To facilitate gene and cell therapy experiments, we created severely immune-deficient mouse models of Duchenne muscular dystrophy (DMD), limb girdle muscular dystrophy 2B (LGMD2B), and limb girdle muscular dystrophy 2D (LGMD2D) by crossing mdx4Cv, Bl/AJ, and Sgca-null mice with NRG immune-deficient mice. The resulting mdx4Cv/NRG, BlAJ/NRG, and Sgca/NRG mice demonstrated the presence of the appropriate mutant alleles at Dmd, Dysf, Sgca, Rag1, and Il2rγ by genotyping PCR. Absence of dystrophin, dysferlin, or α-sarcoglycan protein was confirmed by western blot and immunohistochemistry. We performed centronucleation, Evans blue dye, hydroxyproline, and treadmill assays on the disease model mice versus NRG controls to evaluate muscle histology and function. These studies demonstrated that the mdx4Cv/NRG and Sgca/NRG mice showed significant deficits in muscle structure and function in all the assays and were similar to each other. By contrast, the phenotype of the BlAJ/NRG mice was milder in each case. The results we observed parallel the phenotypes seen in patients with the corresponding disorders. These novel immune-deficient mouse models of DMD, LGMD2B, and LGMD2D will be useful for long-term gene and cell therapy studies involving transfer of foreign genes and cells.
Duchenne muscular dystrophy (DMD or Duchenne) is a progressive, life-limiting muscle-wasting disease that requires comprehensive, multidisciplinary care. This care, at minimum, should include neuromuscular, respiratory, cardiac, orthopedic, endocrine and rehabilitative interventions that address both the primary and secondary manifestations of the disease. The care needs of patients evolve over the cdourse of the disease and as they transition from childhood into young adulthood. In the past two decades, life expectancy has increased significantly by the use of corticosteroids and enhanced clinical management. Nevertheless, each year, patients with Duchenne muscular dystrophy are admitted to emergency departments and intensive care units where medical expertise thrives, but where expertise in rare diseases, such as Duchenne, may not. Emergency care for patients with Duchenne can be as complex as the disease process itself. While any illness or injury may occur in a person with Duchenne, some acute scenarios are much more common in the context of the disease. Making decisions about the clinical care of a person with Duchenne who presents with an acute illness can be quite difficult — in part, because of the extensive use of corticosteroids, which can lead to adrenal suppression. The life of a person with Duchenne needing emergency care may therefore depend upon the ability of the clinician on duty in the emergency department to recognize and mitigate adrenal suppression resulting from corticosteroid dependence. With this in mind, and drawing from expertise and experience with other steroid-dependent diseases, the ‘PJ Nicholoff Steroid Protocol’ was developed. The purpose of this protocol is to provide clinicians information regarding the safe management of corticosteroid during emergency situations in patients who may have accompanying adrenal suppression. The protocol explains how to recognize the signs and symptoms of acute adrenal crisis, how to prevent it with supplemental stress doses of corticosteroids, and how to taper doses after emergency care in order to prevent corticosteroid withdrawal.
Introduction: The Duchenne Regulatory Science Consortium (D-RSC) was established to develop tools to accelerate drug development for DMD. The resulting tools are anticipated to meet validity requirements outlined by qualification/endorsement pathways at both the U.S. Food and Drug Administration (FDA) and European Medicines Administration (EMA), and will be made available to the drug development community. The initial goals of the consortium include the development of a disease progression model, with the goal of creating a model that would be used to forecast changes in clinically meaningful endpoints, which would inform clinical trial protocol development and data analysis.
Methods: In April of 2016 the consortium and other experts met to formulate plans for the development of the model.
Conclusions: Here we report the results of the meeting, and discussion as to the form of the model that we plan to move forward to develop, after input from the regulatory authorities.
The new ‘Recommendation of the Committee of Ministers to member States on research on biological materials of human origin’, adopted in Europe in May 2016 is confusing and lacks specificity on the research use of biomaterials taken from persons not able to consent. It is possible to interpret the relevant clauses in a restrictive manner and doing so would hamper biobank research, by requiring researchers or biobank curators to examine individual records in detail, to check they are adhering to the Recommendation. This would be particularly problematic for muscular dystrophy and other rare disease research, the progress of which relies increasingly on the sharing of biomaterials and data internationally, as it will add complexity to the logistics of biomaterials and data sharing and introduce barriers for researchers preparing biomaterials for sharing. Such barriers are contradictory to EC policies on promoting and funding rare disease research and removing barriers to better care and treatment. Such policies work in concert with international progress in rare disease research, in particular the NIH’s Rare Diseases Clinical Research Network and Genetic and Rare Diseases Information Centre. The rare disease community has in recent years worked to create a common framework of harmonised approaches to enable the responsible, voluntary, and secure sharing of biomaterials and data. These efforts are supported by the European Commission in such moves as FP7 funding to advance rare disease research and the introduction of National Plans for rare disease; and are bolstered by similar efforts in the USA via the Clinical and Translational Science Awards Program and the NIH/NCATS Patient Registry developments. Introducing Recommendations from the Committee of Ministers, containing clauses which are incompatible to the efforts to advance rare disease research, seems counter-productive.
