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Capilla-López J, Hernández RG, Carrero-Rojas G, Calvo PM, Alvarez FJ, de la Cruz RR, Pastor AM. VEGF, but Not BDNF, Prevents the Downregulation of KCC2 Induced by Axotomy in Extraocular Motoneurons. Int J Mol Sci 2024; 25:9942. [PMID: 39337430 PMCID: PMC11432591 DOI: 10.3390/ijms25189942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2024] [Revised: 09/09/2024] [Accepted: 09/11/2024] [Indexed: 09/30/2024] Open
Abstract
The potassium-chloride cotransporter KCC2 is the main extruder of Cl- in neurons. It plays a fundamental role in the activity of the inhibitory neurotransmitters (GABA and glycine) since low levels of KCC2 promote intracellular Cl- accumulation, leading to the depolarizing activity of GABA and glycine. The downregulation of this cotransporter occurs in neurological disorders characterized by hyperexcitability, such as epilepsy, neuropathic pain, and spasticity. KCC2 is also downregulated after axotomy. If muscle reinnervation is allowed, the KCC2 levels recover in motoneurons. Therefore, we argued that target-derived neurotrophic factors might be involved in the regulation of KCC2 expression. For this purpose, we performed the axotomy of extraocular motoneurons via the monocular enucleation of adult rats, and a pellet containing either VEGF or BDNF was chronically implanted in the orbit. Double confocal immunofluorescence of choline acetyl-transferase (ChAT) and KCC2 was carried out in the brainstem sections. Axotomy led to a KCC2 decrease in the neuropil and somata of extraocular motoneurons, peaking at 15 days post-lesion, with the exception of the abducens motoneuron somata. VEGF administration prevented the axotomy-induced KCC2 downregulation. By contrast, BDNF either maintained or reduced the KCC2 levels following axotomy, suggesting that BDNF is involved in the axotomy-induced KCC2 downregulation in extraocular motoneurons. The finding that VEGF prevents KCC2 decrease opens up new possibilities for the treatment of neurological disorders coursing with neuronal hyperactivity due to KCC2 downregulation.
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Affiliation(s)
- Jaime Capilla-López
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Rosendo G Hernández
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Génova Carrero-Rojas
- Center for Anatomy and Cell Biology, Division of Anatomy, Medical University Vienna, 1090 Vienna, Austria
| | - Paula M Calvo
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | | | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain
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2
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Molska M, Mruczyk K, Cisek-Woźniak A, Prokopowicz W, Szydełko P, Jakuszewska Z, Marzec K, Trocholepsza M. The Influence of Intestinal Microbiota on BDNF Levels. Nutrients 2024; 16:2891. [PMID: 39275207 PMCID: PMC11397622 DOI: 10.3390/nu16172891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2024] [Revised: 08/24/2024] [Accepted: 08/26/2024] [Indexed: 09/16/2024] Open
Abstract
The regulation of neurogenesis, the complex process of producing and differentiating new brain tissue cells, is influenced by a complex interaction of internal and external factors. Over the past decade, extensive research has been conducted on neurotrophins and their key role in adult neurogenesis, as well as their impact on diseases such as depression. Among neurotrophins, the brain-derived neurotrophic factor (BDNF) has been the subject of comprehensive studies on adult neurogenesis, and scientific evidence supports its necessity for neurogenesis in the subventricular zone of the hippocampus. A novel area of research is the emerging role of gut microbiota as a significant contributor to neurogenesis and neurotrophin production. Studies have shown that reduced BDNF levels can lead to mood disorders, which are observed in intestinal dysbiosis, characterized by an imbalance in the composition and quantity of the intestinal microbiota. There is evidence in the literature that there is a link between brain function and gut microbiota. Physical activity, and especially the regularity and intensity of exercise, is important in relation to the level of BDNF and the intestinal microbiota. Probiotics, prebiotics and physical activity may have a positive effect on the intestinal microbiota, and therefore also on the level of the brain-derived neurotrophic factor.
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Affiliation(s)
- Marta Molska
- Department of Dietetics, Faculty of Physical Culture in Gorzow Wlkp., Poznan University of Physical Education, Estkowskiego 13, 66-400 Gorzow Wielkopolski, Poland; (K.M.); (A.C.-W.); (P.S.); (Z.J.); (K.M.); (M.T.)
| | - Kinga Mruczyk
- Department of Dietetics, Faculty of Physical Culture in Gorzow Wlkp., Poznan University of Physical Education, Estkowskiego 13, 66-400 Gorzow Wielkopolski, Poland; (K.M.); (A.C.-W.); (P.S.); (Z.J.); (K.M.); (M.T.)
| | - Angelika Cisek-Woźniak
- Department of Dietetics, Faculty of Physical Culture in Gorzow Wlkp., Poznan University of Physical Education, Estkowskiego 13, 66-400 Gorzow Wielkopolski, Poland; (K.M.); (A.C.-W.); (P.S.); (Z.J.); (K.M.); (M.T.)
| | - Wojciech Prokopowicz
- GSP Clinic Limited Liability Company, Kostrzyńska Street 12, 66-400 Gorzow Wielkopolski, Poland;
| | - Patrycja Szydełko
- Department of Dietetics, Faculty of Physical Culture in Gorzow Wlkp., Poznan University of Physical Education, Estkowskiego 13, 66-400 Gorzow Wielkopolski, Poland; (K.M.); (A.C.-W.); (P.S.); (Z.J.); (K.M.); (M.T.)
| | - Zuzanna Jakuszewska
- Department of Dietetics, Faculty of Physical Culture in Gorzow Wlkp., Poznan University of Physical Education, Estkowskiego 13, 66-400 Gorzow Wielkopolski, Poland; (K.M.); (A.C.-W.); (P.S.); (Z.J.); (K.M.); (M.T.)
| | - Karolina Marzec
- Department of Dietetics, Faculty of Physical Culture in Gorzow Wlkp., Poznan University of Physical Education, Estkowskiego 13, 66-400 Gorzow Wielkopolski, Poland; (K.M.); (A.C.-W.); (P.S.); (Z.J.); (K.M.); (M.T.)
| | - Martyna Trocholepsza
- Department of Dietetics, Faculty of Physical Culture in Gorzow Wlkp., Poznan University of Physical Education, Estkowskiego 13, 66-400 Gorzow Wielkopolski, Poland; (K.M.); (A.C.-W.); (P.S.); (Z.J.); (K.M.); (M.T.)
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3
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Tuffaha S, Lee EB. Growth Factors to Enhance Nerve Regeneration: Approaching Clinical Translation. Hand Clin 2024; 40:399-408. [PMID: 38972684 DOI: 10.1016/j.hcl.2024.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/09/2024]
Abstract
Following nerve injury, growth factors (GFs) are transiently upregulated in injured neurons, proliferating Schwann cells, and denervated muscle and skin. They act on these same cells and tissues to promote nerve regeneration and end-organ reinnervation. Consequently, much attention has been focused on developing GF-based therapeutics. A major barrier to clinical translation of GFs is their short half-life. To provide sustained GF treatment to the affected nerve, muscle, and skin in a safe and practical manner, engineered drug delivery systems are needed. This review highlights recent advancements in GF-based therapeutics and discusses the remaining hurdles for clinical translation.
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Affiliation(s)
- Sami Tuffaha
- Department of Plastic and Reconstructive Surgery, Johns Hopkins School of Medicine, Baltimore, MD 21231, USA
| | - Erica B Lee
- Department of Plastic and Reconstructive Surgery, Johns Hopkins School of Medicine, Baltimore, MD 21231, USA.
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4
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Titova A, Nikolaev S, Bilyalov A, Filatov N, Brovkin S, Shestakov D, Khatkov I, Pismennaya E, Bondarev V, Antyuxina M, Shagimardanova E, Bodunova N, Gusev O. Extreme Tolerance of Extraocular Muscles to Diseases and Aging: Why and How? Int J Mol Sci 2024; 25:4985. [PMID: 38732204 PMCID: PMC11084950 DOI: 10.3390/ijms25094985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 04/26/2024] [Accepted: 04/29/2024] [Indexed: 05/13/2024] Open
Abstract
The extraocular muscles (EOMs) possess unique characteristics that set them apart from other skeletal muscles. These muscles, responsible for eye movements, exhibit remarkable resistance to various muscular dystrophies and aging, presenting a significant contrast to the vulnerability of skeletal muscles to these conditions. In this review, we delve into the cellular and molecular underpinnings of the distinct properties of EOMs. We explore their structural complexity, highlighting differences in fiber types, innervation patterns, and developmental origins. Notably, EOM fibers express a diverse array of myosin heavy-chain isoforms, retaining embryonic forms into adulthood. Moreover, their motor innervation is characterized by a high ratio of nerve fibers to muscle fibers and the presence of unique neuromuscular junctions. These features contribute to the specialized functions of EOMs, including rapid and precise eye movements. Understanding the mechanisms behind the resilience of EOMs to disease and aging may offer insights into potential therapeutic strategies for treating muscular dystrophies and myopathies affecting other skeletal muscles.
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Affiliation(s)
- Angelina Titova
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia
| | - Sergey Nikolaev
- SBHI Moscow Clinical Scientific Center Named after Loginov MHD, 111123 Moscow, Russia
| | - Airat Bilyalov
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia
- SBHI Moscow Clinical Scientific Center Named after Loginov MHD, 111123 Moscow, Russia
| | - Nikita Filatov
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia
| | - Sergei Brovkin
- SBHI Moscow Clinical Scientific Center Named after Loginov MHD, 111123 Moscow, Russia
| | | | - Igor Khatkov
- SBHI Moscow Clinical Scientific Center Named after Loginov MHD, 111123 Moscow, Russia
| | | | | | | | - Elena Shagimardanova
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia
- SBHI Moscow Clinical Scientific Center Named after Loginov MHD, 111123 Moscow, Russia
| | - Natalia Bodunova
- SBHI Moscow Clinical Scientific Center Named after Loginov MHD, 111123 Moscow, Russia
| | - Oleg Gusev
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia
- Intractable Disease Research Center, Graduate School of Medicine, Juntendo University, Tokyo 113-8421, Japan
- Life Improvement by Future Technologies (LIFT) Center, 121205 Moscow, Russia
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Hoh JFY. Developmental, Physiological and Phylogenetic Perspectives on the Expression and Regulation of Myosin Heavy Chains in Craniofacial Muscles. Int J Mol Sci 2024; 25:4546. [PMID: 38674131 PMCID: PMC11050549 DOI: 10.3390/ijms25084546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 04/15/2024] [Accepted: 04/18/2024] [Indexed: 04/28/2024] Open
Abstract
This review deals with the developmental origins of extraocular, jaw and laryngeal muscles, the expression, regulation and functional significance of sarcomeric myosin heavy chains (MyHCs) that they express and changes in MyHC expression during phylogeny. Myogenic progenitors from the mesoderm in the prechordal plate and branchial arches specify craniofacial muscle allotypes with different repertoires for MyHC expression. To cope with very complex eye movements, extraocular muscles (EOMs) express 11 MyHCs, ranging from the superfast extraocular MyHC to the slowest, non-muscle MyHC IIB (nmMyH IIB). They have distinct global and orbital layers, singly- and multiply-innervated fibres, longitudinal MyHC variations, and palisade endings that mediate axon reflexes. Jaw-closing muscles express the high-force masticatory MyHC and cardiac or limb MyHCs depending on the appropriateness for the acquisition and mastication of food. Laryngeal muscles express extraocular and limb muscle MyHCs but shift toward expressing slower MyHCs in large animals. During postnatal development, MyHC expression of craniofacial muscles is subject to neural and hormonal modulation. The primary and secondary myotubes of developing EOMs are postulated to induce, via different retrogradely transported neurotrophins, the rich diversity of neural impulse patterns that regulate the specific MyHCs that they express. Thyroid hormone shifts MyHC 2A toward 2B in jaw muscles, laryngeal muscles and possibly extraocular muscles. This review highlights the fact that the pattern of myosin expression in mammalian craniofacial muscles is principally influenced by the complex interplay of cell lineages, neural impulse patterns, thyroid and other hormones, functional demands and body mass. In these respects, craniofacial muscles are similar to limb muscles, but they differ radically in the types of cell lineage and the nature of their functional demands.
