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Shadrach JL, Wagers AJ. Stem cells for skeletal muscle repair. Philos Trans R Soc Lond B Biol Sci 2011; 366:2297-306. [PMID: 21727135 DOI: 10.1098/rstb.2011.0027] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Skeletal muscle is a highly specialized tissue composed of non-dividing, multi-nucleated muscle fibres that contract to generate force in a controlled and directed manner. Skeletal muscle is formed during embryogenesis from a subset of muscle precursor cells, which generate both differentiated muscle fibres and specialized muscle-forming stem cells known as satellite cells. Satellite cells remain associated with muscle fibres after birth and are responsible for muscle growth and repair throughout life. Failure in satellite cell function can lead to delayed, impaired or failed recovery after muscle injury, and such failures become increasingly prominent in cases of progressive muscle disease and in old age. Recent progress in the isolation of muscle satellite cells and elucidation of the cellular and molecular mediators controlling their activity indicate that these cells represent promising therapeutic targets. Such satellite cell-based therapies may involve either direct cell replacement or development of drugs that enhance endogenous muscle repair mechanisms. Here, we discuss recent breakthroughs in understanding both the cell intrinsic and extrinsic regulators that determine the formation and function of muscle satellite cells, as well as promising paths forward to realizing their full therapeutic potential.
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Affiliation(s)
- Jennifer L Shadrach
- Department of Stem Cell and Regenerative Biology, Howard Hughes Medical Institute, Harvard University and Joslin Diabetes Center, Bauer Center, 7 Divinity Avenue, Cambridge, MA 02138, USA
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152
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McCarthy JJ, Mula J, Miyazaki M, Erfani R, Garrison K, Farooqui AB, Srikuea R, Lawson BA, Grimes B, Keller C, Van Zant G, Campbell KS, Esser KA, Dupont-Versteegden EE, Peterson CA. Effective fiber hypertrophy in satellite cell-depleted skeletal muscle. Development 2011; 138:3657-66. [PMID: 21828094 DOI: 10.1242/dev.068858] [Citation(s) in RCA: 443] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
An important unresolved question in skeletal muscle plasticity is whether satellite cells are necessary for muscle fiber hypertrophy. To address this issue, a novel mouse strain (Pax7-DTA) was created which enabled the conditional ablation of >90% of satellite cells in mature skeletal muscle following tamoxifen administration. To test the hypothesis that satellite cells are necessary for skeletal muscle hypertrophy, the plantaris muscle of adult Pax7-DTA mice was subjected to mechanical overload by surgical removal of the synergist muscle. Following two weeks of overload, satellite cell-depleted muscle showed the same increases in muscle mass (approximately twofold) and fiber cross-sectional area with hypertrophy as observed in the vehicle-treated group. The typical increase in myonuclei with hypertrophy was absent in satellite cell-depleted fibers, resulting in expansion of the myonuclear domain. Consistent with lack of nuclear addition to enlarged fibers, long-term BrdU labeling showed a significant reduction in the number of BrdU-positive myonuclei in satellite cell-depleted muscle compared with vehicle-treated muscle. Single fiber functional analyses showed no difference in specific force, Ca(2+) sensitivity, rate of cross-bridge cycling and cooperativity between hypertrophied fibers from vehicle and tamoxifen-treated groups. Although a small component of the hypertrophic response, both fiber hyperplasia and regeneration were significantly blunted following satellite cell depletion, indicating a distinct requirement for satellite cells during these processes. These results provide convincing evidence that skeletal muscle fibers are capable of mounting a robust hypertrophic response to mechanical overload that is not dependent on satellite cells.
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Affiliation(s)
- John J McCarthy
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536, USA
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153
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Steinbacher P, Marschallinger J, Obermayer A, Neuhofer A, Sänger AM, Stoiber W. Temperature-dependent modification of muscle precursor cell behaviour is an underlying reason for lasting effects on muscle cellularity and body growth of teleost fish. ACTA ACUST UNITED AC 2011; 214:1791-801. [PMID: 21562165 DOI: 10.1242/jeb.050096] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Temperature is an important factor influencing teleost muscle growth, including a lasting ('imprinted') influence of embryonic thermal experience throughout all further life. However, little is known about the cellular processes behind this phenomenon. The study reported here used digital morphometry and immunolabelling for Pax7, myogenin and H3P to quantitatively examine the effects of thermal history on muscle precursor cell (MPC) behaviour and muscle growth in pearlfish (Rutilus meidingeri) until the adult stage. Fish were reared at three different temperatures (8.5, 13 and 16°C) until hatching and subsequently kept under the same (ambient) thermal conditions. Cellularity data were combined with a quantitative analysis of Pax7+ MPCs including those that were mitotically active (Pax7+/H3P+) or had entered differentiation (Pax7+/myogenin+). The results demonstrate that at hatching, body lengths, fast and slow muscle cross-sectional areas and fast fibre numbers are lower in fish reared at 8.5 and 13°C than at 16°C. During the larval period, this situation changes in the 13°C-fish, so that these fish are finally the largest. The observed effects can be related to divergent cellular mechanisms at the MPC level that are initiated in the embryo during the imprinting period. Embryos of 16°C-fish have reduced MPC proliferation but increased differentiation, and thus give rise to larger hatchlings. However, their limited MPC reserves finally lead to smaller adults. By contrast, embryos of 13°C-fish and, to a lesser extent, 8.5°-fish, show enhanced MPC proliferation but reduced differentiation, thus leading to smaller hatchlings but allowing for a larger MPC pool that can be used for enhanced post-hatching growth, finally resulting in larger adults.
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Affiliation(s)
- Peter Steinbacher
- Division of Zoology and Functional Anatomy, Department of Organismic Biology, University of Salzburg, Salzburg, Austria.
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154
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Hinits Y, Williams VC, Sweetman D, Donn TM, Ma TP, Moens CB, Hughes SM. Defective cranial skeletal development, larval lethality and haploinsufficiency in Myod mutant zebrafish. Dev Biol 2011; 358:102-12. [PMID: 21798255 DOI: 10.1016/j.ydbio.2011.07.015] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 07/12/2011] [Indexed: 11/18/2022]
Abstract
Myogenic regulatory factors of the myod family (MRFs) are transcription factors essential for mammalian skeletal myogenesis. Here we show that a mutation in the zebrafish myod gene delays and reduces early somitic and pectoral fin myogenesis, reduces miR-206 expression, and leads to a persistent reduction in somite size until at least the independent feeding stage. A mutation in myog, encoding a second MRF, has little obvious phenotype at early stages, but exacerbates the loss of somitic muscle caused by lack of Myod. Mutation of both myod and myf5 ablates all skeletal muscle. Haploinsufficiency of myod leads to reduced embryonic somite muscle bulk. Lack of Myod causes a severe reduction in cranial musculature, ablating most muscles including the protractor pectoralis, a putative cucullaris homologue. This phenotype is accompanied by a severe dysmorphology of the cartilaginous skeleton and failure of maturation of several cranial bones, including the opercle. As myod expression is restricted to myogenic cells, the data show that myogenesis is essential for proper skeletogenesis in the head.
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Affiliation(s)
- Yaniv Hinits
- Randall Division for Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, King's College London, SE1 1UL, UK
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155
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Welle S, Mehta S, Burgess K. Effect of postdevelopmental myostatin depletion on myofibrillar protein metabolism. Am J Physiol Endocrinol Metab 2011; 300:E993-E1001. [PMID: 21406613 PMCID: PMC3118593 DOI: 10.1152/ajpendo.00509.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
It is unclear whether the muscle hypertrophy induced by loss of myostatin signaling in mature muscles is maintained only by increased protein synthesis or whether reduced proteolysis contributes. To address this issue, we depleted myostatin by activating Cre recombinase for 2 wk in mature mice in which Mstn exon 3 was flanked by loxP sequences. The rate of phenylalanine tracer incorporation into myofibrillar proteins was determined 2, 5, and 24 wk after Cre activation ended. At all of these time points, myostatin-deficient mice had increased gastrocnemius and quadriceps muscle mass (≥27%) and increased myofibrillar synthesis rate per gastrocnemius muscle (≥19%) but normal myofibrillar synthesis rates per myofibrillar mass or RNA mass. Mean fractional myofibrillar degradation rates (estimated from the difference between rate of synthesis and rate of change in myofibrillar mass) and muscle concentrations of free 3-methylhistidine (from actin and myosin degradation) were unaffected by myostatin knockout. Overnight food deprivation reduced myofibrillar synthesis and ribosomal protein S6 phosphorylation and increased concentrations of 3-methylhistidine, muscle RING finger-1 mRNA, and atrogin-1 mRNA. Myostatin depletion did not affect these responses to food deprivation. These data indicate that maintenance of the muscle hypertrophy caused by loss of myostatin is mediated by increased protein synthesis per muscle fiber rather than suppression of proteolysis.
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Affiliation(s)
- Stephen Welle
- Department of Medicine, Division of Endocrinology and Metabolism, University of Rochester, Rochester, NY 14642, USA.
