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Su Y, Claflin DR, Huang M, Davis CS, Macpherson PCD, Richardson A, Van Remmen H, Brooks SV. Deletion of Neuronal CuZnSOD Accelerates Age-Associated Muscle Mitochondria and Calcium Handling Dysfunction That Is Independent of Denervation and Precedes Sarcopenia. Int J Mol Sci 2021; 22:ijms221910735. [PMID: 34639076 PMCID: PMC8509582 DOI: 10.3390/ijms221910735] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 09/23/2021] [Accepted: 09/29/2021] [Indexed: 12/17/2022] Open
Abstract
Skeletal muscle suffers atrophy and weakness with aging. Denervation, oxidative stress, and mitochondrial dysfunction are all proposed as contributors to age-associated muscle loss, but connections between these factors have not been established. We examined contractility, mitochondrial function, and intracellular calcium transients (ICTs) in muscles of mice throughout the life span to define their sequential relationships. We performed these same measures and analyzed neuromuscular junction (NMJ) morphology in mice with postnatal deletion of neuronal Sod1 (i-mn-Sod1-/- mice), previously shown to display accelerated age-associated muscle loss and exacerbation of denervation in old age, to test relationships between neuronal redox homeostasis, NMJ degeneration and mitochondrial function. In control mice, the amount and rate of the decrease in mitochondrial NADH during contraction was greater in middle than young age although force was not reduced, suggesting decreased efficiency of NADH utilization prior to the onset of weakness. Declines in both the peak of the ICT and force were observed in old age. Muscles of i-mn-Sod1-/- mice showed degeneration of mitochondrial and calcium handling functions in middle-age and a decline in force generation to a level not different from the old control mice, with maintenance of NMJ morphology. Together, the findings support the conclusion that muscle mitochondrial function decreases during aging and in response to altered neuronal redox status prior to NMJ deterioration or loss of mass and force suggesting mitochondrial defects contribute to sarcopenia independent of denervation.
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Affiliation(s)
- Yu Su
- Department of Neurosurgery, First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Dennis R Claflin
- Department of Surgery, Section of Plastic Surgery, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Meixiang Huang
- Department of Neurology, Second Xiangya Hospital, Central South University, Changsha 410011, China
| | - Carol S Davis
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Peter C D Macpherson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Arlan Richardson
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- VA Medical Center, Oklahoma City, OK 73104, USA
| | - Holly Van Remmen
- VA Medical Center, Oklahoma City, OK 73104, USA
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
- Department of Physiology, Health Science Center, Oklahoma University, Oklahoma City, OK 73104, USA
| | - Susan V Brooks
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
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Markworth JF, Brown LA, Lim E, Castor‐Macias JA, Larouche J, Macpherson PCD, Davis C, Aguilar CA, Maddipati KR, Brooks SV. Metabolipidomic profiling reveals an age-related deficiency of skeletal muscle pro-resolving mediators that contributes to maladaptive tissue remodeling. Aging Cell 2021; 20:e13393. [PMID: 34075679 PMCID: PMC8208786 DOI: 10.1111/acel.13393] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 03/07/2021] [Accepted: 05/08/2021] [Indexed: 12/12/2022] Open
Abstract
Specialized pro-resolving mediators actively limit inflammation and support tissue regeneration, but their role in age-related muscle dysfunction has not been explored. We profiled the mediator lipidome of aging muscle via liquid chromatography-tandem mass spectrometry and tested whether treatment with the pro-resolving mediator resolvin D1 (RvD1) could rejuvenate the regenerative ability of aged muscle. Aged mice displayed chronic muscle inflammation and this was associated with a basal deficiency of pro-resolving mediators 8-oxo-RvD1, resolvin E3, and maresin 1, as well as many anti-inflammatory cytochrome P450-derived lipid epoxides. Following muscle injury, young and aged mice produced similar amounts of most pro-inflammatory eicosanoid metabolites of cyclooxygenase (e.g., prostaglandin E2 ) and 12-lipoxygenase (e.g., 12-hydroxy-eicosatetraenoic