identification of dystrophin as the defective protein in Duchenne muscular dystrophy (DMD), we have continued our work on normal dystrophin function and how it is altered in muscular dystrophy. Our work has led to the identification of the defective genes in three forms of limb girdle muscular dystrophy (LGMD) and a better understanding of how muscle degenerates in many of the different dystrophies. The identification of mutations causing human forms of dystrophy has lead to improved diagnosis for patients with the disease. We are continuing to improve the molecular diagnosis of the dystrophies and have developed a high-throughput sequencing approach for the low-cost rapid diagnosis of all known forms of dystrophy. In addition, we are continuing to work on therapies using available animal models. Currently, there are a number of mouse models of the human dystrophies, the most notable being the mdx mouse with dystrophin deficiency. These mice are being used to test possible therapies, including stem-cell-based approaches. We have been able to systemically deliver human dystrophin to these mice via the arterial circulation and convert 8% of dystrophin-deficient fibers to fibers expressing human dystrophin. We are now expanding our research to identify new forms of LGMD by analyzing zebrafish models of muscular dystrophy. Currently, we have 14 different zebrafish mutants exhibiting various phenotypes of muscular dystrophy, including muscle weakness and inactivity. One of these mutants carries a stop codon mutation in dystrophin, and we have recently identified another carrying a mutation in titin. We are currently positionally cloning the disease-causative mutation in the remaining 12 mutant strains. We hope that one of these new mutant strains of fish will have a mutation in a gene not previously implicated in human muscular dystrophy. This gene would become a candidate gene to be analyzed in patients which do not carry a mutation in any of the known dystrophy-associated genes. By studying both disease pathology and investigating potential therapies, we hope to make a positive difference in the lives of people living with muscular dystrophy.
DNA sequencing; Muscle; Muscular dystrophy; Stem cells; Zebrafish
Calpains likely play a role in the pathogenesis of Duchenne muscular dystrophy (DMD). Accordingly, calpain inhibition may provide therapeutic benefit to DMD patients. In the present study, we sought to measure benefit from administration of a novel calpain inhibitor, C101, in a canine muscular dystrophy model. Specifically, we tested the hypothesis that treatment with C101 mitigates progressive weakness and severe muscle pathology observed in young dogs with golden retriever muscular dystrophy (GRMD). Young (6-week-old) GRMD dogs were treated daily with either C101 (17 mg/kg twice daily oral dose, n = 9) or placebo (vehicle only, n = 7) for 8 weeks. A battery of functional tests, including tibiotarsal joint angle, muscle/fat composition, and pelvic limb muscle strength were performed at baseline and every 2 weeks during the 8-week study. Results indicate that C101-treated GRMD dogs maintained strength in their cranial pelvic limb muscles (tibiotarsal flexors) while placebo-treated dogs progressively lost strength. However, concomitant improvement was not observed in posterior pelvic limb muscles (tibiotarsal extensors). C101 treatment did not mitigate force drop following repeated eccentric contractions and no improvement was seen in the development of joint contractures, lean muscle mass, or muscle histopathology. Taken together, these data do not support the hypothesis that treatment with C101 mitigates progressive weakness or ameliorates severe muscle pathology observed in young dogs with GRMD.
muscular dystrophy; animal; calpain; skeletal muscle; protease; canine
Limb-girdle muscular dystrophy type 2C (LGMD2C) is an autosomal recessive muscle dystrophy that resembles Duchenne muscular dystrophy (DMD). Although DMD is known to affect one in every 3500 males regardless of race, a widespread founder mutation causing LGMD2C has been described in North Africa. However, the incidence of LGMD2C in Japanese has been unknown because the genetic background remains uncharacterized in many patients clinically diagnosed with DMD.
We enrolled 324 patients referred to the Kobe University Hospital with suspected DMD. Mutations in the dystrophin or the SGCG genes were analyzed using not only genomic DNA but also cDNA.
In 322 of the 324 patients, responsible mutations in the dystrophin were successfully revealed, confirming DMD diagnosis. The remaining two patients had normal dystrophin expression but absence of γ-sarcoglycan in skeletal muscle. Mutation analysis of the SGCG gene revealed homozygous deletion of exon 6 in one patient, while the other had a novel single nucleotide insertion in exon 7 in one allele and deletion of exon 6 in the other allele. These mutations created a stop codon that led to a γ-sarcoglycan deficiency, and we therefore diagnosed these two patients as having LGMD2C. Thus, the relative incidence of LGMD2C among Japanese DMD-like patients can be calculated as 1 in 161 patients suspected to have DMD (2 of 324 patients = 0.6%). Taking into consideration the DMD incidence for the overall population (1/3,500 males), the incidence of LGMD2C can be estimated as 1 per 560,000 or 1.8 per million.
To the best of our knowledge, this is the first study to demonstrate a low incidence of LGMD2C in the Japanese population.
Retrospective review of scoliosis progression, pulmonary and cardiac function in a series of patients with Duchenne Muscular Dystrophy (DMD).
To determine whether operative treatment of scoliosis decreases the rate of pulmonary function loss in patients with DMD.
