bims-moremu 2023-05-07 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–05–07
25 papers selected by
Anna Vainshtein, Craft Science Inc.

Exercise is associated with younger methylome and transcriptome profiles in human skeletal muscle.
Expression of Myomaker and Myomerger in myofibers causes muscle pathology.
Single-cell and spatial transcriptomics identify a macrophage population associated with skeletal muscle fibrosis.
NEDD4-1 deficiency impairs satellite cell function during skeletal muscle regeneration.
Distinct human skeletal muscle-derived CD90 progenitor subsets for myo-fibro-adipogenic disease modeling and treatment in multiplexed conditions.
Effects of different modes and intensities of exercise on longevity proteins in middle-aged mouse skeletal muscle.
Post-translational regulation of muscle growth, muscle aging and sarcopenia.
Slow myosin heavy chain 1 is required for slow myofibril and muscle fibre growth but not for myofibril initiation.
Calcium measurements in enzymatically dissociated or mechanically microdissected mouse primary skeletal muscle fibers.
Autoimmunity as a novel mechanism underlying sarcopenia.
Assessment of Cell Viability in Electrically Excitable Muscle Cells Through Intact Twitch Stimulation.
Impacts of Whole-body Vibration on Denervated Skeletal-muscle Atrophy in Rats.
Muscle Injuries Induce a Prostacyclin-PPARγ/PGC1a-FAO Spike That Boosts Regeneration.
Skeletal muscle omics signatures in cancer cachexia: perspectives and opportunities.
The cilium-centrosome axis in coupling cell cycle exit and cell fate.
Diffusion-tensor magnetic resonance imaging captures increased skeletal muscle fibre diameters in Becker muscular dystrophy.
Voltage sensor current, SR Ca2+ release, and Ca2+ channel current during trains of action potential-like depolarizations of skeletal muscle fibers.
A new organisational design in skeletal muscle fibres.
High sensitivity top-down proteomics captures single muscle cell heterogeneity in large proteoforms.
Electrical impedance myography detects age-related skeletal muscle atrophy in adult zebrafish.
Nanopore sequencing identifies a higher frequency and expanded spectrum of mitochondrial DNA deletion mutations in human aging.
Response of terminal Schwann cells following volumetric muscle loss injury.
Progress in muscle research through the international congress of neuromuscular diseases (ICNMD): a narrative review.
Activation of skeletal muscle FAPs by LPA requires the Hippo signaling via the FAK pathway.
Targeting the biology of aging with mTOR inhibitors.

Aging Cell. 2023 May 02. e13859

Exercise is associated with younger methylome and transcriptome profiles in human skeletal muscle.

Sarah Voisin, Kirsten Seale, Macsue Jacques, Shanie Landen, Nicholas R Harvey, Larisa M Haupt, Lyn R Griffiths, Kevin J Ashton, Vernon G Coffey, Jamie-Lee M Thompson, Thomas M Doering, Malene E Lindholm, Colum Walsh, Gareth Davison, Rachelle Irwin, Catherine McBride, Ola Hansson, Olof Asplund, Aino E Heikkinen, Päivi Piirilä, Kirsi H Pietiläinen, Miina Ollikainen, Sara Blocquiaux, Martine Thomis, Coletta K Dawn, Adam P Sharples, Nir Eynon.

  Exercise training prevents age-related decline in muscle function. Targeting epigenetic aging is a promising actionable mechanism and late-life exercise mitigates epigenetic aging in rodent muscle. Whether exercise training can decelerate, or reverse epigenetic aging in humans is unknown. Here, we performed a powerful meta-analysis of the methylome and transcriptome of an unprecedented number of human skeletal muscle samples (n = 3176). We show that: (1) individuals with higher baseline aerobic fitness have younger epigenetic and transcriptomic profiles, (2) exercise training leads to significant shifts of epigenetic and transcriptomic patterns toward a younger profile, and (3) muscle disuse "ages" the transcriptome. Higher fitness levels were associated with attenuated differential methylation and transcription during aging. Furthermore, both epigenetic and transcriptomic profiles shifted toward a younger state after exercise training interventions, while the transcriptome shifted toward an older state after forced muscle disuse. We demonstrate that exercise training targets many of the age-related transcripts and DNA methylation loci to maintain younger methylome and transcriptome profiles, specifically in genes related to muscle structure, metabolism, and mitochondrial function. Our comprehensive analysis will inform future studies aiming to identify the best combination of therapeutics and exercise regimes to optimize longevity.

Keywords:  DNA methylation; aging; cardiorespiratory fitness; exercise training; human skeletal muscle; mRNA expression; meta-analysis

DOI:  https://doi.org/10.1111/acel.13859
Skelet Muscle. 2023 May 01. 13(1): 8

Expression of Myomaker and Myomerger in myofibers causes muscle pathology.

Phillip C Witcher, Chengyi Sun, Douglas P Millay.

   BACKGROUND: Skeletal muscle development and regeneration depend on cellular fusion of myogenic progenitors to generate multinucleated myofibers. These progenitors utilize two muscle-specific fusogens, Myomaker and Myomerger, which function by remodeling cell membranes to fuse to each other or to existing myofibers. Myomaker and Myomerger expression is restricted to differentiating progenitor cells as they are not detected in adult myofibers. However, Myomaker remains expressed in myofibers from mice with muscular dystrophy. Ablation of Myomaker from dystrophic myofibers results in reduced membrane damage, leading to a model where persistent fusogen expression in myofibers, in contrast to myoblasts, is harmful.
METHODS: Dox-inducible transgenic mice were developed to ectopically express Myomaker or Myomerger in the myofiber compartment of skeletal muscle. We quantified indices of myofiber membrane damage, such as serum creatine kinase and IgM+ myofibers, and assessed general muscle histology, including central nucleation, myofiber size, and fibrosis.
RESULTS: Myomaker or Myomerger expression in myofibers independently caused membrane damage at acute time points. This damage led to muscle pathology, manifesting with centrally nucleated myofibers and muscle atrophy. Dual expression of both Myomaker and Myomerger in myofibers exacerbated several aspects of muscle pathology compared to expression of either fusogen by itself.
CONCLUSIONS: These data reveal that while myofibers can tolerate some level of Myomaker and Myomerger, expression of a single fusogen above a threshold or co-expression of both fusogens is damaging to myofibers. These results explain the paradigm that their expression in myofibers can have deleterious consequences in muscle pathologies and highlight the need for their highly restricted expression during myogenesis and fusion.

