Endotrophin, a fibroblast matrikine, may be a driver of fibroblast activation in fibro-inflammatory diseases.

Extracellular matrix proteins harbor signaling domains that once released from the parent molecule can trigger cellular responses. One of these molecules is endotrophin, a type VI collagen derived fragment, whose circulatory levels have been associated to an increased risk of adverse outcome in heart failure with preserved ejection fraction (HFpEF). Here we show that the stimulation of human cardiac fibroblasts by endotrophin upregulates the synthesis of type I collagen, the main interstitial collagen that accumulates in the myocardium during fibrogenesis.

Prevalence of Pre-Existing Neutralizing Antibodies Against Adeno-Associated Virus Serotypes 1, 2, 5, 6, 8, and 9 in Sera of Different Pig Strains.

Pre-existing neutralizing antibodies (NAb) to adeno-associated virus (AAV) may diminish the efficacy of AAV-based therapies depending on the titer. To support gene therapy studies in pigs, the seroprevalence of NAb to AAV1, 2, 5, 6, 8, and 9 serotypes were assessed in the sera of 3 different strains of pigs consisting of 60 Norsvin Topigs-20 strain, 22 Gottingen minipigs, and 40 Yucatan minipigs. Cell-based NAb assays were developed for various AAV serotypes.

Microutrophin expression in dystrophic mice displays myofiber type differences in therapeutic effects.

Gene therapy approaches for DMD using recombinant adeno-associated viral (rAAV) vectors to deliver miniaturized (or micro) dystrophin genes to striated muscles have shown significant progress. However, concerns remain about the potential for immune responses against dystrophin in some patients. Utrophin, a developmental paralogue of dystrophin, may provide a viable treatment option.

Dramatic elevation in urinary amino terminal titin fragment excretion quantified by immunoassay in Duchenne muscular dystrophy patients and in dystrophin deficient rodents.

Enzyme-linked and electrochemiluminescence immunoassays were developed for quantification of amino (N-) terminal fragments of the skeletal muscle protein titin (N-ter titin) and qualified for use in detection of urinary N-ter titin excretion. Urine from normal subjects contained a small but measurable level of N-ter titin (1.0 ± 0.

Loss of niche-satellite cell interactions in syndecan-3 null mice alters muscle progenitor cell homeostasis improving muscle regeneration.

Background: The skeletal muscle stem cell niche provides an environment that maintains quiescent satellite cells, required for skeletal muscle homeostasis and regeneration. Syndecan-3, a transmembrane proteoglycan expressed in satellite cells, supports communication with the niche, providing cell interactions and signals to maintain quiescent satellite cells.

Results: Syndecan-3 ablation unexpectedly improves regeneration in repeatedly injured muscle and in dystrophic mice, accompanied by the persistence of sublaminar and interstitial, proliferating myoblasts.

Fnip1 regulates skeletal muscle fiber type specification, fatigue resistance, and susceptibility to muscular dystrophy.

Mammalian skeletal muscle is broadly characterized by the presence of two distinct categories of muscle fibers called type I "red" slow twitch and type II "white" fast twitch, which display marked differences in contraction strength, metabolic strategies, and susceptibility to fatigue. The relative representation of each fiber type can have major influences on susceptibility to obesity, diabetes, and muscular dystrophies. However, the molecular factors controlling fiber type specification remain incompletely defined.

Muscle structure influences utrophin expression in mdx mice.

Duchenne muscular dystrophy (DMD) is a severe muscle wasting disorder caused by mutations in the dystrophin gene. To examine the influence of muscle structure on the pathogenesis of DMD we generated mdx4cv:desmin double knockout (dko) mice. The dko male mice died of apparent cardiorespiratory failure at a median age of 76 days compared to 609 days for the desmin-/- mice.

Myofiber branching rather than myofiber hyperplasia contributes to muscle hypertrophy in mdx mice.

Background: Muscle hypertrophy in the mdx mouse model of Duchenne muscular dystrophy (DMD) can partially compensate for the loss of dystrophin by maintaining peak force production. Histopathology examination of the hypertrophic muscles suggests the hypertrophy primarily results from the addition of myofibers, and is accompanied by motor axon branching. However, it is unclear whether an increased number of innervated myofibers (myofiber hyperplasia) contribute to muscle hypertrophy in the mdx mice.