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156
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Srikuea R, Pholpramool C, Kitiyanant Y, Yimlamai T. Satellite cell activity in muscle regeneration after contusion in rats. Clin Exp Pharmacol Physiol 2011; 37:1078-86. [PMID: 20726992 DOI: 10.1111/j.1440-1681.2010.05439.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. The role of satellite cells in muscle growth during development is well documented, but the involvement of these cells in muscle repair after contusion is less well known. In the present study, we investigated the time-course of satellite cell activity (from 3h to 7days) after contusion of rat gastrocnemius muscle using specific molecular markers for immunofluorescence and real-time polymerase chain reaction (PCR). 2. Inflammation of the injured muscle occurred within 6h, followed by disintegration of the damaged myofibres within 12h. Newly formed myofibres appeared by Day 7. 3. The number of MyoD-positive nuclei (activated satellite cells) in the injured muscle was significantly increased by 6h, reaching a maximum by 12h after contusion. However, the number of MyoD-positive nuclei decreased towards control levels by Day 7. Changes in the number of bromodeoxyuridine-labelled nuclei (proliferating satellite cells) paralleled the changes seen in the number of MyoD-positive nuclei. Conversely, expression of myogenin protein was not apparent until Day 3 and increased further by Day 7. Colabelling of MyoD and myogenin was seen in only a few cells. 4. The time-course of MyoD mRNA expression corresponded with MyoD protein expression. However, there were two peaks in myogenin mRNA expression: 6h and Day 7 after contusion. The second peak coincided with upregulation of myostatin mRNA levels. 5. The results of the present study suggest that contusion activates a homogeneous population of satellite cells to proliferate within 3days, followed by differentiation to form new myofibres. The latter may be regulated, in part, by myostatin.
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Affiliation(s)
- Ratchakrit Srikuea
- Department of Physiology, Faculty of Science, Mahidol University, Bangkok, Thailand
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157
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van der Meer SF, Jaspers RT, Jones DA, Degens H. Time-course of changes in the myonuclear domain during denervation in young-adult and old rat gastrocnemius muscle. Muscle Nerve 2011; 43:212-22. [DOI: 10.1002/mus.21822] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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158
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Kinsey ST, Locke BR, Dillaman RM. Molecules in motion: influences of diffusion on metabolic structure and function in skeletal muscle. J Exp Biol 2011; 214:263-74. [PMID: 21177946 PMCID: PMC3008633 DOI: 10.1242/jeb.047985] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/2010] [Indexed: 12/23/2022]
Abstract
Metabolic processes are often represented as a group of metabolites that interact through enzymatic reactions, thus forming a network of linked biochemical pathways. Implicit in this view is that diffusion of metabolites to and from enzymes is very fast compared with reaction rates, and metabolic fluxes are therefore almost exclusively dictated by catalytic properties. However, diffusion may exert greater control over the rates of reactions through: (1) an increase in reaction rates; (2) an increase in diffusion distances; or (3) a decrease in the relevant diffusion coefficients. It is therefore not surprising that skeletal muscle fibers have long been the focus of reaction-diffusion analyses because they have high and variable rates of ATP turnover, long diffusion distances, and hindered metabolite diffusion due to an abundance of intracellular barriers. Examination of the diversity of skeletal muscle fiber designs found in animals provides insights into the role that diffusion plays in governing both rates of metabolic fluxes and cellular organization. Experimental measurements of metabolic fluxes, diffusion distances and diffusion coefficients, coupled with reaction-diffusion mathematical models in a range of muscle types has started to reveal some general principles guiding muscle structure and metabolic function. Foremost among these is that metabolic processes in muscles do, in fact, appear to be largely reaction controlled and are not greatly limited by diffusion. However, the influence of diffusion is apparent in patterns of fiber growth and metabolic organization that appear to result from selective pressure to maintain reaction control of metabolism in muscle.
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Affiliation(s)
- Stephen T Kinsey
- Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403-5915, USA.
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159
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Carosio S, Berardinelli MG, Aucello M, Musarò A. Impact of ageing on muscle cell regeneration. Ageing Res Rev 2011; 10:35-42. [PMID: 19683075 DOI: 10.1016/j.arr.2009.08.001] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 08/04/2009] [Accepted: 08/06/2009] [Indexed: 11/29/2022]
Abstract
Skeletal muscle regeneration is a coordinate process in which several factors are sequentially activated to maintain and preserve muscle structure and function. The major role in the growth, remodeling and regeneration is played by satellite cells, a quiescent population of myogenic cells that reside between the basal lamina and plasmalemma and are rapidly activated in response to appropriate stimuli. However, in several muscle conditions, including aging, the capacity of skeletal muscle to sustain an efficient regenerative pathway is severely compromised. Nevertheless, if skeletal muscle possesses a stem cell compartment it is not clear why the muscle fails to regenerate under pathological conditions. Either the resident muscle stem cells are too rare or intrinsically incapable of repairing major damage, or perhaps the injured/pathological muscle is a prohibitive environment for stem cell activation and function. Although we lack definitive answers, recent experimental evidences suggest that the mere presence of endogenous stem cells may not be sufficient to guarantee muscle regeneration, and that the presence of appropriate stimuli and factors are necessary to provide a permissive environment that permits stem cell mediated muscle regeneration and repair. In this review we discuss the molecular basis of muscle regeneration and how aging impacts stem cell mediated muscle regeneration and repair.
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Affiliation(s)
- Silvia Carosio
- Institute Pasteur Cenci-Bolognetti, Department of Histology and Medical Embryology, IIM, Sapienza University of Rome, Via A. Scarpa, 14, Rome 00161, Italy
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160
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Verdijk LB, Snijders T, Beelen M, Savelberg HHCM, Meijer K, Kuipers H, Van Loon LJC. Characteristics of muscle fiber type are predictive of skeletal muscle mass and strength in elderly men. J Am Geriatr Soc 2010; 58:2069-75. [PMID: 21054286 DOI: 10.1111/j.1532-5415.2010.03150.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
OBJECTIVES To investigate the relationship between skeletal muscle fiber type-specific characteristics, circulating hormone concentrations, and skeletal muscle mass and strength in older men. DESIGN Cross-sectional analyses. SETTING University research center. PARTICIPANTS Forty-one community dwelling elderly men (≥ 65). MEASUREMENTS Leg strength (1-repetition maximum, 1RM) and whole-body and limb muscle mass were determined, and muscle fiber type composition, cross-sectional area (CSA), myonuclear content, and satellite cell (SC) content were assessed in skeletal muscle biopsy samples. In addition, blood samples were collected to determine serum testosterone, sex hormone-binding globulin, insulinlike growth factor (IGF)-1, and IGF binding protein-3 concentrations. RESULTS Muscle mass correlated with muscle strength (0.41 ≤ correlation coefficient (r) ≤ 0.72; P < .01). Muscle fiber CSA, myonuclear content, and SC content were significantly lower in type II than in type I muscle fibers. Myonuclear and SC content were positively correlated with muscle fiber CSA. Furthermore, greater muscle fiber CSA (type I and II) was associated with greater thigh muscle area and muscle strength (0.30 ≤ r ≤ 0.45; P < .05). Testosterone concentration was positively correlated with muscle mass and muscle fiber CSA. Regression analysis showed that SC content, myonuclear content, and testosterone concentration are predictive of muscle fiber CSA. Furthermore, muscle mass and type II muscle fiber CSA are predictive of muscle strength. CONCLUSION Skeletal muscle mass and strength in elderly men are positively correlated with muscle fiber type-specific CSA, myonuclear content, and SC content. These findings support the assumption that a decline in SC content plays an important role in age-related decline in muscle mass and strength.
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Affiliation(s)
- Lex B Verdijk
- Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, Maastricht, the Netherlands.
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161
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Shefer G, Rauner G, Yablonka-Reuveni Z, Benayahu D. Reduced satellite cell numbers and myogenic capacity in aging can be alleviated by endurance exercise. PLoS One 2010; 5:e13307. [PMID: 20967266 PMCID: PMC2953499 DOI: 10.1371/journal.pone.0013307] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 08/29/2010] [Indexed: 12/03/2022] Open
Abstract
Background Muscle regeneration depends on satellite cells, myogenic stem cells that reside on the myofiber surface. Reduced numbers and/or decreased myogenic aptitude of these cells may impede proper maintenance and contribute to the age-associated decline in muscle mass and repair capacity. Endurance exercise was shown to improve muscle performance; however, the direct impact on satellite cells in aging was not yet thoroughly determined. Here, we focused on characterizing the effect of moderate-intensity endurance exercise on satellite cell, as possible means to attenuate adverse effects of aging. Young and old rats of both genders underwent 13 weeks of treadmill-running or remained sedentary. Methodology Gastrocnemius muscles were assessed for the effect of age, gender and exercise on satellite-cell numbers and myogenic capacity. Satellite cells were identified in freshly isolated myofibers based on Pax7 immunostaining (i.e., ex-vivo). The capacity of individual myofiber-associated cells to produce myogenic progeny was determined in clonal assays (in-vitro). We show an age-associated decrease in satellite-cell numbers and in the percent of myogenic clones in old sedentary rats. Upon exercise, there was an increase in myofibers that contain higher numbers of satellite cells in both young and old rats, and an increase in the percent of myogenic clones derived from old rats. Changes at the satellite cell level in old rats were accompanied with positive effects on the lean-to-fat Gast muscle composition and on spontaneous locomotion levels. The significance of these data is that they suggest that the endurance exercise-mediated boost in both satellite numbers and myogenic properties may improve myofiber maintenance in aging.