Summary of Background Data
It is generally accepted that surgical intervention should be undertaken in DMD scoliosis once curve sizes reach 35 degrees to allow intervention before critical respiratory decline has occurred. There are conflicting reports, however, regarding the effect of scoliosis stabilization on the rate of pulmonary function decline when compared to non operative cohorts.
We reviewed spinal radiographs, echocardiograms, and spirometry, hospital, and operative records of all patients seen at our tertiary referral center from July 1, 1992 to June 1, 2007 Data was recorded to Microsoft Excel and analyzed with SAS and R statistical processing software.
The percent predicted forced vital capacity (PPFVC) decreased 5% /year prior to operation. The mean PPFVC was 54% (sd=21%) prior to operation with a mean postoperative PPFVC of 43% (sd=14%). Surgical treatment was associated with a 12% decline in PPFVC independent of other treatment variables. PPFVC after operation declined at a rate of 1% per year and while this rate was lower, it was not significantly different than the rate of decline present prior to operation (p=0.18). Cardiac function as measured by left ventricular fractional shortening declined at a rate of 1%/year with most individuals exhibiting an LVFS rate of >30 prior to operation.
Operative treatment of scoliosis in DMD using the Luque Galveston method was associated with a reduction of FVC related to operation. The rate of pulmonary function decline after operation was not significantly reduced when compared to the rate of preoperative FVC decline.
Muscle biopsy specimens from 179 cases of muscular dystrophies and from 140 cases of anterior horn cell disorders (from a total of 1,348 biopsied patients) were examined histologically. There were 72 cases of Duchenne type muscular dystrophy (DMD), five of Becker type MD, four girls with myopathy resembling DMD, 40 with limb-girdle, 10 with facioscapulohumeral, seven with late onset, 13 with congenital, and 28 with unclassifiable muscular dystrophies. Groups of small atrophied muscle fibres were encountered in 42 (23%) of the cases in this group, most frequently in patients with limb-girdle, facioscapulohumeral, and least frequently with DM dystrophy. In the second group there were 25 cases of infantile, 38 of juvenile, and 39 of adult spinal muscular atrophy (SMA); there were 21 patients with motor neurone disease (MND), six with poliomyelitis, and 11 with an unclassifiable type of anterior horn cell disorder. Pseudomyopathic changes were encountered in 43 (30%) of all cases in this group. They were most frequently present among patients with juvenile and adult SMA and in those with MND. The presence of group atrophy in muscular dystrophy is considered significant myopathological evidence of a denervation process. On the other hand, pseudomyopathic changes, variation in fibre size, rounding, central nuclei, and increase in connective tissue occurring in various anterior horn cell disorders are seen not to be specific `myopathic' changes. Thus there was an overlap of pathological reactions in muscles from the dystrophies and the neurogenic atrophies. Comparably atrophied fibres (much less than 2 SDs below the normal mean diameter) and hypertrophied fibres (much more than 2 SDs above the normal mean diameter) were encountered in both dystrophy and neurogenic atrophy, considering the large muscles of the limb. Likewise, the mean fibre diameters were comparable in DMD and in juvenile SMA. The fourth evidence of a neurogenic factor in muscular dystrophy was derived from an examination of SDH preparations of muscle. There was a preponderance of type I muscle fibres in dystrophic muscles compared with specimens from controls, suggesting depletion of type II fibres. It appears that the concept of muscular dystrophy as a primary muscle disease needs to be re-examined.
Antisense oligonucleotide-induced exon skipping is a promising approach for treatment of Duchenne muscular dystrophy (DMD). We have systemically administered an antisense phosphorodiamidate morpholino oligomer (PMO) targeting dystrophin exons 6 and 8 to a dog with canine X-linked muscular dystrophy in Japan (CXMDJ) lacking exon 7 and achieved recovery of dystrophin in skeletal muscle. To date, however, antisense chemical compounds used in DMD animal models have not been directly applied to a DMD patient having the same type of exon deletion. We recently identified a DMD patient with an exon 7 deletion and tried direct translation of the antisense PMO used in dog models to the DMD patient's cells.
We converted fibroblasts of CXMDJ and the DMD patient to myotubes by FACS-aided MyoD transduction. Antisense PMOs targeting identical regions of dog and human dystrophin exons 6 and 8 were designed. These antisense PMOs were mixed and administered as a cocktail to either dog or human cells in vitro. In the CXMDJ and human DMD cells, we observed a similar efficacy of skipping of exons 6 and 8 and a similar extent of dystrophin protein recovery. The accompanying skipping of exon 9, which did not alter the reading frame, was different between cells of these two species.
Antisense PMOs, the effectiveness of which has been demonstrated in a dog model, achieved multi-exon skipping of dystrophin gene on the FACS-aided MyoD-transduced fibroblasts from an exon 7-deleted DMD patient, suggesting the feasibility of systemic multi-exon skipping in humans.
