Tendon Mechanobiology

Tendons transfering muscle forces are exposed to the highest mechanical stresses in the human body. How does the structure and biology of tendon enable this?

Hierarchical organization of load bearing collagen structures enable tendon function

Tendon is designed by Nature to transfer high muscle forces across our joints, often through very tight anatomical spaces. This can require tendon tissues to bear exceptionally high mechanical stress. Tendon injury is common, and recovery from tendon injury is often challenging.

Tendon Multi-Scale Mechanics — Organ and tissue scale: The basic tendon unit is called a “fascicle”. Fascicles can be organized to provide a wide range of tissue biomechanical properties depending upon their organization. Cellular and molecular scale: Inside the fascicles, tendon fibroblasts are interspersed among collagen bundles of approximately 10 microns in diameter called fibres. These fibroblasts monitor tissue deformations and maintain the structure/function of the collagen fibres.

A multi-scale approach

We employ experimental approaches across size scales, aiming to connect tissue-level forces, to matrix-level deformations, to biological cellular response. We perform human-level imaging (ultrasound, endoscopy, MRI), cellular-level imaging (advanced microscopy methods), and molecular-level imaging of matrix structures and their deformations under load (x-ray scattering, electron microscopy, atomic force microscopy).

Enlarged view: Functional Imaging Across Size Scales — Functional Imaging Across Size Scales

Discovering mechanotransducers and defining the mechanical stimulii that trigger them

Tendon tissue remodeling is driven by cell-level mechanical stresses and resulting deformations (in the matrix). Stresses include shear stresses from fluid flow and fascicle sliding, tensile stresses from direct elongation of collagen structures and hydrostatic stresses from the volumetric changes with external loading.

(Left) Cell-level stresses and matrix deformations (Right) Mechanotransducers and pathways — Mechanical stresses and deformations can activate various “vectors” through which tendon cells can potentially “transduce” mechanical forces within the tissue to regulate cell signaling and behavior. These include: 1) stretch activated ion channels (SACs) as mechanosensitive ion channels, 2) focal adhesion-mediated mechanical signal transduction, 3) the primary cilium and 4) nuclear deformations