bims-moremu Biomed News
on Molecular regulators of muscle mass
Issue of 2025–08–03
forty-one papers selected by
Anna Vainshtein, Craft Science Inc.
  1. Absence of Parkin Results in Atrophy of Oxidative Myofibers and Modulation of AKT and MURF1 Signaling in Middle-Aged Male Mice.
  2. Advancing muscle aging and sarcopenia research through spatial transcriptomics.
  3. Zebrafish: Lessons and Insights into Skeletal Muscle Research.
  4. Hyperactivation of TAK1 causes skeletal muscle pathology reminiscent of inflammatory myopathies.
  5. Human umbilical cord-derived mesenchymal stromal cell exosomes ameliorate aging-associated skeletal muscle atrophy and dysfunction in SAMP10 mice.
  6. Klf9 Loss of Function Protects Against Glucocorticoids Induced Skeletal Muscle Wasting.
  7. Cell biomechanics on muscle atrophy: from intricate mechanisms to therapeutic frontiers.
  8. PAI-1 regulates extracellular matrix remodeling and alters fibroblast profibrotic ability in skeletal muscle repair.
  9. Bidirectional role of Costameres in the pathophysiology of mdx skeletal muscles.
  10. Mitochondrial quality control in exercise-mitigated muscular atrophy.
  11. Perspectives on mitochondrial dysfunction in the regeneration of aging skeletal muscle.
  12. Sex-Dependent Effects of Aging and Insulin Resistance on Skeletal Muscle Function and Structure in Rats.
  13. Large MAF transcription factors reawaken evolutionarily dormant fast-glycolytic type IIb myofibers in human skeletal muscle.
  14. Impact of Acute Endurance Exercise on Alternative Splicing in Skeletal Muscle.
  15. Voluntary Exercise-Induced Skeletal Muscle Responses in Young and Aged Mice on a High-Fat Diet.
  16. Deciphering the miRNA-mRNA Interaction Network Regulating Aging Skeletal Muscle in Various Exercise Regimens through Comprehensive Bioinformatics Analysis.
  17. The intersection of exercise, nitric oxide, and metabolism: Unraveling the role of eNOS in skeletal muscle and beyond.
  18. Exon-Skipping Using Antisense Oligonucleotides for Laminin-Alpha2-Deficient Muscular Dystrophy.
  19. The CCL2-CCR2 axis drives neuromuscular denervation in amyotrophic lateral sclerosis.
  20. Turning up the heat on skeletal muscle adaptations and neuromuscular function: key considerations for passive heating prescription and best practices.
  21. Loss of Ufsp1 does not cause major changes at the neuromuscular junction.
  22. The Impact of Exercise Capacity on Complex Neuromuscular Adaptations: A Narrative Review Based on a Rat Model System Selectively Bred for Low and High Response to Training.
  23. Lessons learned from a muscle study in nail-patella syndrome.
  24. Exploring the Role of Oleic Acid in Muscle Cell Differentiation: Mechanisms and Implications for Myogenesis and Metabolic Regulation in C2C12 Myoblasts.
  25. Bulk RNA-seq of skeletal muscle reveals the role of ZBED6 in sepsis-induced muscle atrophy in minipigs.
  26. Aberrant lysosomal dynamics disrupt myogenesis via mTORC1 signalling in X-linked myotubular myopathy.
  27. Small Molecule Oxybutynin Rescues Proliferative Capacity of Complex III-Defective Muscle Progenitor Cells.
  28. LMOD2 interaction with ACTC1 regulates myogenic differentiation.
  29. Mitigating Doxorubicin-Induced Skeletal Muscle Toxicity: A Review of Oxidative Stress Mechanisms and the Therapeutic Role of Exercise.
  30. APE1/Ref-1 inhibition via APX3330 lowers monocyte/macrophage infiltration without ameliorating the structure and function of dystrophic mdx hindlimb muscles.
  31. A new Drosophila model of prolonged inactivity shortens lifespan and impairs muscle function.
  32. In Vitro Evaluation of Exon Skipping in Disease-Specific iPSC-Derived Myocytes.
  33. Ablation of UCP-1+ Cells Impacts FAP Dynamics in Muscle Regeneration.
  34. Engineering of tissue in microphysiological systems demonstrated by modelling skeletal muscle.
  35. Inflammation sends old muscle stem cells into a rusty meltdown.
  36. Synergic action of MicroRNAs and Wnts delivered by motor neuron EVs in promoting AChR clustering.
  37. Sex Differences in Human Myogenesis Following Testosterone Exposure.
  38. Comparative Transcriptomic Profiling in Patients Affected by Duchenne and Becker Muscular Dystrophies: A Focus on ECM Genes Dysregulation.
  39. Influence of neuromuscular transmission and Na+ channel inhibitors on strength-duration relationship in isolated slow- and fast-twitch muscles.
  40. Guide to Selection of Muscle-Homing Peptides After in Vivo Phage Display Biopanning.
  41. Mimicking the health benefits of exercise.
  1. Acta Physiol (Oxf). 2025 Sep;241(9): e70082
    Absence of Parkin Results in Atrophy of Oxidative Myofibers and Modulation of AKT and MURF1 Signaling in Middle-Aged Male Mice.
    Isabela Aparecida Divino, Ana Laura da Vieira-da-Silva, Marcos Vinicius Esteca, Rafael Paschini Tonon, Felipe Oliveira Gomes da Cruz, Renata Rosseto Braga, Eduardo Rochete Ropelle, Paulo Guimarães Gandra, Igor Luchini Baptista.
       AIM: This work aimed to investigate the effects of the loss of Parkin in middle-aged mice skeletal muscle, focusing on different types of myofibers and in the analysis of proteins related to protein synthesis and degradation as well as the analysis of force generation and motor balance.
    METHODS: We used male mice C57BL/6J (WT) and Parkin knockout mice, Parkintm1Shn (Parkin-/-) at 3 and 10 months of age. We used Walking Beam, Open Field, Spider Mice and Maximum Power Tests to assess motor, balance, and endurance functions. We used flexor digitorum brevis (FDB) muscle for force generation analysis, and tibial anterior (TA) and soleus (SOL) muscles were used for biomolecular techniques because of their difference in fiber type. These muscles were used to investigate markers of protein synthesis and degradation, mitochondrial respiration, and myofiber diameter.
    RESULTS: The Absence of Parkin in middle-aged mice leads to a reduction in isometric force generation but maintained overall motor and locomotion abilities, exhibited only minor balance deficits. In the SOL muscle of middle-aged Parkin-/- mice, we observed a reduction of muscle mass and myofiber diameter, also a significant decrease in mitochondrial respiratory capacity and Complex V. In the same group, we observed a reduction in the phosphorylation of AKT and 4E-BP1, and an increase in MURF-1 while Ubiquitin K63 levels decreased. We did not observe relevant differences in the TA muscle.
    CONCLUSION: Our results suggest middle-aged Parkin-/- mice exhibited muscle atrophy and mitochondrial dysfunction primarily in oxidative myofibers before noticeable motor dysfunction occurs.
    Keywords:  E3 ubiquitin ligase; aging; muscle loss; protein synthesis signaling; skeletal muscle
    DOI:  https://doi.org/10.1111/apha.70082
  2. Osteoporos Sarcopenia. 2025 Jun;11(2 Suppl): 22-31
    Advancing muscle aging and sarcopenia research through spatial transcriptomics.
    Byeong-Don Min, Chae Young Hwang, Doyeong Kim, Sang-Yun Kim, Jayasinghage Nirmani Chathurangika Jayasinghe, Minh Nhat Tran, Sang-Min Park, Ki-Sun Kwon.
      Sarcopenia, defined as a decline of muscle mass and function with aging, poses significant health challenges. This decline is driven by multiple factors including cellular dysfunction, mitochondrial impairments, oxidative stress, and chronic inflammation, all of which collectively disrupt muscle homeostasis and regeneration. Despite the lack of approved treatments for sarcopenia, the search for effective therapies continues as various pharmacological interventions are currently in the early stage of development. Recent advances in transcriptomics have enhanced our understanding of the molecular and cellular mechanisms underlying skeletal muscle aging. In particular, spatial transcriptomics (ST) has revolutionized the field of sarcopenia research by capturing the spatial context of gene expression to uncover site-specific regulation and cellular interactions within tissues. In this review, we explore the current knowledge of sarcopenia, the mechanisms underlying muscle aging, and recent developments in therapeutic strategies. Furthermore, we examine recent studies employing ST that have provided critical insights into the spatial heterogeneity of muscle aging and atrophy, revealing novel cellular and molecular targets for intervention. By connecting muscle pathophysiology with spatial information, ST holds promise for guiding the development of novel sarcopenia therapies, ultimately improving outcomes for aging populations worldwide.
    Keywords:  Microenvironment; Muscle aging; Muscle atrophy; Sarcopenia; Spatial transcriptomics
    DOI:  https://doi.org/10.1016/j.afos.2025.05.002
  3. Cold Spring Harb Perspect Biol. 2025 Jul 28. pii: a041515. [Epub ahead of print]
    Zebrafish: Lessons and Insights into Skeletal Muscle Research.
    Yansong Lu, Avnika A Ruparelia, Peter D Currie.
      Recent technological advances in genome editing capabilities and live imaging capacities have greatly increased the use of the zebrafish model in skeletal muscle research, leading to critical discoveries in the cellular and molecular processes regulating skeletal muscle growth, regeneration, and disease. This is highlighted by the characterization of muscle stem cell and progenitor cell dynamics during growth, the visualization of novel cellular interactions driving regeneration, and the identification of complex disease mechanisms and potential therapies for muscle diseases. This review highlights these latest advancements and discuss the limitations and future directions of zebrafish in skeletal muscle research, focusing on muscle growth, regeneration, and disease.
    DOI:  https://doi.org/10.1101/cshperspect.a041515
  4. Am J Pathol. 2025 Jul 24. pii: S0002-9440(25)00249-4. [Epub ahead of print]
    Hyperactivation of TAK1 causes skeletal muscle pathology reminiscent of inflammatory myopathies.
    Meiricris Tomaz da Silva, Anirban Roy, Ashok Kumar.
