Muscle biology
Abstract
Duchenne muscular dystrophy (DMD) is a progressive muscle wasting disorder involving cycles of muscle degeneration and regeneration, leading to accumulation of intramuscular fibrosis and fat. Ablation of Osteopontin/Spp1 in a murine model of DMD (mdx) improves the dystrophic phenotype, but the source of Spp1 and its impact on target cells in dystrophic muscles remain unknown. In dystrophic muscles, macrophages are the predominate infiltrating leukocyte and express high levels of Spp1. We used macrophage-specific ablation combined with single-cell transcriptional profiling to uncover the impact of macrophage-derived Spp1 on cell-cell interactions in mdx muscles. Ablation of macrophage-specific Spp1 (cKO) correlated with reduction of 2 PDGFRa+ stromal cell populations, expressing Lifr+ and Procr+. Sorting and transcriptional profiling of these populations confirmed that they are enriched in adipogenesis genes and are highly related to fibroadipogenic precursors (FAPS). These adipogenic stromal cells (ASC) displayed more adipogenic potential in vitro compared with FAPS, likely due to a more differentiated state. Reduction of ASCs correlated with reduced intramuscular diaphragmatic fat and improved diaphragm function. These data suggest a role for myeloid-derived Spp1 in the differentiation of stromal cells towards an adipogenic fate, leading to accumulation of intramuscular fat in dystrophic muscles.
Authors
Philip K. Farahat, Chino Kumagai-Cresse, Raquel L. Aragón, Feiyang Ma, Justin K. Amakor, Alejandro Espinoza, Irina Kramerova, Robert J. Jimenez, Bradley M. Smith, Jesus Perez, Rachelle H. Crosbie, Apoorva H. Nagendra, Jackie McCourt-Towner, Gerald Coulis, Oluwatayo F. Ikotun, April D. Pyle, Matteo Pellegrini, Elizabeth M. McNally, S. Armando Villalta, Melissa J. Spencer
Abstract
Dominant missense mutations in MYBPC1, the gene encoding the essential sarcomeric slow Myosin Binding Protein-C (sMyBP-C), are associated with Myotrem, a new, early-onset congenital myopathy characterized by muscle weakness, hypotonia, skeletal deformities, and myogenic tremor. Importantly, the clinical manifestation of Myotrem in mid- and late adulthood is unknown. Using the Myotrem MYBPC1 E248K Knock-In (KI) murine model, we interrogated contractile performance of soleus, gastrocnemius, and Tibalis Anterior (TA) muscles in both male and female mice in mid- (12-months) and late (24-months) adulthood. Our findings showed that the phenotypic manifestation of E248K Myotrem differs across muscle-type, sex, and age. While KI soleus muscle consistently exhibited contractile impairment across both sexes and ages, KI gastrocnemius muscle displayed preserved force production. Interestingly, TA muscle showed a sex- and age-specific impact with preserved function through 12-months in both sexes and a sharp decline at 24-months solely in males. Quantitative analysis of TA sarcomeric organization uncovered structural deficits coinciding with contractile dysfunction, supporting the notion that sMyBP-C serves a primarily structural role in skeletal muscle. Collectively, our studies revealed that aging impacts the E248K Myotrem myopathy in a muscle- and sex-dependent fashion and show that sarcomeric disorganization accompanies contractile deterioration in affected muscles.
