Measuring Microscale Structure-Property Relationships in Cartilage Using Elastography and Vibrational Spectroscopy

 Abstract

Articular cartilage is a remarkable material in its ability with withstand hundreds of millions of loading cycles throughout its lifetime with minimal capacity to self-repair.  This load-bearing capacity arises from its unique structure, which is comprised of interpenetrating networks of stiff collagen and highly charged proteoglycans.  These constituents are arranged heterogeneously throughout the tissue, with composition varying locally based on anatomic location and tissue depth. This heterogeneous composition give rise to local heterogeneities in tissue properties, which are relevant to tissue function and signaling of the cells embedded within it. 

We have developed techniques in confocal elastography and both Raman and FTIR microscopy that enable measurement of local mechanics and composition on the length scale of 10-20 µm. These techniques enabled us to identify large mechanical gradients in the tissue, where shear modulus varies by more than a factor of 100 over a length scale of 100 µm.  By spatially registering this information with data from local composition, we have measured structure-property relationships that implicate molecular connectivity as playing a key role in dictating the transition between stiff and compliant regions of the tissue. These findings facilitate a new understanding of this complex tissue as well as give fundamental insight into mechanisms of tissue damage and pathology that occur in tissues such as osteoarthritis.

BIO

Dr. Bonassar joined Cornell University in 2003 after five years on the faculty of the Center for Tissue Engineering at the University of Massachusetts Medical School. He completed postdoctoral fellowships in the Orthopaedic Research Laboratory at the Massachusetts General Hospital and in the Center for Biomedical Engineering at the Massachusetts Institute of Technology. He currently serves on the editorial board of the journal Tissue Engineering.