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Affiliation(s)
- Joseph Foon Yoong Hoh
- Discipline of Physiology, School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW 2006, Australia
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Hao J, Wang M, Liu J, Yusufu M, Cao K, Fu J. Alteration of Neurotrophic Factors and Innervation in Extraocular Muscles of Individuals With Concomitant Esotropia. Invest Ophthalmol Vis Sci 2024; 65:1. [PMID: 38441891 PMCID: PMC10916883 DOI: 10.1167/iovs.65.3.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 02/15/2024] [Indexed: 03/07/2024] Open
Abstract
Purpose To determine whether neurotrophic factors and innervation in extraocular muscles (EOMs) were altered in different types of concomitant esotropia, and to explore the possible association between neurotrophic factors and innervation of EOMs in humans. Methods Patients with concomitant esotropia who required strabismus surgery were recruited from January to December 2022. Lateral rectus EOMs were obtained from patients, and controls were obtained from deceased organ donors. Immunofluorescence (IF) was performed to detect innervation of EOMs (neurofilament and synaptophysin), and immunohistochemistry (IHC) was used to detect the neurotrophic factors insulin-like growth factor-1 (IGF-1), brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF), and neurotrophin-3 (NT-3). The positive IHC results were further verified using western blotting (WB). One-way ANOVA followed by a Dunnett's multiple comparison post hoc test was used for continuous variables and the χ2 test for categorical variables. Spearman correlation analysis was used for the correlation analysis. Results We collected lateral rectus EOM samples from acute and chronic types of concomitant esotropia and controls. Consistent with IHC, WB showed that IGF-1 was significantly increased in patients with acute acquired comitant esotropia or essential infantile esotropia compared with controls. In IF, synaptophysins were significantly increased only in acute acquired comitant esotropia compared with controls. Furthermore, Spearman correlation analysis showed that the correlation between IGF-1 and synaptophysin was borderline (P = 0.057) for patients with acute acquired comitant esotropia. Conclusions Our study highlights the role of IGF-1 and altered innervation of EOMs in acute acquired comitant esotropia, suggesting that an effect of increased IGF-1 on nerve innervation may temporarily cause a compensatory increase in the strength of lateral rectus muscles.
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Affiliation(s)
- Jie Hao
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Ophthalmology & Visual Sciences, Beijing, China
| | - Meixu Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Ophthalmology & Visual Sciences, Beijing, China
| | - Jiawen Liu
- Industrial Engineering and Operations Research, University of California, Berkeley, California, United States
| | - Mayinuer Yusufu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, Australia
- Department of Surgery (Ophthalmology), The University of Melbourne, Melbourne, Australia
| | - Kai Cao
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Ophthalmology & Visual Sciences, Beijing, China
| | - Jing Fu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Ophthalmology & Visual Sciences, Beijing, China
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Benítez-Temiño B, Hernández RG, de la Cruz RR, Pastor AM. BDNF Influence on Adult Terminal Axon Sprouting after Partial Deafferentation. Int J Mol Sci 2023; 24:10660. [PMID: 37445838 DOI: 10.3390/ijms241310660] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 06/20/2023] [Accepted: 06/23/2023] [Indexed: 07/15/2023] Open
Abstract
BDNF is a neurotrophin family member implicated in many different neuronal functions, from neuronal survival during development to synaptic plasticity associated with processes of learning and memory. Its presence in the oculomotor system has previously been demonstrated, as it regulates afferent composition of extraocular motoneurons and their firing pattern. Moreover, BDNF expression increases after extraocular motoneuron partial deafferentation, in parallel with terminal axon sprouting from the remaining axons. To elucidate whether BDNF could play an active role in this process, we performed partial deafferentation of the medial rectus motoneurons through transection of one of the two main afferents, that is, the ascending tract of Deiters, and injected BDNF into the motoneuron target muscle, the medial rectus. Furthermore, to check whether BDNF could stimulate axon sprouting without lesions, we performed the same experiment without any lesions. Axon terminal sprouting was assessed by calretinin immunostaining, which specifically labels the remaining afferent system on medial rectus motoneurons, the abducens internuclear neurons. The results presented herein show that exogenous BDNF stimulated terminal axon growth, allowing the total recovery of synaptic coverage around the motoneuron somata. Moreover, calretinin staining in the neuropil exceeded that present in the control situation. Thus, BDNF could also stimulate axonal sprouting in the neuropil of intact animals. These results point to an active role of BDNF in plastic adaptations that take place after partial deafferentation.
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Affiliation(s)
- Beatriz Benítez-Temiño
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Rosendo G Hernández
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
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Calvo PM, de la Cruz RR, Pastor AM, Alvarez FJ. Preservation of KCC2 expression in axotomized abducens motoneurons and its enhancement by VEGF. Brain Struct Funct 2023; 228:967-984. [PMID: 37005931 PMCID: PMC10428176 DOI: 10.1007/s00429-023-02635-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 03/23/2023] [Indexed: 04/04/2023]
Abstract
The potassium chloride cotransporter 2 (KCC2) is the main Cl- extruder in neurons. Any alteration in KCC2 levels leads to changes in Cl- homeostasis and, consequently, in the polarity and amplitude of inhibitory synaptic potentials mediated by GABA or glycine. Axotomy downregulates KCC2 in many different motoneurons and it is suspected that interruption of muscle-derived factors maintaining motoneuron KCC2 expression is in part responsible. In here, we demonstrate that KCC2 is expressed in all oculomotor nuclei of cat and rat, but while trochlear and oculomotor motoneurons downregulate KCC2 after axotomy, expression is unaltered in abducens motoneurons. Exogenous application of vascular endothelial growth factor (VEGF), a neurotrophic factor expressed in muscle, upregulated KCC2 in axotomized abducens motoneurons above control levels. In parallel, a physiological study using cats chronically implanted with electrodes for recording abducens motoneurons in awake animals, demonstrated that inhibitory inputs related to off-fixations and off-directed saccades in VEGF-treated axotomized abducens motoneurons were significantly higher than in control, but eye-related excitatory signals in the on direction were unchanged. This is the first report of lack of KCC2 regulation in a motoneuron type after injury, proposing a role for VEGF in KCC2 regulation and demonstrating the link between KCC2 and synaptic inhibition in awake, behaving animals.
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Affiliation(s)
- Paula M Calvo
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012, Seville, Spain
- Department of Cell Biology, Emory University, Atlanta, GA, 30322, USA
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012, Seville, Spain
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012, Seville, Spain
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Yu L, Liu M, Li F, Wang Q, Wang M, So KF, Qu Y, Zhou L. Celsr2 Knockout Alleviates Inhibitory Synaptic Stripping and Benefits Motoneuron Survival and Axon Regeneration After Branchial Plexus Avulsion. Mol Neurobiol 2023; 60:1884-1900. [PMID: 36593433 PMCID: PMC9984348 DOI: 10.1007/s12035-022-03198-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 12/23/2022] [Indexed: 01/04/2023]
Abstract
Axotomy-induced synaptic stripping modulates survival and axon regeneration of injured motoneurons. Celsr2 is supposed to mediate homophilic interactions of neighboring cells during development, and its role in synaptic stripping remains unknow. In a model of brachial plexus avulsion, Celsr2 knockout improved functional recovery, motoneuron survival, and axon regeneration. Celsr2 was indicated to express in spinal motoneurons, excitatory and inhibitory interneurons, astrocytes, and a subset of oligodendrocytes using Celsr2LacZ mice. Double immunostaining showed that the coverage of inhibitory and excitatory vesicles on injured motoneurons were remarkably reduced after injury, whereas more inhibitory vesicles were maintained in Celsr2-/- mutants than control mice. In the ultrastructure, the density of inhibitory F-boutons on injured motoneurons was higher in Celsr2-/- mutants than controls. Conditional knockout of Celsr2 in astrocytes or oligodendrocytes showed the similar axotomy-induced synaptic withdrawal to the control. RNAseq of injured spinal samples identified 12 MHC I molecules with significant changes between Celsr2-/- and control mice. After injury, expression of MHC I surrounding injured motoneurons was increased, particularly high in Celsr2-/- mutants. In conclusion, Celsr2 knockout enhances MHC I signaling, alleviates inhibitory synaptic stripping cell-autonomously, and contributes to motoneuron survival and regeneration, and Celsr2 is a potential target for neural repair.
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Affiliation(s)
- Lingtai Yu
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China
| | - Mengfan Liu
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China
| | - Fuxiang Li
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China
| | - Qianghua Wang
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China
| | - Meizhi Wang
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China
| | - Kwok-Fai So
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China.,Department of Neurology and Stroke Center, The First Affiliated Hospital & Clinical Neuroscience Institute of Jinan University, Guangzhou, 510632, People's Republic of China.,Neuroscience and Neurorehabilitation Institute, University of Health and Rehabilitation Sciences, Qingdao, 266071, Shandong, People's Republic of China.,Co-Innovation Center of Neuroregeneration, Nantong University, Jiangsu, People's Republic of China
| | - Yibo Qu
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China.,Co-Innovation Center of Neuroregeneration, Nantong University, Jiangsu, People's Republic of China
| | - Libing Zhou
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, 510632, People's Republic of China. .,Department of Neurology and Stroke Center, The First Affiliated Hospital & Clinical Neuroscience Institute of Jinan University, Guangzhou, 510632, People's Republic of China. .,Neuroscience and Neurorehabilitation Institute, University of Health and Rehabilitation Sciences, Qingdao, 266071, Shandong, People's Republic of China. .,Co-Innovation Center of Neuroregeneration, Nantong University, Jiangsu, People's Republic of China.
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Abstract
VEGF was initially discovered due to its angiogenic activity and therefore named "vascular endothelial growth factor." However, its more recently discovered neurotrophic activity may be evolutionarily more ancient. Our previous work showed that all the changes produced by axotomy on the firing activity and synaptic inputs of abducens motoneurons were completely restored after VEGF administration. Therefore, we hypothesized that the lack of VEGF delivered by retrograde transport from the periphery should also affect the physiology of otherwise intact abducens motoneurons. For VEGF retrograde blockade, we chronically applied a neutralizing VEGF antibody to the lateral rectus muscle. Recordings of extracellular single-unit activity and eye movements were made in alert cats before and after the application of the neutralizing antibody. Our data revealed that intact, noninjured abducens motoneurons retrogradely deprived of VEGF exhibited noticeable changes in their firing pattern. There is a general decrease in firing rate and a significant reduction in eye position and eye velocity sensitivity (i.e., a decrease in the tonic and phasic components of their discharge, respectively). Moreover, by means of confocal immunocytochemistry, motoneurons under VEGF blockade showed a marked reduction in the density of afferent synaptic terminals contacting with their cell bodies. Altogether, the present findings demonstrate that the lack of retrogradely delivered VEGF renders abducens motoneurons into an axotomy-like state. This indicates that VEGF is an essential retrograde factor for motoneuronal synaptic drive and discharge activity.
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11
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Pastor AM, Blumer R, de la Cruz RR. Extraocular Motoneurons and Neurotrophism. ADVANCES IN NEUROBIOLOGY 2022; 28:281-319. [PMID: 36066830 DOI: 10.1007/978-3-031-07167-6_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Extraocular motoneurons are located in three brainstem nuclei: the abducens, trochlear and oculomotor. They control all types of eye movements by innervating three pairs of agonistic/antagonistic extraocular muscles. They exhibit a tonic-phasic discharge pattern, demonstrating sensitivity to eye position and sensitivity to eye velocity. According to their innervation pattern, extraocular muscle fibers can be classified as singly innervated muscle fiber (SIF), or the peculiar multiply innervated muscle fiber (MIF). SIF motoneurons show anatomical and physiological differences with MIF motoneurons. The latter are smaller and display lower eye position and velocity sensitivities as compared with SIF motoneurons.