      Loss of skeletal muscle mass and strength is a debilitating consequence of various chronic diseases, inflammatory myopathies, and neuromuscular disorders. Inflammation plays a major role in the perpetuation of myopathy in degenerative muscle diseases. TGF-β-activated kinase 1 (TAK1) is a major signaling protein that mediates the activation of multiple signaling pathways in response to inflammatory cytokines and microbial products. Recent studies have demonstrated that TAK1 is essential for the growth and maintenance of skeletal muscle mass in adult mice. However, the effects of overstimulation of TAK1 activity in the regulation of skeletal muscle mass remain unknown. The present study investigated the effects of varying levels of TAK1 activation on skeletal muscle in adult mice. Results showed that while low levels of TAK1 activation improve skeletal muscle mass, sustained hyperactivation of TAK1 causes myopathy in adult mice. Excessive stimulation of TAK1 manifested pathological features, such as myofiber degeneration and regeneration, cellular infiltration, increased expression of proinflammatory molecules, and interstitial fibrosis. Hyperactivation of TAK1 also upregulated proteolytic systems and various catabolic signaling pathways in skeletal muscle of adult mice. Altogether, this study demonstrated that physiological levels of activation of TAK1 lead to myofiber hypertrophy, whereas its hyperactivation results in myofiber damage and other pathological features resembling inflammatory myopathies.
    DOI:  https://doi.org/10.1016/j.ajpath.2025.07.005
  5. Stem Cell Res Ther. 2025 Jul 28. 16(1): 410
    Human umbilical cord-derived mesenchymal stromal cell exosomes ameliorate aging-associated skeletal muscle atrophy and dysfunction in SAMP10 mice.
    Zhe Huang, Limei Piao, Xiangkun Meng, Aiko Inoue, Kazuhiro Hitomi, Hiroyuki Umegaki, Masafumi Kuzuya, Xian Wu Cheng.
       BACKGROUND: Loss of skeletal muscle mass and function in aging individuals is closely linked to physical deterioration and disability. Because exosomes of human umbilical cord-derived mesenchymal stem cells (hucMSC-Exos) have been widely used to treat various human diseases, we examined their effects on aging-associated muscle atrophy and dysfunction in senescence-accelerated mouse prone 10 (SAMP10) mice, an animal model of human Sarcopenia.
    METHODS: Twenty-four-week-old male SAMP10 mice were randomly assigned to a non-treatment or hucMSC-Exos treatment group.
    RESULTS: Twelve weeks after intravenous injection of hucMSC-Exos, the treatment group mice showed improvements in skeletal muscle morphology and performance, and elevated levels of the proteins phospho-mammalian target of rapamycin (p-mTOR), myosin heavy chain (MHC), peroxisome proliferator-activated receptor-γ co-activator, and sirtuin1 (Sirt1) in gastrocnemius muscle tissues. HucMSC-Exos also improved muscle mitochondrial biogenesis and lipid drop accumulation in the gastrocnemius muscles. In in vitro experiments, hucMSC-Exos improved cell viability, senescence, apoptosis, and differentiation in association with induction of molecules related to anti-apoptosis (Bcl-2), differentiation (myogenin, MyoD1, myogenic factor-5, and myogenic factor-6), and protein anabolism (p-mTOR, MHC, Sirt1, phospho-AMP-activated protein kinase, phosphor-extracellular signal-regulated kinase1/2, and glycogen synthase kinase3alpha/beta) in C2C12 cells under our experimental conditions.
    CONCLUSIONS: Our findings indicate that hucMSC-Exos treatment ameliorated skeletal muscle atrophy and dysfunction via mitochondrial biogenesis, anti-apoptosis, and protein anabolism mechanisms that might be dependent on an mTOR and Sirt1/PGC1α signaling pathways, indicating that hucMSC-Exos may have promise as a treatment for the management of aging-related frailty and sarcopenia.
    Keywords:  Anabolism; Apoptosis; Exosomes; Frailty; Mesenchymal stromal cell; Sarcopenia
    DOI:  https://doi.org/10.1186/s13287-025-04477-1
  6. J Cachexia Sarcopenia Muscle. 2025 Aug;16(4): e70020
    Klf9 Loss of Function Protects Against Glucocorticoids Induced Skeletal Muscle Wasting.
    Yujie Zhang, Jingran Hao, Yueyao Feng, Tongtong Qiu, Jinjin Wu, Xuenan Zhou, Heng Fan, Yongsheng Chang.
       BACKGROUND: Glucocorticoids (GCs) are the most important and frequently used class of anti-inflammatory drugs. However, the mechanisms underlying excessive glucocorticoid-mediated induction of muscle atrophy remain incompletely understood.
    METHODS: We generated skeletal muscle-specific Klf9 transgenic mice (mKlf9TG) and skeletal muscle-specific Klf9 knockout mice (Klf9mlc-/-). The body weight, tissue weight, body composition, grip strength, running distance and muscle fibre cross section of mKlf9TG, Klf9mlc-/- mice and their littermate controls were examined. Expression of genes related to muscle protein synthesis and degradation pathways were also tested in the mKlf9TG mice, Klf9mlc-/- mice and their littermate controls. We performed Klf9 gain- or loss-of-function studies in differentiated C2C12 myotubes using lentiviruses encoding Klf9 or the shRNA specific to Klf9 in vitro. Luciferase reporter gene assay and ChIP assay were performed to explore the molecular mechanism of Klf9 action. Klf9mlc-/- and Klf9fl/fl mice were treated with dexamethasone (Dex). Multiple genetic and pharmacological approaches were also used to investigate the intracellular signalling cascades underlying the Dex/Klf9-ediated skeletal muscle wasting.
    RESULTS: Skeletal muscle Klf9 gene expression was significantly upregulated by Dex (p < 0.05 or p < 0.01 vs. vehicle group). Compared with littermate control mice (R-loxP), mKlf9TG mice exhibited decreased skeletal muscle mass (TA 0.101 ± 0.018 vs. 0.040 ± 0.007 g, p < 0.001) and impaired grip strength (forelimb 157.4 ± 3.7 vs. 93.45 ± 9.8 and four limbs 255.3 ± 23.1 vs. 170.1 ± 36.2, p < 0.001). Conversely, compared with Klf9fl/fl, Klf9mlc-/- mice exhibited increased skeletal muscle mass (TA 0.103 ± 0.012 vs. 0.123 ± 0.005 g, p < 0.001) and enhanced grip strength (forelimb 110.3 ± 5.8 vs. 156.8 ± 10.0 and four limbs 155.5 ± 6.3 vs. 226.5 ± 19.7, p < 0.001). Skeletal muscle Klf9 deficiency alleviated muscle atrophy induced by acute high-dose Dex treatment (p < 0.001). Mechanistically, Klf9 induces the expression of myostatin (Mstn) and muscle atrophy F-box (MAFbx) by directly binding to and activating the transcription of their promoters. Treatment of AAV-MSTN reduced the increased grip strength of Klf9mlc-/- mice (forelimb 143.5 ± 22.3 vs. 118.8 ± 3.1 and four limbs 249.8 ± 24.7 vs. 208.7 ± 9.0, p < 0.001).
    CONCLUSIONS: In summary, our study provides novel insights into the mechanisms underlying GC-induced muscular atrophy and reveals that skeletal muscle induction of Klf9 expression is a mechanism underlying GC therapy-induced muscle loss. Thus, targeting Klf9 may offer novel approaches to the treatment of skeletal muscle wasting diseases.
    Keywords:  Krüppel‐like factor 9; glucocorticoids; muscle atrophy; myostatin
    DOI:  https://doi.org/10.1002/jcsm.70020
  7. Ann Med. 2025 Dec;57(1): 2540598
    Cell biomechanics on muscle atrophy: from intricate mechanisms to therapeutic frontiers.
    Yilin Wang, Jingyuan Meng, Jiechao Zhang, Lichao Tian, Wenrui Wei, Xiaoye Tang, Qian Zhang, Daofang Ding, Xuepeng Wang, Zicheng Guo, Yong He.
       BACKGROUND: Muscle atrophy-the decline of skeletal muscle volume and function-is pervasive in chronic disease, aging, and inactivity. As the primary driver of human mobility and metabolic health, skeletal muscle loss diminishes quality of life and increases healthcare burden. Atrophy impairs recovery and prognosis by reducing metabolic capacity, accelerating systemic protein catabolism, and compromising the biomechanical support necessary for movement and respiration. Although core molecular pathways and cellular changes are well characterized, the role of mechanical cues in modulating these mechanisms remains underexplored.
    MAIN FINDINGS: Our review reveals five convergent atrophy drivers-mechanical unloading, ECM alterations, mitochondrial dysfunction/oxidative stress, inflammation, and endocrine imbalance-that converge on inhibited mTORC1 signaling, activated FoxO/UPS/autophagy, and impaired satellite-cell function. Quantitative data show that axial stretch preserves PI3K/Akt/mTOR activity, with phosphorylated Akt levels increasing by two- to three-fold and fiber cross-sectional area expanding by 10%-20%; low-intensity compression activates AMPK and autophagy, with AMPK phosphorylation rising by 1.5-fold without triggering excessive protein breakdown; and shear stress enhances VEGF and Nrf2-mediated angiogenesis and antioxidant defenses, doubling VEGF expression and reducing ROS levels by 25% to mitigate neurogenic atrophy. Moreover, stem-cell myogenic differentiation is optimized on 3D biomimetic substrates with stiffness from 11 to 17 kPa under physiological loading, and advances in biomaterials and tissue engineering enable more accurate muscle-tissue models.
    FUTURE DIRECTIONS: Translating these biomechanical insights into tailored clinical interventions-combining stretch, compression, and shear modalities with biomaterials, stem-cell technologies, and personalized exercise programs- holds promise for preventing and reversing muscle atrophy across diverse patient populations.
    Keywords:  Muscle atrophy; cellular biomechanics; exercise therapy; mechanotransduction pathways; stem cell therapy
    DOI:  https://doi.org/10.1080/07853890.2025.2540598
  8. Exp Cell Res. 2025 Jul 23. pii: S0014-4827(25)00277-0. [Epub ahead of print]450(2): 114677
    PAI-1 regulates extracellular matrix remodeling and alters fibroblast profibrotic ability in skeletal muscle repair.
    Na Li, Xing-Yu Lu, Jie-Yun Zhang, Li-Hong Dang, Jin-Fang Liu, Fang-Yu Wu, Xi-Mei Cao, Xin-Hua Liang, Jun-Hong Sun.
      Excessive accumulation of extracellular matrix (ECM) and fibrosis severely impair skeletal muscle function, underscoring the urgent need to explore new strategies for improving muscle regeneration. Fibroblasts, as the primary source of ECM in skeletal muscle, can trigger persistent ECM deposition when aberrantly activated. Here, we identify a pivotal role for plasminogen activator inhibitor type-1 (PAI-1) in modulating fibroblast profibrotic activity and ECM remodeling. Our results show that PAI-1 expression rises at the early stages of muscle repair, and pharmacologic inhibition of PAI-1 increases transient ECM deposition. In vitro, PAI-1 inhibition promotes fibroblast proliferation, activation, and ECM production partly via the Notch signaling pathway, a finding further supported by in vivo evidence of early Notch activation in PAI-1-inhibited muscle. These insights reveal an expanded function for PAI-1 in regulating the behavior of muscle fibroblasts beyond its well-known fibrinolytic role, providing a promising therapeutic avenue for enhancing muscle regeneration and preserving muscle homeostasis.
