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Gros K, Matkovič U, Parato G, Miš K, Luin E, Bernareggi A, Sciancalepore M, Marš T, Lorenzon P, Pirkmajer S. Neuronal Agrin Promotes Proliferation of Primary Human Myoblasts in an Age-Dependent Manner. Int J Mol Sci 2022; 23:ijms231911784. [PMID: 36233091 PMCID: PMC9570459 DOI: 10.3390/ijms231911784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/06/2022] [Accepted: 09/22/2022] [Indexed: 12/02/2022] Open
Abstract
Neuronal agrin, a heparan sulphate proteoglycan secreted by the α-motor neurons, promotes the formation and maintenance of the neuromuscular junction by binding to Lrp4 and activating muscle-specific kinase (MuSK). Neuronal agrin also promotes myogenesis by enhancing differentiation and maturation of myotubes, but its effect on proliferating human myoblasts, which are often considered to be unresponsive to agrin, remains unclear. Using primary human myoblasts, we determined that neuronal agrin induced transient dephosphorylation of ERK1/2, while c-Abl, STAT3, and focal adhesion kinase were unresponsive. Gene silencing of Lrp4 and MuSK markedly reduced the BrdU incorporation, suggesting the functional importance of the Lrp4/MuSK complex for myoblast proliferation. Acute and chronic treatments with neuronal agrin increased the proliferation of human myoblasts in old donors, but they did not affect the proliferation of myoblasts in young donors. The C-terminal fragment of agrin which lacks the Lrp4-binding site and cannot activate MuSK had a similar age-dependent effect, indicating that the age-dependent signalling pathways activated by neuronal agrin involve the Lrp4/MuSK receptor complex as well as an Lrp4/MuSK-independent pathway which remained unknown. Collectively, our results highlight an age-dependent role for neuronal agrin in promoting the proliferation of human myoblasts.
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Affiliation(s)
- Katarina Gros
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Urška Matkovič
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Giulia Parato
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy
- The B.R.A.I.N. Centre for Neuroscience, University of Trieste, 34127 Trieste, Italy
| | - Katarina Miš
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Elisa Luin
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy
- The B.R.A.I.N. Centre for Neuroscience, University of Trieste, 34127 Trieste, Italy
| | - Annalisa Bernareggi
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy
- The B.R.A.I.N. Centre for Neuroscience, University of Trieste, 34127 Trieste, Italy
| | - Marina Sciancalepore
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy
- The B.R.A.I.N. Centre for Neuroscience, University of Trieste, 34127 Trieste, Italy
| | - Tomaž Marš
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Paola Lorenzon
- Department of Life Sciences, University of Trieste, 34127 Trieste, Italy
- The B.R.A.I.N. Centre for Neuroscience, University of Trieste, 34127 Trieste, Italy
- Correspondence: (P.L.); (S.P.)
| | - Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
- Correspondence: (P.L.); (S.P.)
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2
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Castellanos-Montiel MJ, Velasco I, Escobedo-Avila I. Modeling the neuromuscular junction in vitro: an approach to study neuromuscular junction disorders. Ann N Y Acad Sci 2020; 1488:3-15. [PMID: 33040338 DOI: 10.1111/nyas.14504] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 08/24/2020] [Accepted: 09/09/2020] [Indexed: 12/14/2022]
Abstract
The neuromuscular junction (NMJ) is a specialized structure that works as an interface to translate the action potential of the presynaptic motor neuron (MN) in the contraction of the postsynaptic myofiber. The design of appropriate experimental models is essential to have efficient and reliable approaches to study NMJ development and function, but also to generate conditions that recapitulate distinct features of diseases. Initial studies relied on the use of tissue slices maintained under the same environment and in which single motor axons were difficult to trace. Later, MNs and muscle cells were obtained from primary cultures or differentiation of progenitors and cocultured as monolayers; however, the tissue architecture was lost. Current approaches include self-assembling 3D structures or the incorporation of biomaterials with cells to generate engineered tissues, although the incorporation of Schwann cells remains a challenge. Thus, numerous investigations have established different NMJ models, some of which are quite complex and challenging. Our review summarizes the in vitro models that have emerged in recent years to coculture MNs and skeletal muscle, trying to mimic the healthy and diseased NMJ. We expect our review may serve as a reference for choosing the appropriate experimental model for the required purposes of investigation.
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Affiliation(s)
- María José Castellanos-Montiel
- Instituto de Fisiología Celular-Neurociencias, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.,Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montréal, Quebec, Canada
| | - Iván Velasco
- Instituto de Fisiología Celular-Neurociencias, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.,Laboratorio de Reprogramación Celular, Instituto Nacional de Neurología y Neurocirugía "Manuel Velasco Suárez", Mexico City, Mexico
| | - Itzel Escobedo-Avila
- Instituto de Fisiología Celular-Neurociencias, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico
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3
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Yoshioka K, Ito A, Kawabe Y, Kamihira M. Novel neuromuscular junction model in 2D and 3D myotubes co-cultured with induced pluripotent stem cell-derived motor neurons. J Biosci Bioeng 2020; 129:486-493. [DOI: 10.1016/j.jbiosc.2019.10.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 09/30/2019] [Accepted: 10/02/2019] [Indexed: 12/12/2022]
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Arifuzzaman M, Ito A, Ikeda K, Kawabe Y, Kamihira M. Fabricating Muscle–Neuron Constructs with Improved Contractile Force Generation. Tissue Eng Part A 2019; 25:563-574. [DOI: 10.1089/ten.tea.2018.0165] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Md Arifuzzaman
- Department of Chemical Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Japan
| | - Akira Ito
- Department of Chemical Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Japan
| | - Kazushi Ikeda
- Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshinori Kawabe
- Department of Chemical Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Japan
| | - Masamichi Kamihira
- Department of Chemical Engineering, Faculty of Engineering, Kyushu University, Fukuoka, Japan
- Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan
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5
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Kaufman T, Kaplan B, Perry L, Shandalov Y, Landau S, Srugo I, Ad-El D, Levenberg S. Innervation of an engineered muscle graft for reconstruction of muscle defects. Am J Transplant 2019; 19:37-47. [PMID: 29856531 DOI: 10.1111/ajt.14957] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 05/24/2018] [Accepted: 05/27/2018] [Indexed: 01/25/2023]
Abstract
Autologous muscle flaps are commonly used to reconstruct defects that involve muscle impairment. To maintain viability and functionality of these flaps, they must be properly vascularized and innervated. Tissue-engineered muscles could potentially replace autologous muscle tissue, but still require establishment of sufficient innervation to ensure functionality. In this study, we explored the possibility of innervating engineered muscle grafts transplanted to an abdominal wall defect in mice, by transferring the native femoral nerve to the graft. Six weeks posttransplantation, nerve conduction studies and electromyography demonstrated increased innervation in engineered grafts neurotized with the femoral nerve, as compared to non-neurotized grafts. Histologic assessments revealed axonal penetration and formation of neuromuscular junctions within the grafts. The innervation process described here may advance the fabrication of a fully functional engineered muscle graft that will be of utility in clinical settings.
