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Wu S, Su Y, Wang Y, Wang J, Xu D, Liu Y, Yang K, Gao J, Cui J, Bai W. Region-specific response of central microglial cells to sciatic nerve demyelination through sensory and motor pathways. Histol Histopathol 2024; 39:771-781. [PMID: 38051019 DOI: 10.14670/hh-18-681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Peripheral nerve injury can cause changes in microglial cells on the spinal dorsal and ventral horns. This region-specific response implies that central microglial cells could be activated through both sensory and motor pathways. In order to further determine how peripheral nerve injury activates central microglial cells through neural pathways, the sciatic nerve was selected as the target for neural tract tracing and demyelination. Firstly, we used cholera toxin subunit B (CTB) to map the central sensory and motor territories of the sciatic nerve. Secondly, we applied lysophosphatidylcholine to establish the model of sciatic nerve demyelination and examined the distribution of activated microglial cells via immunofluorescence with ionized calcium-binding adapter molecule 1. It was shown that CTB labeling included the transganglionically labeled sensory afferents and retrogradely labeled somata of motor neurons along the sensory and motor pathways of the sciatic nerve ipsilateral to the injection, in which sensory afferents terminated on the gracile nucleus, Clarke's nucleus, and spinal dorsal horn, while motor neurons located on the spinal ventral horn. Consistently, after sciatic nerve demyelination, the activated microglial cells were observed in the same territories as CTB-labeling, showing shortened processes and enlarged cell bodies. These results support the idea that central microglia might be activated by signals from the demyelinated sciatic nerve through both sensory and motor pathways.
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Affiliation(s)
- Shuang Wu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Yuxin Su
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Yuqing Wang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Jia Wang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Dongsheng Xu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Yihan Liu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Kunwu Yang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Junhong Gao
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Jingjing Cui
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China.
| | - Wanzhu Bai
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China.
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da Silva NS, Lombardi J, Kirchhoff F, Ferreira RS, Barraviera B, de Oliveira ALR, Cartarozzi LP. Effects of local and systemic treatment with human natural killer-1 mimetic peptide (HNK-1) after ventral root avulsion and reimplantation in mice. J Venom Anim Toxins Incl Trop Dis 2024; 30:e20230065. [PMID: 38770186 PMCID: PMC11105159 DOI: 10.1590/1678-9199-jvatitd-2023-0065] [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: 08/28/2023] [Accepted: 04/01/2024] [Indexed: 05/22/2024] Open
Abstract
Background Spinal ventral root injuries generate significant motoneuron degeneration, which hinders full functional recovery. The poor prognosis of functional recovery can be attributed to the use or combination of different therapeutic approaches. Several molecules have been screened as potential treatments in combination with surgical reimplantation of the avulsed roots, the gold standard approach for such injuries. Among the studied molecules, human natural killer-1 (HNK-1) stands out as it is related to the stimulation of motor axon outgrowth. Therefore, we aimed to comparatively investigate the effects of local administration of an HNK-1 mimetic peptide (mp-HNK-1) and systemic treatment with ursolic acid (UA), another HNK-1 mimetic, after ventral root avulsion and reimplantation with heterologous fibrin biopolymer (HFB). Methods Female mice of the isogenic strain C57BL/6JUnib were divided into five experimental groups: Avulsion, Reimplantation, mp-HNK-1 (in situ), and UA (systemic treatment). Mice were evaluated 2 and 12 weeks after surgery. Functional assessment was performed every four days using the Catwalk platform. Neuronal survival was analyzed by cytochemistry, and glial reactions and synaptic coverage were evaluated by immunofluorescence. Results Treatment with UA elicited long-term neuroprotection, accompanied by a decrease in microglial reactions, and reactive astrogliosis. The neuroprotective effects of UA were preceded by increased glutamatergic and GABAergic inputs in the ventral spinal cord two weeks after injury. However, a single application of mp-HNK-1 had no significant effects. Functional analysis showed that UA treatment led to an improvement in motor and sensory recovery. Conclusion Overall, the results indicate that UA is neuroprotective, acting on glial cells and synaptic maintenance, and the combination of these findings led to a better functional recovery.
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Affiliation(s)
- Natalia Scanavachia da Silva
- Department of Structural and Functional Biology, Laboratory of Nerve Regeneration, Institute of Biology, University of Campinas (Unicamp), Campinas, SP, Brazil
| | - Julia Lombardi
- Department of Structural and Functional Biology, Laboratory of Nerve Regeneration, Institute of Biology, University of Campinas (Unicamp), Campinas, SP, Brazil
| | - Frank Kirchhoff
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, Homburg, Germany
- Center for Gender-specific Biology and Medicine (CGBM), University of Saarland, Homburg, Germany
| | - Rui Seabra Ferreira
- Center for the Study of Venoms and Venomous Animals (CEVAP), São Paulo State University (UNESP), Botucatu, SP, Brazil
| | - Benedito Barraviera
- Center for the Study of Venoms and Venomous Animals (CEVAP), São Paulo State University (UNESP), Botucatu, SP, Brazil
| | - Alexandre Leite Rodrigues de Oliveira
- Department of Structural and Functional Biology, Laboratory of Nerve Regeneration, Institute of Biology, University of Campinas (Unicamp), Campinas, SP, Brazil
| | - Luciana Politti Cartarozzi
- Department of Structural and Functional Biology, Laboratory of Nerve Regeneration, Institute of Biology, University of Campinas (Unicamp), Campinas, SP, Brazil
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Zhu Y, Luan C, Gong L, Gu Y, Wang X, Sun H, Chen Z, Zhou Q, Liu C, Shan Q, Gu X, Zhou S. SnRNA-seq reveals the heterogeneity of spinal ventral horn and mechanism of motor neuron axon regeneration. iScience 2023; 26:107264. [PMID: 37502257 PMCID: PMC10368823 DOI: 10.1016/j.isci.2023.107264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 05/02/2023] [Accepted: 06/27/2023] [Indexed: 07/29/2023] Open
Abstract
Spinal motor neurons, the distinctive neurons of the central nervous system, extend into the peripheral nervous system and have outstanding ability of axon regeneration after injury. Here, we explored the heterogeneity of spinal ventral horn cells after rat sciatic nerve crush via single-nuclei RNA sequencing. Interestingly, regeneration mainly occurred in a Sncg+ and Anxa2+ motor neuron subtype (MN2) surrounded by a newly emerged microglia subtype (Mg6) after injury. Subsequently, microglia depletion slowed down the regeneration of sciatic nerve. OPCs were also involved into the regeneration process. Knockdown of Cacna2d2 in vitro and systemic blocking of Cacna2d2 in vivo improved the axon growth ability, hinting us the importance of Ca2+. Ultimately, we proposed three possible phases of motor neuron axon regeneration: preparation stage, early regeneration stage, and regeneration stage. Taken together, our study provided a resource for deciphering the underlying mechanism of motor neuron axon regeneration in a single cell dimension.
