RESUMEN

Spinal muscular atrophy (SMA) is a recessive, developmental disorder caused by the genetic loss or mutation of the gene SMN1 (Survival of Motor Neuron 1). SMA is characterized by neuromuscular symptoms and muscle weakness. Several years ago, SMA treatment underwent a radical transformation, with the approval of three different SMN-dependent disease modifying therapies. This includes two SMN2 splicing therapies - Risdiplam and Nusinersen. One main challenge for Type II SMA patients treated with these drugs is ongoing muscle fatigue, limited mobility, and other skeletal problems. To date, few molecular studies have been conducted on SMA-patient derived tissues after treatment, limiting our understanding of what targets remain after the principal spinal cord targeted therapies are applied. Therefore, we collected paravertebral muscle from eight Type II patients undergoing spinal surgery for scoliosis and seven controls. We used RNA-sequencing to characterize their transcriptional profiles and correlate these with muscle histology. Despite the limited cohort size and heterogeneity, we observed a consistent loss of oxidative phosphorylation machinery of the mitochondria, a decrease in mitochondrial DNA copy number, and a correlation between signals of cellular stress, denervation and increased fibrosis. This work provides new putative targets for combination therapies for Type II SMA.

RESUMEN

Our study was to characterize sarcopenia in C57BL/6J mice using a clinically relevant definition to investigate the underlying molecular mechanisms. Aged male (23-32 months old) and female (27-28 months old) C57BL/6J mice were classified as non-, probable-, or sarcopenic based on assessments of grip strength, muscle mass, and treadmill running time, using 2 SDs below the mean of their young counterparts as cutoff points. A 9%-22% prevalence of sarcopenia was identified in 23-26 month-old male mice, with more severe age-related declines in muscle function than mass. Females aged 27-28 months showed fewer sarcopenic but more probable cases compared with the males. As sarcopenia progressed, a decrease in muscle contractility and a trend toward lower type IIB fiber size were observed in males. Mitochondrial biogenesis, oxidative capacity, and AMPK-autophagy signaling decreased as sarcopenia progressed in males, with pathways linked to mitochondrial metabolism positively correlated with muscle mass. No age- or sarcopenia-related changes were observed in mitochondrial biogenesis, OXPHOS complexes, AMPK signaling, mitophagy, or atrogenes in females. Our results highlight the different trajectories of age-related declines in muscle mass and function, providing insights into sex-dependent molecular changes associated with sarcopenia progression, which may inform the future development of novel therapeutic interventions.

Asunto(s)

Envejecimiento , Modelos Animales de Enfermedad , Sarcopenia , Animales , Sarcopenia/patología , Sarcopenia/metabolismo , Masculino , Ratones , Femenino , Envejecimiento/patología , Caracteres Sexuales , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Fenotipo , Ratones Endogámicos C57BL , Factores de Edad , Autofagia , Proteínas Quinasas Activadas por AMP/metabolismo , Proteínas Quinasas Activadas por AMP/genética , Factores Sexuales

RESUMEN

Pulmonary disorders affect 40%-80% of individuals with obesity. Respiratory muscle dysfunction is linked to these conditions; however, its pathophysiology remains largely undefined. Mice subjected to diet-induced obesity (DIO) develop diaphragm muscle weakness. Increased intradiaphragmatic adiposity and extracellular matrix (ECM) content correlate with reductions in contractile force. Thrombospondin-1 (THBS1) is an obesity-associated matricellular protein linked with muscular damage in genetic myopathies. THBS1 induces proliferation of fibro-adipogenic progenitors (FAPs) - mesenchymal cells that differentiate into adipocytes and fibroblasts. We hypothesized that THBS1 drives FAP-mediated diaphragm remodeling and contractile dysfunction in DIO. We tested this by comparing the effects of dietary challenge on diaphragms of wild-type (WT) and Thbs1-knockout (Thbs1-/-) mice. Bulk and single-cell transcriptomics demonstrated DIO-induced stromal expansion in WT diaphragms. Diaphragm FAPs displayed upregulation of ECM and TGF-ß-related expression signatures and augmentation of a Thy1-expressing subpopulation previously linked to type 2 diabetes. Despite similar weight gain, Thbs1-/- mice were protected from these transcriptomic changes and from obesity-induced increases in diaphragm adiposity and ECM deposition. Unlike WT controls, Thbs1-/- diaphragms maintained normal contractile force and motion after DIO challenge. THBS1 is therefore a necessary mediator of diaphragm stromal remodeling and contractile dysfunction in overnutrition and a potential therapeutic target in obesity-associated respiratory dysfunction.