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Affiliation(s)
- Gabi Shefer
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
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162
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Cristea A, Qaisar R, Edlund PK, Lindblad J, Bengtsson E, Larsson L. Effects of aging and gender on the spatial organization of nuclei in single human skeletal muscle cells. Aging Cell 2010; 9:685-97. [PMID: 20633000 DOI: 10.1111/j.1474-9726.2010.00594.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The skeletal muscle fibre is a syncitium where each myonucleus regulates the gene products in a finite volume of the cytoplasm, i.e., the myonuclear domain (MND). We analysed aging- and gender-related effects on myonuclei organization and the MND size in single muscle fibres from six young (21-31 years) and nine old men (72-96 years), and from six young (24-32 years) and nine old women (65-96 years), using a novel image analysis algorithm applied to confocal images. Muscle fibres were classified according to myosin heavy chain (MyHC) isoform expression. Our image analysis algorithm was effective in determining the spatial organization of myonuclei and the distribution of individual MNDs along the single fibre segments. Significant linear relations were observed between MND size and fibre size, irrespective age, gender and MyHC isoform expression. The spatial organization of individual myonuclei, calculated as the distribution of nearest neighbour distances in 3D, and MND size were affected in old age, but changes were dependent on MyHC isoform expression. In type I muscle fibres, average NN-values were lower and showed an increased variability in old age, reflecting an aggregation of myonuclei in old age. Average MND size did not change in old age, but there was an increased MND size variability. In type IIa fibres, average NN-values and MND sizes were lower in old age, reflecting the smaller size of these muscle fibres in old age. It is suggested that these changes have a significant impact on protein synthesis and degradation during the aging process.
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163
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The time course of myonuclear accretion during hypertrophy in young adult and older rat plantaris muscle. Ann Anat 2010; 193:56-63. [PMID: 20833519 DOI: 10.1016/j.aanat.2010.08.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 06/30/2010] [Accepted: 08/10/2010] [Indexed: 02/04/2023]
Abstract
To investigate whether accretion of myonuclei precedes or follows the increase in fibre cross-sectional area and whether this time course is affected by age, left plantaris muscle of 5- and 25-month-old male Wistar rats was overloaded by denervation of its synergists for 1, 2 or 4 weeks. Contralateral plantaris muscle served as control. Myonuclei were counted in haematoxylin-stained cross-sections. While hypertrophy (33% in young adult) became significant after 2 weeks overload (p<0.01), the myonuclear number was increased only at 4 weeks of overload (p<0.001). The time course and magnitude of hypertrophy were similar in young adult and older rats. Older muscles contained 26% more myonuclei per mm fibre length (p=0.001) and had a 10-fold larger proportion of central myonuclei (p<0.001) than young adult muscles. In conclusion, our data indicate that muscle fibre hypertrophy precedes the acquisition of new myonuclei and that the ability to develop hypertrophy is not attenuated or delayed in 25-month-old rat muscle.
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164
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Verma M, Asakura Y, Hirai H, Watanabe S, Tastad C, Fong GH, Ema M, Call JA, Lowe DA, Asakura A. Flt-1 haploinsufficiency ameliorates muscular dystrophy phenotype by developmentally increased vasculature in mdx mice. Hum Mol Genet 2010; 19:4145-59. [PMID: 20705734 DOI: 10.1093/hmg/ddq334] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disease caused by mutations in the gene coding for the protein dystrophin. Recent work demonstrates that dystrophin is also found in the vasculature and its absence results in vascular deficiency and abnormal blood flow. This induces a state of ischemia further aggravating the muscular dystrophy pathogenesis. For an effective form of therapy of DMD, both the muscle and the vasculature need to be addressed. To reveal the developmental relationship between muscular dystrophy and vasculature, mdx mice, an animal model for DMD, were crossed with Flt-1 gene knockout mice to create a model with increased vasculature. Flt-1 is a decoy receptor for vascular endothelial growth factor, and therefore both homozygous (Flt-1(-/-)) and heterozygous (Flt-1(+/-)) Flt-1 gene knockout mice display increased endothelial cell proliferation and vascular density during embryogenesis. Here, we show that Flt-1(+/-) and mdx:Flt-1(+/-) adult mice also display a developmentally increased vascular density in skeletal muscle compared with the wild-type and mdx mice, respectively. The mdx:Flt-1(+/-) mice show improved muscle histology compared with the mdx mice with decreased fibrosis, calcification and membrane permeability. Functionally, the mdx:Flt-1(+/-) mice have an increase in muscle blood flow and force production, compared with the mdx mice. Consequently, the mdx:utrophin(-/-):Flt-1(+/-) mice display improved muscle histology and significantly higher survival rates compared with the mdx:utrophin(-/-) mice, which show more severe muscle phenotypes than the mdx mice. These data suggest that increasing the vasculature in DMD may ameliorate the histological and functional phenotypes associated with this disease.
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Affiliation(s)
- Mayank Verma
- Stem Cell Institute, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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165
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Boldrin L, Muntoni F, Morgan JE. Are human and mouse satellite cells really the same? J Histochem Cytochem 2010; 58:941-55. [PMID: 20644208 DOI: 10.1369/jhc.2010.956201] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Satellite cells are quiescent cells located under the basal lamina of skeletal muscle fibers that contribute to muscle growth, maintenance, repair, and regeneration. Mouse satellite cells have been shown to be muscle stem cells that are able to regenerate muscle fibers and self-renew. As human skeletal muscle is also able to regenerate following injury, we assume that the human satellite cell is, like its murine equivalent, a muscle stem cell. In this review, we compare human and mouse satellite cells and highlight their similarities and differences. We discuss gaps in our knowledge of human satellite cells, compared with that of mouse satellite cells, and suggest ways in which we may advance studies on human satellite cells, particularly by finding new markers and attempting to re-create the human satellite cell niche in vitro.
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Affiliation(s)
- Luisa Boldrin
- Dubowitz Neuromuscular Centre, UCL Institute of Child Health, 30 Guilford Street, London WC1N1EH, United Kingdom.
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166
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Pre-mRNA processing is partially impaired in satellite cell nuclei from aged muscles. J Biomed Biotechnol 2010; 2010:410405. [PMID: 20490357 PMCID: PMC2872765 DOI: 10.1155/2010/410405] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Accepted: 02/03/2010] [Indexed: 01/25/2023] Open
Abstract
Satellite cells are responsible for the capacity of mature mammalian skeletal muscles to repair and maintain mass. During aging, skeletal muscle mass as well as the muscle strength and endurance progressively decrease, leading to a condition termed sarcopenia. The causes of sarcopenia are manifold and remain to be completely elucidated. One of them could be the remarkable decline in the efficiency of muscle regeneration; this has been associated with decreasing amounts of satellite cells, but also to alterations in their activation, proliferation, and/or differentiation. In this study, we investigated the satellite cell nuclei of biceps and quadriceps muscles from adult and old rats; morphometry and immunocytochemistry at light and electron microscopy have been combined to assess the organization of the nuclear RNP structural constituents involved in different steps of mRNA formation. We demonstrated that in satellite cells the RNA pathways undergo alterations during aging, possibly hampering their responsiveness to muscle damage.
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167
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Liu W, Wang Z, Chen Y. Effects of Monochromatic Light on Developmental Changes in Satellite Cell Population of Pectoral Muscle in Broilers During Early Posthatch Period. Anat Rec (Hoboken) 2010; 293:1315-24. [DOI: 10.1002/ar.21174] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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168
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Jang YC, Lustgarten MS, Liu Y, Muller FL, Bhattacharya A, Liang H, Salmon AB, Brooks SV, Larkin L, Hayworth CR, Richardson A, Van Remmen H. Increased superoxide in vivo accelerates age-associated muscle atrophy through mitochondrial dysfunction and neuromuscular junction degeneration. FASEB J 2010; 24:1376-90. [PMID: 20040516 PMCID: PMC2987499 DOI: 10.1096/fj.09-146308] [Citation(s) in RCA: 223] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 12/03/2009] [Indexed: 11/11/2022]
Abstract
Oxidative stress has been implicated in the etiology of age-related muscle loss (sarcopenia). However, the underlying mechanisms by which oxidative stress contributes to sarcopenia have not been thoroughly investigated. To directly examine the role of chronic oxidative stress in vivo, we used a mouse model that lacks the antioxidant enzyme CuZnSOD (Sod1). Sod1(-/-) mice are characterized by high levels of oxidative damage and an acceleration of sarcopenia. In the present study, we demonstrate that muscle atrophy in Sod1(-/-) mice is accompanied by a progressive decline in mitochondrial bioenergetic function and an elevation of mitochondrial generation of reactive oxygen species. In addition, Sod1(-/-) muscle exhibits a more rapid induction of mitochondrial-mediated apoptosis and loss of myonuclei. Furthermore, aged Sod1(-/-) mice show a striking increase in muscle mitochondrial content near the neuromuscular junctions (NMJs). Despite the increase in content, the function of mitochondria is significantly impaired, with increased denervated NMJs and fragmentation of acetylcholine receptors. As a consequence, contractile force in aged Sod1(-/-) muscles is greatly diminished. Collectively, we show that Sod1(-/-) mice display characteristics of normal aging muscle in an accelerated manner and propose that the superoxide-induced NMJ degeneration and mitochondrial dysfunction are potential mechanisms of sarcopenia.
