RESUMO
Following peripheral nerve injury, successful axonal growth and functional recovery require Schwann cell (SC) reprogramming into a reparative phenotype, a process dependent upon c-Jun transcription factor activation. Unfortunately, axonal regeneration is greatly impaired in aged organisms and following chronic denervation, which can lead to poor clinical outcomes. While diminished c-Jun expression in SCs has been associated with regenerative failure, it is unclear whether the inability to maintain a repair state is associated with the transition into an axonal growth inhibition phenotype. We here find that reparative SCs transition into a senescent phenotype, characterized by diminished c-Jun expression and secretion of inhibitory factors for axonal regeneration in aging and chronic denervation. In both conditions, the elimination of senescent SCs by systemic senolytic drug treatment or genetic targeting improved nerve regeneration and functional recovery, increased c-Jun expression and decreased nerve inflammation. This work provides the first characterization of senescent SCs and their influence on axonal regeneration in aging and chronic denervation, opening new avenues for enhancing regeneration and functional recovery after peripheral nerve injuries.
Assuntos
Traumatismos dos Nervos Periféricos , Humanos , Idoso , Traumatismos dos Nervos Periféricos/terapia , Traumatismos dos Nervos Periféricos/genética , Traumatismos dos Nervos Periféricos/metabolismo , Células de Schwann/metabolismo , Envelhecimento , Regulação da Expressão Gênica , DenervaçãoRESUMO
Loss of motoneuron innervation (denervation) is a hallmark of neurodegeneration and aging of the skeletal muscle. Denervation induces fibrosis, a response attributed to the activation and expansion of resident fibro/adipogenic progenitors (FAPs), i.e., multipotent stromal cells with myofibroblast potential. Using in vivo and in silico approaches, we revealed FAPs as a novel cell population that activates the transcriptional coregulators YAP/TAZ in response to skeletal muscle denervation. Here, we found that denervation induces the expression and transcriptional activity of YAP/TAZ in whole muscle lysates. Using the PdgfraH2B:EGFP/+ transgenic reporter mice to trace FAPs, we demonstrated that denervation leads to increased YAP expression that accumulates within FAPs nuclei. Consistently, re-analysis of published single-nucleus RNA sequencing (snRNA-seq) data indicates that FAPs from denervated muscles have a higher YAP/TAZ signature level than control FAPs. Thus, our work provides the foundations to address the functional role of YAP/TAZ in FAPs in a neurogenic pathological context, which could be applied to develop novel therapeutic approaches for the treatment of muscle disorders triggered by motoneuron degeneration.
Assuntos
Adipogenia , Músculo Esquelético , Animais , Camundongos , Adipogenia/genética , Diferenciação Celular/fisiologia , Denervação , Camundongos Transgênicos , Músculo Esquelético/metabolismoRESUMO
Binge Drinking (BD) corresponds to episodes of ingestion of large amounts of ethanol in a short time, typically ≤2 h. BD occurs across all populations, but young and sports-related people are especially vulnerable. However, the short- and long-term effects of episodic BD on skeletal muscle function have been poorly explored. Young rats were randomized into two groups: control and episodic Binge-Like ethanol protocol (BEP) (ethanol 3 g/kg IP, 4 episodes of 2-days ON-2-days OFF paradigm). Muscle function was evaluated two weeks after the last BEP episode. We found that rats exposed to BEP presented decreased muscle strength and increased fatigability, compared with control animals. Furthermore, we observed that skeletal muscle from rats exposed to BEP presented muscle atrophy, evidenced by reduced fiber size and increased expression of atrophic genes. We also observed that BEP induced fibrotic and inflammation markers, accompanied by mislocalization of nNOSµ and high levels of protein nitration. Our findings suggest that episodic binge-like ethanol exposure alters contractile capacity and increases fatigue by mechanisms involving atrophy, fibrosis, and inflammation, which remain for at least two weeks after ethanol clearance. These pathological features are common to several neuromuscular diseases and might affect muscle performance and health in the long term.
