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Brandenburg JE, Fogarty MJ, Zhan WZ, Kopper LA, Sieck GC. Postnatal survival of phrenic motor neurons is promoted by BDNF/TrkB.FL signaling. J Appl Physiol (1985) 2024; 136:1113-1121. [PMID: 38511211 DOI: 10.1152/japplphysiol.00911.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 03/22/2024] Open
Abstract
The number of motor neurons (MNs) declines precipitously during the final trimester before birth. Thereafter, the number of MNs remains relatively stable, with their connections to skeletal muscle dependent on neurotrophins, including brain-derived neurotrophic factor (BDNF) signaling through its high-affinity full-length tropomyosin-related kinase receptor subtype B (TrkB.FL) receptor. As a genetic knockout of BDNF leads to extensive MN loss and postnatal death within 1-2 days after birth, we tested the hypothesis that postnatal inhibition of BDNF/TrkB.FL signaling is important for postnatal phrenic MN (PhMN) survival. In the present study, we used a 1NMPP1-sensitive TrkBF616A mutant mouse to evaluate the effects of inhibition of TrkB kinase activity on phrenic MN (PhMN) numbers and diaphragm muscle (DIAm) fiber cross-sectional area (CSA). Pups were exposed to 1NMPP1 or vehicle (DMSO) from birth to 21 days old (weaning) via the mother's ingestion in the drinking water. Following weaning, the right phrenic nerve was exposed in the neck and the proximal end dipped in a rhodamine solution to retrogradely label PhMNs. After 24 h, the cervical spinal cord and DIAm were excised. Labeled PhMNs were imaged using confocal microscopy, whereas DIAm strips were frozen at ∼1.5× resting length, cryosectioned, and stained with hematoxylin and eosin to assess CSA. We observed an ∼34% reduction in PhMN numbers and increased primary dendrite numbers in 1NMPP1-treated TrkBF616A mice. The distribution of PhMN size (somal surface area) DIAm fiber cross-sectional areas did not differ. We conclude that survival of PhMNs during early postnatal development is sensitive to BDNF/TrkB.FL signaling.NEW & NOTEWORTHY During early postnatal development, BDNF/TrkB signaling promotes PhMN survival. Inhibition of BDNF/TrkB signaling in early postnatal development does not impact PhMN size. Inhibition of BDNF/TrkB signaling in early postnatal development does not impact the number or CSA of DIAm fibers.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota, United States
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Wen-Zhi Zhan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Leo A Kopper
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
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2
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Fogarty MJ, Zhan WZ, Mantilla CB, Sieck GC. Cervical spinal cord hemisection impacts sigh and the respiratory reset in male rats. Physiol Rep 2024; 12:e15973. [PMID: 38467570 DOI: 10.14814/phy2.15973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 02/28/2024] [Accepted: 02/29/2024] [Indexed: 03/13/2024] Open
Abstract
Cervical spinal cord injury impacts ventilatory and non-ventilatory functions of the diaphragm muscle (DIAm) and contributes to clinical morbidity and mortality in the afflicted population. Periodically, integrated brainstem neural circuit activity drives the DIAm to generate a markedly augmented effort or sigh-which plays an important role in preventing atelectasis and thus maintaining lung function. Across species, the general pattern of DIAm efforts during a normal sigh is variable in amplitude and the extent of post-sigh "apnea" (i.e., the post-sigh inter-breath interval). This post-sigh inter-breath interval acts as a respiratory reset, following the interruption of regular respiratory rhythm by sigh. We examined the impact of upper cervical (C2 ) spinal cord hemisection (C2 SH) on the transdiaphragmatic pressure (Pdi ) generated during sighs and the post-sigh respiratory reset in rats. Sighs were identified in Pdi traces by their characteristic biphasic pattern. We found that C2 SH results in a reduction of Pdi during both eupnea and sighs, and a decrease in the immediate post-sigh breath interval. These results are consistent with partial removal of descending excitatory synaptic inputs to phrenic motor neurons that results from C2 SH. Following cervical spinal cord injury, a reduction in the amplitude of Pdi during sighs may compromise the maintenance of normal lung function.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Wen-Zhi Zhan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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3
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Fogarty MJ. Age influences the specific force and fatigability of the external abdominal obliques but not pectoralis major muscles. Respir Physiol Neurobiol 2024; 320:104187. [PMID: 37939865 PMCID: PMC10841851 DOI: 10.1016/j.resp.2023.104187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/30/2023] [Accepted: 11/05/2023] [Indexed: 11/10/2023]
Abstract
In the elderly, airway infections are associated with impaired airway defense behaviors, leading to an increased risk of airway infection. The muscles of the chest and abdominal wall are essential for performing effective airway defense manoeuvres, however, very little is known about their function in aging. Here in the 6- and 24-months old Fischer 344 rat model of aging, we assess the contractility and fatigability of chest (the pectoralis major muscle) and abdominal wall (external abdominal oblique) muscles. We assessed muscle function using an ex vivo approach, measuring isometric specific forces normalised to muscle CSA, via a platinum plate field stimulations at a range of frequencies (5-150 Hz) for 1 s. Surprisingly, we did not observe any effect of age on the specific force and fatigue properties of the pectoral muscle. However, in 24-months old rats, EAO specific force was reduced by ∼32 %. These finding suggest that not all respiratory muscles are equally vulnerable to age-associated weakness.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA.
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4
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Sieck GC, Hernandez-Vizcarrondo GA, Brown AD, Fogarty MJ. Sarcopenia of the longitudinal tongue muscles in rats. Respir Physiol Neurobiol 2024; 319:104180. [PMID: 37863156 PMCID: PMC10851598 DOI: 10.1016/j.resp.2023.104180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/29/2023] [Accepted: 10/14/2023] [Indexed: 10/22/2023]
Abstract
The tongue is a muscular hydrostat, with lingual movements occurring during breathing, chewing, swallowing, vocalization, vomiting, coughing and grooming/sexual activities. In the elderly, reduced lingual dysfunction and weakness contribute to increased risks of obstructive sleep apnea and aspiration pneumonia. In Fischer 344 (F344) rats, a validated model of aging, hypoglossal motor neuron death is apparent, although there is no information regarding tongue strength. The intrinsic tongue muscles, the superior and inferior longitudinal, transversalis and verticalis exist in an interdigitated state. Recently, we established a method to measure the specific force of individual intrinsic tongue muscle, accounting for the tissue bulk that is not in the direction of uniaxial force. In the longitudinal muscles of 6- (n = 10), 18- (n = 9) and 24-month-old (n = 12) female and male F344 rats, we assessed specific force, fatigability, fiber type dependent cross-sectional area (CSA) and overall CSA. Muscle force and fatigue was assessed ex vivo using platinum plate simulation electrodes. Tongue muscles were frozen in melting isopentane, and transverse sections cut at 10 µm. Muscle fiber type was classified based on immunoreactivity to myosin heavy chain (MyHC) isoform antibodies. In H&E stained muscle, CSA and uniaxial muscle contributions to total tongue bulk was assessed. We observed a robust ∼30% loss of longitudinal specific force, with reductions in overall longitudinal muscle fiber CSA and specific atrophy of type IIx/IIb fibers. It will be important to investigate the mechanistic underpinnings of hypoglossal motor neuron death and tongue muscle weakness to eventually provide therapies for age-associated lingual dysfunctions.
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Affiliation(s)
- Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Alyssa D Brown
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA.
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Fogarty MJ. Loss of larger hypoglossal motor neurons in aged Fischer 344 rats. Respir Physiol Neurobiol 2023:104092. [PMID: 37331418 DOI: 10.1016/j.resp.2023.104092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/06/2023] [Accepted: 06/15/2023] [Indexed: 06/20/2023]
Abstract
The intrinsic (longitudinal, transversalis and verticalis) and extrinsic (genioglossus, styloglossus, hyoglossus and geniohyoid) tongue muscles are innervated by hypoglossal motor neurons (MNs). Tongue muscle activations occur during many behaviors: maintaining upper airway patency, chewing, swallowing, vocalization, vomiting, coughing, sneezing and grooming/sexual activities. In the tongues of the elderly, reduced oral motor function and strength contribute to increased risk of obstructive sleep apnoea. Tongue muscle atrophy and weakness is also described in rats, yet hypoglossal MN numbers are unknown. In young (6-months, n=10) and old (24-months, n=8) female and male Fischer 344 (F344) rats, stereological assessment of hypoglossal MN numbers and surface areas were performed on 16µm Nissl-stained brainstem cryosections. We observed a robust loss of ~15% of hypoglossal MNs and a modest ~8% reduction in their surface areas with age. In the larger size tertile of hypoglossal MNs, age-associated loss of hypoglossal MNs approached ~30% These findings uncover a potential neurogenic locus of pathology for age-associated tongue dysfunctions.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55905.
