Treatment with rGDF11 does not improve the dystrophic muscle pathology of mdx mice

Cellular senescence is the irreversible arrest of normally dividing cells and is driven by cell cycle inhibitory proteins such as p16, p21 and p53. When cells enter senescence, they secrete a host of proinflammatory factors known as the senescence associated secretory phenotype which has deleterious effects on surrounding cells and tissues. Little is known of the role of senescence in Duchenne Muscular Dystrophy (DMD), the fatal X-linked neuromuscular disorder typified by chronic inflammation, extracellular matrix remodeling and a progressive loss in muscle mass and function. Here, we demonstrate using C57-mdx (8-week-old) and D2-mdx mice (4-week and 8-week-old), two mouse models of DMD, that cells displaying canonical markers of senescence are found within skeletal muscle. 8-week-old D2-mdx mice, which display severe muscle pathology, had greater numbers of senescent cells associated with areas of inflammation which were mostly Cdkn1a-positive macrophages while in C57-mdx muscle, senescent populations were endothelial cells and macrophages localized to newly regenerated myofibers. Interestingly, this pattern was similar to cardiotoxin (CTX)-injured wildtype (WT) muscle which experienced a transient senescent response. Dystrophic muscle demonstrated significant upregulations in senescence pathway genes (Cdkn1a (p21), Cdkn2a (p16INK4A), Trp53 (p53)) which correlated with the quantity of SA-b-Gal-positive cells. These results highlight an underexplored role for cellular senescence in murine dystrophic muscle.

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Early metabolic changes measured by 1H MRS in healthy and dystrophic muscle after injury

Journal of Applied Physiology ◽

10.1152/japplphysiol.00530.2012 ◽

2012 ◽

Vol 113 (5) ◽

pp. 808-816 ◽

Cited By ~ 14

Author(s):

Su Xu ◽

Stephen J. P. Pratt ◽

Espen E. Spangenburg ◽

Richard M. Lovering

Keyword(s):

Skeletal Muscle ◽

Muscle Injury ◽

Tibialis Anterior Muscle ◽

Metabolic Changes ◽

Mdx Mice ◽

Resonance Spectroscopy ◽

Dystrophic Muscle ◽

1H Mrs ◽

Skeletal Muscle Injury

Skeletal muscle injury is often assessed by clinical findings (history, pain, tenderness, strength loss), by imaging, or by invasive techniques. The purpose of this work was to determine if in vivo proton magnetic resonance spectroscopy (1H MRS) could reveal metabolic changes in murine skeletal muscle after contraction-induced injury. We compared findings in the tibialis anterior muscle from both healthy wild-type (WT) muscles (C57BL/10 mice) and dystrophic ( mdx mice) muscles (an animal model for human Duchenne muscular dystrophy) before and after contraction-induced injury. A mild in vivo eccentric injury protocol was used due to the high susceptibility of mdx muscles to injury. As expected, mdx mice sustained a greater loss of force (81%) after injury compared with WT (42%). In the uninjured muscles, choline (Cho) levels were 47% lower in the mdx muscles compared with WT muscles. In mdx mice, taurine levels decreased 17%, and Cho levels increased 25% in injured muscles compared with uninjured mdx muscles. Intramyocellular lipids and total muscle lipid levels increased significantly after injury but only in WT. The increase in lipid was confirmed using a permeable lipophilic fluorescence dye. In summary, loss of torque after injury was associated with alterations in muscle metabolite levels that may contribute to the overall injury response in mdx mice. These results show that it is possible to obtain meaningful in vivo 1H MRS regarding skeletal muscle injury.

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Degenerative and regenerative pathways underlying Duchenne muscular dystrophy revealed by single-nucleus RNA sequencing

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2018391117 ◽

2020 ◽

Vol 117 (47) ◽

pp. 29691-29701 ◽

Cited By ~ 1

Author(s):

Francesco Chemello ◽

Zhaoning Wang ◽

Hui Li ◽

John R. McAnally ◽

Ning Liu ◽

...