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Affiliation(s)
- Ye Zhu
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300000, China
| | - Chengcheng Luan
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300000, China
| | - Leilei Gong
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Yun Gu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Xinghui Wang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Hualin Sun
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Zhifeng Chen
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Qiang Zhou
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Chang Liu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Qi Shan
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300000, China
| | - Xiaosong Gu
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300000, China
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
| | - Songlin Zhou
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu 226001, China
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4
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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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Arbat-Plana A, Bolívar S, Navarro X, Udina E, Alvarez FJ. Massive Loss of Proprioceptive Ia Synapses in Rat Spinal Motoneurons after Nerve Crush Injuries in the Postnatal Period. eNeuro 2023; 10:ENEURO.0436-22.2023. [PMID: 36759186 PMCID: PMC9948128 DOI: 10.1523/eneuro.0436-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/15/2022] [Accepted: 01/26/2023] [Indexed: 02/11/2023] Open
Abstract
Peripheral nerve injuries (PNIs) induce the retraction from the ventral horn of the synaptic collaterals of Ia afferents injured in the nerve, effectively removing Ia synapses from α-motoneurons. The loss of Ia input impairs functional recovery and could explain, in part, better recovery after PNIs with better Ia synaptic preservation. Synaptic losses correlate with injury severity, speed, and efficiency of muscle reinnervation and requires ventral microglia activation. It is unknown whether this plasticity is age dependent. In neonates, axotomized motoneurons and sensory neurons undergo apoptosis, but after postnatal day 10 most survive. The goal of this study was to analyze vesicular glutamate transporter 1 (VGluT1)-labeled Ia synapses (which also include II afferents) after nerve crush in 10 day old rats, a PNI causing little Ia/II synapse loss in adult rats. We confirmed fast and efficient reinnervation of leg muscles; however, a massive number of VGluT1/Ia/II synapses were permanently lost. This synapse loss was similar to that after more severe nerve injuries involving full transection in adults. In adults, disappearance of ventrally directed Ia/II collaterals targeting α-motoneurons was associated with a prolonged microglia reaction and a CCR2 mechanism that included infiltration of CCR2 blood immune cells. By contrast, microgliosis after P10 injuries was fast, resolved in about a week, and there was no evidence of peripheral immune cell infiltration. We conclude that VGluT1/Ia/II synapse loss in young animals differs in mechanism, perhaps associated with higher microglia synaptic pruning activity at this age and results in larger losses after milder nerve injuries.
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Affiliation(s)
- Ariadna Arbat-Plana
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
- Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Sara Bolívar
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
- Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Xavier Navarro
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
| | - Esther Udina
- Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, 08028 Barcelona, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08193 Bellaterra, Spain
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Gao Z, Pang Z, Lei G, Chen Y, Cai Z, Zhu S, Lin W, Qiu Z, Wang Y, Shen Y, Xu W. Crossing nerve transfer drives sensory input-dependent plasticity for motor recovery after brain injury. SCIENCE ADVANCES 2022; 8:eabn5899. [PMID: 36044580 PMCID: PMC9432844 DOI: 10.1126/sciadv.abn5899] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
Restoring limb movements after central nervous system injury remains a substantial challenge. Recent studies proved that crossing nerve transfer surgery could rebuild physiological connectivity between the contralesional cortex and the paralyzed arm to compensate for the lost function after brain injury. However, the neural mechanism by which this surgery mediates motor recovery remains still unclear. Here, using a clinical mouse model, we showed that this surgery can restore skilled forelimb function in adult mice with unilateral cortical lesion by inducing cortical remapping and promoting corticospinal tract sprouting. After reestablishing the ipsilateral descending pathway, resecting of the artificially rebuilt peripheral nerve did not affect motor improvements. Furthermore, retaining the sensory afferent, but not the motor efferent, of the transferred nerve was sufficient for inducing brain remapping and facilitating motor restoration. Thus, our results demonstrate that surgically rebuilt sensory input triggers neural plasticity for accelerating motor recovery, which provides an approach for treating central nervous system injuries.
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Affiliation(s)
- Zhengrun Gao
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Zhen Pang
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Gaowei Lei
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Yiming Chen
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Zeyu Cai
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Shuai Zhu
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Weishan Lin
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Zilong Qiu
- The National Clinical Research Center for Aging and Medicine, Fudan University, Shanghai, China
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
| | - Yizheng Wang
- The National Clinical Research Center for Aging and Medicine, Fudan University, Shanghai, China
| | - Yundong Shen
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
- The National Clinical Research Center for Aging and Medicine, Fudan University, Shanghai, China
- Department of Hand and Upper Extremity Surgery, Jing‘an District Central Hospital, Fudan University, Shanghai, China
| | - Wendong Xu
- Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China
- The National Clinical Research Center for Aging and Medicine, Fudan University, Shanghai, China
- Department of Hand and Upper Extremity Surgery, Jing‘an District Central Hospital, Fudan University, Shanghai, China
- Institutes of Brain Science, Fudan University, Shanghai, China
- State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center of Brain Science, Fudan University, Shanghai, China
- Co-innovation Center of Neuroregeneration, Nantong University, 226000 Nantong, China
- Research Unit of Synergistic Reconstruction of Upper and Lower Limbs After Brain Injury, Chinese Academy of Medical Sciences, Beijing, China
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7
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Pottorf TS, Rotterman TM, McCallum WM, Haley-Johnson ZA, Alvarez FJ. The Role of Microglia in Neuroinflammation of the Spinal Cord after Peripheral Nerve Injury. Cells 2022; 11:cells11132083. [PMID: 35805167 PMCID: PMC9265514 DOI: 10.3390/cells11132083] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 06/26/2022] [Accepted: 06/27/2022] [Indexed: 12/12/2022] Open
Abstract
Peripheral nerve injuries induce a pronounced immune reaction within the spinal cord, largely governed by microglia activation in both the dorsal and ventral horns. The mechanisms of activation and response of microglia are diverse depending on the location within the spinal cord, type, severity, and proximity of injury, as well as the age and species of the organism. Thanks to recent advancements in neuro-immune research techniques, such as single-cell transcriptomics, novel genetic mouse models, and live imaging, a vast amount of literature has come to light regarding the mechanisms of microglial activation and alluding to the function of microgliosis around injured motoneurons and sensory afferents. Herein, we provide a comparative analysis of the dorsal and ventral horns in relation to mechanisms of microglia activation (CSF1, DAP12, CCR2, Fractalkine signaling, Toll-like receptors, and purinergic signaling), and functionality in neuroprotection, degeneration, regeneration, synaptic plasticity, and spinal circuit reorganization following peripheral nerve injury. This review aims to shed new light on unsettled controversies regarding the diversity of spinal microglial-neuronal interactions following injury.
