Simvastatin Treatment Does Not Ameliorate Muscle Pathophysiology in a Mouse Model for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy is an X-linked, recessive muscular dystrophy in which the absence of the dystrophin protein leads to fibrosis, inflammation and oxidative stress, resulting in loss of muscle tissue. Drug repurposing, i.e. using drugs already approved for other disorders, is attractive as it decreases development time. Recent studies suggested that simvastatin, a cholesterol lowering drug used for cardiovascular diseases, has beneficial effects on several parameters in mdx mice. To validate properly the effectiveness of simvastatin, two independent labs tested the effects of 12-week simvastatin treatment in either young (starting at 4 weeks of age) or adult (starting at 12 weeks of age) mdx mice. In neither study were benefits of simvastatin treatment observed on muscle function, histology or expression of genes involved in fibrosis, regeneration, oxidative stress and autophagy. Unexpectedly, although the treatment protocol was similar, simvastatin plasma levels were found be much lower than observed in a previous study. In conclusion, in two laboratories, simvastatin did not ameliorate disease pathology in mdx mice, which could either be due to the ineffectiveness of simvastatin itself or due to the low simvastatin plasma levels following oral administration via the food

Effect of forced and voluntary exercise on muscle function and integrity in aged mice expressing low dystrophin levels

Imaging- and therapeutic targets in neoplastic and musculoskeletal inflammatory diseas

Voluntary exercise improves muscle function and does not exacerbate muscle and heart pathology in aged Duchenne muscular dystrophy mice

Functional Genomics of Muscle, Nerve and Brain Disorder

Effect of forced and voluntary exercise on heart function in mice with low dystrophin levels

Cardiovascular Aspects of Radiolog

Cyclic Peptides to Improve Delivery and Exon Skipping of Antisense Oligonucleotides in a Mouse Model for Duchenne Muscular Dystrophy

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Natural disease history of the dy2J mouse model of laminin α2 (merosin)-deficient congenital muscular dystrophy.

Merosin deficient congenital muscular dystrophy 1A (MDC1A) is a very rare autosomal recessive disorder caused by mutations in the LAMA2 gene leading to severe and progressive muscle weakness and atrophy. Although over 350 causative mutations have been identified for MDC1A, no treatment is yet available. There are many therapeutic approaches in development, but the lack of natural history data of the mouse model and standardized outcome measures makes it difficult to transit these pre-clinical findings to clinical trials. Therefore, in the present study, we collected natural history data and assessed pre-clinical outcome measures for the dy2J/dy2J mouse model using standardized operating procedures available from the TREAT-NMD Alliance. Wild type and dy2J/dy2J mice were subjected to five different functional tests from the age of four to 32 weeks. Non-tested control groups were taken along to assess whether the functional test regime interfered with muscle pathology. Respiratory function, body weights and creatine kinase levels were recorded. Lastly, skeletal muscles were collected for further histopathological and gene expression analyses. Muscle function of dy2J/dy2J mice was severely impaired at four weeks of age and all mice lost the ability to use their hind limbs. Moreover, respiratory function was altered in dy2J/dy2J mice. Interestingly, the respiration rate was decreased and declined with age, whereas the respiration amplitude was increased in dy2J/dy2J mice when compared to wild type mice. Creatine kinase levels were comparable to wild type mice. Muscle histopathology and gene expression analysis revealed that there was a specific regional distribution pattern of muscle damage in dy2J/dy2J mice. Gastrocnemius appeared to be the most severely affected muscle with a high proportion of atrophic fibers, increased fibrosis and inflammation. By contrast, triceps was affected moderately and diaphragm only mildly. Our study presents a complete natural history dataset which can be used in setting up standardized studies in dy2J/dy2J mice

Dystrophin deficiency leads to dysfunctional glutamate clearance in iPSC derived astrocytes

Duchenne muscular dystrophy (DMD) results, beside muscle degeneration in cognitive defects. As neuronal function is supported by astrocytes, which express dystrophin, we hypothesized that loss of dystrophin from DMD astrocytes might contribute to these cognitive defects. We generated cortical neuronal and astrocytic progeny from induced pluripotent stem cells (PSC) from six DMD subjects carrying different mutations and several unaffected PSC lines. DMD astrocytes displayed cytoskeletal abnormalities, defects in Ca+2 homeostasis and nitric oxide signaling. In addition, defects in glutamate clearance were identified in DMD PSC-derived astrocytes; these deficits were related to a decreased neurite outgrowth and hyperexcitability of neurons derived from healthy PSC. Read-through molecule restored dystrophin expression in DMD PSC-derived astrocytes harboring a premature stop codon mutation, corrected the defective astrocyte glutamate clearance and prevented associated neurotoxicity. We propose a role for dystrophin deficiency in defective astroglial glutamate homeostasis which initiates defects in neuronal development.Genetics of disease, diagnosis and treatmen

Elevated collagen levels in skeletal muscles in SGCA- and SGCD-null mice and in the heart of SGCD-null mice.

