Muscle biology
Abstract
BACKGROUND. During ageing there is a functional decline in the pool of muscle stem cells (MuSCs) which influences the functional and regenerative capacity of skeletal muscle. Preclinical evidence have suggested that Nicotinamide Riboside (NR) and Pterostilbene (PT) can improve muscle regeneration e.g. by increasing MuSC function. The objective of the present study was to investigate if NRPT-supplementation promotes skeletal muscle regeneration after muscle injury in elderly humans by improved recruitment of MuSCs. METHODS. 32 elderly men and women (55-80 yr) were randomized to daily supplementation with either NRPT (1000 mg NR + 200 mg PT) or matched placebo. Two weeks after initiation of supplementation, a skeletal muscle injury was induced by electrically-induced eccentric muscle work. Skeletal muscle biopsies were obtained pre, 2h, 2, 8, and 30 days post injury. RESULTS. A substantial skeletal muscle injury was induced by the protocol and associated with release of myoglobin and creatine kinase, muscle soreness, tissue edema, and a decrease in muscle strength. MuSC content, proliferation and cell size revealed a large demand for recruitment post injury but was not affected by NRPT. Furthermore, histological analyses of muscle fiber area, internal nuclei and embryonic Myosin Heavy Chain showed no effect of NRPT supplementation. CONCLUSION. Daily supplementation with 1000 mg NR+200 mg PT is safe but does not improve recruitment of the MuSC pool or other measures of muscle recovery in response to injury or subsequent regeneration in elderly subjects. TRIAL REGISTRATION. NCT03754842. FUNDING. Novo Nordisk Foundation (Ref. NNF17OC0027242) given to JTT and NJ. JTT, ED, SC, MVD, KT, and TM are supported by the Novo Nordisk Foundation Center for Basic Metabolic Research (CBMR). CBMR is an independent Research Center at the University of Copenhagen that is partially funded by an unrestricted donation from the Novo Nordisk Foundation (NNF18CC0034900).
Authors
Jonas Brorson Jensen, Ole Lindgård Dollerup, Andreas Buch Møller, Tine B. Billeskov, Emilie Dalbram, Sabina Chubanava, Mads V. Damgaard, Ryan W. Dellinger, Kajetan Trošt, Thomas Moritz, Steffen Ringgaard, Niels Møller, Jonas T. Treebak, Jean Farup, Niels Jessen
Abstract
The sarcoplasmic reticulum (SR) plays an important role in calcium homeostasis. SR calcium mishandling is described in pathological conditions such as myopathies. Here, we investigated whether the nuclear receptor subfamily 1 group D member (NR1D1, also called REV-ERBα) regulates skeletal muscle SR calcium homeostasis. Our data demonstrate that NR1D1 deficiency in mice impairs SERCA-dependent SR calcium uptake. NR1D1 acts on calcium homeostasis by repressing the SERCA inhibitor myoregulin through direct binding to its promoter. Restoration of myoregulin counteracts the effects of NR1D1 overexpression on SR calcium content. Interestingly, myoblasts from Duchenne myopathy patients display lower NR1D1 expression, whereas pharmacological NR1D1 activation ameliorates SR calcium homeostasis, and improves muscle structure and function in dystrophic mdx/Utr+/- mice. Our findings demonstrate that NR1D1 regulates muscle SR calcium homeostasis, pointing to its therapeutic interest for mitigating myopathy.