Authors
Jennifer Megan Mariano, Humberto C. Joca, Jacob G. Kallenbach, Natasha Ranu, Julien Ochala, Christopher Ward, Aikaterini Kontrogianni-Konstantopoulos
Abstract
More than one in four men will undergo surgery for inguinal hernia, which is commonly associated with fibrotic degeneration of the lower abdominal muscle (LAM) in the groin region. Utilizing a male mouse model expressing the human aromatase gene (Aromhum), previous studies showed that locally produced estradiol acting via estrogen receptor alpha in LAM fibroblasts leads to fibrosis, myofiber atrophy, and hernia development. Here, we found that upregulation of progesterone receptor (PGR) in a LAM fibroblast population mediates this estrogenic effect. A PGR-selective progesterone antagonist in Aromhum mice decreased LAM fibrosis and atrophy, preventing hernia formation and stopping progression of existing hernias. Addition of progesterone to estradiol treatment was essential for early-onset development of LAM fibrosis and large hernias in wild type mice, which was averted by a progesterone antagonist. Single-nuclei multiomics sequencing of herniated LAM revealed a unique population of Pgr-expressing fibroblasts that promotes fibrosis and myofiber atrophy through transforming growth factor beta-2 signaling. Multiomics findings were validated in vivo in herniated LAM tissues of both mice and adult men. Our findings suggest an important and rare pathologic role of progesterone signaling in males and provide evidence for progesterone antagonists as a non-surgical alternative for inguinal hernia management.
Authors
Tianming You, Mehrdad Zandigohar, Tanvi Potluri, Natalie Piehl, John S. Coon V, Elizabeth Baker, Maya Kafali, Yang Dai, Jonah J. Stulberg, David J. Escobar, Richard L. Lieber, Hong Zhao, Serdar E. Bulun
Abstract
Spinal cord injury (SCI) evokes profound dysfunction in hollow organs such as the urinary bladder and gut. Current treatments are limited by a lack of molecular data to inform novel therapeutic avenues. Previously, we showed systemic treatment with the neuroprotective agent inosine improved bladder function following SCI in rats. Here, we applied integrated multi-omics analysis to explore molecular alterations in the bladder over time and their sensitivity to inosine following SCI. Canonical signaling pathways regulated by SCI included those associated with protein synthesis, neuroplasticity, wound healing, and neurotransmitter degradation. Upstream regulator and causal network analysis predicted multiple effectors of DNA damage response signaling following injury, including PARP1. Markers of DNA damage (gammaH2AX, ATM/ATR substrates) and PARP activity (poly-ADP-ribose) were increased in bladder tissue following SCI and attenuated with inosine treatment. Inosine treatment also attenuated oxidative DNA damage in rat bladder cells in vitro. Proteomics analysis suggested that SCI induced changes in protein synthesis-, neuroplasticity-, and oxidative stress-associated pathways, a subset of which were shown in transcriptomics data to be inosine-sensitive. These findings provide insights into the molecular landscape of the bladder following SCI and identify key inosine-sensitive pathways associated with injury.
Authors
Ali Hashemi Gheinani, Bryan S. Sack, Alexander Bigger-Allen, Hatim Thaker, Hussein Atta, George Lambrinos, Kyle Costa, Claire Doyle, Mehrnaz Gharaee-Kermani, Susan Patalano, Mary Piper, Justin F. Cotellessa, Dijana Vitko, Haiying Li, Manubhai Kadayil Prabhakaran, Vivian Cristofaro, John Froehlich, Richard S. Lee, Wei Yang, Maryrose P. Sullivan, Jill A. Macoska, Rosalyn M. Adam
Abstract
Regulation of organismal homeostasis in response to nutrient availability is a vital physiological process that involves inter-organ communication. The role of the heart in controlling systemic metabolic health is not clear. Adopting a mouse model of diet-induced obesity, we found that the landscape of N6-methyladenosine (m6A) on cardiac mRNA is altered following high fat/high carbohydrate feeding (western diet). m6A is a critical post-transcriptional regulator of gene expression, the formation of which is catalyzed by methyltransferase-like 3 (METTL3). Through parallel unbiased approaches of nanopore sequencing, mass spectrometry, and protein array, we found regulation of circulating factors under the control of METTL3. Mice with cardiomyocyte-specific deletion of METTL3 show a systemic inability to respond to nutritional challenge, thereby mitigating the detrimental effects of western diet. Conversely, increasing cardiac METTL3 level exacerbates diet-induced body weight gain, adiposity, and glucose intolerance. Our findings position the heart at the center of systemic metabolism regulation and highlight an m6A-dependent pathway to be exploited for the battle against obesity.
