Diaphragm muscle fibrosis involves changes in collagen organization with mechanical implications in Duchenne Muscular Dystrophy

In Duchenne muscular dystrophy (DMD), diaphragm muscle dysfunction results in respiratory insufficiency, a leading cause of death in patients. Increased muscle stiffness occurs with buildup of fibrotic tissue, characterized by excessive accumulation of extracellular matrix (ECM) components such as collagen. However, changes in mechanical properties are not explained by collagen amount alone and we must consider the complex structure and mechanics of fibrotic tissue. The goals of our study were to (1) determine if and how collagen organization changes with the progression of DMD in diaphragm muscle tissue, and (2) predict how collagen organization influences the mechanical properties of ECM. We first visualized collagen structure with scanning electron microscopy (SEM) images and then developed an analysis framework to quantify collagen organization and generate image-based finite-element models. The image analysis revealed significant age- and disease-dependent increases in collagen fiber straightness and alignment, ranging from 4.7 to 13.4%, but collagen fibers retained a transverse orientation relative to muscle fibers. The mechanical models predicted significant age- and disease-dependent increases in transverse effective stiffness and average stress, ranging from 8.8 to 12.4%. Additionally, both healthy and diseased models revealed an increase in transverse stiffness relative to longitudinal stiffness, with significant age- and disease-dependent increases in the ratio of transverse to longitudinal stiffness, ranging from 19.7 to 24.5%. This study revealed changes in diaphragm ECM structure and mechanics during the progression of disease in the mdx muscular dystrophy mouse phenotype, highlighting the need to consider the role of collagen organization on diaphragm muscle function.

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Mass Spectrometric Profiling of Extraocular Muscle and Proteomic Adaptations in the mdx-4cv Model of Duchenne Muscular Dystrophy

Life ◽

10.3390/life11070595 ◽

2021 ◽

Vol 11 (7) ◽

pp. 595

Author(s):

Stephen Gargan ◽

Paul Dowling ◽

Margit Zweyer ◽

Jens Reimann ◽

Michael Henry ◽

...

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Biochemical Properties ◽

Mass Spectrometric ◽

Cellular Stress Response ◽

Diaphragm Muscle ◽

Spectrometric Analysis ◽

Mitochondrial Enzymes ◽

Wild Type ◽

Potential Marker

Extraocular muscles (EOMs) represent a specialized type of contractile tissue with unique cellular, physiological, and biochemical properties. In Duchenne muscular dystrophy, EOMs stay functionally unaffected in the course of disease progression. Therefore, it was of interest to determine their proteomic profile in dystrophinopathy. The proteomic survey of wild type mice and the dystrophic mdx-4cv model revealed a broad spectrum of sarcomere-associated proteoforms, including components of the thick filament, thin filament, M-band and Z-disk, as well as a variety of muscle-specific markers. Interestingly, the mass spectrometric analysis revealed unusual expression levels of contractile proteins, especially isoforms of myosin heavy chain. As compared to diaphragm muscle, both proteomics and immunoblotting established isoform MyHC14 as a new potential marker in wild type EOMs, in addition to the previously identified isoforms MyHC13 and MyHC15. Comparative proteomics was employed to establish alterations in the protein expression profile between normal EOMs and dystrophin-lacking EOMs. The analysis of mdx-4cv EOMs identified elevated levels of glycolytic enzymes and molecular chaperones, as well as decreases in mitochondrial enzymes. These findings suggest a process of adaptation in dystrophin-deficient EOMs via a bioenergetic shift to more glycolytic metabolism, as well as an efficient cellular stress response in EOMs in dystrophinopathy.

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Effects of Duchenne muscular dystrophy on muscle stiffness and response to electrically-induced muscle contraction: A 12-month follow-up

Neuromuscular Disorders ◽

10.1016/j.nmd.2017.01.001 ◽

2017 ◽

Vol 27 (3) ◽

pp. 214-220 ◽

Cited By ~ 15

Author(s):

Lilian Lacourpaille ◽

Raphaël Gross ◽

François Hug ◽

Arnaud Guével ◽

Yann Péréon ◽

...

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Muscle Contraction ◽

Muscle Stiffness

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Diaphragm remodeling and compensatory respiratory mechanics in a canine model of Duchenne muscular dystrophy

Journal of Applied Physiology ◽

10.1152/japplphysiol.00833.2013 ◽

2014 ◽

Vol 116 (7) ◽

pp. 807-815 ◽

Cited By ~ 16

Author(s):

A. F. Mead ◽

M. Petrov ◽

A. S. Malik ◽

M. A. Mitchell ◽

M. K. Childers ◽

...