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Affiliation(s)
- Tal Kaufman
- Department of Plastic Surgery, Rabin Medical Center, Petach Tikva, Israel.,Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ben Kaplan
- Department of Biomedical Engineering, Technion - Israel Institute of Technology, Haifa, Israel.,Bruce Rapaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel
| | - Luba Perry
- Bruce Rapaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, Israel.,Inter-departmental Program in Biotechnology, Technion - Israel Institute of Technology, Haifa, Israel
| | - Yulia Shandalov
- Department of Biomedical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Shira Landau
- Department of Biomedical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | | | - Dean Ad-El
- Department of Plastic Surgery, Rabin Medical Center, Petach Tikva, Israel.,Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Shulamit Levenberg
- Department of Biomedical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
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Mis K, Grubic Z, Lorenzon P, Sciancalepore M, Mars T, Pirkmajer S. In Vitro Innervation as an Experimental Model to Study the Expression and Functions of Acetylcholinesterase and Agrin in Human Skeletal Muscle. Molecules 2017; 22:molecules22091418. [PMID: 28846617 PMCID: PMC6151842 DOI: 10.3390/molecules22091418] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 08/18/2017] [Accepted: 08/23/2017] [Indexed: 12/19/2022] Open
Abstract
Acetylcholinesterase (AChE) and agrin, a heparan-sulfate proteoglycan, reside in the basal lamina of the neuromuscular junction (NMJ) and play key roles in cholinergic transmission and synaptogenesis. Unlike most NMJ components, AChE and agrin are expressed in skeletal muscle and α-motor neurons. AChE and agrin are also expressed in various other types of cells, where they have important alternative functions that are not related to their classical roles in NMJ. In this review, we first focus on co-cultures of embryonic rat spinal cord explants with human skeletal muscle cells as an experimental model to study functional innervation in vitro. We describe how this heterologous rat-human model, which enables experimentation on highly developed contracting human myotubes, offers unique opportunities for AChE and agrin research. We then highlight innovative approaches that were used to address salient questions regarding expression and alternative functions of AChE and agrin in developing human skeletal muscle. Results obtained in co-cultures are compared with those obtained in other models in the context of general advances in the field of AChE and agrin neurobiology.
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Affiliation(s)
- Katarina Mis
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, SI-1000 Ljubljana, Slovenia.
| | - Zoran Grubic
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, SI-1000 Ljubljana, Slovenia.
| | - Paola Lorenzon
- Department of Life Sciences, University of Trieste, via A. Fleming 22, I-34127 Trieste, Italy.
| | - Marina Sciancalepore
- Department of Life Sciences, University of Trieste, via A. Fleming 22, I-34127 Trieste, Italy.
| | - Tomaz Mars
- Department of Life Sciences, University of Trieste, via A. Fleming 22, I-34127 Trieste, Italy.
| | - Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, SI-1000 Ljubljana, Slovenia.
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8
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Lojk J, Strojan K, Miš K, Bregar BV, Hafner Bratkovič I, Bizjak M, Pirkmajer S, Pavlin M. Cell stress response to two different types of polymer coated cobalt ferrite nanoparticles. Toxicol Lett 2017; 270:108-118. [DOI: 10.1016/j.toxlet.2017.02.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 01/09/2017] [Accepted: 02/07/2017] [Indexed: 10/20/2022]
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9
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Hepple RT, Rice CL. Innervation and neuromuscular control in ageing skeletal muscle. J Physiol 2015; 594:1965-78. [PMID: 26437581 DOI: 10.1113/jp270561] [Citation(s) in RCA: 209] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 09/28/2015] [Indexed: 12/28/2022] Open
Abstract
Changes in the neuromuscular system affecting the ageing motor unit manifest structurally as a reduction in motor unit number secondary to motor neuron loss; fibre type grouping due to repeating cycles of denervation-reinnervation; and instability of the neuromuscular junction that may be due to either or both of a gradual perturbation in postsynaptic signalling mechanisms necessary for maintenance of the endplate acetylcholine receptor clusters or a sudden process involving motor neuron death or traumatic injury to the muscle fibre. Functionally, these changes manifest as a reduction in strength and coordination that precedes a loss in muscle mass and contributes to impairments in fatigue. Regular muscle activation in postural muscles or through habitual physical activity can attenuate some of these structural and functional changes up to a point along the ageing continuum. On the other hand, regular muscle activation in advanced age (>75 years) loses its efficacy, and at least in rodents may exacerbate age-related motor neuron death. Transgenic mouse studies aimed at identifying potential mechanisms of motor unit disruptions in ageing muscle are not conclusive due to many different mechanisms converging on similar motor unit alterations, many of which phenocopy ageing muscle. Longitudinal studies of ageing models and humans will help clarify the cause and effect relationships and thus, identify relevant therapeutic targets to better preserve muscle function across the lifespan.
