Endomysial fibrosis in duchenne muscular dystrophy: A marker of poor outcome associated with macrophage alternative activation
ABSTRACT There is considerable interindividual variability in motor function among patients with Duchenne muscular dystrophy (DMD); moreover, pathogenetic mechanisms of motor dysfunction in DMD are not understood. Using multiparametric analysis, we correlated initial histologic alterations in quadriceps muscle biopsies from 25 steroid therapy-free patients with DMD with 13 relevant clinical features assessed by a single clinical team during a long-term period (mean, >10 years). There was no residual muscle dystrophin by immunohistochemistry and Western blot analysis in the biopsies. Myofiber size, hypercontracted fibers, necrotic/basophilic fibers, endomysial and perimysial fibrosis, and fatty degeneration were assessed by morphometry. Endomysial fibrosis was the only myopathologic parameter that significantly correlated with poor motor outcome as assessed by quadriceps muscle strength, manual muscle testing of upper and lower limbs at 10 years, and age at ambulation loss (all p<0.002). Motor outcome and fibrosis did not correlate with genotype. Myofibers exhibited oxidative stress-induced protein alterations and became separated from capillaries by fibrosis that was associated with both increase of CD206+ alternatively activated macrophages and a relative decrease of CD56+ satellite cells (both p<0.0001). This study provides a strong rationale for antifibrotic therapeutic strategies in DMD and supports the view that alternatively activated macrophages that are known to inhibit myogenesis while promoting cellular collagen production play a key role in myofibrosis.
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- "Abnormal calcium handling and a concomitant increase in calpain activity were shown to play a critical secondary role in the molecular pathogenesis of DMD   . Importantly, extensive accumulation of collagen and the substitution of contractile fibers with nonfunctional fibrotic tissue are a critical myopathological parameter in dystrophinopathy    and endomysial fibrosis significantly correlates with poor motor outcome in X-linked muscular dystrophy   . "
ABSTRACT: Proteomic profiling plays a decisive role in the identification of novel biomarkers of muscular dystrophy and the elucidation of new pathobiochemical mechanisms that underlie progressive muscle wasting. Building on the findings of recent comparative analyses of tissue samples and body fluids from dystrophic animals and patients afflicted with Duchenne muscular dystrophy, we have used here label-free MS to study the severely dystrophic diaphragm from the not extensively characterized mdx-4cv mouse. This animal model of progressive muscle wasting exhibits less dystrophin-positive revertant fibres than the conventional mdx mouse, making it ideal for the future monitoring of experimental therapies. The pathoproteomic signature of the mdx-4cv diaphragm included a significant increase in the fibrosis marker collagen and related extracellular matrix proteins (asporin, decorin, dermatopontin, prolargin) and cytoskeletal proteins (desmin, filamin, obscurin, plectin, spectrin, tubulin, vimentin, vinculin), as well as decreases in proteins of ion homeostasis (parvalbumin) and the contractile apparatus (myosin binding protein). Importantly, one of the most substantially increased proteins was identified as periostin, a matricellular component and apparent marker of fibrosis and tissue damage. Immunoblotting confirmed a considerable increase of periostin in the dystrophin-deficient diaphragm from both mdx and mdx-4cv mice, suggesting an involvement of this matricellular protein in dystrophinopathy-related fibrosis. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.Proteomics 03/2015; 15(13). DOI:10.1002/pmic.201400471 · 3.97 Impact Factor
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- "Fibrosis is readily seen histologically in DMD (Pearce and Walton 1962) and the mdx (Stedman et al. 1991) and GRMD (Figure 4D) (Kornegay et al. 1988; Valentine et al. 1989) models. Increased endomysial connective tissue occurs early in DMD and correlates with clinical disease progression (Desguerre et al. 2009). Mediators of fibrosis, therefore, are logical therapeutic targets (Klingler et al. 2012). "
ABSTRACT: Duchenne muscular dystrophy (DMD) is an X-linked human disorder in which absence of the protein dystrophin causes degeneration of skeletal and cardiac muscle. For the sake of treatment development, over and above definitive genetic and cell-based therapies, there is considerable interest in drugs that target downstream disease mechanisms. Drug candidates have typically been chosen based on the nature of pathologic lesions and presumed underlying mechanisms and then tested in animal models. Mammalian dystrophinopathies have been characterized in mice (mdx mouse) and dogs (golden retriever muscular dystrophy [GRMD]). Despite promising results in the mdx mouse, some therapies have not shown efficacy in DMD. Although the GRMD model offers a higher hurdle for translation, dogs have primarily been used to test genetic and cellular therapies where there is greater risk. Failed translation of animal studies to DMD raises questions about the propriety of methods and models used to identify drug targets and test efficacy of pharmacologic intervention. The mdx mouse and GRMD dog are genetically homologous to DMD but not necessarily analogous. Subcellular species differences are undoubtedly magnified at the whole-body level in clinical trials. This problem is compounded by disparate cultures in clinical trials and preclinical studies, pointing to a need for greater rigor and transparency in animal experiments. Molecular assays such as mRNA arrays and genome-wide association studies allow identification of genetic drug targets more closely tied to disease pathogenesis. Genes in which polymorphisms have been directly linked to DMD disease progression, as with osteopontin, are particularly attractive targets.ILAR journal / National Research Council, Institute of Laboratory Animal Resources 06/2014; 55(1):119-49. DOI:10.1093/ilar/ilu011 · 1.05 Impact Factor
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- "It is not therefore clear whether there is really a difference in dystrophic mouse/human satellite cell regenerative capacity, and if so, whether it is caused by differences in the satellite cells themselves, or the local muscle (e.g., extent of fibrosis ), or systemic environment, or even by the genetic background of the mouse model (Fukada et al. 2010). Whether satellite cell numbers are altered in dystrophic muscle is difficult to determine, as accurate satellite cell quantification in dystrophic muscle is complicated by substitution of muscle fibers by fibrotic and adipose tissue (Desguerre et al. 2009). In addition, " branching " of regenerated myofibers (Bradley 1979; Blaveri et al. 1999) makes quantification of satellite cell numbers per fiber difficult. "
ABSTRACT: Satellite cells are quiescent cells located under the basal lamina of skeletal muscle fibers that contribute to muscle growth, maintenance, repair, and regeneration. Mouse satellite cells have been shown to be muscle stem cells that are able to regenerate muscle fibers and self-renew. As human skeletal muscle is also able to regenerate following injury, we assume that the human satellite cell is, like its murine equivalent, a muscle stem cell. In this review, we compare human and mouse satellite cells and highlight their similarities and differences. We discuss gaps in our knowledge of human satellite cells, compared with that of mouse satellite cells, and suggest ways in which we may advance studies on human satellite cells, particularly by finding new markers and attempting to re-create the human satellite cell niche in vitro.Journal of Histochemistry and Cytochemistry 11/2010; 58(11):941-55. DOI:10.1369/jhc.2010.956201 · 2.40 Impact Factor