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Thomas NT, Confides AL, Fry CS, Dupont-Versteegden EE. Satellite cell depletion does not affect diaphragm adaptations to hypoxia. J Appl Physiol (1985) 2022; 133:637-646. [PMID: 35861521 PMCID: PMC9448290 DOI: 10.1152/japplphysiol.00083.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 07/01/2022] [Accepted: 07/13/2022] [Indexed: 01/25/2023] Open
Abstract
The diaphragm is the main skeletal muscle responsible for inspiration and is susceptible to age-associated decline in function and morphology. Satellite cells in diaphragm fuse into unperturbed muscle fibers throughout life, yet their role in adaptations to hypoxia in diaphragm is unknown. Given their continual fusion, we hypothesize that satellite cell depletion will negatively impact adaptations to hypoxia in the diaphragm, particularly with aging. We used the Pax7CreER/CreER:R26RDTA/DTA genetic mouse model of inducible satellite cell depletion to investigate diaphragm responses to hypoxia in adult (6 mo) and aged (22 mo) male mice. The mice were subjected to normobaric hypoxia at 10% [Formula: see text] or normoxia for 4 wk. We showed that satellite cell depletion had no effect on diaphragm muscle fiber cross-sectional area, fiber-type distribution, myonuclear density, or regulation of extracellular matrix in either adult or aged mice. Furthermore, we showed lower muscle fiber cross-sectional area with hypoxia and age (main effects), while extracellular matrix content was higher and satellite cell abundance was lower with age (main effect) in diaphragm. Lastly, a greater number of Pax3-mRNA+ cells was observed in diaphragm muscle of satellite cell-depleted mice independent of hypoxia (main effect), potentially as a compensatory mechanism for the loss of satellite cells. We conclude that satellite cells are not required for diaphragm muscle adaptations to hypoxia in either adult or aged mice.NEW & NOTEWORTHY Satellite cells show consistent fusion into diaphragm muscle fibers throughout life, suggesting a critical role in maintaining homeostasis. Here, we report identical diaphragm adaptations to hypoxia with and without satellite cells in adult and aged mice. In addition, we propose that the higher number of Pax3-positive cells in satellite cell-depleted diaphragm muscle acts as a compensatory mechanism.
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Affiliation(s)
- Nicholas T Thomas
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, Kentucky
| | - Amy L Confides
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Department of Physical Therapy, University of Kentucky, Lexington, Kentucky
| | - Christopher S Fry
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, Kentucky
| | - Esther E Dupont-Versteegden
- Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
- Department of Physical Therapy, University of Kentucky, Lexington, Kentucky
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2
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Mortreux M, Rosa‐Caldwell ME, Stiehl ID, Sung D, Thomas NT, Fry CS, Rutkove SB. Hindlimb suspension in Wistar rats: Sex-based differences in muscle response. Physiol Rep 2021; 9:e15042. [PMID: 34612585 PMCID: PMC8493566 DOI: 10.14814/phy2.15042] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 08/27/2021] [Accepted: 08/27/2021] [Indexed: 12/16/2022] Open
Abstract
Ground-based animal models have been used extensively to understand the effects of microgravity on various physiological systems. Among them, hindlimb suspension (HLS), developed in 1979 in rats, remains the gold-standard and allows researchers to study the consequences of total unloading of the hind limbs while inducing a cephalic fluid shift. While this model has already brought valuable insights to space biology, few studies have directly compared functional decrements in the muscles of males and females during HLS. We exposed 28 adult Wistar rats (14 males and 14 females) to 14 days of HLS or normal loading (NL) to better assess how sex impacts disuse-induced muscle deconditioning. Females better maintained muscle function during HLS than males, as shown by a more moderate reduction in grip strength at 7 days (males: -37.5 ± 3.1%, females: -22.4 ± 6.5%, compared to baseline), that remains stable during the second week of unloading (males: -53.3 ± 5.7%, females: -22.4 ± 5.5%, compared to day 0) while the males exhibit a steady decrease over time (effect of sex × loading p = 0.0002, effect of sex × time × loading p = 0.0099). This was further supported by analyzing the force production in response to a tetanic stimulus. Further functional analyses using force production were also shown to correspond to sex differences in relative loss of muscle mass and CSA. Moreover, our functional data were supported by histomorphometric analyzes, and we highlighted differences in relative muscle loss and CSA. Specifically, female rats seem to experience a lesser muscle deconditioning during disuse than males thus emphasizing the need for more studies that will assess male and female animals concomitantly to develop tailored, effective countermeasures for all astronauts.