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Affiliation(s)
- Youngmok C Jang
- Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78245, USA
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169
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Jimenez AG, Kinsey ST, Dillaman RM, Kapraun DF. Nuclear DNA content variation associated with muscle fiber hypertrophic growth in decapod crustaceans. Genome 2010; 53:161-71. [DOI: 10.1139/g09-095] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We tested the hypothesis that hypertrophic muscle growth in decapod crustaceans is associated with increases in both the number of nuclei per fiber and nuclear DNA content. The DNA-localizing fluorochrome DAPI (4′,6-diamidino-2-phenylindole) and chicken erythrocyte standards were used with static microspectrophotometry and image analysis to estimate nuclear DNA content in hemocytes and muscle fibers from eight decapod crustacean species: Farfantepenaeus aztecus , Palaemonetes pugio , Panulirus argus , Homarus americanus , Procambarus clarkii , Cambarus bartonii , Callinectes sapidus , and Menippe mercenaria . Mean diploid (2C) values in hemocytes ranged from 3.6 to 11.7 pg. Hemocyte 2C estimates were used to extrapolate ploidy level in the multinucleated skeletal muscle tissue of juvenile and adult animals. Across all species, mean muscle fiber diameters from adult animals were significantly larger than those in juveniles, and nuclear domains were greater in larger fibers. The number of nuclei per fiber increased with increasing fiber size, as hypothesized. Maximum nuclear DNA content per species in muscle ranged from 4C to 32C, consistent with endopolyploidy. Two patterns of body- and fiber-size-dependent shifts in ploidy were observed: four species had a significantly higher ploidy in the larger fibers of adults, while three species exhibited a significantly lower ploidy in adults than in juveniles. Thus, across species, there was no systematic relationship between nuclear domain size and nuclear DNA content.
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Affiliation(s)
- Ana Gabriela Jimenez
- Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403, USA
| | - Stephen T. Kinsey
- Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403, USA
| | - Richard M. Dillaman
- Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403, USA
| | - Donald F. Kapraun
- Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403, USA
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170
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Matheny RW, Nindl BC, Adamo ML. Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration. Endocrinology 2010; 151:865-75. [PMID: 20130113 PMCID: PMC2840678 DOI: 10.1210/en.2009-1217] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The discovery that IGF-I mRNAs encoding isoforms of the pro-IGF-I molecule are differentially regulated in response to mechanical stress in skeletal muscle has been the impetus for a number of studies designed to demonstrate that alternative splicing of IGF-I pre-mRNA involving exons 4, 5, and 6 gives rise to a unique peptide derived from pro-IGF-I that plays a novel role in myoblast proliferation. Research suggests that after injury to skeletal muscle, the IGF-IEb mRNA splice variant is up-regulated initially, followed by up-regulation of the IGF-IEa splice variant at later time points. Up-regulation of IGF-IEb mRNA correlates with markers of satellite cell and myoblast proliferation, whereas up-regulation of IGF-IEa mRNA is correlated with differentiation to mature myofibers. Due to the apparent role of IGF-IEb up-regulation in muscle remodeling, IGF-IEb mRNA was also named mechano-growth factor (MGF). A synthetically manufactured peptide (also termed MGF) corresponding to the 24 most C-terminal residues of IGF-IEb has been shown to promote cellular proliferation and survival. However, no analogous peptide product of the Igf1 gene has been identified in or isolated from cultured cells, their conditioned medium, or in vivo animal tissues or biological fluids. This review will discuss the relationship of the Igf1 gene to MGF and will differentiate actions of synthetic MGF from any known product of Igf1. Additionally, the role of MGF in satellite cell activation, aging, neuroprotection, and signaling will be discussed. A survey of outstanding questions relating to MGF will also be provided.
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Affiliation(s)
- Ronald W Matheny
- U.S. Army Research Institute of Environmental Medicine, Military Performance Division, 15 Kansas Street, Building 42, Natick, Massachusetts 01760, USA.
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171
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The depletion of skeletal muscle satellite cells with age is concomitant with reduced capacity of single progenitors to produce reserve progeny. Dev Biol 2010; 340:330-43. [PMID: 20079729 DOI: 10.1016/j.ydbio.2010.01.006] [Citation(s) in RCA: 164] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 01/06/2010] [Accepted: 01/07/2010] [Indexed: 01/26/2023]
Abstract
Satellite cells are myogenic progenitors that reside on the myofiber surface and support skeletal muscle repair. We used mice in which satellite cells were detected by GFP expression driven by nestin gene regulatory elements to define age-related changes in both numbers of satellite cells that occupy hindlimb myofibers and their individual performance. We demonstrate a reduction in satellite cells per myofiber with age that is more prominent in females compared to males. Satellite cell loss also persists with age in myostatin-null mice regardless of increased muscle mass. Immunofluorescent analysis of isolated myofibers from nestin-GFP/Myf5(nLacZ/+) mice reveals a decline with age in the number of satellite cells that express detectable levels of betagal. Nestin-GFP expression typically diminishes in primary cultures of satellite cells as myogenic progeny proliferate and differentiate, but GFP subsequently reappears in the Pax7(+) reserve population. Clonal analysis of sorted GFP(+) satellite cells from hindlimb muscles shows heterogeneity in the extent of cell density and myotube formation among colonies. Reserve cells emerge primarily within high-density colonies, and the number of clones that produce reserve cells is reduced with age. Thus, satellite cell depletion with age could be attributed to a reduced capacity to generate a reserve population.
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172
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Abstract
Sarcopenia reflects a progressive withdrawal of anabolism and an increased catabolism, along with a reduced muscle regeneration capacity. Muscle force and power decline more than muscle dimensions: older muscle is intrinsically weak. Sarcopenic obesity (SO) among the elderly corroborates to the loss of muscle mass increasing the risk of metabolic syndrome development. Recent studies on the musculoskeletal adaptations with ageing and key papers on the mechanisms of muscle wasting, its functional repercussions and on SO are included. Neuropathic, hormonal, immunological, nutritional and physical activity factors contribute to sarcopenia. Selective fast fibre atrophy, loss of motor units and an increase in hybrid fibres are typical findings of ageing. Satellite cell number decreases reducing muscle regeneration capacity. SO promotes further muscle wasting and increases risk of metabolic syndrome development. The proportion of fast to slow fibres seems maintained in old age. In elderly humans, nuclear domain is maintained constant. Basal protein synthesis and breakdown show little changes in old age. Instead, blunting of the anabolic response to feeding and exercise and of the antiproteolytic effect of insulin is observed. Further understanding of the mechanisms of sarcopenia requires disentangling of the effects of ageing alone from those of disuse and disease. The causes of the greater anabolic resistance to feeding and exercise of elderly women need elucidating. The enhancement of muscle regeneration via satellite cell activation via the MAPK/notch molecular pathways seems particularly promising.
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Affiliation(s)
- Marco V Narici
- Faculty of Science and Engineering, Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester, UK.
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173
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The impact of sarcopenia and exercise training on skeletal muscle satellite cells. Ageing Res Rev 2009; 8:328-38. [PMID: 19464390 DOI: 10.1016/j.arr.2009.05.003] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 05/04/2009] [Accepted: 05/13/2009] [Indexed: 12/22/2022]
Abstract
It has been well-established that the age-related loss of muscle mass and strength, or sarcopenia, impairs skeletal muscle function and reduces functional performance at a more advanced age. Skeletal muscle satellite cells (SC), as precursors of new myonuclei, have been suggested to be involved in the development of sarcopenia. In accordance with the type II muscle fiber atrophy observed in the elderly, recent studies report a concomitant fiber type specific reduction in SC content. Resistance type exercise interventions have proven effective to augment skeletal muscle mass and improve muscle function in the elderly. In accordance, recent work shows that resistance type exercise training can augment type II muscle fiber size and reverse the age-related decline in SC content. The latter is supported by an increase in SC activation and proliferation factors that generally appear following exercise training. Present findings strongly suggest that the skeletal muscle SC control myogenesis and have an important, but yet unresolved, function in the loss of muscle mass with aging. This review discusses the contribution of skeletal muscle SC in the age-related loss of muscle mass and the efficacy of exercise training as a means to attenuate and/or reverse this process.
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174
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Ljubicic V, Joseph AM, Adhihetty PJ, Huang JH, Saleem A, Uguccioni G, Hood DA. Molecular basis for an attenuated mitochondrial adaptive plasticity in aged skeletal muscle. Aging (Albany NY) 2009; 1:818-30. [PMID: 20157569 PMCID: PMC2815739 DOI: 10.18632/aging.100083] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 09/11/2009] [Indexed: 11/25/2022]
Abstract
Our intent was
to investigate the mechanisms driving the adaptive potential of
subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in young (6
mo) and senescent (36 mo) animals in response to a potent stimulus for
organelle biogenesis. We employed chronic electrical stimulation (10 Hz, 3
h/day, 7 days) to induce contractile activity of skeletal muscle in 6 and
36 mo F344XBN rats. Subsequent to chronic activity, acute stimulation (1
Hz, 5 min) in situ revealed greater fatigue resistance in both age groups.