Asunto(s)

Diafragma , Ratones Noqueados , Obesidad , Trombospondina 1 , Animales , Trombospondina 1/metabolismo , Trombospondina 1/genética , Diafragma/fisiopatología , Diafragma/metabolismo , Diafragma/patología , Obesidad/metabolismo , Ratones , Contracción Muscular/fisiología , Masculino , Adipogénesis , Adipocitos/metabolismo , Adipocitos/patología , Dieta Alta en Grasa/efectos adversos , Fibroblastos/metabolismo , Matriz Extracelular/metabolismo , Células Madre Mesenquimatosas/metabolismo , Ratones Endogámicos C57BL , Diferenciación Celular

RESUMEN

Spinal and bulbar muscular atrophy (SBMA) is a slowly progressing disease with limited sensitive biomarkers that support clinical research. We analyzed plasma and serum samples from patients with SBMA and matched healthy controls in multiple cohorts, identifying 40 highly reproducible SBMA-associated proteins out of nearly 3,000 measured. These proteins were robustly enriched in gene sets of skeletal muscle expression and processes related to mitochondria and calcium signaling. Many proteins outperformed currently used clinical laboratory tests (e.g., creatine kinase [CK]) in distinguishing patients from controls and in their correlations with clinical and functional traits in patients. Two of the 40 proteins, Ectodysplasin A2 receptor (EDA2R) and Repulsive guidance molecule A (RGMA), were found to be associated with decreased survival and body weight in a mouse model of SBMA. In summary, we identified what we believe to be a robust and novel set of fluid protein biomarkers in SBMA that are linked with relevant disease features in patients and in a mouse model of disease. Changes in these SBMA-associated proteins could be used as an early predictor of treatment effects in clinical trials.

Asunto(s)

Biomarcadores , Humanos , Animales , Biomarcadores/sangre , Biomarcadores/metabolismo , Ratones , Masculino , Femenino , Persona de Mediana Edad , Modelos Animales de Enfermedad , Músculo Esquelético/metabolismo , Adulto , Estudios de Casos y Controles , Anciano , Proteínas Ligadas a GPI/sangre , Proteínas Ligadas a GPI/genética , Proteínas Ligadas a GPI/metabolismo

RESUMEN

Cytoplasmic and nuclear iron-sulfur (Fe-S) enzymes that are essential for genome maintenance and replication depend on the cytoplasmic Fe-S assembly (CIA) machinery for cluster acquisition. The core of the CIA machinery consists of a complex of CIAO1, MMS19 and FAM96B. The physiological consequences of loss of function in the components of the CIA pathway have thus far remained uncharacterized. Our study revealed that patients with biallelic loss of function in CIAO1 developed proximal and axial muscle weakness, fluctuating creatine kinase elevation, and respiratory insufficiency. In addition, they presented with CNS symptoms including learning difficulties and neurobehavioral comorbidities, along with iron deposition in deep brain nuclei, mild normocytic to macrocytic anemia, and gastrointestinal symptoms. Mutational analysis revealed reduced stability of the variants compared with WT CIAO1. Functional assays demonstrated failure of the variants identified in patients to recruit Fe-S recipient proteins, resulting in compromised activities of DNA helicases, polymerases, and repair enzymes that rely on the CIA complex to acquire their Fe-S cofactors. Lentivirus-mediated restoration of CIAO1 expression reversed all patient-derived cellular abnormalities. Our study identifies CIAO1 as a human disease gene and provides insights into the broader implications of the cytosolic Fe-S assembly pathway in human health and disease.

Asunto(s)

Proteínas Hierro-Azufre , Humanos , Proteínas Hierro-Azufre/genética , Proteínas Hierro-Azufre/metabolismo , Masculino , Femenino , Enfermedades Neuromusculares/genética , Enfermedades Neuromusculares/enzimología , Enfermedades Neuromusculares/metabolismo , Enfermedades Neuromusculares/patología , Niño , Núcleo Celular/metabolismo , Núcleo Celular/enzimología , Núcleo Celular/genética , Citoplasma/metabolismo , Citoplasma/enzimología , Metalochaperonas

RESUMEN

The complex compositional and functional nature of skeletal muscle makes this organ an essential topic of study for biomedical researchers and clinicians. An additional layer of complexity is added with the consideration of sex as a biological variable. Recent research advances have revealed sexual dimorphisms in developmental biology, muscle homeostasis, adaptive responses, and disorders relating to skeletal muscle. Many of the observed sex differences have hormonal and molecular mechanistic underpinnings, whereas others have yet to be elucidated. Future research is needed to investigate the mechanisms dictating sex-based differences in the various aspects of skeletal muscle. As such, it is necessary that skeletal muscle biologists ensure that both female and male subjects are represented in biomedical and clinical studies to facilitate the successful testing and development of therapeutics for all patients.