    Keywords:  ECM; Fibroblast; Notch signaling; PAI-1; Skeletal muscle
    DOI:  https://doi.org/10.1016/j.yexcr.2025.114677
  9. Hum Mol Genet. 2025 Aug 01. pii: ddaf127. [Epub ahead of print]
    Bidirectional role of Costameres in the pathophysiology of mdx skeletal muscles.
    Glen B Banks, Darren R Bisset, Jeffrey S Chamberlain.
      Skeletal muscles in Duchenne Muscular Dystrophy (DMD) are most susceptible to injury at a point in maturation when dystrophin is absent and utrophin dissipates from the membrane. The lack of the dystrophin glycoprotein complex (DGC) leaves a residual costameric scaffold that structurally connects the peripheral sarcomeres to the sarcolemma. However, the residual costameres are weak and transmit less lateral force making it unclear how they contribute to the pathophysiology of DMD. Here we found that costameres were near absent in mature mdx4cv:desmin double knockout (dko) fast 2b myofibers where the compensating utrophin protein is not upregulated at costameres. The lack of costameres decoupled sarcomere strain injury from tearing the membrane leading to isolated necrotic myofibers. Despite a 30% reduction in the proportion of myofibers with centrally located nuclei (a marker of degenerating/regenerating myofibers), the fast 2b dko muscles were atrophic and profoundly weakened by the sarcomere strain injury. Thus, our data is consistent with the DGC protecting the membrane and peripheral sarcomeres from the bidirectional forces that propagate through the desmin-fortified costameres.
    Keywords:  Duchenne; costamere; desmin; dystrophin; lateral force transmission; skeletal muscle
    DOI:  https://doi.org/10.1093/hmg/ddaf127
  10. Mitochondrion. 2025 Jul 28. pii: S1567-7249(25)00071-6. [Epub ahead of print] 102074
    Mitochondrial quality control in exercise-mitigated muscular atrophy.
    Jingcheng Fan, Xin Wen, Xuemei Duan, Xinyi Zhu, Jianzheng Bai, Tan Zhang.
      Muscle atrophy is a loss of muscle mass, posing a huge burden on patients and society. Increased protein degradation, decreased protein synthesis, inflammatory response, oxidative stress, and mitochondrial dysfunction are risk factors of muscular atrophy. Mitochondrial quality control (MQC) processes maintain mitochondrial health, which is essential to maintain skeletal muscle structural and functional integrity. Of note, it is widely acknowledged that regular exercise induces significant improvements in muscular atrophy. Mechanistically, exercise reinforces mitochondrial function through MQC, as well as mitigate muscular atrophy.. However, the role and molecular mechanism of MQC in exercise-attenuated muscular atrophy have not yet fully elucidated. Here, we review the current knowledge relevant to MQC in the context of muscular atrophy, and focus on MQC in exercise-mediated anti-atrophic effect, which may be conductive to muscular atrophy prevention and therapy through targeting mitochondria.
    Keywords:  Exercise; Mitochondrial quality control; Muscular atrophy
    DOI:  https://doi.org/10.1016/j.mito.2025.102074
  11. Cell Mol Biol Lett. 2025 Jul 28. 30(1): 94
    Perspectives on mitochondrial dysfunction in the regeneration of aging skeletal muscle.
    Kai Wang, Mailin Gan, Yuhang Lei, Tianci Liao, Jiaxin Li, Lili Niu, Ye Zhao, Lei Chen, Yan Wang, Li Zhu, Linyuan Shen.
      As the global population trends toward aging, the number of individuals suffering from age-related debilitating diseases is increasing. With advancing age, skeletal muscle undergoes progressive oxidative stress infiltration, coupled with detrimental factors such as impaired protein synthesis and mitochondrial DNA (mtDNA) mutations, culminating in mitochondrial dysfunction. Muscle stem cells (MuSCs), essential for skeletal muscle regeneration, also experience functional decline during this process, leading to irreversible damage to muscle integrity in older adults. A critical contributing factor is the loss of mitochondrial metabolism and function in MuSCs within skeletal muscle. The mitochondrial quality control system plays a pivotal role as a modulator, counteracting aging-associated abnormalities in energy metabolism and redox imbalance. Mitochondria meet functional demands through processes such as fission, fusion, and mitophagy. The significance of mitochondrial morphology and dynamics in the mechanisms of muscle regeneration has been consistently emphasized. In this review, we provide a comprehensive summary of recent advances in understanding the mechanisms of aging-related mitochondrial dysfunction and its role in hindering skeletal muscle regeneration. Additionally, we present novel insights into therapeutic approaches for treating aging-related myopathies.
    Keywords:  Aging; Mitochondrial dynamics; Mitophagy; Oxidative stress; Skeletal muscle regeneration
    DOI:  https://doi.org/10.1186/s11658-025-00771-1
  12. Int J Mol Sci. 2025 Jul 15. pii: 6783. [Epub ahead of print]26(14):
    Sex-Dependent Effects of Aging and Insulin Resistance on Skeletal Muscle Function and Structure in Rats.
    Patricia Sosa, Javier Angulo, Alberto Sánchez-Ferrer, Maria Carmen Gómez-Cabrera, Argentina Fernández, Leocadio Rodríguez-Mañas, Mariam El Assar.
      Skeletal muscle function is determinant for maintaining functional performance and independence in older adults. Muscle is a primary target of aging and insulin resistance (IR)-two conditions associated with functional decline. Sex-related differences may influence these effects at structural and functional levels. We aimed to evaluate the individual and combined effects of aging and IR on the function and structure of extensor digitorum longus (EDL) and soleus muscles in male and female rats. Animals aged 3 and 20 months were studied, with IR induced by 8 weeks of 20% fructose in drinking water. Muscle contractility was assessed alongside histological and hormonal analyses. In males, aging impaired EDL and soleus contractile force, free testosterone levels, and muscle mass. IR decreased muscle function only in young animals. In females, aging led to muscle loss without affecting contractile strength, but the combination of aging and IR reduced muscle contraction, decreased estradiol and exacerbated muscle loss. Both sexes showed aging-related loss of EDL glycolytic fibers, altered regenerative capacity, and increased fibrosis. IR alone reduced glycolytic fibers in young animals of both sexes but increased fibrosis only in males. These results highlight sex-specific effects of aging and IR on muscle function, relevant for targeted strategies to prevent and treat age- and IR-related muscle function decline.
    Keywords:  aging; contractile responses; fibrosis; glycolytic fiber; insulin resistance; muscle function; sex differences
    DOI:  https://doi.org/10.3390/ijms26146783
  13. Skelet Muscle. 2025 Jul 26. 15(1): 19
    Large MAF transcription factors reawaken evolutionarily dormant fast-glycolytic type IIb myofibers in human skeletal muscle.
    Shunya Sadaki, Ryosuke Tsuji, Takuto Hayashi, Masato Watanabe, Ryoto Iwai, Gu Wenchao, Ekaterina A Semenova, Rinat I Sultanov, Andrey V Zhelankin, Edward V Generozov, Ildus I Ahmetov, Iori Sakakibara, Koichi Ojima, Hidetoshi Sakurai, Masafumi Muratani, Takashi Kudo, Satoru Takahashi, Ryo Fujita.
       BACKGROUND: Small mammals such as mice rely on type IIb myofibers, which express the fast-contracting myosin heavy chain isoform Myh4, to achieve rapid movements. In contrast, larger mammals, including humans, have lost MYH4 expression. Thus, they favor slower-contracting myofiber types. However, the mechanisms underlying this evolutionary shift remain unclear. We recently identified the large Maf transcription factor family (Mafa, Mafb, and Maf) as key regulators of type IIb myofiber specification in mice. In this study, we investigate whether large MAFs play a conserved role in the induction of MYH4 expression and glycolytic metabolism in human and bovine skeletal muscle.
    METHODS: We performed adenovirus-mediated overexpression of large MAFs in iPSC-derived human myotubes and primary bovine myotubes. We subsequently quantified MYH4 expression using RT-qPCR, RNA sequencing (RNA-seq), and LC-MS/MS analysis. Glycolytic capacity was assessed using a flux analyzer and metabolic gene expression profiling. Additionally, RNA-seq analysis of human muscle biopsy samples was conducted to determine the correlations between large MAFs and the expression of MYH4 and other myosin genes, as well as their association with fast fiber composition and athletic training.
    RESULTS: Overexpression of large MAFs in human and bovine myotubes robustly induced MYH4 expression, with mRNA levels increasing by 100- to 1000-fold. LC-MS/MS analysis provided clear evidence of MYH4 protein expression in human myotubes, where it was previously undetectable. RNA-seq and flux analyzer data revealed that large MAFs significantly enhanced glycolytic capacity by upregulating the expression of key genes involved in glucose metabolism. Moreover, RNA-seq analysis of human muscle biopsy samples revealed a positive correlation between MAFA, MAF, and MYH4 expression. Furthermore, MAFA and MAF expression levels were elevated in power-trained individuals, accompanied by increased expression of MYH4 and other fast myosin genes.
    CONCLUSIONS: Our findings establish large MAF transcription factors as key regulators of MYH4 expression and glycolytic metabolism in human skeletal muscle. This discovery provides novel insights into the evolutionary loss of type IIb myofibers in larger mammals and suggests potential strategies for enhancing muscle performance and mitigating fast-twitch fiber loss associated with aging and muscle degeneration.
    Keywords:  Aging; Human muscle; Large MAFs; MYH4; Myofiber type; Myosin heavy chain; Type IIb myofiber
    DOI:  https://doi.org/10.1186/s13395-025-00391-5
  14. FASEB Bioadv. 2025 Aug;7(8): e70024
    Impact of Acute Endurance Exercise on Alternative Splicing in Skeletal Muscle.
    Alexander Ahn, Jeongjin J Kim, Aaron L Slusher, Jeffrey Y Ying, Eric Y Zhang, Andrew T Ludlow.