Microtubule binding distinguishes dystrophin from utrophin.

Dystrophin and utrophin are highly similar proteins that both link cortical actin filaments with a complex of sarcolemmal glycoproteins, yet localize to different subcellular domains within normal muscle cells. In mdx mice and Duchenne muscular dystrophy patients, dystrophin is lacking and utrophin is consequently up-regulated and redistributed to locations normally occupied by dystrophin. Transgenic overexpression of utrophin has been shown to significantly improve aspects of the disease phenotype in the mdx mouse; therefore, utrophin up-regulation is under intense investigation as a potential therapy for Duchenne muscular dystrophy.

Successful regional delivery and long-term expression of a dystrophin gene in canine muscular dystrophy: a preclinical model for human therapies.

Duchenne muscular dystrophy (DMD) is a fatal, X-linked muscle disease caused by mutations in the dystrophin gene. Adeno-associated viral (AAV) vector-mediated gene replacement strategies hold promise as a treatment. Studies in animal models and human trials suggested that immune responses to AAV capsid proteins and transgene products prevented efficient gene therapy.

Animal models of muscular dystrophy.

The muscular dystrophies (MDs) represent a diverse collection of inherited human disorders, which affect to varying degrees skeletal, cardiac, and sometimes smooth muscle (Emery, 2002). To date, more than 50 different genes have been implicated as causing one or more types of MD (Bansal et al., 2003).

Expression of the dystrophin isoform Dp116 preserves functional muscle mass and extends lifespan without preventing dystrophy in severely dystrophic mice.

Dp116 is a non-muscle isoform of dystrophin that assembles the dystrophin-glycoprotein complex (DGC), but lacks actin-binding domains. To examine the functional role of the DGC, we expressed the Dp116 transgene in mice lacking both dystrophin and utrophin (mdx:utrn(-/-)). Unexpectedly, expression of Dp116 prevented the most severe aspects of the mdx:utrn(-/-) phenotype.

Prevention of muscle aging by myofiber-associated satellite cell transplantation.

Skeletal muscle is dynamic, adapting to environmental needs, continuously maintained, and capable of extensive regeneration. These hallmarks diminish with age, resulting in a loss of muscle mass, reduced regenerative capacity, and decreased functionality. Although the mechanisms responsible for this decline are unclear, complex changes within the local and systemic environment that lead to a reduction in regenerative capacity of skeletal muscle stem cells, termed satellite cells, are believed to be responsible.

Sequencing protocols to genotype mdx, mdx(4cv), and mdx(5cv) mice.

Currently available polymerase chain reaction (PCR) genotyping methods for point mutations in the mouse dystrophin gene can lead to false positives and result in wasted time and money due to breeding or treating the wrong mice. Here we describe a simple and accurate method for sequencing the point mutations in mdx, mdx(4cv), and mdx(5cv) mice. This method clearly distinguishes between wildtype, heterozygous, and mutant transcripts, and thereby time and money can be saved by avoiding false positives.

The polyproline site in hinge 2 influences the functional capacity of truncated dystrophins.

Mutations in dystrophin can lead to Duchenne muscular dystrophy or the more mild form of the disease, Becker muscular dystrophy. The hinge 3 region in the rod domain of dystrophin is particularly prone to deletion mutations. In-frame deletions of hinge 3 are predicted to lead to BMD, however the severity of disease can vary considerably.

Preclinical studies for gene therapy of Duchenne muscular dystrophy.

The muscular dystrophies are a diverse group of genetic disorders without an effective treatment. Because they are caused by mutations in various genes, the most direct way to treat them involves correcting the underlying gene defect (ie, gene therapy). Such a gene therapy approach involves delivering a therapeutic gene cassette to essentially all the muscles of the body in a safe and efficacious manner.

The value of mammalian models for duchenne muscular dystrophy in developing therapeutic strategies.

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy. There is no effective treatment and patients typically die in approximately the third decade. DMD is an X-linked recessive disease caused by mutations in the dystrophin gene.

Truncated dystrophins can influence neuromuscular synapse structure.