Asunto(s)

Músculo Esquelético , Caracteres Sexuales , Humanos , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiología , Masculino , Femenino , Animales

RESUMEN

Clinical trials delivering high doses of adeno-associated viruses (AAVs) expressing truncated dystrophin molecules (microdystrophins) are underway for Duchenne muscular dystrophy (DMD). We examined the efficiency and efficacy of this strategy with 4 microdystrophin constructs (3 in clinical trials and a variant of the largest clinical construct), in a severe mouse model of DMD, using AAV doses comparable with those in clinical trials. We achieved high levels of microdystrophin expression in striated muscles with cardiac expression approximately 10-fold higher than that observed in skeletal muscle. Significant, albeit incomplete, correction of skeletal muscle disease was observed. Surprisingly, a lethal acceleration of cardiac disease occurred with 2 of the microdystrophins. The detrimental cardiac effect appears to be caused by variable competition (dependent on microdystrophin design and expression level) between microdystrophin and utrophin at the cardiomyocyte membrane. There may also be a contribution from an overloading of protein degradation. The significance of these observations for patients currently being treated with AAV-microdystrophin therapies is unclear since the levels of expression being achieved in the DMD hearts are unknown. However, these findings suggest that microdystrophin treatments need to avoid excessively high levels of expression in the heart and that cardiac function should be carefully monitored in these patients.

Asunto(s)

Terapia Genética , Distrofia Muscular de Duchenne , Animales , Humanos , Masculino , Ratones , Dependovirus/genética , Modelos Animales de Enfermedad , Distrofina/genética , Terapia Genética/métodos , Vectores Genéticos/administración & dosificación , Vectores Genéticos/genética , Ratones Endogámicos mdx , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/terapia , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/metabolismo , Miocitos Cardíacos/metabolismo , Utrofina/genética , Utrofina/metabolismo

RESUMEN

Sarcopenia burdens the older population through loss of muscle energy and mass, yet treatments to functionally rescue both parameters are lacking. The glucocorticoid prednisone remodels muscle metabolism on the basis of frequency of intake, but its mechanisms in sarcopenia are unknown. We found that once-weekly intermittent prednisone administration rescued muscle quality in aged 24-month-old mice to a level comparable to that seen in young 4-month-old mice. We discovered an age- and sex-independent glucocorticoid receptor transactivation program in muscle encompassing peroxisome proliferator-activated receptor γ coactivator 1 α (PGC1α) and its cofactor Lipin1. Treatment coordinately improved mitochondrial abundance through isoform 1 and muscle mass through isoform 4 of the myocyte-specific PGC1α, which was required for the treatment-driven increase in carbon shuttling from glucose oxidation to amino acid biogenesis. We also probed myocyte-specific Lipin1 as a nonredundant factor coaxing PGC1α upregulation to the stimulation of both oxidative and anabolic effects. Our study unveils an aging-resistant druggable program in myocytes for the coordinated rescue of energy and mass in sarcopenia.

Asunto(s)

Envejecimiento , Glucocorticoides , Músculo Esquelético , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma , Fosfatidato Fosfatasa , Sarcopenia , Animales , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/genética , Sarcopenia/metabolismo , Sarcopenia/tratamiento farmacológico , Sarcopenia/patología , Sarcopenia/genética , Ratones , Envejecimiento/metabolismo , Fosfatidato Fosfatasa/genética , Fosfatidato Fosfatasa/metabolismo , Glucocorticoides/farmacología , Músculo Esquelético/metabolismo , Músculo Esquelético/efectos de los fármacos , Masculino , Modelos Animales de Enfermedad , Femenino

RESUMEN

Proline substitutions within the coiled-coil rod region of the ß-myosin gene (MYH7) are the predominant mutations causing Laing distal myopathy (MPD1), an autosomal dominant disorder characterized by progressive weakness of distal/proximal muscles. We report that the MDP1 mutation R1500P, studied in what we believe to be the first mouse model for the disease, adversely affected myosin motor activity despite being in the structural rod domain that directs thick filament assembly. Contractility experiments carried out on isolated mutant muscles, myofibrils, and myofibers identified muscle fatigue and weakness phenotypes, an increased rate of actin-myosin detachment, and a conformational shift of the myosin heads toward the more reactive disordered relaxed (DRX) state, causing hypercontractility and greater ATP consumption. Similarly, molecular analysis of muscle biopsies from patients with MPD1 revealed a significant increase in sarcomeric DRX content, as observed in a subset of myosin motor domain mutations causing hypertrophic cardiomyopathy. Finally, oral administration of MYK-581, a small molecule that decreases the population of heads in the DRX configuration, significantly improved the limited running capacity of the R1500P-transgenic mice and corrected the increased DRX state of the myofibrils from patients. These studies provide evidence of the molecular pathogenesis of proline rod mutations and lay the groundwork for the therapeutic advancement of myosin modulators.

