Regulators of ECM Structure Enable Functional Adaptation to Tensile Loading in Tendon Explants

Area of Science:

• Biomedical Engineering
• Mechanobiology
• Tissue Engineering

Background:

• Extracellular matrix (ECM) remodeling is crucial for tissue adaptation to mechanical stress.
• Understanding how altered mechanical strain affects tendon structure and function is vital for injury prevention and treatment.

Purpose of the Study:

• To elucidate the molecular and cellular mechanisms governing tendon adaptation to increased (exercise) and decreased (disuse) mechanical strain.
• To link specific mechanical perturbations to changes in ECM organization, composition, and function.

Main Methods:

• Cultured male murine flexor tendon explants in tensile bioreactors.
• Applied step changes in cyclic strain (1% to 5% for exercise, stress deprivation for disuse).
• Conducted multiscale analyses including matrix organization, composition, protein synthesis, signaling, and proteolytic activity.

Main Results:

• Increased strain (exercise) enhanced mechanical properties (elastic modulus, failure stress) via an anabolic program involving TGF-β and IL-6 signaling, increased proteoglycan expression, suppressed MMPs, and improved collagen alignment.
• Decreased strain (disuse) reduced collagen synthesis and induced a catabolic state with increased MMP activity, favoring matrix degradation.
• Demonstrated that ECM organization and turnover regulators are critical for functional adaptation, beyond synthesis alone.

Conclusions:

• Tendon adaptation to mechanical loading involves distinct anabolic (exercise) and catabolic (disuse) remodeling programs.
• Specific signaling pathways and matrix turnover regulators mediate functional outcomes in response to mechanical demands.
• Findings provide insights into adaptive remodeling and offer targets for addressing maladaptive ECM changes in aging, injury, and disease.