Biology subjects

Chazaud, B.

Publications and source records attributed to Chazaud, B..

12 recordsLinked to original sources

bioRxiv2026

NEUROMUSCULAR ELECTRICAL STIMULATION LIMITS MUSCLE WEAKNESS, ATROPHY, MODULATES SATELLITE CELL FUNCTION AND REDUCES INFLAMMATION IN CANCER CACHEXIA

BackgroundCancer cachexia (CC) is characterized by skeletal muscle atrophy and reduced strength, partly linked to dysfunction of muscle stem cells (MuSCs) and alterations in their niche. Although exercise may mitigate muscle loss, its effects in CC remain debated and its feasibility is often limited in advanced patients. Neuromuscular electrical stimulation (NMES) offers a promising alternative, by promoting MuSC proliferation and fusion, increasing muscle size and macrophage content in healthy muscle. This study investigated whether NMES, initiated at tumor onset, could improve MuSC regulation and its niche while limiting muscle atrophy and weakness in a tumor-bearing mouse model. MethodsTen-week-old male BALB/c mice were subcutaneously injected with C26 tumor cells or PBS. Tumor-bearing mice were divided into NMES-treated (C26 NMES) and non-stimulated controls (C26). NMES consisted of six sessions (two series of three consecutive daily sessions separated by one rest day), starting seven days post-inoculation when tumors became visible. Each session was delivered at a submaximal intensity corresponding to 15% of maximal strength. Muscle mass, myofiber size, strength and cellular composition were assessed. ResultsMuscle mass was decreased by 13% in C26 mice as compared to PBS controls, while C26 NMES mice showed a [~]7% improvement over C26 mice. Mean myofiber size decreased similarly in both tumor-bearing groups as compared to PBS controls (-12-14%). However, NMES reduced the proportion of small myofibers (400-600 {micro}m{superscript 2}) as compared to C26 mice. Maximal torque loss was less severe in C26 NMES mice (-28%) than in C26 mice (-34%). As compared with PBS mice, C26 mice exhibited increased MuSC proliferation (+97%) but reduced differentiation (-61%), as indicated by fewer myogenin-positive cells. NMES normalized MuSC proliferation, restored myogenin-positive cell number, and enhanced MuSC fusion, reflected by an increased number of PCM1-positive myonuclei (+8-11%). NMES also modulated inflammation, reducing neutrophils (-42%) and increasing macrophages (+35%), through the proliferation of CD169-positive resident macrophages (+106%). In vitro, macrophages exposed to C26 muscle extracts showed elevated pro-inflammatory markers (COX2 and TNF-; +21% and +16%) as compared to PBS controls. This effect was abolished with extracts from C26 NMES muscles. Additionally, C26 extracts reduced the expression of anti-inflammatory markers by macrophages (CD206 and IL-10; -23%), whereas NMES restored their levels to those of controls. ConclusionNMES-induced mild contractile activity is an effective stimulus for preserving muscle strength and mass, improving MuSC regulation, and modulating muscle inflammation in a mouse model of CC.

cell biology↗

bioRxiv2025

Defective plasticity in dermatomyositis patients muscle stem cells is associated with sustained intrinsic inflammatory signaling and disruption of the histone H3.3 chromatin loading pathway

Skeletal muscle regeneration is driven by muscle stem cells (MuSCs), which proliferate, differentiate and fuse to reform myofibers and restore muscle function. This myogenesis process is driven both by intrinsic MuSC properties and extrinsic cues. While coordinated inflammatory signals are necessary for healthy regeneration, chronic inflammation participates in various pathologies affecting the skeletal muscle. In the idiopathic inflammatory myopathy dermatomyositis (DM), MuSCs exhibit impaired myogenesis in vitro, indicating that they may have acquired intrinsic defects, contributing to the disease and providing a mechanism for sustained patient muscle weakness despite efficient anti-inflammatory treatments. Here, we investigated the transcriptomic regulation of DM-derived MuSCs, with a focus on the H3.3 histone variant which regulates myogenesis progression. DM-derived MuSCs were unable to effectively execute the myogenic transcriptional program during in vitro differentiation. They exhibited an activated canonical TNF- signaling. They also showed reduced expression of H3.3 and its chaperone genes, coupled with a decrease in H3.3 deposition across the entire genome, and particularly at myogenic regulatory factor loci. The loss of H3.3 combined with elevated TNF- signaling was associated with a failure of DM-derived MuSCs to achieve myogenesis, suggesting a mechanistic link between epigenetic dysregulation and defective muscle regeneration in humans.

molecular biology↗

bioRxiv2024

Macrophage-derived RNAseT2 stimulates muscle stem cell fusion via SLK/N-WASP/actin bundling