Asunto(s)

Sustitución de Aminoácidos , Miopatías Distales , Prolina , Animales , Ratones , Humanos , Prolina/genética , Prolina/metabolismo , Miopatías Distales/genética , Miopatías Distales/metabolismo , Miopatías Distales/patología , Mutación Missense , Miosinas Cardíacas/genética , Miosinas Cardíacas/metabolismo , Cadenas Pesadas de Miosina/genética , Cadenas Pesadas de Miosina/metabolismo , Cadenas Pesadas de Miosina/química , Femenino , Masculino , Ratones Transgénicos , Contracción Muscular/genética , Músculo Esquelético/metabolismo , Músculo Esquelético/patología

RESUMEN

Satellite cells, the stem cells of skeletal muscle tissue, hold a remarkable regeneration capacity and therapeutic potential in regenerative medicine. However, low satellite cell yield from autologous or donor-derived muscles hinders the adoption of satellite cell transplantation for the treatment of muscle diseases, including Duchenne muscular dystrophy (DMD). To address this limitation, here we investigated whether satellite cells can be derived in allogeneic or xenogeneic animal hosts. First, injection of CRISPR/Cas9-corrected Dmdmdx mouse induced pluripotent stem cells (iPSCs) into mouse blastocysts carrying an ablation system of host satellite cells gave rise to intraspecies chimeras exclusively carrying iPSC-derived satellite cells. Furthermore, injection of genetically corrected DMD iPSCs into rat blastocysts resulted in the formation of interspecies rat-mouse chimeras harboring mouse satellite cells. Notably, iPSC-derived satellite cells or derivative myoblasts produced in intraspecies or interspecies chimeras restored dystrophin expression in DMD mice following intramuscular transplantation and contributed to the satellite cell pool. Collectively, this study demonstrates the feasibility of producing therapeutically competent stem cells across divergent animal species, raising the possibility of generating human muscle stem cells in large animals for regenerative medicine purposes.

Asunto(s)

Células Madre Pluripotentes Inducidas , Distrofia Muscular de Duchenne , Células Satélite del Músculo Esquelético , Animales , Ratones , Distrofia Muscular de Duchenne/terapia , Distrofia Muscular de Duchenne/genética , Células Madre Pluripotentes Inducidas/trasplante , Células Madre Pluripotentes Inducidas/citología , Células Madre Pluripotentes Inducidas/metabolismo , Ratas , Células Satélite del Músculo Esquelético/trasplante , Células Satélite del Músculo Esquelético/metabolismo , Células Satélite del Músculo Esquelético/citología , Trasplante de Células Madre , Humanos , Distrofina/genética , Distrofina/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/citología , Ratones Endogámicos mdx , Xenoinjertos , Trasplante Heterólogo , Inyecciones Intramusculares , Trasplante Homólogo

RESUMEN

Chronic kidney disease (CKD) causes accumulation of uremic metabolites that negatively affect skeletal muscle. Tryptophan-derived uremic metabolites are agonists of the aryl hydrocarbon receptor (AHR), which has been shown to be activated in CKD. This study investigated the role of the AHR in skeletal muscle pathology of CKD. Compared with controls with normal kidney function, AHR-dependent gene expression (CYP1A1 and CYP1B1) was significantly upregulated in skeletal muscle of patients with CKD, and the magnitude of AHR activation was inversely correlated with mitochondrial respiration. In mice with CKD, muscle mitochondrial oxidative phosphorylation (OXPHOS) was markedly impaired and strongly correlated with the serum level of tryptophan-derived uremic metabolites and AHR activation. Muscle-specific deletion of the AHR substantially improved mitochondrial OXPHOS in male mice with the greatest uremic toxicity (CKD + probenecid) and abolished the relationship between uremic metabolites and OXPHOS. The uremic metabolite/AHR/mitochondrial axis in skeletal muscle was verified using muscle-specific AHR knockdown in C57BL/6J mice harboring a high-affinity AHR allele, as well as ectopic viral expression of constitutively active mutant AHR in mice with normal renal function. Notably, OXPHOS changes in AHRmKO mice were present only when mitochondria were fueled by carbohydrates. Further analyses revealed that AHR activation in mice led to significantly increased pyruvate dehydrogenase kinase 4 (Pdk4) expression and phosphorylation of pyruvate dehydrogenase enzyme. These findings establish a uremic metabolite/AHR/Pdk4 axis in skeletal muscle that governs mitochondrial deficits in carbohydrate oxidation during CKD.