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Affiliation(s)
- Angel M Pastor
- Departamento de Fisiología, Universidad de Sevilla, Seville, Spain.
| | - Roland Blumer
- Center of Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria
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12
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Carrero-Rojas G, Hernández RG, Blumer R, de la Cruz RR, Pastor AM. MIF versus SIF Motoneurons, What Are Their Respective Contribution in the Oculomotor Medial Rectus Pool? J Neurosci 2021; 41:9782-9793. [PMID: 34675089 PMCID: PMC8612643 DOI: 10.1523/jneurosci.1480-21.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 08/18/2021] [Accepted: 10/11/2021] [Indexed: 12/18/2022] Open
Abstract
Multiply-innervated muscle fibers (MIFs) are peculiar to the extraocular muscles as they are non-twitch but produce a slow build up in tension on repetitive stimulation. The motoneurons innervating MIFs establish en grappe terminals along the entire length of the fiber, instead of the typical en plaque terminals that singly-innervated muscle fibers (SIFs) motoneurons establish around the muscle belly. MIF motoneurons have been proposed to participate only in gaze holding and slow eye movements. We aimed to discern the function of MIF motoneurons by recording medial rectus motoneurons of the oculomotor nucleus. Single-unit recordings in awake cats demonstrated that electrophysiologically-identified medial rectus MIF motoneurons participated in different types of eye movements, including fixations, rapid eye movements or saccades, convergences, and the slow and fast phases of the vestibulo-ocular nystagmus, the same as SIF motoneurons did. However, MIF medial rectus motoneurons presented lower firing frequencies, were recruited earlier and showed lower eye position (EP) and eye velocity (EV) sensitivities than SIF motoneurons. MIF medial rectus motoneurons were also smaller, had longer antidromic latencies and a lower synaptic coverage than SIF motoneurons. Peristimulus time histograms (PSTHs) revealed that electrical stimulation to the myotendinous junction, where palisade endings are located, did not recurrently affect the firing probability of medial rectus motoneurons. Therefore, we conclude there is no division of labor between MIF and SIF motoneurons based on the type of eye movement they subserve.SIGNIFICANCE STATEMENT In addition to the common singly-innervated muscle fiber (SIF), extraocular muscles also contain multiply-innervated muscle fibers (MIFs), which are non-twitch and slow in contraction. MIF motoneurons have been proposed to participate only in gaze holding and slow eye movements. In the present work, by single-unit extracellular recordings in awake cats, we demonstrate, however, that both SIF and MIF motoneurons, electrophysiologically-identified, participate in the different types of eye movements. However, MIF motoneurons showed lower firing rates (FRs), recruitment thresholds, and eye-related sensitivities, and could thus contribute to the fine adjustment of eye movements. Electrical stimulation of the myotendinous junction activates antidromically MIF motoneurons but neither MIF nor SIF motoneurons receive a synaptic reafferentation that modifies their discharge probability.
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Affiliation(s)
- Génova Carrero-Rojas
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville 41012, Spain
- Center of Anatomy and Cell Biology, Medical Imaging Cluster, Medical University Vienna, Vienna 1090, Austria
| | - Rosendo G Hernández
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville 41012, Spain
| | - Roland Blumer
- Center of Anatomy and Cell Biology, Medical Imaging Cluster, Medical University Vienna, Vienna 1090, Austria
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville 41012, Spain
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville 41012, Spain
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13
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Abstract
Eye movements are indispensable for visual image stabilization during self-generated and passive head and body motion and for visual orientation. Eye muscles and neuronal control elements are evolutionarily conserved, with novel behavioral repertoires emerging during the evolution of frontal eyes and foveae. The precise execution of eye movements with different dynamics is ensured by morphologically diverse yet complementary sets of extraocular muscle fibers and associated motoneurons. Singly and multiply innervated muscle fibers are controlled by motoneuronal subpopulations with largely selective premotor inputs from task-specific ocular motor control centers. The morphological duality of the neuromuscular interface is matched by complementary biochemical and molecular features that collectively assign different physiological properties to the motor entities. In contrast, the functionality represents a continuum where most motor elements contribute to any type of eye movement, although within preferential dynamic ranges, suggesting that signal transmission and muscle contractions occur within bands of frequency-selective pathways.
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Affiliation(s)
- Anja K E Horn
- Institute of Anatomy and Cell Biology I, Ludwig-Maximilians-University Munich, 80336 Munich, Germany;
| | - Hans Straka
- Department Biology II, Ludwig-Maximilians-University Munich, 82152 Planegg, Germany
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14
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Fouad K, Vavrek R, Cho S. A TrkB Antibody Agonist Promotes Plasticity after Cervical Spinal Cord Injury in Adult Rats. J Neurotrauma 2021; 38:1338-1348. [PMID: 20597685 DOI: 10.1089/neu.2009.1116] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
After spinal cord injury (SCI) in mammals, there is only limited repair and, consequently, only moderate recovery. One mechanism frequently discussed to be involved in this recovery is plasticity (i.e., adaptations in spared neuronal circuitries). In the current study, we tested the effect of an intrathecal application of the TrkB agonist antibody, 29D7, on plasticity after cervical SCI in adult rats. Treatment with 29D7 for 4 weeks resulted in an ∼50% increase in collateral sprouting of severed corticospinal tract fibers above the lesion compared to the control group and enhanced branching in the gray matter rostral to the injury. Growth-associated protein 43 immunoreactivity in the spinal cord rostral to the level of the injury as well as contralateral to the lesion was also increased. These indications of enhanced plasticity by 29D7 were paralleled by improved performances of the mildly affected paw, as assessed by Montoya and tray reaching tasks. The reaching behaviors of the paw ipsilateral to the side of severe injury to the cortico- and rubrospinal tract were not altered by the treatment. The present study suggests that 29D7 may be a potential candidate to promote plasticity and functional recovery, especially after moderate SCI. Future studies confirming these results, along with a potential combinatory therapy including rehabilitative training, will be needed to evaluate the clinical value of such a treatment.
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Affiliation(s)
- Karim Fouad
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Romana Vavrek
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Seongeun Cho
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada.,U.S. Food and Drug Administration, Silver Spring, Maryland, USA
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15
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Rudell JC, Fleuriet J, Mustari MJ, McLoon LK. Childhood Onset Strabismus: A Neurotrophic Factor Hypothesis. J Binocul Vis Ocul Motil 2021; 71:35-40. [PMID: 33872122 PMCID: PMC8102408 DOI: 10.1080/2576117x.2021.1893585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 02/15/2021] [Accepted: 02/17/2021] [Indexed: 10/21/2022]
Abstract
Strabismus is a genetically heterogeneous disorder with complex molecular and neurophysiological causes. Evidence in the literature suggests a strong role for motor innervation in the etiology of strabismus, which connects central neural processes to the peripheral extraocular muscles. Current treatments of strabismus through surgery show that an inherent sensorimotor plasticity in the ocular motor system decreases the effectiveness of treatment, often driving eye alignment back toward its misaligned pre-surgical state by altering extraocular muscle tonus. There is recent interest in capitalizing on existing biological processes in extraocular muscles to overcome these compensatory mechanisms. Neurotrophins are trophic factors that regulate survival and development in neurons and muscle, including extraocular muscles. Local administration of neurotrophins to extraocular muscles partially reversed strabismus in an animal model of strabismus. The hypothesis is that sustained release of neurotrophins gives more time for the ocular motor system to adapt to a slow change in alignment in the desired direction. The effect of neurotrophins on extraocular muscles is complex, as different neurotrophic factors have diverse effects on extraocular muscle contraction profiles, patterns of innervation, and density of extraocular muscle precursor cells. Neurotrophic factors show promise as a therapeutic option for strabismus, which may help to improve treatment outcomes and offset devastating amblyopia and psychosocial effects of disease in strabismus patients.
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Affiliation(s)
- Jolene C Rudell
- Department of Ophthalmology, University California San Diego, San Diego, California
| | - Jérome Fleuriet
- Assistance Publique-Hôpitaux de Paris, Intensive Care Unit, Raymond Poincaré Hospital, Garches, France
| | - Michael J Mustari
- Washington National Primate Research Center, University of Washington, Seattle, Washington
- Department of Ophthalmology, University of Washington, Seattle, Washington
| | - Linda K McLoon
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota
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16
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Hoh JFY. Myosin heavy chains in extraocular muscle fibres: Distribution, regulation and function. Acta Physiol (Oxf) 2021; 231:e13535. [PMID: 32640094 DOI: 10.1111/apha.13535] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 07/02/2020] [Indexed: 12/13/2022]
Abstract
This review examines kinetic properties and distribution of the 11 isoforms of myosin heavy chain (MyHC) expressed in extraocular muscle (EOM) fibre types and the regulation and function of these MyHCs. Although recruitment and discharge characteristics of ocular motoneurons during fixation and eye movements are well documented, work directly linking these properties with motor unit contractile speed and MyHC composition is lacking. Recruitment of motor units according to Henneman's size principle has some support in EOMs but needs consolidation. Both neurogenic and myogenic mechanisms regulate MyHC expression as in other muscle allotypes. Developmentally, multiply-innervated (MIFs) and singly-innervated fibres (SIFs) are derived presumably from distinct myoblast lineages, ending up expressing MyHCs in the slow and fast ends of the kinetic spectrum respectively. They modulate the synaptic inputs of their motoneurons through different retrogradely transported neurotrophins, thereby specifying their tonic and phasic impulse patterns. Immunohistochemical analyses of EOMs regenerating in situ and in limb muscle beds suggest that the very impulse patterns driving various ocular movements equip effectors with appropriate MyHC compositions and speeds to accomplish their tasks. These experiments also suggest that satellite cells of SIFs and MIFs are distinct lineages expressing different MyHCs during regeneration. MyHC compositions and functional characteristics of orbital fibres show longitudinal variations that facilitate linear ocular rotation during saccades. Palisade endings on global MIFs are postulated to respond to active and passive tensions by triggering axon reflexes that play important roles during fixation, saccades and vergence. How EOMs implement Listings law during ocular rotation is discussed.
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Affiliation(s)
- Joseph F. Y. Hoh
- Discipline of Physiology and the Bosch Institute School of Medical Sciences Faculty of Medicine and Health The University of Sydney Sydney NSW Australia
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17
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Neuroprotective Effect of Vascular Endothelial Growth Factor on Motoneurons of the Oculomotor System. Int J Mol Sci 2021; 22:ijms22020814. [PMID: 33467517 PMCID: PMC7830098 DOI: 10.3390/ijms22020814] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/11/2021] [Accepted: 01/13/2021] [Indexed: 01/04/2023] Open
Abstract
Vascular endothelial growth factor (VEGF) was initially characterized as a potent angiogenic factor based on its activity on the vascular system. However, it is now well established that VEGF also plays a crucial role as a neuroprotective factor in the nervous system. A deficit of VEGF has been related to motoneuronal degeneration, such as that occurring in amyotrophic lateral sclerosis (ALS). Strikingly, motoneurons of the oculomotor system show lesser vulnerability to neurodegeneration in ALS compared to other motoneurons. These motoneurons presented higher amounts of VEGF and its receptor Flk-1 than other brainstem pools. That higher VEGF level could be due to an enhanced retrograde input from their target muscles, but it can also be produced by the motoneurons themselves and act in an autocrine way. By contrast, VEGF’s paracrine supply from the vicinity cells, such as glial cells, seems to represent a minor source of VEGF for brainstem motoneurons. In addition, ocular motoneurons experiment an increase in VEGF and Flk-1 level in response to axotomy, not observed in facial or hypoglossal motoneurons. Therefore, in this review, we summarize the differences in VEGF availability that could contribute to the higher resistance of extraocular motoneurons to injury and neurodegenerative diseases.
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18
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Abstract
Neurotrophin-3 (NT-3) belongs to a family of growth factors called neurotrophins whose actions are centered in the nervous system. NT-3 is structurally related to other neurotrophins like brain-derived neurotrophic factor. The expression of NT-3 starts with the onset of neurogenesis and continues throughout life. A wealth of information links NT-3 to the growth, differentiation, and survival of hippocampal cells as well as sympathetic and sensory neurons. These studies have described the distribution of NT-3 and its receptors throughout development and in the mature nervous system. Prior works has begun to cell-type specific impact of NT-3 as well as identify the signaling pathways involved. However, much less is known about how NT-3 regulates synaptic transmission. This chapter focuses role of NT-3 in the modulation of synaptic transmission.