However, the improvement in endurance was significantly greater in the
young, compared to the old animals. Chronic muscle use also augmented SS
and IMF mitochondrial volume to a greater extent in young muscle. The
molecular basis for the diminished organelle expansion in aged muscle was
due, in part, to the collective attenuation of the chronic
stimulation-evoked increase in regulatory proteins involved in mediating
mitochondrial protein import and biogenesis. Furthermore, adaptations in
mitochondrial function were also blunted in old animals. However, chronic
contractile activity evoked greater reductions in mitochondrially-mediated
proapoptotic signaling in aged muscle. Thus, mitochondrial plasticity is
retained in aged animals, however the magnitude of the changes are less
compared to young animals due to attenuated molecular processes regulating
organelle biogenesis.
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Affiliation(s)
- Vladimir Ljubicic
- School of Kinesiology and Health Science, York University, Toronto, Ontario, M3J 1P3, Canada
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175
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Brooks NE, Schuenke MD, Hikida RS. Ageing influences myonuclear domain size differently in fast and slow skeletal muscle of rats. Acta Physiol (Oxf) 2009; 197:55-63. [PMID: 19254285 DOI: 10.1111/j.1748-1716.2009.01983.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
AIM In multinucleated skeletal muscle, a myonuclear domain is the region of cytoplasm governed by one nucleus, and myofibres are mosaics of overlapping myonuclear domains. Association of ageing and myonuclear domain is important in the understanding of sarcopenia and with prevention or combating age-related muscle declines. This study examined the effects of age, fibre type and muscle on nucleo-cytoplasmic (N/C) relationships as reflecting myonuclear domain size. METHODS The N/C was compared in fibre types of soleus and plantaris muscles from young (n = 6) and ageing (n = 8) male Fisher 344 rats. RESULTS There were no significant differences in fibre type composition or cross-sectional area of the soleus across ages. The old soleus had significantly more myonuclei, resulting in a significantly smaller myonuclear domain size. The plantaris muscle showed a higher percentage of slow fibres in old compared with young fibres. There were no differences in the number of myonuclei or in myonuclear domain size between young and older animals. CONCLUSION We found muscle-specific differences in the effects of ageing on myonuclear domain, possibly as a result of reduced efficiency of the myonuclei in the slow muscles.
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Affiliation(s)
- Naomi E Brooks
- Department of Physiological Sciences, Stellenbosch University, Matieland, Stellenbosch, South Africa.
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176
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Augustin H, Partridge L. Invertebrate models of age-related muscle degeneration. Biochim Biophys Acta Gen Subj 2009; 1790:1084-94. [PMID: 19563864 DOI: 10.1016/j.bbagen.2009.06.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 06/12/2009] [Accepted: 06/20/2009] [Indexed: 12/26/2022]
Abstract
Functional and structural deterioration of muscles is an inevitable consequence of ageing in a wide variety of animal species. What underlies these changes is a complex network of interactions between the muscle-intrinsic and muscle-extrinsic factors, making it very difficult to distinguish between the cause and the consequence. Many of the genes, structures, and processes implicated in mammalian skeletal muscle ageing are preserved in invertebrate species Drosophila melanogaster and Caenorhabditis elegans. The absence in these organisms of mechanisms that promote muscle regeneration, and substantially different hormonal environment, warrant caution when extrapolating experimental data from studies conducted in invertebrates to mammalian species. The simplicity and accessibility of these models, however, offer ample opportunities for studying age-related myopathologies as well as investigating drugs and therapies to alleviate them.
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Affiliation(s)
- Hrvoje Augustin
- Institute of Healthy Ageing and GEE, University College London, London WC1E 6BT, UK
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177
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Peroxisome proliferator-activated receptor beta activation promotes myonuclear accretion in skeletal muscle of adult and aged mice. Pflugers Arch 2009; 458:901-13. [PMID: 19415321 PMCID: PMC2719750 DOI: 10.1007/s00424-009-0676-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 04/01/2009] [Accepted: 04/21/2009] [Indexed: 11/01/2022]
Abstract
We reported recently that peroxisome proliferator-activated receptor beta (PPARbeta) activation promotes a calcineurin-dependent exercise-like remodelling characterised by increased numbers of oxidative fibres and capillaries. As physical exercise also induces myonuclear accretion, we investigated whether PPARbeta activation alters myonuclear density. Transgenic muscle-specific PPARbeta over-expression induced 14% increase of myonuclear density. Pharmacological PPARbeta activation promoted rapid and massive myonuclear accretion (20% increase after 48 h), which is dependent upon calcineurin/nuclear factor of activated T cells signalling pathway. In vivo bromodeoxyuridine labelling and proliferating cell nuclear antigen immunodetection revealed that PPARbeta activation did not promote cell proliferation, suggesting that the PPARbeta-promoted myonuclear accretion involves fusion of pre-existing muscle precursor cells to myofibres rather than cell division. Finally, we showed that in skeletal muscle, ageing led to a down-regulation of PPARbeta accompanied by decrease of both oxidative fibre number and myonuclear density. PPARbeta pharmacological activation counteracts, at least in part, the ageing-driven muscle remodelling.
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178
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Relationship between protein and mitochondrial DNA oxidative injury and telomere length and muscle loss in healthy elderly subjects. Arch Gerontol Geriatr 2009; 48:335-9. [DOI: 10.1016/j.archger.2008.02.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 02/26/2008] [Accepted: 02/27/2008] [Indexed: 12/25/2022]
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179
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β-hydroxy-β-methylbutyrate (HMB) stimulates myogenic cell proliferation, differentiation and survival via the MAPK/ERK and PI3K/Akt pathways. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:755-63. [DOI: 10.1016/j.bbamcr.2008.12.017] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Revised: 12/18/2008] [Accepted: 12/22/2008] [Indexed: 11/18/2022]
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180
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Hardy KM, Dillaman RM, Locke BR, Kinsey ST. A skeletal muscle model of extreme hypertrophic growth reveals the influence of diffusion on cellular design. Am J Physiol Regul Integr Comp Physiol 2009; 296:R1855-67. [PMID: 19321701 DOI: 10.1152/ajpregu.00076.2009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Muscle fibers that power swimming in the blue crab Callinectes sapidus are <80 microm in diameter in juveniles but grow hypertrophically, exceeding 600 microm in adults. Therefore, intracellular diffusion distances become progressively greater as the animals grow and, in adults, vastly exceed those in most cells. This developmental trajectory makes C. sapidus an excellent model for characterization of the influence of diffusion on fiber structure. The anaerobic light fibers, which power burst swimming, undergo a prominent shift in organelle distribution with growth. Mitochondria, which require O2 and rely on the transport of small, rapidly diffusing metabolites, are evenly distributed throughout the small fibers of juveniles, but in the large fibers of adults they are located almost exclusively at the fiber periphery where O2 concentrations are high. Nuclei, which do not require O2, but rely on the transport of large, slow-moving macromolecules, have the inverse pattern: they are distributed peripherally in small fibers but are evenly distributed across the large fibers, thereby reducing diffusion path lengths for large macromolecules. The aerobic dark fibers, which power endurance swimming, have evolved an intricate network of cytoplasmically isolated, highly perfused subdivisions that create the short diffusion distances needed to meet the high aerobic ATP turnover demands of sustained contraction. However, fiber innervation patterns are the same in the dark and light fibers. Thus the dark fibers appear to have disparate functional units for metabolism (fiber subdivision) and contraction (entire fiber). Reaction-diffusion mathematical models demonstrate that diffusion would greatly constrain the rate of metabolic processes without these developmental changes in fiber structure.
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Affiliation(s)
- Kristin M Hardy
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403-5915, USA
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181
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Lagirand-Cantaloube J, Cornille K, Csibi A, Batonnet-Pichon S, Leibovitch MP, Leibovitch SA. Inhibition of atrogin-1/MAFbx mediated MyoD proteolysis prevents skeletal muscle atrophy in vivo. PLoS One 2009; 4:e4973. [PMID: 19319192 PMCID: PMC2656614 DOI: 10.1371/journal.pone.0004973] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 02/27/2009] [Indexed: 11/19/2022] Open
Abstract
Ubiquitin ligase Atrogin1/Muscle Atrophy F-box (MAFbx) up-regulation is required for skeletal muscle atrophy but substrates and function during the atrophic process are poorly known. The transcription factor MyoD controls myogenic stem cell function and differentiation, and seems necessary to maintain the differentiated phenotype of adult fast skeletal muscle fibres. We previously showed that MAFbx mediates MyoD proteolysis in vitro. Here we present evidence that MAFbx targets MyoD for degradation in several models of skeletal muscle atrophy. In cultured myotubes undergoing atrophy, MAFbx expression increases, leading to a cytoplasmic-nuclear shuttling of MAFbx and a selective suppression of MyoD. Conversely, transfection of myotubes with sh-RNA-mediated MAFbx gene silencing (shRNAi) inhibited MyoD proteolysis linked to atrophy. Furthermore, overexpression of a mutant MyoDK133R lacking MAFbx-mediated ubiquitination prevents atrophy of mouse primary myotubes and skeletal muscle fibres in vivo. Regarding the complex role of MyoD in adult skeletal muscle plasticity and homeostasis, its rapid suppression by MAFbx seems to be a major event leading to skeletal muscle wasting. Our results point out MyoD as the second MAFbx skeletal muscle target by which powerful therapies could be developed.