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Affiliation(s)
- Tana S. Pottorf
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; (T.S.P.); (W.M.M.); (Z.A.H.-J.)
| | - Travis M. Rotterman
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30318, USA;
| | - William M. McCallum
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; (T.S.P.); (W.M.M.); (Z.A.H.-J.)
| | - Zoë A. Haley-Johnson
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; (T.S.P.); (W.M.M.); (Z.A.H.-J.)
| | - Francisco J. Alvarez
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; (T.S.P.); (W.M.M.); (Z.A.H.-J.)
- Correspondence:
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Progranulin Promotes Functional Recovery in Rats with Acute Spinal Cord Injury via Autophagy-Induced Anti-inflammatory Microglial Polarization. Mol Neurobiol 2022; 59:4304-4314. [PMID: 35505051 DOI: 10.1007/s12035-022-02836-0] [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: 01/25/2022] [Accepted: 04/09/2022] [Indexed: 10/18/2022]
Abstract
Since microglia-associated neuroinflammation plays a critical role in the progression of acute spinal cord injury, modulation of microglial activation has been suggested as a potential therapeutic strategy. Progranulin has been reported to exert neuroprotective effects by attenuating neuroinflammation, but whether these effects are due to the modulation of microglial polarization and the underlying mechanism remain unclear. Here, we investigated the effect of progranulin on microglial polarization and analyzed the crosstalk between microglial autophagy and polarization. We found that progranulin could reduce proinflammatory cytokine production at the lesion site and promote locomotor functional recovery after acute spinal cord injury. In vitro, we found that progranulin could activate microglia to acquire an anti-inflammatory phenotype and express IL-10. Moreover, progranulin-mediated enhancement of anti-inflammatory microglial polarization was attributed to the protection of lysosomal function and the enhancement of autophagic flux. Above all, progranulin exerts anti-inflammatory effects by protecting lysosomal function to enhance microglial autophagy, induce M2 microglial polarization, and ultimately improve neurological function after acute spinal cord injury. These results suggest that targeting the autophagy-lysosomal pathway to modulate microglial polarization and reduce neuroinflammation is a potential treatment for spinal cord injury.
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Plasticity of the Central Nervous System Involving Peripheral Nerve Transfer. Neural Plast 2022; 2022:5345269. [PMID: 35342394 PMCID: PMC8956439 DOI: 10.1155/2022/5345269] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 02/09/2022] [Accepted: 02/28/2022] [Indexed: 11/22/2022] Open
Abstract
Peripheral nerve injury can lead to partial or complete loss of limb function, and nerve transfer is an effective surgical salvage for patients with these injuries. The inability of deprived cortical regions representing damaged nerves to overcome corresponding maladaptive plasticity after the reinnervation of muscle fibers and sensory receptors is thought to be correlated with lasting and unfavorable functional recovery. However, the concept of central nervous system plasticity is rarely elucidated in classical textbooks involving peripheral nerve injury, let alone peripheral nerve transfer. This article is aimed at providing a comprehensive understanding of central nervous system plasticity involving peripheral nerve injury by reviewing studies mainly in human or nonhuman primate and by highlighting the functional and structural modifications in the central nervous system after peripheral nerve transfer. Hopefully, it will help surgeons perform successful nerve transfer under the guidance of modern concepts in neuroplasticity.
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Chen HR, Chen CW, Kuo YM, Chen B, Kuan IS, Huang H, Lee J, Anthony N, Kuan CY, Sun YY. Monocytes promote acute neuroinflammation and become pathological microglia in neonatal hypoxic-ischemic brain injury. Theranostics 2022; 12:512-529. [PMID: 34976198 PMCID: PMC8692901 DOI: 10.7150/thno.64033] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 11/08/2021] [Indexed: 12/17/2022] Open
Abstract
Rationale: Monocytes belong to the mononuclear phagocyte system and are immune responders to tissue injury and infection. There were also reports of monocytes transforming to microglia-like cells. Here we explore the roles of monocytes in microglia ontogeny and the pathogenesis of neonatal cerebral hypoxic-ischemic (HI) brain injury in mice. Methods: We used three genetic methods to track the development of monocytes, including CX3CR1GFP/+; CCR2RFP/+ reporter mice, adoptive transfer of GFP+ monocytes, and fate-mapping with CCR2-CreER mice, in neonatal mouse brains with or without lipopolysaccharide (LPS, 0.3 mg/kg)-sensitized Vannucci HI. We also used genetic (CCR2RFP/ RFP, CCR2 knockout) and pharmacological methods (RS102895, a CCR2 antagonist) to test the roles of monocytic influx in LPS/HI brain injury. Results: CCR2+ monocytes entered the late-embryonic brains via choroid plexus, but rapidly became CX3CR1+ amoeboid microglial cells (AMCs). The influx of CCR2+ monocytes declined after birth, but recurred after HI or LPS-sensitized HI (LPS/HI) brain injury, particularly in the hippocampus. The CCR2-CreER-based fate-mapping showed that CCR2+ monocytes became CD68+ TNFα+ macrophages within 4 d after LPS/HI, and maintained as TNFα+ MHCII+ macrophages or persisted as Tmem119+ Sall1+ P2RY12+ ramified microglia for at least five months after injury. Genetic deletion of the chemokine receptor CCR2 markedly diminished monocytic influx, the expression of pro- and anti-inflammatory cytokines, and brain damage. Post-LPS/HI application of RS102895 also reduced inflammatory responses and brain damage, leading to better cognitive functions. Conclusion: These results suggest that monocytes promote acute inflammatory responses and may become pathological microglia long after the neonatal LPS/HI insult. Further, blocking the influx of monocytes may be a potential therapy for neonatal brain injury.