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19
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Calvo PM, de la Cruz RR, Pastor AM. A Single Intraventricular Injection of VEGF Leads to Long-Term Neurotrophic Effects in Axotomized Motoneurons. eNeuro 2020; 7:ENEURO.0467-19.2020. [PMID: 32371476 PMCID: PMC7266142 DOI: 10.1523/eneuro.0467-19.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 02/21/2020] [Accepted: 03/23/2020] [Indexed: 12/18/2022] Open
Abstract
Vascular endothelial growth factor (VEGF) has been recently demonstrated to induce neuroprotective and synaptotrophic effects on lesioned neurons. Hitherto, the administration of VEGF in different animal models of lesion or disease has been conducted following a chronic protocol of administration. We questioned whether a single dose of VEGF, administered intraventricularly, could induce long-term neurotrophic effects on injured motoneurons. For this purpose, we performed in cats the axotomy of abducens motoneurons and the injection of VEGF into the fourth ventricle in the same surgical session and investigated the discharge characteristics of axotomized and treated motoneurons by single-unit extracellular recordings in the chronic alert preparation. We found that injured motoneurons treated with a single VEGF application discharged with normal characteristics, showing neuronal eye position (EP) and velocity sensitivities similar to control, thereby preventing the axotomy-induced alterations. These effects were present for a prolonged period of time (50 d) after VEGF administration. By confocal immunofluorescence we also showed that the synaptic stripping that ensues lesion was not present, rather motoneurons showed a normal synaptic coverage. Moreover, we demonstrated that VEGF did not lead to any angiogenic response pointing to a direct action of the factor on neurons. In summary, a single dose of VEFG administered just after motoneuron axotomy is able to prevent for a long time the axotomy-induced firing and synaptic alterations without any associated vascular sprouting. We consider that these data are of great relevance due to the potentiality of VEGF as a therapeutic agent in neuronal lesions and diseases.
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Affiliation(s)
- Paula M Calvo
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla 41012, Spain
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla 41012, Spain
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla 41012, Spain
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20
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Rotterman TM, Alvarez FJ. Microglia Dynamics and Interactions with Motoneurons Axotomized After Nerve Injuries Revealed By Two-Photon Imaging. Sci Rep 2020; 10:8648. [PMID: 32457369 PMCID: PMC7250868 DOI: 10.1038/s41598-020-65363-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 05/01/2020] [Indexed: 01/08/2023] Open
Abstract
The significance of activated microglia around motoneurons axotomized after nerve injuries has been intensely debated. In particular, whether microglia become phagocytic is controversial. To resolve these issues we directly observed microglia behaviors with two-photon microscopy in ex vivo spinal cord slices from CX3CR1-GFP mice complemented with confocal analyses of CD68 protein. Axotomized motoneurons were retrogradely-labeled from muscle before nerve injuries. Microglia behaviors close to axotomized motoneurons greatly differ from those within uninjured motor pools. They develop a phagocytic phenotype as early as 3 days after injury, characterized by frequent phagocytic cups, high phagosome content and CD68 upregulation. Interactions between microglia and motoneurons changed with time after axotomy. Microglia first extend processes that end in phagocytic cups at the motoneuron surface, then they closely attach to the motoneuron while extending filopodia over the cell body. Confocal 3D analyses revealed increased microglia coverage of the motoneuron cell body surface with time after injury and the presence of CD68 granules in microglia surfaces opposed to motoneurons. Some microglia formed macroclusters associated with dying motoneurons. Microglia in these clusters display the highest CD68 expression and associate with cytotoxic T-cells. These observations are discussed in relation to current theories on microglia function around axotomized motoneurons.
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Affiliation(s)
- Travis M Rotterman
- Department of Physiology, Emory University, Atlanta, GA, 30322, United States of America.,School of Biological Sciences, Georgia Tech, Atlanta, GA, 30318, United States of America
| | - Francisco J Alvarez
- Department of Physiology, Emory University, Atlanta, GA, 30322, United States of America.
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21
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Alvarez FJ, Rotterman TM, Akhter ET, Lane AR, English AW, Cope TC. Synaptic Plasticity on Motoneurons After Axotomy: A Necessary Change in Paradigm. Front Mol Neurosci 2020; 13:68. [PMID: 32425754 PMCID: PMC7203341 DOI: 10.3389/fnmol.2020.00068] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 04/08/2020] [Indexed: 12/12/2022] Open
Abstract
Motoneurons axotomized by peripheral nerve injuries experience profound changes in their synaptic inputs that are associated with a neuroinflammatory response that includes local microglia and astrocytes. This reaction is conserved across different types of motoneurons, injuries, and species, but also displays many unique features in each particular case. These reactions have been amply studied, but there is still a lack of knowledge on their functional significance and mechanisms. In this review article, we compiled data from many different fields to generate a comprehensive conceptual framework to best interpret past data and spawn new hypotheses and research. We propose that synaptic plasticity around axotomized motoneurons should be divided into two distinct processes. First, a rapid cell-autonomous, microglia-independent shedding of synapses from motoneuron cell bodies and proximal dendrites that is reversible after muscle reinnervation. Second, a slower mechanism that is microglia-dependent and permanently alters spinal cord circuitry by fully eliminating from the ventral horn the axon collaterals of peripherally injured and regenerating sensory Ia afferent proprioceptors. This removes this input from cell bodies and throughout the dendritic tree of axotomized motoneurons as well as from many other spinal neurons, thus reconfiguring ventral horn motor circuitries to function after regeneration without direct sensory feedback from muscle. This process is modulated by injury severity, suggesting a correlation with poor regeneration specificity due to sensory and motor axons targeting errors in the periphery that likely render Ia afferent connectivity in the ventral horn nonadaptive. In contrast, reversible synaptic changes on the cell bodies occur only while motoneurons are regenerating. This cell-autonomous process displays unique features according to motoneuron type and modulation by local microglia and astrocytes and generally results in a transient reduction of fast synaptic activity that is probably replaced by embryonic-like slow GABA depolarizations, proposed to relate to regenerative mechanisms.
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Affiliation(s)
- Francisco J Alvarez
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Travis M Rotterman
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States.,Department of Biomedical Engineering, School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Erica T Akhter
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Alicia R Lane
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Arthur W English
- Department of Cellular Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Timothy C Cope
- Department of Biomedical Engineering, School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
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22
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Silva-Hucha S, Carrero-Rojas G, Fernández de Sevilla ME, Benítez-Temiño B, Davis-López de Carrizosa MA, Pastor AM, Morcuende S. Sources and lesion-induced changes of VEGF expression in brainstem motoneurons. Brain Struct Funct 2020; 225:1033-1053. [PMID: 32189115 DOI: 10.1007/s00429-020-02057-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 03/06/2020] [Indexed: 12/31/2022]
Abstract
Motoneurons of the oculomotor system show lesser vulnerability to neurodegeneration compared to other cranial motoneurons, as seen in amyotrophic lateral sclerosis (ALS). The overexpression of vascular endothelial growth factor (VEGF) is involved in motoneuronal protection. As previously shown, motoneurons innervating extraocular muscles present a higher amount of VEGF and its receptor Flk-1 compared to facial or hypoglossal motoneurons. Therefore, we aimed to study the possible sources of VEGF to brainstem motoneurons, such as glial cells and target muscles. We also studied the regulation of VEGF in response to axotomy in ocular, facial, and hypoglossal motor nuclei. Basal VEGF expression in astrocytes and microglial cells of the cranial motor nuclei was low. Although the presence of VEGF in the different target muscles for brainstem motoneurons was similar, the presynaptic element of the ocular neuromuscular junction showed higher amounts of Flk-1, which could result in greater efficiency in the capture of the factor by oculomotor neurons. Seven days after axotomy, a clear glial reaction was observed in all the brainstem nuclei, but the levels of the neurotrophic factor remained low in glial cells. Only the injured motoneurons of the oculomotor system showed an increase in VEGF and Flk-1, but such an increase was not detected in axotomized facial or hypoglossal motoneurons. Taken together, our findings suggest that the ocular motoneurons themselves upregulate VEGF expression in response to lesion. In conclusion, the low VEGF expression observed in glial cells suggests that these cells are not the main source of VEGF for brainstem motoneurons. Therefore, the higher VEGF expression observed in motoneurons innervating extraocular muscles is likely due either to the fact that this factor is more avidly taken up from the target muscles, in basal conditions, or is produced by these motoneurons themselves, and acts in an autocrine manner after axotomy.
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Affiliation(s)
- Silvia Silva-Hucha
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Génova Carrero-Rojas
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | | | - Beatriz Benítez-Temiño
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | | | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Sara Morcuende
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Seville, Spain.
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23
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Grycz K, Głowacka A, Ji B, Czarkowska-Bauch J, Gajewska-Woźniak O, Skup M. Early pre- and postsynaptic decrease in glutamatergic and cholinergic signaling after spinalization is not modified when stimulating proprioceptive input to the ankle extensor α-motoneurons: Anatomical and neurochemical study. PLoS One 2019; 14:e0222849. [PMID: 31557259 PMCID: PMC6763201 DOI: 10.1371/journal.pone.0222849] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 09/08/2019] [Indexed: 12/23/2022] Open
Abstract
Alpha-motoneurons (MNs) innervating ankle extensor muscles show reduced peripheral inputs from Ia proprioceptive afferents and cholinergic afferents after chronic spinalization (SCT). That phenomenon is not observed on ankle flexor MNs, indicating a smaller vulnerability of the latter MNs circuit to SCT. Locomotor training of spinal rats which partially restored those inputs to extensor MNs tended to hyper innervate flexor MNs, disclosing a need for selective approaches. In rats with intact spinal cord 7-days of low-threshold proprioceptive stimulation of the tibial nerve enriched glutamatergic Ia and cholinergic innervation of lateral gastrocnemius (LG) MNs, suggesting usefulness of selective stimulation for restoration of inputs to extensor MNs after SCT. Accordingly, to examine its effectiveness after SCT, tibial nerves and soleus muscles were implanted bilaterally, and for MN identification fluorescence tracers to LG and tibialis anterior (TA) muscles were injected two weeks prior to spinalization. Stimulation of tibial nerve, controlled by H-reflex recorded in the soleus muscle, started on the third post-SCT day and continued for 7 days. Nine days post-SCT the number and volume of glutamatergic Ia and of cholinergic C-boutons on LG MNs was decreased, but stimulation affected neither of them. Postsynaptically, a threefold decrease of NMDAR NR1 subunit and thirtyfold decrease of M2 muscarinic receptor transcripts caused by SCT were not counteracted by stimulation, whereas a threefold decrease of AMPAR GluR2 subunit tended to deepen after stimulation. We conclude that LG MNs, supported with proprioceptive stimuli after SCT, do not transcribe the perceived cues into compensatory response at the transcriptional level in the early post-SCT period.
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Affiliation(s)
- Kamil Grycz
- Nencki Institute of Experimental Biology, Warsaw, Poland
| | - Anna Głowacka
- Nencki Institute of Experimental Biology, Warsaw, Poland
| | - Benjun Ji
- Nencki Institute of Experimental Biology, Warsaw, Poland
| | | | | | - Małgorzata Skup
- Nencki Institute of Experimental Biology, Warsaw, Poland
- * E-mail: (OG-W); (MS)
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24
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Hernández RG, Djebari S, Vélez-Ortiz JM, de la Cruz RR, Pastor AM, Benítez-Temiño B. Short-term plasticity after partial deafferentation in the oculomotor system. Brain Struct Funct 2019; 224:2717-2731. [PMID: 31375981 DOI: 10.1007/s00429-019-01929-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 07/26/2019] [Indexed: 10/26/2022]
Abstract
Medial rectus motoneurons are innervated by two main pontine inputs. The specific function of each of these two inputs remains to be fully understood. Indeed, selective partial deafferentation of medial rectus motoneurons, performed by the lesion of either the vestibular or the abducens input, initially induces similar changes in motoneuronal discharge. However, at longer time periods, the responses to both lesions are dissimilar. Alterations on eye movements and motoneuronal discharge induced by vestibular input transection recover completely 2 months post-lesion, whereas changes induced by abducens internuclear lesion are more drastic and permanent. Functional recovery could be due to some kind of plastic process, such as reactive synaptogenesis, developed by the remaining intact input, which would occupy the vacant synaptic spaces left after lesion. Herein, by means of confocal microscopy, immunocytochemistry and retrograde labeling, we attempt to elucidate the possible plastic processes that take place after partial deafferentation of medial rectus motoneuron. 48 h post-injury, both vestibular and abducens internuclear lesions produced a reduced synaptic coverage on these motoneurons. However, 96 h after vestibular lesion, there was a partial recovery in the number of synaptic contacts. This suggests that there was reactive synaptogenesis. This recovery was preceded by an increase in somatic neurotrophin content, suggesting a role of these molecules in presynaptic axonal sprouting. The rise in synaptic coverage might be due to terminal sprouting performed by the remaining main input, i.e., abducens internuclear neurons. The present results may improve the understanding of this apparently redundant input system.