Muscle stem cells (MuSCs) fuse to form myofibers to repair skeletal muscle after injury. Within the regenerative MuSC niche, restorative macrophages stimulate MuSC fusion, although the molecular mechanisms involved are largely unknown. Here, we show that restorative macrophages secrete ribonuclease T2 (RNAseT2) to stimulate MuSC fusion. RNAseT2 entered MuSCs via the mannose receptor and induced the formation of actin bundles in MuSCs, enabling cell/cell fusion. Mechanistically, RNAseT2 bound to Ste20-like kinase (SLK), which itself triggered the phosphorylation-mediated activation of N-WASP, through Paxillin phosphorylation, allowing actin bundling necessary for MuSC fusion. In vivo, overexpressing RNAseT2 in regenerating muscle increased fusion in newly formed myofibers in mouse and zebrafish while macrophages deficient for RNAseT2 gene led to fusion defect and smaller myofibers. This study reveals a new function for the highly conserved RNAseT2 and provides a new molecular mechanism by which restorative macrophages support MuSC fusion during muscle repair.

cell biology↗

bioRxiv2024

Immune aging impairs muscle regeneration via macrophage-derived anti-oxidant selenoprotein P

Muscle regeneration is impaired in the aged organism, due to both intrinsic defects of muscle stem cells (MuSCs) and alterations of their environmental niche. However, the latter has still been poorly explored. Here, we compared and analyzed the time course of the various cell types constituting the MuSC niche during muscle generation in young and old mice. Aging altered the amplification of all niche cells with particularly prominent phenotypes in macrophages that impaired the resolution of inflammation in the old regenerating muscle. RNAsequencing of FACs-isolated MuSCs and non-myogenic niche cells during regeneration uncovered specific profiles and kinetics of genes and molecular pathways differentially regulated in old versus young regenerating muscle, indicating that each cell type responded to aging in a specific manner. Through this, we discovered that macrophages have a strong signature of aging with altered the activation of Selenoprotein P (Sepp1) expression in macrophages during the resolution of inflammation in regenerating muscle. Macrophage-specific deletion of Sepp1 gene was sufficient to impair the acquisition of the repair inflammatory profile, perturbed the support of macrophages to MuSCs in vitro and in vivo, and to cause inefficient skeletal muscle regeneration. When transplanted in aged mice, bone marrow from young WT mice, but not Sepp1 KOs, restored muscle regeneration to youthful levels. Altogether this work provides a unique resource to study the aging of the MuSC niche, reveals that aging of niche cells is asynchronous and establishes impaired macrophage dynamics/polarization and the anti-oxidant Selenoprotein P expression as drivers of age-related decline of muscle regeneration. Teaser: Cell profiling reveals asynchronicity of aging in the muscle stem cell niche and age-dependent macrophage/stem cell interactions through anti-oxidant selenoprotein P

physiology↗

bioRxiv2024

Muscle Fibroblasts and Stem Cells Stimulate Motor Neurons in An Age and Exercise-Dependent Manner

Exercise preserves neuromuscular function in ageing through unknown mechanisms. Skeletal muscle fibroblasts (FIB) and stem cells (MuSC) are abundant in skeletal muscle and reside close to neuromuscular junctions, but their relative roles in motor neuron maintenance remain undescribed. Using direct co-cultures of embryonic rat motor neurons with either human MuSC or FIB, RNA sequencing revealed profound differential regulation of the motor neuron transcriptome, with FIB generally favoring neuron growth and cell migration and MuSC favoring production of ribosomes and translational machinery. Conditioned medium from FIB was superior to MuSC in preserving motor neurons and increasing their maturity. Lastly, we established the importance of donor age and exercise status and found an age-related distortion of motor neuron and muscle cell interaction that was fully mitigated by lifelong physical activity. In conclusion, we show that human muscle FIB and MuSC synergistically stimulate the growth and viability of motor neurons, which is further amplified by regular exercise.

physiology↗

bioRxiv2024

Polymeric nanoparticles delivery of AMPK activator 991 prevents its toxicity and improves muscle homeostasis in Duchenne Muscular Dystrophy