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Fogarty MJ, Rana S, Mantilla CB, Sieck GC. Size-dependent differences in mitochondrial volume density in phrenic motor neurons. J Appl Physiol (1985) 2023; 134:1332-1340. [PMID: 37022966 PMCID: PMC10190832 DOI: 10.1152/japplphysiol.00021.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 04/03/2023] [Accepted: 04/05/2023] [Indexed: 04/07/2023] Open
Abstract
Neuromotor control of diaphragm muscle (DIAm) motor units is dependent on an orderly size-dependent recruitment of phrenic motor neurons (PhMNs). Slow (type S) and fast, fatigue resistant (type FR) DIAm motor units, which are frequently recruited to sustain ventilation, comprise smaller PhMNs that innervate type I and IIa DIAm fibers. More fatigable fast (type FF) motor units, which are infrequently recruited for higher force, expulsive behaviors, comprise larger PhMNs that innervate more type IIx/IIb DIAm fibers. We hypothesize that due to the more frequent activation and thus higher energy demand of type S and FR motor units, the mitochondrial volume density (MVD) of smaller PhMNs is greater compared with larger PhMNs. In eight adult (6 mo old) Fischer 344 rats, PhMNs were identified via intrapleural injection of Alexa488-conjugated cholera toxin B (CTB). Following retrograde CTB labeling, mitochondria in PhMNs were labeled by transdural infusion of MitoTracker Red. PhMNs and mitochondria were imaged using multichannel confocal microscopy using a ×60 oil objective. Following optical sectioning and three-dimensional (3-D) rendering, PhMNs and mitochondria were analyzed volumetrically using Nikon Elements software. Analysis of MVD in somal and dendritic compartments was stratified by PhMN somal surface area. Smaller PhMNs (likely S and FR units) had greater somal MVDs compared with larger PhMNs (likely FF units). By contrast, proximal dendrites or larger PhMNs had higher MVD compared with dendrites of smaller PhMNs. We conclude that more active smaller PhMNs have a higher mitochondrial volume density to support their higher energy demand in sustaining ventilation.NEW & NOTEWORTHY Type S and FR motor units, comprising smaller phrenic motor neurons (PhMNs) are regularly activated to perform indefatigable ventilatory requirements. By contrast, type FF motor units, comprising larger PhMNs, are infrequently activated to perform expulsive straining and airway defense maneuvers. This difference in activation history is mirrored in the mitochondrial volume density (MVD), with smaller PhMNs having higher MVD than larger PhMNs. In proximal dendrites, this trend was reversed, with larger PhMNs having higher MVD than smaller PhMNs, likely due to the maintenance requirements for the larger dendritic arbor of FF PhMNs.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Sabhya Rana
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States
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Fogarty MJ. Inhibitory Synaptic Influences on Developmental Motor Disorders. Int J Mol Sci 2023; 24:ijms24086962. [PMID: 37108127 PMCID: PMC10138861 DOI: 10.3390/ijms24086962] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
During development, GABA and glycine play major trophic and synaptic roles in the establishment of the neuromotor system. In this review, we summarise the formation, function and maturation of GABAergic and glycinergic synapses within neuromotor circuits during development. We take special care to discuss the differences in limb and respiratory neuromotor control. We then investigate the influences that GABAergic and glycinergic neurotransmission has on two major developmental neuromotor disorders: Rett syndrome and spastic cerebral palsy. We present these two syndromes in order to contrast the approaches to disease mechanism and therapy. While both conditions have motor dysfunctions at their core, one condition Rett syndrome, despite having myriad symptoms, has scientists focused on the breathing abnormalities and their alleviation-to great clinical advances. By contrast, cerebral palsy remains a scientific quagmire or poor definitions, no widely adopted model and a lack of therapeutic focus. We conclude that the sheer abundance of diversity of inhibitory neurotransmitter targets should provide hope for intractable conditions, particularly those that exhibit broad spectra of dysfunction-such as spastic cerebral palsy and Rett syndrome.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
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8
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Fogarty MJ, Dasgupta D, Khurram OU, Sieck GC. Chemogenetic inhibition of TrkB signalling reduces phrenic motor neuron survival and size. Mol Cell Neurosci 2023; 125:103847. [PMID: 36958643 DOI: 10.1016/j.mcn.2023.103847] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 03/07/2023] [Accepted: 03/16/2023] [Indexed: 03/25/2023] Open
Abstract
Brain derived neurotrophic factor (BDNF) signalling through its high-affinity tropomyosin receptor kinase B (TrkB) is known to have potent effects on motor neuron survival and morphology during development and in neurodegenerative diseases. Here, we employed a novel 1NMPP1 sensitive TrkBF616 rat model to evaluate the effect of 14 days inhibition of TrkB signalling on phrenic motor neurons (PhMNs). Adult female and male TrkBF616 rats were divided into 1NMPP1 or vehicle treated groups. Three days prior to treatment, PhMNs in both groups were initially labeled via intrapleural injection of Alexa-Fluor-647 cholera toxin B (CTB). After 11 days of treatment, retrograde axonal uptake/transport was assessed by secondary labeling of PhMNs by intrapleural injection of Alexa-Fluor-488 CTB. After 14 days of treatment, the spinal cord was excised 100 μm thick spinal sections containing PhMNs were imaged using two-channel confocal microscopy. TrkB inhibition reduced the total number of PhMNs by ~16 %, reduced the mean PhMN somal surface areas by ~25 %, impaired CTB uptake 2.5-fold and reduced the estimated PhMN dendritic surface area by ~38 %. We conclude that inhibition of TrkB signalling alone in adult TrkBF616 rats is sufficient to lead to PhMN loss, morphological degeneration and deficits in retrograde axonal uptake/transport.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Debanjali Dasgupta
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Obaid U Khurram
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905, USA.
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Fogarty MJ, Zhan WZ, Simmon VF, Vanderklish PW, Sarraf ST, Sieck GC. Novel regenerative drug, SPG302 promotes functional recovery of diaphragm muscle activity after cervical spinal cord injury. J Physiol 2023. [PMID: 36815402 PMCID: PMC10404468 DOI: 10.1113/jp284004] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 02/17/2023] [Indexed: 02/24/2023] Open
Abstract
Spinal cord hemisection at C2 (C2 SH), sparing the dorsal column is widely used to investigate the effects of reduced phrenic motor neuron (PhMN) activation on diaphragm muscle (DIAm) function, with reduced DIAm activity on the injured side during eupnoea. Following C2 SH, recovery of DIAm EMG activity may occur spontaneously over subsequent days/weeks. Various strategies have been effective at improving the incidence and magnitude of DIAm recovery during eupnoea, but little is known about the effects of C2 SH on transdiaphragmatic pressure (Pdi ) during other ventilatory and non-ventilatory behaviours. We employ SPG302, a novel type of pegylated benzothiazole derivative, to assess whether enhancing synaptogenesis (i.e., enhancing spared local connections) will improve the incidence and the magnitude of recovery of DIAm EMG activity and Pdi function 14 days post-C2 SH. In anaesthetised Sprague-Dawley rats, DIAm EMG and Pdi were assessed during eupnoea, hypoxia/hypercapnia and airway occlusion prior to surgery (C2 SH or sham), immediately post-surgery and at 14 days post-surgery. In C2 SH rats, 14 days of DMSO (vehicle) or SPG302 treatments (i.p. injection) occurred. At the terminal experiment, maximum Pdi was evoked by bilateral phrenic nerve stimulation. We show that significant EMG and Pdi deficits are apparent in C2 SH compared with sham rats immediately after surgery. In C2 SH rats treated with SPG302, recovery of eupneic, hypoxia/hypercapnia and occlusion DIAm EMG was enhanced compared with vehicle rats after 14 days. Treatment with SPG302 also ameliorated Pdi deficits following C2 SH. In summary, SPG302 is an exciting new therapy to explore for use in spinal cord injuries. KEY POINTS: Despite advances in our understanding of the effects of cervical hemisection (C2 SH) on diaphragm muscle (DIAm) EMG activity, very little is understood about the impact of C2 SH on the gamut of ventilatory and non-ventilatory transdiaphragmatic pressures (Pdi ). Recovery of DIAm activity following C2 SH is improved using a variety of approaches, but very few pharmaceuticals have been shown to be effective. One way of improving DIAm recovery is to enhance the amount of latent local spared connections onto phrenic motor neurons. A novel pegylated benzothiazole derivative enhances synaptogenesis in a variety of neurodegenerative conditions. Here, using a novel therapeutic SPG302, we show that 14 days of treatment with SPG302 ameliorated DIAm EMG and Pdi deficits compared with vehicle controls. Our results show that SPG302 is a compound with very promising potential for use in improving functional outcomes post-spinal cord injury.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Wen-Zhi Zhan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | | | | | | | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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Fogarty MJ, Sieck GC. Aging affects the number and morphological heterogeneity of rat phrenic motor neurons and phrenic motor axons. Physiol Rep 2023; 11:e15587. [PMID: 36695744 PMCID: PMC9875821 DOI: 10.14814/phy2.15587] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/06/2023] [Accepted: 01/08/2023] [Indexed: 01/26/2023] Open
Abstract
Diaphragm muscle (DIAm) motor units comprise a phrenic motor neuron (PhMN), the phrenic nerve and the muscle fibers innervated, with the size of PhMNs and axons characteristic of motor unit type. Smaller PhMNs and their axons comprise slow (type S) and fatigue-resistant (type FR) DIAm motor units, while larger PhMNs and their axons comprise more fatigable (type FF) motor units. With aging, we have shown a loss of larger PhMNs, consistent with selective atrophy of type IIx/IIb DIAm fibers and reduced maximum DIAm force. In the present study, we hypothesized that with aging there is a loss of larger myelinated phrenic α motor axons. Female and male young (6 months) and old (24 months) Fischer 344 rats were studied. PhMNs were retrogradely labeled by intrapleural injection of 488-conjugated CTB. The phrenic nerves were excised ~1 cm from the DIAm insertion and mounted in resin, and phrenic α motor axons were delineated based on size (i.e., >4 μm diameters). In older rats, the number of larger PhMNs and larger phrenic α motor axons were reduced. There were no differences in non-α axons. In addition, there was evidence of demyelination of larger phrenic α motor axons in older rats. Together, these findings are consistent with the selective age-related vulnerability of larger PhMNs and denervation of type FF motor units, which may underlie DIAm sarcopenia.
