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1.
PLoS Genet ; 16(11): e1009179, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-33175853

RESUMO

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. Here we examine the functional capacity of an rAAV-mediated microutrophin (µUtrn) therapy in the mdx4cv mouse model of DMD. We found that rAAV-µUtrn led to improvement in dystrophic histopathology & mostly restored the architecture of the neuromuscular and myotendinous junctions. Physiological studies of tibialis anterior muscles indicated peak force maintenance, with partial improvement of specific force. A fundamental question for µUtrn therapeutics is not only can it replace critical functions of dystrophin, but whether full-length utrophin impacts the therapeutic efficacy of the smaller, highly expressed µUtrn. As such, we found that µUtrn significantly reduced the spacing of the costameric lattice relative to full-length utrophin. Further, immunostaining suggested the improvement in dystrophic pathophysiology was largely influenced by favored correction of fast 2b fibers. However, unlike µUtrn, µdystrophin (µDys) expression did not show this fiber type preference. Interestingly, µUtrn was better able to protect 2a and 2d fibers in mdx:utrn-/- mice than in mdx4cv mice where the endogenous full-length utrophin was most prevalent. Altogether, these data are consistent with the role of steric hindrance between full-length utrophin & µUtrn within the sarcolemma. Understanding the stoichiometry of this effect may be important for predicting clinical efficacy.


Assuntos
Terapia Genética/métodos , Fibras Musculares Esqueléticas/patologia , Distrofia Muscular de Duchenne/terapia , Utrofina/uso terapêutico , Animais , Dependovirus/genética , Modelos Animais de Doenças , Distrofina/genética , Técnicas de Transferência de Genes , Vetores Genéticos/genética , Células HEK293 , Humanos , Camundongos , Camundongos Endogâmicos mdx , Microscopia Eletrônica , Contração Muscular , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/ultraestrutura , Músculo Esquelético , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/patologia , Junção Neuromuscular/patologia , Junção Neuromuscular/ultraestrutura , Sarcolema/patologia , Sarcolema/ultraestrutura , Utrofina/genética
2.
Proc Natl Acad Sci U S A ; 112(2): 424-9, 2015 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-25548157

RESUMO

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. In this study, we describe the control of fiber type specification and susceptibility to metabolic disease by folliculin interacting protein-1 (Fnip1). Using Fnip1 null mice, we found that loss of Fnip1 increased the representation of type I fibers characterized by increased myoglobin, slow twitch markers [myosin heavy chain 7 (MyH7), succinate dehydrogenase, troponin I 1, troponin C1, troponin T1], capillary density, and mitochondria number. Cultured Fnip1-null muscle fibers had higher oxidative capacity, and isolated Fnip1-null skeletal muscles were more resistant to postcontraction fatigue relative to WT skeletal muscles. Biochemical analyses revealed increased activation of the metabolic sensor AMP kinase (AMPK), and increased expression of the AMPK-target and transcriptional coactivator PGC1α in Fnip1 null skeletal muscle. Genetic disruption of PGC1α rescued normal levels of type I fiber markers MyH7 and myoglobin in Fnip1-null mice. Remarkably, loss of Fnip1 profoundly mitigated muscle damage in a murine model of Duchenne muscular dystrophy. These results indicate that Fnip1 controls skeletal muscle fiber type specification and warrant further study to determine whether inhibition of Fnip1 has therapeutic potential in muscular dystrophy diseases.


Assuntos
Proteínas de Transporte/fisiologia , Fibras Musculares de Contração Rápida/patologia , Fibras Musculares de Contração Rápida/fisiologia , Fibras Musculares de Contração Lenta/patologia , Fibras Musculares de Contração Lenta/fisiologia , Distrofia Muscular de Duchenne/patologia , Distrofia Muscular de Duchenne/fisiopatologia , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Proteínas de Transporte/genética , Modelos Animais de Doenças , Masculino , Alvo Mecanístico do Complexo 1 de Rapamicina , Camundongos , Camundongos Endogâmicos mdx , Camundongos Knockout , Mitocôndrias Musculares/metabolismo , Mitocôndrias Musculares/patologia , Complexos Multiproteicos/metabolismo , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Distrofia Muscular de Duchenne/genética , Mioglobina/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Serina-Treonina Quinases TOR/metabolismo , Fatores de Transcrição/deficiência , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
3.
PLoS Genet ; 10(6): e1004431, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24922526