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Affiliation(s)
- Julie Lagirand-Cantaloube
- Laboratoire de Génomique Fonctionnelle et Myogenèse, UMR866 Différenciation Cellulaire et Croissance, INRA UM II, Campus INRA/SupAgro, Montpellier, France
| | - Karen Cornille
- Laboratoire de Génomique Fonctionnelle et Myogenèse, UMR866 Différenciation Cellulaire et Croissance, INRA UM II, Campus INRA/SupAgro, Montpellier, France
| | - Alfredo Csibi
- Laboratoire de Génomique Fonctionnelle et Myogenèse, UMR866 Différenciation Cellulaire et Croissance, INRA UM II, Campus INRA/SupAgro, Montpellier, France
| | | | - Marie Pierre Leibovitch
- Laboratoire de Génomique Fonctionnelle et Myogenèse, UMR866 Différenciation Cellulaire et Croissance, INRA UM II, Campus INRA/SupAgro, Montpellier, France
| | - Serge A. Leibovitch
- Laboratoire de Génomique Fonctionnelle et Myogenèse, UMR866 Différenciation Cellulaire et Croissance, INRA UM II, Campus INRA/SupAgro, Montpellier, France
- * E-mail:
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182
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Liu JX, Höglund AS, Karlsson P, Lindblad J, Qaisar R, Aare S, Bengtsson E, Larsson L. Myonuclear domain size and myosin isoform expression in muscle fibres from mammals representing a 100 000-fold difference in body size. Exp Physiol 2008; 94:117-29. [DOI: 10.1113/expphysiol.2008.043877] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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183
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Berardi E, Aulino P, Murfuni I, Toschi A, Padula F, Scicchitano BM, Coletti D, Adamo S. Skeletal muscle is enriched in hematopoietic stem cells and not inflammatory cells in cachectic mice. Neurol Res 2008; 30:160-9. [PMID: 18397608 DOI: 10.1179/174313208x281046] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVE Cachexia, a debilitating syndrome characterized by skeletal muscle wasting, is associated to many chronic diseases and diminishes the quality of life and survival of patients. Tumor-derived factors and proinflammatory cytokines, including TNF-alpha, IL-6 and IL-1 beta, mediate cachexia. In response to elevated cytokine levels, increased proteasome-mediated proteolysis and auto-phagocytosis result in muscle wasting. The histologic features of muscle cachexia are not fully elucidated. Therefore, we analysed alterations of different cell populations in cachectic muscle. METHODS By immunohistochemical and cytological approaches, we characterized changes in the abundance of cellular populations in the musculature of a murine model of cancer cachexia (C26-bearing mice). RESULTS Cachectic muscle displayed a decreased DNA content proportional to muscle mass wastage. A decrease in the number of nuclei occurred in the muscular but not in the stromal compartment. Cachectic muscle showed: mild modulation of myeloperoxidase activity, a neutrophil marker; reduction of macrophages in the endomysium; decrease in CD3(+) lymphocyte number. Conversely, a statistically significant enrichment in Sca-1(+) CD45(+) hematopoietic stem cells (HSCs) occurred in cachectic muscle. DISCUSSION The elevated levels of cytokines which characterize cachexia may represent a trigger for inflammatory cell activation. However, we find that in cachexia, inflammatory cells in muscle are not increased while muscle tissue nuclei decline. Our data suggest that the inflammatory cell-mediated stress is not an etiologic component of muscle wasting in cachexia. The relative increase in HSCs in cachectic skeletal muscle suggests an attempt to maintain muscle homeostasis by recruitment and/or activation of stem cells.
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Affiliation(s)
- Emanuele Berardi
- Department of Histology and Medical Embryology, Sapienza University of Rome, Interuniversity Institute of Myology, Via Scarpa, 14 00161 Rome, Italy
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184
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Abstract
Apoptosis results in DNA fragmentation and, subsequently, destruction of cells containing a single nucleus. Our hypothesis is that multinucleated cells such as muscle fibers can experience apoptotic-induced loss of single nuclei (nuclear apoptosis) without destruction of the entire fiber. The loss of nuclei likely contributes to atrophy and sarcopenia. Furthermore, increased chronic activity attenuates apoptotic signaling, which may reduce sarcopenia.
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185
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Bruusgaard JC, Gundersen K. In vivo time-lapse microscopy reveals no loss of murine myonuclei during weeks of muscle atrophy. J Clin Invest 2008; 118:1450-7. [PMID: 18317591 DOI: 10.1172/jci34022] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2007] [Accepted: 01/09/2008] [Indexed: 11/17/2022] Open
Abstract
Numerous studies have suggested that muscle atrophy is accompanied by apoptotic loss of myonuclei and therefore recovery would require replenishment by muscle stem cells. We used in vivo time-lapse microscopy to observe the loss and replenishment of myonuclei in murine muscle fibers following induced muscle atrophy. To our surprise, imaging of single fibers for up to 28 days did not support the concept of nuclear loss during atrophy. Muscles were inactivated by denervation, nerve impulse block, or mechanical unloading. Nuclei were stained in vivo either acutely by intracellular injection of fluorescent oligonucleotides or in time-lapse studies after transfection with a plasmid encoding GFP with a nuclear localization signal. We observed no loss of myonuclei in fast- or slow-twitch muscle fibers despite a greater than 50% reduction in fiber cross-sectional area. TUNEL labeling of fragmented DNA on histological sections revealed high levels of apoptotic nuclei in inactive muscles. However, when costained for laminin and dystrophin, virtually none of the TUNEL-positive nuclei could be classified as myonuclei; apoptosis was confined to stromal and satellite cells. We conclude that disuse atrophy is not a degenerative process, but is rather a change in the balance between protein synthesis and proteolysis in a permanent cell syncytium.
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Affiliation(s)
- Jo C Bruusgaard
- Department of Molecular Biosciences, University of Oslo, Oslo, Norway
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186
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Gundersen K, Bruusgaard JC. Nuclear domains during muscle atrophy: nuclei lost or paradigm lost? J Physiol 2008; 586:2675-81. [PMID: 18440990 DOI: 10.1113/jphysiol.2008.154369] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
According to the current paradigm, muscle nuclei serve a certain cytoplasmic domain. To preserve the domain size, it is believed that nuclei are injected from satellite cells fusing to fibres undergoing hypertrophy, and lost by apoptosis during atrophy. Based on single fibre observations in and ex vivo we suggest that nuclear domains are not as constant as is often indicated. Moreover, recent time lapse in vivo imaging of single fibres suggests that at least for the first few weeks, atrophy is not accompanied by any loss of nuclei. Apoptosis is abundant in muscle tissue during atrophy conditions, but in our opinion it has not been unequivocally demonstrated that such nuclei are myonuclei. As we see it, the preponderance of current evidence suggests that disuse atrophy is not accompanied by loss of nuclei, at least not for the first 2 months. Moreover, it has not been proven that myonuclear apoptosis does occur in permanent fibres undergoing atrophy; it seems more likely that it is confined to stromal cells and satellite cells. If muscle atrophy is not related to loss of nuclei, design of intervention therapies should focus on protein metabolism rather than regeneration from stem cells.
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Affiliation(s)
- Kristian Gundersen
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, N-0316 Oslo, Norway.
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187
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Age-related reductions in expression of serum response factor and myocardin-related transcription factor A in mouse skeletal muscles. Biochim Biophys Acta Mol Basis Dis 2008; 1782:453-61. [PMID: 18442487 DOI: 10.1016/j.bbadis.2008.03.008] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 03/27/2008] [Accepted: 03/28/2008] [Indexed: 11/29/2022]
Abstract
The molecular signaling pathways linking the atrophy of skeletal muscle during aging have not been identified. Using reverse transcription (RT)-PCR, Western blotting, and immunofluorescence microscopy, we investigated whether the amounts of RhoA, RhoGDI, SRF, MRTF-A, and MyoD in the triceps brachii and quadriceps muscles change with aging in mice. Young adult (3 mo) and aged (24 mo) C57BL/6J mice were used. Senescent mice possessed many fibers with central nuclei in the quadriceps muscle. Western blotting using a homogenate of whole muscle or the cytosolic fraction clearly showed that the amount of SRF protein was significantly decreased in the aged skeletal muscles. Immunofluorescence labeling indicated more SRF-positive muscle fibers in young mice. Both young and old mice possessed SRF immunoreactivity in some satellite cells expressing Pax7. MRTF-A and STARS mRNA levels significantly declined with aging in the triceps brachii and quadriceps muscles. The amount of MRTF-A protein was markedly reduced in the nuclear fraction of aged muscle of mice. The amounts of RhoA and RhoGDI in the crude homogenate or the cytosolic and membrane fractions were greater in the aged muscle. Senescent mice possessed significantly higher levels of MyoD protein in the cytosol and nucleus. Decreased SRF and MRTF expression may induce the atrophy of skeletal muscle with aging.
