BME Seminar Series: Mark R. Buckley, Ph.D.

Viscoelasticity, Structure and Function in Cartilage and Tendon

Post-doctoral Fellow, University of Pennsylvania, Departments of Bioengineering and Orthopaedic Surgery, McKay Orthopaedic Research Laboratory

Abstract

Cartilage and tendon are compositionally complex materials that sustain large deformations in order to protect surrounding tissues from damage. Their elaborate, heterogeneous structures and associated time-dependent mechanical properties allow them to effectively perform this task through roughly 1 million loading cycles each year. Unfortunately, in part due to their organizational complexity, healing in these tissues is slow and often incomplete. To guide treatment strategies for damaged cartilage and tendon, it is important to understand how their structure and function are related in the healthy state and what processes govern the healing response. To this end, we first describe a study aimed at measuring micro-scale variations in the viscoelastic shear properties of articular cartilage and associating these properties with local structure. We find that the shear modulus is lowest and viscous loss peaks in a thin region near the surface, resulting in a profound focusing of energy dissipation that may help protect joints from damage. We also describe a separate investigation into the role of the proteoglycans decorin and biglycan on tendon mechanics, aging and healing. Our results suggest that biglycan may serve as a modulator of other proteoglycans while decorin is critical for tendon strengthening after injury.