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Dystrophin Gene ◽

Cell Types ◽

Muscle Pathology ◽

Dystrophic Muscle ◽

Nonmuscle Cell ◽

Prevalent Disease ◽

Single Nucleus ◽

Muscle Disorder

Duchenne muscular dystrophy (DMD) is a fatal muscle disorder characterized by cycles of degeneration and regeneration of multinucleated myofibers and pathological activation of a variety of other muscle-associated cell types. The extent to which different nuclei within the shared cytoplasm of a myofiber may display transcriptional diversity and whether individual nuclei within a multinucleated myofiber might respond differentially to DMD pathogenesis is unknown. Similarly, the potential transcriptional diversity among nonmuscle cell types within dystrophic muscle has not been explored. Here, we describe the creation of a mouse model of DMD caused by deletion of exon 51 of the dystrophin gene, which represents a prevalent disease-causing mutation in humans. To understand the transcriptional abnormalities and heterogeneity associated with myofiber nuclei, as well as other mononucleated cell types that contribute to the muscle pathology associated with DMD, we performed single-nucleus transcriptomics of skeletal muscle of mice with dystrophin exon 51 deletion. Our results reveal distinctive and previously unrecognized myonuclear subtypes within dystrophic myofibers and uncover degenerative and regenerative transcriptional pathways underlying DMD pathogenesis. Our findings provide insights into the molecular underpinnings of DMD, controlled by the transcriptional activity of different types of muscle and nonmuscle nuclei.

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Stretch-induced growth in chicken wing muscles: effects on hereditary muscular dystrophy

AJP Cell Physiology ◽

10.1152/ajpcell.1982.242.3.c178 ◽

1982 ◽

Vol 242 (3) ◽

pp. C178-C183 ◽

Cited By ~ 27

Author(s):

C. R. Ashmore

Keyword(s):

Muscular Dystrophy ◽

Normal Values ◽

Muscle Growth ◽

Cross Sectional Area ◽

Muscle Pathology ◽

Sectional Area ◽

Normal Muscle ◽

Dystrophic Muscle ◽

Cross Sectional ◽

Passive Stretch

Skeletal muscle growth induced by passive stretch was characterized in the Patigialis muscle of chicks with hereditary muscular dystrophy. When the muscle of 6-wk-old chicks was stretched for 1 wk, the effects on muscle growth and on muscle pathology were variable, but in general few differences between stretched and unstretched muscles were observed. However, when the muscle of 1-wk-old chicks was stretched for 6 wk, the effects on muscle growth and on prevention of pathology were dramatic. Similar to results obtained previously when normal chick muscles were stretched [Holly et al., Am. J. Physiol. 238 (Cell Physiol. 7): C62-C71, 1980; Barnett et al., Am. J. Physiol. 239 (Cell Physiol. 8): C39-C46, 1980], stretched dystrophic muscle increased in weight (200%), cross-sectional area (107%), and fiber cross-sectional area (82%). DNA concentration, which is severalfold higher in unstretched dystrophic muscle compared with unstretched normal muscle, fell to values not different from normal values after being stretched. Nuclei per square millimeter also were the same for stretched dystrophic and stretched normal muscle. Histograms indicated that stretching induced a fiber distribution in dystrophic muscle qualitatively similar to that found in stretched normal muscle. Cytochemical observations revealed a dramatic protective effect of stretch against the progressive pathology of dystrophy. It is concluded that stretch of muscle applied to newly hatched dystrophic chicks is a powerful deterrent of symptoms characteristic of hereditary muscular dystrophy. Stretch imposed after the symptoms of dystrophy are apparent provides little, if any, protection.

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Overexpression of Galgt2 in skeletal muscle prevents injury resulting from eccentric contractions in both mdx and wild-type mice

AJP Cell Physiology ◽

10.1152/ajpcell.00456.2008 ◽

2009 ◽

Vol 296 (3) ◽

pp. C476-C488 ◽

Cited By ~ 53

Author(s):

Paul T. Martin ◽

Rui Xu ◽

Louise R. Rodino-Klapac ◽

Elaine Oglesbay ◽

Marybeth Camboni ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscular Dystrophy ◽

