Complexes of Aggrecan and Hyaluronic Acid Determine Structural Properties of Soft Tissue

Zina Helal, Sarah Innes-Gold and Dr. Omar Saleh, Materials Department, University of California at Santa Barbara, Lagoon Rd, Santa Barbara, CA 93106

Aggrecan proteoglycans bind to hyaluronic acid (HA) polymers in the extracellular matrix of articular cartilage, forming a molecular complex responsible for resisting compressive loads. Aggrecan’s negative charge attracts water, creating an expanded tissue matrix less susceptible to deformation from external force. Aggrecan-HA breakdown is known to be associated with degenerative bone disease such as osteoarthritis. It is still unclear how changes in concentration of available binding aggrecan affect the size and structure of HA complexes which in turn influence the structural response of tissue to external forces. While there are intricate cellular mechanisms influencing in vivo mechanics, assembling these complexes in vitro allows us to precisely study how concentrations of aggrecan affects the structure of HA polymers. Here, we quantify the extension of single HA polymers in solutions containing aggrecan concentrations between 0 mg/ml – 2 mg/ml. This study was conducted with magnetic tweezers, a microscopic method that applies controlled force to a single polymer chain and measures the associated extension. This technique is advantageous as it allows for measuring the mechanical response of the same molecule in different solutions. From these measurements, we generate force-extension curves that show how polymer structure varies with aggrecan concentration. It is hypothesized that as aggrecan binds more densely, the HA polymers will lengthen, indicated by a larger measured extension. It is expected that a larger extension translates to increased tissue stiffness in vivo. We found individual HA polymers demonstrated an increase in extension up to an aggrecan solution concentration of 1 mg/ml, above which additional aggrecan did not increase HA extension, suggesting saturation. Our results show how insufficient amounts of aggrecan weaken the microscopic components of cartilage that are vital to healthy tissue function.

Additional Abstract Information

Presenter: Zina Helal

Institution: University of Texas at San Antonio

Type: Poster

Subject: Biological & Chemical Engineering

Status: Approved

Time and Location

Session: Poster 2
Date/Time: Mon 3:00pm-4:00pm
Session Number: 2541