AVS 50th International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuP

Paper BI-TuP13
SPARC Binding with ECM Proteins and its Influence on Cell Adhesion

Tuesday, November 4, 2003, 5:30 pm, Room Hall A-C

Session: Poster Session
Presenter: H. Wang, University of Washington
Authors: H. Wang, University of Washington
S. Chen, University of Washington
T. Barker, Hope Heart Institute
H. Sage, Hope Heart Institute
B.D. Ratner, University of Washington
S. Jiang, University of Washington
Correspondent: Click to Email
The secreted protein acidic and rich in cystein (SPARC/osteonectin/BM-40) is associated with events characterized by changes in cell shape and mobility. Although the molecular mechanism remains unclear, it is generally believed that the counter-adhesive properties of SPARC are related to its interactions with ECM proteins. In this study, the interactions of SPARC with ECM proteins, such as collagen I and fibronectin, are characterized and quantified using atomic force microscope (AFM) and surface plasma resonance (SPR), and their influence on cell adhesion are examined. AFM can characterize the binding of SPARC with both collagen I and fibronectin at the molecular level. SPARC has been shown to interact with collagen I, but direct topographic image has not been reported. Whether SPARC interacts with fibronectin still remains inconclusive. In this work, AFM is used to determine the number and location of binding sites on individual collagen I and fibronectin. Monoclonal antibodies of SPARC are used to assist for better visualization. These studies provide direct information about how and where binding occurs. SPR is used to quantify these interactions. It was shown that these interactions have ionic nature. Furthermore, the C-terminal region of SPARC, which contains a high-affinity Ca2+-binding site, may play an important role in its binding with ECM proteins. Thus, the influence of ionic strength and concentration of Ca2+ on binding are studied in SPR experiments. Cell culture and adhesion assays are used to study SPARC as a modulator of the adhesive process of cells seeded on ECM proteins. The influence of SPARC-collagen I interaction is studied using smooth muscle cells while the influence of SPARC-fibronectin interaction is studied using endothelial cells. The number and spreading area of cells, as well as the focal adhesion plagues are obtained as a function of the relative amount of SPARC added.