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Affiliation(s)
- Rosendo G Hernández
- Departamento de Fisiología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012, Seville, Spain
| | - Souhail Djebari
- Departamento de Fisiología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012, Seville, Spain
| | - José Miguel Vélez-Ortiz
- Departamento de Fisiología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012, Seville, Spain
| | - Rosa R de la Cruz
- Departamento de Fisiología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012, Seville, Spain
| | - Angel M Pastor
- Departamento de Fisiología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012, Seville, Spain.
| | - Beatriz Benítez-Temiño
- Departamento de Fisiología, Universidad de Sevilla, Avda. Reina Mercedes, 6, 41012, Seville, Spain
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Health Benefits of Endurance Training: Implications of the Brain-Derived Neurotrophic Factor-A Systematic Review. Neural Plast 2019; 2019:5413067. [PMID: 31341469 PMCID: PMC6613032 DOI: 10.1155/2019/5413067] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 02/07/2019] [Accepted: 02/24/2019] [Indexed: 02/06/2023] Open
Abstract
This article presents a concept that wide expression of brain-derived neurotrophic factor (BDNF) and its receptors (TrkB) in the nervous tissue, evoked by regular endurance training (ET), can cause numerous motor and metabolic adaptations, which are beneficial for human health. The relationships between the training-evoked increase of endogenous BDNF and molecular and/or physiological adaptations in the nervous structures controlling both motor performance and homeostasis of the whole organism have been presented. Due to a very wide range of plastic changes that ET has exerted on various systems of the body, the improvement of motor skills and counteraction of the development of civilization diseases resulting from the posttraining increase of BDNF/TrkB levels have been discussed, as important for people, who undertake ET. Thus, this report presents the influence of endurance exercises on the (1) transformation of motoneuron properties, which are a final element of the motor pathways, (2) reduction of motor deficits evoked by Parkinson disease, and (3) prevention of the metabolic syndrome (MetS). This review suggests that the increase of posttraining levels of BDNF and its TrkB receptors causes simultaneous changes in the activity of the spinal cord, the substantia nigra, and the hypothalamic nuclei neurons, which are responsible for the alteration of the functional properties of motoneurons innervating the skeletal muscles, for the enhancement of dopamine release in the brain, and for the modulation of hormone levels involved in regulating the metabolic processes, responsively. Finally, training-evoked increase of the BDNF/TrkB leads to a change in a manner of regulation of skeletal muscles, causes a reduction of motor deficits observed in the Parkinson disease, and lowers weight, glucose level, and blood pressure, which accompany the MetS. Therefore, BDNF seems to be the molecular factor of pleiotropic activity, important in the modulation processes, underlying adaptations, which result from ET.
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McGregor CE, English AW. The Role of BDNF in Peripheral Nerve Regeneration: Activity-Dependent Treatments and Val66Met. Front Cell Neurosci 2019; 12:522. [PMID: 30687012 PMCID: PMC6336700 DOI: 10.3389/fncel.2018.00522] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/14/2018] [Indexed: 11/29/2022] Open
Abstract
Despite the ability of peripheral nerves to spontaneously regenerate after injury, recovery is generally very poor. The neurotrophins have emerged as an important modulator of axon regeneration, particularly brain derived neurotrophic factor (BDNF). BDNF regulation and signaling, as well as its role in activity-dependent treatments including electrical stimulation, exercise, and optogenetic stimulation are discussed here. The importance of a single nucleotide polymorphism in the BDNF gene, Val66Met, which is present in 30% of the human population and may hinder the efficacy of these treatments in enhancing regeneration after injury is considered. Preliminary data are presented on the effectiveness of one such activity-dependent treatment, electrical stimulation, in enhancing axon regeneration in mice expressing the met allele of the Val66Met polymorphism.
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Affiliation(s)
- Claire Emma McGregor
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Arthur W English
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
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Botulinum Neurotoxin Application to the Severed Femoral Nerve Modulates Spinal Synaptic Responses to Axotomy and Enhances Motor Recovery in Rats. Neural Plast 2018; 2018:7975013. [PMID: 30254669 PMCID: PMC6145158 DOI: 10.1155/2018/7975013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 07/15/2018] [Accepted: 08/05/2018] [Indexed: 12/22/2022] Open
Abstract
Botulinum neurotoxin A (BoNT) and brain-derived neurotrophic factor (BDNF) are known for their ability to influence synaptic inputs to neurons. Here, we tested if these drugs can modulate the deafferentation of motoneurons following nerve section/suture and, as a consequence, modify the outcome of peripheral nerve regeneration. We applied drug solutions to the proximal stump of the freshly cut femoral nerve of adult rats to achieve drug uptake and transport to the neuronal perikarya. The most marked effect of this application was a significant reduction of the axotomy-induced loss of perisomatic cholinergic terminals by BoNT at one week and two months post injury. The attenuation of the synaptic deficit was associated with enhanced motor recovery of the rats 2–20 weeks after injury. Although BDNF also reduced cholinergic terminal loss at 1 week, it had no effect on this parameter at two months and no effect on functional recovery. These findings strengthen the idea that persistent partial deafferentation of axotomized motoneurons may have a significant negative impact on functional outcome after nerve injury. Intraneural application of drugs may be a promising way to modify deafferentation and, thus, elucidate relationships between synaptic plasticity and restoration of function.
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Synaptic loss and firing alterations in Axotomized Motoneurons are restored by vascular endothelial growth factor (VEGF) and VEGF-B. Exp Neurol 2018. [PMID: 29522757 DOI: 10.1016/j.expneurol.2018.03.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Vascular endothelial growth factor (VEGF), also known as VEGF-A, was discovered due to its vasculogenic and angiogenic activity, but a neuroprotective role for VEGF was later proven for lesions and disorders. In different models of motoneuronal degeneration, VEGF administration leads to a significant reduction of motoneuronal death. However, there is no information about the physiological state of spared motoneurons. We examined the trophic role of VEGF on axotomized motoneurons with recordings in alert animals using the oculomotor system as the experimental model, complemented with a synaptic study at the confocal microscopy level. Axotomy leads to drastic alterations in the discharge characteristics of abducens motoneurons, as well as to a substantial loss of their synaptic inputs. Retrograde delivery of VEGF completely restored the discharge activity and synaptically-driven signals in injured motoneurons, as demonstrated by correlating motoneuronal firing rate with motor performance. Moreover, VEGF-treated motoneurons recovered a normal density of synaptic boutons around motoneuronal somata and in the neuropil, in contrast to the low levels of synaptic terminals found after axotomy. VEGF also reduced the astrogliosis induced by axotomy in the abducens nucleus to control values. The administration of VEGF-B produced results similar to those of VEGF. This is the first work demonstrating that VEGF and VEGF-B restore the normal operating mode and synaptic inputs on injured motoneurons. Altogether these data indicate that these molecules are relevant synaptotrophic factors for motoneurons and support their clinical potential for the treatment of motoneuronal disorders.
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Calvo PM, Pastor AM, de la Cruz RR. Vascular endothelial growth factor: an essential neurotrophic factor for motoneurons? Neural Regen Res 2018; 13:1181-1182. [PMID: 30028320 PMCID: PMC6065228 DOI: 10.4103/1673-5374.235024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Affiliation(s)
- Paula M Calvo
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
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Effects of Selective Deafferentation on the Discharge Characteristics of Medial Rectus Motoneurons. J Neurosci 2017; 37:9172-9188. [PMID: 28842421 DOI: 10.1523/jneurosci.1391-17.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 07/11/2017] [Accepted: 08/06/2017] [Indexed: 11/21/2022] Open
Abstract
Medial rectus motoneurons receive two main pontine inputs: abducens internuclear neurons, whose axons course through the medial longitudinal fasciculus (MLF), and neurons in the lateral vestibular nucleus, whose axons project through the ascending tract of Deiters (ATD). Abducens internuclear neurons are responsible for conjugate gaze in the horizontal plane, whereas ATD neurons provide medial rectus motoneurons with a vestibular input comprising mainly head velocity. To reveal the relative contribution of each input to the oculomotor physiology, single-unit recordings from medial rectus motoneurons were obtained in the control situation and after selective deafferentation from cats with unilateral transection of either the MLF or the ATD. Both MLF and ATD transection produced similar short-term alterations in medial rectus motoneuron firing pattern, which were more drastic in MLF of animals. However, long-term recordings revealed important differences between the two types of lesion. Thus, while the effects of the MLF section were permanent, 2 months after ATD lesioning all motoneuronal firing parameters were similar to the control. These findings indicated a more relevant role of the MLF pathway in driving motoneuronal firing and evidenced compensatory mechanisms following the ATD lesion. Confocal immunocytochemistry revealed that MLF transection produced also a higher loss of synaptic boutons, mainly at the dendritic level. Moreover, 2 months after ATD transection, we observed an increase in synaptic coverage around motoneuron cell bodies compared with short-term data, which is indicative of a synaptogenic compensatory mechanism of the abducens internuclear pathway that could lead to the observed firing and morphological recovery.SIGNIFICANCE STATEMENT Eye movements rely on multiple neuronal circuits for appropriate performance. The abducens internuclear pathway through the medial longitudinal fascicle (MLF) and the vestibular neurons through the ascending tract of Deiters (ATD) are a dual system that supports the firing of medial rectus motoneurons. We report the effect of sectioning the MLF or the ATD pathway on the firing of medial rectus motoneurons, as well as the plastic mechanisms by which one input compensates for the lack of the other. This work shows that while the effects of MLF transection are permanent, the ATD section produces transitory effects. A mechanism based on axonal sprouting and occupancy of the vacant synaptic space due to deafferentation is the base for the mechanism of compensation on the medial rectus motoneuron.
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Abstract
PURPOSE OF REVIEW The goal of this review is to summarize the unique regenerative milieu within mature mammalian extraocular muscles (EOMs). This will aid in understanding disease propensity for and sparing of EOMs in skeletal muscle diseases as well as the recalcitrance of the EOM to injury. RECENT FINDINGS The EOMs continually remodel throughout life and contain an extremely enriched number of myogenic precursor cells that differ in number and functional characteristics from those in limb skeletal muscle. The EOMs also contain a large population of Pitx2-positive myogenic precursor cells that provide the EOMs with many of their unusual biological characteristics, such as myofiber remodeling and skeletal muscle disease sparing. This environment provides for rapid and efficient remodeling and regeneration after various types of injury. In addition, the EOMs show a remarkable ability to respond to perturbations of single muscles with coordinated changes in the other EOMs that move in the same plane. SUMMARY These data will inform Ophthalmologists as they work toward developing new treatments for eye movement disorders, new approaches for repair after nerve or direct EOMs injury, as well as suggest potential explanations for the unusual disease propensity and disease sparing characteristics of human EOM.
