Proteoglycans (PGs) are important structural components of cartilage extracellular matrix. It is known that degenerative changes of cartilage structure/composition strongly influence the macroscopic behavior of the tissue.  As cartilage degenerates its swelling and mechanical properties change.  The main macromolecular constituents of cartilage are PGs and collagen. The PG assemblies are enmeshed in the collagen network.  The load bearing properties of the tissue are defined by the PG assemblies, while the collagen network provides tensile stability.  Cartilage swelling is governed by the hydration of the PG molecules, the electrostatic repulsion between the charged carboxylate and sulfate groups, and entropic (mixing) contributions.  Under compressive load, the negatively charged aggrecan molecules approach each other, and the repulsive forces between them increase the stiffness of the system.  Changes in the structure and composition of the aggrecan-hyaluronic acid complex, as well as damage of the collagen matrix affect the swelling and compressive properties of the tissue. Quantifying the interactions between the main macromolecular constituents of cartilage extracellular matrix can help us better understand design principles of nature, and develop novel strategies for tissue engineering.  In this work we report osmotic swelling pressure measurements, static and dynamic light scattering measurements, small-angle neutron and x-ray scattering measurements to study the relation between cartilage components.  Our objective is to understand the implication of the hierarchical bottlebrush architecture of cartilage PGs that ultimately defines the biological function of the tissue.

Biological and mechanical properties of cartilage proteoglycans

249th National Meeting (2015)

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