Sex-Specific Extracellular Matrix Remodeling in Skeletal Muscle After Immobilization

Abstract Purpose Periods of disuse can cause changes to the musculoskeletal system, particularly impacting the composition and strength of skeletal muscle. While many studies have investigated changes in muscle phenotype after unloading, the majority of these studies were performed on animals of a single genetic background or sex. The effect of muscle immobilization on males compared to females, as well as the effect of genetic diversity, is not well understood. The objective of this study was to investigate differential effects of skeletal muscle immobilization in genetically diverse males and females. Methods Diversity Outbred (DO) mice were cast using single limb immobilization (SLI) for three weeks. Total RNA-sequencing was performed on gastrocnemius muscles and analyzed using Ingenuity Pathway Analysis (IPA). Hindlimb muscle morphology and performance were also quantified, using histopathological and functional analyses, respectively. Results Transcriptomic analysis revealed both males and females have downregulated metabolism pathways during unloading. Investigation of matrix modifying pathways revealed differential expression of collagen related pathways, not matrix degradation pathways, in males compared to females. Histopathological analysis of collagen and functional analysis of muscle cross sectional area and volume correlated directly with transcriptomic analysis. Conclusion Together, these findings highlight that despite genetic diversity, immobilization causes similar changes in skeletal muscle metabolism, but differences in extracellular matrix (ECM) remodeling between males and females. This study reveals that sex differences should be considered in designing therapeutics to treat muscle adaptation to immobilization.