Musculoskeletal system

  • Article
    | Open Access

    Dual-energy X-ray absorptiometry and the Fracture Risk Assessment Tool are recommended tools for osteoporotic fracture risk evaluation, but are underutilized. Here, the authors present an opportunistic tool to identify fractures, predict bone mineral density and evaluate fracture risk using plain pelvis and lumbar spine radiographs.

    • Chen-I Hsieh
    • , Kang Zheng
    •  & Chang-Fu Kuo
  • Article
    | Open Access

    Soft tissue trauma can result in aberrant osteochondral differentiation of local mesenchymal progenitor cells. Here the authors show that, in mice, soft tissue trauma results in NGF expression by perivascular cells, which leads to axonal invasion and drives abnormal osteochondral differentiation, and show that this process can be prevented by inhibition of NGF signaling.

    • Seungyong Lee
    • , Charles Hwang
    •  & Benjamin Levi
  • Article
    | Open Access

    Genetic association signals for fractures have been reported at the RSPO3 locus, but the causal gene and the underlying mechanism are unknown. Here, the authors show that RSPO3 exerts an important role for vertebral trabecular bone mass and bone strength in mice and fracture risk in humans.

    • Karin H. Nilsson
    • , Petra Henning
    •  & Claes Ohlsson
  • Article
    | Open Access

    While many genetic loci have been found to be associated with disease, not many have had their causal variants and mechanisms investigated. Here, the authors experimentally dissect two loci near GDF5 which are associated with two different joint disorders and which map to independent regulatory elements.

    • Pushpanathan Muthuirulan
    • , Dewei Zhao
    •  & Terence D. Capellini
  • Article
    | Open Access

    Regular exercise promotes overall health and prevents non-communicable diseases, but the adaptation mechanisms are unclear. Here, the authors perform a meta-analysis to reveal time-specific patterns of the acute and long-term exercise response in human skeletal muscle, and identify sex- and age-specific changes.

    • David Amar
    • , Malene E. Lindholm
    •  & Euan A. Ashley
  • Article
    | Open Access

    Antibody-based Wnt agonists are able to phenocopy Wnt signaling in vivo resulting in increased bone density, repair, and strength. Here, the authors show that Wnt agonists can reverse bone loss associated with ovariectomy and build stronger bone when administered after fracture.

    • Tristan W. Fowler
    • , Troy L. Mitchell
    •  & Yang Li
  • Article
    | Open Access

    Supplementation of magnesium (Mg2+) or its inclusion in biomaterials has beneficial effects for bone formation, but it has also been reported that it can have detrimental effects. Here, the authors analyse dose- and time-dependent effects of Mg2+ on bone regeneration and show that it can stimulate monocyte-macrophage lineage cells to support bone formation in the early phases of repair, but inhibit bone repair and mineralization in later stages by promoting a pro-inflammatory environment.

    • Wei Qiao
    • , Karen H. M. Wong
    •  & Kelvin W. K. Yeung
  • Article
    | Open Access

    Osteocytes are the master regulatory cells within the skeleton. Here, the authors map the transcriptome of osteocytes from diverse skeletal sites, ages and between sexes and identify an osteocyte transcriptome signature associated with rare skeletal disorders and common complex skeletal diseases.

    • Scott E. Youlten
    • , John P. Kemp
    •  & Peter I. Croucher
  • Article
    | Open Access

    The mechanism by which parathyroid hormone mediates the switch from bone resorption to bone formation is unclear. Here, the authors show that SLPI regulates the communication between osteoblasts and osteoclasts to promote the anabolic effect of parathyroid hormone.

    • Akito Morimoto
    • , Junichi Kikuta
    •  & Masaru Ishii
  • Article
    | Open Access

    As human skeletal muscle ages, gene expression programs change and reflect damage accumulation and homeostatic resilience mechanisms. Here, the authors present a detailed framework of the global transcriptome that characterizes skeletal muscle during aging in healthy individuals.

    • Robert A. Tumasian III
    • , Abhinav Harish
    •  & Luigi Ferrucci
  • Article
    | Open Access

    The functional relationship between subchondral bone and articular cartilage is unclear. Here, the authors show that transforming growth factor-beta propagates the mechanical impact of subchondral bone on articular cartilage through αV integrin–talin mechanical transduction system in chondrocytes.