Transgenic Mice ◽

Skeletal Muscles ◽

Eccentric Contractions ◽

Cytotoxic T Cell ◽

Muscle Pathology ◽

Mdx Mice ◽

Specific Force ◽

Wild Type

The cytotoxic T cell (CT) GalNAc transferase, or Galgt2, is a UDP-GalNAc:β1,4- N-acetylgalactosaminyltransferase that is localized to the neuromuscular synapse in adult skeletal muscle, where it creates the synaptic CT carbohydrate antigen {GalNAcβ1,4[NeuAc(orGc)α2, 3]Galβ1,4GlcNAcβ-}. Overexpression of Galgt2 in the skeletal muscles of transgenic mice inhibits the development of muscular dystrophy in mdx mice, a model for Duchenne muscular dystrophy. Here, we provide physiological evidence as to how Galgt2 may inhibit the development of muscle pathology in mdx animals. Both Galgt2 transgenic wild-type and mdx skeletal muscles showed a marked improvement in normalized isometric force during repetitive eccentric contractions relative to nontransgenic littermates, even using a paradigm where nontransgenic muscles had force reductions of 95% or more. Muscles from Galgt2 transgenic mice, however, showed a significant decrement in normalized specific force and in hindlimb and forelimb grip strength at some ages. Overexpression of Galgt2 in muscles of young adult mdx mice, where Galgt2 has no effect on muscle size, also caused a significant decrease in force drop during eccentric contractions and increased normalized specific force. A comparison of Galgt2 and microdystrophin overexpression using a therapeutically relevant intravascular gene delivery protocol showed Galgt2 was as effective as microdystrophin at preventing loss of force during eccentric contractions. These experiments provide a mechanism to explain why Galgt2 overexpression inhibits muscular dystrophy in mdx muscles. That overexpression also prevents loss of force in nondystrophic muscles suggests that Galgt2 is a therapeutic target with broad potential applications.

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Muscle-specific overexpression of IGF-I improves E-C coupling in skeletal muscle fibers from dystrophic mdx mice

AJP Cell Physiology ◽

10.1152/ajpcell.00399.2007 ◽

2008 ◽

Vol 294 (1) ◽

pp. C161-C168 ◽

Cited By ~ 32

Author(s):

Jonathan D. Schertzer ◽

Chris van der Poel ◽

Thea Shavlakadze ◽

Miranda D. Grounds ◽

Gordon S. Lynch

Keyword(s):

Skeletal Muscle ◽

Growth Factor ◽

Muscle Fibers ◽

Transcript Level ◽

Direct Result ◽

Mdx Mice ◽

Contractile Apparatus ◽

Dystrophic Muscle ◽

Insulin Growth Factor ◽

Igf I

Duchenne muscular dystrophy (DMD) is a lethal X-linked disease caused by the absence of functional dystrophin. Abnormal excitation-contraction (E-C) coupling has been reported in dystrophic muscle fibers from mdx mice, and alterations in E-C coupling components may occur as a direct result of dystrophin deficiency. We hypothesized that muscle-specific overexpression of insulin-growth factor-1 (IGF-I) would reduce E-C coupling failure in mdx muscle. Mechanically skinned extensor digitorum longus muscle fibers from mdx mice displayed a faster decline in depolarization-induced force responses (DIFR); however, there were no differences in sarcoplasmic reticulum (SR)-mediated Ca2+ resequestration or in the properties of the contractile apparatus when compared with nondystrophic controls. The rate of DIFR decline was restored to control levels in fibers from transgenic mdx mice that overexpressed IGF-I in skeletal muscle ( mdx/IGF-I mice). Dystrophic muscles have a lower transcript level of a specific dihydropyridine receptor (DHPR) isoform, and IGF-I-mediated changes in E-C coupling were associated with increased transcript levels of specific DHPR isoforms involved in Ca2+ regulation. Importantly, IGF-I overexpression also increased the sensitivity of the contractile apparatus to Ca2+. The results demonstrate that IGF-I can ameliorate fundamental aspects of E-C coupling failure in dystrophic muscle fibers and that these effects are important for the improvements in cellular function induced by this growth factor.

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Gentamicin treatment in exercised mdx mice: Identification of dystrophin-sensitive pathways and evaluation of efficacy in work-loaded dystrophic muscle

Neurobiology of Disease ◽

10.1016/j.nbd.2008.07.009 ◽

2008 ◽

Vol 32 (2) ◽

pp. 243-253 ◽

Cited By ~ 35

Author(s):

Annamaria De Luca ◽

Beatrice Nico ◽

Jean-François Rolland ◽

Anna Cozzoli ◽

Rosa Burdi ◽

...

