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Bornstein B, Watkins B, Passini FS, Blecher R, Assaraf E, Sui XM, Brumfeld V, Tsoory M, Kröger S, Zelzer E. The mechanosensitive ion channel ASIC2 mediates both proprioceptive sensing and spinal alignment. Exp Physiol 2024; 109:135-147. [PMID: 36951012 PMCID: PMC10988735 DOI: 10.1113/ep090776] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 02/20/2023] [Indexed: 03/24/2023]
Abstract
By translating mechanical forces into molecular signals, proprioceptive neurons provide the CNS with information on muscle length and tension, which is necessary to control posture and movement. However, the identities of the molecular players that mediate proprioceptive sensing are largely unknown. Here, we confirm the expression of the mechanosensitive ion channel ASIC2 in proprioceptive sensory neurons. By combining in vivo proprioception-related functional tests with ex vivo electrophysiological analyses of muscle spindles, we showed that mice lacking Asic2 display impairments in muscle spindle responses to stretch and motor coordination tasks. Finally, analysis of skeletons of Asic2 loss-of-function mice revealed a specific effect on spinal alignment. Overall, we identify ASIC2 as a key component in proprioceptive sensing and a regulator of spine alignment.
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Affiliation(s)
- Bavat Bornstein
- Department of Molecular GeneticsWeizmann Institute of ScienceRehovotIsrael
| | - Bridgette Watkins
- Department of Physiological Genomics, Biomedical CenterLudwig‐Maximilians‐UniversityPlanegg‐MartinsriedGermany
| | - Fabian S. Passini
- Department of Molecular GeneticsWeizmann Institute of ScienceRehovotIsrael
| | - Ronen Blecher
- Orthopedic DepartmentAssuta Ashdod University Hospital, Ashdod, Israel, affiliated to Ben Gurion University of the NegevBeer ShebaIsrael
| | - Eran Assaraf
- Department of Orthopedic SurgeryShamir Medical Center, Assaf HaRofeh Campus, Zeffifin, Israel, affiliated to Sackler Faculty of Medicine, Tel Aviv UniversityTel AvivIsrael
| | - Xiao Meng Sui
- Department of Chemical Research SupportWeizmann Institute of ScienceRehovotIsrael
| | - Vlad Brumfeld
- Department of Chemical Research SupportWeizmann Institute of ScienceRehovotIsrael
| | - Michael Tsoory
- Department of Veterinary ResourcesWeizmann Institute of ScienceRehovotIsrael
| | - Stephan Kröger
- Department of Physiological Genomics, Biomedical CenterLudwig‐Maximilians‐UniversityPlanegg‐MartinsriedGermany
| | - Elazar Zelzer
- Department of Molecular GeneticsWeizmann Institute of ScienceRehovotIsrael
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Housley SN, Gardolinski EA, Nardelli P, Reed J, Rich MM, Cope TC. Mechanosensory encoding in ex vivo muscle-nerve preparations. Exp Physiol 2024; 109:35-44. [PMID: 37119460 PMCID: PMC10613129 DOI: 10.1113/ep090763] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 04/12/2023] [Indexed: 05/01/2023]
Abstract
Our objective was to evaluate an ex vivo muscle-nerve preparation used to study mechanosensory signalling by low threshold mechanosensory receptors (LTMRs). Specifically, we aimed to assess how well the ex vivo preparation represents in vivo firing behaviours of the three major LTMR subtypes of muscle primary sensory afferents, namely type Ia and II muscle spindle (MS) afferents and type Ib tendon organ afferents. Using published procedures for ex vivo study of LTMRs in mouse hindlimb muscles, we replicated earlier reports on afferent firing in response to conventional stretch paradigms applied to non-contracting, that is passive, muscle. Relative to in vivo studies, stretch-evoked firing for confirmed MS afferents in the ex vivo preparation was markedly reduced in firing rate and deficient in encoding dynamic features of muscle stretch. These deficiencies precluded conventional means of discriminating type Ia and II afferents. Muscle afferents, including confirmed Ib afferents were often indistinguishable based on their similar firing responses to the same physiologically relevant stretch paradigms. These observations raise uncertainty about conclusions drawn from earlier ex vivo studies that either attribute findings to specific afferent types or suggest an absence of treatment effects on dynamic firing. However, we found that replacing the recording solution with bicarbonate buffer resulted in afferent firing rates and profiles more like those seen in vivo. Improving representation of the distinctive sensory encoding properties in ex vivo muscle-nerve preparations will promote accuracy in assigning molecular markers and mechanisms to heterogeneous types of muscle mechanosensory neurons.