Asunto(s)

Ratones Endogámicos C57BL , Músculo Esquelético , Fosforilación Oxidativa , Piruvato Deshidrogenasa Quinasa Acetil-Transferidora , Receptores de Hidrocarburo de Aril , Insuficiencia Renal Crónica , Triptófano , Animales , Receptores de Hidrocarburo de Aril/metabolismo , Receptores de Hidrocarburo de Aril/genética , Ratones , Masculino , Insuficiencia Renal Crónica/metabolismo , Triptófano/metabolismo , Músculo Esquelético/metabolismo , Humanos , Piruvato Deshidrogenasa Quinasa Acetil-Transferidora/metabolismo , Piruvato Deshidrogenasa Quinasa Acetil-Transferidora/genética , Uremia/metabolismo , Mitocondrias Musculares/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Femenino , Ratones Noqueados , Citocromo P-450 CYP1B1/metabolismo , Citocromo P-450 CYP1B1/genética , Citocromo P-450 CYP1A1/metabolismo , Citocromo P-450 CYP1A1/genética , Persona de Mediana Edad , Metabolismo Energético , Modelos Animales de Enfermedad

RESUMEN

The polymerization of myosin molecules into thick filaments in muscle sarcomeres is essential for cardiac contractility, with the attenuation of interactions between the heads of myosin molecules within the filaments being proposed to result in hypercontractility, as observed in hypertrophic cardiomyopathy (HCM). However, experimental evidence demonstrates that the structure of these giant macromolecular complexes is highly dynamic, with molecules exchanging between the filaments and a pool of soluble molecules on the minute timescale. Therefore, we sought to test the hypothesis that the enhancement of interactions between the heads of myosin molecules within thick filaments limits the mobility of myosin by taking advantage of mavacamten, a small molecule approved for the treatment of HCM. Myosin molecules were labeled in vivo with a green fluorescent protein (GFP) and imaged in intact hearts using multiphoton microscopy. Treatment of the intact hearts with mavacamten resulted in an unexpected > 5-fold enhancement in GFP-myosin mobility within the sarcomere. In vitro biochemical assays suggested that mavacamten enhanced the mobility of GFP-myosin by increasing the solubility of myosin molecules, through the stabilization of a compact/folded conformation of the molecules, once disassociated from the thick filaments. These findings provide alternative insight into the mechanisms by which molecules exchange into and out of thick filaments and have implications for how mavacamten may affect cardiac contractility.

Asunto(s)

Bencilaminas , Miocardio , Sarcómeros , Solubilidad , Uracilo/análogos & derivados , Animales , Sarcómeros/metabolismo , Miocardio/metabolismo , Ratones , Miosinas/metabolismo , Pliegue de Proteína , Proteínas Fluorescentes Verdes/metabolismo , Proteínas Fluorescentes Verdes/genética , Cardiomiopatía Hipertrófica/metabolismo , Contracción Miocárdica , Humanos , Masculino

RESUMEN

Skeletal muscle wasting results from numerous pathological conditions affecting both the musculoskeletal and nervous systems. A unifying feature of these pathologies is the upregulation of members of the E3 ubiquitin ligase family, resulting in increased proteolytic degradation of target proteins. Despite the critical role of E3 ubiquitin ligases in regulating muscle mass, the specific proteins they target for degradation and the mechanisms by which they regulate skeletal muscle homeostasis remain ill-defined. Here, using zebrafish loss-of-function models combined with in vivo cell biology and proteomic approaches, we reveal a role of atrogin-1 in regulating the levels of the endoplasmic reticulum chaperone BiP. Loss of atrogin-1 resulted in an accumulation of BiP, leading to impaired mitochondrial dynamics and a subsequent loss in muscle fiber integrity. We further implicated a disruption in atrogin-1-mediated BiP regulation in the pathogenesis of Duchenne muscular dystrophy. We revealed that BiP was not only upregulated in Duchenne muscular dystrophy, but its inhibition using pharmacological strategies, or by upregulating atrogin-1, significantly ameliorated pathology in a zebrafish model of Duchenne muscular dystrophy. Collectively, our data implicate atrogin-1 and BiP in the pathogenesis of Duchenne muscular dystrophy and highlight atrogin-1's essential role in maintaining muscle homeostasis.