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Affiliation(s)
- Marie Mortreux
- Department of NeurologyHarvard Medical School – Beth Israel Deaconess Medical CenterBostonMassachusettsUSA
| | - Megan E. Rosa‐Caldwell
- Department of NeurologyHarvard Medical School – Beth Israel Deaconess Medical CenterBostonMassachusettsUSA
| | - Ian D. Stiehl
- Department of NeurologyHarvard Medical School – Beth Israel Deaconess Medical CenterBostonMassachusettsUSA
- Department of Physics and AstronomyDartmouth CollegeHanoverNew HampshireUSA
| | - Dong‐Min Sung
- Department of NeurologyHarvard Medical School – Beth Israel Deaconess Medical CenterBostonMassachusettsUSA
| | - Nicholas T. Thomas
- Department of Athletic Training and Clinical NutritionUniversity of KentuckyLexingtonKentuckyUSA
| | - Christopher S. Fry
- Department of Athletic Training and Clinical NutritionUniversity of KentuckyLexingtonKentuckyUSA
| | - Seward B. Rutkove
- Department of NeurologyHarvard Medical School – Beth Israel Deaconess Medical CenterBostonMassachusettsUSA
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3
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Song R, Zhao S, Xu Y, Hu J, Ke S, Li F, Tian G, Zheng X, Li J, Gu L, Xu Y. MRTF-A regulates myoblast commitment to differentiation by targeting PAX7 during muscle regeneration. J Cell Mol Med 2021; 25:8645-8661. [PMID: 34347392 PMCID: PMC8435411 DOI: 10.1111/jcmm.16820] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Revised: 07/11/2021] [Accepted: 07/13/2021] [Indexed: 12/14/2022] Open
Abstract
Myocardin-related transcription factor-A/serum response factor (MRTF-A/SRF), a well-known transcriptional programme, has been proposed to play crucial roles in skeletal muscle development and function. However, whether MRTF-A participates in muscle regeneration and the molecular mechanisms are not completely understood. Here, we show that MRTF-A levels are highly correlated with myogenic genes using a RNA-seq assay, which reveal that MRTF-A knockdown in C2C12 cells significantly reduces PAX7 expression. Subsequent in vitro and in vivo data show that MRTF-A and PAX7 present identical expression patterns during myoblast differentiation and CTX-induced muscle injury and repair. Remarkably, MRTF-A overexpression promotes myoblast proliferation, while inhibiting cell differentiation and the expression of MyoD and MyoG. MRTF-A loss of function produces the opposite effect. Moreover, mice with lentivirus (MRTF-A) injection possesses more PAX7+ satellite cells, but less differentiating MyoD+ and MyoG+ cells, leading subsequently to diminished muscle regeneration. Our mechanistic results reveal that MRTF-A contributes to PAX7-mediated myoblast self-renewal, proliferation, and differentiation by binding to its distal CArG box. Overall, we propose that MRTF-A functions as a novel PAX7 regulator upon myoblast commitment to differentiation, which could provide pathways for dictating muscle stem cell fate and open new avenues to explore stem cell-based therapy for muscle degenerative diseases.