    • Gehua Zhen
    • , Qiaoyue Guo
    •  & Xu Cao
  • Article
    | Open Access

    Sarcopenia is the age-associated functional decline and atrophy of muscle fibers, and it has been proposed that it might be counteracted by inducing myofiber hypertrophy. Here, the authors show that expression levels of the ubiquitin ligase UBR4 are increased with ageing, and that whilst its genetic ablation rescues muscle atrophy, it is also associated with reduced protein quality and impaired force production in Drosophila and mouse models.

    • Liam C. Hunt
    • , Bronwen Schadeberg
    •  & Fabio Demontis
  • Article
    | Open Access

    Muscle atrophy is associated with ageing, but the underlying molecular mechanisms are not well understood. Here, they authors show that ablation of the E3 ubiquitin ligase Mib1 is important for myofibre maintenance via a mechanism that involves targeting and degradation of Actn3, and that Mib1 ablation in mice induces muscle atrophy which can be rescued by knockown of Actn3 expression.

    • Ji-Yun Seo
    • , Jong-Seol Kang
    •  & Young-Yun Kong
  • Article
    | Open Access

    Pelvic radiographs (PXRs) are essential for detecting proximal femur and pelvis injuries in trauma patients, but none of the currently available algorithms can detect all kinds of trauma-related radiographic findings. Here, the authors develop a multiscale deep learning algorithm trained with weakly supervised point annotation.

    • Chi-Tung Cheng
    • , Yirui Wang
    •  & Le Lu
  • Review Article
    | Open Access

    Skeletal muscle has a remarkable regenerative capacity, which can largely be attributed to resident muscle stem cells (MuSCs). Here, the authors review the molecular mechanisms regulating MuSC quiescence, activation and proliferation, how these processes are regulated by the stem cell niche, and the role of MuSCs in neuromuscular diseases.

    • F. Relaix
    • , M. Bencze
    •  & Taglietti V.
  • Article
    | Open Access

    Osteoarthritis is a chronic, heritable disease with no available treatment. Here, the authors show that a validated, rapid-throughput joint phenotyping pipeline detects osteoarthritis in the mouse knee following surgical provocation, in aging and after single gene deletion or point mutation.

    • Natalie C. Butterfield
    • , Katherine F. Curry
    •  & J. H. Duncan Bassett
  • Review Article
    | Open Access

    Loss of muscle mass is associated with ageing and with a number of diseases such as cancer. Here, the authors review the signaling pathways that modulate protein synthesis and degradation and gain or loss of muscle mass, and discuss therapeutic implications and future directions for the field.

    • Roberta Sartori
    • , Vanina Romanello
    •  & Marco Sandri
  • Article
    | Open Access

    Skeletal muscle conveys the beneficial effects of physical exercise but due to its heterogeneity, studying the effects of exercise on muscle fibres is challenging. Here, the authors carry out proteomic analysis of myofibres from freeze-dried muscle biopsies, show fibre-type specific changes in response to exercise, and show that the oxidative and glycolytic muscle fibers adapt differentially to exercise training.

    • A. S. Deshmukh
    • , D. E. Steenberg
    •  & J. F. P. Wojtaszewski
  • Article
    | Open Access

    Muscle fibers are the largest cells in the body and contain less DNA per unit volume than other cells even if they have multiple nuclei. Here, the authors show that the number of nuclei regulates the cell size with similar scaling properties in mice and humans.

    • Kenth-Arne Hansson
    • , Einar Eftestøl
    •  & Kristian Gundersen
  • Article
    | Open Access

    Skeletal muscle is composed of syncytial myofibres, each containing hundreds of nuclei. Through genetic reduction of the number of nuclei per myofibre, the authors confirm that more nuclei produce larger cells but myofibres with fewer nuclei adaptively compensate leading to larger and functional myonuclear domains.

    • Alyssa A. W. Cramer
    • , Vikram Prasad
    •  & Douglas P. Millay
  • Article
    | Open Access

    Duchenne muscular dystrophy (DMD) is characterised by progressive muscle degeneration. Here, the authors show that the BET protein BRD4 is increased in the muscle of DMD mouse models, and that pharmacological inhibition of BRD4 leads to reduced muscle pathology in mice, by modulating NADPH oxidase expression.​

    • Marco Segatto
    • , Roberta Szokoll
    •  & Giuseppina Caretti
  • Article
    | Open Access

    mTORC1 expression is increased during ageing of muscle, and on the other hand, its activation promotes muscle hypertrophy. Here, the authors assess whether mTORC1 has positive or negative effects on ageing, and show that its long-term inhibition preserves muscle mass and function and neuromuscular junction integrity, whereas muscle-specific activation is associated with sarcopenia.