Asunto(s)

Modelos Animales de Enfermedad , Chaperón BiP del Retículo Endoplásmico , Homeostasis , Proteínas Musculares , Músculo Esquelético , Distrofia Muscular de Duchenne , Proteínas Ligasas SKP Cullina F-box , Pez Cebra , Animales , Proteínas Ligasas SKP Cullina F-box/metabolismo , Proteínas Ligasas SKP Cullina F-box/genética , Proteínas Musculares/metabolismo , Proteínas Musculares/genética , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Distrofia Muscular de Duchenne/metabolismo , Distrofia Muscular de Duchenne/patología , Distrofia Muscular de Duchenne/genética , Humanos , Chaperón BiP del Retículo Endoplásmico/metabolismo , Proteínas de Choque Térmico/metabolismo , Proteínas de Choque Térmico/genética , Proteínas de Pez Cebra/metabolismo , Proteínas de Pez Cebra/genética , Retículo Endoplásmico/metabolismo , Dinámicas Mitocondriales

RESUMEN

Tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK) are clinically overlapping disorders characterized by childhood-onset muscle weakness and a variable occurrence of multisystemic signs, including short stature, thrombocytopenia, and hyposplenism. TAM/STRMK is caused by gain-of-function mutations in the Ca2+ sensor STIM1 or the Ca2+ channel ORAI1, both of which regulate Ca2+ homeostasis through the ubiquitous store-operated Ca2+ entry (SOCE) mechanism. Functional experiments in cells have demonstrated that the TAM/STRMK mutations induce SOCE overactivation, resulting in excessive influx of extracellular Ca2+. There is currently no treatment for TAM/STRMK, but SOCE is amenable to manipulation. Here, we crossed Stim1R304W/+ mice harboring the most common TAM/STRMK mutation with Orai1R93W/+ mice carrying an ORAI1 mutation partially obstructing Ca2+ influx. Compared with Stim1R304W/+ littermates, Stim1R304W/+Orai1R93W/+ offspring showed a normalization of bone architecture, spleen histology, and muscle morphology; an increase of thrombocytes; and improved muscle contraction and relaxation kinetics. Accordingly, comparative RNA-Seq detected more than 1,200 dysregulated genes in Stim1R304W/+ muscle and revealed a major restoration of gene expression in Stim1R304W/+Orai1R93W/+ mice. Altogether, we provide physiological, morphological, functional, and molecular data highlighting the therapeutic potential of ORAI1 inhibition to rescue the multisystemic TAM/STRMK signs, and we identified myostatin as a promising biomarker for TAM/STRMK in humans and mice.

Asunto(s)

Trastornos de las Plaquetas Sanguíneas , Dislexia , Ictiosis , Trastornos Migrañosos , Miopatías Estructurales Congénitas , Proteína ORAI1 , Bazo , Animales , Ratones , Calcio/metabolismo , Eritrocitos Anormales , Trastornos Migrañosos/tratamiento farmacológico , Miosis/tratamiento farmacológico , Miosis/genética , Miosis/metabolismo , Fatiga Muscular , Miopatías Estructurales Congénitas/tratamiento farmacológico , Miopatías Estructurales Congénitas/genética , Miopatías Estructurales Congénitas/metabolismo , Proteína ORAI1/genética , Proteína ORAI1/metabolismo , Bazo/metabolismo , Bazo/anomalías

RESUMEN

BACKGROUNDWhile the benefits of statin therapy on atherosclerotic cardiovascular disease are clear, patients often experience mild to moderate skeletal myopathic symptoms, the mechanism for which is unknown. This study investigated the potential effect of high-dose atorvastatin therapy on skeletal muscle mitochondrial function and whole-body aerobic capacity in humans.METHODSEight overweight (BMI, 31.9 ± 2.0) but otherwise healthy sedentary adults (4 females, 4 males) were studied before (day 0) and 14, 28, and 56 days after initiating atorvastatin (80 mg/d) therapy.RESULTSMaximal ADP-stimulated respiration, measured in permeabilized fiber bundles from muscle biopsies taken at each time point, declined gradually over the course of atorvastatin treatment, resulting in > 30% loss of skeletal muscle mitochondrial oxidative phosphorylation capacity by day 56. Indices of in vivo muscle oxidative capacity (via near-infrared spectroscopy) decreased by 23% to 45%. In whole muscle homogenates from day 0 biopsies, atorvastatin inhibited complex III activity at midmicromolar concentrations, whereas complex IV activity was inhibited at low nanomolar concentrations.CONCLUSIONThese findings demonstrate that high-dose atorvastatin treatment elicits a striking progressive decline in skeletal muscle mitochondrial respiratory capacity, highlighting the need for longer-term dose-response studies in different patient populations to thoroughly define the effect of statin therapy on skeletal muscle health.FUNDINGNIH R01 AR071263.