Assuntos
Consumo Excessivo de Bebidas Alcoólicas , Etanol , Ratos , Animais , Etanol/efeitos adversos , Etanol/metabolismo , Músculo Esquelético/metabolismo , Inflamação/metabolismo , Atrofia Muscular/metabolismo , Força Muscular , Fibrose , Consumo Excessivo de Bebidas Alcoólicas/metabolismoRESUMO
Background: Chronic alcohol misuse is associated with alcoholic myopathy, characterized by skeletal muscle weakness and atrophy. Moreover, there is evidence that sports-related people seem to exhibit a greater prevalence of problematic alcohol consumption, especially binge drinking (BD), which might not cause alcoholic myopathy but can negatively impact muscle function and amateur and professional athletic performance.Objective: To review the literature concerning the effects of alcohol consumption on skeletal muscle function and structure that can affect muscle performance.Methodology: We examined the currently available literature (PubMed, Google Scholars) to develop a narrative review summarizing the knowledge about the effects of alcohol on skeletal muscle function and exercise performance, obtained from studies in human beings and animal models for problematic alcohol consumption.Results: Exercise- and sport-based studies indicate that alcohol consumption can negatively affect muscle recovery after vigorous exercise, especially in men, while women seem less affected. Clinical studies and pre-clinical laboratory research have led to the knowledge of some of the mechanisms involved in alcohol-related muscle dysfunction, including an imbalance between anabolic and catabolic pathways, reduced regeneration, increased inflammation and fibrosis, and deficiencies in energetic balance and mitochondrial function. These pathological features can appear not only under chronic alcohol misuse but also in other alcohol consumption patterns.Conclusions: Most laboratory-based studies use chronic or acute alcohol exposure, while episodic BD, the most common drinking pattern in amateur and professional athletes, is underrepresented. Nevertheless, alcohol consumption negatively affects skeletal muscle health through different mechanisms, which collectively might contribute to reduced sports performance.
Assuntos
Alcoolismo , Desempenho Atlético , Doenças Musculares , Consumo de Bebidas Alcoólicas/metabolismo , Alcoolismo/epidemiologia , Animais , Desempenho Atlético/fisiologia , Etanol/farmacologia , Feminino , Humanos , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Doenças Musculares/metabolismo , Doenças Musculares/patologiaRESUMO
Connective tissue growth factor or cellular communication network 2 (CCN2/CTGF) is a matricellular protein member of the CCN family involved in several crucial biological processes. In skeletal muscle, CCN2/CTGF abundance is elevated in human muscle biopsies and/or animal models for diverse neuromuscular pathologies, including muscular dystrophies, neurodegenerative disorders, muscle denervation, and muscle overuse. In this context, CCN2/CTGF is deeply involved in extracellular matrix (ECM) modulation, acting as a strong pro-fibrotic factor that promotes excessive ECM accumulation. Reducing CCN2/CTGF levels or biological activity in pathological conditions can decrease fibrosis, improve muscle architecture and function. In this work, we summarize information about the role of CCN2/CTGF in fibrosis associated with neuromuscular pathologies and the mechanisms and signaling pathways that regulate their expression in skeletal muscle.
RESUMO
The Cellular Communication Network (CCN) family of matricellular proteins comprises six proteins that share conserved structural features and play numerous biological roles. These proteins can interact with several receptors or soluble proteins, regulating cell signaling pathways in various tissues under physiological and pathological conditions. In the skeletal muscle of mammals, most of the six CCN family members are expressed during embryonic development or in adulthood. Their roles during the adult stage are related to the regulation of muscle mass and regeneration, maintaining vascularization, and the modulation of skeletal muscle fibrosis. This work reviews the CCNs proteins' role in skeletal muscle physiology and disease, focusing on skeletal muscle fibrosis and its regulation by Connective Tissue Growth factor (CCN2/CTGF). Furthermore, we review evidence on the modulation of fibrosis and CCN2/CTGF by the renin-angiotensin system and the kallikrein-kinin system of vasoactive peptides.
