100 Section - Effects of Skeletal Muscle Stretching and Aging on Collagen related Factors

Age-related impairment of intramuscular collagen remodeling reduces muscle quality and delays recovery. While collagen is essential for force transmission and regeneration, excessive accumulation and cross-linking cause fibrosis and dysfunction. Collagen cross-linking is influenced by advanced glycation end products (AGEs) and lysyl oxidase (LOX). Although moderate cross-linking stabilizes the extracellular matrix (ECM), the effects of stretching on intramuscular collagen and their modulation by aging remain unclear.

Design:

Two experiments were conducted. (1) Young male C57BL/6J mice were assigned to control, intermittent stretching (IS; 1-min stretches with 30-s intervals), or continuous stretching (CS; 10-min stretch) groups. Stretching was applied to the tibialis anterior for 6 days, and muscles were harvested 24 h later. (2) Tibialis anterior muscles of young and aged mice were compared to examine age-related changes.

Results:

In young mice, stretching did not alter muscle weight or fiber cross-sectional area. Col1a1 expression showed no significant change, whereas Lox was elevated in CS compared with IS, and Mmp2 decreased only in IS. Collagen I immunoreactivity appeared in endomysium and perimysium, with greater collagen area in CS than in control and IS. AGEs were detected in ECM without differences. LOX was localized in fibers and ECM, with LOX-positive cells in ECM increased in IS and CS. In aging analysis, Col1a1 expression was reduced, indicating impaired collagen regulation.

Conclusion:

CS promoted collagen accumulation, while IS and CS increased LOX-positive cells in ECM, suggesting that stretching facilitates LOX-mediated collagen cross-linking. Conversely, aging diminished fibrillar collagen gene expression.