RESUMO

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. An ∼ 2.5 fold increase in utrophin expression in the dko skeletal muscles prevented necrosis in ∼ 91% of 1a, 2a and 2d/x fiber-types. In contrast, utrophin expression was reduced in the extrasynaptic sarcolemma of the dko fast 2b fibers leading to increased membrane fragility and dystrophic pathology. Despite lacking extrasynaptic utrophin, the dko fast 2b fibers were less dystrophic than the mdx4cv fast 2b fibers suggesting utrophin-independent mechanisms were also contributing to the reduced dystrophic pathology. We found no overt change in the regenerative capacity of muscle stem cells when comparing the wild-type, desmin-/-, mdx4cv and dko gastrocnemius muscles injured with notexin. Utrophin could form costameric striations with α-sarcomeric actin in the dko to maintain the integrity of the membrane, but the lack of restoration of the NODS (nNOS, α-dystrobrevin 1 and 2, α1-syntrophin) complex and desmin coincided with profound changes to the sarcomere alignment in the diaphragm, deposition of collagen between the myofibers, and impaired diaphragm function. We conclude that the dko mice may provide new insights into the structural mechanisms that influence endogenous utrophin expression that are pertinent for developing a therapy for DMD.


Assuntos
Desmina/genética , Distrofina/genética , Músculo Esquelético/patologia , Distrofia Muscular de Duchenne/genética , Utrofina/biossíntese , Animais , Proteínas de Ligação ao Cálcio/biossíntese , Proteínas Associadas à Distrofina/biossíntese , Venenos Elapídicos , Inflamação/imunologia , Macrófagos/imunologia , Masculino , Proteínas de Membrana/biossíntese , Camundongos , Camundongos Endogâmicos mdx , Camundongos Knockout , Proteínas Musculares/biossíntese , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/mortalidade , Distrofia Muscular de Duchenne/fisiopatologia , Sarcolema/metabolismo , Sarcômeros/fisiologia
4.
Proc Natl Acad Sci U S A ; 111(15): 5723-8, 2014 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-24706788

RESUMO

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. Here we biochemically compared the previously documented microtubule binding activity of dystrophin with utrophin and analyzed several transgenic mouse models to identify phenotypes of the mdx mouse that remain despite transgenic utrophin overexpression. Our in vitro analyses revealed that dystrophin binds microtubules with high affinity and pauses microtubule polymerization, whereas utrophin has no activity in either assay. We also found that transgenic utrophin overexpression does not correct subsarcolemmal microtubule lattice disorganization, loss of torque production after in vivo eccentric contractions, or physical inactivity after mild exercise. Finally, our data suggest that exercise-induced inactivity correlates with loss of sarcolemmal neuronal NOS localization in mdx muscle, whereas loss of in vivo torque production after eccentric contraction-induced injury is associated with microtubule lattice disorganization.


Assuntos
Distrofina/deficiência , Distrofina/metabolismo , Microtúbulos/metabolismo , Contração Muscular/fisiologia , Músculo Esquelético/fisiopatologia , Utrofina/metabolismo , Animais , Fluorescência , Camundongos , Camundongos Transgênicos , Torque
5.
Hum Mol Genet ; 20(24): 4978-90, 2011 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-21949353

RESUMO

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. Dp116:mdx:utrn(-/-) transgenic mice had dramatic improvements in growth, mobility and lifespan compared with controls. This was associated with increased muscle mass and force generating capacity of limb muscles, although myofiber size and specific force were unchanged. Conversely, Dp116 had no effect on dystrophic injury as determined by muscle histopathology and serum creatine kinase levels. Dp116 also failed to restore normal fiber-type distribution or the post-synaptic architecture of the neuromuscular junction. These data demonstrate that the DGC is critical for growth and maintenance of muscle mass, a function that is independent of the ability to prevent dystrophic pathophysiology. Likewise, this is the first demonstration in skeletal muscle of a positive functional role for a dystrophin protein that lacks actin-binding domains. We conclude that both mechanical and non-mechanical functions of dystrophin are important for its role in skeletal muscle.