The roots of the progress reports on the development of therapies for Duchenne muscular dystrophy (DMD) that since 2000 have been produced at Breitnau/Germany and distributed to the parents of DMD patients cover over 30 years of continual occupation with this disease. The beginning was marked by the development of an early detection programme for the genetic disposition for DMD in infant boys. The next step was the organisation of workshops on the management of DMD and the writing of progress reports on these and other relevant conferences. Getting acquainted with the ideas of the protagonists in the research field by holding interviews was a decisive prerequisite for this activity. This took place in tandem with the development of a new kind of multiplex “family letters” that attempted to answer frequently asked questions to many DMD families at the same time.
When – with the beginning of the new millennium – the endeavours towards gene therapies for DMD started to boom all over the scientific world, progress reports designed to keep the families informed about research on DMD treatment were added to the family letters. These reports that give an account of the latest state of the research are written in a plain language that can be understood by laypersons. In the meantime the reports have adopted the character of reviews that are updated annually. They are written in English and German and translated into Spanish and many other languages.
Duchenne muscular dystrophy; CK screening; multiplex family letters; progress reports; gene therapy; exon skipping
► An early treatment with enalapril was performed in exercised mdx mice. ► In vivo, enalapril increased mouse fore limb strength dose-dependently. ► Ex vivo, enalapril reduced muscular markers of oxidative stress and inflammation. ► Results corroborate an early role of angiotensin II in muscular dystrophy. ► Pre-clinical evidences of therapeutic interest of ACE inhibitors for therapy of DMD.
Inhibitors of angiotensin converting enzymes (ACE) are clinically used to control cardiomyopathy in patients of Duchenne muscular dystrophy. Various evidences suggest potential usefulness of long-term treatment with ACE inhibitors to reduce advanced fibrosis of dystrophic muscle in the mdx mouse model. However, angiotensin II is known to exert pro-inflammatory and pro-oxidative actions that might contribute to early events of dystrophic muscle degeneration. The present study has been aimed at evaluating the effects of an early treatment with enalapril on the pathology signs of exercised mdx mouse model. The effects of 1 and 5 mg/kg enalapril i.p. for 4–8 weeks have been compared with those of 1 mg/kg α-methyl-prednisolone (PDN), as positive control. Enalapril caused a dose-dependent increase in fore limb strength, the highest dose leading to a recovery score similar to that observed with PDN. A dose-dependent reduction of superoxide anion production was observed by dihydroethidium staining in tibialis anterior muscle of enalapril-treated mice, approaching the effect observed with PND. In parallel, a significant reduction of the activated form of the pro-inflammatory Nuclear Factor-kB has been observed in gastrocnemious muscle. Histologically, 5 mg/kg enalapril reduced the area of muscle necrosis in both gastrocnemious muscle and diaphragm, without significant effect on non-muscle area. In parallel no significant changes have been observed in both muscle TGF-β1 and myonuclei positive to phosphorylated Smad2/3. Myofiber functional indices were also monitored by microelectrodes recordings. A dose-dependent recovery of macroscopic chloride conductance has been observed upon enalapril treatment in EDL muscle, with minor effects being exerted in diaphragm. However a modest effect, if any, was found on mechanical threshold, a functional index of calcium homeostasis. No recovery was observed in creatine kinase and lactate dehydrogenase. Finally the results suggest the ability of enalapril to blunt angiotensin-II dependent activation of pro-inflammatory and pro-oxidant pathways which may be earlier events with respect to the pro-fibrotic ones, and may in part account for both functional impairment and muscle necrosis. The PDN-like profile may corroborate the combined use of the two classes of drugs in DMD patients so to potentiate the beneficial effects at skeletal muscle level, while reducing both spontaneous and PDN-aggravated cardiomyopathy.
DMD, Duchenne muscular dystrophy; ACE, angiotensin converting enzyme; RAS, renin-angiotensin system; Ang II, angiotensin II; PDN, α-methylprednisolone; NF-kB, nuclear factor-kB; TGF-β1, trasforming growth factor β1; EDL, extensor digitorum longus; CK, creatine kinase; LDH, lactate dehydrogenase; gCl, sarcolemmal chloride conductance; gK, sarcolemmal potassium conductance; MT, mechanical threshold; Muscular dystrophy; Pre-clinical pharmacological tests; Angiotensin-II; Inflammation; Oxidative stress
Clinical characteristics and complications of Duchenne muscular dystrophy caused by skeletal and cardiac muscle degeneration are well known. Gastro-intestinal involvement has also been recognised in these patients. However an acute perforated gastro-duodenal peptic ulcer has not been documented up to now.
A 26-year-old male with Duchenne muscular dystrophy with a clinical and radiographic diagnosis of acute perforated gastro-duodenal peptic ulcer is treated non-operatively with naso-gastric suction and intravenous medication. Gastrointestinal involvement in Duchenne muscular dystrophy and therapeutic considerations in a high risk patient are discussed.
Non-surgical treatment for perforated gastro-duodenal peptic ulcer should be considered in high risk patients, as is the case in patients with Duchenne muscular dystrophy. Patients must be carefully observed and operated on if non-operative treatment is unsuccessful.
