Real-time Visualization of the Effects of Cyclic and Static Loading on Healthy and Pathological Cartilage Mechanical and Structural Properties

The metabolic activity of articular cartilage and other connective tissues is regulated by mechanical loading. While dynamic loading typically promotes biosynthetic activity and improves mechanical properties, immobilization and static loads inhibit anabolic activity and are detrimental to tissue function. These load-induced changes are mediated in part by cellular deformations induced by tissue-level strains. Osteoarthritis is characterized by reduced matrix synthesis and increased matrix degradation, resulting in pain and loss of mobility. However, it is not known how the sensitivity of cartilage to ameliorative and detrimental loading regimens is impacted by this disease.

We are investigating this question using a unique device allowing for evaluation of tissue-, matrix- and cellular-level mechanical properties in live tissue explants over extended periods of time. Compressive, shear and tensile loading regimens with varying frequencies and stress amplitudes are imposed on both healthy cartilage and cartilage with experimental osteoarthritis. Meanwhile, changes in microscopic mechanical and structural parameters are monitored optically and cell biosynthetic activity is assessed. We hypothesize that osteoarthritic tissue will exhibit a reduced sensitivity to dynamic load-induced improvements in properties and an enhanced sensitivity to degradative changes associated with stress deprivation and static loading.

confocalImages like this confocal reflectance micrograph of healthy articular cartilage are used to track matrix deformation and determine how loading impacts matrix structure.

Researcher: Mark Raymond Buckley, Ph.D.
Viscoelasticity in soft biological tissues; soft tissue aging, disease and repair