      Alternative splicing (AS) is a highly conserved posttranscriptional mechanism, generating mRNA variants to diversify the proteome. Acute endurance exercise appears to transiently perturb AS in skeletal muscle, but transcriptome-wide responses are not well defined. We aimed to better understand differential AS (DAS) and differential isoform expression (DIE) in skeletal muscle by comparing short-read (SRS) and long-read RNA sequencing (LRS) data. Publicly accessible SRS of clinical exercise studies were extracted from the Gene Expression Omnibus. Oxford Nanopore LRS was performed on mouse gastrocnemius before and following treadmill exercise (30 m running, n = 5 mice/group, 20 total, 10 weeks old). Differential gene expression (DGE) and DIE were analyzed and validated using RT-PCR and immunoblots. Both SRS and LRS illustrated significant DGE in skeletal muscle postexercise, including 89 RNA-binding proteins (RBPs). rMATS analysis of SRS revealed that exon-skipping and intron-retaining events were the most common. Swan analysis of LRS revealed several common genes across postexercise cohorts with significant DAS but no DGE: 13 exercise-associated genes, including mSirt2 (24.5% shift at 24 h postexercise [24pe], p = 0.005); 61 RBPs, including mHnrnpa3 (28.5% at 24pe, p = 0.02), mHnrnpa1 (30.6% at 24pe, p = 0.004), and mTia1 (53.6% at 24pe, p = 0.004). We illustrated that acute endurance exercise can elicit changes in AS-related responses and RBP expression in skeletal muscle, especially at 24pe. SRS is a powerful tool for analyzing DGE but lacks isoform detection, posing a major gap in knowledge of "hidden" genes with no transcriptional but significant DIE and protein expression changes. Additionally, LRS can uncover previously unknown transcript diversity and mechanisms influencing endurance exercise adaptations and responses.
    Keywords:  RNA‐binding proteins; alternative RNA splicing; endurance exercise; skeletal muscle; splicing factors
    DOI:  https://doi.org/10.1096/fba.2025-00007
  15. Cureus. 2025 Jun;17(6): e86697
    Voluntary Exercise-Induced Skeletal Muscle Responses in Young and Aged Mice on a High-Fat Diet.
    Yuji Kanazawa, Kenichiro Miyahara, Tatsuo Takahashi, Ryo Miyachi, Takashi Higuchi, Takaaki Nishimura, Hiaki Sato, Yuri Ikeda-Matsuo.
      Background and objective Aging and consumption of a high-fat diet (HFD) are associated with increased body weight and reduced skeletal muscle quality. Although aerobic exercise is generally considered protective against these risks, the impact of self-initiated physical activity on an HFD in older individuals remains unclear. This study aimed to investigate the influence of spontaneous wheel-running on body weight, intramuscular fat accumulation, and mitochondrial metabolic function in the skeletal muscles of young and aged mice on HFD. Methods Male C57BL/6J mice aged 14 weeks (young group) and 84 weeks (aged group) were assigned to either exercise or sedentary groups and fed an HFD for eight weeks. Measurements included body weight, muscle weight (gastrocnemius and soleus), muscle fiber cross-sectional area (FCSA), succinate dehydrogenase (SDH) activity, and intramuscular fat area via Oil Red O staining. Results Voluntary exercise significantly reduced the body weight in both age groups. While the muscle weight and FCSA remained unchanged by exercise, exercise led to elevated SDH activity in the gastrocnemius muscles of both young and aged mice, suggesting increased mitochondrial metabolic activity. Exercise increased intramuscular fat content in the gastrocnemius muscle of young mice, but not in aged mice. The soleus muscle showed a minimal response to both metabolic activity and fat accumulation by exercise, regardless of age. Conclusions Voluntary wheel running under HFD conditions effectively lowered body weight and increased mitochondrial activity in gastrocnemius muscle fibers. However, intramuscular fat responses vary according to muscle type and age, suggesting that aging diminishes skeletal muscle adaptability to exercise in the context of lipid metabolism.
    Keywords:  aging; high-fat diet; intramuscular fat; mitochondrial metabolic activity; voluntary exercise
    DOI:  https://doi.org/10.7759/cureus.86697
  16. Cell Biochem Biophys. 2025 Aug 01.
    Deciphering the miRNA-mRNA Interaction Network Regulating Aging Skeletal Muscle in Various Exercise Regimens through Comprehensive Bioinformatics Analysis.
    Zhi Yu, Pin-Shi Ni, Zhuang-Zhi Wang, Zheng-Yang Zhao, Bao-Yi Chen, Zhen-En Zhang, Fang-Hui Li.
      Understanding the impact of different exercise types on skeletal muscle atrophy in older adults is crucial for designing effective strategies to combat age-related muscle loss. This study explores the molecular mechanisms through which resistance exercise (RES) and endurance exercise (END) mitigate skeletal muscle atrophy. By examining microRNA (miRNA) expression profiles from aging skeletal muscle datasets (GSE165632) in the Gene Expression Omnibus (GEO) database, the research aims to uncover exercise-specific miRNA signatures and their associated regulatory pathways. Using the GEO2R analysis tool, researchers identified differentially expressed miRNAs (DEmiRNAs) between RES and END groups. Predicted target genes of these miRNAs were determined through a combination of miRTarBase, micro-T, and TargetScan databases. Functional enrichment analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, were performed via the DAVID database. Transcription factors were predicted using the ChEA3 database, while protein-protein interaction (PPI) networks were constructed with the STRING database to identify hub genes for further functional enrichment studies. The analysis revealed 30 differentially expressed miRNAs in the RES group and 21 in the END group. In the RES group, key pathways such as FoxO signaling, neurotrophic signaling, insulin resistance, and AMPK were regulated by miRNAs like hsa-miR-574-5p, hsa-miR-34a-5p, and hsa-miR-21-5p. These pathways promote protein synthesis and reduce myocyte apoptosis. In the END group, hub genes were linked to FoxO, TGF-β, MAPK, and cGMP-PKG signaling pathways, regulated by miRNAs such as hsa-miR-194-5p, hsa-miR-146a-5p, and hsa-miR-6831-5p, which enhance mitochondrial function and metabolic regulation. Both exercise types shared common regulatory pathways, including MAPK, TGF-β, and PI3K-Akt, which influence genes like SMAD4 and TRAF6 that are essential for myocyte survival and fibrosis suppression. This study sheds light on the unique and overlapping miRNA-driven regulatory mechanisms behind the effects of RES and END on skeletal muscle atrophy in older adults. Resistance exercise primarily boosts protein synthesis and inhibits apoptosis via pathways like AMPK and p53, while endurance exercise enhances mitochondrial function and energy metabolism through cGMP-PKG signaling. Both exercise modalities converge on critical pathways, providing a scientific basis for developing personalized exercise programs to counteract sarcopenia.
    Keywords:  Bioinformatics analysis; Endurance exercise (END); Resistance exercise (RES); Sarcopenia; miRNA
    DOI:  https://doi.org/10.1007/s12013-025-01848-6
  17. Metabolism. 2025 Jul 30. pii: S0026-0495(25)00229-X. [Epub ahead of print] 156360
    The intersection of exercise, nitric oxide, and metabolism: Unraveling the role of eNOS in skeletal muscle and beyond.
    Pierre-Anne R Laird, Rebecca M Wall, Siobhan M Craige.
      Exercise protects against several diseases including cardiometabolic disorders. However, the molecular mechanisms driving these adaptations remain incompletely defined. Endothelial nitric oxide synthase (eNOS), a key source of nitric oxide (NO), is implicated in regulating glucose uptake, fatty acid metabolism, and mitochondrial remodeling in response to exercise. eNOS is expressed in both endothelial and non-endothelial cells and its effects on metabolism are multifaceted. Notably, eNOS is highly expressed in endothelial cells which are ubiquitous throughout all organ systems allowing them to closely integrate with surrounding cell types. This unique feature of the endothelium enables eNOS to influence both local microenvironments and systemic signaling across organ systems. This review summarizes current findings on the role of eNOS-derived NO in exercise metabolism. Evidence suggests eNOS contributes to improved metabolic flexibility, enhanced mitochondrial function, and tissue crosstalk. However, data across experimental models remain mixed, with both supportive and conflicting results. Collectively, the literature indicates that eNOS plays a central, though context-dependent, role in facilitating exercise-induced metabolic benefits. Identifying the specific mechanisms and tissue contributions of eNOS activity remains an important area for future investigation, with potential relevance to metabolic disease prevention and treatment.
    Keywords:  Endothelial nitric oxide synthase; Endothelium; Exercise; Metabolism; Mitochondria; Nitric oxide; Skeletal muscle
    DOI:  https://doi.org/10.1016/j.metabol.2025.156360
  18. Methods Mol Biol. 2025 ;2964 487-499
    Exon-Skipping Using Antisense Oligonucleotides for Laminin-Alpha2-Deficient Muscular Dystrophy.
    Eri Takeuchi, Chaitra Sathyaprakash, Hotake Takizawa, Norio Motohashi, Yusuke Echigoya, Toshifumi Yokota, Yoshitsugu Aoki.
      Phosphorodiamidate morpholino oligomer (PMO)-mediated exon-skipping is among the more promising approaches available for the treatment of several neuromuscular disorders, including Duchenne muscular dystrophy. The main weakness of this treatment arises from the low efficiency and sporadic nature of the delivery of neutrally charged PMOs into muscle fibres, the mechanism of which is unknown. Recently, using wild-type and dystrophic mdx52 mice, we showed that muscle fibres took up PMOs more efficiently during myotube formation. Interestingly, we detected PMO mainly in embryonic myosin heavy chain-positive regenerating fibres through in situ hybridisation. Next, we tested the therapeutic potential of PMOs in laminin-alpha2 (laminin-α2) chain-null dy3K/dy3K mice, a model of merosin-deficient congenital muscular dystrophy 1A (MDC1A or LAMA2-related muscular dystrophy: LAMA2-MD) with active muscle regeneration. We confirmed the recovery of the laminin-α2 chain following the skipping of the mutated exon 4 in dy3K/dy3K mice, which prolonged the lifespan of the animals slightly. These findings support the theory that PMO entry into fibres is dependent on the developmental stage in myogenesis rather than on dystrophin-deficient muscle membranes, and recommend a platform for the future development of PMO-mediated therapies for a variety of muscular disorders, such as LAMA2-MD, that involve active muscle regeneration. Herein, we describe the methods for PMO transfection/injection and the evaluation of the efficacy of exon-skipping in the laminin-α2-deficient dy3K/dy3K mouse model both in vitro and in vivo.
    Keywords:  Dystrophin; Eteplirsen; Exon-skipping; Laminin-α2 chain; Merosin-deficient congenital muscular dystrophy type 1A (MDC1A or LAMA2-Related muscular dystrophiesMuscular dystrophies: LAMA2-MD); NS-065/NCNP-01; Phosphorodiamidate morpholino oligomer (PMO); Viltolarsen; dy3K/dy3K mouse
    DOI:  https://doi.org/10.1007/978-1-0716-4730-1_33
  19. Nat Commun. 2025 Aug 01. 16(1): 7053
    The CCL2-CCR2 axis drives neuromuscular denervation in amyotrophic lateral sclerosis.