Authors
Charles Rabolli, Jacob Z. Longenecker, Isabel S. Naarmann-de Vries, Joan Serrano, Jennifer M. Petrosino, George A. Kyriazis, Christoph Dieterich, Federica Accornero
Abstract
Adult stem cells decline in number and function in old age and identifying factors that can delay or revert age-associated adult stem cell dysfunction are vital for maintaining healthy lifespan. Here we show that Vitamin A, a micronutrient that is derived from diet and metabolized into retinoic acid, acts as an antioxidant and transcriptional regulator in muscle stem cells. We first show that obstruction of dietary Vitamin A in young animals drives mitochondrial and cell cycle dysfunction in muscle stem cells that mimics old age. Next, we pharmacologically targeted retinoic acid signaling in myoblasts and aged muscle stem cells ex vivo and in vivo and observed reductions in oxidative damage, enhanced mitochondrial function, and improved maintenance of quiescence through fatty acid oxidation. We next detected the receptor for vitamin A derived retinol, stimulated by retinoic acid 6 or Stra6, was diminished with muscle stem cell activation and in old age. To understand the relevance of Stra6 loss, we knocked down Stra6 and observed an accumulation of mitochondrial reactive oxygen species, as well as changes in mitochondrial morphology and respiration. These results demonstrate that Vitamin A regulates mitochondria and metabolism in muscle stem cells and highlight a unique mechanism connecting stem cell function with vitamin intake.
Authors
Paula M. Fraczek, Pamela Duran, Benjamin A. Yang, Valeria Ferre, Leanne Alawieh, Jesus A. Castor-Macias, Vivian T. Wong, Steve D. Guzman, Celeste Piotto, Klimentini Itsani, Jacqueline A Larouche, Carlos A. Aguilar
Abstract
The deleterious consequences of chronic synovitis on cartilage, tendon and bone in rheumatoid arthritis (RA) are well-described. In contrast, its effects on periarticular skeletal muscle are under-studied. Further, while TNF inhibition is an effective therapy for RA synovitis, it exacerbates fibrosis in muscle injury models. We aimed to investigate whether myositis and muscle fibrosis are features of inflammatory arthritis and evaluate whether targeted RA therapies influence these disease features. Periarticular muscle was analysed in murine models of poly- and mono-articular inflammatory arthritis: serum transfer induced arthritis, collagen-induced arthritis, K/BxN, and antigen-induced arthritis (AIA). Periarticular myositis and an increase in muscle fibroadipocyte progenitor cells (FAPs) were observed in all models, despite diverse arthritogenic mechanisms. Periarticular muscle fibrosis was observed from day 15 in AIA. Neither etanercept nor baricitinib suppressed periarticular myositis or subsequent fibrosis compared to vehicle, despite reducing arthritis. Notably, etanercept failed to prevent muscle fibrosis even when initiated early, but this was not linked to increased FAPs survival or collagen production. Corroborating these data, radiographic and histological analyses revealed periarticular myositis in RA patients. We conclude that periarticular myositis and fibrosis are under-recognised features of inflammatory arthritis. Targeted RA therapies may not prevent periarticular muscle sequelae, despite controlling arthritis.
Authors
Jessica Day, Cynthia Louis, Kristy Swiderski, Angus Stock, Huon Wong, Wentao Yao, Bonnia Liu, Suba Nadesapillai, Gordon S. Lynch, Ian P. Wicks
Abstract
Skeletal muscle regeneration in adults is predominantly driven by satellite cells. Loss of satellite cell pool and function leads to skeletal muscle wasting in many conditions and disease states. Here, we demonstrate that the levels of fibroblast growth factor-inducible 14 (Fn14) were increased in satellite cells after muscle injury. Conditional ablation of Fn14 in Pax7-expressing satellite cells drastically reduced their expansion and skeletal muscle regeneration following injury. Fn14 was required for satellite cell self-renewal and proliferation as well as to prevent precocious differentiation. Targeted deletion of Fn14 inhibited Notch signaling but led to the spurious activation of STAT3 signaling in regenerating skeletal muscle and in cultured muscle progenitor cells. Silencing of STAT3 improved proliferation and inhibited premature differentiation of Fn14-deficient satellite cells. Furthermore, conditional ablation of Fn14 in satellite cells exacerbated myopathy in the mdx mouse model of Duchenne muscular dystrophy (DMD) whereas its overexpression improved the engraftment of exogenous muscle progenitor cells into the dystrophic muscle of mdx mice. Altogether, our study highlights the crucial role of Fn14 in the regulation of satellite cell fate and function and suggests that Fn14 can be a potential molecular target to improve muscle regeneration in muscular disorders.
