1
|
Jensen VN, Huffman EE, Jalufka FL, Pritchard AL, Baumgartner S, Walling I, C. Gibbs H, McCreedy DA, Alilain WJ, Crone SA. V2a neurons restore diaphragm function in mice following spinal cord injury. Proc Natl Acad Sci U S A 2024; 121:e2313594121. [PMID: 38442182 PMCID: PMC10945804 DOI: 10.1073/pnas.2313594121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 01/15/2024] [Indexed: 03/07/2024] Open
Abstract
The specific roles that different types of neurons play in recovery from injury is poorly understood. Here, we show that increasing the excitability of ipsilaterally projecting, excitatory V2a neurons using designer receptors exclusively activated by designer drugs (DREADDs) restores rhythmic bursting activity to a previously paralyzed diaphragm within hours, days, or weeks following a C2 hemisection injury. Further, decreasing the excitability of V2a neurons impairs tonic diaphragm activity after injury as well as activation of inspiratory activity by chemosensory stimulation, but does not impact breathing at rest in healthy animals. By examining the patterns of muscle activity produced by modulating the excitability of V2a neurons, we provide evidence that V2a neurons supply tonic drive to phrenic circuits rather than increase rhythmic inspiratory drive at the level of the brainstem. Our results demonstrate that the V2a class of neurons contribute to recovery of respiratory function following injury. We propose that altering V2a excitability is a potential strategy to prevent respiratory motor failure and promote recovery of breathing following spinal cord injury.
Collapse
Affiliation(s)
- Victoria N. Jensen
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH45219
| | - Emily E. Huffman
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY40536
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, KY40536
| | - Frank L. Jalufka
- Department of Biology, Texas A&M University, College Station, TX77843
| | - Anna L. Pritchard
- Department of Biomedical Engineering, Texas A&M University, College Station, TX77843
| | - Sarah Baumgartner
- Division of Neurosurgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
| | - Ian Walling
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH45219
- Medical Scientist Training Program, University of Cincinnati College of Medicine, Cincinnati, OH45267
| | - Holly C. Gibbs
- Department of Biomedical Engineering, Texas A&M University, College Station, TX77843
- Microscopy and Imaging Center, Texas A&M University, College Station, TX77843
| | - Dylan A. McCreedy
- Department of Biology, Texas A&M University, College Station, TX77843
- Department of Biomedical Engineering, Texas A&M University, College Station, TX77843
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, TX77843
| | - Warren J. Alilain
- Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY40536
- Spinal Cord and Brain Injury Research Center, University of Kentucky College of Medicine, Lexington, KY40536
| | - Steven A. Crone
- Division of Neurosurgery, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH45229
- Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, OH45267
| |
Collapse
|
2
|
Li WY, Deng LX, Zhai FG, Wang XY, Li ZG, Wang Y. Chx10+V2a interneurons in spinal motor regulation and spinal cord injury. Neural Regen Res 2022; 18:933-939. [PMID: 36254971 PMCID: PMC9827767 DOI: 10.4103/1673-5374.355746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Chx10-expressing V2a (Chx10+V2a) spinal interneurons play a large role in the excitatory drive of motoneurons. Chemogenetic ablation studies have demonstrated the essential nature of Chx10+V2a interneurons in the regulation of locomotor initiation, maintenance, alternation, speed, and rhythmicity. The role of Chx10+V2a interneurons in locomotion and autonomic nervous system regulation is thought to be robust, but their precise role in spinal motor regulation and spinal cord injury have not been fully explored. The present paper reviews the origin, characteristics, and functional roles of Chx10+V2a interneurons with an emphasis on their involvement in the pathogenesis of spinal cord injury. The diverse functional properties of these cells have only been substantiated by and are due in large part to their integration in a variety of diverse spinal circuits. Chx10+V2a interneurons play an integral role in conferring locomotion, which integrates various corticospinal, mechanosensory, and interneuron pathways. Moreover, accumulating evidence suggests that Chx10+V2a interneurons also play an important role in rhythmic patterning maintenance, left-right alternation of central pattern generation, and locomotor pattern generation in higher order mammals, likely conferring complex locomotion. Consequently, the latest research has focused on postinjury transplantation and noninvasive stimulation of Chx10+V2a interneurons as a therapeutic strategy, particularly in spinal cord injury. Finally, we review the latest preclinical study advances in laboratory derivation and stimulation/transplantation of these cells as a strategy for the treatment of spinal cord injury. The evidence supports that the Chx10+V2a interneurons act as a new therapeutic target for spinal cord injury. Future optimization strategies should focus on the viability, maturity, and functional integration of Chx10+V2a interneurons transplanted in spinal cord injury foci.
