Overload in a Rat In Vivo Model of Synergist Ablation Induces Tendon Multiscale Structural and Functional...

Area of Science:

• Biomedical Engineering
• Orthopedic Research
• Musculoskeletal Science

Background:

• Tendon degeneration is often viewed as an overuse injury, with limited distinction between overload and overuse.
• Existing animal models primarily focus on overuse, leaving a knowledge gap regarding isolated overload effects on tendons.

Purpose of the Study:

• To investigate the structural and functional consequences of isolated overload on the plantaris tendon in a rat model.
• To differentiate the degenerative pathways of tendon overload from overuse.

Main Methods:

• Utilized a rat synergist ablation (SynAb) model to induce isolated overload in the plantaris tendon.
• Employed longitudinal MRI, histology, second harmonic generation microscopy, and SBF-SEM for structural analysis.
• Conducted tissue- and microscale tension tests to assess functional changes.

Main Results:

• Overloaded plantaris tendons showed increased cross-sectional area (CSA), cell density, and collagen damage.
• Observed decreased collagen alignment, reduced modulus, and lower yield stress at 8 weeks post-surgery.
• Fibril diameter increased, indicating significant structural alterations at multiple scales.

Conclusions:

• Isolated tendon overload induces multiscale degenerative changes in structure and function.
• The study introduces a framework to distinguish between tendon overload and overuse mechanisms.
• Findings highlight the distinct pathological impact of overload on tendon tissue.