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Affiliation(s)
- Russell T Hepple
- Department of Kinesiology & Physical Education, McGill University, Montreal, Québec, Canada.,McGill Research Centre for Physical Activity and Health, Montreal, Québec, Canada.,Centre for Translational Biology, Research Institute of the McGill University Health Centre, Montreal, Québec, Canada
| | - Charles L Rice
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada.,Canadian Centre for Activity and Aging, London, Ontario, Canada.,Department of Anatomy & Cell Biology, University of Western Ontario, London, Ontario, Canada
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10
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Lojk J, Mis K, Pirkmajer S, Pavlin M. siRNA delivery into cultured primary human myoblasts - optimization of electroporation parameters and theoretical analysis. Bioelectromagnetics 2015; 36:551-63. [DOI: 10.1002/bem.21936] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 09/02/2015] [Indexed: 02/02/2023]
Affiliation(s)
- Jasna Lojk
- Faculty of Electrical Engineering; University of Ljubljana; Ljubljana Slovenia
| | - Katarina Mis
- Institute of Pathophysiology, Faculty of Medicine; University of Ljubljana; Ljubljana Slovenia
| | - Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine; University of Ljubljana; Ljubljana Slovenia
| | - Mojca Pavlin
- Faculty of Electrical Engineering; University of Ljubljana; Ljubljana Slovenia
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11
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Lojk J, Bregar VB, Rajh M, Miš K, Kreft ME, Pirkmajer S, Veranič P, Pavlin M. Cell type-specific response to high intracellular loading of polyacrylic acid-coated magnetic nanoparticles. Int J Nanomedicine 2015; 10:1449-62. [PMID: 25733835 PMCID: PMC4340463 DOI: 10.2147/ijn.s76134] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Magnetic nanoparticles (NPs) are a special type of NP with a ferromagnetic, electron-dense core that enables several applications such as cell tracking, hyperthermia, and magnetic separation, as well as multimodality. So far, superparamagnetic iron oxide NPs (SPIONs) are the only clinically approved type of metal oxide NPs, but cobalt ferrite NPs have properties suitable for biomedical applications as well. In this study, we analyzed the cellular responses to magnetic cobalt ferrite NPs coated with polyacrylic acid (PAA) in three cell types: Chinese Hamster Ovary (CHO), mouse melanoma (B16) cell line, and primary human myoblasts (MYO). We compared the internalization pathway, intracellular trafficking, and intracellular fate of our NPs using fluorescence and transmission electron microscopy (TEM) as well as quantified NP uptake and analyzed uptake dynamics. We determined cell viability after 24 or 96 hours’ exposure to increasing concentrations of NPs, and quantified the generation of reactive oxygen species (ROS) upon 24 and 48 hours’ exposure. Our NPs have been shown to readily enter and accumulate in cells in high quantities using the same two endocytic pathways; mostly by macropinocytosis and partially by clathrin-mediated endocytosis. The cell types differed in their uptake rate, the dynamics of intracellular trafficking, and the uptake capacity, as well as in their response to higher concentrations of internalized NPs. The observed differences in cell responses stress the importance of evaluation of NP–cell interactions on several different cell types for better prediction of possible toxic effects on different cell and tissue types in vivo.
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Affiliation(s)
- Jasna Lojk
- Group for Nano and Biotechnological Applications, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
| | - Vladimir B Bregar
- Group for Nano and Biotechnological Applications, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
| | - Maruša Rajh
- Group for Nano and Biotechnological Applications, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
| | - Katarina Miš
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Mateja Erdani Kreft
- Institute of Cell Biology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Peter Veranič
- Institute of Cell Biology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Mojca Pavlin
- Group for Nano and Biotechnological Applications, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
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12
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Rezonja K, Sostaric M, Vidmar G, Mars T. Dexamethasone produces dose-dependent inhibition of sugammadex reversal in in vitro innervated primary human muscle cells. Anesth Analg 2014; 118:755-63. [PMID: 24651229 DOI: 10.1213/ane.0000000000000108] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Corticosteroids are frequently used during anesthesia to provide substitution therapy in patients with adrenal insufficiency, as a first-line treatment of several life-threatening conditions, to prevent postoperative nausea and vomiting, and as a component of multimodal analgesia. For these last 2 indications, dexamethasone is most frequently used. Due to the structural resemblance between aminosteroid muscle relaxants and dexamethasone, concerns have been raised about possible corticosteroid inhibition in the reversal of neuromuscular block by sugammadex. We thus investigated the influence of dexamethasone on sugammadex reversal of rocuronium-induced neuromuscular block, which could be relevant in certain clinical situations. METHODS The unique co-culture model of human muscle cells innervated in vitro with rat embryonic spinal cord explants to form functional neuromuscular junctions was first used to explore the effects of 4 and 10 μM rocuronium on muscle contractions, as quantitatively evaluated by counting contraction units in contraction-positive explant co-cultures. Next, equimolar and 3-fold equimolar sugammadex was used to investigate the recovery of contractions from 4 and 10 μM rocuronium block. Finally, 1, 100, and 10 μM dexamethasone (normal, elevated, and high clinical levels) were used to evaluate any effects on the reversal of rocuronium-induced neuromuscular block by sugammadex. RESULTS Seventy-eight explant co-cultures from 3 time-independent experiments were included, where the number of contractions increased to 10 days of co-culturing. Rocuronium showed a time-dependent effect on depth of neuromuscular block (4 μM rocuronium: baseline, 10, 20 minutes administration; P < 0.0001), while the dose-dependent effect was close to nominal statistical significance (4, 10 μM; P = 0.080). This was reversed by equimolar concentrations of sugammadex, with further and virtually complete recovery of contractions with 3-fold equimolar sugammadex (P < 0.0001). Dexamethasone diminished 10 μM sugammadex-induced recovery of contractions from rocuronium-induced neuromuscular block in a dose-dependent manner (P = 0.026) with a higher sugammadex concentration (30 μM) being close to statistically significantly improving recovery (P = 0.065). The highest concentration of dexamethasone decreased the recovery of contractions by equimolar sugammadex by 26%; this effect was more pronounced when 3-fold equimolar (30 μM) sugammadex was used for reversal (48%). CONCLUSIONS This is the first report in which the effects of rocuronium and sugammadex interactions with dexamethasone have been studied in a highly accessible in vitro experimental model of functionally innervated human muscle cells. Sugammadex reverses rocuronium-induced neuromuscular block; however, concomitant addition of high dexamethasone concentrations diminishes the efficiency of sugammadex. Further studies are required to determine the clinical relevance of these interactions.