Assuntos
Distrofina/metabolismo , Longevidade , Músculo Esquelético/patologia , Músculo Esquelético/fisiopatologia , Distrofia Muscular Animal/patologia , Distrofia Muscular Animal/prevenção & controle , Animais , Fenômenos Biomecânicos , Creatina Quinase/sangue , Distrofina/química , Esôfago/patologia , Feminino , Masculino , Camundongos , Camundongos Endogâmicos mdx , Camundongos Transgênicos , Contração Muscular , Músculo Esquelético/ultraestrutura , Distrofia Muscular Animal/sangue , Distrofia Muscular Animal/fisiopatologia , Junção Neuromuscular/metabolismo , Junção Neuromuscular/patologia , Junção Neuromuscular/ultraestrutura , Tamanho do Órgão , Isoformas de Proteínas/metabolismo , Análise de Sobrevida , Utrofina/deficiência , Utrofina/metabolismo
6.
Mol Ther ; 20(8): 1501-7, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22692496

RESUMO

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. In this study, we used widespread intramuscular (i.m.) injection to deliver AAV6-canine micro-dystrophin (c-µdys) throughout a group of skeletal muscles in dystrophic dogs given a brief course of commonly used immunosuppressants. Robust c-µdys expression was obtained for at least two years and was associated with molecular reconstitution of the dystrophin-glycoprotein complex (DGC) at the muscle membrane. Importantly, c-µdys expression was maintained for at least 18 months after discontinuing immunosuppression. The results obtained in a relevant preclinical model of DMD demonstrate feasibility of widespread AAV-mediated muscle transduction and transgene expression in the presence of transient immunosuppression to achieve molecular reconstitution that can be directly translated to human trials.


Assuntos
Distrofina/metabolismo , Distrofia Muscular de Duchenne/metabolismo , Distrofia Muscular de Duchenne/terapia , Animais , Western Blotting , Linhagem Celular , Cães , Distrofina/genética , Ensaio de Imunoadsorção Enzimática , Humanos , Microscopia Eletrônica , Microscopia de Fluorescência , Distrofia Muscular de Duchenne/genética
7.
PLoS Genet ; 6(5): e1000958, 2010 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-20502633

RESUMO

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. Here we performed extensive structure-function analyses of truncated dystrophins with modified hinges and spectrin-like repeats in mdx mice. We found that the polyproline site in hinge 2 profoundly influences the functional capacity of a microdystrophin(DeltaR4-R23/DeltaCT) with a large deletion in the hinge 3 region. Inclusion of polyproline in microdystrophin(DeltaR4-R23/DeltaCT) led to small myofibers (12% smaller than wild-type), Achilles myotendinous disruption, ringed fibers, and aberrant neuromuscular junctions in the mdx gastrocnemius muscles. Replacing hinge 2 of microdystrophin(DeltaR4-R23/DeltaCT) with hinge 3 significantly improved the functional capacity to prevent muscle degeneration, increase muscle fiber area, and maintain the junctions. We conclude that the rigid alpha-helical structure of the polyproline site significantly impairs the functional capacity of truncated dystrophins to maintain appropriate connections between the cytoskeleton and extracellular matrix.


Assuntos
Distrofina/fisiologia , Peptídeos/fisiologia , Animais , Distrofina/química , Distrofina/genética , Camundongos , Camundongos Endogâmicos C57BL , Mutação , Peptídeos/química
8.
Front Mol Biosci ; 10: 1228232, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37503538

RESUMO

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. These data provide a possible mechanistic explanation for the relation between circulating endotrophin levels and risk of outcome in HFpEF.