Asunto(s)

Inhibidores de Hidroximetilglutaril-CoA Reductasas , Enfermedades Musculares , Masculino , Adulto , Femenino , Humanos , Atorvastatina/farmacología , Atorvastatina/metabolismo , Inhibidores de Hidroximetilglutaril-CoA Reductasas/farmacología , Mitocondrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Mitocondrias , Enfermedades Musculares/metabolismo

RESUMEN

Stromal interaction molecule 1 (STIM1) is a Ca2+ sensor located in the sarcoplasmic reticulum (SR) of skeletal muscle, where it is best known for its role in store-operated Ca2+ entry (SOCE). Genetic syndromes resulting from STIM1 mutations are recognized as a cause of muscle weakness and atrophy. Here, we focused on a gain-of-function mutation that occurs in humans and mice (STIM1+/D84G mice), in which muscles exhibited constitutive SOCE. Unexpectedly, this constitutive SOCE did not affect global Ca2+ transients, SR Ca2+ content, or excitation-contraction coupling (ECC) and was therefore unlikely to underlie the reduced muscle mass and weakness observed in these mice. Instead, we demonstrate that the presence of D84G STIM1 in the nuclear envelope of STIM1+/D84G muscle disrupted nuclear-cytosolic coupling, causing severe derangement in nuclear architecture, DNA damage, and altered lamina A-associated gene expression. Functionally, we found that D84G STIM1 reduced the transfer of Ca2+ from the cytosol to the nucleus in myoblasts, resulting in a reduction of [Ca2+]N. Taken together, we propose a novel role for STIM1 in the nuclear envelope that links Ca2+ signaling to nuclear stability in skeletal muscle.

Asunto(s)

Debilidad Muscular , Membrana Nuclear , Molécula de Interacción Estromal 1 , Animales , Humanos , Ratones , Calcio/metabolismo , Señalización del Calcio , Debilidad Muscular/genética , Debilidad Muscular/metabolismo , Músculo Esquelético/metabolismo , Mutación , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Membrana Nuclear/genética , Membrana Nuclear/metabolismo , Proteína ORAI1/genética , Molécula de Interacción Estromal 1/genética , Molécula de Interacción Estromal 1/metabolismo

RESUMEN

OBJECTIVE: To better understand the pathogenesis of juvenile dermatomyositis (JDM), we examined the effect of the cytokines type I interferons (IFN I) and JAK inhibitor drugs (JAKi) on gene expression in bioengineered pediatric skeletal muscle. METHODS: Myoblasts from three healthy pediatric donors were used to create three-dimensional skeletal muscle units termed myobundles. Myobundles were treated with IFN I, either IFNα or IFNß. A subset of IFNß-exposed myobundles was treated with JAKi tofacitinib or baricitinib. RNA sequencing analysis was performed on all myobundles. RESULTS: Seventy-six myobundles were analysed. Principal component analysis showed donor-specific clusters of gene expression across IFNα and IFNß-exposed myobundles in a dose-dependent manner. Both cytokines upregulated interferon response and proinflammatory genes; however, IFNß led to more significant upregulation. Key downregulated pathways involved oxidative phosphorylation, fatty acid metabolism and myogenesis genes. Addition of tofacitinib or baricitinib moderated the gene expression induced by IFNß, with partial reversal of upregulated inflammatory and downregulated myogenesis pathways. Baricitinib altered genetic profiles more than tofacitinib. CONCLUSION: IFNß leads to more pro-inflammatory gene upregulation than IFNα, correlating to greater decrease in contractile protein gene expression and reduced contractile force. JAK inhibitors, baricitinib more so than tofacitinib, partially reverse IFN I-induced genetic changes. Increased IFN I exposure in healthy bioengineered skeletal muscle leads to IFN-inducible gene expression, inflammatory pathway enrichment, and myogenesis gene downregulation, consistent with what is observed in JDM.

Asunto(s)

Azetidinas , Dermatomiositis , Interferón Tipo I , Inhibidores de las Cinasas Janus , Humanos , Dermatomiositis/genética , Dermatomiositis/tratamiento farmacológico , Inhibidores de las Cinasas Janus/uso terapéutico , Inhibidores de las Cinasas Janus/farmacología , Azetidinas/farmacología , Azetidinas/uso terapéutico , Interferón Tipo I/metabolismo , Niño , Sulfonamidas/farmacología , Sulfonamidas/uso terapéutico , Músculo Esquelético/metabolismo , Músculo Esquelético/efectos de los fármacos , Pirimidinas/uso terapéutico , Pirimidinas/farmacología , Pirazoles/uso terapéutico , Pirazoles/farmacología , Purinas/farmacología , Purinas/uso terapéutico , Piperidinas/uso terapéutico , Piperidinas/farmacología , Mioblastos/efectos de los fármacos , Mioblastos/metabolismo , Interferón-alfa