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Affiliation(s)
- Mayank Verma
- Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
| | - Krysta Fitzpatrick
- Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota
| | - Linda K McLoon
- Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
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Hernández RG, Silva-Hucha S, Morcuende S, de la Cruz RR, Pastor AM, Benítez-Temiño B. Extraocular Motor System Exhibits a Higher Expression of Neurotrophins When Compared with Other Brainstem Motor Systems. Front Neurosci 2017; 11:399. [PMID: 28744196 PMCID: PMC5504184 DOI: 10.3389/fnins.2017.00399] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 06/26/2017] [Indexed: 01/01/2023] Open
Abstract
Extraocular motoneurons resist degeneration in diseases such as amyotrophic lateral sclerosis. The main objective of the present work was to characterize the presence of neurotrophins in extraocular motoneurons and muscles of the adult rat. We also compared these results with those obtained from other cranial motor systems, such as facial and hypoglossal, which indeed suffer neurodegeneration. Immunocytochemical analysis was used to describe the expression of nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 in oculomotor, trochlear, abducens, facial, and hypoglossal nuclei of adult rats, and Western blots were used to describe the presence of neurotrophins in extraocular, facial (buccinator), and tongue muscles, which are innervated by the above-mentioned motoneurons. In brainstem samples, brain-derived neurotrophic factor was present both in extraocular and facial motoneuron somata, and to a lesser degree, in hypoglossal motoneurons. Neurotrophin-3 was present in extraocular motor nuclei, while facial and hypoglossal motoneurons were almost devoid of this protein. Finally, nerve growth factor was not present in the soma of any group of motoneurons, although it was present in dendrites of motoneurons located in the neuropil. Neuropil optical density levels were higher in extraocular motoneuron nuclei when compared with facial and hypoglossal nuclei. Neurotrophins could be originated in target muscles, since Western blot analyses revealed the presence of the three molecules in all sampled muscles, to a larger extent in extraocular muscles when compared with facial and tongue muscles. We suggest that the different neurotrophin availability could be related to the particular resistance of extraocular motoneurons to neurodegeneration.
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McLoon LK, Christiansen SP, Ghose GM, Das VE, Mustari MJ. Improvement of Eye Alignment in Adult Strabismic Monkeys by Sustained IGF-1 Treatment. Invest Ophthalmol Vis Sci 2017; 57:6070-6078. [PMID: 27820875 PMCID: PMC5114034 DOI: 10.1167/iovs.16-19739] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The goal of this study was to determine if continuous application of insulin-like growth factor-1 (IGF-1) could improve eye alignment of adult strabismic nonhuman primates and to assess possible mechanisms of effect. Methods A continuous release pellet of IGF-1 was placed on one medial rectus muscle in two adult nonhuman primates (M1, M2) rendered exotropic by the alternating monocular occlusion method during the first months of life. Eye alignment and eye movements were recorded for 3 months, after which M1 was euthanized, and the lateral and medial rectus muscles were removed for morphometric analysis of fiber size, nerve, and neuromuscular density. Results Monkey 1 showed a 40% reduction in strabismus angle, a reduction of exotropia of approximately 11° to 14° after 3 months. Monkey 2 showed a 15% improvement, with a reduction of its exotropia by approximately 3°. The treated medial rectus muscle of M1 showed increased mean myofiber cross-sectional areas. Increases in myofiber size also were seen in the contralateral medial rectus and lateral rectus muscles. Similarly, nerve density increased in the contralateral medial rectus and yoked lateral rectus. Conclusions This study demonstrates that in adult nonhuman primates with a sensory-induced exotropia in infancy, continuous IGF-1 treatment improves eye alignment, resulting in muscle fiber enlargement and altered innervational density that includes the untreated muscles. This supports the view that there is sufficient plasticity in the adult ocular motor system to allow continuous IGF-1 treatment over months to produce improvement in eye alignment in early-onset strabismus.
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Affiliation(s)
- Linda K McLoon
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States 2Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Stephen P Christiansen
- Departments of Ophthalmology and Pediatrics, Boston University School of Medicine, Boston, Massachusetts, United States
| | - Geoffrey M Ghose
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Vallabh E Das
- College of Optometry, University of Houston, Houston, Texas, United States
| | - Michael J Mustari
- Washington National Primate Center and Department of Ophthalmology, University of Washington, Seattle, Washington, United States
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Benítez-Temiño B, Davis-López de Carrizosa MA, Morcuende S, Matarredona ER, de la Cruz RR, Pastor AM. Functional Diversity of Neurotrophin Actions on the Oculomotor System. Int J Mol Sci 2016; 17:E2016. [PMID: 27916956 PMCID: PMC5187816 DOI: 10.3390/ijms17122016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 11/24/2016] [Accepted: 11/25/2016] [Indexed: 11/16/2022] Open
Abstract
Neurotrophins play a principal role in neuronal survival and differentiation during development, but also in the maintenance of appropriate adult neuronal circuits and phenotypes. In the oculomotor system, we have demonstrated that neurotrophins are key regulators of developing and adult neuronal properties, but with peculiarities depending on each neurotrophin. For instance, the administration of NGF (nerve growth factor), BDNF (brain-derived neurotrophic factor) or NT-3 (neurotrophin-3) protects neonatal extraocular motoneurons from cell death after axotomy, but only NGF and BDNF prevent the downregulation in ChAT (choline acetyltransferase). In the adult, in vivo recordings of axotomized extraocular motoneurons have demonstrated that the delivery of NGF, BDNF or NT-3 recovers different components of the firing discharge activity of these cells, with some particularities in the case of NGF. All neurotrophins have also synaptotrophic activity, although to different degrees. Accordingly, neurotrophins can restore the axotomy-induced alterations acting selectively on different properties of the motoneuron. In this review, we summarize these evidences and discuss them in the context of other motor systems.
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Affiliation(s)
- Beatriz Benítez-Temiño
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | | | - Sara Morcuende
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Esperanza R Matarredona
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Rosa R de la Cruz
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
| | - Angel M Pastor
- Departamento de Fisiología, Facultad de Biología, Universidad de Sevilla, 41012 Sevilla, Spain.
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Nelson KR, Stevens SM, McLoon LK. Prolongation of Relaxation Time in Extraocular Muscles With Brain Derived Neurotrophic Factor in Adult Rabbit. Invest Ophthalmol Vis Sci 2016; 57:5834-5842. [PMID: 27802489 PMCID: PMC5096416 DOI: 10.1167/iovs.16-19679] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 09/27/2016] [Indexed: 12/15/2022] Open
Abstract
PURPOSE We tested the hypothesis that short-term treatment with brain derived neurotrophic factor (BDNF) would alter the contractile characteristics of rabbit extraocular muscle (EOM). METHODS One week after injections of BDNF in adult rabbit superior rectus muscles, twitch properties were determined in treated and control muscles in vitro. Muscles were also examined for changes in mean cross-sectional areas, neuromuscular junction size, and percent of myofibers expressing specific myosin heavy chain isoforms, and sarcoendoplasmic reticulum calcium ATPases (SERCA) 1 and 2. RESULTS Brain derived neurotrophic factor-treated muscles had prolonged relaxation times compared with control muscles. Time to 50% relaxation, time to 100% relaxation, and maximum rate of relaxation were increased by 24%, 27%, and 25%, respectively. No significant differences were seen in time to peak force, twitch force, or maximum rate of contraction. Brain derived neurotrophic factor treatment significantly increased mean cross-sectional areas of slow twitch and tonic myofibers, with increased areas ranging from 54% to 146%. Brain derived neurotrophic factor also resulted in an increased percentage of slow twitch myofibers in the orbital layers, ranging from 54% to 77%, and slow-tonic myofibers, ranging from 44% to 62%. No significant changes were seen SERCA1 or 2 expression or in neuromuscular junction size. CONCLUSIONS Short-term treatment with BDNF significantly prolonged the duration and rate of relaxation time and increased expression of both slow-twitch and slow-tonic myosin-expressing myofibers without changes in neuromuscular junctions or SERCA expression. The changes induced by BDNF treatment might have potential therapeutic value in dampening/reducing uncontrolled eye oscillations in nystagmus.
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Affiliation(s)
- Krysta R. Nelson
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
| | - Shanlee M. Stevens
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
| | - Linda K. McLoon
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
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McLoon LK, Willoughby CL, Anderson JS, Bothun ED, Stager D, Felius J, Lee H, Gottlob I. Abnormally Small Neuromuscular Junctions in the Extraocular Muscles From Subjects With Idiopathic Nystagmus and Nystagmus Associated With Albinism. Invest Ophthalmol Vis Sci 2016; 57:1912-20. [PMID: 27092717 PMCID: PMC4849883 DOI: 10.1167/iovs.16-19129] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Purpose Infantile nystagmus syndrome (INS) is often associated with abnormalities of axonal outgrowth and connectivity. To determine if this manifests in extraocular muscle innervation, specimens from children with idiopathic INS or INS and albinism were examined and compared to normal age-matched control extraocular muscles. Methods Extraocular muscles removed during normal surgery on children with idiopathic INS or INS and albinism were immunostained for neuromuscular junctions, myofiber type, the immature form of the acetylcholine receptor, and brain-derived neurotrophic factor (BDNF) and compared to age-matched controls. Results Muscles from both the idiopathic INS and INS and albinism groups had neuromuscular junctions that were 35% to 71% smaller based on myofiber area and myofiber perimeter than found in age-matched controls, and this was seen on both fast and slow myosin heavy chain isoform–expressing myofibers (all P < 0.015). Muscles from subjects with INS and albinism showed a 7-fold increase in neuromuscular junction numbers on fast myofibers expressing the immature gamma subunit of the acetylcholine receptor. The extraocular muscles from both INS subgroups showed a significant increase in the number and size of slow myofibers compared to age-matched controls. Brain-derived neurotrophic factor was expressed in control muscle but was virtually absent in the INS muscles. Conclusions These studies suggest that, relative to the final common pathway, INS is not the same between different patient etiologies. It should be possible to modulate these final common pathway abnormalities, via exogenous application of appropriate drugs, with the hope that this type of treatment may reduce the involuntary oscillatory movements in these children.
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Affiliation(s)
- Linda K McLoon
- Department of Ophthalmology and Visual Neurosciences University of Minnesota, Minneapolis, Minnesota, United States 2Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Christy L Willoughby
- Department of Ophthalmology and Visual Neurosciences University of Minnesota, Minneapolis, Minnesota, United States 2Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Jill S Anderson
- Department of Ophthalmology and Visual Neurosciences University of Minnesota, Minneapolis, Minnesota, United States
| | - Erick D Bothun
- Department of Ophthalmology and Visual Neurosciences University of Minnesota, Minneapolis, Minnesota, United States 3Department of Pediatrics, Minneapolis, Minnesota, United States
| | - David Stager
- Pediatric Ophthalmology and Adult Strabismus, Plano, Texas, United States
| | - Joost Felius
- Retina Foundation of the Southwest, Dallas, Texas, United States
| | - Helena Lee
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Irene Gottlob
- The University of Leicester Ulverscroft Eye Unit, Department of Neuroscience, Psychology and Behaviour, Leicester, United Kingdom
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Electrical Stimulation of Low-Threshold Proprioceptive Fibers in the Adult Rat Increases Density of Glutamatergic and Cholinergic Terminals on Ankle Extensor α-Motoneurons. PLoS One 2016; 11:e0161614. [PMID: 27552219 PMCID: PMC4994941 DOI: 10.1371/journal.pone.0161614] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 08/09/2016] [Indexed: 12/18/2022] Open
Abstract
The effects of stimulation of low-threshold proprioceptive afferents in the tibial nerve on two types of excitatory inputs to α-motoneurons were tested. The first input is formed by glutamatergic Ia sensory afferents contacting monosynaptically α-motoneurons. The second one is the cholinergic input originating from V0c—interneurons, located in lamina X of the spinal cord, modulating activity of α-motoneurons via C-terminals. Our aim was to clarify whether enhancement of signaling to ankle extensor α-motoneurons, via direct electrical stimulation addressed predominantly to low-threshold proprioceptive fibers in the tibial nerve of awake rats, will affect Ia glutamatergic and cholinergic innervation of α-motoneurons of lateral gastrocnemius (LG). LG motoneurons were identified with True Blue tracer injected intramuscularly. Tibial nerve was stimulated for 7 days with continuous bursts of three pulses applied in four 20 min sessions daily. The Hoffmann reflex and motor responses recorded from the soleus muscle, LG synergist, allowed controlling stimulation. Ia terminals and C-terminals abutting on LG-labeled α-motoneurons were detected by immunofluorescence (IF) using input-specific anti- VGLUT1 and anti-VAChT antibodies, respectively. Quantitative analysis of confocal images revealed that the number of VGLUT1 IF and VAChT IF terminals contacting the soma of LG α-motoneurons increased after stimulation by 35% and by 26%, respectively, comparing to the sham-stimulated side. The aggregate volume of VGLUT1 IF and VAChT IF terminals increased by 35% and by 30%, respectively. Labeling intensity of boutons was also increased, suggesting an increase of signaling to LG α-motoneurons after stimulation. To conclude, one week of continuous burst stimulation of proprioceptive input to LG α-motoneurons is effective in enrichment of their direct glutamatergic but also indirect cholinergic inputs. The effectiveness of such and longer stimulation in models of injury is a prerequisite to propose it as a therapeutic method to improve inputs to selected group of α-motoneurons after damage.