9.
Hum Gene Ther ; 33(7-8): 451-459, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34913759

RESUMO

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. The sera were tested for NAb in a Lec-2 cell line for AAV9 vector and in a COS-7 cell line for the other AAV serotypes. In the 60 Topigs-20 strain 2 to 4 years of age, 100% were positive for AAV2 NAb, 45% positive for AAV6 NAb, and ∼20% positive for each of AAV1, 5, 8, and 9 NAb. These data showed that ∼80% of Norsvin Topigs-20 pigs evaluated were seronegative for pre-existing NAb to the AAV1, 5, 8, and 9 serotypes, respectively. In 22 Gottingen minipigs at 5-6 months of age, serum AAV serotype-specific NAb coexisted with that of various other AAV serotypes at 32% to 46% between two serotypes. These results suggested that coexisting NAb resulted either from multiple AAV serotype coinfection or from one (or more) serotypes that can crossreact with other AAV serotypes in some minipigs. Among the 40 Yucatan minipigs, 20 of the minipigs were <3 months old and were all negative for NAb against AAV5, 8, and 9, and only one of these 20 pigs was positive to AAV1 and 6. We further determined the titers in those positive pigs and found most Gottingen minipigs had low titer at 1:20, whereas some of Topigs-20 pigs had titers between 1:80 and 1:320, and some of Yucatan pigs had titers between 1:160 and 1:640. These results suggested that the majority of the pigs in the three strains would be amenable to gene therapy study using AAV1, AAV5, AAV8, and AAV9 and that prescreening on circulating AAV antibodies could be helpful before inclusion of pigs into studies.


Assuntos
Anticorpos Neutralizantes , Dependovirus , Animais , Anticorpos Antivirais , Dependovirus/genética , Vetores Genéticos/genética , Prevalência , Estudos Soroepidemiológicos , Sorogrupo , Suínos , Porco Miniatura/genética
10.
Hum Mol Genet ; 17(24): 3975-86, 2008 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-18799475

RESUMO

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)). We found that muscles with myotendinous strain injury had an increased expression of utrophin and alpha7-integrin together with the dramatic restructuring of peripheral myofibrils into concentric rings. The sarcolemma of the microdystrophin(DeltaR4-R23)/mdx gastrocnemius muscles was highly protected from experimental lengthening contractions, better than wild-type muscles. We also found a positive correlation between myotendinous strain injury and ringed fibers in the HSA(LR) (human skeletal actin, long repeat) mouse model of myotonic dystrophy. We suggest that changes in protein expression and the formation of rings are adaptations to myotendinous strain injury that help to prevent muscle necrosis and retain the function of necessary muscles during injury, ageing and disease.


Assuntos
Tendão do Calcâneo/patologia , Distrofina/biossíntese , Distrofina/genética , Deleção de Genes , Músculo Esquelético/patologia , Distrofia Muscular Animal/genética , Distrofia Muscular Animal/patologia , Entorses e Distensões/patologia , Tendão do Calcâneo/metabolismo , Tendão do Calcâneo/ultraestrutura , Envelhecimento/genética , Animais , Doença Crônica , Modelos Animais de Doenças , Distrofina/fisiologia , Predisposição Genética para Doença , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Camundongos Transgênicos , Músculo Esquelético/metabolismo , Músculo Esquelético/ultraestrutura , Distrofia Muscular Animal/metabolismo , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/metabolismo , Distrofia Muscular de Duchenne/patologia , Necrose/genética , Necrose/prevenção & controle , Entorses e Distensões/genética , Entorses e Distensões/metabolismo
11.
Muscle Nerve ; 42(2): 268-70, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20544945

RESUMO

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.


Assuntos
Distrofina/genética , Camundongos Endogâmicos mdx/genética , Distrofia Muscular Animal/genética , Reação em Cadeia da Polimerase/métodos , Animais , Reações Falso-Positivas , Genótipo , Camundongos
12.
Mol Cell Neurosci ; 40(4): 433-41, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19171194

RESUMO

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. Here we examined the functional capacity of a minidystrophin (minidysGFP) and a microdystrophin (microdystrophin(DeltaR4-R23)) transgene on the maturation and maintenance of neuromuscular junctions (NMJ) in mdx mice. We found that minidysGFP prevents fragmentation and the loss of postsynaptic folds at the NMJ. In contrast, microdystrophin (DeltaR4-R23) was unable to prevent synapse fragmentation in the limb muscles despite preventing muscle degeneration, although fragmentation was observed to temporally correlate with the formation of ringed fibers. Surprisingly, microdystrophin(DeltaR4-R23) increased the length of synaptic folds in the diaphragm muscles of mdx mice independent of muscle degeneration or the formation of ringed fibers. We also demonstrate that the number and depth of synaptic folds influences the density of voltage-gated sodium channels at the neuromuscular synapse in mdx, microdystrophin(DeltaR4-R23)/mdx and mdx:utrophin double knockout mice. Together, these data suggest that maintenance of the neuromuscular synapse is governed through its lateral association with the muscle cytoskeleton, and that dystrophin has a direct role in promoting the maturation of synaptic folds to allow more sodium channels into the junction.