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Affiliation(s)
- Hong-Ru Chen
- Department of Neuroscience, Center for Brain Immunology and Glia (BIG), University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Ching-Wen Chen
- Department of Neuroscience, Center for Brain Immunology and Glia (BIG), University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Yi-Min Kuo
- Department of Anesthesiology, Taipei Veterans General Hospital and National Yang Ming Chiao Tung University School of Medicine, Taipei, Taiwan
| | - Brandon Chen
- University of Louisville School of Medicine, Louisville, KY, USA
| | - Irena S. Kuan
- St. Louis University School of Medicine, St. Louis, MO, USA
| | - Henry Huang
- Department of Anesthesiology, Rhode Island Hospital, Providence, RI, USA
| | - Jolly Lee
- Emory University School of Medicine, Atlanta, GA, USA
| | - Neil Anthony
- Emory Integrated Cellular Imaging, Atlanta, GA, USA
| | - Chia-Yi Kuan
- Department of Neuroscience, Center for Brain Immunology and Glia (BIG), University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Yu-Yo Sun
- Institute of BioPharmaceutical Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan
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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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Blaszkiewicz M, Gunsch G, Willows JW, Gardner ML, Sepeda JA, Sas AR, Townsend KL. Adipose Tissue Myeloid-Lineage Neuroimmune Cells Express Genes Important for Neural Plasticity and Regulate Adipose Innervation. Front Endocrinol (Lausanne) 2022; 13:864925. [PMID: 35795142 PMCID: PMC9251313 DOI: 10.3389/fendo.2022.864925] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 05/05/2022] [Indexed: 12/19/2022] Open
Abstract
Peripheral nerves allow a bidirectional communication between brain and adipose tissues, and many studies have clearly demonstrated that a loss of the adipose nerve supply results in tissue dysfunction and metabolic dysregulation. Neuroimmune cells closely associate with nerves in many tissues, including subcutaneous white adipose tissue (scWAT). However, in scWAT, their functions beyond degrading norepinephrine in an obese state remain largely unexplored. We previously reported that a myeloid-lineage knockout (KO) of brain-derived neurotrophic factor (BDNF) resulted in decreased innervation of scWAT, accompanied by an inability to brown scWAT after cold stimulation, and increased adiposity after a high-fat diet. These data underscored that adipose tissue neuroimmune cells support the peripheral nerve supply to adipose and impact the tissue's metabolic functions. We also reported that a subset of myeloid-lineage monocyte/macrophages (Ly6c+CCR2+Cx3cr1+) is recruited to scWAT in response to cold, a process known to increase neurite density in adipose and promote metabolically healthy processes. These cold-induced neuroimmune cells (CINCs) also expressed BDNF. Here we performed RNAseq on CINCs from cold-exposed and room temperature-housed mice, which revealed a striking and coordinated differential expression of numerous genes involved in neuronal function, including neurotrophin signaling and axonal guidance, further supporting that CINCs fulfill a nerve-supporting role in adipose. The increased expression of leukocyte transendothelial migration genes in cold-stimulated CINCs also confirms prior evidence that they are recruited to scWAT and are not tissue resident. We now provide whole-depot imaging of scWAT from LysM-BDNF KO mice, revealing a striking reduction of innervation across the depot fitting with their reduced energy expenditure phenotype. By contrast, Cx3cr1-BDNF KO mice (a macrophage subset of LysM+ cells) exhibited increased thermogenesis and energy expenditure, with compensatory increased food intake and no change in adiposity or body weight. While these KO mice also exhibit a significantly reduced innervation of scWAT, especially around the subiliac lymph node, they displayed an increase in small fiber sympathetic neurite branching, which may underlie their increased thermogenesis. We propose a homeostatic role of scWAT myeloid-lineage neuroimmune cells together in nerve maintenance and neuro-adipose regulation of energy expenditure.
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Affiliation(s)
- Magdalena Blaszkiewicz
- Neurobiology and Energy Balance Laboratory, Department of Neurological Surgery, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
| | - Gilian Gunsch
- Neurobiology and Energy Balance Laboratory, Department of Neurological Surgery, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
| | - Jake W. Willows
- Neurobiology and Energy Balance Laboratory, Department of Neurological Surgery, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
| | - Miranda L. Gardner
- Department of Cancer Biology and Genetics, Comprehensive Cancer Center, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
- Campus Chemical Instrument Center, Mass Spectrometry and Proteomics Facility, The Ohio State University, Columbus, OH, United States
| | - Jesse A. Sepeda
- Department of Neurology, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
| | - Andrew R. Sas
- Department of Neurology, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
| | - Kristy L. Townsend
- Neurobiology and Energy Balance Laboratory, Department of Neurological Surgery, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
- *Correspondence: Kristy L. Townsend,
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13
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Krukowski K, Nolan A, Becker M, Picard K, Vernoux N, Frias ES, Feng X, Tremblay ME, Rosi S. Novel microglia-mediated mechanisms underlying synaptic loss and cognitive impairment after traumatic brain injury. Brain Behav Immun 2021; 98:122-135. [PMID: 34403733 PMCID: PMC9119574 DOI: 10.1016/j.bbi.2021.08.210] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 08/03/2021] [Accepted: 08/06/2021] [Indexed: 12/30/2022] Open
Abstract
Traumatic brain injury (TBI) is one of the leading causes of long-term neurological disability in the world. Currently, there are no therapeutics for treating the deleterious consequences of brain trauma; this is in part due to a lack of complete understanding of cellular processes that underlie TBI-related pathologies. Following TBI, microglia, the brain resident immune cells, turn into a "reactive" state characterized by the production of inflammatory mediators that contribute to the development of cognitive deficits. Utilizing multimodal, state-of-the-art techniques that widely span from ultrastructural analysis to optogenetic interrogation of circuit function, we investigated the reactive microglia phenotype one week after injury when learning and memory deficits are also measured. Microglia displayed increased: (i) phagocytic activity in vivo, (ii) synaptic engulfment, (iii) increased neuronal contact, including with dendrites and somata (termed 'satellite microglia'). Functionally, satellite microglia might impact somatic inhibition as demonstrated by the associated reduction in inhibitory synaptic drive. Cumulatively, here we demonstrate novel microglia-mediated mechanisms that may contribute to synaptic loss and cognitive impairment after traumatic brain injury.