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Selective Requirement for Maintenance of Synaptic Contacts onto Motoneurons by Target-Derived trkB Receptors. Neural Plast 2016; 2016:2371893. [PMID: 27433358 PMCID: PMC4940568 DOI: 10.1155/2016/2371893] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/07/2016] [Indexed: 11/17/2022] Open
Abstract
Synaptic contacts onto motoneurons were studied in mice in which the gene for the trkB neurotrophin receptor was knocked out selectively in a subset of spinal motoneurons. The extent of contacts by structures immunoreactive for either of two different vesicular glutamate transporters (VGLUT1 and VGLUT2), the vesicular GABA transporter, or glutamic acid decarboxylase 67 (GAD67) with the somata of motoneurons, was studied in wild type and trkB knockout cells in tamoxifen treated male and female SLICK-trkB−/− mice. Selective knockout of the trkB gene resulted in a marked reduction in contacts made by VGLUT2- and GAD67-immunoreactive structures in both sexes and a significant reduction in contacts containing only glycine in male mice. No reduction was found for glycinergic contacts in female mice or for VGLUT1 immunoreactive contacts in either sex. Signaling through postsynaptic trkB receptors is considered to be an essential part of a cellular mechanism for maintaining the contacts of some, but not all, synaptic contacts onto motoneurons.
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Firing frequency and entrainment maintained in primary auditory neurons in the presence of combined BDNF and NT3. Sci Rep 2016; 6:28584. [PMID: 27335179 PMCID: PMC4917828 DOI: 10.1038/srep28584] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 06/07/2016] [Indexed: 12/16/2022] Open
Abstract
Primary auditory neurons rely on neurotrophic factors for development and survival. We previously determined that exposure to brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3) alters the activity of hyperpolarization-activated currents (Ih) in this neuronal population. Since potassium channels are sensitive to neurotrophins, and changes in Ih are often accompanied by a shift in voltage-gated potassium currents (IK), this study examined IK with exposure to both BDNF and NT3 and the impact on firing entrainment during high frequency pulse trains. Whole-cell patch-clamp recordings revealed significant changes in action potential latency and duration, but no change in firing adaptation or total outward IK. Dendrotoxin-I (DTX-I), targeting voltage-gated potassium channel subunits KV1.1 and KV1.2, uncovered an increase in the contribution of DTX-I sensitive currents with exposure to neurotrophins. No difference in Phrixotoxin-1 (PaTX-1) sensitive currents, mediated by KV4.2 and KV4.3 subunits, was observed. Further, no difference was seen in firing entrainment. These results show that combined BDNF and NT3 exposure influences the contribution of KV1.1 and KV1.2 to the low voltage-activated potassium current (IKL). Whilst this is accompanied by a shift in spike latency and duration, both firing frequency and entrainment to high frequency pulse trains are preserved.
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The Effects of Phrenic Nerve Degeneration by Axotomy and Crush on the Electrical Activities of Diaphragm Muscles of Rats. Cell Biochem Biophys 2016; 74:29-34. [PMID: 26972299 DOI: 10.1007/s12013-015-0708-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The aim of this study was to investigate the effect of axotomy and crush-related degeneration on the electrical activities of diaphragm muscle strips of experimental rats. In the present study, twenty-one male Wistar-albino rats were used and divided into three groups. The animals in the first group were not crushed or axotomized and served as controls. Phrenic nerves of the rats in the second and third groups were crushed or axotomized in the diaphragm muscle. Resting membrane potential (RMP) was decreased significantly in both crush and axotomy of diaphragm muscle strips of experimental rats (p < 0.05). Depolarization time (T DEP) and half-repolarization (1/2 RT) time were significantly prolonged in crush and axotomy rats (p < 0.05). Crushing or axotomizing the phrenic nerves may produce electrical activities in the diaphragm muscle of the rat by depolarization time and half-repolarization time prolonged in crush and axotomy rats.
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Jiménez-Maldonado A, Cerna-Cortés J, Castro-Rodríguez EM, Montero SA, Muñiz J, Rodríguez-Hernández A, Lemus M, De Álvarez-Buylla ER. Effects of moderate- and high-intensity chronic exercise on brain-derived neurotrophic factor expression in fast and slow muscles. Muscle Nerve 2015; 53:446-51. [PMID: 26148339 DOI: 10.1002/mus.24757] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 06/23/2015] [Accepted: 06/30/2015] [Indexed: 11/10/2022]
Abstract
INTRODUCTION Brain-derived neurotrophic factor (BDNF) protein expression is sensitive to cellular activity. In the sedentary state, BDNF expression is affected by the muscle phenotype. METHODS Eighteen Wistar rats were divided into the following 3 groups: sedentary (S); moderate-intensity training (MIT); and high-intensity training (HIT). The training protocol lasted 8 weeks. Forty-eight hours after training, total RNA and protein levels in the soleus and plantaris muscles were obtained. RESULTS In the plantaris, the BDNF protein level was lower in the HIT than in the S group (P < 0.05). A similar effect was found in the soleus (without significant difference). In the soleus, higher Bdnf mRNA levels were found in the HIT group (P < 0.001 vs. S and MIT groups). In the plantaris muscle, similar Bdnf mRNA levels were found in all groups. CONCLUSIONS These results indicate that high-intensity chronic exercise reduces BDNF protein level in fast muscles and increases Bdnf mRNA levels in slow muscles.
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Affiliation(s)
- Alberto Jiménez-Maldonado
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, 965 Ave. 25 de Julio, Col. Villas San Sebastián, Colima, 28045, México
| | | | - Elena M Castro-Rodríguez
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, 965 Ave. 25 de Julio, Col. Villas San Sebastián, Colima, 28045, México
| | | | - Jesús Muñiz
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, 965 Ave. 25 de Julio, Col. Villas San Sebastián, Colima, 28045, México
| | | | - Mónica Lemus
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, 965 Ave. 25 de Julio, Col. Villas San Sebastián, Colima, 28045, México
| | - Elena Roces De Álvarez-Buylla
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, 965 Ave. 25 de Julio, Col. Villas San Sebastián, Colima, 28045, México
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Carrascal L, Nieto-González J, Pardillo-Díaz R, Pásaro R, Barrionuevo G, Torres B, Cameron WE, Núñez-Abades P. Time windows for postnatal changes in morphology and membrane excitability of genioglossal and oculomotor motoneurons. World J Neurol 2015; 5:113-131. [DOI: 10.5316/wjn.v5.i4.113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 10/07/2015] [Accepted: 12/08/2015] [Indexed: 02/06/2023] Open
Abstract
Time windows for postnatal changes in morphology and membrane excitability of genioglossal (GG) and oculomotor (OCM) motoneurons (MNs) are yet to be fully described. Analysis of data on brain slices in vitro of the 2 populations of MNs point to a well-defined developmental program that progresses with common age-related changes characterized by: (1) increase of dendritic surface along with length and reshaping of dendritic tree complexity; (2) disappearance of gap junctions early in development; (3) decrease of membrane passive properties, such as input resistance and time constant, together with an increase in the number of cells displaying sag, and modifications in rheobase; (4) action potential shortening and afterhyperpolarization; and (5) an increase in gain and maximum firing frequency. These modifications take place at different time windows for each motoneuronal population. In GG MNs, active membrane properties change mainly during the first postnatal week, passive membrane properties in the second week, and dendritic increasing length and size in the third week of development. In OCM MNs, changes in passive membrane properties and growth of dendritic size take place during the first postnatal week, while active membrane properties and rheobase change during the second and third weeks of development. The sequential order of changes is inverted between active and passive membrane properties, and growth in size does not temporally coincide for both motoneuron populations. These findings are discussed on the basis of environmental cues related to maturation of the respiratory and OCM systems.
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Willoughby CL, Fleuriet J, Walton MM, Mustari MJ, McLoon LK. Adaptation of slow myofibers: the effect of sustained BDNF treatment of extraocular muscles in infant nonhuman primates. Invest Ophthalmol Vis Sci 2015; 56:3467-83. [PMID: 26030102 DOI: 10.1167/iovs.15-16852] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
PURPOSE We evaluated promising new treatment options for strabismus. Neurotrophic factors have emerged as a potential treatment for oculomotor disorders because of diverse roles in signaling to muscles and motor neurons. Unilateral treatment with sustained release brain-derived neurotrophic factor (BDNF) to a single lateral rectus muscle in infant monkeys was performed to test the hypothesis that strabismus would develop in correlation with extraocular muscle (EOM) changes during the critical period for development of binocularity. METHODS The lateral rectus muscles of one eye in two infant macaques were treated with sustained delivery of BDNF for 3 months. Eye alignment was assessed using standard photographic methods. Muscle specimens were analyzed to examine the effects of BDNF on the density, morphology, and size of neuromuscular junctions, as well as myofiber size. Counts were compared to age-matched controls. RESULTS No change in eye alignment occurred with BDNF treatment. Compared to control muscle, neuromuscular junctions on myofibers expressing slow myosins had a larger area. Myofibers expressing slow myosin had larger diameters, and the percentage of myofibers expressing slow myosins increased in the proximal end of the muscle. Expression of BDNF was examined in control EOM, and observed to have strongest immunoreactivity outside the endplate zone. CONCLUSIONS We hypothesize that the oculomotor system adapted to sustained BDNF treatment to preserve normal alignment. Our results suggest that BDNF treatment preferentially altered myofibers expressing slow myosins. This implicates BDNF signaling as influencing the slow twitch properties of EOM.
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Affiliation(s)
- Christy L Willoughby
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States 2Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
| | - Jérome Fleuriet
- Washington National Primate Research Center, Seattle, Washington, United States 4Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - Mark M Walton
- Washington National Primate Research Center, Seattle, Washington, United States
| | - Michael J Mustari
- Washington National Primate Research Center, Seattle, Washington, United States 4Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - Linda K McLoon
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States 2Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
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Astrocytes and Microglia-Mediated Immune Response in Maladaptive Plasticity is Differently Modulated by NGF in the Ventral Horn of the Spinal Cord Following Peripheral Nerve Injury. Cell Mol Neurobiol 2015; 36:37-46. [PMID: 26084599 DOI: 10.1007/s10571-015-0218-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 05/29/2015] [Indexed: 01/12/2023]
Abstract
Reactive astrocytes and activated microglia are the key players in several pathophysiologic modifications of the central nervous system. We used the spared nerve injury (SNI) of the sciatic nerve to induce glial maladaptive response in the ventral horn of lumbar spinal cord and examine its role in the remodeling of the tripartite synapse plasticity. Imaging the ventral horn revealed that SNI was associated with both an early microglial and astrocytic activation, assessed, respectively, by analysis of Iba1 and GFAP expression. Microglia, in particular, localized peculiarly surrounding the motor neurons somata. Perineuronal astrocytes, which play a key role in maintaining the homeostasis of neuronal circuitry, underwent a substantial phenotypic change following peripheral axotomy, producing reactive gliosis. The gliosis was associated with the reduction of glial aminoacid transporters (GLT1 and GlyT1) and increase of neuronal glutamate transporter EAAC1. Although the expression of GABAergic neuronal marker GAD65/67 showed no change, glutamate increase, as demonstrated by HPLC analysis, shifted the excitatory/inhibitory balance as showed by the net increase of the glutamate/GABA ratio. Moreover, endogenous NGF levels were altered in SNI animals and not restored by the intrathecal NGF administration. This treatment reverted phenotypic changes associated with reactive astrocytosis, but failed to modify microglia activation. These findings on one hand confirm the correlation between gliopathy and maladaptive plasticity of the spinal synaptic circuitry, on the other hand add new data concerning the complex peculiar behavior of different glial cells in neuronal degenerative processes, defining a special role of microglia in sustaining the inflammatory response.