Biomarkers are critically important for disease diagnosis and monitoring. In particular, close monitoring of disease evolution is eminently required for the evaluation of therapeutic treatments. Classical monitoring methods in muscular dystrophies are largely based on histological and molecular analyses of muscle biopsies. Such biopsies are invasive and therefore difficult to obtain. The serum protein creatine kinase is a useful biomarker, which is however not specific for a given pathology and correlates poorly with the severity or course of the muscular pathology. The aim of the present study was the systematic evaluation of serum microRNAs (miRNAs) as biomarkers in striated muscle pathologies. Mouse models for five striated muscle pathologies were investigated: Duchenne muscular dystrophy (DMD), limb-girdle muscular dystrophy type 2D (LGMD2D), limb-girdle muscular dystrophy type 2C (LGMD2C), Emery-Dreifuss muscular dystrophy (EDMD) and hypertrophic cardiomyopathy (HCM). Two-step RT-qPCR methodology was elaborated, using two different RT-qPCR miRNA quantification technologies. We identified miRNA modulation in the serum of all the five mouse models. The most highly dysregulated serum miRNAs were found to be commonly upregulated in DMD, LGMD2D and LGMD2C mouse models, which all exhibit massive destruction of striated muscle tissues. Some of these miRNAs were down rather than upregulated in the EDMD mice, a model without massive myofiber destruction. The dysregulated miRNAs identified in the HCM model were different, with the exception of one dysregulated miRNA common to all pathologies. Importantly, a specific and distinctive circulating miRNA profile was identified for each studied pathological mouse model. The differential expression of a few dysregulated miRNAs in the DMD mice was further evaluated in DMD patients, providing new candidates of circulating miRNA biomarkers for DMD.
"In never considering neuromuscular disease to be untreatable, Yves Rideau has found ways to ameliorate every aspect of these conditions. His work has resulted in immeasurably enhancing the quality of life of his patients". This dedication included into the Guide to Evaluation in Management of Neuromuscular Diseases, 1999, made by a coworker who studied in Poitiers from 1981 to 1983, summarizes the content of this paper.
Duchenne muscular dystrophy; rehabilitation; surgery; ventilation
Duchenne muscular dystrophy (DMD) is the most common genetic muscle disease affecting 1 in 3,500 live male births. It is an X-linked recessive disease caused by a defective dystrophin gene. The disease is characterized by progressive limb weakness, respiratory and cardiac failure and premature death. Fibrosis is a prominent pathological feature of muscle biopsies from patients with DMD. It directly causes muscle dysfunction and contributes to the lethal DMD phenotype. Although gene therapy and cell therapy may ultimately provide a cure for DMD, currently the disease is devastating, with no effective therapies. Recent studies have demonstrated that ameliorating muscle fibrosis may represent a viable therapeutic approach for DMD. By reducing scar formation, antifibrotic therapies may not only improve muscle function but also enhance muscle regeneration and promote gene and stem cell engraftment. Antifibrotic therapy may serve as a necessary addition to gene and cell therapies to treat DMD in the future. Therefore, understanding cellular and molecular mechanisms underlying muscle fibrogenesis associated with dystrophin deficiency is key to the development of effective antifibrotic therapies for DMD.
Antifibrotic therapy; Duchenne muscular dystrophy; Muscle fibrosis
Surgical treatment of spinal deformities in Duchenne muscular dystrophy (DMD) is influenced by a number of factors which have proven to be a difficult challenge. Each case should be carefully evaluated, considering not only the natural history of the spinal deformity, but also the patient’s general condition. These should be thoroughly assessed through clinical and radiographic investigations together with other medical specialists. Life expectancy should be determined according to the cardio-respiratory function, and both preoperative and postoperative quality of life should be taken into consideration, trying to imagine the functional status of each patient after surgery.
From February 1985 to February 2000, 58 patients with spinal deformity in DMD were surgically treated. Of 25 patients that were operated on between 1985 and 1995, only 20 were followed-up after 5 years because 5 of them had died during this time. Therefore, the present study focuses on the results obtained in 20 cases. The 20 cases reviewed presented with a mean angular value of scoliosis equal to 48° (range 10–92°). Spinal fusion with our modified Luque technique  was performed in 19 cases, whereas CD instrumentation was applied in only one case.
At the 5 year follow-up (range 5.6–10 years), the age ranged from 18 to 24 years and averaged 20.4 years. The postoperative angular value of scoliosis averaged 22° (58%, range 0–43°), the mean correction at follow-up was 28° (range 0–60°), and the mean loss of correction was equal to 6° (range, 0–11°). Vital capacity showed a slow progression, slightly inferior to its natural evolution in untreated patients. The severest complication was the death that occurred in one of the patients.
According to the present study, an early surgery (angular value lower than 35–40°) dramatically reduces the rate of risk factors associated with spinal deformities in DMD, and its advantages far exceed the disadvantages, above all in terms of quality of life.