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Affiliation(s)
- Matthew J. Fogarty
- Department of Physiology & Biomedical EngineeringMayo ClinicRochesterMinnesotaUSA
| | - Gary C. Sieck
- Department of Physiology & Biomedical EngineeringMayo ClinicRochesterMinnesotaUSA
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Fogarty MJ, Khurram OU, Mantilla CB, Sieck GC. Brain derived neurotrophic factor/tropomyosin related kinase B signaling impacts diaphragm neuromuscular transmission in a novel rat chemogenetic model. Front Cell Neurosci 2022; 16:1025463. [PMID: 36385943 PMCID: PMC9650098 DOI: 10.3389/fncel.2022.1025463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 10/12/2022] [Indexed: 11/29/2022] Open
Abstract
The neuromuscular junction (NMJ) mediates neural control of skeletal muscle fibers. Neurotrophic signaling, specifically brain derived neurotrophic factor (BDNF) acting through its high-affinity tropomyosin related kinase B (TrkB) receptor is known to improve neuromuscular transmission. BDNF/TrkB signaling also maintains the integrity of antero- and retrograde communication between the motor neuron soma, its distal axons and pre-synaptic terminals and influences neuromuscular transmission. In this study, we employed a novel rat chemogenetic mutation (TrkB F616), in which a 1-naphthylmethyl phosphoprotein phosphatase 1 (1NMPP1) sensitive knock-in allele allowed specific, rapid and sustained inhibition of TrkB kinase activity. In adult female and male TrkB F616 rats, treatment with either 1NMPP1 (TrkB kinase inhibition) or DMSO (vehicle) was administered in drinking water for 14 days. To assess the extent of neuromuscular transmission failure (NMTF), diaphragm muscle isometric force evoked by nerve stimulation at 40 Hz (330 ms duration trains repeated each s) was compared to isometric forces evoked by superimposed direct muscle stimulation (every 15 s). Chronic TrkB kinase inhibition (1NMPP1 group) markedly worsened NMTF compared to vehicle controls. Acute BDNF treatment did not rescue NMTF in the 1NMPP1 group. Chronic TrkB kinase inhibition did not affect the apposition of pre-synaptic terminals (labeled with synaptophysin) and post-synaptic endplates (labeled with α-Bungarotoxin) at diaphragm NMJs. We conclude that inhibition of BDNF/TrkB signaling in TrkB F616 rats disrupts diaphragm neuromuscular transmission in a similar manner to TrkB F616A mice, likely via a pre-synaptic mechanism independent of axonal branch point failure.
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Affiliation(s)
- Matthew J. Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Obaid U. Khurram
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Carlos B. Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Gary C. Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
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12
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Davis LA, Fogarty MJ, Brown A, Sieck GC. Structure and Function of the Mammalian Neuromuscular Junction. Compr Physiol 2022; 12:3731-3766. [PMID: 35950651 PMCID: PMC10461538 DOI: 10.1002/cphy.c210022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The mammalian neuromuscular junction (NMJ) comprises a presynaptic terminal, a postsynaptic receptor region on the muscle fiber (endplate), and the perisynaptic (terminal) Schwann cell. As with any synapse, the purpose of the NMJ is to transmit signals from the nervous system to muscle fibers. This neural control of muscle fibers is organized as motor units, which display distinct structural and functional phenotypes including differences in pre- and postsynaptic elements of NMJs. Motor units vary considerably in the frequency of their activation (both motor neuron discharge rate and duration/duty cycle), force generation, and susceptibility to fatigue. For earlier and more frequently recruited motor units, the structure and function of the activated NMJs must have high fidelity to ensure consistent activation and continued contractile response to sustain vital motor behaviors (e.g., breathing and postural balance). Similarly, for higher force less frequent behaviors (e.g., coughing and jumping), the structure and function of recruited NMJs must ensure short-term reliable activation but not activation sustained for a prolonged period in which fatigue may occur. The NMJ is highly plastic, changing structurally and functionally throughout the life span from embryonic development to old age. The NMJ also changes under pathological conditions including acute and chronic disease. Such neuroplasticity often varies across motor unit types. © 2022 American Physiological Society. Compr Physiol 12:1-36, 2022.
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Affiliation(s)
- Leah A. Davis
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Matthew J. Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Alyssa Brown
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Gary C. Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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13
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Brown AD, Fogarty MJ, Davis LA, Dasgupta D, Mantilla CB, Sieck GC. Mitochondrial adaptations to inactivity in diaphragm muscle fibers. J Appl Physiol (1985) 2022; 133:191-204. [PMID: 35678745 PMCID: PMC9291409 DOI: 10.1152/japplphysiol.00090.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Type I and IIa diaphragm muscle (DIAm) fibers comprise slow and fast fatigue-resistant motor units that are recruited to accomplish breathing and thus have a high duty cycle. In contrast, type IIx/IIb fibers comprise more fatigable fast motor units that are infrequently recruited for airway protective and straining behaviors. We hypothesize that mitochondrial structure and function in type I and IIa DIAm fibers adapt in response to inactivity imposed by spinal cord hemisection at C2 (C2SH). At 14 days after C2SH, the effect of inactivity on mitochondrial structure and function was assessed in DIAm fibers. Mitochondria in DIAm fibers were labeled using MitoTracker Green (Thermo Fisher Scientific), imaged in three-dimensions (3-D) by fluorescence confocal microscopy, and images were analyzed for mitochondrial volume density (MVD) and complexity. DIAm homogenate from either side was assessed for PGC1α, Parkin, MFN2, and DRP1 using Western blot. In alternate serial sections of the same DIAm fibers, the maximum velocity of the succinate dehydrogenase reaction (SDHmax) was determined using a quantitative histochemical technique. In all groups and both sides of the DIAm, type I and IIa DIAm fibers exhibited higher MVD, with more filamentous mitochondria and had higher SDHmax normalized to both fiber volume and mitochondrial volume compared with type IIx/IIb Diam fibers. In the inactive right side of the DIAm, mitochondria became fragmented and MVD decreased in all fiber types compared with the intact side and sham controls, consistent with the observed reduction in PGC1α and increased Parkin and DRP1 expression. In the inactive side of the DIAm, the reduction in SDHmax was found only for type I and IIa fibers. These results show that there are intrinsic fiber-type-dependent differences in the structure and function of mitochondria in DIAm fibers. Following C2SH-induced inactivity, mitochondrial structure (MVD and fragmentation) and function (SDHmax) were altered, indicating that inactivity influences all DIAm fiber types, but inactivity disproportionately affected SDHmax in the more intrinsically active type I and IIa fibers.NEW & NOTEWORTHY Two weeks of diaphragm (DIAm) inactivity imposed by C2SH caused reduced mitochondrial volume density, mitochondrial fragmentation, and a concomitant reduction of SDHmax in type I and IIa DIAm fibers on the lesioned side. Type I and IIa DIAm fibers were far more sensitive to inactivation than type IIx/IIb fibers, which exhibited little pathology. Our results indicate that mitochondria in DIAm fibers are plastic in response to varying levels of activity.
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14
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Fogarty MJ, Brandenburg JE, Zhan WZ, Sieck GC. Diaphragm Muscle Function in a Mouse Model of Early Onset Spasticity. J Appl Physiol (1985) 2022; 133:60-68. [DOI: 10.1152/japplphysiol.00157.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spasticity is a common symptom in many developmental motor disorders, including spastic cerebral palsy (sCP). In sCP, respiratory dysfunction is a major contributor to morbidity and mortality, yet it is unknown how spasticity influences respiratory physiology or diaphragm muscle (DIAm) function. To investigate the influence of spasticity on DIAm function, we assessed in vivo transdiaphragmatic pressure (Pdi - measured using intra-esophageal and intragastric pressure catheters under conditions of eupnea, hypoxia/hypercapnia and occlusion) including maximum Pdi (Pdimax via bilateral phrenic nerve stimulation), ex vivo DIAm specific force and fatigue (using muscle strips stimulated with platinum plate electrodes) and type-specific characteristics of DIAm fiber cross-sections (using immunoreactivity against myosin heavy chain slow and 2A) in spa and wildtype mice. Spa mice show reduced Pdimax, reduced DIAm specific force, altered fatigability and atrophy of type IIx/IIb fibers. These findings suggest marked DIAm dysfunction may underlie the respiratory phenotype of sCP.
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Affiliation(s)
- Matthew J. Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
| | - Joline E. Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN, United States
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN, United States
| | - Wen-Zhi Zhan
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
| | - Gary C. Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States
- Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN, United States
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15
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Hernandez‐Vizcarrondo GA, Brown AD, Davis LA, Fogarty MJ, Mantilla CB, Sieck GC. Fiber Type Differences in SDH
max
and Mitochondrial Volume Density between Diaphragm and Tibialis Anterior Muscles. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Leah A. Davis
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
| | | | | | - Gary C. Sieck
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
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16
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Davis LA, Brown AD, Fogarty MJ, Mantilla CB, Sieck GC. Aging Selectively Reduces Mitochondrial Volume Density and Respiratory Capacity in Type IIx/IIb Diaphragm Muscle Fibers. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r3573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Leah A. Davis
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
| | | | | | | | - Gary C. Sieck
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
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17
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Brandenburg JE, Fogarty MJ, Davis LA, Sieck GC. Postnatal Phrenic Motor Neuron and Diaphragm Maturation in the Mouse. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.0r541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Joline E. Brandenburg
- Physical Medicine and RehabilitationMayo ClinicRochesterMN
- Pediatric and Adolescent MedicineMayo ClinicRochesterMN
| | | | - Leah A. Davis
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
| | - Gary C. Sieck
- Physical Medicine and RehabilitationMayo ClinicRochesterMN
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
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18
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Brown AD, Fogarty MJ, Dasgupta D, Davis LA, Mantilla CB, Sieck GC. Mitochondria Adapt to Diaphragm Muscle Inactivity Imposed by Cervical Spinal Cord Injury. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r3364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Alyssa D. Brown
- Physiology and Biomedical EngineeringMayo ClinicLouisvilleKY
| | | | | | - Leah A. Davis
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
| | | | - Gary C. Sieck
- Physiology and Biomedical EngineeringMayo ClinicRochesterMN
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19
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de Zélicourt A, Fayssoil A, Dakouane-Giudicelli M, De Jesus I, Karoui A, Zarrouki F, Lefebvre F, Mansart A, Launay JM, Piquereau J, Tarragó MG, Bonay M, Forand A, Moog S, Piétri-Rouxel F, Brisebard E, Chini CCS, Kashyap S, Fogarty MJ, Sieck GC, Mericskay M, Chini EN, Gomez AM, Cancela JM, de la Porte S. CD38-NADase is a new major contributor to Duchenne muscular dystrophic phenotype. EMBO Mol Med 2022; 14:e12860. [PMID: 35298089 PMCID: PMC9081905 DOI: 10.15252/emmm.202012860] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 03/02/2022] [Accepted: 03/03/2022] [Indexed: 01/14/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration. Two important deleterious features are a Ca2+ dysregulation linked to Ca2+ influxes associated with ryanodine receptor hyperactivation, and a muscular nicotinamide adenine dinucleotide (NAD+) deficit. Here, we identified that deletion in mdx mice of CD38, a NAD+ glycohydrolase‐producing modulators of Ca2+ signaling, led to a fully restored heart function and structure, with skeletal muscle performance improvements, associated with a reduction in inflammation and senescence markers. Muscle NAD+ levels were also fully restored, while the levels of the two main products of CD38, nicotinamide and ADP‐ribose, were reduced, in heart, diaphragm, and limb. In cardiomyocytes from mdx/CD38−/− mice, the pathological spontaneous Ca2+ activity was reduced, as well as in myotubes from DMD patients treated with isatuximab (SARCLISA®) a monoclonal anti‐CD38 antibody. Finally, treatment of mdx and utrophin–dystrophin‐deficient (mdx/utr−/−) mice with CD38 inhibitors resulted in improved skeletal muscle performances. Thus, we demonstrate that CD38 actively contributes to DMD physiopathology. We propose that a selective anti‐CD38 therapeutic intervention could be highly relevant to develop for DMD patients.