Keywords:  Muscle pathology; Myocyte fusion; Myomaker; Myomerger/Myomixer

DOI:  https://doi.org/10.1186/s13395-023-00317-z
bioRxiv. 2023 Apr 18. pii: 2023.04.18.537253. [Epub ahead of print]

Single-cell and spatial transcriptomics identify a macrophage population associated with skeletal muscle fibrosis.

Gerald Coulis, Diego Jaime, Christian Guerrero-Juarez, Jenna M Kastenschmidt, Philip K Farahat, Quy Nguyen, Nicholas Pervolarakis, Katherine McLinden, Lauren Thurlow, Saba Movahedi, Jorge Duarte, Andrew Sorn, Elizabeth Montoya, Izza Mozaffar, Morgan Dragan, Shivashankar Othy, Trupti Joshi, Chetan P Hans, Virginia Kimonis, Adam L MacLean, Qing Nie, Lindsay M Wallace, Scott Q Harper, Tahseen Mozaffar, Marshall W Hogarth, Surajit Bhattacharya, Jyoti K Jaiswal, David R Golann, Qi Su, Kai Kessenbrock, Michael Stec, Melissa J Spencer, Jesse R Zamudio, S Armando Villalta.

The monocytic/macrophage system is essential for skeletal muscle homeostasis, but its dysregulation contributes to the pathogenesis of muscle degenerative disorders. Despite our increasing knowledge of the role of macrophages in degenerative disease, it still remains unclear how macrophages contribute to muscle fibrosis. Here, we used single-cell transcriptomics to determine the molecular attributes of dystrophic and healthy muscle macrophages. We identified six novel clusters. Unexpectedly, none corresponded to traditional definitions of M1 or M2 macrophage activation. Rather, the predominant macrophage signature in dystrophic muscle was characterized by high expression of fibrotic factors, galectin-3 and spp1. Spatial transcriptomics and computational inferences of intercellular communication indicated that spp1 regulates stromal progenitor and macrophage interactions during muscular dystrophy. Galectin-3 + macrophages were chronically activated in dystrophic muscle and adoptive transfer assays showed that the galectin-3 + phenotype was the dominant molecular program induced within the dystrophic milieu. Histological examination of human muscle biopsies revealed that galectin-3 + macrophages were also elevated in multiple myopathies. These studies advance our understanding of macrophages in muscular dystrophy by defining the transcriptional programs induced in muscle macrophages, and reveal spp1 as a major regulator of macrophage and stromal progenitor interactions.

DOI: https://doi.org/10.1101/2023.04.18.537253
Biol Res. 2023 May 05. 56(1): 21

NEDD4-1 deficiency impairs satellite cell function during skeletal muscle regeneration.

Felipe Cabezas, Claudio Cabello-Verrugio, Natalia González, Jeremy Salas, Manuel J Ramírez, Eduardo de la Vega, Hugo C Olguín.

   BACKGROUND: Satellite cells are tissue-specific stem cells primarily responsible for the regenerative capacity of skeletal muscle. Satellite cell function and maintenance are regulated by extrinsic and intrinsic mechanisms, including the ubiquitin-proteasome system, which is key for maintaining protein homeostasis. In this context, it has been shown that ubiquitin-ligase NEDD4-1 targets the transcription factor PAX7 for proteasome-dependent degradation, promoting muscle differentiation in vitro. Nonetheless, whether NEDD4-1 is required for satellite cell function in regenerating muscle remains to be determined.
RESULTS: Using conditional gene ablation, we show that NEDD4-1 loss, specifically in the satellite cell population, impairs muscle regeneration resulting in a significant reduction of whole-muscle size. At the cellular level, NEDD4-1-null muscle progenitors exhibit a significant decrease in the ability to proliferate and differentiate, contributing to the formation of myofibers with reduced diameter.
CONCLUSIONS: These results indicate that NEDD4-1 expression is critical for proper muscle regeneration in vivo and suggest that it may control satellite cell function at multiple levels.

Keywords:  Muscle differentiation; Muscle stem cells; NEDD4-1; Satellite cells; Skeletal muscle regeneration

DOI:  https://doi.org/10.1186/s40659-023-00432-7
Front Cell Dev Biol. 2023 ;11 1173794

Distinct human skeletal muscle-derived CD90 progenitor subsets for myo-fibro-adipogenic disease modeling and treatment in multiplexed conditions.

Angela Li, Madhavan Anbuchelvan, Amir Fathi, Maya Abu-Zahra, Denis Evseenko, Frank A Petrigliano, Ayelet Dar.

