Date of Award
10-11-2024
Publication Type
Thesis
Degree Name
M.Sc.
Department
Kinesiology
Keywords
Circadian Rhythms;Skeletal Muscle
Supervisor
Matthew Krause
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Abstract
Skeletal muscle regeneration is a dynamic process involving the diurnal expression of key factors. As a result, muscle injury sustained during different circadian phases may have influence on regeneration. The previous studies examining this have focused on muscle regeneration at early time points: within 7 days post-injury (DPI). However, it is unknown if any regeneration deficits are retained beyond this early regeneration window. The purpose of this study was to investigate if there are time-of-day-dependent changes in the function and morphology of skeletal muscle in mice following cardiotoxin (CTX)-induced skeletal muscle injury. 40 C57BL/6N mice received an intramuscular CTX injection to each tibialis anterior (TA) and soleus muscles of both legs, and 40 remained uninjured as control (n=5/sex/group). CTX injury was administered near the start of the rest phase (8:00AM-10:00AM) or active phase (8:00PM-10:00PM). Mice underwent routine functional testing with a Rotarod and grip strength meter, and were subsequently euthanized at 7 or 42DPI. Functional testing with the Rotarod and grip strength meter displayed no differences between AM and PM injury groups (p>0.05), and a recovery to control levels by 41DPI (p0.05) between AM and PM groups at either time point, there was an apparent effect on myofibre CSA (cross sectional area) distributions depending on the time of day. AM groups at 7 and 42DPI displayed a distribution curve of myofibre sizes that were smaller than PM groups (p>0.05), regardless of sex. The data suggests that the phasic point of an isolated muscle injury may bear influence on the size of skeletal muscle at both the tissue and cell level, yet the exact mechanisms are yet to be determined.
Recommended Citation
Scurto, Daniel Leonardo, "Time of Day of Skeletal Muscle Injury as a Critical Factor in Post-Regeneration Outcomes" (2024). Electronic Theses and Dissertations. 9563.
https://scholar.uwindsor.ca/etd/9563