    Bernát Nógrádi, Kinga Molnár, Rebeka Kristóf, Orsolya Horváth, Yu-Ting Huang, Zara Ridgway, Amaia Elicegui, Sandra Fuertes-Alvarez, Sonia Alonso-Martin, Gábor J Szebeni, Nikolett Gémes, Abdullah Ramadan, Hannah L Smith, István A Krizbai, Roland Patai, László Siklós, Péter Klivényi, Helena Chaytow, Thomas H Gillingwater.
      Systemic immune changes have been implicated in amyotrophic lateral sclerosis (ALS), but precise mechanisms and cellular targets remain unknown. Neuromuscular junction (NMJ) denervation is another major pathophysiological event in ALS, but it remains unclear whether immune system dysregulation contributes to this process. Here, we report leukocyte and macrophage infiltration in ALS patient-derived skeletal muscle biopsies. Immune cell infiltration was replicated across the hTDP-43, TDP-43A315T (male only) and TDP-43M337V mouse models, occurring from pre-symptomatic stages and targeted to NMJ-enriched muscle regions. Proteomic analysis implicated the CCL2-CCR2 axis as a driving factor. CCL2+ cells were enriched around NMJs in hTDP-43 mice, and in ALS patient skeletal muscle. Local treatment with CCL2-neutralising antibodies or normal IgG antibodies in hTDP-43 mice reduced leukocyte infiltration and ameliorated NMJ denervation. These results demonstrate that the CCL2-CCR2 axis drives immune cell infiltration targeting NMJs in ALS, identifying a potential avenue for therapeutic intervention to prevent NMJ denervation.
    DOI:  https://doi.org/10.1038/s41467-025-62351-3
  20. Eur J Appl Physiol. 2025 Jul 29.
    Turning up the heat on skeletal muscle adaptations and neuromuscular function: key considerations for passive heating prescription and best practices.
    Patrick Rodrigues, Geoffrey M Minett, Lucas B R Orssatto.
      Despite compelling evidence supporting the benefits of passive heat therapy in promoting skeletal muscle adaptation and enhancing neuromuscular function, the topic remains debated. Some recent studies report no significant effects on muscle protein synthesis, muscle mass, recovery, strength, or power. This raises critical questions: is passive heat therapy not actually effective? Or do these discrepancies reflect inconsistencies in study protocols and an overgeneralisation of the term passive heating? Despite its growing recognition as a health treatment, exercise mimetic, and tool for sport performance and recovery, the interpretation of outcomes is often simplistic or misinformed. In this opinion article, we discuss the disparities in the literature and highlight the risks of oversimplification, such as the binary view that passive heat therapy either "works" or "does not work." We also propose incorporating the FITT (Frequency, Intensity, Time, and Type) principles from exercise science into thermal therapy research to enhance methodological consistency and clarity. By adopting a more structured and rigorous approach, the field can better realise the potential of passive heat therapy as a scientifically grounded intervention for both health and sport performance applications.
    Keywords:  FITT principles; Heat therapy; Hot-water immersion; Neuromuscular function; Passive heating; Skeletal muscle adaptation
    DOI:  https://doi.org/10.1007/s00421-025-05917-9
  21. PLoS One. 2025 ;20(8): e0328690
    Loss of Ufsp1 does not cause major changes at the neuromuscular junction.
    Cristofer Calvo, Coalesco Smith, Taejeong Song, Fabian Montecino-Morales, Sakthivel Sadayappan, Douglas P Millay, Minchul Kim.
      UFMylation is a Ubiquitin-like post-translational modification involved in myriad of cellular processes. Enzymes involved in this pathway, including ligases and UFM1-specific proteases, are essential for development and homeostasis. Our previous transcriptomic analyses identified an enrichment of Ufsp1 at the neuromuscular junction of skeletal muscle cells. Ufsp1, one of the two UFM1 proteases, had been considered a pseudogene due to truncation of its catalytic domain in several species, including humans. However, recent findings revealed that Ufsp1 is translated from a non-canonical start codon in humans, yielding a catalytically active enzyme. This discovery has revived interest in studying Ufsp1's role in vivo. We generated two mutant mouse models, one with a point mutation abolishing catalytic activity and another with complete knockout of the gene. Unlike other UFMylation pathway enzymes, both Ufsp1 mutants were born in normal ratios and did not exhibit gross phenotypic abnormalities. Despite the enrichment of Ufsp1 at neuromuscular junctions, only mild structural alterations of this synapse were detected, which did not impact overall muscle function. Our findings indicate that Ufsp1 is dispensable for normal development and homeostasis in mice, but further exploration of its function is needed in pathological conditions.
    DOI:  https://doi.org/10.1371/journal.pone.0328690
  22. Compr Physiol. 2025 Aug;15(4): e70029
    The Impact of Exercise Capacity on Complex Neuromuscular Adaptations: A Narrative Review Based on a Rat Model System Selectively Bred for Low and High Response to Training.
    Vinicius Guzzoni, Upasana Shrestha, Nicholas J Kesler, Aditya Acharya, Samantha J McKee, Tatiana Sousa Cunha, Dulce Elena Casarini, Steven T Haller, David J Kennedy, Steven L Britton, Lauren Gerard Koch.
      There is scientific evidence that supports the association between aerobic exercise capacity and the risk of developing complex metabolic diseases. The factors that determine aerobic capacity can be categorized into two groups: intrinsic and extrinsic components. While exercise capacity is influenced by both the intrinsic fitness levels of an organism and the extrinsic factors that emerge during training, physiological adaptations to exercise training can differ significantly among individuals. The interplay between intrinsic and acquired exercise capacities represents an obstacle to recognizing the exact mechanisms connecting aerobic exercise capacity and human health. Despite robust clinical associations between disease and a sedentary state or condition, the precise causative links between aerobic exercise capacity and disease susceptibility are yet to be fully uncovered. To provide clues into the intricacies of poor aerobic metabolism in an exercise-resistant phenotype, over two decades ago a novel rat model system was developed through two-way artificial selection and raised the question of whether large genetic differences in training responsiveness would bring about aberrant systemic disorders and closely regulate the risk factors in health and diseases. Genetically heterogeneous outbred (N/NIH) rats were used as a founder population to develop contrasting animal models of high versus low intrinsic running capacity (HCR vs. LCR) and high versus low responsiveness to endurance training (HRT vs. LRT). The underlying hypothesis was that variation in capacity for energy transfer is the central mechanistic determinant of the divide between complex disease and health. The use of the outbred, genetically heterogeneous rat models for exercise capacity aims to capture the genetic complexity of complex diseases and mimic the diversity of exercise traits among humans. Accumulating evidence indicates that epigenetic markers may facilitate the transmission of effects from exercise and diet to subsequent generations, implying that both exercise and diet have transgenerational effects on health and fitness. The process of selective breeding based on the acquired change in maximal running distance achieved during a treadmill-running tests before and after 8 weeks of training generated rat models of high response to training (HRT) and low response to training (LRT). In an untrained state, both LRT and HRT rats exhibit comparable levels of exercise capacity and show no major differences in cardiorespiratory fitness (maximal oxygen consumption, VO2max). However, after training, the HRT rats demonstrate significant improvements in running distance, VO2max, as well as other classic markers of cardiorespiratory fitness. The LRT rats, on the other hand, show no gain in running distance or VO2max upon completing the same training regime. The purpose of this article is to provide an overview of studies using LRT and HRT models with a focus on differences in neuromuscular adaptations. This review also summarizes the involved molecular and cellular signaling pathways underlying skeletal muscle adaptations in LRT models in comparison to the HRT model, which responds positively to endurance training. The LRT-related adverse effects in neuromuscular responses seem to be primarily driven by: (i) impaired glucose tolerance or impaired insulin sensitivity, (ii) increased extracellular matrix (ECM) remodeling, (iii) loss of type I muscle fibers, (iv) mitochondrial dysfunction, and (v) intricate cellular signaling orchestrated by TGF-ß1-JNK and TNF-α-MAPK pathways. Alternatively, the HRT model demonstrates improved neurovascular and muscle remodeling responses and increased central nervous system excitability, which might reflect an inherent protective mechanism to stress events.
    Keywords:  aerobic exercise; central nervous system; exercise‐resistant phenotype; intrinsic running capacity; skeletal muscle
    DOI:  https://doi.org/10.1002/cph4.70029
  23. Orphanet J Rare Dis. 2025 Jul 28. 20(1): 384
    Lessons learned from a muscle study in nail-patella syndrome.
    Luisa Paul, Anne Schänzer, Christel Depienne, Andreas Hentschel, Nicolai Kohlschmidt, Ulrike Schara-Schmidt, Christopher Jannik Nelke, Andreas Roos, Heike Kölbel.
       BACKGROUND: Nail-patella (NPS) syndrome is an autosomal dominant disorder caused by mutations in the LMX1B gene and manifests with involvement of kidneys, nails, eyes as well as skeletal musculature. NPS shows some clinical similarities with Emery-Dreifuss muscular dystrophy. However, thus far human muscle tissue has not been analysed in the context of NPS to precisely clarify the muscular involvement in this multi-systemic disease.
    METHODS: To study the effects of a missense variant in LMX1B on human skeletal muscle, histological, immunofluorescence and ultra-structural studies were performed on a deltoid muscle biopsy performed at the age of 2 aiming to analyse potential pathologies in muscle fibres in addition to unbiased proteomic profiling to identify dysregulated proteins.
    RESULTS: Microscopic work-up of the muscle biopsy revealed no striking pathologies, except for some atrophic fibres. The proteomic analyses unveiled a clustered number of dysregulated keratin proteins among the downregulated proteins.
    CONCLUSION: Although NPS can also present with a muscular phenotype indicated by muscular weakness of the upper extremities, elevated CK levels and contractures of the elbow joint, there is no evidence of primary muscular involvement due to expression of mutant LMX1B. The examination of human skeletal muscle tissue confirmed the findings from the animal models showing that the skeletal muscle symptoms of NPS may be the result of a developmental disorder of the extremities that leads to impaired muscle mobilisation.
    Keywords:  Elbow contractures; Emery dreyfuss muscle dystrophy; LMX1B; Muscle proteomics; Nail-patella syndrome
    DOI:  https://doi.org/10.1186/s13023-025-03911-0
  24. Biomedicines. 2025 Jun 26. pii: 1568. [Epub ahead of print]13(7):
    Exploring the Role of Oleic Acid in Muscle Cell Differentiation: Mechanisms and Implications for Myogenesis and Metabolic Regulation in C2C12 Myoblasts.