RESUMEN

Myotonic dystrophy type 1 (DM1) involves misregulated alternative splicing for specific genes. We used exon or nucleotide deletion to mimic altered splicing of genes central to muscle excitation-contraction coupling in mice. Mice with forced skipping of exon 29 in the CaV1.1 calcium channel combined with loss of ClC-1 chloride channel function displayed markedly reduced lifespan, whereas other combinations of splicing mimics did not affect survival. The Ca2+/Cl- bi-channelopathy mice exhibited myotonia, weakness, and impairment of mobility and respiration. Chronic administration of the calcium channel blocker verapamil rescued survival and improved force generation, myotonia, and respiratory function. These results suggest that Ca2+/Cl- bi-channelopathy contributes to muscle impairment in DM1 and is potentially mitigated by common clinically available calcium channel blockers.

Asunto(s)

Canalopatías , Miotonía , Distrofia Miotónica , Ratones , Animales , Distrofia Miotónica/tratamiento farmacológico , Distrofia Miotónica/genética , Distrofia Miotónica/metabolismo , Calcio/metabolismo , Cloruros/metabolismo , Miotonía/metabolismo , Verapamilo/farmacología , Verapamilo/metabolismo , Canalopatías/genética , Canalopatías/metabolismo , Empalme Alternativo , Canales de Cloruro/genética , Canales de Cloruro/metabolismo , Músculo Esquelético/metabolismo

RESUMEN

The Murphy Roths Large (MRL) mouse strain has "super-healing" properties that enhance recovery from injury. In mice, the DBA/2J strain intensifies many aspects of muscular dystrophy, so we evaluated the ability of the MRL strain to suppress muscular dystrophy in the Sgcg-null mouse model of limb girdle muscular dystrophy. A comparative analysis of Sgcg-null mice in the DBA/2J versus MRL strains showed greater myofiber regeneration, with reduced structural degradation of muscle in the MRL strain. Transcriptomic profiling of dystrophic muscle indicated strain-dependent expression of extracellular matrix (ECM) and TGF-ß signaling genes. To investigate the MRL ECM, cellular components were removed from dystrophic muscle sections to generate decellularized myoscaffolds. Decellularized myoscaffolds from dystrophic mice in the protective MRL strain had significantly less deposition of collagen and matrix-bound TGF-ß1 and TGF-ß3 throughout the matrix. Dystrophic myoscaffolds from the MRL background, but not the DBA/2J background, were enriched in myokines like IGF-1 and IL-6. C2C12 myoblasts seeded onto decellularized matrices from Sgcg-/- MRL and Sgcg-/- DBA/2J muscles showed the MRL background induced greater myoblast differentiation compared with dystrophic DBA/2J myoscaffolds. Thus, the MRL background imparts its effect through a highly regenerative ECM, which is active even in muscular dystrophy.

Asunto(s)

Distrofia Muscular de Cinturas , Distrofias Musculares , Ratones , Animales , Ratones Endogámicos DBA , Distrofias Musculares/genética , Músculos , Matriz Extracelular , Ratones Noqueados

RESUMEN

Cachexia is a debilitating skeletal muscle wasting condition for which we currently lack effective treatments. In the context of cancer, certain chemotherapeutics cause DNA damage and cellular senescence. Senescent cells exhibit chronic activation of the transcription factor NF-κB, a known mediator of the proinflammatory senescence-associated secretory phenotype (SASP) and skeletal muscle atrophy. Thus, targeting NF-κB represents a logical therapeutic strategy to alleviate unintended consequences of genotoxic drugs. Herein, we show that treatment with the IKK/NF-κB inhibitor SR12343 during a course of chemotherapy reduces markers of cellular senescence and the SASP in liver, skeletal muscle, and circulation and, correspondingly, attenuates features of skeletal muscle pathology. Lastly, we demonstrate that SR12343 mitigates chemotherapy-induced reductions in body weight, lean mass, fat mass, and muscle strength. These findings support senescent cells as a promising druggable target to counteract the SASP and skeletal muscle wasting in the context of chemotherapy.

Asunto(s)

Antineoplásicos , FN-kappa B , Humanos , FN-kappa B/metabolismo , Transducción de Señal , Caquexia/inducido químicamente , Caquexia/tratamiento farmacológico , Senoterapéuticos , Atrofia Muscular/inducido químicamente , Atrofia Muscular/tratamiento farmacológico , Antineoplásicos/efectos adversos