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Affiliation(s)
- Stephen N. Housley
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
| | | | - Paul Nardelli
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
| | - J'Ana Reed
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
| | - Mark M. Rich
- Department of Neuroscience, Cell Biology and PhysiologyWright State UniversityDaytonOHUSA
| | - Timothy C. Cope
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaGAUSA
- W.H. Coulter Department of Biomedical EngineeringEmory University and Georgia Institute of Technology, Georgia Institute of TechnologyAtlantaGAUSA
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Watkins B, Schultheiß J, Rafuna A, Hintze S, Meinke P, Schoser B, Kröger S. Degeneration of muscle spindles in a murine model of Pompe disease. Sci Rep 2023; 13:6555. [PMID: 37085544 PMCID: PMC10121695 DOI: 10.1038/s41598-023-33543-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 04/14/2023] [Indexed: 04/23/2023] Open
Abstract
Pompe disease is a debilitating medical condition caused by a functional deficiency of lysosomal acid alpha-glucosidase (GAA). In addition to muscle weakness, people living with Pompe disease experience motor coordination deficits including an instable gait and posture. We reasoned that an impaired muscle spindle function might contribute to these deficiencies and therefore analyzed proprioception as well as muscle spindle structure and function in 4- and 8-month-old Gaa-/- mice. Gait analyses showed a reduced inter-limb and inter-paw coordination in Gaa-/- mice. Electrophysiological analyses of single-unit muscle spindle proprioceptive afferents revealed an impaired sensitivity of the dynamic and static component of the stretch response. Finally, a progressive degeneration of the sensory neuron and of the intrafusal fibers was detectable in Gaa-/- mice. We observed an increased abundance and size of lysosomes, a fragmentation of the inner and outer connective tissue capsule and a buildup of autophagic vacuoles in muscle spindles from 8-month-old Gaa-/- mice, indicating lysosomal defects and an impaired autophagocytosis. These results demonstrate a structural and functional degeneration of muscle spindles and an altered motor coordination in Gaa-/- mice. Similar changes could contribute to the impaired motor coordination in patients living with Pompe disease.
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Affiliation(s)
- Bridgette Watkins
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Grosshaderner Strasse 9, 82152, Planegg-Martinsried, Germany
| | - Jürgen Schultheiß
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Grosshaderner Strasse 9, 82152, Planegg-Martinsried, Germany
| | - Andi Rafuna
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Grosshaderner Strasse 9, 82152, Planegg-Martinsried, Germany
| | - Stefan Hintze
- Department of Neurology, Friedrich-Baur-Institute, LMU Klinikum, Ludwig-Maximilians-University, Munich, Germany
| | - Peter Meinke
- Department of Neurology, Friedrich-Baur-Institute, LMU Klinikum, Ludwig-Maximilians-University, Munich, Germany
| | - Benedikt Schoser
- Department of Neurology, Friedrich-Baur-Institute, LMU Klinikum, Ludwig-Maximilians-University, Munich, Germany
| | - Stephan Kröger
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Grosshaderner Strasse 9, 82152, Planegg-Martinsried, Germany.
