Collagen fibrils in functionally distinct tendons have differing structural responses to tendon rupture and fatigue...

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Biophysics

Background:

• Collagen fibrils are essential load-bearing structures in human tissues.
• Their nanoscale structure varies significantly, impacting tissue function.
• Understanding collagen fibril structure-function is crucial for tissue homeostasis and disease research.

Purpose of the Study:

• To investigate the relationship between collagen fibril nanoscale structure and macroscale functional response in distinct tendon types.
• To compare positional (flexor) and energy-storing (extensor) tendons in a bovine model.
• To elucidate how structural differences influence mechanical loading responses.

Main Methods:

• Differential Scanning Calorimetry (DSC) for molecular assessment.
• Hydrothermal Isometric Tension (HIT) analysis for crosslink assessment.
• Scanning Electron Microscopy (SEM) for ultrastructural analysis.
• Mechanical testing of undamaged, ruptured, and cyclically loaded tendon samples.

Main Results:

• Extensor tendons, despite lower crosslink density, were stronger and tougher than flexor tendons.
• SEM revealed greater plastic deformation in extensor tendon fibrils.
• Cyclic loading caused rapid fatigue damage (kink bands) in extensor tendon fibrils, unlike flexor tendons.

Conclusions:

• Collagen fibrils in functionally distinct tendons exhibit differential responses to mechanical loading.
• A tradeoff exists between collagen fibril strength and fatigue resistance.
• Fibril structure dictates mechanical properties and damage susceptibility.