Muscular dystrophies, such as Duchenne muscular dystrophy (DMD), are caused by permanent muscle injuries leading to chronic inflammation. In that context, macrophages harbor an altered inflammatory profile that contributes to fibrosis through the secretion of the profibrotic cytokine TGF{beta}1. We previously showed that AMP-activated protein kinase (AMPK) activation reduces TGF{beta}1 secretion by macrophages and improves muscle homeostasis and muscle force in a mouse model of DMD. This makes AMPK an attractive therapeutic target for treating chronic inflammation and fibrosis in DMD. However, potent direct AMPK activators like compound 991 show strong adverse effects in vivo, preventing their direct use. Here, we encapsulated 991 into biodegradable polymeric poly(lactic-co-glycolic) acid (PLGA) nanoparticles for in vivo delivery, in an attempt to overcome toxicity issues. We show that 991-loaded PLGA nanoparticles retained drug activity on fibrotic macrophages in vitro, by reducing their secretion of TGF{beta}1. In the D2-mdx pre-clinical DMD mouse model, intravenously injected PLGA nanoparticles reached gastrocnemius and diaphragm muscles, which are the most affected muscles in this model. Chronic intravenous injections of 991-loaded PLGA nanoparticles decreased inflammation in both muscles, which was associated with fibrosis reduction and increase in myofiber size and muscle mass in the gastrocnemius. No impact on blood cell counts and liver enzymes was observed. These results demonstrate that nanomedicine is an efficient strategy to deliver AMPK activators in vivo to target inflammation and improve the dystrophic muscle phenotype.

pathology↗

bioRxiv2024

Skeletal Muscle Stem Cells Modulate Niche Function in Duchenne Muscular Dystrophy through YY1-CCL5 Axis

Stem cell activity is known to be tightly regulated by both intrinsic and extrinsic pathways but less is known about whether and how stem cells modulate their niche microenvironment. Adult skeletal muscle stem cells (MuSCs) are indispensable for muscle regeneration and also tightly regulated by macrophages (MPs) and fibro-adipogenic progenitors (FAPs) in the niche. Deregulated MuSC/MP/FAP interactions and the ensuing inflammation and fibrosis are hallmarks of dystrophic muscle. Here in this study we demonstrate that intrinsic deletion of transcription factor YY1 in MuSCs exacerbates dystrophic pathologies by altering the cellular composition and heterogeneity of MPs and FAPs. Further analysis reveals that the YY1 loss induces the expression of immune genes in MuSCs, including Ccl5. Augmented secretion of CCL5 from MuSCs promotes the recruitment of MPs via CCL5/CCR5 mediated crosstalk, which subsequently hinders the apoptosis and clearance of FAPs through elevated TGF{beta}1 accumulation. Maraviroc mediated pharmacological blockade of the CCL5/CCR5 axis effectively mitigates muscle dystrophy and improves muscle performance. Lastly, we further demonstrate that YY1 represses Ccl5 transcription in MuSCs by directly binding to its enhancer thus facilitating promoter-enhancer looping. Altogether, our study has demonstrated the previously unappreciated role of MuSCs in actively shaping their niche microenvironment through secreting immunomodulatory cytokines, and has also provided novel insight into the therapeutic intervention of muscle dystrophy.

cell biology↗

bioRxiv2023

Epigenetic control of myogenic identity of human muscle stem cells in Duchenne Muscular Dystrophy

In Duchenne Muscular Dystrophy (DMD), the absence of the subsarcolemmal dystrophin protein leads to repeated myofiber damages inducing cycles of muscle regeneration that is driven by muscle stem cells (MuSCs). With time, MuSC regenerative capacities are overwhelmed, leading to fibrosis and muscle atrophy. Whether MuSCs from DMD muscle have intrinsic defects that limit regenerative potential or are disrupted by their degenerative/regenerative environment is unclear. We investigated cell behavior and gene expression in human using MuSCs derived from DMD or healthy muscles. We found that proliferation, differentiation and fusion were not altered in DMD-MuSCs, but with time, they lost their myogenic identity twice as fast as healthy MuSCs. The rapid drift towards a fibroblast-like cell identity was observed at the clonal level, and resulted from the altered expression of epigenetic enzymes required to maintain the myogenic cell fate. Indeed, the re-expression of CBX3, SMC3, H2AFV and H3F3B prevented the MuSC identity drift. Amongst the epigenetic changes, a closing of chromatin at the gene encoding the transcription factor MEF2B caused a down-regulation of its expression and a loss of the myogenic fate. Thus, MEF2B is a key mediator of the myogenic identity in human MuSCs, that is altered in DMD pathology.

genomics↗

bioRxiv2023

Altered muscle niche contributes to myogenic deficit in the D2-mdx model of severe DMD