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Affiliation(s)
- Karen Krukowski
- Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, CA, USA, Brain and Spinal Injury Center, University of California, San Francisco, CA, USA
| | - Amber Nolan
- Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, CA, USA, Brain and Spinal Injury Center, University of California, San Francisco, CA, USA
| | - McKenna Becker
- Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, CA, USA, Brain and Spinal Injury Center, University of California, San Francisco, CA, USA
| | - Katherine Picard
- Axe Neurosciences, CRCHU de Québec-Université Laval, Québec, QC, Canada
| | - Nathalie Vernoux
- Axe Neurosciences, CRCHU de Québec-Université Laval, Québec, QC, Canada
| | - Elma S. Frias
- Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, CA, USA, Brain and Spinal Injury Center, University of California, San Francisco, CA, USA, Department of Biomedical Sciences, University of California, San Francisco, CA, USA
| | - Xi Feng
- Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, CA, USA, Brain and Spinal Injury Center, University of California, San Francisco, CA, USA
| | - Marie-Eve Tremblay
- Axe Neurosciences, CRCHU de Québec-Université Laval, Québec, QC, Canada; Molecular Medicine Department, Université Laval, Québec, QC, Canada; Division of Medical Sciences, University of Victoria, Victoria, BC, Canada; Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada.
| | - Susanna Rosi
- Department of Physical Therapy and Rehabilitation Science, University of California, San Francisco, CA, USA; Brain and Spinal Injury Center, University of California, San Francisco, CA, USA; Department of Biomedical Sciences, University of California, San Francisco, CA, USA; Department of Neurological Surgery, University of California, San Francisco, CA, USA; Weill Institute for Neuroscience, University of California San Francisco, CA, USA; Kavli Institute of Fundamental Neuroscience, University of California San Francisco, CA, USA.
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14
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Gras S, Blasco A, Mòdol-Caballero G, Tarabal O, Casanovas A, Piedrafita L, Barranco A, Das T, Rueda R, Pereira SL, Navarro X, Esquerda JE, Calderó J. Beneficial effects of dietary supplementation with green tea catechins and cocoa flavanols on aging-related regressive changes in the mouse neuromuscular system. Aging (Albany NY) 2021; 13:18051-18093. [PMID: 34319911 PMCID: PMC8351677 DOI: 10.18632/aging.203336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/19/2021] [Indexed: 12/17/2022]
Abstract
Besides skeletal muscle wasting, sarcopenia entails morphological and molecular changes in distinct components of the neuromuscular system, including spinal cord motoneurons (MNs) and neuromuscular junctions (NMJs); moreover, noticeable microgliosis has also been observed around aged MNs. Here we examined the impact of two flavonoid-enriched diets containing either green tea extract (GTE) catechins or cocoa flavanols on age-associated regressive changes in the neuromuscular system of C57BL/6J mice. Compared to control mice, GTE- and cocoa-supplementation significantly improved the survival rate of mice, reduced the proportion of fibers with lipofuscin aggregates and central nuclei, and increased the density of satellite cells in skeletal muscles. Additionally, both supplements significantly augmented the number of innervated NMJs and their degree of maturity compared to controls. GTE, but not cocoa, prominently increased the density of VAChT and VGluT2 afferent synapses on MNs, which were lost in control aged spinal cords; conversely, cocoa, but not GTE, significantly augmented the proportion of VGluT1 afferent synapses on aged MNs. Moreover, GTE, but not cocoa, reduced aging-associated microgliosis and increased the proportion of neuroprotective microglial phenotypes. Our data indicate that certain plant flavonoids may be beneficial in the nutritional management of age-related deterioration of the neuromuscular system.
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Affiliation(s)
- Sílvia Gras
- Unitat de Neurobiologia Cel·lular, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Spain
| | - Alba Blasco
- Unitat de Neurobiologia Cel·lular, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Spain
| | - Guillem Mòdol-Caballero
- Grup de Neuroplasticitat i Regeneració, Institut de Neurociències, Departament de Biologia Cellular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona and CIBERNED, Bellaterra, Spain
| | - Olga Tarabal
- Unitat de Neurobiologia Cel·lular, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Spain
| | - Anna Casanovas
- Unitat de Neurobiologia Cel·lular, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Spain
| | - Lídia Piedrafita
- Unitat de Neurobiologia Cel·lular, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Spain
| | - Alejandro Barranco
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, University of Granada, Granada, Spain
| | - Tapas Das
- Abbott Nutrition, Research and Development, Columbus, OH 43215, USA
| | - Ricardo Rueda
- Abbott Nutrition, Research and Development, Granada, Spain
| | | | - Xavier Navarro
- Grup de Neuroplasticitat i Regeneració, Institut de Neurociències, Departament de Biologia Cellular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona and CIBERNED, Bellaterra, Spain
| | - Josep E. Esquerda
- Unitat de Neurobiologia Cel·lular, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Spain
| | - Jordi Calderó
- Unitat de Neurobiologia Cel·lular, Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Spain
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15
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Shadrach JL, Stansberry WM, Milen AM, Ives RE, Fogarty EA, Antonellis A, Pierchala BA. Translatomic analysis of regenerating and degenerating spinal motor neurons in injury and ALS. iScience 2021; 24:102700. [PMID: 34235408 PMCID: PMC8246596 DOI: 10.1016/j.isci.2021.102700] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 10/09/2020] [Accepted: 06/07/2021] [Indexed: 12/23/2022] Open
Abstract
The neuromuscular junction is a synapse critical for muscle strength and coordinated motor function. Unlike CNS injuries, motor neurons mount robust regenerative responses after peripheral nerve injuries. Conversely, motor neurons selectively degenerate in diseases such as amyotrophic lateral sclerosis (ALS). To assess how these insults affect motor neurons in vivo, we performed ribosomal profiling of mouse motor neurons. Motor neuron-specific transcripts were isolated from spinal cords following sciatic nerve crush, a model of acute injury and regeneration, and in the SOD1G93A ALS model. Of the 267 transcripts upregulated after nerve crush, 38% were also upregulated in SOD1G93A motor neurons. However, most upregulated genes in injured and ALS motor neurons were context specific. Some of the most significantly upregulated transcripts in both paradigms were chemokines such as Ccl2 and Ccl7, suggesting an important role for neuroimmune modulation. Collectively these data will aid in defining pro-regenerative and pro-degenerative mechanisms in motor neurons.