    Francesco Vari, Elisa Bisconti, Ilaria Serra, Eleonora Stanca, Marzia Friuli, Daniele Vergara, Anna Maria Giudetti.
      Background/Objectives: Myogenesis, the process by which myoblasts differentiate into multinucleated muscle fibers, is tightly regulated by transcription factors, signaling pathways, and metabolic cues. Among these, fatty acids have emerged as key regulators beyond their traditional role as energy substrates. Oleic acid, a monounsaturated fatty acid, has been shown to modulate muscle differentiation, potentially influencing myogenic pathways. This study examines the role of oleic acid in promoting C2C12 myoblast differentiation and its associated molecular mechanisms, comparing it to standard horse serum (HS)-based differentiation protocols. Methods: C2C12 murine myoblasts were cultured under proliferative conditions and differentiated using DMEM supplemented with either 2% HS or oleic acid (C18:1, n-9). The molecular signaling pathway was evaluated by measuring the expression of p38 MAPK, β-catenin, GLUT4, and NDRG1. Results: Oleic acid promoted the differentiation of C2C12 cells, as evidenced by a progressively elongated morphology, as well as the induction of muscle-specific myogenin, myosin heavy chain (MHC), and MyoD. Moreover, oleic acid reduced the expression of Atrogin-1 and MuRF1 ubiquitin E3 ligase. BODIPY staining revealed the enhanced accumulation of lipid droplets in oleic acid-treated cells. The Western blot analysis demonstrated robust activation of p38 MAPK and β-catenin pathways in response to oleic acid, compared with HS. Additionally, oleic acid upregulated GLUT4 expression and increased the phosphorylation of insulin receptor and NDRG1, indicating an enhanced glucose uptake capacity. Conclusions: These findings demonstrate that oleic acid promotes C2C12 myoblast differentiation and improves glucose uptake via GLUT4. Oleic acid emerges as a promising metabolic regulator of myogenesis, offering potential therapeutic applications for muscle regeneration in muscle-related pathologies.
    Keywords:  C2C12 myoblast differentiation; glucose uptake; lipid droplets; oleic acid; skeletal muscle
    DOI:  https://doi.org/10.3390/biomedicines13071568
  25. Sci Data. 2025 Jul 29. 12(1): 1312
    Bulk RNA-seq of skeletal muscle reveals the role of ZBED6 in sepsis-induced muscle atrophy in minipigs.
    Huan Liu, Wen Shi, Yanjun Zheng, Song Yang, Yihui Wang, Maosen Yang, Zhitao Yang, Enqiang Mao, Hanbing Shang, Erzhen Chen, Ying Chen.
      Sepsis is a severe disease and induces skeletal muscle atrophy, which has a significant impact on patients. Moreover, the onset and severity of muscle atrophy can vary across different anatomical regions during sepsis. Our previous study demonstrated that ZBED6 knockout not only promotes skeletal muscle growth under physiological conditions, but also alleviates systemic muscle atrophy during sepsis. However, its region-specific effects on sepsis-induced muscle atrophy have not been analyzed. In this study, we performed RNA sequencing for 54 samples of skeletal muscle from nine different anatomical regions from male ZBED6 knockout and wild-type (WT) minipigs subjected to sepsis. We generated 364.63 Gb of high-quality bulk RNA sequencing data from the skeletal muscle samples (approximately 6.75 Gb per sample). This dataset provided insightful gene expression information to understand the role of ZBED6 in region-specific muscle atrophy during sepsis. In addition, this dataset can be used for heterogeneity analysis between skeletal muscle tissues from multiple species or female pigs.
    DOI:  https://doi.org/10.1038/s41597-025-05620-6
  26. Brain. 2025 Jul 29. pii: awaf278. [Epub ahead of print]
    Aberrant lysosomal dynamics disrupt myogenesis via mTORC1 signalling in X-linked myotubular myopathy.
    Kengo Kora, Takeshi Yoshida, Atsushi Yokoyama, Kei Fujiwara, Naoko Yano, Taisei Kayaki, Satoshi Kajimoto, Kinuko Nishikawa, Hidetoshi Sakurai, Junko Takita.
      X-linked myotubular myopathy is a severe congenital muscle disorder caused by pathogenic variants in the MTM1 gene, which encodes the phosphoinositide phosphatase myotubularin. Muscle biopsies from patients with X-linked myotubular myopathy exhibit distinctive histopathological features, including small, rounded myofibres with centrally located nuclei, indicating a developmental defect in muscle maturation. While earlier studies have indicated that myotubularin dysfunction causes dysregulation of mechanistic target of rapamycin complex 1 (mTORC1) signalling, the underlying mechanisms and phenotypic impact on human muscle cells remain poorly understood. Currently, there are no approved therapies available for the treatment of this disorder. In this study, we established an induced pluripotent stem cell-based model of X-linked myotubular myopathy using two pairs of isogenic induced pluripotent stem cells: healthy-control versus MTM1-knockout and patient-derived versus gene-corrected induced pluripotent stem cells. Through MyoD-inducible myogenic differentiation, this model successfully recapitulates the key pathological features of X-linked myotubular myopathy, including elevated phosphatidylinositol-3-phosphate levels, hyperactivation of mTORC1 signalling, and increased expression of integrin-β1 and dynamin 2. We identified impaired lysosomal dynamics as a novel pathogenic mechanism in X-linked myotubular myopathy. Our induced pluripotent stem cell-derived X-linked myotubular myopathy myotubes exhibited an abnormal redistribution of lysosomes, with peripheral accumulation, leading to abnormally activated mTORC1 signalling. FYCO1 knockdown, a key regulator of lysosomal trafficking, ameliorated this hyperactivation of mTORC1 signalling. Comprehensive transcriptome analysis revealed distinct gene expression patterns associated with altered mTORC1 signalling and lysosomal localisation in X-linked myotubular myopathy myotubes. Network analysis suggested the central role of the mTORC1 signalling pathway and its connections to disrupted muscle development and differentiation. To investigate the influence of mTORC1 signalling and myotubularin deficiency on myogenic differentiation, we established two mouse myoblast models: one with constitutively activated mTORC1 signalling and another with Mtm1 knockout. Increased mTORC1 signalling in mouse myoblasts impaired myogenic differentiation, and this impairment was reversed by mTORC1 inhibitor rapamycin. Notably, rapamycin treatment also ameliorated the impaired myogenic differentiation observed in Mtm1-knockout mouse myoblasts, supporting the causative role of mTORC1 hyperactivation in X-linked myotubular myopathy pathogenesis. In conclusion, our findings establish the first human cell model of XLMTM, revealing that myotubularin deficiency leads to impaired lysosomal dynamics, which in turn causes mTORC1 dysregulation, a critical factor in the early stage of myogenic differentiation in X-linked myotubular myopathy. These findings provide new insights into the pathogenesis of X-linked myotubular myopathy and suggest that targeting mTORC1 signalling may be a promising therapeutic strategy for this debilitating disorder.
    Keywords:  MTM1; X-linked myotubular myopathy; induced pluripotent stem cell; lysosomal dynamics; mTORC1 signalling; myogenic differentiation
    DOI:  https://doi.org/10.1093/brain/awaf278
  27. Am J Physiol Cell Physiol. 2025 Jul 31.
    Small Molecule Oxybutynin Rescues Proliferative Capacity of Complex III-Defective Muscle Progenitor Cells.
    Yue Qu, Kaydine Edwards, Muying Li, Matthew Williams, Yang Liu, Pei-Yin Tsai, Chloe Cheng, Jamie E Blum, Noel Acor, Tenzin Oshoe, Claire Walter, Venkatesh Thirumalaikumar, Anna E Thalacker-Mercer, Aleksandra Skirycz, Joeva Barrow.
      Mitochondrial disease encompasses a group of genetically inherited disorders hallmarked by an inability of the respiratory chain to produce sufficient ATP. These disorders present with multisystemic pathologies that predominantly impact highly energetic tissues such as skeletal muscle. There is no cure or effective treatment for mitochondrial disease. We have discovered a small molecule known as oxybutynin that can bypass Complex III mitochondrial dysfunction in primary murine and human skeletal muscle progenitor cells (MPCs). Oxybutynin administration improves MPC proliferative capacity, enhances cellular glycolytic function, and improves myotube formation. Mechanistically, results from our isothermal shift assay indicates that oxybutynin interacts with a suite of proteins involved in mRNA processing which then trigger the upregulation biological pathways to circumvent CIII mitochondrial dysfunction. Taken together, we provide evidence for the small molecule oxybutynin as a potential therapeutic candidate for the future treatment of CIII mitochondrial dysfunction.
    Keywords:  Complex III; Mitochondrial Disease; Muscle Progenitor Cells; Oxybutynin; Uqcrfs1
    DOI:  https://doi.org/10.1152/ajpcell.00141.2025
  28. BMC Genomics. 2025 Jul 31. 26(1): 709
    LMOD2 interaction with ACTC1 regulates myogenic differentiation.
    Kaiming Wang, Caihong Liu, Lei Yi, Sui Liufu, Wenwu Chen, Xiaolin Liu, Bohe Chen, Xin Xu, Jingwen Liu, Xibing Liu, Yulong Yin, Haiming Ma.
       BACKGROUND: Skeletal muscle is the largest tissue in mammals, and it plays a crucial role in metabolism and homeostasis. Skeletal muscle development and regeneration consist of a series of carefully regulated changes in gene expression. Leiomodin2 (LMOD2) gene is specifically expressed in the heart and skeletal muscle. But the physiological functions and mechanisms of LMOD2 on skeletal muscle development are unknown.
    RESULTS: In this study, we examined the expression levels of the LMOD2 in porcine tissues and C2C12 cells. LMOD2 is mainly expressed in the heart, followed by skeletal muscle. The expression level of LMOD2 gradually decreased with skeletal muscle growth, but increased after injury. LMOD2 expression levels increased gradually with C2C12 cells proliferation and differentiation. In terms of function, the muscle fiber types were altered after LMOD2 was knocked out in C2C12 cells, MyHC-I and MyHC-2b were inhibited, whereas MyHC-2a and MyHC-2x were promoted. LMOD2 knockout has different effects on LMOD family, LMOD1 expression level was promoted, while LMOD3 was inhibited. Loss of LMOD2 suppressed cell viability and PAX7 protein expression. At the transcriptome level, proliferation-related genes and muscle contraction-related genes were respectively inhibited after LMOD2 knockout. In terms of molecular networks, a series of experiments have shown that MyoG is a transcription factor for LMOD2, while miR-335-3p can negatively regulate LMOD2 expression. We screened ACTC1 as a candidate interacting protein for LMOD2 using protein prediction software and RNA-seq, and Co-IP experiments confirmed the relationship between LMOD2 and ACTC1. In vivo, Lentivirus-mediated LMOD2 knockdown reduces muscle mass. LMOD2 knockdown inhibited MyHC-I mRNA expression, but had no effect on MyHC-2b. The protein expression of MyHC-I, MyHC-2x, and MyHC-2b was suppressed after LMOD2 knockdown.
