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Sherman DA, Rush J, Stock MS, D. Ingersoll C, E. Norte G. Neural drive and motor unit characteristics after anterior cruciate ligament reconstruction: implications for quadriceps weakness. PeerJ 2023; 11:e16261. [PMID: 37818333 PMCID: PMC10561646 DOI: 10.7717/peerj.16261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 09/18/2023] [Indexed: 10/12/2023] Open
Abstract
Purpose The purpose of this investigation was to compare the quality of neural drive and recruited quadriceps motor units' (MU) action potential amplitude (MUAPAMP) and discharge rate (mean firing rate (MFR)) relative to recruitment threshold (RT) between individuals with anterior cruciate ligament reconstruction (ACLR) and controls. Methods Fourteen individuals with ACLR and 13 matched controls performed trapezoidal knee extensor contractions at 30%, 50%, 70%, and 100% of their maximal voluntary isometric contraction (MVIC). Decomposition electromyography (dEMG) and torque were recorded concurrently. The Hoffmann reflex (H-reflex) and central activation ratio (CAR) were acquired bilaterally to detail the proportion of MU pool available and volitionally activated. We examined MUAPAMP-RT and MFR-RT relationships with linear regression and extracted the regression line slope, y-intercept, and RT range for each contraction. Linear mixed effect modelling used to analyze the effect of group and limb on regression line slope and RT range. Results Individuals with ACLR demonstrated lower MVIC torque in the involved limb compared to uninvolved limb. There were no differences in H-reflex or CAR between groups or limbs. The ACLR involved limb demonstrated smaller mass-normalized RT range and slower MU firing rates at high contraction intensities (70% and 100% MVIC) compared to uninvolved and control limbs. The ACLR involved limb also demonstrated larger MU action potentials in the VM compared to the contralateral limb. These differences were largely attenuated with relative RT normalization. Conclusions These results suggest that persistent strength deficits following ACLR may be attributable to a diminished quadriceps motor neuron pool and inability to upregulate the firing rate of recruited MUs.
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Affiliation(s)
- David A. Sherman
- Live4 Physical Therapy and Wellness, Acton, Massachusetts, United States of America
- Chobanian & Avedisian School of Medicine, Boston University, Boston, Massachusetts, United States of America
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America
| | - Justin Rush
- Division of Physical Therapy, School of Rehabilitation and Communication Sciences, College of Health Sciences and Professions, Ohio University, Athens, Ohio, United States of America
| | - Matt S. Stock
- Cognition, Neuroplasticity, & Sarcopenia (CNS) Lab, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, United States of America
| | - Christopher D. Ingersoll
- College of Health Professions and Sciences, School of Kinesiology and Rehabilitation Sciences, University of Central Florida, Orlando, Florida, United States of America
| | - Grant E. Norte
- Cognition, Neuroplasticity, & Sarcopenia (CNS) Lab, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, FL, United States of America
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Keeble AR, Brightwell CR, Latham CM, Thomas NT, Mobley CB, Murach KA, Johnson DL, Noehren B, Fry CS. Depressed Protein Synthesis and Anabolic Signaling Potentiate ACL Tear-Resultant Quadriceps Atrophy. Am J Sports Med 2023; 51:81-96. [PMID: 36475881 PMCID: PMC9813974 DOI: 10.1177/03635465221135769] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Anterior cruciate ligament (ACL) tear (ACLT) leads to protracted quadriceps muscle atrophy. Protein turnover largely dictates muscle size and is highly responsive to injury and loading. Regulation of quadriceps molecular protein synthetic machinery after ACLT has largely been unexplored, limiting development of targeted therapies. PURPOSE To define the effect of ACLT on (1) the activation of protein synthetic and catabolic signaling within quadriceps biopsy specimens from human participants and (2) the time course of alterations to protein synthesis and its molecular regulation in a mouse ACL injury model. STUDY DESIGN Descriptive laboratory study. METHODS Muscle biopsy specimens were obtained from the ACL-injured and noninjured vastus lateralis of young adult humans after an overnight fast (N = 21; mean ± SD, 19 ± 5 years). Mice had their limbs assigned to ACLT or control, and whole quadriceps were collected 6 hours or 1, 3, or 7 days after injury with puromycin injected before tissue collection for assessment of relative protein synthesis. Muscle fiber size and expression and phosphorylation of protein anabolic and catabolic signaling proteins were assessed at the protein and transcript levels (RNA sequencing). RESULTS Human quadriceps showed reduced phosphorylation of ribosomal protein S6 (-41%) in the ACL-injured limb (P = .008), in addition to elevated phosphorylation of eukaryotic initiation factor 2α (+98%; P = .006), indicative of depressed protein anabolic signaling in the injured limb. No differences in E3 ubiquitin ligase expression were noted. Protein synthesis was lower at 1 day (P = .01 vs control limb) and 3 days (P = .002 vs control limb) after ACLT in mice. Pathway analyses revealed shared molecular alterations between human and mouse quadriceps after ACLT. CONCLUSION (1) Global protein synthesis and anabolic signaling deficits occur in the quadriceps in response to ACL injury, without notable changes in measured markers of muscle protein catabolism. (2) Importantly, these deficits occur before the onset of significant atrophy, underscoring the need for early intervention. CLINICAL RELEVANCE These findings suggest that blunted protein anabolism as opposed to increased catabolism likely mediates quadriceps atrophy after ACL injury. Thus, future interventions should aim to restore muscle protein anabolism rapidly after ACLT.