Collapse
Affiliation(s)
- Wen-Yuan Li
- Institute of Neural Tissue Engineering, Mudanjiang College of Medicine, Mudanjiang, Heilongjiang Province, China
| | - Ling-Xiao Deng
- Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Feng-Guo Zhai
- Department of Pharmacy, Mudanjiang College of Medicine, Mudanjiang, Heilongjiang Province, China
| | - Xiao-Yu Wang
- Institute of Neural Tissue Engineering, Mudanjiang College of Medicine, Mudanjiang, Heilongjiang Province, China
| | - Zhi-Gang Li
- Department of General Surgery, Hongqi Hospital, Mudanjiang College of Medicine, Mudanjiang, Heilongjiang Province, China,Correspondence to: Ying Wang, ; Zhi-Gang Li, .
| | - Ying Wang
- Institute of Neural Tissue Engineering, Mudanjiang College of Medicine, Mudanjiang, Heilongjiang Province, China,Correspondence to: Ying Wang, ; Zhi-Gang Li, .
| |
Collapse
|
3
|
Jensen VN, Seedle K, Turner SM, Lorenz JN, Crone SA. V2a Neurons Constrain Extradiaphragmatic Respiratory Muscle Activity at Rest. eNeuro 2019; 6:ENEURO. [PMID: 31324674 DOI: 10.1523/ENEURO.0492-18.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 05/28/2019] [Accepted: 06/17/2019] [Indexed: 02/01/2023] Open
Abstract
Breathing requires precise control of respiratory muscles to ensure adequate ventilation. Neurons within discrete regions of the brainstem produce oscillatory activity to control the frequency of breathing. Less is understood about how spinal and pontomedullary networks modulate the activity of respiratory motor neurons to produce different patterns of activity during different behaviors (i.e., during exercise, coughing, swallowing, vocalizing, or at rest) or following disease or injury. Here, we use a chemogenetic approach to inhibit the activity of glutamatergic V2a neurons in the brainstem and spinal cord of neonatal and adult mice to assess their potential roles in respiratory rhythm generation and patterning respiratory muscle activity. Using whole-body plethysmography (WBP), we show that V2a neuron function is required in neonatal mice to maintain the frequency and regularity of respiratory rhythm. However, silencing V2a neurons in adult mice increases respiratory frequency and ventilation, without affecting regularity. Thus, the excitatory drive provided by V2a neurons is less critical for respiratory rhythm generation in adult compared to neonatal mice. In addition, we used simultaneous EMG recordings of the diaphragm and extradiaphragmatic respiratory muscles in conscious adult mice to examine the role of V2a neurons in patterning respiratory muscle activity. We find that silencing V2a neurons activates extradiaphragmatic respiratory muscles at rest, when they are normally inactive, with little impact on diaphragm activity. Thus, our results indicate that V2a neurons participate in a circuit that serves to constrain the activity of extradiaphragmatic respiratory muscles so that they are active only when needed.
Collapse
|
4
|
Romer SH, Seedle K, Turner SM, Li J, Baccei ML, Crone SA. Accessory respiratory muscles enhance ventilation in ALS model mice and are activated by excitatory V2a neurons. Exp Neurol 2016; 287:192-204. [PMID: 27456268 DOI: 10.1016/j.expneurol.2016.05.033] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 05/09/2016] [Accepted: 05/26/2016] [Indexed: 02/06/2023]
Abstract
Inspiratory accessory respiratory muscles (ARMs) enhance ventilation when demands are high, such as during exercise and/or pathological conditions. Despite progressive degeneration of phrenic motor neurons innervating the diaphragm, amyotrophic lateral sclerosis (ALS) patients and rodent models are able to maintain ventilation at early stages of disease. In order to assess the contribution of ARMs to respiratory compensation in ALS, we examined the activity of ARMs and ventilation throughout disease progression in SOD1G93A ALS model mice at rest using a combination of electromyography and unrestrained whole body plethysmography. Increased ARM activity, accompanied by increased ventilation, is observed beginning at the onset of symptoms. However, ARM recruitment fails to occur at rest at late stages of disease, even though the same ARMs are used for other behaviors. Using a chemogenetic approach, we demonstrate that a glutamatergic class of neurons in the brainstem and spinal cord, the V2a class, is sufficient to drive increased ARM activity at rest in healthy mice. Additionally, we reveal pathology in the medial reticular formation of the brainstem of SOD1G93A mice using immunohistochemistry and confocal imaging. Both spinal and brainstem V2a neurons degenerate in ALS model mice, accompanied by regional activation of astrocytes and microglia. These results establish inspiratory ARM recruitment as one of the compensatory mechanisms that maintains breathing at early stages of disease and indicate that V2a neuron degeneration may contribute to ARM failure at late stages of disease.
Collapse
Affiliation(s)
- Shannon H Romer
- Division of Neurosurgery, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229
| | - Kari Seedle
- Division of Neurosurgery, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229
| | - Sarah M Turner
- Division of Neurosurgery, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229
| | - Jie Li
- Pain Research Center, Dept. of Anesthesiology, University of Cincinnati Medical Center, 231 Albert Sabin Way, Cincinnati, OH 45267
| | - Mark L Baccei
- Pain Research Center, Dept. of Anesthesiology, University of Cincinnati Medical Center, 231 Albert Sabin Way, Cincinnati, OH 45267
| | - Steven A Crone
- Division of Neurosurgery, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229; Division of Developmental Biology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229.
| |
Collapse
|