Authors
Alexis Boulinguiez, Christian Duhem, Alicia Mayeuf-Louchart, Benoit Pourcet, Yasmine Sebti, Kateryna Kondratska, Valérie Montel, Stéphane Delhaye, Quentin Thorel, Justine Beauchamp, Aurore Hebras, Marion Gimenez, Marie Couvelaere, Mathilde Zecchin, Lise Ferri, Natalia Prevarskaya, Anne Forand, Christel Gentil, Jessica Ohana, France Piétri-Rouxel, Bruno Bastide, Bart Staels, Helene Duez, Steve Lancel
Abstract
Membrane instability and disruption underlie myriad acute and chronic disorders. Anxa6 encodes the membrane-associated protein annexin A6 and was identified as a genetic modifier of muscle repair and muscular dystrophy. To evaluate annexin A6’s role in membrane repair in vivo, we inserted sequences encoding green fluorescent protein (GFP) into the last coding exon of Anxa6. Heterozygous Anxa6gfp mice expressed a normal pattern of annexin A6 with reduced annexin A6GFP mRNA and protein. High-resolution imaging of wounded muscle fibers showed annexin A6GFP rapidly formed a repair cap at the site of injury. Injured cardiomyocytes and neurons also displayed repair caps after wounding, highlighting annexin A6–mediated repair caps as a feature in multiple cell types. Using surface plasmon resonance, we showed recombinant annexin A6 bound phosphatidylserine-containing lipids in a Ca2+- and dose-dependent fashion with appreciable binding at approximately 50 μM Ca2+. Exogenously added recombinant annexin A6 localized to repair caps and improved muscle membrane repair capacity in a dose-dependent fashion without disrupting endogenous annexin A6 localization, indicating annexin A6 promotes repair from both intracellular and extracellular compartments. Thus, annexin A6 orchestrates repair in multiple cell types, and recombinant annexin A6 may be useful in additional chronic disorders beyond skeletal muscle myopathies.
Authors
Alexis R. Demonbreun, Elena Bogdanovic, Lauren A. Vaught, Nina L. Reiser, Katherine S. Fallon, Ashlee M. Long, Claire C. Oosterbaan, Michele Hadhazy, Patrick G.T. Page, Prem Raj B. Joseph, Gabrielle Cowen, Alexander M. Telenson, Ammaarah Khatri, Katherine R. Sadleir, Robert Vassar, Elizabeth M. McNally
Abstract
Striated preferentially expressed protein kinase (SPEG), a myosin light chain kinase, is mutated in centronuclear myopathy (CNM) and/or dilated cardiomyopathy. No precise therapies are available against this disorder, and gene replacement therapy is not a feasible option due to the large size of SPEG. We evaluated the potential of dynamin-2 (DNM2) reduction as a potential therapeutic strategy as it has been shown to revert muscle phenotypes in mouse models of CNM caused by MTM1, DNM2, and BIN1 mutations. We determined that SPEGβ interacts with DNM2, and SPEG deficiency causes an increase in DNM2 levels. The DNM2 reduction strategy in Speg-KO mice was associated with an increase in life span, body weight, and motor performance. Additionally, it normalized the distribution of triadic proteins, triad ultrastructure, and triad number, and restored phosphatidylinositol-3-phosphate levels in SPEG-deficient skeletal muscles. While DNM2 reduction rescued the myopathy phenotype, it did not improve cardiac dysfunction, indicating a differential tissue-specific function. Combining DNM2 reduction with other strategies may be needed to target both the cardiac and skeletal defects associated with SPEG deficiency. DNM2 reduction should be explored as a therapeutic strategy against other genetic myopathies (and dystrophies) associated with a high level of DNM2.
Authors
Qifei Li, Jasmine Lin, Jeffrey J. Widrick, Shiyu Luo, Gu Li, Yuanfan Zhang, Jocelyn Laporte, Mark A. Perrella, Xiaoli Liu, Pankaj B. Agrawal
Abstract
LAMA2-deficiency, resulting from a defective or absent laminin α2-subunit, is a common cause of congenital muscular dystrophy. It is characterized by muscle weakness from myofiber degeneration and neuropathy from Schwann cell amyelination. Previously it was shown that transgenic muscle-specific expression of αLNNd, a laminin-γ1-binding linker protein that ena-bles polymerization in defective laminins, selectively ameliorates the muscle abnormality in mouse disease models. Here, adeno-associated virus (AAV) was used to deliver linker mini-genes to dystrophic dy2J/dy2J mice for expression of either αLNNd in muscle, or αLNNdΔG2’, a shortened linker, in muscle, nerve and other tissues. Linker and laminin-α2 levels were higher in αLNNdΔG2’-treated mice. Both αLNNd- and αLNNdΔG2’-treated mice exhibited increased fore-limb grip strength. Further, αLNNdΔG2’-treated mice achieved hindlimb and all-limb grip strength levels approaching those of wild-type mice as well as ablation of hindlimb paresis and contractures. Improvement of muscle histology was evident in the muscle-specific αLNNd-ex-pressing mice but more extensive in the αLNNdΔG2'-expressing mice, along with restoration of sciatic nerve axonal envelopment and myelination. The results reveal that an αLN-linker mini-gene, driven by a ubiquitous promoter is superior to muscle-specific delivery through higher ex-pression that extends to peripheral nerve. These studies support a novel approach of somatic gene therapy.