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Affiliation(s)
- Katja Rezonja
- From the *Department of Anesthesiology and Intensive Therapy, University Medical Centre Ljubljana; and †Institute for Biostatistics and Medical Informatics and ‡Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
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Guo X, Greene K, Akanda N, Smith A, Stancescu M, Lambert S, Vandenburgh H, Hickman J. In vitro Differentiation of Functional Human Skeletal Myotubes in a Defined System. Biomater Sci 2014; 2:131-138. [PMID: 24516722 DOI: 10.1039/c3bm60166h] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In vitro human skeletal muscle systems are valuable tools for the study of human muscular development, disease and treatment. However, published in vitro human muscle systems have so far only demonstrated limited differentiation capacities. Advanced differentiation features such as cross-striations and contractility have only been observed in co-cultures with motoneurons. Furthermore, it is commonly regarded that cultured human myotubes do not spontaneously contract, and any contraction has been considered to originate from innervation. This study developed a serum-free culture system in which human skeletal myotubes demonstrated advanced differentiation. Characterization by immunocytochemistry, electrophysiology and analysis of contractile function revealed these major features: A) well defined sarcomeric development, as demonstrated by the presence of cross-striations. B) finely developed excitation-contraction coupling apparatus characterized by the close apposition of dihydropyridine receptors on T-tubules and Ryanodine receptors on sarcoplasmic reticulum membranes. C) spontaneous and electrically controlled contractility. This report not only demonstrates an improved level of differentiation of cultured human skeletal myotubes, but also provides the first published evidence that such myotubes are capable of spontaneous contraction. Use of this functional in vitro human skeletal muscle system would advance studies concerning human skeletal muscle development and physiology, as well as muscle-related disease and therapy.
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Affiliation(s)
- Xiufang Guo
- NanoScience Technology Center, University of Central Florida, Orlando, Florida 32826, USA
| | - Keshel Greene
- Biomolecular Science Center, Burnett School of Biomedical Sciences, University of Central Florida, Orlando, Florida 32826, USA
| | - Nesar Akanda
- NanoScience Technology Center, University of Central Florida, Orlando, Florida 32826, USA
| | - Alec Smith
- NanoScience Technology Center, University of Central Florida, Orlando, Florida 32826, USA
| | - Maria Stancescu
- NanoScience Technology Center, University of Central Florida, Orlando, Florida 32826, USA ; Department of Chemistry, 4000 Central Florida Blvd., Physical Sciences Building (PS) Room 255, University of Central Florida, Orlando, FL 32816-2366, USA
| | - Stephen Lambert
- NanoScience Technology Center, University of Central Florida, Orlando, Florida 32826, USA ; College of Medicine, University of Central Florida, 12201 Research Parkway, Suite 479, Room 463, Orlando, FL 32826, USA
| | - Herman Vandenburgh
- Brown University, Professor Emeritus, Department of Pathology and Lab Medicine, Providence, Rhode Island, 02913 USA ; Myomics, 148 West River Str, Providence, Rhode Island 02904
| | - James Hickman
- NanoScience Technology Center, University of Central Florida, Orlando, Florida 32826, USA ; Biomolecular Science Center, Burnett School of Biomedical Sciences, University of Central Florida, Orlando, Florida 32826, USA ; Department of Chemistry, 4000 Central Florida Blvd., Physical Sciences Building (PS) Room 255, University of Central Florida, Orlando, FL 32816-2366, USA
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Opposing effects of dexamethasone, agrin and sugammadex on functional innervation and constitutive secretion of IL-6 in in vitro innervated primary human muscle cells. Neurosci Lett 2013; 549:186-90. [PMID: 23791923 DOI: 10.1016/j.neulet.2013.06.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 05/28/2013] [Accepted: 06/05/2013] [Indexed: 11/24/2022]
Abstract
Neuromuscular junction development is the key process required for successful neuromuscular transmission and functional innervation of skeletal muscle fibres. Various substances can influence these processes, some of which are in common use in clinical practice. In the present study, the effects of the potentially new therapeutic agent agrin were followed, along with the widely used glucocorticoid dexamethasone. The in vitro experimental model used was functional innervation and constitutive interleukin 6 (IL-6) secretion of human muscle cells. Additionally, the selective relaxant binding agent sugammadex and its possible interaction with dexamethasone were followed. Dexamethasone impaired functional innervation while agrin had opposing effects. Furthermore, based on interference with IL-6 secretion, we show potential (chemical) interactions between dexamethasone and sugammadex. The physiological effects of this interaction should be taken into consideration under clinical conditions where these two drugs might be applied simultaneously.
