Muscle biology
Abstract
Collagen VI–related disorders (COL6-RDs) are a group of rare muscular dystrophies caused by pathogenic variants in collagen VI genes (COL6A1, COL6A2, and COL6A3). Collagen type VI is a heterotrimeric, microfibrillar component of the muscle extracellular matrix (ECM), predominantly secreted by resident fibroadipogenic precursor cells in skeletal muscle. The absence or mislocalization of collagen VI in the ECM underlies the noncell-autonomous dysfunction and dystrophic changes in skeletal muscle with a yet elusive direct mechanistic link between the ECM and myofiber dysfunction. Here, we conducted a comprehensive natural history and outcome study in a mouse model of COL6-RDs (Col6a2–/– mice) using standardized (TREAT-NMD) functional, histological, and physiological parameters. Notably, we identify a conspicuous dysregulation of the TGF-β pathway early in the disease process and propose that the collagen VI–deficient matrix is not capable of regulating the dynamic TGF-β bioavailability both at baseline and in response to muscle injury. Thus, we propose a new mechanism for pathogenesis of the disease that links the ECM regulation of TGF-β with downstream skeletal muscle abnormalities, paving the way for the development and validation of therapeutics that target this pathway.
Authors
Payam Mohassel, Hailey Hearn, Jachinta Rooney, Yaqun Zou, Kory Johnson, Gina Norato, Matthew A. Nalls, Pomi Yun, Tracy Ogata, Sarah Silverstein, David A. Sleboda, Thomas J. Roberts, Daniel B. Rifkin, Carsten G. Bönnemann
Abstract
BACKGROUND. Adipose tissue-derived endotrophin, a peptide cleaved from the α3 chain of collagen VI during fibrogenesis, causes systemic insulin resistance in rodent models. Here, we evaluated the potential importance of endotrophin in regulating whole-body insulin sensitivity in people. METHODS. We evaluated: i) plasma endotrophin concentration, insulin sensitivity (assessed by using the hyperinsulinemic-euglycemic clamp procedure in conjunction with stable isotopically labeled glucose tracer infusion) and adipose tissue expression of genes involved in endotrophin production in three groups of participants that were rigorously stratified by adiposity and insulin sensitivity [lean insulin-sensitive (Lean-IS; n=10), obese insulin-sensitive (Obese-IS; n=10), and obesity insulin-resistant (Obese-IR; n=10)]; ii) plasma endotrophin concentration and insulin sensitivity in 15 people with obesity and type 2 diabetes before and after marked (~18%) weight loss; and iii) the effect of endotrophin on insulin signaling (AKTser473 phosporylation) and insulin action (insulin-stimulated glucose uptake) in primary human skeletal muscle myotubes. RESULTS. Plasma endotrophin progressively increased from the Lean-IS to the Obese-IS to the Obese-IR group, was negatively associated with insulin sensitivity and positively associated with factors involved in adipose tissue endotrophin production, namely adipose tissue gene expression of matrix metalloproteinases and markers of hypoxia, inflammation, and fibrosis. Marked weight loss increased insulin sensitivity in conjunction with a decrease in plasma endotrophin concentration. Endotrophin inhibited insulin insulin-stimulated AKTser473 phosphorylation and insulin-stimulated glucose uptake in myotubes, which was restored by incubation with a neutralizing endotrophin antibody. CONCLUSIONS. These results suggest plasma endotrophin is both a biomarker and cause of whole-body insulin resistance in people with obesity.
Authors
Gordon I. Smith, Samuel Klein
Abstract
Cancer cachexia is a multifactorial condition characterized by skeletal muscle wasting that impairs quality of life and longevity for many cancer patients. A greater understanding of the molecular etiology of this condition is needed for effective therapies to be developed. We performed a quantitative proteomic analysis of skeletal muscle from cachectic pancreatic ductal adenocarcinoma (PDAC) patients and non-cancer controls, followed by immunohistochemical analyses of muscle cross-sections. These data provide evidence of a local inflammatory response in muscles of cachectic PDAC patients, including an accumulation of plasma proteins and recruitment of immune cells into muscle that may promote the pathological remodeling of muscle. Our data further support the complement system as a potential mediator of these processes, which we tested by injecting murine pancreatic cancer cells into wild type (WT) mice, or mice with genetic deletion of the central complement component 3 (C3–/– mice). Compared to WT mice, C3–/– mice showed attenuated tumor-induced muscle wasting and dysfunction and reduced immune cell recruitment and fibrotic remodeling of muscle. These studies demonstrate that complement activation is contributory to the skeletal muscle pathology and dysfunction in PDAC, suggesting that the complement system may possess therapeutic potential in preserving skeletal muscle mass and function.