Duchenne muscular dystrophy (DMD) is characterized by muscle degeneration and structural defects in the neuromuscular synapse that are caused by mutations in dystrophin. Whether aberrant neuromuscular synapse structure is an indirect consequence of muscle degeneration or a direct result of loss of dystrophin function is not known. Rational design of truncated dystrophins has enabled the design of expression cassettes highly effective at preventing muscle degeneration in mouse models of DMD using gene therapy.

Molecular and cellular adaptations to chronic myotendinous strain injury in mdx mice expressing a truncated dystrophin.

Myotendinous strain injury is the most common injury of human skeletal muscles because the majority of muscle forces are transmitted through this region. Although the immediate response to strain injury is well characterized, the chronic response to myotendinous strain injury is less clear. Here we examined the molecular and cellular adaptations to chronic myotendinous strain injury in mdx mice expressing a microdystrophin transgene (microdystrophin(DeltaR4-R23)).

rAAV6-microdystrophin rescues aberrant Golgi complex organization in mdx skeletal muscles.

Muscular dystrophies are a diverse group of severe degenerative muscle diseases. Recent interest in the role of the Golgi complex (GC) in muscle disease has been piqued by findings that several dystrophies result from mutations in putative Golgi-resident glycosyltransferases. Given this new role of the Golgi in sarcolemmal stability, we hypothesized that abnormal Golgi distribution, regulation and/or function may constitute part of the pathology of other dystrophies, where the primary defect is independent of Golgi function.

Functional capacity of dystrophins carrying deletions in the N-terminal actin-binding domain.

Duchenne muscular dystrophy and Becker muscular dystrophy (BMD) are caused by mutations in the dystrophin gene. Although many in-frame deletions in the dystrophin gene lead to mild cases of BMD, truncations within the N-terminal actin-binding domain (ABD1) typically decrease dystrophin expression and lead to more severe cases of BMD. Because of the large reduction in protein expression, the functional capacity of dystrophin proteins deleted for subportions of ABD1 has been difficult to ascertain.

Relevance of motoneuron specification and programmed cell death in embryos to therapy of ALS.

The molecular cues that generate spinal motoneurons in early embryonic development are well defined. Motoneurons are generated in excess and consequently undergo a natural period of programmed cell death. Although it is not known exactly how motoneurons compete for survival in embryonic development, it is hypothesized that they rely on the ability to access limited amounts of trophic factors from peripheral tissues, a process that is tightly regulated by skeletal muscle activity.

Glycinergic and GABAergic synaptic activity differentially regulate motoneuron survival and skeletal muscle innervation.

GABAergic and glycinergic synaptic transmission is proposed to promote the maturation and refinement of the developing CNS. Here we provide morphological and functional evidence that glycinergic and GABAergic synapses control motoneuron development in a region-specific manner during programmed cell death. In gephyrin-deficient mice that lack all postsynaptic glycine receptor and some GABA(A) receptor clusters, there was increased spontaneous respiratory motor activity, reduced respiratory motoneuron survival, and decreased innervation of the diaphragm.

The postsynaptic submembrane machinery at the neuromuscular junction: requirement for rapsyn and the utrophin/dystrophin-associated complex.

Neuromuscular synapse formation is brought about by a complex bi-directional exchange of information between the innervating motor neuron and its target skeletal muscle fiber. Agrin, a heparin sulfate proteoglycan, is released from the motor nerve terminal to activate its muscle-specific kinase (MuSK) receptor that leads to a second messenger cascade requiring rapsyn to ultimately bring about AChR clustering in the muscle membrane. Rapsyn performs many functions in skeletal muscle.

Neuromuscular synapses mediate motor axon branching and motoneuron survival during the embryonic period of programmed cell death.

The embryonic period of motoneuron programmed cell death (PCD) is marked by transient motor axon branching, but the role of neuromuscular synapses in regulating motoneuron number and axonal branching is not known. Here, we test whether neuromuscular synapses are required for the quantitative association between reduced skeletal muscle contraction, increased motor neurite branching, and increased motoneuron survival. We achieved this by comparing agrin and rapsyn mutant mice that lack acetylcholine receptor (AChR) clusters.