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Affiliation(s)
- Alexander R. Keeble
- Department of Physiology, College of Medicine, University of Kentucky
- Center for Muscle Biology, University of Kentucky
| | - Camille R. Brightwell
- Center for Muscle Biology, University of Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky
| | - Christine M. Latham
- Center for Muscle Biology, University of Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky
| | - Nicholas T. Thomas
- Center for Muscle Biology, University of Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky
| | - C. Brooks Mobley
- Department of Physiology, College of Medicine, University of Kentucky
- Center for Muscle Biology, University of Kentucky
| | - Kevin A. Murach
- Center for Muscle Biology, University of Kentucky
- Department of Physical Therapy, University of Kentucky
| | - Darren L. Johnson
- Department of Orthopaedic Surgery & Sports Medicine, University of Kentucky
| | - Brian Noehren
- Center for Muscle Biology, University of Kentucky
- Department of Physical Therapy, University of Kentucky
- Department of Orthopaedic Surgery & Sports Medicine, University of Kentucky
| | - Christopher S. Fry
- Center for Muscle Biology, University of Kentucky
- Department of Athletic Training and Clinical Nutrition, University of Kentucky
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Yang X, Li M, Ji Y, Lin Y, Xu L, Gu X, Sun H, Wang W, Shen Y, Liu H, Zhu J. Changes of Gene Expression Patterns of Muscle Pathophysiology-Related Transcription Factors During Denervated Muscle Atrophy. Front Physiol 2022; 13:923190. [PMID: 35812340 PMCID: PMC9263185 DOI: 10.3389/fphys.2022.923190] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 06/07/2022] [Indexed: 12/11/2022] Open
Abstract
Peripheral nerve injury is common, and can lead to skeletal muscle atrophy and dysfunction. However, the underlying molecular mechanisms are not fully understood. The transcription factors have been proved to play a key role in denervated muscle atrophy. In order to systematically analyze transcription factors and obtain more comprehensive information of the molecular regulatory mechanisms in denervated muscle atrophy, a new transcriptome survey focused on transcription factors are warranted. In the current study, we used microarray to identify and analyze differentially expressed genes encoding transcription factors in denervated muscle atrophy in a rat model of sciatic nerve dissection. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were used to explore the biological functions of differentially expressed transcription factors and their target genes related to skeletal muscle pathophysiology. We found that the differentially expressed transcription factors were mainly involved in the immune response. Based on correlation analysis and the expression trends of transcription factors, 18 differentially expressed transcription factors were identified. Stat3, Myod1, Runx1, Atf3, Junb, Runx2, Myf6, Stat5a, Tead4, Klf5, Myog, Mef2a, and Hes6 were upregulated. Ppargc1a, Nr4a1, Lhx2, Ppara, and Rxrg were downregulated. Functional network mapping revealed that these transcription factors are mainly involved in inflammation, development, aging, proteolysis, differentiation, regeneration, autophagy, oxidative stress, atrophy, and ubiquitination. These findings may help understand the regulatory mechanisms of denervated muscle atrophy and provide potential targets for future therapeutic interventions for muscle atrophy following peripheral nerve injury.
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Affiliation(s)
- Xiaoming Yang
- School of Biology and Basic Medical Sciences, Medical College of Soochow University, Suzhou, China
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-Innovation Center of Neuroregeneration, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Ming Li
- Department of Laboratory Medicine, Binhai County People’s Hospital affiliated to Kangda College of Nanjing Medical University, Yancheng, China
| | - Yanan Ji
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-Innovation Center of Neuroregeneration, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Yinghao Lin
- Department of Orthopedics, Affiliated Hospital of Nantong University, Nantong, China
| | - Lai Xu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-Innovation Center of Neuroregeneration, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Xiaosong Gu
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-Innovation Center of Neuroregeneration, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Hualin Sun
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-Innovation Center of Neuroregeneration, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Wei Wang
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-Innovation Center of Neuroregeneration, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
| | - Yuntian Shen
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Co-Innovation Center of Neuroregeneration, Jiangsu Clinical Medicine Center of Tissue Engineering and Nerve Injury Repair, Nantong University, Nantong, China
- *Correspondence: Yuntian Shen, ; Hua Liu, ; Jianwei Zhu,
| | - Hua Liu
- Department of Orthopedics, Haian Hospital of Traditional Chinese Medicine, Nantong, China
- *Correspondence: Yuntian Shen, ; Hua Liu, ; Jianwei Zhu,
| | - Jianwei Zhu
- Department of Orthopedics, Affiliated Hospital of Nantong University, Nantong, China
- *Correspondence: Yuntian Shen, ; Hua Liu, ; Jianwei Zhu,
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