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Animal models for muscular dystrophy show different patterns of sarcolemmal disruption.

Straub V, Rafael JA, Chamberlain JS, Campbell KP - J. Cell Biol. (1997)

Bottom Line: However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue.One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage.Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

View Article: PubMed Central - PubMed

Affiliation: Department of, Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.

ABSTRACT
Genetic defects in a number of components of the dystrophin-glycoprotein complex (DGC) lead to distinct forms of muscular dystrophy. However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue. One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage. Using tracer molecules, we compared sarcolemmal integrity in animal models for muscular dystrophy and in muscular dystrophy patient samples. Evans blue, a low molecular weight diazo dye, does not cross into skeletal muscle fibers in normal mice. In contrast, mdx mice, a dystrophin-deficient animal model for Duchenne muscular dystrophy, showed significant Evans blue accumulation in skeletal muscle fibers. We also studied Evans blue dispersion in transgenic mice bearing different dystrophin mutations, and we demonstrated that cytoskeletal and sarcolemmal attachment of dystrophin might be a necessary requirement to prevent serious fiber damage. The extent of dye incorporation in transgenic mice correlated with the phenotypic severity of similar dystrophin mutations in humans. We furthermore assessed Evans blue incorporation in skeletal muscle of the dystrophia muscularis (dy/dy) mouse and its milder allelic variant, the dy2J/dy2J mouse, animal models for congenital muscular dystrophy. Surprisingly, these mice, which have defects in the laminin alpha2-chain, an extracellular ligand of the DGC, showed little Evans blue accumulation in their skeletal muscles. Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

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Macroscopic and microscopic evaluation of EBD staining after intravenous dye injection into 3-mo-old normal control (a and  b), mdx (c and d), and dy/dy (e and f) mice. Uptake of dye into the hind legs of the mice was examined 6 h after the injection. The hind  legs were fixed in a 8% formaldehyde solution. In contrast to mdx mice (c), dy/dy (e) or dy2J/dy2J mice never showed localized EBD uptake into skeletal muscles by visual inspection. Blue coloration of dy/dy and dy2J/dy2J mice observed by macroscopic evaluation was  caused by dye uptake into the connective tissue, which is increased in these dystrophic animals. This finding was confirmed by fluorescence microscopy analysis of 7-μm cryosections from the quadriceps femoris muscle of injected animals. Grouped EBD-positive fibers  were only detected in mdx mice (d), whereas cryosections from normal control mice (b), dy/dy (f), or dy2J/dy2J mice did not show dye uptake into groups of muscle fibers. On cryosections of dy/dy (f) mice, single necrotic fibers showed EBD staining by fluorescence microscopy. Bar, 50 μm.
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Figure 6: Macroscopic and microscopic evaluation of EBD staining after intravenous dye injection into 3-mo-old normal control (a and b), mdx (c and d), and dy/dy (e and f) mice. Uptake of dye into the hind legs of the mice was examined 6 h after the injection. The hind legs were fixed in a 8% formaldehyde solution. In contrast to mdx mice (c), dy/dy (e) or dy2J/dy2J mice never showed localized EBD uptake into skeletal muscles by visual inspection. Blue coloration of dy/dy and dy2J/dy2J mice observed by macroscopic evaluation was caused by dye uptake into the connective tissue, which is increased in these dystrophic animals. This finding was confirmed by fluorescence microscopy analysis of 7-μm cryosections from the quadriceps femoris muscle of injected animals. Grouped EBD-positive fibers were only detected in mdx mice (d), whereas cryosections from normal control mice (b), dy/dy (f), or dy2J/dy2J mice did not show dye uptake into groups of muscle fibers. On cryosections of dy/dy (f) mice, single necrotic fibers showed EBD staining by fluorescence microscopy. Bar, 50 μm.

Mentions: Interestingly, dy/dy and dy2J/dy2J mice did not reveal dye incorporation into skeletal muscles (Fig. 6). Because of the increase in connective tissue in dystrophic muscle, the mice showed a blue aspect resulting from dye accumulation into their connective tissue. Otherwise, we did not detect any dye accumulation in the inspected muscles (Table I).


Animal models for muscular dystrophy show different patterns of sarcolemmal disruption.