Keyword(s):

Mdx Mice ◽

Dystrophic Muscle ◽

Gentamicin Treatment

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Sulforaphane mitigates muscle fibrosis in mdx mice via Nrf2-mediated inhibition of TGF-β/Smad signaling

Journal of Applied Physiology ◽

10.1152/japplphysiol.00721.2015 ◽

2016 ◽

Vol 120 (4) ◽

pp. 377-390 ◽

Cited By ~ 37

Author(s):

Chengcao Sun ◽

Shujun Li ◽

Dejia Li

Keyword(s):

Signaling Pathway ◽

Transforming Growth Factor ◽

Smooth Muscle Actin ◽

Mdx Mice ◽

Related Factor ◽

Dependent Manner ◽

Dystrophic Muscle ◽

Smad Signaling ◽

Muscle Fibrosis ◽

Smad Signaling Pathway

Sulforaphane (SFN), an activator of NF-E2-related factor 2 (Nrf2), has been found to have an antifibrotic effect on liver and lung. However, its effects on dystrophic muscle fibrosis remain unknown. This work was undertaken to evaluate the effects of SFN-mediated activation of Nrf2 on dystrophic muscle fibrosis. Male mdx mice (age 3 mo) were treated with SFN by gavage (2 mg/kg body wt per day) for 3 mo. Experimental results demonstrated that SFN remarkably attenuated skeletal and cardiac muscle fibrosis as indicated by reduced Sirius Red staining and immunostaining of the extracellular matrix. Moreover, SFN significantly inhibited the transforming growth factor-β (TGF-β)/Smad signaling pathway and suppressed profibrogenic gene and protein expressions such as those of α-smooth muscle actin (α-SMA), fibronectin, collagen I, plasminogen activator inhibitor-1 (PAI-1), and tissue inhibitor metalloproteinase-1 (TIMP-1) in an Nrf2-dependent manner. Furthermore, SFN significantly decreased the expression of inflammatory cytokines CD45, TNF-α, and IL-6 in mdx mice. In conclusion, these results show that SFN can attenuate dystrophic muscle fibrosis by Nrf2-mediated inhibition of the TGF-β/Smad signaling pathway, which indicates that Nrf2 may represent a new target for dystrophic muscle fibrosis.

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37. Long-Term Expression of Mini-Human Dystrophin in Transgenic mdx Mice Improves Dystrophic Muscle Functions

Molecular Therapy ◽

10.1016/j.ymthe.2006.08.050 ◽

2006 ◽

Vol 13 ◽

pp. S16

Author(s):

Bing Wang ◽

Juan Li ◽

Chunlian Chen ◽

Xiancheng Jiang ◽

Terry O'Day ◽

...

Keyword(s):

Mdx Mice ◽

Dystrophic Muscle ◽

Human Dystrophin ◽

Muscle Functions

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Extensive but Coordinated Reorganization of the Membrane Skeleton in Myofibers of Dystrophic (mdx) Mice

The Journal of Cell Biology ◽

10.1083/jcb.144.6.1259 ◽

1999 ◽

Vol 144 (6) ◽

pp. 1259-1270 ◽

Cited By ~ 65

Author(s):

McRae W. Williams ◽

Robert J. Bloch

Keyword(s):

Skeletal Muscle ◽

Membrane Proteins ◽

Muscle Fibers ◽

Membrane Skeleton ◽

Confocal Imaging ◽

Mdx Mouse ◽

Mdx Mice ◽

Intracellular Membrane ◽

Dystrophic Muscle ◽

Dihydropyridine Receptors

We used immunofluorescence techniques and confocal imaging to study the organization of the membrane skeleton of skeletal muscle fibers of mdx mice, which lack dystrophin. β-Spectrin is normally found at the sarcolemma in costameres, a rectilinear array of longitudinal strands and elements overlying Z and M lines. However, in the skeletal muscle of mdx mice, β-spectrin tends to be absent from the sarcolemma over M lines and the longitudinal strands may be disrupted or missing. Other proteins of the membrane and associated cytoskeleton, including syntrophin, β-dystroglycan, vinculin, and Na,K-ATPase are also concentrated in costameres, in control myofibers, and mdx muscle. They also distribute into the same altered sarcolemmal arrays that contain β-spectrin. Utrophin, which is expressed in mdx muscle, also codistributes with β-spectrin at the mutant sarcolemma. By contrast, the distribution of structural and intracellular membrane proteins, including α-actinin, the Ca-ATPase and dihydropyridine receptors, is not affected, even at sites close to the sarcolemma. Our results suggest that in myofibers of the mdx mouse, the membrane- associated cytoskeleton, but not the nearby myoplasm, undergoes widespread coordinated changes in organization. These changes may contribute to the fragility of the sarcolemma of dystrophic muscle.

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