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Affiliation(s)
- Antoine de Zélicourt
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, Versailles, France.,Institut des Neurosciences Paris-Saclay, CNRS, Université Paris-Saclay, Saclay, France
| | | | | | - Isley De Jesus
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, Versailles, France
| | - Ahmed Karoui
- Signalisation et Physiopathologie Cardiovasculaire, INSERM, UMR-S 1180 - Université Paris-Saclay, Châtenay-Malabry, France
| | - Faouzi Zarrouki
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, Versailles, France
| | - Florence Lefebvre
- Signalisation et Physiopathologie Cardiovasculaire, INSERM, UMR-S 1180 - Université Paris-Saclay, Châtenay-Malabry, France
| | - Arnaud Mansart
- Université Paris-Saclay, UVSQ, Inserm, 2I, Versailles, France
| | - Jean-Marie Launay
- Service de Biochimie, INSERM UMR S942, Hôpital Lariboisière, Paris, France
| | - Jerome Piquereau
- Signalisation et Physiopathologie Cardiovasculaire, INSERM, UMR-S 1180 - Université Paris-Saclay, Châtenay-Malabry, France
| | - Mariana G Tarragó
- Department of Anesthesiology and Kogod Aging Center, Mayo Clinic, Rochester, Minnesota, USA
| | - Marcel Bonay
- Université Paris-Saclay, UVSQ, Inserm, END-ICAP, Versailles, France
| | - Anne Forand
- Centre de Recherche en Myologie, Faculté de Médecine de la Pitié Salpêtrière, Sorbonne Université-UMRS974-Inserm-Institut de Myologie, Paris, France.,Inovarion, Paris, France
| | - Sophie Moog
- Centre de Recherche en Myologie, Faculté de Médecine de la Pitié Salpêtrière, Sorbonne Université-UMRS974-Inserm-Institut de Myologie, Paris, France.,Inovarion, Paris, France
| | - France Piétri-Rouxel
- Centre de Recherche en Myologie, Faculté de Médecine de la Pitié Salpêtrière, Sorbonne Université-UMRS974-Inserm-Institut de Myologie, Paris, France
| | | | - Claudia C S Chini
- Department of Anesthesiology and Kogod Aging Center, Mayo Clinic, Rochester, Minnesota, USA
| | - Sonu Kashyap
- Department of Anesthesiology and Kogod Aging Center, Mayo Clinic, Rochester, Minnesota, USA
| | - Matthew J Fogarty
- Department of Anesthesiology and Kogod Aging Center, Mayo Clinic, Rochester, Minnesota, USA
| | - Gary C Sieck
- Department of Anesthesiology and Kogod Aging Center, Mayo Clinic, Rochester, Minnesota, USA
| | - Mathias Mericskay
- Signalisation et Physiopathologie Cardiovasculaire, INSERM, UMR-S 1180 - Université Paris-Saclay, Châtenay-Malabry, France
| | - Eduardo N Chini
- Department of Anesthesiology and Kogod Aging Center, Mayo Clinic, Rochester, Minnesota, USA
| | - Ana Maria Gomez
- Signalisation et Physiopathologie Cardiovasculaire, INSERM, UMR-S 1180 - Université Paris-Saclay, Châtenay-Malabry, France
| | - José-Manuel Cancela
- Institut des Neurosciences Paris-Saclay, CNRS, Université Paris-Saclay, Saclay, France
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20
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Mazzone SB, Yang SK, Keller JA, Simanauskaite J, Arikkatt J, Fogarty MJ, Moe AAK, Chen C, Trewella MW, Tian L, Ritchie ME, Chua BY, Phipps S, Short KR, McGovern AE. Modulation of Vagal Sensory Neurons via High Mobility Group Box-1 and Receptor for Advanced Glycation End Products: Implications for Respiratory Viral Infections. Front Physiol 2021; 12:744812. [PMID: 34621188 PMCID: PMC8490771 DOI: 10.3389/fphys.2021.744812] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 08/19/2021] [Indexed: 11/28/2022] Open
Abstract
Vagal sensory neurons contribute to the symptoms and pathogenesis of inflammatory pulmonary diseases through processes that involve changes to their morphological and functional characteristics. The alarmin high mobility group box-1 (HMGB1) is an early mediator of pulmonary inflammation and can have actions on neurons in a range of inflammatory settings. We hypothesized that HMGB1 can regulate the growth and function of vagal sensory neurons and we set out to investigate this and the mechanisms involved. Culturing primary vagal sensory neurons from wildtype mice in the presence of HMGB1 significantly increased neurite outgrowth, while acute application of HMGB1 to isolated neurons under patch clamp electrophysiological investigation produced inward currents and enhanced action potential firing. Transcriptional analyses revealed the expression of the cognate HMGB1 receptors, Receptor for Advanced Glycation End products (RAGE) and Toll-like Receptor 4 (TLR4), in subsets of vagal sensory neurons. HMGB1-evoked growth and electrophysiological responses were significantly reduced in primary vagal sensory neurons harvested from RAGE deficient mice and completely absent in neurons from RAGE/TLR4 double deficient mice. Immunohistochemical analysis of vagal sensory neurons collected from mice after intranasal infection with murine pneumovirus or influenza A virus (IAV), or after intratracheal administration with the viral mimetic PolyI:C, revealed a significant increase in nuclear-to-cytoplasm translocation of HMGB1 compared to mock-inoculated mice. Neurons cultured from virus infected wildtype mice displayed a significant increase in neurite outgrowth, which was not observed for neurons from virus infected RAGE or RAGE/TLR4 deficient mice. These data suggest that HMGB1 can enhance vagal sensory neuron growth and excitability, acting primarily via sensory neuron RAGE. Activation of the HMGB1-RAGE axis in vagal sensory neurons could be an important mechanism leading to vagal hyperinnervation and hypersensitivity in chronic pulmonary disease.
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Affiliation(s)
- Stuart B Mazzone
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Seung-Kwon Yang
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Jennifer A Keller
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Juste Simanauskaite
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Jaisy Arikkatt
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Matthew J Fogarty
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Aung Aung Kywe Moe
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Chen Chen
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Matthew W Trewella
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Luyi Tian
- Molecular Medicine Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
| | - Matthew E Ritchie
- Molecular Medicine Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
| | - Brendan Y Chua
- The Peter Doherty Institute for Infection and Immunity, Department of Microbiology and Immunology, University of Melbourne, Melbourne, VIC, Australia
| | - Simon Phipps
- QIMR Berghofer Medical Research Institute, Herston, QLD, Australia
| | - Kirsty R Short
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | - Alice E McGovern
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, VIC, Australia
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21
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Brown AD, Davis LA, Fogarty MJ, Sieck GC. Mitochondrial Fragmentation and Dysfunction in Type IIx/IIb Diaphragm Muscle Fibers in 24-Month Old Fischer 344 Rats. Front Physiol 2021; 12:727585. [PMID: 34650442 PMCID: PMC8505889 DOI: 10.3389/fphys.2021.727585] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 09/09/2021] [Indexed: 12/31/2022] Open
Abstract
Sarcopenia is characterized by muscle fiber atrophy and weakness, which may be associated with mitochondrial fragmentation and dysfunction. Mitochondrial remodeling and biogenesis in muscle fibers occurs in response to exercise and increased muscle activity. However, the adaptability mitochondria may decrease with age. The diaphragm muscle (DIAm) sustains breathing, via recruitment of fatigue-resistant type I and IIa fibers. More fatigable, type IIx/IIb DIAm fibers are infrequently recruited during airway protective and expulsive behaviors. DIAm sarcopenia is restricted to the atrophy of type IIx/IIb fibers, which impairs higher force airway protective and expulsive behaviors. The aerobic capacity to generate ATP within muscle fibers depends on the volume and intrinsic respiratory capacity of mitochondria. In the present study, mitochondria in type-identified DIAm fibers were labeled using MitoTracker Green and imaged in 3-D using confocal microscopy. Mitochondrial volume density was higher in type I and IIa DIAm fibers compared with type IIx/IIb fibers. Mitochondrial volume density did not change with age in type I and IIa fibers but was reduced in type IIx/IIb fibers in 24-month rats. Furthermore, mitochondria were more fragmented in type IIx/IIb compared with type I and IIa fibers, and worsened in 24-month rats. The maximum respiratory capacity of mitochondria in DIAm fibers was determined using a quantitative histochemical technique to measure the maximum velocity of the succinate dehydrogenase reaction (SDH max ). SDH max per fiber volume was higher in type I and IIa DIAm fibers and did not change with age. In contrast, SDH max per fiber volume decreased with age in type IIx/IIb DIAm fibers. There were two distinct clusters for SDH max per fiber volume and mitochondrial volume density, one comprising type I and IIa fibers and the second comprising type IIx/IIb fibers. The separation of these clusters increased with aging. There was also a clear relation between SDH max per mitochondrial volume and the extent of mitochondrial fragmentation. The results show that DIAm sarcopenia is restricted to type IIx/IIb DIAm fibers and related to reduced mitochondrial volume, mitochondrial fragmentation and reduced SDH max per fiber volume.