Assuntos
Distrofina , Terapia Genética/métodos , Distrofia Muscular de Duchenne , Junção Neuromuscular/ultraestrutura , Animais , Citoesqueleto/metabolismo , Distrofina/genética , Distrofina/metabolismo , Glicoproteínas/genética , Glicoproteínas/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos mdx/anatomia & histologia , Camundongos Endogâmicos mdx/genética , Músculo Esquelético/citologia , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/metabolismo , Distrofia Muscular de Duchenne/terapia , Junção Neuromuscular/metabolismo , Junção Neuromuscular/patologia , Óxido Nítrico Sintase Tipo I/genética , Óxido Nítrico Sintase Tipo I/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Canais de Sódio/metabolismo , Sinapses/metabolismo , Sinapses/patologia , Sinapses/ultraestrutura , Utrofina/genética , Utrofina/metabolismo
13.
Neuromuscul Disord ; 27(7): 635-645, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28554556

RESUMO

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 ± 0.4 ng/ml). A 365-fold increase (365.4 ± 65.0, P = 0.0001) in urinary N-ter titin excretion was seen in Duchene muscular dystrophy (DMD) patients. Urinary N-ter titin was also evaluated in dystrophin deficient rodent models. Mdx mice exhibited low urinary N-ter titin levels at 2 weeks of age followed by a robust and sustained elevation starting at 3 weeks of age, coincident with the development of systemic skeletal muscle damage in this model; fold elevation could not be determined because urinary N-ter titin was not detected in age-matched wild type mice. Levels of serum creatine kinase and serum skeletal muscle troponin I (TnI) were also low at 2 weeks, elevated at later time points and were significantly correlated with urinary N-ter titin excretion in mdx mice. Corticosteroid treatment of mdx mice resulted in improved exercise performance and lowering of both urinary N-ter titin and serum skeletal muscle TnI concentrations. Low urinary N-ter titin levels were detected in wild type rats (3.0 ± 0.6 ng/ml), while Dmdmdx rats exhibited a 556-fold increase (1652.5 ± 405.7 ng/ml, P = 0.002) (both at 5 months of age). These results suggest that urinary N-ter titin is present at low basal concentrations in normal urine and increases dramatically coincident with muscle damage produced by dystrophin deficiency. Urinary N-ter titin has potential as a facile, non-invasive and translational biomarker for DMD.


Assuntos
Conectina/urina , Distrofia Muscular de Duchenne/urina , Adolescente , Corticosteroides/uso terapêutico , Fatores Etários , Animais , Estudos de Casos e Controles , Criança , Pré-Escolar , Conectina/sangue , Creatina Quinase/sangue , Estudos Transversais , Humanos , Técnicas Imunoenzimáticas , Camundongos , Camundongos Endogâmicos mdx , Distrofia Muscular Animal/sangue , Distrofia Muscular Animal/tratamento farmacológico , Distrofia Muscular Animal/urina , Distrofia Muscular de Duchenne/sangue , Distrofia Muscular de Duchenne/genética
14.
J Neurosci ; 25(5): 1249-59, 2005 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-15689563

RESUMO

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. In contrast, limb-innervating motoneurons showed decreased spontaneous activity, increased survival, and increased innervation of their target muscles. Both GABA and glycine increased limb-innervating motoneuron activity and decreased respiratory motoneuron activity in wild-type mice, but only glycine responses were abolished in gephyrin-deficient mice. Our results provide genetic evidence that the development of glycinergic and GABAergic synaptic inputs onto motoneurons plays an important role in the survival, axonal branching, and spontaneous activity of motoneurons in developing mammalian embryos.