  Chronic muscle injuries, such as massive rotator cuff tears, are associated with progressive muscle wasting, fibrotic scarring, and intramuscular fat accumulation. While progenitor cell subsets are usually studied in culture conditions that drive either myogenic, fibrogenic, or adipogenic differentiation, it is still unknown how combined myo-fibro-adipogenic signals, which are expected to occur in vivo, modulate progenitor differentiation. We therefore evaluated the differentiation potential of retrospectively generated subsets of primary human muscle mesenchymal progenitors in multiplexed conditions in the presence or absence of 423F drug, a modulator of gp130 signaling. We identified a novel CD90+CD56- non-adipogenic progenitor subset that maintained a lack of adipogenic potential in single and multiplexed myo-fibro-adipogenic culture conditions. CD90-CD56- demarcated fibro-adipogenic progenitors (FAP) and CD56+CD90+ progenitors were typified as myogenic. These human muscle subsets exhibited varying degrees of intrinsically regulated differentiation in single and mixed induction cultures. Modulation of gp130 signaling via 423F drug mediated muscle progenitor differentiation in a dose-, induction-, and cell subset-dependent manner and markedly decreased fibro-adipogenesis of CD90-CD56- FAP. Conversely, 423F promoted myogenesis of CD56+CD90+ myogenic subset, indicated by increased myotube diameter and number of nuclei per myotube. 423F treatment eliminated FAP-derived mature adipocytes from mixed adipocytes-FAP cultures but did not modify the growth of non-differentiated FAP in these cultures. Collectively, these data demonstrate that capability of myogenic, fibrogenic, or adipogenic differentiation is largely dependent on the intrinsic features of cultured subsets, and that the degree of lineage differentiation varies when signals are multiplexed. Moreover, our tests performed in primary human muscle cultures reveal and confirm the potential triple-therapeutic effects of 423F drug which simultaneously attenuates degenerative fibrosis, fat accumulation and promotes myo-regeneration.

Keywords:  CD90; gp130 signaling; human muscle mesenchymal subsets; in vitro drug screening; myo-fibro-adipogenesis; skeletal muscle differentiation

DOI:  https://doi.org/10.3389/fcell.2023.1173794
Physiol Int. 2023 May 02.

Effects of different modes and intensities of exercise on longevity proteins in middle-aged mouse skeletal muscle.

Shota Inoue, Kyohei Matsuura, Daisuke Eguchi, Masahiro Wakayama, Kosuke Ono, Hanlin Jiang, Hideki Moriyama.

  Physical exercise represents one of the most effective approaches to anti-aging. The goal of this study was to verify the effects of different modes and intensities of exercise on longevity proteins in the skeletal muscle in midlife. Middle-aged mice were trained in aerobic or resistance exercise for 8 weeks, and the changes in sirtuin 1 (SIRT1), adenosine monophosphate-activated kinase (AMPK), and mammalian target of rapamycin (mTOR) pathways in the skeletal muscle were evaluated by western blotting. Long-term exercise had no effects on skeletal muscle SIRT1 abundance, whereas high-intensity aerobic exercise increased AMPK phosphorylation and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). Low-intensity resistance exercise facilitated Akt/mTOR/p70 ribosomal protein kinase S6 (p70S6K) signaling but did not induce muscle hypertrophy. Conversely, high-intensity resistance exercise stimulated muscle hypertrophy without phosphorylation of mTOR signaling-related proteins. These results suggest the importance of setting exercise modes and intensities for anti-aging in midlife.

Keywords:  AMPK; SIRT1; exercise; mTOR; skeletal muscle

DOI:  https://doi.org/10.1556/2060.2023.00152
J Cachexia Sarcopenia Muscle. 2023 May 01.

Post-translational regulation of muscle growth, muscle aging and sarcopenia.

Qian Zhong, Kun Zheng, Wanmeng Li, Kang An, Yu Liu, Xina Xiao, Shan Hai, Biao Dong, Shuangqing Li, Zhenmei An, Lunzhi Dai.

  Skeletal muscle makes up 30-40% of the total body mass. It is of great significance in maintaining digestion, inhaling and exhaling, sustaining body posture, exercising, protecting joints and many other aspects. Moreover, muscle is also an important metabolic organ that helps to maintain the balance of sugar and fat. Defective skeletal muscle function not only limits the daily activities of the elderly but also increases the risk of disability, hospitalization and death, placing a huge burden on society and the healthcare system. Sarcopenia is a progressive decline in muscle mass, muscle strength and muscle function with age caused by environmental and genetic factors, such as the abnormal regulation of protein post-translational modifications (PTMs). To date, many studies have shown that numerous PTMs, such as phosphorylation, acetylation, ubiquitination, SUMOylation, glycosylation, glycation, methylation, S-nitrosylation, carbonylation and S-glutathionylation, are involved in the regulation of muscle health and diseases. This article systematically summarizes the post-translational regulation of muscle growth and muscle atrophy and helps to understand the pathophysiology of muscle aging and develop effective strategies for diagnosing, preventing and treating sarcopenia.

Keywords:  muscle aging; muscle growth; muscle repair; post-translational modifications; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13241
Dev Biol. 2023 Apr 28. pii: S0012-1606(23)00063-5. [Epub ahead of print]

Slow myosin heavy chain 1 is required for slow myofibril and muscle fibre growth but not for myofibril initiation.

Hoi-Ting A Hau, Jeffrey J Kelu, Julien Ochala, Simon M Hughes.

Slow myosin heavy chain 1 (Smyhc1) is the major sarcomeric myosin driving early contraction by slow skeletal muscle fibres in zebrafish. New mutant alleles lacking a functional smyhc1 gene move poorly, but recover motility as the later-formed fast muscle fibres of the segmental myotomes mature, and are adult viable. By motility analysis and inhibiting fast muscle contraction pharmacologically, we show that a slow muscle motility defect persists in mutants until about 1 month of age. Breeding onto a genetic background marking slow muscle fibres with EGFP revealed that mutant slow fibres undergo terminal differentiation, migration and fibre formation indistinguishable from wild type but fail to generate large myofibrils and maintain cellular orientation and attachments. In mutants, initial myofibrillar structures with 1.67 μm periodic actin bands fail to mature into the 1.96 μm sarcomeres observed in wild type, despite the presence of alternative myosin heavy chain molecules. The poorly-contractile mutant slow muscle cells generate numerous cytoplasmic organelles, but fail to grow and bundle myofibrils or to increase in cytoplasmic volume despite passive movements imposed by fast muscle. The data show that both slow myofibril maturation and cellular volume increase depend on the function of a specific myosin isoform and suggest that appropriate force production regulates muscle fibre growth.

