BME Ph.D. Thesis Defense Seminar

Goergen Hall 101 (Sloan Auditorium)

"Using Fibronectin Matrix Mimetics to Stimulate Three-Dimensional Cellular Self-Assembly"

Presented by James Brennan

Supervised by Professor Denise Hocking

Abstract: Cellular self-assembly is a process that occurs during embryonic development in which cells and extracellular matrix (ECM) spontaneously organize into three-dimensional (3D) tissues in the absence of external forces. Cellular self-assembly can also be initiated in vitro, and represents a potential tool for tissue engineers to organize cells and ECM in an in vivo-like manner. Understanding the cell-ECM interactions that lead to the formation of 3D cellular structures will better allow tissue engineers to develop biological constructs in vitro for regenerative medicine purposes. Fibronectin is an ECM protein that plays an important role in tissue formation during embryonic development as well as 3D cellular self-assembly in vitro. Our lab has developed a series of fibronectin matrix mimetic proteins that mimic many of the cellular effects of the bioactive, ECM form of fibronectin. The goal of this work was use fibronectin matrix mimetics to identify the cell-fibronectin interactions that lead to cellular self-assembly. 

In this work, we showed that fibronectin matrix mimetic substrates are able to stimulate fibronectin-dependent cellular self-assembly. The fibronectin matrix mimetic substrate conditions that permit cellular self-assembly are dependent on the cell-substrate binding strength. We have identified roles for fibronectin matrix assembly and Rac GTPase in mediating cell-substrate binding strength and subsequently cellular self-assembly. These findings were then applied to tissue engineering applications. We showed that fibronectin matrix mimetics are also able to control cellular self-assembly of mesenchymal stem cells (MSCs) and stimulate early osteogenic differentiation based on substrate coating concentration. The studies presented herein suggest that fibronectin matrix mimetics provide a model for studying the role that fibronectin matrix assembly and cell-substrate binding strength play in stimulating tissue development.