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Affiliation(s)
- Jennifer L. Shadrach
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI, USA
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Wesley M. Stansberry
- Department of Anatomy, Cell Biology & Physiology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Allison M. Milen
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI, USA
| | - Rachel E. Ives
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI, USA
| | | | - Anthony Antonellis
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Brian A. Pierchala
- Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor, MI, USA
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, USA
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
- Department of Anatomy, Cell Biology & Physiology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
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16
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Campos RM, Barbosa-Silva MC, Ribeiro-Resende VT. Comparison of effect of crush or transection peripheral nerve lesion on lumbar spinal cord synaptic plasticity and microglial dynamics. IBRO Neurosci Rep 2021; 10:225-235. [PMID: 34179871 PMCID: PMC8211924 DOI: 10.1016/j.ibneur.2021.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 05/10/2021] [Accepted: 05/12/2021] [Indexed: 11/22/2022] Open
Abstract
In an injury to the peripheral nervous system, the spinal cord and brain structure reorganize connections to optimize the function of the remaining parts. Many cell events are triggered in the spinal cord to support changes in the synaptic connections around motoneurons, where old connections are removed, and new ones created. Microglial cells are primitive macrophages that invade the central nervous system in early stages of neurodevelopment and have several functions, such as eliminating synapses. We investigated the synaptic plasticity after different types of peripheral (sciatic) nerve injury (crush or total transection), as well as the behavior of microglial cells for 2 weeks after a peripheral lesion. As expected, sciatic-nerve injury reduced motor performance in mice, but crushed animals regained partial motor control. Because of sciatic-nerve injury, pre-synaptic inputs decreased around the motoneurons in the ventro-lateral horn, while microglial cells increased around these cells. Microglial cells also exhibited altered morphology in both types of peripheral lesion, indicating a similar underlying mechanism of plasticity. To investigate the involvement of microglia in this scenario, microglial activation was modulated by daily administration of minocycline. The minocycline treatment directly affected the microglial response and impacted the synapse rearrangement in the spinal cord. Together, these results demonstrate that microglia cells are involved in synaptic plasticity in the lumbar spinal cord in both nerve-injury scenarios. SUMMARY OF STATEMENT Here, we demonstrated that acute plasticity in the lumbar spinal cord (LSC) did not differ between crush and transection of peripheral nerve, and that microglial reactivity in the LSC was important after both injury types.
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Affiliation(s)
- Raquel M.P. Campos
- Instituto de Biofísica Carlos Chagas Filho, Laboratório de Neuroquímica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
| | - Maria Carolina Barbosa-Silva
- Instituto de Biofísica Carlos Chagas Filho, Laboratório de Neuroquímica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
| | - Victor T. Ribeiro-Resende
- Instituto de Biofísica Carlos Chagas Filho, Laboratório de Neuroquímica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-902, Brazil
- Núcleo Multidisciplinar de Pesquisa em Biologia (Numpex-Bio), Campus de Duque de Caxias Geraldo Guerra Cidade, Universidade Federal do Rio de Janeiro, Duque de Caxias, RJ 25255-030, Brazil
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17
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Pretreatment with High Mobility Group Box-1 Monoclonal Antibody Prevents the Onset of Trigeminal Neuropathy in Mice with a Distal Infraorbital Nerve Chronic Constriction Injury. Molecules 2021; 26:molecules26072035. [PMID: 33918407 PMCID: PMC8038245 DOI: 10.3390/molecules26072035] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 03/25/2021] [Accepted: 03/31/2021] [Indexed: 12/18/2022] Open
Abstract
Persistent pain following orofacial surgery is not uncommon. High mobility group box 1 (HMGB1), an alarmin, is released by peripheral immune cells following nerve injury and could be related to pain associated with trigeminal nerve injury. Distal infraorbital nerve chronic constriction injury (dIoN-CCI) evokes pain-related behaviors including increased facial grooming and hyper-responsiveness to acetone (cutaneous cooling) after dIoN-CCI surgery in mice. In addition, dIoN-CCI mice developed conditioned place preference to mirogabalin, suggesting increased neuropathic pain-related aversion. Treatment of the infraorbital nerve with neutralizing antibody HMGB1 (anti-HMGB1 nAb) before dIoN-CCI prevented both facial grooming and hyper-responsiveness to cooling. Pretreatment with anti-HMGB1 nAb also blocked immune cell activation associated with trigeminal nerve injury including the accumulation of macrophage around the injured IoN and increased microglia activation in the ipsilateral spinal trigeminal nucleus caudalis. The current findings demonstrated that blocking of HMGB1 prior to nerve injury prevents the onset of pain-related behaviors, possibly through blocking the activation of immune cells associated with the nerve injury, both within the CNS and on peripheral nerves. The current findings further suggest that blocking HMGB1 before tissue injury could be a novel strategy to prevent the induction of chronic pain following orofacial surgeries.
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18
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Salvany S, Casanovas A, Piedrafita L, Tarabal O, Hernández S, Calderó J, Esquerda JE. Microglial recruitment and mechanisms involved in the disruption of afferent synaptic terminals on spinal cord motor neurons after acute peripheral nerve injury. Glia 2021; 69:1216-1240. [PMID: 33386754 PMCID: PMC7986680 DOI: 10.1002/glia.23959] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 12/11/2020] [Accepted: 12/14/2020] [Indexed: 12/12/2022]
Abstract
Peripheral nerve section with subsequent disconnection of motor neuron (MN) cell bodies from their skeletal muscle targets leads to a rapid reactive response involving the recruitment and activation of microglia. In addition, the loss of afferent synapses on MNs occurs in concomitance with microglial reaction by a process described as synaptic stripping. However, the way in which postaxotomy‐activated microglia adjacent to MNs are involved in synaptic removal is less defined. Here, we used confocal and electron microscopy to examine interactions between recruited microglial cells and presynaptic terminals in axotomized MNs between 1 and 15 days after sciatic nerve transection in mice. We did not observe any bulk engulfment of synaptic boutons by microglia. Instead, microglial cells internalized small membranous‐vesicular fragments which originated from the acute disruption of synaptic terminals involving the activation of the necroptotic pathway. The presence of abundant extracellular vesicles in the perineuronal space after axotomy, together with the increased expression of phospho‐mixed lineage kinase domain‐like protein and, later, of extracellular vesicle markers, such as CD9, CD63, and flotillin, indicate that the vesicles mainly originated in synapses and were transferred to microglia. The upregulation of Rab7 and Rab10 in microglia interacting with injured MNs, indicated the activation of endocytosis. As activated microglia and synaptic boutons displayed positive C1q immunoreactivity, a complement‐mediated opsonization may also contribute to microglial‐mediated synaptic disruption. In addition to the relevance of our data in the context of neuroinflammation and MN disease, they should also be taken into account for understanding functional recovery after peripheral nerve injury.