Assuntos
Fator de Crescimento do Tecido Conjuntivo/metabolismo , Músculo Esquelético/fisiologia , Peptídeos/metabolismo , Animais , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Cininas/metabolismo , Família Multigênica , Proteínas Musculares/metabolismo , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/patologia , Atrofia Muscular/metabolismo , Atrofia Muscular/patologia , Doenças Musculares/metabolismo , Doenças Musculares/patologia , Regeneração , Sistema Renina-AngiotensinaRESUMO
Several skeletal muscle diseases are characterized by fibrosis, the excessive accumulation of extracellular matrix. Transforming growth factor-ß (TGF-ß) and connective tissue growth factor (CCN2/CTGF) are two profibrotic factors augmented in fibrotic skeletal muscle, together with signs of reduced vasculature that implies a decrease in oxygen supply. We observed that fibrotic muscles are characterized by the presence of positive nuclei for hypoxia-inducible factor-1α (HIF-1α), a key mediator of the hypoxia response. However, it is not clear how a hypoxic environment could contribute to the fibrotic phenotype in skeletal muscle. We evaluated the role of hypoxia and TGF-ß on CCN2 expression in vitro. Fibroblasts, myoblasts and differentiated myotubes were incubated with TGF-ß1 under hypoxic conditions. Hypoxia and TGF-ß1 induced CCN2 expression synergistically in myotubes but not in fibroblasts or undifferentiated muscle progenitors. This induction requires HIF-1α and the Smad-independent TGF-ß signaling pathway. We performed in vivo experiments using pharmacological stabilization of HIF-1α or hypoxia-induced via hindlimb ischemia together with intramuscular injections of TGF-ß1, and we found increased CCN2 expression. These observations suggest that hypoxic signaling together with TGF-ß signaling, which are both characteristics of a fibrotic skeletal muscle environment, induce the expression of CCN2 in skeletal muscle fibers and myotubes.
Assuntos
Fator de Crescimento do Tecido Conjuntivo/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Músculo Esquelético/patologia , Fator de Crescimento Transformador beta1/administração & dosagem , Regulação para Cima , Animais , Diferenciação Celular , Hipóxia Celular , Linhagem Celular , Modelos Animais de Doenças , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Fibrose , Injeções Intramusculares , Isquemia/etiologia , Camundongos , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/efeitos dos fármacos , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/citologia , Músculo Esquelético/metabolismo , Mioblastos/citologia , Mioblastos/efeitos dos fármacos , Mioblastos/metabolismo , Células NIH 3T3 , Transdução de Sinais , Fator de Crescimento Transformador beta1/farmacologiaRESUMO
Problematic alcohol drinking and alcohol dependence are an increasing health problem worldwide. Alcohol abuse is responsible for approximately 5% of the total deaths in the world, but addictive consumption of it has a substantial impact on neurological and memory disabilities throughout the population. One of the better-studied brain areas involved in cognitive functions is the hippocampus, which is also an essential brain region targeted by ethanol. Accumulated evidence in several rodent models has shown that ethanol treatment produces cognitive impairment in hippocampal-dependent tasks. These adverse effects may be related to the fact that ethanol impairs the cellular and synaptic plasticity mechanisms, including adverse changes in neuronal morphology, spine architecture, neuronal communication, and finally an increase in neuronal death. There is evidence that the damage that occurs in the different brain structures is varied according to the stage of development during which the subjects are exposed to ethanol, and even much earlier exposure to it would cause damage in the adult stage. Studies on the cellular and cognitive deficiencies produced by alcohol in the brain are needed in order to search for new strategies to reduce alcohol neuronal toxicity and to understand its consequences on memory and cognitive performance with emphasis on the crucial stages of development, including prenatal events to adulthood.