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Affiliation(s)
- Ruhui Song
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Shengnan Zhao
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Yue Xu
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Jian Hu
- Animal Disease Control and Prevention Centre of Chongqing City, Chongqing, 401120, China
| | - Shuangao Ke
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Fan Li
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Gaohui Tian
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Xiao Zheng
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Jiajun Li
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Lixing Gu
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
| | - Yao Xu
- Institute of Biology and Medicine, College of Life Science and Health, Wuhan University of Science and Technology, Wuhan, Hubei, 430081, China
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4
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Knuth CM, Auger C, Jeschke MG. Burn-induced hypermetabolism and skeletal muscle dysfunction. Am J Physiol Cell Physiol 2021; 321:C58-C71. [PMID: 33909503 DOI: 10.1152/ajpcell.00106.2021] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Critical illnesses, including sepsis, cancer cachexia, and burn injury, invoke a milieu of systemic metabolic and inflammatory derangements that ultimately results in increased energy expenditure leading to fat and lean mass catabolism. Burn injuries present a unique clinical challenge given the magnitude and duration of the hypermetabolic response compared with other forms of critical illness, which drastically increase the risk of morbidity and mortality. Skeletal muscle metabolism is particularly altered as a consequence of burn-induced hypermetabolism, as it primarily provides a main source of fuel in support of wound healing. Interestingly, muscle catabolism is sustained long after the wound has healed, indicating that additional mechanisms beyond wound healing are involved. In this review, we discuss the distinctive pathophysiological response to burn injury with a focus on skeletal muscle function and metabolism. We first examine the diverse consequences on skeletal muscle dysfunction between thermal, electrical, and chemical burns. We then provide a comprehensive overview of the known mechanisms underlying skeletal muscle dysfunction that may be attributed to hypermetabolism. Finally, we review the most promising current treatment options to mitigate muscle catabolism, and by extension improve morbidity and mortality, and end with future directions that have the potential to significantly improve patient care.
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Affiliation(s)
- Carly M Knuth
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Christopher Auger
- Department of Biological Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Marc G Jeschke
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada.,Department of Immunology, University of Toronto, Toronto, Ontario, Canada.,Ross Tilley Burn Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
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5
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Ahmad A, Druzhyna N, Szabo C. Effect of 3-mercaptopyruvate Sulfurtransferase Deficiency on the Development of Multiorgan Failure, Inflammation, and Wound Healing in Mice Subjected to Burn Injury. J Burn Care Res 2020; 40:148-156. [PMID: 30649358 DOI: 10.1093/jbcr/irz007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The gaseous transmitter hydrogen sulfide (H2S) has been implicated in various forms of critical illness. Here, we have compared the outcome of scald burn injury in wild-type mice and in mice deficient in 3-mercaptopyruvate sulfurtransferase (3-MST), a mammalian H2S-generating enzyme. Outcome variables included indices of organ injury, clinical chemistry parameters, and plasma levels of inflammatory mediators. Plasma levels of H2S significantly increased in response to burn in wild-type mice, but remained unchanged in 3-MST-/- mice. The capacity of tissue homogenates to produce H2S from 3-mercaptopyruvate was unaffected by burn injury. In 3-MST-/- mice, compared to wild-type controls, there was a significant enhancement in the accumulation of polymorphonuclear cells (as assessed by the quantification of myeloperoxidase) in the liver (but not heart, lung, or skin) at 7 days postburn. Oxidative tissue damage (as assessed by malon dialdehyde content) was comparable between wild-type and 3-MST-deficient mice in all tissues studied. 3-MST-/- and wild-type mice exhibited comparable burn-induced elevations in circulating plasma levels of hepatic injury; however, 3-MST-/- mice exhibited a higher degree of renal injury (as reflected by elevated blood urea nitrogen levels) at 7 days postburn. Inflammatory mediators (eg, TNF-α, IL-1β, IL-2, IL-6, IL-10, and IL-12) increased in burn injury, but without significant differences between the 3-MST-/- and wild-type groups. The healing of the burn wound was also unaffected by 3-MST deficiency. In conclusion, the absence of the H2S-producing enzyme 3-MST slightly exacerbates the development of multiorgan dysfunction but does not affect inflammatory mediator production or wound healing in a murine model of burn injury.