Authors
Andrew C. D'Lugos, Jeremy B. Ducharme, Chandler S. Callaway, Jose G. Trevino, Carl Atkinson, Sarah M. Judge, Andrew R. Judge
Abstract
Fibrosis of the lower abdominal muscle (LAM) contributes to muscle weakening and inguinal hernia formation, an ailment affecting a noteworthy fifty percent of men by age 75, necessitating surgical correction as the singular therapy. Despite its prevalence, the mechanisms driving LAM fibrosis and hernia development remain poorly understood. Utilizing a humanized mouse model that replicates elevated skeletal muscle tissue estrogen concentrations akin to aging men, we identified estrogen receptor alpha (ESR1) as a key driver of LAM fibroblast proliferation, extracellular matrix deposition, and hernia formation. Fibroblast-specific ESR1 ablation effectively prevented muscle fibrosis and herniation, while pharmacological ESR1 inhibition with fulvestrant reversed hernias and restored normal muscle architecture. Multiomic analyses on in vitro LAM fibroblasts unveiled an estrogen/ESR1-mediated activation of a distinct profibrotic cistrome and gene expression signature, concordant with observations in inguinal hernia tissues in human males. Our findings hold significant promise for prospective medical interventions targeting fibrotic conditions and presenting non-surgical avenues for addressing inguinal hernias.
Authors
Tanvi Potluri, Tianming You, Ping Yin, John S. Coon V, Jonah J. Stulberg, Yang Dai, David J Escobar, Richard L. Lieber, Hong Zhao, Serdar E. Bulun
Abstract
Background: Myotonic dystrophy type 1 (DM1) is a multisystemic, CTG repeat expansion disorder characterized by a slow, progressive decline in skeletal muscle function. A biomarker correlating RNA mis-splicing, the core pathogenic disease mechanism, and muscle performance is crucial for assessing response to disease-modifying interventions. We evaluated the Myotonic Dystrophy Splice Index (SI), a composite RNA splicing biomarker incorporating 22 disease-specific events, as a potential biomarker of DM1 muscle weakness. Methods: Total RNA sequencing of tibialis anterior biopsies from 58 DM1 participants and 33 unaffected/disease controls was used to evaluate RNA splicing events across the disease spectrum. Targeted RNA sequencing was used to derive the SI from biopsies collected at baseline (n = 52) or a 3-month (n = 37) follow-up visit along with clinical measures of muscle performance. Results: The SI demonstrated significant associations with measures of muscle strength and ambulation, including ankle dorsiflexion strength (ADF) and 10-meter run/fast walk (Pearson r = -0.719 and -0.680, respectively). The SI was relatively stable over 3-months (ICC = 0.863). Latent-class analysis identified three DM1 subgroups stratified by baseline SI (SIMild, SIModerate, SISevere); SIModerate individuals had a significant increase in the SI over 3-months. Multiple linear regression modeling revealed that baseline ADF and SI were predictive of strength at 3-months (adjusted R² = 0.830). Conclusion: The SI is a reliable biomarker that captures associations of RNA mis-splicing with physical strength and mobility and has prognostic utility to predict future function, establishing it as a potential biomarker for assessment of therapeutic target engagement. Trial Registration: NCT03981575 Funding: FDA (7R01FD006071), Myotonic Dystrophy Foundation, Wyck Foundation, Muscular Dystrophy Association, Novartis, Dyne, Avidity, PepGen, Takeda, Sanofi Genzyme, Pfizer, Arthex, and Vertex Pharmaceuticals.