Background: In the absence of a curative treatment for Duchenne Muscular Dystrophy (DMD), corticosteroid therapy (prednisone, deflazacort) has been adopted as the standard of care, as it slows the progression of muscle weakness and enables longer retention of functional mobility. The ongoing development of novel pharmacological agents that target the genetic defect underlying DMD offer hope for a significant alteration in disease progression; however, substantiation of therapeutic efficacy has proved challenging. Identifying functional outcomes sensitive to the early, subtle changes in muscle function has confounded clinical trials. Additionally, the alterations in disease progression secondary to corticosteroid therapy are not well described making it difficult to ascertain the benefits of novel agents, often taken concurrently with corticosteroids.
Objective: The purpose of this study was to examine outcome responsiveness to corticosteroid therapy and age at the onset of a natural history study of ambulatory boys with DMD.
Methods: Eighty-five ambulatory boys with DMD (mean age 93 mo, range 49 to 180 mo) were recruited into this study. Fifty participants were on corticosteroid therapy, while 33 were corticosteroid naïve at the baseline assessment. Within each treatment group boys were divided in two age groups, 4 to 7 years and 8 and greater years of age. The Biodex System 3 Pro isokinetic dynamometer was used to assess muscle strength. Motor skills were assessed using the upper two dimensions (standing/walking, running & jumping) of the Gross Motor Function Measure (GMFM 88) and Timed Motor Tests (TMTs) (10-meter run, sit to stand, supine to stand, climb 4-stairs). Two way analysis of variance and Pearson correlations were used for analysis.
Results: A main effect for age was seen in select lower extremity muscle groups (hip flexors, knee extensors and ankle dorsiflexors), standing dimension skills, and all TMTs with significantly greater weakness and loss of motor skill ability seen in the older age group regardless of treatment group. Interaction effects were seen for the walking, running, and jumping dimension of the GMFM with the naïve boys scoring higher in the younger group and boys on corticosteroid therapy scoring higher in the older group. The TMT of climb 4-stairs demonstrated a significant treatment effect with the boys on corticosteroid therapy climbing stairs faster than those who were naïve, regardless of age. Examination of individual items within the upper level GMFM dimensions revealed select motor skills are more informative of disease progression than others; indicating their potential to be sensitive indicators of alterations in disease progression and intervention efficacy. Analysis of the relationship between muscle group strength and motor skill performance revealed differences in use patterns in the corticosteroid versus naïve boys.
Conclusion: Significant muscle weakness is apparent in young boys with DMD regardless of corticosteroid treatment; however, older boys on corticosteroid therapy tend to have greater retention of muscle strength and motor skill ability than those who are naive. Quantification of muscle strength via isokinetic dynamometry is feasible and sensitive to the variable rates of disease progression in lower extremity muscle groups, but possibly most informative are the subtle changes in the performance characteristics of select motor skills. Further analysis of longitudinal data from this study will explore the influence of corticosteroid therapy on muscle strength and further clarify its impact on motor performance.
The aim of this study was to determine whether prednisone and deflazacort play a different role in child behavior and perceived health related psychosocial quality of life in ambulant boys with Duchenne Muscular Dystrophy. As part of a prospective natural-history study, parents of sixty-seven ambulant boys with DMD (27 taking prednisone, 15 taking deflazacort, 25 were steroid naïve) completed the Child Behavior Checklist (CBCL) for assessment of behavioral, emotional and social problems and both parents and boys with DMD completed the PedsQL™4.0 generic core scale short form. Boys with DMD had higher rates of general behavioral problems than age-matched peers. No significant differences were found among the groups for any of the CBCL syndrome scales raw scores, including internalizing and externalizing behaviors; however, on average boys taking deflazacort demonstrated more withdrawn behaviors than those taking prednisone, while on average the boys taking prednisone demonstrated more aggressive behaviors than boys taking deflazacort. Age, internalizing and externalizing behaviors accounted for 39 and 48% of the variance in psychosocial quality of life for both parents and boys with DMD, respectively. Overall, the use of steroids was not associated with more behavioral problems in boys with DMD. As behavior played a significant role in psychosocial quality of life, comprehensive assessment and treatment of behavioral problems is crucial in this population.