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Watkins B, Schuster HM, Gerwin L, Schoser B, Kröger S. The effect of methocarbamol and mexiletine on murine muscle spindle function. Muscle Nerve 2022; 66:96-105. [PMID: 35373353 DOI: 10.1002/mus.27546] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 02/23/2022] [Accepted: 02/25/2022] [Indexed: 11/10/2022]
Abstract
INTRODUCTION/AIMS The muscle relaxant methocarbamol and the antimyotonic drug mexiletine are widely used for the treatment of muscle spasms, myotonia, and pain syndromes. To determine whether these drugs affect muscle spindle function, we studied their effect on the resting discharge and on stretch-induced action potential frequencies of proprioceptive afferent neurons. METHODS Single unit action potential frequencies of proprioceptive afferents from muscle spindles in the murine extensor digitorum longus muscle of adult C57BL/6J mice were recorded under resting conditions and during ramp-and-hold stretches. Maximal tetanic force of the same muscle after direct stimulation was determined. High-resolution confocal microscopy analysis was performed to determine the distribution of Nav 1.4 channels, a potential target for both drugs. RESULTS Methocarbamol and mexiletine inhibited the muscle spindle resting discharge in a dose-dependent manner with IC50 values around 300 μM and 6 μM, respectively. With increasing concentrations of both drugs, the response to stretch was also affected, with the static sensitivity first followed by the dynamic sensitivity. At high concentrations, both drugs completely blocked muscle spindle afferent output. Both drugs also reversibly reduced the specific force of the extensor digitorum longus muscle after tetanic stimulation. Finally, we present evidence for the presence and specific localization of the voltage-gated sodium channel Nav 1.4 in intrafusal fibers. DISCUSSION In this study we demonstrate that both muscle relaxants affect muscle spindle function, suggesting impaired proprioception as a potential side effect of both drugs. Moreover, our results provide additional evidence of a peripheral activity of methocarbamol and mexiletine.
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Affiliation(s)
- Bridgette Watkins
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| | - Hedwig M Schuster
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| | - Laura Gerwin
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
| | - Benedikt Schoser
- Department of Neurology, LMU Klinikum, Friedrich-Baur-Institute, Ludwig-Maximilians-University, Munich, Germany
| | - Stephan Kröger
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Planegg-Martinsried, Germany
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Wilkinson KA. Molecular determinants of mechanosensation in the muscle spindle. Curr Opin Neurobiol 2022; 74:102542. [PMID: 35430481 PMCID: PMC9815952 DOI: 10.1016/j.conb.2022.102542] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 01/12/2022] [Accepted: 03/13/2022] [Indexed: 01/11/2023]
Abstract
The muscle spindle (MS) provides essential sensory information for motor control and proprioception. The Group Ia and II MS afferents are low threshold slowly-adapting mechanoreceptors and report both static muscle length and dynamic muscle movement information. The exact molecular mechanism by which MS afferents transduce muscle movement into action potentials is incompletely understood. This short review will discuss recent evidence suggesting that PIEZO2 is an essential mechanically sensitive ion channel in MS afferents and that vesicle-released glutamate contributes to maintaining afferent excitability during the static phase of stretch. Other mechanically gated ion channels, voltage-gated sodium channels, other ion channels, regulatory proteins, and interactions with the intrafusal fibers are also important for MS afferent mechanosensation. Future studies are needed to fully understand mechanosensation in the MS and whether different complements of molecular mediators contribute to the different response properties of Group Ia and II afferents.
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Muscle spindles of the multifidus muscle undergo structural change after intervertebral disc degeneration. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2022; 31:1879-1888. [PMID: 35618974 PMCID: PMC7613463 DOI: 10.1007/s00586-022-07235-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 03/14/2022] [Accepted: 04/17/2022] [Indexed: 11/05/2022]
Abstract
Purpose Proprioceptive deficits are common in low back pain. The multifidus muscle undergoes substantial structural change after back injury, but whether muscle spindles are affected is unclear. This study investigated whether muscle spindles of the multifidus muscle are changed by intervertebral disc (IVD) degeneration in a large animal model. Methods IVD degeneration was induced by partial thickness annulus fibrosus lesion to the L3-4 IVD in nine sheep. Multifidus muscle tissue at L4 was harvested at six months after lesion, and from six age-/sex-matched naïve control animals. Muscle spindles were identified in Van Gieson’s-stained sections by morphology. The number, location and cross-sectional area (CSA) of spindles, the number, type and CSA of intrafusal fibers, and thickness of the spindle capsule were measured. Immunofluorescence assays examined Collagen I and III expression. Results Multifidus muscle spindles were located centrally in the muscle and generally near connective tissue. There were no differences in the number or location of muscle spindles after IVD degeneration and only changes in the CSA of nuclear chain fibers. The thickness of connective tissue surrounding the muscle spindle was increased as was the expression of Collagen I and III. Conclusion Changes to the connective tissue and collagen expression of the muscle spindle capsule are likely to impact their mechanical properties. Changes in capsule stiffness may impact the transmission of length change to muscle spindles and thus transduction of sensory information. This change in muscle spindle structure may explain some of the proprioceptive deficits identified with low back pain.
