Biomedical Engineering Reference
In-Depth Information
Micro and Nano Engineered
Extracellular Matrices
James J. Norman and Tejal A. Desai
Cells in our body are in intimate contact with the extracellular matrix (ECM), the
substratum in which cells live. The ECM is composed of proteins, glycoproteins
and proteoglycans that are arranged in tissue-specifi c structures. Cells form adhe-
sions to the ECM via integrins, transmembrane proteins that interact with specifi c
amino acid sequences found within the proteins that make up the ECM (for exam-
ple, the arginine-glycine-aspartic acid, RGD, sequence). These adhesions are one
way the cell interacts with its environment. The cell can infl uence the physical
arrangement of the ECM through these adhesions and the cell itself can be infl u-
enced through the adhesions. When cells migrate, they extend psuedopods (fi lipo-
dia) from the main body of the cell. Gustafson and Wolpert have made striking
observations of psuedopods on the order of 500 nm extending from the body of a
cell (sea urchin mesenchymal cells) to explore and probe the surrounding environ-
ment (Gustafson and Wolpert 1999 ). This exploration by the cells appears to happen
randomly with psuedopods sweeping the surface until a point of stable contact is
made. Cell movement then occurs in the direction of the contact through retraction
of the attached psuedopod. This apparent exploration by cells of their surround-
ings has led researchers to develop scaffolds that provide cues to the cells as they
migrate across its surface. Finding the exact cues that will cause the cells to make a
J. J. Norman
Warner Babcock Institute for Green Chemistry, LLC ,
Wilmington , MA , USA
T. A. Desai ( * )
Department of Physiology and Division of Bioengineering , University of California,
San Francisco , CA , USA
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