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Mis K, Matkovic U, Pirkmajer S, Sciancalepore M, Lorenzon P, Mars T, Grubic Z. Acetylcholinesterase and agrin: different functions, similar expression patterns, multiple roles. Chem Biol Interact 2012; 203:297-301. [PMID: 23117006 DOI: 10.1016/j.cbi.2012.10.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 10/16/2012] [Accepted: 10/17/2012] [Indexed: 12/31/2022]
Abstract
Acetylcholinesterase (AChE) and agrin play unique functional roles in the neuromuscular junction (NMJ). AChE is a cholinergic and agrin a synaptogenetic component. In spite of their different functions, they share several common features: their targeting is determined by alternative splicing; unlike most other NMJ components they are expressed in both, muscle and motor neuron and both reside on the synaptic basal lamina of the NMJ. Also, both were reported to play various nonjunctional roles. However, while the origin of basal lamina bound agrin is undoubtedly neural, the neural origin of AChE, which is anchored to the basal lamina with collagenic tail ColQ, is elusive. Hypothesizing that motor neuron proteins targeted to the NMJ basal lamina share common temporal pattern of expression, which is coordinated with the formation of basal lamina, we compared expression of agrin isoforms with the expression of AChE-T and ColQ in the developing rat spinal cord at the stages before and after the formation of NMJ basal lamina. Cellular origin of AChE-T and agrin was determined by in situ hybridization and their quantitative levels by RT PCR. We found parallel increase in expression of the synaptogenetic (agrin 8) isoform of agrin and ColQ after the formation of basal lamina supporting the view that ColQ bound AChE and agrin 8 isoform are destined to the basal lamina. Catalytic AChE-T subunit and agrin isoforms 19 and 0 followed different expression patterns. In accordance with the reports of other authors, our investigations also revealed various alternative functions for AChE and agrin. We have already demonstrated participation of AChE in myoblast apoptosis; here we present the evidence that agrin promotes the maturation of heavy myosin chains and the excitation-contraction coupling. These results show that common features of AChE and agrin extend to their capacity to play multiple roles in muscle development.
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Affiliation(s)
- Katarina Mis
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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Guo X, Gonzalez M, Stancescu M, Vandenburgh HH, Hickman JJ. Neuromuscular junction formation between human stem cell-derived motoneurons and human skeletal muscle in a defined system. Biomaterials 2011; 32:9602-11. [PMID: 21944471 DOI: 10.1016/j.biomaterials.2011.09.014] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 09/06/2011] [Indexed: 12/28/2022]
Abstract
Functional in vitro models composed of human cells will constitute an important platform in the next generation of system biology and drug discovery. This study reports a novel human-based in vitro Neuromuscular Junction (NMJ) system developed in a defined serum-free medium and on a patternable non-biological surface. The motoneurons and skeletal muscles were derived from fetal spinal stem cells and skeletal muscle stem cells. The motoneurons and skeletal myotubes were completely differentiated in the co-culture based on morphological analysis and electrophysiology. NMJ formation was demonstrated by phase contrast microscopy, immunocytochemistry and the observation of motoneuron-induced muscle contractions utilizing time-lapse recordings and their subsequent quenching by d-Tubocurarine. Generally, functional human based systems would eliminate the issue of species variability during the drug development process and its derivation from stem cells bypasses the restrictions inherent with utilization of primary human tissue. This defined human-based NMJ system is one of the first steps in creating functional in vitro systems and will play an important role in understanding NMJ development, in developing high information content drug screens and as test beds in preclinical studies for spinal or muscular diseases/injuries such as muscular dystrophy, Amyotrophic lateral sclerosis and spinal cord repair.
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Affiliation(s)
- Xiufang Guo
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, Orlando, FL 32826, USA
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17
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Deželak M, Bavec A. Glucagon like-peptide-1 receptor is covalently modified by endogenous mono-ADP-ribosyltransferase. Mol Biol Rep 2011; 39:4375-81. [DOI: 10.1007/s11033-011-1225-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 06/20/2011] [Indexed: 10/17/2022]
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Filipović D, Pirkmajer S, Mis K, Mars T, Grubic Z. Expression of glucocorticoid receptors in the regenerating human skeletal muscle. Physiol Res 2011; 60:S147-54. [PMID: 21777031 DOI: 10.33549/physiolres.932171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Many stress conditions are accompanied by skeletal muscle dysfunction and regeneration, which is essentially a recapitulation of the embryonic development. However, regeneration usually occurs under conditions of hypothalamus-pituitary-adrenal gland axis activation and therefore increased glucocorticoid (GC) levels. Glucocorticoid receptor (GR), the main determinant of cellular responsiveness to GCs, exists in two isoforms (GRalpha and GRbeta) in humans. While the role of GRalpha is well characterized, GRbeta remains an elusive player in GC signalling. To elucidate basic characteristics of GC signalling in the regenerating human skeletal muscle we assessed GRalpha and GRbeta expression pattern in cultured human myoblasts and myotubes and their response to 24-hour dexamethasone (DEX) treatment. There was no difference in GRalpha mRNA and protein expression or DEX-mediated GRalpha down-regulation in myoblasts and myotubes. GRbeta mRNA level was very low in myoblasts and remained unaffected by differentiation and/or DEX. GRbeta protein could not be detected. These results indicate that response to GCs is established very early during human skeletal muscle regeneration and that it remains practically unchanged before innervation is established. Very low GRbeta mRNA expression and inability to detect GRbeta protein suggests that GRbeta is not a major player in the early stages of human skeletal muscle regeneration.