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22
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Abstract
The intrinsic and extrinsic tongue muscles manipulate the position and shape of the tongue and are activated during many oral and respiratory behaviors. In the present study, in 6-mo-old Fischer 344 rats, we examined mechanical and fatigue properties of tongue muscles in relation to their fiber type composition. In an ex vivo preparation, isometric force and fatigue was assessed by direct muscle stimulation. Tongue muscles were frozen in melting isopentane and transverse sections cut at 10 µm. In hematoxylin-eosin (H&E)-stained muscle sections, the relative fractions of muscle versus extracellular matrix were determined. Muscle fibers were classified as type I, IIa and IIx, and/or IIb based on immunoreactivity to specific myosin heavy chain isoform antibodies. Cross-sectional areas (CSAs) and proportions of different fiber types were used to calculate their relative contribution to total muscle CSAs. We found that the superior and inferior longitudinal intrinsic muscles (4.4 N/cm2) and genioglossus muscle (3.0 N/cm2) generated the greatest maximum isometric force compared with the transversalis muscle (0.9 N/cm2). The longitudinal muscles and the transversalis muscle displayed greater fatigue during repetitive stimulation consistent with the greater relative contribution of type IIx and/or IIb fibers. By contrast, the genioglossus, comprising a higher proportion of type I and IIa fibers, was more fatigue resistant. This study advances our understanding of the force, fatigue, and fiber type-specific properties of individual tongue musculature. The assessments and approach provide a readily accessible muscular readout for scenarios where motor control dysfunction or tongue weakness is evident.NEW & NOTEWORTHY For the individual tongue muscles, relatively little quantification of uniaxial force, fatigue, and fiber type-specific properties has been documented. Here, we assessed uniaxial-specific force generation, fatigability, and muscle fiber type-specific properties in the superior and inferior longitudinal muscles, the transversalis, and the genioglossus in Fischer 344 rats. The longitudinal muscles produced the greatest isometric tetanic-specific forces. The genioglossus was more fatigue resistant and comprised higher proportions of I and IIa fibers.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, grid.66875.3aMayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, grid.66875.3aMayo Clinic, Rochester, Minnesota
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23
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Fogarty MJ. Neuronal Hypoexcitability and Dendritic Overbranching - The Case for Failed Compensatory Mechanisms in ALS Aetiology. Neuroscience 2021; 465:231-232. [PMID: 34053505 DOI: 10.1016/j.neuroscience.2021.02.034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 02/28/2021] [Indexed: 12/15/2022]
Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA; School of Biomedical Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
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24
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Fogarty MJ, Losbanos LL, Craig TA, Reynolds CJ, Brown AD, Kumar R, Sieck GC. Muscle-specific deletion of the vitamin D receptor in mice is associated with diaphragm muscle weakness. J Appl Physiol (1985) 2021; 131:95-106. [PMID: 34013750 DOI: 10.1152/japplphysiol.00194.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Diseases or conditions where diaphragm muscle (DIAm) function is impaired, including chronic obstructive pulmonary disease, cachexia, asthma, and aging, are associated with an increased risk of pulmonary symptoms, longer duration of hospitalizations, and increasing requirements for mechanical ventilation. Vitamin D deficiency is associated with proximal muscle weakness that resolves following therapy with vitamin D3. Skeletal muscle expresses the vitamin D receptor (VDR), which responds to the active form of vitamin D, 1,25-dihydroxyvitamin D3 by altering gene expression in target cells. In knockout mice without skeletal muscle VDRs, there is marked atrophy of muscle fibers and a change in skeletal muscle biochemistry. We used a tamoxifen-inducible skeletal muscle Cre recombinase in Vdrfl/fl mice (Vdrfl/fl actin.iCre+) to assess the role of muscle-specific VDR signaling on DIAm-specific force, fatigability, and fiber type-dependent morphology. Vdrfl/fl actin.iCre+ mice treated with vehicle and Vdrfl/fl mice treated with tamoxifen served as controls. Seven days following the final treatment, mice were euthanized, the DIAm was removed, and isometric force and fatigue were assessed in DIAm strips using direct muscle stimulation. The proportion and cross-sectional areas of DIAm fiber types were evaluated by immunolabeling with myosin heavy chain antibodies differentiating type I, IIa and IIx, and/or IIb fibers. We show that in mice with skeletal muscle-specific VDR deletion, maximum specific force and residual force following fatigue are impaired, along with a selective atrophy of type IIx and/or IIb fibers. These results show that the VDR has a significant biological effect on DIAm function independent of systemic effects on mineral metabolism.NEW & NOTEWORTHY Vitamin D deficiency and vitamin D receptor (VDR) polymorphisms are associated with adverse pulmonary and diaphragm muscle (DIAm)-associated respiratory outcomes. We used a skeletal muscle-specific tamoxifen-inducible VDR knockout to investigate DIAm dysfunction following reduced VDR signaling. Marked DIAm weakness and atrophy of type IIx and/or IIb fibers are present in muscle-specific tamoxifen-induced VDR knockout mice compared with controls. These results show that the VDR has a significant biological effect on DIAm function independent of systemic effects on mineral metabolism.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Louis L Losbanos
- Division of Nephrology & Hypertension, Department of Medicine, Mayo Clinic, Rochester, Minnesota
| | - Theodore A Craig
- Division of Nephrology & Hypertension, Department of Medicine, Mayo Clinic, Rochester, Minnesota
| | - Carmen J Reynolds
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Alyssa D Brown
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Rajiv Kumar
- Division of Nephrology & Hypertension, Department of Medicine, Mayo Clinic, Rochester, Minnesota.,Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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25
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Fogarty MJ, Rana S, Mantilla CB, Sieck GC. Quantifying mitochondrial volume density in phrenic motor neurons. J Neurosci Methods 2021; 353:109093. [PMID: 33549636 PMCID: PMC7990712 DOI: 10.1016/j.jneumeth.2021.109093] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/26/2021] [Accepted: 02/01/2021] [Indexed: 12/31/2022]
Abstract
BACKGROUND Previous assessments of mitochondrial volume density within motor neurons used electron microscopy (EM) to image mitochondria. However, adequate identification and sampling of motor neurons within a particular motor neuron pool is largely precluded using EM. Here, we present an alternative method for determining mitochondrial volume density in identified motor neurons within the phrenic motor neuron (PhMN) pool, with greatly increased sampling. NEW METHOD This novel method for assessing mitochondrial volume density in PhMNs uses a combination of intrapleural injection of Alexa 488-conjugated cholera toxin B (CTB) to retrogradely label PhMNs, followed by intrathecal application of MitoTracker Red to label mitochondria. This technique was validated by comparison to 3D EM determination of mitochondrial volume density as a "gold standard". RESULTS A mean mitochondrial volume density of ∼11 % was observed across PhMNs using the new MitoTracker Red method. This compared favourably with mitochondrial volume density (∼11 %) measurements using EM. COMPARISON WITH EXISTING METHOD The range, mean and variance of mitochondrial volume density estimates in PhMNs were not different between EM and fluorescent imaging techniques. CONCLUSIONS Fluorescent imaging may be used to estimate mitochondrial volume density in a large sample of motor neurons, with results similar to EM, although EM did distinguish finer mitochondrion morphology compared to MitoTracker fluorescence. Compared to EM methods, the assessment of a larger sample size and unambiguous identification of motor neurons belonging to a specific motor neuron pool represent major advantages over previous methods.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States; School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4067, Australia
| | - Sabhya Rana
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States
| | - Carlos B Mantilla
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States; Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55905, United States
| | - Gary C Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, United States.