Duchenne muscular dystrophy; Scoliosis; Vital capacity; Arthrodesis
"Use it or lose it" is a well known saying which is applicable to boys with Duchenne Muscular Dystrophy (DMD). Besides the direct effects of the muscular dystrophy, the increasing effort to perform activities, the fear of falling and the use of personal aids indirectly impair leg and arm functions as a result of disuse. Physical training could oppose this secondary physical deterioration. The No Use is Disuse (NUD) study is the first study in human subjects with DMD that will examine whether a low-intensity physical training is beneficial in terms of preservation of muscle endurance and functional abilities. The study consists of two training intervention studies: study 1 "Dynamic leg and arm training for ambulant and recently wheelchair-dependent boys with DMD and, study 2 "Functional training with arm support for boys with DMD who have been confined to a wheelchair for several years". This paper describes the hypotheses and methods of the NUD study.
Study 1 is an explorative randomized controlled trial with multiple baseline measurements. Thirty boys with a DNA-established diagnosis of DMD will be included. The intervention consists of a six-months physical training during which boys train their legs and arms with active and/or assisted cycling training equipment. The primary study outcomes are muscle endurance and functional abilities, assessed with a Six-Minute Bicycle Test and the Motor Function Measure. Study 2 has a within-group repeated measurements design and will include ten boys with DMD who have already been confined to a wheelchair for several years. The six-months physical training program consists of 1) a computer-assisted training and 2) a functional training with an arm support. The primary study outcome is functional abilities of the upper extremity, assessed with the Action Research Arm Test.
The NUD study will fill part of the gap in the current knowledge about the possible effects of training in boys with DMD and will increase insight into what type of exercise should be recommended to boys with DMD. The study will finish at the end of 2010 and results are expected in 2011.
The Netherlands National Trial Register1631
Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive disorders caused by mutations of the DMD gene located at Xp21. In DMD patients, dystrophin is virtually absent; whereas BMD patients have 10% to 40% of the normal amount. Deletions in the dystrophin gene represent 65% of mutations in DMD/BMD patients. To explain the contribution of immunohistochemical and genetic analysis in the diagnosis of these dystrophies, we present 10 cases of DMD/BMD with particular features. We have analyzed the patients with immunohistochemical staining and PCR multiplex to screen for exons deletions. Determination of the quantity and distribution of dystrophin by immunohistochemical staining can confirm the presence of dystrophinopathy and allows differentiation between DMD and BMD, but dystrophin staining is not always conclusive in BMD. Therefore, only identification involved mutation by genetic analysis can establish a correct diagnosis.
The cardiomyopathy found in Duchenne muscular dystrophy (DMD) is responsible for death due to heart failure in ∼30% of patients and additionally contributes to many DMD morbidities. Strategies to bypass DMD-causing mutations to allow an increase in body-wide dystrophin have proved promising, but increasing cardiac dystrophin continues to be challenging. The purpose of this study was to determine if therapeutic restoration of cardiac dystrophin improved the significant cardiac hypertrophy and diastolic dysfunction identified in X-linked muscular dystrophy (mdx) dystrophin-null mouse due to a truncation mutation over time after treatment.
Methods and results
Mice lacking dystrophin due to a truncation mutation (mdx) were given an arginine-rich, cell-penetrating, peptide-conjugated phosphorodiamidate morpholino oligomer (PPMO) that delivered a splice-switching oligonucleotide-mediated exon skipping therapy to restore dystrophin in mdx mice before the development of detectable cardiomyopathy. PPMO successfully restored cardiac dystrophin expression, preserved cardiac sarcolemma integrity, and prevented the development of cardiac pathology that develops in mdx-null mice over time. By echocardiography and Doppler analysis of the mitral valve, we identified that PPMO treatment of mdx mice prevented the cardiac hypertrophy and diastolic dysfunction identified in sham-treated, age-matched mdx mice, characteristic of DMD patients early in the disease process, in as little as 5–6 weeks after the initiation of treatment. Surprisingly, despite the short-term replacement of cardiac dystrophin (<1% present after 12 weeks by immunodetection), PPMO therapy also provided a durable cardiac improvement in cardiac hypertrophy and diastolic dysfunction for up to 7 months after the initiation of treatment.
These results demonstrate for the first time that PPMO-mediated exon skipping therapy early in the course of DMD may effectively prevent or slow down associated cardiac hypertrophy and diastolic dysfunction with significant long-term impact.
Duchenne muscular dystrophy; Morpholino; Oligomers; Cardiomyopathy; Therapy; Exon skipping; Alternative RNA splicing
Muscular dystrophies are a heterogeneous group of genetic disorders characterized by muscle weakness and wasting. Duchenne muscular dystrophy (DMD) is the most common and severe form of muscular dystrophy, and although the molecular mechanisms of the disease have been extensively investigated since the discovery of the gene in 1986, there is currently no effective treatment. However, new gene-based therapies have recently emerged with particular noted advances in using conventional gene replacement strategies, RNA-based technology and pharmacological approaches. While the proof of principle has been demonstrated in animal models, several clinical trials have recently been undertaken to investigate the feasibility of these strategies in patients. In particular, antisense-mediated exon skipping has shown encouraging results and holds promise for the treatment of dystrophic muscle. Here, we summarize the recent progress in therapeutic approaches to muscular dystrophies, with an emphasis on gene therapy and exon skipping for DMD.