Authors
Meiricris Tomaz da Silva, Aniket S. Joshi, Ashok Kumar
Abstract
Obscurin is a giant protein that coordinates diverse aspects of striated muscle physiology. Obscurin immunoglobulin domains 58/59 (Ig58/59) associate with essential sarcomeric and Ca2+ cycling proteins. To explore the pathophysiological significance of Ig58/59, we generated the Obscn-ΔIg58/59 mouse model, expressing obscurin constitutively lacking Ig58/59. Males in this line develop atrial fibrillation by 6-months, with atrial and ventricular dilation by 12-months. As Obscn-ΔIg58/59 left ventricles at 6-months exhibit no deficits in sarcomeric ultrastructure or Ca2+ signaling, we hypothesized that susceptibility to arrhythmia may emanate from the atria. Ultrastructural evaluation of male Obscn-ΔIg58/59 atria uncovered prominent Z-disk streaming by 6-months and further misalignment by 12-months. Relatedly, isolated Obscn-ΔIg58/59 atrial cardiomyocytes exhibited increased Ca2+ spark frequency and age-specific alterations in Ca2+ cycling dynamics, coinciding with arrythmia onset and progression. Quantitative analysis of the transverse-axial tubule (TAT) network using super-resolution microscopy demonstrated significant TAT depletion in Obscn-ΔIg58/59 atria. These structural and Ca2+ signaling deficits were accompanied by age-specific alterations in the expression and/or phosphorylation of T-cap, which links transverse-tubules to Z-disks, and junctophilin-2, which connects transverse-tubules to the sarcoplasmic reticulum. Collectively, our work establishes the Obscn-ΔIg58/59 model as a reputable genetic model for atrial cardiomyopathy and provides mechanistic insights into atrial fibrillation and remodeling.
Authors
Alyssa Grogan, Annie Brong, Humberto C. Joca, Liron Boyman, Aaron D. Kaplan, Christopher W. Ward, Maura Greiser, Aikaterini Kontrogianni-Konstantopoulos
Abstract
Disruption of the circadian clock in skeletal muscle worsens local and systemic health, leading to decreased muscle strength, metabolic dysfunction, and aging-like phenotypes. Whole-body knockout mice that lack Bmal1, a key component of the molecular clock, display premature aging. Here, by using adeno-associated viruses, we rescued Bmal1 expression specifically in the skeletal muscle fibers of Bmal1-KO mice and found that this engaged the circadian clock and clock output gene expression contributing to extended lifespan. Time course phenotypic analyses found that muscle strength, mobility, and glucose tolerance were improved with no effects on muscle mass, fiber size or type. A multi-omics approach at two ages further determined that restored muscle Bmal1 improved glucose handling pathways while concomitantly reducing lipid and protein metabolic pathways. The improved glucose tolerance and metabolic flexibility resulted in the systemic reduction of inflammatory signatures across peripheral tissues including liver, lung, and white adipose fat. Together, these findings highlight the critical role of muscle Bmal1 and downstream target genes for skeletal muscle homeostasis with considerable implications for systemic health.
Authors
Miguel A. Gutierrez-Monreal, Christopher A. Wolff, Eduardo E. Rijos, Mark R. Viggars, Collin M. Douglas, Vishwajeeth Pagala, Junmin Peng, Liam C. Hunt, Haocheng Ding, Fabio Demontis, Zhiguang Huo, Karyn A. Esser
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