    • Daniel J. Ham
    • , Anastasiya Börsch
    •  & Markus A. Rüegg
  • Article
    | Open Access

    Skeletal muscle cells have long been considered to be made primarily of many individual, parallel myofibrils. Here, the authors show that the striated muscle contractile machinery forms a highly branched, mesh-like myofibrillar matrix connected across the entire length and width of the muscle cell.

    • T. Bradley Willingham
    • , Yuho Kim
    •  & Brian Glancy
  • Article
    | Open Access

    Chondrocytes have altered cellular metabolism in the context of osteoarthritis, but whether and how these changes are associated with inflammation is a controversial area. Here the authors show that inflammatory NF-κB signalling drives a glycolytic shift in chondrocytes and the production of ROS, which drives cartilage catabolism.

    • Manoj Arra
    • , Gaurav Swarnkar
    •  & Yousef Abu-Amer
  • Article
    | Open Access

    Bone marrow adipose tissue (BMAT) comprises over 10% of total fat mass but its systemic metabolic role is unclear. Here, the authors show that BMAT glucose uptake is not insulin or cold responsive; however, BMAT basal glucose uptake is higher than in white adipose tissue or skeletal muscle, underscoring BMAT’s potential to influence systemic glucose homeostasis.

    • Karla J. Suchacki
    • , Adriana A. S. Tavares
    •  & William P. Cawthorn
  • Article
    | Open Access

    Nebulin-based nemaline myopathy is a heterogenous disease with unclear pathological mechanisms. Here, the authors generate a mouse model that mimics the most common genetic cause of the disease and demonstrate that muscle weakness in this model is associated with twisted actin filaments and altered tropomyosin and troponin behaviour.

    • Johan Lindqvist
    • , Weikang Ma
    •  & Henk Granzier
  • Article
    | Open Access

    Glucose metabolism is regulated by hypothalamic brain functions and factors produced by peripheral tissues. Here, the authors show that the regulator of food intake Brain-derived neurotrophic factor is also produced and secreted by muscle and stimulates pancreas insulin release.

    • Gianluca Fulgenzi
    • , Zhenyi Hong
    •  & Lino Tessarollo
  • Article
    | Open Access

    Denervation of muscle fibres induces muscle atrophy, via mechanisms that remain unclear. Here, the authors show that binding of acetylcoline to its receptor at the neuromuscular junction represses the expression of connexins 43 and 45, which promote atrophy, and is sufficient to prevent denervation-induced loss of myofibre mass.

    • Bruno A. Cisterna
    • , Aníbal A. Vargas
    •  & Juan C. Sáez
  • Article
    | Open Access

    An endothelial cell subtype, expressing endomucin and CD31, has been reported to couple angiogenesis with osteogenesis. Here, the authors show that loss of ZEB1 in these cells epigenetically suppresses Notch signaling, leading to impaired angiogenesis and osteogenesis, and that Zeb1 delivery via liposomes ameliorates bone loss in osteoporotic mice

    • Rong Fu
    • , Wen-Cong Lv
    •  & Zhao-Qiu Wu
  • Article
    | Open Access

    Sarcopenia is the loss of muscle mass and strength associated with physical disability during ageing. Here, the authors analyse muscle biopsies from 119 patients with sarcopenia and age-matched controls of different ethnic groups and find transcriptional signatures indicating mitochondrial dysfunction, associated with reduced mitochondria numbers and lower NAD+ levels in older individuals with sarcopenia.

    • Eugenia Migliavacca
    • , Stacey K. H. Tay
    •  & Jerome N. Feige
  • Article
    | Open Access

    Skeletal muscle stem cells express the transcription factor Pax7. Here, the authors isolate, from human muscle, cells that are positive for the endothelial marker CLEC14A and show that despite not expressing pax7, these cells regenerate muscle and contribute to the muscle stem cell niche when transplanted into mice.