In Duchenne muscular dystrophy (DMD), dystrophin deficiency leading to progressive muscular degeneration is caused by frame-shifting mutations in the DMD gene. Antisense oligonucleotides (AONs) aim to restore the reading frame by skipping of a specific exon(s), thereby allowing the production of a shorter, but semifunctional protein, as is found in the mostly more mildly affected patients with Becker muscular dystrophy. AONs are currently being investigated in phase 3 placebo-controlled clinical trials. Most of the participating patients are treated symptomatically with corticosteroids (mainly predniso[lo]ne) to stabilize the muscle fibers, which might affect the uptake and/or efficiency of AONs. Therefore the effect of prednisolone on 2′-O-methyl phosphorothioate AON efficacy in patient-derived cultured muscle cells and the mdx mouse model (after local and systemic AON treatment) was assessed in this study. Both in vitro and in vivo skip efficiency and biomarker expression were comparable between saline- and prednisolone-cotreated cells and mice. After systemic exon 23-specific AON (23AON) treatment for 8 weeks, dystrophin was detectable in all treated mice. Western blot analyses indicated slightly higher dystrophin levels in prednisolone-treated mice, which might be explained by better muscle condition and consequently more target dystrophin pre-mRNA. In addition, fibrotic and regeneration biomarkers were normalized to some extent in prednisolone- and/or 23AON-treated mice. Overall these results show that the use of prednisone forms no barrier to participation in clinical trials with AONs.
Verhaart and colleagues examine the effects of prednisolone, a corticosteroid, on the function of antisense oligonucleotide (AON) therapy for Duchenne muscular dystrophy. They show that prednisolone treatment does not interfere with AON uptake and exon-skipping levels in patient-derived muscle cells in vitro and in mdx mice in vivo. In fact, they suggest that prednisolone might even enhance the dystrophin expression induced by exon 23-specific AONs in mdx mice.
Duchenne muscular dystrophy usually affects males. However, females are also affected in rare instances. Approximately 8% of female Duchenne muscular dystrophy (DMD) carriers are manifesting carriers and have muscle weakness to some extent. We investigated the clinical features of 3 female patients with dystrophinopathy diagnosed by clinical, pathological, and genetic studies at our neuromuscular disease clinic. The onset age of manifesting symptoms varied (8-28 years). Muscle weakness grade varied as follows: patient 1 showed asymmetrical bilateral proximal upper and lower extremities weakness, patient 2 showed asymmetrical bilateral upper extremities weakness similar to scapulohumoral muscular dystrophy, and patient 3 had only bilateral asymmetric proximal lower extremities weakness. Two patients had familial histories of DMD (their sons were diagnosed with DMD), but the 1 remaining patient had no familial history of DMD. The serum creatine kinase level was elevated in all patients, but it was not correlated with muscular weakness. An electromyography study showed findings of myopathy in all patients. One patient was diagnosed with a DMD carrier by a muscle biopsy with an immunohistochemical stain (dystrophin). The remaining 2 patients with familial history of DMD were diagnosed by multiplex ligation-dependent probe amplification (MLPA). There were inconsistent clinical features in the female carriers. An immunohistochemical analysis of dystrophin could be useful for female carrier patients. Also, multiplex ligation-dependent probe amplification is essential for the diagnosis of a manifesting female carrier DMD in female myopathic patients because conventional multiplex PCR could not detect the duplication and is less accurate compared to MLPA.
Dystrophinopathy; female carrier; multiplex ligation-dependent probe amplification
A non-randomised retrospective study to compare the results of surgical correction of scoliosis in Duchenne’s muscular dystrophy (DMD) patients using three different instrumentation systems—Sublaminar instrumentation system (Group A), a hybrid of sublaminar and pedicle screw systems (Group B) and pedicle screw system alone (Group C). Between 1993 and 2003, 43 patients with DMD underwent posterior spinal fusion and instrumentation. Group A (n = 19) had sublaminar instrumentation system, Group B (n = 13) had a hybrid construct and Group C (n = 11) was treated with pedicle system. The mean blood loss in Group A was 4.1 l, 3.2 l in Group B and 2.5 l in Group C. Average operating times in Group A, B and C were 300, 274 and 234 min, respectively. Mean pre-operative, post-operative and final Cobb angle in Group A was 50.05 ± 15.46°, 15.68 ± 11.23° and 21.57 ± 11.63°, Group B was 17.76 ± 8.50°, 3.61 ± 2.53° and 6.69 ± 4.19° and Group C was 25.81 ± 9.94°, 5.45 ± 3.88°, 8.90 ± 5.82°, respectively. Flexibility index or the potential correction calculated from bending radiographs were 60 ± 6.33, 70 ± 4.65 and 67 ± 6.79% for Group A, Group B and Group C respectively. The percentage correction achieved was 72.5 ± 14.5% in Group A, 82 ± 6% in Group B and 82 ± 8% in Group C. The difference between percentage correction achieved and the flexibility index was 12.45 ± 8.22, 12.05 ± 1.3 and 15.00 ± 1.21% in Group A, B and C, respectively The percentage loss of correction in Cobb angles at final follow-up in Group A, B and C was 12.5 ± 3.5, 16.5 ± 1. and 12.5 ± 2.5%, respectively. Complications seen in Group A were three cases of wound infection and two cases of implant failure; Group B had a single case of implant failure and Group C had one patient with wound infection and one case with a partial screw pull out. Early surgery and smaller curve corrections appears to be the current trend in the management of scoliosis in DMD. This has been possible due to early curve detection and surgery thus having the advantage of less post-operative respiratory complications and stay in paediatric intensive care. Also, early surgery avoids development of pelvic deformity and extension of instrumentation to the pelvis thereby reducing blood loss. This trend reflects the advent of newer and safer instrumentation systems, advanced techniques in anaesthesia and cord monitoring. Sublaminar instrumentation system group had increased operating times and blood loss compared to both the hybrid and pedicle screw instrumentation systems due to increased bleeding from epidural vessels and pelvic instrumentation. Overall, the three instrumentation constructs appear to provide and maintain an optimal degree of correction at medium to long term follow up but the advantages of lesser blood loss and surgical time without the need for pelvic fixation seem to swing the verdict in favour of the pedicle screw system.