DOI: https://doi.org/10.1016/j.ydbio.2023.04.002
STAR Protoc. 2023 Apr 30. pii: S2666-1667(23)00218-6. [Epub ahead of print]4(2): 102260

Calcium measurements in enzymatically dissociated or mechanically microdissected mouse primary skeletal muscle fibers.

Sonia Youhanna, Joseph Bruton, Kent Jardemark, Håkan Westerblad, Volker M Lauschke.

  Here, we provide a protocol for isolation of mouse primary skeletal muscle fibers using two alternative approaches-enzymatic dissociation or mechanical microdissection. We describe the procedures for surgical removal of muscle of interest and isolation of intact single-muscle fibers by either collagenase digestion or mechanical microdissection. We then detail intracellular calcium measurements by microinjecting or loading the isolated muscle fibers with membrane permeable calcium dyes. Finally, we outline steps for intracellular calcium quantification by fluorescent measurement. For complete details on the use and execution of this protocol, please refer to Gineste et al.1.

Keywords:  Biotechnology and bioengineering; Cell culture; Cell isolation; Microscopy

DOI:  https://doi.org/10.1016/j.xpro.2023.102260
Aging (Albany NY). 2023 May 01. 15

Autoimmunity as a novel mechanism underlying sarcopenia.

Tan Zhang.



Keywords:  autoimmunity; sarcopenia; skeletal muscle; troponin T

DOI:  https://doi.org/10.18632/aging.204703
Methods Mol Biol. 2023 ;2644 177-192

Assessment of Cell Viability in Electrically Excitable Muscle Cells Through Intact Twitch Stimulation.

Julian Bauer, Stewart I Head, Oliver Friedrich.

  Muscle cells (i.e. skeletal muscle fibers) are fully viable and functional when their excitation-contraction (EC) coupling machinery is intact. This involves intact membrane integrity with polarized membrane, functional ion channels for action potential generation and conduction, an intact electro-chemical interface at the level of the fiber's triad, followed by sarcoplasmic reticulum Ca2+ release, and subsequent activation of the chemico-mechanical interface at the level of the contractile apparatus. The ultimate end result is then a visible twitch contraction upon a brief electrical pulse stimulation. For many biomedical studies involving single muscle cells, intact and viable myofibers are of utmost importance. Thus, a simple global screening method that involves a brief electrical stimulus applied to single muscle fibers and assessment of visible contraction would be of high value. In this chapter, we describe step-by-step protocols to (i) obtain intact single muscle fibers from freshly dissected muscle tissue using an enzymatic digestion procedure and (ii) provide a workflow for the assessment of twitch response of single fibers that can be ultimately classified as viable. For this, we have prepared a unique stimulation pen for which we provide the fabrication guide for do-it-yourself rapid prototyping to eliminate the need for expensive specialized commercial equipment.

Keywords:  Contraction; Electrical stimulator; Enzymatic dissociation; Single fiber; Skeletal muscle; Twitch stimulation

DOI:  https://doi.org/10.1007/978-1-0716-3052-5_11
J Orthop Res. 2023 May 03.

Impacts of Whole-body Vibration on Denervated Skeletal-muscle Atrophy in Rats.

Eun Sil Koh, Jae-Young Lim.

  Whole-body vibration has been considered as a countermeasure against muscle atrophy. However, its effects on muscle atrophy are poorly understood. We evaluated the effects of whole-body vibration on denervated skeletal muscle atrophy. Whole-body vibration was performed on rats from day 15 to 28 after denervation injury. Motor performance was evaluated using an inclined-plane test. Compound muscle action potentials of the tibial nerve were examined. Muscle wet weight and muscle fiber cross-sectional area were measured. Myosin heavy chain isoforms were analyzed in both muscle homogenates and single myofibers. Whole-body vibration resulted in a significantly decreased inclination angle and muscle weight, but not muscle fiber cross-sectional area of fast-twitch gastrocnemius compared to denervation only. In denervated gastrocnemius, a fast-to-slow shift was observed in myosin heavy chain isoform composition following whole-body vibration. There were no significant changes in muscle weight, muscle fiber cross-sectional area, and myosin heavy chain isoform composition in denervated slow-twitch soleus. These results imply that whole-body vibration does not promote recovery of denervation-induced muscle atrophy. This article is protected by copyright. All rights reserved.

Keywords:  denervation; muscle atrophy; myosin heavy chain; whole-body vibration

DOI:  https://doi.org/10.1002/jor.25589
Adv Sci (Weinh). 2023 May 04. e2301519

Muscle Injuries Induce a Prostacyclin-PPARγ/PGC1a-FAO Spike That Boosts Regeneration.

Lanfang Luo, Yan-Jiang Benjamin Chua, Taoyan Liu, Kun Liang, Min-Wen Jason Chua, Wenwu Ma, Jun-Wei Goh, Yuefan Wang, Jiali Su, Ying Swan Ho, Chun-Wei Li, Ke Hui Liu, Bin Tean Teh, Kang Yu, Ng Shyh-Chang.

  It is well-known that muscle regeneration declines with aging, and aged muscles undergo degenerative atrophy or sarcopenia. While exercise and acute injury are both known to induce muscle regeneration, the molecular signals that help trigger muscle regeneration have remained unclear. Here, mass spectrometry imaging (MSI) is used to show that injured muscles induce a specific subset of prostanoids during regeneration, including PGG1, PGD2, and the prostacyclin PGI2. The spike in prostacyclin promotes skeletal muscle regeneration via myoblasts, and declines with aging. Mechanistically, the prostacyclin spike promotes a spike in PPARγ/PGC1a signaling, which induces a spike in fatty acid oxidation (FAO) to control myogenesis. LC-MS/MS and MSI further confirm that an early FAO spike is associated with normal regeneration, but muscle FAO became dysregulated during aging. Functional experiments demonstrate that the prostacyclin-PPARγ/PGC1a-FAO spike is necessary and sufficient to promote both young and aged muscle regeneration, and that prostacyclin can synergize with PPARγ/PGC1a-FAO signaling to restore aged muscles' regeneration and physical function. Given that the post-injury prostacyclin-PPARγ-FAO spike can be modulated pharmacologically and via post-exercise nutrition, this work has implications for how prostacyclin-PPARγ-FAO might be fine-tuned to promote regeneration and treat muscle diseases of aging.