acid), but aged mice produced fewer markers of pro-resolving mediators including the lipoxins (15-hydroxy-eicosatetraenoic acid), D-resolvins/protectins (17-hydroxy-docosahexaenoic acid), E-resolvins (18-hydroxy-eicosapentaenoic acid), and maresins (14-hydroxy-docosahexaenoic acid). Similar absences of downstream pro-resolving mediators including lipoxin A4 , resolvin D6, protectin D1/DX, and maresin 1 in aged muscle were associated with greater inflammation, impaired myofiber regeneration, and delayed recovery of strength. Daily intraperitoneal injection of RvD1 had minimal impact on intramuscular leukocyte infiltration and myofiber regeneration but suppressed inflammatory cytokine expression, limited fibrosis, and improved recovery of muscle function. We conclude that aging results in deficient local biosynthesis of specialized pro-resolving mediators in muscle and that immunoresolvents may be attractive novel therapeutics for the treatment of muscular injuries and associated pain in the elderly, due to positive effects on recovery of muscle function without the negative side effects on tissue regeneration of non-steroidal anti-inflammatory drugs.
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Affiliation(s)
- James F. Markworth
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor MI USA
| | - Lemuel A. Brown
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor MI USA
| | - Eunice Lim
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor MI USA
| | | | - Jacqueline Larouche
- Department of Biomedical Engineering University of Michigan Ann Arbor MI USA
| | - Peter C. D. Macpherson
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor MI USA
| | - Carol Davis
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor MI USA
| | - Carlos A. Aguilar
- Department of Biomedical Engineering University of Michigan Ann Arbor MI USA
| | - Krishna Rao Maddipati
- Department of Pathology Lipidomics Core Facility Wayne State University Detroit MI USA
| | - Susan V. Brooks
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor MI USA
- Department of Biomedical Engineering University of Michigan Ann Arbor MI USA
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Su Y, Ahn B, Macpherson PCD, Ranjit R, Claflin DR, Van Remmen H, Brooks SV. Transgenic expression of SOD1 specifically in neurons of Sod1 deficient mice prevents defects in muscle mitochondrial function and calcium handling. Free Radic Biol Med 2021; 165:299-311. [PMID: 33561489 PMCID: PMC8026109 DOI: 10.1016/j.freeradbiomed.2021.01.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 01/09/2021] [Accepted: 01/25/2021] [Indexed: 01/21/2023]
Abstract
Aging is accompanied by loss of muscle mass and force, known as sarcopenia. Muscle atrophy, weakness, and neuromuscular junction (NMJ) degeneration reminiscent of normal muscle aging are observed early in adulthood for mice deficient in Cu, Zn-superoxide dismutase (SOD, Sod1-/-). Muscles of Sod1-/- mice also display impaired mitochondrial ATP production and increased mitochondrial reactive oxygen species (ROS) generation implicating oxidative stress in sarcopenia. Restoration of CuZnSOD specifically in neurons of Sod1-/- mice (SynTgSod1-/-) prevents muscle atrophy and loss of force, but whether muscle mitochondrial function is preserved is not known. To establish links among CuZnSOD expression, mitochondrial function, and sarcopenia, we examined contractile properties, mitochondrial function and ROS production, intracellular calcium transients (ICT), and NMJ morphology in lumbrical muscles of 7-9 month wild type (WT), Sod1-/-, and SynTgSod1-/- mice. Compared with WT values, mitochondrial ROS production was increased 2.9-fold under basal conditions and 2.2-fold with addition of glutamate and malate in Sod1-/- muscle fibers while oxygen consumption was not significantly altered. In addition, NADH recovery was blunted following contraction and the peak of the ICT was decreased by 25%. Mitochondrial function, ROS generation and calcium handling were restored to WT values in SynTgSod1-/- mice, despite continued lack of CuZnSOD in muscle. NMJ denervation and fragmentation were also fully rescued in SynTgSod1-/- mice suggesting that muscle mitochondrial and calcium handling defects in Sod1-/- mice are secondary to neuronal oxidative stress and its effects on the NMJ rather than the lack of muscle CuZnSOD. We conclude that intact neuronal function and innervation are key to maintaining excitation-contraction coupling and muscle mitochondrial function.