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Affiliation(s)
- Akbar Ahmad
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston
| | - Nadiya Druzhyna
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston
| | - Csaba Szabo
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston.,Shriners Hospital for Children, Galveston, Texas.,Chair of Pharmacology, Faculty of Science and Medicine, University of Fribourg, Switzerland
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6
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Brightwell CR, Hanson ME, El Ayadi A, Prasai A, Wang Y, Finnerty CC, Fry CS. Thermal injury initiates pervasive fibrogenesis in skeletal muscle. Am J Physiol Cell Physiol 2020; 319:C277-C287. [PMID: 32432932 DOI: 10.1152/ajpcell.00337.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Severe burn injury induces a myriad of deleterious effects to skeletal muscle, resulting in impaired function and delayed recovery. Following burn, catabolic signaling and myofiber atrophy are key fiber-intrinsic determinants of weakness; less well understood are alterations in the interstitial environment surrounding myofibers. Muscle quality, specifically alterations in the extracellular matrix (ECM), modulates force transmission and strength. We sought to determine the impact of severe thermal injury on adaptation to the muscle ECM and quantify muscle fibrotic burden. After a 30% total body surface area dorsal burn, spinotrapezius muscle was harvested from mice at 7 (7d, n = 5), 14 (14d, n = 4), and 21 days (21d, n = 4), and a sham control group was also examined (Sham, n = 4). Expression of transforming growth factor-β (TGFβ), myostatin, and downstream effectors and proteases involved in fibrosis and collagen remodeling were measured by immunoblotting, and immunohistochemical and biochemical analyses assessed fibrogenic cell abundance and collagen deposition. Myostatin signaling increased progressively through 21 days postburn alongside fibrogenic/adipogenic progenitor cell expansion, with abundance peaking at 14 days postburn. Postburn, elevated expression of tissue inhibitor of matrix metalloproteinase 1 supported collagen remodeling resulting in a net accumulation of muscle collagen content. Collagen accumulation peaked at 14 days postburn but remained elevated through 21 days postburn, demonstrating minimal resolution of burn-induced fibrosis. These findings highlight a progressive upregulation of fibrogenic processes following burn injury, eliciting a fibrotic muscle phenotype that hinders regenerative capacity and is not resolved with 21 days of recovery.
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Affiliation(s)
- Camille R Brightwell
- Cell Biology Graduate Program, University of Texas Medical Branch, Galveston, Texas.,Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, Kentucky.,Center for Muscle Biology, University of Kentucky, Lexington, Kentucky
| | - Madeline E Hanson
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas
| | - Amina El Ayadi
- Department of Surgery, University of Texas Medical Branch, Galveston, Texas.,Shriners Hospitals for Children, Galveston, Texas
| | - Anesh Prasai
- Department of Surgery, University of Texas Medical Branch, Galveston, Texas.,Shriners Hospitals for Children, Galveston, Texas
| | - Ye Wang
- Department of Surgery, University of Texas Medical Branch, Galveston, Texas.,Shriners Hospitals for Children, Galveston, Texas
| | - Celeste C Finnerty
- Department of Surgery, University of Texas Medical Branch, Galveston, Texas.,Shriners Hospitals for Children, Galveston, Texas
| | - Christopher S Fry
- Department of Athletic Training and Clinical Nutrition, University of Kentucky, Lexington, Kentucky.,Center for Muscle Biology, University of Kentucky, Lexington, Kentucky.,Shriners Hospitals for Children, Galveston, Texas
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7
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Arentson-Lantz EJ, Fiebig KN, Anderson-Catania KJ, Deer RR, Wacher A, Fry CS, Lamon S, Paddon-Jones D. Countering disuse atrophy in older adults with low-volume leucine supplementation. J Appl Physiol (1985) 2020; 128:967-977. [PMID: 32191600 DOI: 10.1152/japplphysiol.00847.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Older adults are at increased risk of being bedridden and experiencing negative health outcomes including the loss of muscle tissue and functional capacity. We hypothesized that supplementing daily meals with a small quantity (3-4 g/meal) of leucine would partially preserve lean leg mass and function of older adults during bed rest. During a 7-day bed rest protocol, followed by 5 days of inpatient rehabilitation, healthy older men and women (67.8 ± 1.1 yr, 14 men; 6 women) were randomized to receive isoenergetic meals supplemented with leucine (LEU, 0.06 g/kg/meal; n = 10) or an alanine control (CON, 0.06 g/kg/meal; n = 10). Outcomes were assessed at baseline, following bed rest, and after rehabilitation. Body composition was measured by dual-energy X-ray absorptiometry. Functional capacity was assessed by knee extensor isokinetic and isometric dynamometry, peak aerobic capacity, and the short physical performance battery. Muscle fiber type, cross-sectional area, signaling protein expression levels, and single fiber characteristics were determined from biopsies of the vastus lateralis. Leucine supplementation reduced the loss of leg lean mass during bed rest (LEU vs. CON: -423 vs. -1035 ± 143 g; P = 0.008) but had limited impact on strength or endurance-based functional outcomes. Similarly, leucine had no effect on markers of anabolic signaling and protein degradation during bed rest or rehabilitation. In conclusion, providing older adults with supplemental leucine has minimal impact on total energy or protein consumption and has the potential to partially counter some, but not all, of the negative effects of inactivity on muscle health.NEW & NOTEWORTHY Skeletal muscle morphology and function in older adults was significantly compromised by 7 days of disuse. Leucine supplementation partially countered the loss of lean leg mass but did not preserve muscle function or positively impact changes at the muscle fiber level associated with bed rest or rehabilitation. Of note, our data support a relationship between myonuclear content and adaptations to muscle atrophy at the whole limb and single fiber level.