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Affiliation(s)
- D Filipović
- Laboratory of Molecular Biology and Endocrinology, Institute of Nuclear Sciences Vinča, Belgrade, Serbia
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19
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Deželak M, Bavec A. Third intracellular loop of glucagon like-peptide-1 receptor is coupled with endogenous mono-ADP-ribosyltransferase - novel type of receptor regulation? Eur J Pharmacol 2011; 666:35-42. [PMID: 21635883 DOI: 10.1016/j.ejphar.2011.05.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 05/13/2011] [Accepted: 05/17/2011] [Indexed: 10/18/2022]
Abstract
Our previous studies revealed the main role of the third intracellular loop (IC(3)) of glucagon-like peptide-1 receptor (GLP-1 receptor), in G-protein activation, where the presence or absence of agonist and the receptor phosphorylation seemed to be the only regulatory mechanisms. In order to further study the signaling mechanisms of GLP-1 receptor, we investigated the effect of the third intracellular loop-derived peptide on endogenous mono-ADP-ribosyltransferase mediated mono-ADP-ribosylation of G-proteins β subunit in CHO cells. Results showed an inhibitory effect of IC(3) peptide on mono-ADP-ribosylation of β subunit, obviously via the mechanism of competitive inhibition. Excluding the activity of this inhibitory mechanism via pertussis toxin-sensitive G proteins, the direct functional coupling of IC(3) of GLP-1 receptor and endogenous mono-ADP-ribosyltransferase was confirmed. We suggest that this arginine specific enzymatic posttranslational modification of third intracellular loop of GLP-1 receptor might represent a possible novel mechanism of receptor activity regulation and the pharmacological potential in treatment of diabetes mellitus type 2.
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Affiliation(s)
- Matjaž Deželak
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia
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Pirkmajer S, Filipovic D, Mars T, Mis K, Grubic Z. HIF-1alpha response to hypoxia is functionally separated from the glucocorticoid stress response in the in vitro regenerating human skeletal muscle. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1693-700. [PMID: 20943857 DOI: 10.1152/ajpregu.00133.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Injury of skeletal muscle is followed by muscle regeneration in which new muscle tissue is formed from the proliferating mononuclear myoblasts, and by systemic response to stress that exposes proliferating myoblasts to increased glucocorticoid (GC) concentration. Because of its various causes, hypoxia is a frequent condition affecting skeletal muscle, and therefore both processes, which importantly determine the outcome of the injury, often proceed under hypoxic conditions. It is therefore important to identify and characterize in proliferating human myoblasts: 1) response to hypoxia which is generally organized by hypoxia-inducible factor-1α (HIF-1α); 2) response to GCs which is mediated through the isoforms of glucocorticoid receptors (GRs) and 11β-hydroxysteroid dehydrogenases (11β-HSDs), and 3) the response to GCs under the hypoxic conditions and the influence of this combination on the factors controlling myoblast proliferation. Using real-time PCR, Western blotting, and HIF-1α small-interfering RNA silencing, we demonstrated that cultured human myoblasts possess both, the HIF-1α-based response to hypoxia, and the GC response system composed of GRα and types 1 and 2 11β-HSDs. However, using combined dexamethasone and hypoxia treatments, we demonstrated that these two systems operate practically without mutual interactions. A seemingly surprising separation of the two systems that both organize response to hypoxic stress can be explained on the evolutionary basis: the phylogenetically older HIF-1α response is a protection at the cellular level, whereas the GC stress response protects the organism as a whole. This necessitates actions, like downregulation of IL-6 secretion and vascular endothelial growth factor, that might not be of direct benefit for the affected myoblasts.
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Affiliation(s)
- Sergej Pirkmajer
- Laboratory for Molecular Neurobiology, Institute of Pathophysiology, Faculty of Medicine, Univ. of Ljubljana, Zaloska 4, 1000 Ljubljana, Slovenia
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Kang SB, Lee TG. Muscle Regeneration: Research for the Treatment of Fecal Incontinence. JOURNAL OF THE KOREAN SOCIETY OF COLOPROCTOLOGY 2010. [DOI: 10.3393/jksc.2010.26.1.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Sung-Bum Kang
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
| | - Taek-Gu Lee
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
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Neural agrin changes the electrical properties of developing human skeletal muscle cells. Cell Mol Neurobiol 2008; 29:123-31. [PMID: 18807173 DOI: 10.1007/s10571-008-9304-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 08/04/2008] [Indexed: 12/21/2022]
Abstract
Recent investigations suggest that the effects of neural agrin might not be limited to neuromuscular junction formation and maintenance and that other aspects of muscle development might be promoted by agrin. Here we tested the hypothesis that agrin induces a change in the excitability properties in primary cultures of non-innervated human myotubes. Electrical membrane properties of human myotubes were recorded using the whole-cell patch-clamp technique. Cell incubation with recombinant chick neural agrin (1 nM) led to a more negative membrane resting potential. Addition of strophanthidin, a blocker of the Na(+)/K(+) ATPase, depolarized agrin-treated myotubes stronger than control, indicating, in the presence of agrin, a higher contribution of the Na(+)/K(+) ATPase in establishing the resting membrane potential. Indeed, larger amounts of both the alpha1 and the alpha2 isoforms of the Na(+)/K(+) ATPase protein were expressed in agrin-treated cells. A slight but significant down-regulation of functional apamin-sensitive K(+) channels was observed after agrin treatment. These results indicate that neural agrin might act as a trophic factor promoting the maturation of membrane electrical properties during differentiation, confirming the role of agrin as a general promoter of muscle development.
