Comprehensive analysis of cellular contribution to delayed skeletal muscle recovery after disuse
Choi, Sung Jun
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Permalink
https://hdl.handle.net/2142/120366
Description
Title
Comprehensive analysis of cellular contribution to delayed skeletal muscle recovery after disuse
Author(s)
Choi, Sung Jun
Issue Date
2023-04-17
Director of Research (if dissertation) or Advisor (if thesis)
Boppart, Marni
Committee Member(s)
Burd, Nicholas
Department of Study
Kinesiology & Community Health
Discipline
Kinesiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
pericyte
skeletal muscle
immobilization, disuse atrophy
remobilization
snRNA-seq
Abstract
Extended periods of inactivity or immobilization often result in significant loss of skeletal muscle mass and function. Physical rehabilitation is the most effective approach to recovery, yet deficits persist during rehabilitation that often become permanent in vulnerable populations. While significant progress has been made in identifying the mechanisms that underlie muscle atrophy during a period of disuse, much less is known about the mechanisms that drive sustained delays in muscle recovery during reload. Our laboratory previously demonstrated that perivascular stem/stromal cells (CD146+ pericytes) are deficient in the capacity to synthesize antioxidants after disuse, and transplantation of healthy pericytes can restore redox imbalance and effectively rebuild muscle structure, suggesting an important role for pericytes in the recovery process. Currently, the precise antioxidants or factors required for recovery remain unknown. PURPOSE: The primary purpose of the study in this thesis was to evaluate single cell transcriptional profiles during recovery after immobilization and identify the cells and precise factors that contribute to prolonged atrophy. METHODS: Young adult wild-type mice underwent 2 weeks of unilateral hindlimb immobilization and 3 days of remobilization before the skeletal muscles (mobile control or remobilized limb; n=15/group) were collected for single nuclei isolation. Single-nuclei RNA sequencing (snRNA-seq) was performed using 10X Genomics Chromium Platform for evaluation of transcriptional differences. RESULTS: A total of 19,059 genes were analyzed by 10X Genomics Cell Ranger software (v7.1.0). Integrated gene expression data were used to identify a total of 14 cell clusters. Gene Ontology (GO) analysis demonstrated similar upregulation of genes associated with skeletal muscle contraction, muscle cell development, cytoskeletal organization, and myofibril assembly across clusters. In contrast, GO terms associated with downregulated genes differed widely among clusters and included acetylation, oxidative phosphorylation, extracellular matrix organization, RNA splicing, angiogenesis. Unexpectedly, the pericyte gene signature suggests that decreased adherence to endothelial cells, rather than antioxidant synthesis, appears to be the primary functional deficit during recovery. CONCLUSION: Overall, this study provides extensive insight on cellular contribution to the lack of recovery at the initial phase of remobilization. Our study suggests that most cells demonstrate an initial attempt to recover cellular structure, yet clear deficits in cellular function remain present in all cells within skeletal muscle. This dataset will provide valuable information to the field and accelerate the design of new cellular and molecular therapeutic targets.
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