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Fogarty MJ, Enninga EAL, Ibirogba ER, Ruano R, Sieck GC. Impact of congenital diaphragmatic hernia on diaphragm muscle function in neonatal rats. J Appl Physiol (1985) 2021; 130:801-812. [PMID: 33507852 DOI: 10.1152/japplphysiol.00852.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Congenital diaphragmatic hernia (CDH) is characterized by incomplete partitioning of the thoracic and abdominal cavities by the diaphragm muscle (DIAm). The resulting in utero invasion of the abdominal viscera into the thoracic cavity leads to impaired fetal breathing movements, severe pulmonary hypoplasia, and pulmonary hypertension. We hypothesized that in a well-established rodent model of Nitrofen-induced CDH, DIAm isometric force generation, and DIAm fiber cross-sectional areas would be reduced compared with nonlesioned littermate and Control pups. In CDH and nonlesioned pups at embryonic day 21 or birth, DIAm isometric force responses to supramaximal field stimulation (200 mA, 0.5 ms duration pulses in 1-s duration trains at rates ranging from 10 to 100 Hz) was measured ex vivo. Further, DIAm fatigue was determined in response to 120 s of repetitive stimulation at 40 Hz in 330-ms duration trains repeated each second. The DIAm was then stretched to Lo, frozen, and fiber cross-sectional areas were measured in 10 μm transverse sections. In CDH pups, there was a marked reduction in DIAm-specific force and force following 120 s of fatiguing contraction. The cross-sectional area of DIAm fibers was also reduced in CDH pups compared with nonlesioned littermates and Control pups. These results show that CDH is associated with a dramatic weakening of the DIAm, which may contribute to poor survival despite various surgical efforts to repair the hernia and improve lung development.NEW & NOTEWORTHY There are notable respiratory deficits related to congenital diaphragmatic hernia (CDH), yet the contribution, if any, of frank diaphragm muscle weakness to CDH is unexplored. Here, we use the well-established Nitrofen teratogen model to induce CDH in rat pups, followed by diaphragm muscle contractility and morphological assessments. Our results show diaphragm muscle weakness in conjunction with reduced muscle fiber density and size, contributing to CDH morbidity.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | | | - Eniola R Ibirogba
- Department of Obstetrics and Gynecology, Mayo Clinic, Rochester, Minnesota
| | - Rodrigo Ruano
- Department of Obstetrics and Gynecology, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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Fogarty MJ, Brandenburg JE, Sieck GC. Diaphragm neuromuscular transmission failure in a mouse model of an early-onset neuromotor disorder. J Appl Physiol (1985) 2020; 130:708-720. [PMID: 33382958 DOI: 10.1152/japplphysiol.00864.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The spa transgenic mouse displays spasticity and hypertonia that develops during the early postnatal period, with motor impairments that are remarkably similar to symptoms of human cerebral palsy. Previously, we observed that spa mice have fewer phrenic motor neurons innervating the diaphragm muscle (DIAm). We hypothesize that spa mice exhibit increased susceptibility to neuromuscular transmission failure (NMTF) due to an expanded innervation ratio. We retrogradely labeled phrenic motor neurons with rhodamine and imaged them in horizontal sections (70 µm) using confocal microscopy. Phrenic nerve-DIAm strip preparations from wild type and spa mice were stretched to optimal length, and force was evoked by phrenic nerve stimulation at 10, 40, or 75 Hz in 330-ms duration trains repeated each second (33% duty cycle) across a 120-s period. To assess NMTF, force evoked by phrenic nerve stimulation was compared to force evoked by direct DIAm stimulation superimposed every 15 s. Total DIAm fiber number was estimated in hematoxylin and eosin-stained strips. Compared to wild type, spa mice had over twofold greater NMTF during the first stimulus train that persisted throughout the 120 s period of repetitive activation. In both wild type and spa mice, NMTF was stimulation-frequency dependent. There was no difference in neuromuscular junction morphology or the total number of DIAm fibers between wild type and spa mice, however, there was an increase innervation ratio (39%) in spa mice. We conclude that early-onset developmental neuromotor disorders impair the efficacy of DIAm neuromuscular transmission, likely to contribute to respiratory complications.NEW & NOTEWORTHY Individuals with motor control deficits, including cerebral palsy (CP) often have respiratory impairments. Glycine-receptor mutant spa mice have early-onset hypertonia, and limb motor impairments, similar to individuals with CP. We hypothesized that in the diaphragm of spa mice, disruption of glycinergic inputs to MNs would result in increased phrenic-DIAm neuromuscular transmission failure. Pathophysiologic abnormalities in neuromuscular transmission may contribute to respiratory dysfunction in conditions where early developmental MN loss or motor control deficits are apparent.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,School of Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota.,Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota
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Abstract
Characterization of growth and survival of mice displaying early onset hypertonic symptoms is critical as these animals are important for research investigating mechanisms and treatments of pediatric conditions associated with hypertonia, such as cerebral palsy. Currently, most animal models of cerebral palsy reproduce risk factors for developing this condition, with most failing to develop the physical symptoms or failing to survive in the postnatal period. The B6.Cg-Glrbspa /J (Gly receptor mutation) transgenic mouse (spa mouse), displays symptoms of early onset hypertonia, though little has been reported on growth and survival, with no reports of growth and survival since genotyping became available. We found that the majority of spa mice display symptoms by P14-P16. Of mice surviving to weaning, only ~9% were spa mice. By weaning age, spa mice had significantly lower weights than their heterozygote and wild-type littermates. Of mice that died after weaning and prior to use in experiments or being culled, 48% were spa mice. The poor growth and decreased survival of spa mice across multiple developmental and adult ages resembled the varied survival rates observed in humans with mild or severe cerebral palsy. The understanding of the expected survival of these mice is helpful for planning breeding and animal numbers for experiments. Due to the symptoms and timing of symptom onset, spa mice will be valuable in uncovering mechanisms and long-term effects of early onset hypertonia in order to move toward interventions for these conditions.
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Affiliation(s)
- Joline E. Brandenburg
- Department of Physical Medicine and RehabilitationMayo Clinic College of MedicineRochesterMNUSA
- Department of Pediatric and Adolescent MedicineMayo Clinic College of MedicineRochesterMNUSA
| | - Matthew J. Fogarty
- Department of Physiology and Biomedical EngineeringMayo Clinic College of MedicineRochesterMNUSA
- School of Biomedical SciencesThe University of QueenslandBrisbaneAustralia
| | - Gary C. Sieck
- Department of Physical Medicine and RehabilitationMayo Clinic College of MedicineRochesterMNUSA
- Department of Physiology and Biomedical EngineeringMayo Clinic College of MedicineRochesterMNUSA
- Department of AnesthesiologyMayo Clinic College of MedicineRochesterMNUSA
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29
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Klenowski PM, Fogarty MJ, Drieberg-Thompson JR, Bellingham MC, Bartlett SE. Reduced Inhibitory Inputs On Basolateral Amygdala Principal Neurons Following Long-Term Alcohol Consumption. Neuroscience 2020; 452:219-227. [PMID: 33212222 DOI: 10.1016/j.neuroscience.2020.10.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 12/16/2022]
Abstract
Recent studies have shown that manipulating basolateral amygdala (BLA) activity can affect alcohol consumption, particularly following chronic and/or long-term intake. Although the mechanisms underlying these effects remain unclear, the BLA is highly sensitive to emotional stimuli including stress and anxiety. Negative emotional states facilitate alcohol craving and relapse in patients with alcohol use disorders. Consequently, the aim of this study was to determine the effect of long-term (10 weeks) alcohol drinking on synaptic activity in BLA principal neurons. We utilized an intermittent drinking paradigm in rats, which facilitated escalating, binge-like alcohol intake over the 10 week drinking period. We then recorded spontaneous excitatory and inhibitory postsynaptic currents of BLA principal neurons from long-term alcohol drinking rats and aged-matched water drinking controls. Excitatory postsynaptic current properties from long-term alcohol drinking rats were unchanged compared to those from age-matched water drinking controls. Conversely, we observed significant reductions of inhibitory postsynaptic current amplitude and frequency in long-term ethanol drinking rats compared to age-matched water drinking controls. These results highlight substantive decreases in basal inhibitory synaptic activity of BLA principal neurons following long-term alcohol consumption. A loss of inhibitory control in the BLA could explain the high incidence of compulsive drinking and stress- or anxiety-induced relapse in patients with alcohol use disorders.
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Affiliation(s)
- Paul M Klenowski
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA; School of Biomedical Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Joy R Drieberg-Thompson
- School of Biomedical Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Mark C Bellingham
- School of Biomedical Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Selena E Bartlett
- Translational Research Institute, Queensland University of Technology, Brisbane 4102, Australia.
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30
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Fogarty MJ, Mu EWH, Lavidis NA, Noakes PG, Bellingham MC. Size‐dependent dendritic maladaptations of hypoglossal motor neurons in SOD1
G93A
mice. Anat Rec (Hoboken) 2020; 304:1562-1581. [DOI: 10.1002/ar.24542] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 09/14/2020] [Accepted: 09/22/2020] [Indexed: 12/14/2022]
Affiliation(s)
- Matthew J. Fogarty
- School of Biomedical Sciences The University of Queensland St Lucia Australia
- Department of Physiology and Biomedical Engineering, Mayo Clinic Rochester Minnesota USA
| | - Erica W. H. Mu
- School of Biomedical Sciences The University of Queensland St Lucia Australia
| | - Nickolas A. Lavidis
- School of Biomedical Sciences The University of Queensland St Lucia Australia
| | - Peter G. Noakes
- School of Biomedical Sciences The University of Queensland St Lucia Australia
- Queensland Brain Institute The University of Queensland St Lucia Australia
| | - Mark C. Bellingham
- School of Biomedical Sciences The University of Queensland St Lucia Australia
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Abstract
Introduction: Neuromotor control of diaphragm muscle and the recovery of diaphragm activity following spinal cord injury have been narrowly focused on ventilation. By contrast, the understanding of neuromotor control for non-ventilatory expulsive/straining maneuvers (including coughing, defecation, and parturition) is relatively impoverished. This variety of behaviors are achieved via the recruitment of the diverse array of motor units that comprise the diaphragm muscle.Areas covered: The neuromotor control of ventilatory and non-ventilatory behaviors in health and in the context of spinal cord injury is explored. Particular attention is played to the neuroplasticity of phrenic motor neurons in various models of cervical spinal cord injury.Expert opinion: There is a remarkable paucity in our understanding of neuromotor control of maneuvers in spinal cord injury patients. Dysfunction of these expulsive/straining maneuvers reduces patient quality of life and contributes to severe morbidity and mortality. As spinal cord injury patient life expectancies continue to climb steadily, a nexus of spinal cord injury and age-associated comorbidities are likely to occur. While current research remains concerned only with the minutiae of ventilation, the major functional deficits of this clinical cohort will persist intractably. We posit some future research directions to avoid this scenario.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, USA
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32