Keywords:  MSI; muscle regeneration; muscle stem cell (MuSC); myobolites; prostanoids

DOI:  https://doi.org/10.1002/advs.202301519
J Natl Cancer Inst Monogr. 2023 May 04. 2023(61): 30-42

Skeletal muscle omics signatures in cancer cachexia: perspectives and opportunities.

L Anne Gilmore, Traci L Parry, Gwendolyn A Thomas, Andy V Khamoui.

Cachexia is a life-threatening complication of cancer that occurs in up to 80% of patients with advanced cancer. Cachexia reflects the systemic consequences of cancer and prominently features unintended weight loss and skeletal muscle wasting. Cachexia impairs cancer treatment tolerance, lowers quality of life, and contributes to cancer-related mortality. Effective treatments for cancer cachexia are lacking despite decades of research. High-throughput omics technologies are increasingly implemented in many fields including cancer cachexia to stimulate discovery of disease biology and inform therapy choice. In this paper, we present selected applications of omics technologies as tools to study skeletal muscle alterations in cancer cachexia. We discuss how comprehensive, omics-derived molecular profiles were used to discern muscle loss in cancer cachexia compared with other muscle-wasting conditions, to distinguish cancer cachexia from treatment-related muscle alterations, and to reveal severity-specific mechanisms during the progression of cancer cachexia from early toward severe disease.

DOI: https://doi.org/10.1093/jncimonographs/lgad006
J Cell Sci. 2023 May 01. pii: jcs260454. [Epub ahead of print]136(9):

The cilium-centrosome axis in coupling cell cycle exit and cell fate.

Priti S Atmakuru, Jyotsna Dhawan.

  The centrosome is an evolutionarily conserved, ancient organelle whose role in cell division was first described over a century ago. The structure and function of the centrosome as a microtubule-organizing center, and of its extracellular extension - the primary cilium - as a sensory antenna, have since been extensively studied, but the role of the cilium-centrosome axis in cell fate is still emerging. In this Opinion piece, we view cellular quiescence and tissue homeostasis from the vantage point of the cilium-centrosome axis. We focus on a less explored role in the choice between distinct forms of mitotic arrest - reversible quiescence and terminal differentiation, which play distinct roles in tissue homeostasis. We outline evidence implicating the centrosome-basal body switch in stem cell function, including how the cilium-centrosome complex regulates reversible versus irreversible arrest in adult skeletal muscle progenitors. We then highlight exciting new findings in other quiescent cell types that suggest signal-dependent coupling of nuclear and cytoplasmic events to the centrosome-basal body switch. Finally, we propose a framework for involvement of this axis in mitotically inactive cells and identify future avenues for understanding how the cilium-centrosome axis impacts central decisions in tissue homeostasis.

Keywords:  Cell cycle; Cell fate; Centrosome; Differentiation; Muscle stem cells; Primary cilium; Quiescence; RNA

DOI:  https://doi.org/10.1242/jcs.260454
J Cachexia Sarcopenia Muscle. 2023 May 01.

Diffusion-tensor magnetic resonance imaging captures increased skeletal muscle fibre diameters in Becker muscular dystrophy.

Donnie Cameron, Tooba Abbassi-Daloii, Laura G M Heezen, Nienke M van de Velde, Zaïda Koeks, Thom T J Veeger, Melissa T Hooijmans, Salma El Abdellaoui, Sjoerd G van Duinen, Jan J G M Verschuuren, Maaike van Putten, Annemieke Aartsma-Rus, Vered Raz, Pietro Spitali, Erik H Niks, Hermien E Kan.

   BACKGROUND: Becker muscular dystrophy (BMD) is an X-linked disorder characterized by slow, progressive muscle damage and muscle weakness. Hallmarks include fibre-size variation and replacement of skeletal muscle with fibrous and adipose tissues, after repeated cycles of regeneration. Muscle histology can detect these features, but the required biopsies are invasive, are difficult to repeat and capture only small muscle volumes. Diffusion-tensor magnetic resonance imaging (DT-MRI) is a potential non-invasive alternative that can calculate muscle fibre diameters when applied with the novel random permeable barrier model (RPBM). In this study, we assessed muscle fibre diameters using DT-MRI in BMD patients and healthy controls and compared these with histology.
METHODS: We included 13 BMD patients and 9 age-matched controls, who underwent water-fat MRI and DT-MRI at multiple diffusion times, allowing RPBM parameter estimation in the lower leg muscles. Tibialis anterior muscle biopsies were taken from the contralateral leg in 6 BMD patients who underwent DT-MRI and from an additional 32 BMD patients and 15 healthy controls. Laminin and Sirius-red stainings were performed to evaluate muscle fibre morphology and fibrosis. Twelve ambulant patients from the MRI cohort underwent the North Star ambulatory assessment, and 6-min walk, rise-from-floor and 10-m run/walk functional tests.
RESULTS: RPBM fibre diameter was significantly larger in BMD patients (P = 0.015): mean (SD) = 68.0 (25.3) μm versus 59.4 (19.2) μm in controls. Inter-muscle differences were also observed (P ≤ 0.002). Both inter- and intra-individual RPBM fibre diameter variability were similar between groups. Laminin staining agreed with the RPBM, showing larger median fibre diameters in patients than in controls: 72.5 (7.9) versus 63.2 (6.9) μm, P = 0.006. However, despite showing similar inter-individual variation, patients showed more intra-individual fibre diameter variability than controls-mean variance (SD) = 34.2 (7.9) versus 21.4 (6.9) μm, P < 0.001-and larger fibrosis areas: median (interquartile range) = 21.7 (5.6)% versus 14.9 (3.4)%, P < 0.001. Despite good overall agreement of RPBM and laminin fibre diameters, they were not associated in patients who underwent DT-MRI and muscle biopsy, perhaps due to lack of colocalization of DT-MRI with biopsy samples.
CONCLUSIONS: DT-MRI RPBM metrics agree with histology and can quantify changes in muscle fibre size that are associated with regeneration without the need for biopsies. They therefore show promise as imaging biomarkers for muscular dystrophies.