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Moyle LA, Davoudi S, Gilbert PM. Innovation in culture systems to study muscle complexity. Exp Cell Res 2021; 411:112966. [PMID: 34906582 DOI: 10.1016/j.yexcr.2021.112966] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 10/31/2021] [Accepted: 12/04/2021] [Indexed: 11/19/2022]
Abstract
Endogenous skeletal muscle development, regeneration, and pathology are extremely complex processes, influenced by local and systemic factors. Unpinning how these mechanisms function is crucial for fundamental biology and to develop therapeutic interventions for genetic disorders, but also conditions like sarcopenia and volumetric muscle loss. Ex vivo skeletal muscle models range from two- and three-dimensional primary cultures of satellite stem cell-derived myoblasts grown alone or in co-culture, to single muscle myofibers, myobundles, and whole tissues. Together, these systems provide the opportunity to gain mechanistic insights of stem cell behavior, cell-cell interactions, and mature muscle function in simplified systems, without confounding variables. Here, we highlight recent advances (published in the last 5 years) using in vitro primary cells and ex vivo skeletal muscle models, and summarize the new insights, tools, datasets, and screening methods they have provided. Finally, we highlight the opportunity for exponential advance of skeletal muscle knowledge, with spatiotemporal resolution, that is offered by guiding the study of muscle biology and physiology with in silico modelling and implementing high-content cell biology systems and ex vivo physiology platforms.
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Affiliation(s)
- Louise A Moyle
- Institute of Biomedical Engineering, Toronto, ON, M5S 3G9, Canada; Donnelly Centre for Cellular and Biomolecular Research, Toronto, ON, M5S 3E1, Canada
| | - Sadegh Davoudi
- Institute of Biomedical Engineering, Toronto, ON, M5S 3G9, Canada; Donnelly Centre for Cellular and Biomolecular Research, Toronto, ON, M5S 3E1, Canada
| | - Penney M Gilbert
- Institute of Biomedical Engineering, Toronto, ON, M5S 3G9, Canada; Donnelly Centre for Cellular and Biomolecular Research, Toronto, ON, M5S 3E1, Canada; Department of Cell and Systems Biology, University of Toronto, Toronto, ON, M5S 1A8, Canada.
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Bornstein B, Konstantin N, Alessandro C, Tresch MC, Zelzer E. More than movement: the proprioceptive system as a new regulator of musculoskeletal biology. CURRENT OPINION IN PHYSIOLOGY 2021. [DOI: 10.1016/j.cophys.2021.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Kröger S, Watkins B. Muscle spindle function in healthy and diseased muscle. Skelet Muscle 2021; 11:3. [PMID: 33407830 PMCID: PMC7788844 DOI: 10.1186/s13395-020-00258-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 12/20/2020] [Indexed: 12/16/2022] Open
Abstract
Almost every muscle contains muscle spindles. These delicate sensory receptors inform the central nervous system (CNS) about changes in the length of individual muscles and the speed of stretching. With this information, the CNS computes the position and movement of our extremities in space, which is a requirement for motor control, for maintaining posture and for a stable gait. Many neuromuscular diseases affect muscle spindle function contributing, among others, to an unstable gait, frequent falls and ataxic behavior in the affected patients. Nevertheless, muscle spindles are usually ignored during examination and analysis of muscle function and when designing therapeutic strategies for neuromuscular diseases. This review summarizes the development and function of muscle spindles and the changes observed under pathological conditions, in particular in the various forms of muscular dystrophies.
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Affiliation(s)
- Stephan Kröger
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University Munich, Großhaderner Str. 9, 82152, Planegg-Martinsried, Germany.
| | - Bridgette Watkins
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University Munich, Großhaderner Str. 9, 82152, Planegg-Martinsried, Germany
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Papaioannou S, Dimitriou M. Muscle spindle function in muscular dystrophy: A potential target for therapeutic intervention. J Physiol 2020; 598:1433-1434. [PMID: 32128822 DOI: 10.1113/jp279611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Accepted: 03/02/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Stylianos Papaioannou
- Physiology Section, Department of Integrative Medical Biology, University of Umeå, Umeå, Sweden
| | - Michael Dimitriou
- Physiology Section, Department of Integrative Medical Biology, University of Umeå, Umeå, Sweden
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