A multiscale study of morphological changes in tendons following repeated cyclic loading.

Area of Science:

• Biomechanics
• Cell Biology
• Tendon Research

Background:

• Tendon injuries are common, affecting mechanical function and cellular structure.
• Understanding the multiscale response of tendons to load is crucial for injury prevention and treatment.

Purpose of the Study:

• To concurrently assess the mechanical and morphological changes in rabbit Achilles tendons under fatigue loading.
• To investigate the relationship between cellular changes, structural alterations, and mechanical decline.

Main Methods:

• Utilized mechanical testing and confocal arthroscopy (CA) on white New Zealand rabbit Achilles tendons.
• Applied prolonged cyclic and static loading at varying strain levels (3%, 6%, 9%) for up to four hours.
• Assessed macroscale properties including tenocyte morphology, fiber anisotropy, waviness, and mechanical profiles.

Main Results:

• Increased strain and loading cycles significantly reduced mechanical function (p < 0.05).
• Repeated loading led to loss of mechanical and structural resilience at the macroscale (p < 0.05).
• Lengthening of D-periodicity strongly correlated with mechanical decline and tenocyte shape loss.

Conclusions:

• This study provides the first concurrent assessment of form and function in tendons under strain-mediated loading.
• Identified multiscale properties contributing to tendon pathology mechanisms.
• Highlights the link between cellular morphology, structural changes, and functional impairment in tendons.