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Affiliation(s)
- Emily J Arentson-Lantz
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.,Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, Texas
| | - Kinga N Fiebig
- Institute for Physical Activity and Nutrition (IPAN), Faculty of Health, Deakin University, Melbourne, Australia
| | - Kim J Anderson-Catania
- Institute for Physical Activity and Nutrition (IPAN), Faculty of Health, Deakin University, Melbourne, Australia
| | - Rachel R Deer
- Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, Texas.,Division of Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas
| | - Adam Wacher
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, Texas
| | - Christopher S Fry
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.,Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, Texas
| | - Séverine Lamon
- Institute for Physical Activity and Nutrition (IPAN), Faculty of Health, Deakin University, Melbourne, Australia
| | - Douglas Paddon-Jones
- Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.,Center for Recovery, Physical Activity and Nutrition, University of Texas Medical Branch, Galveston, Texas
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8
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Yousuf Y, Datu A, Barnes B, Amini-Nik S, Jeschke MG. Metformin alleviates muscle wasting post-thermal injury by increasing Pax7-positive muscle progenitor cells. Stem Cell Res Ther 2020; 11:18. [PMID: 31915055 PMCID: PMC6950874 DOI: 10.1186/s13287-019-1480-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/14/2019] [Accepted: 10/31/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Profound skeletal muscle wasting and weakness is common after severe burn and persists for years after injury contributing to morbidity and mortality of burn patients. Currently, no ideal treatment exists to inhibit muscle catabolism. Metformin is an anti-diabetic agent that manages hyperglycemia but has also been shown to have a beneficial effect on stem cells after injury. We hypothesize that metformin administration will increase protein synthesis in the skeletal muscle by increasing the proliferation of muscle progenitor cells, thus mitigating muscle atrophy post-burn injury. METHODS To determine whether metformin can attenuate muscle catabolism following burn injury, we utilized a 30% total burn surface area (TBSA) full-thickness scald burn in mice and compared burn injuries with and without metformin treatment. We examined the gastrocnemius muscle at 7 and 14 days post-burn injury. RESULTS At 7 days, burn injury significantly reduced myofiber cross-sectional area (CSA) compared to sham, p < 0.05. Metformin treatment significantly attenuated muscle catabolism and preserved muscle CSA at the sham size. To investigate metformin's effect on satellite cells (muscle progenitors), we examined changes in Pax7, a transcription factor regulating the proliferation of muscle progenitors. Burned animals treated with metformin had a significant increase in Pax7 protein level and the number of Pax7-positive cells at 7 days post-burn, p < 0.05. Moreover, through BrdU proliferation assay, we show that metformin treatment increased the proliferation of satellite cells at 7 days post-burn injury, p < 0.05. CONCLUSION In summary, metformin's various metabolic effects and its modulation of stem cells make it an attractive alternative to mitigate burn-induced muscle wasting while also managing hyperglycemia.