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Synaptogenetic mechanisms controlling postsynaptic differentiation of the neuromuscular junction are nerve-dependent in human and nerve-independent in mouse C2C12 muscle cultures. Chem Biol Interact 2008; 175:50-7. [PMID: 18691702 DOI: 10.1016/j.cbi.2008.05.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2007] [Revised: 05/14/2008] [Accepted: 05/15/2008] [Indexed: 11/23/2022]
Abstract
Acetylcholinesterase (EC 3.1.1.7, AChE) is one of the components of the neuromuscular junction (NMJ). Its expression and targeting in the skeletal muscle fiber is therefore under the control of the mechanisms responsible for the formation of the highly complex structure of this synapse. Recently, it has been demonstrated that myotubes of the C2C12 mouse muscle cell line form highly differentiated pretzel-like postsynaptic accumulations of acetylcholine receptors (AChRs) in the complete absence of the nerve if they are cultured on the laminin coating. This finding questions previously stressed importance of the nerve-derived factors in NMJ synaptogenesis and therefore deserves additional testing. The aim of this paper was to test whether the reported nerve-independency can be demonstrated also in the cultured human muscle meaning that the findings on C2C12 cultures can be extrapolated also to the human muscle. In our experiments aneurally cultured human myotubes failed to form AChR clusters on its surface, no matter if they were grown on normal gelatine or laminin coating. However, when innervated by neurons extending from the rat embryonic spinal cord, human myotubes formed AChR clusters with elaborate topography but strictly on the areas contacted by the nerve. One can hypothesize that higher nerve dependency of the NMJ synaptogenesis in humans in comparison to other species reflects species-specific differences in the organization of movement. Humans have the highest "fractionation of movement" capacity which probably requests different, more nerve-controlled development of the motor system including nerve-restricted development of the neuromuscular contacts.
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Dhawan V, Lytle IF, Dow DE, Huang YC, Brown DL. Neurotization improves contractile forces of tissue-engineered skeletal muscle. ACTA ACUST UNITED AC 2008; 13:2813-21. [PMID: 17822360 DOI: 10.1089/ten.2007.0003] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Engineered functional skeletal muscle would be beneficial in reconstructive surgery. Our previous work successfully generated 3-dimensional vascularized skeletal muscle in vivo. Because neural signals direct muscle maturation, we hypothesized that neurotization of these constructs would increase their contractile force. Additionally, should neuromuscular junctions (NMJs) develop, indirect stimulation (via the nerve) would be possible, allowing for directed control. Rat myoblasts were cultured, suspended in fibrin gel, and implanted within silicone chambers around the femoral vessels and transected femoral nerve of syngeneic rats for 4 weeks. Neurotized constructs generated contractile forces 5 times as high as the non-neurotized controls. Indirect stimulation via the nerve elicited contractions of neurotized constructs. Curare administration ceased contraction in these constructs, providing physiologic evidence of NMJ formation. Histology demonstrated intact muscle fibers, and immunostaining positively identified NMJs. These results indicate that neurotization of engineered skeletal muscle significantly increases force generation and causes NMJs to develop, allowing indirect muscle stimulation.
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MESH Headings
- Animals
- Bungarotoxins/metabolism
- Cell Separation
- Cells, Cultured
- Centrifugation
- Collagenases/pharmacology
- Culture Media, Serum-Free
- Curare/pharmacology
- Femoral Artery/surgery
- Femoral Nerve/surgery
- Femoral Vein/surgery
- Fibrin/chemistry
- Filtration
- Fluorescein-5-isothiocyanate/metabolism
- Fluorescent Dyes/metabolism
- Gels/chemistry
- Immunohistochemistry
- Models, Biological
- Muscle Contraction/drug effects
- Muscle, Skeletal/cytology
- Muscle, Skeletal/physiology
- Neuromuscular Junction/metabolism
- Rats
- Rats, Inbred F344
- Satellite Cells, Skeletal Muscle/cytology
- Satellite Cells, Skeletal Muscle/physiology
- Satellite Cells, Skeletal Muscle/transplantation
- Temperature
- Time Factors
- Tissue Culture Techniques
- Tissue Engineering/methods
- Transplantation, Isogeneic
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Affiliation(s)
- Vikas Dhawan
- Section of Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, Michigan 48109, USA
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Bandi E, Jevšek M, Mars T, Jurdana M, Formaggio E, Sciancalepore M, Fumagalli G, Grubič Z, Ruzzier F, Lorenzon P. Neural agrin controls maturation of the excitation-contraction coupling mechanism in human myotubes developing in vitro. Am J Physiol Cell Physiol 2008; 294:C66-73. [DOI: 10.1152/ajpcell.00248.2007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to elucidate the mechanisms responsible for the effects of innervation on the maturation of excitation-contraction coupling apparatus in human skeletal muscle. For this purpose, we compared the establishment of the excitation-contraction coupling mechanism in myotubes differentiated in four different experimental paradigms: 1) aneurally cultured, 2) cocultured with fetal rat spinal cord explants, 3) aneurally cultured in medium conditioned by cocultures, and 4) aneurally cultured in medium supplemented with purified recombinant chick neural agrin. Ca2+ imaging indicated that coculturing human muscle cells with rat spinal cord explants increased the fraction of cells showing a functional excitation-contraction coupling mechanism. The effect of spinal cord explants was mimicked by treatment with medium conditioned by cocultures or by addition of 1 nM of recombinant neural agrin to the medium. The treatment with neural agrin increased the number of human muscle cells in which functional ryanodine receptors (RyRs) and dihydropyridine-sensitive L-type Ca2+ channels were detectable. Our data are consistent with the hypothesis that agrin, released from neurons, controls the maturation of the excitation-contraction coupling mechanism and that this effect is due to modulation of both RyRs and L-type Ca2+ channels. Thus, a novel role for neural agrin in skeletal muscle maturation is proposed.
