Biomedical Engineering Reference
In-Depth Information
a
TABLE 6.5
Components of the Extracellular Matrix
—Cont'd
Component
Function
Location
Tenascin
Modulates cell-matrix interaction
Transiently expressed associated with
remodeling matrix
Antiadhesive
Antiproliferative
SPARC
b
(osteonectin)
Modulates cell-matrix interaction
Transiently expressed associated with
remodeling matrix
Antiadhesive
Antiproliferative
Thrombospodin
Modulates cell-matrix interaction
Platelet
a
granules
Adhesion molecules
Cell surface proteins mediating cell adhesion
to matrix or adjacent cells
Ubiquitously distributed
Mediators of transmembrane signals
von Willebrand
factor
Mediates platelet adhesion
Plasma protein
Carrier for procoagulant factor VIII
Subendothelium
a
Mutsaers et al., 1997.
b
SPARC, secreted protein acidic and rich in cysteine.
EXAMPLE PROBLEM 6.4
How many receptor sites are needed for various cellular functions?
Solution
The RGD (arginine-glycine-aspartic acid) tripeptide binding sequence has been immobilized on
a cell growth surface at varying densities. Cell attachment, spreading, and growth were examined
as a function of the surface density of RGD binding sites for fibroblasts. The results showed
that an average receptor spacing of 440 nm was sufficient for cell attachment and spreading,
and 160 nm for focal point adhesion formation. This type of experiment and analysis can provide
insight into how cells adhere and migrate on different substrates.
A main thrust of tissue engineering efforts has been the design and fabrication of mate-
rials that mimic the ECM. These matrices can be used as scaffolds to support tissue growth.
A variety of natural and synthetic materials have been used for this purpose. In some cases
these materials are designed to be bioresorbable to allow the cells to replace the supplied
ECM as they establish themselves and reconstruct tissue function. It is challenging to design
such matrices because many of the functions of the ECM are still incompletely understood
and involve two-way communication between cells and the matrix. The full spectrum of
ECM functionality is perhaps something that can only be provided by the cells themselves
(Table 6.6).