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Neuronal BDNF signaling is necessary for the effects of treadmill exercise on synaptic stripping of axotomized motoneurons. Neural Plast 2015; 2015:392591. [PMID: 25918648 PMCID: PMC4397030 DOI: 10.1155/2015/392591] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Revised: 03/09/2015] [Accepted: 03/16/2015] [Indexed: 11/18/2022] Open
Abstract
The withdrawal of synaptic inputs from the somata and proximal dendrites of spinal motoneurons following peripheral nerve injury could contribute to poor functional recovery. Decreased availability of neurotrophins to afferent terminals on axotomized motoneurons has been implicated as one cause of the withdrawal. No reduction in contacts made by synaptic inputs immunoreactive to the vesicular glutamate transporter 1 and glutamic acid decarboxylase 67 is noted on axotomized motoneurons if modest treadmill exercise, which stimulates the production of neurotrophins by spinal motoneurons, is applied after nerve injury. In conditional, neuron-specific brain-derived neurotrophic factor (BDNF) knockout mice, a reduction in synaptic contacts onto motoneurons was noted in intact animals which was similar in magnitude to that observed after nerve transection in wild-type controls. No further reduction in coverage was found if nerves were cut in knockout mice. Two weeks of moderate daily treadmill exercise following nerve injury in these BDNF knockout mice did not affect synaptic inputs onto motoneurons. Treadmill exercise has a profound effect on synaptic inputs to motoneurons after peripheral nerve injury which requires BDNF production by those postsynaptic cells.
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Arbat-Plana A, Torres-Espín A, Navarro X, Udina E. Activity dependent therapies modulate the spinal changes that motoneurons suffer after a peripheral nerve injury. Exp Neurol 2014; 263:293-305. [PMID: 25448160 DOI: 10.1016/j.expneurol.2014.10.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 10/10/2014] [Accepted: 10/14/2014] [Indexed: 12/11/2022]
Abstract
Injury of a peripheral nerve not only leads to target denervation, but also induces massive stripping of spinal synapses on axotomized motoneurons, with disruption of spinal circuits. Even when regeneration is successful, unspecific reinnervation and the limited reconnection of the spinal circuits impair functional recovery. The aim of this study was to describe the changes that axotomized motoneurons suffer after peripheral nerve injury and how activity-dependent therapies and neurotrophic factors can modulate these events. We observed a marked decrease in glutamatergic synapses, with a maximum peak at two weeks post-axotomy, which was only partially reversed with time. This decrease was accompanied by an increase in gephyrin immunoreactivity and a disintegration of perineuronal nets (PNNs) surrounding the motoneurons. Direct application of neurotrophins at the proximal stump was not able to reverse these effects. In contrast, activity-dependent treatment, in the form of treadmill running, reduced the observed destructuring of perineuronal nets and the loss of glutamatergic synapses two weeks after injury. These changes were proportional to the intensity of the exercise protocol. Blockade of sensory inputs from the homolateral hindlimb also reduced PNN immunoreactivity around intact motoneurons, and in that case treadmill running did not reverse that loss, suggesting that the effects of exercise on motoneuron PNN depend on increased sensory activity. Preservation of motoneuron PNN and reduction of synaptic stripping by exercise could facilitate the maintenance of the spinal circuitry and benefit functional recovery after peripheral nerve injury.
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Affiliation(s)
- Ariadna Arbat-Plana
- Institute of Neurosciences, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain
| | - Abel Torres-Espín
- Institute of Neurosciences, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain
| | - Xavier Navarro
- Institute of Neurosciences, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain
| | - Esther Udina
- Institute of Neurosciences, Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Bellaterra, Spain.
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Zong H, Zhao H, Zhao Y, Jia J, Yang L, Ma C, Zhang Y, Dong Y. Nanoparticles carrying neurotrophin-3-modified Schwann cells promote repair of sciatic nerve defects. Neural Regen Res 2014; 8:1262-8. [PMID: 25206420 PMCID: PMC4107647 DOI: 10.3969/j.issn.1673-5374.2013.14.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 04/25/2013] [Indexed: 12/03/2022] Open
Abstract
Schwann cells and neurotrophin-3 play an important role in neural regeneration, but the secretion of neurotrophin-3 from Schwann cells is limited, and exogenous neurotrophin-3 is inactived easily in vivo. In this study, we have transfected neurotrophin-3 into Schwann cells cultured in vitro using nanoparticle liposomes. Results showed that neurotrophin-3 was successfully transfected into Schwann cells, where it was expressed effectively and steadily. A composite of Schwann cells transfected with neurotrophin-3 and poly(lactic-co-glycolic acid) biodegradable conduits was transplanted into rats to repair 10-mm sciatic nerve defects. Transplantation of the composite scaffold could restore the myoelectricity and wave amplitude of the sciatic nerve by electrophysiological examination, promote nerve axonal and myelin regeneration, and delay apoptosis of spinal motor neurons. Experimental findings indicate that neurotrophin-3 transfected Schwann cells combined with bridge grafting can promote neural regeneration and functional recovery after nerve injury.
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Affiliation(s)
- Haibin Zong
- Functional Laboratory, School of Basic Medical Sciences, Xinxiang Medical College, Xinxiang 453003, Henan Province, China
| | - Hongxing Zhao
- Department of Orthopedics, the First Affiliated Hospital of Xinxiang Medical College, Weihui 453100, Henan Province, China
| | - Yilei Zhao
- Department of Orthopedics, the First Affiliated Hospital of Xinxiang Medical College, Weihui 453100, Henan Province, China
| | - Jingling Jia
- Department of Orthopedics, the First Affiliated Hospital of Xinxiang Medical College, Weihui 453100, Henan Province, China
| | - Libin Yang
- Department of Orthopedics, the First Affiliated Hospital of Xinxiang Medical College, Weihui 453100, Henan Province, China
| | - Chao Ma
- Department of Orthopedics, the First Affiliated Hospital of Xinxiang Medical College, Weihui 453100, Henan Province, China
| | - Yang Zhang
- Functional Laboratory, School of Basic Medical Sciences, Xinxiang Medical College, Xinxiang 453003, Henan Province, China
| | - Yuzhen Dong
- Department of Orthopedics, the First Affiliated Hospital of Xinxiang Medical College, Weihui 453100, Henan Province, China
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González-Forero D, Moreno-López B. Retrograde response in axotomized motoneurons: nitric oxide as a key player in triggering reversion toward a dedifferentiated phenotype. Neuroscience 2014; 283:138-65. [PMID: 25168733 DOI: 10.1016/j.neuroscience.2014.08.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 08/03/2014] [Accepted: 08/14/2014] [Indexed: 12/11/2022]
Abstract
The adult brain retains a considerable capacity to functionally reorganize its circuits, which mainly relies on the prevalence of three basic processes that confer plastic potential: synaptic plasticity, plastic changes in intrinsic excitability and, in certain central nervous system (CNS) regions, also neurogenesis. Experimental models of peripheral nerve injury have provided a useful paradigm for studying injury-induced mechanisms of central plasticity. In particular, axotomy of somatic motoneurons triggers a robust retrograde reaction in the CNS, characterized by the expression of plastic changes affecting motoneurons, their synaptic inputs and surrounding glia. Axotomized motoneurons undergo a reprograming of their gene expression and biosynthetic machineries which produce cell components required for axonal regrowth and lead them to resume a functionally dedifferentiated phenotype characterized by the removal of afferent synaptic contacts, atrophy of dendritic arbors and an enhanced somato-dendritic excitability. Although experimental research has provided valuable clues to unravel many basic aspects of this central response, we are still lacking detailed information on the cellular/molecular mechanisms underlying its expression. It becomes clear, however, that the state-switch must be orchestrated by motoneuron-derived signals produced under the direction of the re-activated growth program. Our group has identified the highly reactive gas nitric oxide (NO) as one of these signals, by providing robust evidence for its key role to induce synapse elimination and increases in intrinsic excitability following motor axon damage. We have elucidated operational principles of the NO-triggered downstream transduction pathways mediating each of these changes. Our findings further demonstrate that de novo NO synthesis is not only "necessary" but also "sufficient" to promote the expression of at least some of the features that reflect reversion toward a dedifferentiated state in axotomized adult motoneurons.
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Affiliation(s)
- D González-Forero
- Grupo de Neurodegeneración y Neuroreparación (GRUNEDERE), Área de Fisiología, Instituto de Biomoléculas (INBIO), Facultad de Medicina, Universidad de Cádiz, Cádiz, Spain.
| | - B Moreno-López
- Grupo de Neurodegeneración y Neuroreparación (GRUNEDERE), Área de Fisiología, Instituto de Biomoléculas (INBIO), Facultad de Medicina, Universidad de Cádiz, Cádiz, Spain.
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Neural progenitor cell implants in the lesioned medial longitudinal fascicle of adult cats regulate synaptic composition and firing properties of abducens internuclear neurons. J Neurosci 2014; 34:7007-17. [PMID: 24828653 DOI: 10.1523/jneurosci.4231-13.2014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Transplants of neural progenitor cells (NPCs) into the injured CNS have been proposed as a powerful tool for brain repair, but, to date, few studies on the physiological response of host neurons have been reported. Therefore, we explored the effects of NPC implants on the discharge characteristics and synaptology of axotomized abducens internuclear neurons, which mediate gaze conjugacy for horizontal eye movements. NPCs were isolated from the subventricular zone of neonatal cats and implanted at the site of transection in the medial longitudinal fascicle of adult cats. Abducens internuclear neurons of host animals showed a complete restoration of axotomy-induced alterations in eye position sensitivity, but eye velocity sensitivity was only partially regained. Analysis of the inhibitory and excitatory components of the discharge revealed a normal re-establishment of inhibitory inputs, but only partial re-establishment of excitatory inputs. Moreover, their inhibitory terminal coverage was similar to that in controls, indicating that there was ultimately no loss of inhibitory synaptic inputs. Somatic coverage by synaptophysin-positive contacts, however, showed intermediate values between control animals and animals that had undergone axotomy, likely due to partial loss of excitatory inputs. We also demonstrated that severed axons synaptically contacted NPCs, most of which were VEGF immunopositive, and that abducens internuclear neurons expressed the VEGF receptor Flk1. Together, our results suggest that VEGF neurotrophic support might underlie the increased inhibitory-to-excitatory balance observed in the postimplant cells. The noteworthy improvement of firing properties of injured neurons following NPC implants indicates that these cells might provide a promising therapeutic strategy after neuronal lesions.
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Liu C, Ward PJ, English AW. The effects of exercise on synaptic stripping require androgen receptor signaling. PLoS One 2014; 9:e98633. [PMID: 24887087 PMCID: PMC4041790 DOI: 10.1371/journal.pone.0098633] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 05/06/2014] [Indexed: 11/19/2022] Open
Abstract
Following peripheral nerve injury, synapses are withdrawn from axotomized motoneurons. Moderate daily treadmill exercise, which promotes axon regeneration of cut peripheral nerves, also influences this synaptic stripping. Different exercise protocols are required to promote axon regeneration in male and female animals, but the sex requirements for an effect of exercise on synaptic stripping are unknown. In male and female C57BL/6 mice, the sciatic nerve was transected in the mid-thigh. Mice were then exercised five days per week for two weeks, beginning on the third post-transection day. Half of the exercised mice were trained by walking slowly (10 M/min) on a level treadmill for one hour per day (continuous training). Other mice were interval trained; four short (two min) sprints at 20 M/min separated by five minute rest periods. A third group was untrained. The extent of synaptic contacts made by structures immunoreactive to vesicular glutamate transporter 1 and glutamic acid decarboxylase 67 onto axotomized motoneurons was studied in confocal images of retrogradely labeled cells. Both types of presumed synaptic contacts were reduced markedly in unexercised mice following nerve transection, relative to intact mice. No significant reduction was found in continuous trained males or interval trained females. Reductions in these contacts in interval trained males and continuous trained females were identical to that observed in untrained mice. Treatments with the anti-androgen, flutamide, blocked the effect of sex-appropriate exercise on synaptic contacts in both males and females. Moderate daily exercise has a potent effect on synaptic inputs to axotomized motoneurons. Successful effects of exercise have different requirements in males and females, but require androgen receptor signaling in both sexes.
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Affiliation(s)
- Caiyue Liu
- Department of Plastic and Reconstructive Surgery, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Patricia J. Ward
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Arthur W. English
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia, United States of America
- * E-mail:
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