RESUMO
Amyotrophic lateral sclerosis (ALS) is a devastating adult-onset progressive neurodegenerative disease characterized by upper and lower motoneuron degeneration. A total of 20% of familial ALS (fALS) cases are explained by mutations in the superoxide dismutase 1 (SOD1) enzyme. Although more than 20 years have passed since the generation of the first ALS mouse model, the precise molecular mechanisms of ALS pathogenesis remain unknown. CTGF/CCN2 is a matricellular protein with associated fibrotic activity that is up-regulated in several chronic diseases. The inhibition of CTGF/CCN2 with the monoclonal neutralizing antibody FG-3019 reduces fibrosis in several chronic disorders including the mdx mice, a murine model for Duchenne muscular dystrophy (DMD). In this work, we show that there are increased levels of CTGF/CCN2 in skeletal muscle and spinal cord of hSOD1G93A mice. In this scenario, we show evidence that FG-3019 not only reduces fibrosis in skeletal muscle of hSOD1G93A mice, but also improves muscle and locomotor performance. We demonstrate that treatment with FG-3019 reduces muscle atrophy in hSOD1G93A mice. We also found improvement of neuromuscular junction (NMJ) innervation together with a reduction in myelin degeneration in the sciatic nerve, suggesting that alterations in nerve-muscle communication are partially improved in FG-3019-treated hSOD1G93A mice. Moreover, we also found that CTGF/CCN2 is expressed in astrocytes and neurons, predominantly in dorsal areas of spinal cord from symptomatic hSOD1G93A mice. Together, these results reveal that CTGF/CCN2 might be a novel therapeutic target to ameliorate symptoms and improve the quality of life of ALS patients.
Assuntos
Esclerose Lateral Amiotrófica/tratamento farmacológico , Fator de Crescimento do Tecido Conjuntivo/genética , Distrofia Muscular de Duchenne/tratamento farmacológico , Superóxido Dismutase-1/genética , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/patologia , Animais , Anticorpos Neutralizantes/administração & dosagem , Astrócitos/efeitos dos fármacos , Astrócitos/patologia , Modelos Animais de Doenças , Fibrose/tratamento farmacológico , Fibrose/genética , Fibrose/patologia , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Locomoção/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos mdx , Camundongos Transgênicos , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/patologia , Distrofia Muscular de Duchenne/genética , Distrofia Muscular de Duchenne/patologia , Junção Neuromuscular/efeitos dos fármacos , Junção Neuromuscular/patologia , Neurônios/efeitos dos fármacos , Neurônios/patologiaRESUMO
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease in which upper and lower motoneurons degenerate leading to muscle wasting, paralysis and eventually death from respiratory failure. Several studies indicate that skeletal muscle contributes to disease progression; however the molecular mechanisms remain elusive. Fibrosis is a common feature in skeletal muscle under chronic damage conditions such as those caused by muscular dystrophies or denervation. However, the exact mechanisms of fibrosis induction and the cellular bases of this pathological response are unknown. We show that extracellular matrix (ECM) components are augmented in skeletal muscles of symptomatic hSOD1G93A mice, a widely used murine model of ALS. These mice also show increased TGF-ß1 mRNA levels, total Smad3 protein levels and p-Smad3 positive nuclei. Furthermore, platelet-derived growth factor receptor-α (PDGFRα), Tcf4 and α-smooth muscle actin (α-SMA) levels are augmented in the skeletal muscle of symptomatic hSOD1G93A mice. Additionally, the fibro/adipogenic progenitors (FAPs), which are the main producers of ECM constituents, are also increased in these pathogenic conditions. Therefore, FAPs and ECM components are more abundant in symptomatic stages of the disease than in pre-symptomatic stages. We present evidence that fibrosis observed in skeletal muscle of symptomatic hSOD1G93A mice is accompanied with an induction of TGF-ß signaling, and also that FAPs might be involved in triggering a fibrotic response. Co-localization of p-Smad3 positive cells together with PDGFRα was observed in the interstitial cells of skeletal muscles from symptomatic hSOD1G93A mice. Finally, the targeting of pro-fibrotic factors such as TGF-ß, CTGF/CCN2 and platelet-derived growth factor (PDGF) signaling pathway might be a suitable therapeutic approach to improve muscle function in several degenerative diseases.