Authors
Marina Provenzano, Kobe Ikegami, Kameron Bates, Alison Gaynor, Julia M. Hartman, Aileen S. Jones, Amanda Butler, Kiera N. Berggren, Jeanne Dekdebrun, Man Hung, Dana M. Lapato, Michael Kiefer, Charles A. Thornton, Nicholas E. Johnson, Melissa A. Hale
Abstract
Eccentric contraction- (ECC) induced force loss is a hallmark of murine dystrophin-deficient (mdx) skeletal muscle that is used to assess efficacy of potential therapies for Duchenne muscular dystrophy. While virtually all key proteins involved in muscle contraction have been implicated in ECC force loss, a unifying mechanism that orchestrates force loss across such diverse molecular targets has not been identified. We showed that correcting defective hydrogen sulfide (H2S) signaling in mdx muscle prevented ECC force loss. We also showed that the cysteine proteome of skeletal muscle functioned as a redox buffer in WT and mdx muscle during ECCs, but that buffer capacity in mdx muscle was significantly compromised by elevated basal protein oxidation. Finally, chemo-proteomic data suggested that H2S protected several proteins central to muscle contraction against irreversible oxidation through persulfidation-based priming. Our results support a unifying, redox-based mechanism of ECC force loss in mdx muscle.
Authors
W. Michael Southern, Erynn E. Johnson, Elizabeth K. Fasbender, Katherine S. Fallon, Courtney L. Cavazos, Dawn A. Lowe, George G. Rodney, James M. Ervasti
Abstract
Skeletal muscle relies on resident muscle stem cells (MuSCs) for growth and repair. Aging and muscle diseases impair MuSC function, leading to stem cell exhaustion and regenerative decline that contribute to the progressive loss of skeletal muscle mass and strength. In the absence of clinically available nutritional solutions specifically targeting MuSCs, we used a human myogenic progenitor (hMP) high-content imaging screen of natural molecules from food to identify nicotinamide (NAM) and pyridoxine (PN) as bioactive nutrients that stimulate MuSCs and have history of safe human use. NAM and PN synergize via CK1-mediated cytoplasmic β-catenin activation and AKT signaling to promote amplification and differentiation of MuSCs. Oral treatment with a combination of NAM/PN accelerates muscle regeneration in vivo by stimulating MuSCs, increases muscle strength during recovery, and overcomes MuSC dysfunction and regenerative failure during aging. Levels of NAM and bioactive PN spontaneously decline during aging in model organisms and inter-independently associate with muscle mass and walking speed in a human cohort of 186 aged people. Collectively, our results establish NAM/PN as a new nutritional intervention that stimulates MuSCs, enhances muscle regeneration, and alleviates age-related muscle decline with a direct opportunity for clinical translation.
Authors
Sara Ancel, Joris Michaud, Eugenia Migliavacca, Charline Jomard, Aurélie Fessard, Pauline Garcia, Sonia Karaz, Sruthi Raja, Guillaume E. Jacot, Thibaut Desgeorges, José-Luis Sánchez-García, Loic Tauzin, Yann Ratinaud, Benjamin Brinon, Sylviane Métairon, Lucas Pinero, Denis Barron, Stephanie Blum, Leonidas G. Karagounis, Ramin Heshmat, Afshin Ostovar, Farshad Farzadfar, Isabella Scionti, Rémi Mounier, Julien Gondin, Pascal Stuelsatz, Jerome N. Feige
Abstract
Our study was to characterize sarcopenia in C57BL/6J mice using a clinically relevant definition to investigate the underlying molecular mechanisms. Aged male (23–32 months old) and female (27–28 months old) C57BL/6J mice were classified as non-, probable-, or sarcopenic based on assessments of grip strength, muscle mass, and treadmill running time, using 2 SDs below the mean of their young counterparts as cutoff points. A 9%–22% prevalence of sarcopenia was identified in 23–26 month-old male mice, with more severe age-related declines in muscle function than mass. Females aged 27–28 months showed fewer sarcopenic but more probable cases compared with the males. As sarcopenia progressed, a decrease in muscle contractility and a trend toward lower type IIB fiber size were observed in males. Mitochondrial biogenesis, oxidative capacity, and AMPK-autophagy signaling decreased as sarcopenia progressed in males, with pathways linked to mitochondrial metabolism positively correlated with muscle mass. No age- or sarcopenia-related changes were observed in mitochondrial biogenesis, OXPHOS complexes, AMPK signaling, mitophagy, or atrogenes in females. Our results highlight the different trajectories of age-related declines in muscle mass and function, providing insights into sex-dependent molecular changes associated with sarcopenia progression, which may inform the future development of novel therapeutic interventions.