Keywords:  Becker muscular dystrophy; diffusion-tensor MRI; histopathology; immunohistochemistry; skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13242
Physiol Rep. 2023 May;11(9): e15675

Voltage sensor current, SR Ca2+ release, and Ca2+ channel current during trains of action potential-like depolarizations of skeletal muscle fibers.

Hugo Bibollet, Elton L Nguyen, Daniel R Miranda, Christopher W Ward, Andrew A Voss, Martin F Schneider, Erick O Hernández-Ochoa.

In skeletal muscle, CaV 1.1 serves as the voltage sensor for both excitation-contraction coupling (ECC) and L-type Ca2+ channel activation. We have recently adapted the technique of action potential (AP) voltage clamp (APVC) to monitor the current generated by the movement of intramembrane voltage sensors (IQ ) during single imposed transverse tubular AP-like depolarization waveforms (IQAP ). We now extend this procedure to monitoring IQAP , and Ca2+ currents during trains of tubular AP-like waveforms in adult murine skeletal muscle fibers, and compare them with the trajectories of APs and AP-induced Ca2+ release measured in other fibers using field stimulation and optical probes. The AP waveform remains relatively constant during brief trains (<1 sec) for propagating APs in non-V clamped fibers. Trains of 10 AP-like depolarizations at 10 Hz (900 ms), 50 Hz (180 ms), or 100 Hz (90 ms) did not alter IQAP amplitude or kinetics, consistent with previous findings in isolated muscle fibers where negligible charge immobilization occurred during 100 ms step depolarizations. Using field stimulation, Ca2+ release did exhibit a considerable decline from pulse to pulse during the train, also consistent with previous findings, indicating that the decline of Ca2+ release during a short train of APs is not correlated to modification of charge movement. Ca2+ currents during single or 10 Hz trains of AP-like depolarizations were hardly detectable, were minimal during 50 Hz trains, and became more evident during 100 Hz trains in some fibers. Our results verify predictions on the behavior of the ECC machinery in response to AP-like depolarizations and provide a direct demonstration that Ca2+ currents elicited by single AP-like waveforms are negligible, but can become more prominent in some fibers during short high-frequency train stimulation that elicits maximal isometric force.

DOI: https://doi.org/10.14814/phy2.15675
Cell Tissue Res. 2023 May 02.

A new organisational design in skeletal muscle fibres.

Eric Parmentier, Marc Thiry.

  In vertebrate skeletal muscles, the architecture of myofibrils is particularly well conserved throughout the taxa. It is composed of suites of repeating functional units called sarcomeres which give the muscle its striated structure. Here, we show that the skeletal sound producing muscles of the cusk eel Parophidion vassali have a different organisation, distinct from the classical type found in textbooks. Within sarcomeres, filaments are not straight lines but have a Y-shaped structure. This looks like chicken wire, with one branch connecting to a branch from the myofibril above and the other connecting to a branch from the myofibril below. This organisation seems to be an adaptation to counteract a trade-off between the speed and force. The low ratio of myofibrils within cell muscles and the high volume of sarcoplasmic reticulum strongly suggest that these muscles are capable of fast contractions. In parallel, the Z-bands are quite wide about 30% of the sarcomere length. This extraordinary long Z-band could smooth out the tension variations found in high-speed muscle contraction, helping to produce sounds with low variabilities in the sound features. Simultaneously, the Y-shaped structure allows having more cross-bridges, increasing the force in this high-speed muscle.

Keywords:  Cusk eel; Fast muscle; Sarcomere; Sarcoplasmic reticulum; Z-band

DOI:  https://doi.org/10.1007/s00441-023-03775-5
Proc Natl Acad Sci U S A. 2023 May 09. 120(19): e2222081120

High sensitivity top-down proteomics captures single muscle cell heterogeneity in large proteoforms.

Jake A Melby, Kyle A Brown, Zachery R Gregorich, David S Roberts, Emily A Chapman, Lauren E Ehlers, Zhan Gao, Eli J Larson, Yutong Jin, Justin R Lopez, Jared Hartung, Yanlong Zhu, Sean J McIlwain, Daojing Wang, Wei Guo, Gary M Diffee, Ying Ge.

  Single-cell proteomics has emerged as a powerful method to characterize cellular phenotypic heterogeneity and the cell-specific functional networks underlying biological processes. However, significant challenges remain in single-cell proteomics for the analysis of proteoforms arising from genetic mutations, alternative splicing, and post-translational modifications. Herein, we have developed a highly sensitive functionally integrated top-down proteomics method for the comprehensive analysis of proteoforms from single cells. We applied this method to single muscle fibers (SMFs) to resolve their heterogeneous functional and proteomic properties at the single-cell level. Notably, we have detected single-cell heterogeneity in large proteoforms (>200 kDa) from the SMFs. Using SMFs obtained from three functionally distinct muscles, we found fiber-to-fiber heterogeneity among the sarcomeric proteoforms which can be related to the functional heterogeneity. Importantly, we detected multiple isoforms of myosin heavy chain (~223 kDa), a motor protein that drives muscle contraction, with high reproducibility to enable the classification of individual fiber types. This study reveals single muscle cell heterogeneity in large proteoforms and establishes a direct relationship between sarcomeric proteoforms and muscle fiber types, highlighting the potential of top-down proteomics for uncovering the molecular underpinnings of cell-to-cell variation in complex systems.

