Limits...
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.

Show MeSH

Related in: MedlinePlus

EBD (a–e) and  H&E staining (f) on 7-μm (a,  b, e, and f) and 15-μm (c and  d) skeletal muscle cryosections from 8- (a, b, e, and f)  and 16-wk-old (c and d) intravenously (a, b, e, and f)  and intraperitoneally (c and  d) injected mdx mice. In  some animals, the number of  dye-positive fibers in the  femoral quadriceps muscle  was >70% (a). b shows a  magnification of a in which  the fascia demarcates a  highly damaged muscle region from the unaffected adjacent muscle. Other muscles,  including the intercostal  muscles (c, white asterisks indicate rips) and gluteal muscles (d, longitudinal section)  took up the dye. EBD staining in mdx diaphragm (e)  demonstrated variation in  the dye-positive fibers. Dye  positive fibers in the corresponding H&E staining (f)  revealed morphological features of normal fibers (asterisk) as well as of necrosis (arrowhead). Hypercontracted  fibers did not necessarily indicate membrane damage,  since some of them did not  take up EBD (arrows). Bars,  100 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2139791&req=5

Figure 2: EBD (a–e) and H&E staining (f) on 7-μm (a, b, e, and f) and 15-μm (c and d) skeletal muscle cryosections from 8- (a, b, e, and f) and 16-wk-old (c and d) intravenously (a, b, e, and f) and intraperitoneally (c and d) injected mdx mice. In some animals, the number of dye-positive fibers in the femoral quadriceps muscle was >70% (a). b shows a magnification of a in which the fascia demarcates a highly damaged muscle region from the unaffected adjacent muscle. Other muscles, including the intercostal muscles (c, white asterisks indicate rips) and gluteal muscles (d, longitudinal section) took up the dye. EBD staining in mdx diaphragm (e) demonstrated variation in the dye-positive fibers. Dye positive fibers in the corresponding H&E staining (f) revealed morphological features of normal fibers (asterisk) as well as of necrosis (arrowhead). Hypercontracted fibers did not necessarily indicate membrane damage, since some of them did not take up EBD (arrows). Bars, 100 μm.

Mentions: In the mdx mutant, administered EBD always resulted in blue discoloration of skeletal muscles (Fig. 1). This result was independent of the age of the animals used. The accumulation of EBD tended to be more intense at certain anatomical sites, forming a characteristic topographic pattern of staining. Areas of blue staining appeared mainly within the regions of the proximal limb muscles, as well as the pelvic and the shoulder girdle (Fig. 1). The dye was particularly incorporated in gluteal, femoral quadriceps, and the ischiocrural muscles (hind limbs) and sometimes the pectoral and the triceps brachii muscles (forelimbs; Fig. 1). Affected muscles were not stained homogeneously, but they typically showed blue strands representing damaged muscle fibers. In a longitudinal alignment, these strands could be seen throughout the entire length of the muscles (Fig. 1). Although there was a general topographic distribution of the dye in skeletal muscles of mdx mice, permeability of a given muscle region varied from animal to animal and even between opposing limbs within the same animal. We found differences in both the intensity and the extent of stained regions in left and right limbs (Fig. 1 b). In addition to the proximal limb muscles, we also found discoloration of the external oblique muscle of the abdomen, the longest thoracic and lumbar muscles, the cutaneous muscle of the trunk (Fig. 1 c), and in intercostal muscles (Fig. 2 c). Anterior tibial muscles in mdx mice were often spared from dye staining. In contrast, the diaphragm of mdx mice showed areas of dye incorporation in all tested animals (Fig. 2 e). Because of the variability in dye accumulation and distribution, there was no significant difference in the staining pattern among mice that were 4–52 wk old.


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

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

EBD (a–e) and  H&E staining (f) on 7-μm (a,  b, e, and f) and 15-μm (c and  d) skeletal muscle cryosections from 8- (a, b, e, and f)  and 16-wk-old (c and d) intravenously (a, b, e, and f)  and intraperitoneally (c and  d) injected mdx mice. In  some animals, the number of  dye-positive fibers in the  femoral quadriceps muscle  was >70% (a). b shows a  magnification of a in which  the fascia demarcates a  highly damaged muscle region from the unaffected adjacent muscle. Other muscles,  including the intercostal  muscles (c, white asterisks indicate rips) and gluteal muscles (d, longitudinal section)  took up the dye. EBD staining in mdx diaphragm (e)  demonstrated variation in  the dye-positive fibers. Dye  positive fibers in the corresponding H&E staining (f)  revealed morphological features of normal fibers (asterisk) as well as of necrosis (arrowhead). Hypercontracted  fibers did not necessarily indicate membrane damage,  since some of them did not  take up EBD (arrows). Bars,  100 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139791&req=5

Figure 2: EBD (a–e) and H&E staining (f) on 7-μm (a, b, e, and f) and 15-μm (c and d) skeletal muscle cryosections from 8- (a, b, e, and f) and 16-wk-old (c and d) intravenously (a, b, e, and f) and intraperitoneally (c and d) injected mdx mice. In some animals, the number of dye-positive fibers in the femoral quadriceps muscle was >70% (a). b shows a magnification of a in which the fascia demarcates a highly damaged muscle region from the unaffected adjacent muscle. Other muscles, including the intercostal muscles (c, white asterisks indicate rips) and gluteal muscles (d, longitudinal section) took up the dye. EBD staining in mdx diaphragm (e) demonstrated variation in the dye-positive fibers. Dye positive fibers in the corresponding H&E staining (f) revealed morphological features of normal fibers (asterisk) as well as of necrosis (arrowhead). Hypercontracted fibers did not necessarily indicate membrane damage, since some of them did not take up EBD (arrows). Bars, 100 μm.
Mentions: In the mdx mutant, administered EBD always resulted in blue discoloration of skeletal muscles (Fig. 1). This result was independent of the age of the animals used. The accumulation of EBD tended to be more intense at certain anatomical sites, forming a characteristic topographic pattern of staining. Areas of blue staining appeared mainly within the regions of the proximal limb muscles, as well as the pelvic and the shoulder girdle (Fig. 1). The dye was particularly incorporated in gluteal, femoral quadriceps, and the ischiocrural muscles (hind limbs) and sometimes the pectoral and the triceps brachii muscles (forelimbs; Fig. 1). Affected muscles were not stained homogeneously, but they typically showed blue strands representing damaged muscle fibers. In a longitudinal alignment, these strands could be seen throughout the entire length of the muscles (Fig. 1). Although there was a general topographic distribution of the dye in skeletal muscles of mdx mice, permeability of a given muscle region varied from animal to animal and even between opposing limbs within the same animal. We found differences in both the intensity and the extent of stained regions in left and right limbs (Fig. 1 b). In addition to the proximal limb muscles, we also found discoloration of the external oblique muscle of the abdomen, the longest thoracic and lumbar muscles, the cutaneous muscle of the trunk (Fig. 1 c), and in intercostal muscles (Fig. 2 c). Anterior tibial muscles in mdx mice were often spared from dye staining. In contrast, the diaphragm of mdx mice showed areas of dye incorporation in all tested animals (Fig. 2 e). Because of the variability in dye accumulation and distribution, there was no significant difference in the staining pattern among mice that were 4–52 wk old.

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