Duchenne’s muscular dystrophy; Scoliosis; Sublaminar instrumentation; Hybrid instrumentation; Pedicle screw system
First-trimester chorionic-villi-derived cells (FTCVs) are the earliest fetal material that can be obtained for prenatal diagnosis of fetal disorders such as Duchenne muscular dystrophy (DMD). DMD is a devastating X-linked disorder characterized by the absence of dystrophin at the sarcolemma of muscle fibers. Currently, a limited number of treatment options are available for DMD, although cell therapy is a promising treatment strategy for muscle degeneration in DMD patients. A novel candidate source of cells for this approach is FTCVs taken between the 9th and 11th weeks of gestation. FTCVs might have a higher undifferentiated potential than any other tissue-derived cells because they are the earliest fetal material. We examined the expression of mesenchymal stem cell and pluripotent stem cell markers in FTCVs, in addition to their myogenic potential. FTCVs expressed mesenchymal stem cell markers and Nanog and Sox2 transcription factors as pluripotent stem cell markers. These cells efficiently differentiated into myotubes after myogenic induction, at which point Nanog and Sox2 were down-regulated, whereas MyoD, myogenin, desmin and dystrophin were up-regulated. To our knowledge, this is the first demonstration that FTCVs can be efficiently directed to differentiate in vitro into skeletal muscle cells that express dystrophin as the last stage marker of myogenic differentiation. The myogenic potential of FTCVs reveals their promise for use in cell therapy for DMD, for which no effective treatment presently exists.
Electronic supplementary material
The online version of this article (doi:10.1007/s00441-012-1340-9) contains supplementary material, which is available to authorized users.
Duchenne muscular dystrophy; First-trimester chorionic villi; Myogenic differentiation; Dystrophin; Cell therapy
Duchenne muscular dystrophy (DMD) arises as a consequence of mutations in the dystrophin gene. Dystrophin is a membrane-spanning protein that connects the cytoskeleton and the basal lamina. The most distinctive features of DMD are a progressive muscular dystrophy, a myofiber degeneration with fibrosis and metabolic alterations such as fatty infiltration, however, little is known on lipid metabolism changes arising in Duchenne patient cells. Our goal was to identify metabolic changes occurring in Duchenne patient cells especially in terms of L-carnitine homeostasis, fatty acid metabolism both at the mitochondrial and peroxisomal level and the consequences on the membrane structure and function. In this paper, we compared the structural and functional characteristics of DMD patient and control cells. Using radiolabeled L-carnitine, we found, in patient muscle cells, a marked decrease in the uptake and the intracellular level of L-carnitine. Associated with this change, a decrease in the mitochondrial metabolism can be seen from the analysis of mRNA encoding for mitochondrial proteins. Probably, associated with these changes in fatty acid metabolism, alterations in the lipid composition of the cells were identified: with an increase in poly unsaturated fatty acids and a decrease in medium chain fatty acids, mono unsaturated fatty acids and in cholesterol contents. Functionally, the membrane of cells lacking dystrophin appeared to be less fluid, as determined at 37°C by fluorescence anisotropy. These changes may, at least in part, be responsible for changes in the phospholipids and cholesterol profile in cell membranes and ultimately may reduce the fluidity of the membrane. A supplementation with L-carnitine partly restored the fatty acid profile by increasing saturated fatty acid content and decreasing the amounts of MUFA, PUFA, VLCFA. L-carnitine supplementation also restored muscle membrane fluidity. This suggests that regulating lipid metabolism in DMD cells may improve the function of cells lacking dystrophin.