Keywords:  mass spectrometry; proteoform; proteomics; single cell; single muscle fiber

DOI:  https://doi.org/10.1073/pnas.2222081120
Sci Rep. 2023 May 03. 13(1): 7191

Electrical impedance myography detects age-related skeletal muscle atrophy in adult zebrafish.

Seward B Rutkove, Santiago Callegari, Holly Concepcion, Tyler Mourey, Jeffrey Widrick, Janice A Nagy, Anjali K Nath.

Age-related deficits in skeletal muscle function, termed sarcopenia, are due to loss of muscle mass and changes in the intrinsic mechanisms underlying contraction. Sarcopenia is associated with falls, functional decline, and mortality. Electrical impedance myography (EIM)-a minimally invasive, rapid electrophysiological tool-can be applied to animals and humans to monitor muscle health, thereby serving as a biomarker in both preclinical and clinical studies. EIM has been successfully employed in several species; however, the application of EIM to the assessment of zebrafish-a model organism amenable to high-throughput experimentation-has not been reported. Here, we demonstrated differences in EIM measures between the skeletal muscles of young (6 months of age) and aged (33 months of age) zebrafish. For example, EIM phase angle and reactance at 2 kHz showed significantly decreased phase angle (5.3 ± 2.1 versus 10.7 ± 1.5°; p = 0.001) and reactance (89.0 ± 3.9 versus 172.2 ± 54.8 ohms; p = 0.007) in aged versus young animals. Total muscle area, in addition to other morphometric features, was also strongly correlated to EIM 2 kHz phase angle across both groups (r = 0.7133, p = 0.01). Moreover, there was a strong correlation between 2 kHz phase angle and established metrics of zebrafish swimming performance, including turn angle, angular velocity, and lateral motion (r = 0.7253, r = 0.7308, r = 0.7857, respectively, p < 0.01 for all). In addition, the technique was shown to have high reproducibility between repeated measurements with a mean percentage difference of 5.34 ± 1.17% for phase angle. These relationships were also confirmed in a separate replication cohort. Together, these findings establish EIM as a fast, sensitive method for quantifying zebrafish muscle function and quality. Moreover, identifying the abnormalities in the bioelectrical properties of sarcopenic zebrafish provides new opportunities to evaluate potential therapeutics for age-related neuromuscular disorders and to interrogate the disease mechanisms of muscle degeneration.

DOI: https://doi.org/10.1038/s41598-023-34119-6
Aging Cell. 2023 May 03. e13842

Nanopore sequencing identifies a higher frequency and expanded spectrum of mitochondrial DNA deletion mutations in human aging.

Amy R Vandiver, Austin N Hoang, Allen Herbst, Cathy C Lee, Judd M Aiken, Debbie McKenzie, Michael A Teitell, Winston Timp, Jonathan Wanagat.

  Mitochondrial DNA (mtDNA) deletion mutations cause many human diseases and are linked to age-induced mitochondrial dysfunction. Mapping the mutation spectrum and quantifying mtDNA deletion mutation frequency is challenging with next-generation sequencing methods. We hypothesized that long-read sequencing of human mtDNA across the lifespan would detect a broader spectrum of mtDNA rearrangements and provide a more accurate measurement of their frequency. We employed nanopore Cas9-targeted sequencing (nCATS) to map and quantitate mtDNA deletion mutations and develop analyses that are fit-for-purpose. We analyzed total DNA from vastus lateralis muscle in 15 males ranging from 20 to 81 years of age and substantia nigra from three 20-year-old and three 79-year-old men. We found that mtDNA deletion mutations detected by nCATS increased exponentially with age and mapped to a wider region of the mitochondrial genome than previously reported. Using simulated data, we observed that large deletions are often reported as chimeric alignments. To address this, we developed two algorithms for deletion identification which yield consistent deletion mapping and identify both previously reported and novel mtDNA deletion breakpoints. The identified mtDNA deletion frequency measured by nCATS correlates strongly with chronological age and predicts the deletion frequency as measured by digital PCR approaches. In substantia nigra, we observed a similar frequency of age-related mtDNA deletions to those observed in muscle samples, but noted a distinct spectrum of deletion breakpoints. NCATS-mtDNA sequencing allows the identification of mtDNA deletions on a single-molecule level, characterizing the strong relationship between mtDNA deletion frequency and chronological aging.

Keywords:  DNA sequencing; aging; human; mitochondrial DNA; skeletal muscle; substantia nigra

DOI:  https://doi.org/10.1111/acel.13842
Exp Neurol. 2023 May 02. pii: S0014-4886(23)00116-4. [Epub ahead of print] 114431

Response of terminal Schwann cells following volumetric muscle loss injury.

Daniel B Hoffman, Alec M Basten, Jacob R Sorensen, Christiana J Raymond-Pope, Thomas J Lillquist, Jarrod A Call, Benjamin T Corona, Sarah M Greising.

  An often-overlooked component of traumatic skeletal muscle injuries is the impact on the nervous system and resultant innervation of the affected muscles. Recent work in a rodent model of volumetric muscle loss (VML) injury demonstrated a progressive, secondary loss of neuromuscular junction (NMJ) innervation, supporting a role of NMJ dysregulation in chronic functional deficits. Terminal Schwann cells (tSCs) are known to be vital for the maintenance of NMJ structure and function, in addition to guiding repair and regeneration after injury. However, the tSC response to a traumatic muscle injury such as VML is not known. Thus, a study was conducted to investigate the effect of VML on tSC morphological characteristics and neurotrophic signaling proteins in adult male Lewis rats that underwent VML injury to the tibialis anterior muscle using a temporal design with outcome assessments at 3, 7, 14, 21, and 48 days post-injury. The following salient observations were made; first, although there is a loss of innervation over time, the number of tSCs per NMJ increases, significantly so at 48 days post-injury compared to control. The degree of NMJ fragmentation was positively correlated with tSC number after injury. Moreover, neurotrophic factors such as NRG1 and BDNF are elevated after injury through at least 48 days. These results were unanticipated and in contrast to neurodegenerative disease models, in which there is a reduction in tSC number that precedes denervation. However, we found that while there are more tSCs per NMJ after injury, they cover a significantly smaller percent of the post-synaptic endplate area compared to control. These findings support a sustained increase in neurotrophic activity and tSC number after VML, which is a maladaptive response occurring in parallel to other aspects of the VML injury, such as over-accumulation of collagen and aberrant inflammatory signaling.