    CONCLUSIONS: Collectively, our data indicates that LMOD2 knockout inhibits myoblast proliferation and alters muscle fiber types. MyoG is a transcription factor for LMOD2, while miR-335-3p can negatively regulate LMOD2 expression. Moreover, LMOD2 and ACTC1 interact to regulate myogenic differentiation. Our study provides a new target for skeletal muscle development.
    Keywords:   ACTC1 ; LMOD2 ; Knockout; Myoblast; Skeletal muscle
    DOI:  https://doi.org/10.1186/s12864-025-11897-z
  29. Antioxidants (Basel). 2025 Jul 16. pii: 870. [Epub ahead of print]14(7):
    Mitigating Doxorubicin-Induced Skeletal Muscle Toxicity: A Review of Oxidative Stress Mechanisms and the Therapeutic Role of Exercise.
    Quinten W Pigg, Dillon R Harris, Daniela Sayuri Inoue, Mariana Janini Gomes.
      Doxorubicin (DOX) is a highly effective chemotherapy drug used in the treatment of many cancers, including solid tumors, hematological malignancies, and soft tissue sarcomas. Despite its potent antitumor effects, DOX is known to have toxic effects in non-tumorous tissues, such as skeletal muscle. Potential mediators of DOX-induced skeletal muscle toxicity are reactive oxygen species (ROS). An overproduction of ROS can disrupt the balance between oxidants and antioxidants in a cell, leading to oxidative stress. Chronic oxidative stress has been shown to upregulate proteolysis, ultimately leading to muscle wasting. Exercise stands as a potent nonpharmacological therapy capable of attenuating muscle wasting by enhancing metabolic function and antioxidant defenses while suppressing harmful ROS production. This review focuses on the current understanding of the role of oxidative stress in DOX-induced skeletal muscle toxicity. In addition, we highlight the effects of various exercise types on oxidative stress and muscle remodeling during DOX chemotherapy.
    Keywords:  chemotherapy; endurance training; metabolism; reactive oxygen species; resistance training
    DOI:  https://doi.org/10.3390/antiox14070870
  30. Physiol Rep. 2025 Aug;13(15): e70494
    APE1/Ref-1 inhibition via APX3330 lowers monocyte/macrophage infiltration without ameliorating the structure and function of dystrophic mdx hindlimb muscles.
    Hannah Lalunio, Craig A Goodman, Nicole Stupka, Nicholas Giourmas, Danielle A Debruin, Lauren Sahakian, Kulmira Nurgali, Alan Hayes.
      Chronic inflammation and oxidative stress exacerbate muscle wasting and weakness in Duchenne muscular dystrophy (DMD). Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) regulates transcription factors involved in inflammatory and oxidative stress pathways. APE1/Ref-1 is an emerging therapeutic target in inflammatory conditions. This study aimed to investigate the effects of APX3330, a small molecule inhibitor of APE1's Ref-1 on mdx mouse pathology, a model of DMD. Six-week-old mdx mice and wild type (WT) C57Bl/10 mice were treated with APX3330 (25 mg·kg-1) or vehicle for 6 weeks. Ex vivo contractile function, histological and biochemical analysis were performed in extensor digitorum longus (EDL) and soleus muscles. APE1/Ref-1 protein was greater in mdx hindlimb muscles compared to WT (p < 0.0001) and APE1/Ref-1 protein abundance was not altered by treatment with APX3330. In dystrophic EDL muscles, APX3330 treated mice had fewer (47%) infiltrating CD68-positive monocytes/macrophages (p < 0.05) compared to vehicle-treated mdx mice. Markers of oxidative stress, NRF2/KEAP-1, were unchanged, yet phospho-NF-κB abundance was higher with treatment (p < 0.01). APX3330 treatment neither improve force output and fatiguability of isolated hindlimb muscles, nor affect muscle pathology. As APE1/Ref-1 inhibition modestly lowered inflammation, with no improved contractile function, targeting solely inflammation and oxidative stress in 6-week-old mdx mice appears insufficient.
    Keywords:  inflammation; mdx mouse; muscular dystrophy; oxidative stress; skeletal muscle
    DOI:  https://doi.org/10.14814/phy2.70494
  31. Sci Rep. 2025 Jul 31. 15(1): 27908
    A new Drosophila model of prolonged inactivity shortens lifespan and impairs muscle function.
    Jodi Protasiewicz, Sarah Snider, Mousumee Khan, Li Tao, Robert J Wessells, Alyson Sujkowski.
      Prolonged inactivity due to medical conditions can cause chronic muscle disuse and lead to physical incapacity and poor quality of life. Here, we developed a Drosophila model of confinement inactivity (CI) to observe its effects on lifespan and muscle function. We found that, similar to mammalian models and humans, CI negatively impacted longevity and function in Drosophila. Confined flies had impaired mobility, shorter lifespan, and reduced muscle integrity compared to their freely mobile siblings. These findings establish a new, highly efficient platform for studying long term effects of chronic sedentary behavior and muscle disuse in the genetically tractable Drosophila model. In addition, we found that temporarily removing flies from CI for scheduled bouts of forced physical exercise ameliorated negative effects, in part by improving muscle homeostasis. Finally, we tested whether muscle overexpression of 3 exercise-responsive genes, dPGC-1α, dFNDC5, or dSesn, could prevent the negative impact of CI on fly aging, even without physical exercise. We previously established that overexpression of these factors phenocopies exercise effects in aging wild-type and disease model flies. We found that when overexpressed in muscle, dSesn prevented premature declines in endurance, and dFNDC5 protected speed and endurance. This new model can be used in the future for mechanistic studies to identify preventative and therapeutic targets for diseases associated with chronic inactivity.
    Keywords:   Drosophila melanogaster ; Confinement; Exercise; Prolonged inactivity
    DOI:  https://doi.org/10.1038/s41598-025-13446-w
  32. Methods Mol Biol. 2025 ;2964 163-178
    In Vitro Evaluation of Exon Skipping in Disease-Specific iPSC-Derived Myocytes.
    Hidetoshi Sakurai.
      Patient-derived disease-specific induced pluripotent stem cells (iPSCs) have opened the door to recreating pathological conditions in vitro using differentiation into diseased cells corresponding to each target tissue. To investigate muscular diseases, we have established a myogenic differentiation protocol mediated by inducible MYOD1 expression that drives human iPSCs into myocytes. This highly reproducible differentiation protocol yields a homogenous skeletal muscle cell population, reaching efficiencies as high as 90%. Such high efficiency enables us to evaluate the efficacy of exon skipping in disease-specific myocytes. These disease-specific iPSC-derived myocytes can be applied not only for the validation of the therapeutic efficacy of specific antisense oligonucleotide, but also for the screening of exon skipping chemicals combined with the multi-well differentiation system. Although we previously presented the protocol in 2018, we have updated the myogenic differentiation protocol to the current version.
    Keywords:  Disease-specific iPS cells; Doxycycline inducible differentiation; Exon skipping; MyoD; Myogenic differentiation
    DOI:  https://doi.org/10.1007/978-1-0716-4730-1_11
  33. Am J Physiol Cell Physiol. 2025 Jul 28.
    Ablation of UCP-1+ Cells Impacts FAP Dynamics in Muscle Regeneration.
    Jacob C Parson, Gretchen A Meyer.
      Uncoupling protein-1 (UCP-1+) cells found in brown adipose tissue and subtypes of white (a.k.a. beige) adipose tissue have been a focus of intensive investigation for their role in energy metabolism and are emerging as potential endocrine regulators of physiology. More recently, UCP-1+ subpopulations have also been found in skeletal muscle fibro-adipogenic progenitors (FAPs), which play an important role in regeneration. Both UCP-1+ adipocytes and FAPs secrete pro-myogenic cytokines further supporting their potential for pro-regenerative signaling. To investigate whether signaling from UCP-1+ cells does indeed promote regeneration, we examined injury-induced muscle regeneration in a mouse model with constitutive UCP-1+ cell ablation (UCP1-DTA) at three timepoints: early (3 and 7 days post injury [dpi]) intermediate (14dpi), and late (21dpi). We hypothesized that without UCP-1+ cells, muscle regeneration would be impaired at all timepoints. At 3 and 7dpi, we found significantly reduced numbers of FAPs in male UCP1-DTA mice, but with no accompanying changes in muscle-derived stem (satellite) cells or immune cells. However, at 14dpi, we observed signficantly higher numbers of FAP in male UCP1-DTA mice and evidence of ongoing early-phase regeneration including signifcantly increased histological and gene expression of early regenerative markers and significantly smaller regenerating fibers. However, these changes were not associated with fibrosis and fatty infiltration typical of impaired regeneration, nor were differences in contractile force recovery observed between genotypes. These findings suggest UCP-1+ cells (adipocytes or FAPs) may regulate FAP dynamics in early regeneration, but without major effects on the recovery of structure and function.
    Keywords:  Brown adipose tissue; contractile function; fibro-adipogenic progenitors; glycerol injury
    DOI:  https://doi.org/10.1152/ajpcell.00249.2025
  34. Regen Biomater. 2025 ;12 rbaf059
    Engineering of tissue in microphysiological systems demonstrated by modelling skeletal muscle.
    Yuan Gao, Zilin Zhang, Yu Yao, Jing Zhang, Xiaoran Li, Keyu Yang, Nuo Si, Zaozao Chen, Zhongze Gu, Ningbei Yin.
      Research on myogenesis and myogenic pathologies has garnered significant attention in recent years. However, traditional in vitro modeling approaches have struggled to fully replicate the complex functions of skeletal muscle. This limitation is primarily due to the insufficient reconstruction of the muscle tissue microenvironment and the role of physical cues in regulating muscle cell activity. Recent studies have highlighted the importance of the microenvironment, which includes cells, extracellular matrix (ECM) and cytokines, in influencing myogenesis, regeneration and inflammation. This review focuses on advances in skeletal muscle construction toward a complete microphysiological system, such as organoids and muscle-on-a-chip technology, as well as innovative interventions like bioprinting and electrical stimulation. These advancements have enabled researchers to restore functional skeletal muscle tissue, bringing us closer to achieving a fully functional microphysiological system. Compared to traditional models, these systems allow for the collection of more comprehensive data, providing insights across multiple scales. Researchers can now study skeletal muscle and disease models in vitro with increased precision, enabling more advanced research into the physiological and biochemical cues affecting skeletal muscle activity. With these advancements, new applications are emerging, including drug screening, disease modeling and the development of artificial tissues. Progression in this field holds great promise for advancing our understanding of skeletal muscle function and its associated pathologies, offering potential therapeutic solutions for a variety of muscle-related diseases.