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Affiliation(s)
- Sara Salvany
- Patologia Neuromuscular Experimental Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Anna Casanovas
- Patologia Neuromuscular Experimental Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Lídia Piedrafita
- Patologia Neuromuscular Experimental Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Olga Tarabal
- Patologia Neuromuscular Experimental Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Sara Hernández
- Patologia Neuromuscular Experimental Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Jordi Calderó
- Patologia Neuromuscular Experimental Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
| | - Josep E Esquerda
- Patologia Neuromuscular Experimental Departament de Medicina Experimental, Facultat de Medicina, Universitat de Lleida and Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida, Catalonia, Spain
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19
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Zhou W, Zhou Y, Wang M, Qian C, Wang C, Tang J, Cai Z, Dai W, Zhu X. Pharmacological inhibition of CXCR2 alleviates neuropathic pain by inactivating microglia in a rat L5 spinal nerve ligation model. Am J Transl Res 2020; 12:3803-3812. [PMID: 32774736 PMCID: PMC7407742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 05/31/2020] [Indexed: 06/11/2023]
Abstract
Peripheral nerve injury (PNI)-induced neuropathic pain is a prevalent and severe clinical problem. It has been shown that microglia-mediated neuroinflammation plays a crucial role in neuropathic pain. The present study investigated the abnormal expression of C-X-C motif chemokine receptor type 2 (CXCR2) in a rat L5 spinal nerve ligation (SNL) model and evaluated the role of SB225002, a specific antagonist of CXCR2, in repressing neuroinflammation and neuropathic pain. It was found that CXCR2 expression was significantly upregulated in the dorsal horn of L5-SNL rats compared with sham control. Moreover, CXCR2 expression was increased in spinal microglia of rats after L5-SNL. Based on these results, the present study further examined whether pharmacological inhibition of CXCR2 suppressed microglial activation and neuropathic pain. It was demonstrated that SB225002 treatment inhibited L5-SNL-induced microglia proliferation and activation. Furthermore, SB225002 also significantly suppressed the L5-SNL-induced pro-inflammatory response, as indicated by decreased production of tumor necrosis factor-α, interleukin (IL)-1β and IL-6 in spinal cord tissues. The results indicated that SB225002 also significantly inhibited microglial cell viability and lipopolysaccharide-induced production of pro-inflammatory cytokines in cultured microglia. Functionally, SB225002 treatment effectively repressed mechanical and cold hypersensitivity after peripheral nerve injury. Collectively, the present results suggested that pharmacological inhibition of CXCR2 by SB225002 suppressed L5-SNL-induced neuroinflammation and neuropathic pain, thus offering a potential therapeutic strategy for neuropathic pain treatment.
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Affiliation(s)
- Wang Zhou
- Department of Anesthesiology, Affiliated Hospital of Nantong UniversityNantong 226001, Jiangsu, P. R. China
- School of Medicine, Nantong UniversityNantong 226001, Jiangsu, P. R. China
| | - Yuan Zhou
- Department of Anesthesiology, Affiliated Hospital of Nantong UniversityNantong 226001, Jiangsu, P. R. China
| | - Miqun Wang
- Department of Anesthesiology, Qingdao Women and Children’s HospitalQingdao 266034, P. R. China
| | - Cheng Qian
- Department of Traditional Chinese Medicine, Affiliated Hospital of Nantong UniversityNantong 226001, Jiangsu, P. R. China
| | - Cancan Wang
- School of Medicine, Nantong UniversityNantong 226001, Jiangsu, P. R. China
| | - Jiani Tang
- School of Medicine, Nantong UniversityNantong 226001, Jiangsu, P. R. China
| | - Zhenyuan Cai
- School of Medicine, Nantong UniversityNantong 226001, Jiangsu, P. R. China
| | - Wei Dai
- School of Medicine, Nantong UniversityNantong 226001, Jiangsu, P. R. China
| | - Xiang Zhu
- Department of Anesthesiology, Affiliated Hospital of Nantong UniversityNantong 226001, Jiangsu, P. R. China
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20
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Fan A, Oladiran O, Shi XQ, Zhang J. High-salt diet decreases mechanical thresholds in mice that is mediated by a CCR2-dependent mechanism. J Neuroinflammation 2020; 17:179. [PMID: 32517772 PMCID: PMC7282096 DOI: 10.1186/s12974-020-01858-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 05/27/2020] [Indexed: 02/07/2023] Open
Abstract
Background Though it is well-known that a high-salt diet (HSD) is associated with many chronic diseases, the effects of long-term high-salt intake on physiological functions and homeostasis remain elusive. In this study, we investigated whether and how an HSD affects mouse nociceptive thresholds, and myeloid cell trafficking and activation. Methods Healthy C57BL/6 male and female mice were fed an HSD (containing 4% NaCl in chow and 1% NaCl in water) from the time of weaning for 3 to 4 months. Circulating monocytes, nerve macrophages, spinal microglia, and associated inflammatory responses were scrutinized using flow cytometry, immunohistochemistry, and quantitative real-time polymerase chain reaction (qPCR) approaches. Mouse pain sensitivity to mechanical stimuli was monitored with von Frey tests along the experimental duration. Results Mice on an HSD have reduced mechanical thresholds. They feel more pain than those on a normal diet (ND), e.g., regular laboratory chow (0.3% NaCl in chow). An HSD induced not only a remarkable expansion of circulating monocytes, CCR2+Ly6Chi inflammatory monocytes in particular, but also an accumulation of CD11b+F4/80+ macrophages in the peripheral nerves and an activation of Iba-1+ spinal microglia. Replacing an HSD with a ND was unable to reverse the HSD-induced mechanical hypersensitivity or rescue the altered immune responses. However, treating HSD-fed mice with a chemokine receptor CCR2 antagonist effectively normalized the pain thresholds and immune cell profile in the periphery and spinal cord. An HSD failed to alter pain thresholds and myeloid cell activation in CCR2-deficient mice. Spinal microglial activation is required for HSD-induced mechanical hypersensitivity in male, but not in female mice. Conclusion Overall, this study provides evidence that an HSD has a long-term impact on physiological function. CCR2-mediated cellular response, including myeloid cell trafficking and associated inflammation, plays pivotal roles in salt-dietary modulation of pain sensitivity.
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Affiliation(s)
- Anni Fan
- The Alan Edwards Centre for Research on Pain, McGill University, 740, Dr. Penfield Avenue, Montreal, QC, H3A 0G1, Canada
| | - Oladayo Oladiran
- The Alan Edwards Centre for Research on Pain, McGill University, 740, Dr. Penfield Avenue, Montreal, QC, H3A 0G1, Canada
| | - Xiang Qun Shi
- The Alan Edwards Centre for Research on Pain, McGill University, 740, Dr. Penfield Avenue, Montreal, QC, H3A 0G1, Canada
| | - Ji Zhang
- The Alan Edwards Centre for Research on Pain, McGill University, 740, Dr. Penfield Avenue, Montreal, QC, H3A 0G1, Canada. .,Department of Microbiology and Immunology, Faculty of Medicine, McGill University, Montreal, Canada. .,Department of Neurology and Neurosurgery, Faculty of Medicine, McGill University, Montreal, Canada. .,Faculty of Dentistry, McGill University, Montreal, Canada.