    • Andreas Marg
    • , Helena Escobar
    •  & Simone Spuler
  • Article
    | Open Access

    During high-intensity exercise, muscles convert glucose to lactate, in a process that is energetically less efficient than respiration. Here the authors develop a computational model based on muscle proteomic data showing that bypassing mitochondrial complex I increases ATP production rates, and validate these model predictions in an exercise test on 5 subjects.

    • Avlant Nilsson
    • , Elias Björnson
    •  & Jens Nielsen
  • Article
    | Open Access

    Reactive oxygen species (ROS) stimulate GLUT4-mediated glucose transport following contraction of isolated muscle, but it is not clear if this occurs in vivo. Here, the authors show in human volunteers that exercise induces ROS increase in muscle and, using loss of-function animal models, they demonstrate that NOX2 is a major ROS source required to stimulate glucose uptake during exercise.

    • Carlos Henríquez-Olguin
    • , Jonas R. Knudsen
    •  & Thomas E. Jensen
  • Article
    | Open Access

    Leflunomide is used for the treatment of rheumatoid arthritis. Here, the authors show that effectiveness is limited in patients with higher levels of serum c-reactive protein (CRP). Using animal models, they show that higher CRP induces HIF1a expression, which in turn interferes with Leflunomide signalling, and that effectiveness of the drug is restored when HIF1a is pharmacologically inhibited.

    • Chao Liang
    • , Jie Li
    •  & Aiping Lu
  • Article
    | Open Access

    HuR is an RNA-binding protein that regulates myotube differentiation in vitro. Here, the authors show that the muscle-specific ablation of HuR in mice leads to enhanced endurance capacity and an increase in oxidative fibres by destabilising PGC1α-mRNA, and show that the mice are protected against cancer cachexia

    • Brenda Janice Sánchez
    • , Anne-Marie K. Tremblay
    •  & Imed-Eddine Gallouzi
  • Article
    | Open Access

    Denervation leads to muscle atrophy and neuromuscular endplate remodeling. Here, the authors show that a balanced activation of mTORC1 contributes to the dynamic regulation of autophagic flux in denervated muscle and that activation of PKB/Akt promotes the nuclear import of HDAC4, which is essential for endplate maintenance upon nerve injury

    • Perrine Castets
    • , Nathalie Rion
    •  & Markus A. Rüegg
  • Article
    | Open Access

    A number of therapeutic agents aimed at reducing pathology in Duchenne muscular dystrophy have been developed, but may have off-target effects when delivered systemically. Here, the authors express the therapeutic LIF transgene in leukocytes, and show this results in targeting to inflamed dystrophic muscle and reduced fibrosis by suppressing type 2 immunity.

    • Steven S. Welc
    • , Ivan Flores
    •  & James G. Tidball
  • Article
    | Open Access

    In vivo decorporation of U(VI) from bones is an unsolved challenge because of the formation of stable uranium phosphate complexes. Here, the authors develop a hydroxypyridonone-based ligand with strong uranium complexation and low cytotoxicity. They find this ligand effectively removes uranium from kidney and bones in mice, and is suitable for oral administration.

    • Xiaomei Wang
    • , Xing Dai
    •  & Shuao Wang
  • Article
    | Open Access

    Muscle loss is associated with altered expression of proteins involved in mitochondrial homeostasis, but whether this is causative remains unclear. Here, the authors show that genetic ablation of the pro-fission protein DRP1 leads to accumulation of abnormal mitochondria that induce muscle atrophy by altering Ca2+ homeostasis and cellular stress responses.

    • Giulia Favaro
    • , Vanina Romanello
    •  & Marco Sandri
  • Article
    | Open Access

    Arthroplasty is the main clinical option for the treatment of osteoarticular lesions, but has limited efficacy. Here, the authors use a wound dressing with autologous mesenchymal stromal cells, functionalised for local BMP2 delivery, and show feasibility and safety in standardised preclinical tests in animal models, suggesting suitability for use in clinical trials.

    • Laetitia Keller
    • , Luc Pijnenburg
    •  & Nadia Benkirane-Jessel
  • Article
    | Open Access

    Size and shape of bones are important for height and body shape. Here, Styrkarsdottir et al identify 12 loci in a GWAS for bone area derived from DXA scans and show that these loci associate with other bone-related phenotypes including osteoarthritis, height, bone mineral density and risk of hip fracture.

    • Unnur Styrkarsdottir
    • , Olafur A. Stefansson
    •  & Kari Stefansson