Straub V, Rafael JA, Chamberlain JS, Campbell KP - J. Cell Biol. (1997)

Macroscopic and microscopic evaluation of EBD staining after intravenous dye injection into 3-mo-old normal control (a and  b), mdx (c and d), and dy/dy (e and f) mice. Uptake of dye into the hind legs of the mice was examined 6 h after the injection. The hind  legs were fixed in a 8% formaldehyde solution. In contrast to mdx mice (c), dy/dy (e) or dy2J/dy2J mice never showed localized EBD uptake into skeletal muscles by visual inspection. Blue coloration of dy/dy and dy2J/dy2J mice observed by macroscopic evaluation was  caused by dye uptake into the connective tissue, which is increased in these dystrophic animals. This finding was confirmed by fluorescence microscopy analysis of 7-μm cryosections from the quadriceps femoris muscle of injected animals. Grouped EBD-positive fibers  were only detected in mdx mice (d), whereas cryosections from normal control mice (b), dy/dy (f), or dy2J/dy2J mice did not show dye uptake into groups of muscle fibers. On cryosections of dy/dy (f) mice, single necrotic fibers showed EBD staining by fluorescence microscopy. Bar, 50 μm.
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Figure 6: Macroscopic and microscopic evaluation of EBD staining after intravenous dye injection into 3-mo-old normal control (a and b), mdx (c and d), and dy/dy (e and f) mice. Uptake of dye into the hind legs of the mice was examined 6 h after the injection. The hind legs were fixed in a 8% formaldehyde solution. In contrast to mdx mice (c), dy/dy (e) or dy2J/dy2J mice never showed localized EBD uptake into skeletal muscles by visual inspection. Blue coloration of dy/dy and dy2J/dy2J mice observed by macroscopic evaluation was caused by dye uptake into the connective tissue, which is increased in these dystrophic animals. This finding was confirmed by fluorescence microscopy analysis of 7-μm cryosections from the quadriceps femoris muscle of injected animals. Grouped EBD-positive fibers were only detected in mdx mice (d), whereas cryosections from normal control mice (b), dy/dy (f), or dy2J/dy2J mice did not show dye uptake into groups of muscle fibers. On cryosections of dy/dy (f) mice, single necrotic fibers showed EBD staining by fluorescence microscopy. Bar, 50 μm.
Mentions: Interestingly, dy/dy and dy2J/dy2J mice did not reveal dye incorporation into skeletal muscles (Fig. 6). Because of the increase in connective tissue in dystrophic muscle, the mice showed a blue aspect resulting from dye accumulation into their connective tissue. Otherwise, we did not detect any dye accumulation in the inspected muscles (Table I).

Bottom Line: However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue.One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage.Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

View Article: PubMed Central - PubMed

Affiliation: Department of, Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.

ABSTRACT
Genetic defects in a number of components of the dystrophin-glycoprotein complex (DGC) lead to distinct forms of muscular dystrophy. However, little is known about how alterations in the DGC are manifested in the pathophysiology present in dystrophic muscle tissue. One hypothesis is that the DGC protects the sarcolemma from contraction-induced damage. Using tracer molecules, we compared sarcolemmal integrity in animal models for muscular dystrophy and in muscular dystrophy patient samples. Evans blue, a low molecular weight diazo dye, does not cross into skeletal muscle fibers in normal mice. In contrast, mdx mice, a dystrophin-deficient animal model for Duchenne muscular dystrophy, showed significant Evans blue accumulation in skeletal muscle fibers. We also studied Evans blue dispersion in transgenic mice bearing different dystrophin mutations, and we demonstrated that cytoskeletal and sarcolemmal attachment of dystrophin might be a necessary requirement to prevent serious fiber damage. The extent of dye incorporation in transgenic mice correlated with the phenotypic severity of similar dystrophin mutations in humans. We furthermore assessed Evans blue incorporation in skeletal muscle of the dystrophia muscularis (dy/dy) mouse and its milder allelic variant, the dy2J/dy2J mouse, animal models for congenital muscular dystrophy. Surprisingly, these mice, which have defects in the laminin alpha2-chain, an extracellular ligand of the DGC, showed little Evans blue accumulation in their skeletal muscles. Taken together, these results suggest that the pathogenic mechanisms in congenital muscular dystrophy are different from those in Duchenne muscular dystrophy, although the primary defects originate in two components associated with the same protein complex.

Show MeSH
Related in: MedlinePlus