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Gajsek N, Jevsek M, Grubic Z. Expression of MuSK in in vitro-innervated human muscle. J Mol Neurosci 2007; 30:27-8. [PMID: 17192614 DOI: 10.1385/jmn:30:1:27] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 11/11/2022]
Abstract
Unlike rodent or avian muscle, which forms clusters of acetylcholine receptors (AChRs) on its surface, exhibits cross striations, and contracts spontaneously even if cultured in the absence of the nerve, human muscle must be innervated to reach such differentiation level under in vitro conditions (Kobayashi and Askanas, 1985; Mars et al., 2001). Because it is known that AChR clustering and other aspects of neuromuscular junction (NMJ) formation necessitate the activation of muscle-specific kinase (MuSK), one explanation of this inability of human muscle is that it has no MuSK or that it cannot be activated in the absence of the nerve. To test this hypothesis we analyzed cultured human muscle for the expression of MuSK at two stages of differentiation: postfusion myotube and innervated, contracting myotube. Analyses were carried out at the mRNA level, as no reliable anti-MuSK antibodies are available for the immunocytochemical demonstration of MuSK in cultured human muscle. The presence of MuSK, however, can be tested indirectly, as it can be activated in the absence of the nerve simply by growing muscle culture on laminin coating (Kummer et al., 2004). In the second part of our study, we therefore tested human myotubes for the presence and activation of MuSK by exposing them to laminin coating and by analyzing them afterwards for the areas of postsynaptic differentiation typical for NMJ formation.
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Affiliation(s)
- Nina Gajsek
- Institute of Pathophysiology, Medical Faculty, University of Ljubljana, Slovenia SI-1000
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Mis K, Mars T, Jevsek M, Strasek H, Golicnik M, Brecelj J, Komel R, King MP, Miranda AF, Grubic Z. Expression and distribution of acetylcholinesterase among the cellular components of the neuromuscular junction formed in human myotube in vitro. Chem Biol Interact 2005; 157-158:29-35. [PMID: 16256091 DOI: 10.1016/j.cbi.2005.10.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The results of our recent investigations on the expression and distribution of acetylcholinesterase (EC. 3.1.1.7, AChE) in the experimental model of the in vitro innervated human muscle are summarized and discussed here. This is the only model allowing studies on AChE expression at all stages of the neuromuscular junction (NMJ) formation in the human muscle. Since it consists not only of the motor neurons and myotubes but also of glial cells, which are essential for the normal development of the motor neurons, NMJs become functional and differentiated in this system. We followed AChE expression at various stages of the NMJ formation and in the context of other events characteristic for this process. Neuronal and muscular part were analysed at both, mRNA and mature enzyme level. AChE is expressed in motor neurons and skeletal muscle at the earliest stages of their development, long before NMJ starts to form and AChE begins to act as a cholinergic component. Temporal pattern of AChE mRNA expression in motor neurons is similar to the pattern of mRNA encoding synaptogenetic variant of agrin. There are no AChE accummulations at the NMJ at the early stage of its formation, when immature clusters of nicotinic receptors are formed at the neuromuscular contacts and when occasional NMJ-mediated contractions are already observed. The transformation from immature, bouton-like neuromuscular contacts into differentiated NMJs with mature, compact receptor clusters, myonuclear accumulations and dense AChE patches begins at the time when basal lamina starts to form in the synaptic cleft. Our observations support the concept that basal lamina formation is the essential event in the transformation of immature neuromuscular contact into differentiated NMJ, with the accumulation of not only muscular but also neuronal AChE in the synaptic cleft.
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Affiliation(s)
- Katarina Mis
- Laboratory for Molecular Neurobiology, Institute of Pathophysiology, Medical Faculty, School of Medicine, University of Ljubljana, Zaloska 4, 1000 Ljubljana, Slovenia
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Nicholas A. K, Jacques P. B. Basement Membranes in Development. CURRENT TOPICS IN MEMBRANES 2005. [DOI: 10.1016/s1063-5823(05)56003-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Jevsek M, Mars T, Mis K, Grubic Z. Origin of acetylcholinesterase in the neuromuscular junction formed in the in vitro innervated human muscle. Eur J Neurosci 2004; 20:2865-71. [PMID: 15579140 DOI: 10.1111/j.1460-9568.2004.03752.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Synaptic basal lamina is interposed between the pre- and postsynaptic membrane of the neuromuscular junction (NMJ). This position permits deposition of basal lamina-bound NMJ components of both neuronal and muscle fibre origin. One such molecule is acetylcholinesterase (AChE). The origin of NMJ AChE has been investigated previously as the answer would elucidate the relative contributions of muscle fibers and motor neurons to NMJ formation. However, in the experimental models used in prior investigations either the neuronal or muscular components of the NMJs were removed, or the NMJs were poorly differentiated. Therefore, the question of AChE origin in the intact and functional NMJ remains open. Here, we have approached this question using an in vitro model in which motor neurons, growing from embryonic rat spinal cord explants, form well differentiated NMJs with cultured human myotubes. By immunocytochemical staining with species-specific anti-AChE antibodies, we are able to differentiate between human (muscular) and rat (neuronal) AChE at the NMJ. We observed strong signal at the NMJ after staining with human AChE antibodies, which suggests a significant muscular AChE contribution. However, a weaker, but still clearly recognizable signal is observed after staining with rat AChE antibodies, suggesting a smaller fraction of AChE was derived from motor neurons. This is the first report demonstrating that both motor neuron and myotube contribute synaptic AChE under conditions where they interact with each other in the formation of an intact and functional NMJ.
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Affiliation(s)
- Marko Jevsek
- Laboratory for Molecular Neurobiology, Institute of Pathophysiology, Medical School, University of Ljubljana, Zaloska 4, 1000 Ljubljana, Slovenia
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