Aged tendons lack adaptive response to acute compressive injury

Area of Science:

• Biomedical Engineering
• Musculoskeletal Biology
• Tendon Pathophysiology

Background:

• Rotator cuff tendinopathy is multifactorial, influenced by aging and compression.
• Understanding tendon response to these factors is limited, and in vivo models struggle to isolate effects.
• Existing models lack the ability to directly assess tendon response to mechanical compression.

Purpose of the Study:

• To develop and validate a novel explant culture model for applying direct compression to tendons.
• To investigate the biological and mechanical responses of young and aged tendons to acute compressive injury.
• To elucidate age-dependent differences in tendon adaptation and injury response.

Main Methods:

• Developed a tendon explant culture system enabling direct application of compressive force.
• Applied a single acute compressive load to young and aged C57BL/6J flexor digitorum longus tendon explants.
• Assessed changes in cell viability, metabolic activity, matrix composition, gene expression, and mechanical properties.

Main Results:

• Young tendons demonstrated adaptive matrix turnover, including altered proteoglycan content and increased collagen synthesis and MMP-9 expression.
• Aged tendons exhibited decreased metabolic activity and collagen synthesis, lacking adaptive responses seen in young tendons.
• Acute compression induced lasting, age-dependent changes in tendon structure and function.

Conclusions:

• The novel explant model effectively demonstrates age-dependent responses to compressive tendon injury.
• Aged tendons possess diminished adaptive capacity, increasing susceptibility to compression-induced damage.
• This model provides a platform for future studies on tendon injury and aging under various loading conditions.