1
|
Guzman SD, Abu-Mahfouz A, Davis CS, Ruiz LP, Macpherson PC, Brooks SV. Decoding muscle-resident Schwann cell dynamics during neuromuscular junction remodeling. bioRxiv 2023:2023.10.06.561193. [PMID: 38370853 PMCID: PMC10871306 DOI: 10.1101/2023.10.06.561193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Understanding neuromuscular junction (NMJ) repair mechanisms is essential for addressing degenerative neuromuscular conditions. Here, we focus on the role of muscle-resident Schwann cells in NMJ reinnervation. In young Sod1-/- mice, a model of progressive NMJ degeneration, we identified a clear NMJ 'regenerative window' that allowed us to define regulators of reinnervation and crossing Sod1-/- mice with S100GFP-tg mice permitted visualization and analysis of Schwann cells. High-resolution imaging and single-cell RNA sequencing provide a detailed analysis of Schwann cell number, morphology, and transcriptome revealing multiple subtypes, including a previously unrecognized terminal Schwann cell (tSC) population expressing a synapse promoting signature. We also discovered a novel SPP1-driven cellular interaction between myelin Schwann cells and tSCs and show that it promotes tSC proliferation and reinnervation following nerve injury in wild type mice. Our findings offer important insights into molecular regulators critical in NMJ reinnervation that are mediated through tSCs to maintain NMJ function.
Collapse
Affiliation(s)
- Steve D Guzman
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
| | - Ahmad Abu-Mahfouz
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Carol S Davis
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Lloyd P Ruiz
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Peter C Macpherson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Susan V Brooks
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| |
Collapse
|
2
|
Abstract
Contractions of skeletal muscles provide the stability and power for all body movements. Consequently, any impairment in skeletal muscle function results in some degree of instability or immobility. Factors that influence skeletal muscle structure and function are therefore of great interest scientifically and clinically. Injury, neuromuscular disease, and old age are among the factors that commonly contribute to impairments in skeletal muscle function. The goal of this chapter is to summarize the fundamentals of skeletal muscle structure and function to provide foundational knowledge for this Handbook volume. We examine the molecular interactions that provide the basis for the generation of force and movement, discuss mechanisms of the regulation of contraction at the level of myofibers, and introduce concepts of the activation and control of muscle function in vivo. Where appropriate, the chapter updates the emerging science that will increase understanding of muscle function.
Collapse
Affiliation(s)
- Susan V Brooks
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, United States; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.
| | - Steve D Guzman
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Lloyd P Ruiz
- Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| |
Collapse
|
3
|
Guzman SD, Abu‐Mahfouz A, Macpherson PC, Brooks SV. Schwann Cell Derived Signals Enhance AChR Clustering in C2C12 Myotubes. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Steve D. Guzman
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
| | - Ahmad Abu‐Mahfouz
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
| | | | - Susan V. Brooks
- Molecular and Integrative PhysiologyUniversity of MichiganAnn ArborMI
- Biomedical EngineeringUniversity of MichiganAnn ArborMI
| |
Collapse
|
4
|
Guzman SD, Judge J, Shigdar SM, Paul TA, Davis CS, Macpherson PC, Markworth JF, Van Remmen H, Richardson A, McArdle A, Brooks SV. Removal of p16 INK4 Expressing Cells in Late Life has Moderate Beneficial Effects on Skeletal Muscle Function in Male Mice. Front Aging 2021; 2:821904. [PMID: 35821997 PMCID: PMC9261355 DOI: 10.3389/fragi.2021.821904] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 12/27/2021] [Indexed: 01/21/2023]
Abstract
Aging results in the progressive accumulation of senescent cells in tissues that display loss of proliferative capacity and acquire a senescence-associated secretory phenotype (SASP). The tumor suppressor, p16 INK4A , which slows the progression of the cell cycle, is highly expressed in most senescent cells and the removal of p16-expressing cells has been shown to be beneficial to tissue health. Although much work has been done to assess the effects of cellular senescence on a variety of different organs, little is known about the effects on skeletal muscle and whether reducing cellular senescent load would provide a therapeutic benefit against age-related muscle functional decline. We hypothesized that whole-body ablation of p16-expressing cells in the advanced stages of life in mice would provide a therapeutic benefit to skeletal muscle structure and function. Treatment of transgenic p16-3MR mice with ganciclovir (GCV) from 20 to 26 months of age resulted in reduced p16 mRNA levels in muscle. At 26 months of age, the masses of tibialis anterior, extensor digitorum longus, gastrocnemius and quadriceps muscles were significantly larger in GCV-treated compared with vehicle-treated mice, but this effect was limited to male mice. Maximum isometric force for gastrocnemius muscles was also greater in GCV-treated male mice compared to controls. Further examination of muscles of GCV- and vehicle-treated mice showed fewer CD68-positive macrophages present in the tissue following GCV treatment. Plasma cytokine levels were also measured with only one, granulocyte colony stimulating factor (G-CSF), out of 22 chemokines analyzed was reduced in GCV-treated mice. These findings show that genetic ablation of p16+ senescent cells provides moderate and sex specific therapeutic benefits to muscle mass and function.
Collapse
Affiliation(s)
- Steve D. Guzman
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Jennifer Judge
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Shahjahan M. Shigdar
- Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool and MRC-Arthritis Research UK Centre for Integrated Research Into Musculoskeletal Ageing (CIMA), Liverpool, United Kingdom
| | - Thomas A. Paul
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
| | - Carol S. Davis
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Peter C. Macpherson
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - James F. Markworth
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
| | - Holly Van Remmen
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, United States
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Oklahoma City VA Medical Center, Oklahoma City, OK, United States
| | - Arlan Richardson
- Oklahoma City VA Medical Center, Oklahoma City, OK, United States
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Anne McArdle
- Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool and MRC-Arthritis Research UK Centre for Integrated Research Into Musculoskeletal Ageing (CIMA), Liverpool, United Kingdom
| | - Susan V. Brooks
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, United States
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States
- *Correspondence: Susan V. Brooks,
| |
Collapse
|
5
|
Brown LA, Guzman SD, Brooks SV. Emerging molecular mediators and targets for age-related skeletal muscle atrophy. Transl Res 2020; 221:44-57. [PMID: 32243876 PMCID: PMC8026108 DOI: 10.1016/j.trsl.2020.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Revised: 02/28/2020] [Accepted: 03/03/2020] [Indexed: 12/20/2022]
Abstract
The age-associated decline in muscle mass has become synonymous with physical frailty among the elderly due to its major contribution in reduced muscle function. Alterations in protein and redox homeostasis along with chronic inflammation, denervation, and hormonal dysregulation are all hallmarks of muscle wasting and lead to clinical sarcopenia in older adults. Reduction in skeletal muscle mass has been observed and reported in the scientific literature for nearly 2 centuries; however, identification and careful examination of molecular mediators of age-related muscle atrophy have only been possible for roughly 3 decades. Here we review molecular targets of recent interest in age-related muscle atrophy and briefly discuss emerging small molecule therapeutic treatments for muscle wasting in sarcopenic susceptible populations.
Collapse
Affiliation(s)
- Lemuel A Brown
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Steve D Guzman
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Susan V Brooks
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan.
| |
Collapse
|