Authors
Karen K. McKee, Peter D. Yurchenco
Abstract
The survival of motor neuron (SMN) protein is a major component of the pre-mRNA splicing machinery and is required for RNA metabolism. Although SMN has been considered a fundamental gene for the central nervous system, due to its relationship with neuromuscular diseases, such as spinal muscular atrophy, recent studies have also revealed the requirement of SMN in non-neuronal cells in the peripheral regions. Here, we report that the fibro-adipogenic progenitor subpopulation expressing Dpp4 (Dpp4+ FAPs) is required for the neuromuscular system. Furthermore, we also reveal that BRCA1-associated protein-1 (Bap1) is crucial for the stabilization of SMN in FAPs by preventing its ubiquitination-dependent degradation. Inactivation of Bap1 in FAPs decreased SMN levels and accompanied degeneration of the neuromuscular junction, leading to loss of motor neurons and muscle atrophy. Overexpression of the ubiquitination-resistant SMN variant, SMNK186R, in Bap1-null FAPs completely prevented neuromuscular degeneration. In addition, transplantation of Dpp4+ FAPs, but not Dpp4– FAPs, completely rescued neuromuscular defects. Our data reveal the crucial role of Bap1-mediated SMN stabilization in Dpp4+ FAPs for the neuromuscular system and provide the possibility of cell-based therapeutics to treat neuromuscular diseases.
Authors
Ji-Hoon Kim, Jong-Seol Kang, Kyusang Yoo, Jinguk Jeong, Inkuk Park, Jong Ho Park, Joonwoo Rhee, Shin Jeon, Young-Woo Jo, Sang-Hyeon Hann, Minji Seo, Seungtae Moon, Soo-Jong Um, Rho Hyun Seong, Young-Yun Kong
Abstract
Nemaline Myopathy (NM) is the most common congenital myopathy, characterized by extreme weakness of the respiratory, limb, and facial muscles. Pathogenic variants in Tropomyosin 2 (TPM2), which encodes a skeletal muscle specific actin binding protein essential for sarcomere function, cause a spectrum of musculoskeletal disorders that include NM as well as Cap Myopathy, congenital fiber type disproportion, and distal arthrogryposis (DA). The in vivo pathomechanisms underlying TPM2-related disorders are unknown, so we expressed a series of dominant, pathogenic TPM2 variants in Drosophila embryos and found four variants significantly affected muscle development and muscle function. Transient overexpression of the four variants also disrupted the morphogenesis of mouse myotubes in vitro, and negatively affected zebrafish muscle development in vivo. We used transient overexpression assays in zebrafish to characterize two novel TPM2 variants and one recurring variant that we identified in DA patients (V129A, E139K, A155T), and found these variants caused musculoskeletal defects similar to those of known pathogenic variants. The consistency of musculoskeletal phenotypes in our assays correlated with the severity of clinical phenotypes observed in our DA patients, suggesting disrupted myogenesis is a novel pathomechanism of TPM2 disorders, and that our myogenic assays can predict the clinical severity of TPM2 variants.