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Affiliation(s)
- Yusef Yousuf
- Sunnybrook Research Institute, 2075 Bayview Ave., Rm. D704, Toronto, ON, M4N 3M5, Canada
| | - Andrea Datu
- Sunnybrook Research Institute, 2075 Bayview Ave., Rm. D704, Toronto, ON, M4N 3M5, Canada
| | - Ben Barnes
- Sunnybrook Research Institute, 2075 Bayview Ave., Rm. D704, Toronto, ON, M4N 3M5, Canada
| | - Saeid Amini-Nik
- Sunnybrook Research Institute, 2075 Bayview Ave., Rm. D704, Toronto, ON, M4N 3M5, Canada. .,Laboratory in Medicine and Pathobiology, University of Toronto, Toronto, Canada. .,Division of Plastic Surgery, Department of Surgery, University of Toronto, Toronto, Canada.
| | - Marc G Jeschke
- Sunnybrook Research Institute, 2075 Bayview Ave., Rm. D704, Toronto, ON, M4N 3M5, Canada. .,Division of Plastic Surgery, Department of Surgery, University of Toronto, Toronto, Canada. .,Ross Tilley Burn Centre, Sunnybrook Health Sciences Centre, Toronto, Canada. .,Department of Immunology, University of Toronto, Toronto, Canada.
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9
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D'Lugos AC, Fry CS, Ormsby JC, Sweeney KR, Brightwell CR, Hale TM, Gonzales RJ, Angadi SS, Carroll CC, Dickinson JM. Chronic doxorubicin administration impacts satellite cell and capillary abundance in a muscle-specific manner. Physiol Rep 2019; 7:e14052. [PMID: 30963722 PMCID: PMC6453819 DOI: 10.14814/phy2.14052] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 03/15/2019] [Accepted: 03/16/2019] [Indexed: 01/23/2023] Open
Abstract
Anthracycline chemotherapies are effective at reducing disease recurrence and mortality in cancer patients. However, these drugs also contribute to skeletal muscle wasting and dysfunction. The purpose of this study was to assess the impact of chronic doxorubicin (DOX) administration on satellite cell and capillary densities in different skeletal muscles. We hypothesized that DOX would reduce satellite cell and capillary densities of the soleus (SOL) and extensor digitorum longus (EDL) muscles, along with muscle fiber size. Ovariectomized female Sprague-Dawley rats were randomized to receive three bi-weekly intraperitoneal injections of DOX (4 mg∙kg-1 ; cumulative dose 12 mg∙kg-1 ) or vehicle (VEH; saline). Animals were euthanized 5d following the last injection and the SOL and EDL were dissected and prepared for immunohistochemical and RT-qPCR analyses. Relative to VEH, CSA of the SOL and EDL fibers were 26% and 33% smaller, respectively, in DOX (P < 0.05). In the SOL, satellite cell and capillary densities were 39% and 35% lower, respectively, in DOX (P < 0.05), whereas in the EDL satellite cell and capillary densities were unaffected by DOX administration (P > 0.05). Proliferating satellite cells were unaffected by DOX in the SOL (P > 0.05). In the SOL, MYF5 mRNA expression was increased in DOX (P < 0.05), while in the EDL MGF mRNA expression was reduced in DOX (P < 0.05). Chronic DOX administration is associated with reduced fiber size in the SOL and EDL; however, DOX appeared to reduce satellite cell and capillary densities only in the SOL. These findings highlight that therapeutic targets to protect skeletal muscle from DOX may vary across muscles.
