Biomedical Engineering Reference
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FIGURE 7.5: (See color insert.) Magnification of four representative single-
TEC motion trajectories obtained from a time-lapse simulation. The initial
(i.e., at 0 h) position of individuals is labeled with 1, while the final (i.e., at 12
h) with 2. Each segment tracks a displacement of 2 h. In the background the
concentration field of VEGF is pseudocolor-scaled so that the maximum level
is red and minimum level is blue. The TECs move in the directions of higher
morphogen concentrations, displaying a persistent directional migration. The
image also captures the polarization process typical of vascular cells: it is useful
to underline that cell elongation is realistically reproduced in the model, as
it emerges as the natural consequence of the interplay between the calcium-
induced reorganization of the cell cytoskeleton and the VEGF chemotactic
stimulus.
120 m to 250 m, and a mean chord length (measured as the segment from
one node to another) of 180 10 m.
The geometrical description of the emerging structure is in good agreement
with the experimental analysis provided in [133] on a culture of endothelial
cells derived from human breast carcinomas (B-TECs), plated on a growth
factor-reduced Matrigel and stimulated with angiogenic factors. Moreover,
the network sizes captured by the model are surprisingly consistent also with
those measured in the case of tubulogenic assays performed with \normal"
endothelial cells, i.e., human umbilical vein ECs (HUVECs) [360]. In particu-
lar, such natural length scales have been demonstrated to be dictated by the
effective range of cell-to-cell interactions, which is mediated by the activity
of the soluble VEGF (in particular by its diffusion coecient and decay rate,
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