Duchenne muscular dystrophy (DMD) is the most common X-linked disorder in children affecting 1 in 3500 males. Since, as of now, we have no treatment for DMD, carrier detection and prenatal diagnosis is the most important preventive strategy. Multiplex PCR helps in rapid detection of hot spot exonal deletions (positive in 65% of cases) as many exons can be identified in a single run. 10 children with characterstic clinical features of DMD and chorionic villus samples of 10 antenatal patients with positive family history were studied. We identified a deletion mutation in exon 49 of the dystrophin gene in a 4 yr old boy referred with signs and symptoms suggestive of DMD using primers for exons 45, 48, 49, 43, 44, 19, 3, 8, 13 and muscle promoter, subjected to multiplex polymerase chain reaction (PCR) and agarose/Nu-Sieve gel electrophoresis. These genetic methods aid in prenatal diagnosis of DMD as well as confirmation of diagnosis in children with signs and symptoms suggestive of the disease.
Duchenne muscular dystrophy; multiplex PCR; exons; Hot-spot deletions; prenatal diagnosis
Mutations that disrupt the open reading frame and prevent full translation of DMD, the gene that encodes dystrophin, underlie the fatal X-linked disease Duchenne muscular dystrophy. Oligonucleotides targeted to splicing elements (splice switching oligonucleotides) in DMD pre-mRNA can lead to exon skipping, restoration of the open reading frame, and the production of functional dystrophin in vitro and in vivo, which could benefit patients with this disorder.
We did a single-blind, placebo-controlled, dose-escalation study in patients with DMD recruited nationally, to assess the safety and biochemical efficacy of an intramuscular morpholino splice-switching oligonucleotide (AVI-4658) that skips exon 51 in dystrophin mRNA. Seven patients with Duchenne muscular dystrophy with deletions in the open reading frame of DMD that are responsive to exon 51 skipping were selected on the basis of the preservation of their extensor digitorum brevis (EDB) muscle seen on MRI and the response of cultured fibroblasts from a skin biopsy to AVI-4658. AVI-4658 was injected into the EDB muscle; the contralateral muscle received saline. Muscles were biopsied between 3 and 4 weeks after injection. The primary endpoint was the safety of AVI-4658 and the secondary endpoint was its biochemical efficacy. This trial is registered, number NCT00159250.
Two patients received 0·09 mg AVI-4658 in 900 μL (0·9%) saline and five patients received 0·9 mg AVI-4658 in 900 μL saline. No adverse events related to AVI-4658 administration were reported. Intramuscular injection of the higher-dose of AVI-4658 resulted in increased dystrophin expression in all treated EDB muscles, although the results of the immunostaining of EDB-treated muscle for dystrophin were not uniform. In the areas of the immunostained sections that were adjacent to the needle track through which AVI-4658 was given, 44–79% of myofibres had increased expression of dystrophin. In randomly chosen sections of treated EDB muscles, the mean intensity of dystrophin staining ranged from 22% to 32% of the mean intensity of dystrophin in healthy control muscles (mean 26·4%), and the mean intensity was 17% (range 11–21%) greater than the intensity in the contralateral saline-treated muscle (one-sample paired t test p=0·002). In the dystrophin-positive fibres, the intensity of dystrophin staining was up to 42% of that in healthy muscle. We showed expression of dystrophin at the expected molecular weight in the AVI-4658-treated muscle by immunoblot.
Intramuscular AVI-4658 was safe and induced the expression of dystrophin locally within treated muscles. This proof-of-concept study has led to an ongoing systemic clinical trial of AVI-4658 in patients with DMD.
UK Department of Health.
The dystrophinopathies comprise a group of X-linked genetic diseases that feature dystrophin deficiency. Duchenne and Becker muscular dystrophy are characterized by progressive weakness and wasting of skeletal, smooth, and/or cardiac muscle. Duchenne's Muscular Dystrophy (DMD) is the most severe dystrophinopathy, and with an incidence of 1:3500 male births. Despite understanding the structural and genetic basis for DMD, the pathogenesis and clinical basis for more severe involvement in specific skeletal muscle groups and the heart are poorly understood. Current techniques, such as strength testing, for monitoring progress of disease and therapy in DMD patients, are imprecise and physically demanding for test subjects. Ultrasound is well-suited to detect changes in structure and organization in muscle tissue in a manner that makes low demands on the patient. Therefore, we investigated the use of ultrasound to quantitatively phenotype the remodeling process in patients with DMD. Beam-formed RF data were acquired from the skeletal muscles of nine DMD and five normal subjects imaged with a clinical imaging system (HDI5000 w/7 MHz probe applied above left biceps muscle). From these data, images were reconstructed using B-mode (log of analytic signal magnitude) and information-theoretic receivers (Hf -receiver). Hf images obtained from dystrophic muscle contained extensive “mottled” regions (i.e. areas with heterogeneous image contrast) that were not readily apparent from the B-Mode images. The two dimensional autocorrelation of DMD Hf images have broader peaks than those of normal subjects, which is indicative of larger scatterer sizes, consistent with pathological changes of fibers, edema, and fatty infiltration. Comparison of the relative peak widths (Full width measured at 60% maximum) of the autocorrelation of the DMD and normal Hf images shows a quantitative difference between the two groups (p < 0.005, student two-tailed paired t-test). Consequently, these imaging techniques may prove useful for longitudinal monitoring of disease progression and therapy.
Entropy-Based Imaging; Shannon Entropy; Reference-Free Tissue Characterization