Assuntos
Proteínas de Transporte/fisiologia , Glicina/fisiologia , Proteínas de Membrana/fisiologia , Neurônios Motores/fisiologia , Músculo Esquelético/inervação , Transmissão Sináptica/fisiologia , Ácido gama-Aminobutírico/fisiologia , Animais , Apoptose , Axônios/ultraestrutura , Proteínas de Transporte/genética , Sobrevivência Celular , Células Cultivadas/efeitos dos fármacos , Diafragma/embriologia , Diafragma/inervação , Diafragma/fisiopatologia , Membro Posterior/inervação , Proteínas de Membrana/deficiência , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios Motores/citologia , Músculo Esquelético/embriologia , Músculo Esquelético/fisiopatologia , Receptores de GABA-A/deficiência , Receptores de GABA-A/fisiologia , Respiração
15.
Skelet Muscle ; 6: 34, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27757223

RESUMO

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. Additionally, muscle aging is improved in syndecan-3 null mice. Since syndecan-3 null myofiber-associated satellite cells downregulate Pax7 and migrate away from the niche more readily than wild type cells, syxndecan-3 appears to regulate satellite cell homeostasis and satellite cell homing to the niche. CONCLUSIONS: Manipulating syndecan-3 provides a promising target for development of therapies to enhance muscle regeneration in muscular dystrophies and in aged muscle.


Assuntos
Homeostase , Músculo Esquelético/fisiologia , Regeneração , Células Satélites de Músculo Esquelético/fisiologia , Nicho de Células-Tronco , Sindecana-3/fisiologia , Animais , Feminino , Masculino , Camundongos , Camundongos Knockout , Músculo Esquelético/lesões , Músculo Esquelético/patologia , Células Satélites de Músculo Esquelético/patologia , Sindecana-3/genética
16.
Int J Dev Biol ; 46(4): 551-8, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12141443

RESUMO

Approximately half of the motoneurons generated during normal embryonic development undergo programmed cell death. Most of this death occurs during the time when synaptic connections are being formed between motoneurons and their target, skeletal muscle. Subsequent muscle activity stemming from this connection helps determine the final number of surviving motoneurons. These observations have given rise to the idea that motoneuron survival is dependent upon access to muscle derived trophic factors, presumably through intact neuromuscular synapses. However, it is not yet understood how the muscle regulates the supply of such trophic factors, or if there are additional mechanisms operating to control the fate of the innervating motoneuron. Recent observations have highlighted target independent mechanisms that also operate to support the survival of motoneurons, such as early trophic-independent periods of motoneuron death, trophic factors derived from Schwann cells and selection of motoneurons during pathfinding. Here we review recent investigations into motoneuron cell death when the molecular signalling between motoneurons and muscle has been genetically disrupted. From these studies, we suggest that in addition to trophic factors from muscle and/or Schwann cells, specific adhesive interactions between motoneurons and muscle are needed to regulate motoneuron survival. Such interactions, along with intact synaptic basal lamina, may help to regulate the supply and presentation of trophic factors to motoneurons.


Assuntos
Apoptose , Regulação da Expressão Gênica no Desenvolvimento , Neurônios/citologia , Agrina/metabolismo , Animais , Anoikis , Morte Celular , Sobrevivência Celular , Embrião de Galinha , Dimerização , Humanos , Camundongos , Modelos Biológicos , Proteínas Musculares/metabolismo , Músculo Esquelético/citologia , Músculo Esquelético/embriologia , Músculo Esquelético/metabolismo , Neurônios/patologia , Ratos , Receptores Proteína Tirosina Quinases/metabolismo , Receptores Colinérgicos/metabolismo , Células de Schwann , Fatores de Tempo
17.
Int J Dev Biol ; 47(1): 41-9, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12653250

RESUMO

In the rodent central nervous system (CNS) during the five days prior to birth, both growth hormone (GH) and its receptor (GHR) undergo transient increases in expression to levels considerably higher than those found postnatally. This increase in expression coincides with the period of neuronal programmed cell death (PCD) in the developing CNS. To evaluate the involvement of growth hormone in the process of PCD, we have quantified the number of motoneurons in the spinal cord and brain stem of wild type and littermate GHR-deficient mice at the beginning and end of the neuronal PCD period. We found no change in motoneuron survival in either the brachial or lumbar lateral motor columns of the spinal cord or in the trochlear, trigeminal, facial or hypoglossal nuclei in the brain stem. We also found no significant differences in spinal cord volume, muscle fiber diameter, or body weight of GHR-deficient fetal mice when compared to their littermate controls. Therefore, despite considerable in vitro evidence for GH action on neurons and glia, genetic disruption of GHR signalling has no effect on prenatal motoneuron number in the mouse, under normal physiological conditions. This may be a result of compensation by the signalling of other neurotrophic cytokines.