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Fogarty MJ, Sieck GC, Brandenburg JE. Impaired neuromuscular transmission of the tibialis anterior in a rodent model of hypertonia. J Neurophysiol 2020; 123:1864-1869. [PMID: 32292122 DOI: 10.1152/jn.00095.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Early-onset hypertonia is characteristic of developmental neuromotor disorders, including cerebral palsy (CP). The spa transgenic mouse displays early-onset spasticity, abnormal gait, and motor impairments that are remarkably similar to symptoms of human CP. Previously, we showed that spa mice have fewer motor neurons innervating the tibialis anterior (TA). An expanded innervation ratio may result in increased susceptibility to neuromuscular transmission failure (NMTF). We assessed NMTF in an ex vivo TA muscle nerve preparation from spa and wild-type (WT) mice by comparing forces elicited by nerve versus muscle stimulation. TA muscle innervation ratio was assessed by counting the number of muscle fibers and dividing by the number of TA motor neurons. Muscle fiber cross-sectional areas were also assessed in the TA muscle. We observed that NMTF was immediately present in spa mice, increased with repetitive stimulation, and associated with increased innervation ratio. These changes were concomitant with reduced TA muscle fiber cross-sectional area in spa mice compared with WT. Early-onset hypertonia is associated with increased innervation ratio and impaired neuromuscular transmission. These disturbances may exacerbate the underlying gait abnormalities present in individuals with hypertonia.NEW & NOTEWORTHY Nerve-muscle interaction is poorly understood in the context of early-onset spasticity and hypertonia. In an animal model of early-onset spasticity, spa mice, we found a marked impairment of tibialis anterior neuromuscular transmission. This impairment is associated with an increased innervation ratio (mean number of muscle fibers innervated by a single motor neuron). These disturbances may underlie weakness and gait disturbances observed in individual with developmental hypertonia and spasticity.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,School of Biomedical Sciences, University of Queensland, St. Lucia, Queensland, Australia
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota
| | - Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, Minnesota.,Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, Minnesota
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Fogarty MJ, Enninga EAL, Ibrogba ER, Ruano RR, Sieck GC. Diaphragm Muscle Weakness Contributes to Ventilatory Deficits in an Animal Model of Congenital Diaphragmatic Hernia. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Fogarty MJ. Needles in straw-stacks on camel’s backs: Globalized versus specific loci of dysfunction in amyotrophic lateral sclerosis. Clin Neurophysiol 2020; 131:940-941. [DOI: 10.1016/j.clinph.2019.12.402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 12/26/2019] [Indexed: 11/29/2022]
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Brown AD, Rana SD, Fogarty MJ, Mantilla CB, Sieck GC. TNFα Increases Mitochondrial Biogenesis in Motor Neurons. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.05727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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36
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Heino AD, Yap JD, Brown AD, Rana SD, Fogarty MJ, Mantilla CB, Sieck GC. TNFα Exposure Decreases Mitochondrial O
2
Consumption in Motor Neurons. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.02049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Wilfred AM, Fogarty MJ, Mantilla CB, Sieck GC. Age‐Related Loss of Phrenic Motor Neurons: Reduced Myogenic Influence? FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.03480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
Phrenic motor neuron (PhMN) development in early onset hypertonia is poorly understood. Respiratory disorders are one of the leading causes of morbidity and mortality in individuals with early onset hypertonia, such as cerebral palsy (CP), but they are largely overshadowed by a focus on physical function in this condition. Furthermore, while the brain is the focus of CP research, motor neurons, via the motor unit and neurotransmitter signaling, are the targets in clinical interventions for hypertonia. Furthermore, critical periods of spinal cord and motor unit development also coincide with the timing that the supposed brain injury occurs in CP. Using an animal model of early-onset spasticity (spa mouse [B6.Cg-Glrbspa/J] with a glycine receptor mutation), we hypothesized that removal of effective glycinergic neurotransmitter inputs to PhMNs during development will result in fewer PhMNs and reduced PhMN somal size at maturity. Adult spa (Glrb-/-), and wild-type (Glrb+/+) mice underwent unilateral retrograde labeling of PhMNs via phrenic nerve dip in tetramethylrhodamine. After three days, mice were euthanized, perfused with 4% paraformaldehyde, and the spinal cord excised and processed for confocal imaging. Spa mice had ~30% fewer PhMNs (P = 0.005), disproportionately affecting larger PhMNs. Additionally, a ~22% reduction in PhMN somal surface area (P = 0.019), an 18% increase in primary dendrites (P < 0.0001), and 24% decrease in dendritic surface area (P = 0.014) were observed. Thus, there are fewer larger PhMNs in spa mice. Fewer and smaller PhMNs may contribute to impaired diaphragm neuromotor control and contribute to respiratory morbidity and mortality in conditions of early onset hypertonia.NEW & NOTEWORTHY Phrenic motor neuron (PhMN) development in early-onset hypertonia is poorly understood. Yet, respiratory disorders are a common cause of morbidity and mortality. In spa mice, an animal model of early-onset hypertonia, we found ~30% fewer PhMNs, compared with controls. This PhMN loss disproportionately affected larger PhMNs. Thus, the number and heterogeneity of the PhMN pool are decreased in spa mice, likely contributing to the hypertonia, impaired neuromotor control, and respiratory disorders.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, Minnesota.,Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota.,School of Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - Alyssa D Brown
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, Minnesota.,Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
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Fogarty MJ, Rana S, Mantilla CB, Sieck GC. Size‐Dependence of Mitochondrial Density & Morphology in Phrenic Motor Neurons. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Yap JQ, Heino A, Brown AD, Rana SD, Fogarty MJ, Delmotte PD, Mantilla CB, Sieck GC. TNFα Decreases Succinate Dehydrogenase Activity in Motor Neurons. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.02113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
Respiratory dysfunction is a leading cause of morbidity and mortality in individuals with cerebral palsy (CP). In children and adults with CP, movement and physical function is always affected. Yet, many clinicians overlook potential for impaired movement and function of the diaphragm muscle (DIAm) in individuals with CP. Since individuals with pre-existing respiratory disorders are at greater risk for respiratory complications if they contract COVID-19, understanding potential risks to individuals with CP is important. In this review we present research on respiratory function and DIAm force generation in children with CP. We compare this clinical work to basic science research investigating phrenic motor neuron and DIAm motor unit dysfunction in an animal model with CP symptoms, the spa mouse. Finally, we integrate the clinical and basic science work in respiratory function in CP, discussing potential for individuals with CP to have severe respiratory symptoms from COVID-19.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, MN, USA.,Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA
| | - Gary C Sieck
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, Rochester, MN, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA
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Fogarty MJ, Brown AD, Sieck GC. MOTOR NEURON LOSS IN AGING AND AMYOTROPHIC LATERAL SCLEROSIS: DIFFERENT FUSE LENGTHS, SAME EXPLOSION. Physiol Mini Rev 2020; 13:1-11. [PMID: 37577056 PMCID: PMC10416778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Advanced age and amyotrophic lateral sclerosis (ALS) are both associated with a loss of motor neurons resulting in muscle fiber atrophy and muscle weakness. Aging associated muscle fiber atrophy and weakening is termed sarcopenia, but the association with motor neuron loss is not as clearly established as in ALS, probably related to the prolonged time course of aging-related changes. Although aging and ALS effects on limb muscle strength and neuromotor performance are serious, such effects on the diaphragm muscle can be life threatening. Converging evidence indicates that larger phrenic motor neurons, innervating more fatigable type IIx and/or IIb diaphragm muscle fibers (fast fatigue intermediate, FInt and fast fatigable, FF motor units) are more susceptible to degeneration with both aging and ALS compared to smaller phrenic motor neurons innervating type I and IIa diaphragm muscle fibers (slow and fast fatigue resistant motor units, respectively). The etiology of ALS and age-related loss of motor neurons appears to involve mitochondrial function and neuroinflammation, both chronic and acute exacerbation. How mitochondrial dysfunction, neuroinflammation and motor neuron size intersect is the focus of continuing investigation.
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Affiliation(s)
- Matthew J. Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
| | - Alyssa D. Brown
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
| | - Gary C. Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
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Fogarty MJ, Marin Mathieu N, Mantilla CB, Sieck GC. Aging reduces succinate dehydrogenase activity in rat type IIx/IIb diaphragm muscle fibers. J Appl Physiol (1985) 2019; 128:70-77. [PMID: 31774353 DOI: 10.1152/japplphysiol.00644.2019] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In aged rats, diaphragm muscle (DIAm) reduced specific force and fiber cross-sectional area, sarcopenia, is selective for vulnerable type IIx and/or IIb DIAm fibers, with type I and IIa fibers being resilient. In humans, the oxidative capacity [as measured by maximum succinate dehydrogenase (SDHmax) activity] of fast-type muscle is reduced with aging, with slow-type muscle being unaffected. We hypothesized that in aged Fischer rat DIAm exhibiting sarcopenia, reduced SDHmax activity would occur in type IIx and/or IIb fibers. Rats obtained from the NIA colony (6, 18, and 24 mo old) were euthanized, and ~2-mm-wide DIAm strips were obtained. For SDHmax and fiber type assessments, DIAm strips were stretched (approximately optimal length), fresh frozen in isopentane, and sectioned on a cryostat at 6 μm. SDHmax, quantified by intensity of nitroblue tetrazolium diformazan precipitation, was assessed in a fiber type-specific manner by comparing serial sections labeled with myosin heavy chain (MyHC) antibodies differentiating type I (MyHCSlow), IIa (MyHC2A), and IIx and/or IIb fibers. Isometric DIAm force and fatigue were assessed in DIAm strips by muscle stimulation with supramaximal pulses at a variety of frequencies (5-100 Hz) delivered in 1-s trains. By 24 mo, DIAm sarcopenia was apparent and SDHmax in type IIx and/or IIb fibers activity was reduced ~35% compared with 6-mo-old control DIAm. These results underscore the remarkable fiber type selectivity of type IIx and/or IIb fibers to age-associated perturbations and suggest that reduced mitochondrial oxidative capacity is associated with DIAm sarcopenia.NEW & NOTEWORTHY We examined the oxidative capacity as measured by maximum succinate dehydrogenase activity in older (18 or 24 mo old) Fischer 344 rat diaphragm muscle (DIAm) compared with young rats (6 mo old). In 24-mo-old rats, SDH activity was reduced in type IIx/b DIAm fibers. These SDH changes were concomitant with sarcopenia (reduced specific force and atrophy of type IIx/b DIAm fibers) at 24 mo old. At 18 mo old, there was no change in SDH activity and no evidence of sarcopenia.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Natalia Marin Mathieu
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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Abstract
Breathing is achieved without thought despite being controlled by a complex neural network. The diaphragm is the predominant muscle responsible for force/pressure generation during breathing, but it is also involved in other non-ventilatory expulsive behaviors. This review considers alterations in diaphragm muscle fiber types and the neural control of the diaphragm across our lifespan and in various disease conditions.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55905, USA
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Fogarty MJ, Mu EWH, Lavidis NA, Noakes PG, Bellingham MC. Size-Dependent Vulnerability of Lumbar Motor Neuron Dendritic Degeneration in SOD1 G93A Mice. Anat Rec (Hoboken) 2019; 303:1455-1471. [PMID: 31509351 DOI: 10.1002/ar.24255] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 05/22/2019] [Accepted: 06/29/2019] [Indexed: 12/14/2022]
Abstract
The motor neuron (MN) soma surface area is correlated with motor unit type. Larger MNs innervate fast fatigue-intermediate (FInt) or fast-fatiguable (FF) muscle fibers in type FInt and FF motor units, respectively. Smaller MNs innervate slow-twitch fatigue-resistant (S) or fast fatigue-resistant (FR) muscle fibers in type S and FR motor units, respectively. In amyotrophic lateral sclerosis (ALS), FInt and FF motor units are more vulnerable, with denervation and MN death occurring for these units before the more resilient S and FR units. Abnormal MN dendritic arbors have been observed in ALS in humans and rodent models. We used a Golgi-Cox impregnation protocol to examine soma size-dependent changes in the dendritic morphology of lumbar MNs in SOD1G93A mice, a model of ALS, at pre-symptomatic, onset and mid-disease stages. In wildtype control mice, the relationship between MN soma surface area and dendritic length or dendritic spine number was highly linear (i.e., increased MN soma size correlated with increased dendritic length and spines). By contrast, in SOD1G93A mice, this linear relationship was lost and dendritic length reduction and spine loss were observed in larger MNs, from pre-symptomatic stages onward. These changes correlated with the neuromotor symptoms of ALS in rodent models. At presymptomatic ages, changes were restricted to the larger MNs, likely to comprise vulnerable FInt and FF motor units. Our results suggest morphological changes of MN dendrites and dendritic spines are likely to contribute ALS pathogenesis, not compensate for it. Anat Rec, 303:1455-1471, 2020. © 2019 American Association for Anatomy.