Authors
Haiming L. Kerr, Kora Krumm, Barbara Anderson, Anthony Christiani, Lena Strait, Theresa Li, Brynn Irwin, Siyi Jiang, Artur Rybachok, Amanda Chen, Elizabeth Dacek, Lucas Caeiro, Gennifer E. Merrihew, James W. MacDonald, Theo K. Bammler, Michael J. MacCoss, Jose M. Garcia
Abstract
Cytoplasmic and nuclear iron-sulfur (Fe-S) enzymes that are essential for genome maintenance and replication depend on the cytoplasmic Fe-S assembly (CIA) machinery for cluster acquisition. The core of the CIA machinery consists of a complex of CIAO1, MMS19 and FAM96B. The physiological consequences of loss of function in the components of the CIA pathway have thus far remained uncharacterized. Our study revealed that patients with biallelic loss of function in CIAO1 developed proximal and axial muscle weakness, fluctuating creatine kinase elevation, and respiratory insufficiency. In addition, they presented with CNS symptoms including learning difficulties and neurobehavioral comorbidities, along with iron deposition in deep brain nuclei, mild normocytic to macrocytic anemia, and gastrointestinal symptoms. Mutational analysis revealed reduced stability of the variants compared with WT CIAO1. Functional assays demonstrated failure of the variants identified in patients to recruit Fe-S recipient proteins, resulting in compromised activities of DNA helicases, polymerases, and repair enzymes that rely on the CIA complex to acquire their Fe-S cofactors. Lentivirus-mediated restoration of CIAO1 expression reversed all patient-derived cellular abnormalities. Our study identifies CIAO1 as a human disease gene and provides insights into the broader implications of the cytosolic Fe-S assembly pathway in human health and disease.
Authors
Nunziata Maio, Rotem Orbach, Irina T. Zaharieva, Ana Töpf, Sandra Donkervoort, Pinki Munot, Juliane Mueller, Tracey Willis, Sumit Verma, Stojan Peric, Deepa Krishnakumar, Sniya Sudhakar, A. Reghan Foley, Sarah Silverstein, Ganka Douglas, Lynn Pais, Stephanie DiTroia, Christopher Grunseich, Ying Hu, Caroline Sewry, Anna Sarkozy, Volker Straub, Francesco Muntoni, Tracey A. Rouault, Carsten G. Bönnemann
Abstract
Satellite cells, the stem cells of skeletal muscle tissue, hold a remarkable regeneration capacity and therapeutic potential in regenerative medicine. However, low satellite cell yield from autologous or donor-derived muscles hinders the adoption of satellite cell transplantation for the treatment of muscle diseases, including Duchenne muscular dystrophy (DMD). To address this limitation, here we investigated whether satellite cells can be derived in allogeneic or xenogeneic animal hosts. First, injection of CRISPR/Cas9-corrected mouse DMD-induced pluripotent stem cells (iPSCs) into mouse blastocysts carrying an ablation system of host satellite cells gave rise to intraspecies chimeras exclusively carrying iPSC-derived satellite cells. Furthermore, injection of genetically corrected DMD-iPSCs into rat blastocysts resulted in the formation of interspecies rat-mouse chimeras harboring mouse satellite cells. Remarkably, iPSC-derived satellite cells or derivative myoblasts produced in intraspecies or interspecies chimeras restored dystrophin expression in DMD mice following intramuscular transplantation, and contributed to the satellite cell pool. Collectively, this study demonstrates the feasibility of producing therapeutically competent stem cells across divergent animal species, raising the possibility of generating human muscle stem cells in large animals for regenerative medicine purposes.
Authors
Ajda Lenardič, Seraina A. Domenig, Joel Zvick, Nicola Bundschuh, Monika Tarnowska-Sengül, Regula Furrer, Falko J. Noé, Christine Ling Li Trautmann, Adhideb Ghosh, Giada Bacchin, Pjeter Gjonlleshaj, Xhem Qabrati, Evi Masschelein, Katrien De Bock, Christoph Handschin, Ori Bar-Nur
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)