Assuntos
Apoptose/fisiologia , Neurônios Motores/citologia , Receptores da Somatotropina/metabolismo , Medula Espinal/embriologia , Animais , Sobrevivência Celular , Feminino , Hormônio do Crescimento/metabolismo , Immunoblotting , Técnicas Imunoenzimáticas , Vértebras Lombares/citologia , Vértebras Lombares/embriologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios Motores/metabolismo , Músculo Esquelético/citologia , Músculo Esquelético/embriologia , Receptores da Somatotropina/deficiência , Receptores da Somatotropina/genética , Transdução de Sinais , Medula Espinal/citologia , Medula Espinal/metabolismo
18.
Skelet Muscle ; 4: 10, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24910770

RESUMO

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. METHODS: To better understand the cellular mechanisms of muscle hypertrophy in mdx mice, we directly compared the temporal progression of the dystrophic pathology in the extensor digitorum longus (EDL) muscle to myofiber number, myofiber branching, and innervation, from 3 to 20 weeks of age. RESULTS: We found that a 28% increase in the number of fibers in transverse sections of muscle correlated with a 31% increase in myofiber branching. Notably, the largest increases in myofiber number and myofiber branching occurred after 12 weeks of age when the proportion of myofibers with central nuclei had stabilized and the mdx mouse had reached maturity. The dystrophic pathology coincided with profound changes to innervation of the muscles that included temporary denervation of necrotic fibers, fragmentation of synapses, and ultra-terminal axon sprouting. However, there was little evidence of synapse formation in the mdx mice from 3 to 20 weeks of age. Only 4.4% of neuromuscular junctions extended ultra-terminal synapses, which failed to mature, and the total number of neuromuscular junctions remained constant. CONCLUSIONS: Muscle hypertrophy in mdx mice results from myofiber branching rather than myofiber hyperplasia.

19.
Prog Mol Biol Transl Sci ; 105: 83-111, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22137430

RESUMO

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). In many cases, invaluable insights into disease mechanisms, structure and function of gene products, and approaches for therapeutic interventions have benefited from the study of animal models of the different MDs (Arnett et al., 2009). The large number of genes that are associated with MD and the tremendous number of animal models that have been developed preclude a complete discussion of each in the context of this review. However, we summarize here a number of the more commonly used models together with a mixture of different types of gene and MD, which serves to give a general overview of the value of animal models of MD for research and therapeutic development.


Assuntos
Modelos Animais de Doenças , Distrofias Musculares/patologia , Animais , Cálcio/metabolismo , Humanos , Proteínas Musculares/química , Proteínas Musculares/metabolismo , Distrofias Musculares/metabolismo
20.
Sci Transl Med ; 2(57): 57ra83, 2010 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-21068442

RESUMO

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. We demonstrate that engraftment of myofiber-associated satellite cells, coupled with an induced muscle injury, markedly alters the environment of young adult host muscle, eliciting a near-lifelong enhancement in muscle mass, stem cell number, and force generation. The abrogation of age-related atrophy appears to arise from an increased regenerative capacity of the donor stem cells, which expand to occupy both myonuclei in myofibers and the satellite cell niche. Further, these cells have extensive self-renewal capabilities, as demonstrated by serial transplantation. These near-lifelong, physiological changes suggest an approach for the amelioration of muscle atrophy and diminished function that arise with aging through myofiber-associated satellite cell transplantation.


Assuntos
Transplante de Células , Senescência Celular , Músculo Esquelético/citologia , Animais , Proteínas de Fluorescência Verde/genética , Camundongos , Músculo Esquelético/fisiologia , Regeneração , Engenharia Tecidual
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