Authors
Jennifer McAdow, Shuo Yang, Tiffany Ou, Gary Huang, Matthew B. Dobbs, Christina A. Gurnett, Michael J. Greenberg, Aaron N. Johnson
Abstract
Friedreich’s ataxia (FRDA) is an inherited disorder caused by reduced levels of frataxin (FXN), which is required for iron-sulfur cluster biogenesis. Neurological and cardiac comorbidities are prominent and have been a major focus of study. Skeletal muscle has received less attention despite indications that FXN loss affects it. Here, we show that lean mass is lower, whereas body mass index is unaltered, in separate cohorts of adults and children with FRDA. In adults, lower lean mass correlated with disease severity. To further investigate FXN loss in skeletal muscle, we used a transgenic mouse model of whole-body inducible and progressive FXN depletion. There was little impact of FXN loss when FXN was approximately 20% of control levels. When residual FXN was approximately 5% of control levels, muscle mass was lower along with absolute grip strength. When we examined mechanisms that can affect muscle mass, only global protein translation was lower, accompanied by integrated stress response (ISR) activation. Also in mice, aerobic exercise training, initiated prior to the muscle mass difference, improved running capacity, yet, muscle mass and the ISR remained as in untrained mice. Thus, FXN loss can lead to lower lean mass, with ISR activation, both of which are insensitive to exercise training.
Authors
César Vásquez-Trincado, Julia Dunn, Ji In Han, Briyanna Hymms, Jaclyn Tamaroff, Monika Patel, Sara Nguyen, Anna Dedio, Kristin Wade, Chinazo Enigwe, Zuzana Nichtova, David R. Lynch, Gyorgy Csordas, Shana E. McCormack, Erin L. Seifert
Abstract
Greater than 25% of all men develop an inguinal hernia in their lifetime, and more than 20 million inguinal hernia repair surgeries are performed worldwide each year. The mechanisms causing abdominal muscle weakness, the formation of inguinal hernias, or their recurrence are largely unknown. We previously reported that excessively produced estrogen in the lower abdominal muscles (LAM) triggers extensive LAM fibrosis, leading to hernia formation in a transgenic male mouse model expressing the human aromatase gene (Aromhum). To understand the cellular basis of estrogen-driven muscle fibrosis, we performed single-cell RNA-sequencing on LAM tissue from Aromhum and wild-type littermates. We found a fibroblast-like cell group comprised of six clusters, two of which were validated for their enrichment in Aromhum LAM tissue. One of the novel hernia-associated fibroblast clusters in Aromhum was enriched for the estrogen receptor-α gene (Esr1Hi). Esr1Hi fibroblasts maximally expressed estrogen target genes and seemed to serve as the progenitors of another cluster expressing ECM-altering enzymes (Mmp3Hi) and upregulate expression of pro-inflammatory, pro-fibrotic genes. The discovery of these two novel and unique hernia-associated fibroblasts may lead to the development of novel treatments that can non-surgically prevent or reverse inguinal hernias.
Authors
Tanvi Potluri, Matthew J. Taylor, Jonah J. Stulberg, Richard L. Lieber, Hong Zhao, Serdar E. Bulun
Abstract
Sex/gender disparity in asthma is recognized, and suggests a modulatory role for sex-steroids, particularly estrogen. However, studies including our own show a dichotomous role for estrogen in airway remodeling, making it unclear whether sex hormones are protective or detrimental in asthma, and suggesting a need to explore mechanisms upstream or independent of estrogen. We hypothesize that Kisspeptin (Kp)/KISS1R signaling serves this role. Airway smooth muscle (ASM) is a key structural cell type that contributes to remodeling in asthma. We explored the role of Kp/KISS1R in regulating ASM proliferation. We report novel data that Kp and KISS1R are expressed in human airways, especially ASM, with lower expression in ASM from females compared to males, and asthmatics showing lowest expression compared to non-asthmatics. Proliferation studies showed that cleaved forms of Kp, particularly Kp-10 mitigates PDGF-induced ASM proliferation. Pharmacological inhibition and shRNA knockdown of KISS1R increased basal ASM proliferation, further amplified by PDGF. The anti-proliferative effect of Kp-10 in ASM was found to be mediated by inhibition of MAPK-ERK-Akt pathways, with altered expression of PCNA, C/EBP-alpha, Ki-67, Cyclin-D1, and Cyclin-E leading to cell-cycle arrest at G0/G1 phase. Overall, we demonstrate the importance of Kp/KISS1R signaling in regulating ASM proliferation and a potentially novel therapeutic avenue to blunt remodeling in asthma.
Authors
Niyati A. Borkar, Nilesh Sudhakar Ambhore, Rama Satyanarayana Raju Kalidhindi, Christina M. Pabelick, Y.S. Prakash, Venkatachalem Sathish
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