    Keywords:  bioengineering; in vitro modeling; microenvironment; microphysiological system; skeletal muscle
    DOI:  https://doi.org/10.1093/rb/rbaf059
  35. Nat Aging. 2025 Jul 25.
    Inflammation sends old muscle stem cells into a rusty meltdown.
    Ohanes Ashekyan, Michael A Rudnicki.
      
    DOI:  https://doi.org/10.1038/s43587-025-00937-8
  36. Cell Commun Signal. 2025 Aug 01. 23(1): 360
    Synergic action of MicroRNAs and Wnts delivered by motor neuron EVs in promoting AChR clustering.
    Rachele Agostini, Paola Ceccaroli, Emanuela Polidori, Manuela Ferracin, Ilaria Pace, Serena Maggio, Andrea Cioccoloni, Michela Battistelli, Giulia Matacchione, Matilde Sbriscia, Fabiola Olivieri, Fabrizia Cesca, Vilberto Stocchi, Michele Guescini.
       BACKGROUND: The neuromuscular junction (NMJ) establishment occurs through complex communication events between motor neurons and muscle fibers; however, the molecular mechanisms leading to NMJ formation have yet to be fully elucidated. Little is known about the significance of extracellular vesicles (EVs) in mediating the interaction between motor neurons and muscle fiber in the NMJ establishment; this study investigates the role of motor neuron-derived EVs during the earliest stages of NMJ formation.
    METHODS: NSC-34 cells have been used as a model of motor neurons; EVs have been isolated during neurite development using a serial ultracentrifugation protocol specifically adjusted to isolate large and small EVs. Isolated EVs were quantified through Nanoparticles Tracking Assay and characterized by Western Blot and TEM analyses. The microRNA (miRNA) cargo of EV subpopulations was identified by small-RNA sequencing and the predicted miRNA downstream targets were investigated.
    RESULTS: NGS analysis of small RNAs carried by NSC-34-derived EVs identified a total of 245 EV specific miRNAs, most of which are up-regulated in NSC-34 cells and EVs during neurite stretching. Target prediction analysis evidenced how these miRNAs synergically target the Wnt signaling pathway. Moreover, we found that NSC-34-derived EVs carry Wnt proteins, including Wnt11, Wnt4 and Wnt3a. Since several studies suggested a role for the Wnt-associated signaling network in NMJ formation, we investigated the potential role of NSC-34 EVs in NMJ development and demonstrated that EV administration to myotubes increases acetylcholine receptor (AChR) cluster formation, as revealed by immunofluorescence staining with α-bungarotoxin. Moreover, myotube treatment with NSC-34-derived EVs led to GSK3β and JNK phosphorylation, followed by β-catenin nuclear translocation, suggesting that neuron-derived EVs can induce AChR clustering through Wnt pathway activation.
    CONCLUSION: These data demonstrate that EVs released from differentiated motor neurons carry multimodal signals, miRNAs, and Wnts, which can stimulate AChR clustering in myotubes, a fundamental preparatory stage for NMJ formation. These new data highlight that EVs may play a role in the NMJ establishment and function under physiological and pathological conditions, particularly neurodegenerative diseases.
    Keywords:  Acetylcholine receptor; Agrin; Extracellular vesicles; Neuromuscular junctions; Wnt signalling; β-catenin
    DOI:  https://doi.org/10.1186/s12964-025-02312-x
  37. Biology (Basel). 2025 Jul 14. pii: 855. [Epub ahead of print]14(7):
    Sex Differences in Human Myogenesis Following Testosterone Exposure.
    Paolo Sgrò, Cristina Antinozzi, Guglielmo Duranti, Ivan Dimauro, Zsolt Radak, Luigi Di Luigi.
      Previous research has demonstrated sex-specific differences in muscle cells regarding sex hormone release and steroidogenic enzyme expression after testosterone exposure. The present study aims to elucidate sex-related differences in intracellular processes involved in myogenesis and regeneration. Neonatal 46XX and 46XY human primary skeletal muscle cells were treated with increasing doses of testosterone (0.5, 2, 5, 10, 32, and 100 nM) for 24 h. The molecular pathways involved in muscle metabolism and growth, as well as the release of myokines involved in satellite cell activation, were analyzed using western blot, real-time PCR, and a Luminex assay. The unpaired Student's t-test and one-way ANOVA for repeated measures were used to determine significant variations within and between groups. An increase in the expression and release of MYF6, IGF-I, IGF-II, and CXCL1, as well as a decrease in GM-CSF, IL-9, and IL-12, was observed in 46XX cells. Conversely, testosterone up-regulated GM-CSF and CXCL1 in 46XY cells but did not affect the release of the other myokines. Preferential activation of the MAPK pathway was observed in 46XX cells, while the PI3K/AKT pathway was preferentially activated in 46XY cells. In conclusion, our findings demonstrate differential responses to androgen exposure in 46XX and 46XY cells, resulting in the activation of muscle cell growth and energy metabolic pathways in a sex-specific manner.
    Keywords:  androgens; gender medicine; sex dimorphism; skeletal muscle cells
    DOI:  https://doi.org/10.3390/biology14070855
  38. Int J Mol Sci. 2025 Jul 09. pii: 6594. [Epub ahead of print]26(14):
    Comparative Transcriptomic Profiling in Patients Affected by Duchenne and Becker Muscular Dystrophies: A Focus on ECM Genes Dysregulation.
    Bartolo Rizzo, Francesca Dragoni, Maria Irene Dainesi, Rosalinda Di Gerlando, Evelyne Minucchi, Angela Lucia Berardinelli, Stella Gagliardi.
      The complexity of RNA metabolism has become crucial in neuromuscular diseases, especially for Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). Our goal was to search for possible pathways that differ between the two diseases, in which DMD develops a severe phenotype compared to BMD. In this work, we aimed to evaluate the transcriptomic profile in skeletal muscle biopsies derived from patients with either DMD or BMD. We collected RNA obtained from pediatric patients with DMD (n = 12) and with BMD (n = 6). Compared to patients with BMD, patients with DMD showed a particular activation of genes involved in collagen synthesis, extracellular matrix organization, and Oncostatin M-dependent pathways, important for fibrotic processes. This suggests that a more severe phenotype in patients with DMD compared to those with BMD may be due to greater deregulation of these pathways, reflecting the clinical picture of patients observed. Our results allowed us to highlight the molecular differences between the two phenotypic groups, shedding light on the pathways that make Duchenne dystrophy more severe than its counterpart does. This study provides preliminary insights into the difference in gene expression between the two groups and lays the basis for the identification of possible mechanisms that differentiate between the two diseases.
    Keywords:  Becker muscular dystrophy; Duchenne muscular dystrophy; ECM; RNA-seq; collagen; fibrosis; inflammation; skeletal muscle
    DOI:  https://doi.org/10.3390/ijms26146594
  39. J Muscle Res Cell Motil. 2025 Jul 28.
    Influence of neuromuscular transmission and Na+ channel inhibitors on strength-duration relationship in isolated slow- and fast-twitch muscles.
    Mari S Matsumoto, Taku Hamada, Daiki Watanabe.
      Strength-duration (S-D) relationship reflects muscle excitability which partially determines force production. Isolated muscle contains part of nerve and neuromuscular junction, suggesting that muscle excitation initiates not only muscle membrane but also nerve terminals and hence neuromuscular transmission (NMT). This study aimed to examine the effects of inhibition of neuromuscular transmission on S-D relationship in slow- and fast-twitch muscles of mice. Isolated slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) muscles were electrically stimulated, and minimal field strength required for force generation [threshold field strength (ThFS)] was determined at various duration. ThFS significantly increased in the presence of NMT inhibitors including pancuronium (Pan) and succinylcholine in both SOL and EDL muscles. Moreover, ThFS in the presence of NMT inhibitors was higher in SOL compared to EDL. To clarify the mechanism of the different ThFS between SOL and EDL, contribution of Na+ channel was investigated. In the presence of 1 μM Pan, partial inhibition of Na+ channel by tetrodotoxin eliminated the difference in ThFS between EDL and SOL. These results suggest that (1) NMT significantly enhances muscle excitability, (2) threshold of action potential in fast-twitch muscle is greater compared with slow-twitch muscle if no existence of NMT, and (3) Na+ channel likely contribute to the difference between slow- and fast-twitch muscles.
    Keywords:  Acetylcholine receptor; Muscle excitability; Voltage-dependent Na+ channel
    DOI:  https://doi.org/10.1007/s10974-025-09702-1
  40. Methods Mol Biol. 2025 ;2964 209-230
    Guide to Selection of Muscle-Homing Peptides After in Vivo Phage Display Biopanning.
    Anne-Fleur Schneider, Silvana Jirka, Leon Mei, Annemieke Aartsma-Rus.
      Drug delivery is a hurdle that has to be overcome every time a new therapeutic approach is devised or tested in a new tissue. Identifying peptides for conjugation to the therapeutic compound to improve delivery to the target tissue or cells could help improve therapy efficacy. We make use of phage display biopanning in two mouse models for Duchenne muscular dystrophy (DMD) to find muscle homing peptides to advance therapeutic uptake of antisense oligonucleotides (AON). AONs are pieces of short, modified RNA that can restore the distorted reading frame of dystrophin that is causing DMD. Uptake of these AONs into muscle tissues is currently suboptimal. Following in vivo phage display biopanning, we made use of next-generation sequencing to ensure that our analysis could be carried out as unbiased as possible. A selection strategy was devised to screen for muscle homing peptides, resulting in a list of potential muscle homing peptides that can be tested further to check for improved delivery. In this chapter, we describe the protocols that were carried out and point out notable steps to consider when executing this method.
    Keywords:  Drug delivery; In vivo phage display biopanning; Muscle homing peptide; Next-generation sequencing
    DOI:  https://doi.org/10.1007/978-1-0716-4730-1_14
  41. Nat Rev Drug Discov. 2025 Jul 28.
    Mimicking the health benefits of exercise.
    Sarah Crunkhorn.
      
    DOI:  https://doi.org/10.1038/d41573-025-00127-6
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