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Respiratory Mechanics ◽

Ex Vivo ◽

Functional Decline ◽

Respiratory Control ◽

Muscle Stiffness ◽

Integrative Approach ◽

Primary Role ◽

Starting Point

Ventilatory insufficiency remains the leading cause of death and late stage morbidity in Duchenne muscular dystrophy (DMD). To address critical gaps in our knowledge of the pathobiology of respiratory functional decline, we used an integrative approach to study respiratory mechanics in a translational model of DMD. In studies of individual dogs with the Golden Retriever muscular dystrophy (GRMD) mutation, we found evidence of rapidly progressive loss of ventilatory capacity in association with dramatic morphometric remodeling of the diaphragm. Within the first year of life, the mechanics of breathing at rest, and especially during pharmacological stimulation of respiratory control pathways in the carotid bodies, shift such that the primary role of the diaphragm becomes the passive elastic storage of energy transferred from abdominal wall muscles, thereby permitting the expiratory musculature to share in the generation of inspiratory pressure and flow. In the diaphragm, this physiological shift is associated with the loss of sarcomeres in series (∼60%) and an increase in muscle stiffness (∼900%) compared with those of the nondystrophic diaphragm, as studied during perfusion ex vivo. In addition to providing much needed endpoint measures for assessing the efficacy of therapeutics, we expect these findings to be a starting point for a more precise understanding of respiratory failure in DMD.

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Performance of Passive Muscle Stiffness in Diagnosis and Assessment of Disease Progression in Duchenne Muscular Dystrophy

Ultrasound in Medicine & Biology ◽

10.1016/j.ultrasmedbio.2021.09.003 ◽

2021 ◽

Author(s):

Hong-Kui Yu ◽

Xiao Liu ◽

Min Pan ◽

Jin-Wei Chen ◽

Chen Liu ◽

...

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Disease Progression ◽

Muscle Stiffness ◽

Passive Muscle ◽

Passive Muscle Stiffness

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Description of a Novel Mechanism Possibly Explaining the Antiproliferative Properties of Glucocorticoids in Duchenne Muscular Dystrophy Fibroblasts Based on Glucocorticoid Receptor GR and NFAT5

International Journal of Molecular Sciences ◽

10.3390/ijms21239225 ◽

2020 ◽

Vol 21 (23) ◽

pp. 9225

Author(s):

Sandrine Herbelet ◽

Boel De Paepe ◽

Jan L. De Bleecker

Keyword(s):

Skeletal Muscle ◽

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Glucocorticoid Receptor ◽

Fibroblast Cell ◽

Nuclear Factor ◽

Fibroblast Proliferation ◽

Activated T Cells ◽

Fibrotic Tissue ◽

Fibroblast Cell Culture

Glucocorticoids are drugs of choice in Duchenne muscular dystrophy (DMD), prolonging patients’ ambulation. Their mode of action at the protein level is not completely understood. In DMD, muscle tissue is replaced by fibrotic tissue produced by fibroblasts, reducing mobility. Nuclear factor of activated T-cells 5 (NFAT5) is involved in fibroblast proliferation. By treating one DMD fibroblast cell culture and one of unaffected skeletal muscle fibroblasts with methylprednisolone (MP) or hydrocortisone (HC) for 24 h or 12 d, the antiproliferative properties of glucocorticoids could be unraveled. NFAT5 localization and expression was explored by immunocytochemistry (ICC), Western blotting (WB) and RT-qPCR. NFAT5 and glucocorticoid receptor (GR) colocalization was measured by ImageJ. GR siRNA was used, evaluating GR’s influence on NFAT5 expression during MP and HC treatment. Cell proliferation was monitored by IncuCyte ZOOM. In DMD fibroblasts, treatment with MP for 24 h induced dots (ICC) positive for NFAT5 and colocalizing with GR. After 12 d of MP or HC in DMD fibroblasts, NFAT5 expression was decreased (RT-qPCR and WB) and growth arrest was observed (Incucyte ZOOM), whereas NFAT5 expression and cell growth remained unchanged in unaffected skeletal muscle fibroblasts. This study may help understand the antiproliferative properties of glucocorticoids in DMD fibroblasts.

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