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Affiliation(s)
- Yu Su
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA; Department of Orthopedics, Second Xiangya Hospital, Central South University, Changsha, PR China
| | - Bumsoo Ahn
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Peter C D Macpherson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Rojina Ranjit
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Dennis R Claflin
- Department of Surgery, Section of Plastic Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Holly Van Remmen
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA; Department of Physiology, Oklahoma University Health Science Center, Oklahoma City, OK, USA; VA Medical Center, Oklahoma City, OK, USA
| | - Susan V Brooks
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
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Novakova SS, Rodriguez BL, Vega-Soto EE, Nutter GP, Armstrong RE, Macpherson PCD, Larkin LM. Repairing Volumetric Muscle Loss in the Ovine Peroneus Tertius Following a 3-Month Recovery. Tissue Eng Part A 2020; 26:837-851. [PMID: 32013753 DOI: 10.1089/ten.tea.2019.0288] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Much effort has been made to fabricate engineered tissues on a scale that is clinically relevant to humans; however, scale-up remains one of the most significant technological challenges of tissue engineering to date. To address this limitation, our laboratory has developed tissue-engineered skeletal muscle units (SMUs) and engineered neural conduits (ENCs), and modularly scaled them to clinically relevant sizes for the treatment of volumetric muscle loss (VML). The goal of this study was to evaluate the SMUs and ENCs in vitro, and to test the efficacy of our SMUs and ENCs in restoring muscle function in a clinically relevant large animal (sheep) model. The animals received a 30% VML injury to the peroneus tertius muscle and were allowed to recover for 3 months. The animals were divided into three experimental groups: VML injury without a repair (VML only), repair with an SMU (VML+SMU), or repair with an SMU and ENC (VML+SMU+ENC). We evaluated the SMUs before implantation and found that our single scaled-up SMUs were characterized by the presence of contracting myotubes, linearly aligned extracellular matrix proteins, and Pax7+ satellite cells. Three months after implantation, we found that the repair groups (VML+SMU and VML+SMU+ENC) had restored muscle mass and tetanic force production to a level that was statistically indistinguishable from the uninjured contralateral muscle after 3 months in vivo. Furthermore, we demonstrated the ability of our ENCs to effectively bridge the gap between native nerve and the repair site by eliciting a muscle contraction through direct electrical stimulation of the re-routed nerve. Impact statement The fabrication of tissues of clinically relevant sizes is one of the largest obstacles preventing engineered tissues from achieving widespread use in the clinic. This study aimed to combat this limitation by developing a fabrication method to scale-up tissue-engineered skeletal muscle for the treatment of volumetric muscle loss in a large animal (sheep) model and evaluating the efficacy of the tissue-engineered constructs after a 3-month recovery.
