Skeletal muscle regeneration at different phases of the menstrual cycle

Abstract

INTRODUCTION: The effect of estrogen on muscle function and recovery from damage has been studied, but the effects of estrogen fluctuations during the menstrual cycle on muscle regeneration remain inconclusive. PURPOSE: The purpose of this study was to examine the effects of menstrual cycle phases on muscle regeneration after electrically stimulated muscle damage. We hypothesized that muscle damage during the late follicular (LF) phase results in better muscle regeneration as compared to muscle damage during the early follicular (EF) phase. METHODS: 23 premenopausal females (21.3±2 yrs) were recruited and split into two groups, EF and LF. After menstrual cycle tracking and phase confirmation, subjects underwent 200 electrically stimulated eccentric muscle contractions one week after providing a muscle biopsy. 7 days after inducing muscle damage, the subjects reported to give a final biopsy. Sections from muscle samples were stained for markers of laminin, dystrophin, satellite cells (SCs; Pax7), nuclei, total macrophages (CD68), and anti-inflammatory macrophages (CD206/CD68). Data for SCs, and %CD206+CD68+ cells are presented as mean±SD, and damaged fibers and CD206+CD68+ cells/fiber are presented as median±interquartile range. RESULTS: Electrical stimulation caused muscle fiber necrosis (0.005±0.018 damaged fiber/fiber, p=0.0002) as measured by the laminin-containing and dystrophin-deficient fibers. There was no difference between EF and LF groups for the number of damaged fibers (p=0.055) Muscle damage resulted in ~200% increase in the total number of CD68+ macrophages (p=0.008), and ~ 40% increase in the number of SCs (p=0.001) in both groups. However, there was no significant difference between EF and LF groups for the change in total macrophages per fiber (p=0.07) or SCs/fiber (p=0.25) in response to electrically stimulated muscle damage. Anti-inflammatory macrophages increased by about 104%±127 in EF and 240%±390 in LF group, but the difference between groups was not significant (p=0.39). A comparison of the proportion of anti-inflammatory macrophages per total macrophages before and one week after muscle damage did not show any time effect (p=0.25), which could indicate the regenerative and anti-inflammatory state of skeletal muscle one week after damage. CONCLUSION: Contrary to our hypothesis, our data indicate that skeletal muscle regeneration is not affected by different phases of the menstrual cycle. However, this finding is limited to only some of the markers of regeneration one week after muscle damage. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.