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188
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Wada KI, Katsuta S, Soya H. Formation process and fate of the nuclear chain after injury in regenerated myofiber. Anat Rec (Hoboken) 2008; 291:122-8. [PMID: 18085626 DOI: 10.1002/ar.20626] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Although it is well known that regenerated myofibers contain nuclear chains (arrayed nuclear clusters), details of its process of formation and fate are still remained unclear. In the present study, we isolated single myofibers from injured ICR mouse tibialis anterior muscles by the alkali maceration-based method, and carried out histological observation and bromodeoxyuridine (BrdU) pulse-chase analysis on the nuclear chains. The nuclear chains were formed after injury and remained stable for at least 6 months after injury. When BrdU was administered during the first 4 days after injury, up to 56% of nuclei in the nuclear chains were labeled with BrdU, whereas when BrdU was administered 5 days or later after injury, less than 3% of myonuclei were labeled with BrdU. Among BrdU-positive nuclei in the nuclear chains, the nuclei showing attenuated and strong BrdU signal were dominant when BrdU was administered at the time points of 0-2 and 3-4 days after injury, respectively. These results suggest that successive nuclear divisions occur during the first 4 days after injury and might be involved in the appearance of the stable nuclear chains in regenerated myofibers.
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Affiliation(s)
- Ken-Ichi Wada
- Cell-Sensing Group, Biomaterials Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan.
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189
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Cellular and molecular mechanisms underlying age-related skeletal muscle wasting and weakness. Biogerontology 2008; 9:213-28. [PMID: 18299960 DOI: 10.1007/s10522-008-9131-0] [Citation(s) in RCA: 277] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2007] [Accepted: 02/06/2008] [Indexed: 01/02/2023]
Abstract
Some of the most serious consequences of ageing are its effects on skeletal muscle. The term 'sarcopenia' describes the slow but progressive loss of muscle mass with advancing age and is characterised by a deterioration of muscle quantity and quality leading to a gradual slowing of movement and a decline in strength. The loss of muscle mass and strength is thought to be attributed to the progressive atrophy and loss of individual muscle fibres associated with the loss of motor units, and a concomitant reduction in muscle 'quality' due to the infiltration of fat and other non-contractile material. These age-related changes in skeletal muscle can be largely attributed to the complex interaction of factors affecting neuromuscular transmission, muscle architecture, fibre composition, excitation-contraction coupling, and metabolism. Given the magnitude of the growing public health problems associated with sarcopenia, there is considerable interest in the development and evaluation of therapeutic strategies to attenuate, prevent, or ultimately reverse age-related muscle wasting and weakness. The aim is to review our current understanding of some of the cellular and molecular mechanisms responsible for age-related changes in skeletal muscle.
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190
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Brack AS, Rando TA. Intrinsic changes and extrinsic influences of myogenic stem cell function during aging. ACTA ACUST UNITED AC 2008; 3:226-37. [PMID: 17917136 DOI: 10.1007/s12015-007-9000-2] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 12/29/2022]
Abstract
The myogenic stem cell (satellite cell) is almost solely responsible for the remarkable regeneration of adult skeletal muscle fibers after injury. The availability and the functionality of satellite cells are the determinants of efficient muscle regeneration. During aging, the efficiency of muscle regeneration declines, suggesting that the functionality of satellite cells and their progeny may be altered. Satellite cells do not sit in isolation but rather are surrounded by, and influenced by, many extrinsic factors within the muscle tissue that can alter their functionality. These factors likely change during aging and impart both reversible and irreversible changes to the satellite cells and on their proliferating progeny. In this review, we discuss the possible mechanisms of impaired muscle regeneration with respect to the biology of satellite cells. Future studies that enhance our understanding of the interactions between stem cells and the environment in which they reside will offer promise for therapeutic applications in age-related diseases.
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Affiliation(s)
- Andrew S Brack
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305-5235, USA
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191
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Favier FB, Benoit H, Freyssenet D. Cellular and molecular events controlling skeletal muscle mass in response to altered use. Pflugers Arch 2008; 456:587-600. [DOI: 10.1007/s00424-007-0423-z] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Accepted: 12/06/2007] [Indexed: 12/21/2022]
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192
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Abstract
Adult stem cells have become the focus of intense research in recent years as a result of their role in the maintenance and repair of tissues. They exert this function through their extensive expansion (self-renewal) and multipotent differentiation capacity. Understanding whether adult stem cells retain this capacity throughout the lifespan of the individual, or undergo a process of ageing resulting in a decreased stem cell pool, is an important area of investigation. Progress in this area has been hampered by lack of suitable models and of appropriate markers and assays to identify stem cells. However, recent data suggest that an understanding of the mechanisms governing stem cell ageing can give insight into the mechanism of tissue ageing and, most importantly, advance our ability to use stem cells in cell and gene therapy strategies.
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193
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Hammond CL, Simbi BH, Stickland NC. In ovo temperature manipulation influences embryonic motility and growth of limb tissues in the chick (Gallus gallus). ACTA ACUST UNITED AC 2007; 210:2667-75. [PMID: 17644681 DOI: 10.1242/jeb.005751] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The chick embryo, developing in the egg, is an ideal system in which to investigate the effects of incubation environment on the development of the embryo. We show that raising the temperature of the eggs by just one degree, from 37.5 degrees C to 38.5 degrees C, during embryonic days (ED) 4-7 causes profound changes in development. We demonstrate that embryonic movement is significantly increased in the chicks raised at 38.5 degrees C both during the period in which they are at the higher temperature but also 4 days after their return to the control temperature. Concomitant with this increase in embryonic activity, the embryos raised at higher temperature grow to significantly heavier weights and exhibit significantly longer leg bones (tibia and tarsus) than the controls from ED12 onwards, although mineralization occurs normally. Additionally, the number of leg myonuclei is increased from ED12 in the embryos raised at the higher temperature. This is likely to promote greater leg muscle growth later in development, which may provide postural stability to the chicks posthatch. These changes are similar to those seen when drugs are injected to increase embryonic activity. We therefore believe that the increased embryonic activity provides a mechanism that can explain the increased growth of leg muscle and bone seen when the eggs are incubated for 3 days at higher temperature.
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Affiliation(s)
- Christina L Hammond
- Department of Veterinary Basic Sciences, The Royal Veterinary College, Royal College Street, London, NW1 0TU, UK.
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194
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Pruitt SC, Bailey KJ, Freeland A. Reduced Mcm2 expression results in severe stem/progenitor cell deficiency and cancer. Stem Cells 2007; 25:3121-32. [PMID: 17717065 DOI: 10.1634/stemcells.2007-0483] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mcm2 is a component of the DNA replication licensing complex that marks DNA replication origins during G1 of the cell cycle for use in the subsequent S-phase. It is expressed in stem/progenitor cells in a variety of regenerative tissues in mammals. Here, we have used the Mcm2 gene to develop a transgenic mouse in which somatic stem/progenitor cells can be genetically modified in the adult. In these mice, a tamoxifen-inducible form of Cre recombinase is integrated 3' to the Mcm2 coding sequence and expressed via an internal ribosome entry site (IRES). Heterozygous Mcm2(IRES-CreERT2/wild-type (wt)) mice are phenotypically indistinguishable from wild-type at least through 1 year of age. In bigenic Mcm2(IRES-CreERT2/wt); Z/EG reporter mice, tamoxifen-dependent enhanced green fluorescence protein expression is inducible in a wide variety of somatic stem cells and their progeny. However, in Mcm2(IRES-CreERT2/IRES-CreERT2) homozygous embryos or mouse embryonic fibroblasts, Mcm2 is reduced to approximately one-third of wild-type levels. Despite the fact that these mice develop normally and are asymptomatic as young adults, life span is greatly reduced, with most surviving to only approximately 10-12 weeks of age. They demonstrate severe deficiencies in the proliferative cell compartments of a variety of tissues, including the subventricular zone of the brain, muscle, and intestinal crypts. However, the immediate cause of death in most of these animals is cancer, where the majority develop lymphomas. These studies directly demonstrate that deficiencies in the function of the core DNA replication machinery that are compatible with development and survival nonetheless result in a chronic phenotype leading to stem cell deficiency in multiple tissues and cancer. Disclosure of potential conflicts of interest is found at the end of this article.
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Affiliation(s)
- Steven C Pruitt
- Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York 14263, USA.