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21
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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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22
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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: 30] [Impact Index Per Article: 7.5] [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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23
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Rigby MJ, Gomez TM, Puglielli L. Glial Cell-Axonal Growth Cone Interactions in Neurodevelopment and Regeneration. Front Neurosci 2020; 14:203. [PMID: 32210757 PMCID: PMC7076157 DOI: 10.3389/fnins.2020.00203] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 02/24/2020] [Indexed: 12/19/2022] Open
Abstract
The developing nervous system is a complex yet organized system of neurons, glial support cells, and extracellular matrix that arranges into an elegant, highly structured network. The extracellular and intracellular events that guide axons to their target locations have been well characterized in many regions of the developing nervous system. However, despite extensive work, we have a poor understanding of how axonal growth cones interact with surrounding glial cells to regulate network assembly. Glia-to-growth cone communication is either direct through cellular contacts or indirect through modulation of the local microenvironment via the secretion of factors or signaling molecules. Microglia, oligodendrocytes, astrocytes, Schwann cells, neural progenitor cells, and olfactory ensheathing cells have all been demonstrated to directly impact axon growth and guidance. Expanding our understanding of how different glial cell types directly interact with growing axons throughout neurodevelopment will inform basic and clinical neuroscientists. For example, identifying the key cellular players beyond the axonal growth cone itself may provide translational clues to develop therapeutic interventions to modulate neuron growth during development or regeneration following injury. This review will provide an overview of the current knowledge about glial involvement in development of the nervous system, specifically focusing on how glia directly interact with growing and maturing axons to influence neuronal connectivity. This focus will be applied to the clinically-relevant field of regeneration following spinal cord injury, highlighting how a better understanding of the roles of glia in neurodevelopment can inform strategies to improve axon regeneration after injury.
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Affiliation(s)
- Michael J Rigby
- Department of Medicine, University of Wisconsin-Madison, Madison, WI, United States.,Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI, United States.,Waisman Center, University of Wisconsin-Madison, Madison, WI, United States
| | - Timothy M Gomez
- Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI, United States.,Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, United States
| | - Luigi Puglielli
- Department of Medicine, University of Wisconsin-Madison, Madison, WI, United States.,Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI, United States.,Waisman Center, University of Wisconsin-Madison, Madison, WI, United States.,Geriatric Research Education Clinical Center, Veterans Affairs Medical Center, Madison, WI, United States
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24
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Akhter ET, Griffith RW, English AW, Alvarez FJ. Removal of the Potassium Chloride Co-Transporter from the Somatodendritic Membrane of Axotomized Motoneurons Is Independent of BDNF/TrkB Signaling But Is Controlled by Neuromuscular Innervation. eNeuro 2019; 6:ENEURO.0172-19.2019. [PMID: 31541001 PMCID: PMC6795555 DOI: 10.1523/eneuro.0172-19.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 08/21/2019] [Accepted: 09/15/2019] [Indexed: 01/09/2023] Open
Abstract
The potassium-chloride cotransporter (KCC2) maintains the low intracellular chloride found in mature central neurons and controls the strength and direction of GABA/glycine synapses. We found that following axotomy as a consequence of peripheral nerve injuries (PNIs), KCC2 protein is lost throughout the somatodendritic membrane of axotomized spinal cord motoneurons after downregulation of kcc2 mRNA expression. This large loss likely depolarizes the reversal potential of GABA/glycine synapses, resulting in GABAergic-driven spontaneous activity in spinal motoneurons similar to previous reports in brainstem motoneurons. We hypothesized that the mechanism inducing KCC2 downregulation in spinal motoneurons following peripheral axotomy might be mediated by microglia or motoneuron release of BDNF and TrkB activation as has been reported on spinal cord dorsal horn neurons after nerve injury, motoneurons after spinal cord injury (SCI), and in many other central neurons throughout development or a variety of pathologies. To test this hypothesis, we used genetic approaches to interfere with microglia activation or delete bdnf from specifically microglia or motoneurons, as well as pharmacology (ANA-12) and pharmacogenetics (F616A mice) to block TrkB activation. We show that KCC2 dysregulation in axotomized motoneurons is independent of microglia, BDNF, and TrkB. KCC2 is instead dependent on neuromuscular innervation; KCC2 levels are restored only when motoneurons reinnervate muscle. Thus, downregulation of KCC2 occurs specifically while injured motoneurons are regenerating and might be controlled by target-derived signals. GABAergic and glycinergic synapses might therefore depolarize motoneurons disconnected from their targets and contribute to augment motoneuron activity known to promote motor axon regeneration.
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Affiliation(s)
- Erica Tracey Akhter
- Departments of Physiology, Emory University, Atlanta, GA 30322
- Cell Biology, Emory University, Atlanta, GA 30322
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25
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Akhter ET, Rotterman TM, English AW, Alvarez FJ. Sciatic Nerve Cut and Repair Using Fibrin Glue in Adult Mice. Bio Protoc 2019; 9:e3363. [PMID: 31788507 PMCID: PMC6884152 DOI: 10.21769/bioprotoc.3363] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 07/30/2019] [Accepted: 08/11/2019] [Indexed: 02/01/2023] Open
Abstract
Peripheral nerve injury (PNI) is an excellent model for studying neural responses to injury and elucidating the mechanisms that can facilitate axon regeneration. As such, several animal models have been employed to study regenerative mechanisms after PNI, including Aplysia, zebrafish, rabbits, cats and rodents. This protocol describes how to perform a sciatic nerve injury and repair in mice, one of the most frequently used models to study mechanisms that facilitate recovery after PNI, and that takes advantage of the availability of many genetic models. In this protocol, we describe a method for using fibrin glue to secure the proximal and distal stumps of an injured nerve in close alignment. This method facilitates the alignment of nerve stumps, which aids in regeneration of both sensory and motor axons and allows successful reconnection with peripheral targets.
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Affiliation(s)
- Erica T. Akhter
- Department of Physiology, Emory University, Atlanta, USA
- Department of Cell Biology, Emory University, Atlanta, USA
| | - Travis M. Rotterman
- Department of Physiology, Emory University, Atlanta, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, USA
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