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Affiliation(s)
- Matthew J Fogarty
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Erica W H Mu
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Nickolas A Lavidis
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Peter G Noakes
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia.,Queensland Brain Institute, The University of Queensland, St Lucia, Queensland, Australia
| | - Mark C Bellingham
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
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Khurram OU, Fogarty MJ, Sarrafian TL, Bhatt A, Mantilla CB, Sieck GC. Impact of aging on diaphragm muscle function in male and female Fischer 344 rats. Physiol Rep 2019; 6:e13786. [PMID: 29981218 PMCID: PMC6035336 DOI: 10.14814/phy2.13786] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 06/08/2018] [Accepted: 06/12/2018] [Indexed: 11/24/2022] Open
Abstract
The diaphragm muscle (DIAm) is the primary inspiratory muscle in mammals and is active during ventilatory behaviors, but it is also involved in higher-force behaviors such as those necessary for clearing the airway. Our laboratory has previously reported DIAm sarcopenia in rats and mice characterized by DIAm atrophy and a reduction in maximum specific force at 24 months of age. In Fischer 344 rats, these studies were limited to male animals, although in other studies, we noted a more rapid increase in body mass from 6 to 24 months of age in females (~140%) compared to males (~110%). This difference in body weight gain suggests a possible sex difference in the manifestation of sarcopenia. In mice, we previously measured transdiaphragmatic pressure (Pdi) to evaluate in vivo DIAm force generation across a range of motor behaviors, but found no evidence of sex-related differences. The purpose of this study in Fischer 344 rats was to evaluate if there are sex-related differences in DIAm sarcopenia, and if such differences translate to a functional impact on Pdi generation across motor behaviors and maximal Pdi (Pdimax ) elicited by bilateral phrenic nerve stimulation. In both males and females, DIAm sarcopenia was apparent in 24-month-old rats with a ~30% reduction in both maximum specific force and the cross-sectional area of type IIx and/or IIb fibers. Importantly, in both males and females, Pdi generated during ventilatory behaviors was unimpaired by sarcopenia, even during more forceful ventilatory efforts induced via airway occlusion. Although ventilatory behaviors were preserved with aging, there was a ~20% reduction in Pdimax , which likely impairs the ability of the DIAm to generate higher-force expulsive airway clearance behaviors necessary to maintain airway patency.
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Affiliation(s)
- Obaid U Khurram
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,School of Biomedical Sciences, The University of Queensland, Brisbane, Australia
| | - Tiffany L Sarrafian
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Arjun Bhatt
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota
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Fogarty MJ, Gonzalez Porras MA, Mantilla CB, Sieck GC. Diaphragm neuromuscular transmission failure in aged rats. J Neurophysiol 2019; 122:93-104. [PMID: 31042426 PMCID: PMC6689786 DOI: 10.1152/jn.00061.2019] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/26/2019] [Accepted: 04/26/2019] [Indexed: 12/16/2022] Open
Abstract
In aging Fischer 344 rats, phrenic motor neuron loss, neuromuscular junction abnormalities, and diaphragm muscle (DIAm) sarcopenia are present by 24 mo of age, with larger fast-twitch fatigue-intermediate (type FInt) and fast-twitch fatigable (type FF) motor units particularly vulnerable. We hypothesize that in old rats, DIAm neuromuscular transmission deficits are specific to type FInt and/or FF units. In phrenic nerve/DIAm preparations from rats at 6 and 24 mo of age, the phrenic nerve was supramaximally stimulated at 10, 40, or 75 Hz. Every 15 s, the DIAm was directly stimulated, and the difference in forces evoked by nerve and muscle stimulation was used to estimate neuromuscular transmission failure. Neuromuscular transmission failure in the DIAm was observed at each stimulation frequency. In the initial stimulus trains, the forces evoked by phrenic nerve stimulation at 40 and 75 Hz were significantly less than those evoked by direct muscle stimulation, and this difference was markedly greater in 24-mo-old rats. During repetitive nerve stimulation, neuromuscular transmission failure at 40 and 75 Hz worsened to a greater extent in 24-mo-old rats compared with younger animals. Because type IIx and/or IIb DIAm fibers (type FInt and/or FF motor units) display greater susceptibility to neuromuscular transmission failure at higher frequencies of stimulation, these data suggest that the age-related loss of larger phrenic motor neurons impacts nerve conduction to muscle at higher frequencies and may contribute to DIAm sarcopenia in old rats. NEW & NOTEWORTHY Diaphragm muscle (DIAm) sarcopenia, phrenic motor neuron loss, and perturbations of neuromuscular junctions (NMJs) are well described in aged rodents and selectively affect FInt and FF motor units. Less attention has been paid to the motor unit-specific aspects of nerve-muscle conduction. In old rats, increased neuromuscular transmission failure occurred at stimulation frequencies where FInt and FF motor units exhibit conduction failures, along with decreased apposition of pre- and postsynaptic domains of DIAm NMJs of these units.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
| | | | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
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Fogarty MJ. Strong links in a weak chain: skeletal muscle fibres in amyotrophic lateral sclerosis. J Physiol 2019; 597:3799-3800. [PMID: 31206712 DOI: 10.1113/jp278331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
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Brandenburg JE, Fogarty MJ, Sieck GC. A Critical Evaluation of Current Concepts in Cerebral Palsy. Physiology (Bethesda) 2019; 34:216-229. [PMID: 30968751 PMCID: PMC7938766 DOI: 10.1152/physiol.00054.2018] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 01/11/2019] [Accepted: 01/23/2019] [Indexed: 11/22/2022] Open
Abstract
Spastic cerebral palsy (CP), despite the name, is not consistently identifiable by specific brain lesions. CP animal models focus on risk factors for development of CP, yet few reproduce the diagnostic symptoms. Animal models of CP must advance beyond risk factors to etiologies, including both the brain and spinal cord.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Gary C Sieck
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Anesthesiology, Mayo Clinic College of Medicine , Rochester, Minnesota
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50
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Abstract
NEW FINDINGS What is the central question of this study? Is the residual force generated by the diaphragm muscle after repeated activation reduced with sarcopenia, and is the residual force generated after fatiguing activation sufficient to sustain ventilatory behaviours of diaphragm muscle in young and old rats? What is the main finding and its importance? After diaphragm muscle fatigue, the residual specific force after 120 s of repeated stimulation was unaffected by ageing and was sufficient to accomplish ventilatory behaviours, but not expulsive manoeuvres (e.g. coughing). The inability to perform expulsive behaviours might underlie the increased susceptibility of older individuals to respiratory tract infections. ABSTRACT Type IIx and/or IIb diaphragm muscle (DIAm) fibres make up more fatigable motor units that are more vulnerable to sarcopenia, i.e. age-associated reductions of specific force and cross-sectional area. In contrast, type I and IIa DIAm fibres form fatigue-resistant motor units that are relatively unchanged with age. The fatigue resistance of the DIAm is assessed by normalizing the residual force generated after a period of repeated supramaximal stimulation (e.g. 120 s) to the initial maximal force. Given that sarcopenia primarily affects more fatigable DIAm motor units, apparent fatigue resistance improves with ageing. However, the central question is whether there is an ageing-related difference in the residual force generated by the DIAm after repeated stimulation and whether this force is sufficient to sustain ventilatory behaviours of DIAm. In 6- and 24-month-old Fischer 344 rats, we assessed the loss of ex vivo DIAm force throughout 120 s of repeated supramaximal stimulation at 10, 40 and 75 Hz. We found that relative fatigue resistance improved in older rats at 40 and 75 Hz stimulation. Across all stimulation frequencies, DIAm residual force was unchanged with age (∼5 N cm-2 ). We conclude that ageing increases the relative contribution of type I and IIa fibres to DIAm force, with decreased contributions of type IIx and/or IIb fibres. The residual force generated by the DIAm after repeated stimulation is sufficient to accomplish ventilatory behaviours, regardless of age.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA.,Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
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