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Affiliation(s)
- Stoyna S Novakova
- Department of Molecular and Integrative Physiology and University of Michigan, Ann Arbor, Michigan, USA
| | - Brittany L Rodriguez
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Emmanuel E Vega-Soto
- Department of Molecular and Integrative Physiology and University of Michigan, Ann Arbor, Michigan, USA
| | - Genevieve P Nutter
- Department of Molecular and Integrative Physiology and University of Michigan, Ann Arbor, Michigan, USA
| | - Rachel E Armstrong
- Department of Molecular and Integrative Physiology and University of Michigan, Ann Arbor, Michigan, USA
| | - Peter C D Macpherson
- Department of Molecular and Integrative Physiology and University of Michigan, Ann Arbor, Michigan, USA
| | - Lisa M Larkin
- Department of Molecular and Integrative Physiology and University of Michigan, Ann Arbor, Michigan, USA.,Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
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Tang H, Inoki K, Brooks SV, Okazawa H, Lee M, Wang J, Kim M, Kennedy CL, Macpherson PCD, Ji X, Van Roekel S, Fraga DA, Wang K, Zhu J, Wang Y, Sharp ZD, Miller RA, Rando TA, Goldman D, Guan K, Shrager JB. mTORC1 underlies age-related muscle fiber damage and loss by inducing oxidative stress and catabolism. Aging Cell 2019; 18:e12943. [PMID: 30924297 PMCID: PMC6516169 DOI: 10.1111/acel.12943] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 01/15/2019] [Accepted: 02/03/2019] [Indexed: 12/15/2022] Open
Abstract
Aging leads to skeletal muscle atrophy (i.e., sarcopenia), and muscle fiber loss is a critical component of this process. The mechanisms underlying these age-related changes, however, remain unclear. We show here that mTORC1 signaling is activated in a subset of skeletal muscle fibers in aging mouse and human, colocalized with fiber damage. Activation of mTORC1 in TSC1 knockout mouse muscle fibers increases the content of morphologically abnormal mitochondria and causes progressive oxidative stress, fiber damage, and fiber loss over the lifespan. Transcriptomic profiling reveals that mTORC1's activation increases the expression of growth differentiation factors (GDF3, 5, and 15), and of genes involved in mitochondrial oxidative stress and catabolism. We show that increased GDF15 is sufficient to induce oxidative stress and catabolic changes, and that mTORC1 increases the expression of GDF15 via phosphorylation of STAT3. Inhibition of mTORC1 in aging mouse decreases the expression of GDFs and STAT3's phosphorylation in skeletal muscle, reducing oxidative stress and muscle fiber damage and loss. Thus, chronically increased mTORC1 activity contributes to age-related muscle atrophy, and GDF signaling is a proposed mechanism.
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Affiliation(s)
- Huibin Tang
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia
| | - Ken Inoki
- Life Science InstituteUniversity of MichiganAnn ArborMichigan,Department of Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMichigan
| | - Susan V. Brooks
- Department of Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMichigan
| | - Hideki Okazawa
- Department of Pharmacology and Moores Cancer CenterUniversity of California San DiegoLa JollaCalifornia
| | - Myung Lee
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia
| | - Junying Wang
- Life Science InstituteUniversity of MichiganAnn ArborMichigan
| | - Michael Kim
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia
| | - Catherine L. Kennedy
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia
| | - Peter C. D. Macpherson
- Molecular and Behavioral Neuroscience Institute and Department of Biological ChemistryUniversity of MichiganAnn ArborMichigan
| | - Xuhuai Ji
- Human Immune Monitoring Center, Stanford University School of MedicineStanfordCalifornia
| | - Sabrina Van Roekel
- Department of Pathology and Geriatrics CenterUniversity of MichiganAnn ArborMichigan
| | - Danielle A. Fraga
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia
| | - Kun Wang
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia,Present address:
The Department of Thoracic SurgeryThird Affiliated Hospital of Kunming Medical UniversityKunmingChina
| | - Jinguo Zhu
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia,Present address:
Department of Cardiothoracic SurgeryGuangxi International Zhuang Hospital of GuangXi University of Chinese MedicineNanNingChina