Lack of dystrophin is the genetic basis for the Duchenne muscular dystrophy (DMD). However, disease severity varies between patients, based on specific genetic modifiers. D2-mdx is a model for severe DMD that exhibits exacerbated muscle degeneration and failure to regenerate even in the juvenile stage of the disease. We show that poor regeneration of juvenile D2-mdx muscles is associated with enhanced inflammatory response to muscle damage that fails to resolve efficiently and supports excessive accumulation of fibroadipogenic progenitors (FAPs). Unexpectedly, the extent of damage and degeneration of juvenile D2-mdx muscle is reduced in adults and is associated with the restoration of the inflammatory and FAP responses to muscle injury. These improvements enhance myogenesis in the adult D2-mdx muscle, reaching levels comparable to the milder (B10-mdx) mouse model of DMD. Ex vivo co-culture of healthy satellite cells (SCs) with the juvenile D2-mdx FAPs reduced their fusion efficacy and in vivo glucocorticoid treatment of juvenile D2 mouse improved muscle regeneration. Our findings indicate that aberrant stromal cell response contributes to poor myogenesis and greater muscle degeneration in dystrophic juvenile D2-mdx muscles and reversal of this reduces pathology in adult D2-mdx mouse muscle, identifying these as therapeutic targets to treat dystrophic DMD muscles.

pathology↗

bioRxiv2021

Individualized isometric neuromuscular electrical stimulation training promotes myonuclear accretion in mouse skeletal muscle

Skeletal muscle is a plastic tissue that adapts to exercise through fusion of muscle stem cells (MuSCs) with myofibers, a physiological process referred to as myonuclear accretion. However, it is still unclear whether myonuclear accretion is driven by increased mechanical loading per se, or occurs, at least in part, in response to exercise-induced muscle injury. Here, we developed a carefully monitored and individualized neuromuscular electrical stimulation (NMES) training protocol of the mouse plantar flexor muscles. Each NMES training session consisted of 80 isometric contractions at a submaximal mechanical intensity corresponding to ~ 15% of maximal tetanic force to avoid muscle damage. NMES trained mice were stimulated for 2 x 3 consecutive days separated by one day of rest, for a total of 6 sessions. Experiments were conducted on C57BL/6J and BALB/c males at 10-12 weeks of age. NMES led to a robust myonuclear accretion and higher MuSC content in gastrocnemius muscle of both mouse lines, without overt signs of muscle damage/regeneration or muscle hypertrophy or force improvement. This new mouse model of myonuclear accretion relying on the main function of skeletal muscles, i.e., force production in response to electrical stimuli, will be of utmost interest to further understand the role of MuSCs in skeletal muscle adaptations.

physiology↗

bioRxiv2020

Myofiber / pro-inflammatory macrophage interplay controls muscle damage in mdx mice

Duchenne Muscular Dystrophy is a genetic muscle disease characterized by chronic inflammation and fibrosis, which is mediated by a pro-fibrotic macrophage population expressing pro-inflammatory markers. The aim of this study was to characterize cellular events leading to the alteration of macrophage properties, and to modulate macrophage inflammatory status using the gaseous mediator H2S. We first analyzed the relationship between myofibers and macrophages in the mdx mouse model of Duchenne Muscular Dystrophy using coculture experiments. We showed that normal myofibers derived from mdx mice strongly skewed the polarization of resting macrophages towards a pro-inflammatory phenotype. Treatment of mdx mice with NaHS, an H2S donor, reduced the number of pro-inflammatory macrophages in skeletal muscle, which was associated with a decrease in the number of nuclei per fiber, a reduction of myofiber branching and a reduced fibrosis. These results identify an interplay between myofibers and macrophages where dystrophic myofibers contribute to the maintenance of a highly inflammatory environment that skews the macrophage status, which in turn favors myofiber damage, myofiber branching and fibrosis establishment. They also identify H2S donors as a potential therapeutic strategy to improve dystrophic muscle phenotype by modulating macrophage inflammatory status.

cell biology↗

bioRxiv2020

AMPKα1 is essential for Glucocorticoid Receptor triggered anti-inflammatory macrophage activation

SummaryMacrophages are key immune cells which mediate both the acute inflammatory phase and the repair phase after tissue damage. Macrophages switch from pro-inflammatory to anti-inflammatory cells that sustain repair and return to tissue homeostasis. We show that the metabolic sensor, AMP-activated protein kinase (AMPK) is essential for glucocorticoid induction of an anti-inflammatory macrophage phenotype. While canonical gene regulation by glucocorticoids was not affected by loss of AMPK, we identified AMPK-dependent glucocorticoid-regulated genes in macrophages, related to efferocytosis. AMPK-deficient macrophages do not acquire phenotypic and functional anti-inflammatory features upon glucocorticoid exposure. We identified FOXO3 as an AMPK-dependent regulator of glucocorticoid activity in macrophages. Loss of AMPK in macrophages in vivo abrogates glucocorticoid anti-inflammatory actions during post-injury muscle regeneration and endotoxin induced acute lung injury. These data highlight that the glucocorticoid receptor is dependent on AMPK for its immunomodulatory actions in macrophages, linking their metabolic status to transcriptional control in resolving inflammation.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