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195
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Gonzalez JM, Carter JN, Johnson DD, Ouellette SE, Johnson SE. Effect of ractopamine-hydrochloride and trenbolone acetate on longissimus muscle fiber area, diameter, and satellite cell numbers in cull beef cows1. J Anim Sci 2007; 85:1893-901. [PMID: 17468415 DOI: 10.2527/jas.2006-624] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The objective of this study was to evaluate the effects of coadministration of ractopamine-HCl (RAC) and trenbolone acetate plus estradiol (TBA) on LM fiber cross-sectional area (CSA), diameter, fiber-associated myonuclei, and satellite cell number. Culled crossbred beef cows (n = 98; 11 +/- 1.8 yr old; BCS 4.3 +/- 0.03) from a single ranch in south Florida were fed a concentrate diet for 92 d in a 2 x 2, randomized block design. Cows were blocked by BW on arrival into light (initial BW = 369.75 +/- 2.68 kg and end BW = 501.96 +/- 6.90 kg) and heavy (initial BW = 418.31 +/- 2.75 kg and end BW = 522.15 +/- 7.09 kg) groups before assignment to treatment. Factors included dietary treatment (0 or 15 ppm) and implant status (0 or 80 mg of trenbolone acetate + 16 mg of estradiol). Ractopamine was provided in the diet to 2 pens or half the treatments during the final 35 d of feeding. Cows were slaughtered on d 92. Forty-eight hours postmortem, the 6th-rib portions of the LM were obtained from 10 randomly selected carcasses from each treatment group (n = 40). Cryosections (12 mum) were immunostained for dystrophin and myosin heavy chain I or II for the measurement of fiber CSA and type, respectively. Fiber-associated nuclei and satellite cell numbers were measured in serial cryosections. There was a RAC x TBA interaction (P < 0.05). Type I fiber CSA and diameter were increased (P < 0.05) by TBA and RAC. Type I CSA and diameter were larger (P < 0.05) in TBA + RAC than RAC only. Type II fiber CSA and diameter were not affected by TBA (P = 0.48), RAC (P = 0.15), or TBA + RAC (P = 0.60). Satellite cell numbers and fiber-associated nuclei were not affected (P > 0.05) by implant status or ractopamine supplementation. These results indicate that TBA and RAC preferentially increase the size of type I fibers in cull cows.
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Affiliation(s)
- J M Gonzalez
- Department of Animal Sciences, University of Florida, Gainesville 32611, USA
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196
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Abstract
Satellite cells are small, mononuclear cells found in close association with striated skeletal muscles cells (myofibers). These cells appear to function as reserve myoblasts. A critical role for these cells in the process of muscle regeneration following injury has been clearly established. In that role, satellite cells have been shown to proliferate extensively. Some of the progeny of these cells then fuse with each other to form replacement myofibers, whereas others return to quiescence, thereby maintaining this reserve population. In response to injury, activated satellite cells can also fuse with damaged but viable myofibers to promote repair and regeneration. It has also been observed that satellite cells are activated during periods of significantly increased muscle loading and that some of these cells fuse with apparently undamaged myofibers as part of the hypertrophy process. The observation that the inactivation of satellite cell proliferation prevents most of the hypertrophy response to chronic increases in loading has lead to the hypothesis that a limitation to the expansion of myofiber size is imposed by the number of myonuclei present. Recent evidence suggests that a potential limitation to muscle hypertrophy, in the absence of a reserve supply of myonuclei, may be the inability to sustain increases in ribosomes, thereby limiting translational capacity.
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Affiliation(s)
- Gregory R Adams
- Department of Physiology and Biophysics, Medical Science I D335, University of California, Irvine, CA 92697, USA.
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197
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Collins CA, Zammit PS, Ruiz AP, Morgan JE, Partridge TA. A population of myogenic stem cells that survives skeletal muscle aging. Stem Cells 2007; 25:885-94. [PMID: 17218401 DOI: 10.1634/stemcells.2006-0372] [Citation(s) in RCA: 211] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Age-related decline in integrity and function of differentiated adult tissues is widely attributed to reduction in number or regenerative potential of resident stem cells. The satellite cell, resident beneath the basal lamina of skeletal muscle myofibers, is the principal myogenic stem cell. Here we have explored the capacity of satellite cells within aged mouse muscle to regenerate skeletal muscle and to self-renew using isolated myofibers in tissue culture and in vivo. Satellite cells expressing Pax7 were depleted from aged muscles, and when aged myofibers were placed in culture, satellite cell myogenic progression resulted in apoptosis and fewer total differentiated progeny. However, a minority of cultured aged satellite cells generated large clusters of progeny containing both differentiated cells and new cells of a quiescent satellite-cell-like phenotype characteristic of self-renewal. Parallel in vivo engraftment assays showed that, despite the reduction in Pax7(+) cells, the satellite cell population associated with individual aged myofibers could regenerate muscle and self-renew as effectively as the larger population of satellite cells associated with young myofibers. We conclude that a minority of satellite cells is responsible for adult muscle regeneration, and that these stem cells survive the effects of aging to retain their intrinsic potential throughout life. Thus, the effectiveness of stem-cell-mediated muscle regeneration is determined by both extrinsic environmental influences and diversity in intrinsic potential of the stem cells themselves.
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Affiliation(s)
- Charlotte A Collins
- The Dubowitz Neuromuscular Unit, Department of Paediatrics, Imperial College London, Hammersmith Hospital, London, U.K
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198
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Verdijk LB, Koopman R, Schaart G, Meijer K, Savelberg HHCM, van Loon LJC. Satellite cell content is specifically reduced in type II skeletal muscle fibers in the elderly. Am J Physiol Endocrinol Metab 2007; 292:E151-7. [PMID: 16926381 DOI: 10.1152/ajpendo.00278.2006] [Citation(s) in RCA: 334] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Satellite cells (SC) are essential for skeletal muscle growth and repair. Because sarcopenia is associated with type II muscle fiber atrophy, we hypothesized that SC content is specifically reduced in the type II fibers in the elderly. A total of eight elderly (E; 76 +/- 1 yr) and eight young (Y; 20 +/- 1 yr) healthy males were selected. Muscle biopsies were collected from the vastus lateralis in both legs. ATPase staining and a pax7-antibody were used to determine fiber type-specific SC content (i.e., pax7-positive SC) on serial muscle cross sections. In contrast to the type I fibers, the proportion and mean cross-sectional area of the type II fibers were substantially reduced in E vs. Y. The number of SC per type I fiber was similar in E and Y. However, the number of SC per type II fiber was substantially lower in E vs. Y (0.044 +/- 0.003 vs. 0.080 +/- 0.007; P < 0.01). In addition, in the type II fibers, the number of SC relative to the total number of nuclei and the number of SC per fiber area were also significantly lower in E. This study is the first to show type II fiber atrophy in the elderly to be associated with a fiber type-specific decline in SC content. The latter is evident when SC content is expressed per fiber or per fiber area. The decline in SC content might be an important factor in the etiology of type II muscle fiber atrophy, which accompanies the loss of skeletal muscle with aging.
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Affiliation(s)
- Lex B Verdijk
- Dept. of Movement Sciences, Faculty of Health Sciences, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands.
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199
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Baker DJ, Hepple RT. Elevated caspase and AIF gene expression correlate with progression of sarcopenia during aging in male F344BN rats. Exp Gerontol 2006; 41:1149-56. [PMID: 17029665 DOI: 10.1016/j.exger.2006.08.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2006] [Revised: 08/02/2006] [Accepted: 08/04/2006] [Indexed: 11/17/2022]
Abstract
To establish the relationship between the progression of sarcopenia and apoptosis we examined apoptotic gene expression in plantaris muscles (Pl) from 8 mo old (n=8), 30 mo old (n=8) and 35 mo old (n=6) male rats by real-time PCR. Pl mass declined from 368 +/- 7 mg at 8 mo to 333 +/- 7 mg at 30 mo (P<0.05) and 210 +/- 15 mg at 35 mo of age (P<0.05). BAX, Bcl-2, and Apaf-1 expression decreased by 62-74% at 30 mo and by 90-96% at 35 mo of age (all P<0.05 vs 8 mo old). In contrast, the expression of Caspases 3, 8, and 9 and AIF increased 3- to 5-fold at 30 mo (NS) and 7- to 50-fold at 35 mo of age (P<0.05). There were significant (P<0.05) correlations between Pl mass and Caspase 3 (r(2)=-0.60), Caspase 9 (r(2)=-0.58), Caspase 8 (r(2)=-0.50), and AIF (r(2)=-0.48). Thus, our results show that the expression of some genes involved in apoptosis increase with aging in Pl and correlate with progression of sarcopenia (Caspase 3, Caspase 9, Caspase 8, and AIF), whereas others decline with aging (BAX, Bcl-2, and Apaf-1).
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Affiliation(s)
- David J Baker
- University of Calgary, Calgary, Alta., Canada T2N 1N4
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200
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Abstract
Cardiovascular disease is a major public health challenge in the western world. Mortality of acute events has improved, but more patients develop HF--a condition affecting up to 22 million people worldwide. Cell transplantation is the first therapy to attempt replacement of lost cardiomyocytes and vasculature to restore lost contractile function. Since the first reported functional repair after injection of autologous skeletal myoblasts into the injured heart in 1998, a variety of cell types have been proposed for transplantation in different stages of cardiovascular disease. Fifteen years of preclinical research and the rapid move into clinical studies have left us with promising results and a better understanding of cells as a potential clinical tool. Cell-based cardiac repair has been the first step, but cardiac regeneration remains the more ambitious goal. Promising new cell types and the rapidly evolving concept of adult stem and progenitor cell fate may enable us to move towards regenerating viable and functional myocardium. Meeting a multidisciplinary consensus will be required to translate these findings into safe and applicable clinical tools.
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Affiliation(s)
- Harald C Ott
- Massachusetts General Hospital, Department of Surgery, Boston, MA, USA
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