Keywords:  Denervation; Musculoskeletal trauma; Neuromuscular junction; Neurotrophic factors

DOI:  https://doi.org/10.1016/j.expneurol.2023.114431
Eur J Transl Myol. 2023 May 05.

Progress in muscle research through the international congress of neuromuscular diseases (ICNMD): a narrative review.

Corrado Angelini.

Progress in muscle research has been through different phases over the past decades. Here are reviewed the advances presented at the International Congresses of Neuromuscular Diseases (ICNMD). In the '60 to '80 muscle physiology and interpretations of muscle biopsy were the major focuses, diagnosis of muscle disorders was advanced utilizing histochemical, and ultrastructural techniques, and the focus of first to IVth ICNMD was prevention and Muscle Disorders classification as major issues. After that from '80 to 2000 muscle neuromuscular junction (NMJ) immunology, biochemistry, molecular biology , therapeutic trials, and genetics were the major developments and represented the focus of research in following ICNMD from the Vth to the Xth. From 2000 to 2020 personalized medicine,genotype-phenotype correlation, and the use of DNA/RNA profiling , Imaging was developed and represented substantial signs of progress that were presented in ICNMD XIth to XVIIth. The future is evolving toward a major involvement of the pharmaceutical industry with new drugs and gene-delivered therapy, the use of biomarkers and robotics as well as of artificial intelligence, both for interpreting morphology, DNA, and imaging diagnostic, and such developments will be reflected in research presented in future Congresses.

DOI: https://doi.org/10.4081/ejtm.2023.11239
Matrix Biol. 2023 May;pii: S0945-053X(23)00047-1. [Epub ahead of print]119 57-81

Activation of skeletal muscle FAPs by LPA requires the Hippo signaling via the FAK pathway.

Meilyn Cruz-Soca, Jennifer Faundez-Contreras, Adriana Córdova-Casanova, Felipe S Gallardo, Alexia Bock-Pereda, Jerold Chun, Juan Carlos Casar, Enrique Brandan.

  Lysophosphatidic acid (LPA) is a lysophospholipid that signals through six G-protein coupled receptors (LPARs), LPA1 to LPA6. LPA has been described as a potent modulator of fibrosis in different pathologies. In skeletal muscle, LPA increases fibrosis-related proteins and the number of fibro/adipogenic progenitors (FAPs). FAPs are the primary source of ECM-secreting myofibroblasts in acute and chronic damage. However, the effect of LPA on FAPs activation in vitro has not been explored. This study aimed to investigate FAPs' response to LPA and the downstream signaling mediators involved. Here, we demonstrated that LPA mediates FAPs activation by increasing their proliferation, expression of myofibroblasts markers, and upregulation of fibrosis-related proteins. Pretreatment with the LPA1/LPA3 antagonist Ki16425 or genetic deletion of LPA1 attenuated the LPA-induced FAPs activation, resulting in decreased expression of cyclin e1, α-SMA, and fibronectin. We also evaluated the activation of the focal adhesion kinase (FAK) in response to LPA. Our results showed that LPA induces FAK phosphorylation in FAPs. Treatment with the P-FAK inhibitor PF-228 partially prevented the induction of cell responses involved in FAPs activation, suggesting that this pathway mediates LPA signaling. FAK activation controls downstream cell signaling within the cytoplasm, such as the Hippo pathway. LPA induced the dephosphorylation of the transcriptional coactivator YAP (Yes-associated protein) and promoted direct expression of target pathway genes such as Ctgf/Ccn2 and Ccn1. The blockage of YAP transcriptional activity with Super-TDU further confirmed the role of YAP in LPA-induced FAPs activation. Finally, we demonstrated that FAK is required for LPA-dependent YAP dephosphorylation and the induction of Hippo pathway target genes. In conclusion, LPA signals through LPA1 to regulate FAPs activation by activating FAK to control the Hippo pathway.

Keywords:  Fibro/adipogenic progenitors; Fibrosis; LPARs; Lysophosphatidic acid; Myofibroblasts

DOI:  https://doi.org/10.1016/j.matbio.2023.03.010
Nat Aging. 2023 May 04.

Targeting the biology of aging with mTOR inhibitors.

Joan B Mannick, Dudley W Lamming.

Inhibition of the protein kinase mechanistic target of rapamycin (mTOR) with the Food and Drug Administration (FDA)-approved therapeutic rapamycin promotes health and longevity in diverse model organisms. More recently, specific inhibition of mTORC1 to treat aging-related conditions has become the goal of basic and translational scientists, clinicians and biotechnology companies. Here, we review the effects of rapamycin on the longevity and survival of both wild-type mice and mouse models of human diseases. We discuss recent clinical trials that have explored whether existing mTOR inhibitors can safely prevent, delay or treat multiple diseases of aging. Finally, we discuss how new molecules may provide routes to the safer and more selective inhibition of mTOR complex 1 (mTORC1) in the decade ahead. We conclude by discussing what work remains to be done and the questions that will need to be addressed to make mTOR inhibitors part of the standard of care for diseases of aging.

DOI: https://doi.org/10.1038/s43587-023-00416-y