<p><b>(a)</b> Immunofluorescent images of skeletal muscles stained with collagen type I (fibrotic marker, green) and laminin (extracellular matrix of muscle fibres, red) Scale bar: 100 μm. <b>(b)</b> Quantification of collagen type I positive area in skeletal muscles relative to wild type muscles. A significant increase in the percentage of collagen type I positive area was found in diaphragm and quadriceps muscles of SGCA- and SGCD-null mice, while no difference was found in the gastrocnemius. Tibialis anterior muscles of female SGCD-null mice showed a significant increase in collagen type I positive area compared to wild type. <b>(c)</b> Fibrotic and inflammatory gene expression measured by qPCR, normalized to <i>Gapdh</i> (n = 5 mice per group) in skeletal muscles of LGMD and wild type mice. A significant increase in <i>Col1a1</i> and <i>Cd68</i> expression was found in SGCA- and SGCD-null muscles when compared to wild type muscles. <b>(d)</b> Immunofluorescence images of the heart stained with collagen type I (fibrotic marker, green). Scale bar: 1000 μm. <b>(e)</b> The percentage of collagen type I positive area, measured with Image J was significantly increased in SGCD-null mice compared to wild type mice; males showed a significantly higher increase in collagen than did female SGCD-null mice. Q, quadriceps; GC, gastrocnemius; TA, tibialis anterior; Dia, diaphragm. * Indicates a significant difference from WT controls. # Indicates a significant difference from female SGCD-null mice. Error bars represent ± SD.</p

Respiratory function and creatine kinase levels in <i>dy</i>^<i>2J</i><i>/dy</i>^<i>2J</i> mice.

<p><b>(a)</b> Respiration rate was significantly lower (<i>P</i><0.001) in <i>dy</i>^<i>2J</i><i>/dy</i>^<i>2J</i> mice at 15 and 34 weeks of age, as compared to wild type mice (WT). <i>Dy</i>^<i>2J</i><i>/dy</i>^<i>2J</i> mice aged 34 weeks showed a significantly lower (<i>P</i><0.05) respiration rate than 15 weeks old mice, while no differences were found with age in wild type mice. <b>(b)</b> Respiration amplitude normalized to body weight was significantly higher (<i>P</i><0.001) in <i>dy</i>^<i>2J</i><i>/dy</i>^<i>2J</i> mice at 15 and 34 weeks of age, as compared to wild type mice. No differences in normalized respiration amplitude were found with age and between genders in wild type and <i>dy</i>^<i>2J</i><i>/dy</i>^<i>2J</i> mice. Males are indicated by squares and females by circles. <b>(c)</b> Creatine kinase levels were significantly higher (<i>P</i><0.01) in females <i>dy</i>^<i>2J</i><i>/dy</i>^<i>2J</i> and wild type mice at four and eight weeks of age. * Indicates a significant difference. Error bars represent ± SEM, n = 6 per genotype per gender.</p

Accumulation of fat infiltrates in LGMD strains.

<p><b>(a)</b> Immunofluorescent images of skeletal muscles stained with Nile-red (infiltrated lipids, red) Scale bar: 100 μm <b>(b)</b> Quantification of the immunofluorescent areas. A significant increase in Nile red -positive areas (n = 5 mice per group) was found in SGCD-null diaphragm and SGCA-null gastrocnemius muscles when compared to wild type muscles. <b>(c)</b> Adipogenic gene expression measured by qPCR, normalized to <i>Gapdh</i> (n = 5 mice per group). Upregulation of adipogenic gene expression (<i>Adipoq</i>, <i>Ppar-gamma</i>, <i>Atgl</i>) was found in diaphragm muscle of both LGMD strains and <i>Hsl</i> was significantly upregulated in SGCA-null diaphragm muscle compared to wild type. Q, quadriceps; GC, gastrocnemius; TA, tibialis anterior; Dia, diaphragm. * Indicates significant difference from WT controls. Error bars represent ± SD.</p