| | - Yoyo Wang
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia
| | - Zelton D. Sharp
- Department of Molecular MedicineUniversity of Texas Health Science Center at San AntonioSan AntonioTexas
| | - Richard A. Miller
- Department of Pathology and Geriatrics CenterUniversity of MichiganAnn ArborMichigan
| | - Thomas A. Rando
- VA Palo Alto Healthcare SystemPalo AltoCalifornia,Paul F. Glenn Laboratories for the Biology of Aging and Department of Neurology and Neurological SciencesStanford University School of MedicineStanfordCalifornia
| | - Daniel Goldman
- Molecular and Behavioral Neuroscience Institute and Department of Biological ChemistryUniversity of MichiganAnn ArborMichigan
| | - Kun‐Liang Guan
- Department of Pharmacology and Moores Cancer CenterUniversity of California San DiegoLa JollaCalifornia
| | - Joseph B. Shrager
- Division of Thoracic Surgery, Department of Cardiothoracic SurgeryStanford University School of MedicineStanfordCalifornia,VA Palo Alto Healthcare SystemPalo AltoCalifornia
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Macpherson PCD, Farshi P, Goldman D. Dach2-Hdac9 signaling regulates reinnervation of muscle endplates. Development 2015; 142:4038-48. [PMID: 26483211 DOI: 10.1242/dev.125674] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 10/01/2015] [Indexed: 02/04/2023]
Abstract
Muscle denervation resulting from injury, disease or aging results in impaired motor function. Restoring neuromuscular communication requires axonal regrowth and endplate reinnervation. Muscle activity inhibits the reinnervation of denervated muscle. The mechanism by which muscle activity regulates muscle reinnervation is poorly understood. Dach2 and Hdac9 are activity-regulated transcriptional co-repressors that are highly expressed in innervated muscle and suppressed following muscle denervation. Dach2 and Hdac9 control the expression of endplate-associated genes such as those encoding nicotinic acetylcholine receptors (nAChRs). Here we tested the idea that Dach2 and Hdac9 mediate the effects of muscle activity on muscle reinnervation. Dach2 and Hdac9 were found to act in a collaborative fashion to inhibit reinnervation of denervated mouse skeletal muscle and appear to act, at least in part, by inhibiting denervation-dependent induction of Myog and Gdf5 gene expression. Although Dach2 and Hdac9 inhibit Myog and Gdf5 mRNA expression, Myog does not regulate Gdf5 transcription. Thus, Myog and Gdf5 appear to stimulate muscle reinnervation through parallel pathways. These studies suggest that manipulating the Dach2-Hdac9 signaling system, and Gdf5 in particular, might be a good approach for enhancing motor function in instances where neuromuscular communication has been disrupted.
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Affiliation(s)
- Peter C D Macpherson
- Molecular and Behavioral Neuroscience Institute, Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Pershang Farshi
- Molecular and Behavioral Neuroscience Institute, Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Daniel Goldman
- Molecular and Behavioral Neuroscience Institute, Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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Abstract
Muscle inactivity due to injury or disease results in muscle atrophy. The molecular mechanisms contributing to muscle atrophy are poorly understood. However, it is clear that expression of atrophy-related genes, like Atrogin-1 and MuRF-1, are intimately tied to loss of muscle mass. When these atrophy-related genes are knocked out, inactive muscles retain mass. Muscle denervation stimulates muscle atrophy and Myogenin (Myog) is a muscle-specific transcription factor that is highly induced following muscle denervation. To investigate if Myog contributes to muscle atrophy, we have taken advantage of conditional Myog null mice. We show that in the denervated soleus muscle Myog expression contributes to reduced muscle force, mass, and cross-sectional area. We found that Myog mediates these effects, at least in part, by regulating expression of the Atrogin-1 and MuRF-1 genes. Indeed Myog over-expression in innervated muscle stimulates Atrogin-1 gene expression and Myog over-expression stimulates Atrogin-1 promoter activity. Thus, Myog and the signaling cascades regulating its induction following muscle denervation may represent novel targets for therapies aimed at reducing denervation-induced muscle atrophy.
