Biomedical Engineering Reference
In-Depth Information
Fig. 3 Orientation of neonatal cardiac myocytes grown on grooved surfaces mimic that found in
intact neonatal heart. Left , growth on non-textured surface. Center , growth on grooved surface;
corner inset presents a three-dimesional diagram of a grooved substrate. Right , frozen section from
an intact neonatal heart. Confocal fl uorescence images show electrical gap junction connexin43
protein ( green ), actin fi laments ( red ) and nuclei ( blue )
One important area of cardiac tissue engineering is the control of fi broplasia
(excessive fi broblast growth) in primary cultures of cardiac myocytes. Neonatal rat
ventricular fi broblasts (NRVF) were cultured on the microtextured surfaces to deter-
mine how the topography of the substrate infl uences the fi broblast population. Cell
proliferation decreased markedly on microtextured membranes as measured by cell
counts and Western blotting of cyclin D1. Myocyte to fi broblast ratios are higher on
microprojections, due to reduced proliferation of fi broblasts (Boateng et al. 2003 ) . It
was also determined that the mechanisms underlying these responses depend upon
focal adhesion stabilization by use of a Rho kinase inhibitor (Y27632) to decrease
NRVF mobility. It is hypothesized that cells sense the reactive forces on attachment
to the micropeg. These forces are transferred from the membrane to the cytoskeleton,
which leads to blockage of proliferation, which in turn matures them.
By examining the organizational pattern of the ventricular mycoytes in vivo, a
substrate was fabricated that was tailored to control cellular and subcellular organi-
zation in vitro. The cells were able to recognize variations in the substrate architec-
ture and to internalize these forces localized to small parts of the cell membrane in
order to infl uence protein organization and to effect genetic expression leading to
more natural growth.
Three-Dimensional Scaffolds for Tissue Engineering
The importance of culturing cells in three-dimensional (3D) artifi cial matrices to
mimic the body's own ECM is becoming more apparent. The third dimension has
numerous advantages for cells (Powell 2005 ). Cells show a more life-like gene
expression profi le and subcellular architecture when grown in three-dimensional
instead of conventional fl at two-dimensional (2D) surfaces (Cukierman et al. 2001 ;
Pedrotty et al. 2005 ; Powell 2005 ) .
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