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Affiliation(s)
| | - Christopher S. Fry
- Department of Nutrition and MetabolismUniversity of Texas Medical BranchGalvestonTexas
| | - Jordan C. Ormsby
- College of Health SolutionsArizona State UniversityPhoenixArizona
| | | | - Camille R. Brightwell
- Department of Nutrition and MetabolismUniversity of Texas Medical BranchGalvestonTexas
| | - Taben M. Hale
- Department of Basic Medical SciencesCollege of Medicine‐PhoenixUniversity of ArizonaPhoenixArizona
| | - Rayna J. Gonzales
- Department of Basic Medical SciencesCollege of Medicine‐PhoenixUniversity of ArizonaPhoenixArizona
| | | | - Chad C. Carroll
- Department of PhysiologyMidwestern UniversityGlendaleArizona
- Department of Health and KinesiologyPurdue UniversityWest LafayetteIndiana
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10
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2,000 Steps/Day Does Not Fully Protect Skeletal Muscle Health in Older Adults During Bed Rest. J Aging Phys Act 2019; 27:191-197. [PMID: 29989486 DOI: 10.1123/japa.2018-0093] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Physical activity in an inpatient setting is often limited to brief periods of walking. For healthy adults, public health agencies recommend a minimum of 150 min/week of moderate-intensity exercise. The authors sought to determine if meeting this activity threshold, in the absence of incidental activities of daily living, could protect skeletal muscle health during bed rest. Healthy older adults (68 ± 2 years) were randomized to 7-day bed rest with (STEP, n = 7) or without (CON, n = 10) a 2,000 steps/day intervention. Performing 2018 ± 4 steps/day did not prevent the loss of lean leg mass and had no beneficial effect on aerobic capacity, strength, or muscle fiber volume. However, the insulin response to an oral glucose challenge was preserved. Performing a block of 2,000 steps/day, in the absence of incidental activities of daily living, was insufficient to fully counter the catabolic effects of bed rest in healthy older adults.
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11
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Cho DS, Doles JD. Skeletal Muscle Progenitor Cell Heterogeneity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1169:179-193. [PMID: 31487024 DOI: 10.1007/978-3-030-24108-7_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Tissue-specific stem cells contribute to adult tissue maintenance, repair, and regeneration. In skeletal muscle, many different mononuclear cell types are capable of giving rise to differentiated muscle. Of these tissue stem-like cells, satellite cells (SCs) are the most studied muscle stem cell population and are widely considered the main cellular source driving muscle repair and regeneration in adult tissue. Within the satellite cell pool, many distinct subpopulations exist, each exhibiting differential abilities to exit quiescence, expand, differentiate, and self-renew. In this chapter, we discuss the different stem cell types that can give rise to skeletal muscle tissue and then focus on satellite cell heterogeneity during the process of myogenesis/muscle regeneration. Finally, we highlight emerging opportunities to better characterize muscle stem cell heterogeneity, which will ultimately deepen our appreciation of stem cells in muscle development, repair/regeneration, aging, and disease.
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Affiliation(s)
- Dong Seong Cho
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Jason D Doles
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA.
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The RNA-binding proteins Zfp36l1 and Zfp36l2 act redundantly in myogenesis. Skelet Muscle 2018; 8:37. [PMID: 30526691 PMCID: PMC6286576 DOI: 10.1186/s13395-018-0183-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/22/2018] [Indexed: 01/07/2023] Open
Abstract
Background Members of the ZFP36 family of RNA-binding proteins regulate gene expression post-transcriptionally by binding to AU-rich elements in the 3’UTR of mRNA and stimulating mRNA degradation. The proteins within this family target different transcripts in different tissues. In particular, ZFP36 targets myogenic transcripts and may have a role in adult muscle stem cell quiescence. Our study examined the requirement of ZFP36L1 and ZFP36L2 in adult muscle cell fate regulation. Methods We generated single and double conditional knockout mice in which Zfp36l1 and/or Zfp36l2 were deleted in Pax7-expressing cells. Immunostained muscle sections were used to analyse resting skeletal muscle, and a cardiotoxin-induced injury model was used to determine the regenerative capacity of muscle. Results We show that ZFP36L1 and ZFP36L2 proteins are expressed in satellite cells. Mice lacking the two proteins in Pax7-expressing cells have reduced body weight and have reduced skeletal muscle mass. Furthermore, the number of satellite cells is reduced in adult skeletal muscle and the capacity of this muscle to regenerate following muscle injury is diminished. Conclusion ZFP36L1 and ZFP36L2 act redundantly in myogenesis. These findings add further intricacy to the regulation of the cell fate of Pax7-expressing cells in skeletal muscle by RNA-binding proteins. Electronic supplementary material The online version of this article (10.1186/s13395-018-0183-9) contains supplementary material, which is available to authorized users.
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