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Affiliation(s)
- Peter C D Macpherson
- Molecular and Behavioral Neuroscience Institute and Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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8
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Macpherson PCD, Cieslak D, Goldman D. Myogenin-dependent nAChR clustering in aneural myotubes. Mol Cell Neurosci 2006; 31:649-60. [PMID: 16443371 DOI: 10.1016/j.mcn.2005.12.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Revised: 12/07/2005] [Accepted: 12/13/2005] [Indexed: 10/25/2022] Open
Abstract
During development of the neuromuscular junction, nerve-derived agrin and the cell substrate laminin stimulate postsynaptic nAChR clustering. This clustering is dependent on activation of the tyrosine kinase, MuSK, which signals receptor clustering via a rapsyn-dependent mechanism. Myogenin is a muscle-specific transcription factor that controls myoblast differentiation and nAChR gene expression. Here, we used RNA interference to investigate if myogenin is also necessary for nAChR clustering. We find that myogenin expression is essential for robust nAChR clustering and cannot be compensated by the muscle regulatory factors MyoD, myf5, and MRF4. In addition, we show that clustering cannot be rescued in myogenin-depleted myotubes by simply overexpressing the essential clustering molecules MuSK, rapsyn, and nAChRs. These data suggest that myogenin controls the expression of molecules crucial to nAChR clustering in addition to its role in regulating nAChR gene expression.
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Affiliation(s)
- Peter C D Macpherson
- Molecular and Behavioral Neurosciences Institute and Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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9
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Abstract
Skeletal muscle contractile activity has been implicated in many aspects of muscle cell differentiation and maturation. Much of the research in this area has depended upon costly and labor-intensive cultures of isolated primary muscle cells because widely available immortalized muscle cell lines often do not display a high level of either spontaneous or stimulated contractile activity. We sought to develop conditionally-immortalized skeletal muscle cell lines that would provide a source of myofibers that exhibit robust spontaneous contractile activity similar to primary muscle cultures. Using a tetracycline-regulated retroviral vector expressing a temperature-sensitive T-antigen to infect primary myoblasts, we isolated individual clonal muscle precursor cell lines that have characteristics of activated satellite cells during growth and rapidly differentiate into mature myotubes with spontaneous contractile activity after culture in non-transformation-permissive conditions. Comparison of these cell lines (known as rat myoblast-like tetracycline (RMT) cell lines) to primary cell cultures revealed that they share a wide variety of morphological, physiological, and biochemical characteristics. Most importantly, the time-course and extent of activity-dependent gene regulation observed in primary cell culture for all genes tested, including subunits of the nicotinic acetylcholine receptor (nAChR), muscle specific kinase (MuSK), and myogenin, is reproduced in RMT lines. These immortalized cell lines are a useful alternative to primary cultures for studying muscle differentiation and molecular and physiological aspects of electrical activity in muscle fibers.
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Affiliation(s)
- Peter C D Macpherson
- Mental Health Research Institute, University of Michigan, Ann Arbor, 205 Zina Pitcher Pl., Ann Arbor, Michigan 48109-0720, USA.
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Carlson BM, Borisov AB, Dedkov EI, Khalyfa A, Kostrominova TY, Macpherson PCD, Wang E, Faulkner JA. Effects of long-term denervation on skeletal muscle in old rats. J Gerontol A Biol Sci Med Sci 2002; 57:B366-74. [PMID: 12242312 DOI: 10.1093/gerona/57.10.b366] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We compared the reactions to denervation of limb muscles between young adult and old rats. After denervation for up to 4 months in 24-month-old rats, limb muscles were removed and analyzed for contractile properties, morphology, and levels of several key molecules, including the peptide elongation factors eEF1A-1 and eEF1A-2/S1, myogenin, gamma-subunit of the acetylcholine receptor, and cyclin D3. The principal difference between denervated old and young muscle is a somewhat slower rate of atrophy in denervated older muscle, especially among the type II fibers. Expression levels of certain molecules were higher in old than in young control muscle, but after denervation, levels of these molecules increased to the same absolute values in both young and old rats. Although many aspects of postdenervation reactions do not differ greatly between young and old animals, the lesser degree of atrophy in the old rats may reflect significant age-based mechanisms.
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Affiliation(s)
- Bruce M Carlson
- Institute of Gerontology, University of Michigan, Ann Arbor, MI 48109-2007, USA.
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