Exon-skipping via synthetic antisense oligonucleotides represents one of the most promising potential therapies for Duchenne muscular dystrophy (DMD), yet this approach is highly sequence-specific and thus each oligonucleotide is of benefit to only a subset of patients. The discovery that dystrophin mRNA is subject to translational suppression by the microRNA miR31, and that miR31 is elevated in the muscle of DMD patients, raises the possibility that the same oligonucleotide chemistries employed for exon skipping could be directed toward relieving this translational block. This approach would act synergistically with exon skipping where possible, but by targeting the 3’UTR it would further be of benefit to the many DMD patients who express low levels of in-frame transcript. We here present investigations into the feasibility of combining exon skipping with several different strategies for miR31-modulation, using both in vitro models and the mdx mouse (the classical animal model of DMD), and monitoring effects on dystrophin at the transcriptional and translational level. We show that despite promising results from our cell culture model, our in vivo data failed to demonstrate similarly reproducible enhancement of dystrophin translation, suggesting that miR31-modulation may not be practical under current oligonucleotide approaches. Possible explanations for this disappointing outcome are discussed, along with suggestions for future investigations.
Wire hang tests are simple and cheap methods to assess muscle performance in small rodents, but do not always yield consistent results. We describe a simple wire hang apparatus that comprises a continuous rolling loop. Wire hang times measured using the rolling wire provide consistent and reliable data that more accurately reflect the output of a continuous physical effort. As such data obtained in mice using a rolling wire are more representative of the physical changes in the mouse muscle and less susceptible to individual mouse behaviour and differences in animal handling.
Background: The mdx mouse model for the fatal muscle wasting disease Duchenne Muscular Dystrophy (DMD) shows a very mild pathology once growth has ceased, with low levels of myofibre necrosis in adults. However, from about 3 weeks of post-natal age, muscles of juvenile mdx mice undergo an acute bout of severe necrosis and inflammation: this subsequently decreases and stabilises to lower adult levels by about 6 weeks of age. Prior to the onset of this severe dystropathology, we have shown that mdx mice are deficient in the amino acid taurine (potentially due to weaning), and we propose that this exacerbates myofibre necrosis and inflammation in juvenile mdx mice. Objectives: The purpose of this study was to increase taurine availability to pre-weaned juvenile mdx mice (from 14 days of age), to evaluate the impact on levels of myofibre necrosis and inflammation (at 22 days) during the acute period of severe dystropathology. Results: Untreated 22 day old mdx muscle was not deficient in taurine, with similar levels to normal C57 control muscle. However taurine treatment, which increased the taurine content of young dystrophic muscle (by 40%), greatly reduced myofibre necrosis (by 75%) and prevented significant increases in 3 markers of inflammation. Conclusion: Taurine was very effective at preventing the acute phase of muscle damage that normally results in myofibre necrosis and inflammation in juvenile mdx mice, supporting continued research into the use of taurine as a therapeutic intervention for protecting growing muscles of young DMD boys
Background: Dysferlin is a sarcolemmal protein that is defective in Miyoshi myopathy and limb-girdle muscular dystrophy type 2B, and is involved in sarcolemmal repair. Primary cultured myoblasts and myotubes established from patient muscle biopsies have been widely utilized to explore the molecular mechanism of dysferlinopathy.
Objectives: The purpose of this study was to explore the possible utility of dermal fibroblasts from dysferlin-deficient patients and SJL mice as a tool for studying dysferlinopathy.
Methods: Dysferlin protein expression in fibroblasts from dysferlin-deficient patients and SJL mice was analyzed by immunoblotting and immunocytochemistry. The membrane wound-repair assay was performed on the fibroblasts using a confocal microscope equipped with a UV-laser. The membrane blebbing assay using hypotonic shock, in which normal membrane blebbing is detected only in the presence of dysferlin, was also performed using human and mouse fibroblasts.
Results: Mis-sense mutated dysferlin was expressed at a very low level in fibroblasts from a dysferlinopathy patient, and lower expression level of truncated dysferlin was observed in SJL mouse fibroblast. Fibroblasts from patients with dysferlinopathy and SJL mice showed attenuated membrane repair and did not form membrane blebs in response to hypoosmotic shock. Proteosomal inhibitior increased mis-sense mutated or truncated dysferlin levels, and restored membrane blebbing, however, proteosomal inhibition failed to improve levels of dysferlin with non-sense or frame-shift mutation.
Conclusion: Fibroblasts from dysferlinopathy patients and SJL mice showed attenuated plasma membrane repair, and could be a tool for studying dysferlinopathy.